title: Supersaturation driven tailoring of photoluminescence efficiency and size distribution: a simplified aqueous approach for producing high-quality, biocompatible quantum dots.
abstract: Supersaturation was found to play a pivotal role during nanoparticle-synthesis and its subtle variation helped achieve two prime objectives: (a) high photoluminescence quantum efficiency (PLQE) and (b) narrow size distribution, thereby obviating the need for post-preparative treatments. Degree of supersaturation of initial synthetic mixture was varied by changing the concentration of reagents while keeping their molar ratio constant at 1:2.5:0.5 for [Cd(2+)]:[cysteine]:[chalcogenide]. An eight-fold increase in supersaturation caused a sharp focusing of size distribution by 64% for CdS quantum dots (QDs). The as-prepared CdS and CdTe QDs were found to have size distribution as low as 4% at higher supersaturation. For a four-fold increase in supersaturation, PLQE of as-prepared CdTe QDs (4.3 nm) rose by 5 times to a remarkably high value of 54%. The focusing of size distribution with increasing supersaturation was found to work well even in the absence of any stabilizer. A substantial overlap of nucleation and growth was found at low supersaturation (0.5S(CdTe)), whereas a good separation of the two events is achieved at a higher supersaturation (4S(CdTe)). This study provides a simplified aqueous route for producing highly monodisperse, photoluminescent and biocompatible nanoparticles.
authors.affiliation: UGC-DAE Consortium for Scientific Research, Kolkata Centre, III/LB-8, Bidhannagar, Kolkata-700098, India.
authors.forename: A
authors.initials: A
authors.lastname: Priyam
authors.forename: S
authors.initials: S
authors.lastname: Ghosh
authors.forename: S C
authors.initials: SC
authors.lastname: Bhattacharya
authors.forename: A
authors.initials: A
authors.lastname: Saha
mesh_terms: D001672:Biocompatible Materials / Q000138:chemical synthesis* / Q000737:chemistry; D019187:Cadmium Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D049449:Luminescence; D010316:Particle Size; D045663:Quantum Dots; D013440:Sulfides / Q000138:chemical synthesis* / Q000737:chemistry; D013499:Surface Properties; D013691:Tellurium / Q000737:chemistry; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D001672:Biocompatible Materials; D019187:Cadmium Compounds; D013440:Sulfides; C034939:cadmium sulfide; D014867:Water; D013691:Tellurium; C028337:cadmium telluride