A. B. Mandale

Investigation into the interaction between surface-bound alkylamines and gold nanoparticles

In addition to alkanethiols and phosphine derivatives, alkylamines have been investigated as capping agents in the synthesis of organically dispersible gold nanoparticles. However, reports pertaining to gold nanoparticle derivatization with alkylamines are relatively scarce and their interaction with the underlying gold support is poorly understood. In this paper, we attempt a more detailed examination of this problem and present results on the Fourier transform infrared spectroscopy, thermogravimetry, nuclear magnetic resonance, and X-ray photoemission (XPS) characterization of gold nanoparticles capped with the alkylamines laurylamine (LAM) and octadecylamine (ODA). The capping of the gold nanoparticles with the alkylamines was accomplished during phase transfer of aqueous gold nanoparticles to chloroform containing fatty amine molecules. Thermogravimetry and XPS analysis of purified powders of the amine-capped gold nanoparticles indicated the presence of two different modes of binding of the alkylamines with the gold surface. The weakly bound component is attributed to the formation of an electrostatic complex between protonated amine molecules and surface-bound AuCl4-/AuCl2- ions, while the more strongly bound species is tentatively assigned to a complex of the form [AuCl(NH2R)]. The alkylamine monolayer on the gold nanoparticle surface may be place exchanged with other amine derivatives present in solution.

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

We demonstrate the phase transfer of silver nanoparticles synthesized in an aqueous medium into hexane containing the cationic surfactant octadecylamine (ODA). During vigorous shaking of the biphasic mixture, rapid phase transfer of the silver nanoparticles into the organic phase was observed. The phase transfer of the silver nanoparticles arises due to coupling of the silver nanoparticles with the ODA molecules present in organic phase via either coordination bond formation or weak covalent interaction. This process renders the nanoparticles sufficiently hydrophobic and dispersible in the organic phase. The ODA-stabilized silver nanoparticles could be separated out from the organic phase in the form of a powder and are readily redispersible in different organic solvents. The nature of binding of the ODA molecules to the silver nanoparticle surface was characterized using UV-vis spectroscopy, thermogravimetry, transmission electron microscopy, nuclear magnetic resonance spectroscopy, X-ray photoemission spectroscopy, and Fourier transform infrared spectroscopy.

Linear Superclusters of Colloidal Gold Particles by Electrostatic Assembly on DNA Templates

The organization of nanoparticles into superstructures of predefined geometry is an important challenge in the area of nanoscale architecture. Attractive Coulombic interaction between positively charged amine groups on gold particle surfaces and negatively charged phosphate backbones of DNA molecules drives the self-assembly of gold nanoparticles into linear supercluster structures.

Attenuation length measurements in cadmium arachidate Langmuir–Blodgett films

Attenuation lengths in cadmium arachidate [(C19H39COO)2Cd] multilayer Langmuir–Blodgett films deposited on thick lead arachidate [(C19H39COO)2Pb] films have been determined in this communication. A discrete layer model appropriate to the ordered structure of these built‐up films is proposed and applied for the first time to the measurements of the x‐ray photoemission intensity variation with electron takeoff angle and attenuation lengths for 950–1350 eV electrons are evaluated. These lengths agree with earlier attenuation length measurements in Langmuir–Blodgett films and are higher than in most inorganic materials.

Glucose induced in-situ reduction of chloroaurate ions entrapped in a fatty amine film: formation of gold nanoparticle–lipid composites

The formation of gold nanoparticle–lipid composite films by glucose-induced reduction of chloroaurate ions entrapped in thermally evaporated fatty amine films is described. Simple immersion of films of the salt of octadecylamine and chloroaurate ions (formed by immersion of thermally evaporated fatty amine films in chloroauric acid solution) in glucose solution leads to the facile in-situ reduction of the metal ions to form gold nanoparticles in the fatty amine matrix. The formation of gold nanoparticles is readily detected by the appearance of a violet color in the film and thus forms the basis of a possible new, gold nanoparticle-based colorimetric sensor for glucose. The formation of the fatty amine salt of chloroauric acid and the subsequent reduction of the metal ions by glucose has been followed by quartz crystal microgravimetry, Fourier transform infrared spectroscopy, X-ray photoemission spectroscopy and transmission electron microscopy measurements.

Attenuation length measurements in lead arachidate Langmuir Blodgett films

In this paper the attenuation length measurements in lead arachidate [(C19H39COO)2Pb] Langmuir Blodgett films deposited on copper was reported on. A discrete layer model appropriate to the ordered structure of these built up films is applied to the measurements of the x‐ray photoemission intensity variation with electron takeoff angle and attenuation lengths for Pb 4f7/2, O 1s and Cu 2p3/2 electrons (kinetic energy range 550–1350 eV) are determined. There is evidence for the dependence of the attenuation length on the dielectric properties of the film/substrate interface through a variation of the film thickness.