适体修饰纳米金催化-共振散射光谱测定凝血酶

用核酸适体修饰纳米金制备了识别凝血酶(TB)的适体修饰纳米金(AptAu)共振散射光谱探针. 在pH 7.40 的Na₂HPO₄-NaH₂PO₄缓冲溶液中及NaCl, KCl存在下, AptAu探针中的适配体特异识别凝血酶, 生成稳定的G-四分体和大粒径的纳米金聚集体. 经微孔滤膜过滤后, 纳米金聚集体被分离, 以滤液中未反应的AptAu作催化晶种, 在20.0 μg/mL HAuCl₄-5.01 mmol/L HCl-1.83 mg/mL CTMAB-50.1 μg/mL VC条件下, 催化维生素C (VC)还原HAuCl₄生成较大粒径的金颗粒, 体系在600 nm处有一共振散射峰. 随着凝血酶浓度的增大, 滤液中AptAu浓度降低, 催化作用减弱, 600 nm处的共振散射峰降低, 其降低值ΔI_{600 nm}与凝血酶浓度在6.40×10^－3～0.150 U/mL范围内存在良好线性关系, 回归方程为ΔI＝1.26×10³C＋1.50, 相关系数为0.999, 检出限为1.30×10^－3 U/mL. 该法用于定量分析人血浆中凝血酶, 结果满意.     

锰(Ⅱ)-纳米银体系共振散射光谱法检测痕量过氧化氢

利用纳米银(AgNPs)作为共振散射探针,根据反应前后纳米银聚集状态改变所引起的体系的共振散射信号的变化,对H_2O_2进行定量检测。采用硼氢化钠还原法,在柠檬酸三钠保护下将银从硝酸银中还原,合成了平均粒径约为4 nm的银纳米微粒。Mn~(2+)和覆盖在纳米银表面的柠檬酸根负离子络合诱导纳米银聚集,导致体系的共振散射强度增强;当体系中存在H_2O_2时,H_2O_2和Mn~(2+)发生类Fenton反应生成Mn~(3+)和羟基自由基(·OH)。Mn~(3+)和纳米银不能形成稳定的络合物,·OH氧化蚀刻纳米银,两种反应共同导致纳米银的聚集程度减弱,体系的共振散射信号强度相应减弱,据此建立了一种检测痕量H_2O_2的共振散射光谱新方法。在最佳条件下,波长411 nm处,体系的共振散射强度变化值(ΔI)与H_2O_2浓度在7.88×10~(-8)~1.418×10~(-5)mol/L范围内呈线性关系,相关系数为0.996 7,检出限为4.04×10-8mol/L。该方法应用于湖水和雨水中H_2O_2的检测,结果满意。     

核酸适体修饰纳米金共振散射光谱探针快速检测痕量Pb~(2+)

以柠檬酸三钠做稳定剂,用硼氢化钠还原氯金酸制备了粒径为5nm的纳米金.用铅离子核酸适体aptamer保护纳米金获得了检测铅离子的适体纳米金(aptamer-NG)共振散射光谱探针.在pH7.0的Na2HPO4-NaH2PO4缓冲溶液中及30mmol·L-1NaCl存在下,aptamer-NG稳定而不聚集.Pb2+可与该探针中的aptamer形成非常稳定的G-四分体结构,并释放出纳米金.在NaCl作用下纳米金聚集形成较大的微粒,导致552nm处共振散射峰强度增大.Pb2+浓度在0.07～42nmol·L-1范围内与552nm处共振散射强度增大值ΔI成线性关系,其回归方程为ΔI=12.0c+9.2,线性相关系数为0.9965,方法检出限为0.03nmol·L-1Pb2+.该方法用于水样中铅离子检测,结果与石墨炉原子吸收光谱法结果一致.     

