Green Synthesis of Sodium Alginate Capped -CuInS 2 Quantum Dots with Improved Fluorescence Properties
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ORIGINAL ARTICLE
Green Synthesis of Sodium Alginate Capped -CuInS2 Quantum Dots with Improved Fluorescence Properties R. Jose Varghese 1,2 & Sundararajan Parani 1,2 & Olufemi O. Adeyemi 3 & V. R. Remya 1,2 & El Hadji Mamour Sakho 1,2 & Rodney Maluleke 1,2 & Sabu Thomas 4 & Oluwatobi S. Oluwafemi 1,2 Received: 18 May 2020 / Accepted: 4 August 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract CuInS2 (CIS) quantum dots (QDs) are known to be ideal fluorophores based on their low toxicity and tunable emission. However, due to low quantum yield (QY) and photostability, the surface is usually passivated by a higher bandgap shell (e.g. ZnS). This always resulted in a blue-shifted emission position which is not usually favourable for biological imaging. To address this problem, we herein report the passivation of green synthesized near infra-red emitting glutathione (GSH) capped CuInS2 QDs using different concentration of sodium alginate (SA) at different temperatures. The as-synthesized QDs are small (~ 3.2 nm), highly crystalline and emitted in the near infra-red region. The optical results showed a 36% increase in photostability and a 2-fold increase in quantum yield at ratio 1:8 (SA: CIS) which is suitable for prolonged biological imaging applications. Transmission electron microscope and X-ray diffraction (XRD) analyses showed that the materials are highly crystalline without any change in shape and size after passivation with the biopolymer. Keywords CuInS2 QDs . Sodium alginate . Nanocomposite . Optical materials . Photostability
Introduction Recently the use of CuInS2 (CIS) quantum dots (QDs) for bioimaging application as an alternative to toxic binary QDs has generated a lot of interest due to their tunable emission profile to near infra-red (NIR) range Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10895-020-02604-0) contains supplementary material, which is available to authorized users. * Oluwatobi S. Oluwafemi [email protected] 1
Department of Chemical Sciences (formerly Applied Chemistry), University of Johannesburg, P.O. Box 17011, Johannesburg, Doornfontein 2028, South Africa
2
Centre for Nanomaterials Science Research, University of Johannesburg, P.O. Box 17011, Johannesburg, Doornfontein 2028, South Africa
3
Department of Chemical Sciences, Olabisi Onabanjo University, P.O. Box 364, Ago-Iwoye, Ogun State, Nigeria
4
International and Inter University Center for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala, India
and low toxicity [1, 2]. This interest has led to the synthesis of CIS via greener synthetic routes and its passivation by a higher bandgap material due to its low quantum yield (QY) and photostability [2, 3]. Chen et al. reported a facile method for the aqueous synthesis of CuInS 2 /ZnS core/shell (CIS/ZnS) QDs using electric pressure cooker [3]. The emission position of the resultant core/shell was significantly blue-shifted compared to the core and this was attrib
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