The elastic properties of poly(vinyl alcohol) (PVA) were investigated on the nanoscale using the new technique of single molecule force spectroscopy by atomic force microscopy (AFM). It was found that the elastic properties of PVA molecules scale linearly with their contour lengths. This finding corroborates that the deformation of individual PVA chains is measured. The force spectra of PVA show a kink at around 200 pN and cannot be fitted by an extended Langevin function. The deviation of the elastic behavior of PVA from a freely jointed chain model may indicate the presence of a suprastructure of PVA in NaCl solution. 相似文献
Organometallic halide perovskites have attracted great research interest as light‐active materials for use in optoelectronics. Here, we report a high‐performance photoconductor based on a methylammonium lead iodide (MAPbI3) film that was prepared from a methylamine‐treated MAPbI3/PbI2 perovskite film. An ultrahigh responsivity of 3.6 A W?1 and detectivity of 5.4×1012 Jones were obtained for the film under 0.5 mW cm?2 white‐light illumination. In addition, under 420 nm light irradiation, the film exhibited its highest responsivity and detectivity of 30 A W?1 and 2.4×1014 Jones, respectively. The excellent photo‐response performance results from the improved electronic quality and suppressed nonradiative recombination channels of the treated perovskite thin film. 相似文献
The first ratiometric fluorescent probe for hypochlorite has been developed through regulation of the electron‐withdrawing ability of the electron acceptor in an intramolecular charge‐transfer (ICT) system by a deoximation reaction (see figure; EWG=electron‐withdrawing group).
Multilayer films of tungstophosphate anion (P2W18) and poly(allylamine hydrochloride) (PAH) were fabricated on quartz and ITO substrates by layer-by-layer self-assembly method. These films were characterized by UV–vis spectroscopy, cyclic voltammetry (CV), chronoamperometric (CA), chronocoulometry (CC) and atomic force microscopy (AFM). The effects of film structure on multilayer electrochromic properties were investigated. The electrochromic responses of the composite films were related to the surface coverage of anion and multilayer thickness. It was found that higher concentration of polycation and anion, or adding salt to the polycation solution used for multilayer film preparation led to thicker and denser film structure which improved optical contrast and coloration efficiency whereas prolonged response time. 相似文献
Conventional carbonate solvents with low HOMO levels are theoretically compatible with the low-cost, high-voltage chemistry of Zn/graphite batteries. However, the nucleophilic attack of the anion on carbonates induces an oxidative breakdown at high potentials. Here, we restore the inherent anodic stability of carbonate electrolytes by designing a micro-heterogeneous anion solvation network. Based on the addition of a strongly electron-donating solvent, trimethyl phosphate (TMP), the oxidation-vulnerable anion-carbonate affinities are decoupled because of the preferential sequestration of anions into solvating TMP domains around the metal cations. The hybridized electrolytes elevate the electrochemical window of carbonate electrolytes by 0.45 V and enable the operation of Zn/graphite dual-ion cells at 2.80 V with a long cycle life (92 % capacity retention after 1000 cycles). By inheriting the non-flammability from TMP and the high ion-transport kinetics from the carbonate systems, this facile strategy provides cells with the additional benefits of fire retardancy and high-power capability. 相似文献
The structure and properties of a 16-atom body-centered cubic lithium cell with an interstitial hydrogen atom are studied
using a pseudopotential-plane-wave method within the density functional theory at 0 K and high pressures. The host lattice
is dramatically distorted by the introduction of H. Although the hydrogen atom is stable at the tetragonal site in perfect
bcc host lattice, it favors the octahedral site formed by six non-equivalent Li atoms after full relaxation of the cell, showing
P4/mmm symmetry within the pressures ranging from 0 to 6 GPa. The lattice ratio (a/c) changes irregularly with external pressure at about 3 GPa. The hydrogen band lies in the bottom of the valence band, separated
by a gap from the metallic bands, illustrating the electronegativity of hydrogen. High reflectivity in the low frequency area
induced by the impurity hydrogen is observed when only interband transitions are taken account of. A dip in reflectivity due
to parallel band transitions is observed at ∼0.4 eV. Another dip at ∼4.3 eV appears when external pressure increases over
4 GPa. 相似文献