ZnO@SiO_2核壳量子点的制备及其荧光性能的研究

用一种操作简单、反应条件温和的方法制备了分散性好的超微小Zn O@Si O2核壳量子点透明溶液,利用透射电子显微镜(TEM)、紫外吸收光谱(UV)、荧光光谱(FL)、纳米粒度和ZETA电位分析仪等技术对所制备纳米粒子的粒径大小、吸收光谱、发光性质进行表征。结果表明,Zn O@Si O2核壳量子点平均粒径在3~5 nm,在紫外灯下发出黄绿色荧光,紫外最大吸收在330 nm左右,可以发射出510 nm的荧光。同时,系统地考察了p H值、温度、不同金属阳离子以及不同阴离子对量子点荧光强度的影响。实验结果表明:当p H≤7时,量子点荧光完全猝灭;当p H7时,量子点荧光强度随着p H值的增加而增强,当p H为9.0时,荧光强度达到最大,然后随着p H值的升高荧光略有降低。量子点随着温度的升高荧光强度逐渐降低,当温度达到50℃以上荧光完全猝灭。一价金属离子对量子点荧光强度基本没有影响,二价金属离子对量子点荧光削弱程度的大小顺序为Fe2+Mn2+Cu2+Pb2+Co2+Ba2+Mg2+,三价金属离子对量子点荧光削弱程度的大小顺序为Fe3+Cr3+Bi3+Al3+。其中,Fe3+、Fe2+、Bi3+、Cr3+、Mn2+等金属离子对量子点的荧光有猝灭作用,PO43-、HPO42-、H2PO4-等离子对量子点荧光稍有增加作用,HCO3-、CO32-、CH3COO-、SO32-等阴离子对量子点的荧光有削弱甚至猝灭的作用,Cl-、SO42-、NO3-等离子对量子点荧光几乎没有影响。     

纳米晶ZrO2：Dy3+的光致发光和能量传递性质

研究了Dy³⁺离子掺杂的ZrO₂纳米粉体的光致发光性质。观测到Dy³⁺离子的室温强特征发射和浓度猝灭现象以及基质ZrO₂与Dy³⁺离子之间的能量传递过程。发现了煅烧温度对样品的晶相有明显的影响,随着煅烧温度的变化,晶相也随之改变。晶相的改变使样品的荧光发射产生较大的差异,并观测到两个发射中心。通过对荧光强度与激活离子Dy³⁺离子浓度的关系研究发现,Dy³⁺离子在纳米ZrO₂基质中存在浓度猝灭现象,最佳掺杂浓度取决于ZrO₂基质的晶相,不同晶相导致不同的猝灭浓度,当基质晶相表现为四方相时,猝灭浓度为0.5%,而基质晶相为混合相时,猝灭浓度为1%。能量传递也依赖于样品的晶相。当煅烧温度为950℃时能量传递效果最好,并且从微观结构上给出了解释基质与Dy³⁺离子之间的能量传递的模型。     

金属离子修饰的ZnS/PAMAM纳米复合材料的荧光性能研究

用荧光分光光度法研究了Zn2+,Mn2+,Cd2+,Na+,K+,Ag+,Cu2+和Pb2+等金属离子修饰的ZnS/PAMAM树形分子纳米复合材料的荧光发射性能。结果表明：不同金属离子修饰效果不同。Zn2+,Mn2+和Cd2+修饰后,ZnS/PAMAM树形分子纳米复合材料的荧光发射强度有不同程度提高;Ag+,Cu2+和Pb2+的修饰对荧光有不同程度的猝灭作用;而Na+和K+的修饰对荧光发射无明显影响。与修饰前相比,Cd2+离子修饰的ZnS/PAMAM树形分子纳米复合材料标记的潜指纹发射的蓝色荧光更加明亮,与背景反差更加明显。这对提高潜指纹的显现精度和准确率有很好的借鉴价值。     

