Co/AAO纳米有序阵列复合结构的光致发光和光吸收特性

以草酸电解液制备的高度有序的纳米级多孔阳极氧化铝(AAO)为模板,采用交流电化学沉积工艺合成了Co/AAO纳米有序阵列复合结构。分别研究了AAO模板和Co/AAO结构的光致发光和光吸收特性。结果表明,AAO模板在350～550nm范围内存在较强的光致发光带,其峰位在395nm处;Co/AAO纳米有序阵列复合结构的光致发射峰位亦在395nm处,且发光峰强度随Co沉积量的增加而迅速减弱。实验发现,Co/AAO纳米有序阵列复合结构的光吸收边从近紫外至近红外的波段范围内发生大幅度红移,最大红移量甚至超过380nm。文章定性分析并解释了Co/AAO纳米有序阵列复合结构吸收边大幅度红移及其光发射峰位不变、而峰强减弱的主要原因。     

Ni、Co/AAO纳米有序阵列复合结构光吸收特性的比较研究

在多孔阳极氧化铝(AAO)模板中分别沉积金属镍(Ni)、钴(Co),制备了Ni／AAO和Co／AAO纳米有序阵列复合结构,对其光吸收特性进行了比较研究。实验结果表明．相同结构参量的模板中,Ni、Co纳米粒子的表观形状随沉积时间的变化规律基本一致．但Co/AAO及Ni／AAO复合结构的光吸收特性却有较大差异。Ni／AAO复合结构表现出间接带隙半导体的光学特征．而Co／AAO复合结构具有直接带隙半导体的光学特征。同时,随金属沉积量的增加,Ni／AAO吸收边的红移量仅约为13nm．而Co/AAO复合结构的吸收边红移量却超过了80nm。用Maxwell-Garnett(M-G)理论分析了导致二者光吸收特性存在较大差异的主要原因。     

纳米银对表面吸附核黄素分子光谱性质的影响

采用氧化还原法制备了纳米尺寸的银溶胶,研究了纳米银粒子对核黄素(Riboflavin,Ri)水溶液吸收光谱和荧光光谱的影响.Ri溶液中加入纳米银粒子,随着纳米银浓度的增大,吸收强度不断增强,372 nm处吸收峰红移,而444 nm处吸收峰蓝移,同时发生荧光猝灭现象.从无辐射通道增强、纳米银表面局域场减弱及Ri分子第一激...     

高质量多孔氧化铝模板的制备

在草酸电解液中研究了阳极氧化法制备多孔氧化铝模板(AAO模板)。采用场发射扫描电子显微镜对多孔模板的形貌进行表征,结果表明:模板孔的分布均匀有序,孔径在40~70 nm;电解液浓度、氧化电压、氧化温度和氧化时间都会影响模板的形态;不经过高温退火及抛光也可以制得规则排布的多孔AAO模板。X射线衍射分析表明:氧化铝膜的主要成分为非晶态Al2O3。     

光照法在玻璃基底上原位生长金纳米结构及其光谱性质

 以硅烷化后吸附粒径小于10 nm的金种子的玻璃片为基底,聚乙烯吡咯烷酮为还原剂,在荧光灯照射条件下还原氯金酸,制备出表面具有金纳米粒子聚集结构的基底。用原子力显微镜、扫描电镜、X射线衍射、吸收和荧光光谱研究了基底的性质。结果表明：随着光照时间增加至20 h,金种子长大为平均粒径140 nm的不规则状多晶粒子,且出现双层粒子堆叠。基底的吸收光谱上出现了由金粒子的表面等离子体激元偶极子耦合引发的强烈吸收峰,随着粒子粒径增大,耦合峰在600~800 nm波段内连续红移升高,表明耦合程度不断增强。在223 nm紫外光的激发下,基底的荧光光谱上在405 nm处出现发射峰,是由金粒子表面激发电子和空穴的复合辐射造成的,发光强度随着基底上粒子平均尺度增加而减弱。     

