Eco-friendly synthetic route for layered zinc compound and its conversion to ZnO with photocatalytical properties Greta Patrinoiu a , Jose Maria Calderón-Moreno a , Daniela C. Culita a , Ruxandra Birjega b , Ramona Ene a , Oana Carp a, * a “Ilie Murgulescu” Institute of Physical Chemistry, Romanian Academy, Splaiul Independentei 202, 060021 Bucharest, Romania b National Institute for Lasers, Plasma and Radiation Physics, P.O. Box Mg e 27, Magurele, Bucharest, Romania article info Article history: Received 23 January 2013 Received in revised form 13 June 2013 Accepted 19 June 2013 Available online 27 June 2013 Keywords: Green synthesis Layered compounds Zinc oxide Photocatalyst abstract Layered basic zinc salt (LBZS) that contains both carbonate and acetate as intercalated anions was ob- tained by a sonochemical procedure, using a non-basic zinc acetate aqueous solution. The compound was characterized by IR spectroscopy, thermal analysis, SEM and XRD investigations. The LBZS consists in a lamellar structure with two interlayer distances (13.70 and 19.34  A), the XRD pattern and SEM images being characteristic for turbostratic materials. The acetate anions are intercalated as free anions and monodentate ligands, while carbonate anions behave as bidentate ligands. A growth mechanism for the LBZS is advanced. Its calcination at 600  C led to ZnO porous sheets with uniform pores and pore density and a BET surface of 10.9 g/m 2 . ZnO exhibits interesting photoluminescence features, with two multi- peaks bands covering the visible region. The UV photocatalytical activity tested for phenol degrada- tion shows that ZnO acts as a promising photocatalyst, w90% of the phenol being mineralized. Ó 2013 Elsevier Masson SAS. All rights reserved. 1. Introduction The sonochemical method, i.e. chemical reaction in the presence of ultrasonic waves, proves to be an efficient, versatile and facile procedure to synthesize a large variety of materials (metals, alloys, oxides, chalcogenides, carbides, carbons, polymers, biomaterials, composites etc.) [1,2]. Additionally, sonochemically-assisted syn- thesis is a green technique since the mild, nonhazardous sound waves are capable of producing high temperature and pressure in a more energy efficient way, reducing also the reaction time and presenting often a higher selectivity and yield comparative with traditional techniques [3]. On the other hand, layered hydroxide metal salts represent a family of compounds that trigger a meaningful current interest due to their own applications in numerous and various fields (support materials [4], adsorbents [5], catalysts [6], electric devices [7], ion exchangers [8], etc.). Supplementary, layered compounds may act as substrates for different materials [9]. Since they are single-source precursors with one or more metals and with controlled structure and cationic distribution, due to the topotactic decompositions, one of the most illustrative open options is their use as precursors of simple and mixed oxides [10e13]. To date, layered compounds are usually obtained by solution methods, such as partial basic titration (NaOH [14], NH 3 [15], etc), hydrothermal methods mainly performed in basic media (HMTA [10], NH 3 [12], etc.) although there are reports that mention an acid pH [16]. The controlled hydrolysis in monools (methanol [17,18], ethanol [17], 2-methoxyethanol [17]) and polyols (diethyleneglycol [19], 1,2-propanediol [19]) solvents can also be used for the syn- thesis of layered compounds. The objective of this study is to extend the ultrasonic method to the synthesis of layered compounds, procedure tailored in our case to zinc-containing compounds. Metal acetates characterized by high water solubility, low conversion temperatures to oxides and low prices represent an appropriate choice as raw material. Generally, the hydrolysis of zinc acetate under ultrasound irradia- tion leads to crystalline ZnO, whose particles’ morphology, crys- tallinity and porosity depend on extrinsic parameters such as applied sonication output power, solvent nature, etc. In a reaction medium of watereDMF, a moderate ultrasound power led to crystalline mesoporous ZnO characterized by triangular and hex- agonal morphologies and a low density of lattice defects, while higher ultrasound power produced mesoporous ZnO nanoparticles of arbitrary morphology with higher density of lattice defects [20]. The nature of alcohol (5%) influences the crystallinity degree and the morphology of the obtained ZnO: methanol induces a flaky morphology, whereas ethanol or iso-propanol solvent determines * Corresponding author. Tel.: þ40 21367912; fax: þ40 213121147. E-mail address: ocarp@icf.ro (O. Carp). Contents lists available at SciVerse ScienceDirect Solid State Sciences journal homepage: www.elsevier.com/locate/ssscie 1293-2558/$ e see front matter Ó 2013 Elsevier Masson SAS. All rights reserved. http://dx.doi.org/10.1016/j.solidstatesciences.2013.06.011 Solid State Sciences 23 (2013) 58e64