变温下Y2O3∶Eu3+纳米晶的荧光光谱和动力学过程

通过分析影响Y2O3:Eu3+在488nm激光激发下的5D0→7F2变温荧光发射强度的因素,建立起公式并对实验数据进行拟合,得到纳米晶的温度猝灭速率大于体材料的温度猝灭速率.测得Y2O3:Eu3+纳米晶和体材料的5D0→7F2发射峰的变温线宽,通过内应力和量子限域效应对其不同进行了解释.测量了Y2O3:Eu3+在共振激发下的5D0能级的荧光衰减时间随温度的变化,又利用公式对其进行拟合,得出了相比于体材料,纳米晶的辐射跃迁速率和无辐射跃迁速率均增大,但量子效率变小的结论.然后利用晶格畸变和表面态效应对上述结 关键词： 温度猝灭 Y2O3:Eu3+纳米晶 荧光衰减 线宽     

荧光法研究Pb2+与牛血清白蛋白的相互作用

在模拟生理条件下, 用荧光光谱法研究了Pb2+与牛血清白蛋白(BSA)的相互作用. 结果表明 BSA分子中色氨酸和酪氨酸残基具有荧光发射性质, 以283 nm激发BSA, 在341 nm处有很强的荧光发射. 在加入Pb2+ 后, 发现Pb2+-BSA强荧光峰的位置不变, 但荧光强度随着Pb2+浓度的增大而明显减弱, 说明Pb2+对BSA有荧光猝灭现象, 猝灭以静态猝灭为主, 由Stern-Volmer方程求得Pb2+表观猝灭常数Kq=9.5×1012 L·mol-1·s-1. Pb2+主要与BSA中的N配位形成21配合物, 表观络合常数lgK=11.61.     

Pb2+对鱼肠DNA光谱特性的影响

利用紫外吸收光谱、荧光光谱、电泳手段研究了不同浓度Pb2+与鱼肠DNA的相互作用. 紫外吸收光谱测试表明 随着Pb2+的加入, DNA产生明显的减色效应, 同时DNA的207 nm峰发生明显蓝移; 荧光发射光谱结果表明, 随着Pb2+的加入, DNA荧光发射强度逐渐降低, Pb2+在DNA上的结合位点数为0.8个, Pb2+引起DNA的荧光猝灭属于静态猝灭, 结合位点的结合常数分别为6.08×104和2.82×104 L·mol-1; 电泳结果表明, 不同浓度的外源Pb2+处理未引起DNA的断裂. 认为外源Pb2+ 对DNA的构象有一定的破坏作用, 但并不引起DNA的断裂.     

不同壳层厚度的LaF_3∶Eu~(3+)/LaF_3核壳结构纳米颗粒制备及发光性质

表面缺陷会使纳米材料的发光中心产生严重的猝灭,而适当厚度的同质包覆层会减少其猝灭。本文利用共沉淀法合成了LaF3∶Eu3+纳米颗粒和LaF3∶Eu3+/LaF3核壳结构纳米颗粒,研究了颗粒的晶体结构、形貌以及不同壳层厚度对发光性能的影响。研究发现:LaF3∶Eu3+核心和LaF3∶Eu3+/LaF3核壳结构均为六方结构。包覆同质壳层可以提高稀土离子的发光性能,包覆厚度的不同导致LaF3∶Eu3+/LaF3核壳结构的荧光强度与衰减时间均发生改变。其原因是未掺杂的LaF3壳层可以将发光中心Eu3+离子与LaF3∶Eu3+核心的表面隔离,进而减少表面对发光中心的猝灭,提高材料的发光性能。这种修饰作用与壳层厚度相关。     

纳米银胶中PVP和Alq3的荧光猝灭研究

本文通过湿法化学还原法合成了平均粒径为4.42nm、标准差为0.98nm的球形银纳米颗粒,并研究了在不同反应时间后获得的银纳米颗粒对PVP和Alq3的荧光猝灭效应。通过深入研究发现,PVP的荧光猝灭效应主要由于其分子链上的酮基与Ag颗粒之间发生了静电吸附,进而导致处在激发态的PVP分子与银颗粒之间产生电子或者能量转移(即非辐射弛豫),猝灭了PVP的荧光发光;而Alq3的荧光猝灭效应则主要归因于银纳米颗粒的欧姆损耗。通过采用时域有限差分法进行模拟发现,溶液中随机分布的银纳米颗粒,不仅能够吸收激发电磁波,削弱激发场强度,而且能够吸收荧光分子辐射的电磁波,进而猝灭了Alq3分子的荧光效应。这些研究成果将有利于了解金属纳米颗粒与PVP及Alq3分子荧光发光之间的关系,为调控荧光发光提供指导。     

