A Sensitive Biosensor for Determination of Cu2+ by One‐step Electrodeposition

A simple one‐step electrodeposition method is described to fabricate three dimensional ordered macroporous chitosan?prussian blue?single walled carbon nanotubes (3DOM CS?PB?SWCNTs) film onto the gold electrode surface to fabricate a copper ions (Cu²⁺)‐specific DNAzyme biosensor. The new sensing strategy for sensitive and selective detection of Cu²⁺ was based on Au nanorods (AuNRs) as signal amplification labels. The electrochemical signal of glucose increased with the concentration of Cu²⁺ increasing. The morphologies and electrochemistry of the composites were investigated by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical techniques including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) and so on. Linear correlations of copper ion concentration were obtained in the range from 10^?18 M to 10^?5 M, achieving with a limit of detection of 10^?19 M (S/N=3). Parameters affecting the biosensor response such as temperature, the cleavage time and the time of hybridization were optimized. This biosensor showed a wide range, low detection limit, good reproducibility and high stability. Additionally, these striking properties endow the biosensor with a great promise for analytical applications.     

Gelatin-coated gold nanoparticles as an effective pH-sensitive methotrexate drug delivery system for breast cancer treatment

The present study investigates the synthesis and effectiveness of gold/gelatin nanoparticles (NPs) biopolymer as a carrier for methotrexate (MTX) drug. Two different shapes of gold particles, including spherical AuNPs (50 & 100 nm) and gold nanorods (AuNRs) with three different sizes (20, 50 and 100 nm length) were synthesized using the chemical reduction method. The effect of AuNPs size and shape on the entrapment efficiency (E.E), the release rate of the drug, and cellular uptake were investigated. The surfaces of both AuNPs and AuNRs were coated with a gelatin biopolymer, and the stability and property of the generated compounds were studied. Moreover, MTX as a chemotherapeutic agent was loaded on the gelatin-coated AuNPs/AuNRs complexes. The physicochemical properties of the gelatin-coated AuNPs/AuNRs complexes were studied using ultraviolet-visible (UV–Vis) spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy. The E.E and MTX release behavior from the complexes at pH values of 7.4 and 5.4 and temperatures of 37 and 40 °C were investigated in vitro. The cytotoxic effects of AuNPs, AuNPs-Gelatin, AuNPs-Gelatin-MTX, AuNRs, AuNRs-Gelatin, AuNRs-Gelatin-MTX and free MTX were studied. The results indicated that the E.E of AuNPs was higher than that of AuNRs. The highest release rate of the drug was related to the AuNR1-gelatin complex (pH 5.4 and temperature of 40 °C). In addition, MTX loaded AuNR2-gelatin showed the highest cytotoxic effect on the MCF-7 breast cancer cell line so that even its cell cytotoxicity was more than that of the free drug.     

New aspects of gold nanorod formation via seed-mediated method

Gold nanorods (AuNRs) were obtained via a wet chemistry technique, in aqueous medium, employing crystallisation seeds. The kinetics of formation, the aspect ratio, and the selectivity of the particles were evaluated according to the parameters of synthesis: the growth-driving agent, seed, and gold precursor concentrations. In 2–4 h, the rod particles attained the expected size and shape under kinetic control, and were stable for at least 2 days. In order to obtain good quality AuNRs in good yields, without enrichment, we suggest keeping the growth-driving agent/gold molar ratio, the Au^I/seed ratio, and the concentration of the reagents in the final solution within specific ranges. For example, even if good molar ratios between the reagents are maintained, relatively highly concentrated reaction solutions lead to AuNRs with lower aspect ratios. The main properties of the prepared colloidal systems and the nanoparticles were evaluated by UV–vis spectroscopy and transmission electron microscopy, respectively.     

Preparation of Polyethylenimine‐Functionalized Graphene Oxide Composite and Its Application in Electrochemical Ammonia Sensors

In this study, branched polyethyleneimine (PEI) was covalently linked to carboxylic acid functionalized graphene (GO‐COOH) to form GO‐COOH/PEI composites. Transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectra and thermogravimetric analysis were used to characterize the obtained composites. Electrochemical measurements indicated that the modification of the composites on the electrode could efficiently enhance the voltammetric response, suggesting the potential application for making electrochemical sensors. Moreover, our results also indicated that the electrocatalytic oxidation of ammonia could be observed on the GO‐COOH/PEI composites modified glassy carbon electrode. Consequently, our observations demonstrated that GO‐COOH/PEI composites were excellent materials for electrochemical sensing.     

