Au/Ag芯-壳复合结构纳米颗粒的制备和表征

利用二步液相还原法制备了 Au/Ag 芯 壳复合结构的纳米颗粒。用 TEM对反应液中金离子和银离子的摩尔比分别为1∶2和1∶1时所制备的 Au/Ag芯 壳复合结构的纳米颗粒的尺寸和形貌进行了表征。其紫外 可见吸收光谱具有 2 个可区分的吸收带,与纯金和纯银纳米颗粒的光学吸收特性对比后认为:随着反应液中银离子摩尔份数的增加,等离子体共振吸收峰始终位于 410nm附近的吸收带为银纳米颗粒的等离子体吸收带;另一个将随之产生蓝移的吸收带为Au/Ag芯 壳复合结构纳米颗粒的等离子体吸收带,蓝移是由于银壳厚度的增加而引起的。     

花状纳米氧化锌颗粒的制备及其光学性能研究

以硬脂酸锌和过氧化氢为原料，采用油相法一步合成出一种特殊的氧化锌花状纳米结构。利用透射电镜、高分辨电镜、X射线衍射等对其形貌和结构的分析表明：花状氧化锌纳米颗粒结构为六方晶相，大小约为30nm。吸收光谱和荧光光谱测量显示该纳米结构有显著的近带边紫光发射特性，对应的缺陷发光强度较弱，表明这一纳米结构有较好的光学特性，因此在生物荧光标记方面有着潜在的应用价值。     

纳米颗粒的短脉冲激光烧蚀制备及其非线性光学应用

本文主要介绍了纳米颗粒的短脉冲激光制备及其在非线性光学领域的应用。短脉冲激光制备纳米颗粒具有纯度高、操作简单和适用性广等优点,所制备的非线性纳米颗粒尺寸分布均匀,粒度小且可调控,在非线性光学材料中有着独特的地位。为了更深入地对此进行研究,本文介绍了纳米颗粒的光学非线性和激光的特点和原理。在此基础上,通过阐述短脉冲激光与物质相互作用的机理,说明了激光制备纳米颗粒所具有的优点,详细分析了制备条件对合成纳米颗粒的影响,并结合激光制备不同的纳米颗粒,介绍当前激光制备各类纳米颗粒的研究现状。激光制备纳米颗粒是一种操作简便、适用性广,且对环境友好的方法。

     

工艺参数对纳米颗粒Cu/SiO_2复合薄膜结构和光谱特性的影响

用离子束溅射法制备了具有反常光吸收特性的纳米颗粒CU／SiO2复合薄膜。获得了在离子来参数一定时，基片温度、膜料的沉积时间和镀膜后的保温时间等工艺参数对这种薄膜结构和光学特性的影响规律，并对纳米颗粒Cu／SiO2复合薄膜的反常光吸收特性作了计算和解释。     

纳米SiO2的光学特性研究

纳米SiO2的独特结构使其表现出一些特殊的光学特性，但文献对其紫外区光学性质的报道不一致。本文对几种不同类型的纳米SiO2进行了紫外—可见光谱测试，结果表明纳米SiO2在紫外—可见光范围内具有较强的光反射性能，但在λ=230nm附近有一强度不一的吸收峰，该吸收峰的强度可能与纳米SiO2的结构和表面状态有关。     

CuO/ZnO复合纳米树阵列的制备及光学特性

通过热氧化法在铜基板上制备CuO纳米线,采用凝胶法制备ZnO/CuO复合纳米树阵列。通过扫描电镜(SEM)、X射线衍射(XRD)、光致发射光谱对样品结构、形貌、光学特性进行表征。结果表明,CuO/ZnO纳米树形貌规整完美,在CuO纳米线上二次生长的ZnO纳米棒具有各向晶体生长性质,CuO/ZnO复合纳米树在可见光区域出现了优越的发光性能;以甲基橙为模拟污染物,通过光催化测试表明,CuO/ZnO复合纳米树还具有卓越的光催化性能。     

银纳米颗粒有序阵列光学偏振玻璃特性研究

银纳米椭球微粒有序掺杂的光学偏振玻璃具有光学玻璃的高透过率特性和本征的偏振特性,是综合性能好的光学偏振器件。利用米氏理论和电偶极子理论分析了光入射到椭球形银纳米微粒产生的消光特性和偏振机理;建立椭球形纳米微粒周期阵列分布的光学偏振玻璃模型,采用有限元数值算法模拟计算近红外光入射该模型后的偏振光输出特性。通过优化玻璃内部椭球微粒的几何参数,获得波长在700~1 100nm近红外全波段内的偏振玻璃的透过率达到80%以上,消光比达20dB以上;尤其当波长在740~840nm范围内,透过率高达90%以上,消光比达50dB以上。     

