1
|
Belashov AV, Zhikhoreva AA, Salova AV, Belyaeva TN, Litvinov IK, Kornilova ES, Semenova IV, Vasyutinskii OS. Automatic segmentation of lysosomes and analysis of intracellular pH with Radachlorin photosensitizer and FLIM. Biochem Biophys Res Commun 2024; 710:149835. [PMID: 38574457 DOI: 10.1016/j.bbrc.2024.149835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 03/17/2024] [Accepted: 03/25/2024] [Indexed: 04/06/2024]
Abstract
We report application of the fluorescence lifetime imaging microscopy (FLIM) for analysis of distributions of intracellular acidity using a chlorin-e6 based photosensitizer Radachlorin. An almost two-fold increase of the photosensitizer fluorescence lifetime in alkaline microenvironments as compared to acidic ones allowed for clear distinguishing between acidic and alkaline intracellular structures. Clusterization of a phasor plot calculated from fits of the FLIM raw data by two Gaussian distributions provided accurate automatic segmentation of lysosomes featuring acidic contents. The approach was validated in colocalization experiments with LysoTracker fluorescence in living cells of four established lines. The dependence of photosensitizer fluorescence lifetime on microenvironment acidity allowed for estimation of pH inside the cells, except for the nuclei, where photosensitizer does not penetrate. The developed method is promising for combined application of the photosensitizer for both photodynamic treatment and diagnostics.
Collapse
Affiliation(s)
- A V Belashov
- Ioffe Institute, Russian Academy of Sciences, 26, Polytekhnicheskaya, St.Petersburg, 194021, Russia
| | - A A Zhikhoreva
- Ioffe Institute, Russian Academy of Sciences, 26, Polytekhnicheskaya, St.Petersburg, 194021, Russia
| | - A V Salova
- Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Pr., 4, St. Petersburg, 194064, Russia
| | - T N Belyaeva
- Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Pr., 4, St. Petersburg, 194064, Russia
| | - I K Litvinov
- Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Pr., 4, St. Petersburg, 194064, Russia
| | - E S Kornilova
- Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Pr., 4, St. Petersburg, 194064, Russia
| | - I V Semenova
- Ioffe Institute, Russian Academy of Sciences, 26, Polytekhnicheskaya, St.Petersburg, 194021, Russia.
| | - O S Vasyutinskii
- Ioffe Institute, Russian Academy of Sciences, 26, Polytekhnicheskaya, St.Petersburg, 194021, Russia
| |
Collapse
|
2
|
Torres R, Thal LB, McBride JR, Cohen BE, Rosenthal SJ. Quantum Dot Fluorescent Imaging: Using Atomic Structure Correlation Studies to Improve Photophysical Properties. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2024; 128:3632-3640. [PMID: 38476823 PMCID: PMC10926165 DOI: 10.1021/acs.jpcc.3c07367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 01/12/2024] [Accepted: 01/12/2024] [Indexed: 03/14/2024]
Abstract
Efforts to study intricate, higher-order cellular functions have called for fluorescence imaging under physiologically relevant conditions such as tissue systems in simulated native buffers. This endeavor has presented novel challenges for fluorescent probes initially designed for use in simple buffers and monolayer cell culture. Among current fluorescent probes, semiconductor nanocrystals, or quantum dots (QDs), offer superior photophysical properties that are the products of their nanoscale architectures and chemical formulations. While their high brightness and photostability are ideal for these biological environments, even state of the art QDs can struggle under certain physiological conditions. A recent method correlating electron microscopy ultrastructure with single-QD fluorescence has begun to highlight subtle structural defects in QDs once believed to have no significant impact on photoluminescence (PL). Specific defects, such as exposed core facets, have been shown to quench QD PL in physiologically accurate conditions. For QD-based imaging in complex cellular systems to be fully realized, mechanistic insight and structural optimization of size and PL should be established. Insight from single QD resolution atomic structure and photophysical correlative studies provides a direct course to synthetically tune QDs to match these challenging environments.
Collapse
Affiliation(s)
- Ruben Torres
- Department
of Chemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
- Vanderbilt
Institute of Chemical Biology, Vanderbilt
University, Nashville, Tennessee 37240, United States
- Vanderbilt
Institute for Nanoscale Science and Engineering, Vanderbilt University, Nashville, Tennessee 37240, United States
| | - Lucas B. Thal
- Department
of Chemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
- Vanderbilt
Institute of Chemical Biology, Vanderbilt
University, Nashville, Tennessee 37240, United States
- Vanderbilt
Institute for Nanoscale Science and Engineering, Vanderbilt University, Nashville, Tennessee 37240, United States
| | - James R. McBride
- Department
of Chemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
- Vanderbilt
Institute for Nanoscale Science and Engineering, Vanderbilt University, Nashville, Tennessee 37240, United States
- Department
of Electrical and Computer Engineering, Vanderbilt University, Nashville, Tennessee 37240, United States
| | - Bruce E. Cohen
- The
Molecular Foundry and Division of Molecular Biophysics & Integrated
Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Sandra J. Rosenthal
- Department
of Chemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
- Vanderbilt
Institute of Chemical Biology, Vanderbilt
University, Nashville, Tennessee 37240, United States
- Vanderbilt
Institute for Nanoscale Science and Engineering, Vanderbilt University, Nashville, Tennessee 37240, United States
- Department
of Pharmacology, Vanderbilt University, Nashville, Tennessee 37240, United States
- Department
of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37240, United States
- Vanderbilt
Interdisciplinary Materials Science Program, Vanderbilt University, Nashville, Tennessee 37240, United States
| |
Collapse
|
3
|
Nguyen AT, Baucom DR, Wang Y, Heyes CD. Compact, Fast Blinking Cd-Free Quantum Dots for Super-Resolution Fluorescence Imaging. CHEMICAL & BIOMEDICAL IMAGING 2023; 1:251-259. [PMID: 37388960 PMCID: PMC10302876 DOI: 10.1021/cbmi.3c00018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 03/20/2023] [Accepted: 03/21/2023] [Indexed: 07/01/2023]
Abstract
Quantum dots (QDs) can be used as fluorescent probes in single molecule localization microscopy to achieve subdiffraction limit resolution (super-resolution fluorescence imaging). However, the toxicity of Cd in the prototypical CdSe-based QDs can limit their use in biological applications. Furthermore, commercial CdSe QDs are usually modified with relatively thick shells of both inorganic and organic materials to render them in the 10-20 nm size range, which is relatively large for biological labels. In this report, we present compact (4-6 nm) CuInS2/ZnS (CIS/ZnS) and compare them to commercially sourced CdSe/ZnS QDs for their blinking behavior, localization precision and super-resolution imaging. Although commercial CdSe/ZnS QDs are brighter than the more compact Cd-free CIS/ZnS QD, both give comparable results of 4.5-5.0-fold improvement in imaging resolution over conventional TIRF imaging of actin filaments. This likely results from the fact that CIS/ZnS QDs show very short on-times and long off times which leads to less overlap in the point spread functions of emitting CIS/ZnS QD labels on the actin filaments at the same labeling density. These results demonstrate that CIS/ZnS QDs are an excellent candidate to complement and perhaps even replace the larger and more toxic CdSe-based QDs for robust single- molecule super-resolution imaging.
Collapse
Affiliation(s)
- Anh T. Nguyen
- Department
of Chemistry and Biochemistry, University
of Arkansas, 345 North Campus Drive, Fayetteville, Arkansas 72701, United States
| | - Dustin R. Baucom
- Department
of Chemistry and Biochemistry, University
of Arkansas, 345 North Campus Drive, Fayetteville, Arkansas 72701, United States
| | - Yong Wang
- Department
of Physics, University of Arkansas, 825 West Dickson Street, Fayetteville, Arkansas 72701, United States
| | - Colin D. Heyes
- Department
of Chemistry and Biochemistry, University
of Arkansas, 345 North Campus Drive, Fayetteville, Arkansas 72701, United States
| |
Collapse
|
4
|
Alvelid J, Bucci A, Testa I. Far Red-Shifted CdTe Quantum Dots for Multicolour Stimulated Emission Depletion Nanoscopy. Chemphyschem 2023; 24:e202200698. [PMID: 36239140 PMCID: PMC10098508 DOI: 10.1002/cphc.202200698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 10/07/2022] [Indexed: 02/03/2023]
Abstract
Stimulated emission depletion (STED) nanoscopy is a widely used nanoscopy technique. Two-colour STED imaging in fixed and living cells is standardised today utilising both fluorescent dyes and fluorescent proteins. Solutions to image additional colours have been demonstrated using spectral unmixing, photobleaching steps, or long-Stokes-shift dyes. However, these approaches often compromise speed, spatial resolution, and image quality, and increase complexity. Here, we present multicolour STED nanoscopy with far red-shifted semiconductor CdTe quantum dots (QDs). STED imaging of the QDs is optimized to minimize blinking effects and maximize the number of detected photons. The far-red and compact emission spectra of the investigated QDs free spectral space for the simultaneous use of fluorescent dyes, enabling straightforward three-colour STED imaging with a single depletion beam. We use our method to study the internalization of QDs in cells, opening up the way for future super-resolution studies of particle uptake and internalization.
