1
|
Shulenberger KE, Jilek MR, Sherman SJ, Hohman BT, Dukovic G. Electronic Structure and Excited State Dynamics of Cadmium Chalcogenide Nanorods. Chem Rev 2023; 123:3852-3903. [PMID: 36881852 DOI: 10.1021/acs.chemrev.2c00676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
Abstract
The cylindrical quasi-one-dimensional shape of colloidal semiconductor nanorods (NRs) gives them unique electronic structure and optical properties. In addition to the band gap tunability common to nanocrystals, NRs have polarized light absorption and emission and high molar absorptivities. NR-shaped heterostructures feature control of electron and hole locations as well as light emission energy and efficiency. We comprehensively review the electronic structure and optical properties of Cd-chalcogenide NRs and NR heterostructures (e.g., CdSe/CdS dot-in-rods, CdSe/ZnS rod-in-rods), which have been widely investigated over the last two decades due in part to promising optoelectronic applications. We start by describing methods for synthesizing these colloidal NRs. We then detail the electronic structure of single-component and heterostructure NRs and follow with a discussion of light absorption and emission in these materials. Next, we describe the excited state dynamics of these NRs, including carrier cooling, carrier and exciton migration, radiative and nonradiative recombination, multiexciton generation and dynamics, and processes that involve trapped carriers. Finally, we describe charge transfer from photoexcited NRs and connect the dynamics of these processes with light-driven chemistry. We end with an outlook that highlights some of the outstanding questions about the excited state properties of Cd-chalcogenide NRs.
Collapse
Affiliation(s)
| | - Madison R Jilek
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Skylar J Sherman
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Benjamin T Hohman
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Gordana Dukovic
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States.,Renewable and Sustainable Energy Institute (RASEI), University of Colorado Boulder, Boulder, Colorado 80309, United States.,Materials Science and Engineering, University of Colorado Boulder, Boulder, Colorado 80303, United States
| |
Collapse
|
2
|
Ghosh S, Mukherjee S, Mandal S, De CK, Mardanya S, Saha A, Mandal PK. Beneficial Intrinsic Hole Trapping and Its Amplitude Variation in a Highly Photoluminescent Toxic-Metal-Free Quantum Dot. J Phys Chem Lett 2023; 14:260-266. [PMID: 36595225 DOI: 10.1021/acs.jpclett.2c03373] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Intrinsic hole trapping as well as hole detrapping have not been observed for any quantum dot (QD) or perovskite nanocrystal (PNC) system. Moreover, amplitude variation of intrinsic hole trapping (or detrapping) has not been reported at all for any QD or PNC system. However, for a CuInS2-based core/alloy-shell (CAS) QD system, (a) both intrinsic hole trapping and detrapping have been observed and (b) very significant amplitude variations of hole trapping (∼16 to ∼42%) and hole detrapping (∼44 to 23%) have been observed. Unlike detrimental electron trapping, hole trapping has been shown to be beneficial, having a direct correlation toward increasing PLQY to 96%. Simultaneous electron and hole trapping has been shown to be quite beneficial for the CuInS2-based CAS QD system leading to the longest ON time (∼130 s) for which a nontoxic metal-based QD remains only in the ON-state without blinking.
Collapse
|
3
|
Roy D, Ghosh S, De CK, Mukherjee S, Mandal S, Mandal PK. Excitation-Energy-Dependent Photoluminescence Quantum Yield is Inherent to Optically Robust Core/Alloy-Shell Quantum Dots in a Vast Energy Landscape. J Phys Chem Lett 2022; 13:2404-2417. [PMID: 35257586 DOI: 10.1021/acs.jpclett.2c00157] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The importance of alloy-shelling in optically robust Core/Alloy-Shell (CAS) QDs has been described from structural and energetic aspects. Unlike fluorescent dyes, both Core/Shell (CS) and CAS QDs exhibit excitation-energy-dependent photoluminescence quantum yield (PLQY). For both CdSe and InP CAS QDs (with metal- and nonmetal-based alloy-shelling, respectively), with increasing excitation energy, (a) the ultrafast rise-time or relaxation-time to the band-edge increases and (b) the magnitude of the normalized bleach signal decreases. Ultrasensitive single-particle spectroscopic investigation results showed that with decreasing excitation energy, (a) the fraction of ON events increases, (b) the ratio of exciton-detrapping rate/trapping rate increases, and (c) the extent of beneficial hole trapping increases. A relative decrease in PLQY with increasing excitation energy is much less pronounced in CAS QDs than in CS QDs. Unless trap states are removed completely especially in the higher-energy landscape, PLQY will remain inherently dependent on excitation energy for QDs in the vast energy landscape. When reporting the PLQY of QDs, the magnitude of the excitation energy must be mentioned.
