Papers by Keyword: Hybrid Material

Abstract: While searching for adequate sol-gel methodologies for successfully trapping in monomeric and stable form either porphyrins or phthalocyanines, inside translucent monolithic silica xerogels, it was discovered that the interactions of these trapped tetrapyrrole macrocycles with Si-OH surface groups inhibit or spoil the efficient display of physicochemical, especially optical, properties of the confined species. Consequently, we have developed strategies to keep the inserted macrocycle species as far as possible from these interferences by substituting the surface ^-OH groups for alkyl or aryl groups or trapping these species inside alternative metal oxide networks, such as ZrO₂, TiO₂, and Al₂O₃. In the present manuscript, we present, for the first time to our knowledge, a methodology for preserving the spectroscopic characteristics of metal tetrasulfophthalocyanines and cobalt tetraphenylporphyrins trapped inside the pores of ZrO₂ xerogels. The results obtained are contrasting with analogous silica systems and demonstrate that, in ZrO₂ networks, the macrocyclic species remain trapped in stable and monomeric form while keeping their original spectroscopic characteristics in a better way than when captured inside silica systems. This outcome imply a lower hydrophilic character linked to the existence of a smaller amount of surface hydroxyl groups in ZrO₂ networks, if compared to analogous SiO₂ xerogel systems. The development and study of the possibility of trapping or fixing synthetic or natural tetrapyrrole macrocycles inside inorganic networks suggest the possibility of synthesizing hybrid solid systems suitable for important applications in technological areas such as optics, catalysis, sensoring and medicine

Abstract: Reducing vehicle weight to decrease energy consumption and engine emissions is one of the major objectives of the automotive industry today. This goal is mainly achieved by developing new manufacturing technologies for structural lightweight components, such as the hybrid injection molding/composite forming process, which involves preforming a thermoplastic composite laminate and overmolding it to add ribs, attachment points and other features. High part lightness, short cycle times and high degree of automation have recently made this technology an effective solution for the manufacturing of automotive interiors, including door side-impact beams and front ends. In this paper a model of the adhesion bonding mechanism between the overmolded reinforced thermoplastic and the formed composite sheet is proposed, and its dependence on the main process parameters is investigated. The model has been developed conducting experimental tests and eventually validated by means of a significant case study.

Abstract: A new hybrid material performed by the immobilization of indigo particles on nanocarbonaceous matrix has been developed, characterized and implemented with chemoresistors. If phthalocyanine-based chemoresistors provide a high sensitivity, a low threshold of detection and a partial selectivity towards oxidizing pollutants, indigo/nanocarbons hybrid material acts as a selective ozone filter from air sample and so strongly enhances the sensor selectivity towards nitrogen dioxide. The functionalization, highlighted by scanning electron microscopy, X-ray diffraction and thermogravimetric analysis, occurs in a non-covalent way and proceeds through pi-stacking interactions. With filtering yields higher than 99.5% for ozone and less than 5% for nitrogen dioxide, indigo adsorbed onto multi-wall carbon nanotubes has been identified as the most selective filtering material while exhibiting a much greater durability than indigo or nanotubes separately. Associated to phthalocyanine-based gas sensor, the sustainable, selective and real-time monitoring of NO₂ in ppb range has been successfully achieved.

Abstract: Hybrid nanomaterials based on organic layer covalently grafted on porous silicon (PSi) nanostructure appear as promising systems for innovative applications such as detecting of traces amounts and/or removing metal cations in water effluents. In this work, we focused on the functionalization of the PSi nanostructure by the peptide GlyCysGlyCys, which forms stable complexes with metal ions. This property is exploited to achieve toxic metal recognition in water using electrochemical methods. Peptide immobilization was achieved using multi-step reactions; GlyCysGlyCys was anchored on a previously prepared carboxyl-terminated PSi surface, using EDC/NHS coupling agents. This scheme is compatible with the mild conditions required for preserving the probe activity of the peptide. At each step of the functionalization, the surface was monitored by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Electrochemical behavior of such modified electrode was carried out after Nickel accumulation on the surface, by means of cyclic voltammetry. The recorded cyclic voltammograms showed a quasi-irreversible process corresponding to the Ni²⁺/Ni⁰ couple.

