Surface‐Enhanced Raman Scattering Using Microstructured Optical Fiber Substrates

Microstructured optical fibers (MOFs) represent a promising platform technology for fully integrated next generation surface enhanced Raman scattering (SERS) sensors and plasmonic devices. In this paper we demonstrate silver nanoparticle substrates for SERS detection within MOF templates with exceptional temporal and mechanical stability, using organometallic precursors and a high‐pressure chemical deposition technique. These 3D substrates offer significant benefits over conventional planar detection geometries, with the long electromagnetic interaction lengths of the optical guided fiber modes exciting multiple plasmon resonances along the fiber. The large Raman response detected when analyte molecules are infiltrated within the structures can be directly related to the deposition profile of the nanoparticles within the MOFs via electrical characterization.     

Dynamic nuclear polarization studies of nitroxyl spin probes in agarose gel using Overhauser‐enhanced magnetic resonance imaging

Agarose is a tissue‐equivalent material and its imaging characteristics similar to those of real tissues. Hence, the dynamic nuclear polarization studies of 3‐carboxy‐2,2,5,5‐tetramethyl‐pyrrolidine‐1‐oxyl (carboxy‐PROXYL) in agarose gel were carried out. The dynamic nuclear polarization parameters such as spin lattice relaxation time, longitudinal relaxivity, leakage factor, saturation parameter and coupling parameter were estimated for 2 mM carboxy‐PROXYL in phosphate‐buffered saline solution and water/agarose mixture (99 : 1). From these results, the spin probe concentration was optimized as 2 mM, and the reduction in enhancement was observed for carboxy‐PROXYL in water/agarose mixture (99 : 1) compared with phosphate‐buffered saline solution. Phantom imaging was also performed with 2 mM concentration of carboxy‐PROXYL in various concentrations of agarose gel at various radio frequency power levels. The results from the dynamic nuclear polarization measurements agree well with the phantom imaging results. These results pave the way for designing model system for human tissues suited to the biological applications of electron spin resonance/Overhauser‐enhanced magnetic resonance imaging.     

SERS decoding of micro gold shells moving in microfluidic systems

In this study, in situ surface‐enhanced Raman scattering (SERS) decoding was demonstrated in microfluidic chips using novel thin micro gold shells modified with Raman tags. The micro gold shells were fabricated using electroless gold plating on PMMA beads with diameter of 15 μm. These shells were sophisticatedly optimized to produce the maximum SERS intensity, which minimized the exposure time for quick and safe decoding. The shell surfaces produced well‐defined SERS spectra even at an extremely short exposure time, 1 ms, for a single micro gold shell combined with Raman tags such as 2‐naphthalenethiol and benzenethiol. The consecutive SERS spectra from a variety of combinations of Raman tags were successfully acquired from the micro gold shells moving in 25 μm deep and 75 μm wide channels on a glass microfluidic chip. The proposed functionalized micro gold shells exhibited the potential of an on‐chip microfluidic SERS decoding strategy for micro suspension array.     

UV Photodissociation Dynamics of Nitric Acid： The Hydroxyl Elimination Channel

Sliced velocity mapping ion imaging technique was employed to investigate the dynamics of the hydroxyl elimination channel in the photodissociaiton of nitric acid in the ultraviolet region. The OH product was detected by （2＋1） resonance enhanced multiphoton ionization via the D^2∑^- electronic state. The total kinetic energy spectra of the OH＋NO2 channel from the photolysis of HONO2 show that both ：NO2（X2A1） and NO2（A2B2） channels are present, suggesting that both 1^1A″ and 2^1A″ excited electronic states of HONO2 are involved in the excitation. The parallel angular distributions suggest that the dissociation of the nitric acid is a fast process in comparison with the rotational period of the HNO3 molecule. The anisotropy parameter β for the hydroxyl elimination channel is found to be dependent on the OH product rotational state as well as the photolysis energy.     

