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131.
Electron transport through a self-assembled monolayer of thiol-end-functionalized tetraphenylporphines and metal tetraphenylporphines 总被引:1,自引:0,他引:1
Lu X Li M Yang C Zhang L Li Y Jiang L Li H Jiang L Liu C Hu W 《Langmuir : the ACS journal of surfaces and colloids》2006,22(7):3035-3039
The monolayers of several thiol-end-functionalized tetraphenylphophines (SH-TPP) and metal tetraphenylporphines (SH-MTPP) were self-assembled on gold surfaces and identified by cyclic voltammetry (CV), electrochemical impedance spectroscopy, scanning electrochemical microscopy, and the contact angle. The CV peaks of the [Fe(CN)6]3-/ [Fe(CN)6]4- couple were used to identify the efficiency of electrons transferring through the self-assembled monolayer (SAM). The results suggested that SH-TPP and SH-MTPP could form high-quality SAMs on gold surfaces. The SAMs blocked electron transport from the gold electrode to solution. When the length of the thiol-end-link spacer (alkyl group) increased, the electron transport ability of the SAM decreased because of the increased insulator properties of the alkyl chain. With the insertion of metallic ions, the electron transport ability of the SAM of SH-MTPP increased compared to that of the SAM of SH-TPP, which was probably due to the fact that (i) the insertion of metallic ions changed the molecular structure and the molecular structure of SH-MTPP played an important role in electron transport through the SAM and (ii) the insertion of metallic ions increased the electron tunneling probability through the monolayer. 相似文献
132.
133.
Yongfang Zheng Meng Xu Lanlan Yu Fuyang Qu Yuchen Lin Jing Xu Yimin Zou Prof. Yanlian Yang Prof. Chen Wang 《Chemphyschem》2019,20(1):103-107
The abnormal accumulation of beta-amyloids (Aβ) in brain is considered as a key initiating cause for Alzheimer's disease (AD) due to their richness in plaques and self-aggregate propensity. In recent studies, N-terminally extended Aβ peptides (NTE-Aβ) with the N-terminus originating prior to the canonical β-secretase cleavage site were found in humans and suggested to have possible relevance to AD. However, the effects of the extended N-terminus on the amyloidegenic structure and aggregation propensity have not been fully elucidated. Herein, we characterized the assembly structures of Aβ1-42, Aβ(−5)-42, Aβ(−10)–42 and Aβ(−15)-42 with both normal and reversed sequences on highly oriented pyrolytic graphite (HOPG) surfaces with scanning tunneling microscopy (STM). The molecularly resolved surface-mediated peptide assemblies enable identification of amyloidegenic fragments. The observations reveal that the assembly propensity of the C-terminal strand of Aβ1-42 is highly conserved and insensitive to N-terminal extensions. In contrast, different assembly structures of the N-terminal strand of Aβ variants can be observed with possible assignment of varied amyloidegenic fragments in the extended N-termini, which may contribute to the varied aggregation propensities of Aβ42 species. 相似文献
134.
Yehui Ma Xiaobei Wang Jin Ye Kai Ge Yuanyuan Wang Jiahui He Yue Zhang Yongfang Yang 《化学:亚洲杂志》2019,14(7):1066-1075
PDMAEMA‐b‐PMAA block copolymers were prepared by the sequential RAFT polymerization of DMAEMA and tBMA, followed by hydrolysis. Phosphotungstic acid (HPW) was anchored to the PDMAEMA blocks through electrostatic interactions and the as‐obtained HPW/PDMAEMA‐b‐PMAA was added to the synthesis of ZIF‐8. During the formation of ZIF‐8, the PMAA blocks coordinated to the Zn2+ ions through their carboxy groups, along with the HPW groups that were anchored to the PDMAEMA blocks. In this way, the block copolymer could consolidate the interactions between HPW and ZIF‐8 and prevent the leakage of HPW. Finally, the HPW/PDMAEMA‐b‐PMAA/ZIF‐8 ternary lamellar composite was obtained and the structure of the HPW/PDMAEMA‐b‐PMAA/ZIF‐8 hybrid material was characterized by using powder X‐ray diffraction (PXRD), X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). As a photocatalyst, the HPW/PDMAEMA‐b‐PMAA/ZIF‐8 ternary lamellar composite showed excellent photoactivity for the degradation of methylene blue (MB). The rate of degradation of MB was 0.0240 min?1, which was 7.5‐times higher than that of commercially available P25 (0.0032 min?1). In the presence of H2O2, the kinetic degradation parameters of the composite reached 0.0634 min?1, which was about 19.8‐times higher than that of P25. 相似文献
135.
Qunping Fan Ulises A. Mndez‐Romero Xia Guo Ergang Wang Maojie Zhang Yongfang Li 《化学:亚洲杂志》2019,14(18):3085-3095
Over the past decade, organic solar cells (OSCs) have achieved a dramatic boost in their power conversion efficiencies from about 6 % to over 16 %. In addition to developments in device engineering, innovative photovoltaic materials, especially fluorinated donors and acceptors, have become the dominant factor for improved device performance. This minireview highlights fluorinated photovoltaic materials that enable efficient OSCs. Impressive OSCs have been obtained by developing some important molds of fluorinated donor and acceptor systems. The molecular design strategy and the matching principle of fluorinated donors and acceptors in OSCs are discussed. Finally, a concise summary and outlook are presented for advances in fluorinated materials to realize the practical application of OSCs. 相似文献
136.
