Raman spectra of ZnSe nanoparticles synthesized by thermal evaporation method

ZnSe nanoparticles were synthesized by using a thermal evaporation method for a vapour phase reaction of zinc and selenium sources. The sample was characterized by XRD, TEM, HRTEM and Raman spectroscopy. Raman spectra of longitudinal-optical (LO) like mode was analysed by a macroscopic continuum dielectric model. Large broadening of LO-mode is homogeneous and comes from the relaxation of the phonons at the interface and contribution of defects. Surface modes give the main contribution to the asymmetry of the lineshape.     

用光测法研究颈段脊柱的应力状态

本文用光测力学实验方法研究了人体颈段脊柱的应力场和位移场。并且从生物力学角度进行了理论分析和讨论,实验结果与理论分析和医学统计相符,从而为研究颈椎病发病机制提供了力学依据。     

HXeBr与苯和苯的衍生物弱相互作用的理论研究

采用MP2/aug-cc-pVDZ (对于Xe和I原子采用aug-cc-pVDZ-PP基组)优化了复合物HXeBr…C₆H₅X (X=H, CH₃, NH₂, N(CH₃)₂, NHCH₃, OH, OCH₃, CN, F, Cl, Br, I, COOH, SO₃H, CF₃)及单体的几何构型, 详细分析了π…H键和双齿氢键两种弱相互作用类型的特征, 以及不同的取代基对这两种弱相互作用能的影响. 对14个双齿氢键型复合物, 我们发现复合物的相互作用能与苯环衍生物(C₆H₅X)的偶极矩, 复合物中Xe-Br键键长的变化, H-Xe键键长的变化和H-Xe键振动频率的变化, 以及双齿氢键上Br原子和两个H原子范德华表面相互穿透距离之和均有较好的线性关系. 另外, 我们还发现复合物的相互作用能与双齿氢键上两个键临界点的电子密度之和, 电子密度Laplacian值之和, 静电势之和, 以及双齿氢键和苯环碳原子形成环的环临界点处的电子密度, 电子密度Laplacian值以及静电势均有着较好的线性关系.     

Bias-dependent timing jitter of 1-GHz sinusoidally gated InGaAs/InP avalanche photodiode

We characterized the dependence of the timing jitter of an InGaAs/InP single-photon avalanche diode on the excess bias voltage(V_(ex)) when operated in 1-GHz sinusoidally gated mode.The single-photon avalanche diode was cooled to-30 degrees Celsius.When the V_(ex) is too low(0.2 V-0.8 V) or too high(3 V-4.2 V),the timing jitter is increased with the V_(ex),particularly at high V_(ex).While at middle V_(ex)(1 V-2.8 V),the timing jitter is reduced.Measurements of the timing jitter of the same avalanche diode with pulsed gating show that this effect is likely related to the increase of both the amplitude of the V_(ex) and the width of the gate-on time.For the 1-GHz sinusoidally gated detector,the best jitter of 93 ps is achieved with a photon detection efficiency of 21.4%and a dark count rate of ~2.08×10~(-5) per gate at the V_(ex) of 2.8 V.To evaluate the whole performance of the detector,we calculated the noise equivalent power(NEP) and the afterpulse probability(P_(ap)).It is found that both NEP and P_(ap) increase quickly when the V_(ex) is above 2.8 V.At ~2.8-V V_(ex),the NEP and P_(ap) are ~2.06×10~(16)W/Hz~(1/2) and 7.11%,respectively.Therefore,the detector should be operated with V_(ex) of 2.8 V to exploit the fast time response,low NEP and low P_(ap).     

碳点嫁接海藻酸钙复合结构的制备及其对Cu2+的检测

基于铜离子与碳点的荧光猝灭作用,建立了用碳点作为荧光探针来检测铜离子的新方法。该方法将碳点还原后再嫁接于海藻酸钙,从而得到一种新型的含还原碳点的海藻酸钙薄膜荧光探针。用荧光分光光度计和紫外-可见分光光度计对探针的荧光特性以及探针与金属离子的相互作用进行了研究。研究结果表明：改性后的荧光探针具有很高的荧光强度,因此可以根据探针荧光强度的变化实现对铜离子的检测,并通过乙二胺四乙酸二钠（EDTA）的作用实现对铜离子的重复检测。铜离子浓度在5×10^-6~100×10^-6 mol·L^-1范围内与该荧光探针的荧光猝灭强度呈良好的线性关系。该方法不仅可以对铜离子检测,更实现了对碳点的固载,该技术有望实现荧光探针的回收再利用。