Int. J. Adv. Sci. Eng. Vol.4 No.1 512-524 (2017) 512 ISSN 2349 5359 Jayaprakash et al., International Journal of Advanced Science and Engineering www.mahendrapublications.com ABSTRACT: The uncapped and capped CuO nanocrystals were synthesized by sol–gel method. Tetra Ethyl Ammonium Bromide (TEABr) used as a capping agent to control the size and morphology of the CuO nanocrystals. Control the nanostructure and optical properties of CuO nanocrystals are premeditated by using capping agent. The obtained samples were characterized by means of UV-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), Field Emission Scanning electron microscopy (FESEM) along with Energy dispersive X-ray spectroscopy (EDS). UV-Visible technique is used to measure the band gap of the synthesized samples. The XRD spectra of the synthesized samples established the CuO nanocrystals with monoclinic structure. The occurrences of capping agent have been analyzed by Fourier transform-infrared spectroscopy (FT-IR). The FT-IR study discovered that the transmittance peaks at 501 cm -1 and 592 cm -1 were Cu-O stretching mode, and 677 cm -1 was Cu-O monoclinic phase of the uncapped CuO nanocrystals. Further, FESEM study find out the morphology of the synthesized samples, where the surface morphology changes occurred with an addition of capping agent. Antioxidant of CuO nanocrystals evaluated using L- ascorbic acid and BHA as standards. The antioxidant capacity was expressed as ascorbic acid equivalent. Cyclic voltammetry applications investigated of uncapped and TEABr capped CuO nanocrystals. KEYWORDS: CuO nanocrystals, band gap, Tetra ethyl ammonium bromide (TEABr), surface morphology. © 2015 mahendrapublications.com, All rights reserved *Corresponding Author: jayaprakash@gmail.com Received: 18.04.2017 Accepted: 10.06.2017 Published on: 27.07.2017 Synthesis, Optical, Morphological and Antioxidant Evaluation Studies on CuO Nanocrystals using TEABr as Capping Agent by Sol-Gel Technique J. Jayaprakash * , A. Sadham Hussain, R. Balaji Department of Physics, AVS College of Arts and Science, Salem-636 106. 1. INTRODUCTION Copper oxide (CuO) is an significant p-type metal oxide semiconductor with narrow band gap (1.2 eV) [1]. When the dimension of CuO decreases to nanoscale, such nanostructure exhibits influential structural characteristics and size confinement effects along with novel physical properties [2]. Nanoscale CuO with different shapes and dimensions, such as nanotubes [3], nanowires [4], nanosheets [5] and nanoneedles [6] have been synthesized by using several methodologies. More than a few complex nanostructures including nanoflowers [7], spherical-like [8], urchin-like [9], tadpole-shaped [10] and other exceptional morphology have been explored. Recently, research on the shape control of various nanostructures has been broadly developed because physical and chemical properties are strongly dependent on the sizes, shapes, compositions, and structures of the nanocrystals. Synthesis of nanomaterials with controllable orientation and crystalline morphology without the addition of any surfactants (or) template has concerned more attention because of their novel physical properties [11]. Many methods have been adopted for the fabrication of nano and microstructures. Generally, they can be classified into two kinds: the template methods which employ hard templates (silicon wafers, metallic foils) and soft templates (surfactant and capping agents), and the template free method. However, the surfactants or organic additives attached to the surfaces are difficult to handle and cause problems in their applications [12]. CuO is extensively used in electro chemical cells [13], gas sensors [14, 15], magnetic storage media [16, 17], photovoltaic cells [18], light emitters [19], thermoelectric materials [20, 21], heat transfer nanofluids and for catalysis [22–24]. Using CuO nanocrystals with fine size distribution for these applications would further promote the chemical reactivity of the nanocrystals because as the particle's size reduces the surface-to volume ratio increases, and accordingly the number of reactive sites increases [25–31]. Many methods have been developed to prepare CuO nanostructures including pulsed laser deposition [32], thermal oxidation [33], ultrasonic spray pyrolysis [34], chemical bath deposition [35], microwave [36], sol–gel method [37], electro-deposition [38], sputtering [39], solvothermal [40], solid-state reaction [41], surfactant templating method [42] solution-phase route [43], and hydrothermal [44]. Moreover, adjusting the morphology, size, by the interaction of inorganic species with capping agent had been effectively used in controllable synthesis of the nanocrystals. Therefore, sol-gel synthesis combining with a capping agent is a influential, simple and effective method for the controllable synthesis of CuO nanocrystals.