核壳结构纳米颗粒Gd2O3:Tb3+/SiOx的制备及发光性能研究

以二甘醇为溶剂合成Gd2O3:Tb3+纳米颗粒,并在其表面包覆聚硅氧烷层,得到核壳结构纳米颗粒Gd2O3∶Tb3+/SiOx。为了研究Tb3+离子掺杂浓度对纳米颗粒发光性能的影响,采用几种不同Tb3+掺杂浓度进行纳米颗粒的合成,并对其发光性能进行了检测。结果表明:包裹聚硅氧烷层后的Gd2O3∶Tb3+纳米颗粒分散较好,聚硅氧烷层不会减弱Gd2O3∶Tb3+纳米颗粒的发光性能。Tb3+掺杂浓度对核壳结构纳米颗粒Gd2O3∶Tb3+/SiOx的发光存在浓度猝灭现象,猝灭摩尔分数为5%。这种具有发光特性的核壳结构纳米颗粒可作为生物传感器的探针用于生物分子的检测。     

纳米晶ZrO_2∶Dy~(3 )的光致发光和能量传递性质

研究了Dy3 离子掺杂的ZrO2纳米粉体的光致发光性质。观测到Dy3 离子的室温强特征发射和浓度猝灭现象以及基质ZrO2与Dy3 离子之间的能量传递过程。发现了煅烧温度对样品的晶相有明显的影响,随着煅烧温度的变化,晶相也随之改变。晶相的改变使样品的荧光发射产生较大的差异,并观测到两个发射中心。通过对荧光强度与激活离子Dy3 离子浓度的关系研究发现,Dy3 离子在纳米ZrO2基质中存在浓度猝灭现象,最佳掺杂浓度取决于ZrO2基质的晶相,不同晶相导致不同的猝灭浓度,当基质晶相表现为四方相时,猝灭浓度为0.5%,而基质晶相为混合相时,猝灭浓度为1%。能量传递也依赖于样品的晶相。当煅烧温度为950℃时能量传递效果最好,并且从微观结构上给出了解释基质与Dy3 离子之间的能量传递的模型。     

局域表面等离激元对InGaN/GaN多量子阱发光效率的影响

Ag纳米粒子的形貌对InGaN/Ga N多量子阱(MQWs)的光致发光(PL)效率有着显著影响。本文采用离子束沉积(IBD)技术将Ag沉积在InGaN/Ga N MQWs上,然后通过快速热退火处理制备Ag纳米粒子。通过改变Ag的沉积时间获得了具有不同Ag纳米粒子形貌的样品。用原子力显微镜对各样品的Ag纳米粒子形貌和尺寸进行了表征,并且测试了吸收谱、室温和变温PL谱及时间分辨光致发光(TRPL)谱。结果表明:随着Ag沉积时间的延长,所得Ag纳米粒子粒径增大,粒子纵横比先增大后减小且吸收谱峰红移。由于不同形貌的Ag纳米粒子在入射光作用下产生的局域表面等离激元(LSPs)与MQWs中激子耦合强度不同,光发射能力也不同,与没有Ag纳米粒子的样品相比,沉积时间为15 s的样品室温PL积分强度被抑制6.74倍,沉积时间为25 s和35 s的样品室温PL积分强度分别增强1.55和1.72倍且峰位发生红移,沉积时间为45 s的样品室温PL积分强度基本没有变化。TRPL与变温PL的测试结果证明,室温PL积分强度的改变是由于LSPs与MQWs中的激子耦合作用引起的。纵横比大且吸收谱与MQWs的PL谱交叠大的Ag纳米粒子能够更好地增强InGaN/Ga N MQWs的发光。     

Zn2+掺杂对GdTaO4:Eu3+荧光粉结构和发光性能的影响

采用高温固相反应法制备了掺杂不同浓度Zn2 的GdTaO4:Eu0.1荧光粉,研究了Zn2 掺杂对GdTaO4:Eu3 的结晶性能,晶粒形貌和光致发光特性的影响.以X射线衍射(XRD)、扫描电子显微镜(SEM)、激发-发射谱、衰减时间谱等方法对其性能进行了表征.结果表明,Zn2 掺杂可显著提高GdTaO4:Eu3 的光致发光强度,当掺杂浓度x=0.01时,光强被提高至2.7倍,可归因于的Zn2 进入了GdTaO4:Eu3 基质晶格,产生了一定浓度的氧空位以达到电荷平衡,并导致发光中心Eu3 的晶格场发生畸变;当x=0.13时,光强提高至3.2倍,且其衰减时间被缩短至40%,可归因于Zn2 的助熔剂效果;但当x＞0.13时,ZnO和GdTa7O19杂相的出现将导致发光强度减弱和衰减时间延长.另外,初步探索表明,Li2CO3和.KCl的共掺杂能进一步提高G.dTaO4:Eu0.1,Zn0.13的发光强度.     

