The characteristics of lysine-mediated self-assembly of gold nanoparticles on the ITO glass

In this study, lysine was investigated as a cross-linker to induce the self-assembly of gold nanoparticles (GNPs) with the variation of solution pH, dosage amounts of lysine, and GNP size. Lysine molecules at acidic pH ranges induced the aggregation of Au colloids via α, ?-amine mediated self-assembly of GNPs, consequently leading to the generation of secondary peak at longer wavelength for aggregated GNPs. At intermediate and basic pH ranges, however, the ionization of carboxylic acid groups in lysine hindered the cross-linking between Au colloids with the consequent disappearance of secondary peak. For the array of small Au colloids (ca. 43 nm), lysine induced heavily-aggregated GNPs on the ITO glass at strongly acidic condition (pH2～3) through its molecular bridging effect. For the array of large Au colloids (ca.70 nm), lysine produced one-dimensional assembly of GNPs on the ITO glass at slightly acidic condition (at pH4.7) through zwitterions-mediated interactions.     

耐热硅树脂材料的光学特性研究

遴先出了具有200℃高耐热性的硅树脂，根据185 nm到104 nm波段的透射谱，发现材料在300 nm到3000 nm范围内无吸收峰.用Manificier方法，推算出了600 nm到1600 nm波段上的光学常量，650 nm和1550 nm波长的折射率分别为1.513和1.498（温度为26℃时）；对薄膜进行紫外曝光后，相应的折射率减小到1.512和1.489.用激光－V棱镜装置检测出该材料无偏振特性，根据薄膜材料的表面形貌图均方高差和传输损耗分析，波导散射损耗约为0.5 dB/cm.研究结果表明，这种硅树脂可用于制作光通信系统中的波导器件，特别是塑料光纤通信网络中的波导器件.     

Gd3Ga5O12:Ag薄膜电致发光材料的制备及其发光性质

研究了Gd3 Ga5O12 :Ag材料的制备及其发光性质 .Gd3 Ga5O12 :Ag材料通过固相反应法制得 ,采用X射线衍射法分析了材料的结晶度及成分 .用电子束蒸发将该材料制备成交流的薄膜电致发光器件 ,得到了较好的蓝紫色发光 ,发光峰分别位于 397和 46 7nm .通过对材料的光致发光和激发光谱的研究和比较 ,得出 397和 46 7nm分别来自于氧空位和Ag 的发光 .     

石墨烯气凝胶复合相变材料的热物性研究

相变材料利用其相变潜热能力可吸收储存和释放利用热量,同时在相变过程中其温度浮动小,能够实现温度控制从而用于热管理.但是其低热导率和易泄露问题严重制约了其性能.石墨烯气凝胶因其丰富的多孔结构而具有较大的比表面积,可吸附相变材料解决其泄露问题,同时石墨烯的高导热系数可提高相变材料的热导率.这里选取正十八烷为相变材料,制备了不同质量分数的石墨烯气凝胶复合相变材料.测得石墨烯气凝胶含量为13.99 wt%的样品,其导热系数比纯正十八烷高出306.2%,熔化潜热和凝固潜热分别下降了13.8%和10.8%.分子动力学模拟结果表明,石墨烯气凝胶的引入会在一定程度上增强正十八烷分子的有序性和一致性,即在同一温度下复合相变材料中的正十八烷分子比纯正十八烷分子拥有更集中分布的末端距和扭转角,径向分布函数和自扩散系数都相对较低,说明石墨烯材料的引入可以提升正十八烷的导热系数.     

锌基复合气凝胶的微观结构

以ZnCl2为前躯物,不同相对分子质量的聚丙烯酸为模版剂,环氧丙烷作为催化剂,超临界干燥成功制得了锌基复合气凝胶。运用场发射扫描电镜、高分辨透射电子显微镜和N2等温吸附测试对气凝胶的微观结构进行了表征。结果表明,制备的锌基复合气凝胶呈现三维网络状结构,其三维结构是由大量微小颗粒组成,颗粒的粒径为nm量级,为介孔材料。选用相对分子质量为1800的聚丙烯酸作为模版剂制备的气凝胶的微观结构最好,无明显的塌陷和团聚现象,其比表面积为236 m2/g,平均孔径分布在11 nm左右,总的孔体积为0.179 cm3/g。     

