ZnO纳米棒/CdS量子点的制备及紫外-可见探测性能研究

本文采用水热法在ITO衬底上制备了ZnO纳米棒阵列,然后用化学水浴沉积法在纳米棒上制备CdS量子点。分别利用SEM和XRD对样品形貌和晶体结构进行表征。结果表明,球状的CdS量子点均匀地包覆在ZnO纳米棒表面,且结晶质量较好。基于ZnO纳米棒和ZnO纳米棒/CdS量子点制备的探测器对紫外光都具有很好的响应,然而与ZnO纳米棒探测器相比,ZnO纳米棒/CdS量子点探测器在相同条件下的光电流提高了7倍,为0. 52 mA。此外,ZnO纳米棒/CdS量子点探测器对绿光和蓝光也表现出了很好的响应。     

纳米CdS/碳纳米管复合材料的光电特性

基于CdS良好的光学性质和单壁碳纳米管(SWCNT)优异的电子学性质, 制备了纳米CdS/SWCNT复合材料和纳米CdS/聚乙烯亚胺(PEI)功能化SWCNT复合材料, 并利用日光灯光源模拟太阳光研究了它们的光电性质. 结果表明, 纳米CdS/SWCNT复合材料呈现显著的负光电导现象, 而纳米CdS/PEI-SWCNT复合材料呈现强烈的正光电导现象. 用电子转移理论对这一结果进行了解释. 两样品在大角度弯折的情况下, 光电性质均基本没有变化. 因此, 纳米CdS/碳纳米管复合材料在光电领域, 尤其是新兴的柔性光电子学领域有着良好的应用前景. 关键词： 碳纳米管 CdS 光电材料 复合材料     

掺银氧化锌纳米棒的水热法制备研究

利用水热法在直流磁控溅射制备的掺铝氧化锌 (AZO) 种子层上制备了不同形貌和光学性能的掺银ZnO纳米棒, 并采用XRD、扫描电镜、透射谱、光发射谱和EDS谱详细研究了Ag离子与Zn离子的摩尔百分比 (R_Ag/Zn) 及AZO种子层对掺银ZnO纳米棒的结构和光学性质的影响. 随着R_Ag/Zn的增加, 掺银ZnO 纳米棒的微结构和光学性质的变化与银掺杂诱导的纳米棒的端面尺寸变化有关. 平均端面尺寸的变化归结于种子层颗粒大小和颗粒数密度不同导致掺入的Ag离子的相对比例不同. 溅射15 min的AZO种子层上生长的ZnO纳米棒由于缺陷增多导致在可见光区的发光峰明显强于溅射10 min 的AZO种子层上、相同R_Ag/Zn 条件下生长的ZnO纳米棒. Ag掺杂产生的点缺陷增多导致可见光区PL波包较宽. 纯ZnO纳米棒的微结构与种子层厚度导致的结晶度和颗粒大小有关. 关键词： ZnO纳米棒 水热法 Ag掺杂 直流磁控溅射     

ZnO纳米棒的低温溶液法制备、光电特性研究及其在有机/无机复合电致发光中的应用

利用水热法制备了垂直于衬底的定向生长的ZnO纳米棒,利用扫描电子显微镜及光致发光的方法对其形貌及光学特性进行了表征,利用场发射性能测试装置对ZnO纳米棒的场发射性能进行了测试.结果表明:利用水热法在较低的温度(95 ℃) 下生长了具有较好形貌和结构的ZnO纳米棒,并表现出了较好的场发射特性,当电流密度为1 μA/cm²时,开启电场是2.8 V/μm,当电场为6.4 V/μm时,电流密度可以达到0.67 mA/cm²,场增强因子为3360.稳定性测试表明,在5 h内,4.5 V/μm的电场下,其波动不超过25%.将制备的ZnO纳米棒应用到有机/无机电致发光中,其中ZnO纳米棒为电子传输层,m-MTDATA(4,4',4″-tris{N,(3-methylphenyl)-N-phenylamino}-triphenylamine) 为空穴传输层,得到了ZnO的342 nm的紫外电致发光,此发光较ZnO纳米棒光致发光的紫外发射有约40 nm的蓝移. 关键词： ZnO纳米棒 场发射 水热法 有机/无机复合电致发光     