离子束混合诱导稀土金属Ce与Si的界面反应及硅化物的形成

本文详细讨论了离子束混合下,Ce/Si〈100〉双层膜体系界面反应的动力学过程以及硅化物的形成规律.样品经150KeV Ar离子注入,辐照温度从LNT到300℃,剂量从5×X10~(14)到8.1×10~(16)Ar/cm~2.界面反应形成的硅化物为CeSi_2,其结构为体心正交结构.硅化物是分层生长的,厚度与注入剂量的平方根成线性关系,这说明界面反应是扩散控制的.与近贵金属/硅体系和难熔金属/硅体系相比较可以看出,稀土金属Ce/Si体系的相变过程与难熔金属/硅体系的相似;而混合的动力学行为与近贵金属/硅体系的相似.本文还讨论了化学驱动力和辐射增强扩散对混合的贡献.     

Pilot‐Based Coding Scheme for Parametric Stereo in Enhanced aacPlus

We propose a pilot‐based coding (PBC) scheme for lossless bit rate reduction of parametric stereo (PS) in enhanced aacPlus. It uses PBC in addition to the existing frequency and time differential coding to encode and decode PS parameter indexes. We also design optimal Huffman codebooks (HCBs) for PBC in the proposed scheme. Experiments show that the proposed scheme is superior to the original coding scheme, where both the new coding structure and the optimal HCBs contribute to the bit rate reduction.     

过渡金属络合物的非线性光学性质的研究

报道了具有良好电荷转移特性的Ｒｕ络合物，采用四波混频方法对其非线性光学性能进行了测量，由此推算出三阶非线性光学极化率和分子的超极化率，并讨论了不同配体对三阶非线性光学系数的影响     

非水体系中哌啶在银电极表面的表面增强喇曼散射

本文测定了哌啶在甲醇溶液中吸附在银电极表面的表面增强喇曼散射(SERS)光谱,及其随电位的变化,同时还测定了电极经不同氧化-还原循环(ORC)预处理时的SERS谱,对所得结果进行了分析比较,并进一步研究了非水体系和水体系SERS谱之间的关系.实验结果表明:哌啶在甲醇体系中比在水体系中SERS谱的增强因子要小,并且它们的SERS谱线随电位的变化也有一定的差别.     

Low‐Temperature Growth of SiO2 Films by Plasma‐Enhanced Atomic Layer Deposition

Silicon dioxide (SiO₂) films prepared by plasma‐enhanced atomic‐layer deposition were successfully grown at temperatures of 100 to 250 °C, showing self‐limiting characteristics. The growth rate decreases with an increasing deposition temperature. The relative dielectric constants of SiO₂ films are ranged from 4.5 to 7.7 with the decrease of growth temperature. A SiO₂ film grown at 250 °C exhibits a much lower leakage current than that grown at 100°C due to its high film density and the fact that it contains deeper electron traps.     

Piezoelectricity of ordered (ScxGa1-xN) alloys from first principles

First-principles calculations are performed to compute the e₃₃ piezoelectric coefficients of GaN, ScN and (Sc_xGa_1-xN) alloys exhibiting an alternation of hexagonal GaN, with hexagonal ScN along the c-axis. For Sc compositions larger than 50%, each atom has nearly five nearest neighbors (i.e., the ground state exhibits a phase that is five-fold coordinated). On the other hand, Sc-deficient (Sc, Ga) N alloys adopt a ground-state that is four-fold coordinated). The magnitude of e₃₃ in the Sc-deficient ideally ordered (Sc_0.25Ga_0.75N) is found to be larger than the magnitude of the corresponding e₃₃ coefficients resulting from the compositional weighted average over the hexagonal (h-ScN) and the wurtzite (w-GaN) parent compounds. On the other hand, the e₃₃ coefficients of the Sc-rich ordered (Sc_0.75Ga_0.25N) is found to be negligibly small. In addition, e₃₃ piezoelectric coefficients in ordered (Sc_0.5Ga_0.5N) exhibit quite large magnitudes, due to the nonpolar to polar transition occurs at Sc composition x = 0.5, and thus can bridge the corresponding coefficients of (Ga, In) N and ferroelectric alloys. The microscopic origins for this huge enhancement in the piezoelectric behavior in Sc-low and Sc-intermediate alloys and the role of each atom are revealed and discussed.