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UV-vis spectra of Au particles prepared at various pH values. Figure 5. Au colloids prepared employing lysine as capping agent at pH ) 9 (Au/lysine ) 1:0.5) under ultrasonic irradiation. No Au linear aggregates appear under sonication.
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A simple and convenient method is described to produce gold nanowires. A controlled organization of Au colloids into linear assemblies was achieved without using any templates. HAuCl4 was reduced by NaBH4 in the presence of lysine to act as capping and bridging agent. At a molar ratio of Au/Lys = 1:0.5 and pH in the range 8.4−9.5, linear aggregates...
Context in source publication
Context 1
... a comparison, we prepared one sample under the same procedures except that when NaBH 4 was added to the Au precursor solution the solution was subjected to ultrasonic irradiation. A purple solution was obtained, and TEM confirmed that only discrete spherical Au colloids were formed, with particle diameters in the range 3-5 nm ( Figure 5). Clearly, the ultrasonic irradiation has a strong (dispersing) impact on the aggregation state of Au colloids. ...
Citations
... This aggregation tendency was visible also in the UV-Vis spectrum of the dye -AgNPs assembly as a slight red shift of the LSPR position. The reason for this behaviour is attributed to TC molecules adsorbed on NP surfaces in J-aggregate forms, which are involved in the interlinking of metal NPs(Zhong et al. 2004). ...
... Investigations have also revealed that nanostructure morphology plays a pivotal role in inducing SERS exertion. Noble metal nanostructures, including nanostars, nanofilms, nanocarpets, nanorods and hollow or solid nanocubes, have been synthesized for investigation in this direction [146][147][148][149] . However, noble metal and semiconductornoble-metal hybrid nanomaterials have several limitations making them undesirable for a variety of biomedical applications. ...
... In other words, in the case without sonication, large Au particles and low deposition efficiency will be obtained. In addition, when the solution pH value is close to the isoelectric point (IEP) of the catalyst support, the electrostatic repulsion between the Au colloids and the catalyst support such as TiO 2 (with IEP about 6) becomes weak, which will facilitate deposition of Au colloids [14,15]. Based on the finding, we invented a sonication-assisted precipitation-reduction for preparation of supported Au catalysts on a series of supports [16,17]. ...
... The large Pd particle size and wide distribution probably are related to the nature of Pd and low pH value used, because the PdCl 2 precursor is not completely dissolved in high pH aqueous solution. However, the low pH value leads to the growth of large particles due to the crosslinking of metal particles by lysine molecules [14]. it was found that the use of ethanol solvent led to the formation of larger metal particles, including Au and Pd, etc. ...
This work aims to develop a rapid and efficient strategy for preparing supported metal catalysts for catalytic applications. The sonication-assisted reduction-precipitation method was employed to prepare the heterogeneous mono- and bi-metallic catalysts for photocatalytic degradation of methyl orange (MO) and preferential oxidation (PROX) of CO in H2-rich gas. In general, there are three advantages for the sonication-assisted method as compared with the conventional methods, including high dispersion of metal nanoparticles on the catalyst support, the much higher deposition efficiency (DE) than those of the deposition-precipitation (DP) and co-precipitation (CP) methods, and the very fast preparation, which only lasts 10-20 seconds for the deposition. In the AuPd/TiO2 catalysts series, the AuPd(3:1)/TiO2 catalyst is the most active for MO photocatalytic degradation; while for PROX reaction, Ru/TiO2, Au-Cu/SBA-15 and Pt/γ-Al2O3 catalysts are very active, and the last one showed high stability in the lifetime test. The structural characterization revealed that in the AuPd(3:1)/TiO2 catalyst, Au-Pd alloy particles were formed and a high percentage of Au atoms was located at the surface. Therefore, this sonication-assisted method is efficient and rapid in the preparation of supported metal catalysts with obvious structural characteristics for various catalytic applications.
... Gold nanoparticles can self-assemble into highly anisotropic nanostructures by using biomolecules either as capping agents or as a template (amino acids, DNA, collagen) (Selvakannan 2003;Ongaro et al. 2005;Wei et al. 2007). Zwitterionic properties of amino acids have been successfully used in order to self-assemble metallic nanoparticles such as silver and gold (Gedanken et al. 2004;Zhong et al. 2004;Selvakannan et al. 2004;Shao and Dong 2004;Zhong et al. 2005;Polavarapu and Xu 2008). Their mechanism of binding is based on their ability to cap the nanoparticles either by their thiol group, a-or side-chain amine group, or a-carboxylic group. ...