复合纳米金膜的制备及其光学性质

本文利用化学还原法制备了不同尺寸的金纳米颗粒,并利用离子自组装多层技术在玻璃基底上沉积了基于金纳米颗粒的复合纳米金膜,研究了颗粒尺寸和成膜厚度对复合金膜光学性质的影响。不同比例的柠檬酸钠与氯金酸产生的金纳米颗粒溶液的紫外-可见光谱随着金颗粒直径增大而红移展宽。适量比例的柠檬酸钠与氯金酸能够产生平均直径为14±1.2nm且尺寸分布均匀的金纳米球;其溶液在518nm处有一特征吸收峰。不同大小的金纳米颗粒形成的薄膜的紫外-可见光谱形状不同,局域表面等离子体共振峰的位置随着颗粒直径的减小而向短波方向迁移。薄膜的沉积层数越多,薄膜表面的颗粒分布越均匀,局域表面等离子体峰的峰值变化也将减小。本工作证实了利用离子自组装多层技术能够快速、简易、低成本地在玻璃基底上沉积具有局域表面等离子体共振的复合纳米金膜。     

纳米Fe-ZnSe颗粒膜的光学特性

研究了射频溅射法制备的纳米"铁磁金属一半导体基体"Fex(ZnSe)1-x颗粒膜的光学特性.透射光谱测量结果表明,当Fe体积分数为35%时,颗粒膜样品的可见光透过率达到50%以上.研究发现,在ZnSe薄膜基体中嵌入纳米铁颗粒的Fe-ZnSe颗粒膜中,电子的带间跃迁为直接跃迁,其带隙随着Fe在颗粒膜中所占体积分数的增加而变宽.     

Morphological and optical properties of PdxAg1-x alloy nanoparticles

Alloy nanoparticles (NPs) can offer a wide range of opportunities for various applications due to their composition and structure dependent properties such as multifunctionality, electronic heterogeneity, site-specific response, and multiple plasmon resonance bands. In this work, the fabrication of self-assembled Pd_xAg_1-x NPs alloy nanostructures with distinct size, density, shape, and composition is demonstrated via the solid-state dewetting of sputtered Pd/Ag thin films on c-plane sapphire. The initial stage of bilayer dewetting exhibits the nucleation of voids, followed by the expansion of voids and cluster breakdown and finally shape transformation along with the temperature control. Bilayer composition shows a substantial influence on the dewetting such that the overall dewetting is enhanced along with the increased Ag composition, i.e. Pd_0.25Ag_0.75 > Pd_0.5Ag_0.5 > Pd_0.75Ag_0.25. On the other hand, the size and density of NPs can be efficiently controlled by varying the initial thickness of bilayers. Reflectance peaks in UV and near-infrared (NIR) regions and a wide absorption band in the visible region arisen from the surface plasmon resonance are observed in reflectance spectra. The peak intensity depends on the composition of Pd_xAg_1-x NPs and the NIR peaks gradually blue-shift with the size decrement.     

Tuning optical properties of poly(3-hexylthiophene) nanoparticles through hydrothermal processing

Abstract

Poly(3-hexylthiophene) (P3HT) nanoparticles (NPs) were prepared by a reprecipitation method. Hydrothermal processing applied external pressure to the pristine P3HT NPs at temperatures ranging from 60 to 150 °C. Optical absorption and photoluminescence (PL) spectra for the hydrothermally treated P3HT NPs varied markedly with the processing temperature. With increasing treatment temperature, the absorption peak broadened and the peak position shifted from 510 to 623 nm; moreover, the intensity ratio of the 0–1 to 0–0 emission varied. These changes were caused by interactions between the P3HT main chains and alkyl side groups and conformational modifications induced by the high pressure during the hydrothermal process. The evolution of the optical absorption spectra of the P3HT NPs during the hydrothermal processing was strongly correlated with the variation of PL excitation spectra and with the PL emission spectra of a single NP.     

