Size Of Noble Metal Nanoparticles Research Articles

Effects of geometry and size of noble metal nanoparticles on enhanced refractive index sensitivity

Effects of geometry and size of noble metal nanoparticles on enhanced refractive index sensitivity

Continuous synthesis of TiO2-supported noble metal nanoparticles and their application in ammonia borane hydrolysis

A stabilizer-free method based on segmented flow for the continuous synthesis of TiO2 supported noble metal nanoparticles (M/TiO2-MR, M = Pd, Pt or Au) was proposed. Due to the enhanced mixing performance arising from the internal circulation in the discrete plugs, the particle size of noble metal nanoparticles could be well controlled by reducing the metal precursors with NaBH4 just in the presence of TiO2 without using any stabilizer. In comparison with the batch method, the as-prepared M/TiO2-MR had smaller noble metal particle size and better dispersity. Experimental results showed that adjusting the oil-to-water phase ratio or increasing the total volume flow rate and synthetic temperature could lead to smaller average particle size with narrower distribution. The as-prepared M/TiO2-MR possessed higher catalytic activities in the hydrolysis of ammonia borane than those prepared by the batch method, which could be ascribed to smaller noble metal nanoparticles, exposing more active sites.

Morphology, Photocatalytic and Antimicrobial Properties of TiO2 Modified with Mono- and Bimetallic Copper, Platinum and Silver Nanoparticles.

Noble metal nanoparticles (NMNPs) enhanced TiO2 response and extended its activity under visible light. Photocatalytic activity of TiO2 modified with noble metal nanoparticles strongly depends on the physicochemical properties of NMNPs. Among others, the differences in the size of NMNPs seems to be one of the most important factors. In this view, the effect of the metal’s nanoparticles size, type and amount on TiO2 photocatalytic and biocidal activity was investigated. TiO2 modified with mono- and bimetallic nanoparticles of Pt, Cu and Ag were prepared using chemical and thermal reduction methods. Obtained nanocomposites were characterized using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and diffuse-reflectance spectroscopy (DR/UV-Vis) techniques. The photocatalytic activity was examined in 2-propanol oxidation and hydrogen generation processes. The mechanism of modified TiO2 excitation was evaluated in action spectrum measurements during phenol oxidation. A possibility of using less energy-consuming light sources as a set of light-emitting diodes (LEDs) selected based on action spectrum results was examined. It was found that the differences in NMNPs size were the result of the reduction method. Moreover, coupling with a second metal strongly affected and differentiated the photocatalytic and biocidal activity of the obtained TiO2-based photocatalysts.

A Review on Metallic Gold and Silver Nanoparticles

Recent developments in material synthesis involve avariety of physical and chemical approaches which has substantially influenced the field of nanotechnology. These strategies play a significant role in many prospects such as synthesis of nanoparticles of variable shapes and uniform particle size distribution. Toxic chemicals in these strategies for the synthesis of metal nanoparticles create hazardous concerns for the environment. In contrary, the biological approach includes the use of bioactive components which are highly biodegradable in nature. Hence biological approach is considered as a promising method for the eco-friendly synthesis of noble metal nanoparticles. Although these noble metal nanoparticles can be synthesised in various forms such as nano-sols, nano-colloids, nano-crystallines, nanorods, nanotubes and nanowires using a variety of physical as well as chemical approaches. Besides their shape and morphology, the size of noble metal nanoparticles should be efficiently tailored to achieve the desired medical application. The increase in surface area increases the possibility of causing the aggregation of nanoparticles which limit their functionalities. The surface functionalization of noble metal nanoparticles was done using chemical dispersants such as surfactants or polyelectrolytes to avoid the aggregation. This functionalisation improves the stability of the noble metal nanoparticles but at the same time it alters the surface chemistry of the nanoparticles. It is crucial for producing the nanoparticles in such a way that they could be size controlled, inexpensive and eco-friendly. The objective of this review is, therefore, to reveal the past and present scenarios, specifically the possibilities of noble metal nanoparticles in applications. Furthermore, it also documents the detailed information about the strategies involved in the use of plant extracts as reducing agents in the synthesis of metal nanoparticles and the incorporation of metal nanoparticles into polymeric materials for environmental applications. This review paper mainly summarizes the various synthesis methods of gold and silver nanoparticles and their applications in biomedicine.

Fabrication of Rhodium Nanoparticles with Reduced Sizes: An Exploration of Confined Spaces

The catalytic activity of supported noble metal nanoparticles (NPs) is strongly dependent on their size. However, it is still a pronounced challenge to develop a facile method to reduce the size of noble metal NPs. Here we report a facile but efficient strategy by utilizing confined spaces between templates and silica walls in as-prepared SBA-15 (AS) to regulate the size of a well-known noble metal, rhodium (Rh). Rh NPs formed in confined spaces possess obviously smaller size than their counterparts generated in traditional calcined SBA-15 (CS) without confined spaces. Our results also demonstrate that the obtained materials are highly active in CO oxidation. For a typical material 5.0RhAS containing 5.02 wt % of Rh, the complete conversion of CO is achieved at 70 °C, which is evidently lower than that of its analogue 5.0RhCS (102 °C).

Dilute cationic surfactant-assisted synthesis of polyaniline nanotubes and application as reactive support for various noble metal nanocatalysts

Well-defined and individual polyaniline (PANI) nanotubes have been synthesized by the oxidative polymerization of aniline in dilute solution in the presence of low-concentration cationic surfactant cetyltrimethylammonium bromide (CTAB). The role of the surfactant in the formation of the PANI nanostructures was discussed by changing its concentration in the reaction system, and the polymerization processes of low-concentration aniline in the dilute CTAB medium were deduced to explain the formation mechanism of the PANI nanotubes. Furthermore, noble metal (Au, Ag, Pt or Pd) nanoparticles that were supported on the as-synthesized PANI nanotubes have been achieved by utilizing the reactivity of PANI towards noble metal ions. Control over the size of noble metal nanoparticles, typical Au nanoparticles, that were uniformly supported on the surfaces of the PANI nanotubes has been realized by introducing a functional doping acid as the linkage. In addition, PANI nanotube/Au nanoparticle composites were found to serve as effective catalysts to activate the reduction of 4-nitrophenol (4NP) in the presence of NaBH4, and the size effects of the catalyst on the catalytic activity were also investigated.

Decoration of electro-reduced graphene oxide with uniform gold nanoparticles based on in situ diazonium chemistry and their application in methanol oxidation

Decorating graphene with high destiny and uniform size of noble metal nanoparticles is very important for a number of applications including sensing and electrocatalysis. Herein, a novel approach based on in situ diazonium chemistry was reported to design gold nanoparticles/graphene hybrid materials (Au-NPs/G). Graphene oxide was firstly electro-reduced on the glassy carbon electrode, and then this modified electrode was grafted by aminophenyl diazonium cations, generated in situ from p-phenylenediamine. Subsequently, gold nanoparticles (Au-NPs) were deposited on the p-phenylenediamine grafted electrode by a potentiostatic method. X-ray photoelectron spectroscopy, scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the Au-NPs/G. The results demonstrated that the Au-NPs with high destiny and uniform size were dispersed on the electro-reduced graphene oxide. In addition, the obtained Au-NPs/G was utilized in electrocatalysis toward the oxidation of methanol showing excellent catalytic activity.