Dr. Syed Arshad Hussain Wellcomes You


My recent paper at Elsevier Journal

Title: Preparation and characterization of an anionic dye–polycation molecular films by electrostatic layer-by-layer adsorption process

D. Dey1, S. A. Hussain1, R. K. Nath2 and D. Bhattacharjee1
1. Department of Physics, Tripura University, Suryamaninagar 799130, Tripura, India
2. Department of Chemistry, Tripura University, Suryamaninagar 799130, Tripura, India Journal: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy

Abstract:
This communication reports the formation and characterization of self-assembled films of a low molecular weight anionic dye amaranth and polycation poly(allylamine hydrochloride) (PAH) by electrostatic alternating layer-by-layer (LBL) adsorption. It was observed that there was almost no material loss occurred during adsorption process. The UV–vis absorption and fluorescence spectra of amaranth solution reveal that with the increase in amaranth concentration in solution, the aggregated species starts to dominate over the monomeric species. New aggregated band at 600 nm was observed in amaranth–PAH mixture solution absorption spectrum. A new broad low intense band at the longer wavelength region, in the amaranth–PAH mixture solution fluorescence spectrum was observed due to the closer association of amaranth molecule while tagged into the polymer backbone of PAH and consequent formation of aggregates. The broad band system in the 650–750 nm region in the fluorescence spectra of different layered LBL films changes in intensity distribution among various bands within itself, with changing layer number and at 10 bilayer LBL films the longer wavelength band at 710 nm becomes prominent. Existence of dimeric or higher order n-meric species in the LBL films was confirmed by excitation spectroscopic studies. Almost 45 min was required to complete the interaction between amaranth and PAH molecules in the one-bilayer LBL film.

Keywords: Adsorption; Deposition process; Multilayer; Layer-by-layer (LBL) self-assembled films; UV–vis absorption and fluorescence spectroscopy
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Immobilization of single strand DNA on solid support

Recently we have demonstrated the immobilization of single strand DNA onto a solid support by electrostatic interaction with a polycation poly(allylamine hydrochloride) (PAH). The films were analyzed by UV–vis spectroscopy. We have shown that single stranded DNA gets immobilized on the PAH backbone of Layer-by-Layer (LbL) films when the films are fabricated above the melting temperature of DNA. Singly stranded DNA immobilized in the LbL films is not restored into double stranded DNA at room temperature.

Read the article here at Chemical Physics Letters



Langmuir-Blodgett (LB) Films of water-soluble materials
September 11, 2007, 8:57 am
Filed under: Langmuir-Blodgett Films, Water-soluble materials

 

Ideal LB compatible material is amphiphilic molecules having a hydrophilic (water loving) head group and a hydrophobic (water hating) tale part. Due to this amphiphatic balance these types of materials float onto water.

 

However recent observation reveal that good quality LB films can be prepared using water soluble materials. Recently we prepare the LB films of water soluble CTAB. First of all a model monolayer of a suitable amphiphilic molecule was prepared on the air-water interface. Then the solution of the sample molecule was spread from the back side of tha barrier. The water-soluble sample molecules come into the contact of the molecules of the model monolayer and interacted and forms complex. Thus a complex Langmuir monolayer of water soluble material is formed. Once this complex Langmuir monolayer is formed then it is easy to form mono- and multilayer LB films of this complex monolayer (Journal of Colloid and Interface Science 311(2) (2007) 361-367).