| 1. |
- An, Rui, et al.
(författare)
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Photostability and Photodegradation Processes in Colloidal CsPbI3 Perovskite Quantum Dots
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 10:45, s. 39222-39227
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Tidskriftsartikel (refereegranskat)abstract
- All-inorganic CsPbI3 perovskite quantum dots (QDs) have attracted intense attention for their successful application in photovoltaics (PVs) and optoelectronics that are enabled by their superior absorption capability and great photoluminescence (PL) properties. However, their photostability remains a practical bottleneck and further optimization is highly desirable. Here, we studied the photostability of as-obtained colloidal CsPbI3 QDs suspended in hexane. We found that light illumination does induce photodegradation of CsPbI3 QDs. Steady-state spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and transient absorption spectroscopy verified that light illumination leads to detachment of the capping agent, collapse of the CsPbI3 QD surface, and finally aggregation of surface Pb0. Both dangling bonds containing surface and Pb0 serve as trap states causing PL quenching with a dramatic decrease of PL quantum yield. Our work provides a detailed insight about the correlation between the structural and photophysical consequences of the photodegradation process in CsPbI3 QDs and may lead to the optimization of such QDs toward device applications.
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| 2. |
- Liu, Yang, et al.
(författare)
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Inorganic ligands-mediated hole attraction and surface structuralreorganization in InP/ZnS QD photocatalysts studied via ultrafast visibleand midinfrared spectroscopies
- 2022
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Ingår i: SCIENCE CHINA Materials. - : Springer Science and Business Media LLC. - 2095-8226 .- 2199-4501. ; 65:9, s. 2529-2539
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Tidskriftsartikel (refereegranskat)abstract
- Photoinduced carrier dynamical processes dominate the optical excitation properties of photocatalysts and further determine the photocatalytic performance. In addition, as the electrons generally possess a faster transfer rate than holes, hole transfer and accumulation are critical, and they play the key efficiency-limiting step during the photocatalytic process. Therefore, a comprehensive understanding of the dynamics of photogenerated holes and their determining factors in the photocatalytic system is highly essential to rationalize the full catalytic mechanism and develop highly efficient photocatalysts, which have not yet been revealed. In this work, the photoinduced charge carrier dynamics in InP/ZnS quantum dots (QDs) capped with long-chain L-typed ligands (oleylamine) and inorganic ligands (sulfide ion (S2−)) were explored. Time-resolved photoluminescence and femtosecond transient-absorption spectroscopy unambiguously confirmed the ultrafast hole transfer from the InP core to S2− ligands. Moreover, by probing the bleach of vibrational stretching of the ligands with transient midinfrared absorption spectroscopy, the hole transfer time was determined to be 4.2 ps. The injected holes are long-lived at the S2− ligands (>4.5 ns), and they can remove electrostatically attached surfactants to compensate for the spatial charge redistribution. Finally, compared with other inorganic ligands such as Cl− and PO43−, S2− balances the ionic radii and net charge to ensure the optimal condition for charge transfer. Such observation rationalizes the excellent photocatalytic H2 evolution (213.6 µmol mg−1 within 10 h) in InP/ZnS QDs capped with S2− compared with those capped with other ligands and elucidates the role of surface ligands in the photocatalytic activity of colloidal QDs.
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| 3. |
- Lv, Jinmei, et al.
(författare)
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Identification of human age using trace element concentrations in hair and the support vector machine method
- 2011
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Ingår i: Biological Trace Element Research. - : Springer Science and Business Media LLC. - 0163-4984 .- 1559-0720. ; 143:3, s. 1441-1450
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Tidskriftsartikel (refereegranskat)abstract
- Trace element content in hair is affected by the age of the donor. Hair samples of subjects from four counties in China where people are known to have long lifespan (“longevity counties”) were collected and the trace element content determined. Samples were subdivided into three age groups based on the age of the donors from whom these were taken: children (0–15 years); elderly (80–99 years); and centenarians (≥100 years). We compared the trace element content in hair of different age groups of subjects. Support vector machine classification results showed that a non-linear polynomial kernel function could be used to classify the three age groups of people. Age did not have a significant effect on the content of Ca and Cd in human hair. The content of Li, Mg, Mn, Zn, Cr, Cu, and Ni in human hair changed significantly with age. The magnitude of the age effect on trace element content in hair was in the order Cu > Zn > Ni > Mg > Mn > Cr > Li. Cu content in hair decreased significantly with increasing age. The hair of centenarians had higher levels of Li and Mn, and lower levels of Cr, Cu, and Ni comparing with that of the children and elderly subjects. This could be a beneficial factor of their long lifespan.