Abstract: The 0.5-3.0 mol% Er³⁺-Ce³⁺ co-doped TiO₂ powders have been prepared by sintering the hybrid materials Er_0.5Ce_0.5(AA)₃phen-doped TiO₂/PMMA, which were prepared by sol-gel method, using the modified titanium (IV) n-butoxide [Ti(O-Bu)_4-x(AAPhen)_x] as precursors which were given by the chelate reaction between Ti(O-Bu)₄, AA and Phen at 70°C. The hybrid matrix TiO₂/PMMA improved the dispersion of Er³⁺, which caused an enhancement in the photoluminescence (PL) peak intensity at 1.53 mm of the 1 mol% Er (AA)₃phen-doped TiO₂/PMMA powders sintered at 700 °C of about 23 times higher than that only had TiO₂ as its matrix. When co-doped with Ce³⁺, the above ratio of the PL peak intensity was raised to 75 times, which illustrated the obvious sensitization and dispersion effects of Ce³⁺ on Er³⁺.

Abstract: Hybrid silica xerogel mesoporous composite was synthesized by a mild temperature acid catalysed sol-gel route where a natural copolymer; sodium alginate (Na-COOH) together with calcium oxide (CaO) powder were incorporated into silica sol precursor prior to gel formation. For this study, bulk xerogels samples were prepared with the amount of silica precursor and the natural copolymer was fixed meanwhile the loading of calcium oxide was varied at 10 and 20 wt%. The monolith silica was also synthesized as control parameter. The preliminary properties were investigated using XRD, FTIR and SEM together with EDS for elemental analysis. The calcium oxide powder used in this study was prepared from calcium hydroxide, CaOH compound, which was previously calcined at 1000°C for 3 hours in normal air. The component of calcium oxide and sodium alginate were found to be uniformly dispersed in matrixes without affecting the cross-linked silica formation. As the presence of the components in the silica matrixes, the synthesized hybrid xerogels were found to be crack-free, structurally amorphous and physically opaque. Furthermore, the hybrid xerogels samples were found to have denser bodies, smoother surface, and decreased in particle sizes and thus might produced less brittleness in nature compared to the monolith xerogels.

Abstract: Hybrid silica xerogel mesoporous composite was synthesized by a low temperature acid catalysed sol-gel route where a natural copolymer; sodium alginate (Na-COOH) together with calcium oxide (CaO) powder were incorporated into silica sol precursor prior to gel formation. For this study, bulk xerogels samples were prepared with the amount of silica precursor and the natural copolymer was fixed meanwhile the loading of calcium oxide was varied at 10 and 20 wt%. The porous properties were studied and the comparison between the hybrid silica and monolith was made. The calcium oxide powder used in this study was prepared from calcium hydroxide, CaOH compound, which been calcined at 1000°C for 3 hours in normal air. Mesoporous structure with small particle size and glassy phase of matrixes are the main features of the prepared xerogels. The presence of sodium alginate and calcium oxide in silica matrixes produces a significant decrease especially in total surface area and porosity volume of the xerogel samples. Monolith silica xerogels exhibits a very large surface area approximately at 600 m²/g compared to the hybrid xerogels which showed 120m²/g and 25m²/g for the respective 10 and 20 wt.% of calcium oxide loading. Nevertheless, only a slight increased in pore size has been observed due to the increased amount of calcium oxide loading.

Abstract: Novel ladderlike polysilsesquioxanes containing polypropylene moieties (LPS-PP) were synthesized from LPS having chloromethylphenyl groups (LPS) and polypropylene having hydroxyl groups (PP-OH). LPS-PP was characterized by FT-IR, DSC, SEM, EDX, and TGA. The obtained LPS-PP shows no melting temperature due to the disappearance of melting temperature of PP, indicating the rigidity of Si-O-Si backbone in ladderlike LPS. The char yield of LPS-PP is higher than that of PP-OH because of the silica parts of LPS. This new LPS-PP can be an interesting candidate to fabricate hybrid materials using interactions or compatibility between PP moieties of LPS and various organic polymers.

Abstract: Carbon nanotubes (CNTs) doped TiO₂/glass fiber reinforced plastics (GRP) hybrid materials were prepared by first step sol-gel and then hand lay-up method, using modified CNTs doped tetrabutyl titanate as precursor. The results showed that TiO₂ component as the inorganic material, could improve the high temperature stability of the GRP, and the latticework structure of the hybrid material could disperse the CNTs well and prevented them from gathering at high temperature.

Abstract: A novel sol-gel hybrid material was synthesized based on sol-gel method using TEOS as precursors, KH570 as modifying agent, and EGDMA as cross linking agent. The obtained hybrid material exhibited excellent affinity to clenbuterol and florfenicol, and successfully applied to the home-made miniaturized SPE device for extraction and clean-up of clenbuterol and florfenicol from milk samples. Under the optimized conditions, the consumption of the hybrid material as SPE sorbent was low to 20 mg. Satisfactory linearity ranging from 0.2-20 μg/mL were obtained with r²0.9990, and the recoveries at three spiked levels were ranged from 90.7-103.7% with RSD less than 2.7%.