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Ye C, Zhang DS, Chen B, Tung CH, Wu LZ. Interfacial Charge Transfer Regulates Photoredox Catalysis. ACS CENTRAL SCIENCE 2024; 10:529-542. [PMID: 38559307 PMCID: PMC10979487 DOI: 10.1021/acscentsci.3c01561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 02/06/2024] [Accepted: 02/06/2024] [Indexed: 04/04/2024]
Abstract
Photoredox catalytic processes offer the potential for precise chemical reactions using light and materials. The central determinant is identified as interfacial charge transfer, which simultaneously engenders distinctive behavior in the overall reaction. An in-depth elucidation of the main mechanism and highlighting of the complexity of interfacial charge transfer can occur through both diffusive and direct transfer models, revealing its potential for sophisticated design in complex transformations. The fundamental photophysics uncover these comprehensive applications and offer a clue for future development. This research contributes to the growing body of knowledge on interfacial charge transfer in photoredox catalysis and sets the stage for further exploration of this fascinating area of research.
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Affiliation(s)
- Chen Ye
- Key
Laboratory of Photochemical Conversion and Optoelectronic Materials,
New Cornerstone Laboratory, Technical Institute
of Physics and Chemistry, The Chinese Academy of Sciences, Beijing 100190, P. R. China
- School
of Future Technology, University of Chinese
Academy of Sciences, Beijing 100049, P. R. China
| | - De-Shan Zhang
- Key
Laboratory of Photochemical Conversion and Optoelectronic Materials,
New Cornerstone Laboratory, Technical Institute
of Physics and Chemistry, The Chinese Academy of Sciences, Beijing 100190, P. R. China
- School
of Future Technology, University of Chinese
Academy of Sciences, Beijing 100049, P. R. China
| | - Bin Chen
- Key
Laboratory of Photochemical Conversion and Optoelectronic Materials,
New Cornerstone Laboratory, Technical Institute
of Physics and Chemistry, The Chinese Academy of Sciences, Beijing 100190, P. R. China
- School
of Future Technology, University of Chinese
Academy of Sciences, Beijing 100049, P. R. China
| | - Chen-Ho Tung
- Key
Laboratory of Photochemical Conversion and Optoelectronic Materials,
New Cornerstone Laboratory, Technical Institute
of Physics and Chemistry, The Chinese Academy of Sciences, Beijing 100190, P. R. China
- School
of Future Technology, University of Chinese
Academy of Sciences, Beijing 100049, P. R. China
| | - Li-Zhu Wu
- Key
Laboratory of Photochemical Conversion and Optoelectronic Materials,
New Cornerstone Laboratory, Technical Institute
of Physics and Chemistry, The Chinese Academy of Sciences, Beijing 100190, P. R. China
- School
of Future Technology, University of Chinese
Academy of Sciences, Beijing 100049, P. R. China
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2
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Rosner T, Pavlopoulos NG, Shoyhet H, Micheel M, Wächtler M, Adir N, Amirav L. The Other Dimension-Tuning Hole Extraction via Nanorod Width. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:nano12193343. [PMID: 36234471 PMCID: PMC9565346 DOI: 10.3390/nano12193343] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 09/14/2022] [Accepted: 09/21/2022] [Indexed: 05/10/2023]
Abstract
Solar-to-hydrogen generation is a promising approach to generate clean and renewable fuel. Nanohybrid structures such as CdSe@CdS-Pt nanorods were found favorable for this task (attaining 100% photon-to-hydrogen production efficiency); yet the rods cannot support overall water splitting. The key limitation seems to be the rate of hole extraction from the semiconductor, jeopardizing both activity and stability. It is suggested that hole extraction might be improved via tuning the rod's dimensions, specifically the width of the CdS shell around the CdSe seed in which the holes reside. In this contribution, we successfully attain atomic-scale control over the width of CdSe@CdS nanorods, which enables us to verify this hypothesis and explore the intricate influence of shell diameter over hole quenching and photocatalytic activity towards H2 production. A non-monotonic effect of the rod's diameter is revealed, and the underlying mechanism for this observation is discussed, alongside implications towards the future design of nanoscale photocatalysts.
