Design of vertical diamond Schottky barrier diode with junction terminal extension structure by using the n-Ga2O3/p-diamond heterojunction

A novel junction terminal extension structure is proposed for vertical diamond Schottky barrier diodes (SBDs) by using an n-Ga₂O₃/p-diamond heterojunction. The depletion region of the heterojunction suppresses part of the forward current conduction path, which slightly increases the on-resistance. On the other hand, the reverse breakdown voltage is enhanced obviously because of attenuated electric field crowding. By optimizing the doping concentration, length, and depth of n-Ga₂O₃, the trade-off between on-resistance and breakdown voltage with a high Baliga figure of merit (FOM) value is realized through Silvaco technology computer-aided design simulation. In addition, the effect of the work functions of the Schottky electrodes is evaluated. The results are beneficial to realizing a high-performance vertical diamond SBD.     

Simultaneous determination of ternary cephalosporin solutions by Raman spectroscopy

Cephalosporins are widely used as veterinary and human antibiotics. However, cephalosporin abuse is harmful to human health and causes allergic reactions or antibiotic resistance. We investigate a method fea- turing Raman spectroscopy and chemometrics to quantify mixture solutions of three typical cephalosporins, namely, ceftriaxone, cefotaxime sodium, and cefazolin sodium. Partial least-squares regression models are built on spectral data that are preprocessed by various methods. With prediction relative errors within 5% and high correlation coefficients of 0.998, we demonstrate that Raman spectroscopy combined with multivariate analysis is feasible for use in the quantitative determination of cephalosporin solutions. OCIS codes： 300.6450. 070.4340. 070.4790.     

1,4-苯二硫醇的表面增强拉曼光谱和激发态的密度泛函理论研究

利用密度泛函理论(density functional theory,DFT)在B3LYP/6-311+g(d)(C,H,S)和Lanl2dz(Ag、Au)基组下对1,4-苯二硫醇分子及其复合物进行了结构优化和频率计算,得到了分子及其复合物稳定的化学构型和拉曼光谱。优化后的1,4-苯二硫醇分子的S—H键和苯环所在平面夹角为20.2°,分子非平面结构。模拟了金银团簇在苯硫醇分子表面的吸附行为,得到了金团簇和银团簇在分子表面的吸附方式,即,金团簇以接近平行的方向吸附于苯硫酚分子的表面而银团簇则以几乎垂直的方向吸附于分子表面。此外,还分析了静态极化率数值变化和自然键轨道(natural bond orbital,NBO)布局分析得到的电荷分布对拉曼光谱的强度变化的影响。复合物1,4-BDT-Au2,1,4-BDT-Ag2和三明治结构的Ag2-1,4-BDT-Au2拉曼光谱谱峰强度与静态极化率数值变化有很好的吻合。采用含时密度泛函理论(time dependent density functional theory,TDDFT)对Ag2-1,4-BDT-Au2复合物进行了激发态的分析计算,通过模拟吸收光谱和计算轨道跃迁单激发态,分析计算了三明治结构的电荷转移激发态,利用可视化的电荷转移,研究了表面增强拉曼(surface enhanced Raman scattering,SERS)化学增强机理。     

新型螯合磁性纳米Fe_3O_4的制备及其性能研究

采用共沉淀法制备了磁性四氧化三铁(Fe3O4)纳米粒子,并通过硅烷偶联剂对其表面进行改性,进一步在其表面偶联修饰氨基硫脲,制备了螯合磁性纳米Fe3O4粒子。利用广角X射线衍射仪(WAXD)、红外光谱仪(FTIR)、分光光度计等对磁性纳米粒子的结构和性能进行了表征。结果表明,纳米Fe3O4为反尖晶石结构,通过偶联修饰可以实现氨基硫脲在纳米粒子表面的化学改性。螯合磁性纳米粒子具有良好的分散性和磁响应性,且对多种金属离子(Pb2+、Hg2+、Zn2+、Cd2+)具有良好的螯合效果。