Formation Of Gold Nanoplates Research Articles

Investigation on the Growth Process of Gold Nanoplates Formed by Seed Mediated Growth Method

Gold nanostructures have unique surface plasmon resonance (SPR) properties and it is widely used in photolectronic and sensing applications. In this study, gold nanostructures focusing on gold nanoplates have been fabricated on the quartz substrate using seed mediated growth method (SMGM). The SMGM consists of two processes which are seeding process and growth process. The effect of growth time during growth process on the formation of gold nanoplates on substrate surface was studied. The growth time was varied from 30minutes to 18hours to observe its density and optical properties on the substrate surface. The XRD analysis shows two peaks occurs at the plane (111) in position ∼ 38.2° and plane (200) at ∼ 44.3°. Through variation of the growth time, the optimum surface density is 93.5% with a total of 59.4% of the nanoplates shape from 5hours growth time sample. The optical absorption spectrum of the sample shows two resonance peaks, ∼ 558nm and 675nm, which are corresponding to the transverse surface plasmon resonance (t-SPR) and the longitudinal surface plasmon resonance (l-SPR) respectively. Hence, it is found that the growth time affected the formation of the gold nanostructures. Longer growth period caused an increase in the formation of gold nanorods instead of gold nanoplates.

Simple and rapid green synthesis of micrometer scale single crystalline gold nanoplates using chitosan as the reducing agent

A simple, rapid and green chemical method for the synthesis of single crystalline gold nanoplates of several micrometeres in size has been demonstrated. The synthesis involved the reduction of HAuCl4 in aqueous solution using low molecular weight chitosan at boiling temperature for 25min. The [Au3+]:[chitosan] molar ratio plays an important role in the formation of gold nanoplates and found that an optimized molar ratio in the range of 80 to 125 was suitable for the formation of nanoplates. The size and morphology of the nanoplates can be tuned by adjusting the molar ratio. In this process, the chitosan functions both as a reducing as well as a stabilizing agent and no other special agents were added to induce the nanoplate formation. The obtained nanoplates were single crystals with (111) planes as the basal planes with shapes of hexagonal, triangular, or truncated triangular plates.

UV irradiation induced formation of single-crystal gold nanonetworks with controllable pore distribution

Single-crystal gold nanonetworks and nanoplates with novel porous structures were synthesized through a continuous UV irradiation method. The structures of the porous nanonetworks and the nanoplates were found to be citric acid concentration dependent. Transmission electron microscopy (TEM) showed that the two-dimensional (2-D) nanonetworks prepared at the lower citric acid concentration (0.5 mM) had irregular pores and bigger area. Increasing the citric acid concentration resulted in formation of gold nanoplates with hexagonal, triangular or truncated triangular pores. When the acid concentration came to 2 mM, the nanoplates with single and double pores were observable. The selected area electron diffraction (SAED) patterns showed that both the nanonetworks and porous nanoplates were single-crystal. The presence of 1/3{4 2 2} reflections indicated that the surface of the gold nanonetwork and nanoplates is atomically flat.

Submicrometre scale single-crystalline gold plates of nanometre thickness: synthesisthrough a nucleobase process and growth mechanism

Synthesis of submicrometre scale single-crystalline gold plates of nanometrethickness in the presence of nucleobase guanine through chemical reduction ofHAuCl4 was investigated. The elemental composition of the as-prepared gold nanoplates wasestimated using energy-dispersive x-ray spectroscopy. The as-prepared gold plates werecomposed of essentially (111) lattice planes, as revealed by both x-ray diffraction (XRD)and transmission electron microscopy (TEM) results. It was found that the molar ratio ofHAuCl4 to guanine played a very important role in the formation of goldnanoplates. Gold nanoplates could be produced at a molar ratio of[HAuCl4]/[guanine] = 50:1 while only smaller gold spherical nanoparticles were obtained at molar ratios of[HAuCl4]/[guanine]≤20:1. A possible growth mechanism of the as-prepared gold nanoplates is proposed anddiscussed. The results and conclusion presented in this work may be valuablefor our further understanding of the roles of precursor ligands in the control ofnanoparticles aggregation states and the preparation of shape-controlled nanoparticles.

Effects of Alkylated Polyethylenimines on the Formation of Gold Nanoplates

Mono- and dialkylated polyethylenimines (PEI-1R and PEI-2R) were used for the facile synthesis of gold nanoplates with a preferential growth direction along the Au (111) plane. It was found that polymer hydrophobicity greatly influenced the nanoparticle morphology. PEI-1R in the acidic aqueous solution with a smaller degree of alkylation effectively adsorbed on the surface of gold nanoplates with the protonated ethylenimine groups rather than being aggregated in the bulk aqueous phase to form polymer aggregates as compared to the situation for PEI-2R. Loose alkylated PEI aggregates in acidic solution promote the formation of gold nanoplates by means of the anion-induced cation adsorption on certain crystallographic facets during the growth of gold particles. Without incorporating alkyl groups, however, the TEM image of the gold colloid solution with PEI showed only the formation of spherical gold nanoparticles by the same process. The morphology of gold nanoparticles was tuned not only by varying the degree of alkylation of PEI samples but also by the solvent type and pH value of the solution. By utilizing differently alkylated PEIs as reducing agents, this facile synthetic procedure can selectively result in the formation of gold nanoplates at room temperature without an extra inducing process.

Formation of Gold Nanoplates on Indium Tin Oxide Surfaces and the Electrochemical Applications

not Available.

Formation of Gold Nanoplates on Indium Tin Oxide Surface: Two-Dimensional Crystal Growth from Gold Nanoseed Particles in the Presence of Poly(vinylpyrrolidone)

The crystal growth of a two-dimensional plate structure of Au that covers the indium tin oxide (ITO) surface has been realized for the first time through liquid-phase reduction from Au nanoseed particles attached to the ITO surface in the presence of poly(vinylpyrrolidone) (PVP). By control of the concentration of PVP in the growth process, the formation of Au nanoplates was possible with surface coverage as high as 30%, although various shaped Au nanocrystals were concurrently formed on ITO. The Au nanoplates were single crystalline in nature with the (111) basal plane and the edge length of up to ca. ∼2 μm, growing parallel to the surface of ITO. The concentration of PVP in the growth solution was a key factor for the formation of Au nanoplates, because at higher or lower concentrations of PVP the purely spherical or irregular-shaped nanoparticles were formed. The absorption spectra implied anisotropic and specific optical characteristics of the Au nanoplate-attached ITO.

Optimization of High‐Yield Biological Synthesis of Single‐Crystalline Gold Nanoplates.

AbstractFor Abstract see ChemInform Abstract in Full Text.

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%.