... Gold nanoparticles can self-assemble into highly anisotropic nanostructures by using biomolecules either as capping agents or as a template (amino acids, DNA, collagen) (Selvakannan 2003;Ongaro et al. 2005;Wei et al. 2007). Zwitterionic properties of amino acids have been successfully used in order to self-assemble metallic nanoparticles such as silver and gold (Gedanken et al. 2004;Zhong et al. 2004;Selvakannan et al. 2004;Shao and Dong 2004;Zhong et al. 2005;Polavarapu and Xu 2008). Their mechanism of binding is based on their ability to cap the nanoparticles either by their thiol group, a-or side-chain amine group, or a-carboxylic group. ...
... Their mechanism of binding is based on their ability to cap the nanoparticles either by their thiol group, a-or side-chain amine group, or a-carboxylic group. Several methods have been reported that control the nanostructure formation (Zhong et al. 2004): using different capping agents (alkanthiols or aminoacids). Selvakannan et al. (2003Selvakannan et al. ( , 2004 reported the capping of gold nanoparticles using lysine and tryptophan as stabilizers and reducing the HAuCl4 solution using a strong reduction agent, NaBH4, and high temperature. ...
... Gold nanoparticles can self-assemble into highly anisotropic nanostructures by using biomolecules either as capping agents or as a template (amino acids, DNA, collagen) (Selvakannan 2003;Ongaro et al. 2005;Wei et al. 2007). Zwitterionic properties of amino acids have been successfully used in order to self-assemble metallic nanoparticles such as silver and gold (Gedanken et al. 2004;Zhong et al. 2004;Selvakannan et al. 2004;Shao and Dong 2004;Zhong et al. 2005;Polavarapu and Xu 2008). Their mechanism of binding is based on their ability to cap the nanoparticles either by their thiol group, a-or side-chain amine group, or a-carboxylic group. ...
... Gold nanoparticles can self-assemble into highly anisotropic nanostructures by using biomolecules either as capping agents or as a template (amino acids, DNA, collagen) (Selvakannan 2003;Ongaro et al. 2005;Wei et al. 2007). Zwitterionic properties of amino acids have been successfully used in order to self-assemble metallic nanoparticles such as silver and gold (Gedanken et al. 2004;Zhong et al. 2004;Selvakannan et al. 2004;Shao and Dong 2004;Zhong et al. 2005;Polavarapu and Xu 2008). Their mechanism of binding is based on their ability to cap the nanoparticles either by their thiol group, a-or side-chain amine group, or a-carboxylic group. ...
... Their mechanism of binding is based on their ability to cap the nanoparticles either by their thiol group, a-or side-chain amine group, or a-carboxylic group. Several methods have been reported that control the nanostructure formation (Zhong et al. 2004): using different capping agents (alkanthiols or aminoacids). Selvakannan et al. (2003Selvakannan et al. ( , 2004 reported the capping of gold nanoparticles using lysine and tryptophan as stabilizers and reducing the HAuCl4 solution using a strong reduction agent, NaBH4, and high temperature. ...
Gold nanochains/nanowires were prepared by simultaneously reducing the gold salt in the presence of stabilizing biomolecules L-aspartate and L-lysine, Collagenthat acts as capping agent and as a template in the formation of two-dimensional gold nanostructures. L-aspartate and L-lysine were used in order to form nanochains due to their ability to cap gold nanoparticles through an oriented attachment mechanism that leads to the formation of one-dimensional nanostructures. The formation of the nanowires was controlled by reducing the gold salt onto the surface of the collagen template. Transmission electron microscopy (TEM) and x-ray powder diffraction were employed in order to demonstrate the morphological and structural properties of the nanowires. In order to provide evidence of the possible applications of gold nanostructures as biocompatible substrates for tissue engineering, mesenchymal stem cells were cultured in their presence. MTT proliferation assays, as well as immunohistochemistry assays, were performed. The experiments demonstrated that each nanostructure stimulates cell proliferation, but better results were obtained in the case of collagen. Moreover, we noticed that the nanostructures are tracked inside of the cells, most likely in the perinuclear region of the stem cells.
