Growth of TiO<SUB>2</SUB> nanoparticles in thermally evaporated fatty amine thin films by a method of ion entrapment

The synthesis of titania nanoparticles within thermally evaporated octadecylamine (ODA) thin films is described. Synthesis of the nanoparticles was achieved by electrostatically entrapping TiF62&#8722; ions in thin films of the fatty amine by a simple immersion technique followed by in-situ hydrolysis of the metal ions. Without any further heat treatment, it was observed that titania nanoparticles of the brookite polymorph were formed within the film. By this simple procedure, uniformly distributed fairly monodisperse titania nanoparticles of ca. 4 nm diameter were synthesized within the lipid matrix and investigated using a host of techniques

Phase transfer of platinum nanoparticles from aqueous to organic solutions using fatty amine molecules

In this report we demonstrate a simple process based on amine chemistry for the phase transfer of platinum nanoparticles from an aqueous to an organic solution. The phase transfer was accomplished by vigorous shaking of a biphasic mixture of platinum nanoparticles synthesised in an aqueous medium and octadecylamine (ODA) in hexane. During shaking of the biphasic mixture, the aqueous platinum nanoparticles complex via either coordination bond formation or weak covalent interaction with the ODA molecules present in the organic phase. This process renders the nanoparticles sufficiently hydrophobic and dispersible in the organic phase. The ODA-stabilised platinum nanoparticles could be separated out from hexane in the form of a powder that is readily redispersible in weakly polar and non-polar organic solvents. The ODA-capped platinum nanoparticles show high catalytic activity in hydrogenation reactions and this is demonstrated in the efficient conversion of styrene to ethyl benzene. The nature of binding of the ODA molecules to the platinum nanoparticles surface was characterised by thermogravimetry, transmission electron microscopy (TEM), X-ray photoemission spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR)

Formation of platinum nanoparticles at air–water interfaces by the spontaneous reduction of subphase chloroplatinate anions by hexadecylaniline Langmuir monolayers

The one-step electrostatic complexation, reduction of aqueous chloroplatinate ions, and capping of the platinum nanoparticles thus formed by hexadecylaniline Langmuir monolayers is described. The capping of the platinum nanoparticles formed spontaneously at the air–water interface by hexadecylaniline enables their facile transfer as multilayers onto suitable solid substrates by the Langmuir–Blodgett technique. The real-time reduction of the aqueous chloroplatinate ions at the air–water interface was followed by measurement of the pressure–area isotherms, while the multilayer Langmuir–Blodgett films were characterized by quartz crystal microgravimetry, transmission electron microscopy, electron diffraction, and X-ray photoemission spectroscopy

Synthesis of aqueous Au core-Ag shell nanoparticles using tyrosine as a pH-dependent reducing agent and assembling phase-transferred silver nanoparticles at the air-water interface

We demonstrate that the amino acid tyrosine is an excellent reducing agent under alkaline conditions and may be used to reduce Ag+ ions to synthesize stable silver nanoparticles in water. The tyrosine-reduced silver nanoparticles may be separated out as a powder that is readily redispersible in water. The silver ion reduction at high pH occurs due to ionization of the phenolic group in tyrosine that is then capable of reducing Ag+ ions and is in turn converted to a semi-quinone structure. These silver nanoparticles can easily be transferred to chloroform containing the cationic surfactant octadecylamine by an electrostatic complexation process. The now hydrophobic silver nanoparticles may be spread on the surface of water and assembled into highly ordered, linear superstructures that could be transferred as multilayers onto suitable supports by the versatile Langmuir-Blodgett technique. Further, tyrosine molecules bound to the surface of Au nanoparticles through amine groups in the amino acid may be used to selectively reduce silver ions at high pH on the surface of the Au nanoparticles, thus leading to a simple strategy for realizing phase-pure Au core-Ag shell nanostructures