Fluorescence dynamics of bovine serum albumin (BSA) conjugated CdZnS nanocrystallites

¹ Nanoscience Laboratory, Department of Physics, Tezpur University, PO Napaam, Dist. Sonitpur, Assam-784 028, India
² Laboratory for Molecular Scale Engineering, 1415 Engineering Dr., Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
³ S.N. Bose National Centre for Basic Sciences, Salt Lake, Kolkata 700 098, India

Corresponding author: best@tezu.ernet.in

Received: 12 December 2007
Revised: 1 March 2008
Accepted: 7 April 2008
Published online: 30 May 2008

Abstract

We report on the production of composite semiconductor CdZnS nanoparticles by adopting an inverse micellar route, using bis (2-ethylhexyl) sulfosuccinate (aerosol-AOT) as surfactant and with a degree of hydration w₀ = [ H₂O] : [AOT] = 8.9. Prior to bioconjugation (conjugation with bovine serum albumin (BSA)), the hydrophobic surface of the nanocrystals were made hydrophilic with thiol treatment (reacting with mercapto acetic acid). We compare photophysical nature of as prepared, thio-stabilized and bioconjugated CdZnS nanoparticles using absorption/emission spectroscopy and ultrafast photoluminescence decay measurements. The change-over from nonzero anisotropy (untreated) to zero anisotropy (bioconjugated) is assigned to the depolarized emission due to the surface reconstruction owing to BSA adsorption into the surface vacancies. Exploration of the dynamics of photophysical features would be promising for biomolecular sensing, labeling, and imaging applications.