负电性纳米银溶胶SERS活性及稳定性的比较研究

用单宁还原硝酸银可制得表面带负电的、对阳离子型分子具有较强SERS效应的纳米银。为了进一步测试负电性纳米银溶胶的SERS活性及稳定性,在室温下用制针剂的封装机将样品(old NCS)封装并保存。两年后与新制备的负电性纳米银溶胶(new NCS)比较,用透射电镜观测发现old NCS与new NCS相比银粒子尺寸增大;用紫外可见吸收光谱测定old NCS的吸收峰为431 nm,new NCS的吸收峰为418 nm,old NCS与new NCS相比吸收峰发生红移。为比较old NCS及new NCS的SERS活性选取阳离子型分子、中性分子及阴离子型分子作为测试分子,用拉曼光谱仪测试这些分子在两种纳米银上的SERS谱,结果发现,阳离子型分子碱性品红、中性分子吖啶橙在old NCS及new NCS上SERS较强,阳离子型分子亚甲基蓝在old NCS上与在new NCS上相比SERS较弱,阴离子型分子苯甲酸在old NCS及new NCS均未观察到SERS信号。     

高氧空位浓度对锐钛矿TiO2莫特相变和光谱红移及电子寿命影响的第一性原理研究

基于密度泛函理论的第一性原理研究,通过对锐钛矿TiO₂高氧空位浓度、态密度图及吸收光谱图的分析,发现锐钛矿TiO₂高氧空位浓度的条件下,高氧空位浓度对禁带变窄、吸收光谱红移和电子寿命都有很大的影响,从理论上进一步解释了高氧空位浓度对禁带变窄的原因.同时,锐钛矿半导体在高氧空位浓度时发生莫特相变和锐钛矿氧空位在等离子体中吸收光谱红移实验进行比较,发现锐钛矿TiO₂应适量控制高氧空位浓度对吸收光谱红移好于前者.适量控制高氧空位浓度的锐钛矿TiO 关键词： 锐钛矿 高氧空位浓度 吸收光谱红移 第一性原理     

Cu/AAO纳米有序阵列复合结构的光学特性研究

用电化学方法制备了Cu/AAO纳米有序阵列复合结构,实验研究了该结构的光吸收与光致发光特性。结果表明,植入阳极氧化铝模板中Cu纳米粒子对结构的光吸收和光致发光影响非常敏感。即随着Cu沉积量的增加,致使该复合结构的吸收边大幅度红移,从近紫外至近红外其最大频移量可超过500 nm;同时还伴随使阳极氧化铝模板的光致发光峰位稍有蓝移、强度逐渐削弱直至猝灭的过程。分析了Cu纳米粒子使Cu/AAO复合结构出现上述现象的原因。     

光谱学在金黄色海水珍珠鉴定中的应用

为了有效鉴别区分金黄色海水珍珠(简称金珠)和改色金珠,通过拉曼光谱和紫外可见吸收光谱对二者进行了检测分析.结果表明,拉曼光谱中,金珠的谱线稳定杂峰少,荧光背景弱,改色金珠的谱线杂峰多,荧光背景很强.0～1000 cm-1拉曼位移内金珠的光谱基线强度在1000以下,改色金珠的光谱基线强度在2000以上;金珠在拉曼位移275 cm-1处出现明显的拉曼特征峰,改色金珠275 cm-1处的拉曼特征峰基本被荧光谱线覆盖而变弱或消失;紫外可见吸收光谱中,金珠在200 nm～400 nm的近紫外区有284 nm,357 nm两个明显的紫外吸收峰.由于颜色处理过程中对珍珠表面破坏程度的不同,导致改色金珠在近紫外区无特征吸收,吸收峰发生红移(408 nm)或消失.     