Collapse
Affiliation(s)
- Jonatan Alvelid
- Department of Applied Physics and SciLifeLab, KTH Royal Institute of Technology, 114 28, Stockholm, Sweden
| | - Andrea Bucci
- Department of Applied Physics and SciLifeLab, KTH Royal Institute of Technology, 114 28, Stockholm, Sweden
| | - Ilaria Testa
- Department of Applied Physics and SciLifeLab, KTH Royal Institute of Technology, 114 28, Stockholm, Sweden
| |
Collapse
|
5
|
Litvinov I, Salova A, Aksenov N, Kornilova E, Belyaeva T. Microenvironmental Impact on InP/ZnS-Based Quantum Dots in In Vitro Models and in Living Cells: Spectrally- and Time-Resolved Luminescence Analysis. Int J Mol Sci 2023; 24:ijms24032699. [PMID: 36769021 PMCID: PMC9916881 DOI: 10.3390/ijms24032699] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 01/15/2023] [Accepted: 01/21/2023] [Indexed: 02/04/2023] Open
Abstract
Quantum dots (QDs) have attracted great attention as tools for theranostics that combine the possibility of simultaneous biological target visualization and medicine delivery. Here, we address whether core/shell InP/ZnS QDs (InP-QDs) may be an alternative to toxic Cd-based QDs. We analyze InP-QD photophysical characteristics in cell culture medium, salt solutions, and directly in the cells. It was demonstrated that InP-QDs were internalized into endolysosomes in HeLa and A549 cells with dynamics similar to Cd-based QDs of the same design, but the two cell lines accumulated them with different efficiencies. InP-QDs were reliably detected in the endosomes despite their low quantum yields. Cell culture medium efficiently decreased the InP-QD photoluminescence lifetime by 50%, acidic pH (4.0) had a moderate effect (20-25% reduction), and quenching by salt solutions typical of intra-endosomal medium composition resulted in a decrease of about 10-15%. The single-vesicle fluorescence-lifetime imaging microscopy analysis of QDs inside and outside the cells shows that the scatter between endosomes in the same cell can be significant, which indicates the complex impact of the abovementioned factors on the state of InP-QDs. The PI test and MTT test demonstrate that InP-QDs are toxic for both cell lines at concentrations higher than 20 nM. Possible reasons for InP-QD toxicity are discussed.
Collapse
Affiliation(s)
- Ilia Litvinov
- Institute of Cytology, Russian Academy of Sciences,194064 Saint Petersburg, Russia
| | - Anna Salova
- Institute of Cytology, Russian Academy of Sciences,194064 Saint Petersburg, Russia
| | - Nikolay Aksenov
- Institute of Cytology, Russian Academy of Sciences,194064 Saint Petersburg, Russia
| | - Elena Kornilova
- Institute of Cytology, Russian Academy of Sciences,194064 Saint Petersburg, Russia
- Higher School of Biomedical Systems and Technologies, Peter the Great St. Petersburg Polytechnic University, 195251 Saint Petersburg, Russia
- Correspondence: ; Tel.: +7-921-302-59-05
| | - Tatiana Belyaeva
- Institute of Cytology, Russian Academy of Sciences,194064 Saint Petersburg, Russia
| |
Collapse
|
6
|
Xu K, Bechu A, Basu N, Ghoshal S, Moores A, George S. Hazard Profiling of Commercially Relevant Quantum Dot Components Revealed Synergistic Interactions between Heavy Metals and Polymers. Chem Res Toxicol 2022; 35:1457-1466. [PMID: 35943131 DOI: 10.1021/acs.chemrestox.1c00382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Commercially used quantum dots (QDs) exemplify complex nanomaterials with multiple components, though little is known about the type of interactions between these components in determining the overall toxicity of this material. We synthesized and characterized a functional QD (CdSe/ZnS_P&E) that was identical in structure and composition to a patented and commercially applied QD and the combinations of its components (CdSe, CdSe/ZnS, ZnS, CdSe_P&E, ZnS_P&E, and P&E). Cells exposed to incremental concentrations of these materials were investigated for cell viability and cellular perturbations, contributing to a final common pathway of cell death using high-content screening assays in model human intestinal epithelial cells (HIEC-6). The concentrations that resulted in a loss of 20% cell viability (EC20 values) for each tested component were used for estimating the combination index (CI) to evaluate synergistic or antagonistic effects between the components. Complete QD (core/shell-polymer) showed the highest toxic potential due to synergistic interactions between core and surface functional groups. The cationic polymer coating enhanced cellular uptake of the QD, ensuing lysosome acidification and release of heavy metal ions to the intracellular milieu, and caused oxidative stress and cytotoxicity. Overall, this study advances our understanding of the collective contribution of individual components of a functional QD toward its toxic potential and emphasizes the need to study multilayered nanomaterials in their entirety for hazard characterization.
Collapse
Affiliation(s)
- Ke Xu
- Department of Food Science and Agricultural Chemistry, McGill University, Montreal H3A 0G4, Canada
| | - Aude Bechu
- Department of Chemistry, McGill University, Montreal H3A 0G4, Canada
| | - Niladri Basu
- Department of Natural Resources Sciences, McGill University, Montreal H3A 0G4, Canada
| | - Subhasis Ghoshal
- Department of Civil Engineering, McGill University, Montreal H3A 0G4, Canada
| | - Audrey Moores
- Department of Natural Resources Sciences, McGill University, Montreal H3A 0G4, Canada.,Centre for Green Chemistry and Catalysis, Department of Chemistry, McGill University, Montreal H3A 0G4, Canada.,Department of Mining and Materials Engineering, McGill University, Montreal H3A 0G4, Canada
| | - Saji George
- Department of Food Science and Agricultural Chemistry, McGill University, Montreal H3A 0G4, Canada
| |
Collapse
|
7
|
Zhu H, Zan W, Chen W, Jiang W, Ding X, Li BL, Mu Y, Wang L, Garaj S, Leong DT. Defect-Rich Molybdenum Sulfide Quantum Dots for Amplified Photoluminescence and Photonics-Driven Reactive Oxygen Species Generation. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2200004. [PMID: 35688799 DOI: 10.1002/adma.202200004] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2022] [Revised: 05/18/2022] [Indexed: 06/15/2023]
Abstract
Transition metal dichalcogenide (TMD) quantum dots (QDs) with defects have attracted interesting chemistry due to the contribution of vacancies to their unique optical, physical, catalytic, and electrical properties. Engineering defined defects into molybdenum sulfide (MoS2 ) QDs is challenging. Herein, by applying a mild biomineralization-assisted bottom-up strategy, blue photoluminescent MoS2 QDs (B-QDs) with a high density of defects are fabricated. The two-stage synthesis begins with a bottom-up synthesis of original MoS2 QDs (O-QDs) through chemical reactions of Mo and sulfide ions, followed by alkaline etching that creates high sulfur-vacancy defects to eventually form B-QDs. Alkaline etching significantly increases the photoluminescence (PL) and photo-oxidation. An increase in defect density is shown to bring about increased active sites and decreased bandgap energy; which is further validated with density functional theory calculations. There is strengthened binding affinity between QDs and O2 due to lower gap energy (∆EST ) between S1 and T1 , accompanied with improved intersystem crossing (ISC) efficiency. Lowered gap energy contributes to assist e- -h+ pair formation and the strengthened binding affinity between QDs and 3 O2 . Defect engineering unravels another dimension of material properties control and can bring fresh new applications to otherwise well characterized TMD nanomaterials.
Collapse
Affiliation(s)
- Houjuan Zhu
- Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore, 117585, Singapore
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, Singapore, 138634, Singapore
- Centre for Advanced 2D Materials, Graphene Research Centre, National University of Singapore, Singapore, 117546, Singapore
| | - Wenyan Zan
- Institute of Molecular Science, Shanxi University, Taiyuan, 034000, P. R. China
| | - Wanli Chen
- Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore, 117585, Singapore
| | - Wenbin Jiang
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, Singapore, 138634, Singapore
| | - Xianguang Ding
- Key Laboratory for Organic Electronics and Information Displays and Jiangsu Key Laboratory for Biosensors, Nanjing University of Posts and Telecommunications, Nanjing, 210023, P. R. China
| | - Bang Lin Li
- Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University), Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing, 400715, P. R. China
| | - Yuewen Mu
- Institute of Molecular Science, Shanxi University, Taiyuan, 034000, P. R. China
| | - Lei Wang
- Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore, 117585, Singapore
| | - Slaven Garaj
- Centre for Advanced 2D Materials, Graphene Research Centre, National University of Singapore, Singapore, 117546, Singapore
- Department of Physics, National University of Singapore, Singapore, 117542, Singapore
- Department of Biomedical Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117575, Singapore
| | - David Tai Leong
- Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore, 117585, Singapore
| |
Collapse
|
8
|
Kim D, Calabro RL, Masud AA, Kothalawala NL, Gu M, Kwak SY, Son WJ, Hwang KY, Choi H, Richards CI, Kim DY, Kim BS. Exploring the Role of Surface States in Emissive Carbon Nanodots: Analysis at Single-Particle Level. Chem Asian J 2021; 16:4155-4164. [PMID: 34734682 DOI: 10.1002/asia.202101087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 11/01/2021] [Indexed: 11/11/2022]
Abstract
Fluorescent carbon nanodots (CDs) have been highlighted as promising semiconducting materials due to their outstanding chemical and optical properties. However, the intrinsic heterogeneity of CDs has impeded a clear understanding of the mechanisms behind their photophysical properties. In this study, as-prepared CDs are fractionated via chromatography to reduce their structural and chemical heterogeneity and analyzed through ensemble and single-particle spectroscopies. Many single particles reveal fluorescence intensity fluctuations between two or more discrete levels with bi-exponential decays. While the intrinsic τ1 components are uniform among single particles, the τ2 components from molecule-like emissions spans a wider range of lifetimes, reflecting the inhomogeneity of the surface states. Furthermore, it is concluded that the relative population and chemical states of surface functional groups in CDs have a significant impact on emissive states, brightness, blinking, stability, and lifetime distribution of photoluminescence.
