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Grega MN, Gan J, Noman M, Asbury JB. Reversible Ligand Detachment from CdSe Quantum Dots Following Photoexcitation. J Phys Chem Lett 2024; 15:3987-3995. [PMID: 38573308 DOI: 10.1021/acs.jpclett.4c00529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2024]
Abstract
The nanocrystal-ligand boundaries of colloidal quantum dots (QDs) mediate charge and energy transfer processes that underpin photochemical and photocatalytic transformations at their surfaces. We used time-resolved infrared spectroscopy combined with transient electronic spectroscopy to probe vibrational modes of the carboxylate anchoring groups of stearate ligands attached to cadmium selenide (CdSe) QDs that were optically excited in solid nanocrystal films. The vibrational frequencies of surface-bonded carboxylate groups revealed their interactions with surface-localized holes in the excited states of the QDs. We also observed transient and reversible photoinduced ligand detachment from CdSe nanocrystals within their excited state lifetime. By probing both surface charge distributions and ligand dynamics on QDs in their excited states, we open a pathway to explore how the nanocrystal-ligand boundary can be understood and controlled for the design of QD architectures that most effectively drive charge transfer processes in solar energy harvesting and photoredox catalysis applications.
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Affiliation(s)
- McKenna N Grega
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Jianing Gan
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Muhammad Noman
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - John B Asbury
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Intercollege Materials Science and Engineering Program, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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2
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Deore JP, De M. Semiconductor Quantum Dots Act as Photocatalysts for Carbon-Carbon Bond Formation: Selective Functionalization of Xanthene's 9H Position. J Org Chem 2023; 88:16292-16301. [PMID: 37978938 DOI: 10.1021/acs.joc.3c01801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2023]
Abstract
The potential of CdSe, CdS, MoS2, and WS2 QDs as semiconductor photocatalysts for selective functionalization of the xanthene 9H position through carbon-carbon bond formation has been investigated. Our study reveals valuable insights into the energy-transfer and electron-transfer pathways involved in these reactions, as well as the radical polar crossover (RPC) and triplet-to-triplet energy transfer (TTEnT) processes. Notably, this approach offers a range of intriguing features, including visible-light-mediated processes, inexpensive catalytic systems, mild reaction conditions, broad substrate scope, unfunctionalized starting materials, and suitability for gram-scale synthesis. This study makes a significant contribution to the newly emerging field of QD-catalyzed reactions, paving the way for future explorations.
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Affiliation(s)
- Jiteshkumar P Deore
- Department of Organic Chemistry, Indian Institute of Science, Bengaluru 560012, India
| | - Mrinmoy De
- Department of Organic Chemistry, Indian Institute of Science, Bengaluru 560012, India
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3
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Deore JP, De M. Synthesis of biologically important tetrahydroisoquinoline (THIQ) motifs using quantum dot photocatalyst and evaluation of their anti-bacterial activity. Org Biomol Chem 2023; 21:9049-9053. [PMID: 37936558 DOI: 10.1039/d3ob01305g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2023]
Abstract
Our study introduces an efficient photocatalytic approach for synthesizing biologically significant C1-substituted tetrahydroisoquinoline (THIQ) motifs, employing WS2 quantum dots (QDs) as catalysts. This method enables the formation of C-C and C-P bonds at the C1 position of the THIQ motif. The resulting compounds exhibit substantial antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA) bacteria, with low minimum inhibitory concentration (MIC) values. Notably, the WS2 QD catalyst demonstrates recyclability and suitability for gram-scale reactions, underscoring the sustainability and scalability of our approach. Overall, our research presents a versatile and cost-effective strategy for synthesizing C1-substituted THIQ derivatives, highlighting their potential as novel therapeutic agents in biology and medicinal chemistry.
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Affiliation(s)
- Jiteshkumar P Deore
- Department of Organic Chemistry, Indian Institute of Science, Bangalore-560012, India.
| | - Mrinmoy De
- Department of Organic Chemistry, Indian Institute of Science, Bangalore-560012, India.
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4
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Dones Lassalle CY, Kelm JE, Dempsey JL. Characterizing the Semiconductor Nanocrystal Surface through Chemical Reactivity. Acc Chem Res 2023. [PMID: 37307510 DOI: 10.1021/acs.accounts.3c00125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
ConspectusMany desirable and undesirable properties of semiconductor nanocrystals (NCs) can be traced to the NC surface due to the large surface-to-volume ratio. Therefore, precise control of the NC surface is imperative to achieve NCs with the desired qualities. Ligand-specific reactivity and surface heterogeneity make it difficult to accurately control and tune the NC surface. Without a molecular-level appreciation of the NC surface chemistry, modulating the NC surface is impossible and the risk of introducing deleterious surface defects is imminent. To gain a more comprehensive understanding of the surface reactivity, we have utilized a variety of spectroscopic techniques and analytical methods in concert.This Account describes our use of robust characterization techniques and ligand exchange reactions in effort to establish a molecular-level understanding of NC surface reactivity. The utility of NCs in target applications such as catalysis and charge transfer hangs on precise tunability of NC ligands. Modulating the NC surface requires the necessary tools to monitor chemical reactions. One commonly utilized analytical method to achieve targeted surface compositions is 1H nuclear magnetic resonance (NMR) spectroscopy. Here we describe our use of 1H NMR spectroscopy to monitor chemical reactions at CdSe and PbS NC surfaces to identify ligand specific reactivity. However, seemingly straightforward ligand exchange reactions can vary widely depending on the NC materials and anchoring group. Some non-native X-type ligands will irreversibly displace native ligands. Other ligands exist in equilibrium with native ligands. Depending on the application, it is important to understand the nature of exchange reactions. This level of understanding can be obtained by extracting exchange ratios, exchange equilibrium, and reaction mechanism information from 1H NMR spectroscopy to establish precise NC reactivity.Reactivity that occurs through multiple, parallel ligand exchange mechanisms can involve both the liberation of metal-based Z-type ligands in addition to reactivity of X-type ligands. In these reactions, 1H NMR spectroscopy fails to discern between an X-type oleate or a Z-type Pb(oleate)2 because only the alkene resonance of the organic constituent is probed by this method. Multiple, parallel reaction pathways occur when thiol ligands are introduced to oleate-capped PbS NCs. This necessitated the use of synergistic characterization methods including 1H NMR spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and inductively coupled plasma mass spectrometry (ICP-MS) to characterize both surface-bound and liberated ligands.Similar analytical methods have been employed to probe the NC topology, which is an important, but often overlooked, component to NC reactivity given the facet-specific reactivity of PbS NCs. Through the tandem use of NMR spectroscopy and ICP-MS, we have monitored the liberation of Pb(oleate)2 as an L-type ligand is titrated to the NC to determine the quantity and equilibrium of Z-type ligands. By studying a variety of NC sizes, we correlated the number of liberated ligands with the size-dependent topology of PbS NCs.Lastly, we incorporate redox-active chemical probes into our toolbox to study NC surface defects. We describe how the site-specific reactivity and relative energetics of redox-active surface-based defects are elucidated using redox probes and show that this reactivity is highly dependent on the surface composition. This Account is designed to encourage readers to consider the necessary characterization techniques needed establish a molecular-level understanding of NC surfaces in their own work.
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Affiliation(s)
- Christian Y Dones Lassalle
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, United States
| | - Jennica E Kelm
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, United States
| | - Jillian L Dempsey
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, United States
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5
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Sanmartín-Matalobos J, Bermejo-Barrera P, Aboal-Somoza M, Fondo M, García-Deibe AM, Corredoira-Vázquez J, Alves-Iglesias Y. Semiconductor Quantum Dots as Target Analytes: Properties, Surface Chemistry and Detection. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:2501. [PMID: 35889725 PMCID: PMC9318497 DOI: 10.3390/nano12142501] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2022] [Revised: 07/17/2022] [Accepted: 07/19/2022] [Indexed: 02/04/2023]
Abstract
Since the discovery of Quantum Dots (QDs) by Alexey I. Ekimov in 1981, the interest of researchers in that particular type of nanomaterials (NMs) with unique optical and electrical properties has been increasing year by year. Thus, since 2009, the number of scientific articles published on this topic has not been less than a thousand a year. The increasing use of QDs due to their biomedical, pharmaceutical, biological, photovoltaics or computing applications, as well as many other high-tech uses such as for displays and solid-state lighting (SSL), has given rise to a considerable number of studies about its potential toxicity. However, there are a really low number of reported studies on the detection and quantification of QDs, and these include ICP-MS and electrochemical analysis, which are the most common quantification techniques employed for this purpose. The knowledge of chemical phenomena occurring on the surface of QDs is crucial for understanding the interactions of QDs with species dissolved in the dispersion medium, while it paves the way for a widespread use of chemosensors to facilitate its detection. Keeping in mind both human health and environmental risks of QDs as well as the scarcity of analytical techniques and methodological approaches for their detection, the adaptation of existing techniques and methods used with other NMs appears necessary. In order to provide a multidisciplinary perspective on QD detection, this review focused on three interrelated key aspects of QDs: properties, surface chemistry and detection.
