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

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. PACS. 78.55.Et II-VI semiconductors – 78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures – 78.47.+p Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter – 81.07.-b Nanoscale materials and structures: fabrication and characterization – 82.70.Uv Surfactants, micellar solutions, vesicles, lamellae, amphiphilic systems – 87.14.-g Biomolecules: types