Silica Meets Tannic Acid: Designing Green Nanoplatforms for Environment Preservation

Hybrid tannic acid-silica-based porous nanoparticles, TA-SiO2 NPs, have been synthesized under mild conditions in the presence of green and renewable tannic acid biopolymer, a glycoside polymer of gallic acid present in a large part of plants. Tannic acid (TA) was exploited as both a structuring directing agent and green chelating site for heavy metal ions recovery from aqueous solu-tions. Particles morphologies and porosity were easily tuned by varying the TA initial amount. The sample produced with the largest TA amount showed a specific surface area an order of magnitude larger than silica nanoparticles. The adsorption performance was investigated by using TA-5SiO2 NPs as adsorbents for copper (II) ions from an aqueous solution. The effects of the initial Cu2+ ions concentration and the pH values on the adsorption capability were also investigated. The resulting TA-SiO2 NPs exhibited a different adsorption behaviour towards Cu2+, which was demonstrated through different tests. The largest adsorption (i.e., ~50 wt% of the initial Cu2+ amount) was obtained with the more porous nanoplatforms bearing a higher final TA content. The TA-nanoplatforms, stable in pH value around neutral conditions, can be easily produced and their use would well comply with a green strategy to reduce wastewater pollution

Synthesis structure and stability of amino functionalized PEGylated silica nanoparticles

Amino functionalized PEGylated silica nanoparticles were prepared by one pot-procedure, based on ammonia catalysed hydrolysis and polycondensation of Tetraethoxysilane (TEOS) and 3-Aminopropyltriethoxysylane (APTS), in alcohol medium (ethanol) (Sather method), containing PEG 5000 monomethyl ether. Particles size was studied using Transmission Electron Spectroscopy (TEM). PEGylation and amino functionalization was investigated through FT-IR and Thermogravimetric analysis (TG). The structure of nanoparticles consists of nanosilica (a few nanometers in size) dispersed into a PEG matrix, produced by entanglement of PEG chains. The stability of the water colloidal suspension depends on the PEG/silica mass ratio, that changes with PEG concentration in the reaction batch. By properly selecting the PEG concentration, nanoparticles smaller than 150 nm were obtained, stable towards aggregation in water media up to 6 months. The observed need of an optimal PEG/silica mass ratio for long-term stability can be explained on the basis of particles structure and assuming that both steric and electrostatic effect concur to stabilisation. (C) 2010 Elsevier BM. All rights reserved

Bioactive poly(2-hydroxyethylmethacrylate) (pHEMA)/Silica gel hybrid nanocomposites prepared by sol-gel process

A hybrid of poly(2-hydroxyethyl methacrylate) (pHEMA), a polymer widely employed for biomedical applications, and silica gel, exhibiting a well-known bioactivity, was produced by sol-gel. The amt. of the inorg. precursor, tetraethoxysilane (TEOS), was mixed to the org. monomer, so as to have a final concn. of 30% (wt./wt.) of silica gel to the mass of polymer. The nanocomposite was characterized for its compn. by thermogravimetric (TG) anal., swelling behavior, glass transition temp. using DTA, morphol. through SEM, and bioactivity using FT-IR spectroscopy, SEM, and energy dispersive system (EDS). The nanocomposite showed phase sepn. between the polymer and the silica gel, improved thermal stability and swelling properties and higher glass transition temp. than pHEMA. Moreover, bioactive SiO2 gel nanoparticles promoted apatite formation on the surface of the modified hydrogel, when it was soaked in SBF. Therefore, the obtained bioactive nanocomposite can be used to make bioactive scaffold for bone engineering

A new methodology to recognize the use of long aged lime putties

In this paper a new methodology, combining chemical and thermogravimetric (TG) investigations, is proposed useful to get information about the use of lime putties after long aging. The method is applied with reference to two Roman mortars with different age: I C AD, when the technology of aging lime putty in deep ground hollows under a thin water layer for long times was fully assessed, and II C BC, when the Roman hydraulic mortars technology was in its infancy. The amounts of binder phase were estimated from the residue of HCl attack; a simple method was followed to assess the length of the chemical attack. The composition of the binder phase (as calcite and hydraulic components contents) were estimated from the TG curves. By combining the above results, the structurally bound water contents in the hydraulic components could be estimated. With respect to the II C BC mortar, the I C AD one shows: a) much greater structurally bound water content; b) an earlier CO2 removal during a TG run. These differences are explained on the basis of the use of differently aged lime putties, in good agreement with the expectations based on the mortars dating. © 2016 Elsevier B.V. All rights reserved

Heparin conjugated silica nanoparticle synthesis

We report on a facile method towards a synthesis of novel hybrid heparin silica nanoparticles involving a modification of the Stober method. Tetra-Pr orthosilicate (TPOS) was used instead of the traditional TEOS or TMOS; by this way we could overcome the soly. problems of heparin in ethanol and exploit the good soly. of heparin in proper isopropanol-water mixts. Aminopropyl triethoxysilane (APTS) was also used to have a good link of heparin to silica particles. SEM, DLS, FTIR and NMR proved that we did find conditions in which heparin conjugated silica particles were produced.Thermogravimetry allowed to evaluate the heparin/silica wt. ratio to be 0.61. The efficiency of heparin binding to the particles was appreciated to be 35 wt.%

A new extra situ sol-gel route to silica/epoxy (DGEBA) nanocomposite. A DTA study of imidazole cure kinetic

Silica nanoparticles were obtained through the Stober method, from mixtures of tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTS). The nanoparticles were dispersed in tetrahydrofuran (THF) and coupled to bisphenol A epoxy resin (DGEBA) through surface amino groups. After removing THF non-isothermal cure was performed at different heating rates (2-20A degrees C/min), using imidazole (2-4 wt%) as curing agent. For the sake of comparison bare DGEBA epoxy polymers were also prepared with similar schedule A nanocomposite of well-dispersed silica nanoparticles (5 wt%) in a fully cured epoxy matrix was easily obtained. Lower cure kinetics were observed with silica addition. This was attributed to reduction of the imidazole volume concentration. Cure activation energy was not influenced by silica presence, whereas it changed with the imidazole content. Therefore, experimental results suggested that silica had only an indirect effect (the reduction of the imidazole molar concentration) on the epoxy matrix cure kinetics. Glass transformation temperatures, T (g), as high as 175A degrees C were recorded. The nanocomposite glass transformation temperature depended on the heating rate of the cure process, the imidazole and silica content. T (g) changes as high as 40A degrees C were detected as a function of the heating rate. At higher imidazole content no differences in T (g) values between bare polymer and the nanocomposite were observed. This suggests that a higher imidazole content assures a better interconnection between the compatibilizing epoxy shell around the nanoparticles and the epoxy matrix. The new proposed methodology is an easy route to engineer both nanocomposites structure and interfacial interactions, thus tailoring their properties