Al纳米颗粒表面等离激元对ZnO光致发光增强的研究

基于聚苯乙烯球自组装法,在P型氮化镓(P-GaN)衬底上制备了有序致密的掩模板;采用热蒸发法在该模板上沉积金属Al薄膜,通过甲苯溶液去除聚苯乙烯球,得到了金属Al纳米颗粒阵列;采用原子层沉积法,在Al纳米颗粒阵列表面依次沉积氧化铝(Al_2O_3)和氧化锌(ZnO).通过测试Al纳米颗粒阵列的消光谱以及ZnO薄膜的光致发光谱,研究了Al纳米颗粒表面等离激元与ZnO薄膜激子之间的耦合效应.实验结果表明:引入Al纳米颗粒后,在约380 nm位置附近的ZnO近带边发光峰积分强度增强了1.91倍.对Al纳米颗粒表面等离激元增强ZnO光致发光的机理进行探讨.     

Zno纳米粒子在PS中空微反应器中的合成与光学性能

通过种子乳液聚合合成核壳结构的聚甲基丙烯酸甲酯/聚苯乙烯(PMMA/PS)复合微球,通过酸碱溶胀法进一步制备出次微米级的PS中空微球. 将此中空微球作为微反应器,使在ZnO纳米粒子前驱体溶液中溶胀, 最终ZnO纳米粒子在PS中空微球中原位生成. 实验表明, 组成ZnO纳米粒子前驱体溶液的两种组 分(CH₃COO)₂Zn和LiOH的滴加顺序不同对最终生成的ZnO纳米粒子的尺寸和负载效率有很大的影响,但并不改变ZnO纳米粒子的晶型. 复合物的光致发光和UV-Vis吸     

孔雀石绿在镁铝水滑石负载纳米氧化锌上的快速光降解

用共沉淀法制备Mg-Al水滑石纳米粉,ZnO纳米颗粒均相地覆盖在Mg-Al水滑石表面. 在500 ℃煅烧4 h后,采用XRD和SEM分析晶体结构和形貌. 研究表明在Mg-Al水滑石表面成功地制备了纳米ZnO. 所获得的纳米ZnO光催化剂对孔雀石绿表现出高的光催化降解性能. 归因于ZnO表面的高光催化活性以及Mg-Al水滑石较好的吸附性能,其中Mg-Al水滑石层片结构起了重要作用.     

ZnO纳米球的溶剂热合成及其结构和光学性质

针对目前采用溶剂热方法制备的ZnO纳米球尺寸比较大,而模板法制备技术又比较复杂的缺点,用六甲基次胺(HDA)作为辅助试剂,采用溶剂热法制备出了小尺寸的ZnO纳米球。本方法不采任何模板,制备过程简单易操作,重复性好。在场发射电子显微镜下可清楚地看到所制得纳米球尺寸分布比较均匀,每一个纳米球都是由许多粒径在20~30nm的小球共同组成的。X射线衍射结果表明所得产物均为六角纤锌矿结构的ZnO。用谢乐公式算得的粒子尺寸在5~11nm,而且随着制备时间的延长和制备温度的升高,ZnO激子吸收峰发生红移,显示出明显的量子限制效应,这表明那些小球可能是由尺寸更小的ZnO纳米粒子所组成。光致发光谱中紫外发射与可见发射的强度比随着制备时间的延长和制备温度的升高而大,表明ZnO纳米粒子的尺寸增大,结晶性变好。     

紫外发光增强的石墨烯-氧化锌纳米复合物

采用溶剂热法在相同条件下分别制备了纯ZnO和石墨烯-氧化锌纳米复合物,通过SEM、TEM、拉曼和红外光谱等手段,对纳米复合物样品进行了形貌和结构表征。实验结果显示ZnO纳米颗粒成功地分散在少层石墨烯上。通过对比纯ZnO与复合物的形貌和光致发光谱,发现在没有石墨烯时,ZnO能够择优取向生长成六方棱柱,紫外发光峰弱且宽;在有石墨烯时,ZnO聚集成表面不规则的球形颗粒,紫外发光峰强且窄。上述结果表明ZnO形貌的变化和石墨烯的等离子体效应共同影响了ZnO的紫外发光,但石墨烯的表面等离子体效应起主导作用。     

