title: Luminescent quantum clusters of gold in bulk by albumin-induced core etching of nanoparticles: metal ion sensing, metal-enhanced luminescence, and biolabeling.
abstract: The synthesis of a luminescent quantum cluster (QC) of gold with a quantum yield of approximately 4 % is reported. It was synthesized in gram quantities by the core etching of mercaptosuccinic acid protected gold nanoparticles by bovine serum albumin (BSA), abbreviated as Au(QC)@BSA. The cluster was characterized and a core of Au(38) was assigned tentatively from mass spectrometric analysis. Luminescence of the QC is exploited as a "turn-off" sensor for Cu(2+) ions and a "turn-on" sensor for glutathione detection. Metal-enhanced luminescence (MEL) of this QC in the presence of silver nanoparticles is demonstrated and a ninefold maximum enhancement is seen. This is the first report of the observation of MEL from QCs. Folic acid conjugated Au(QC)@BSA was found to be internalized to a significant extent by oral carcinoma KB cells through folic acid mediated endocytosis. The inherent luminescence of the internalized Au(QC)@BSA was used in cell imaging.
authors.affiliation: DST Unit on Nanoscience (DST UNS), Department of Chemistry and Sophisticated Analytical Instrument Facility, Indian Institute of Technology Madras, Chennai 600 036, India.
authors.forename: Madathumpady Abubaker
authors.initials: MA
authors.lastname: Habeeb Muhammed
authors.forename: Pramod Kumar
authors.initials: PK
authors.lastname: Verma
authors.forename: Samir Kumar
authors.initials: SK
authors.lastname: Pal
authors.forename: Archana
authors.initials: A
authors.lastname: Retnakumari
authors.forename: Manzoor
authors.initials: M
authors.lastname: Koyakutty
authors.forename: Shantikumar
authors.initials: S
authors.lastname: Nair
authors.forename: Thalappil
authors.initials: T
authors.lastname: Pradeep
mesh_terms: D000818:Animals; D002412:Cations / Q000737:chemistry; D002417:Cattle; D006046:Gold / Q000737:chemistry*; D006801:Humans; D049449:Luminescence; D053768:Metal Nanoparticles / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry*
chemical_list: D002412:Cations; D012710:Serum Albumin, Bovine; D006046:Gold