Laser Irradiation Of Aqueous Solution Research Articles

Core-shell like Au-Ir nanoparticles with spatially variant electronic state of Au synthesized by femtosecond laser irradiation of solution

In this work, nanoparticles were obtained via laser-induced nucleation. Specifically, the fabrication of Au-Ir core-shell like nanoparticles was demonstrated, based on the femtosecond laser irradiation of aqueous solution of HAuCl4 and H2IrCl6. UV–vis transmission spectra showed that the metal ions were reduced and nanoparticles were generated in response to the laser irradiation of these solutions. In addition, elemental mapping by energy dispersive X-ray spectroscopy confirmed a core (Ir)-shell (Au) in which a portion of the Ir was exposed to the surface. The formation of this nanostructure is ascribed to the relative probabilities of interactions between the incident laser light and the two types of anions. Electron energy loss spectroscopy demonstrated that the electronic states in the Au region of Au7Ir3 core-shell like nanoparticles were quite different from those of pure Au nanoparticles and also exhibited spatial variations. We propose that the strain at the Au/Ir interface induced by a lattice mismatch could be responsible for the spatial variation of the electronic states.

Laser Irradiation of Aqueous Solutions for Application in Inductively Coupled Plasma Spectrometry

Laser Irradiation of Aqueous Solutions for Application in Inductively Coupled Plasma Spectrometry

Synthesis of gold nanoparticle colloids by highly intense laser irradiation of aqueous solution by flow system

Highly intense femtosecond laser irradiation of a metallic ion solution is a potential technique to produce nanoparticles of noble metals and their alloys without any reducing agents. In addition, all-proportional solid-solution alloy nanoparticles of noble metals even with immiscible nature in a multimetallic system can be easily formed in the mixed ion solution. The method has many advantages compared to conventional chemical and/or physical methods with regard to not only the simplicity of the method itself but also the purity and the controllability of alloy composition of fabricated nanoparticles. However, the productivity of a stationary production system has been limited by the volume of a glass cuvette containing ion solution. In the present study, larger-scale production by applying a flow system of ion solution was demonstrated for improving the productivity. The influence of irradiation time and repetition rate of the femtosecond laser, and flow rate of the solution on the efficiency of nanoparticles formation was studied. The flow system showed similar results with the stationary system with respect to the mechanism for the nanoparticles formation. In addition, the pulse repetition rate was effective to increase the productivity by more than 200 % compared to the stationary system.

All-proportional solid-solution Rh–Pd–Pt alloy nanoparticles by femtosecond laser irradiation of aqueous solution with surfactant

Formation of Rh–Pd–Pt solid-solution alloy nanoparticles (NPs) by femtosecond laser irradiation of aqueous solution in the presence of polyvinylpyrrolidone (PVP) or citrate as a stabilizer was studied. It was found that the addition of surfactant (PVP or citrate) significantly contributed to reduce the mean size of the particles to 3 nm for PVP and 10 nm for citrate, which was much smaller than that of the particles fabricated without any surfactants (20 nm), and improved the dispersion state as well as the colloidal stability. The solid-solution formation of the Rh–Pd–Pt alloy NPs was confirmed by the XRD results that the diffraction pattern was a single peak, which was found between the positions corresponding to each pure Rh, Pd, and Pt NPs. Moreover, all the elements were homogeneously distributed in every particle by STEM-EDS elemental mapping, strongly indicating the formation of homogeneous solid-solution alloy. Although the Rh–Pd–Pt alloy NPs fabricated with PVP was found to be Pt rich by EDS observation, the composition of NPs fabricated with citrate almost exactly preserved the feeding ratio of ions in the mixed solution. To our best knowledge, these results demonstrated for the first time, the formation of all-proportional solid-solution Rh–Pd–Pt alloy NPs with well size control.

Green and Facile Synthesis of Pd-Pt Alloy Nanoparticles by Laser Irradiation of Aqueous Solution.