光谱学研究银纳米颗粒在玻璃中的生成规律

通过离子交换法将银离子引入白硅酸盐玻璃和绿硅酸盐玻璃,利用光致发光(photoluminescence-PL)和光吸收(optical absorption-OA)谱研究银离子的团簇化、成核和生长.由于白硅酸盐玻璃不含二价铁离子,因此,银纳米颗粒形成困难,颗粒体积分数非常低,以致样品中银纳米颗粒的共振吸收峰不明显.在这种条件下,样品中存在大量银离子和银的小原子团簇.在绿玻璃中,氧化铁含量较高,引入到玻璃中的银离子大部分被二价铁离子还原成中性银原子,通过热处理,银离子在玻璃中成核和生长.在相近的热处理条件下,绿玻璃有利于银纳米颗粒的生成.银纳米颗粒在形成过程中,消耗大量银离子,造成样品的发光强度逐渐降低.     

Tuning optical properties of poly(3-hexylthiophene) nanoparticles through hydrothermal processing

Poly(3-hexylthiophene) (P3HT) nanoparticles (NPs) were prepared by a reprecipitation method. Hydrothermal processing applied external pressure to the pristine P3HT NPs at temperatures ranging from 60 to 150 °C. Optical absorption and photoluminescence (PL) spectra for the hydrothermally treated P3HT NPs varied markedly with the processing temperature. With increasing treatment temperature, the absorption peak broadened and the peak position shifted from 510 to 623 nm; moreover, the intensity ratio of the 0–1 to 0–0 emission varied. These changes were caused by interactions between the P3HT main chains and alkyl side groups and conformational modifications induced by the high pressure during the hydrothermal process. The evolution of the optical absorption spectra of the P3HT NPs during the hydrothermal processing was strongly correlated with the variation of PL excitation spectra and with the PL emission spectra of a single NP.     

Alkyl-functionalized oxide-free silicon nanoparticles: synthesis and optical properties

Highly monodisperse silicon nanoparticles (1.57 +/- 0.21 nm) are synthesized with a covalently attached alkyl monolayer on a gram scale. Infrared spectroscopy shows that these silicon nanoparticles contain only a few oxygen atoms per nanoparticle. XPS spectra clearly show the presence of unoxidized Si and attached alkyl chains. Owing to the relatively efficient synthesis (yields approximately 100-fold higher than of those previously reported) the molar extinction coefficient epsilon can be measured: epsilon(max) = 1.7 x 10(-4) M(-1)cm(-1), only a factor of 4 lower than that of CdS and CdSe nanoparticles of that size. The quantum yield of emission ranges from 0.12 (C(10)H(21)-capping) to 0.23 (C(16)H(33)-capping). UV/Vis absorption and emission spectroscopy show clear vibrational progressions (974 +/- 14 cm(-1); up to five vibrational bands visible at room temperature), resembling bulk SiC phonons, which support the monodispersity observed by TEM. This was also confirmed by time-resolved fluorescence anisotropy measurements, which display a strictly monoexponential decay that can only be indicative of monodisperse, ball-shaped nanoparticles.     

化学镀Co—B合金对Fe3O4吸波性能的影响

采用化学共沉淀法制备纳米Fe3O4颗粒，通过胶体钯活化敏化一步法处理后，以KBH4为还原剂、C4H4O6Na2-2H2O为络合剂进行Co-B化学镀，对包覆前后的样品进行了XRD、SEM、TEM、电磁参数等表征以及吸波性能分析。结果表明：Fe3O4表面包覆的纤维状Co-B合金以无定形形式存在，Co-B包覆Fe3O4在2．0～18GHz具有良好的吸波效果．     

Structural, optical, and nonlinear optical absorption/refraction studies of the manganese nanoparticles prepared by laser ablation in ethanol

The structural, optical, and nonlinear optical properties of the manganese nanoparticles prepared by laser ablation in various liquids were investigated using the 532 and 1064 nm, 50 ps laser pulses. The TEM and spectral measurements showed temporal dynamics of size distribution of Mn nanoparticles in solutions. The nonlinear absorption (β = 2 × 10⁻¹⁰ and 4 × 10⁻¹¹ cm W⁻¹) and positive nonlinear refraction (γ = 8 × 10⁻¹⁵ and 2 × 10⁻¹⁴ cm² W⁻¹) of picosecond radiation were observed in the Mn colloidal suspensions using the 1064 and 532 nm radiation, respectively