Shape-Controlled Synthesis Of Gold Nanoparticles Research Articles

Shape-controlled Synthesis of Gold Nanoparticles by a Green Approach

Shape-controlled Synthesis of Gold Nanoparticles by a Green Approach

Unraveling the Design Rules in Ultrashort Amyloid-Based Peptide Assemblies toward Shape-Controlled Synthesis of Gold Nanoparticles.

The fundamental understanding of the detailed relationship between molecular structure and material function remains a challenging task, until now. In order to understand the relative contribution of aromatic moieties and hydrophobicity of amino acid chains, we designed a library of ultrashort amyloid-like peptides based on Ar-Phe-X (where "Ar" represents different aromatic moieties and "X" represents amino acids having varied side-chain functionalities). Our research clearly indicated that the alteration in the size and hydrophobicity of the aromatic capping play a crucial role compared to the subtle change in the amino acid sequence of the dipeptide in dictating the final self-assembled structure and properties of these short peptide amphiphiles. Further, we explored our detailed understanding toward the controlled synthesis of bioinspired organic-inorganic hybrids. For the first time, we established the differential role of aliphatic and aromatic hydroxyl moieties toward the in situ shape-controlled synthesis of gold nanoparticles in three-dimensional nanostructures of hydrogels. To the best of our knowledge, it is the first report which demonstrated the formation of rectangular platonic gold nanoparticles using simple dipeptide hydrogels, exhibiting pH-dependent size control. Our study shows promising implications in bottom-up nanofabrication of next-generation nanomaterials with emergent properties.

Morphological Control of Gold Nanoparticles by Green Synthesis Using l-Tryptophan and Other Additives

This study focuses on shape-controlled synthesis of gold nanoparticles, using the green reducing agent l-Tryptophan (l-Trp), which is non-toxic and eco-friendly. This specific agent was investigated to realize certain morphology controlling effects by changing the relative growth rates among various crystal planes. Experimental samples were characterized by transmission electron microscope, UV–Vis spectrophotometer and X-ray diffraction (XRD) for size and morphological information. The effects of the specific additives of PVP ((C6H9NO) n ), CTAB (C16H33(CH3)3NBr), and KBr were examined for their morphological control individually and synergistically in this system. Hexagonal gold nanoparticles were successfully obtained via the PVP/CTAB and PVP/KBr systems. Particular amounts of PVP/KBr produced various polyhedron structures, such as cubes, and others with triangular and rhombic straight-side cross sections.

Influence of Surfactant Bilayers on the Refractive Index Sensitivity and Catalytic Properties of Anisotropic Gold Nanoparticles.

Shape-controlled synthesis of gold nanoparticles generally involves the use of surfactants, typically cetyltrimethylammonium (CTAX, X = Cl(-) , Br(-)), to regulate the nucleation growth process and to obtain colloidally stable nanoparticles. The surfactants adsorb on the nanoparticle surface making further functionalization difficult and therefore limit their use in many applications. Herein, the influence of CTAX on nanoparticle sensitivity to local dielectric environment changes is reported. It is shown, both experimentally and theoretically, that the CTAX bilayer significantly reduces the refractive index (RI) sensitivity of anisotropic gold nanoparticles such as nanocubes and concave nanocubes, nanorods, and nanoprisms. The RI sensitivity can be increased by up to 40% by removing the surfactant layer from nanoparticles immobilized on a solid substrate using oxygen plasma treatment. This increase compensates for the otherwise problematic decrease in RI sensitivity caused by the substrate effect. Moreover, the removal of the surfactants both facilitates nanoparticle biofunctionalization and significantly improves their catalytic properties. The strategy presented herein is a simple yet effective universal method for enhancing the RI sensitivity of CTAX-stabilized gold nanoparticles and increasing their potential as transducers in nanoplasmonic sensors, as well as in catalytic and biomedical applications.

