金纳米粒子比色探针检测牛奶及鸡蛋中的三聚氰胺

三聚氰胺能诱导金纳米粒子(AuNPs)团聚,溶液颜色由酒红色变为紫色或蓝灰色.以AuNPs作为比色探针,建立了快速检测牛奶和鸡蛋中三聚氰胺的方法.实验优化得最佳反应条件为:AuNPs粒径13 min、pH=7、反应时间10 min和温度为室温.对样品中常见物质进行了干扰实验.样品经10％三氯乙酸和氯仿提取、离心分离后可...     

Nanoporous Ge coated by Au nanoparticles for electrochemical application

We present an innovative device based on a nanoporous Ge electrode decorated by gold nanoparticles (AuNPs). A study aimed at obtaining the best AuNP deposition conditions, which allow the decoration of Ge walls with AuNPs, avoiding particles aggregation is reported.The performance of the electrode has been evaluated by the electrocatalytic reduction of iodoethane in acetonitrile solution, a model reaction in organic electrocatalysis.     

Michael addition reactions for the modification of gold nanoparticles facilitated by hyperbaric conditions

The chemical interfacial modification of organic solvent soluble 2.4 ± 0.5 nm maleimide-modified monolayer protected gold nanoparticles (2-C(12)AuNPs) with primary or secondary amines via Michael addition reactions is demonstrated. Michael addition reactions between 2-C(12)AuNPs and primary or secondary amines at ambient temperature and pressure and under the conditions where the AuNP is soluble and stable are possible albeit sluggish, often taking days to weeks to go to completion. The rates and efficacies of the these same reactions are drastically increased at hyperbaric pressure conditions (11?000 atm) with no observed adverse effect to the gold nanoparticle stability. The resulting Michael addition adducts (3-C(12)AuNPs) formed from 2-C(12)AuNPs and the corresponding amines were characterized by TEM and by comparison of the (1)H NMR spectra of the 3-C(12)AuNPs with those of model reactions of the same amines with N-dodecylmaleimide, 2. The Michael addition reactions occur more readily with 2 rather than 2-C(12)AuNPs, consistent with the local environment of the latter imposing additional steric or other barriers to the reaction. The use of hyperbaric conditions makes the reaction of the organic solvent soluble 2-C(12)AuNP via Michael addition a viable interfacial modification process that is otherwise impractical. The results also suggest that it is a useful protocol for facilitating Michael addition reactions generally in solution at low temperatures.     

Dendronized Anionic Gold Nanoparticles: Synthesis,Characterization, and Antiviral Activity

Anionic carbosilane dendrons decorated with sulfonate functions and one thiol moiety at the focal point have been used to synthesize water‐soluble gold nanoparticles (AuNPs) through the direct reaction of dendrons, gold precursor, and reducing agent in water, and also through a place‐exchange reaction. These nanoparticles have been characterized by NMR spectroscopy, TEM, thermogravimetric analysis, X‐ray photoelectron spectroscopy (XPS), UV/Vis spectroscopy, elemental analysis, and zeta‐potential measurements. The interacting ability of the anionic sulfonate functions was investigated by EPR spectroscopy with copper(II) as a probe. Different structures and conformations of the AuNPs modulate the availability of sulfonate and thiol groups for complexation by copper(II). Toxicity assays of AuNPs showed that those produced through direct reaction were less toxic than those obtained by ligand exchange. Inhibition of HIV‐1 infection was higher in the case of dendronized AuNPs than in dendrons.     

Label-free colorimetric sensing of ascorbic acid based on Fenton reaction with unmodified gold nanoparticle probes and multiple molecular logic gates