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Affiliation(s)
- Tal Rosner
- Schulich Faculty of Chemistry, The Russell Berrie Nanotechnology Institute, The Nancy and Stephen Grand Technion Energy Program, Technion−Israel Institute of Technology, Haifa 32000, Israel
| | - Nicholas G. Pavlopoulos
- Schulich Faculty of Chemistry, The Russell Berrie Nanotechnology Institute, The Nancy and Stephen Grand Technion Energy Program, Technion−Israel Institute of Technology, Haifa 32000, Israel
| | - Hagit Shoyhet
- Schulich Faculty of Chemistry, The Russell Berrie Nanotechnology Institute, The Nancy and Stephen Grand Technion Energy Program, Technion−Israel Institute of Technology, Haifa 32000, Israel
| | - Mathias Micheel
- Department Functional Interfaces, Leibniz Institute of Photonic Technology Jena, Albert-Einstein-Straße 9, 07745 Jena, Germany
| | - Maria Wächtler
- Department Functional Interfaces, Leibniz Institute of Photonic Technology Jena, Albert-Einstein-Straße 9, 07745 Jena, Germany
- Institute of Physical Chemistry and Abbe Center of Photonics, Friedrich Schiller University Jena, Helmholtzweg 4, 07743 Jena, Germany
- Correspondence: (M.W.); (N.A.); (L.A.)
| | - Noam Adir
- Schulich Faculty of Chemistry, The Russell Berrie Nanotechnology Institute, The Nancy and Stephen Grand Technion Energy Program, Technion−Israel Institute of Technology, Haifa 32000, Israel
- Correspondence: (M.W.); (N.A.); (L.A.)
| | - Lilac Amirav
- Schulich Faculty of Chemistry, The Russell Berrie Nanotechnology Institute, The Nancy and Stephen Grand Technion Energy Program, Technion−Israel Institute of Technology, Haifa 32000, Israel
- Correspondence: (M.W.); (N.A.); (L.A.)
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3
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Magnetic nanoparticles for the recovery of uranium from sea water: Challenges involved from research to development. J IND ENG CHEM 2020. [DOI: 10.1016/j.jiec.2020.07.035] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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4
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Zhang Y, Wu G, Liu F, Ding C, Zou Z, Shen Q. Photoexcited carrier dynamics in colloidal quantum dot solar cells: insights into individual quantum dots, quantum dot solid films and devices. Chem Soc Rev 2020; 49:49-84. [PMID: 31825404 DOI: 10.1039/c9cs00560a] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The certified power conversion efficiency (PCE) record of colloidal quantum dot solar cells (QDSCs) has considerably improved from below 4% to 16.6% in the last few years. However, the record PCE value of QDSCs is still substantially lower than the theoretical efficiency. So far, there have been several reviews on recent and significant achievements in QDSCs, but reviews on photoexcited carrier dynamics in QDSCs are scarce. The photovoltaic performances of QDSCs are still limited by the photovoltage, photocurrent and fill factor that are mainly determined by the photoexcited carrier dynamics, including carrier (or exciton) generation, carrier extraction or transfer, and the carrier recombination process, in the devices. In this review, the photoexcited carrier dynamics in the whole QDSCs, originating from individual quantum dots (QDs) to the entire device as well as the characterization methods used for analyzing the photoexcited carrier dynamics are summarized and discussed. The recent research including photoexcited multiple exciton generation (MEG), hot electron extraction, and carrier transfer between adjacent QDs, as well as carrier injection and recombination at each interface of QDSCs are discussed in detail herein. The influence of photoexcited carrier dynamics on the physiochemical properties of QDs and photovoltaic performances of QDSC devices is also discussed.
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Affiliation(s)
- Yaohong Zhang
- Faculty of Informatics and Engineering, The University of Electro-Communications, Tokyo 182-8585, Japan.