Collapse
Affiliation(s)
- Debjit Roy
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, West Bengal, India 741246
| | - Swarnali Ghosh
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, West Bengal, India 741246
| | - Chayan K De
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, West Bengal, India 741246
| | - Soumen Mukherjee
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, West Bengal, India 741246
| | - Saptarshi Mandal
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, West Bengal, India 741246
| | - Prasun K Mandal
- Department of Chemical Sciences & Centre for Advanced Functional Materials, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, West Bengal, India 741246
| |
Collapse
|
4
|
Vicente JR, Rafiei Miandashti A, Sy Piecco KWE, Pyle JR, Kordesch ME, Chen J. Single-Particle Organolead Halide Perovskite Photoluminescence as a Probe for Surface Reaction Kinetics. ACS APPLIED MATERIALS & INTERFACES 2019; 11:18034-18043. [PMID: 31007015 DOI: 10.1021/acsami.9b03822] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Photoluminescence (PL) of organolead halide perovskites (OHPs) is sensitive to OHPs' surface conditions and is an effective way to report surface states. Literature has reported that at the ensemble level, the PL of photoexcited OHP nanorods declines under an inert nitrogen (N2) atmosphere and recovers under subsequent exposure to oxygen (O2). At the single-particle level, we observed that OHP nanorods photoblink at rates dependent on both the excitation intensity and the O2 concentration. Combining the two sets of information with the charge-trapping/detrapping mechanism, we are able to quantitatively evaluate the interaction between a single surface defect and a single O2 molecule using a new kinetic model. The model predicts that the photodarkening of OHP nanorods in the N2 atmosphere has a different mechanism than conventional PL quenching, which we call photo-knockout. This model provides fundamental insights into the interactions of molecular O2 with OHP materials and helps design a suitable OHP interface for a variety of applications in photovoltaics and optoelectronics.
Collapse
Affiliation(s)
- Juvinch R Vicente
- Department of Chemistry , University of the Philippines Visayas , Miagao, Iloilo 5023 , Philippines
| | | | - Kurt Waldo E Sy Piecco
- Department of Chemistry , University of the Philippines Visayas , Miagao, Iloilo 5023 , Philippines
| | | | | | | |
Collapse
|
5
|
Zhang H, He H, Jiang X, Xia Z, Wei W. Preparation and Characterization of Chiral Transition-Metal Dichalcogenide Quantum Dots and Their Enantioselective Catalysis. ACS APPLIED MATERIALS & INTERFACES 2018; 10:30680-30688. [PMID: 30113158 DOI: 10.1021/acsami.8b10594] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Two-dimensional transition-metal dichalcogenides (TMDs) had attracted enormous interests owing to their extraordinary optical, physical, and chemical properties. Herein, we prepared for the first time a series of chiral TMD quantum dots (QDs) from MoS2 and WS2 bulk crystals by covalent modification with chiral ligands cysteine and penicillamine. The chiral TMD QDs were carefully investigated by spectroscopic and microscopic techniques. Their chiral optical activity was confirmed by distinct circular dichroism signals different to those of the chiral ligands. Interestingly, with the assistance of copper ions, the chiral QDs displayed strong and chiral selective peroxidase-like activity. Up to now, inorganic nanomaterials with peroxidase-like activity were tremendous but seldom examples with enantioselectivity. The enantioselectivity of our chiral TMD QDs toward chiral substrates d- and l-tyrosinol was highly up to 6.77, which was almost the best performance ever reported. The mechanisms of enantioselectivity was further investigated by quartz crystal microbalance assays. We believed that because of the extraordinary electronic and optical properties, the chiral TMD QDs should be useful for nonlinear optical materials, asymmetric catalysis, chiral and biological sensors, and so on.
Collapse
Affiliation(s)
- Huan Zhang
- School of Pharmaceutical Sciences and Innovative Drug Research Centre , Chongqing University , Chongqing 401331 , P. R. China
| | - Hui He
- School of Pharmaceutical Sciences and Innovative Drug Research Centre , Chongqing University , Chongqing 401331 , P. R. China
| | - Xuemei Jiang
- School of Pharmaceutical Sciences and Innovative Drug Research Centre , Chongqing University , Chongqing 401331 , P. R. China
| | - Zhining Xia
- School of Pharmaceutical Sciences and Innovative Drug Research Centre , Chongqing University , Chongqing 401331 , P. R. China
| | - Weili Wei
- School of Pharmaceutical Sciences and Innovative Drug Research Centre , Chongqing University , Chongqing 401331 , P. R. China
| |
Collapse
|
6
|
Groß H, Hamm JM, Tufarelli T, Hess O, Hecht B. Near-field strong coupling of single quantum dots. SCIENCE ADVANCES 2018; 4:eaar4906. [PMID: 29511739 PMCID: PMC5837425 DOI: 10.1126/sciadv.aar4906] [Citation(s) in RCA: 79] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Accepted: 01/30/2018] [Indexed: 05/10/2023]
Abstract
Strong coupling and the resultant mixing of light and matter states is an important asset for future quantum technologies. We demonstrate deterministic room temperature strong coupling of a mesoscopic colloidal quantum dot to a plasmonic nanoresonator at the apex of a scanning probe. Enormous Rabi splittings of up to 110 meV are accomplished by nanometer-precise positioning of the quantum dot with respect to the nanoresonator probe. We find that, in addition to a small mode volume of the nanoresonator, collective coherent coupling of quantum dot band-edge states and near-field proximity interaction are vital ingredients for the realization of near-field strong coupling of mesoscopic quantum dots. The broadband nature of the interaction paves the road toward ultrafast coherent manipulation of the coupled quantum dot-plasmon system under ambient conditions.