Biosynthesis of gold nanoparticles using Capsicum annuum var. grossum pulp extract and its catalytic activity

Biological synthesis approach has been regarded as a green, eco-friendly and cost effective method for nanoparticles preparation without any toxic solvents and hazardous bi-products during the process. This present study reported a facile and rapid biosynthesis method for gold nanoparticles (GNPs) from Capsicum annuum var. grossum pulp extract in a single-pot process. The aqueous pulp extract was used as biotic reducing agent for gold nanoparticle growing. Various shapes (triangle, hexagonal, and quasi-spherical shapes) were observed within range of 6–37 nm. The UV–Vis spectra showed surface plasmon resonance (SPR) peak for the formed GNPs at 560 nm after 10 min incubation at room temperature. The possible influences of extract amount, gold ion concentration, incubation time, reaction temperature and solution pH were evaluated to obtain the optimized synthesis conditions. The effects of the experimental factors on NPs synthesis process were also discussed. The produced gold nanoparticles were characterized by transform electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray (EDS) and Fourier Transform infrared spectroscopy (FTIR). The results demonstrated that the as-obtained GNPs were well dispersed and stable with good catalytic activity. Biomolecules in the aqueous extract were responsible for the capping and stabilization of GNPs.     

Composite of discotic liquid crystal and gold nanoparticles: A comperative band gap study

Nanocomposites of discotic liquid crystal namely 2, 3, 6, 7, 10, 11-hexabutyloxytryphenylene (HAT4) in existence of variable concentration of gold nanoparticles (GNPs) have been studied at room temperature and zero pressure. The absorption spectra of nanocomposites are captured by a Shimadzu UV–VIS Spectrophotometer, model UV-1800, in the wavelength range 900–200?nm. In this paper using the Tauc’s relation, the absorption spectra fitting method was applied to estimate the optical band gap. Nanocomposites are prepared by mixing of GNPs with four concentrations in pure HAT4 viz. 0.2, 0.6, 1.2 and 3?wt%. From the investigation of absorption spectra, it has been observed that with the enhance of GNPs concentration in pure HAT4 band gap has decreased for lower concentrations but for higher concentration (3?wt%) it increases.     

Sol-gel synthesis of nanocomposite crystalline HMX/AP coated by resorcinol-formaldehyde

This work aims to improve the performance of composite explosive by using the sol-gel method to mix high explosive and oxidizer in nanoscale. Nanocomposite materials of HMX and AP were prepared by using resorcinol-formaldehyde (RF) as binder. Its structure was characterized by scanning electron microscopy (SEM), BET method, X-ray powder diffraction (XRD), and DSC. SEM images indicate that HMX/AP/RF aerogel has a laminate-like structure with uniform pores. The XRD results show that the mean crystal size of HMX is less than 100 nm; HMX and AP are mixed uniformly in nanoscale. The specific surface area of HMX/AP/RF is 27 m²/g and much less than that of RF aerogel. The mesopores and micropores of HMX/AP/RF aerogel mainly focus in the range of 2-20 and 0.6-1.6 nm, respectively. DSC analysis indicates that the thermal decomposition temperature of HMX/AP/RF is reduced compared to that of original HMX.     

三层材料纳米颗粒形状对消光特性的影响

通过高分辨率电子束光刻方法制备了不同形状的三层复合材料纳米颗粒,研究了这种纳米颗粒的形状变化对消光特性的影响。测试结果表明,当入射波偏振方向平行于短轴时,随着长宽比的增大,共振峰位置发生蓝移;当光源偏振方向平行于长轴时,随着长宽比的增大,共振峰位置发生红移。还用时域有限差分算法以及表面等离波子的Lorentz模型对纳米颗粒的消光特性进行数值计算,所得的消光频谱曲线、共振峰位置变化趋势与实验基本一致。此外,还研究了主体材料层厚度对消光特性的影响,发现其厚度在20～90nm变化时,共振峰发生3～115nm的蓝移。     

Synthesis and characterization of silver nanoparticles in a nanoporous glass

We obtained a metal-dielectric composite by thermal restoration of silver atoms from an alcohol solution of a precursor in nanoporous glass with pores with a radius of 2 nm. The concentration, size, and asphericity degree of metal nanoparticles formed in the pores are characterized according to the measured extinction spectra of the material.     

