壳聚糖介质金纳米盘的可控合成及生长机理

水浴加热氯金酸、壳聚糖和纳米金种子的混合液,以壳聚糖为稳定剂和还原剂成功合成了表面等离子体共振(SPR)吸收峰位可调的金纳米盘.SEM电镜图像表明纳米金盘主要为三角形和截角三角形,其边长在170 nm左右.X射线衍射分析表明金纳米盘是以{111}面为盘状面的高纯金单晶.讨论了金纳米盘的生长机理.在最佳条件下金纳米盘的面内偶极等离子共振吸收峰位于920 nm.实验结果表明通过控制壳聚糖的量、金种子的加入量、水浴温度及水浴时间可以有效地控制近红外等离子吸收峰位及吸收强度.     

聚乙烯吡咯烷酮碱性水溶液中金纳米花的简易合成

以聚乙烯吡咯烷酮(PVP)兼作保护剂和还原剂在碱性水溶液中直接还原HAuCl₄制备出了60-80 nm的三维(3D)金纳米花. 产物的透射电子显微镜(TEM)和扫描电子显微镜(SEM)图像显示, 金纳米花表面布满10-15 nm左右的纳米触角, X射线衍射(XRD)表征揭示产物为金的面心立方晶体, 选区电子衍射(SAED)花样说明金纳米花为多晶结构. 金纳米花的生长经历了三个关键步骤, 即初级纳米晶聚集成多脚状纳米粒子, 随后在合适的PVP/HAuCl₄浓度比及NaOH浓度下, 多脚状纳米粒子进一步聚集形成疏松的花状粒子, 最终经过Ostwald熟化形成致密的花状产物. 一定HAuCl₄浓度下PVP/HAuCl₄浓度比和NaOH浓度对产物的形貌影响显著, 因此通过同时调控合适的PVP/HAuCl₄浓度比和NaOH浓度, 就能得到适应各种应用需求的尺度可控和纳米触角形貌可控的金纳米花.     

Au-Ag合金纳米粒子制备及其表面增强拉曼光谱研究

首先采用柠檬酸钠法制得Au-Ag合金纳米种子, 然后采用盐酸羟胺生长法得到不同组成的Au-Ag合金纳米粒子. 在其UV-Vis光谱中只观察到一个位于单金属银和金之间的等离子体共振峰, 表明Au-Ag合金纳米粒子已经形成. TEM结果表明, 合金纳米粒子的粒径约为60 nm, 且颜色均一, 没有明显的核壳结构. 用苯硫酚(TP)作为探针分子研究了合金纳米粒子的表面增强拉曼光谱(SERS). 结果表明, SERS强度与合金纳米粒子的组成和尺寸有关. 当纳米粒子粒径一定时, 除Au25Ag75外, 随着金的增加SERS强度增强. Au25Ag75的粒径比Ag小, 导致SERS强度比Ag低. Au50Ag50和Au75Ag25加入TP分子后, 其聚集方式与Au相似, 等离子体共振峰逐渐靠近1064 nm, 金含量较高时, TP的SERS归于聚集体的等离子体共振增强的贡献.     

PVP 稳定的纳米 Au 溶胶对葡萄糖液相选择氧化的催化性能

 采用化学还原法制备了聚乙烯吡咯烷酮 (PVP) 稳定的纳米 Au 溶胶, 这种 Au 溶胶在葡萄糖空气氧化制葡萄糖酸反应中具有良好的催化性能. 考察了 PVP 加入量和氯金酸前驱液的浓度对反应活性的影响. 紫外-可见吸收光谱和透射电镜分析结果表明, 含有较小 Au 粒子的 Au 溶胶体系具有较高的催化活性. 当 PVP/Au 质量比为 40, 氯金酸浓度为100 μg/ml 时, 得到稳定的 Au 溶胶体系具有金粒子尺寸小、分布均匀的特点, 对葡萄糖氧化反应活性高, 葡萄糖的转化率达到 54.4%.     