核酸适体修饰纳米金-钌催化共振散射光谱法测定痕量Pb2+

用铅离子的特异性核酸适体（aptamer）修饰AuRu复合纳米微粒（AuRu的摩尔比为5:1）制备了铅离子的核酸适体纳米探针（AptAuRu）.在pH 7.0的Na2HPO4-NaH2PO4缓冲溶液及85 mmol/L NaCl存在下,AptAuRu纳米探针亦不聚集. 当Pb2+ 存在时,Pb2+可与探针中的aptamer形成较稳定的G-四分体结构,从而析放出AuRu复合纳米微粒并进一步聚集形成较大的微粒,导致592 nm处的共振散射光强度线性增大. 该反应液经0.15 μm滤膜过滤后,获得未反应的AptAuRu滤液. 滤液中的纳米微粒对氯酸钠-碘化钠反应具有较强的催化作用,其产物与阳离子表面活性剂形成缔合微粒,在472 nm处有一较强的共振散射峰. 随着Pb2+浓度增大,滤液中金钌纳米微粒浓度降低,其催化作用减弱,共振散射强度值降低. Pb2+浓度在0.12～60 pM范围与其共振散射强度降低值ΔI472nm呈线性关系,回归方程、相关系数分别为ΔI472nm =3.1C+7.3,0.9967, 检出限为0.08 pM Pb2+. 将本法用于废水中Pb2+的检测,其结果令人满意.     

非标记纳米银探针催化共振散射光谱检测痕量ATP

在pH 7.8 Tris-HCl缓冲液中, 三磷酸腺苷(adenosine triphosphate, ATP)的核酸适体(Apt 1)与其互补链(Apt 2)结合生成双链DNA (double-strand DNA, dsDNA). 此dsDNA不能稳定纳米银(AgNP), NaCl可致AgNP聚集, 在500 nm波长处产生一个较强的共振散射峰. 加入ATP后, ATP与dsDNA中的Apt 1结合形成较稳定的发夹结构结合物并释放出可稳定AgNP的Apt 2. 随着ATP浓度(16.5～1650 nmol/L)增加, 生成的Apt 2增加, 被Apt 2稳定的AgNP即AgNP-Apt 2结合物增加, 聚集的AgNP减少, 500 nm处的共振散射值线性减小. 该适配体反应中的AgNP-Apt 2对葡萄糖-铜(II)微粒反应具有较强的催化作用, 其产物氧化亚铜微粒在610 nm处有一较强共振散射峰. 随着ATP浓度增大, 反应液中AgNP-Apt 2增多, 催化作用增强, 610 nm处的共振散射峰增强. ATP浓度在4.95～165 nmol/L范围内与共振散射增大值ΔI_{610 nm}呈线性关系, 检出限为1.8 nmol/L ATP. 据此建立了灵敏度高、选择性好、简便快速检测ATP的共振散射光谱新方法.     

单分子荧光成像研究凝血酶核酸适体的折叠

通过对固定在表面的TMR标记凝血酶核酸适体进行单分子荧光成像, 在单分子水平上研究了凝血酶核酸适体的折叠. 在有K+存在的条件下, 核酸适体分子与K+结合后发生折叠, 形成G四分体结构, 使得TMR靠近富含鸟嘌呤的G四分体, 并与鸟嘌呤发生电子转移, 从而导致TMR荧光强度降低. 根据TMR的单分子荧光强度观察到不同K+浓度下核酸适体在折叠和无规卷曲两种状态下的分布. 结果表明, 可利用电子转移引起的荧光强度变化在单分子水平上研究核酸适体构象变化, 这一新方法的建立是对常用的单分子荧光共振能量转移(FRET)法的重要补充.     

基于水溶性共轭聚合物分子刷的高灵敏凝血酶生物传感器

以刷子状水溶性共轭聚芴（PFNI）为传感材料,以荧光素标记的核酸适体（FAM-apt15）为探针,设计了一种检测凝血酶的高灵敏度蛋白质传感器. PFNI的刷状结构带有大量正电荷,与负电荷的柔性单链核酸探针形成静电复合物,使能量供体（PFNI）与受体（FAM）之间的距离较近,发生高效荧光共振能量转移（Föster resonance energy transfer,FRET）. 当探针与靶凝血酶结合时,形成刚性且体积较大的G-四链体/凝血酶复合物,由于体积位阻和密集的刷子的阻碍作用,PFNI与FAM之间的距离被拉大,FRET效率显著降低. 对缓冲溶液中凝血酶检测的最低检测限可达0.05 nmol/L. 与基于线型共轭聚合物的蛋白质检测方法相比,灵敏度提高了至少一个数量级.     

