Thermally Activated Delayed Near-Infrared Photoluminescence from Functionalized Lead-Free Nanocrystals

As an analogue to thermally activated delayed fluorescence (TADF) of organic molecules, thermally activated delayed photoluminescence (TADPL) observed in molecule-functionalized semiconductor nanocrystals represents an exotic mechanism to harvest energy from dark molecular triplets and to obtain controllable, long-lived PL from nanocrystals. The reported TADPL systems have successfully covered the visible spectrum. However, TADF molecules already emit very efficiently in the visible, diminishing the technological impact of the less-efficient nanocrystal-molecule TADPL. Here we report bright, near-infrared TADPL in lead-free CuInSe₂ nanocrystals functionalized with carboxylated tetracene ligands, which results from efficient triplet energy transfer from photoexcited nanocrystals to ligands, followed with thermally activated reverse energy transfer from ligand triplets back to nanocrystals. This strategy prolonged the nanocrystal exciton lifetime from 100 ns to 60 μs at room temperature.     

Preparation of TiO2 Nanoflakes and Their Influence on Lithium Ion Battery Storage Performance

TiO₂ nanoflakes were prepared by hydrothermal precipitation method using Ti(SO₄)₂ as titanium source and NaOH solution as alkaline medium. Their surface morphology, grain size measured after high temperature calcination and effect on the electrochemical performance of Li ion battery were discussed. TiO₂ nanoflakes were characterizated by means of transmission electron microscopy(TEM), X^-ray powder diffraction(XRD), N₂ adsorption-desorption isothermal assay, cyclic voltammetry(CV) and cycle performance test. The result of electrochemical performance test shows that the prepared TiO₂ nanoflakes have high discharge specific capacity and good cycle performance. Discharge specific capacity for the first circle at the discharge rate of 0.1 C is 261.5 mA·h·g^-1. After 90 cycles, the discharge capacity reduces to 172.2 mA·h·g^-1.     

超薄多晶硅的掺杂、钝化及光伏特性研究

本文对70 nm超薄多晶硅的掺杂工艺、钝化性能及光伏特性进行了研究。确定了70 nm超薄多晶硅的掺杂工艺,研究表明当离子注入剂量为3.2×10¹⁵ cm^-3,在855 ℃退火20 min时,70 nm超薄多晶硅的钝化性能可以达到与常规120 nm多晶硅相当的水平,且70 nm多晶硅的表面掺杂浓度达到5.6×10²⁰ atoms/cm³,远高于120 nm掺杂多晶硅的表面掺杂浓度(2.5×10²⁰ atoms/cm³)。基于70 nm超薄多晶硅厚度减薄和高表面浓度掺杂的特点,较低的寄生吸收和强场钝化效应使得在大尺寸(6英寸)直拉单晶硅片上加工的N型TOPCon太阳能电池的光电转换效率得到明显提升,主要电性能参数表现为:电流I_sc升高20 mA,串联电阻R_s降低,填充因子FF增加0.3%,光电转换效率升高0.13%。     

同时反演材料热传导系数和比热的算法

讨论同时反演随温度变化的热传导系数和比热的算法.首先将材料的热传导系数和比热表示成随位置和时间变化的函数,利用伴随方程法获得目标函数对k(x,t),C(x,t)的梯度;然后将材料的热传导系数和比热直接按温度区间分段离散,建立目标函数对k(T),C(T)梯度与目标函数对k(x,t),C(x,t)的梯度的关系;随后利用这种关系进行反演计算.算例表明,这样建立的将热传导系数和比热表示为温度的分段函数进行反演的方法是可靠有效的,并且具有良好的抗噪性能.     