Ag-Au二元纳米微粒吸收谱的计算

纳米微粒的光学性能与其表面等离子体共振关系密切.本文利用推广的Mie理论计算研究了Au-Ag体系单质、合金以及核壳结构纳米颗粒的消光、吸收和散射的性能(包括壳核结构Ag-Au微粒在紫外-可见光的吸收性能),计算结果与实验值相符合得很好.研究表明,随着粒径的增加,微粒表面等离子体共振偶极吸收峰出现红移,波峰位置与纳米微粒的尺寸具有线性关系.壳核结构中,粒径与核壳比决定了整个微粒的吸收性能.进一步研究表明,当Au壳层较薄时,可以获得具有可调光学性能的壳核纳米结构;而当Au壳层较厚时,其光学性能与同尺寸单质Au微粒一致.通过计算分析,本文还将Mie理论推广到具有空腔结构并且壳层厚度达到一定值的纳米微粒.另外,研究发现合金结构纳米微粒的吸收峰位置与合金成分有着线性关系.本研究表明,人们可以通过控制纳米微粒的尺寸、形貌和结构,调节其表面等离子体共振峰位,这大大拓展了纳米微粒的应用范围.     

醋酸锌热解温度对ZnO纳米棒的结构及光学性质的影响

采用水热法在普通载玻片上热解醋酸锌生成的ZnO种子层上制备ZnO纳米棒, 采用 X射线衍射仪、扫描电镜、分光光度计等测试手段详细研究了醋酸锌热解温度对 ZnO纳米棒的结构和光学性质的影响. 结果表明: 纳米棒的结晶质量、端面尺寸、宏观应力和透射率与醋酸锌热解温度有密切关系. 随着热解温度的增加, ZnO纳米棒具有的c轴择优取向性先增强后减弱, 拉应力先减小后增大, 可见光区的平均透射率先增大后减小. 热解温度为350 ℃时, ZnO纳米棒c轴择优取向性最强, 拉应力最小, 平均透射率最大. 端面尺寸诱导的表面散射 是影响ZnO纳米棒可见光区平均透射率的主要机制. 关键词： 醋酸锌 水热法 ZnO纳米棒     

两步法制备超疏水性ZnO纳米棒薄膜

采用两步法制备了超疏水性ZnO纳米棒薄膜,在用磁控溅射在普通玻璃衬底上生长一层ZnO籽晶层基础上,利用液相法制备了空间取向高度一致的ZnO纳米棒阵列,经修饰后由亲水性转变为超疏水性.用扫描电子显微镜观察了纳米棒的表面结构,用接触角测量仪测出水滴在ZnO纳米棒薄膜表面的接触角为151°±05°,滚动角为7°.用Cassie模型对ZnO纳米棒薄膜的超疏水性进行了验证. 关键词： ZnO纳米棒 超疏水 两步法     

纳米Lu2O3:Eu局域结构的EXAFS研究

利用EXAFS对燃烧法制备的不同粒径的纳米Lu₂O₃:Eu(10%)进行了研究. 结果显示, 随着纳米颗粒尺寸的减小, 第一壳层(Lu-O和Eu-O)的配位数、配位距离、无序度都呈现增大的趋势, 其配位距离与颗粒直径 倒数呈线性关系, 证实该材料中有纳米晶粒核和非晶的颗粒表面两种不同的局域结构成分. 在小颗粒尺寸下, 非晶态成分占主要部分, 显著地影响其发光等物理性质.     

海胆状ZnO纳米线阵列的制备及其光学性能

采用一种低成本的有效方法制备出了有序排列的海胆状ZnO纳米线阵列。首先利用自组装的方法得到了单层的聚苯乙烯(PS)小球,以其为模板用水热法在小球表面生长ZnO纳米线,得到了由PS小球和ZnO纳米线构成的海胆状结构。纳米线的直径均一,长度可通过水热反应时间进行控制。利用这种方法制备的一维ZnO纳米结构在传感器、太阳能电池及光催化领域有潜在的应用价值。     

