Abstract
Anatase nanoparticles synthesized by the sol-gel method were surface-functionalized with long alkyl chain coupling agents as compatibilizers for a nonpolar environment, containing different anchor groups for surface interaction namely phosphonate (dodecyl phosphonate), carboxylate (dodecanoic acid), sulfate (sodium dodecyl sulphate), and amine (dodecyl amine). It was shown that the surface of the nanoparticles can be functionalized with the various surface groups applying similar reaction conditions. The kind of surface interaction was analyzed applying FTIR spectroscopy. The phosphonate and the carboxylate groups interact with the surface via quite strong covalent or coordinative interactions, respectively. The sulfate and amine based coupling agents on the other hand exhibit electrostatic interactions. UV stability studies of the surface bound groups revealed different degradation mechanisms for the various functionalities and moreover showed that phosphonates are the most stable among the investigated surface capping groups.
Highlights
Semiconductor photocatalysis represents a versatile tool for the removal of pollutants from water and air and has gained considerable interest in the field of Green Chemistry in recent decades [1,2,3,4].Titanium dioxide nanoparticles have been applied extensively for this purpose, because their band gap energy and the redox potentials of the photo-generated electrons and holes allow the degradation of organic pollutants upon illumination with solar light
Titania nanoparticles were prepared by the hydrolysis and condensation of titanium isopropoxide under highly acidic conditions achieved by addition of nitric acid according to Choi et al [30]
Particle size of the titania nanoparticles was investigated using dynamic light scattering (DLS) from the dried sample redispersed in water
Summary
Titanium dioxide nanoparticles have been applied extensively for this purpose, because their band gap energy and the redox potentials of the photo-generated electrons and holes allow the degradation of organic pollutants upon illumination with solar light. Anatase is generally accepted to exhibit highest photocatalytic activity among the crystalline phases of titanium dioxide [4,5]. The modification of metal oxide nanoparticles with organic ligands, coupling agents and surfactants is a hot topic these days [8]. A large variety of investigations have been conducted in the past regarding the adsorption of surfactants to metal oxides for specific interaction with molecules or materials, to prevent agglomeration or to induce self-organization [9]. There are many discussions about the mechanism of interaction of ionic surfactants to the metal oxide nanoparticles. The factors that are important in surface-functionalization of metal oxides with the above mentioned organic compounds are pH conditions and surface properties of the metal oxides
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