原子力显微技术研究ZnO纳米棒的压电放电特性

在原子力显微镜的接触扫描模式下,研究了半导体ZnO纳米棒的压电放电特性.采用两步湿化学法制备沿c轴择优生长的ZnO纳米棒阵列;利用镀Pt探针接触扫描ZnO纳米棒获得峰值达120 pA电流脉冲,脉冲持续时间可达30 ms,电流脉冲与纳米棒的形貌存在对应关系.镀Pt探针与ZnO纳米棒接触形成肖特基二极管,I-V特性研究表明放电的ZnO纳米棒压电电势必须大于03 V,以驱动肖特基二极管并输出电流;放电时肖特基二极管的结电阻达吉欧(GΩ)量级,是影响压电电势输出的主要因 关键词： ZnO 纳米棒 压电放电 肖特基接触     

水热反应中籽晶层对ZnO纳米棒的影响

以Zn(NO3)2·6H2O/HMT为反应物,通过低温水热反应过程,在籽晶衬底上制备了ZnO纳米棒,分别用场发射扫描电子显微镜和X射线衍射仪对ZnO纳米棒形貌与晶体结构进行了表征,并研究了不同方法制备的ZnO籽晶层以及籽晶层厚度对ZnO纳米棒形貌及结晶质量的影响.结果表明磁控溅射籽晶衬底上生长的ZnO纳米棒结晶质量最好,而籽晶层的厚度对ZnO纳米棒的垂直取向性有一定的影响.     

多环类苝四甲酸二酐插入层对ZnO纳米棒和聚合物复合太阳电池性能的影响

以ZnO纳米棒和聚[2-甲氧基-5-(2-乙基-己氧基)-1,4-苯撑乙烯撑](MEH-PPV)的复合体系作为光敏层制备了太阳电池.为了增大电池的光吸收,在ZnO纳米棒与MEH-PPV之间插入了有机n型小分子多环类苝四甲酸二酐(PTCDA),制备了不同厚度的PTCDA、结构为ITO/ZnO纳米棒/PTCDA/MEH-PPV/Au的太阳电池.实验发现,插入PTCDA后,电池在可见光区的吸收增强,光生激子数量增大,光电流密度增大.当蒸镀的PTCDA厚度为40 nm时,薄膜的粗糙度适中,表面形貌较为平滑,器件性 关键词： 有机太阳电池 ZnO纳米棒 聚合物     

DBU液相催化法原位合成四苯氧基酞菁锌/ZnO复合材料的制备及光催化选择性研究

在负载于氧化铟锡(ITO)导电玻璃上、哑铃状纳米ZnO表面配位未饱和锌离子作为“模板”,以苯氧基邻苯二腈作为“分子碎片”,利用DBU液相催化法,在亲水性纳米ZnO表面,原位合成疏水性四苯氧基酞菁锌(ZnTPPc)。通过多种表征手段,分析证实了所合成的ZnTPPc分子结构、ZnTPPc/ZnO界面及光生电荷转移特性。在可见光下,分别以亲水性亚甲基蓝(MB)、疏水性苯酚(PL)及其混合液为待降解反应物,定量分析疏水性ZnTPPc/ZnO复合材料对降解疏水性PL的光催化选择性。结果表明： 原位合成ZnTPPc在ZnO表面呈现单分子层,具有较好的疏水性能,ZnTPPc可优先选择性降解疏水性PL,且在可见光光催化中对PL的相对降解效率是对MB分子的1.21倍。     

