[show abstract][hide abstract] ABSTRACT: A thien-2-yl substituted, electron-rich phenothiazine has been converted over several steps into a redox active sol-gel precursor. Following a fluoride-catalyzed synthesis, a phenothiazine-based mesoporous hybrid organosilica was obtained. The electrochemical behavior and the luminescence properties of the immobilized chromophore have been studied using solid state fluorescence spectroscopy, electron paramagnetic resonance spectroscopy (EPR) and solid state voltammetry (CV and DPV). The influence of both the presence of fluoride anions and the acidic pH during the material synthesis were explored by means of scanning and transition electron microscopy (SEM and TEM), X-ray powder diffraction (XRD) and nitrogen physisorption measurements. While a combination of acidic pH and fluoride was found necessary for the material formation, partial cleavage of the precursor was observed. Data obtained from both the chemical as well as the electrochemical oxidation / reduction of the immobilized PT dye indicates the formation of an organic layer containing several species inside the pore channels.
[show abstract][hide abstract] ABSTRACT: The synthesis of strongly fluorescent silica alcogels and glasses containing covalently bound thienyl arenes as organic chromophores and their luminescence properties are described. The rational design of a white light emitting gel is explained with respect to the principle of additive color mixing. CIE coordinates for the different emitters have been determined, illustrating how mixtures of chromophores can create different shades of white to off-white light. 5,8-Dithien-2-ylquinoxaline, which was embedded in one of the alcogels, was found to be a white light emitting molecule itself. For a representative fluorogel incorporating an acridone dye, quantum yield and excitation measurements were conducted on silica samples incorporated in layers of PMMA. This revealed absolute quantum yields of 5.6% to 7.4% for the analyzed species at concentrations of 10 weight-% of silica. With respect to the facile synthesis of the glasses and the extremely low dye concentrations of approximately 6 × 10^-6 mol/g, these new hybrid compounds pave the way towards the use of enhanced metal-free hybrid emitters in various coating and lighting applications.
Microporous and Mesoporous Materials 02/2013; · 3.37 Impact Factor
[show abstract][hide abstract] ABSTRACT: Three highly fluorescent phosphonates have been prepared in good yields from different arylene bridged 5-iodothiophenes by following an optimized four-step procedure. The compounds have been immobilised on mesoporous zirconia, alumina and titania particles in order to probe their luminescence properties on the surfaces. The organic compounds as well as the obtained hybrid materials have been characterised using liquid phase or MAS NMR spectroscopy, N(2) physisorption measurements, ATR-IR spectroscopy and elemental analysis. The luminescence intensity of the organic molecules was found to be in general much more dependent on the surface used for grafting rather than on the dye loading obtained for different metal oxides powders. The luminescence extinction, which has been detected for all coated TiO(2) samples, is most likely due to the different electronic properties of this semiconducting support compared to the other surfaces. The method described shows how fluorescent tracers can be easily synthesised and applied in surface analytics after exploring the interaction of the corresponding organophosphonates with several ceramic interfaces.
[show abstract][hide abstract] ABSTRACT: A Mobil Composition of Matter (MCM)-41 type mesoporous silica material containing N-propylacridone groups has been successfully prepared by co-condensation of an appropriate organic precursor with tetraethyl orthosilicate (TEOS) under alkaline sol-gel conditions. The resulting material was fully characterized by means of X-ray diffraction (XRD), N(2)-adsorption-desorption, transmission electron microscopy (TEM), IR and UV-vis spectroscopy, as well as (29)Si and (13)C CP-MAS NMR techniques. The material features a high inner surface area and a highly ordered two-dimensional hexagonal pore structure. The fluorescence properties of the organic chromophore can be tuned via complexation of its carbonyl group with scandium triflate, which makes the material a good candidate for solid state sensors and optics. The successful synthesis of highly ordered MCM materials through co-condensation was found to be dependent on the chemical interaction of the different precursors.
Beilstein Journal of Nanotechnology 01/2011; 2:284-92. · 2.37 Impact Factor
[show abstract][hide abstract] ABSTRACT: Triethoxysilyl functionalized phenothiazinyl ureas were synthesized and immobilized by in situ synthesis into mesoporous hybrid materials. The designed precursor molecules influence the structure of the final materials and the intermolecular distance of the phenothiazines. XRD and N(2) adsorption measurements indicate the presence of highly ordered two-dimensional hexagonally structured functional materials, while the incorporation of the organic compounds in the solid materials was proved by means of (13)C and (29)Si solid state NMR spectroscopy as well as by FT-IR spectroscopy. Upon oxidation with (NO)BF(4) or SbCl(5), stable phenothiazine radical cations were generated in the pores of the materials, which was detected by means of UV/Vis, emission, and EPR spectroscopies.
Chemistry - An Asian Journal 09/2010; 5(9):2001-15. · 4.57 Impact Factor