Aqueous phase-synthesized small CdSe quantum dots: adsorption layer structure and strong band-edge and surface trap emission

作者：Park Yeon Su^*; Okamoto Yukihiro; Kaji Noritada; Tokeshi Manabu; Baba Yoshinobu

来源：Journal of Nanoparticle Research, 2011, 13(11): 5781-5798.

DOI：10.1007/s11051-011-0273-7

• Aqueous synthesis
• Adsorption layer
• CdSe
• Photoluminescence
• Quantum dot
• Quantum yield

We synthesized, in aqueous solution at room temperature, small water-soluble CdSe quantum dots (QDs) with strong photoluminescence (PL) and then correlated the PL with their adsorption layer structure. For synthesizing the QDs, their initial synthesis condition was controlled to form small Cd-containing species capable of passivating dangling bonds on the CdSe core surface. Each CdSe QD (d similar to 2.5 nm) consisted of a CdSe core (d similar to 2.1 nm), a cysteine (cys)-ligand shell, and an adsorption layer composed of Cd-cys complexes (mainly CdL(-H)(-), cys a parts per thousand H2L), cys (as L2-), Cd(OH)(2), and CdO (x) (x a parts per thousand yen 1). Our CdSe QDs showed strong blue band-edge PL as well as strong green surface trap PL. Their PL quantum yield (QY) of similar to 18% was unexpectedly high, considering their extremely small core size and their absence of any wide-bandgap inorganic shell. We attributed the QY to their adsorption layer species. The small weakly charged Cd-cys complex and the small neutral cadmium oxides in the adsorption layer could relatively readily diffuse into the unprotected surface sites on the core. These wide-bandgap species coalesced selectively on the unprotected surface sites with minimal spatial disturbance to the preexisting surface Cd-ligand coordination, and passivated them effectively. These decreased nonradiative recombination of the excitons significantly and thus led to the unexpectedly high QYs.

• 出版日期2011-11