Collapse
Affiliation(s)
- Heiko Groß
- Nano-Optics and Biophotonics Group, Experimentelle Physik 5 and Röntgen Research Center for Complex Material Systems, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Joachim M. Hamm
- The Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2AZ, UK
| | - Tommaso Tufarelli
- The Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2AZ, UK
| | - Ortwin Hess
- The Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2AZ, UK
- Corresponding author. (B.H.); (O.H.)
| | - Bert Hecht
- Nano-Optics and Biophotonics Group, Experimentelle Physik 5 and Röntgen Research Center for Complex Material Systems, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Corresponding author. (B.H.); (O.H.)
| |
Collapse
|
7
|
Chen JS, Zang H, Li M, Cotlet M. Hot excitons are responsible for increasing photoluminescence blinking activity in single lead sulfide/cadmium sulfide nanocrystals. Chem Commun (Camb) 2018; 54:495-498. [DOI: 10.1039/c7cc08356d] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The kinetics of PL blinking for isolated PbS/CdS nanocrystals changes with the photon excitation energy, with PL blinking increasing in frequency and changing from a two-state to a multistate on/off switching when the excitation energy changes from 1Sh–1Se (≈1.4 eV) to 1Ph–1Pe (≈2.4 eV).
Collapse
Affiliation(s)
- Jia-Shiang Chen
- Center for Functional Nanomaterials
- Brookhaven National Laboratory
- Upton
- USA
- Department of Materials Science and Chemical Engineering
| | - Huidong Zang
- Center for Functional Nanomaterials
- Brookhaven National Laboratory
- Upton
- USA
| | - Mingxing Li
- Center for Functional Nanomaterials
- Brookhaven National Laboratory
- Upton
- USA
| | - Mircea Cotlet
- Center for Functional Nanomaterials
- Brookhaven National Laboratory
- Upton
- USA
| |
Collapse
|
8
|
Fisher AAE, Osborne MA. Sizing Up Excitons in Core-Shell Quantum Dots via Shell-Dependent Photoluminescence Blinking. ACS NANO 2017; 11:7829-7840. [PMID: 28679040 DOI: 10.1021/acsnano.7b01978] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Semiconductor nanocrystals or quantum dots (QDs) are now widely used across solar cell, display, and bioimaging technologies. While advances in multishell, alloyed, and multinary core-shell QD structures have led to improved light-harvesting and photoluminescence (PL) properties of these nanomaterials, the effects that QD-capping have on the exciton dynamics that govern PL instabilities such as blinking in single-QDs is not well understood. We report experimental measurements of shell-size-dependent absorption and PL intermittency in CdSe-CdS QDs that are consistent with a modified charge-tunnelling, self-trapping (CTST) description of the exciton dynamics in these nanocrystals. By introducing an effective, core-exciton size, which accounts for delocalization of charge carriers across the QD core and shell, we show that the CTST models both the shell-depth-dependent red-shift of the QD band gap and changes in the on/off-state switching statistics that we observe in single-QD PL intensity trajectories. Further analysis of CdSe-ZnS QDs, shows how differences in shell structure and integrity affect the QD band gap and PL blinking within the CTST framework.
Collapse
Affiliation(s)
- Aidan A E Fisher
- Department of Chemistry, School of Life Sciences, University of Sussex , Falmer, Brighton BN1 9QJ, United Kingdom
| | - Mark A Osborne
- Department of Chemistry, School of Life Sciences, University of Sussex , Falmer, Brighton BN1 9QJ, United Kingdom
| |
Collapse
|
9
|
Zhang Q, Wu L, Wong TI, Zhang J, Liu X, Zhou X, Bai P, Liedberg B, Wang Y. Surface plasmon-enhanced fluorescence on Au nanohole array for prostate-specific antigen detection. Int J Nanomedicine 2017; 12:2307-2314. [PMID: 28392689 PMCID: PMC5376189 DOI: 10.2147/ijn.s128172] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Localized surface plasmon (LSP) has been widely applied for the enhancement of fluorescence emission for biosensing owing to its potential for strong field enhancement. However, due to its small penetration depth, LSP offers limited fluorescence enhancement over a whole sensor chip and, therefore, insufficient sensitivity for the detection of biomolecules, especially large molecules. We demonstrate the simultaneous excitation of LSP and propagating surface plasmon (PSP) on an Au nanohole array under Kretschmann configuration for the detection of prostate-specific antigen with a sandwich immunoassay. The proposed method combines the advantages of high field enhancement by LSP and large surface area probed by PSP field. The simulated results indicated that a maximum enhancement of electric field intensity up to 1,600 times can be achieved under the simultaneous excitation of LSP and PSP modes. The sandwich assay of PSA carried out on gold nanohole array substrate showed a limit of detection of 140 fM supporting coexcitation of LSP and PSP modes. The limit of detection was approximately sevenfold lower than that when only LSP was resonantly excited on the same substrate. The results of this study demonstrate high fluorescence enhancement through the coexcitation of LSP and PSP modes and pave a way for its implementation as a highly sensitive bioassay.
