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71.
Bofeng Zhang Hong Zhang Jiahe Lin Xinlu Cheng 《International journal of quantum chemistry》2020,120(13):e26232
Recently, all-inorganic perovskite nanostructures have become a hot research topic due to their unique optical response and novel properties. Here, we theoretically study the optical response in Cs2PbX4 and CsPb2X5 (X = Cl, Br, and I) nanostructures. First, to study the ground state, we calculate the band structures of the periodic system using the HSE06 method, which shows that all those periodic perovskites possess the direct band gaps, with distribution from 2.225 to 3.536 eV. Their valence band maximum are mainly contributed from both halogen and lead atoms, while the conduction band minimum are mainly contributed from lead atoms. Then, we study the excited state using the time-dependent density functional theory method and find that, with the increase of halogen atom radius, the photogenerated carrier concentrations in perovskite nanostructures become larger, while the surface plasmon resonance becomes localized rather than long-range. Moreover, through the analysis of photocurrent and local field enhancement, Cs2PbX4 and CsPb2X5 nanostructures exhibit nearly 40 μA photocurrent along the direction of optical polarization. Besides, by regulating the different anions, we predict that field enhancement in Cs2PbI4 and CsPb2I5 share a much stronger distribution at both the center and border parts of Pb-I planes due to localized plasmon resonance, while other perovskites are distributed at the edge parts of Pb-I planes, caused by long-range plasmon resonance. Our research shows that all-inorganic perovskite nanostructures are great candidate materials for developing optoelectronic devices working in high-frequency and high-energy regions and improving their application in sensitive detection and sensors. 相似文献
72.
Surface‐enhanced Raman scattering (SERS) spectroscopy on semiconductors has attracted increasing attention due to its high spectral reproducibility and unique selectively to target molecules. Recently, endeavors have been made in fabricating novel SERS‐active semiconductor substrates and exploring new enhancement mechanisms to improve the sensitivity of semiconductor substrates. This Minireview explains the enhancement mechanism of the semiconductor SERS effect in a brief tutorial and summarize recent developments of novel semiconductor substrates, in particular with regard to the remarkable SERS activity of amorphous semiconductor nanomaterials. Potential applications of semiconductor SERS are also a key issue of concern. We discuss a variety of promising applications of semiconductor SERS in the fields of in situ analytical chemistry, spectroelectrochemical analysis, biological sensing, and trace detection. 相似文献
73.
Mumdooh Ahmed Alexander Marchanka Teresa Carlomagno 《Angewandte Chemie (International ed. in English)》2020,59(17):6866-6873
Solid‐state NMR (ssNMR) is applicable to high molecular‐weight (MW) protein assemblies in a non‐amorphous precipitate. The technique yields atomic resolution structural information on both soluble and insoluble particles without limitations of MW or requirement of crystals. Herein, we propose and demonstrate an approach that yields the structure of protein–RNA complexes (RNP) solely from ssNMR data. Instead of using low‐sensitivity magnetization transfer steps between heteronuclei of the protein and the RNA, we measure paramagnetic relaxation enhancement effects elicited on the RNA by a paramagnetic tag coupled to the protein. We demonstrate that this data, together with chemical‐shift‐perturbation data, yields an accurate structure of an RNP complex, starting from the bound structures of its components. The possibility of characterizing protein–RNA interactions by ssNMR may enable applications to large RNP complexes, whose structures are not accessible by other methods. 相似文献
74.
