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991.
992.
Kaushik Kundu Paribesh Acharyya Krishnendu Maji Ranjan Sasmal Sarit S. Agasti Kanishka Biswas 《Angewandte Chemie (International ed. in English)》2020,59(31):13093-13100
Two‐dimensional (2D) lead‐free halide perovskites have generated enormous perception in the field of optoelectronics due to their fascinating optical properties. However, an in‐depth understanding on their shape‐controlled charge‐carrier recombination dynamics is still lacking, which could be resolved by exploring the photoluminescence (PL) blinking behaviour at the single‐particle level. Herein, we demonstrate, for the first time, the synthesis of nanocrystals (NCs) and 2D nanosheets (NSs) of layered mixed halide, Cs3Bi2I6Cl3, by solution‐based method. We applied fluorescence microscopy and super‐resolution optical imaging at single‐particle level to investigate their morphology‐dependent PL properties. Narrow emission line widths and passivation of non‐radiative defects were evidenced for 2D layered nanostructures, whereas the activation of shallow trap states was recognized at 77 K. Interestingly, individual NCs were found to display temporal intermittency (blinking) in PL emission. On the other hand, NS showed temporal PL intensity fluctuations within localized domains of the crystal. In addition, super‐resolution optical image of the NS from localization‐based method showed spatial inhomogeneity of the PL intensity within perovskite crystal. 相似文献
993.
Dr. Wu-Qiang Wu Dr. Jin-Feng Liao Jun-Xing Zhong Dr. Yang-Fan Xu Prof. Lianzhou Wang Prof. Jinsong Huang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(47):21166-21173
The performances of electron-transport-layer (ETL)-free perovskite solar cells (PSCs) are still inferior to ETL-containing devices. This is mainly due to severe interfacial charge recombination occurring at the transparent conducting oxide (TCO)/perovskite interface, where the photo-injected electrons in the TCO can travel back to recombine with holes in the perovskite layer. Herein, we demonstrate for the first time that a non-annealed, insulating, amorphous metal oxyhydroxide, atomic-scale thin interlayer (ca. 3 nm) between the TCO and perovskite facilitates electron tunneling and suppresses the interfacial charge recombination. This largely reduced the interfacial charge recombination loss and achieved a record efficiency of 21.1 % for n-i-p structured ETL-free PSCs, outperforming their ETL-containing metal oxide counterparts (18.7 %), as well as narrowing the efficiency gap with high-efficiency PSCs employing highly crystalline TiO2 ETLs. 相似文献
994.
Dr. Huan Wang Dr. Jian Qi Prof. Nailiang Yang Dr. Wei Cui Prof. Jiangyan Wang Dr. Qinghao Li Dr. Qinghua Zhang Prof. Xiqian Yu Prof. Lin Gu Dr. Jiong Li Prof. Ranbo Yu Prof. Keke Huang Prof. Shuyan Song Prof. Shouhua Feng Prof. Dan Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(44):19859-19863
To boost the performance for various applications, a rational bottom-up design on materials is necessary. The defect engineering on nanoparticle at the atomic level can efficiently tune the electronic behavior, which offers great opportunities in enhancing the catalytic performance. In this paper, we optimized the surface oxygen vacancy concentration and created the lattice distortion in rare-earth-based perovskite oxide through gradient replacement of the B site with valence alternated element. The dual defects make the electron spin state transit from low spin state to high spin state, thus decreasing the charge transport resistance. Furthermore, assembly the modified nanoparticle subunits into the micro-sized hollow multishelled structures can provide porous shells, abundant interior space and effective contact, which enables an enhanced mass transfer and a shorter charge transport path. As a result, the systemic design in the electronic and nano-micro structures for catalyst has brought an excellent oxygen evolution performance. 相似文献
995.
Dr. Yucheng Yuan Dr. Hua Zhu Dr. Katie Hills-Kimball Tong Cai Wenwu Shi Zichao Wei Hanjun Yang Yolanda Candler Prof. Ping Wang Prof. Jie He Prof. Ou Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(50):22752-22758
Semiconductor quantum dots (QDs) have attracted tremendous attention in the field of photocatalysis, owing to their superior optoelectronic properties for photocatalytic reactions, including high absorption coefficients and long photogenerated carrier lifetimes. Herein, by choosing 2-(3,4-dimethoxyphenyl)-3-oxobutanenitrile as a model substrate, we demonstrate that the stereoselective (>99 %) C−C oxidative coupling reaction can be realized with a high product yield (99 %) using zwitterionic ligand capped CsPbBr3 perovskite QDs under visible light illumination. The reaction can be generalized to different starting materials with various substituents on the phenyl ring and varied functional moieties, producing stereoselective dl-isomers. A radical mediated reaction pathway has been proposed. Our study provides a new way of stereoselective C−C oxidative coupling via a photocatalytic means using specially designed perovskite QDs. 相似文献
996.
Zhiyun Xu Wen Weng Yaobin Li Dr. Xitao Liu Tao Yang Maofan Li Prof. Xiaoying Huang Prof. Junhua Luo Prof. Zhihua Sun 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(48):21877-21881
Polarized-light detection in solar-blind ultraviolet region is indispensable for optoelectronic applications, whereas new 2D candidates targeted at solar-blind UV range remain extremely scarce. 2D hybrid perovskite ferroelectrics that combine polarization and semiconducting properties are of increasing interest. Here, using the 3D-to-2D dimensional reduction of CH3NH3PbCl3, we designed a multilayered hybrid perovskite ferroelectric, (CH3CH2NH3)2(CH3NH3)2Pb3Cl10, which shows spontaneous polarization and a high Curie temperature (390 K) comparable with that of BaTiO3 (393 K). The wide band gap (ca. 3.35 eV) and anisotropic absorbance stemming from its intrinsic 2D motif, greatly favor its polarization-sensitive activity in UV region. The device displays excellent polarization-sensitive behavior under 266 nm, along with a large dichroic ratio (ca. 1.38) and high on/off current ratio (ca. 2.3×103). 相似文献
997.