Direct Observation of the Orientation Dynamics of Single Protein‐Coated Nanoparticles at Liquid/Solid Interfaces

We have observed the rotational dynamics of single protein‐coated gold nanorods (AuNRs) on C₁₈‐modified silica surfaces in real time by dual‐channel polarization dark‐field microscopy. Four different rotational states were identified, depending on the apparent strength of interactions between the AuNRs and the surface. The distributions of the states could be regulated by adjusting the salt concentration, and the state transitions were verified by monitoring the entire desorption process of a single AuNR. Our study provides insight into the interfacial orientation and dynamics of nanoparticles and could be useful for in vitro biophysics and the separation of proteins.     

Formation of core-shell Au@Ag nanorods induced by catecholamines: A comparative study and an analytical application

Gold nanorods (AuNRs) stabilized by cetyltrimethylammonium bromide (CTAB) were synthesized and an interaction of catecholamines (CAs) with silver ions in the presence of the obtained AuNRs was studied. The reaction results into formation of core-shell Au@Ag nanorods (Au@AgNRs) and leads to a hypsochromic shift of the long-wave surface plasmon resonance (SPR) band in the absorption spectrum of AuNRs. The influence of a CA structure, excess of CTAB, interaction time, pH, concentration of AuNRs, silver ions and CAs on this interaction was studied. Based on correlation of the NRs spectral characteristics with the concentration of CAs, a method for spectrophotometric determination of dobutamine, epinephrine, norepinephrine and dopamine with detection limits 27, 18, 16 and 13 μg L⁻¹, respectively, has been developed. The method can be applied to the analysis of medicines.     

Characterization and Electrocatalytic Activity of Nanocomposites Consisting of Nanosized Cobalt Tetraaminophenoxy Phthalocyanine,Multi‐walled Carbon Nanotubes and Gold Nanoparticles

Glassy carbon electrodes were modified with composites containing cobalt tetraaminophenoxy phthalocyanine nanoparticles (CoTAPhPc NP ), multi‐walled carbon nanotubes (MWCNT) and gold nanorods (AuNRs). The modified electrodes were studied for their electrocatalytic behavior towards the reduction of hydrogen peroxide. Phthalocyanine nanoparticles significantly improved electron transfer kinetics as compared to phthalocyanines which are not in the nanoparticle form when alone or in the presence of multiwalled carbon nanotubes (MWCNTs). CoTAPhPc NP ‐MWCNT‐GCE proved to be suitable for hydrogen peroxide detection with a catalytic rate constant of 3.45×10³ M^?1 s^?1 and a detection limit of 1.61×10^?7 M. Adsorption Gibbs free energy ΔG^o was found to be ?19.22 kJ mol^?1 for CoTAPhPc NP ‐MWCNT‐GCE.     

Chemical‐Bonding‐Directed Hierarchical Assembly of Nanoribbon‐Shaped Nanocomposites of Gold Nanorods and Poly(3‐hexylthiophene)

Nanoribbon‐shaped nanocomposites composed of conjugated polymer poly(3‐hexylthiophene) (P3HT) nanoribbons and plasmonic gold nanorods (AuNRs) were crafted by a co‐assembly of thiol‐terminated P3HT (P3HT‐SH) nanofibers with dodecanethiol‐coated AuNRs (AuNRs‐DDT). First, P3HT‐SH nanofibers were formed due to interchain π–π stacking. Upon the addition of AuNRs‐DDT, P3HT‐SH nanofibers were transformed into nanoribbons decorated with the aligned AuNRs on the surface (i.e., nanoribbon‐like P3HT/AuNRs nanocomposites). Depending on the surface coverage of the P3HT nanoribbons by AuNRs, these hierarchically assembled nanocomposites exhibited broadened and red‐shifted absorption bands of AuNRs in nIR region due to the plasmon coupling of adjacent aligned AuNRs and displayed quenched photoluminescence of P3HT. Such conjugated polymer/plasmonic nanorod nanocomposites may find applications in fields, such as building blocks for complex superstructures, optical biosensors, and optoelectronic devices.     

