A simple one-pot environmentally benign synthesis of ascorbic acid-capped CdSe nanoparticles at room temperature Oluwatobi S. Oluwafemi a, ⁎, Sandile P. Songca b a Department of Chemistry and Chemical Technology, Walter Sisulu University, Mthatha Campus, Private Bag XI, Mthatha 5117, South Africa b Faculty of Science, Engineering and Technology, Walter Sisulu University, PO BOX 19712, Tecoma, East-London, South Africa abstract article info Article history: Received 31 December 2011 Accepted 26 January 2012 Available online 4 February 2012 Keywords: CdSe Nanoparticles Ascorbic-acid Nanostructures Optical spectroscopy Quantum confinement Ascorbic acid-capped CdSe nanoparticles have been successfully synthesised at room temperature via a simple, one-pot environmentally benign solution growth technique without the use of additional stabilisers. The UV–vis absorption and photoluminescence spectroscopy (PL) showed that the particles exhibited quantum confinement in their optical spectra with emission in the blue region. The transmission electron microscopy (TEM) image showed that the particles are small and spherical in shape. The high resolution transmission elec- tron microscopy (HRTEM) image confirmed the crystalline nature of the material while the Fourier transform infra-red (FTIR) analysis confirmed the capping of the nanoparticles by the ascorbic acid. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Nanometre sized semiconductor nanoparticles (NPs) also known as quantum dots (QDs) of metal chalcogenides show unique physical and chemical properties, such as size-dependent band gap, size de- pendent excitonic emission and enhanced nonlinear optical proper- ties when compared to the corresponding bulk materials [1,2]. Thus, they have been extensively studied over the past decade for possible applications in photovoltaic cell, lasers, and optoelectronic devices; and hold immense promise as versatile labels for biological applica- tions [2–4]. Compared with the conventional organic fluorophores, they exhibit high quantum yield, resistance against photobleaching, broad excitation, and narrow emission; and can be prepared with high stability [5,6]. Many synthetic methods have been developed for the preparation of monodispersed NPs of various semiconductor materials, ranging from aqueous precipitation route to high tempera- ture hot injection method. Though these methods have been proven to be effective in synthesising high-quality chalcogenide quantum dots using stabilisers such as thiols, ethyl hexanoate, polyphosphate, trioctylphosphine oxide (TOPO), polyesters, starburst dendrimers and amino-derivatised polysaccharides [7–15], most of these methods usually involve the use of sophisticated equipments, com- plex or toxic reagents which are not environmentally benign, and rig- orous conditions in order to protect the reaction reagents and the as- synthesised material from oxidation: a major source of NPs cytotoxicity. This cytotoxicity has posed a major concern regarding the use of NPs in biological application. The generation of cadmium ions and reactive oxygen species in solution as a result of the oxida- tion of the QDs surface by O 2 in air was proposed as the major source of this toxicity [16,17]. As a result of these toxicity concerns, the search for QDs with high photostability and biocompatibility, pre- pared via a greener, sustainable and environmentally benign method, is still an area of immense interest. We have recently reported the synthesis of CdSe nanoparticles via a simple environmentally benign method using cysteine and starch as passivating agent [18,19]. In this work we have adapted the synthetic method to synthesise ascor- bic acid-capped CdSe nanoparticles. Ascorbic acid also known as anti- scorbutic vitamin, an effective antioxidant, was chosen because as an efficient oxygen scavenger, it will improve photochemical stability and reduce cytotoxicity that might arise from photo degradation [20–22]; hence no additional stabilisers are required. In addition, the hydroxyl groups of the ligands are expected to control the com- plexation of the metal ion, solubilisation in water and act as conjuga- tion site for further functionalisation of the as-synthesised nanoparticles to biomolecules. 2. Materials and methods 2.1. Materials Cadmium chloride (CdCl 2 ), sodium borohydride (NaBH 4 ), deio- nised water (HPLC grade) and ascorbic acid were purchased from Al- drich and the selenium powder from Merck. All the chemicals were of analytical grade and used as purchased without further purification. Materials Letters 75 (2012) 84–86 ⁎ Corresponding author. Tel.: + 27 765110322. E-mail address: oluwafemi.oluwatobi@gmail.com (O.S. Oluwafemi). 0167-577X/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2012.01.121 Contents lists available at SciVerse ScienceDirect Materials Letters journal homepage: www.elsevier.com/locate/matlet