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Affiliation(s)
- Jesús Sanmartín-Matalobos
- Coordination and Supramolecular Chemistry Group (SupraMetal), Department of Inorganic Chemistry, Faculty of Chemistry, Institute of Materials (iMATUS), Universidade de Santiago de Compostela, Avenida das Ciencias s/n, 15782 Santiago de Compostela, Spain; (M.F.); (J.C.-V.); (Y.A.-I.)
| | - Pilar Bermejo-Barrera
- Trace Element, Speciation and Spectroscopy Group (GETEE), Department of Analytical Chemistry, Nutrition and Bromatology, Faculty of Chemistry, Institute of Materials (iMATUS), Universidade de Santiago de Compostela, Avenida das Ciencias s/n, 15782 Santiago de Compostela, Spain; (P.B.-B.); (M.A.-S.)
| | - Manuel Aboal-Somoza
- Trace Element, Speciation and Spectroscopy Group (GETEE), Department of Analytical Chemistry, Nutrition and Bromatology, Faculty of Chemistry, Institute of Materials (iMATUS), Universidade de Santiago de Compostela, Avenida das Ciencias s/n, 15782 Santiago de Compostela, Spain; (P.B.-B.); (M.A.-S.)
| | - Matilde Fondo
- Coordination and Supramolecular Chemistry Group (SupraMetal), Department of Inorganic Chemistry, Faculty of Chemistry, Institute of Materials (iMATUS), Universidade de Santiago de Compostela, Avenida das Ciencias s/n, 15782 Santiago de Compostela, Spain; (M.F.); (J.C.-V.); (Y.A.-I.)
| | - Ana M. García-Deibe
- Coordination and Supramolecular Chemistry Group (SupraMetal), Department of Inorganic Chemistry, Faculty of Chemistry, Institute of Materials (iMATUS), Universidade de Santiago de Compostela, Avenida das Ciencias s/n, 15782 Santiago de Compostela, Spain; (M.F.); (J.C.-V.); (Y.A.-I.)
| | - Julio Corredoira-Vázquez
- Coordination and Supramolecular Chemistry Group (SupraMetal), Department of Inorganic Chemistry, Faculty of Chemistry, Institute of Materials (iMATUS), Universidade de Santiago de Compostela, Avenida das Ciencias s/n, 15782 Santiago de Compostela, Spain; (M.F.); (J.C.-V.); (Y.A.-I.)
| | - Yeneva Alves-Iglesias
- Coordination and Supramolecular Chemistry Group (SupraMetal), Department of Inorganic Chemistry, Faculty of Chemistry, Institute of Materials (iMATUS), Universidade de Santiago de Compostela, Avenida das Ciencias s/n, 15782 Santiago de Compostela, Spain; (M.F.); (J.C.-V.); (Y.A.-I.)
- Trace Element, Speciation and Spectroscopy Group (GETEE), Department of Analytical Chemistry, Nutrition and Bromatology, Faculty of Chemistry, Institute of Materials (iMATUS), Universidade de Santiago de Compostela, Avenida das Ciencias s/n, 15782 Santiago de Compostela, Spain; (P.B.-B.); (M.A.-S.)
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6
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Das D, Saha M, Das AR. Synthesis, properties and catalysis of quantum dots in C–C and C-heteroatom bond formations. PHYSICAL SCIENCES REVIEWS 2022. [DOI: 10.1515/psr-2021-0093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Luminescent quantum dots (QDs) represent a new form of carbon nanomaterials which have gained widespread attention in recent years, especially in the area of chemical sensing, bioimaging, nanomedicine, solar cells, light-emitting diode (LED), and electrocatalysis. Their extremely small size renders some unusual properties such as quantum confinement effects, good surface binding properties, high surface‐to‐volume ratios, broad and intense absorption spectra in the visible region, optical and electronic properties different from those of bulk materials. Apart from, during the past few years, QDs offer new and versatile ways to serve as photocatalysts in organic synthesis. Quantum dots (QD) have band gaps that could be nicely controlled by a number of factors in a complicated way, mentioned in the article. Processing, structure, properties and applications are also reviewed for semiconducting quantum dots. Overall, this review aims to summarize the recent innovative applications of QD or its modified nanohybrid as efficient, robust, photoassisted redox catalysts in C–C and C-heteroatom bond forming reactions. The recent structural modifications of QD or its core structure in the development of new synthetic methodologies are also highlighted. Following a primer on the structure, properties, and bio-functionalization of QDs, herein selected examples of QD as a recoverable sustainable nanocatalyst in various green media are embodied for future reference.
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Affiliation(s)
- Dwaipayan Das
- Department of Chemistry , University of Calcutta , Kolkata 700009 , India
| | - Moumita Saha
- Department of Chemistry , University of Calcutta , Kolkata 700009 , India
| | - Asish. R. Das
- Department of Chemistry , University of Calcutta , Kolkata 700009 , India
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7
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Milam A, Wasdin PT, Turner H, Salyards ME, Clay A, McPhail MR. Quantum dot thin film imaging enables in situ, benchtop analysis of ligand exchange at the solution-film interface. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.127457] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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8
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Kennehan ER, Munson KT, Grieco C, Doucette GS, Marshall AR, Beard MC, Asbury JB. Influence of Ligand Structure on Excited State Surface Chemistry of Lead Sulfide Quantum Dots. J Am Chem Soc 2021; 143:13824-13834. [PMID: 34420309 DOI: 10.1021/jacs.1c06248] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The ligand-nanocrystal boundaries of colloidal quantum dots (QDs) mediate the primary energy and electron transfer processes that underpin photochemical and photocatalytic transformations at their surfaces. We use mid-infrared transient absorption spectroscopy to reveal the influence that ligand structure and bonding to nanocrystal surfaces have on the changes of the excited state surface chemistry of this boundary in PbS QDs and the corresponding impact on charge transfer processes between nanocrystals. We demonstrate that oleate ligands undergo marked changes in their bonding to surfaces in the excitonic excited states of the nanocrystals, indicating that oleate passivated PbS surfaces undergo significant structural changes following photoexcitation. These changes can impact the surface mobility of the ligands and the ability of redox shuttles to approach the nanocrystal surfaces to undergo charge transfer in photocatalytic reactions. In contrast, markedly different transient vibrational features are observed in iodide/mercaptoproprionic acid passivated PbS QD films that result from charge transfer between neighboring nanocrystals and localization of holes at the nanocrystal surfaces near MPA ligands. This ability to distinguish the influence that excitonic excited states vs charge transfer processes have on the surface chemistry of the ligand-nanocrystal boundary lays the groundwork for exploration of how this boundary can be understood and controlled for the design of nanocrystalline materials tailored for specific applications in solar energy harvesting and photocatalytic reactions.
