Synthesis and Properties of Cupric Sulphate Doped Polyvinyl Pyrrolidone (PVP) Solutions

The optical, electrical and acoustical properties of polymer solutions based on polyvinyl pyrrolidone (PVP) doped with cupric sulphate (CuSO₄) were studied. The polymer solutions were prepared by varying the concentration of Cu in the PVP using a simple chemical route. The UV-visible spectroscopy results showed that the optical absorbance decreased with an increase in wavelength from 300 to 700 nm. The optical band gaps were found to decrease with addition of the Cu salt in the polymer. The refractive index also showed significant variation with the doping of the CuSO₄. The electrical conductivity of the polymer solutions was found to increase with temperature as well as concentration of Cu while the activation energy of electrical conduction decreased with concentration of Cu. The ultrasonic velocities of the polymer solutions were measured at a frequency of 1 MHz using an ultrasonic interferometer. The ultrasonic velocity and surface tension were increased while the adiabatic compressibility, acoustic impedance and intermolecular free length, the average distance between the surfaces of the coils of adjacent molecules, were decreased with increase in the concentration of CuSO₄ in the PVP.     

(Au)_核(Ag)_壳纳米微粒-火焰原子吸收光谱法测定过氧化氢

在90 ℃水浴条件下,以粒径为10 nm的纳米金做晶种,用柠檬酸三钠还原硝酸银,制备了平均粒径为30 nm的（Au）核（Ag）壳纳米微粒,用高速离心纯化除去过量的柠檬酸三钠获得了较纯的（Au）核（Ag）壳纳米微粒。在pH 3.8的HAc-NaAc缓冲溶液中,Fe2＋催化H2O2反应产生的羟基自由基可氧化（Au）核（Ag）壳纳米微粒生成银离子。离心后,离心液中的银离子可用火焰原子吸收光谱法在328.1 nm波长处测量。随着H2O2浓度增大,离心液中银离子浓度增加,其吸光度值增加。H2O2浓度在2.64～42.24 μmol·L-1范围内与上清液中银离子的原子吸收值ΔA呈良好的线性关系,回归方程为ΔA=0.014c-0.013 1, 相关系数为0.998 4,检出限为0.81 μmol·L-1 H2O2。当用于水样中H2O2的测定,获得了满意的结果。     

Effect of ultrasonic wave on the syntheses of Au and ZnO nanoparticles by laser ablation in water

We synthesized Au and ZnO nanoparticles by laser ablation in distilled water with the superposition of an ultrasonic wave. The effect of the ultrasonic wave was examined on the optical absorbance of colloidal solution and the crystallinity of synthesized nanoparticles. The absorbance of colloidal solution was enhanced by the ultrasonic wave, indicating more efficient production rate of nanoparticles. In addition, the ultrasonic wave enhanced the crystallinity of synthesized nanoparticles. These enhancements are attributed to the fact that the ultrasonic wave drives the repetitive formations and collapses of cavitation bubbles.     

Anomalous elastic behaviour of Bi-Pb-Ag composites

Bi-Pb and Bi-Pb-Ag superconducting composites have been prepared by the solid state reaction method. After the usual characterization, ultrasonic longitudinal velocity and attenuation studies have been undertaken over a temperature range 80–300 K by the pulse transmission technique. In contrast to normal solids, the ultrasonic velocities of both the samples in the temperature range 200-100 K are found to decrease with decreasing temperature (softening), followed by a velocity maximum. The samples are also found to exhibit longitudinal attenuation peaks at TEMPERATURES = 260, 160 and 120 K. An attempt has also been made to verify whether the Wachtman's equations can theoretically explain the low-temperature behaviour of the Young's modulus of these materials. A qualitative explanation for both the phenomena of softening of velocity as well as the occurrence of attenuation peaks is given.     

Temperature dependent ultrasonic properties of aluminium nitride

Hexagonal wurtzite structured aluminium nitride has been characterized by the theoretical calculation of ultrasonic attenuation, ultrasonic velocity, higher order elastic constants, thermal relaxation time, acoustic coupling constants and other related parameters in temperature range 200-800 K for wave propagation along the unique axis of the crystal. Higher order elastic constants of AlN at different temperatures are calculated using Lennard-Jones potential for the determination of ultrasonic attenuation. A decrease in ultrasonic velocity with temperature has been predicted, which is caused by reduction in higher order elastic constants with temperature. The temperature dependent ultrasonic properties have been discussed in correlation with higher order elastic constants, thermal relaxation time, thermal conductivity, acoustic coupling constants and thermal energy density. Anomalous behaviour of the attenuation is found at 400 K. On the basis of attenuation, the ductility and performance of AlN have been studied.     