... The use of amino acids play important roles in the preparation of different shaped (sphere-, dumbbell-, corn-, pearl-necklace-and I-shaped) and sized silver-gold nanocomposites in the presence of cetyltrimethylammonium bromide [1]. It has been established that amino acid acts as reducing-and capping-agents for the reduction and stabilisation of metal ions (silver and/or gold) and their nanoparticles, respectively [2][3][4][5]. Amino acids are known to provide different coordination sites: at the N-, O-and S-centres that can coordinate with silver ions and with metallic nanoparticles. Sulphur has been established as the most susceptible to gain electrons from the oxidising agents [6]. ...
... As a result, the slow and irregular adsorption of methionine and/or its oxidation product occurs onto the surface of Ag particles leading to the formation of corn-shaped small-scale nanoparticles. TEM images (Figures 4 and 5) further verify that Ag nanoparticles undergo aggregation and/or cross-linking because methionine is a basic amino acid which may be responsible for such processes [2]. However, since we did not have a dynamic light scattering (DLS) spectrophotometer available, we were restricted to conditions in which the size and shape of Ag nanoparticles could be determined using TEM. ...
Conventional UV-vis spectroscopic and transmission electron microscopy methods were used to monitor the kinetics, formation and characterisation of silver nanoparticles in the methionine-promoted reduction of silver(I). The silver nanoparticles (purple colour; λmax = 550 nm) are corn-shaped and aggregated, and the average particle size is about 23 nm. The kinetics of silver nanoparticles formation has been studied as a function of [Ag(I)], [methionine] and [CTAB]. We see that [Ag(I)] has no effect on the rate of silver nanoparticles formation. At higher [CTAB] ≥ 40.0 × 10 mol dm, silver nanoparticles were not observed. Methionine is responsible for interparticle interaction, increase in aggregate size and cross-linking between the particles, and it acts as complexing, reducing, adsorbing and capping agents. A mechanism consistent with the observed kinetics has been proposed and discussed.
... Amino acids are the monomers of protein which find a large number of applications in different biochemical processes such as nutrition, metabolism, and fortification of seeds and specially in the synthesis of the advanced nanomaterials as reducing, capping and stabilizing agents12345. The kinetic and mechanistic features of a particular oxidation reaction are likely to be affected by the polar and non-polar nature of the side chain of amino acid in solution and the active species of the oxidant [6,3]. ...
a b s t r a c t In this paper we report the effect of cationic micelles of cetyltrimethylammonium bromide (CTAB) in the oxidation of valine by permanganate in the absence and presence of sulphuric acid media. The reac-tion follows fractional-and first-order kinetics with respect to [valine] and [H 2 SO 4 ] in the presence of CTAB whereas [H 2 SO 4 ] has no effect on the reaction rate in the absence of CTAB under our experimental conditions. The observed catalytic effect of CTAB is discussed in terms of penetration of non-polar side chain of valine into the palisade layer of CTAB micelles through hydrophobic interactions. The Menger and Portony model of micelles and the model modified by Bunton's group have been used to explain the catalytic role of CTAB. On the basis of various observations, the most plausible mechanism is proposed and discussed.
... Because amino acids can contain a range of functional groups (e.g., COOH, OH, NH 2 , and SH), they should interact differently with silver and gold ions and with metallic nanomaterials. Gold nanowires (NWs) have been prepared previously in the presence of lysine (Lys) [20]. At a Au/Lys molar ratio of 1:0.5 and at values of pH within the range 8.4-9.5, linear aggregates of Au were prepared having diameters of about 5 nm and variable lengths (80-200 nm). ...
... The key factor for formation of Au NWs is the balance between the attractive (cross-linking) force, provided by Lys units, working against the electrostatic repulsion of the Au-Ag nanocomposites, whose surfaces bear negative charges (see below) [20]. In Met solution at pH 9.0 and 10.0, corn-shaped Au-Ag nanocomposites were dominant (yields > 92%), presumably due mainly to reduction of gold and silver ions by Met (which contains a sulfur atom) to form sphereshaped Au and Ag NPs [28]. ...
... It has been reported that the pH and the Lys/Au molar ratio play important roles in determining the formation of Au nanowires [20]. That study suggested that the product consists of shorter, but more thickly bound, Au NWs at pH 11.1 than does that formed at pH 9.0; the optimum Lys/Au molar ratio was 0.5:1. ...
