MCM-41-CdS nanoparticle composite material: Preparation and characterization E. Caponetti a,b, * , L. Pedone a , M.L. Saladino a , D. Chillura Martino a , G. Nasillo b a Dipartimento di Chimica Fisica ‘‘F. Accascina”, Università di Palermo, Viale delle Scienze pad. 17, Parco d’Orleans II, Palermo I-90128, Italy b Centro Grandi Apparecchiature, Università di Palermo, Via Marini 14, Palermo I-90128, Italy article info Article history: Received 24 March 2009 Received in revised form 6 August 2009 Accepted 10 August 2009 Available online 14 August 2009 Keywords: Mesoporous Hierarchical structures MCM-41 CdS nanoparticles abstract The preparation and characterization of a hierarchical material constituted by a mesoporous silica MCM-41 whose mesochannels contain CdS nanoparticles capped with both bis(2-ethylhexyl) amine and bis(2-ethylhexyl) sodium sulfosuccinate is reported. MCM-41 powder was synthesized by using the LCT methodology. CdS nanoparticles were obtained within the inversed micelle core of a water/ AOT/n-heptane microemulsion. Nanoparticles growth was followed by means of UV–Vis spectroscopy and was inhibited by BEA addition. The CdS-capped nanoparticles were separated by centrifugation, washed with water and ethanol and finally dispersed in n-heptane. The insertion of CdS nanoparticles into MCM-41 mesochannels was obtained by adding mesoporous silica into the n-heptane nanoparticles dispersion. The yellow MCM-41-CdS nanoparticles composite was characterized by using different structural (X-ray diffraction, nitrogen adsorption–desorption isotherm and small angle neutron scatter- ing coupled with the contrast variation method), spectroscopic (diffuse reflection UV–Vis, attenuated total reflection and diffuse reflectance Fourier transform infrared) and morphological techniques (high resolution transmission electron microscopy). The CdS nanoparticles, significantly capped by both the amine and the surfactant molecules, were found to be localized inside the cylindrical silica pores. The mesoporous material loses its long-range order while the incorporation process does not affect the size and electronic structure of CdS nanoparticles. Ó 2009 Elsevier Inc. All rights reserved. 1. Introduction One of the new aims in the materials science is the creation of hierarchical structures having a long-range order gotten from the assemblage of preformed components, with the purpose to pro- duce an ordered material whose properties show synergic effects with respect to those of the individual constituents. Beside, nanomaterials with an ordered structure have properties that can be discussed on the basis of their defined nanoscopic structures. Chemical, physical and mechanical properties, insofar, can be con- trolled organizing guest–host species into matrixes with appropri- ate geometry and chemical environments [1,2]. In this paper, the preparation and the characterization of a hier- archical material constituted by a mesoporous silica whose meso- channels contain two different amounts of semiconductor (CdS) nanoparticles capped with bis(2-ethylhexyl) sodium sulfosucci- nate (AOT) and bis(2-ethylhexyl) amine (BEA) are reported. MCM-41 can be considered the most important mesoporous material of a class of materials, known as MCM (mobil composition of matter). It can be depicted as an array of cylindrical pores having diameter in the range between 2 and 50 nm, surrounded by amor- phous silica and organized in a hexagonal long-range structure; cylinders length results in the range of microns [2]. The prominent features of MCM-41, whose pores can be tailored and finely tuned, are: very high surface area and reactivity, well-defined pore shape with a narrow size distribution, large amounts of internal hydroxyl groups, ease modification of the surface properties, enhanced cat- alytic selectivity, and excellent thermal, chemical and mechanical stability. These features have allowed using MCM-materials as cat- alysts of many petrol–chemical [3–5] and redox process in liquid phase [6,7], as heteropolyacid support [8], as highly efficient adsor- bents [9,10] and as molecular hosts [11,12]. Nanoparticles are characterized by a high surface/volume ratio and this has opened the field to the applications where the surface properties result important. The chemical and physical properties of nanoparticles sensibly differ from those of bulk material and of isolated atoms and molecules. Insofar the interest in their re- spects derives from the drastic change that electric, magnetic, cat- alytic and optical properties undergo when the size of a material is reduced from infinite to nanometric dimensions. During the last decade, the preparation and the characterization of a variety of nanometric metals, oxides and sulfides have been re- ported [13–15]. Among them, semiconductor nanoparticles are 1387-1811/$ - see front matter Ó 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.micromeso.2009.08.010 * Corresponding author. Address: Dipartimento di Chimica Fisica ‘‘F. Accascina”, Università di Palermo, Viale delle Scienze pad. 17, Parco d’Orleans II, Palermo I- 90128, Italy. Tel.: +39 091 6459842; fax: +39 091 590015. E-mail address: caponett@unipa.it (E. Caponetti). Microporous and Mesoporous Materials 128 (2010) 101–107 Contents lists available at ScienceDirect Microporous and Mesoporous Materials journal homepage: www.elsevier.com/locate/micromeso