Stability Investigation of CuInS 2 based heavy-metal free nanocrystals
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Stability Investigation of CuInS2 based heavy-metal free nanocrystals Chuang Xie1, 2, Yu Zhang2, Andrew Y. Wang3, William W. Yu4, Jingkang Wang1, Jian Xu2 1
School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China Department of Engineering Science and Mechanics, Penn State, State College, PA 16802, USA 3 Ocean Nano Tech LLC., Springdale, Arkansas 72764, USA 4 Worcester Polytechnic Worcester, MA, USA 2
ABSTRACT In the present work the photostability of high-quality CuInS2 based nanocrystals (ZnCu-In-S/ZnSe/ZnS and CuInS2/ZnS core/shell nanocrystals) of different sizes and concentrations were investigated at ambient condition both under UV irradiation and in the darkness. The photostability of commercial CdSe/ZnS core/shell nanocrystals were used as reference to compare to that of CuInS2 based nanocrystals. The half-life times of the CuInS2 base nanocrystals are 2-8 times that of the reference which indicates the CuInS2 base NCs we obtained in the present work are very stable, reliable and competent for the application in biomedical fields. INTRODUCTION CuInS2, as a well-known and important photovoltaic material,[1] also has perspective application in biomedical labeling. Due to the toxicity and environment considerations,[2, 3] CuInS2 nanocrystals (NCs) take big advantages of Cd and Pb based NCs although they were well developed and have attractive optical properties[4-6]. Recent progresses suggest that CuInS2 based heavy metal free NCs, such as Zn-Cu-InS[7] and CuInS2/ZnS core/shell[8] NCs, are good enough and have been employed in vivo biological labeling within visible and NIR windows. However, little has been reported on testing the stability of the optical property of CuInS2 based NCs which is very important to its biomedical applications. In this work, the CuInS2 based NCs were synthesized and their photostability were investigated. EXPERIMENTAL DETAILS Materials: Oleylamine (OAm) was purchased from TCI. Copper (I) iodide (CuI), indium (III) iodide (InI3), and 1-dodecanthiol (DDT) were purchased from Alfa Aesar. Zinc oxide (ZnO), oleic acid (OA), selenium powder (Se), tri-butylphosphine (TBP), and diethyldithiocarbamide zinc (DECZn) were purchased from Aldrich. All the chemicals were used without further purification. Zn-Cu-In-S/ZnSe/ZnS (ZCIS/ZnSe/ZnS) core/shell NCs were prepared by successive growth of ZnSe and ZnS shells on the Zn-Cu-In-S (ZCIS) core. The ZCIS core was synthesized based on the method of Maeda[7] with some modifications: 2mL of CuI/OAm solution (45mM) and 2mL of InI3/OAm solution (45mM) were mixed with 6mL of DECZn/TBP/ODE (16.7mM) in the flask. The mixture was heated to the desired temperature (100-230 °C) followed by growth of shell at the same temperature. Se/TBP (0.1M), ZnO/OA/ODE (0.1M) and DECZn/TBP/ODE (16.7mM) were used as the shell precursors. To determine the influence of the shells on the stability, same amount of the
shell precursors were used to vary the shell thickness. CuInS2/ZnS (CIS/ZnS) core/shell NCs were prepared by adding ZnS shell on
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