Cu/PMMA复合材料的声速与冲击响应行为

基于熔融共混法,制备了一系列不同配比且随机分散的Cu/PMMA复合材料,重点研究了Cu颗粒含量对PMMA基体声速与冲击压缩行为的影响。超声测试结果表明,随着Cu颗粒含量的增加,声波的衰减使材料的横、纵波声速皆呈缓慢下降趋势,由此使体积声速亦呈减小趋势。基于平板撞击实验,获得了冲击压力在1.1~6.0 GPa范围内各复合材料的冲击波速度-粒子速度方程。Cu/PMMA复合材料声阻抗的升高使Hugoniot参数λ逐渐增大,而零压体积声速减小,与常压体积声速所表现出的变化趋势一致。结合已有的压力-粒子速度关系模型,对各材料的压力-粒子速度曲线进行了讨论。在此基础上,归纳出一种基于上述模型的用于预测金属粒子填充聚合物基复合材料压力-密度关系的可靠方法。     

Ultrasonic investigation of magnetic nanoparticles suspension with PEG biocompatible coating

Water suspension of nanoparticles was studied by ultrasound spectroscopy. Nanoparticles have a core-shell structure with magnetic core Fe₃O₄ and surfactant shells. The surface of magnetic particles was coated with oleate sodium as the primary layer and polyethylene glycol as the secondary layer. The acoustic properties of suspensions, such as velocity and attenuation of ultrasonic waves, have been measured. From experimental data mechanical properties have been determined. Adiabatic compressibility of nanoparticles suspension decreased with increase of temperature. The changes of ultrasonic wave attenuation under the influence of the external magnetic field, show that magnetic liquids with high concentration of magnetic material (despite two surfactant shells) show tendency to aggregate.     

Modeling of light absorption and scattering by metal nanoparticles coated with organic dye J-aggregate

The results of the theoretical study of optical properties of composite nanoparticles consisting of a metal core (Ag, Au, Cu, Al, Ni, Cr) and a J-aggregate shell of organic dye are presented. Light extinction, absorption, and scattering coefficients in colloidal solutions were calculated within the model based on the Mie theory modified taking into account dimensional phenomena and complemented by calculations of complex dielectric functions of the metal core and J-aggregate shell. The model adequately explains the features observed in light absorption and scattering spectra by hybrid nanoparticles, associated with the plasmon resonance in the metal core and with electronic excitation of the J-aggregate. The strong dependence of the results on geometrical parameters of nanoparticles and dielectric constants of core and shell materials was demonstrated. Methods for controlling the effects of the plasmon-exciton interaction in the system and optical properties of composite materials developed based on nanoparticles under study are discussed.     

Nanocomposite ZnO/Au formation by pulsed laser irradiation

The ZnO/Au nanocomposite formation involves synthesis of Au and ZnO colloidal solutions by 532 nm pulse laser ablation of metal targets in deionized water followed by laser irradiation of the mixed colloidal solution. The transmission electron microscope (TEM) and high-resolution transmission electron microscope (HRTEM) images show evolution of spherical particles into ZnO/Au nanonetworks with irradiation time. The formation mechanism of the nanonetwork can be explained on the basis of near resonance absorption of 532 nm irradiation by gold nanoparticles which can cause selective melting and fusion of gold nanoparticles to form network. The ZnO/Au nanocomposites show blue shift in the ZnO exciton absorption and red shift in the Au plasmon resonance absorption due to interfacial charge transfer.     

A study of the thermal-induced nonlinearity of Au and Ag colloids prepared by the chemical reaction method

The nonlinear optical properties of metal Au and Ag colloidal solutions prepared by the chemical reaction method were investigated by a single beam Z-scan technique. Under CW 633 nm excitation, the Au and Ag colloidal solutions exhibited a large thermal-induced refractive index n₂. At the same time, the thermo-optic coefficients dn/dT of the Au and Ag colloidal solutions were obtained. The mechanism responsible for the process of nonlinear refraction was discussed in term of laser heating effect.     

