Aging studies and sensing applications of protein-templated gold nanoclusters
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Protein-templated gold nanoclusters (AuNCs) were synthesized using lysozyme VI (Lys VI), bovine serum albumin (BSA), and BSA nanoparticles (BSA NPs) as individual protein sources. Fluorescent quantum yields (Φf) were investigated over time, comparing the effect of different synthesis methods as well as the effect of storage temperature on the Φf. The study showed that the highest Φf were exhibited by BSA-stabilized AuNCs (BSA−AuNCs) prepared using microwave irradiation exhibited higher Φf (max. 13.33 ± 0.98%) stored at 4°C and Lys VI-stabilized AuNCs (Lys VI−AuNCs) (max. 17.44 ± 0.17%) that were conventionally synthesized. While AuNCs were successfully shown to be embedded in BSA NPs (BSA NPs−AuNCs) the Φf were found to be rather low (~2-3%) for both preparation routes. BSA−AuNCs prepared by microwave irradiation were then used for the ratiometric sensing of metal ions in solution and sol-gel thin films. The systems showed high selectivity towards Hg[superscript 2+] with nearly complete fluorescence quenching of the Au25 peak upon the addition of 25 μM Hg[superscript 2+]. Next, BSA-AuNCs were immobilized on cellulose filter paper for the visual detection of metal ions, displaying selectivity towards Hg[superscript 2+], Cu[superscript 2+], and Ni[superscript 2+] with Hg[superscript 2+] showing the most visible change in fluorescence upon the smallest addition of ions.
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