A label-free strategy based on Fenton reaction with unmodified gold nanoparticles (AuNPs) as probe is demonstrated for ascorbic acid (AA) sensing. AuNPs is stable in the presence of single stranded DNA (ssDNA) which prevents salt-induced aggregation of AuNPs in solution. The hydroxyl free radicals generated by Fenton reaction lead to ssDNA cleavage into different sequence fragments which induce aggregation of AuNPs to produce a red-to-blue color change. As an efficient biological antioxidant, AA could effectively scavenge free radicals to avoid the cleavage of ssDNA, so that it prevents color change of the AuNPs solution. Thus, the color change of AuNPs in the presence and absence of AA provides a new approach for the detection of AA. The absorbance ratio at two wavelengths, A₆₇₀/A₅₂₀, decreases linearly with AA content within 1–15 μM, giving rise to a detection limit of 0.3 μM and a RSD of 2.8% (10 μM). The color display of AuNPs solution makes it feasible for the estimation of AA content by naked eye visualization. Moreover, based on Fenton reaction and unmodified gold nanoparticles, a multiple logic gate system includes two logic operations, i.e., INHIBIT and NOR, has been designed with small molecules (AA, l-cysteine, glutathione) as inputs and the colorimetric changes of AuNPs solution as outputs.     

Direct electrochemical detection of kanamycin based on peroxidase-like activity of gold nanoparticles

An enzyme-free, ultrasensitive electrochemical detection of kanamycin residue was achieved based on mimetic peroxidase activity of gold nanoparticles (AuNPs) and target-induced replacement of the aptamer. AuNPs which were synthesized using tyrosine as a reducing and capping agent, exhibited mimetic peroxidase activity. In the presence of kanamycin-specific aptamer, however, the single-stranded DNA (ssDNA) adsorbed on the surface of AuNPs via the interaction between the bases of ssDNA and AuNPs, and therefore blocked the catalytic site of AuNPs, and inhibited their peroxidase activity. While in the presence of target kanamycin, it bound with the adsorbed aptamer on AuNPs with high affinity, exposed the surface of AuNPs and recovered the peroxidase activity. Then AuNPs catalyzed the reaction between H₂O₂ and reduced thionine to produce oxidized thionine. The latter exhibited a distinct reduction peak on gold electrode in differential pulse voltammetry (DPV), and could be utilized to quantify the concentration of kanamycin. Under the optimized conditions, the proposed electrochemical assay showed an extremely high sensitivity towards kanamycin, with a linear relationship between the peak current and the concentration of kanamycin in the range of 0.1–60 nM, and a detection limit of 0.06 nM. Moreover, the established approach was successfully applied in the detection of kanamycin in honey samples. Therefore, the proposed electrochemical assay has great potential in the fields of food quality control and environmental monitoring.     

Topochemical synthesis and catalysis of metal nanoparticles exposed on crystalline cellulose nanofibers

Topochemical synthesis of gold nanoparticles (AuNPs) was achieved on crystalline cellulose single nanofibers (CSNFs), which were tailored from native cellulose. Exposed AuNPs@CSNFs composite exhibited an excellent catalytic efficiency: the turnover frequency of the AuNPs@CSNFs was up to 840 times that of conventional polymer-supported AuNPs, for a model aqueous reduction reaction. Our novel strategy provides a promising solution to realize efficient use of limited noble metals using natural bioresources.     

Small Size Effect and Concentration Response of Gold Nanoparticles in Electrochemiluminescence Reaction

Recent reports have used gold nanoparticles (AuNPs) as a co‐reactant for the electrochemiluminescence (ECL) reaction of ruthenium complex. However, understanding the size effect of AuNPs on ECL reaction is very meaningful to explore its unknowns and develop its applications at the molecular level. In this paper, we examined the behavior of various small‐size AuNPs in ECL reaction, focusing on changes in ECL caused by AuNPs size and reasons for this change. Although the luminescence spectra and excitation potential have hardly changed in ECL reaction, the difference of ECL intensities induced by different sizes AuNPs is very obviously. Our experimental results revealed disparate behaviors depending on AuNPs size: the small‐sized AuNPs can lead to stronger ECL, and ECL intensities increase as the addition of AuNPs concentration in the wider range. This small size effect is related to an intermediate process of charge‐discharge in electric double layer formed by adsorbing ruthenium complex with AuNPs, and the surface and quantum size effect of AuNPs may affect this intermediate process. More importantly, AuNPs can act as a marker, has the same small size effect and concentration response, and bring about a promising platform for biochemical analysis.     

