Efficient Approaches for the Surface Modification of Platinum Nanoparticles via Click Chemistry

Soft Hybrid Nanoparticles: from Preparation to Biomedical Applications

Hybrid particles are a class of materials that include both organic and inorganic moieties at the same time and possess interesting magnetic, optical and mechanical properties. Extensive research is being carried out to develop soft hybrid nanoparticles utilizing their superparamagnetic, biodegradable and fluorescence properties and to explore their biomedical applications. This chapter discusses the important methods for the development of different types of soft hybrid nanoparticles, including polymer immobilization on preformed particles, adsorption of polymers on colloidal particles, adsorption of polymers via layer-by-layer self-assembly, adsorption of nanoparticles on colloidal particles, chemical grafting of preformed polymers, polymerization from and on to colloidal particles, click chemistry, atom-transfer radical polymerization (ATRP), reversible addition–fragmentation chain-transfer radical (RAFT) polymerization, nitroxide-mediated polymerization (NMP) and conventional seed radical polymerization. With current rapid advances in nanomedicine, colloidally engineered hybrid particles are gaining immense importance in fields such as cancer therapy, gene therapy, disease diagnosis and bioimaging. The applications of soft hybrid nanoparticles with respect to diagnosis are discussed briefly and a comprehensive account of their applications in the capture and extraction of nucleic acids, proteins and viruses is presented in this chapter.

'Click' preparation of CuPt nanorod-anchored graphene oxide as a catalyst in water

In this paper, a simple and powerful method of producing nanoparticle-anchored graphene oxide (GO) composites using a 'click' reaction is demonstrated. This method affords a facile means of anchoring of nanoparticles with various shapes and sizes on the GO. CuPt nanorods with controlled size, aspect ratio (from 1 to 11), and uniformity are synthesized. Transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy measurements are made to monitor the formation and characterize the properties of the CuPt nanorod-grafted GO composites. Their catalytic properties in the water phase are investigated using an o-phenylenediamine oxidation reaction. The results of this study clearly demonstrate that nonpolar CuPt nanorods immobilized on GO can function as a catalyst in an aqueous solution and that GO can be used as a catalytic nanorod support.

Synthesis and characterization of silica nanoparticles with well-defined thermoresponsive PNIPAM via a combination of RAFT and click chemistry

Covalent functionalization of azide-modified SiO(2) with well-defined, alkyne-terminated poly(N-isopropylacrylamide) was accomplished by the Cu(I)-catalyzed [3 + 2] Huisgen cycloaddition. The alkyne-terminated RAFT chain transfer agent was first synthesized, and then the alkyne-terminated thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) with different molecular weights were synthesized by the RAFT of NIPAM monomer. The polymerization kinetics and the evolution of number-average molecular weights (M(n)), and polydispersities (M(w)/M(n)), with monomer conversions were investigated. A copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) "grafting to" method was used to attach thermoresponsive polymers onto the exterior surface of SiO(2) nanoparticles which produced relatively high grafting density. The as-synthesized hybrid nanoparticles showed thermoresponsive behavior and were characterized by FTIR, XPS, TGA, DLS, and TEM, etc.

Versatility of alkyne-modified poly(glycidyl methacrylate) layers for click reactions

Functional soft interfaces are of interest for a variety of technologies. We describe three methods for preparing substrates with alkyne groups, which show versatility for "click" chemistry reactions. Two of the methods have the same root: formation of thin, covalently attached, reactive interfacial layers of poly(glycidyl methacrylate) (PGMA) via spin coating onto silicon wafers followed by reactive modification with either propargylamine or 5-hexynoic acid. The amine or the carboxylic acid moieties react with the epoxy groups of PGMA, creating interfacial polymer layers decorated with alkyne groups. The third method consists of using copolymers comprising glycidyl methacrylate and propargyl methacrylate (pGP). The pGP copolymers are spin coated and covalently attached on silicon wafers. For each method, we investigate the factors that control film thickness and content of alkyne groups using ellipsometry, and study the nanophase structure of the films using neutron reflectometry. Azide-terminated polymers of methacrylic acid and 2-vinyl-4,4-dimethylazlactone synthesized via reversible addition-fragmentation chain transfer polymerization were attached to the alkyne-modified substrates using "click" chemistry, and grafting densities in the range of 0.007-0.95 chains nm(-2) were attained. The maximum density of alkyne groups attained by functionalization of PGMA with propargylamine or 5-hexynoic acid was approximately 2 alkynes nm(-3). The alkyne content obtained by the three decorating approaches was sufficiently high that it was not the limiting factor for the click reaction of azide-capped polymers.