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Fluorescent organic-inorganic mesoporous hybrid materials have been prepared and characterised, and their behaviour against nitroaromatic explosives have been tested. MCM-41 silica was used as an inorganic scaffold and pyrene ( P derivative containing trialkoxysilane moieties), dansyl and fluorescein ( D and F derivatives also containing trialkoxysilane groups, respectively) fluorophores have been anchored on hybrid materials by a co-condensation method to obtain a homogenous distribution of dyes into the pores of the support. Six sensing materials have been prepared, of which SP, SD, SF were hydrophilic and SPh, SDh, SFh were hydrophobic. Template-free hydrophilic materials ( SP, SD, SF) were obtained after repeated NH4NO3/ethanol extractions under temperature from as-synthesised ( MP, MD and MF supports, respectively) solids. Hydrophobic materials (SPh, SDh, SFh) were prepared by using excess 1,1,1,3,3,3-hexamethyldisilazane with template-free hydrophilic ( SP, SD and SF) materials. The six final materials displayed the typical emission bands of the grafted fluorophores. In particular, SP and SPh show the typical pyrene monomer (370-420 nm) and excimer (430-600 nm) emissions. SD and SDh exhibit the broad dansyl fluorescence band in the 450-600 nm range, whereas solids SF and SFh present sharp fluorescein emission centred at 525 nm. The fluorescent behaviour of the six final materials was tested in the presence of explosives (pentaerythritol tetranitrate (PETN), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), nitrobenzene (NB), 1,3,5-trinitrobenzene (TNB), 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), 2,4,6-trinitrophenylmethylnitramine (Tetryl) and picric acid (PA)). Only nitroaromatic compounds were able to induce emission quenching. As a general trend, the quenching degree depended on the nature of the final material. The best response was obtained with explosives PA and Tetryl, which were able to significantly quench the emission of the sensing supports. The observed quenching was ascribed to the π-π stacking interactions between the electron-donor fluorophores and the electron-withdrawing nitroaromatic explosives. When using SPh for Tetryl and PA, the limits of detection were 8.5 and 1.4 ppm, respectively, whereas they were 14.4 and 1.2 ppm for SDh. Principal component analysis algorithms were applied to the fluorescence measurements taken with the six hybrid materials and the seven explosives. The obtained score plot showed well-defined clusters for the seven explosives tested. Finally, solid SDh was applied to detect trace amounts of Tetryl in soil samples with good results. [ABSTRACT FROM AUTHOR]

Abstract: Designing and synthesis of inorganic materials containing magnetic elements with nanoscale periodicity is one of the areas of major research interests due to their potential memory applications. A series of ordered mesoporous lanthanum–manganese oxides has been synthesized hydrothermally using saturated fatty acids as templates in the presence of ethylenediamine (EDA) as mineralizer. Templates are removed from these as-synthesized materials through repeated ethanol–EDA extraction at 333K. As-synthesized and template-free samples have been characterized by powder X-ray diffraction, transmission and scanning electron microscopy, N2 sorption and X-ray photoelectron spectroscopic studies. The observed BET surface area for the template-extracted sample synthesized by using lauric acid is 304m2 g−1, which on further heating at 673K resulted in a nonstoichiometric porous LaMnO3+ δ manganite material having a further improved BET surface area of 406m2 g−1. The low temperature magnetic measurements revealed that the material becomes ferromagnetic at 45K. [Copyright &y& Elsevier]

A new Pd(ii) bounded 2D-hexagonally ordered functionalized MCM-41 type material (IV) has been synthesized. Functionalization was carried out by the anchoring of 3-aminopropyltriethoxysilane in the MCM-41 type mesoporous material, followed by grafting with 2,6-diacetylpyridine (DAP) to give a N3-type Schiff base chelating attachment for the Pd(ii) species. Fourier transform infrared (FTIR), powder X-ray diffraction (PXRD) and high resolution transmission electron microscopy (HRTEM) studies have been used to characterize the material. Material IVbehaves as a highly active catalyst towards Suzuki–Miyaura cross-coupling reaction for the synthesis of biaryl organics. In addition, IVacts as a true heterogeneous catalyst in coupling reaction. It was found that this catalyst is highly efficient and recyclable towards Suzuki–Miyaura reaction with high turn over frequencies. X-Ray photoelectron spectroscopic (XPS) analysis was employed to understand the oxidation state of the palladium atom in the catalyst (IV) and its loading in the material. [ABSTRACT FROM AUTHOR]