Three low bandgap copolymers of thiophene and benzothiadiazole with electron‐donating and electron‐withdrawing substituents, P1 , P2 , and P3 , have been synthesized by Pd‐catalyzed Stille‐coupling. Electronic energy levels of the polymers are estimated by cyclic voltammetry. The polymer films show a broad absorption band in the wavelength range from 300 to 750 nm. Among the polymers, the polymer that contains the 5,6‐dinitrobenzothiadiazole unit, P3 , possesses the smallest bandgap of 1.55 eV calculated from its absorption band‐edge at ≈800 nm. With the increase of the electron‐withdrawing ability of the substituents on the benzothiadiazole unit, the energy bandgap of the polymers decreased in the order P1 > P2 > P3 . The results indicate that stronger electron‐withdrawing substituents on the acceptor unit can effectively decrease the bandgap of the polymers.
137.
Two polythiophene derivatives with electron‐donating alkylthio side chains, poly[(3‐hexylthio)thiophene] (P3HST) and poly[(3‐hexylthio)thiophene‐alt‐thiophene] (P3HST‐co‐Th) have been synthesized and characterized. Both P3HST and P3HST‐co‐Th show broader absorption peaks than poly(3‐hexylthiophene). Meanwhile, the alkylthio side chains decrease the HOMO energy level of the polymers, which benefits the higher open circuit voltage of the polymer solar cells (PSCs) based on the polymer as donor. PSCs have been fabricated with the polymers as donor and [6,6]‐phenyl C61 butyric acid methyl ester as acceptor (1: 1, w/w). The devices based on P3HST and P3HST‐co‐Th show an open circuit voltage of 0.63 V, and a power conversion efficiency of 0.34% and 0.5%, respectively, under the illumination of AM1.5, 80 mW · cm−2.
138.
Fei Pan Xiaojun Li Song Bai Tianhao Liu Xian Wei Yingfen Li Shanshan Chen Changduk Yang Xiwen Chen Menglan Lv Yongfang Li 《中国化学快报》2021,32(3):1257-1262
Indacenodithiophene (IDT) derivatives are kinds of the most representative and widely used cores of small molecule acceptors (SMAs) in organic solar cells (OSCs). Here we systematically investigate the influence of end-group fluorination density and position on the photovoltaic properties of the IDT-based SMAs IDIC-nF (n = 0, 2, 4). The absorption edge of IDIC-nF red-shifts with the π-π stacking and crystallinity improvement, and their electronic energy levels downshift with increasing n. Due to the advantages of Jsc and FF as well as acceptable Voc, the difluorinated IDIC-2F acceptor based OSCs achieve the highest power conversion efficiency (PCE) of 13%, better than the OSC devices based on IDIC and IDIC-4F as acceptors. And the photovoltaic performance of the PTQ10: IDIC-2F OSCs is insensitive to the active layer thickness: PCE still keep high values of 12.00% and 11.46% for the devices with active layer thickness of 80 and 354 nm, respectively. This work verifies that fine and delicate modulation of the SMAs molecular structure could optimize photovoltaic performance of the corresponding OSCs. Meanwhile, the thickness-insensitivity property of the OSCs has potential for large-scale and printable fabrication technology. 相似文献
139.
In recent years,conjugated polymers have attracted great attention in the application as photovoltaic donor materials in polymer solar cells(PSCs).Broad absorption,lower-energy bandgap,higher hole mobility,relatively lower HOMO energy levels,and higher solubility are important for the conjugated polymer donor materials to achieve high photovoltaic performance.Side-chain engineering plays a very important role in optimizing the physicochemical properties of the conjugated polymers.In this article,we review recent progress on the side-chain engineering of conjugated polymer donor materials,including the optimization of flexible side-chains for balancing solubility and intermolecular packing(aggregation),electron-withdrawing substituents for lowering HOMO energy levels,and two-dimension(2D)-conjugated polymers with conjugated side-chains for broadening absorption and enhancing hole mobility.After the molecular structural optimization by side-chain engineering,the2D-conjugated polymers based on benzodithiophene units demonstrated the best photovoltaic performance,with powerconversion efficiency higher than 9%. 相似文献
140.
Ultrafine Molybdenum Carbide Nanoparticles Composited with Carbon as a Highly Active Hydrogen‐Evolution Electrocatalyst 下载免费PDF全文
Ruguang Ma Yao Zhou Yongfang Chen Pengxi Li Prof. Qian Liu Prof. Jiacheng Wang 《Angewandte Chemie (International ed. in English)》2015,54(49):14723-14727
The replacement of platinum with non‐precious‐metal electrocatalysts with high efficiency and superior stability for the hydrogen‐evolution reaction (HER) remains a great challenge. Herein, we report the one‐step synthesis of uniform, ultrafine molybdenum carbide (Mo2C) nanoparticles (NPs) within a carbon matrix from inexpensive starting materials (dicyanamide and ammonium molybdate). The optimized catalyst consisting of Mo2C NPs with sizes lower than 3 nm encapsulated by ultrathin graphene shells (ca. 1–3 layers) showed superior HER activity in acidic media, with a very low onset potential of ?6 mV, a small Tafel slope of 41 mV dec?1, and a large exchange current density of 0.179 mA cm?2, as well as good stability during operation for 12 h. These excellent properties are similar to those of state‐of‐the‐art 20 % Pt/C and make the catalyst one of the most active acid‐stable electrocatalysts ever reported for HER. 相似文献