Solid-solution palladium-platinum (Pd-Pt) alloy nanoparticles (NPs) with fully tunable compositions were directly fabricated through high-intensity laser irradiation of an aqueous solution of palladium and platinum ions without using any reducing agents or thermal processes. Transmission electron microscopy (TEM) observations showed that nanometer-sized particles were fabricated by laser irradiation of mixed aqueous solutions of palladium and platinum ions with different feeding ratios. The crystalline nature of the NPs was precisely characterized by X-ray diffraction (XRD). Despite the fact that, for the bulk systems, a pair of XRD peak was detected between the palladium and platinum peaks because of the large miscibility gap in the Pd-Pt binary phase diagram, only a single XRD peak was seen for the Pd-Pt NPs fabricated in the present study. Moreover, the peak position shifted from that of pure palladium towards platinum with increasing fraction of platinum ions in solution. Consequently, the interplanar spacings of the alloy NPs agreed well with the estimated values obtained from Vegard's law. These observations strongly indicate the formation of solid-solution Pd-Pt alloy NPs with fully tunable compositions. This technique is not only a "green" (environmentally-friendly) and facile process, but is also widely applicable to other binary and ternary systems.

Facile synthesis of bimetallic nanoparticles by femtosecond laser irradiation method

Bimetallic Pt–Au and Fe–Pt nanoparticles are successfully fabricated by high-intensity laser irradiation of aqueous solution without any chemical reducing agent. The mechanism of the formation of bimetallic nanoalloys by laser irradiation of the solution without using any reducing agent was mainly attributed to the optically induced decomposition of water molecule. When an intense femtosecond laser field is focused in an aqueous solution containing metal ions, the free electrons will be produced by the dissociation of water molecules, these free electrons and hydrogen radicals contained in the plasma might be caught by H+ or OH− ions to form the bubbles of H2 and O2 gases or they can be trapped by metal ions, resulting in the formation of metal atoms during the femtosecond laser irradiation process. The average size of the bimetallic nanoparticles increases with irradiation time. This technique is simple and ‘green’ process without using any chemicals except for metal salt and dispersing agent.

Synthesis of platinum-based binary and ternary alloy nanoparticles in an intense laser field

Gold–platinum–silver (Au–Pt–Ag) ion mixtures produced nanoparticle alloys with an average particle size of 5nm after co-reduction of metal ions by femtosecond laser irradiation of aqueous solutions in the presence of ammonia and polyvinylpyrrolidone, which was used as a stabilizer. Alloy formation was confirmed by analyzing the interplanar spacings measured by diffraction techniques; the interplanar spacings obtained showed good agreement with those derived from Vegard’s law. The nanoparticles had elemental composition ratios close to the molar ratios of ions in the mixed solutions, implying a high reduction yield. High-resolution transmission electron microscopy images of nanoparticles revealed that the particles were crystalline and were not phase segregated. Binary nanoparticles from Au–Pt and Ag–Pt immiscible systems were also synthesized to confirm the applicability of this method to ternary systems. The formation of nanoalloys by intense femtosecond laser irradiation was possible due to the fast reduction of the mixed ions by solvated electrons and hydrogen radicals generated in situ during irradiation.

Fabrication of solid-solution gold–platinum nanoparticles with controllable compositions by high-intensity laser irradiation of solution

In the present study, solid-solution gold–platinum (Au–Pt) nanoparticles with controllable compositions were fabricated by high-intensity femtosecond laser irradiation of an aqueous solution of gold and platinum ions without any chemicals and complicated processes. Transmittance electron microscopy revealed that the single nanometer-sized particles were fabricated by femtosecond laser irradiation of mixed aqueous solutions of gold and platinum ions. The crystalline structure of nanoparticles was characterized by electron and X-ray diffractions. Contrary to the bulk Au–Pt binary systems, which commonly contain a pair of diffraction peaks between pure gold and platinum peaks because of its large miscibility gap in phase diagram, or mixture of Au and Pt, the diffraction peaks of Au–Pt nanoparticles fabricated in the experiment showed a characteristic of the fcc-type lattice. Moreover, the diffraction patterns shifted monotonically from the peak position of pure gold to that of pure platinum as the fractions of platinum ions in the solution were increased. These observations strongly imply that the Au–Pt nanoparticles were solid solution with intended compositions. This technique is not only simple and environmentally friendly, but also applicable to other binary and ternary systems.