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Affiliation(s)
- Eric R Kennehan
- Magnitude Instruments, State College, Pennsylvania 16803, United States.,Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Kyle T Munson
- Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Christopher Grieco
- Magnitude Instruments, State College, Pennsylvania 16803, United States.,Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Grayson S Doucette
- Intercollege Materials Science and Engineering Program, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Ashley R Marshall
- Chemical and Materials Science, National Renewable Energy Laboratory (NREL), Golden, Colorado 80401, United States.,Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, United States
| | - Matthew C Beard
- Chemical and Materials Science, National Renewable Energy Laboratory (NREL), Golden, Colorado 80401, United States.,Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, United States
| | - John B Asbury
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.,Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.,Intercollege Materials Science and Engineering Program, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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9
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Kennehan ER, Munson KT, Doucette GS, Marshall AR, Beard MC, Asbury JB. Dynamic Ligand Surface Chemistry of Excited PbS Quantum Dots. J Phys Chem Lett 2020; 11:2291-2297. [PMID: 32131595 DOI: 10.1021/acs.jpclett.0c00539] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The ligand shell around colloidal quantum dots mediates the electron and energy transfer processes that underpin their use in optoelectronic and photocatalytic applications. Here, we show that the surface chemistry of carboxylate anchoring groups of oleate ligands passivating PbS quantum dots undergoes significant changes when the quantum dots are excited to their excitonic states. We directly probe the changes of surface chemistry using time-resolved mid-infrared spectroscopy that records the evolution of the vibrational frequencies of carboxylate groups following excitation of the electronic states. The data reveal a reduction of the Pb-O coordination of carboxylate anchoring groups to lead atoms at the quantum dot surfaces. The dynamic surface chemistry of the ligands may increase their surface mobility in the excited state and enhance the ability of molecular species to penetrate the ligand shell to undergo energy and charge transfer processes that depend sensitively on distance.
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Affiliation(s)
- Eric R Kennehan
- Magnitude Instruments, State College, Pennsylvania 16803, United States
| | - Kyle T Munson
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Grayson S Doucette
- Intercollege Materials Science and Engineering Program, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Ashley R Marshall
- Chemical and Materials Science, National Renewable Energy Laboratory (NREL), Golden, Colorado 80401, United States
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, United States
| | - Matthew C Beard
- Chemical and Materials Science, National Renewable Energy Laboratory (NREL), Golden, Colorado 80401, United States
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, United States
| | - John B Asbury
- Magnitude Instruments, State College, Pennsylvania 16803, United States
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Intercollege Materials Science and Engineering Program, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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10
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Maity P, Ghosh HN. Strategies for extending charge separation in colloidal nanostructured quantum dot materials. Phys Chem Chem Phys 2019; 21:23283-23300. [PMID: 31621729 DOI: 10.1039/c9cp03551f] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Semiconductor colloidal metal chalcogenides (II-VI) in the form of quantum dots (QDs) and different heterostructures (core/shell, alloys, etc.) are of extensive interest in scientific research for both a fundamental understanding and technological applications because of their quantized size and different optical properties; however, due to their small size, the exciton (bound electron and hole) experiences a strong Coulombic attraction, which has a remarkable impact on the charge separation and photophysical properties of QDs. Thus, to achieve an efficient charge separation, numerous attempts have been made via the formation of different heterostructures, QD/molecular adsorbate (either organic or inorganic) assemblies, etc. These hybrid materials ameliorated the absorption of the incident light as well as charge separation. This article reviews the strategies for extending charge separation in these colloidal nanocrystals (NCs), which is one of the crucial steps to elevate the solar to electrical energy conversion efficiency in a quantum dot-sensitized solar cell (QDSC). The article summarizes the benefits of co-sensitization and experimental shreds of evidence for the multiple charge transfer processes involved in a QDSC. Studies have shown that in the co-sensitization process, prolonged charge separation occurs via the dual behavior of the molecular adsorbate, sensitization (electron injection) and capture of holes from photoexcited QDs. This perspective emphases band edge engineering and control of charge carrier dynamics in various core/shell structures. The impact of colloidal alloy NCs on charge separation and interesting photophysical properties was recapitulated via the steady-state and time-resolved photoluminescence (PL) and femtosecond transient absorption spectroscopic techniques. Finally, the prolonged lifetime and extent of charge separation for these hybrid NCs (or the composites) assisted in the development of a better light harvester as compared to the case of their pure counterparts.
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Affiliation(s)
- Partha Maity
- Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Homi Bhabha National Institute, Mumbai-400085, India.
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11
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Arcudi F, Westmoreland DE, Weiss EA. Colloidally Stable CdS Quantum Dots in Water with Electrostatically Stabilized Weak-Binding, Sulfur-Free Ligands. Chemistry 2019; 25:14469-14474. [PMID: 31486120 DOI: 10.1002/chem.201903908] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Indexed: 01/19/2023]
Abstract
Colloidal quantum dot (QD) photocatalysts have the electrochemical and optical properties to be highly effective for a range of redox reactions. QDs are proven photo-redox catalysts for a variety of reactions in organic solvents but are less prominent for aqueous reactions. Aqueous QD photocatalysts require hydrophilic ligand shells that provide long-term colloidal stability but are not so tight-binding as to prevent catalytic substrates from accessing the QD surface. Common thiolate ligands, which also poison many co-catalysts and undergo photo-oxidative desorption, are therefore often not an option. This paper describes a framework for the design of water-solubilizing ligands that are in dynamic exchange on and off the QD surface, but still provide long-term colloidal stability to CdS QDs. The binding affinity and inter-ligand electrostatic interactions of a bifunctional ligand, aminoethyl phosphonic acid (AEP), are tuned with the pH of the dispersion. The key to colloidal stability is electrostatic stabilization of the monolayer. This work demonstrates a means of mimicking the stabilizing power of a thiolate-bound ligand with a zwitterionic tail group, but without the thiolate binding group.
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Affiliation(s)
- Francesca Arcudi
- Department of Chemistry, Northwestern University, 2145 Sheridan Rd., Evanston, IL-60208-3113, USA
| | - Dana Emily Westmoreland
- Department of Chemistry, Northwestern University, 2145 Sheridan Rd., Evanston, IL-60208-3113, USA
| | - Emily Allyn Weiss
- Department of Chemistry, Northwestern University, 2145 Sheridan Rd., Evanston, IL-60208-3113, USA
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12
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Moroz P, Jin Z, Sugiyama Y, Lara D, Razgoniaeva N, Yang M, Kholmicheva N, Khon D, Mattoussi H, Zamkov M. Competition of Charge and Energy Transfer Processes in Donor-Acceptor Fluorescence Pairs: Calibrating the Spectroscopic Ruler. ACS NANO 2018; 12:5657-5665. [PMID: 29883087 DOI: 10.1021/acsnano.8b01451] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Sensing strategies utilizing Förster resonance energy transfer (FRET) are widely used for probing biological phenomena. FRET sensitivity to the donor-acceptor distance makes it ideal for measuring the concentration of a known analyte or determining the spatial separation between fluorescent labels in a macromolecular assembly. The difficulty lies in extracting the FRET efficiency from the acceptor-induced quenching of the donor emission, which may contain a significant non-FRET contribution. Here, we demonstrate a general spectroscopic approach for differentiating between charge transfer and energy transfer (ET) processes in donor-acceptor assemblies and apply the developed method for unravelling the FRET/non-FRET contributions in cyanine dye-semiconductor quantum dot (QD) constructs. The present method relies on correlating the amplitude of the acceptor emission to specific changes in the donor excitation profile in order to extract ET-only transfer efficiencies. Quenching of the donor emission is then utilized to determine the non-ET component, tentatively attributed to the charge transfer. We observe that the latter accounts for 50-99% of donor emission quenching in QD-Cy5 and QD-Cy7 systems, stressing the importance of determining the non-FRET efficiency in a spectroscopic ruler and other FRET-based sensing applications.
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Affiliation(s)
| | - Zhicheng Jin
- Department of Chemistry and Biochemistry , Florida State University , Tallahassee , Florida 32303 , United States
| | - Yuya Sugiyama
- Department of Chemistry and Biochemistry , Florida State University , Tallahassee , Florida 32303 , United States
| | - D'Andree Lara
- Department of Chemistry and Biochemistry , St. Mary's University , San Antonio , Texas 78228 , United States
| | | | | | | | - Dmitriy Khon
- Department of Chemistry and Biochemistry , St. Mary's University , San Antonio , Texas 78228 , United States
| | - Hedi Mattoussi
- Department of Chemistry and Biochemistry , Florida State University , Tallahassee , Florida 32303 , United States
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13
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He C, Zhang Z, Wang C, Jiang Y, Weiss EA. Reversible Modulation of the Electrostatic Potential of a Colloidal Quantum Dot through the Protonation Equilibrium of Its Ligands. J Phys Chem Lett 2017; 8:4981-4987. [PMID: 28949145 DOI: 10.1021/acs.jpclett.7b02101] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
This Letter describes the reversible modulation of the electrostatic potential at the interface between a colloidal PbS quantum dot (QD) and solvent, through the protonation equilibrium of the QD's histamine-derivatized dihydrolipoic acid (DHLA) ligand shell. The electrostatic potential is sensitively monitored by the yield of photoinduced electron transfer from the QD to a charged electron acceptor, 9,10-anthraquinone-2-sulfonate (AQ). The permeability of the DHLA coating to the AQ progressively increases as the average degree of protonation of the ligand shell increases from 0 to 92%, as quantified by 1H NMR, upon successive additions of p-toluenesulfonic acid; this increase results in a decrease in the photoluminescence (PL) intensity of the QDs by a factor of 6.7. The increase in permeability is attributable to favorable electrostatic interactions between the ligands and AQ. This work suggests the potential of the combination of near-IR-emitting QDs and molecular quenchers as robust local H+ sensors.