Collapse
Affiliation(s)
- Dongseok Kim
- Department of Chemistry, Yonsei University, Seoul, 03722, Republic of Korea
| | - Rosemary L Calabro
- Department of Chemistry, University of Kentucky, 505 Rose Street, Lexington, Kentucky, 40506-0055, United States
| | - Abdullah A Masud
- Department of Chemistry, University of Kentucky, 505 Rose Street, Lexington, Kentucky, 40506-0055, United States
| | - Nadeesha L Kothalawala
- Department of Chemistry, University of Kentucky, 505 Rose Street, Lexington, Kentucky, 40506-0055, United States
| | - Minsu Gu
- Department of Chemistry, Yonsei University, Seoul, 03722, Republic of Korea.,Department of Chemical Engineering (BK21 FOUR), Dong-A University, Busan, 49315, Republic of Korea
| | - Seung-Yeon Kwak
- Samsung Advanced Institute of Technology (SAIT), Samsung Electronics Co. Ltd., Suwon, 16678, Republic of Korea
| | - Won-Joon Son
- Data and Information Technology (DIT) Center, Samsung Electronics, Hwaseong, 18448, Republic of Korea
| | - Kyu Young Hwang
- Samsung Advanced Institute of Technology (SAIT), Samsung Electronics Co. Ltd., Suwon, 16678, Republic of Korea
| | - Hyeonho Choi
- Samsung Advanced Institute of Technology (SAIT), Samsung Electronics Co. Ltd., Suwon, 16678, Republic of Korea
| | - Christopher I Richards
- Department of Chemistry, University of Kentucky, 505 Rose Street, Lexington, Kentucky, 40506-0055, United States
| | - Doo Young Kim
- Department of Chemistry, University of Kentucky, 505 Rose Street, Lexington, Kentucky, 40506-0055, United States
| | - Byeong-Su Kim
- Department of Chemistry, Yonsei University, Seoul, 03722, Republic of Korea
| |
Collapse
|
9
|
Vonk SW, Fridriksson MB, Hinterding SOM, Mangnus MJJ, van Swieten TP, Grozema FC, Rabouw FT, van der Stam W. Trapping and Detrapping in Colloidal Perovskite Nanoplatelets: Elucidation and Prevention of Nonradiative Processes through Chemical Treatment. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2020; 124:8047-8054. [PMID: 32421082 PMCID: PMC7217613 DOI: 10.1021/acs.jpcc.0c02287] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Indexed: 05/05/2023]
Abstract
Metal-halide perovskite nanocrystals show promise as the future active material in photovoltaics, lighting, and other optoelectronic applications. The appeal of these materials is largely due to the robustness of the optoelectronic properties to structural defects. The photoluminescence quantum yield (PLQY) of most types of perovskite nanocrystals is nevertheless below unity, evidencing the existence of nonradiative charge-carrier decay channels. In this work, we experimentally elucidate the nonradiative pathways in CsPbBr3 nanoplatelets, before and after chemical treatment with PbBr2 that improves the PLQY. A combination of picosecond streak camera and nanosecond time-correlated single-photon counting measurements is used to probe the excited-state dynamics over 6 orders of magnitude in time. We find that up to 40% of the nanoplatelets from a synthesis batch are entirely nonfluorescent and cannot be turned fluorescent through chemical treatment. The other nanoplatelets show fluorescence, but charge-carrier trapping leads to losses that are prevented by chemical treatment. Interestingly, even without chemical treatment, some losses due to trapping are mitigated because trapped carriers spontaneously detrap on nanosecond-to-microsecond timescales. Our analysis shows that multiple nonradiative pathways are active in perovskite nanoplatelets, which are affected differently by chemical treatment with PbBr2. More generally, our work highlights that in-depth studies using a combination of techniques are necessary to understand nonradiative pathways in fluorescent nanocrystals. Such understanding is essential to optimize synthesis and treatment procedures.
Collapse
Affiliation(s)
- Sander
J. W. Vonk
- Debye
Institute for Nanomaterials Science, Utrecht
University, Princetonplein 1, 3584 CC Utrecht, The Netherlands
| | - Magnus B. Fridriksson
- Opto-Electronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Stijn O. M. Hinterding
- Debye
Institute for Nanomaterials Science, Utrecht
University, Princetonplein 1, 3584 CC Utrecht, The Netherlands
| | - Mark J. J. Mangnus
- Debye
Institute for Nanomaterials Science, Utrecht
University, Princetonplein 1, 3584 CC Utrecht, The Netherlands
| | - Thomas P. van Swieten
- Debye
Institute for Nanomaterials Science, Utrecht
University, Princetonplein 1, 3584 CC Utrecht, The Netherlands
| | - Ferdinand C. Grozema
- Opto-Electronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Freddy T. Rabouw
- Debye
Institute for Nanomaterials Science, Utrecht
University, Princetonplein 1, 3584 CC Utrecht, The Netherlands
| | - Ward van der Stam
- Opto-Electronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands
| |
Collapse
|
10
|
Paydary P, Larese-Casanova P. Water chemistry influences on long-term dissolution kinetics of CdSe/ZnS quantum dots. J Environ Sci (China) 2020; 90:216-233. [PMID: 32081318 DOI: 10.1016/j.jes.2019.11.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 11/07/2019] [Accepted: 11/14/2019] [Indexed: 06/10/2023]
Abstract
Widespread usage of engineered metallic quantum dots (QDs) within consumer products has evoked a need to assess their fate within environmental systems. QDs are mixed-metal nanocrystals that often include Cd2+ which poses a health risk as a nanocrystal or when leached into water. The goal of this work is to study the long-term metal cation leaching behavior and the factors affecting the dissolution processes of mercaptopropionic acid (MPA) capped CdSe/ZnS QDs in aphotic conditions. QD suspensions were prepared in different water conditions, and release of Zn2+ and Cd2+ cations were monitored over time by size exclusion chromatography-inductively coupled plasma-mass spectrometry. In most conditions with dissolved O2 present, the ZnS shell degraded fairly rapidly over ~1 week, while some of the CdSe core remained up to 80 days. Additional MPA, Zn2+, and Cd2+ temporarily delayed dissolution, indicating a moderate role for capping agent detachment and mineral solubility. The presence of H2O2 and the ligand ethylenediaminetetraacetate accelerated dissolution, while NOM had no kinetic effect. No dissolution of CdSe core was observed when O2 was absent or when QDs formed aggregates at higher concentrations with O2 present. The shrinking particle model with product layer diffusion control best describes Zn2+ and Cd2+ dissolution kinetics. The longevity of QDs in their nanocrystal form appears to be partly controlled by environmental conditions, with anoxic, aphotic environments preserving the core mineral phase, and oxidants or complexing ligands promoting shell and core mineral dissolution.
Collapse
Affiliation(s)
- Pooya Paydary
- Department of Civil and Environmental Engineering, Northeastern University, Boston, MA, USA.
| | - Philip Larese-Casanova
- Department of Civil and Environmental Engineering, Northeastern University, Boston, MA, USA.