Lu_2O_3晶体在高压下的光学性质第一性原理研究

本文采用第一性原理方法,计算了Lu_2O_3(氧化镥)的理想晶体和含氧、镥空位点缺陷晶体在100 GPa压力范围内的光吸收谱和折射率性质.结果表明:在100 GPa范围内, Lu_2O_3理想晶体在可见光及红外光区不具有光吸收现象,空位点缺陷的存在将导致吸收边红移,其中氧空位点缺陷引起的红移行为更显著,但这些吸收边仍未进入可见光区的高波段. 532 nm处的折射率数据表明,在立方结构和单斜结构相区, Lu_2O_3晶体的折射率随压力的增加而增大,高压结构相变以及氧、镥空位的存在也会使得折射率增大.结合温度效应分析推测, Lu_2O_3晶体在近红外区有可能透明.     

Silver nanorods used to promote SERS as a quantitative analytical tool

We have fabricated silver nanorod arrays by electrodepositing the nanorods evenly in the shallow pores of porous anodic aluminum oxide (AAO) templates. The diameter and length were 28 and 44 nm, respectively. The maxima of the transverse and longitudinal modes of the surface plasmon were near 417 and 511 nm, respectively. A good surface‐enhanced Raman scattering (SERS) spectrum was observed by excitation with the 514.5‐nm laser line. The SERS intensity increased almost linearly upon malachite green isothiocyanate adsorption on the tips of the silver nanorods as the concentration of the mother solutions increased. Our results show that silver nanorods fabricated on AAO templates could be used as an SERS substrate for quantitative analyses. Copyright © 2009 John Wiley & Sons, Ltd.     

Comparison of Surface-Enhanced Raman Scattering Spectra of Azo Dye Sudan III on Several Substrates

On several substrates, including dried silver-coated filter paper, electro-polishing aluminum foils, and anodic aluminum oxide (AAO) nanometer array templates, surface-enhanced Raman scattering (SERS) spectra of Azo Dye Sudan III molecules were studied, and high-quality SERS spectra were obtained, which indicated that electro-polishing aluminum foils and AAO nanometer array templates were also active SERS substrates. A number of additional modes were presented, as well as some split peaks, which were especially obvious on electro-polishing aluminum foil and AAO nanometer array template. The enhancement mechanisms were discussed and the enhancement factors G were calculated as 10⁴, 10⁶, and 10⁵, respectively.     

Silver nanostructure arrays abundant in sub-5 nm gaps as highly Raman-enhancing substrates

Two types of highly Raman-enhancing arrays substrates were fabricated using anodic aluminum oxide (AAO) templates by controlling the AAO template temperature and evaporated silver thickness during e-beam evaporating: complex patterned Ag nanoparticle arrays abundant in sub-5 nm gaps (type I); hexagonal Ag nanopore arrays (type II). The surface enhanced Raman scattering (SERS) enhancement factors (EF) of both substrates are estimated experimentally to exceed 10⁵, especially that of type I reaches 10⁷ due to the existence of numerous sub-5 nm gaps. The simulation using finite-difference time-domain (FDTD) method confirmed that gap effect has significantly improved the substrates’ SERS activity.     

Controllable fabrication of highly ordered thin AAO template on Si substrate for electrodeposition of nanostructures

In this work, simple fabrication of hexagonally highly ordered porous anodic aluminum oxide (AAO) of Al thin film (1 μm) on Si substrate is described using two-step anodization method for electrochemical synthesis of nanostructures. In this method, the templates were prepared under the controllable conditions of the parameters, which give rise to the possibility of highly ordered nanopore arrays with a well aspect ratio. Pore widening was then fulfilled in 5 wt% phosphoric acid solution at 25 °C. The pore diameter and spacing are proportional to the applied voltage, which is due to the mechanical stress associated with the volume expansion of the aluminum during the anodization according to the mechanical stress model. Pore-widening solution adjusted the pore diameter and thinned the AAO barrier layer at room temperature under the control of etching time. As an application, Cu nanorods arrays embedded in anodic alumina (AAO) template were fabricated by dc electrodeposition. The characterization of the AAO templates and the Cu nanorods produced was made by X-ray diffraction, field emission scanning microscope, energy dispersive X-ray spectroscopy and atomic force microscope (AFM). The images of AFM show that porous AAO template under constant voltage is 40 V which presents the optimum ordering.     

