Dr. Syed Arshad Hussain Wellcomes You


Md. N. Islam, D. Dey, D. Bhattacharjee, S. A. Hussain
International Journal of Modern Physics B 25 (2011)1905-1914.


Self-assembled films of organic dye Chicago Sky Blue 6B (CSB) have been fabricated onto solid substrate by electrostatic alternate adsorption of polycation ploy(allylamine hydrochloride) (PAH) and CSB. UV–Vis absorption spectroscopic studies reveal the successful incorporation of CSB molecules into Layer-by-Layer (LbL) films and consequent formation of aggregates. This view is supported by FTIR spectroscopic studies. Scanning electron microscope picture confirms the formation of nanocrystalline aggregates in the LbL films. About 15 min is required to complete the electrostatic interaction between PAH and CSB molecules in one bilayer LbL film.

Keywords:      Layer-by-layer (LbL) self-assembled films; adsorption; multilayer; FTIR; SEM

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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

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

SEM image of 10 layer RB-PAH LbL films

SEM image of RB-PAH LbL films