| |
Collapse
|
11
|
Hu Z, Liu S, Qin H, Zhou J, Peng X. Oxygen Stabilizes Photoluminescence of CdSe/CdS Core/Shell Quantum Dots via Deionization. J Am Chem Soc 2020; 142:4254-4264. [DOI: 10.1021/jacs.9b11978] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Zhuang Hu
- Center for Chemistry of Novel & High-Performance Materials, and Department of Chemistry, Zhejiang University, Hangzhou 310027, People’s Republic of China
| | - Shaojie Liu
- Center for Chemistry of Novel & High-Performance Materials, and Department of Chemistry, Zhejiang University, Hangzhou 310027, People’s Republic of China
| | - Haiyan Qin
- Center for Chemistry of Novel & High-Performance Materials, and Department of Chemistry, Zhejiang University, Hangzhou 310027, People’s Republic of China
| | - Jianhai Zhou
- Center for Chemistry of Novel & High-Performance Materials, and Department of Chemistry, Zhejiang University, Hangzhou 310027, People’s Republic of China
| | - Xiaogang Peng
- Center for Chemistry of Novel & High-Performance Materials, and Department of Chemistry, Zhejiang University, Hangzhou 310027, People’s Republic of China
| |
Collapse
|
12
|
Salerno G, Scarano S, Mamusa M, Consumi M, Giuntini S, Macagnano A, Nativi S, Fragai M, Minunni M, Berti D, Magnani A, Nativi C, Richichi B. A small heterobifunctional ligand provides stable and water dispersible core-shell CdSe/ZnS quantum dots (QDs). NANOSCALE 2018; 10:19720-19732. [PMID: 30256371 DOI: 10.1039/c8nr05566a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
We describe a simple method to prepare water dispersible core-shell CdSe/ZnS quantum dots (QDs) 1 by capping QDs with a new thiol-containing heterobifunctional dicarboxylic ligand 4 (DHLA-EDADA). This ligand, obtained on a gram scale through a few synthetic steps, provides a compact layer on the QDs, whose hydrodynamic size in H2O is 15 nm ± 3 nm. The colloidal stability is dramatically enhanced with respect to the well-known (±) α-lipoic acid (DHLA). The ligand affinity towards QDs and the water dispersibility of nanocrystals 1 are addressed by the dithiol groups of DHLA, which chelate the zinc of the shell, and by the dicarboxylic groups of the ethylenediamine-N,N-diacetic acid (EDADA) residue, respectively. The effects of pH, buffer solutions, and biological medium on the stability of QDs 1 were assessed by monitoring the photoluminescence (PL) and hydrodynamic size over time. Highly fluorescent QD dispersions, stable over extended periods of time and over broad pH ranges and buffer types, were obtained. Furthermore, we show that the DHLA-EDADA ligand 4 also endows QDs with functional groups suitable for further conjugation and for metal ion detection. As a case study to illustrate the potential of our approach, we report the preparation and characterization of a highly luminescent orange light emitting polymer-QD 1 composite film.
Collapse
Affiliation(s)
- Gianluca Salerno
- Department of Chemistry 'Ugo Schiff', University of Florence, Via della Lastruccia 13, 50019 Sesto F.no, FI, Italy.
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Thomas EM, Ghimire S, Kohara R, Anil AN, Yuyama KI, Takano Y, Thomas KG, Biju V. Blinking Suppression in Highly Excited CdSe/ZnS Quantum Dots by Electron Transfer under Large Positive Gibbs (Free) Energy Change. ACS NANO 2018; 12:9060-9069. [PMID: 30103604 DOI: 10.1021/acsnano.8b03010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Semiconductor quantum dots with stable photoluminescence are necessary for next generation optoelectronic and photovoltaic devices. Photoluminescence intensity fluctuations of cadmium and lead chalcogenide quantum dots have been extensively investigated since the first observation of blinking in CdSe nanocrystals in 1996. In a quantum dot, blinking originates from stochastic photocharging, nonradiative Auger recombination, and delayed neutralization. So far, blinking is suppressed by defect passivation, electron transfer, and shell preparation, but without any deep insight into free energy change of electron transfer. We report real-time detection of significant blinking suppression for CdSe/ZnS quantum dots exposed to N, N-dimethylaniline, which is accompanied by a considerable increase in the time-averaged photoluminescence intensity of quantum dots. Although the Gibbs (free) energy change (Δ Get = +2.24 eV), which is estimated electrochemically and from density functional theory calculations, is unfavorable for electron transfer from N, N-dimethylaniline to a quantum dot in the minimally excited (band-edge) state, electron transfer is obvious when a quantum dot is highly excited. Nonetheless, Δ Get crosses from the positive to negative scale as the solvent dielectric constant exceeds 5, favoring electron transfer from N, N-dimethylaniline to a quantum dot excited to the band-edge state. Based on single-molecule photoluminescence and ensemble electron transfer studies, we assign blinking suppression to the transfer of an electron from N, N-dimethylaniline to the hot hole state of a quantum dot. In addition to blinking suppression by electron transfer, complete removal of blinking is limited by short-living OFF states induced by the negative trion.
Collapse
Affiliation(s)
- Elizabeth Mariam Thomas
- Research Institute for Electronic Science , Hokkaido University , Sapporo , Hokkaido 001-0020 , Japan
- School of Chemistry , Indian Institute of Science Education and Research Thiruvananthapuram (IISER-TVM) , Thiruvananthapuram 695551 , India
| | - Sushant Ghimire
- Research Institute for Electronic Science , Hokkaido University , Sapporo , Hokkaido 001-0020 , Japan
- Graduate School of Environmental Science , Hokkaido University , Sapporo , Hokkaido 060-0810 , Japan
| | - Reiko Kohara
- Research Institute for Electronic Science , Hokkaido University , Sapporo , Hokkaido 001-0020 , Japan
- Graduate School of Environmental Science , Hokkaido University , Sapporo , Hokkaido 060-0810 , Japan
| | - Ajith Nair Anil
- Research Institute for Electronic Science , Hokkaido University , Sapporo , Hokkaido 001-0020 , Japan
- Graduate School of Environmental Science , Hokkaido University , Sapporo , Hokkaido 060-0810 , Japan
| | - Ken-Ichi Yuyama
- Research Institute for Electronic Science , Hokkaido University , Sapporo , Hokkaido 001-0020 , Japan
- Graduate School of Environmental Science , Hokkaido University , Sapporo , Hokkaido 060-0810 , Japan
| | - Yuta Takano
- Research Institute for Electronic Science , Hokkaido University , Sapporo , Hokkaido 001-0020 , Japan
- Graduate School of Environmental Science , Hokkaido University , Sapporo , Hokkaido 060-0810 , Japan
| | - K George Thomas
- School of Chemistry , Indian Institute of Science Education and Research Thiruvananthapuram (IISER-TVM) , Thiruvananthapuram 695551 , India
| | - Vasudevanpillai Biju
- Research Institute for Electronic Science , Hokkaido University , Sapporo , Hokkaido 001-0020 , Japan
- Graduate School of Environmental Science , Hokkaido University , Sapporo , Hokkaido 060-0810 , Japan
| |
Collapse
|
14
|
Bahmani Jalali H, Melikov R, Sadeghi S, Nizamoglu S. Excitonic Energy Transfer within InP/ZnS Quantum Dot Langmuir-Blodgett Assemblies. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2018; 122:11616-11622. [PMID: 30057655 PMCID: PMC6057685 DOI: 10.1021/acs.jpcc.8b00744] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 05/05/2018] [Indexed: 05/11/2023]
Abstract
Interparticle energy transfer offers great promise to a diverse range of applications ranging from artificial solar energy harvesting to nanoscale rulers in biology. Here, we assembled InP/ZnS core/shell quantum dot monolayers via the Langmuir-Blodgett technique and studied the effect of ZnS shell thickness on the excitonic energy transfer within these core/shell quantum dots. Three types of InP-based core/shell quantum dot Langmuir-Blodgett assemblies with different ZnS shell thicknesses were assembled. The structural and optical properties of colloidal quantum dots reveal the successful multiple ZnS shell growth, and atomic force microscopy studies show the smoothness of the assembled monolayers. Time-resolved photoluminescence (PL) and fluorescence lifetime imaging microscopy (FLIM) studies of the thick-shell QD monolayer reveal narrower lifetime distribution in comparison with the thin-shell QD monolayer. The interparticle excitonic energy transfer was studied by spectrally resolved PL traces, and higher energy transfer was observed for the thin-shell InP/1ZnS QD monolayer. Finally, we calculated the average exciton energy and indicated that the energy transfer induced exciton energy shift decreased significantly from 95 to 27 meV after multiple ZnS shell growth.
Collapse
Affiliation(s)
- Houman Bahmani Jalali
- Department
of Biomedical Science and Engineering, Koç
University, Istanbul 34450, Turkey
| | - Rustamzhon Melikov
- Department
of Electrical and Electronics Engineering, Koç University, Istanbul 34450, Turkey
| | - Sadra Sadeghi
- Department
of Material Science and Engineering, Koç
University, Istanbul 34450, Turkey
| | - Sedat Nizamoglu
- Department
of Biomedical Science and Engineering, Koç
University, Istanbul 34450, Turkey
- Department
of Electrical and Electronics Engineering, Koç University, Istanbul 34450, Turkey
- Department
of Material Science and Engineering, Koç
University, Istanbul 34450, Turkey
- E-mail:
| |
Collapse
|
15
|
Abbandonato G, Hoffmann K, Resch-Genger U. Determination of quantum yields of semiconductor nanocrystals at the single emitter level via fluorescence correlation spectroscopy. NANOSCALE 2018; 10:7147-7154. [PMID: 29616686 DOI: 10.1039/c7nr09332b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Comparing the photoluminescence (PL) properties of ensembles of nanocrystals like semiconductor quantum dots (QDs) with single particle studies is of increasing interest for many applications of these materials as reporters in bioimaging studies performed under very dilute conditions or even at the single particle level. Particularly relevant is here the PL quantum yield (ΦF), which determines the signal size together with the reporter's molar extinction coefficient and is a direct measure for nanocrystal quality, especially for the inorganic surface passivation shell and its tightness, which can be correlated also with nanocrystal stability and the possible release of heavy metal ions. Exemplarily for red and green emitting CdTe nanocrystals, we present a method for the determination of ΦF of nanoparticle dispersions at ultralow concentration compared to cuvette measurements using fluorescence correlation spectroscopy (FCS), a single molecule method, and compared to molecular dyes with closely matching spectral properties and known ΦF. Our results underline the potential of this approach, provided that material-inherent limitations like ligand- and QD-specific aggregation affecting particle diffusion and QD drawbacks such as their complex and power-dependent blinking behavior are properly considered as shown here.
