title: Aqueous synthesis of Cu-doped ZnCdS/ZnS core/shell nanocrystals with a new and highly reactive sulfur source.
abstract: A new sulfur precursor with a highly reactive chemical nature was prepared with S powder and NaBH₄ at the high temperature of 180 °C in a closed autoclave and made it possible to carry out the synthesis of high quality metal sulfide nanocrystals (NCs) with diverse composition and structure. Using this new sulfur source, we demonstrated aqueous synthesis of colloidal Cu-doped ZnCdS NCs (d-dots) with pure, color-tunable photoluminescence (PL) in a wide spectral range (from 517 to 650 nm) based on the 'co-nucleation doping' strategy. The influences of the various experimental variables, including Cd/Zn ratio, Cu-doping concentration, pH value and amount of mercaptopropionic acid (MPA), on the optical properties of Cu-doped ZnCdS NCs were systematically investigated. Furthermore, highly efficient and stable dopant emission from Cu:ZnCdS/ZnS core/shell d-dots with PL quantum yield as high as 40% was achieved by the deposition of a ZnS shell around the bare Cu:ZnCdS cores; this is the highest reported to date for aqueous doped NCs. The optical properties and structure of the d-dots were characterized by UV-vis absorption spectra, PL spectra, x-ray photoelectron spectroscopy, powder x-ray diffraction, and transmission electron microscopy. The experimental results indicated that this facile synthesis route would provide a versatile approach for the preparation of other water-soluble sulfide NCs.
authors.affiliation: Key Lab for Functional Materials Chemistry of Guizhou Province, School of Chemistry and Materials Science, Guizhou Normal University, Guiyang 550001, People's Republic of China.
authors.forename: Ruosheng
authors.initials: R
authors.lastname: Zeng
authors.forename: Rongan
authors.initials: R
authors.lastname: Shen
authors.forename: Yunqiang
authors.initials: Y
authors.lastname: Zhao
authors.forename: Xingsheng
authors.initials: X
authors.lastname: Li
authors.forename: Zhiguo
authors.initials: Z
authors.lastname: Sun
authors.forename: Yayun
authors.initials: Y
authors.lastname: Shen