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Affiliation(s)
- Chen He
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Zhengyi Zhang
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Chen Wang
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Yishu Jiang
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Emily A Weiss
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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14
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He C, Nguyen TD, Edme K, Olvera de la Cruz M, Weiss EA. Noncovalent Control of the Electrostatic Potential of Quantum Dots through the Formation of Interfacial Ion Pairs. J Am Chem Soc 2017; 139:10126-10132. [DOI: 10.1021/jacs.7b05501] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Chen He
- Department
of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Trung D. Nguyen
- Department
of Materials Science and Engineering, Northwestern University, 2220 Campus
Drive, Evanston, Illinois 60208-3108, United States
| | - Kedy Edme
- Department
of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Monica Olvera de la Cruz
- Department
of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
- Department
of Materials Science and Engineering, Northwestern University, 2220 Campus
Drive, Evanston, Illinois 60208-3108, United States
| | - Emily A. Weiss
- Department
of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
- Department
of Materials Science and Engineering, Northwestern University, 2220 Campus
Drive, Evanston, Illinois 60208-3108, United States
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15
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Li JX, Ye C, Li XB, Li ZJ, Gao XW, Chen B, Tung CH, Wu LZ. A Redox Shuttle Accelerates O 2 Evolution of Photocatalysts Formed In Situ under Visible Light. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1606009. [PMID: 28218472 DOI: 10.1002/adma.201606009] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 12/15/2016] [Indexed: 06/06/2023]
Abstract
A redox shuttle strategy is demonstrated to be a promising approach to accelerate hole removal for efficient O2 production with mesoporous graphitic carbon nitride, WO3 , BiVO4 , NiTi-LDH, and Ag3 PO4 water-oxidation catalysts under visible-light irradiation.
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Affiliation(s)
- Jia-Xin Li
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Chen Ye
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Xu-Bing Li
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Zhi-Jun Li
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Xue-Wang Gao
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Bin Chen
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Chen-Ho Tung
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Li-Zhu Wu
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100190, P. R. China
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16
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Zhang Z, Edme K, Lian S, Weiss EA. Enhancing the Rate of Quantum-Dot-Photocatalyzed Carbon–Carbon Coupling by Tuning the Composition of the Dot’s Ligand Shell. J Am Chem Soc 2017; 139:4246-4249. [DOI: 10.1021/jacs.6b13220] [Citation(s) in RCA: 96] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Zhengyi Zhang
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Kedy Edme
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Shichen Lian
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Emily A. Weiss
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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17
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Caputo JA, Frenette LC, Zhao N, Sowers KL, Krauss TD, Weix DJ. General and Efficient C–C Bond Forming Photoredox Catalysis with Semiconductor Quantum Dots. J Am Chem Soc 2017; 139:4250-4253. [DOI: 10.1021/jacs.6b13379] [Citation(s) in RCA: 146] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Jill A. Caputo
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, United States
| | - Leah C. Frenette
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, United States
| | - Norman Zhao
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, United States
| | - Kelly L. Sowers
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, United States
| | - Todd D. Krauss
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, United States
| | - Daniel J. Weix
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, United States
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18
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Moro F, Turyanska L, Wilman J, Williams HEL, Fielding AJ, Patanè A. Surface Sensing of Quantum Dots by Electron Spins. NANO LETTERS 2016; 16:6343-6348. [PMID: 27624349 DOI: 10.1021/acs.nanolett.6b02727] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The nanoscale design of quantum dots (QDs) requires advanced analytical techniques. However, those that are commonly used do not have sufficient sensitivity or spatial resolution. Here, we use magnetic resonance techniques combined with paramagnetic Mn impurities in PbS QDs for sensitive probing of the QD surface and environment. In particular, we reveal inequivalent proton spin relaxations of the capping ligands and solvent molecules, strengths and anisotropies of the Mn nuclear spin interactions, and Mn nuclei distances with ∼1 Å sensitivity. These findings demonstrate the potential of magnetically doped QDs as sensitive magnetic nanoprobes and the use of electron spins for surface sensing.
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Affiliation(s)
- Fabrizio Moro
- School of Physics and Astronomy, The University of Nottingham , Nottingham NG7 2RD, United Kingdom
| | - Lyudmila Turyanska
- School of Physics and Astronomy, The University of Nottingham , Nottingham NG7 2RD, United Kingdom
- School of Chemistry, University of Lincoln , Lincoln LN6 7DL, United Kingdom
| | - James Wilman
- School of Physics and Astronomy, The University of Nottingham , Nottingham NG7 2RD, United Kingdom
| | - Huw E L Williams
- Centre for Biomolecular Sciences, School of Chemistry, The University of Nottingham , Nottingham NG7 2RD, United Kingdom
| | - Alistair J Fielding
- The Photon Science Institute and School of Chemistry, University of Manchester , Manchester M13 9PL, United Kingdom
| | - Amalia Patanè
- School of Physics and Astronomy, The University of Nottingham , Nottingham NG7 2RD, United Kingdom
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19
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Harris RD, Bettis Homan S, Kodaimati M, He C, Nepomnyashchii AB, Swenson NK, Lian S, Calzada R, Weiss EA. Electronic Processes within Quantum Dot-Molecule Complexes. Chem Rev 2016; 116:12865-12919. [PMID: 27499491 DOI: 10.1021/acs.chemrev.6b00102] [Citation(s) in RCA: 171] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The subject of this review is the colloidal quantum dot (QD) and specifically the interaction of the QD with proximate molecules. It covers various functions of these molecules, including (i) ligands for the QDs, coupled electronically or vibrationally to localized surface states or to the delocalized states of the QD core, (ii) energy or electron donors or acceptors for the QDs, and (iii) structural components of QD assemblies that dictate QD-QD or QD-molecule interactions. Research on interactions of ligands with colloidal QDs has revealed that ligands determine not only the excited state dynamics of the QD but also, in some cases, its ground state electronic structure. Specifically, the article discusses (i) measurement of the electronic structure of colloidal QDs and the influence of their surface chemistry, in particular, dipolar ligands and exciton-delocalizing ligands, on their electronic energies; (ii) the role of molecules in interfacial electron and energy transfer processes involving QDs, including electron-to-vibrational energy transfer and the use of the ligand shell of a QD as a semipermeable membrane that gates its redox activity; and (iii) a particular application of colloidal QDs, photoredox catalysis, which exploits the combination of the electronic structure of the QD core and the chemistry at its surface to use the energy of the QD excited state to drive chemical reactions.
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Affiliation(s)
- Rachel D Harris
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Stephanie Bettis Homan
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Mohamad Kodaimati
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Chen He
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | | | - Nathaniel K Swenson
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Shichen Lian
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Raul Calzada
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Emily A Weiss
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
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20
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Lim SJ, Ma L, Schleife A, Smith AM. Quantum Dot Surface Engineering: Toward Inert Fluorophores with Compact Size and Bright, Stable Emission. Coord Chem Rev 2016; 320-321:216-237. [PMID: 28344357 PMCID: PMC5363762 DOI: 10.1016/j.ccr.2016.03.012] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The surfaces of colloidal nanocrystals are complex interfaces between solid crystals, coordinating ligands, and liquid solutions. For fluorescent quantum dots, the properties of the surface vastly influence the efficiency of light emission, stability, and physical interactions, and thus determine their sensitivity and specificity when they are used to detect and image biological molecules. But after more than 30 years of study, the surfaces of quantum dots remain poorly understood and continue to be an important subject of both experimental and theoretical research. In this article, we review the physics and chemistry of quantum dot surfaces and describe approaches to engineer optimal fluorescent probes for applications in biomolecular imaging and sensing. We describe the structure and electronic properties of crystalline facets, the chemistry of ligand coordination, and the impact of ligands on optical properties. We further describe recent advances in compact coatings that have significantly improved their properties by providing small hydrodynamic size, high stability and fluorescence efficiency, and minimal nonspecific interactions with cells and biological molecules. While major progress has been made in both basic and applied research, many questions remain in the chemistry and physics of quantum dot surfaces that have hindered key breakthroughs to fully optimize their properties.
