Preparation of Ultrafine Fe-Pt Alloy and Au Nanoparticle Colloids by KrF Excimer Laser Solution Photolysis

A Mechanistic Study of the Multiple Roles of Oleic Acid in the Oil-Phase Synthesis of Pt Nanocrystals

Oleic acid (OAc) is commonly used as a surfactant and/or solvent for the oil-phase synthesis of metal nanocrystals but its explicit roles are yet to be resolved. Here, we report a systematic study of this problem by focusing on a synthesis that simply involves heating of Pt(acac)₂ in OAc for the generation of Pt nanocrystals. When heated at 80 °C, the ligand exchange between Pt(acac)₂ and OAc leads to the formation of a Pt^II -oleate complex that serves as the actual precursor to Pt atoms. Upon increasing the temperature to 120 °C, the decarbonylation of OAc produces CO, which can act as a reducing agent for the generation of Pt atoms and thus formation of nuclei. Afterwards, several catalytic reactions can take place on the surface of the Pt nuclei to produce more CO, which also serves as a capping agent for the formation of Pt nanocrystals enclosed by {100} facets. The emergence of Pt nanocrystals further promotes the autocatalytic surface reduction of Pt^II precursor to enable the continuation of growth. This work not only elucidates the critical roles of OAc at different stages in a synthesis of Pt nanocrystals, but also represents a pivotal step forward toward the rational synthesis of metal nanocrystals.

Ag@Au core-shell nanoparticles synthesized by pulsed laser ablation in water: Effect of plasmon coupling and their SERS performance

Ag@Au core-shell nanoparticles are synthesised by pulsed laser ablation in water using low energy laser pulses. The plasmon characteristics of these core-shell nanoparticles are found to be highly sensitive to the thickness of Au coating. In the synthesis, at first silver nanocolloid was prepared by ablating Ag target and then it is followed by ablation of Au target for different time durations to form Ag@Au core-shell nanostructures. The effect of plasmon-plasmon coupling on the absorption spectra is investigated by decreasing the effective distance between the nanoparticles. This is achieved by reducing the total volume of the colloidal suspension by simple evaporation of water, the solvent used. The suitability of these core-shell nanostructures for application as surface enhanced Raman scattering substrates are tested with crystal violet as probe molecules. Influence of plasmon coupling on the enhancement of Raman bands is found to be different for different bands.

Facile synthesis of gold–silver alloy nanoparticles for application in metal enhanced bioluminescence

In the present study we explored metal enhanced bioluminescence in luciferase enzymes for the first time.

Synthesis and characterization of potential iron-platinum drugs and supplements by laser liquid photolysis

Highly crystalline nanospherical iron-platinum systems were produced by 248 nm laser irradiation of a liquid precursor at different laser fluences, ranging from 100-375 mJ/cm(2). The influence of laser intensity on particle size, iron composition, and structure was systematically investigated. Different nanostructures of iron-platinum alloy and chemically disordered iron-platinum L10 phase were obtained without annealing. The prepared precursor solution underwent deep photolysis to polycrystalline iron-platinum nanoalloys through Fe(III) acetylacetonate and Pt(II) acetylacetonate. Fe(II) and Pt(I) acetylacetone decomposed into Fe(0) and Pt(0) nanoparticles. We found that the (001) diffraction peak shifted linearly to a lower angle, with the last peak shifting in opposition to the others. This caused the face-centered cubic L10 structure to change its composition according to laser fluence. The nanostructures were shown to contain iron and platinum only by energy-dispersive spectroscopy at several spots. The response of these iron-platinum nanoparticles to infrared depends on their stoichiometric composition, which is controlled by laser fluence.

Nonlinear thermo-optical properties of two-layered spherical system of gold nanoparticle core and water vapor shell during initial stage of shell expansion

Nonlinear thermo-optical properties of two-layered spherical system of gold nanoparticle core and water vapor shell, created under laser heating of nanoparticle in water, were theoretically investigated. Vapor shell expansion leads to decreasing up to one to two orders of magnitude in comparison with initial values of scattering and extinction of the radiation with wavelengths 532 and 633 nm by system while shell radius is increased up to value of about two radii of nanoparticle. Subsequent increasing of shell radius more than two radii of nanoparticle leads to rise of scattering and extinction properties of system over initial values. The significant decrease of radiation scattering and extinction by system of nanoparticle-vapor shell can be used for experimental detection of the energy threshold of vapor shell formation and investigation of the first stages of its expansion.PACS: 42.62.BE. 78.67. BF.

Self Assembly and Properties of C:WO(3) Nano-Platelets and C:VO(2)/V(2)O(5) Triangular Capsules Produced by Laser Solution Photolysis

Laser photolysis of WCl(6) in ethanol and a specific mixture of V(2)O(5) and VCl(3) in ethanol lead to carbon modified vanadium and tungsten oxides with interesting properties. The presence of graphene's aromatic rings (from the vibrational frequency of 1,600 cm(-1)) together with C-C bonding of carbon (from the Raman shift of 1,124 cm(-1)) present unique optical, vibrational, electronic and structural properties of the intended tungsten trioxide and vanadium dioxide materials. The morphology of these samples shows nano-platelets in WO(x) samples and, in VO(x) samples, encapsulated spherical quantum dots in conjunction with fullerenes of VO(x). Conductivity studies revealed that the VO(2)/V(2)O(5) nanostructures are more sensitive to Cl than to the presence of ethanol, whereas the C:WO(3) nano-platelets are more sensitive to ethanol than atomic C.

Size-controlled synthesis of colloidal gold nanoparticles at room temperature under the influence of glow discharge

Highly dispersed colloidal gold (Au) nanoparticles were synthesized at room temperature using glow discharge plasma within only 5 min. The prepared Au colloids were characterized with UV-visible absorption spectra (UV-vis), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) equipped with an energy dispersion X-ray spectrometer (EDX). UV-vis, XPS and EDX results confirmed that Au3+ ions in HAuCl4 solution could be effectively reduced into the metallic state at room temperature with the glow discharge plasma. TEM images showed that Au nanoparticles were highly dispersed. The size of colloidal Au nanoparticles could be easily tuned in the nanometer range by adjusting the initial concentration of HAuCl4 solution. Moreover, the as-synthesized Au colloids (dav = 3.64 nm) exhibited good catalytic activity for glucose oxidation. The nucleation and growth of colloidal Au particles under the influence of the plasma was closely related with the high-energy electrons generated by glow discharge plasma.