234 Revista Română de Materiale / Romanian Journal of Materials 2011, 41 (2), 234 - 239 SILICE NANOSTRUCTURATĂ DOPATĂ CU Cr OBŢINUTĂ PRIN INTERMEDIUL AGENŢILOR DE DIRECŢIONARE A STRUCTURII ŞI A TRICARBONIL-CROM-1-FENILETILAMINEI CHORALE Cr- DOPED NANOSTRUCTURED SILICA OBTAINED VIA STRUCTURE DIRECTING AGENTS AND CHIRAL 1-PHENYLETHYLAMINE- TRICARBONYL-CHROMIUM RALUCA STAN ∗1 , CRISTINA OTT 1 , GEORGETA VOICU 2 , ADRIANA LUNGU 3 , SORIN I. ROŞCA 1 1 Catedra de Chimie Organică “C. Nenitzescu”, Str. G. Polizu nr.1, sector 1, Bucureşti, România 2 Catedra de Ştiinţa şi Ingineria Materialelor Oxidice şi Nanomateriale, Str. G. Polizu nr.1, sector 1, Bucureşti, România 3 Catedra de Ştiinţa şi Ingineria Polimerilor, Universitatea Politehnica Bucureşti, Spl. Independenţei nr. 313, sect. 6, Bucureşti, România Raportăm sinteza unor silice dopate cu Cr cu diferite morfologii obţinute prin polimerizarea sol-gel a tetraetoxisilicatului în prezenţa unor organogelifianţi derivaţi de D-sorbitol (1,3 :2,4-bis-O-benzilidene-D-sorbitol, DBS şi derivaţii săi substituiţi cu grupe nitro şi metoxi) şi a bromurii de hexadeciltrimetilamoniu, catalizată de S-(+)-1- feniletilamină-tricarbonil-crom care este şi sursa de Cr pentru o încărcare de 10% Cr/SiO 2 . Au fost observate două tipuri de morfologii : tuburi de silice cu diametre de 300- 500nm şi lungimi între 10-15µm pentru organogelifiantul cu grupe nitro şi respectiv granule aglomerate tip « colier » pentru ceilalţi Analizele EDX şi XPS au arătat o distribuţie uniformă a ionilor de Cr pe suprafaţa matricei de silice constând în 80%Cr 3+ şi respectiv 20%Cr 6+ . We report the synthesis of Cr-doped silica with different morphologies by sol-gel polymerization of tetraethoxysilicate in the presence of D-sorbitol derived organogelators (1,3:2,4-bis-O-benzylidene-D-sorbitol, DBS and its p-nitro and p-methoxy derivatives) and hexadecyltrimethylamonium bromide with S-(+)-1- phenylethylamine-tricarbonyl-chromium, acting both as chiral catalyst and source of chromium, for a 10 wt% Cr/SiO 2 loading. Two different types of morphologies were observed: silica tubes with 300-500nm diameter and 10- 15µm length for the nitro-substituted template and “necklace” type agglomerated silica granules for the other templates. EDX and XPS analyses revealed a uniform distribution of Cr ions on silica matrix consisting of 80% Cr 3+ and 20% Cr 6+ . Keywords: sol-gel, Cr-doped nanostructured silica, arene-tricarbonyl-chromium complexes, organogelator 1. Introduction Chromium ions incorporated in silica matrices with different morphologies are of great interests for spectroscopy and laser physics [1-4], anticorrosion pretreatments of metal substrates [5] and catalysis. Morphologies of the silica matrices, the nature of Cr ions and the chromium content (% wt Cr/SiO 2 ), affords special catalytic properties. Such catalysts are extensively utilized for ethylene polymerization [6], and scarcely in dehydrogenation [7, 8,] and oxidation reactions [9]. Several methods are reported for the preparation chromium doped silica, chemical vapor deposition [10], sol-gel technique [5, 11-14] and treatment of preformed silica matrices with organometallic compounds [15, 16]. The sol gel polymerization of tetraethoxysilicate (TEOS) and its derivatives is a relatively low temperature procedure which allows the control of morphology of the nanostructured silica by using different structure directing agents (SDA) and the incorporation of a large number of organic and inorganic additives [17-19]. The use of organogelators as templates for nanostructured inorganic and hybrid materials, first reported more than ten years ago [20], was summarized and discussed in a recent review [21]. Applications of sol-gel technology in order to obtained doped silica matrices present a common problem: attainment of a uniform distribution of doping constituents in the matrix. In the stage of wet gels, metallic ions migrate freely in the matrix and have the tendency to aggregate in clusters at the surface of the material during thermal treatment of the gels. In this paper we report the synthesis of nanostructured chromium-doped silica with different morphologies by sol-gel polymerization of tetraehoxysilicate (TEOS) in the presence of mixtures structure directing agents (SDA), D- sorbitol derived organogelators, (1,3:2,4-bis-O- benzylidene-D-sorbitol, DBS and its p-nitro, p-NO 2 - DBS and p-methoxy, p-CH 3 O-DBS, derivatives, previously synthesized [22-23]) and an ionic surfactant, hexadecyltrimethyl ammonium bromide (CTAB), with S-(+)-1-phenylethylamine-tricarbonyl- chromium, (MBA-Cr(CO) 3 ) acting both as a chiral catalyst and a source of chromium. We used the in-situ co-assembly templating strategy [21] in order to achieve an intimate contact of the catalyst/source of chromium with the template ∗ Autor corespondent/Corresponding author, Tel. +40-214023912, e-mail: rl_stan@chim.upb.ro , rl_stan2000@yahoo.com