金纳米微粒共振光散射光谱探针测定维生素B4-水溶性腺嘌呤的研究

建立了一种以金纳米微粒为探针共振光散射(RLS)法测定维生素B4的新方法.在弱酸性介质中(pH 4.2),金纳米微粒在635 nm有一最大共振散射峰.加入微量维生素B4后,金纳米微粒与维生素B4通过静电引力结合.形成了粒径较大的聚集体,导致RLS强度显著增强.研究了体系的共振光散射光谱特征和反应适宜条件,探讨了共振光散射增强的机理.结果表明,维生素B4质量浓度在0.1～5.0μg/mL 时与散射强度(△I)呈线性关系,检出限(3σ)为12.0 ng/mL,相对标准偏差(RSD)为2.2%.该方法已用于片剂中维生素B4的测定.     

免疫金铂纳米合金催化共振散射光谱法测定痕量人绒毛膜促性腺激素

以NaBH₄为还原剂, 制备了金与铂物质的量比为49∶1的金铂纳米合金(GP). 用兔抗人绒毛膜促性腺激素抗体(RhCG)修饰AuPt获得了免疫纳米合金探针(GP-RhCG). 在pH 5.8磷酸氢二钠-柠檬酸缓冲溶液及KCl存在的条件下, GP-RhCG探针发生非特异性聚集, 在590 nm处有一个较强的共振散射峰. 当有人绒毛膜促性腺激素(hCG)存在时, 聚集的GP-RhCG探针与hCG发生特异性结合, 生成分散性较好的GP-RhCG-hCG免疫复合物, 导致590 nm处共振散射峰强度降低. 其共振散射峰强度降低值ΔI_{590 nm}与hCG浓度在6.67～86.7 ng/mL范围内呈现良好线性关系. 免疫反应液中形成的GP-RhCG-hCG免疫复合物对葡萄糖-铜(II)体系具有较强的催化作用, 其产物在610 nm处有一较强共振散射峰. 随着hCG浓度增大, 形成的GP-RhCG-hCG复合物越多, 其催化作用增强, 610 nm处的共振散射峰增强. 其共振散射峰增大值ΔI_{610 nm}与hCG浓度在3.33～133 ng/mL范围内呈线性关系.     

基于阳离子荧光共轭聚合物和核酸适体探针的蛋白质检测新方法

以核酸适体为识别分子, 阳离子荧光共轭聚合物为报告分子, 建立了一种蛋白质检测新方法. 修饰有荧光熄灭基团的核酸适体探针通过静电作用与阳离子荧光共轭聚合物结合, 导致后者荧光熄灭. 当加入靶蛋白后, 核酸适体探针与其特异性结合, 荧光熄灭基团与阳离子荧光共轭聚合物远离, 聚合物荧光信号得以恢复. 实验结果表明, 荧光恢复程度与靶蛋白的浓度正相关. 采用该方法检测凝血酶的线性范围为17～40 nmol/L.     

Selective dissolution of the silver component in colloidal Au and Ag multilayers: a facile way to prepare nanoporous gold film materials

Colloidal Au/Ag multilayer films were prepared by alternate assembly of Au nanoparticles with a size of 5 +/- 1.2 nm and Ag nanoparticles with a size of 10 +/- 2.4 nm by using 1,5-pentanedithiol as cross-linker. Nanoporous gold films with a ligament size of 26.7 +/- 4.6 nm were then prepared by selective dissolution of sacrificial templates of silver particles in colloidal Au/Ag multilayers. The complete dissolution of Ag particles in colloidal Au/Ag multilayers in a mixture solution of 3.0 mM HAuCl(4) and 3 M NaCl took place at room temperature without damage of the colloidal Au film. This method to prepare nanoporous gold films was further extended to the preparation of nanoporous gold nanotubes by depositing colloidal Au/Ag film on the inner wall of anodic aluminum oxides (AAO) followed by dissolution of colloidal Ag and removal of AAO templates.     

Laser-assisted synthesis of Au-Ag alloy nanoparticles in solution

By using laser-induced heating, we prepared Au-Ag nanoalloys via three different procedures: (i) mixture of Au nanoparticles and Ag(+) ions irradiated by a 532 nm laser, (ii) mixture of Au and Ag nanoparticles irradiated by a 532 nm laser, and (iii) mixture of Au and Ag nanoparticles irradiated by a 355 nm laser. Procedure i is advantageous for the production of spherical alloy nanoparticles; in procedures ii and iii, nanoalloys with a sintered structure have been obtained. The morphology of the obtained nanoalloys depends not only on the laser wavelength but also on the concentration of nanoparticles in the initial mixture. When the total concentration of Ag and Au nanoparticles in the mixture is increased, large-scale interlinked networks have been observed upon laser irradiation. It is expected that this selective heating strategy can be extended to prepare other bi- or multi-metallic nanoalloys.     

