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Quantum dots (QDs) have shown great potential to provide spatial, temporal, and structural information for biological systems. However, blinking, photobleaching, and spectral blueshift are adverse effects on their practical applications in biomedical research. An investigation of the effects of six reducing agents including cysteine (Cys), 1,4‐dithiothreitol (DTT), ethyl gallate (EG), L ‐glutathione (GSH), mercaptoacetic acid (MAA), and thiourea (TU) on the photostability of single QDs was studied. Our experiments demonstrate that both DTT and EG effectively inhibit blinking, photobleaching, and spectral blueshift. GSH molecules block blinking and photobleaching of QDs. The other reagents, Cys, MAA, and TU, only have the ability to counteract blinking. Possible explanations are given on the basis of research evidence. The results suggest possibilities for significant improvements in QDs for biological applications by adjusting the environmental conditions. 相似文献
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Tao Zhang Jingxiang Low Jiaguo Yu Alexei M. Tyryshkin Elika Mikmekov Tewodros Asefa 《Angewandte Chemie (International ed. in English)》2020,59(35):15000-15007
A mesoporous TiO2?x material comprised of small, crystalline, vacancy‐rich anatase nanoparticles (NPs) shows unique optical, thermal, and electronic properties. It is synthesized using polymer‐derived mesoporous carbon (PDMC) as a template. The PDMC pores serve as physical barriers during the condensation and pyrolysis of a titania precursor, preventing the titania NPs from growing beyond 10 nm in size. Unlike most titania nanomaterials, during pyrolysis the NPs undergo no transition from the anatase to rutile phase and they become catalytically active reduced TiO2?x. When exposed to a slow electron beam, the NPs exhibit a charge/discharge behavior, lighting up and fading away for an average period of 15 s for an extended period of time. The NPs also show a 50 nm red‐shift in their UV/Vis absorption and long‐lived charge carriers (electrons and holes) at room temperature in the dark, even long after UV irradiation. The NPs as photocatalysts show a good activity for CO2 reduction. 相似文献
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Fluorescence Blinking Beyond Nanoconfinement: Spatially Synchronous Intermittency of Entire Perovskite Microcrystals 下载免费PDF全文
Nithin Pathoor Ansuman Halder Amitrajit Mukherjee Jaladhar Mahato Dr. Shaibal K. Sarkar Dr. Arindam Chowdhury 《Angewandte Chemie (International ed. in English)》2018,57(36):11603-11607
Abrupt fluorescence intermittency or blinking is long recognized to be characteristic of single nano‐emitters. Extended quantum‐confined nanostructures also undergo spatially heterogeneous blinking; however, there is no such precedent in dimensionally unconfined (bulk) materials. Herein, we report multi‐level blinking of entire individual organo–lead bromide perovskite microcrystals (volume=0.1–3 μm3) under ambient conditions. Extremely high spatiotemporal correlation (>0.9) in intracrystal emission intensity fluctuations signifies effective communication amongst photogenerated carriers at distal locations (up to ca. 4 μm) within each crystal. Fused polycrystalline grains also exhibit this intriguing phenomenon, which is rationalized by correlated and efficient migration of carriers to a few transient nonradiative traps, the nature and population of which determine blinking propensity. Observation of spatiotemporally correlated emission intermittency in bulk semiconductor crystals opens the possibility of designing novel devices involving long‐range (mesoscopic) electronic communication. 相似文献
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G Chirico A Diaspro F Cannone M Collini S Bologna V Pellegrini F Beltram 《Chemphyschem》2005,6(2):328-335
We report the two-photon excitation and emission or a recently developed green fluorescent protein (GFP) mutant, E(2)GFP. Two main excitation bands are found at 780 and 870 nm. Blinking and irreversible and reversible bleaching were observed. Fluorescence blinking occurs in the millisecond range and has been ascribed to conversions between the neutral, anionic and dark zwitterionic states. Bleaching is observed after approximately 10 to 400 ms depending on the excitation power, and it is probably due to a conversion to a dark state. The striking feature of this GFP mutant is that the fluorescence can be recovered with very high efficiency only upon irradiation at 720 +/- 10 nm. This GFP mutant therefore seems promising as an almost permanent chromophore for two-photon excitation (TPE) microscopy or for applications in single-molecule memory arrays. 相似文献