金纳米粒子的细胞毒性

金纳米粒子(AuNPs)是构建用于诊断和治疗的纳米药物/探针的理想纳米材料之一,因此研究AuNPs与细胞的相互作用具有重要意义。 本文详细分析了金纳米簇(AuNCs)、球形金纳米粒子A(AuNPss)、金纳米球壳(AuNSs)和金纳米棒(AuNRs)等不同形貌的Au NPs对不同细胞模型的细胞毒性;讨论了AuNPs的理化性质(大小、形状、化学功能和表面电荷)对其细胞毒性的影响。 总结了AuNP细胞毒性研究遇到的挑战并提出相应解决方法。     

Gold nanoparticles incarcerated in nanoporous syndiotactic polystyrene matrices as new and efficient catalysts for alcohol oxidations

The controlled synthesis of gold nanoparticles (AuNPs), incarcerated in a semicrystalline nanoporous polymer matrix that consisted of a syndiotactic polystyrene-co-cis-1,4-polybutadiene multi-block copolymer is described. This catalyst was successfully tested in the oxidation of primary and secondary alcohols, in which we used dioxygen as the oxidant under mild conditions. Accordingly, (±)-1-phenylethanol was oxidised to acetophenone in high yields (96%) in 1 h, at 35 °C, whereas benzyl alcohol was quantitatively oxidised to benzaldehyde with a selectivity of 96% in 6 h. The specific rate constants calculated from the corresponding kinetic plots were among the highest found for polymer-incarcerated AuNPs. Similar values in terms of reactivity and selectivity were found in the oxidation of primary alcohols, such as cinnamyl alcohol and 2-thiophenemethanol, and secondary alcohols, such as indanol and α-tetralol. The remarkable catalytic properties of this system were attributed to the formation, under these reaction conditions, of the nanoporous ε crystalline form of syndiotactic polystyrene, which ensures facile and selective accessibility for the substrates to the gold catalyst incarcerated in the polymer matrix. Moreover, the polymeric crystalline domains produced reversible physical cross-links that resulted in reduced gold leaching and also allowed the recovery and reuse of the catalyst. A comparison of catalytic performance between AuNPs and annealed AuNPs suggested that multiple twinned defective nanoparticles of about 9 nm in diameter constituted the active catalyst in these oxidation reactions.     

溶胶-凝胶法原位复合PVA/HA水凝胶的结构表征与性能研究

采用溶胶-凝胶原位复合的方法制备了聚乙烯醇/羟基磷灰石生物活性复合水凝胶,探讨了HA含量对复合水凝胶结构性能的影响,用X射线衍射分析、红外光谱分析、DSC、扫描电镜等方法对HA在PVA水凝胶体系中的晶态结构及分散状态进行了表征,并与物理共混复合法进行了比较.研究发现,采用溶胶-凝胶法原位复合可在PVA水凝胶中形成具有生物活性的HA结晶结构,且分散良好,分布均匀.HA粉体作为异相成核剂,促进了PVA水凝胶基体的结晶,提高了复合水凝胶的力学性能.     

Gold-catalyzed cyanosilylation reaction: homogeneous and heterogeneous pathways

Gold had been considered to be an extremely inert metal, but recently it was found that nanometer-sized gold particles on metal-oxide supports acted as catalysts for simple organic reactions, such as oxidation and hydrogenation, even at or below room temperature. Herein, we report that gold nanoparticles (AuNPs) of zero oxidation state (Au0) are catalytically active for a C--C bond-forming reaction, the cyanosilylation of aldehydes. The AuNP-catalyzed cyanosilylation proceeded smoothly at room temperature with 0.2 wt % loading of AuNPs. The reactions of aromatic aldehydes were almost quantitative, except for benzaldehyde derivatives containing the electron-withdrawing NO2 group, and alpha,beta-unsaturated aromatic aldehydes were the most reactive substrates. The reactions also went smoothly for aliphatic aldehydes. Mechanistic studies indicated that the reactions proceeded both homogeneously and heterogeneously: homogeneous catalysis by leached gold species and heterogeneous catalysis by the adsorption of the reactants (aldehydes and trimethylsilyl cyanide) onto AuNPs. The ratio of homogeneous and heterogeneous catalysis was estimated to be approximately 4:1.     

