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

Yeon Su Park, Yukihiro Okamoto, Noritada Kaji, Manabu Tokeshi, Yoshinobu Baba

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

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 Cdcontaining species capable of passivating dangling bonds on the CdSe core surface. Each CdSe QD (d ∼ 2.5 nm) consisted of a CdSe core (d ∼ 2.1 nm), a cysteine (cys)-ligand shell, and an adsorption layer composed of Cd-cys complexes (mainly CdL(-H) -, cys ≡ H 2L), cys (as L 2-), Cd(OH) 2, and CdO x (x ≥ 1). Our CdSe QDs showed strong blue bandedge PL as well as strong green surface trap PL. Their PL quantum yield (QY) of ∼ 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.

Original languageEnglish
Pages (from-to)5781-5798
Number of pages18
JournalJournal of Nanoparticle Research
Volume13
Issue number11
DOIs
Publication statusPublished - Nov 1 2011
Externally publishedYes

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cysteine
Photoluminescence
Quantum Dots
Trap
Adsorption
Semiconductor quantum dots
Cysteine
quantum dots
traps
photoluminescence
adsorption
Quantum yield
Shell
Energy gap
Ligands
ligands
Dangling bonds
Exciton
Recombination
Excitons

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics
  • Modelling and Simulation
  • Chemistry(all)
  • Materials Science(all)
  • Bioengineering

Cite this

Aqueous phase-synthesized small CdSe quantum dots : Adsorption layer structure and strong band-edge and surface trap emission. / Park, Yeon Su; Okamoto, Yukihiro; Kaji, Noritada; Tokeshi, Manabu; Baba, Yoshinobu.

In: Journal of Nanoparticle Research, Vol. 13, No. 11, 01.11.2011, p. 5781-5798.

Research output: Contribution to journalArticle

Park, Yeon Su ; Okamoto, Yukihiro ; Kaji, Noritada ; Tokeshi, Manabu ; Baba, Yoshinobu. / Aqueous phase-synthesized small CdSe quantum dots : Adsorption layer structure and strong band-edge and surface trap emission. In: Journal of Nanoparticle Research. 2011 ; Vol. 13, No. 11. pp. 5781-5798.
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