Abstract
We report a highly bright and stable aqueous dispersion of CuInS2/ZnS (CIS/ZnS) nanocrystals (NCs) using surfactant-assisted microemulsion and cold treatment. CIS/ZnS NCs were facilely synthesized via a stepwise, consecutive hybrid flow reactor approach. To stabilize the optical properties of hydrophobic CIS/ZnS NCs, cetyltrimethylammonium bromide (CTAB) was chosen as a matrix for aqueous phase transfer. As the result, a high quantum yield (QY) of 56.0% and excellent photostability were acquired in aqueous media. For removing excessive surfactants, cold treatment (4°C) of the CTAB-water solution was adopted to prevent further agglomeration of CIS/ZnS NCs, which could secure high stability over 6 months (less 2% reduction in QY). The optical features and structure of the obtained CTAB stabilized CIS/ZnS (CTAB-CIS/ZnS) NCs have been characterized by UV–vis and photoluminescence (PL) spectroscopies, XRD, XPS, EDX, and TEM. The high stability and PL of water soluble CTAB-CIS/ZnS NCs suggest their potential in nanoelectronics and bioapplications.
Highlights
Among the several types of inorganic nanocrystals (NCs), CuInS2 (CIS) NCs have been receiving enormous interests due to their non-toxic behavior and ecofriendly properties of in comparison with CdSe, CdS, PbSe, and PbS NCs containing Cd and Pb atomic pollutants
The location of the pattern is in good agreement with the Joint Committee on Powder Diffraction Standards (JCPDS) reference diagrams in the bottom inset (JCPDS No 32–0339: CuInS2 and 10–0434: ZnS)
In summary, we have demonstrated that CIS/ZnS NCs synthesized on a large scale using a hybrid flow reactor in a simple, one-step process can be effectively transferred into aqueous solution by adding cetyltrimethylammonium bromide (CTAB)
Summary
Among the several types of inorganic nanocrystals (NCs), CuInS2 (CIS) NCs have been receiving enormous interests due to their non-toxic behavior and ecofriendly properties of in comparison with CdSe, CdS, PbSe, and PbS NCs containing Cd and Pb atomic pollutants. While the Restriction of Hazardous Substances Directive forbids the use of compound semiconductors containing Cd and Pb atoms in devices, the usage of CIS nanomaterials are permitted [1]. This material might be a promising candidate for optical imaging, which offers the opportunity to develop semiconductor NCs without the toxicity limitations encountered by IIVI NCs, especially at low concentrations. CIS is an I-IIIVI2 semiconductor with a direct band gap of 1.5 eV, corresponding to an 827 nm emission wavelength. This CIS NCs provides multicolor photoluminescence (PL) emission ranging from the visible to the NIR wavelengths (600 to 900 nm) [2].
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