Collapse
Affiliation(s)
- Gerardo Abbandonato
- Federal Institute for Materials Research and Testing (BAM), Division Biophotonics, Richard-Willstaetter-Str. 11, 12489 Berlin, Germany.
| | | | | |
Collapse
|
16
|
Roy D, Mandal S, De CK, Kumar K, Mandal PK. Nearly suppressed photoluminescence blinking of small-sized, blue–green–orange–red emitting single CdSe-based core/gradient alloy shell/shell quantum dots: correlation between truncation time and photoluminescence quantum yield. Phys Chem Chem Phys 2018; 20:10332-10344. [DOI: 10.1039/c8cp00952j] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Nearly suppressed PL blinking of small sized CdSe based CGASS QDs.
Collapse
Affiliation(s)
- Debjit Roy
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Kolkata
- Mohanpur
- India
| | - Saptarshi Mandal
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Kolkata
- Mohanpur
- India
| | - Chayan K. De
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Kolkata
- Mohanpur
- India
| | - Kaushalendra Kumar
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Kolkata
- Mohanpur
- India
| | - Prasun K. Mandal
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Kolkata
- Mohanpur
- India
- Centre for Advanced Functional Materials
| |
Collapse
|
17
|
Targeting breast cancer cells with a CuInS 2/ZnS quantum dot-labeled Ki-67 bioprobe. Oncol Lett 2017; 15:2471-2476. [PMID: 29434960 DOI: 10.3892/ol.2017.7615] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Accepted: 10/20/2017] [Indexed: 01/18/2023] Open
Abstract
The aim of the present study was to develop a water-soluble biomarker for the detection of breast cancer using quantum dots (QDs) conjugated to Ki-67, a nuclear protein associated with the cell cycle. Ki-67 is also a marker of cell proliferation, with expression levels categorizing good and poor prognosis in invasive breast cancer. Ki-67 is a clinically used biomarker for breast cancer diagnosis, treatment and prognosis. Owing to the optical and chemical advantages of QDs, QD-based nanotechnology may aid the construction of a biomedical imaging platform for the study of cancer cell behavior. In the present study, a biomarker was prepared by employing the water-soluble CuInS2/ZnS QDs conjugated to an anti-Ki-67 monoclonal antibody to detect Ki-67 expression in breast cancer. The QDs, which were hydrophobic and coated with octadecylamine, were encapsulated with an amphiphilic biocompatible centipede-like polymer, and then conjugated to anti-Ki-67 monoclonal antibodies (QD-Ki-67 probes). The QD-Ki-67 probes retained the original optical properties of the unadorned QDs and did not exhibit distinct toxic side effects in in vitro cytotoxicity experiments. Therefore, this CuInS2/ZnS QD-labeled bioprobe, with a high quantum yield and low cytotoxicity, is a promising candidate for bioimaging and may be used as a cell label.
Collapse
|
18
|
Kaiser M, Würth C, Kraft M, Hyppänen I, Soukka T, Resch-Genger U. Power-dependent upconversion quantum yield of NaYF 4:Yb 3+,Er 3+ nano- and micrometer-sized particles - measurements and simulations. NANOSCALE 2017; 9:10051-10058. [PMID: 28686275 DOI: 10.1039/c7nr02449e] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Photophysical studies of nonlinear lanthanide-doped photon upconverting nanoparticles (UCNPs) increasingly used in biophotonics and photovoltaics require absolute measurements of the excitation power density (P)-dependent upconversion luminescence (UCL) and luminescence quantum yields (ΦUC) for quantifying the material performance, UCL deactivation pathways, and possible enhancement factors. We present here the P-dependence of the UCL spectra, ΦUC, and slope factors of the different emission bands of representative 25 nm-sized oleate-capped β-NaYF4:17% Yb3+, 3% Er3+ UCNPs dispersed in toluene and as powder as well as ΦUC of 3 μm-sized upconversion particles (UCμP), all measured with a newly designed integrating sphere setup, enabling controlled variation of P over four orders of magnitude. This includes quantifying the influence of the beam shape on the measured ΦUC and comparison of experimental ΦUC with simulations utilizing the balancing power density model of the Andersson-Engels group and the simulated ΦUC of UCμP from the Berry group, underpinned by closely matching decay kinetics of our UC material. We obtained a maximum ΦUC of 10.5% for UCμP and a ΦUC of 0.6% and 2.1% for solid and dispersed UCNPs, respectively. Our results suggest an overestimation of the contribution of the purple and an underestimation of that of the red emission of β-NaYF4:Yb3+,Er3+: microparticles by the simulations of the Berry group. Moreover, our measurements can be used as a guideline to the absolute determination of UCL and ΦUC.
Collapse
Affiliation(s)
- Martin Kaiser
- Federal Institute for Materials Research and Testing (BAM), Division Biophotonics (1.10), Richard-Willstaetter-Str. 11, D-12489 Berlin, Germany.
| | | | | | | | | | | |
Collapse
|
19
|
Angeloni I, Raja W, Polovitsyn A, De Donato F, Zaccaria RP, Moreels I. Band-edge oscillator strength of colloidal CdSe/CdS dot-in-rods: comparison of absorption and time-resolved fluorescence spectroscopy. NANOSCALE 2017; 9:4730-4738. [PMID: 28327734 DOI: 10.1039/c6nr09021d] [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
We studied the oscillator strength fgap of the band gap transition in heteronanocrystals (hNCs) with a spherical CdSe core embedded in an elongated CdS shell. A comparison with fgap of core-only CdSe NCs confirmed a reduction of the electron-hole overlap in hNCs with a band gap larger than 2.05 eV or smaller than 1.98 eV. However, the decrease in fgap is limited to about 50% when compared to CdSe NCs, suggesting that residual confinement still localizes the electron near the core. We correlated fgap with the radiative lifetime obtained from multiexponential photoluminescence (PL) decay traces. The different components were attributed to radiative decay, or deep and shallow carrier trapping, respectively, using the PL quantum efficiency (QE) as a guideline. Our data highlight the challenges associated when extracting the radiative decay, and demonstrate the added value of absorption spectroscopy to obtain the band-edge oscillator strength and the associated radiative recombination rate in colloidal hNCs.
Collapse
Affiliation(s)
- I Angeloni
- Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy. and Dipartimento di Chimica e Chimica Industriale, Università di Genova, Via Dodecaneso 33, 16146 Genova, Italy
| | - W Raja
- Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy. and Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova, Italy
| | - A Polovitsyn
- Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy. and Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova, Italy
| | - F De Donato
- Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy.
| | | | - I Moreels
- Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy.
| |
Collapse
|
20
|
Gao F, Bajwa P, Nguyen A, Heyes CD. Shell-Dependent Photoluminescence Studies Provide Mechanistic Insights into the Off-Grey-On Transitions of Blinking Quantum Dots. ACS NANO 2017; 11:2905-2916. [PMID: 28221750 DOI: 10.1021/acsnano.6b08040] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The majority of quantum dot (QD) blinking studies have used a model of switching between two distinct fluorescence intensity levels, "on" and "off". However, a distinct intermediate intensity level has been identified in some recent reports, a so-called "grey" or "dim" state, which has brought this binary model into question. While this grey state has been proposed to result from the formation of a trion, it is still unclear under which conditions it is present in a QD. By performing shell-dependent blinking studies on CdSe QDs, we report that the populations of the grey state and the on state are strongly dependent on both the shell material and its thickness. We found that adding a ZnS shell did not result in a significant population of the grey state. Using ZnSe as the shell material resulted in a slightly higher population of the grey state, although it was still poorly resolved. However, adding a CdS shell resulted in the population of a grey state, which depended strongly on its thickness up to 5 ML. Interestingly, while the frequency of transitions to and from the grey state showed a very strong dependence on CdS shell thickness, the brightness of and the dwell time in the grey state did not. Moreover, we found that the grey state acts as an on-pathway intermediate state between on and off states, with the thickness of the shell determining the transition probability between them. We also identified two types of blinking behavior in QDs, one that showed long-lived but lower intensity on states and another that showed short-lived but brighter on states that also depended on the shell thickness. Intensity-resolved single QD fluorescence lifetime analysis was used to identify the relationship between the various exciton decay pathways and the resulting intensity levels. We used this data to propose a model in which multiple on, grey, and off states exist whose equilibrium populations vary with time that give rise to the various intensity levels of single QDs and which depends on shell composition and thickness.
Collapse
Affiliation(s)
- Feng Gao
- Department of Chemistry and Biochemistry, University of Arkansas , 345 North Campus Drive, Fayetteville, Arkansas 72701, United States
| | - Pooja Bajwa
- Department of Chemistry and Biochemistry, University of Arkansas , 345 North Campus Drive, Fayetteville, Arkansas 72701, United States
| | - Anh Nguyen
- Department of Chemistry and Biochemistry, University of Arkansas , 345 North Campus Drive, Fayetteville, Arkansas 72701, United States
| | - Colin D Heyes
- Department of Chemistry and Biochemistry, University of Arkansas , 345 North Campus Drive, Fayetteville, Arkansas 72701, United States
| |
Collapse
|
21
|
Geißler D, Würth C, Wolter C, Weller H, Resch-Genger U. Excitation wavelength dependence of the photoluminescence quantum yield and decay behavior of CdSe/CdS quantum dot/quantum rods with different aspect ratios. Phys Chem Chem Phys 2017; 19:12509-12516. [DOI: 10.1039/c7cp02142a] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Our results reveal a strong λexc-dependence of PL quantum yields and decay times, particularly for longer quantum dot-quantum rods with high aspect ratios.