金纳米粒子-胱氨酸三维网状结构的形成及其光谱特性研究

用柠檬酸三钠还原法制备了水溶性金纳米粒子, 粒子的平均粒径为4.5 nm, 它与胱氨酸作用后, 胱氨酸利用双硫键在其表面成功地进行了自组装, 获得了金纳米粒子-胱氨酸的三维网状结构. 用紫外-可见光谱、光散射光谱、透射电子显微镜等手段对胱氨酸组装前后的金纳米粒子进行了表征. 结果显示, 粒子与粒子之间, 通过静电引力形成了离子键, 吸收光谱变化明显, 金纳米粒子特征吸收峰由组装前518 nm红移到670 nm, 溶液颜色也相应由酒红色变为蓝紫色, 求出了金纳米粒子-胱氨酸三维网状结构形成过程中胱氨酸的最佳量, 金与胱氨酸的物质的量比为1∶1. 对于4.5 nm的金纳米粒子, 只有14%左右的胱氨酸在金纳米粒子的表面进行了自组装, 而多余的86%的胱氨酸未与金纳米粒子作用; 其共振瑞利散射光谱具有潜在的应用价值. 该研究对以金纳米粒子为基础的新材料制备进行了有益的探索.     

金纳米粒子的共振散射光谱

采用Frens 法制备了粒径为10～95 nm的金纳米粒子.它们均在580 nm处产生一个共振散射峰.从液相纳米粒子的波动观点出发,解释了金纳米粒子共振散射光谱的产生原因.用超分子界面能带理论解释了金纳米粒子的颜色与粒径的关系.根据最大吸收波长与粒径的关系,建立了一种测量金纳米粒子粒径的光度标尺.     

在SDS-PVP团簇软模板中自组装多脚状金纳米粒子

利用十二烷基硫酸钠(SDS)与聚乙烯吡咯烷酮(PVP)组成的团簇为软模板, 在微波辅助下以柠檬酸钠为还原剂快速还原氯金酸生成金晶并自组装成多脚状金纳米粒子. TEM结果显示, 得到回转直径约为50 nm的多脚状纳米结构, 电子衍射(ED)证实其为多晶结构. XRD结果表明, 该多脚状金纳米结构主要沿(111)晶面生长, 构成该纳米结构的晶粒尺寸约为12.7 nm. SDS与PVP组成的团簇结构对金纳米粒子的形貌有显著影响, 固定PVP浓度时, 随着SDS浓度增大, 金纳米粒子的形貌由球形向多脚状转变, 同时还原产物水溶液的UV-Vis光谱在800 nm附近的吸收逐渐增强.     

步步种子法制备形态及尺寸可控的花状金纳米粒子

系统研究了以20 nm球形金纳米粒子为种子,抗坏血酸和HAuCl4为生长溶液,利用步步种子法制备花状金纳米粒子的方法。实验结果表明,抗坏血酸可以快速有效地使HAuCl4还原成Au0单体,并在反应溶液中形成小的金纳米粒子;采用步步种子法以抗坏血酸还原HAuCl4,通过球形金纳米种子的核生长过程使种子粒径增大,继而通过二次成核过程使金纳米粒子表面出现突起,最终形成粒径均一可控的花状金纳米粒子结构,通过改变抗坏血酸和种子溶液的加入量可以得到不同粒径及形态的花状金纳米粒子。该粒子由于较大的表面粗糙度和分支上的特殊电磁场效应,从而在表面增强荧光光谱中表现出良好的增强效果。     

步步种子法制备形态及尺寸可控的花状金纳米粒子

系统研究了以20 nm球形金纳米粒子为种子,抗坏血酸和HAuCl4为生长溶液,利用步步种子法制备花状金纳米粒子的方法。实验结果表明,抗坏血酸可以快速有效地使HAuCl4还原成Au0单体,并在反应溶液中形成小的金纳米粒子;采用步步种子法以抗坏血酸还原HAuCl4,通过球形金纳米种子的核生长过程使种子粒径增大,继而通过二次成核过程使金纳米粒子表面出现突起,最终形成粒径均一可控的花状金纳米粒子结构,通过改变抗坏血酸和种子溶液的加入量可以得到不同粒径及形态的花状金纳米粒子。该粒子由于较大的表面粗糙度和分支上的特殊电磁场效应,从而在表面增强荧光光谱中表现出良好的增强效果。     

超细纳米Pd粒子与聚乙烯吡咯烷酮的相互作用

在微量聚乙烯吡咯烷酮(PVP)存在下, 利用超声还原氯化钯水溶液, 制备出超细纳米Pd颗粒, 用高分辨透射电镜、红外光谱、紫外-可见光谱和X射线光电子能谱等技术对其表面形貌及结构进行了表征. 结果表明, 纳米Pd粒子的粒径均一, 大约为3 nm. 纳米Pd/PVP复合粉末的羰基红外吸收峰比PVP的羰基吸收峰红移9 cm^-1; 且当超声反应50 min时, PVP紫外吸收波峰蓝移16 nm, 表明了纳米Pd与PVP之间存在一定的相互作用力. XPS结果证明, 纳米Pd与PVP的羰基基团通过配位作用使超细纳米Pd粒子得以稳定分散存在.     