Simple fabrication of hexagonally well-ordered AAO template on silicon substrate in two dimensions

In this study, thin anodic aluminum oxide (AAO) templates both on silicon substrates (AAO template/SiO₂/Si) and Ti-coated silicon substrates (AAO template/Ti/SiO₂/Si) were developed for design of magnetic, electronic and optoelectronic devices, chemical sensors and chip-scale lithium-ion rechargeable microbatteries. Two types of AAO template were prepared by using a two-step anodization procedure. The templates were characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. The obtained thin AAO templates were approximately 50 nm in diameter and 700 nm in length with 80-nm interpore distances in a relatively large area of 6 cm². A barrier layer of the AAO templates was removed by a cathodic polarization method in KCl solution for several seconds. The current–time transient during removing the alumina barrier layer of the thin AAO template and the mechanism of electrochemical dissolution of the barrier layer are given in detail.     

氧化铝模板制备过程中酸性电解液对模板参数的影响

多孔阳极氧化铝模板表面分布有纳米级微孔,其尺寸可调、有序性高,并且制备工艺简单,价格低廉,是合成各种纳米材料的重要方法.本文详细讨论了制备过程中各种实验条件对氧化铝膜参数的影响;给出了制备各种孔径高质量氧化铝模板的最佳实验条件,并对多孔氧化铝模板的应用前景做出了展望.     

钛酸锶钡纳米管的制备及其红外吸收性能研究

首次采用溶胶凝胶法结合通孔阳极氧化铝模板, 成功制备出了钛酸锶钡纳米管. 该制备工艺简单、易实现而且成本低. 首先制备通孔阳极氧化铝模板和钛酸锶钡溶胶, 然后通过浸渍加上匀胶的方法将钛酸锶钡溶胶引入到通孔阳极氧化铝模板的纳米孔洞中, 最后在650℃下煅烧1 h形成钛酸锶钡纳米管. X射线衍射(XRD)证明, 制得的钛酸锶钡纳米管为立方钙钛矿相, 主要沿(110)晶向生长. 扫描电子显微镜(SEM)显示, 钛酸锶钡纳米管外径、内径和管长分别为75 nm, 50 nm, 16 μm. 傅里叶变换显微红外光谱仪(FTIR)测试结果表明在波数为1350-1650 cm^-1红外波段, 阳极氧化铝/钛酸锶钡纳米管复合结构较钛酸锶钡薄膜有两处明显的吸收峰, 吸收峰位于1470和1550 cm^-1处, 与通孔阳极氧化铝模板相比其吸收峰强度高出一倍, 最后分析了出现这一现象的可能原因.     

银纳米颗粒阵列的表面增强拉曼散射效应研究

利用具有高密度拉曼热点的金属纳米结构作为表面增强拉曼散射(SERS)基底,可以显著增强吸附分子的拉曼信号.本文通过阳极氧化铝模板辅助电化学法沉积制备了高密度银(Ag)纳米颗粒阵列;利用扫描电子显微镜和反射谱表征了样品的结构形貌和表面等离激元特性;用1, 4-苯二硫醇(1, 4-BDT)为拉曼探针分子,研究了Ag纳米颗粒阵列的SERS效应.通过优化沉积时间,制备出高SERS探测灵敏度的Ag纳米颗粒阵列,检测极限可达10~(-13)mol/L;时域有限差分法模拟结果证实了纳米颗粒间存在强的等离激元耦合作用,且发现纳米颗粒底端的局域场增强更大.研究结果表明Ag纳米颗粒阵列可作为高效的SERS基底.