Collapse
Affiliation(s)
- Qingwen Zhang
- School of Ophthalmology and Optometry, Eye Hospital, School of Biomedical Engineering, Wenzhou Medical University; Wenzhou Institute of Biomaterials and Engineering, Chinese Academy of Sciences, Wenzhou, People's Republic of China
| | - Lin Wu
- Electronics and Photonics Department, Institute of High Performance Computing
| | - Ten It Wong
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (ASTAR)
| | - Jinling Zhang
- Centre for Biomimetic Sensor Science, School of Materials Science and Engineering, Nanyang Technological University, Singapore
| | - Xiaohu Liu
- Centre for Biomimetic Sensor Science, School of Materials Science and Engineering, Nanyang Technological University, Singapore
| | - Xiaodong Zhou
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (ASTAR)
| | - Ping Bai
- Electronics and Photonics Department, Institute of High Performance Computing
| | - Bo Liedberg
- Centre for Biomimetic Sensor Science, School of Materials Science and Engineering, Nanyang Technological University, Singapore
| | - Yi Wang
- School of Ophthalmology and Optometry, Eye Hospital, School of Biomedical Engineering, Wenzhou Medical University; Wenzhou Institute of Biomaterials and Engineering, Chinese Academy of Sciences, Wenzhou, People's Republic of China; Centre for Biomimetic Sensor Science, School of Materials Science and Engineering, Nanyang Technological University, Singapore
| |
Collapse
|
10
|
Zang H, Li H, Makarov NS, Velizhanin KA, Wu K, Park YS, Klimov VI. Thick-Shell CuInS 2/ZnS Quantum Dots with Suppressed "Blinking" and Narrow Single-Particle Emission Line Widths. NANO LETTERS 2017; 17:1787-1795. [PMID: 28169547 DOI: 10.1021/acs.nanolett.6b05118] [Citation(s) in RCA: 91] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Quantum dots (QDs) of ternary I-III-VI2 compounds such as CuInS2 and CuInSe2 have been actively investigated as heavy-metal-free alternatives to cadmium- and lead-containing semiconductor nanomaterials. One serious limitation of these nanostructures, however, is a large photoluminescence (PL) line width (typically >300 meV), the origin of which is still not fully understood. It remains even unclear whether the observed broadening results from considerable sample heterogeneities (due, e.g., to size polydispersity) or is an unavoidable intrinsic property of individual QDs. Here, we answer this question by conducting single-particle measurements on a new type of CuInS2 (CIS) QDs with an especially thick ZnS shell. These QDs show a greatly enhanced photostability compared to core-only or thin-shell samples and, importantly, exhibit a strongly suppressed PL blinking at the single-dot level. Spectrally resolved measurements reveal that the single-dot, room-temperature PL line width is much narrower (down to ∼60 meV) than that of the ensemble samples. To explain this distinction, we invoke a model wherein PL from CIS QDs arises from radiative recombination of a delocalized band-edge electron and a localized hole residing on a Cu-related defect and also account for the effects of electron-hole Coulomb coupling. We show that random positioning of the emitting center in the QD can lead to more than 300 meV variation in the PL energy, which represents at least one of the reasons for large PL broadening of the ensemble samples. These results suggest that in addition to narrowing size dispersion, future efforts on tightening the emission spectra of these QDs might also attempt decreasing the "positional" heterogeneity of the emitting centers.
Collapse
Affiliation(s)
| | | | | | | | | | - Young-Shin Park
- Center for High Technology Materials, University of New Mexico , Albuquerque, New Mexico 87131, United States
| | | |
Collapse
|
11
|
Suzuki S, Hattori Y, Kuwabata S, Torimoto T. Improvement of photoluminescence stability of ZnS-AgInS2 nanoparticles through interactions with ionic liquids. J Photochem Photobiol A Chem 2017. [DOI: 10.1016/j.jphotochem.2016.08.034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
|
12
|
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.
Collapse
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
| |
Collapse
|
13
|
Gao Y, Yu G, Wang Y, Dang C, Sum TC, Sun H, Demir HV. Green Stimulated Emission Boosted by Nonradiative Resonant Energy Transfer from Blue Quantum Dots. J Phys Chem Lett 2016; 7:2772-2778. [PMID: 27388758 DOI: 10.1021/acs.jpclett.6b01122] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Thanks to their tunability and versatility, the colloidal quantum dots (CQDs) made of II-VI semiconductor compound offer the potential to bridge the "green gap" in conventional semiconductors. However, when the CQDs are pumped to much higher initial excitonic states compared to their bandgap, multiexciton interaction is enhanced, leading to a much higher stimulated emission threshold. Here, to circumvent this drawback, for the first time, we show a fully colloidal gain in green enabled by a partially indirect pumping approach assisted by Förster resonance energy transfer process. By introducing the blue CQDs as exciton donors, the lasing threshold of the green CQDs, is reduced dramatically. The blue CQDs thus serve as an energy-transferring buffer medium to reduce excitation energy from pumping photons in a controlled way by injecting photoinduced excitons into green CQDs. Our newly developed colloidal pumping scheme could enable efficient CQD lasers of full visible colors by a single pump source and cascaded exciton transfer. This would potentially pave the way for an efficient multicolor laser for lighting and display applications.