Tuning the Bandgap and Cytotoxicity of ZnO by Tailoring the Nanostructures

Tuning the bandgap and cytotoxicity of ZnO nanoparticles (NPs) is very important, not only for customizing their optoelectronic and biomedical applications, but also for their cytotoxicity assay and safe usage. A unique soft‐template of polyvinylpyrrolidone has been developed here to realize a rapid room‐temperature neutral synthesis of ZnO with controlled nanostructures for tuning the bandgap and cytotoxicity of ZnO. By simply changing the reagent stoichiometry and the soft‐template shape, high‐purity ZnO rods, tripods, tubes, and unique T‐like tubes with tunable size, surface composition/charge, bandgap, and cytotoxicity are obtained. It has been revealed that the ZnO bandgap can be remarkably reduced by introducing the surface nonstoichiometry; and the ZnO‐induced cytotoxicity can be tuned by the size, shape, surface charge/composition, and bandgap of ZnO NPs at different degrees. Significantly, both the photochemistry reaction and the reactive oxygen species induced by ZnO NPs are not necessary for the ZnO‐induced cytotoxicity.     

Optical characterization of ZnO nanoparticles capped with various surfactants

The presence of surfactants (Hexamine, tetraethylammonium bromide (TEAB), cetyltrimethylammonium bromide (CTAB), tetraoctylammonium bromide (TOAB) and PVP) on the surface of zinc oxide (ZnO) nanoparticles resulted variation in their optical properties. The optical properties of each surfactant-capped zinc oxide nanoparticles were investigated using UV-visible absorption and fluorescence techniques. The particle size of these nanoparticles were calculated from their absorption edge, and found to be in the quantum confinement range. The absorption spectra and fluorescent emission spectra showed a significant blue shift compared to that of the bulk zinc oxide. Large reduction in the intensity of visible emission of zinc oxide/surfactant was observed and these emissions were vanished more quickly, with the decrease in excitation energy, for the smaller nanoparticles. Out of the four surfactants (other than PVP), CTAB-capped zinc oxide has smallest particle size of 2.4 nm, as calculated from the absorption spectrum. Thus the presence of surfactant on the surface of zinc oxide plays a significant role in reducing defect emissions. Furthermore, ZnO/PVP nanoparticles showed no separate UV emission peak; however, the excitonic UV emission and the visible emission at 420 nm overlap to form a single broad band around 420 nm.     

Tunable surface and/or interface ferromagnetism of ZnO nanoparticles

The ZnO-based diluted magnetic semiconductor materials have been widely investigated since the room temperature ferromagnetism (FM) was predicted in the p$p$-type Mn doped ZnO. However, it is now clear that magnetic dopants or impurities are not necessary for introducing FM into ZnO. As confirmed by numerous theoretical and experimental works, tunable FM can be effectively introduced into ZnO nanoparticles (NPs) by controlling the surface and/or interface nanostructures. This review describes the recent advances in the surface and/or interface FM of ZnO NPs without any magnetic impurities. On the basis of the previous reports including our recent works, the origin of FM of ZnO NPs has been overviewed and discussed in terms of defects, complex reactions or compounds, and electron transfer at the NP surface or interface.     

基于氧化锌纳米颗粒-石墨烯异质结构的高性能紫外光探测器 (cited: 5)

报道了一种基于水热反应制备无表面活性剂的氧化锌纳米颗粒-还原石墨烯异质结构的新方法. 研究表明异质结构中氧化锌纳米晶体颗粒的平均直径为5 nm,这些颗粒均匀分布在还原石墨烯表面,其密度可以通过反应物的浓度进行有效调节. 并进一步构建了基于这种异质结构的光电探测器. 该探测器对紫外光的响应很快,光电流响应变化可达四个量级. 这些结果表明该异质结构特别适合作为替代材料用于设计和构建高性能的紫外光探测器件.     

The effect of morphology and doping on photoluminescence of ZnO nanostructures

In this work, optical properties of ZnO nanostructures prepared by chemical vapor deposition under different conditions were investigated. ZnO nanostructures were characterized by electron microscopy and photoluminescence. A high intensity green emission and a narrow UV emission band are observed in photoluminescence spectra of ZnO nanostructures related to the below-band-gap and band-edge that their intensities depend on the morphology of the nanostructures. It is considered that the green emission is originated from structural defects. In addition, the influence of thermal treatment and dopants such as iron and copper, on the photoluminescence (PL) properties of the ZnO nanostructures was investigated.     