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5
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Dutta P, Tang Y, Mi C, Saniepay M, McGuire JA, Beaulac R. Ultrafast hole extraction from photoexcited colloidal CdSe quantum dots coupled to nitroxide free radicals. J Chem Phys 2019; 151:174706. [DOI: 10.1063/1.5124887] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Affiliation(s)
- Poulami Dutta
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824-1322, USA
| | - Yanhao Tang
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824-1322, USA
| | - Chenjia Mi
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824-1322, USA
| | - Mersedeh Saniepay
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824-1322, USA
| | - John A. McGuire
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824-1322, USA
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Rémi Beaulac
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824-1322, USA
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6
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Singhal P, Pulhani V. Effect of Ligand Concentration, Dilution, and Excitation Wavelength on the Emission Properties of CdSe/CdS Core Shell Quantum Dots and Their Implication on Detection of Uranium. ChemistrySelect 2019. [DOI: 10.1002/slct.201900792] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Pallavi Singhal
- Environmental Monitoring and Assessment DivisionBhabha Atomic Research Centre Mumbai 400085 India
| | - Vandana Pulhani
- Environmental Monitoring and Assessment DivisionBhabha Atomic Research Centre Mumbai 400085 India
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7
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Maiti S, Dana J, Ghosh HN. Correlating Charge‐Carrier Dynamics with Efficiency in Quantum‐Dot Solar Cells: Can Excitonics Lead to Highly Efficient Devices? Chemistry 2018; 25:692-702. [DOI: 10.1002/chem.201801853] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2018] [Revised: 07/06/2018] [Indexed: 11/06/2022]
Affiliation(s)
- Sourav Maiti
- Radiation & Photochemistry DivisionBhabha Atomic Research Centre Mumbai 400085 India
- Department of ChemistrySavitribai Phule Pune University Ganeshkhind Pune 411007 India
| | - Jayanta Dana
- Radiation & Photochemistry DivisionBhabha Atomic Research Centre Mumbai 400085 India
| | - Hirendra N. Ghosh
- Radiation & Photochemistry DivisionBhabha Atomic Research Centre Mumbai 400085 India
- Institute of Nano Science and Technology Mohali Punjab 160062 India
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8
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Singhal P, Jha SK, Vats BG, Ghosh HN. Electron-Transfer-Mediated Uranium Detection Using Quasi-Type II Core-Shell Quantum Dots: Insight into Mechanistic Pathways. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:8114-8122. [PMID: 28749681 DOI: 10.1021/acs.langmuir.7b00926] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Uranium is one of the most toxic and important elements present in the environment, and because of its high toxicity, ultra-trace-level detection is of utmost importance. Many methods were reported earlier for this purpose, but each has its own limitations such as high cost, sophisticated instrumentation, sample processing, and so forth. Herein we have demonstrated an alternate method that is much simpler and can be used for the ultra-trace-level detection of uranium. We have synthesized 3-mercaptopropionic acid (MPA)-capped CdSe/CdS core-shell quantum dots (CSQDs) and used its photoluminescence properties to detect uranium in solution. Steady-state emission studies suggest the luminescence quenching of CSQDs in the presence of uranium. Redox levels of CSQDs and uranium suggests that the electron-transfer process from photoexcited CSQDs to uranium is a thermodynamically viable process, which has subsequently been confirmed by time-resolved studies. A Stern-Volmer plot of CSQDs with uranium suggests that the detection limit of this method is 74.5 ppb. The method has an advantage over other reported methods for being simple and low cost and requiring a small amout of sample processing. To the best of our knowledge, we are reporting for the first time uranium detection using quasi-type II CSQDs and proposing the mechanistic path through luminescence spectroscopy, which in turn helps us to design an efficient detection method.
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Affiliation(s)
| | - Sanjay K Jha
- Homi Bhabha National Institute , Mumbai 400094, India
| | | | - Hirendra N Ghosh
- Institute of Nano Science and Technology , Habitat Centre Mohali, Punjab 160062, India
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9
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Singhal P, Maity P, Jha SK, Ghosh HN. Metal-Ligand Complex-Induced Ultrafast Charge-Carrier Relaxation and Charge-Transfer Dynamics in CdX (X=S, Se, Te) Quantum Dots Sensitized with Nitrocatechol. Chemistry 2017; 23:10590-10596. [PMID: 28556260 DOI: 10.1002/chem.201701271] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Indexed: 11/10/2022]
Abstract
The present work describes the effect of interfacial complex formation on charge carrier dynamics in CdX (X=S, Se, Te) quantum dots (QDs) sensitized nitro catechol (NCAT). To compare experiments were also carried out with catechol (CAT) where no such complexation was observed. Time-resolved emission studies suggest faster charge separation in CdS(Se)/NCAT system as compared to CdS(Se)/CAT although change in Gibbs free energy for hole transfer is less in former as compared to later. This suggests that complex formation favours charge separation. Similar studies were also carried out in CdTe/NCAT system where hole transfer process was not viable thermodynamically but due to complex formation charge separation was observed. Femtosecond transient absorption studies have been carried out to monitor charge carrier dynamics in early time scale. Transient studies show faster electron cooling in QDs/NCAT system as compared to pure QDs and has been assigned to the complex formation on QDs surface. Interestingly charge recombination dynamics is much faster in QDs/NCAT system as compared to pure QDs which can be attributed to the stronger coupling between QDs and NCAT. Our results suggest a strong metal-ligand complex formation on QDs surface that controls charge carrier dynamics in QDs/molecular adsorbate system and to the best of our knowledge it has never been reported.