Collapse
Affiliation(s)
- Yuan Gao
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, 637371, Singapore
- LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering and The Photonics Institute, Nanyang Technological University , 50 Nanyang Avenue, 639798, Singapore
| | - Guannan Yu
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, 637371, Singapore
| | - Yue Wang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, 637371, Singapore
| | - Cuong Dang
- LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering and The Photonics Institute, Nanyang Technological University , 50 Nanyang Avenue, 639798, Singapore
| | - Tze Chien Sum
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, 637371, Singapore
| | - Handong Sun
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, 637371, Singapore
- LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering and The Photonics Institute, Nanyang Technological University , 50 Nanyang Avenue, 639798, Singapore
| | - Hilmi Volkan Demir
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, 637371, Singapore
- LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering and The Photonics Institute, Nanyang Technological University , 50 Nanyang Avenue, 639798, Singapore
- Department of Electrical and Electronics Engineering and Department of Physics, UNAM - Institute of Materials Science and Nanotechnology, Bilkent University , 06800 Bilkent, Ankara, Turkey
| |
Collapse
|
14
|
Hu F, Lv B, Yin C, Zhang C, Wang X, Lounis B, Xiao M. Carrier Multiplication in a Single Semiconductor Nanocrystal. PHYSICAL REVIEW LETTERS 2016; 116:106404. [PMID: 27015498 DOI: 10.1103/physrevlett.116.106404] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Indexed: 06/05/2023]
Abstract
To confirm the existence of the carrier multiplication (CM) effect and estimate its generation efficiency of multiple excitons in semiconductor nanocrystals (NCs), it is imperative to completely exclude the false contribution of charged excitons from the measured CM signal. Here we place single CdSe NCs above an aluminum film and successfully resolve their UV-excited photoluminescence (PL) time trajectories where the true and false CM signals are contained in the blinking "on" and "off" levels, respectively. By analyzing the PL dynamics of the on-level photons, an average CM efficiency of ∼20.2% can be reliably estimated when the UV photon energy is ∼2.46 times the NC energy gap.
Collapse
Affiliation(s)
- Fengrui Hu
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Bihu Lv
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Chunyang Yin
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Chunfeng Zhang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Xiaoyong Wang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Brahim Lounis
- Laboratoire Photonique Numérique et Nanosciences, Université de Bordeaux, Institut d'Optique Graduate School and CNRS, Talence 33405, France
| | - Min Xiao
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
- Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA
| |
Collapse
|
15
|
Early KT, Nesbitt DJ. Ultrafast Laser Studies of Two-Photon Excited Fluorescence Intermittency in Single CdSe/ZnS Quantum Dots. NANO LETTERS 2015; 15:7781-7787. [PMID: 26542640 DOI: 10.1021/acs.nanolett.5b01139] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Two-photon fluorescence microscopy of single quantum dots conditions has been reported by several groups, with contrasting observations regarding the kinetics and dynamics of fluorescence intermittency or "blinking". Here, we investigate the power dependence, kinetics, and statistics of two photon-excited fluorescence intermittency from single CdSe/ZnS quantum dots in a solid PMMA film as a function of sub-bandgap laser intensity at 800 nm. Fluorescence intermittency is observed at all excitation powers and a quadratic (n = 1.97(3)) dependence of the shot noise-limited fluorescence intensity on the incident laser power is verified, confirming essentially zero background contribution from one-photon excitation processes. Such analyses permit two photon absorption cross sections for single quantum dots to be extracted quantitatively from the data, which reveal good agreement with those obtained from previous two-photon FCS measurements. Strictly inverse power law-distributed off-state dwell times are observed for all excitation powers, with a mean power law exponent ⟨m(off)⟩ = 1.65(4) in excellent agreement with the behavior observed under one-photon excitation conditions. Finally, a superquadratic (n = 2.3(2)) rather than quartic (n = 4) power dependence is observed for the on-state blinking dwell times, which we kinetically analyze and interpret in terms of a novel 2 + 1 "hot" exciton ionization/blinking mechanism due to partially saturated 1-photon sub-bandgap excitation out of the two-photon single exciton state. The kinetic results are consistent with quantum dot photoionization quantum yields from "hot" exciton states (4(1) × 10(-6)) comparable with experimental estimates (10(-6)-10(-5)) of Auger ionization efficiencies out of the biexcitonic state.
Collapse
Affiliation(s)
- Kevin T Early
- Joint Institute for Lab Astrophysics, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309, United States
- Department of Chemistry and Biochemistry, University of Colorado Boulder, Colorado 80309, United States
| | - David J Nesbitt
- Joint Institute for Lab Astrophysics, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309, United States
- Department of Chemistry and Biochemistry, University of Colorado Boulder, Colorado 80309, United States
| |
Collapse
|
16
|
Abstract
Luminescence blinking is an inherent feature of optical emission from individual fluorescent molecules and quantum dots. There have been intense efforts, although not with complete resolution, toward the understanding of the mechanistic origin of blinking and also its mitigation in quantum dots. As an advance in our microscopic view of blinking, we show that the luminescence blinking of a quantum dot becomes unusually heavy in the temporal vicinity of a reactive transformation. This stage of heavy blinking is a result of defects/dopants formed within the quantum dot on its path to conversion. The evolution of blinking behavior along the reaction path allows us to measure the lifetime of the critical dopant-related intermediate in the reaction. This work establishes luminescence blinking as a single-nanocrystal level probe of catalytic, photocatalytic, and electrochemical events occurring in the solid-state or on semiconductor surfaces.