Temperature and concentration dependences of the photoluminescence of MEH-PPV polymer composite films with ZnO nanoparticles

The absorption and photoluminescence (PL) spectra of MEH-PPV: ZnO composite films have been investigated at different concentrations of ZnO nanoparticles and at different temperatures (in the case of PL). It has been shown that, at 297 K, with increasing concentration of ZnO nanoparticles in the composite, the intensity of the PL lines of MEH-PPV decreases, whereas the intensity of the PL lines of ZnO increases. At a relatively low concentration of ZnO nanoparticles, a decrease in the temperature leads to an increase in the intensity of PL lines associated with MEH-PPV and ZnO, whereas at higher concentrations of ZnO nanoparticles, the intensity of these lines decreases. This is accompanied by a slight shift in the maximum of the PL toward the infrared (IR) region and a narrowing of the PL line of MEH-PPV with a decrease in the temperature and with an increase in the ZnO concentration. The mechanism of energy transfer in composite systems consisting of a polymer and inorganic nanoparticles that can be responsible for the observed effects has been discussed.     

Photoluminescence and optical characterization of CdS nanoparticles prepared by solid-state method at low temperature

The photoluminescence (PL) and optical properties of CdS nanoparticles prepared by the solid-state method at low temperature have been discussed. The effects of NaCl and anionic surfactant SDBS (sodium dodecylbenzene sulfonate) on the luminescent properties of CdS nanophosphors prepared using this method, without the inert gas or the H₂S environment, were studied separately. The synthesized products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscope (FESEM), and energy dispersive X-ray spectroscopy (EDAX). UV–VIS absorption and PL spectra were also studied. XRD studies confirmed the single-phase formation of CdS nanoparticles. TEM micrograph revealed the formation of nearly spherical nanoparticles with a diameter of 2.5 nm. The PL emission for the CdS shows the main peak at 560 nm with a shoulder at 624 nm, with an increase in the PL intensity after the addition of SDBS. The effect of Mn doping on PL intensity has also been investigated. The PL spectra show that the emission intensity decreases as the dopant concentration increases.     

催化剂对类石墨烯纳米片结构和发光性能的影响

利用热丝化学气相沉积在沉积有碳点和金催化剂层的Si衬底上制备了类石墨烯纳米片。分别用扫描电子显微镜、透射电子显微镜、显微Raman光谱仪、傅立叶变换红外光谱仪、X光电子谱仪和Ramalog系统对它的结构、组成和发光性能进行了研究。结果表明碳点和金引起了类石墨烯纳米片厚度和缺陷的变化,进而导致了发光带的漂移和发光强度的改变。根据表征结果,分析了类石墨烯纳米片结构的变化引起发光性能改变的原因。     

Si基CeO_2薄膜的发光特性

利用电子束蒸发技术在p型硅衬底上沉积了200 nm厚的CeO2薄膜样品,将样品置于弱还原气氛中高温退火后,观察到薄膜在385,418 nm以及445 nm左右出现三个明显的发光峰。结合激发光谱、吸收光谱以及XRD分析表明:CeO2薄膜在高温下容易发生失氧反应,出现Ce4+→Ce3+离子转变,Ce3+离子在紫外光的激发下,电子由O2p跃迁到5d能级,再由5d能级向4f能级跃迁,从而产生强烈的蓝紫外发射,而445 nm左右的发光峰则来自于SiO2薄膜的缺陷发光。样品选择900~1 200℃不同温度退火,并且在1 200℃下进行了不同时间的退火。研究结果显示:在1 200℃下进行2 h的退火,薄膜发光强度达到最大。     

Surface Plasmon Resonance and Aggregate Stability of Silver Nanoparticle Complexes with Chemotripsin

