Greytak, Andrew B.Allen, Peter M.Liu, WenhaoZhao, JingYoung, Elizabeth R.Popovic, ZoranWalker, Brian J.Nocera, DanielBawendi, Moungi G.2017-07-202012Greytak, Andrew B., Peter M. Allen, Wenhao Liu, Jing Zhao, Elizabeth R. Young, Zoran Popović, Brian J. Walker, Daniel G. Nocera, and Moungi G. Bawendi. 2012. “Alternating Layer Addition Approach to CdSe/CdS Core/shell Quantum Dots with Near-Unity Quantum Yield and High on-Time Fractions.” Chemical Science 3 (6): 2028. doi:10.1039/c2sc00561a.2041-6520http://nrs.harvard.edu/urn-3:HUL.InstRepos:33468927We report single-particle photoluminescence (PL) intermittency (blinking) with high on-time fractions in colloidal CdSe quantum dots (QD) with conformal CdS shells of 1.4 nm thickness, equivalent to approximately 4 CdS monolayers. All QDs observed displayed on-time fractions > 60% with the majority > 80%. The high-on-time-fraction blinking is accompanied by fluorescence quantum yields (QY) close to unity (up to 98% in an absolute QY measurement) when dispersed in organic solvents and a monoexponential ensemble photoluminescence (PL) decay lifetime. The CdS shell is formed in high synthetic yield using a modified selective ion layer adsorption and reaction (SILAR) technique that employs a silylated sulfur precursor. The CdS shell provides sufficient chemical and electronic passivation of the QD excited state to permit water solubilization with greater than 60% QY via ligand exchange with an imidazole-bearing hydrophilic polymer.en-USJournal Article2017-05-1120122017-07-2010.1039/C2SC00561A