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Coherent Magnetic Resonance of Nanocrystal Quantum‐Dot Luminescence as a Window to Blinking Mechanisms 下载免费PDF全文
Dr. Kipp J. van Schooten Prof. Christoph Boehme Prof. John M. Lupton 《Chemphyschem》2014,15(9):1737-1746
Blinking of colloidal nanocrystal quantum dots, random intermittency in the stream of photons emitted by single particles, has long commanded the curiosity of researchers. Why does the particle suddenly shut off, and what are the pathways to quench emission? Single‐particle microscopy is not the only way to approach these fundamental questions on the interaction of light and matter: time‐domain sub‐ensemble spectroscopies can also yield relevant information on microscopic electronic processes. We illustrate recent advances in pulsed optically detected magnetic resonance and highlight the conceptual relevance to unravelling mechanisms controlling intermittency on the single‐particle level. Magnetic resonance reveals two distinct luminescence quenching channels, which appear to be related to those previously surmised from single‐particle studies: a trapped charge‐separated state in which the exciton is quenched by dissociation and the particle remains neutral; and a charged state of the particle in which spin‐dependent Auger recombination quenches luminescence. 相似文献
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Abhishek Swarnkar Ramya Chulliyil Vikash Kumar Ravi Dr. Mir Irfanullah Dr. Arindam Chowdhury Dr. Angshuman Nag 《Angewandte Chemie (International ed. in English)》2015,54(51):15424-15428
Traditional CdSe‐based colloidal quantum dots (cQDs) have interesting photoluminescence (PL) properties. Herein we highlight the advantages in both ensemble and single‐nanocrystal PL of colloidal CsPbBr3 nanocrystals (NCs) over the traditional cQDs. An ensemble of colloidal CsPbBr3 NCs (11 nm) exhibits ca. 90 % PL quantum yield with narrow (FWHM=86 meV) spectral width. Interestingly, the spectral width of a single‐NC and an ensemble are almost identical, ruling out the problem of size‐distribution in PL broadening. Eliminating this problem leads to a negligible influence of self‐absorption and Förster resonance energy transfer, along with batch‐to‐batch reproducibility of NCs exhibiting PL peaks within ±1 nm. Also, PL peak positions do not alter with measurement temperature in the range of 25 to 100 °C. Importantly, CsPbBr3 NCs exhibit suppressed PL blinking with ca. 90 % of the individual NCs remain mostly emissive (on‐time >85 %), without much influence of excitation power. 相似文献
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Jacob P Hoogenboom Jordi Hernando Erik M H P van Dijk Niek F van Hulst Maria F García-Parajó 《Chemphyschem》2007,8(6):823-833
The blinking behavior of perylene diïmide molecules is investigated at the single‐molecule level. We observe long‐time scale blinking of individual multi‐chromophoric complexes embedded in a poly(methylmethacrylate) matrix, as well as for the monomeric dye absorbed on a glass substrate at ambient conditions. In both these different systems, the blinking of single molecules is found to obey analogous power‐law statistics for both the on and off periods. The observed range for single‐molecular power‐law blinking extends over the full experimental time window, covering four orders of magnitude in time and six orders of magnitude in probability density. From molecule to molecule, we observe a large spread in off‐time power‐law exponents. The distributions of off‐exponents in both systems are markedly different whereas both on‐exponent distributions appear similar. Our results are consistent with models that ascribe the power‐law behavior to charge separation and (environment‐dependent) recombination by electron tunneling to a dynamic distribution of charge acceptors. As a consequence of power‐law statistics, single molecule properties like the total number of emitted photons display non‐ergodicity. 相似文献