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Affiliation(s)
- Sung Jun Lim
- Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Liang Ma
- Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - André Schleife
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Andrew M. Smith
- Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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21
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He C, Weinberg DJ, Nepomnyashchii AB, Lian S, Weiss EA. Control of the Redox Activity of PbS Quantum Dots by Tuning Electrostatic Interactions at the Quantum Dot/Solvent Interface. J Am Chem Soc 2016; 138:8847-54. [PMID: 27341608 DOI: 10.1021/jacs.6b03970] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
This paper describes the control of electron exchange between a colloidal PbS quantum dot (QD) and a negatively charged small molecule (9,10-anthraquinone-2-sulfonic acid sodium salt, AQ), through tuning of the charge density in the ligand shell of the QD, within an aqueous dispersion. The probability of electron exchange, measured through steady-state and time-resolved optical spectroscopy, is directly related to the permeability of the protective ligand shell, which is a mixed monolayer of negatively charged 6-mercaptohexanoate (MHA) and neutral 6-mercaptohexanol (MHO), to AQ. The composition of the ligand shell is quantitatively characterized by (1)H NMR. The dependence of the change in Gibbs free energy, ΔGobs, for the diffusion of AQ through the charged ligand shell and its subsequent adsorption to the QD surface is well-described with an electrostatic double-layer model for the QD/solvent interface. Fits of the optical data to this model yield an increase in the free energy for transfer of AQ from bulk solution to the surface of the QD (where it exchanges electrons with the QD) of 154 J/mol upon introduction of each additional charged MHA ligand to the ligand shell. This work expands the set of chemical parameters useful for controlling the redox activity of QDs via surface modification and suggests strategies for the use of nanoparticles for molecular and biomolecular recognition within chemically complex environments and for design of chemically stable nanoparticles for aqueous photocatalytic systems.
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Affiliation(s)
- Chen He
- Department of Chemistry, Northwestern University , 2145 Sheridan Rd., Evanston, Illinois 60208-3113, United States
| | - David J Weinberg
- Department of Chemistry, Northwestern University , 2145 Sheridan Rd., Evanston, Illinois 60208-3113, United States
| | - Alexander B Nepomnyashchii
- Department of Chemistry, Northwestern University , 2145 Sheridan Rd., Evanston, Illinois 60208-3113, United States
| | - Shichen Lian
- Department of Chemistry, Northwestern University , 2145 Sheridan Rd., Evanston, Illinois 60208-3113, United States
| | - Emily A Weiss
- Department of Chemistry, Northwestern University , 2145 Sheridan Rd., Evanston, Illinois 60208-3113, United States
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22
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McPhail MR, Campbell GP, Bedzyk MJ, Weiss EA. Structural Features of PbS Nanocube Monolayers upon Treatment with Mono- and Dicarboxylic Acids and Thiols at a Liquid-Air Interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:6666-6673. [PMID: 27297625 DOI: 10.1021/acs.langmuir.6b01444] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This paper describes the ordering of PbS nanocubes (NCs) within free-standing monolayers (suspended on acetonitrile), upon exchanging the native oleate ligands for a series of thiolate and carboxylate ligands at the liquid-air interface. Treatment with either carboxylic acids or thiols effectively decreases the inter-NC separation of nearest-neighbor particles without etching the NC surface. Dicarboxylic acids and dithiols bridge neighboring NCs with an interparticle separation that is consistent with fully extended, bridging ligands. Monocarboxylic acids and monothiols separate NCs by an amount governed by their length, with long-chain ligands showing significant intercalation. (1)H NMR spectroscopy shows carboxylic acids are more effective at replacing the native oleate than are thiols, which we ascribe to the lower pKa values of carboxylic acids. The fast exchange that occurs upon treatment with monocarboxylic acids kinetically traps the clusters of particles in nonclosed packed geometries, so monolayers treated with monocarboxylic acids are, on average, less ordered than those treated with monothiols. Ex situ electron microscopy and grazing incidence small-angle X-ray scattering (GISAXS) analyses of deposited films on Si/SiO2 substrates show that NCs exchanged with nonbridging ligands pack more efficiently at long length scales than do NCs exchanged with bridging ligands, due primarily to the creation of defects within the NC lattice in response to the rigidity of the bridging ligand.
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Affiliation(s)
- Martin R McPhail
- Department of Chemistry, ‡Department of Materials Science and Engineering, and §Department of Physics and Astronomy, Northwestern University , Evanston, Illinois 60208-3113, United States
| | - Gavin P Campbell
- Department of Chemistry, ‡Department of Materials Science and Engineering, and §Department of Physics and Astronomy, Northwestern University , Evanston, Illinois 60208-3113, United States
| | - Michael J Bedzyk
- Department of Chemistry, ‡Department of Materials Science and Engineering, and §Department of Physics and Astronomy, Northwestern University , Evanston, Illinois 60208-3113, United States
| | - Emily A Weiss
- Department of Chemistry, ‡Department of Materials Science and Engineering, and §Department of Physics and Astronomy, Northwestern University , Evanston, Illinois 60208-3113, United States
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23
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Kunal P, Li H, Dewing BL, Zhang L, Jarvis K, Henkelman G, Humphrey SM. Microwave-Assisted Synthesis of PdxAu100–x Alloy Nanoparticles: A Combined Experimental and Theoretical Assessment of Synthetic and Compositional Effects upon Catalytic Reactivity. ACS Catal 2016. [DOI: 10.1021/acscatal.6b01014] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Pranaw Kunal
- Department
of Chemistry, The University of Texas at Austin, 6.336 Norman Hackerman Building, 100 E 24th St. Stop A1590, Austin, Texas 78712-1224, United States
| | - Hao Li
- Department
of Chemistry, The University of Texas at Austin, 6.336 Norman Hackerman Building, 100 E 24th St. Stop A1590, Austin, Texas 78712-1224, United States
| | - Beth L. Dewing
- Department
of Chemistry, The University of Texas at Austin, 6.336 Norman Hackerman Building, 100 E 24th St. Stop A1590, Austin, Texas 78712-1224, United States
| | - Liang Zhang
- Department
of Chemistry, The University of Texas at Austin, 6.336 Norman Hackerman Building, 100 E 24th St. Stop A1590, Austin, Texas 78712-1224, United States
| | - Karalee Jarvis
- Texas
Materials Institute, The University of Texas at Austin, 204 E. Dean
Keeton St. Stop C2201, Austin, Texas 78712-1591, United States
| | - Graeme Henkelman
- Department
of Chemistry, The University of Texas at Austin, 6.336 Norman Hackerman Building, 100 E 24th St. Stop A1590, Austin, Texas 78712-1224, United States
| | - Simon M. Humphrey
- Department
of Chemistry, The University of Texas at Austin, 6.336 Norman Hackerman Building, 100 E 24th St. Stop A1590, Austin, Texas 78712-1224, United States
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24
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Johnston KA, Smith AM, Marbella LE, Millstone JE. Impact of As-Synthesized Ligands and Low-Oxygen Conditions on Silver Nanoparticle Surface Functionalization. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:3820-3826. [PMID: 27077550 DOI: 10.1021/acs.langmuir.6b00232] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Here, we compare the ligand exchange behaviors of silver nanoparticles synthesized in the presence of two different surface capping agents: poly(vinylpyrrolidone) (MW = 10 or 40 kDa) or trisodium citrate, and under either ambient or low-oxygen conditions. In all cases, we find that the polymer capping agent exhibits features of a weakly bound ligand, producing better ligand exchange efficiencies with an incoming thiolated ligand compared to citrate. The polymer capping agent also generates nanoparticles that are more susceptible to reactions with oxygen during both synthesis and ligand exchange. The influence of the original ligand on the outcome of ligand exchange reactions with an incoming thiolated ligand highlights important aspects of silver nanoparticle surface chemistry, crucial for applications ranging from photocatalysis to antimicrobials.