Collapse
Affiliation(s)
- Aaron L Routzahn
- †Department of Chemistry, ‡Department of Physics, and §Materials Research Lab, University of Illinois, Urbana-Champaign, Illinois 61801, United States
| | - Prashant K Jain
- †Department of Chemistry, ‡Department of Physics, and §Materials Research Lab, University of Illinois, Urbana-Champaign, Illinois 61801, United States
| |
Collapse
|
17
|
Xu Q, Zhou Q, Hua Z, Xue Q, Zhang C, Wang X, Pan D, Xiao M. Single-particle spectroscopic measurements of fluorescent graphene quantum dots. ACS NANO 2013; 7:10654-10661. [PMID: 24251867 DOI: 10.1021/nn4053342] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We have performed the first single-particle spectroscopic measurements on individual graphene quantum dots (GQDs) and revealed several intriguing fluorescent phenomena that are otherwise hidden in the optical studies of ensemble GQDs. First, despite noticeable differences in the size and the number of layers from particle to particle, all of the GQDs studied possess almost the same spectral lineshapes and peak positions. Second, GQDs with more layers are normally brighter emitters but are associated with shorter fluorescent lifetimes. Third, the fluorescent spectrum of GQDs was red-shifted upon being aged in air, possibly due to the water desorption effect. Finally, the missing emission of single photons and stable fluorescence without any intermittent behavior were observed from individual GQDs.
Collapse
Affiliation(s)
- Qinfeng Xu
- National Laboratory of Solid State Microstructures and School of Physics, Nanjing University , Nanjing 210093, China
| | | | | | | | | | | | | | | |
Collapse
|
18
|
Blumling DE, McGill S, Knappenberger KL. The influence of applied magnetic fields on the optical properties of zero- and one-dimensional CdSe nanocrystals. NANOSCALE 2013; 5:9049-9056. [PMID: 23945622 DOI: 10.1039/c3nr03252c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Shape-dependent exciton relaxation dynamics of CdSe 0-D nanocrystals and 1-D nanorods were studied using low-temperature (4.2 K), time-resolved and intensity-integrated magneto-photoluminscence (MPL) spectroscopy. Analysis of the average MPL rate constants from several different nanocrystal quantum dots and rods excited by 400 nm light in applied magnetic fields up to 17.5 T revealed size-dependent energy gaps separating bright and dark exciton fine-structure states. For 1-D nanorods under strong cross-sectional confinement and large length-to-diameter aspect ratios, efficient mixing of bright and dark exciton states was achieved using relatively low applied field strengths (≤4 T). The effect was attributed, in part, to decreased confinement of CdSe hole states associated with the long axis of the nanorod, which resulted in reduction of the energy gaps separating the bright and dark states. Increased control over the angle formed between the applied field vectors and the nanocrystal c-axis led to more efficient and uniform mixing of nanorod exciton states than for quantum dots. The findings suggest 1-D nanostructures are advantageous over 0-D ones for field-responsive applications.
Collapse
Affiliation(s)
- Daniel E Blumling
- Department of Natural Sciences, Tennessee Wesleyan College, Athens, TN 37303, USA
| | | | | |
Collapse
|
19
|
Hoy J, Morrison PJ, Steinberg LK, Buhro WE, Loomis RA. Excitation Energy Dependence of the Photoluminescence Quantum Yields of Core and Core/Shell Quantum Dots. J Phys Chem Lett 2013; 4:2053-60. [PMID: 26283252 DOI: 10.1021/jz4004735] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The photoluminescence (PL) intensity of semiconductor quantum dots (QDs) is routinely monitored to track the chemical and physical properties within a sample or device incorporating the QDs. A dependence of the PL quantum yields (QYs) on the excitation energy could lead to erroneous conclusions but is commonly not considered. We summarize previous evidence and present results from two methodologies that confirm the possibility of a dependence of the PL QYs on the excitation energy. The data presented indicate that PL QYs of CdSe and CdSe/ZnS QDs suspended in toluene are highest for excitation just above the band gap, Eg, of each. The PL QYs decrease with increasing excitation energies up to 1 eV above Eg. The PL intensity decay profiles recorded for these samples at varying emission and excitation energies indicate that the changes in the PL QYs result from the nonradiative relaxation pathways sampled as the charge carriers relax down to the band edge.