Rapid synthesis of highly monodisperse Au(x)Ag(1-x) alloy nanoparticles via a half-seeding approach

Gold-silver alloy Au(x)Ag(1-x) is an important class of functional materials promising new applications across a wide array of technological fields. In this paper, we report a fast and facile synthetic protocol for preparation of highly monodisperse Au(x)Ag(1-x) alloy nanoparticles in the size range of 3-6 nm. The precursors employed in this work are M(I)-alkanethiolates (M = Au and Ag), which can be easily prepared by mixing common chemicals such as HAuCl(4) or AgNO(3) with alkanethiols at room temperature. In this half-seeding approach, one of the M(I)-alkanethiolates is first heated and reduced in oleylamine solvent, and freshly formed metal clusters will then act as premature seeds on which both the first and second metals (from M(I)-alkanethiolates, M = Au and Ag) can grow accordingly without additional nucleation and thus achieve high monodispersity for product alloy nanoparticles. Unlike in other prevailing methods, both Au and Ag elements present in these solid precursors are in the same monovalent state and have identical supramolecular structures, which may lead to a more homogeneous reduction and complete interdiffusion at elevated reaction temperatures. When the M(I)-alkanethiolates are reduced to metallic forms, the detached alkanethiolate ligands will serve as capping agent to control the growth. More importantly, composition, particle size, and optical properties of Au(x)Ag(1-x) alloy nanoparticles can be conveniently tuned with this approach. The optical limiting properties of the prepared particles have also been investigated at 532 and 1064 nm using 7 ns laser pulses, which reveals that the as-prepared alloy nanoparticles exhibit outstanding broadband optical limiting properties with low thresholds.     

Ag_核Au_壳金属复合纳米粒子的制备及表面增强拉曼光谱研究

在已制备好的Ag纳米粒子表面,通过化学还原的方法沉积生长Au包裹层,制备了粒子尺寸为50-70nm的Ag核Au壳复合纳米粒子.通过改变AuCl₄^-量,使Ag_100-xAu_x中Au的含量由x=0变为x=30.用UV-Vis吸收光谱和透射电子显微镜(TEM)对该结构纳米粒子进行了表征,并以对巯基苯胺(PATP)为探针分子进行表面增强拉曼光谱(SERS)研究.表面拉曼光谱表明,该结构的纳米粒子具有比Ag更强的SERS活性,随着Au:Ag比例的逐渐增加,其活性呈现先增大后减小的趋势,其最大增强约为Ag纳米粒子的10倍.     

Spectrophotometric and physicochemical investigations of Congo,alizarin red dyes and BSA interactions with Au,Ag and Au/Ag mix nanoparticles,and their antimicrobial activities

Individual and mix metal nanoparticles of Ag and Au have been prepared by the reducing method where citrate was used as reducing/stabilizing agent. The prepared NPs were characterized with UV/Visible and transmission electron microscopic (TEM) tools. The characteristic peak in UV/Visible at 525, 444 and 531 nm for Au, Ag and Ag/Au mix NPs respectively, gave primary confirmation of prepared NPs. TEM analysis showed the size of nanoparticles as 44.04, 19.78 and 30.93 nm for Ag, Au and Ag/Au mix NPs respectively. Congo and alizarin red dye interactions studies have been performed with prepared NPs to see the removal of the pollutants from water. Congo dye has shown weaker interaction as compared to alizarin due to structural symmetry. Amongst all, the AgNPs have shown maximum 67% and 75% interactions with Congo red and alizarin respectively due to high negative charges on the surface. The Au, Ag and Au/Ag mix NPs have shown stronger interaction with bovine serum albumin (BSA) protein up to 51, 59, 55% respectively, estimated through UV/Vis and physicochemical analysis. The biological evaluations of the prepared NPs have shown their antibacterial activity against Gram + ve and –ve species showing up to 9 cm zone of inhibition. The BSA interaction and antibacterial activity of NPs reveal the importance of NPs in medicinal field.     