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Affiliation(s)
- Kathryn A Johnston
- Department of Chemistry, University of Pittsburgh , 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260, United States
| | - Ashley M Smith
- Department of Chemistry, University of Pittsburgh , 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260, United States
| | - Lauren E Marbella
- Department of Chemistry, University of Pittsburgh , 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260, United States
| | - Jill E Millstone
- Department of Chemistry, University of Pittsburgh , 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260, United States
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25
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Li XB, Liu B, Wen M, Gao YJ, Wu HL, Huang MY, Li ZJ, Chen B, Tung CH, Wu LZ. Hole-Accepting-Ligand-Modified CdSe QDs for Dramatic Enhancement of Photocatalytic and Photoelectrochemical Hydrogen Evolution by Solar Energy. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2016; 3:1500282. [PMID: 27774400 PMCID: PMC5063123 DOI: 10.1002/advs.201500282] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2015] [Revised: 10/16/2015] [Indexed: 05/21/2023]
Abstract
Solar H2 evolution of CdSe QDs can be significantly enhanced simply by introducing a suitable hole-accepting-ligand for achieving efficient hole extraction and transfer at the nanoscale interfaces, which opens an effective pathway for dissociation of excitons to generate long-lived charge separation, thus improving the solar-to-fuel conversion efficiency.
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Affiliation(s)
- Xu-Bing Li
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials Technical Institute of Physics and Chemistry The Chinese Academy of Sciences Beijing 100190 P. R. China
| | - Bin Liu
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials Technical Institute of Physics and Chemistry The Chinese Academy of Sciences Beijing 100190 P. R. China
| | - Min Wen
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials Technical Institute of Physics and Chemistry The Chinese Academy of Sciences Beijing 100190 P. R. China
| | - Yu-Ji Gao
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials Technical Institute of Physics and Chemistry The Chinese Academy of Sciences Beijing 100190 P. R. China
| | - Hao-Lin Wu
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials Technical Institute of Physics and Chemistry The Chinese Academy of Sciences Beijing 100190 P. R. China
| | - Mao-Yong Huang
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials Technical Institute of Physics and Chemistry The Chinese Academy of Sciences Beijing 100190 P. R. China
| | - Zhi-Jun Li
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials Technical Institute of Physics and Chemistry The Chinese Academy of Sciences Beijing 100190 P. R. China
| | - Bin Chen
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials Technical Institute of Physics and Chemistry The Chinese Academy of Sciences Beijing 100190 P. R. China
| | - Chen-Ho Tung
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials Technical Institute of Physics and Chemistry The Chinese Academy of Sciences Beijing 100190 P. R. China
| | - Li-Zhu Wu
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials Technical Institute of Physics and Chemistry The Chinese Academy of Sciences Beijing 100190 P. R. China
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26
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Nepomnyashchii AB, Harris RD, Weiss EA. Composition and Permeability of Oleate Adlayers of CdS Quantum Dots upon Dilution to Photoluminescence-Relevant Concentrations. Anal Chem 2016; 88:3310-6. [DOI: 10.1021/acs.analchem.5b04786] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Alexander B. Nepomnyashchii
- Department
of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Rachel D. Harris
- Department
of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Emily A. Weiss
- Department
of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
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27
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Weinberg DJ, He C, Weiss EA. Control of the Redox Activity of Quantum Dots through Introduction of Fluoroalkanethiolates into Their Ligand Shells. J Am Chem Soc 2016; 138:2319-26. [DOI: 10.1021/jacs.5b13077] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- David J. Weinberg
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Chen He
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Emily A. Weiss
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
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28
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Jensen SC, Homan SB, Weiss EA. Photocatalytic Conversion of Nitrobenzene to Aniline through Sequential Proton-Coupled One-Electron Transfers from a Cadmium Sulfide Quantum Dot. J Am Chem Soc 2016; 138:1591-600. [PMID: 26784531 DOI: 10.1021/jacs.5b11353] [Citation(s) in RCA: 100] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
This paper describes the use of cadmium sulfide quantum dots (CdS QDs) as visible-light photocatalysts for the reduction of nitrobenzene to aniline through six sequential photoinduced, proton-coupled electron transfers. At pH 3.6-4.3, the internal quantum yield of photons-to-reducing electrons is 37.1% over 54 h of illumination, with no apparent decrease in catalyst activity. Monitoring of the QD exciton by transient absorption reveals that, for each step in the catalytic cycle, the sacrificial reductant, 3-mercaptopropionic acid, scavenges the excitonic hole in ∼5 ps to form QD(•-); electron transfer to nitrobenzene or the intermediates nitrosobenzene and phenylhydroxylamine then occurs on the nanosecond time scale. The rate constants for the single-electron transfer reactions are correlated with the driving forces for the corresponding proton-coupled electron transfers. This result suggests, but does not prove, that electron transfer, not proton transfer, is rate-limiting for these reactions. Nuclear magnetic resonance analysis of the QD-molecule systems shows that the photoproduct aniline, left unprotonated, serves as a poison for the QD catalyst by adsorbing to its surface. Performing the reaction at an acidic pH not only encourages aniline to desorb but also increases the probability of protonated intermediates; the latter effect probably ensures that recruitment of protons is not rate-limiting.
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Affiliation(s)
- Stephen C Jensen
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Stephanie Bettis Homan
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Emily A Weiss
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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29
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Olshansky JH, Ding TX, Lee YV, Leone SR, Alivisatos AP. Hole Transfer from Photoexcited Quantum Dots: The Relationship between Driving Force and Rate. J Am Chem Soc 2015; 137:15567-75. [DOI: 10.1021/jacs.5b10856] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jacob H. Olshansky
- Kavli Energy NanoScience Institute, Berkeley, California 94720, United States
| | - Tina X. Ding
- Kavli Energy NanoScience Institute, Berkeley, California 94720, United States
| | | | | | - A. Paul Alivisatos
- Kavli Energy NanoScience Institute, Berkeley, California 94720, United States
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30
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Reeves KG, Schleife A, Correa AA, Kanai Y. Role of Surface Termination on Hot Electron Relaxation in Silicon Quantum Dots: A First-Principles Dynamics Simulation Study. NANO LETTERS 2015; 15:6429-6433. [PMID: 26331672 DOI: 10.1021/acs.nanolett.5b01707] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The role of surface termination on phonon-mediated relaxation of an excited electron in quantum dots was investigated using first-principles simulations. The surface terminations of a silicon quantum dot with hydrogen and fluorine atoms lead to distinctively different relaxation behaviors, and the fluorine termination shows a nontrivial relaxation process. The quantum confined electronic states are significantly affected by the surface of the quantum dot, and we find that a particular electronic state dictates the relaxation behavior through its infrequent coupling to neighboring electronic states. Dynamical fluctuation of this electronic state results in a slow shuttling behavior within the manifold of unoccupied electronic states, controlling the overall dynamics of the excited electron with its characteristic frequency of this shuttling behavior. The present work revealed a unique role of surface termination, dictating the hot electron relaxation process in quantum-confined systems in the way that has not been considered previously.
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Affiliation(s)
- Kyle G Reeves
- Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27514, United States
| | - André Schleife
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign , Champaign, Illinois 61820, United States
| | - Alfredo A Correa
- Condensed Matter and Materials Division, Lawrence Livermore National Laboratory , Livermore, California 94550, United States
| | - Yosuke Kanai
- Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27514, United States
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31
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Aruda KO, Bohlmann Kunz M, Tagliazucchi M, Weiss EA. Temperature-Dependent Permeability of the Ligand Shell of PbS Quantum Dots Probed by Electron Transfer to Benzoquinone. J Phys Chem Lett 2015; 6:2841-2846. [PMID: 26266870 DOI: 10.1021/acs.jpclett.5b01256] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
This paper describes an increase in the yield of collisionally gated photoinduced electron transfer (electron transfer events per collision) from oleate-capped PbS quantum dots (QDs) to benzoquinone (BQ) with increasing temperature (from 0 to 50 °C), due to increased permeability of the oleate adlayer of the QDs to BQ. The same changes in intermolecular structure of the adlayer that increase its permeability to BQ also increase its permeability to the solvent, toluene, resulting in a decrease in viscous drag and an apparent increase in the diffusion coefficient of the QDs, as measured by diffusion-ordered spectroscopy (DOSY) NMR. Comparison of NMR and transient absorption spectra of QDs capped with flexible oleate with those capped with rigid methylthiolate provides evidence that the temperature dependence of the permeability of the oleate ligand shell is due to formation of transient gaps in the adlayer through conformational fluctuations of the ligands.