Murraya Koenigii leaf-assisted rapid green synthesis of silver and gold nanoparticles

A facile bottom-up 'green' and rapid synthetic route using Murraya Koenigii leaf extract as reducing and stabilizing agent produced silver nanoparticles at ambient conditions and gold nanoparticles at 373 K. The nanoparticles were characterized using UV-vis, transmission electron microscopy (TEM), X-ray diffraction (XRD) and FTIR analysis. This method allows the synthesis of well-dispersed silver and gold nanoparticles having size ～10 nm and ～20 nm, respectively. Silver nanoparticles with size ～10 nm having symmetric SPR band centered at 411 nm is obtained within 5 min of addition of the extract to the solution of AgNO3 at room temperature. Nearly spherical gold nanoparticles having size ～20 nm with SPR at 532 nm is obtained on adding the leaf extract to the boiling solution of HAuCl4. Crystallinity of the nanoparticles is confirmed from the high-resolution TEM images, selected area electron diffraction (SAED) and XRD patterns. From the FTIR spectra it is found that the biomolecules responsible for capping are different in gold and silver nanoparticles. A comparison of the present work with the author's earlier reports on biosynthesis is also included.     

Synthesis and optical properties of triangular gold nanoplates with controllable edge length

Gold triangular nanoplates with a uniform size were synthesized by a simple seeds-growth method in a lamellar lyotropic liquid crystal (LLC) medium consisting of F127, n-C₄H₉OH and H₂O. The edge length of gold nanoplates can be adjusted from tens to several hundreds nanometers (and even a few micrometers) by varying the concentration of Au³⁺ and the seeds solution volume. The optical properties of the synthesized gold nanoplates were studied. The vis-NIR spectra of the synthesized gold nanoplates exhibited a good linear correlation between the in-plane plasmon resonance λ_max and the average edge length of the corresponding nanoplates.

     

用双还原法制备三角形银纳米片及其光学性能

在硼氢化钠和柠檬酸三钠共存的体系中还原硝酸银, 以聚乙烯吡咯烷酮(PVP)为表面活性剂和保护剂, 水浴加热制备得到三角形银纳米片, 用X射线衍射(XRD)、透射电子显微镜(TEM)、紫外-可见(UV-Vis)吸收光谱、表面增强拉曼散射(SERS)光谱对其进行了表征. 结果表明: 三角形银纳米片产物为立方相金属银, 边长为(100±40) nm, 厚度为(10±5) nm; 产物表现出与球形银纳米粒子完全不同的吸收光谱; 柠檬酸根在银晶核不同晶面的选择吸附、PVP的包覆作用及Ag(111)晶面的层错对产物的形成起决定作用; 与球形纳米颗粒相比, 三角形银纳米片膜对吡啶(Py)分子有显著的SERS活性.     

Organic dye molecules as reducing agent for the synthesis of electroactive gold nanoplates

Highly crystalline, hexagonal and triangular nanoplates of gold are synthesized in high yield by a new wet chemical method using multifunctional molecules, Bismarck brown R (BBR) and Bismarck brown Y (BBY). This method involves a simple approach by keeping a mixture of aqueous HAuCl4 solution and BBR/BBY solution in presence of poly(vinyl pyrrolidone) for 24 h. These nanostructures show unprecedented electrochemical properties exhibiting surface confinement effect. The UV-visible (UV-vis) spectrum shows certain distinct features with absorptions at 300, 400, and 650 nm extending up to the near infrared region. Selected area electron diffraction patterns of these nanoparticles show highly oriented (111) crystal facets. X-ray diffraction analysis also confirms the predominant orientation in the (111) crystal planes with lattice constant approximately 4.07 angstroms of face-centered-cubic (fcc) gold. X-ray photoelectron (XP) and Fourier transform infrared (FTIR) spectroscopic analysis shows the presence of a fraction of reducing molecules as surface passivating agent either in the unreacted molecular state or as a mixture of reacted and unreacted product, which probably undergoes charge transfer with gold nanocrystals giving absorption at approximately 300 nm.     