TiO2膜消光系数的确定及制备参量的影响

基于窄带干涉滤光片的峰值透射率测量可以直接反演出薄膜的消光系数,从而得到了一种简易而又精确的评价薄膜微弱损耗的新方法。阐述了确定弱吸收薄膜消光系数的基本原理,并分析了这种评价方法的基本精度。讨论了离子束溅射TiO2薄膜的制备参量对薄膜消光系数的影响。发现溅射速率和氧分压是影响TiO2薄膜损耗的灵敏因素。在保持其它参量不变的条件下,溅射速率从0.35nm/s下降到0.23nm/s,TiO2薄膜的消光系数从3.9×10-5下降到2.1×10-5;辅助离子源的Ar∶O比从1∶2变化为1∶4,对应的消光系数从5.6×10-5下降到2.3×10-5。此外,随着基板温度的提高,损耗也会有所增加。TiO2薄膜消光系数评价的合理性表明由窄带滤光片的峰值透射率来反演薄膜的消光系数是可行的。     

Electrochromic properties of WO3 thin film onto gold nanoparticles modified indium tin oxide electrodes

Gold nanoparticles (GNPs) thin films, electrochemically deposited from hydrogen tetrachloroaurate onto transparent indium tin oxide (ITO) thin film coated glass, have different color prepared by variation of the deposition condition. The color of GNP film can vary from pale red to blue due to different particle size and their interaction. The characteristic of GNPs modified ITO electrodes was studied by UV-vis spectroscopy, scanning electron microscope (SEM) images and cyclic voltammetry. WO₃ thin films were fabricated by sol-gel method onto the surface of GNPs modified electrode to form the WO₃/GNPs composite films. The electrochromic properties of WO₃/GNPs composite modified ITO electrode were investigated by UV-vis spectroscopy and cyclic voltammetry. It was found that the electrochromic performance of WO₃/GNPs composite films was improved in comparison with a single component system of WO₃.     

Size-controlled aerosol synthesis of silver nanoparticles for plasmonic materials

Aerosol techniques were used to synthesize spherical and monodisperse silver nanoparticles for plasmonic materials. The particles were generated with an evaporation-condensation technique followed by size selection and sintering with a differential mobility analyzer and a tube furnace, respectively. Finally, the nanoparticles were collected on a glass substrate with an electrostatic precipitator. The particle size distributions were measured with a scanning mobility particle sizer and verified with a transmission electron microscope. A spectrophotometer was used to measure the optical extinction spectra of the prepared samples, which contained particles with diameters of approximately 50, 90 and 130?nm. By controlling the particle size, the dipolar peak of the localized surface plasmon resonance was tuned between wavelengths of 398 and 448?nm. In addition, quadrupolar resonances were observed at shorter wavelengths as predicted by the simplified theoretical model used to characterize the measured spectra.     

23W peak power picosecond pulses from a single-stage all-semiconductor master oscillator power amplifier

Using a single-stage all-semiconductor master oscillator-power amplifier, we generate narrow-band laser pulses of 23?W peak power at 1063?nm wavelength. These pulses of 40?ps length FWHM have a variable repetition rate and pulse energies around 2?nJ, which exceeds previous realizations and makes them ideally suited for second harmonic generation. With a spectral filter, an extinction ratio above 36?dB could be achieved at nearly 10?W peak power. We use a novel spectral method to reliably determine pulse energies independently of the background level.     

Laser-assisted one-step fabrication of homogeneous glass–silver composite

Glass doped with silver ions was fabricated using a dry technique and then irradiated at the scanning speed of 14 mm?s^?1 using a nanosecond pulsed Nd:YVO₄ laser operating at 355?nm. This led to the spatially selective, one-step precipitation of silver particles and fabrication of a homogeneously structured optical composite material: glass?Csilver composite. The optical and structural properties of such composite material can be designed at will, which could have potential impact on light/plasmon wave and sensing technologies, optoelectronics, and surface enhanced Raman spectroscopy.     