Jun Su Tao Zhu Thierry Pauporté Ilaria Ciofini Frédéric Labat 《Journal of computational chemistry》2020,41(19):1740-1747
A periodic hybrid density functional theory computational strategy is presented to model the heterointerface between the methylammonium lead iodide (MAPI) perovskite and titanium dioxide (TiO2), as found in perovskite solar cells (PSC), where the 4-chlorobenzoic acid (CBA) ligand is used to improve the stability and the band alignment at the interface. The CBA ligand acts as a bifunctional linker to efficiently connect the perovskite and the oxide moieties, ensuring the stability of the interface through Ti–O and Pb–Cl interactions. The computed density of states reveals that the perovskite contributes to the top of the valence band while the oxide contributes to the bottom of the conduction band with a direct bandgap of 2.16 eV, indicating a possible electron transfer from MAPI to TiO2. Dipole moment analysis additionally reveals that the CBA ligand can induce a favorable effect to improve band alignment and thus electron transfer from MAPI to TiO2. This latter has been quantified by calculation of the spin density of the reduced MAPI/CBA/TiO2 system and indicates an almost quantitative (99.94%) electron transfer from MAPI to TiO2 for the surface engineered system, together with an ultrafast electron injection time in the femtosecond timescale. Overall, the proposed DFT-based computational protocol therefore indicates that surface engineering and the use of a bifunctional linker can lead to a better stability, together with improved band alignment and electron injection in PSC systems. 相似文献
998.
采用无皂乳液聚合法制备了聚苯乙烯(PS)聚合物微球,并采用胶晶模板法制备了三维有序大孔3DOM LaFeO3钙钛矿型氧化物.通过扫描电镜、X射线衍射和傅里叶变换红外光谱等手段对氧化物的性能进行了表征.利用程序升温还原和多次氧化还原循环反应评价了氧化物的反应性,并在固定床反应器上研究了其甲烷氧化性能.结果表明,与离心法和蒸发法相比,垂直沉积法获得的PS微球模板排列更均匀有序;前驱物溶剂及浓度对最终的三维有序大孔材料的结构有显著影响,利用乙醇为前驱物溶剂所制备的样品比利用乙烯为溶剂的样品具有更好的三维有序大孔结构,前驱物乙醇溶液浓度在1.0 mol/L为宜.甲烷氧化实验表明,3DOM-LaFeO3钙钛矿型氧化物中存在两种氧物种:表面吸附氧和体相晶格氧.表面吸附氧主要在反应初期将甲烷完全氧化为CO2和水蒸汽,而体相晶格氧主要将甲烷部分氧化为H2和CO.在甲烷部分氧化反应中,三维有序大孔LaFeO3钙钛矿型氧化物比相同质量的纳米LaFeO3氧化物提供了更多的氧,并且可使甲烷在较宽的反应阶段生成H2和CO摩尔比为2:1的合成气,从而更有利于后续的费托合成等工艺. 相似文献
999.
T. HernÁndez F. Plazaola J. M. Barandiarán J. M. Greneche 《Hyperfine Interactions》2005,161(1-4):113-122
We have synthesized by sol–gel method the following polycrystalline double perovskite samples: Sr2Fe1?x Sc x ReO6 (x = 0, 0.05, 0.1). The results of the Rietveld refinements presented single double perovskite phases with orthorhombic symmetry for the system Sr2Fe1?x Sc x ReO6, the differences in atomic radii between Fe3+ and Sc3+ cause a lowering in symmetry with respect to the parent Sr2FeReO6 tetragonal compound. The Curie temperatures are found at about 426 and 436 (±5) K for Sr2Fe0.9Sc0.1ReO6 and Sr2Fe0.9Sc0.05ReO6, respectively. The Mössbauer spectra measured at 77 K show complex hyperfine structures resulting from different magnetic contributions at Fe3+ sites; the average hyperfine field is estimated 50 T and the isomer shift at 0.5 mm/s. At room temperature an intermediate valence state for Fe is also observed. 相似文献
1000.
Yu. I. Pyatnitskii A. I. Bostan L. N. Raevskaya S. A. Nedil’ko A. G. Dzyaz’ko E. G. Zen’kovich 《Theoretical and Experimental Chemistry》2005,41(2):117-121
The catalytic properties of complex oxide catalysts with ABO3 perovskite structure (A = Sr, Ba, La; B = Mn, Co, Ni) in the oxidative coupling of methane were studied with separate introduction of methane and oxygen onto the catalyst. The greatest catalytic activity was found for the nickel-containing oxides but these catalysts have much lower operational stability than Mn- and Co-containing catalysts. Modification of the oxide systems studied by partial replacement of the strontium or transition metal ions by alkali metal ions considerably improves their activity and selectivity.__________Translated from Teoreticheskaya i Eksperimental’naya Khimiya, Vol. 41, No. 2, pp. 110–114, March– April, 2005. 相似文献