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31.
Jesús Toribio 《哲学杂志》2015,95(31):3429-3451
Continuum modelling of hydrogen diffusion in metals, which accounts for both trapping and an imposed force field, is revisited. A generalised model of hydrogen diffusion and trapping is developed as a continuous interpretation of the discrete random-walk theory. A system of nonlinear equations describing the phenomenon of diffusion with multiple types of traps is derived without the assumption of a local equilibrium among hydrogen populations in dissimilar positions. Lattice-trap interchange kinetics can degenerate into local equilibrium as a limit case. Moreover, certain terms in general equations may be negligible in specific situations. By removing these terms, known particularised models of hydrogen diffusion and trapping are recovered. Determining the terms, which are disregarded in reduced models, enables a straightforward assessment of the applicability of these models. The advantages and limitations of particularised models applied to hydrogen embrittlement analyses are discussed. 相似文献
32.
Mapping of the Photoinduced Electron Traps in TiO2 by Picosecond X‐ray Absorption Spectroscopy
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Dr. M. Hannelore Rittmann‐Frank Dr. Chris J. Milne Dr. Jochen Rittmann Dr. Marco Reinhard Dr. Thomas J. Penfold Prof. Majed Chergui 《Angewandte Chemie (International ed. in English)》2014,53(23):5858-5862
Titanium dioxide (TiO2) is the most popular material for applications in solar‐energy conversion and photocatalysis, both of which rely on the creation, transport, and trapping of charges (holes and electrons). The nature and lifetime of electron traps at room temperature have so far not been elucidated. Herein, we use picosecond X‐ray absorption spectroscopy at the Ti K‐edge and the Ru L3‐edge to address this issue for photoexcited bare and N719‐dye‐sensitized anatase and amorphous TiO2 nanoparticles. Our results show that 100 ps after photoexcitation, the electrons are trapped deep in the defect‐rich surface shell in the case of anatase TiO2, whereas they are inside the bulk in the case of amorphous TiO2. In the case of dye‐sensitized anatase or amorphous TiO2, the electrons are trapped at the outer surface. Only two traps were identified in all cases, with lifetimes in the range of nanoseconds to tens of nanoseconds. 相似文献
33.
Björn Johansson Prof. Fredrik Höök Prof. David Klenerman Dr. Peter Jönsson 《Chemphyschem》2014,15(3):486-491
An important and characteristic property of a cell membrane is the lateral mobility of protein molecules in the lipid bilayer. This has conventionally been measured by labeling the molecules with fluorescent markers and monitoring their mobility by different fluorescence‐based techniques. However, adding the label to the studied molecule may affect the system, so it is an assumption in almost all experiments that the measured mobility of the biomolecule with its label is the same as that of the unlabeled molecule. However, this assumption is rarely tested due to a lack of suitable methods. In this work, a new technique to perform label‐free diffusivity measurements is developed and used to measure the effect of the label for two common protein–lipid systems: 1) streptavidin (SA) coupled to a supported lipid bilayer (SLB) through biotinylated lipids and 2) the extracellular part of the T‐cell adhesion protein CD2, coupled to an SLB through histidine tags to nickel‐chelating lipids. A measurable (≈12 %) decrease in diffusivity is found for both labeled proteins, even though the molecular mass of the label is almost 100 times smaller than those of the proteins (≈50 kDa). The results illustrate the importance of being able to study different biophysical properties of cell membranes and their mimics without relying on fluorescent labels, especially if fluorescent labeling is difficult or is expected to affect the nature of the intermolecular interactions being studied. 相似文献
34.
Songhao Guo Yongsheng Zhao Kejun Bu Yongping Fu Hui Luo Mengting Chen Matthew P. Hautzinger Yingqi Wang Prof. Song Jin Prof. Wenge Yang Prof. Xujie Lü 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(40):17686-17692
A remarkable PL enhancement by 12 fold is achieved using pressure to modulate the structure of a recently developed 2D perovskite (HA)2(GA)Pb2I7 (HA=n-hexylammonium, GA=guanidinium). This structure features a previously unattainable, extremely large cage. In situ structural, spectroscopic, and theoretical analyses reveal that lattice compression under a mild pressure within 1.6 GPa considerably suppresses the carrier trapping, leading to significantly enhanced emission. Further pressurization induces a non-luminescent amorphous yellow phase, which is retained and exhibits a continuously increasing band gap during decompression. When the pressure is released to 1.5 GPa, emission can be triggered by above-band gap laser irradiation, accompanied by a color change from yellow to orange. The obtained orange phase could be retained at ambient conditions and exhibits two-fold higher PL emission compared with the pristine (HA)2(GA)Pb2I7. 相似文献
35.
