Synthesis of mesostructured metal sulfide films using [M(H 2 O) n ](NO 3 ) 2 :P85 (M ¼ Cd(II) and Zn(II)) liquid crystalline mesophases Yurdanur Tu ¨rker and O ¨ mer Dag * Received 13th March 2008, Accepted 13th May 2008 First published as an Advance Article on the web 17th June 2008 DOI: 10.1039/b804344b Transition metal salt–pluronic liquid crystalline (TMS–PLC) mesophases of A–P85, B–P85 and ((1  x)A + xB)–P85 (where A is [Cd(H 2 O) 4 ](NO 3 ) 2 , B is [Zn(H 2 O) 6 ](NO 3 ) 2 and P85 is a triblock copolymer, HO(CH 2 CH 2 O) 26 (CH 2 (CH 3 )CHO) 40 (CH 2 CH 2 O) 26 H) have been used to produce mesostructured metal sulfide films. The TMS–PLC mesophases of A–P85, B–P85 and (A + B)–P85 are well ordered with a salt/P85 mole ratio between 3.0 and 11.0 with a 3D hexagonal structure. The reaction between the mesophases of A–P85, B–P85 and ((1  x)A + xB)-P85 and H 2 S gas at room temperature produces mesostructured CdS, ZnS and Cd 1x Zn x S films, respectively. The initial salt concentrations in the TMS–PLC phase determine the final Cd(II) and Zn(II) ions in the Cd 1x Zn x S crystal structure, where x can be controlled between 0.0 and 1.0. Fresh samples of the mesophase reacted under an H 2 S atmosphere are continues films that slowly leach out excess P85 producing P85 rich dendrite domains and aggregates of 50 to 100 nm particles of mesostructured CdS, ZnS or Cd 1x Zn x S. However, well homogenized TMS–PLC mesophases produce stable film samples upon H 2 S reaction. 1. Introduction Mesoporous materials 1 were discovered in the early 1990s using the surfactant templating approach. This approach has been expanded to produce many mesostructured insulators, 1–3 semi- conductors 4,5 and metals. 6,7 The polymerization of the inorganic/ organic precursors (IP/OP) can also be carried in a liquid crys- talline mesophase (LCM) to produce mesostructured materials. 3 In the liquid crystalline templating process, the initial mixture (water : surfactant : acid : IP/OP) is usually a liquid that trans- forms into an LCM and finally to solid mesostructures upon several minutes of aging. 3 This approach has already been employed to produce silica, 3 metal sulfides, 4,5 and metals. 6,7 Kuroda et al. 7 have expanded the system using ethanol solutions of a water : salt : surfactant systems that form the LCM with the evaporation of ethanol on an electrode surface to produce mesostructured Pt and Pt–Ru. Recently, Dag et al. have discovered a new LC mesophase that consists of transition metal salt and non-ionic surfactants or pluronics at high metal salt concentrations. 8 The salt–surfactant LC mesophase exist because the metal ions that are dissolved in the media have coordinated water molecules, M–OH 2 , that induce self-assembly in surfactant molecules to form hexagonal, tetragonal, lamellar and cubic mesophases through hydrogen bonding (M–OH 2 /(OCH 2 CH 2 ) x -R) with ethylene oxide units of the surfactant molecules. 5,8 Controlling the quantity and type of the anion (as the counter ion in the metal salt) allows one to control the structure of salt–surfactant LC mesophases. 8c The mixed salt systems, (A + B)-P85 (where A and B are two different transition metal salts), also form LC mesophases that are important for incorporating more than one type of metal ions at a time into the LC structure and into mesostructured solid materials. Specifically, this allows one to incorporate magnetic or optical components into metal oxides and wide band gap semi- conductors, leading to advanced functional materials. The II–VI semiconductors belong to an important class of materials due to their useful functionality, such as photo- luminescence, photonics and photocatalysis. 9,10 The alloy metal sulfides also have the advantage that it is possible to tune the band gaps and, as a result, the optical output of the metal sulfide materials. 11,12 In this contribution, we have focused on the LC mesophases of the [Cd(H 2 O) 4 ](NO 3 ) 2 and [Zn(H 2 O) 6 ](NO 3 ) 2 salts with P85. As in the individual salt–P85 systems, the mixed salt–P85 systems also form hexagonal mesophases between a salt/P85 mole ratio of 3.0 and 11.0. The TMS–PLC mesophases were reacted under an H 2 S gas atmosphere at RT to produce mesostructured Cd 1x Zn x S, where x can be controlled between 0.0 and 1.0. Cd 1x Zn x S and Cd 1x Mn x S nanocrystallites have been produced in various media, 11,12 however, to the best of our knowledge, this is the first investigation of mesostructured Cd 1x Zn x S films. The LC mesophase of the mixed salt–P85 systems and mesostructured Cd 1x Zn x S films have been char- acterized using XRD, EDS, SEM, TEM, FTIR, micro-Raman, and UV-Vis absorption techniques. 2. Experimental 2.1. Synthesis of CdS, ZnS and Cd 1x Zn x S in salt:P85 LC media The [Zn(H 2 O) 6 ](NO 3 ) 2 and [Cd(H 2 O) 4 ](NO 3 ) 2 salts were dis- solved in 10 ml ethanol by targeting the total salt surfactant mole ratios of 1.0, 3.0, 5.0, 7.0, 9.0, 11.0, 13.0 and 20.0. To this solution 1.0 g of P85 was added. The resulting solutions were Laboratory for Advanced Functional Materials, Department of Chemistry and Institute of Materials Science and Nanotechnology – UNAM, Bilkent University, 06800, Ankara, Turkey. E-mail: dag@fen.bilkent.edu.tr; Fax: +90-312-2664068; Tel: +90-312-2903918 This journal is ª The Royal Society of Chemistry 2008 J. Mater. Chem., 2008, 18, 3467–3473 | 3467 PAPER www.rsc.org/materials | Journal of Materials Chemistry Published on 17 June 2008. Downloaded by Bilkent University on 28/08/2017 12:59:09. View Article Online / Journal Homepage / Table of Contents for this issue