Pd-Partially Reduced Graphene Oxide Catalysts (Pd/PRGO): Laser Synthesis of Pd Nanoparticles Supported on PRGO Nanosheets for Carbon–Carbon Cross Coupling Reactions

This paper reports the development of a new family of highly active Pd nanoparticle catalysts supported on partially reduced graphene oxide nanosheets for carbon–carbon cross-coupling reactions. We report, for the first time, the synthesis of Pd nanoparticle catalysts supported on partially reduced graphene nanosheets (Pd/PRGO) by pulsed laser irradiation of aqueous solutions of graphene oxide and palladium ions without the use of chemical reducing or capping agents. The redox reactions initiated by the photoexcitation of GO using two 532 nm photons in different reducing environments of appropriate protic solvents (water, methanol, and ethanol) result in the formation of Pd nanoparticles with different sizes supported on the PRGO nanosheets. The laser irradiation process leads to the formation of multiple defect sites on the surface of the PRGO nanosheets which provide an excellent environment for anchoring the Pd nanoparticles, thus impeding the particles’ migration and increasing the catalyst–support in...

Fabrication of silver nanoparticles by highly intense laser irradiation of aqueous solution

Silver (Ag) nanoparticles were fabricated by highly intense femtosecond laser irradiation of aqueous solutions of silver nitrate (AgNO3) with various concentrations. After irradiation, a broad absorption peak at around 420 nm originating from surface plasmon resonance of Ag nanoparticles was observed in 30 and 300 mM solutions. Transmission electron microscopy revealed that Ag nanoparticles produced in 300 mM AgNO3 solution had a typical size in the range of 2 to 20 nm and a mean size of 4 nm. The addition of 1.0×10−2 wt% polyvinylpyrrolidone as a dispersant to the 300 mM solution caused a narrower particle size distribution as well as a narrower absorption peak width after the laser irradiation. As a result, Ag nanoparticles with a mean particle size of about 2 nm were fabricated.

3D nanotube-based composites produced by laser irradiation

3D nanocomposites have been fabricated through self-assembly under near-IR cw laser irradiation, using four types of multiwalled and single-walled carbon nanotubes produced by chemical vapour deposition, disproportionation on Fe clusters and cathode sputtering in an inert gas. The composites were prepared by laser irradiation of aqueous solutions of bovine serum albumin until the solvent was evaporated off and a homogeneous black material was obtained: modified albumin reinforced with nanotubes. The consistency of the composites ranged from paste-like to glass-like. Atomic force microscopy was used to study the surface morphology of the nanomaterials. The nanocomposites had a 3D quasi-periodic structure formed by almost spherical or toroidal particles 200–500 nm in diameter and 30–40 nm in visible height. Their inner, quasi-periodic structure was occasionally seen through surface microfractures. The density and hardness of the nanocomposites exceed those of microcrystalline albumin powder by 20% and by a factor of 3–5, respectively.

Fabrication of gold nanoparticles in intense optical field by femtosecond laser irradiation of aqueous solution

Gold particles were fabricated by the high-intensity femtosecond laser irradiation of gold (III) chloride trihydrate (HAuCl4) aqueous solution. The structure and size distribution of the prepared particles were evaluated by transmission electron microscopy. The configuration of the gold particles varied with the concentration of the HAuCl4 aqueous solution. The mean particle size and size distribution were changed by the addition of polyvinylpyrrolidone (PVP), which acted as a dispersant, and monodispersed gold nanoparticles with a diameter of about 3 nm were successfully fabricated. The formation process of the nanoparticles is discussed in terms of the optical decomposition of molecules in the highly intense optical field generated by femtosecond laser irradiation.

Preparation of Nonmetallic Silver Clusters in Aqueous Solutions Using UV Lasers

Abstract Nonmetallic silver clusters (λmax = 275 nm) were prepared by UV laser irradiation of aqueous solutions of silver perchlorate in the presence of 2-propanol and sodium polyphosphate. They were transformed into silver colloids (λmax = 380 nm) obeying second-order kinetics. Effects of added electrolytes on the kinetics were studied.

Two-photon photolysis of water and its role in two-stage photodecompositon of aqueous solutions of DNA components

It is found that as a result of high-power ultraviolet laser irradiation of aqueous solutions of nucleic acid components, the water is ionized by a two-photon mechanism. The product water radicals interact with highly excited molecules of the nucleic acid components, resulting in their decomposition.