Abstract

Commercial use of quantum dots (QDs) will lead to their entry into aquatic environments. This study examines the characteristics and stability of CdTe QDs with thioglycolate capping ligands in water as well as their removal by alum salts. The capping ligands of QDs are a key factor in determining their fate in water. Protonated thioglycolate capping ligands cause QDs to aggregate. The stability of QDs depends more on their ionic composition in water than on the ionic strength. In KCl solution, QDs remain stable even under 0.15 M ionic strength. Relatively low concentrations (≤2 meq/L) of divalent (Mg 2+ and Ca2+) or trivalent (Al3+) cations, however, can induce aggregation. The proposed mechanism for this phenomenon is that multivalent metal cations (or their hydrated species) react with capping ligands to form complexes that bridge QDs or neutralize their surface charges. Because the complexation of hydrated Al3+ with capping ligands inhibits the formation of Al(OH)3 precipitates, alum dosages higher than the Al3+ solubility are required to form settleable floes and remove QDs from nanopure water by sedimentation. Divalent cations (Mg 2+ and Ca2+) in tap water induce the formation of settleable QD floes such that 70-80% of the QDs by mass settle out.

Original languageEnglish (US)
Pages (from-to)321-325
Number of pages5
JournalEnvironmental Science and Technology
Volume42
Issue number1
DOIs
StatePublished - Jan 1 2008

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capping
Semiconductor quantum dots
ligand
Water
cation
Ligands
water
Thioglycolates
ionic composition
Positive ions
Ionic strength
complexation
aquatic environment
Cations
solubility
removal
sedimentation
salt
metal
Divalent Cations

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Science(all)
  • Environmental Chemistry

Cite this

Stability and removal of water soluble CdTe quantum dots in water. / Zhang, Yang; Chen, Yongsheng; Westerhoff, Paul; Crittenden, John C.

In: Environmental Science and Technology, Vol. 42, No. 1, 01.01.2008, p. 321-325.

Research output: Contribution to journalArticle

Zhang, Yang ; Chen, Yongsheng ; Westerhoff, Paul ; Crittenden, John C. / Stability and removal of water soluble CdTe quantum dots in water. In: Environmental Science and Technology. 2008 ; Vol. 42, No. 1. pp. 321-325.
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