《Arabian Journal of Chemistry》2020,13(12):8697-8707
A dipodal fluorescent probe 3, with imine and hydroxyl moieties as binding sites, has been synthesized and characterized with spectroscopic methods, single-crystal X-ray techniques, and DFT. The synthesized probe 3 (φ = 0.0028) showed highly sensitive and highly specific fluorescent ‘turn-on’ effect (λem = 453 nm) for the 1:1 binding with Fe3+ ions to form probe 3.Fe3+ complex (φ = 0.203) in semi-aqueous medium (acetonitrile:water (50:50; v/v)) and live cells. The 1:1 binding stoichiometry of probe 3 and Fe3+ ions was proposed by DFT calculations and confirmed by the NMR spectroscopy, crystal structures of probe 3 and 3.Fe3+ complex, and mass spectrum of probe 3.Fe3+ complex. The stability of probe 3.Fe3+ complex in a wide pH range (pH 2–12) and reversibility for binding with Fe3+ ions in the presence of EDTA indicates that it can be an effective chemosensor for the detection of Fe3+ ions in various samples, including living cells. Importantly, with the LOD of 21.5 nM for the detection of Fe3+ ions, probe 3 did not show any interference from potentially competing ions even at a 1:3 ratio, indicates its biocompatibility. The nanomolar limit of detection (21.5 nM), cell permeability, and low cytotoxicity allows the probe 3 to be an excellent tool for the live-cell imaging and detection of ferric ions in live cells. 相似文献
75.
76.
基于灰度冗余的红外图像自适应输出窗技术 总被引:6,自引:4,他引:2
根据红外图像的特点,提出了一种基于灰度冗余的红外图像自适应输出窗技术.该技术通过对图像灰度直方图的统计,设定适当的阈值,将灰度像素分布为零的灰度级进行完全压缩,将小于阈值的灰度级映射到阈值灰度级,然后将有效灰度级在整个可显示灰度级范围内作等间距排列.该算法在压缩灰度冗余的同时,实现了对有效图像灰度级的无损均衡,提高了图像质量,并能实现实时处理. 相似文献
77.
78.
广东博罗横岭山商周时期墓地是广东省目前所发现的最重要的商周时期墓葬群,该墓地出土的玉器样品通过一系列的科学鉴定研究后发现,玉器的红外光谱在2 960 cm-1(相对较弱)、2 920和2 853 cm-1附近出现了2~3个明显的特征性吸收峰,结合对纯蜡样品、现代上蜡玉器样品的测试比较,认为博罗横岭山墓地出土玉器在加工过程中曾经经过上蜡处理,首次揭示出商周时期岭南先民掌握了在加工中利用蜡来增加玉器美观技术的事实。 相似文献
79.
Plasmonic-enhanced luminescence of single molecules enables imaging and detection of low quantities of fluorophores, down to individual molecules. In this work, we present two-photon excited luminescence of single gold nanoclusters, Au18(SG)14, in close proximity to bare gold nanorods (AuNRs). We observed 25-times enhanced emission of gold nanoclusters (AuNCs) in near infrared region, which was mainly attributed to the resonant excitation of localized surface plasmon resonance (LSPR) of AuNRs and spectral overlap of LSPR band with photoluminescence of AuNCs. This work is an initial step in application of combined nanoparticles: gold nanorods and ultrasmall nanoclusters in a wide range of multiphoton imaging and biosensing applications. 相似文献
80.
We examined the flow behaviors and mixing characteristics of double-concentric jets using laser-assisted smoke flow visualization method to analyze typical flow patterns and binary boundary detection technique to investigate jet spread width. Time-averaged velocity vectors, streamline patterns, velocity distributions, turbulence properties, and vorticity contours were analyzed using Particle Image Velocimetry (PIV). Topological flow patterns were analyzed to interpret the vortical flow structures. Mixing properties were investigated using a tracer-gas concentration detection method. Four characteristic modes were observed: annular flow dominated mode, transition mode, central jet dominated mode-low shear, and central jet dominated mode-high shear. The jets’ mixing properties were enhanced by two major phenomena: the merging of annular flow and central jet at the centerline and the large turbulence fluctuations produced in the flow field. The merging of the jets induced stagnation points on the central axis in the annular flow dominated mode, which caused reverse flow on the central axis and drastic turbulence fluctuations of the near field region. When the central jet penetrated the recirculation region in the other three modes, the stagnation points on the central axis and the reverse flow vanished. Therefore, the mixing behaviors were prominently enhanced in the annular flow dominated mode. 相似文献