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| 4. |
- Yang, B, et al.
(författare)
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Ultrasensitive and Fast All-Inorganic Perovskite-Based Photodetector via Fast Carrier Diffusion
- 2017
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648. ; 29:40, s. 1703758-1703758
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Tidskriftsartikel (refereegranskat)abstract
- Low trap-state density, high carrier mobility, and efficient charge carrier collection are key parameters for photodetectors with high sensitivity and fast response time. This study demonstrates a simple solution growth method to prepare CsPbBr3 microcrystals (MCs) with low trap-state density. Time-dependent photoluminescence study with one-photon excitation (OPE) and two-photon excitation (TPE) indicates that CsPbBr3 MCs exhibit fast carrier diffusion with carrier mobility over 100 cm2 V-1 S-1. Furthermore, CsPbBr3 MC-based photodetectors with high charge carriers' collection efficiency are fabricated. Such photodetectors show ultrahigh responsivity (R) up to 6 × 104 A W-1 with OPE and high R up to 6 A W-1 with TPE. The R for OPE is over one order of magnitude higher (the R for TPE is three orders of magnitude higher) than that of previously reported all-inorganic perovskite-based photodetectors. Moreover, the photodetectors exhibit fast response time of ≈1 ms, which corresponds to a gain ≈105 and a gain- bandwidth product of 108 Hz for OPE (a gain ≈103 and a gain-bandwidth product of 106 Hz for TPE).
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| 5. |
- Zhang, Fengying, et al.
(författare)
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Effect of synthesis methods on photoluminescent properties for CsPbBr3 nanocrystals : Hot injection method and conversion method
- 2020
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 220
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Tidskriftsartikel (refereegranskat)abstract
- Multiple facile synthetic strategies for all inorganic perovskite CsPbBr3 nanocrystals (NCs) have been established and developed, profiting from their excellent performance and great potential applied in the field of photonic and optoelectronic. Here, CsPbBr3 NCs were synthesized by both hot injection method (method 1) and conversion method (method 2), and the discrepancy of their photophysical properties is elucidated via the complementary studies between time-resolved photoluminescence (TRPL) and transient-absorption (TA) spectroscopy. We found that CsPbBr3 NCs prepared by conversion method exhibited lower PL quantum yield (QY), which was ascribed to the larger partition of the NCs being passivated from the quenchers from the deep trap states. On the other hand, we also observed different radiative recombination rates between two samples which should be due to various trapping/detrapping times prior to the radiative recombination of the charge carriers in two samples. These results provide better guidance for the development and improvement of synthesis methodology for perovskite NCs.
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| 6. |
- Zhang, Fengying, et al.
(författare)
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Exploration of ultrafast dynamic processes in photocatalysis : Advances and challenges
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Ingår i: Fundamental Research. - 2096-9457.
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Forskningsöversikt (refereegranskat)abstract
- Photocatalysis plays a crucial role in harnessing renewable energy by efficiently converting solar energy into chemical energy. Adequate cognition of photogenerated charge carrier dynamics in photocatalysis is the key to realizing efficient solar energy utilization, and provides guidance for breaking through the efficiency bottleneck. However, a convincing correlation between those photophysical processes and the photocatalytic performance has yet been established due to the complexity of photocatalytic reactions. In this review, we overviewed the detailed ultrafast photophysics in photocatalysis based on three typical ultrafast spectroscopic techniques (TRPL, TA and TRIR), and put a special focus on the justification as well as the limitation on correlating those photophysics with the actual catalytic performance. The classification of carrier behaviors after photoexcitation as well as typical time-resolved spectroscopic characterization techniques are briefly introduced first. State-of-the-art studies on the excited state dynamics in photocatalysis and its correlation to catalytic performance are then systematically presented from three types of common photocatalysts including quantum dots, polymeric photocatalysts, and traditional semiconductors. Finally, a summary on the correlation between ultrafast photophysics and the final photocatalytic performance is provided, and challenges and limitations of current photophysical characterization to rationalize the catalytic performance are outlined.
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| 7. |
- Zhang, Fengying, et al.