Acoustic anomalies in SrTiO<Subscript>3</Subscript>−BiFeO<Subscript>3</Subscript> solid solutions

The results of acoustic investigations of solid solutions SrTiO₃?BiFeO₃ in the temperature range from 100 to 650 K have been presented. The measurements of the velocity and attenuation of the longitudinal ultrasonic mode at a frequency of 10 MHz were carried out by the pulse-echo method. The observed anomalies in velocity and attenuation correlate with the maxima of the dielectric constant in the temperature range of the relaxor state. In addition, the attenuation peaks in the temperature range 400–600 K, which define Burns and T* temperatures, which are characteristic of relaxors, have been identified. The obtained results have allowed the clarifying of the phase diagram of the solid solution system SrTiO₃?BiFeO₃.     

Effects of the embedding kinetics on the surface nano-morphology of nano-grained Au and Ag films on PS and PMMA layers annealed above the glass transition temperature

The morphology evolution of nano-grained Ag and Au films deposited on polystyrene (PS) and poly(methyl methacrylate) (PMMA) polymeric layers were studied, using the atomic force microscopy technique, when annealed above the polymers glass transition temperature. The main effects on the morphology changes were identified with those concerning the embedding kinetics of the Ag and Au nanoparticles in the PS or PMMA layers. The embedding process of the nanoparticles follows as a consequence of the long-range mobility of the polymeric chains above the glass transition temperature. In particular, the dependence of the nanoparticles mean height and surface density on the annealing time at various temperatures was quantified. The analyses of these behaviors allowed us: (1) to distinguish the overall embedding process in a first stage in which a thin wetting layer of the polymer coats the nanoparticles followed by a true embedding process of the nanoparticles into the polymer layer; (2) to evaluate the characteristic coating time for the Ag and Au nanoparticles in the PS and PMMA in the first stage; (3) to evaluate the characteristic embedding velocity for the Ag and Au nanoparticles in the PS and PMMA in the second stage; (4) to derive the activation energies for the embedding process of the Ag and Au nanoparticles in PS and PMMA; (5) to identify the embedding statistics of the Ag and Au nanoparticles in PS and PMMA with a “failure” Weibull statistics.     

Absorption and velocity dispersion due to crystallization and melting of emulsion droplets

The influence of droplet crystallization and melting on the ultrasonic properties of oil-in-water emulsions has been investigated. The ultrasonic velocity and attenuation were measured in a series of 3 wt% n-hexadecane-in-water emulsions as a function of frequency (0.3–4 MHz), droplet diameter (0.4 and 1 μm) and temperature (0–25°C). The emulsified n-hexadecane crystallized at about 5°C due to supercooling effects and melted at about 18°C. As solid and liquid n-hexadecane have significantly different ultrasonic properties, an appreciable change in the velocity and attenuation is observed during the phase transition. This behaviour is modified significantly in systems where the emulsion droplets are partially crystalline because the temperature fluctuations associated with the ultrasonic wave can perturb the phase equilibria solid liquid causing excess attenuation and velocity dispersion. The magnitude of this effect depends on the ultrasonic frequency and the average droplet size.     

A Comparative Study of Chemical Routes for Coating Gold Nanoparticles via Controlled RAFT Emulsion Polymerization

The synthesis of core‐shell Au nanoparticles protected by an amphiphilic block copolymer is investigated by distinct reversible addition fragmentation chain transfer (RAFT) emulsion polymerization routes. The controlled polymerization of polymer shells onto Au nanoparticles is attempted by using the macroRAFT (MR) agent based on 2‐(dodecylthiocarbonothioylthio)‐2‐methylpropionic acid synthesized via RAFT polymerization of poly(ethylene glycol) methyl ether acrylate and exploring several approaches, which include (i) post‐modification; (ii) in situ synthesis and (iii) “grafting from” strategies. In the conditions investigated here all these strategies lead to Au polymer nanocomposites but morphological well‐defined core‐shell nanoparticles are only obtained by applying the “grafting from” strategy. In particular, conditions that promote chain extension from the MR agent adsorbed onto the Au nanoparticles are found necessary to obtain nanostructures with such morphological characteristics and that still show the localized surface plasmon resonance typical of colloidal Au nanoparticles.     