Collapse
Affiliation(s)
- D. Geißler
- Federal Institute for Materials Research and Testing (BAM)
- Berlin
- Germany
| | - C. Würth
- Federal Institute for Materials Research and Testing (BAM)
- Berlin
- Germany
| | - C. Wolter
- University of Hamburg
- Institute of Physical Chemistry
- Hamburg
- Germany
| | - H. Weller
- University of Hamburg
- Institute of Physical Chemistry
- Hamburg
- Germany
| | - U. Resch-Genger
- Federal Institute for Materials Research and Testing (BAM)
- Berlin
- Germany
| |
Collapse
|
22
|
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]
|
23
|
|
24
|
Omogo B, Gao F, Bajwa P, Kaneko M, Heyes CD. Reducing Blinking in Small Core-Multishell Quantum Dots by Carefully Balancing Confinement Potential and Induced Lattice Strain: The "Goldilocks" Effect. ACS NANO 2016; 10:4072-82. [PMID: 27058120 DOI: 10.1021/acsnano.5b06994] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Currently, the most common way to reduce blinking in quantum dots (QDs) is accomplished by using very thick and/or perfectly crystalline CdS shells on CdSe cores. Ideally, a nontoxic material such as ZnS is preferred to be the outer material in order to reduce environmental and cytotoxic effects. Blinking suppression with multishell configurations of CdS and ZnS has been reported only for "giant" QDs of 15 nm or more. One of the main reasons for the limited progress is that the role that interfacial trap states play in blinking in these systems is not very well understood. Here, we show a "Goldilocks" effect to reduce blinking in small (∼7 nm) QDs by carefully controlling the thicknesses of the shells in multishell QDs. Furthermore, by correlating the fluorescence lifetime components with the fraction of time that a QD spends in the on-state, both with and without applying a threshold, we found evidence for two types of blinking that separately affect the average fluorescence lifetime of a single QD. A thorough characterization of the time-resolved fluorescence at the ensemble and single-particle level allowed us to propose a detailed physical model involving both short-lived interfacial trap states and long-lived surface trap states that are coupled. This model highlights a strategy of reducing QD blinking in small QDs by balancing the magnitude of the induced lattice strain, which results in the formation of interfacial trap states between the inner shell and the outer shell, and the confinement potential that determines how accessible the interfacial trap states are. The combination of reducing blinking while maintaining a small overall QD size and using a Cd-free outer shell of ZnS will be useful in a wide array of applications, particularly for advanced bioimaging.
Collapse
Affiliation(s)
- Benard Omogo
- Department of Chemistry and Biochemistry, University of Arkansas , Fayetteville, Arkansas 72701, United States
| | - Feng Gao
- Department of Chemistry and Biochemistry, University of Arkansas , Fayetteville, Arkansas 72701, United States
| | - Pooja Bajwa
- Department of Chemistry and Biochemistry, University of Arkansas , Fayetteville, Arkansas 72701, United States
| | - Mizuho Kaneko
- Department of Chemistry and Biochemistry, University of Arkansas , Fayetteville, Arkansas 72701, United States
| | - Colin D Heyes
- Department of Chemistry and Biochemistry, University of Arkansas , Fayetteville, Arkansas 72701, United States
| |
Collapse
|
25
|
Wen Q, Kershaw SV, Kalytchuk S, Zhovtiuk O, Reckmeier C, Vasilevskiy MI, Rogach AL. Impact of D2O/H2O Solvent Exchange on the Emission of HgTe and CdTe Quantum Dots: Polaron and Energy Transfer Effects. ACS NANO 2016; 10:4301-11. [PMID: 26958866 DOI: 10.1021/acsnano.5b07852] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
We have studied light emission kinetics and analyzed carrier recombination channels in HgTe quantum dots that were initially grown in H2O. When the solvent is replaced by D2O, the nonradiative recombination rate changes highlight the role of the vibrational degrees of freedom in the medium surrounding the dots, including both solvent and ligands. The contributing energy loss mechanisms have been evaluated by developing quantitative models for the nonradiative recombination via (i) polaron states formed by strong coupling of ligand vibration modes to a surface trap state (nonresonant channel) and (ii) resonant energy transfer to vibration modes in the solvent. We conclude that channel (i) is more important than (ii) for HgTe dots in either solution. When some of these modes are removed from the relevant spectral range by the H2O to D2O replacement, the polaron effect becomes weaker and the nonradiative lifetime increases. Comparisons with CdTe quantum dots (QDs) served as a reference where the resonant energy loss (ii) a priori was not a factor, also confirmed by our experiments. The solvent exchange (H2O to D2O), however, is found to slightly increase the overall quantum yield of CdTe samples, probably by increasing the fraction of bright dots in the ensemble. The fundamental study reported here can serve as the foundation for the design and optimization principles of narrow bandgap quantum dots aimed at applications in long wavelength colloidal materials for infrared light emitting diodes and photodetectors.
Collapse
Affiliation(s)
- Qiannan Wen
- Department of Physics and Materials Science and Centre for Functional Photonics (CFP), City University of Hong Kong , Kowloon, Hong Kong S.A.R
| | - Stephen V Kershaw
- Department of Physics and Materials Science and Centre for Functional Photonics (CFP), City University of Hong Kong , Kowloon, Hong Kong S.A.R
| | - Sergii Kalytchuk
- Department of Physics and Materials Science and Centre for Functional Photonics (CFP), City University of Hong Kong , Kowloon, Hong Kong S.A.R
| | - Olga Zhovtiuk
- Department of Physics and Materials Science and Centre for Functional Photonics (CFP), City University of Hong Kong , Kowloon, Hong Kong S.A.R
| | - Claas Reckmeier
- Department of Physics and Materials Science and Centre for Functional Photonics (CFP), City University of Hong Kong , Kowloon, Hong Kong S.A.R
| | - Mikhail I Vasilevskiy
- Department of Physics and Materials Science and Centre for Functional Photonics (CFP), City University of Hong Kong , Kowloon, Hong Kong S.A.R
- Centro de Fisica, Universidade do Minho, Campus de Gualtar , Braga 4710-057, Portugal
| | - Andrey L Rogach
- Department of Physics and Materials Science and Centre for Functional Photonics (CFP), City University of Hong Kong , Kowloon, Hong Kong S.A.R
| |
Collapse
|
26
|
Wang ZG, Liu SL, Hu YJ, Tian ZQ, Hu B, Zhang ZL, Pang DW. Dissecting the Factors Affecting the Fluorescence Stability of Quantum Dots in Live Cells. ACS APPLIED MATERIALS & INTERFACES 2016; 8:8401-8408. [PMID: 26998815 DOI: 10.1021/acsami.6b01742] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Labeling and imaging of live cells with quantum dots (QDs) has attracted great attention in the biomedical field over the past two decades. Maintenance of the fluorescence of QDs in a biological environment is crucial for performing long-term cell tracking to investigate the proliferation and functional evolution of cells. The cell-penetrating peptide transactivator of transcription (TAT) is a well-studied peptide to efficiently enhance the transmembrane delivery. Here, we used TAT peptide-conjugated QDs (TAT-QDs) as a model system to examine the fluorescence stability of QDs in live cells. By confocal microscopy, we found that TAT-QDs were internalized into cells by endocytosis, and transported into the cytoplasm via the mitochondria, Golgi apparatus, and lysosomes. More importantly, the fluorescence of TAT-QDs in live cells was decreased mainly by cell proliferation, and the low pH value in the lysosomes could also lower the fluorescence intensity of intracellular QDs. Quantitative analysis of the amount of QDs in the extracellular region and whole cells indicated that the exocytosis was not the primary cause of fluorescence decay of intracellular QDs. This work facilitates a better understanding of the fluorescence stability of QDs for cell imaging and long-term tracking in live cells. Also, it provides insights into the utility of TAT for transmembrane transportation, and the preparation and modification of QDs for cell imaging and tracking.