Radiation-induced synthesis of gold nanoparticles within lamellar phases. Formation of aligned colloidal gold by radiolysis

A sheared lamellar phase has been used as a nanoreactor for the synthesis of gold nanoparticles by radiolysis and by a photochemical approach. A gold salt solution (KAuCl4, 10(-2) M) is introduced into the aqueous compartments between the lipid-based bilayers. Gold nanoparticles grow within the lamellar phase as shown by TEM analysis and X-ray diffraction, limiting the particle size. Homodisperse, 2.4- and 5.9-nm-sized, spherical nanoparticles are produced by gamma irradiation and UV irradiation, respectively. When produced by radiolysis, they are perfectly aligned along the lamellae. Their UV-vis spectra display a maximum at 565 nm suggesting that nanoparticles are coupled by dipole-dipole interactions within the lamellar phase.     

Optimization of high-yield biological synthesis of single-crystalline gold nanoplates

In this work, single-crystalline gold nanoplates were obtained by reducing aqueous chloroauric acid solution with the extract of Sargassum sp. (brown seaweed) at room temperature. The gold nanoplates so obtained were characterized by UV-vis spectroscopy, X-ray diffraction, atomic force microscopy, and transmission electron microscopy. The formation of gold nanoplates was found to depend on a number of environmental factors, such as the time taken to age the seaweed extract, pH of the reaction medium, reaction temperature, reaction time, and initial reactant concentrations. The size of the gold nanoplates could be controlled to between 200 and 800 nm by manipulating the initial reactant concentrations. The yield of the flat gold nanocrystals relative to the total number of nanoparticles formed was as high as approximately 80-90%.     

Facile Synthesis of BiOI Nanoparticles at Room Temperature and Evaluation of their Photoactivity Under Sunlight Irradiation

In this study, highly photoactive BiOI nanoparticles (NPs) under sunlight irradiation were synthesized by a facile precipitation method using polyvinylpyrrolidone (PVP) at room temperature. The as‐prepared catalysts were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transition electron microscopy (TEM), energy‐dispersive X‐ray spectroscopy (EDX), Fourier transform infrared (FTIR) and UV–vis diffuse reflectance spectra (UV–vis DRS). The results of XRD showed that PVP did not have any significant effect on tetragonal crystalline structure of BiOI. Also, using different amounts of PVP in the synthesis led to different morphologies and sizes of BiOI particles. It was found that using 0.2 g of PVP in the synthesis method changed morphology from 1‐μm platelets to NPs with size under 10 nm. In addition, the photocatalytic performance of prepared photocatalysts was evaluated in the photodegradation of reactive blue 19 (RB19) dye under sunlight irradiation. The BiOI synthesized using 0.2 g PVP (BiOI0.2) showed higher degradation efficiency compared to BiOI prepared without any additive. Excellent visible light photocatalytic properties of nano‐scaled BiOI0.2 samples compared to BiOI platelets could be attributed to higher surface‐to‐volume ratio and narrow band‐gap energy of as‐prepared BiOI0.2 NPs.     

Studies on photocatalytic performance and photodegradation kinetics of zinc oxide nanoparticles prepared by microwave-assisted sol–gel technique using ethylene glycol

ZnO nanoparticles with an average particle size of 27 nm were fabricated using a microwave-assisted sol–gel method in the presence of ethylene glycol. The nanoparticles were characterized by X-ray diffraction, Monshi’s equation, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. The band gap energy of the nanoparticles was measured to be 3.27 eV by UV–Vis absorption and reflection spectroscopy. Photocatalytic activity of the synthesized nanoparticles was assessed by degrading nitrophenol in aqueous solution under UV-C irradiation. The effects of initial nitrophenol concentration, amount of photocatalyst, and of pH on the photodegradation process were investigated. Degradation samples were analyzed by UV–Vis spectroscopy. Nitrophenol was removed by 98 % within 240 min. The degradation kinetics were studied and fitted well to pseudo-first-order and Langmuir–Hinshelwood models.