INTRODUCTION Semiconductor nanoparticles have attracted much attention during the past decades in both fundamental researches and technical applications due to their unique size and shape dependent optical and electronic properties 1 . CdS has promising applications in several technical fields, including mechanical and optoelectronics, Quantum dot memory devices 2 , photo degeneration of water pollutants 3 , light emitting diode (LED) 4 and solar cells 5 . The cadmium sulfide cell or CdS is in actuality a light variable resistor which is made by depositing a small amount of doped cadmium sulfide on a ceramic substrate. Several studies have been reported for preparation of CdS nanomaterials. To produce CdS nano- crystals, many techniques have been employed such as electro- chemically induced deposition, thermal decomposition, ultra- sound irradiation 6 , solvothermal and hydrothermal methods. Ionic liquids (ILs) consist of cations and anions and are commonly understood as green solvents. The ionic liquids was stimulated increasing interest because of their unique proper- ties of high thermal stability and electrical conductivity. Ionic liquids can act as the reactants and morphological templates 7 for the products at the same time, which enable the synthesis Single Pot Microwave Synthesis of CdS Nanoparticles in Ionic Liquid and Their Photocatalytic Application† P. DEVENDRAN 1 , T. ALAGESAN 1,* and K. PANDIAN 2,* 1 Department of Physics, Presidency College, Chennai-600 005, India 2 Department of Inorganic Chemistry, University of Madras, Guindy Campus, Chennai-600 025, India *Corresponding authors: E-mail: talagesan@yahoo.com; jeevapandian@yahoo.co.uk AJC-12797 CdS nanoparticles were synthesized with uniformed nano size by thermal decomposition of cadmium diethyldithiocarbamate Cd[Ddtc]2 in 1-hexyl-3-methylimidazolium tetrafluroborate ([C6MIM]BF4) ionic liquid in the presence of hexadecylamine as a capping agent. The particles were isolated and then characterized with various experimental techniques to study the particles sizes and crystalline nature. The XRD studies confirmed that the synthesized CdS have hexagonal wurzite crystal structure. The optical and electronic properties of the nanoparticles were derived from UV-Visible spectral studies as well as photoluminescence and Raman studies. The scanning electron microscopic studies reveal that the particles have a spherical shape with a diameter of 5 nm. Long chain hexadecylamine acts as a shape directing agent while ionic liquid act as a solvent medium. The synthesized nanoparticles can be utilized for the effective photocatalytic decoloration of methylene blue. Key Words: CdS nanoparticles, Metal complex, Ionic liquids, Microwave irradiation, Photodegradation. †International Conference on Nanoscience & Nanotechnology, (ICONN 2013), 18-20 March 2013, SRM University, Kattankulathur, Chennai, India of inorganic materials with novel or superior properties. It has various potential applications such as industrial solvent, solar energy conversion, fuel cells batteries, enzymatic catalysis, etc. In this study, microwave irradiated CdS nanoparticles have been synthesized from single source precursor Cd(Ddtc)2 in presence of [C6MIM]BF4 ionic liquids. The most beneficial aspect in the microwave-irradiate preparations is the consi- derably shortened reaction time compared to the conventional methods. The as-synthesized ionic liquids assisted CdS nanoparticles were successfully utilized for the effective photocatalytic degradation of methylene blue using UV and visible irradiations. EXPERIMENTAL 1-Methylimidazol, 1-bromohexane cadmium nitrate, hexadecylamine and cadmium diethyldithiocarbamate were purchased from SRL Chemical, Pvt., Ltd, India. Methylene blue dye was obtained from commercial source. All solvents used were of analytical grade. Powder XRD patterns were recorded on a [PAN analytical X'Pert PRO with 2θ ranging from 20º to 80º in steps of 0.0017 º/s] X-ray diffractometer using CuK α irradiation. FESEM Asian Journal of Chemistry; Vol. 25, Supplementary Issue (2013), S79-S82