Local Kramers–Kronig Relations between the Attenuation Coefficient and Phase Velocity of Longitudinal Ultrasonic Waves in Polymer Composites

Acoustical Physics - The relationship between the experimentally obtained attenuation coefficient and dispersion of the phase velocity of longitudinal ultrasonic waves in polymer composite...     

基于遗传算法的Au-Cu-Pt三元合金纳米粒子的稳定结构研究

合金纳米粒子展示出单金属粒子所不具有的多功能性能, 而其稳定结构的研究对于进一步了解其催化性能具有重要的意义. 本文采用改进的遗传算法和量子修正Sutton-Chen型多体势对二十四面体Au-Cu-Pt三元合金纳米粒子的稳态结构进行了系统的研究. 针对不同尺寸、不同组成比例的合金纳米粒子, 探讨了遗传算法的收敛性及初始构型对稳态结构的影响. 计算的结果表明: 初始结构的选取并不影响最终的稳定结构, 并且改进的遗传算法具有较好的稳定性; Au和Cu形成表面偏聚, 而Pt则倾向于分布在内层; 当Au或Cu比例较小时, Au和Cu表现出表面最大偏聚; 当Au与Cu原子数之和大于表面原子数时, 二者表现出竞争偏聚, 且Cu的偏聚效应较强; 随着Au, Cu原子数继续增长至大于表面和次表面原子数之和时, Au的偏聚性能增强. 此外, Cu在占据表面后, 会越过次外层, 与Pt在内层形成混合相结构.     

Interphase synthesis and some characteristics of aqueous nickel dispersions

The facilities of one-step preparation method of nickel nanoparticles by the interphase reduction of nickel oleate using sodium borohydride at room temperature without soluble polymer as a protective agent were studied. Nickel obtained by such technique was concentrated in aqueous phase as a black dispersion. The composition and morphology of the colloid's dispersive phase were investigated by transmission electron microscopy, XRD and IR-spectroscopy. The dispersive phase of the prepared colloidal solution represents crystalline spherical nickel nanoparticles with some admixture of nickel boride. Their average size varies between 2 and 6 nm. In accordance with the IR-spectroscopy results the stability of the nickel colloidal dispersions was provided by the surfactant produced through the interphase reaction.     

Pr1/3Sr2/3FeO3中电荷有序现象的超声研究

系统研究了Pr1/3Sr2/3FeO3单相多晶样品在低温下的电荷输运性质和超声特性.电阻测量表明,Pr1/3Sr2/3FeO3在162K发生了电荷有序相变.而超声声速从室温开始就出现了明显的软化,在电荷有序温度附近达到最小值,随后又急剧硬化,同时伴随着一个巨大的衰减峰.分析指出这是由于电-声子相互作用导致的结果,该电-声子耦合可能起源于Fe4 的Jahn-Teller效应.     

Relaxation Contribution of a System of Jahn–Teller Complexes to the Elastic Moduli of Doped Fluorites

Journal of Experimental and Theoretical Physics - The results of the study of the temperature dependence of attenuation and velocity of ultrasonic waves are presented for CaF2:Cr and CaF2:Ni...     

Dual plasmonic‐enhanced bulk‐heterojunction solar cell incorporating gold nanoparticles into solution‐processed anode buffer layer and active layer

A dual plasmonic resonance effect on the performance of poly(3‐hexylthiophene) (P3HT):phenyl C61‐butyricacid methyl ester (PC61BM) based polymer solar cells (PSCs) has been demonstrated by selectively incorporating 25 nm colloidal gold nanoparticles (Au NPs) in a solution‐processed molybdenum oxide (MoO₃) anode buffer layer and 5 nm colloidal Au NPs in the active P3HT:PCBM layer. The devices exhibit up to ～20% improvement in power conversion efficiency which is attributed to the dual effect of localized surface plasmon resonance (LSPR) of Au NPs with enhanced light absorption and exciton generation. Our report shows a guideline on the usage of dual LSPR effect for the solution‐processed polymer solar cells to achieve high efficiencies. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)