材料物理的新进展—纳米固体材料

纳米固体材料（ｎａｎｏｍｅｔｅｒ ｓｉｚｅｄ ｍａｔｅｒｉａｌｓ）的出现，引起了国际上物理、材料、化学及工程科学家们的很大兴趣．这是由晶粒或颗垃尺寸为 １—１５ ｎｍ（１ｎｍ＝１０－９ｍ）的超细金属、陶瓷、高分子组成的固体材料．与固体中传统的晶体、非晶体不同的是，纳米晶体材料中存在着既无长程序、又无短程序的新的固态结构．由于其特殊的原子组态，已观察到一系列不寻常的物理学和力学效应。同时也为制备相图限制之外的合金或具有特殊结合键的新型材料提供了可能性．     

Controlling optical responses through local dielectric resonance in nanometre metallic clusters

Optical responses in dilute composites are controlled through the local dielectric resonance of metallic clusters. We consider two located metallic clusters close to each other with admittances \varepsilon₁ and \varepsilon₂. Through varying the difference admittance ratio \eta [ = (\varepsilon₂- \varepsilon ₀) / (\varepsilon₁- \varepsilon₀)], we find that their optical responses are determined by the local resonance. There is a blueshift of absorption peaks with the increase of \eta. Simultaneously, it is known that the absorption peaks will be redshifted by enlarging the cluster size. By adjusting the nano-metallic cluster geometry, size and admittances, we can control the positions and intensities of absorption peaks effectively. We have also deduced the effective linear optical responses of three-component composites \varepsilon_e= \varepsilon₀ \bigl(1 + \sum_n=1^{n_s} [(\gamma_n2+ \eta \gamma_n2)/({\varepsilon₀(s - s_n))]} \bigr), and the sum rule of cross sections: \sum_n=1^{n_s} {(\gamma_n2+ \eta \gamma_n2 ) = N_h1+ N_h2, where N_h1and N_h2 are the numbers of \varepsilon₁ and \varepsilon₂ bonds along the electric field, respectively. These results may be beneficial to the study of surface plasmon resonances on a nanometre scale.     

水催化脱卤反应:构建每次一个水分子的纳米化学反应体系(英文)

pacc:8240,8760E Acombinedexperimentalandtheoretical studyofthephotochemistryofCHBr3inpurewa terandinacetonitrile/watermixedsolventsisre portedthatelucidatesthereactionsandmecha nismsresponsibleforthephotochemicalconver sionofthehalogenatomsinCHBr3intothre…     

Structured mirror array for two-dimensional collimation of a chromium beam in atom lithography

Direct-write atom lithography,one of the potential nanofabrication techniques,is restricted by some difficulties in producing optical masks for the deposition of complex structures.In order to make further progress,a structured mirror array is developed to transversely collimate the chromium atomic beam in two dimensions.The best collimation is obtained when the laser red detunes by natural line-width of transition 7S3 → 7P40 of the chromium atom.The collimation ratio is 0.45 vertically(in x axis),and it is 0.55 horizontally(in y axis).The theoretical model is also simulated,and success of our structured mirror array is achieved.     

金属纳米颗粒的热导率

本文使用统计模拟方法对金属纳米颗粒的电子平均自由程进行了计算,并考察了纳米颗粒的晶格比热和声子平均群速度,最后应用动力学理论对纳米颗粒的电子热导率和声子热导率分别进行了求解.研究结果表明:具有相同特征尺寸的方形、球形纳米颗粒的无量纲电子(或声子)平均自由程比较接近.金属纳米颗粒的电子热导率远大于声子热导率;电子、声子热导率随着直径减小呈现降低趋势,而电子热导率的颗粒尺度依赖性比声子热导率更为明显;随着颗粒直径进一步减小,声子热导率与电子热导率趋于同一数量级.当纳米颗粒特征尺寸大于4倍块材电子(或声子)平均自由程,其电子(或声子)热导率的颗粒尺度依赖性将减弱.     

纳米多晶铜中冲击波阵面的分子动力学研究

冲击波阵面反映材料在冲击压缩下的弹塑性变形行为以及屈服强度、应变率条件等宏观量, 还与冲击压缩后的强度变化联系. 本文使用分子动力学方法, 模拟研究了冲击压缩下纳米多晶铜中的动态塑性变形过程, 考察了冲击波阵面和弹塑性机理对晶界存在的依赖, 并与纳米多晶铝的冲击压缩进行了比较. 研究发现: 相比晶界对纳米多晶铝的贡献而言, 纳米多晶铜中晶界对冲击波阵面宽度的影响较小; 并且其塑性变形机理主要以不全位错的发射和传播为主, 很少观察到全位错和形变孪晶的出现. 模拟还发现纳米多晶铜的冲击波阵面宽度随着冲击应力的增加而减小, 并得到了冲击波阵面宽度与冲击应力之间的定量反比关系, 该定量关系与他人纳米多晶铜模拟结果相近, 而与粗晶铜的冲击压缩实验结果相差较大.     

DNA酶裂解-纳米金共振瑞利散射光谱法测定痕量Cu2+

在pH 7.0HEPES(4-羟乙基哌嗪乙磺酸)缓冲溶液中和0.19mol.L-1 NaCl存在下,单链底物DNA(SS)和酶链DNA(ES)在80℃杂交形成双链DNA(dsDNA)。Cu2+可切割dsDNA中的底物链释放出单链DNA(ssDNA),此ssDNA与金纳米粒子(NG)作用形成NGssDNA结合物不被NaCl聚集,而未保护的NG聚集形成较大粒径的聚集体(NGA),在627nm处有一个较强的共振瑞利散射峰。随着Cu2+浓度的增大,该共振瑞利散射峰降低,其降低值ΔI与Cu2+浓度在15～1 250nmol.L-1范围呈线性关系,其回归方程为ΔI=0.17c-2.3,线性相关系数为0.989 5,检出限为8nmol.L-1。据此建立了一个高灵敏、高选择性、简便测定Cu2+的共振瑞利散射光谱分析法。该法用于水样中Cu2+的检测,结果满意。