Collapse
Affiliation(s)
- Jessica Hoy
- Department of Chemistry and Center for Materials Innovation, Washington University in Saint Louis, One Brookings Drive, CB 1134, Saint Louis, Missouri 63130, United States
| | - Paul J Morrison
- Department of Chemistry and Center for Materials Innovation, Washington University in Saint Louis, One Brookings Drive, CB 1134, Saint Louis, Missouri 63130, United States
| | - Lindsey K Steinberg
- Department of Chemistry and Center for Materials Innovation, Washington University in Saint Louis, One Brookings Drive, CB 1134, Saint Louis, Missouri 63130, United States
| | - William E Buhro
- Department of Chemistry and Center for Materials Innovation, Washington University in Saint Louis, One Brookings Drive, CB 1134, Saint Louis, Missouri 63130, United States
| | - Richard A Loomis
- Department of Chemistry and Center for Materials Innovation, Washington University in Saint Louis, One Brookings Drive, CB 1134, Saint Louis, Missouri 63130, United States
| |
Collapse
|
20
|
Stopel MHW, Prangsma JC, Blum C, Subramaniam V. Blinking statistics of colloidal quantum dots at different excitation wavelengths. RSC Adv 2013. [DOI: 10.1039/c3ra43637c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
21
|
Cordones AA, Leone SR. Mechanisms for charge trapping in single semiconductor nanocrystals probed by fluorescence blinking. Chem Soc Rev 2013; 42:3209-21. [DOI: 10.1039/c2cs35452g] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
|
22
|
Zhao Y, Riemersma C, Pietra F, Koole R, Donegá CDM, Meijerink A. High-temperature luminescence quenching of colloidal quantum dots. ACS NANO 2012; 6:9058-67. [PMID: 22978378 DOI: 10.1021/nn303217q] [Citation(s) in RCA: 127] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Thermal quenching of quantum dot (QD) luminescence is important for application in luminescent devices. Systematic studies of the quenching behavior above 300 K are, however, lacking. Here, high-temperature (300-500 K) luminescence studies are reported for highly efficient CdSe core-shell quantum dots (QDs), aimed at obtaining insight into temperature quenching of QD emission. Through thermal cycling (yoyo) experiments for QDs in polymer matrices, reversible and irreversible luminescence quenching processes can be distinguished. For a variety of core-shell systems, reversible quenching is observed in a similar temperature range, between 100 and 180 °C. The irreversible quenching behavior varies between different systems. Mechanisms for thermal quenching are discussed.
Collapse
Affiliation(s)
- Yiming Zhao
- Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
| | | | | | | | | | | |
Collapse
|
23
|
Abstract
Recent experimental and theoretical studies of photoluminescence intermittency (PI) or “blinking” exhibited by single core/shell quantum dots and single organic luminophores are reviewed. For quantum dots, a discussion of early models describing the origin of PI in these materials and recent challenges to these models are presented. For organic luminophores the role of electron transfer, proton transfer and other photophysical processes in PI are discussed. Finally, new experimental and data analysis methods are outlined that promise to be instrumental in future discoveries regarding the origin(s) of PI exhibited by single emitters.
Collapse
|
24
|
Cordones AA, Knappenberger KL, Leone SR. Linking On-State Memory and Distributed Kinetics in Single Nanocrystal Blinking. J Phys Chem B 2012; 117:4241-8. [DOI: 10.1021/jp3041549] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Amy A. Cordones
- Departments
of Chemistry and Physics, University of California and Lawrence Berkeley National Laboratory, Berkeley, California
94720, United States
| | - Kenneth L. Knappenberger
- Department
of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, United States
| | - Stephen R. Leone
- Departments
of Chemistry and Physics, University of California and Lawrence Berkeley National Laboratory, Berkeley, California
94720, United States
| |
Collapse
|
25
|
Riley EA, Hess CM, Whitham PJ, Reid PJ. Beyond power laws: A new approach for analyzing single molecule photoluminescence intermittency. J Chem Phys 2012; 136:184508. [DOI: 10.1063/1.4717618] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
|
26
|
Xu Z, Cotlet M. Photoluminenscence blinking dynamics of colloidal quantum dots in the presence of controlled external electron traps. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2012; 8:253-258. [PMID: 22180124 DOI: 10.1002/smll.201101643] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Indexed: 05/31/2023]
Abstract
The effect of the external charge trap on the photoluminescence blinking dynamics of individual colloidal quantum dots is investigated with a series of colloidal quantum dot-bridge-fullerene dimers with varying bridge lengths, where the fullerene moiety acts as a well-defined, well-positioned external charge trap. It is found that charge transfer followed by charge recombination is an important mechanism in determining the blinking behavior of quantum dots when the external trap is properly coupled with the excited state of the quantum dot, leading to a quasi-continuous distribution of 'on' states and an early fall-off from a power-law distribution for both 'on' and 'off' times associated with quantum dot photoluminescence blinking.