Extinction spectra, effective sizes, and aggregate stability of silver nanoparticles and nanocomplexes of silver nanoparticles with chymotrypsin obtained by the reactions of chemical reduction of silver nitrate using sodium borohydride as a reducing agent are studied. It is shown that silver nanoparticles obtained in the absence of chymotrypsin are aggregatively stable only at pH values immediately after synthesis. The placement of the synthesized silver nanoparticles in buffer solutions with pH values from 3.0 to 12.0 resulted in the appearance of a wide absorption band in the visible region of the spectrum, which is due to the agglomeration of silver nanoparticles, which appears to be the result of the destruction of the double electric layer formed by the ions making up sodium borohydride. The presence of chymotrypsin in the reaction medium resulted in significant spectral changes. Unlike silver nanoparticles synthesized in the absence of chymotrypsin, for nanocomplexes of silver nanoparticles with chymotrypsin with a change in pH, the shape of the extinction spectra and the position of the surface plasmon resonance band were preserved, while nanocomplexes of silver nanoparticles with chymotrypsin retained the aggregative stability in solutions in the pH range from 3.0 to 12.0 within a month. The observed stabilization effect of silver nanoparticles over a wide pH range induced by the presence of chymotrypsin in the reaction medium can be used further to develop methods for immobilizing enzymes on nanoparticles of biogenic elements and for creating polyfunctional pharmaceuticals, in which the components of nanocomplexes have different biological activity.     

In situ-monitored enhancement and quenching effect of Cu nanoclusters on Sm3+ photoluminescence in glass

An assessment of the influence of heat treatment temperature and retention time on the optical properties of a Cu⁺ and Sm³⁺ co-doped phosphate glass of interest to photonic applications is reported. Particularly, the enhancement of the orange-red photoluminescence (PL) from Sm³⁺ ions has been realized in the glass through the development of non-plasmonic Cu clusters. It was exposed during an in situ isothermal treatment wherein optical absorption and PL were monitored together in real time. Following the PL increase, a drop in the Sm³⁺ emission intensity was produced concurring with the appearance of Cu nanoparticles (NPs) exhibiting the surface plasmon resonance. Hence, the connection between energy donor (sensitizing) effects of small Cu clusters and the energy acceptor (quenching) character of Cu NPs is supported. It is the first time to the author's knowledge that the enhancement of Sm³⁺ luminescence via Cu clusters embedded in glass is indicated.     

溶胶-凝胶法制备Zn2SiO4:Eu3+红色荧光粉

采用溶胶-凝胶法在Zn2SiO4基质中掺杂Eu3+,合成了红色荧光粉Zn2SiO4:Eu3+.通过样品的X射线衍射光谱、红外光谱、扫描电镜以及光致发光光谱的测试和表征,研究了Zn2SiO4:Eu3+的内部结构和发光特性.扣描电镜结果显示样品为球状荧光粉,颗粒直径为1～3μm.在395 nm激发下,样品在613 nm处发射出很强的红光.结合荧光光谱,分析了样品的退火温度,Eu3+的浓度,电荷补偿剂Li+的浓度对样品发光强度的影响.研究发现,红色荧光粉Zn2SiO4:Eu3+的发光强度随退火温度的升高而增加,发光强度随Eu3+和Li+浓度的增加先增大后减小.     

Size controlled gold nanoparticle formation by <Emphasis Type="Italic">Avena sativa</Emphasis> biomass: use of plants in nanobiotechnology

Oat (Avena sativa) biomass was studied as an alternative to recover Au(III) ions from aqueous solutions and for its capacity to reduce Au(III) to Au(0) forming Au nanoparticles. To study the binding trend of Au(III) to oat and the possible formation of Au nanoparticles, the biomass and a solution of Au(III) were reacted for a period of 1 h at pH values ranging from 2 to 6. The results demonstrated that Au(III) ions were bound to oat biomass in a pH-dependent manner, with the highest adsorption (about 80%) at pH 3. HRTEM studies showed that oat biomass reacted with Au(III) ions formed Au nanoparticles of fcc tetrahedral, decahedral, hexagonal, icosahedral multitwinned, irregular, and rod shape. To our knowledge, this is the second report about the production of nanorods as a product of the reaction of a Au(III) solution with a biological material. These studies also showed that the pH of the reaction influenced the nanoparticle size. The smaller nanoparticles and the higher occurrence of these were observed at pH values of 3 and 4, whereas the larger nanoparticles were observed at pH 2.