Influence of surfactant structures in luminescence enhancement dynamics during nucleation and growth of aqueous ZnS nanoparticles and their photoactivation due to illumination with UV/visible light

Nanostructured semiconductor architectures have attractive optical properties mainly including bright photoluminescence (PL) resulting from the radiative recombination of charge carriers on surface states. Various approaches have been employed for the modification of surface states of these nanostructures to design new nanomaterials with enhanced PL primarily in aqueous medium to enable their applications in biological samples. Here, we report the varying efficiencies of three commercial surfactants viz. cetyltrimethylammonium bromide (CTAB), cetyltrimethylammonium chloride (CTAC) and cetylpyridinium chloride (CPyC) on the dynamics of PL emission enhancement during initial growth and Ostwald ripening of ZnS nanoparticles (NPs). The counterion has been estimated to behave differently to govern the PL enhancement. The exceptionally high tendency of CPyC in PL enhancement has been assigned to participation of π-electrons of pyridinium ring. The impact of UV-light in photoactivation of surfactant stabilized ZnS NPs has been utilized in exploring significance of surfactants in improving the surface emitting states in water soluble semiconductor NPs.     

Physicochemical properties of nanoparticles affect translocation across pulmonary surfactant monolayer

Interaction between nanoparticles (NPs) and pulmonary surfactant monolayer is one of the most important parts in NP-based pulmonary drug delivery system, which can affect the result of the inhaled nano-drugs and their potential efficacy. Here, we show how surface charge of NPs affects translocation across pulmonary surfactant monolayer with coarse-grained molecular dynamics simulations. The results reveal that the surface charge position of NPs can determine the fate of the inhaled NPs about whether they can have the ability of translocation across the pulmonary surfactant monolayer, which is that NPs with face surface charge can penetrate the pulmonary surfactant monolayer and NPs with edge surface charge cannot. Besides, dynamic process, phase state and the potential of mean force profiles further confirm this result. Moreover, compared to anionic NPs, there is a greater chance for cationic NPs to be adsorbed on the surface of the pulmonary surfactant monolayer, which can further decrease the thickness of the pulmonary surfactant monolayer and reduce the distance between charged NPs and the pulmonary surfactant monolayer. Our researches provide a novel simulation model of NPs on translocation across pulmonary surfactant monolayer and the study of NP-based pulmonary drug delivery system should consider the surface charge of NPs.     

Ultrafast dephasing of localized surface plasmons in colloidal silver nanoparticles: the influence of stabilizing agents

Localized surface plasmon dephasing times for aqueous colloidal silver nanoparticles (NPs) stabilized with three different capping agents (trisodium citrate??TSC, poly(vinylpyrrolidone)??PVP, and poly(vinylalcohol)?? PVA) were measured using the persistent spectral hole burning technique. The results obtained by fitting a theoretical curve to the experimental data show that the dephasing times are dependent on the chosen stabilizer (3.0, 2.3, and 1.8?fs for TSC, PVP, and PVA, respectively), and the differences are attributed to changes in the electronic density of states due to the interaction between the NPs and the capping agents. The results are supported by ab initio calculations for the chemisorbate and metallic cluster interaction.     

Laser synthesis of aluminium nanoparticles in biocompatible polymer solutions

Pulsed laser ablation of Aluminium (Al) in pure water rapidly forms a thin alumina (Al₂O₃) layer which drastically modifies surface plasmon resonance (SPR) absorption characteristics in deep-UV region. Initially, pure aluminium nanoparticles (NPs) are generated in water without any stabilizers or surfactants at low laser fluence which gradually transform to stable Al-Al₂O₃ core-shell nanostructure with increasing either residency time or fluence. The role of laser wavelength and fluence on the SPR properties and oxidation characteristics of Al NPs has been investigated in detail. We also present a one-step in situ synthesis of oxide-free stable Al NPs in biocompatible polymer solutions using laser ablation in liquid method. We have used nonionic polymers (PVP, PVA and PEG) and anionic surfactant (SDS) stabilizer to suppress the Al₂O₃ formation and studied the effect of polymer functional group, polymeric chain length, polymer concentration and anionic surfactant on the incipient embryonic aluminium particles and their sizes. The different functional groups of polymers resulted in different oxidation states of Al. PVP and PVA polymers resulted in pure Al NPs; however, PEG and SDS resulted in alumina-modified Al NPs. The Al nanoparticles capped with PVP, PVA, and PEG show a good correlation between nanoparticle stability and monomeric length of the polymer chain.