镉掺杂氧化锌纳米花的制备及其光催化活性

以氯化锌、氯化镉、氢氧化钠为原料,采用水热法合成Cd掺杂纳米花状ZnO光催化剂,并通过该样品对罗丹明B水溶液的降解来研究其光催化活性。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线能量色散谱(EDS)、光致发光谱(PL)及紫外-可见分光光度计(UV-Vis)等测试手段对材料物性进行表征。实验结果表明:当掺杂Cd2+时,样品形貌发生变化、粒径减小;掺杂Cd2+后的ZnO的吸收边和紫外峰对比于纯ZnO均发生红移,禁带宽度由3.24 eV减小到3.16 eV。通过光催化实验分析可知,掺杂后纳米ZnO光催化剂对罗丹明B水溶液的降解率有所提高,光照3 h其降解率高达98%,说明与纯ZnO相比,Cd掺杂ZnO纳米花具有更高的光催化活性。     

CdS/ZnO纳米复合结构制备及荧光特性研究

为增强CdS纳米粒子的荧光强度,以及稳定性,研究了Cd,S不同质量比,有无稳定剂等条件下CdS纳米粒子的制备及荧光特性。在碱性条件下,利用水热法合成了CdS/ZnO的纳米复合结构,并对所有样品进行了XRD、荧光光谱和SEM表征。测试结果表明所制备的CdS纳米粒子和CdS/ZnO的纳米复合结构粒子成分单一且纯净;ZnO复合在CdS表面;在紫外光(328.5 nm)激发下,CdS/ZnO纳米复合结构的发射峰位于463 nm处,峰形窄而对称,CdS/ZnO纳米复合结构的荧光强度比CdS纳米粒子的荧光强度有显著增强,且CdS和ZnO物质量之比为1∶1条件下,荧光强度最高,其荧光效率比单一CdS纳米粒子高出11%。通过第一性原理计算结果表明,CdS能带结构中,Cd-4d,S-3p和Cd-5s能带分别由5条、3条和1条能级构成,对比不同轨道的分态密度强度,看出CdS的导带边主要由Cd-5s轨道贡献,而价带边主要由S-3p轨道贡献,能量在-7 eV附近的电子态主要由Cd-4d轨道贡献。而ZnO上价带主要由O-2p电子构成,靠近费米能级的价带区域则主要由Zn-3d电子贡献,在导带部分,主要来源于Zn-4s和O-2p电子。由于在两种材料的复合结构中Zn-3d电子的能级和S-3p电子的能级接近,存在着二型带阶结构使能带变窄,容易形成跃迁,减小电子-空穴的复合,从而促进复合结构荧光效率的提高。     

CdS/PbS co-sensitized ZnO nanorods and its photovoltaic properties

Nanoparticles co-sensitized nanorods were designed and prepared by assembled CdS and PbS nanoparticles over ZnO nanorods using successive ionic layer adsorption and reaction (SILAR) method. The results showed that the uniform CdS and PdS nanoparticles could be deposited on the lateral and top of the ZnO nanorods when the precursor concentration was 0.05 M and 0.02 M, respectively. Solar cells based on CdS and PbS nanoparticles sensitized ZnO nanorods arrays were assembled successfully. A cell efficiency of 0.38% was obtained in ZnO/CdS/PbS in comparison with ZnO/PbS/CdS mainly due to the stepwise band edge structure constructed in this system except the coverage density of nanoparticles.     

Microstructure and photoluminescence of MoOx decorated ZnO nanorods

Various MoO_x decorated ZnO nanorods (ZnO-MoO_x) samples were fabricated by physical vapor deposition of MoO_x on the surface of ZnO nanorods with varying deposition time and temperature. The microstructure and photoluminescence (PL) of the ZnO-MoO_x samples were investigated. It was found that the morphology of the ZnO nanorods is changed from hexagonal prisms to lotus-roots-like shapes by the decoration of MoO_x. The lotus-roots-like shapes may be formed by partial melting and evaporating of ZnO-MoO_x during the MoO_x decoration. This result shows that one can use the thermal instability of a nano-material to obtain an interesting structure, although a thermal instability should often be avoided. The intensity of the ultraviolet and visible light emission the of ZnO nanorods have different dependencies on the MoO_x decoration. Although the position of the ultraviolet light emission is not obviously changed by the MoO_x decoration, the ultraviolet light emission intensity is greatly weakened. In contrast, the intensity and position of visible light emission is largely changed. The blue shift of the visible light emission might be related to defects introduced by melting of the ZnO nanorods.     