Headspace solid‐phase microextraction is a solvent‐free sample preparation technique that is based on the equilibrium among a three‐phase system, i.e., sample‐headspace‐fiber. A compromise between sensitivity and extraction time is usually needed to optimize the sample throughput, especially when a large number of samples are analyzed, as usually the case in cross‐samples studies. This work explores the capability of multiple‐cumulative trapping solid‐phase microextraction on the characterization of the aroma profiling of olive oils, exploiting the automation capability of a novel headspace autosampler. It was shown that multiple‐cumulative solid‐phase microextraction has the potential to improve the overall sensitivity and burst the level of information for cross‐sample studies by using cumulative shorter extraction times. 相似文献
36.
全色显示是有机电致发光显示(OLED)器件发展的目标,而高性能红色发光器件一直是制约全彩色OLED器件实用化的瓶颈,也是目前有机电致发光显示研究的热点。制作了掺杂DCJTB和不同浓度的rubrene两种荧光染料的红色有机电致发光显示器件,以NPB和Alq3分别作为空穴传输层和电子传输层,发现器件性能与只掺杂DCJTB的器件相比有明显提高,发光效率提高到2~3倍。通过Frster理论和能带理论分析了器件的能量转移机理,研究发现Frster能量转移不是掺杂器件能量转移的主要形式,载流子俘获机制才是器件效率提高的主要原因;rubrene的引入使得能量能够更有效地从Alq3转移到DCJTB,从而显著地提高了器件的发光效率和性能。 相似文献
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Ganesh Shenoy Jessica Ettedgui Chandrasekhar Mushti Jennifer Hong Kelly Lane Burchelle Blackman Hak-Sung Jung Yasuharu Takagi Yeonee Seol Martin Brechbiel Rolf E. Swenson Keir C. Neuman 《Molecules (Basel, Switzerland)》2022,27(3)
Carboxylic acid is a commonly utilized functional group for covalent surface conjugation of carbon nanoparticles that is typically generated by acid oxidation. However, acid oxidation generates additional oxygen containing groups, including epoxides, ketones, aldehydes, lactones, and alcohols. We present a method to specifically enrich the carboxylic acid content on fluorescent nanodiamond (FND) surfaces. Lithium aluminum hydride is used to reduce oxygen containing surface groups to alcohols. The alcohols are then converted to carboxylic acids through a rhodium (II) acetate catalyzed carbene insertion reaction with tert–butyl diazoacetate and subsequent ester cleavage with trifluoroacetic acid. This carboxylic acid enrichment process significantly enhanced nanodiamond homogeneity and improved the efficiency of functionalizing the FND surface. Biotin functionalized fluorescent nanodiamonds were demonstrated to be robust and stable single-molecule fluorescence and optical trapping probes. 相似文献
40.
Yifeng Xiang Xi Tang Changjun Min Guanghao Rui Yan Kuai Fengya Lu Pei Wang Hai Ming Qiwen Zhan Xiaocong Yuan Joseph R. Lakowicz Douguo Zhang 《Annalen der Physik》2020,532(4):1900497
Near-field optical trapping can be realized with focused evanescent waves that are excited at the water–glass interface due to the total internal reflection, or with focused plasmonic waves excited on the water–gold interface. Herein, the performance of these two kinds of near-field optical trapping techniques is compared using the same optical microscope configuration. Experimental results show that only a single-micron polystyrene bead can be trapped by the focused evanescent waves, whereas many beads are simultaneously attracted to the center of the excited region by focused plasmonic waves. This difference in trapping behavior is analyzed from the electric field intensity distributions of these two kinds of focused surface waves and the difference in trapping behavior is attributed to photothermal effects due to the light absorption by the gold film. 相似文献