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Affiliation(s)
- Kenneth O Aruda
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Miriam Bohlmann Kunz
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Mario Tagliazucchi
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Emily A Weiss
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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32
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Acebrón M, Galisteo-López JF, Granados D, López-Ogalla J, Gallego JM, Otero R, López C, Juárez BH. Protective ligand shells for luminescent SiO₂-coated alloyed semiconductor nanocrystals. ACS APPLIED MATERIALS & INTERFACES 2015; 7:6935-45. [PMID: 25756519 DOI: 10.1021/acsami.5b00820] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
SiO2 encapsulation of alloyed CdSeZnS nanocrystals (NCs) shows differences in terms of optical properties and luminescence quantum yield, depending on the surface composition, size, and ligand content. In this work, emphasis has been placed on the fine control required to obtain luminescent SiO2 encapsulated NCs by studying the role of oleic acid (OA), stearic acid (SA), and dodecanethiol (DDT) ligands on the alloyed NCs. While the use of anchored DDT molecules is essential to preserve the optical properties, intercalated OA and SA play a critical role for SiO2 nucleation, as stated by (1)H NMR (including DOSY and NOESY) spectroscopy. These results emphasize the importance of surface chemistry in NCs; it is crucial to control their reactivity, and therefore their impact, in different applications, from optics to biomedicine.
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Affiliation(s)
- María Acebrón
- †Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanoscience), Cantoblanco 28049, Madrid, Spain
| | - Juan F Galisteo-López
- ‡Instituto de Ciencias de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), Calle Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain
| | - Daniel Granados
- †Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanoscience), Cantoblanco 28049, Madrid, Spain
| | - Javier López-Ogalla
- †Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanoscience), Cantoblanco 28049, Madrid, Spain
| | - José M Gallego
- †Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanoscience), Cantoblanco 28049, Madrid, Spain
- ‡Instituto de Ciencias de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), Calle Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain
| | - Roberto Otero
- †Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanoscience), Cantoblanco 28049, Madrid, Spain
- ∥Departamento de Física de la Materia Condensada and Instituto Nicolás Cabrera, Universidad Autónoma de Madrid, 28049 Cantoblanco, Madrid, Spain
| | - Cefe López
- ‡Instituto de Ciencias de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), Calle Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain
| | - Beatriz H Juárez
- †Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanoscience), Cantoblanco 28049, Madrid, Spain
- ⊥Departamento de Química-Física Aplicada, Universidad Autónoma de Madrid, 28049 Cantoblanco, Madrid, Spain
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33
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Singhal P, Ghosh HN. Hot-Hole Extraction from Quantum Dot to Molecular Adsorbate. Chemistry 2015; 21:4405-12. [DOI: 10.1002/chem.201405947] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Indexed: 11/11/2022]
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34
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Lee D, DuBois JL, Kanai Y. Importance of excitonic effect in charge separation at quantum-dot/organic interface: first-principles many-body calculations. NANO LETTERS 2014; 14:6884-6888. [PMID: 25388898 DOI: 10.1021/nl502894b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The staggered alignment of quasiparticle energy levels is widely regarded to be the key criterion necessary for electron-hole charge separation to occur at heterogeneous material interfaces. However, staggered energy levels at nanoscale interfaces, such as those between organic molecules and inorganic quantum dots, do not necessarily imply charge separation across the interface because the excitonic effect is often significant. Using quantum Monte Carlo calculations, we perform a detailed study of the role of the excitonic effects on charge separation across a representative set of interfaces between organic molecules and quantum dots. We find that the exciton binding energy of charge transfer excitons is significantly larger than would be estimated from a simple Coulombic analysis and, at these nanoscale interfaces, can be as significant as that of Frenkel excitons. This implies that charge transfer excitons can act as trap states and facilitate electron-hole recombination instead of charge separation. We conclude that in general, for nanoscale interfaces, high-fidelity quantum many-body calculations are essential for an accurate evaluation of the detailed energetic balance between localized and delocalized excitons and, thus, are crucial for the predictive treatment of interfacial charge separation processes.
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Affiliation(s)
- Donghwa Lee
- Condensed Matter and Materials Division, Lawrence Livermore National Laboratory , Livermore, California 94550, United States
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35
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Algar WR, Stewart MH, Scott AM, Moon WJ, Medintz IL. Quantum dots as platforms for charge transfer-based biosensing: challenges and opportunities. J Mater Chem B 2014; 2:7816-7827. [DOI: 10.1039/c4tb00985a] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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36
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Jin S, Harris RD, Lau B, Aruda KO, Amin VA, Weiss EA. Enhanced rate of radiative decay in CdSe quantum dots upon adsorption of an exciton-delocalizing ligand. NANO LETTERS 2014; 14:5323-5328. [PMID: 25167466 DOI: 10.1021/nl5023699] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
This paper describes the enhancement of the quantum yield of photoluminescence (PL) of CdSe quantum dots (QDs) upon the adsorption of an exciton-delocalizing ligand, phenyldithiocarbamate. Increasing the apparent excitonic radius by only 10% increases the value of the radiative rate constant by a factor of 1.8 and the PL quantum yield by a factor of 2.4. Ligand exchange therefore simultaneously perturbs the confinement energy of charge carriers and enhances the probability of band-edge transitions.
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Affiliation(s)
- Shengye Jin
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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37
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Colloidal, water soluble probes constructed with quantum dots and amphiphilic poly(ferrocenylsilane) for smart redox sensing. Eur Polym J 2014. [DOI: 10.1016/j.eurpolymj.2014.02.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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38
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Tarafder K, Surendranath Y, Olshansky JH, Alivisatos AP, Wang LW. Hole Transfer Dynamics from a CdSe/CdS Quantum Rod to a Tethered Ferrocene Derivative. J Am Chem Soc 2014; 136:5121-31. [DOI: 10.1021/ja500936n] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Kartick Tarafder
- Materials
Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Department
of Physics, BITS-PILANI Hyderabad Campus, Andhra Pradesh 500078, India
| | - Yogesh Surendranath
- Materials
Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
- Kavli Energy Nanosciences Institute, University of California, Berkeley, California 94720, United States
- Miller Institute for Basic Research in Science, University of California, Berkeley, California 94720, United States
| | - Jacob H. Olshansky
- Materials
Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
- Kavli Energy Nanosciences Institute, University of California, Berkeley, California 94720, United States
| | - A. Paul Alivisatos
- Materials
Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
- Kavli Energy Nanosciences Institute, University of California, Berkeley, California 94720, United States
| | - Lin-Wang Wang
- Materials
Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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39
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Anderson NC, Hendricks MP, Choi JJ, Owen JS. Ligand exchange and the stoichiometry of metal chalcogenide nanocrystals: spectroscopic observation of facile metal-carboxylate displacement and binding. J Am Chem Soc 2013; 135:18536-48. [PMID: 24199846 PMCID: PMC4102385 DOI: 10.1021/ja4086758] [Citation(s) in RCA: 430] [Impact Index Per Article: 39.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
We demonstrate that metal carboxylate complexes (L-M(O2CR)2, R = oleyl, tetradecyl, M = Cd, Pb) are readily displaced from carboxylate-terminated ME nanocrystals (ME = CdSe, CdS, PbSe, PbS) by various Lewis bases (L = tri-n-butylamine, tetrahydrofuran, tetradecanol, N,N-dimethyl-n-butylamine, tri-n-butylphosphine, N,N,N',N'-tetramethylbutylene-1,4-diamine, pyridine, N,N,N',N'-tetramethylethylene-1,2-diamine, n-octylamine). The relative displacement potency is measured by (1)H NMR spectroscopy and depends most strongly on geometric factors such as sterics and chelation, although also on the hard/soft match with the cadmium ion. The results suggest that ligands displace L-M(O2CR)2 by cooperatively complexing the displaced metal ion as well as the nanocrystal. Removal of up to 90% of surface-bound Cd(O2CR)2 from CdSe and CdS nanocrystals decreases the Cd/Se ratio from 1.1 ± 0.06 to 1.0 ± 0.05, broadens the 1S(e)-2S(3/2h) absorption, and decreases the photoluminescence quantum yield (PLQY) from 10% to <1% (CdSe) and from 20% to <1% (CdS). These changes are partially reversed upon rebinding of M(O2CR)2 at room temperature (∼60%) and fully reversed at elevated temperature. A model is proposed in which electron-accepting M(O2CR)2 complexes (Z-type ligands) reversibly bind to nanocrystals, leading to a range of stoichiometries for a given core size. The results demonstrate that nanocrystals lack a single chemical formula, but are instead dynamic structures with concentration-dependent compositions. The importance of these findings to the synthesis and purification of nanocrystals as well as ligand exchange reactions is discussed.