CdS quantum dot-sensitized ZnO nanorod-based photoelectrochemical solar cells

ZnO nanorods have been grown using ZnO seed layer onto ITO-coated glass substrates. CdS quantum dots have been deposited onto ZnO nanorods using simple precursors by chemical method and the assembly of CdS quantum dots with ZnO nanorod has been used as photo-electrode in quantum dot-sensitized solar cells. X-ray diffraction results show that ZnO seed layer, ZnO nanorods, and CdS quantum dot-sensitized ZnO nanorods exhibit hexagonal structure. The particle size of CdS nanoparticle is 5 nm. The surface morphology studied using scanning electron microscope shows that the top surface of the vertically aligned ZnO nanorods is fully covered by CdS quantum dots. The ZnO nanorods have diameter ranging from 100 to 200 nm. The absorption spectra reveal that the absorption edge of CdS quantum dot-sensitized ZnO nanorods shift toward longer wavelength side when compared to the absorption edge of ZnO. The efficiency of the fabricated CdS quantum dot-sensitized ZnO nanorod-based solar cell is 0.69% and is the best efficiency reported so far for this type of solar cells.     

CdS-ZnO composite nanorods: Synthesis, characterization and application for photocatalytic degradation of 3,4-dihydroxy benzoic acid

Well-aligned arrays of CdS-ZnO composite nanorods were grown on indium tin oxide substrates. ZnO nanorods, deposited by a low temperature aqueous chemical growth technique, were dip coated with CdS. The CdS-ZnO nanorods were polycrystalline as confirmed from the low angle X-rays diffraction study. Photon to current conversion efficiency of CdS-ZnO composite nanorod was observed to be higher than that of CdS. In the micro-Raman spectrum, we observed longitudinal optical modes of CdS and ZnO showing their co-existence. The appealing application of CdS-ZnO nanorod as a visible photocatalyst was demonstrated and the possible mechanism was discussed.     

Photoresistor based on ZnO nanorods grown on a p-type silicon substrate

In this work we discuss a method of preparation of a highly sensitive light detector based on ZnO nanorods. A photoresistor constructed by us is based on a heterojunction between high quality ZnO nanorods and high resistivity p-type Si used as a substrate for nanorods’ deposition. ZnO nanorods are grown by a modified version of a microwave assisted hydrothermal method which allows for growth of high quality ZnO nanorods in a few minutes. The obtained photoresistor responds to a wide spectral range of light starting from near infrared (IR) to ultraviolet (UV). Properties of the detector are evaluated. We propose the use of the detector as an optical switch.     

反胶束软模板法合成PANI/TiO2纳米棒复合材料及其性能研究

以阳离子表面活性剂十六烷基三甲基溴化胺(CTAB)形成的反胶束为模板,制备了一系列不同纳米TiO2含量的PANI/TiI2纳米复合材料.利用FTIR,UV-Vis,TG,TEM和荧光光谱等方法对产物进行了结构表征和性能研究.探讨了反胶束体系中PANI/TiO2复合纳米棒形成的自组装机理.结果表明:复合材料主要为直径30～40 nm,长约400 nm的PANI/TiO2复合纳米棒,二氧化钛纳米粒子与聚苯胺大分子之间存在强的相互作用,并对复合材料的热稳定性起到提高作用,PANI/TiO2纳米复合材料在紫外和可见光区域均有吸收,并在416 nm处激发产生荧光,荧光强度随着掺杂TiO2含量的提高得到了较大的增强.通过PANI/TiO2纳米棒复合材料中的激子离化和电荷传输过程探讨了PANI/TiO2的荧光量子效率和荧光强度增加的机理.     