One-pot synthesis of Ag-Au bimetallic nanoparticles with Au shell and their high catalytic activity for aerobic glucose oxidation

PVP-protected Ag(core)/Au(shell) bimetallic nanoparticles of enough small size, i.e., 1.4nm in diameter were synthesized in one-vessel using simultaneous reduction of the corresponding ions with rapid injection of NaBH(4), and characterized by HR-TEM. The Ag(core)/Au(shell) bimetallic nanoparticles show a high and durable catalytic activity for the aerobic glucose oxidation, and the catalyst can be stably kept for more than 2months under ambient conditions. The highest activity (16,890mol-glucoseh(-1)mol-metal(-1)) was observed for the bimetallic nanoparticles with Ag/Au atomic ratio of 2/8, the TOF value of which is several times higher than that of Au nanoparticles with nearly the same particle size. The higher catalytic activity of the prepared bimetallic nanoparticles than the usual Au nanoparticles can be ascribed to: (1) the small average diameter, usually less than 2.0nm, and (2) the electronic charge transfer effect from adjacent Ag atoms and protecting PVP to Au active sites. In contrast, the Ag-Au alloy nanoparticles, synthesized by dropwise addition of NaBH(4) into the starting solution and having the large mean particle size, showed a low catalytic activity.     

Biogenic synthesis of Ag, Au and bimetallic Au/Ag alloy nanoparticles using aqueous extract of mahogany (Swietenia mahogani JACQ.) leaves

In this paper, we have demonstrated for the first time, the superb efficiency of aqueous extract of dried leaves of mahogany (Swietenia mahogani JACQ.) in the rapid synthesis of stable monometallic Au and Ag nanoparticles and also Au/Ag bimetallic alloy nanoparticles having spectacular morphologies. Our method was clean, nontoxic and environment friendly. When exposed to aqueous mahogany leaf extract, competitive reduction of Au(III) and Ag(I) ions present simultaneously in same solution leads to the production of bimetallic Au/Ag alloy nanoparticles. UV-visible spectroscopy was used to monitor the kinetics of nanoparticles formation. UV-visible spectroscopic data and TEM images revealed the formation of bimetallic Au/Ag alloy nanoparticles. Mahogany leaf extract contains various polyhydroxy limonoids which are responsible for the reduction of Au(III) and Ag(I) ions leading to the formation and stabilization of Au and Ag nanopaticles.     

Preparation and characterization of Ag(Au) bimetallic core–shell nanoparticles with new seed growth method

Ag(Au) bimetallic core–shell nanoparticles were prepared by a new seed growth method. Ascorbic acid was used to reduce the complex of HAuCl₄ and hexadecyltrimethylammoniumbromide (CTAB). This resulted in the forming of colorless Au(I) (AuCl₂⁻). It was used as the growth solution to prepare these bimetallic core–shell nanoparticles. These nanoparticles were characterized by UV–vis spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results showed these nanoparticles exhibited core–shell shape and there was large amount of Ag in the shell. These nanoparticles could be produced in a few minutes without violent stirring and the method was easy and convenient compared with others. The effect of amount of AuCl₂⁻ on the shape of nanoparticles was also studied. Many small gold nanoparticles were formed on the surface of bimetallic core–shell nanoparticles in the presence of excess AuCl₂⁻. The mechanisms were also proposed to explain the process of colloidal preparation.     

Ag/Au纳米粒子的没食子酸还原制备及其共振瑞利散射光谱测定人血清总蛋白

以没食子酸为还原剂和稳定剂,用种子生长法制备出粒径均匀、单分散性和稳定性好、近球形的Ag/Au 核壳纳米粒子.高分辨透射电镜(HRTEM)与 X-射线能量色散光谱仪(EDX)测试表明,在Ag/Au摩尔比为1:1.6时,Au已完全包裹在Ag纳米粒子表面时,平均粒径为25 nm.以此摩尔比制备的Ag/Au核壳纳米粒子为探针...     

Fabrication of Ag/Au bimetallic nanoparticles by UPD-redox replacement: Application in the electrochemical reduction of benzyl chloride

The bimetallic Ag/Au nanoparticles were prepared by underpotential deposition-redox replacement technique on the basis of Au nanoparticles modified glassy carbon (GC) electrode. The as-prepared Ag/Au nanoparticles were characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The Ag/Au bimetallic nanoparticles modified GC electrode with low-Ag loading exhibits much better catalytic activity for the reduction of benzyl chloride than Ag nanoparticles modified GC electrode. The result is attributed to the synergic effect between Ag and Au in the reduction process. The chronoamperometry test shows that the Ag/Au nanoparticles possess long-term performance in the electrolysis.