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Affiliation(s)
- Nicholas C. Anderson
- Department of Chemistry, Columbia University, 3000 Broadway, MC 3121, New York, NY 10027
| | - Mark P. Hendricks
- Department of Chemistry, Columbia University, 3000 Broadway, MC 3121, New York, NY 10027
| | - Joshua J. Choi
- Department of Chemistry, Columbia University, 3000 Broadway, MC 3121, New York, NY 10027
| | - Jonathan S. Owen
- Department of Chemistry, Columbia University, 3000 Broadway, MC 3121, New York, NY 10027
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40
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Weiss EA. Organic molecules as tools to control the growth, surface structure, and redox activity of colloidal quantum dots. Acc Chem Res 2013; 46:2607-15. [PMID: 23734589 DOI: 10.1021/ar400078u] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In order to achieve efficient and reliable technology that can harness solar energy, the behavior of electrons and energy at interfaces between different types or phases of materials must be understood. Conversion of light to chemical or electrical potential in condensed phase systems requires gradients in free energy that allow the movement of energy or charge carriers and facilitate redox reactions and dissociation of photoexcited states (excitons) into free charge carriers. Such free energy gradients are present at interfaces between solid and liquid phases or between inorganic and organic materials. Nanostructured materials have a higher density of these interfaces than bulk materials. Nanostructured materials, however, have a structural and chemical complexity that does not exist in bulk materials, which presents a difficult challenge: to lower or eliminate energy barriers to electron and energy flux that inevitably result from forcing different materials to meet in a spatial region of atomic dimensions. Chemical functionalization of nanostructured materials is perhaps the most versatile and powerful strategy for controlling the potential energy landscape of their interfaces and for minimizing losses in energy conversion efficiency due to interfacial structural and electronic defects. Colloidal quantum dots are semiconductor nanocrystals synthesized with wet-chemical methods and coated in organic molecules. Chemists can use these model systems to study the effects of chemical functionalization of nanoscale organic/inorganic interfaces on the optical and electronic properties of a nanostructured material, and the behavior of electrons and energy at interfaces. The optical and electronic properties of colloidal quantum dots have an intense sensitivity to their surface chemistry, and their organic adlayers make them dispersible in solvent. This allows researchers to use high signal-to-noise solution-phase spectroscopy to study processes at interfaces. In this Account, I describe the varied roles of organic molecules in controlling the structure and properties of colloidal quantum dots. Molecules serve as surfactant that determines the mechanism and rate of nucleation and growth and the final size and surface structure of a quantum dot. Anionic surfactant in the reaction mixture allows precise control over the size of the quantum dot core but also drives cation enrichment and structural disordering of the quantum dot surface. Molecules serve as chemisorbed ligands that dictate the energetic distribution of surface states. These states can then serve as thermodynamic traps for excitonic charge carriers or couple to delocalized states of the quantum dot core to change the confinement energy of excitonic carriers. Ligands, therefore, in some cases, dramatically shift the ground state absorption and photoluminescence spectra of quantum dots. Molecules also act as protective layers that determine the probability of redox processes between quantum dots and other molecules. How much the ligand shell insulates the quantum dot from electron exchange with a molecular redox partner depends less on the length or degree of conjugation of the native ligand and more on the density and packing structure of the adlayer and the size and adsorption mode of the molecular redox partner. Control of quantum dot properties in these examples demonstrates that nanoscale interfaces, while complex, can be rationally designed to enhance or specify the functionality of a nanostructured system.
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Affiliation(s)
- Emily A. Weiss
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, United States
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41
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Bakulin AA, Neutzner S, Bakker HJ, Ottaviani L, Barakel D, Chen Z. Charge trapping dynamics in PbS colloidal quantum dot photovoltaic devices. ACS NANO 2013; 7:8771-9. [PMID: 24069878 DOI: 10.1021/nn403190s] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The efficiency of solution-processed colloidal quantum dot (QD) based solar cells is limited by poor charge transport in the active layer of the device, which originates from multiple trapping sites provided by QD surface defects. We apply a recently developed ultrafast electro-optical technique, pump-push photocurrent spectroscopy, to elucidate the charge trapping dynamics in PbS colloidal-QD photovoltaic devices at working conditions. We show that IR photoinduced absorption of QD in the 0.2-0.5 eV region is partly associated with immobile charges, which can be optically detrapped in our experiment. Using this absorption as a probe, we observe that the early trapping dynamics strongly depend on the nature of the ligands used for QD passivation, while it depends only slightly on the nature of the electron-accepting layer. We find that weakly bound states, with a photon-activation energy of 0.2 eV, are populated instantaneously upon photoexcitation. This indicates that the photogenerated states show an intrinsically bound-state character, arguably similar to charge-transfer states formation in organic photovoltaic materials. Sequential population of deeper traps (activation energy 0.3-0.5 eV) is observed on the ~0.1-10 ns time scales, indicating that most of carrier trapping occurs only after substantial charge relaxation/transport. The reported study disentangles fundamentally different contributions to charge trapping dynamics in the nanocrystal-based optoelectronic devices and can serve as a useful tool for QD solar cell development.
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Affiliation(s)
- Artem A Bakulin
- FOM Institute AMOLF , Science Park 104, Amsterdam 1098 XG, The Netherlands
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42
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Cass LC, Malicki M, Weiss EA. The chemical environments of oleate species within samples of oleate-coated PbS quantum dots. Anal Chem 2013; 85:6974-9. [PMID: 23786216 DOI: 10.1021/ac401623a] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A combination of FT-IR, (1)H NMR, nuclear Overhauser effect (NOESY), and diffusion-ordered (DOSY) NMR spectroscopies shows that samples of oleate-coated PbS quantum dots (QDs) with core radii ranging from 1.6 to 2.4 nm, and purified by washing with acetone, contain two species of oleate characterized by the stretching frequencies of their carboxylate groups, the chemical shifts of their protons, and their diffusion coefficients. One of these oleate species exists primarily on the surfaces of the QDs and either chelates a Pb(2+) ion or bridges two Pb(2+) ions. The ratio of bridging oleates to chelating oleates on the surfaces of the QDs is approximately 1:1 for all sizes of the QDs we studied. The second oleate species in these samples bridges two Pb(2+) ions within clusters or oligomers of lead oleate (with a hydrodynamic radius of ~1.4 nm), which are byproducts of the QD synthesis. The concentration of these clusters increases with increasing size of the QDs because larger QDs are produced by increasing the concentration of the oleic acid ligand in the reaction mixture. The oleate molecules on the surfaces of the QDs and within the lead oleate clusters are in rapid exchange with each other. Additional washes with methanol progressively eliminate the contaminating clusters from the PbS QD samples. This work quantitatively characterizes the distribution of binding geometries at the inorganic/organic interface of the nanocrystals and demonstrates the utility of using organic ligands as probes for the composition of a colloidal QD sample as a function of the preparation procedure.
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Affiliation(s)
- Laura C Cass
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, United States
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43
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Knowles KE, Malicki M, Weiss EA. Dual-Time Scale Photoinduced Electron Transfer from PbS Quantum Dots to a Molecular Acceptor. J Am Chem Soc 2012; 134:12470-3. [DOI: 10.1021/ja3060222] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kathryn E. Knowles
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113,
United States
| | - Michał Malicki
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113,
United States
| | - Emily A. Weiss
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113,
United States
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