金纳米粒子膜的电化学合成及SERS活性分析

Surface-enhanced Raman scattering(SERS)-active gold nanoparticles(AuNPs) films were prepared with a one-step electrochemical method. The orthogonal design was used to investigate the experimental conditions influencing the morphologies and the SERS activity of the AuNPs. A condition was found to obtain the optimal SERS activity. The SEM study reveals that the AuNPs films were composed of closely packed AuNPs. The Finite Difference Time Domain(FDTD) simulation result indicates that the coupling between particles plays an important role in the enhancement SERS of AuNPs.     

Colloids based on gold nanoparticles dispersed in castor oil: Synthesis parameters and the effect of the free fatty acid content

Herein, we present our results related to the synthesis of colloidal solutions of gold nanoparticles (AuNPs) dispersed in castor oil. These colloids were prepared via a wet chemistry process by mixing specific amounts of castor oil, ethanol, and aqueous solutions of tetrachloroauric(III) acid and sodium hydroxide. The size and shape of the AuNPs obtained could be modulated by the amount of gold source added and the Au/OH^– molar ratio used. In this study, we observed that the free fatty acid content in the reaction medium was an important parameter to be considered in the syntheses of the colloidal solutions and the respective form and shape of the AuNPs produced. Thus, we evaluated the effect of oil acidity by adding different amounts of myristic acid (MA) in the reaction medium. The colloids were characterized by UV–vis spectroscopy, and the size and shape of the AuNPs produced were characterized by transmission electron microscopy (TEM).     

Gold nanoparticles-based colorimetric and visual creatinine assay

We demonstrate a selective and sensitive method for determination of creatinine using citrate-stabilized gold nanoparticles (AuNPs) as a colorimetric probe. It is based on a direct cross-linking reaction that occurs between creatinine and AuNPs that causes aggregation of AuNPs and results in a color change from wine red to blue. The absorption peak is shifted from 520 to 670 nm. Under the optimized conditions, the shift in the absorption peak is related the logarithm of the creatinine concentration in the 0.1 to 20 mM range, and the instrumental detection limit (LOD) is 80 μM. This LOD is about one order of magnitude better than that that of the Jaffé method (720 μM). The assay displays good selectivity over interfering substances including various inorganic ions, organic small compounds, proteins, and biothiols. It was successfully employed to the determination of creatinine in spiked human urine.

The colorimetric assay for creatinine uses citrate-stabilized gold nanoparticles (AuNPs) and a direct cross-linking reaction that occurs between creatinine and AuNPs that causes aggregation of AuNPs and results in a color change from wine red to blue.

     

Ultrasensitive SERS Detection of Lysozyme by a Target‐Triggering Multiple Cycle Amplification Strategy Based on a Gold Substrate

An ultrasensitive surface enhanced Raman scattering (SERS) method has been designed to selectively and sensitively detect lysozyme. The gold chip as the detection substrate, the aptamer‐based target‐triggering cascade multiple cycle amplification, and gold nanoparticles (AuNPs) bio‐barcode Raman probe enhancement on the gold substrate are employed to enhance the SERS signals. The cascade amplification process consists of the nicking enzyme signaling amplification (NESA), the strand displacement amplification (SDA), and the circular‐hairpin‐assisted exponential amplification reaction (HA‐EXPAR). With the involvement of an aptamer‐based probe, two amplification reaction templates, and a Raman probe, the whole circle amplification process is triggered by the target recognition of lysozyme. The products of the upstream cycle (NESA) could act as the “DNA trigger” of the downstream cycle (SDA and circular HA‐EXPAR) to generate further signal amplification, resulting in the immobility of abundant AuNPs Raman probes on the gold substrate. “Hot spots” are produced between the Raman probe and the gold film, leading to significant SERS enhancement. This detection method exhibits excellent specificity and sensitivity towards lysozyme with a detection limit of 1.0×10^?15 M . Moreover, the practical determination of lysozyme in human serum demonstrates the feasibility of this SERS approach in the analysis of a variety of biological specimens.     

