title: Luminescent Gold Nanoparticles with Size-Independent Emission.
abstract: Size-independent emission has been widely observed for ultrasmall thiolated gold nanoparticles (AuNPs) but our understanding of the photoluminescence mechanisms of noble metals on the nanoscale has remained limited. Herein, we report how the emission wavelength of a AuNP and the local binding geometry of a thiolate ligand (glutathione) on the AuNP are correlated, as these AuNPs emit at different wavelengths in spite of their identical size (ca. 2.5 nm). By using circular dichroism, X-ray absorption, and fluorescence spectroscopy, we found that a high Au-S coordination number (CN) and a high surface coverage resulted in strong Au(I) -ligand charge transfer, a chiral conformation, and 600 nm emission, whereas a low Au-S CN and a low surface coverage led to weak charge transfer, an achiral conformation, and 810 nm emission. These two size-independent emissions can be integrated into one single 2.5 nm AuNP by fine-tuning of the surface coverage; a ratiometric pH response was then observed owing to strong energy transfer between two emission centers, opening up new possibilities for the design of ultrasmall ratiometric pH nanoindicators.
authors.affiliation: Department of Chemistry and Biochemistry, The University of Texas at Dallas, 800 W. Campbell Rd., Richardson, TX, 75080, USA.
authors.forename: Jinbin
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Chemistry, Dalhousie University, 6274 Coburg Rd., Halifax, N, S, B3H 4J3, Canada.
authors.forename: Paul N
authors.initials: PN
authors.lastname: Duchesne
authors.affiliation: Department of Chemistry and Biochemistry, The University of Texas at Dallas, 800 W. Campbell Rd., Richardson, TX, 75080, USA.
authors.forename: Mengxiao
authors.initials: M
authors.lastname: Yu
authors.affiliation: Department of Chemistry and Biochemistry, The University of Texas at Dallas, 800 W. Campbell Rd., Richardson, TX, 75080, USA.
authors.forename: Xingya
authors.initials: X
authors.lastname: Jiang
authors.affiliation: Department of Chemistry and Biochemistry, The University of Texas at Dallas, 800 W. Campbell Rd., Richardson, TX, 75080, USA.
authors.forename: Xuhui
authors.initials: X
authors.lastname: Ning
authors.affiliation: Department of Chemistry and Biochemistry, The University of Texas at Dallas, 800 W. Campbell Rd., Richardson, TX, 75080, USA.
authors.forename: Rodrigo D
authors.initials: RD
authors.lastname: Vinluan
authors.affiliation: Department of Chemistry, Dalhousie University, 6274 Coburg Rd., Halifax, N, S, B3H 4J3, Canada.
authors.forename: Peng
authors.initials: P
authors.lastname: Zhang
authors.affiliation: Department of Chemistry and Biochemistry, The University of Texas at Dallas, 800 W. Campbell Rd., Richardson, TX, 75080, USA. jiezheng@utdallas.edu.|Department of Urology, The University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390, USA. jiezheng@utdallas.edu.
authors.forename: Jie
authors.initials: J
authors.lastname: Zheng
mesh_terms: D006046:Gold / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D049449:Luminescence; D053768:Metal Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D013455:Sulfur / Q000737:chemistry; D013499:Surface Properties
chemical_list: D013455:Sulfur; D006046:Gold
keywords: emission; gold; luminescence; nanoparticles; pH sensors