金原子团簇的分频散射光谱研究

液相金原子团簇是一种非线性光学介质.它在580nm处产生一个最强共振散射峰.当激发波长为290nm(1.03×10¹⁵Hz)时,液相金原子团簇在580nm(1/2×1.03×10¹⁵Hz)和870nm(1/3×1.03×10¹⁵Hz)分别产生一个1/2分频和1/3分频散射峰;当激发波长为580nm(5.02×10¹⁴Hz)时在290nm(2×5.02×10^-14Hz)和870nm(2/3×5.02×10¹⁴Hz)分别产生一个2倍频和2/3分频散射峰;当激发波长为870nm(3.34×10¹⁴Hz)时在580nm(3/2×3.34×10¹⁴Hz)和290nm(3×3.34×10¹⁴Hz)分别产生一个3/2分频和3倍频散射峰.分频散射和倍频散射峰与共振散射峰具有相似的散射行为.从激励光与液相金原子团簇相互作用的运动方程出发,根据傅氏变换理论,较好地解释了液相金原子团簇产生的一些非线性散射光谱.     

Some comments on superfluid 3He placed in globally deformed aerogel

New experimental results focused on the behavior of the superfluid A-like phase placed in globally deformed aerogel environment are considered. We compare experimental data collected by using optically attested axially stretched silica aerogel, on the one hand, and “nematically ordered” aerogel consisting of nearly parallel Al₂O₃ · H₂O polymer strands, on the other. In the case of axially stretched silica aerogel the point of view was adopted according to which the orbital anisotropy axis l? is long-ranged. The experiments were carried out by pulsed NMR techniques in keeping the direction of an externally applied magnetic field normal to aerogel stretching axis. We have generalized the dipole-locked configuration for arbitrary angle of inclination of the magnetic field with respect to aerogel stretching axis. The experimental data collected in using “nematically ordered” aerogel cannot be reconciled with above-mentioned results.     

基于光子晶体光纤中的自相位调制的全光再生

利用高非线性光子晶体光纤中的自相位调制效应产生的超连续谱,理论上推导了超窄脉冲信号的再生机制。分别从频域和时域上形象的解释了脉冲再生的原理,该本再生方法可以适用于OTDM的信号再生。实验上对劣化了的脉冲宽度为1.7ps的携带信息的超窄脉冲信号进行了再生,再生之后的信号峰值均衡,消光比达到了15dB。再生前信号中心波长是1548.2nm,重复频率是9.96872GHz。实验中,在1554nm—1570nm和1530nm—1543nm范围内都可以得到10dB以上的再生质量。同时拟合了信号峰值功率和波长关系,得到的曲线和超连续谱曲线相吻合。     

Measurement of mean size and evaluation of polydispersity of gold nanoparticles from spectra of optical absorption and scattering

Two methods for determination of the mean size of gold nanoparticles, based on measurement of the wavelengths of the maxima λ_max of side scattering and extinction in the range 400–700 nm, are compared. Four sols with mean particle diameters d of about 15, 20, 25, and 30 nm, measured using the dynamic light-scattering technique, were studied experimentally. The slope of the size dependence λ_max(d) of the spectral position of the scattering peak exceeded that for the extinction peak by a factor of 2.4. This fact ensures a substantially higher accuracy of the scattering method. For simulating polydispersity, mixtures of three colloids with particle diameters of 20, 25, and 30 nm were used: sample S1, with a size distribution close to the normal one of around 25 nm, and sample S2, with equal concentrations of each of the components. The extinction spectra of mixtures S1 and S2 and the initial 25-nm sol (S0) were virtually identical, whereas their scattering spectra showed a pronounced increase in the peak amplitude in the series S0, S1, S2. These results agree with calculations based on the Mie theory. Thus, scattering spectra offer advantages over extinction spectra not only in measuring the mean size of gold particles but also in evaluating their polydispersity.     

Preparation and optical constants of the nano-crystal and polymer composite Bi4Ti3O12/PMMA thin films

Bismuth titanate, Bi₄Ti₃O₁₂ (BTO), is a typical ferroelectric material with useful properties for optical memory, piezoelectric and electro-optic devices. Its nano-crystals were compounded by the chemical solution decomposition technique. Its structure and size were analyzed by X-ray diffraction and transmissive electron microscopy. The composite thin film of BTO nano-crystals and high transparency polymethylmethacrylate (PMMA) polymer was prepared by spin coating. The transmitted spectrum of BTO/PMMA composite thin film in 300–1500 nm was measured. The film thickness d and the optical constants of the film, such as the refractive index n, the absorption coefficient α, and the extinction coefficient κ were obtained using the data from the transmitted spectrum.