Collapse
Affiliation(s)
- Zhi-Gang Wang
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, State Key Laboratory of Virology, The Institute for Advanced Studies, and Wuhan Institute of Biotechnology, Wuhan University , Wuhan 430072, People's Republic of China
| | - Shu-Lin Liu
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, State Key Laboratory of Virology, The Institute for Advanced Studies, and Wuhan Institute of Biotechnology, Wuhan University , Wuhan 430072, People's Republic of China
| | - Yuan-Jun Hu
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, State Key Laboratory of Virology, The Institute for Advanced Studies, and Wuhan Institute of Biotechnology, Wuhan University , Wuhan 430072, People's Republic of China
| | - Zhi-Quan Tian
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, State Key Laboratory of Virology, The Institute for Advanced Studies, and Wuhan Institute of Biotechnology, Wuhan University , Wuhan 430072, People's Republic of China
| | - Bin Hu
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, State Key Laboratory of Virology, The Institute for Advanced Studies, and Wuhan Institute of Biotechnology, Wuhan University , Wuhan 430072, People's Republic of China
| | - Zhi-Ling Zhang
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, State Key Laboratory of Virology, The Institute for Advanced Studies, and Wuhan Institute of Biotechnology, Wuhan University , Wuhan 430072, People's Republic of China
| | - Dai-Wen Pang
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, State Key Laboratory of Virology, The Institute for Advanced Studies, and Wuhan Institute of Biotechnology, Wuhan University , Wuhan 430072, People's Republic of China
| |
Collapse
|
27
|
Bajwa P, Gao F, Nguyen A, Omogo B, Heyes CD. Influence of the Inner-Shell Architecture on Quantum Yield and Blinking Dynamics in Core/Multishell Quantum Dots. Chemphyschem 2016; 17:731-40. [PMID: 26693950 PMCID: PMC5086001 DOI: 10.1002/cphc.201500868] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 11/16/2015] [Indexed: 11/11/2022]
Abstract
Choosing the composition of a shell for QDs is not trivial, as both the band-edge energy offset and interfacial lattice mismatch influence the final optical properties. One way to balance these competing effects is by forming multishells and/or gradient-alloy shells. However, this introduces multiple interfaces, and their relative effects on quantum yield and blinking are not yet fully understood. Here, we undertake a systematic, comparative study of the addition of inner shells of a single component versus gradient-alloy shells of cadmium/zinc chalogenides onto CdSe cores, and then capping with a thin ZnS outer shell to form various core/multishell configurations. We show that architecture of the inner shell between the CdSe core and the outer ZnS shell significantly influences both the quantum yield and blinking dynamics, but that these effects are not correlated-a high ensemble quantum yield doesn't necessarily equate to reduced blinking. Two mathematical models have been proposed to describe the blinking dynamics-the more common power-law model and a more recent multiexponential model. By binning the same data with 1 and 20 ms resolution, we show that the on times can be better described by the multiexponential model, whereas the off times can be better described by the power-law model. We discuss physical mechanisms that might explain this behavior and how it can be affected by the inner-shell architecture.
Collapse
Affiliation(s)
- Pooja Bajwa
- Department of Chemistry and Biochemistry, University of Arkansas, 345 N. Campus Drive, Fayetteville, AR, 72701, USA
| | - Feng Gao
- Department of Chemistry and Biochemistry, University of Arkansas, 345 N. Campus Drive, Fayetteville, AR, 72701, USA
| | - Anh Nguyen
- Department of Chemistry and Biochemistry, University of Arkansas, 345 N. Campus Drive, Fayetteville, AR, 72701, USA
| | - Benard Omogo
- Department of Chemistry and Biochemistry, University of Arkansas, 345 N. Campus Drive, Fayetteville, AR, 72701, USA
| | - Colin D Heyes
- Department of Chemistry and Biochemistry, University of Arkansas, 345 N. Campus Drive, Fayetteville, AR, 72701, USA
| |
Collapse
|
28
|
Liu J, Hu R, Liu J, Zhang B, Wang Y, Liu X, Law WC, Liu L, Ye L, Yong KT. Cytotoxicity assessment of functionalized CdSe, CdTe and InP quantum dots in two human cancer cell models. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2015; 57:222-31. [DOI: 10.1016/j.msec.2015.07.044] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Revised: 06/09/2015] [Accepted: 07/23/2015] [Indexed: 01/09/2023]
|
29
|
Debruyne D, Deschaume O, Coutiño-Gonzalez E, Locquet JP, Hofkens J, Van Bael MJ, Bartic C. The pH-dependent photoluminescence of colloidal CdSe/ZnS quantum dots with different organic coatings. NANOTECHNOLOGY 2015; 26:255703. [PMID: 26031426 DOI: 10.1088/0957-4484/26/25/255703] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The photoluminescence (PL) of colloidal quantum dots (QDs) is known to be sensitive to the solution pH. In this work we investigate the role played by the organic coating in determining the pH-dependent PL. We compare two types of CdSe/ZnS QDs equipped with different organic coatings, namely dihydrolipoic acid (DHLA)-capped QDs and phospholipid micelle-encapsulated QDs. Both QD types have their PL intensity quenched at acidic pH values, but they differ in terms of the reversibility of the quenching process. For DHLA-capped QDs, the quenching is nearly irreversible, with a small reversible component visible only on short time scales. For phospholipid micelle-encapsulated QDs the quenching is notably almost fully reversible. We suggest that the surface passivation by the organic ligands is reversible for the micelle-encapsulated QDs. Additionally, both coatings display pH-dependent spectral shifts. These shifts can be explained by a combination of irreversible processes, such as photo-oxidation and acid etching, and reversible charging of the QD surface, leading to the quantum-confined Stark effect (QCSE), the extent of each effect being coating-dependent. At high ionic strengths, the aggregation of QDs also leads to a spectral (red) shift, which is attributable to the QCSE and/or electronic energy transfer.
Collapse
Affiliation(s)
- David Debruyne
- Laboratory of Solid State Physics and Magnetism, KU Leuven, Celestijnenlaan 200D, BE-3001 Leuven, Belgium
| | | | | | | | | | | | | |
Collapse
|
30
|
Götz MG, Takeuchi H, Goldfogel MJ, Warren JM, Fennell BD, Heyes CD. Visible-light photocatalyzed cross-linking of diacetylene ligands by quantum dots to improve their aqueous colloidal stability. J Phys Chem B 2014; 118:14103-9. [PMID: 25036275 PMCID: PMC4266359 DOI: 10.1021/jp505340c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Ligand cross-linking is known to
improve the colloidal stability
of nanoparticles, particularly in aqueous solutions. However, most
cross-linking is performed chemically, in which it is difficult to
limit interparticle cross-linking, unless performed at low concentrations.
Photochemical cross-linking is a promising approach but usually requires
ultraviolet (UV) light to initiate. Using such high-energy photons
can be harmful to systems in which the ligand–nanoparticle
bond is fairly weak, as is the case for the commonly used semiconductor
quantum dots (QDs). Here, we introduce a novel approach to cross-link
thiolated ligands on QDs by utilizing the photocatalytic activity
of QDs upon absorbing visible light. We show that using visible light
leads to better ligand cross-linking by avoiding the problem of ligand
dissociation that occurs upon UV light exposure. Once cross-linked,
the ligands significantly enhance the colloidal stability of those
same QDs that facilitated cross-linking.
Collapse
Affiliation(s)
- Marion G Götz
- Department of Chemistry, Whitman College , 345 Boyer Avenue, Walla Walla, Washington 99362, United States
| | | | | | | | | | | |
Collapse
|
31
|
Dong C, Liu H, Ren J. Assessing the blinking state of fluorescent quantum dots in free solution by combining fluorescence correlation spectroscopy with ensemble spectroscopic methods. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:12969-12976. [PMID: 25290853 DOI: 10.1021/la503055v] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The current method for investigating the blinking behavior is to immobilize quantum dots (QDs) in the matrix and then apply a fluorescent technique to monitor the fluorescent trajectories of individual QDs. So far, no method can be used to directly assess the blinking state of ensemble QDs in free solution. In this study, a new method was described to characterize the blinking state of the QDs in free solution by combining single molecule fluorescence correlation spectroscopy (FCS) with ensemble spectroscopic methods. Its principle is based on the observation that the apparent concentration of bright QDs obtained by FCS is less than its actual concentration measured by ensemble spectroscopic method due to the QDs blinking. We proposed a blinking index (Kblink) for characterizing the blinking state of QDs, and Kblink is defined as the ratio of the actual concentration (Cb,actual) measured by the ensemble spectroscopic method to the apparent concentration (Cb,app) of QDs obtained by FCS. The effects of certain factors such as laser intensity, growth process, and ligands on blinking of QDs were investigated. The Kblink data of QDs obtained were successfully used to characterize the blinking state of QDs and explain certain experimental results.
Collapse
Affiliation(s)
- Chaoqing Dong
- School of Chemistry & Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University , 800 Dongchuan Road, Shanghai 200240, P. R. China
| | | | | |
Collapse
|
32
|
Würth C, Geißler D, Behnke T, Kaiser M, Resch-Genger U. Critical review of the determination of photoluminescence quantum yields of luminescent reporters. Anal Bioanal Chem 2014; 407:59-78. [DOI: 10.1007/s00216-014-8130-z] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 08/15/2014] [Accepted: 08/22/2014] [Indexed: 12/13/2022]
|
33
|
Gao F, Kreidermacher A, Fritsch I, Heyes CD. 3D imaging of flow patterns in an internally-pumped microfluidic device: redox magnetohydrodynamics and electrochemically-generated density gradients. Anal Chem 2013; 85:4414-22. [PMID: 23537496 PMCID: PMC3838996 DOI: 10.1021/ac3036926] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Redox magnetohydrodynamics (MHD) is a promising technique for developing new electrochemical-based microfluidic flow devices with unique capabilities, such as easily switching flow direction and adjusting flow speeds and flow patterns as well as avoiding bubble formation. However, a detailed description of all the forces involved and predicting flow patterns in confined geometries is lacking. In addition to redox-MHD, density gradients caused by the redox reactions also play important roles. Flow in these devices with small fluid volumes has mainly been characterized by following microbead motion by optical microscopy either by particle tracking velocimetry (PTV) or by processing the microbead images by particle image velocimetry (PIV) software. This approach has limitations in spatial resolution and dimensionality. Here we use fluorescence correlation spectroscopy (FCS) to quantitatively and accurately measure flow speeds and patterns in the ~5-50 μm/s range in redox-MHD-based microfluidic devices, from which 3D flow maps are obtained with a spatial resolution down to 2 μm. The 2 μm spatial resolution flow speeds map revealed detailed flow profiles during redox-MHD in which the velocity increases linearly from above the electrode and reaches a plateau across the center of the cell. By combining FCS and video-microscopy (with PTV and PIV processing approaches), we are able to quantify a vertical flow of ~10 μm/s above the electrodes as a result of density gradients caused by the redox reactions and follow convection flow patterns. Overall, combining FCS, PIV, and PTV analysis of redox-MHD is a powerful combination to more thoroughly characterize the underlying forces in these promising microfluidic devices.