A simple shape-controlled synthesis of gold nanoparticles using nonionic surfactants

Green and simple synthesis strategies have gained tremendous popularity for the production of anisotropically-shaped noble metallic nanoparticles. The long-term stability of the produced particles, the short timescale of the target reaction(s), as well as the use of non-toxic chemicals, are pivotal features of a useful green procedure. Herein we describe a simple and convenient wet-chemical approach to synthesize stable, non-toxic and water-soluble small gold nanotriangles (GNTs) and gold nanospheres (GNSs) in one step at room temperature, using Tween 20 and Tween 80, respectively. A high level of purity and monodispersity was obtained for the GNTs, in addition to an excellent colloidal stability of both GNTs and GNSs in media exhibiting a high ionic strength and over a wide pH range. The presented strategy, which exploits the dual functional properties of Tween as a co-reducing and stabilizing agent, eliminates the presence of hazardous chemicals such as toxic surfactants, hazardous organic solvents and harsh reducing agents during the synthesis process, and hence could pave the way for the facile usage of the spherical and triangular gold nanoparticles for clinical or biological applications. The resulted particles were characterized by UV-Vis spectroscopy, dynamic light scattering and transmission electron microscopy.

Carbon-Nanotube-Guiding Oriented Growth of Gold Shrubs on TiO2 Nanotube Arrays

Shape-controlled synthesis of gold nanoparticles is common, while the crystal growth of dendritic gold architectures is rare, especially the perpendicular growth of shrub-like gold crystals on substrate. Herein, a simple potential-static electrodeposition method was developed to fabricate shrub-like gold nanostructures on TiO2 nanotube (NT) arrays assisted by acidified carbon nanotubes (CNTs). Au crystals were electro-stacked along the electric field lines that are perpendicular to the TiO2 substrate, constructing beautiful shrubs on TiO2 NT arrays. In this process, the acidified CNTs with rich electrons attract Au3+ through electric attraction and work as primers guiding the Au growth along the direction of the electric field. The Au shrubs are single crystalline with intertwined symmetrical nanostructures. The as-prepared Au shrub/TiO2 NTs exhibited a more sensitive response in sensing highly toxic As3+ than Au films due to the higher surface area and unique three-dimensional structures.

Shape-Controlled Synthesis of Gold Nanoparticles Under UV Irradiation in the Presence of Poly(Ethylene Glycol)

Dendritic gold nanoparticles and triangular gold plates were synthesized via a simple photochemical reduction protocol. The shape of nanoparticles depended on the concentration of poly(ethylene glycol), which was used on the preparation in an aqueous solution. On the other hand, the size of nanoparticles was controlled by the duration of UV irradiation. The mechanism of morphology variation was discussed. Keywords: Gold nanoparticle, dendritic gold nanoparticle, triangular gold plate, photochemical reduction, poly(ethylene glycol), UV irradiation

Shape-controlled Synthesis of Gold Nanoparticles from Gold(III)-chelates of β-diketones

Chelating ligands with β-diketone skeleton have been employed for the first time as reductant to produce ligand stabilized gold nanoparticles of different shapes out of aqueous HAuCl4 solutions. Evolution of stable gold nanoparticles happens to be first order with respect to gold particles having rate constants ∼ ∼10−2 min−1 and subsequent chlorine insertion in the β-diketone skeleton is reported as a general feature. Spherical or triangular or hexagonal particle evolution goes selectively under the influence of different β-diketones in terms of capping and reducing capabilities of the reductants.

A Novel Ultraviolet Irradiation Technique for Shape-Controlled Synthesis of Gold Nanoparticles at Room Temperature

Shape-controlled gold nanoparticles were synthesized using a novel ultraviolet irradiation technique at room temperature. The very slow ultraviolet irradiation photoreduction process may favor the formation of the shaped gold nanoparticles. It was found that not only the concentration of gold cations and the irradiation time but also the concentration and the species of polymer capping materials play important roles in the morphology control of the gold nanoparticles.