NH3处理温度对N掺杂P25-TiO2的可见光催化活性的影响

研究了NH3处理温度对N掺杂P25-TiO2可见光催化活性的影响以及可见光催化活性与表面组成和结构的关系．实验结果表明：NH3处理温度在600℃时,有最高活性;在700℃,P25-TiO2转变为以金红石相为主,表面未发生N掺杂,这与700℃时NH3分解有关;N掺杂浓度、可见光吸收两者与可见光催化活性之间均不存在顺变关系．讨论揭示：N掺杂P25-TiO2的可见光催化活性是由三个要素协同作用产生：（i）表面生成大量束缚单电子氧空位（Vo）,（ii）表面有N掺入,（iii）晶型以锐态矿为主,三者缺一不可．     

TDDFT investigation on electronically excited-state hydrogen-bonding properties and ESIPT mechanism for the 2-(1H-imidazol-2-yl)-phenol compound

Structural Chemistry - In this work, DFT and TDDFT approaches have been executed to make a detailed exploration about the excited state luminescent properties as well as excited state...     

An adapted isotope dilution 1H–13C heteronuclear single-quantum correlation (ID-HSQC) for rapid and accurate quantification of endogenous and exogenous plasma glucose

Analytical and Bioanalytical Chemistry - A wide variety of methods, such as enzymatic methods, LC-MS, and LC-MS/MS, are currently available for the concentration determination of plasma glucose in...     

Incorporating Transition-Metal Phosphides Into Metal-Organic Frameworks for Enhanced Photocatalysis

Metal-organic frameworks (MOFs) have been shown to be an excellent platform in photocatalysis. However, to suppress electron–hole recombination, a Pt cocatalyst is usually inevitable, especially in photocatalytic H₂ production, which greatly limits practical application. Herein, for the first time, monodisperse, small-size, and noble-metal-free transitional-metal phosphides (TMPs; for example, Ni₂P, Ni₁₂P₅), are incorporated into a representative MOF, UiO-66-NH₂, for photocatalytic H₂ production. Compared with the parent MOF and their physical mixture, both TMPs@MOF composites display significantly improved H₂ production rates. Thermodynamic and kinetic studies reveal that TMPs, behaving similar ability to Pt, greatly accelerate the linker-to-cluster charge transfer, promote charge separation, and reduce the activation energy of H₂ production. Significantly, the results indicate that Pt is thermodynamically favorable, yet Ni₂P is kinetically preferred for H₂ production, accounting for the higher activity of Ni₂P@UiO-66-NH₂ than Pt@UiO-66-NH₂.     

Homogeneous and stable carbon nanotube dispersion assisted by cellulose in NaOH/thiourea aqueous solution

Cellulose - Carbon nanotubes (CNTs) have been proposed as next-generation lightweight structural materials, yet their application is facing challenges due to the poor dispersity in most solvents,...     

Investigation of enzymatic C–P bond formation using multiple quantum HCP nuclear magnetic resonance spectroscopy

The biochemical mechanism for the formation of the C–P–C bond sequence found in l ‐phosphinothricin, a natural product with antibiotic and herbicidal activity, remains unclear. To obtain further insight into the catalytic mechanism of PhpK, the P‐methyltransferase responsible for the formation of the second C–P bond in l ‐phosphinothricin, we utilized a combination of stable isotopes and two‐dimensional nuclear magnetic resonance spectroscopy. Exploiting the newly emerged Bruker QCI probe (Bruker Corp.), we specifically designed and ran a ¹³C‐³¹P multiple quantum ¹H‐¹³C‐³¹P (HCP) experiment in ¹H‐³¹P two‐dimensional mode directly on a PhpK‐catalyzed reaction mixture using ¹³CH₃‐labeled methylcobalamin as the methyl group donor. This method is particularly advantageous because minimal sample purification is needed to maximize product visualization. The observed 3:1:1:3 multiplet specifically and unequivocally illustrates direct bond formation between ¹³CH₃ and ³¹P. Related nuclear magnetic resonance experiments based upon these principles may be designed for the study of enzymatic and/or synthetic chemical reaction mechanisms. Copyright © 2015 John Wiley & Sons, Ltd.