Graphite‐Supported Gold Nanoparticles as Efficient Catalyst for Aerobic Oxidation of Benzylic Amines to Imines and N‐Substituted 1,2,3,4‐Tetrahydroisoquinolines to Amides: Synthetic Applications and Mechanistic Study

Selective oxidation of amines using oxygen as terminal oxidant is an important area in green chemistry. In this work, we describe the use of graphite‐supported gold nanoparticles (AuNPs/C) to catalyze aerobic oxidation of cyclic and acyclic benzylic amines to the corresponding imines with moderate‐to‐excellent substrate conversions (43–100 %) and product yields (66–99 %) (19 examples). Oxidation of N‐substituted 1,2,3,4‐tetrahydroisoquinolines in the presence of aqueous NaHCO₃ solution gave the corresponding amides in good yields (83–93 %) with high selectivity (up to amide/enamide=93:4) (6 examples). The same protocol can be applied to the synthesis of benzimidazoles from the reaction of o‐phenylenediamines with benzaldehydes under aerobic conditions (8 examples). By simple centrifugation, AuNPs/C can be recovered and reused for ten consecutive runs for the oxidation of dibenzylamine to N‐benzylidene(phenyl)methanamine without significant loss of catalytic activity and selectivity. This protocol “AuNPs/C+O₂” can be scaled to the gram scale, and 8.9 g (84 % isolated yield) of 3,4‐dihydroisoquinoline can be obtained from the oxidation of 10 g 1,2,3,4‐tetrahydroisoquinoline in a one‐pot reaction. Based on the results of kinetic studies, radical traps experiment, and Hammett plot, a mechanism involving the hydrogen‐transfer reaction from amine to metal and oxidation of M‐H is proposed.     

Gold nanoparticles prepared by glycinate ionic liquid assisted multi-photon photoreduction

We have successfully prepared gold nanoparticles (AuNPs) with flower-like and spherical morphology through multi-photon photoreduction (MPR) of an aqueous solution of HAuCl(4) and (2-hydroxyethyl) trimethylammonium glycinate ([HETMA][Gly]) ionic liquid (IL) through the use of a femtosecond laser. The results of (1)H NMR and UV-Vis absorption indicated that AuNPs were produced from the photoreduction of the [Gly]-Au(iii) complex. Spherical AuNPs of about 2.5 nm were obtained on the solution when irradiated for 2 h, then aggregated into flower-like AuNPs of several tens of nanometers assisted by the IL with an increase in the irradiation time. Furthermore, precipitates of spherical AuNPs with the size of around 15 nm were formed after being irradiated for 6 h. The mechanisms of the MPR reaction and controlled growth of AuNPs have also been discussed.     

One-pot aqueous phase growth of biocompatible 15-130 nm gold nanoparticles stabilized with bidentate PEG

We describe a new, single pot, aqueous phase method for synthesizing water soluble gold nanoparticles (AuNPs) over a size range of 15-130 nm. Poly(ethylene glycol)-appended thioctic acid ligands were used to control the growth rates and stabilize the AuNPs. Critical factors that enable the controlled growth of the AuNPs over this size range include the pH, the choice of reducing agent, the reaction temperature and the sequential addition of gold precursor and ligand with specific ligand-to-gold ratios. We describe the synthetic procedure in detail. Optical and structural characterization of the AuNPs was accomplished using UV-vis absorption spectroscopy, dynamic light scattering, and transmission and scanning electron microscopy.     

A sensitive and rapid UV–vis spectrophotometry for organophosphorus pesticides detection based on Ytterbium (Yb3+) functionalized gold nanoparticle

AuNPs possess oxygen-containing functional groups and strong complexation reaction with Yb3+. While oxygen-containing thiophosphate in the OPs molecule can combine with Yb³⁺ as a cross-linking molecule to produce insoluble yetterbium phosphate, resulting in the aggregation of AuNPs and great decrease in ultraviolet absorbance strength at 520 nm by ultraviolet visible (UV-vis) spectrophotometer.