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Stability of core/shell quantum dots-role of pH and small organic ligands
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Resumo(s)
The improvement of knowledge about the toxicity and even processability, and stability of quantum dots (QD) requires the understanding of the relationship between
the QD binding head group, surface structure, and interligand interaction. The scanned stripping chronopotentiometry
and absence of gradients and Nernstian equilibrium stripping techniques were used to determine the concentration of Cd dissolved from a polyacrylate-stabilized CdTe/CdS QD. The effects of various concentrations of small organic ligands such as citric acid, glycine, and histidine
and the roles of pH (4.5–8.5) and exposure time (0–48 h) were evaluated. The highest QD dissolution was obtained at the more acidic pH in absence of the ligands (52 %) a result
of the CdS shell solubility. At pH 8.5 the largest PAA ability to complex the dissolved Cd leads to a further QD solubility until the equilibrium is reached (24 % of dissolved Cd vs.4 % at pH 6.0). The citric acid presence resulted in greater QD dissolution, whereas glycine, an amino acid, acts against QD dissolution. Surprisingly, the presence of histidine, an amino acid with an imidazole functional group, leads to the formation of much strong Cd complexes over time, which may be non-labile, inducing variations in the local environment
of the QD surface.
Descrição
Palavras-chave
Quantum dots Dissolution Stability Speciation Bioavailability Organic ligands
Contexto Educativo
Citação
Domingos, R.F.; Franco, C.; Pinheiro, J.P. Stability of core/shell quantum dots-role of pH and small organic ligands, Environmental Science and Pollution Research, 20, 7, 4872-4880, 2013.