Modern physicochemical research on Langmuir monolayers

Three- and low-dimensional inorganic semiconductors

Magnetic and conductive Fe3O4–polyaniline nanoparticles with core–shell structure

Pure polyaniline (PAN) film, polyaniline and acetic acid (AA) mixed film, as well as PAN and polystyrenesulfonic acid (PSSA) composite film with various number of layers were prepared by Langmuir–Blodgett (LB) and self-assembly (SA) techniques. These ultra-thin films were characterized by ultraviolet–visible (UV–VIS) spectroscopy and ellipsometry. It is found that the thickness of PAN-based ultra-thin films increases linearly with the increase of the number of film layers. The gas-sensitivity of these ultra-thin films with various layers to NO 2 was studied. It is found that pure polyaniline films prepared by LB technique had good sensitivity to NO 2 , while SA films exhibited faster recovery property. The response time to NO 2 and the relative change of resistance of ultra-thin films increased with the increase of the number of film layers. The response time of three-layer PAN film prepared by LB technique to 20 ppm NO 2 was about 10 s, two-layer SA film was about 8 s. The mechanism of sensitivity to NO 2 of PAN-based ultra-thin films was also discussed.

Fabrication and characterization of polyaniline-based gas sensor by ultra-thin film technology

The structures of Langmuir–Blodgett films of fatty acids and their salts

Formation of a stable monolayer of polyaniline (EB) at the air−water interface has been obtained, employing N-methylpyrrolidone (NMP) as processing solvent. Surface pressure−mean molecular area isotherm and compressibility of the polyaniline monolayer were studied under different subphase conditions such as the subphase temperature, the subphase pH, and the nature of counterions in the subphase. The mean molecular area found and compressibility results have been interpreted in terms of the rigidity of the polymer chains at the air−water interface. Further, polyaniline monolayers have been transferred onto different substrates and the multilayers were characterized by spectroscopic, electrical, and electrochemical techniques. The Langmuir−Blodgett multilayers were also deposited at different surface pressures. The transfer behavior and the electrochemical characteristics of these films indicate differences in their packing arrangement.

A Study of Langmuir and Langmuir−Blodgett Films of Polyaniline

Structure of CdS nanoparticles containing cadmium arachidate LB films

Preparation and characterization of mixed LB films of polyaniline and cadmium arachidate

Variation of monolayer behaviour and molecular packing in zinc arachidate LB films with subphase pH

A composite multilayer consisting of semiconducting CdS distributed in Cd-arachidate/arachidic acid layers was prepared by exposing the precursor Cd-arachidate multilayers to H 2 S. The structures of the precursor multilayers and the modified multilayers were studied by grazing incidence reflection/diffraction using X-rays from a conventional generator and a synchrotron source. The formation of CdS in arachidic acid/Cd-arachidate composite multilayers resulted in the introduction of a new layered structure with a period of 4.37 nm compared to the precursor multilayer period of 5.55 nm. The reduction in the period of the multilayers is consistent with the observation of a tilted structure found in alkanethiol and H 2 S exposed Cd-stearate multilayers. The lateral morphology ofCdS which is replicated between the successive layers in the vertical direction is different when compared to the head group morphology in the precursor multilayer. The molecular arrangement in the plane of the Cd-arachidate precursor multilayer is found to be orthorhombic while the CdS molecules in the modified multilayer are arranged in a hexagonal array. The lateral size of the CdS domains/particles is found to be 13 nm, at least an order of magnitude greater than the layer thickness. This clearly indicates that the CdS particles are quasi-2D in nature and are disk shaped.

A. Dhanabalan

Papers

A Study of Langmuir and Langmuir−Blodgett Films of Polyaniline

Structure of CdS nanoparticles containing cadmium arachidate LB films

Preparation and characterization of mixed LB films of polyaniline and cadmium arachidate

Variation of monolayer behaviour and molecular packing in zinc arachidate LB films with subphase pH

Structure of CdS-Cd-arachidate/arachidic acid composite multilayers