Collapse
Affiliation(s)
- Zhihua Xu
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton New York 11973, USA
| | | |
Collapse
|
27
|
Wen X, Sitt A, Yu P, Toh YR, Tang J. Temperature dependent spectral properties of type-I and quasi type-II CdSe/CdS dot-in-rod nanocrystals. Phys Chem Chem Phys 2012; 14:3505-12. [DOI: 10.1039/c2cp23844f] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
28
|
Blumling DE, Tokumoto T, McGill S, Knappenberger KL. Temperature- and field-dependent energy transfer in CdSe nanocrystal aggregates studied by magneto-photoluminescence spectroscopy. Phys Chem Chem Phys 2012; 14:11053-9. [DOI: 10.1039/c2cp41586k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
29
|
Bixby TJ, Cordones AA, Leone SR. CdSe/ZnS quantum dot intermittency in N,N′-diphenyl-N,N′-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (TPD). Chem Phys Lett 2012. [DOI: 10.1016/j.cplett.2011.11.051] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
30
|
Attar AR, Blumling DE, Knappenberger KL. Photodissociation of thioglycolic acid studied by femtosecond time-resolved transient absorption spectroscopy. J Chem Phys 2011; 134:024514. [DOI: 10.1063/1.3526746] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
31
|
Riley EA, Bingham C, Bott ED, Kahr B, Reid PJ. Two mechanisms for fluorescence intermittency of single violamine R molecules. Phys Chem Chem Phys 2011; 13:1879-87. [DOI: 10.1039/c0cp01716g] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
32
|
Bott ED, Riley EA, Kahr B, Reid PJ. Unraveling the Dispersed Kinetics of Dichlorofluorescein in Potassium Hydrogen Phthalate Crystals. J Phys Chem A 2010; 114:7331-7. [DOI: 10.1021/jp102194u] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Eric D. Bott
- Department of Chemistry, University of Washington, Seattle, Washington 98195, and Department of Chemistry, New York University, 100 Washington Square East, Room 1001, New York, New York 10003
| | - Erin A. Riley
- Department of Chemistry, University of Washington, Seattle, Washington 98195, and Department of Chemistry, New York University, 100 Washington Square East, Room 1001, New York, New York 10003
| | - Bart Kahr
- Department of Chemistry, University of Washington, Seattle, Washington 98195, and Department of Chemistry, New York University, 100 Washington Square East, Room 1001, New York, New York 10003
| | - Philip J. Reid
- Department of Chemistry, University of Washington, Seattle, Washington 98195, and Department of Chemistry, New York University, 100 Washington Square East, Room 1001, New York, New York 10003
| |
Collapse
|
33
|
Crouch CH, Sauter O, Wu X, Purcell R, Querner C, Drndic M, Pelton M. Facts and artifacts in the blinking statistics of semiconductor nanocrystals. NANO LETTERS 2010; 10:1692-1698. [PMID: 20364845 DOI: 10.1021/nl100030e] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Since its initial discovery just over a decade ago, blinking of semiconductor nanocrystals has typically been described in terms of probability distributions for durations of bright, or "on," states and dark, or "off," states. These distributions are obtained by binning photon counts in order to construct a time series for emission intensity and then applying a threshold to distinguish on states from off states. By examining experimental data from CdSe/ZnS core/shell nanocrystals and by simulating this data according to a simple, two-state blinking model, we find that the apparent truncated power-law distributions of on times can depend significantly on the choices of binning time and threshold. For example, increasing the binning time by a factor of 10 can double the apparent truncation time and change the apparent power-law exponent by 30%, even though the binning time is only 3% of the truncation time. Our findings indicate that stringent experimental conditions are needed to accurately determine blinking-time probability distributions. Similar considerations should apply to any phenomenon characterized by time series data that displays telegraph noise.
Collapse
Affiliation(s)
- Catherine H Crouch
- Department of Physics and Astronomy, Swarthmore College, Swarthmore, Pennsylvania 19081, USA.
| | | | | | | | | | | | | |
Collapse
|
34
|
Chon B, Lim SJ, Kim W, Seo J, Kang H, Joo T, Hwang J, Shin SK. Shell and ligand-dependent blinking of CdSe-based core/shell nanocrystals. Phys Chem Chem Phys 2010; 12:9312-9. [DOI: 10.1039/b924917f] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
35
|
Li S, Steigerwald ML, Brus LE. Surface states in the photoionization of high-quality CdSe core/shell nanocrystals. ACS NANO 2009; 3:1267-73. [PMID: 19374391 DOI: 10.1021/nn900189f] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
We use electric force microscopy (EFM) to study single nanocrystal photoionization in two classes of high-quality nanocrystals whose exciton luminescence quantum yields approach unity in solution. The CdSe/CdS/ZnS core/shell nanocrystals do not photoionize, while the CdSe/CdS nanocrystals do show substantial photoionization. This verifies the theoretical prediction that the ZnS shell confines the excited electron within the nanocrystal. Despite the high luminescence quantum yield, photoionization varies substantially among the CdSe/CdS nanocrystals. We have studied the nanocrystal photoionization with both UV (396 nm) and green (532 nm) light, and we have found that the magnitude of the charge due to photoionization per absorbed photon is greater for UV excitation than for green excitation. A fraction of the photoionization occurs directly via a "hot electron" process, using trap states that are either on the particle surface, within the ligand sphere, or within the silicon oxide layer. This must occur without relaxation to the thermalized, lowest-energy, emitting exciton. We discuss the occurrence of hot carrier processes that are common to photoionization, luminescence blinking, and the fast transient optical absorption that is associated with multiple exciton generation MEG studies.
Collapse
Affiliation(s)
- Shu Li
- Chemistry Department, Columbia University, New York, New York 10027, USA.
| | | | | |
Collapse
|