Contents lists available at ScienceDirect Materials Science in Semiconductor Processing journal homepage: www.elsevier.com/locate/mssp Photocatalytic activity of bismuth silicate heterostructures synthesized via surfactant mediated sol-gel method K. Karthik a , K.R Sunaja Devi a,* , Dephan Pinheiro a , S. Sugunan b a Department of Chemistry, CHRIST (Deemed to Be University), Hosur Road, Bangalore, Karnataka, 560029, India b Department of Applied Chemistry, Cochin University of Science and Technology, Kochi, Kerala, 682022, India ARTICLEINFO Keywords: Bismuth silicates heterostructures Photodegradation Malachite green Rhodamine B Sol-gel Surfactant-mediated ABSTRACT A surfactant mediated sol-gel method is employed to synthesize bismuth silicate heterostructures with tunable morphologies and properties. The synthesized nanoparticle samples were characterized by XRD, FTIR Spectroscopy, SEM-EDAX and UV-DRS. The synthesized bismuth silicates exhibit excellent photodegradation against malachite green and rhodamine B dyes in the aqueous medium. Bismuth silicates (10% SiO 2 -Bi 2 O 3 ) show superior photocatalytic property and outstanding reusability compared to pure bismuth oxide. The kinetics of the photodegradation of the dyes shows that the reaction follows frst-order kinetics with the regression coef- fcient of 0.99. Thus, enabling Bismuth silicates heterostructures practical application as a photocatalyst for clean water. 1. Introduction Solar energy is the most abundant source of light energy on this planet while being the cleanest and cheapest [1]. Thus, there has been extensive research and development of materials that can utilize solar energy in the feld of energy storage and environmental remediation from harmful pollutants [2]. The oxidation and reduction of organic pollutants by novel materials through advanced oxidation processes (AOPs) play a vital role in cleaning the environment on a large scale. The area of photocatalysis has played a great role in eradicating these pollutants by catalyst mediated degradation via oxidation and reduc- tion reactions [3]. Dyes and other organic pollutants block the penetration of sunlight into water bodies, thereby afecting the process of photosynthesis and productivity of the autotrophs [4]. Rh B is highly soluble in water and widely used as a colorant in the textile, paper and food industry [5,6]. It is also used as a fuorescent water tracer [7]. Usually, efuents from industries are released into the nearby water bodies and other water sources thereby polluting the water, thus afecting the aquatic life in the water bodies. Rh B is carcinogenic to human beings and animals and can cause eye, skin and respiratory tract irritation [8,9]. Malachite green (MG) is a triphenylmethane dye which is widely used in the manufacturing of textiles, leather and ceramics [10]. Due to its property of disinfection, it is efciently used in the aquaculture industry and act as an antibacterial agent. MG and its reduced forms are very toxic, carcinogenic in nature and it is also proven to be mutagenic [11]. Chen et al., studied the photocatalytic degradation of MG under UV irradia- tion using TiO 2 . The fragmentation studies using HPLC-ESI technique revealed the breakdown of the dye molecule into de-methylated MG molecules. The reaction mechanism involves the formation of the acid ions as an intermediate during the overall degradation process [12]. Thus, it is very essential to remove these hazardous pollutants using cost-efective photochemical techniques. Nanostructures of metal and transition metal oxides show inter- esting catalytic properties due to their large surface and variable oxi- dation states [13]. TiO 2 and ZnO based semiconductor photocatalysts have been extensively investigated and exploited for UV region pho- tocatalytic activity in water purifcation and other technologies [14–16]. Most of the conventional photocatalysts are UV or UV-Vis active catalysts. The UV light comprises only 3–5% of the total solar radiation [17]. Therefore, the visible region active photocatalyst with tunable band gap are of great interest in research. Oxides of bismuth have been studied extensively due to their unique properties like large band gap and high photoconductivity [18]. Bismuth oxide is the most industrially important compound of bismuth. Bi 2 O 3 is widely used in optoelectronics, optical coatings, solid-state fuel cells, gas sensors and catalysts [19–21]. Bismuth oxide nanoparticles have been synthesized using various surfactants like PEG and SDS to get the desired phases of Bi 2 O 3 by diferent preparational techniques [22–24]. Silicates have been extensively studied in various felds such as catalysis, sensors and https://doi.org/10.1016/j.mssp.2019.104589 Received 31 March 2019; Received in revised form 29 May 2019; Accepted 21 June 2019 * Corresponding author. E-mail address: sunajadevi.kr@christuniversity.in (K.R.S. Devi). Materials Science in Semiconductor Processing 102 (2019) 104589 1369-8001/ © 2019 Elsevier Ltd. All rights reserved. T