Amphipol-encapsulated CuInS2/ZnS quantum dots with excellent colloidal stability

Abstract

CuInS 2 quantum dots encapsulated in ZnS shells have emerged as less-toxic alternatives to cadmiumbased nanoparticles. A well-established synthesis route for hydrophobic CIS/ZnS core/shell QDs has been developed using dodecanethiol as a ligand, solvent and source of sulfur, although the transfer of these 10 nanoparticles into the aqueous phase still proves to be non-trivial. In this study we demonstrate that coating CIS/ZnS with an amphipol, poly(maleic anhydride-alt-1-tetradecene), 3-(dimethylamino)-1-propylamine derivative is an effective method to disperse CIS/ZnS QDs in the aqueous environment. The polymer-coated QDs display good colloidal stability over a wide pH range and low sensitivity to the presence of various metal salts, except Cu 2+ for which some sensitivity is observed. Cytotoxic effects 15 were tested in HaCat cells and compared to thioglycolic acid modified CdTe/ZnS QDs. Neither CdTe nor CIS QDs decreased viability until above 10 g/mL in a WST-1 assay. By also assessing the toxicity of the PMAL-d polymer it is clear that remaining toxicity of the CIS/ZnS QDs is predominately due to the polymer coating rather than the QD core. Interestingly, MTT assays seem to artificially exaggerate cytotoxicity of the QDs, which we ascribe to the QDs interfering with the MTT or formazan crystals.

A polymer encapsulation approach to prepare zwitterion-like, biocompatible quantum dots with wide pH and ionic stability

“…3). The surface modification method is good in preparing brighter QDs in aqueous solutions, compared to previously reported approaches, where QDs suffer 20 ~ 50 % loss of QY (or photoluminescent intensity) during phase transfer (Breus et al 2009; Muro et al 2010; Muro et al 2012; Liu et al 2013; Booth et al 2013). …”

“…Second, thiols are apt to oxidize in the presence of oxygen and therefore lose their binding affinity to deteriorate QD stability. On the other hand, polymer encapsulation does not involve the drawbacks of ligand exchange and thus are of interests for the preparation of ZW-QDs or zwitterion-like (ZWL) QDs (Yezhelyev et al 2008; Bagalkot and Gao 2011; Booth et al 2013). In this study, considering the incorporation of positive/negative charges in amphiphilic polymer to form zwitterion-like quantum dots (ZWL-QDs) is feasible, a surface modification method adopting the charge incorporation strategy as well as polymer encapsulation has been developed to prepare ZWL-QDs.…”

Thermal decomposition based synthesis of Ag-In-S/ZnS quantum dots and their chlorotoxin-modified micelles for brain tumor cell targeting

“…The red-shift and the QY drop after the phase transfer is believed to be caused by a compact QD cluster in micelle cores. 30–31 In the compact cluster, the emission photons from smaller QDs are absorbed by larger QDs to emit at longer wavelengths (a Förster resonance energy transfer process). Moreover, the cluster reduces the total excitation and emission surface area of QDs, resulting in a QY drop.…”

Facilitated preparation of bioconjugatable zwitterionic quantum dots using dual-lipid encapsulation

“…In addition, thiols are apt to oxidize in the presence of oxygen and therefore lose their binding affinity, deteriorating QD stability [3, 5–6]. More specifically, in the case of CuInS 2 /ZnS QDs, ligand exchange is less favorable compared to tri-octylphosphine oxide stabilized QDs such as CdSe/ZnS, because CuInS 2 /ZnS QDs are normally coated with dodecanethiol resulting from production, and dodecanethiol has a higher binding affinity to QD surface Zn atoms than tri-octylphosphine oxide [17]. On the other hand, several reports describe the preparation of ZW-QDs through encapsulating single or multiple QDs in zwitterionic amphiphilic polymers [17–21].…”

“…More specifically, in the case of CuInS 2 /ZnS QDs, ligand exchange is less favorable compared to tri-octylphosphine oxide stabilized QDs such as CdSe/ZnS, because CuInS 2 /ZnS QDs are normally coated with dodecanethiol resulting from production, and dodecanethiol has a higher binding affinity to QD surface Zn atoms than tri-octylphosphine oxide [17]. On the other hand, several reports describe the preparation of ZW-QDs through encapsulating single or multiple QDs in zwitterionic amphiphilic polymers [17–21]. However, the ZW-QD preparation requires multiple time-intensive steps including an overnight air-dry from chloroform.…”