Microwave assisted preparation of bismuth oxyhalide microflowers comprised of nanolayers and investigation of its photocatalytic activity Azadeh Tadjarodi a, *, Mohammad Moghaddasi a , Keyvan Bijanzad a , Omid Akhavan b,c a Research Laboratory of Inorganic Materials Synthesis, Department of Chemistry, Iran University of Science and Technology, Narmak, Tehran 16846-13114, Iran (E-mail:tajarodi@iust.ac.ir) b Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran,Iran, c Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 14588-89694, Tehran, Iran Abstract Today, bismuth based oxides, which have already been used as pigments and catalysts, are showing excellent photocatalytic performances. In this field, ternary bismuth oxyhalides (BiOX) are flourishing promptly. Bismuth nitrate pentahydrate and sodium chloride were utilized to fabricate the product in a domestic microwave instrument. The SEM images showed the microflowers which were comprised of nanolayers with the thickness of about 29 nm. From energy dispersive X-ray analysis, its empirical formula was estimated to be Bi2.27O9.31Cl. Fourier transform infrared spectroscopy showed that the peak at 567 cm -1 was attributed to the stretching vibration of Bi-O. Diffuse reflectance spectrum showed band gap energy of 3.5 eV for this compound. It showed a high photocatalytic performance in photodegradation of Rhodamine B. Keywords: Microwave sytnthesis, Bismuth oxychloride, photocatalyst, Rhodamine B. 1. Introduction In the recent years, Kudo et al. discovered that bismuth-based oxide semiconductors could show high photocatalytic activity because the Bi 6s and O 2p levels form largely dispersed hybridized valence bands [1]. The band gap of BiOX is strictly dependent on the halide participated in its composition and ranges from 3.19–3.44, 2.64–2.91 and 1.77–1.92 eV, respectively for Cl, Br and I [2]. In this field, so far, researchers have also investigated photocatalytic activities of various bismuth compounds such as: Ag/AgI/BiOI [3], Bi2S3 [4], Bi2Ti2O7 [5], N-doped (BiO)2CO3 [6], Bi5O7NO3[7], BiOI [8], Bi2O3, BiVO4, Bi2WO6 [9,10], BiNbO4 and BiTaO4 [11] and Black BiOCl [12]. Among different ternary bismuth based