电化学沉积法制备ZnO纳米柱及自驱动紫外探测性能研究

采用提拉法在ITO衬底上制备种子层,并使用电化学沉积制备高度取向的氧化锌纳米棒,研究了不同提拉次数下籽晶层厚度与电化学沉积电位对氧化锌纳米棒形貌的影响。在此基础上,制备了自驱动型紫外探测器并测试了其光响应谱。结果表明,该探测器可以对部分紫外波段(300~400 nm)有选择性地光响应,峰值响应度为0.012 A/W。     

ZnO/TiO2 core–shell heterojunction for CdS and PbS quantum dot-cosensitized solar cells

ZnO nanorods (NRs) with regular morphology were prepared through hydrothermal method, and the TiO₂ shell was assembled onto the surface of ZnO NRs by spin coating to the ZnO/TiO₂ core–shell heterojunction. CdS and PbS quantum dots (QDs) were used to cosensitize the ZnO/TiO₂ nanostructure by direct adsorption (DA) and successive ionic layer adsorption and reaction, respectively. SEM, TEM, and HRTEM images show that the samples possessed a rough surface and four lattice fringes indicating the successful synthesis of the ZnO/TiO₂/CdS/PbS composite structure. The ZnO/TiO₂(10T)/CdS/PbS sample showed a high absorption intensity at a broad range of wavelength to visible light region. The ZnO/TiO₂(10T)/CdS/PbS photoelectrode with QDSSCs showed the highest IPCE of 36.04% and photoelectric efficiency (η) of 1.59%; these values increased by approximately 550% and 150% compared with those of unsensitized ZnO (0.29%) and ZnO/TiO₂(10T) (1.04%) and about 146% and 120% compared with those of ZnO/TiO₂(10T)/CdS and ZnO/TiO₂(10T)/PbS, respectively. The fill factor was 0.36, and the photocurrent density (J_sc) and open circuit voltage (V_oc) reached the maximum values of 9.73 mA cm⁻² and 0.46 V, respectively.     

Synthesis and optical properties of flower-like ZnO nanorods by thermal evaporation method

Flower-like ZnO nanorods have been synthesized by heating a mixture of ZnO/graphite powders using the thermal evaporation and vapor transport on Si (1 0 0) substrates without any catalyst. The structures, morphologies and optical properties of the products were characterized in detail by using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and Raman spectroscopy. The synthesized products consisted of large quantities of flower-like ZnO nanostructures in the form of uniform nanorods. The flower-like ZnO nanorods had high purity and well crystallized wurtzite structure, whose high crystalline quality was proved by Raman spectroscopy. The as-synthesized flower-like ZnO nanorods showed a strong ultraviolet emission at 386 nm and a weak and broad yellow-green emission in visible spectrum in its room temperature photoluminescence (PL) spectrum. In addition, the growth mechanism of the flower-like ZnO nanorods was discussed based on the reaction conditions.     

One step synthesis and characterization of CdS nanorod/graphene nanosheet composite

In this work, an one-step approach to synthesize a CdS nanorod/graphene nanosheet (CdS/GNS) nanocomposite by the pyrolysis of a single-source precursor (bis(2-mercaptobenzothiazolato)-cadmium (II)) under nitrogen atmosphere were reported. X-ray diffraction result showed that the CdS nanorods belong to hexagonal crystal system. Transmission electron microscopy observations demonstrated that the CdS nanorods were coated by the graphene nanosheets effectively. Furthermore, the optical properties of the CdS/GNS nanocomposite were characterized by fluorescence spectroscopy. The nanocomposite displayed remarkable fluorescence quenching effect, implying that there was a high-efficiency energy transfer between graphene nanosheets and coated CdS nanorods, which could be applied in new optoelectronic or photovoltaic devices.