Collapse
Affiliation(s)
| | | | - Ingrid Fritsch
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701
| | - Colin D. Heyes
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701
| |
Collapse
|
34
|
Omogo B, Aldana JF, Heyes CD. Radiative and Non-Radiative Lifetime Engineering of Quantum Dots in Multiple Solvents by Surface Atom Stoichiometry and Ligands. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2013; 117:2317-2327. [PMID: 23543893 PMCID: PMC3610600 DOI: 10.1021/jp309368q] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
CdTe quantum dots have unique characteristics that are promising for applications in photoluminescence, photovoltaics or optoelectronics. However, wide variations of the reported quantum yields exist and the influence of ligand-surface interactions that are expected to control the excited state relaxation processes remains unknown. It is important to thoroughly understand the fundamental principles underlying these relaxation processes to tailor the QDs properties to their application. Here, we systematically investigate the roles of the surface atoms, ligand functional groups and solvent on the radiative and non-radiative relaxation rates. Combining a systematic synthetic approach with X-ray photoelectron, quantitative FT-IR and time-resolved visible spectroscopies, we find that CdTe QDs can be engineered with average radiative lifetimes ranging from nanoseconds up to microseconds. The non-radiative lifetimes are anticorrelated to the radiative lifetimes, although they show much less variation. The density, nature and orientation of the ligand functional groups and the dielectric constant of the solvent play major roles in determining charge carrier trapping and excitonic relaxation pathways. These results are used to propose a coupled dependence between hole-trapping on Te atoms and strong ligand coupling, primarily via Cd atoms, that can be used to engineer both the radiative and non-radiative lifetimes.
Collapse
|
35
|
Mandal G, Darragh M, Wang YA, Heyes CD. Cadmium-free quantum dots as time-gated bioimaging probes in highly-autofluorescent human breast cancer cells. Chem Commun (Camb) 2013; 49:624-6. [PMID: 23223513 PMCID: PMC3570570 DOI: 10.1039/c2cc37529j] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
We report cadmium-free, biocompatible (Zn)CuInS(2) quantum dots with long fluorescence lifetimes as superior bioimaging probes using time-gated detection to suppress cell autofluorescence and improve the signal : background ratio by an order of magnitude. These results will be important for developing non-toxic fluorescence imaging probes for ultrasensitive biomedical diagnostics.
Collapse
Affiliation(s)
- Gopa Mandal
- Department of Chemistry and Biochemistry, University of Arkansas, 345 N. Campus Drive, Fayetteville, AR, 72701, U.S.A. Fax: 479-575-4049; Tel: 479-575-5607
| | - Molly Darragh
- Ocean NanoTech, 2143 Worth Lane, Springdale, AR, 72764
| | | | - Colin D. Heyes
- Department of Chemistry and Biochemistry, University of Arkansas, 345 N. Campus Drive, Fayetteville, AR, 72701, U.S.A. Fax: 479-575-4049; Tel: 479-575-5607
| |
Collapse
|
36
|
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
|
37
|
Opperwall SR, Divakaran A, Porter EG, Christians JA, Denhartigh AJ, Benson DE. Wide dynamic range sensing with single quantum dot biosensors. ACS NANO 2012; 6:8078-8086. [PMID: 22924857 DOI: 10.1021/nn303347k] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Single-particle analysis of biosensors that use charge transfer as the means for analyte-dependent signaling with semiconductor nanoparticles, or quantum dots, was examined. Single-particle analysis of biosensors that use energy transfer show analyte-dependent switching of nanoparticle emission from off to on. The charge-transfer-based biosensors reported here show constant emission, where the analyte (maltose) increases the emission intensity. By monitoring the same nanoparticles under various conditions, a single charge-transfer-based biosensor construct (one maltose binding protein, one protein attachment position for the reductant, one type of nanoparticle) showed a dynamic range for analyte (maltose) detection spanning from 100 pM to 10 μM while the emission intensities increase from 25 to 175% at the single-particle level. Since these biosensors were immobilized, the correlation between the detected maltose concentration and the maltose-dependent emission intensity increase could be examined. Minimal correlation between maltose detection limits and emission increases was observed, suggesting a variety of reductant-nanoparticle surface interactions that control maltose-dependent emission intensity responses. Despite the heterogeneous responses, monitoring biosensor emission intensity over 5 min provided a quantifiable method to monitor maltose concentration. Immobilizing and tracking these biosensors with heterogeneous responses, however, expanded the analyte-dependent emission intensity and the analyte dynamic range obtained from a single construct. Given the wide dynamic range and constant emission of charge-transfer-based biosensors, applying these single molecule techniques could provide ultrasensitive, real-time detection of small molecules in living cells.
Collapse
Affiliation(s)
- Stacey R Opperwall
- Department of Chemistry & Biochemisty, Calvin College, 1726 Knollcrest Circle SE, Grand Rapids, Michigan 49546, United States
| | | | | | | | | | | |
Collapse
|
38
|
Gómez-Campos FM, Califano M. Hole surface trapping in CdSe nanocrystals: dynamics, rate fluctuations, and implications for blinking. NANO LETTERS 2012; 12:4508-4517. [PMID: 22849432 DOI: 10.1021/nl3016279] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Carrier trapping is one of the main sources of performance degradation in nanocrystal-based devices. Yet the dynamics of this process is still unclear. We present a comprehensive investigation into the efficiency of hole transfer to a variety of trap sites located on the surface of the core or the shell or at the core/shell interface in CdSe nanocrystals with both organic and inorganic passivation, using the atomistic semiempirical pseudopotential approach. We separate the contribution of coupling strength and energetics in different systems and trap configurations, obtaining useful general guidelines for trapping rate engineering. We find that trapping can be extremely efficient in core-only systems, with trapping times orders of magnitude faster than radiative recombination. The presence of an inorganic shell can instead bring the trapping rates well below the typical radiative recombination rates observed in these systems.
Collapse
Affiliation(s)
- Francisco M Gómez-Campos
- Departamento de Electrónica y Tecnología de Computadores, Facultad de Ciencias, Universidad de Granada, 18071 Granada, Spain
| | | |
Collapse
|
39
|
Ji X, Palui G, Avellini T, Na HB, Yi C, Knappenberger KL, Mattoussi H. On the pH-dependent quenching of quantum dot photoluminescence by redox active dopamine. J Am Chem Soc 2012; 134:6006-17. [PMID: 22394283 DOI: 10.1021/ja300724x] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
We investigated the charge transfer interactions between luminescent quantum dots (QDs) and redox active dopamine. For this, we used pH-insensitive ZnS-overcoated CdSe QDs rendered water-compatible using poly (ethylene glycol)-appended dihydrolipoic acid (DHLA-PEG), where a fraction of the ligands was amine-terminated to allow for controlled coupling of dopamine-isothiocyanate onto the nanocrystal. Using this sample configuration, we probed the effects of changing the density of dopamine and the buffer pH on the fluorescence properties of these conjugates. Using steady-state and time-resolved fluorescence, we measured a pronounced pH-dependent photoluminescence (PL) quenching for all QD-dopamine assemblies. Several parameters affect the PL loss. First, the quenching efficiency strongly depends on the number of dopamines per QD-conjugate. Second, the quenching efficiency is substantially increased in alkaline buffers. Third, this pH-dependent PL loss can be completely eliminated when oxygen-depleted buffers are used, indicating that oxygen plays a crucial role in the redox activity of dopamine. We attribute these findings to charge transfer interactions between QDs and mainly two forms of dopamine: the reduced catechol and oxidized quinone. As the pH of the dispersions is changed from acidic to basic, oxygen-catalyzed transformation progressively reduces the dopamine potential for oxidation and shifts the equilibrium toward increased concentration of quinones. Thus, in a conjugate, a QD can simultaneously interact with quinones (electron acceptors) and catechols (electron donors), producing pH-dependent PL quenching combined with shortening of the exciton lifetime. This also alters the recombination kinetics of the electron and hole of photoexcited QDs. Transient absorption measurements that probed intraband transitions supported those findings where a simultaneous pronounced change in the electron and hole relaxation rates was measured when the pH was changed from acidic to alkaline.
Collapse
Affiliation(s)
- Xin Ji
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, USA
| | | | | | | | | | | | | |
Collapse
|