单金纳米棒的光散射分析化学:径向比与分析灵敏度的关系

单纳米颗粒作为信号感应单元在化学与生物传感应用中已引起广泛关注.本文通过暗场显微成像(iDFM)研究了不同径向比金纳米棒的光散射性质.将iDFM与扫描电子显微镜(SEM)结合表征种子生长法制备的金纳米棒,结果发现,因局域表面等离子体共振而展示出的红色散射光随单个金纳米棒的径向比增大逐渐红移,且金纳米棒对其周围介质折光率(RI)变化的敏感程度随径向比增大而增大.这一结果对设计高灵敏的生物纳米传感器、提高分析检测的灵敏度具有很好的指导意义.     

金纳米棒荧光探针应用于多酚化合物检测新方法

以金纳米棒为荧光探针,在20％甲醇(pH 5.0～6.0)介质中,以植物多酚化合物芒果苷、瑞香素和白藜芦醇为检测对象,建立了3种植物多酚的灵敏、简便、快速检测新方法.多酚化合物基于其与金纳米棒表面的十六烷基三甲基溴化铵(CTAB)分子间的疏水作用而在金纳米棒表面富集,同时使金纳米棒在719 nm处的荧光强度减弱,在一定范围内多酚化合物的浓度与金纳米棒荧光强度成正比,其检出限分别为5.0×10-8、8.0×10-8、2.0×10 -7mol/L.     

Amperometric sensor for nitrite using a glassy carbon electrode modified with thionine functionalized MWCNTs/Au nanorods/SDS nanohybrids

A sensitive nitrite (NO₂^‐) biosensor was fabricated by using sodium dodecyl sulfate (SDS), Au nanorods, and thionine functionalized MWCNTs (TH‐f‐MWCNTs) nanohybrids modified glassy carbon electrode. TH was covalently immobilized on the MWCNTs via a carbodiimide reaction. Comparing with MWCNTs/GCE, TH‐f‐MWCNTs/GCE displays higher catalytic activity toward the oxidation of NO₂^‐, since TH not only promoted the electronic transmission but also could improve the concentration of NO₂^‐ at the surface of the modified electrode in acidic solutions. The Au nanorods (AuNRs) were prepared through a simple wet chemical method and were characterized by TEM. The extremely high surface‐to‐volume ratios associated with one dimension nanostructures make their electrical properties extremely sensitive to species adsorbed on surfaces and result in excellent sensitivity and selectivity. SDS displays excellent film forming ability, which made the electrode stable. Under optimal conditions, the linear range for the detection of nitrite was 0.26 to 51 μM, and the low detection limit was 20 nM. In addition, the modified electrode was successfully applied to determine nitrite in real water samples. Copyright © 2012 John Wiley & Sons, Ltd.     

二元混合表面活性剂用于窄吸收金纳米棒的无种子合成

利用十六烷基三甲基溴化铵(CTAB)和油酸钠(NaOL)二元混合表面活性剂体系, 开发了一种高质量金纳米棒(AuNRs)的无种子合成方法. 通过透射电子显微镜(TEM)、 紫外-可见-近红外吸收光谱(UV-Vis-NIR)和热成像仪对金纳米棒的形貌、 光学性质及光热性能进行了表征. 实验结果表明, 当NaOL浓度为8.21~11.5 mmol/L时, 能够获得形貌均匀的AuNRs, 其纵向表面等离子体共振吸收(LSPR)在650~1150 nm范围内可调. 该方法制得的样品具有较窄的LSPR半峰宽, 特别是在制备LSPR在近红外二区(NIR-II, 大于1000 nm)的AuNRs方面具有明显优势. 在1064 nm激光的辐照下, 金纳米棒溶液能够快速升温至67 ℃, 光热转换效率可达31.5%, 同时表现出优秀的光热稳定性, 在近红外二区光声成像和光热治疗方面具有良好的应用价值.     