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Affiliation(s)
- Pallavi Singhal
- Homi Bhabha National Institute, Mumbai, 400 085, India.,Health Physics Division, Bhabha Atomic Research Centre, Mumbai, 400 085, India
| | - Partha Maity
- Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai, 400 085, India
| | - Sanjay K Jha
- Homi Bhabha National Institute, Mumbai, 400 085, India.,Health Physics Division, Bhabha Atomic Research Centre, Mumbai, 400 085, India
| | - Hirendra N Ghosh
- Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai, 400 085, India.,Institute of Nano Science and Technology, Habitat Centre, Mohali, Punjab, 160062, India
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10
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Singhal P, Vats BG, Jha SK, Neogy S. Green, Water-Dispersible Photoluminescent On-Off-On Probe for Selective Detection of Fluoride Ions. ACS APPLIED MATERIALS & INTERFACES 2017; 9:20536-20544. [PMID: 28537079 DOI: 10.1021/acsami.7b03346] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Considering the high toxicity and widespread availability of fluoride ions in different environmental matrices, it is imperative to design a probe for its detection. In view of this, a selective fluorescent on-off-on probe based on carbon quantum dots (CQDs) and Eu3+ has been designed. We have synthesized water-soluble carboxylic acid-functionalized CQDs and monitored their interaction with Eu3+. Luminescence quenching in the CQD emission was observed (switch-off) on adding Eu3+ ions. We investigate the reason for this luminescence quenching using time-resolved emission and high-resolution transmission electron microscopy (HRTEM) studies and observed that both electron transfer from CQDs to Eu3+ and aggregation of CQDs are responsible for the luminescence quenching. ζ-Potential and X-ray photoelectron spectroscopy studies confirm Eu3+ binding with the COOH groups on CQD surface. Interestingly, luminescence regains after the addition of fluoride ions to the CQDs/Eu3+ system (switch-on). This has been assigned to the removal of Eu3+ from the CQD surface due to the formation of EuF3 and is confirmed by X-ray diffraction and HRTEM measurements. The sensitivity of the probe was tested by carrying out experiments with other competing ions and was found to be selective for fluoride ions. Experiments with variable concentrations of fluoride ions suggest that the working range of the probe is 1-25 ppm. The probe has been successfully tested for the detection of fluoride ions in a toothpaste sample and the results were compared to those of ion chromatography. To the best of our knowledge, this is the first report based on CQDs and Eu3+ for the detection of fluoride ions, wherein a clear mechanism of the detection has been demonstrated, which, in turn, will help to develop better detection methods. The suggested probe is green, economical, rapid, efficient, and, most importantly, selective and can be used for the detection of fluoride ions in real environmental samples.