In this paper, we describe an easy procedure for the preparation of differently shaped and sized Au–Ag nanocomposites from gold nanorod (AuNR) seeds in various amino acid solutions—arginine (Arg), cysteine (Cys), glycine (Gly), glutamate (Glu), glutamine (Gln), histidine (His), lysine (Lys), and methionine (Met), respectively—at values of pH ranging from 8.0 to 11.5. Our results suggest that the pH, the nature of the amino acid, and its concentration all have significant impact on the preparation of Au–Ag nanocomposites; these factors exhibit their effects mainly through control over the reducing ability of ascorbate and/or its recognition capability, as well as through control over the surface charges of the amino acids on the AuNRs. Depending on the value of pH, we were able to prepare I-shaped, dumbbell-shaped, and/or sphere-shaped Au–Ag nanocomposites in 0.1 M solutions of Arg, Gly, Glu, Gln, Lys, and Met. In His solutions at pH 8.0 and 9.0, we obtained peanut-shaped Au–Ag nanocomposites. Corn-shaped Au–Ag nanocomposites were prepared in 0.1 M Met solutions (pH 9.0 and 10.0). By controlling the Lys concentration at pH 10.0, we synthesized pearl-necklace-shaped Au–Ag nanoparticles and Au–Ag wires. Based on the TEM images, we conclude that this simple and reproducible synthetic approach allows preparation of high-quality (>87%, beside>77% in His solutions) Au–Ag nanocomposites with various shapes and sizes under different conditions.
... Recently, the amount of research on the unidirectional assembly of metal NPs without templates has increased rapidly. Zhong et al attained gold linear assembles by virtue of two amino groups of lysine binding with two Au NPs by adjusting the pH of the reactant [20], Liao et al reported Au NPs self-organized into chain-like structures in ethanol [21], and Liu and co-workers described how β-D glucose-stabilized Pt nanocrystals could self-assemble into nanowires under suitable pH conditions [22]. In the future, controlling the interparticle distances in NP chains to produce new and fascinating materials with tunable optical and electronic properties (photonic and electronic transfer along the chains depend on distance) should become an important research direction [9]. ...
... The average diameters of the Au particles observed are 7.2 ± 1.3, 5.4 ± 0.9 and 4.8 ± 0.6 nm, respectively. The result shows that the size of the particles is smaller and more controllable than that of Au NPs prepared by other wet-chemical routes [20,21]. The Au NP assemblies were found to depend on the change of the molar ratio of CA to HAuCl 4 . ...
... In theory, the form of minimal electrostatic repulsive forces of particles with the same charge should be a linear configuration in the process of NP assembly [20], thus we can change the amount of charge on the particles' surfaces by varying the environmental conditions, by which the Au NP interaction can be controlled. In our work, there are two primary factors influencing the self-assembly of Au NPs: the molar ratio of CA to HAuCl 4 and the pH of the colloidal solution. ...
In this work, a new capping agent, cinnamic acid (CA) was used to synthesize Au nanoparticles (NPs) under ambient conditions. The size of the NPs can be controlled by adjusting the concentration of reductant (in our experiment sodium borohydride was used) or CA. The CA-stabilized Au NPs can self-assemble into 'nanowire-like' or 'pearl-necklace-like' nanostructures by adjusting the molar ratio of CA to HAuCl4 or by tuning the pH value of the Au colloidal solution. The process of Au NPs self-assembly was investigated by UV–vis spectroscopy and transmission electron microscopy. The results reveal that the induced dipole–dipole interaction is the driving force of Au NP linear assemblies.
... Several physical and chemical strategies have been tested for organizing nanoparticles into defined architectures. They include template-directed synthesis, such as pore alumna-mediated hard template, (Korgel and Fitzmaurice, 1998) and polymer-mediated soft-templates (Wyrwa et al., 2002) construction using bridging molecules (Zhong et al., 2004), and self-assembly by dipole-dipole interactions between nanoparticles without template or linker (Tang et al., 2004). Silica-based nanomaterials have been intensively investigated because of their wide applications in optics, catalysts, sensors, solar energy collectors, and so on (Schatz et al., 1998). ...
Silica nanoparticles were linked by using 3-mercaptopropyltrimethoxysilane (MPS) as a coupling agent and Cd2+ as bridging ions. The TEM micrographs showed approximately linear linkage between the silica nanoparticles rather than dense packing. The UV-visible absorption spectra confirmed the formation of S-Cd-S bonds between the silica nanoparticles. The alternative films of MPS-modified SiO2 nanoparticles and Cd2+ ions were also prepared using the layer-by-layer self-assembly technique and characterized by AFM.