Fabrication of SERS active gold nanorods using benzalkonium chloride,and their application to an immunoassay for potato virus X

The authors report on a robust method for the synthesis of gold nanorods (AuNRs) with tunable dimensions and longitudinal surface plasmon resonance. The method relies on seed-mediated particle growth in the presence of benzalkonium chloride (BAC) in place of the widely used surfactant cetyltrimethyl ammonium bromide (CTAB). Uniform AuNRs were obtained by particle growth in solution, and BAC is found to stabilize the AuNRs for >1 year. The SERS activity of the resulting AuNRs is essentially identical to that of CTAB-protected nanorods. The SERS activity of the BAC protected nanorods was applied to the quantitative analysis of potato virus X (PVX). The calibration plot for PVX is linear in the 10 to 750 ng?mL^?1 concentration range, and the detection limit is 2.2 ng?mL^?1.

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Graphical abstract SERS-active gold nanorods (AuNRs) have been prepared by using benzalkonium chloride as stabilization agent. Effects of chemical parameters on AuNRs have been explored and AuNRs were used in quantitative analysis of potato virus X (PVX).

     

碳纳米管/氧化石墨烯/硫复合正极材料的制备及其电化学性能

以碳纳米管和氧化石墨烯(CNTs/GO)为主体材料, 通过化学还原法制备了CNTs/GO 负载硫的复合正极材料CNTs/GO/S. 扫描电子显微镜(SEM)及透射电子显微镜(TEM)测试表明, CNTs 均匀插层在GO片间, 从而形成三维多孔结构, 有利于电解液的浸润; 活性物质硫均匀地负载在CNTs/GO 表面. 电化学测试表明,CNTs/GO/S复合材料具有高的比容量和良好的循环稳定性: 在1C倍率电流密度下, 复合材料首次放电比容量高达904 mAh·g^-1, 经过50圈循环之后, 复合材料的比容量仍保持在578 mAh·g^-1.     

Gram-Scale Synthesis of Isolated Monodisperse Gold Nanorods

Although gold nanorods (AuNRs) have strong potential applications in nanotechnology, plasmonics, and sensing, the scale-up synthesis of isolated AuNRs in gram quantities remains a challenge. Nearly all previously reported methods produce aqueous solutions of cetyltrimethylammonium bromide (CTAB)-coated AuNRs in milligram quantities with yields of approximately 20–30 % in terms of Au^I to Au⁰ conversion. In addition, it is difficult to remove the CTAB bilayer from the surface of AuNRs and yet make them soluble and functionalized for further processing and chemical modification. This report describes the synthesis of monodisperse functionalized AuNRs (standard deviation, σ≈5 %) in gram quantities. Our approach involved increasing the concentration of HAuCl₄ ⋅ 3 H₂O in the growth solution to produce larger quantities of starting AuNRs and further reducing the remaining Au^I ions onto the surface of AuNRs. The slow and controlled addition of ascorbic acid as a reducing agent continued the conversion of Au^I into Au⁰ (through a disproportionation reaction) onto the surface of the nanorods, which maintained their uniform morphology without creating any unwanted impurities of various shapes. In addition, this approach significantly narrowed the size distribution owing to continuous growth of the partially grown AuNRs during the initial stage of the synthesis. To isolate a 1 g quantity of the AuNRs and to make them functionalized for further chemical reactions, a ligand-exchange approach was utilized, in which the CTAB surfactant was replaced with 4-mercaptophenol. The thiol group from 4-mercaptophenol formed a covalent bond with the surface of the AuNRs, leaving free functional OH groups available for further chemical coupling reactions. For the ligand-exchange process, a concentrated solution of 4-mercaptophenol in tetrahydrofuran solution was introduced into the AuNRs solution. Pure AuNRs functionalized with 4-mercaptophenol were isolated by dispersion and rinsing with an excess amount of THF, followed by centrifugation.     

Silver deposition directed by self-assembled gold nanorods for amplified electrochemical immunoassay

A novel electrochemical immunoassay was developed based on the signal amplification strategy of silver deposition directed by gold nanorods (AuNRs), which was in-situ assembled on the sandwich immunocomplex. The superstructure formed by the self-assembly of AuNRs provided abundant active sites for the nucleation of silver nanoparticles. In this pathway, the stripping current of silver was greatly enhanced. Using human immunoglobulin G (HIgG) as a model analyte, the ultrasensitive immunoassay showed a wide linear range of six orders of magnitude from 0.1 fg mL⁻¹ to 100 pg mL⁻¹, with the low detection limit down to 0.08 fg mL⁻¹. The practicality of this electrochemical immunoassay for detection of HIgG in serum was validated with the average recovery of 93.9%. In addition, this enzyme-free immunoassay also has the advantages of acceptable reproducibility and specificity, and thus this immunosensing protocol can be extended to the detection of other low-abundant protein biomarkers.     