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Affiliation(s)
| | | | - Sanjay K Jha
- Homi Bhabha National Institute , Mumbai 400094, India
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11
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Debnath T, Sebastian D, Maiti S, Ghosh HN. Tuning Hole and Electron Transfer from Photoexcited CdSe Quantum Dots to Phenol Derivatives: Effect of Electron-Donating and -Withdrawing Moieties. Chemistry 2017; 23:7306-7314. [PMID: 28345273 DOI: 10.1002/chem.201700166] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Indexed: 11/09/2022]
Abstract
Charge-transfer processes from photoexcited CdSe quantum dots (QDs) to phenol derivatives with electron- donating (4-methoxy) and -withdrawing (4-nitro) moieties have been demonstrated by using steady-state and time- resolved emission and femtosecond transient absorption spectroscopy. Steady-state and time-resolved emission studies suggest that in the presence of both 4-nitrophenol (4NP) and 4-methoxyphenol (4MP) CdSe QDs luminescence is quenched. Stern-Volmer analysis suggests both static and dynamic mechanisms are active for both the QD/phenol composites. Cyclic voltammetric analysis recommends that photoexcited CdSe QDs can donate electrons to 4NP and holes to 4MP. To reconfirm both electron- and hole-transfer mechanisms, CdSe/CdS quasi-type II and CdSe/CdTe type II core-shell nanocrystals were synthesized and photoluminescence quenching was monitored in the absence and presence of both 4NP and 4MP, for which hole and electron transfer were systematically restricted. Results suggest that indeed electron and hole transfer take place from photoexcited CdSe to 4NP and 4MP, respectively. To monitor the charge-transfer dynamics in both systems on an early timescale, femtosecond transient absorption spectroscopic techniques have been employed. Electron and hole transfer and charge-recombination dynamics are discussed and the effect of electron-donating and -withdrawing groups has been demonstrated.
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Affiliation(s)
- Tushar Debnath
- Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai, 400 085, India
| | - Deepa Sebastian
- Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai, 400 085, India
| | - Sourav Maiti
- Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai, 400 085, India.,Department of Chemistry, Savitribai Phule Pune University, Pune, 411007, India
| | - Hirendra N Ghosh
- Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai, 400 085, India.,Institute of Nano Science and Technology, Mohali, Punjab, 160062, India
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12
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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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13
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Singhal P, Ghorpade PV, Shankarling GS, Singhal N, Jha SK, Tripathi RM, Ghosh HN. Exciton delocalization and hot hole extraction in CdSe QDs and CdSe/ZnS type 1 core shell QDs sensitized with newly synthesized thiols. NANOSCALE 2016; 8:1823-1833. [PMID: 26698125 DOI: 10.1039/c5nr07605f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The present work describes ultrafast thermalized and hot hole transfer processes from photo-excited CdSe quantum dots (QDs) and CdSe/ZnS core-shell QDs (CSQDs) to newly synthesized thiols. Three thiols namely 2-mercapto-N-phenylacetamide (AAT), 3-mercapto-N-phenylpropanamide (APT) and 3-mercapto-N-(4-methoxyphenyl) propanamide (ADPT) were synthesized and their interaction with both CdSe QDs and CdSe/ZnS CSQDs was monitored. Steady state absorption study suggests the exciton delocalization from CdSe QDs in the presence of the thiols. However similar features were not observed in the presence of a ZnS shell over a CdSe core, instead a broadening in the excitonic peak was observed with both APT and ADPT but not with AAT. This exciton delocalization and broadening in the excitonic peak was also confirmed by ultrafast transient absorption studies. Steady state and time resolved emission studies show hole transfer from photo-excited QDs and CSQDs to the thiols. A signature of hot hole extraction was observed in transient absorption studies which was confirmed by fluorescence upconversion studies. Both hot and thermalized hole transfer rates from CdSe QDs and CdSe/ZnS CSQDs to the thiols were determined using the fluorescence up-conversion technique. Experiments with different ZnS shell thicknesses have been carried out which suggest that hole transfer is possible till 2.5 monolayer of the ZnS shell. To the best of our knowledge we are reporting for the first time the extraction of hot holes from CdSe/ZnS type I CSQDs by a molecular adsorbate.
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Affiliation(s)
- Pallavi Singhal
- Health Physics Division, Bhabha Atomic Research Centre, Mumbai, India.
| | - Prashant V Ghorpade
- Department of Dyestuff Technology, Institute Of Chemical Technology, Mumbai, India.
| | | | - Nancy Singhal
- Department of Chemistry, Indian Institute of Technology, Mumbai, India
| | - Sanjay K Jha
- Health Physics Division, Bhabha Atomic Research Centre, Mumbai, India.
| | - Raj M Tripathi
- Health Physics Division, Bhabha Atomic Research Centre, Mumbai, India.
| | - Hirendra N Ghosh
- Radiation & Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
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