(författare)
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Formamidinium Lead Bromide (FAPbBr3) Perovskite Microcrystals for Sensitive and Fast Photodetectors
- 2018
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Ingår i: Nano-Micro Letters. - : Springer Science and Business Media LLC. - 2311-6706 .- 2150-5551. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- Because of the good thermal stability and superior carrier transport characteristics of formamidinium lead trihalide perovskite HC(NH2)2PbX3 (FAPbX3), it has been considered to be a better optoelectronic material than conventional CH3NH3PbX3 (MAPbX3). Herein, we fabricated a FAPbBr3 microcrystal-based photodetector that exhibited a good responsivity of 4000 A W−1 and external quantum efficiency up to 106% under one-photon excitation, corresponding to the detectivity greater than 1014 Jones. The responsivity is two orders of magnitude higher than that of previously reported formamidinium perovskite photodetectors. Furthermore, the FAPbBr3 photodetector’s responsivity to two-photon absorption with an 800-nm excitation source can reach 0.07 A W−1, which is four orders of magnitude higher than that of its MAPbBr3 counterparts. The response time of this photodetector is less than 1 ms. This study provides solid evidence that FAPbBr3 can be an excellent candidate for highly sensitive and fast photodetectors.[Figure not available: see fulltext.].
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| 8. |
- Zhang, Fengying, et al.
(författare)
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Microscopic morphology independence in linear absorption cross-section of CsPbBr3 nanocrystalsMicroscopic morphology independence in linear absorption cross-section of CsPbBr3 nanocrystals
- 2021
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Ingår i: SCIENCE CHINA Materials. - : Springer Science and Business Media LLC. - 2095-8226 .- 2199-4501. ; 64:6, s. 1418-1426
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Tidskriftsartikel (refereegranskat)abstract
- Multiple morphologies of colloidal perovskite nanocrystals (NCs) diversify their optical and electronic properties. Among them, the linear absorption cross-section (σ) is a primary parameter to determine their intrinsic photophysical features, and consequently, application potential. Herein, three morphologies of all-inorganic hybrid colloidal perovskite CsPbBr3 NCs, nanocubes (NBs), nanoplatelets (NLs), and nanowires (NWs), were targeted, and their linear σ values were obtained through femtosecond transient absorption (TA) spectroscopy analysis. At high excitation energy well above the bandgap, the σ per particle of all CsPbBr3 NCs linearly increased with the particle volume (VNC) regardless of the morphology with the value of σ400 = 9.45 × 104 cm−1 × VNC (cm2). Density functional theory (DFT) calculation confirmed the negligible influence of shapes on the optical selection rules. The Einstein spontaneous emission coefficients calculated from the σ values define the intrinsic radiative recombination rate. However, reduced size dependence is observed when the excitation energy is close to the bandgap (i.e., at 460 nm) with the value of σ460 = 2.82 × 108 cm0.65 × (VNC)0.45 (cm2). This should be ascribed to the discrete energy levels as well as lower density of states close to the band edge for perovskite NCs. These results provide in-depth insight into the optical characteristics for perovskite NCs.
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| 9. |
- Zhu, Ziqiang, et al.
(författare)
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Integrative microRNA and mRNA expression profiling in acute aristolochic acid nephropathy in mice
- 2020
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Ingår i: Molecular Medicine Reports. - : Spandidos Publications. - 1791-2997 .- 1791-3004. ; 22:4, s. 3367-3377
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Tidskriftsartikel (refereegranskat)abstract
- In acute aristolochic acid nephropathy (AAN), aristolochic acid (AA) induces renal injury and tubulointerstitial fibrosis. However, the roles of microRNAs (miRNAs/miRs) and mRNAs involved in AAN are not clearly understood. The aim of the present study was to examine AA-induced genome-wide differentially expressed (DE) miRNAs and DE mRNAs using deep sequencing in mouse kidneys, and to analyze their regulatory networks. In the present self-controlled study, mice were treated with 5 mg/kg/day AA for 5 days, following unilateral nephrectomy. AA-induced renal injury and tubulointerstitial fibrosis were detected using hematoxylin and eosin staining and Masson's trichrome staining in the mouse kidneys. A total of 82 DE miRNAs and 4,605 DE mRNAs were identified between the AA-treated group and the self-control group. Of these DE miRNAs and mRNAs, some were validated using reverse transcription-quantitative PCR. Expression levels of the profibrotic miR-21, miR-433 and miR-132 families were significantly increased, whereas expression levels of the anti-fibrotic miR-122-5p and let-7a-1-3p were significantly decreased. Functions and signaling pathways associated with the DE miRNAs and mRNAs were analyzed using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG). A total of 767 DE pairs (in opposing directions) of miRNAs and their mRNA targets were identified. Among these, regulatory networks of miRNAs and mRNAs were analyzed using KEGG to identify enriched signaling pathways and extracellular matrix-associated pathways. In conclusion, the present study identified genome-wide DE miRNAs and mRNAs in the kidneys of AA-treated mice, as well as their regulatory pairs and signaling networks. The present results may improve the understanding of the role of DE miRNAs and their mRNA targets in the pathophysiology of acute AAN.
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