Quadruple‐Responsive Nanocomposite Based on Dextran–PMAA–PNIPAM,Iron Oxide Nanoparticles,and Gold Nanorods

A quadruple‐responsive nanocomposite that responds to temperature, pH, magnetic field, and NIR is obtained by incorporating superparamagnetic iron oxide nanoparticles (SPIONs) and gold nanorods (AuNRs) into a dextran‐based smart copolymer network. The dual‐sensitive copolymer is prepared by sequential RAFT polymerization of methacrylic acid and N‐isopropylacrylamide from trithiocarbonate groups linked to dextran in one pot. These functionalized nanocomposites with superior stability can respond to the four stimuli mentioned above well. As evidenced by UV–vis and TEM measurements, the temperature‐induced unusual blue‐shift in the longitudinal plasmon band is possibly due to the side‐to‐side assembly of AuNRs.     

Thorough tuning of the aspect ratio of gold nanorods using response surface methodology

In the present work a central composite design based on response surface methodology (RSM) is employed for fine tuning of the aspect ratios of seed-mediated synthesized gold nanorods (GNRs). The relations between the affecting parameters, including ratio of l-ascorbic acid to Au³⁺ ions, concentrations of silver nitrate, CTAB, and CTAB-capped gold seeds, were explored using a RSM model. It is observed that the effect of each parameter on the aspect ratio of developing nanorods highly depends on the value of the other parameters. The concentrations of silver ions, ascorbic acid and seeds are found to have a high contribution in controlling the aspect ratios of NRs. The optimized parameters led to a high yield synthesis of gold nanorods with an ideal aspect ratio ranging from 1 (spherical particle) to 4.9. In addition, corresponding tunable surface Plasmon absorption band has been extended to 880 nm. The resulted nanorods were characterized by UV–visible spectrometry and transmission electron microscopy.     

Synthesis and characterization of a nanocomposite of goethite nanorods and reduced graphene oxide for electrochemical capacitors

We report a one-step synthesis of a nanocomposite of goethite (α-FeOOH) nanorods and reduced graphene oxide (RGO) using a solution method in which ferrous cations serve as a reducing agent of graphite oxide (GO) to graphene and a precursor to grow goethite nanorods. As-prepared goethite nanorods have an average length of 200 nm and a diameter of 30 nm and are densely attached on both sides of the RGO sheets. The electrochemical properties of the nanocomposite were characterized by cyclic voltammetry (CV) and chronopotentiometry (CP) charge–discharge tests. The results showed that goethite/RGO composites have a high electrochemical capacitance of 165.5 F g^?1 with an excellent recycling capability making the material promising for electrochemical capacitors.     

Rapid and fine tailoring longitudinal surface plasmon resonances of gold nanorods by end-selective oxidation

Facile achievement of gold nanorods (AuNRs) with controllable longitudinal surface plasmon resonance (LSPR) is of great importance for their applications in various fields. The LSPR of AuNRs is sensitive to their aspect ratio, which is still hard to be precisely tuned by direct synthesis. In this work, we report a simple approach for end-selective etching of AuNRs by a rapid oxidation process with Au(III) in cetyltrimethylammonium bromide (CTAB) solution at a mild temperature. The LSPR wavelength and the length of AuNRs blue shifted linearly as a function of the amount of Au(III), while the diameter of AuNRs remained nearly constant. The oxidative rate is temperature dependent, and the oxidative process for a desired LSPR can be accomplished within 15 min at 60 °C. Further investigations indicated that Br^– determine the occurrence of the oxidation between AuNRs and Au(III), and a small amount of surfactant chain (CTA⁺) is crucial for stabilizing AuNRs. This method presents a quick but robust strategy for acquiring AuNRs with an arbitrary intermediate LSPR wavelength using the same starting AuNRs, and can be a powerful tool for subsequent applications.