One-step Synthesis of Water-dispersible ZnSe(S)-alloy Quantum Dots in the Presence of Thiol Species
Semiconductors quantum dots (QD) exhibit unique size-dependent optical properties which enable them to be considered for
biomedical applications, including diagnosis and cancer treatment. Furthermore, the synthesis of less toxic and Cd-free QDs directly in
aqueous phase assures their biocompatibility as required for nanomedicine applications. Accordingly, the present work was focused on
the direct synthesis of alloyed ZnSe(S) QDs capped with thioglycolic acid (TGA) or 3-mercaptopropionic acid (MPA) in aqueous medium
under microwave irradiation conditions. X-ray diffraction measurements suggested that as-synthesized QDs exhibited a solidsolution
like structure with an average crystallite size of 3.8 ± 0.1 nm and 2.1 ± 0.2 nm for TGA- and MPA-capped Zn-based QDs, respectively.
HRTEM measurements confirmed the small size and monodispersity of the synthesized QDs. The chemisorption of carboxylate
groups in TGA (vas COO at 1577 cm-1 and vs COO at 1388 cm-1) and MPA (vas COO at 1560 cm-1 and vs COO at 1401 cm-1) onto the
QDs was confirmed by FT-IR spectroscopy analyses. The band gap energy values were estimated at 3.1eV or 3.3eV, respectively, when
the QDs were synthesized in the presence of TGA or MPA species. QDs suspended in biocompatible Phosphate Buffer Saline (PBS) exhibited
a remarkable photo-stability; the corresponding photo-luminescence spectra recorded under 302nm excitation evidenced strong
emission peaks centered on 390nm and 395nm for TGA- and MPA-capped QDs, respectively. As-synthesized thiol-capped alloyed
ZnSe(S) QDs can be considered very promising biocompatible candidates for nanomedicine applications.
Keywords: FT-IR, nanoparticles, photoluminescence, photo-stability, quantum dots, X-Ray diffraction
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