Synthesis of mesoporous alumina with CO2 expanded carbonation and its catalytic oxidation of cyclohexanone

Adsorption of free radical TEMPO onto Al2O3 nanoparticles and evaluation of radical scavenging activity

This study describes the adsorption of free radical TEMPO onto Al₂O₃ nanoparticles in the solvents with different polarities including DMF, methanol, acetone, THF, petroleum ether and n-hexane at ambient temperature to evaluate the radical scavenging activity. The adsorption percentage of radical is calculated by measuring the maximum adsorption intensity of the ultraviolet (UV) absorption spectrum of TEMPO in the presence and the absence of Al₂O₃ nanoparticles. The morphology of Al₂O₃ nanoparticles before and after adsorption of TEMPO is studied using transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) spectroscopy. The adsorption energy and other thermochemical data for the adsorption of TEMPO over different active sites of Al₂O₃ are estimated via dispersion corrected density functional theory (DFT + Disp). The donor-acceptor interactions between Al₂O₃ and TEMPO are calculated using natural bond orbital (NBO) theory. It is found that Al₂O₃ nanoparticles have efficient radical scavenging activity (RSA) in the range of 50-72%. Approximately, a linear relationship between dielectric constant of solvent and the absorption percentage of TEMPO over Al₂O₃ nanoparticles is achieved. So that with decreasing the polarity of solvent, the adsorption of TEMPO onto Al₂O₃ nanoparticles is increased. The adsorption of TEMPO over Lewis acidic sites of Al₂O₃ is more favored than Brønsted acidic and basic sites. The comparison between experimental and calculated IR spectra of TEMPO/Al₂O₃ complexes provides the good evidence for adsorption of TEMPO onto the surface of Al₂O₃ nanoparticles.

Facile synthesis of mesoporous alumina using hexadecyltrimethylammonium bromide (HTAB) as template: simplified sol-gel approach

Herein the authors present the synthesis of surface functionalised mesoporous alumina (MeAl) for textural characterisation by a simplified sol-gel method obtained by using hexadecyltrimethylammonium bromide as a template. Etoricoxib (ETOX) was used as a model drug for the study. Alumina supported mesoporous material containing drug was characterised using instrumental technique namely Brunauer-Emmett-Teller surface area, Fourier transform-infrared, differential scanning calorimetry, transmission electron microscopy, X-ray diffraction, and field emission scanning electron microscopy. Diffusion study using a dialysis bag method used to check the release pattern of ETOX-loaded-MeAl. Results of characterisation study revealed the successful surface functionalisation of the drug on nanocomposite. The IC50 value obtained from cell viability study demonstrated the non-toxic behaviour of synthesised drug-loaded mesoporous alumina up to the tested concentration range. The present work has demonstrated that synthesised MeAl showed excellent stability with an expanded surface area suitable for carrier material for drug delivery system.

Chemical Synthesis and Characterization of Nano Alumina, Nano Composite of Carbon–Alumina and Their Comparative Studies

Aluminium oxide (Al2O3) nano particles were synthesized by using both the sol gel technique and solid state reaction (SSR) method. Different proportion of nano carbon cones from 0.5% to 3.5% is doped with aluminium nitrate nano hydrate and annealed subsequently at 1000°C for 3 h to synthesize the nano composite of carbon–alumina. The synthesized samples were characterized by X-ray diffraction to identify the presence of different phases and transitions during this process. The average crystallite size of the nano alumina is found to be 45 nm by sol gel and 43 nm by SSR method respectively by Debye–Scherrer method. Average crystallite size and lattice strain of nano alumina are also estimated from Williamson Hall (WH) plot analysis. It is found to be 69 nm with the strain of 3.3×10−3 in sol gel, and in SSR method, it is 72 nm with the strain is 3.9×10−3. The interplanar distance of various planes of alumina are estimated and compared with JCPDS values. Similar analysis has also been extended for the nano composite of carbon–alumina. The surface morphology of the samples are analyzed using scanning electron microscopy and rough estimate of the crystallites is also given. From the Raman analysis, the presence of alpha phase of alumina has been confirmed. The presence of carbon in the composite has been established through diffuse reflectance spectroscopy. The FTIR spectra of the composite samples ensured the presence of Al–O–Al, O–H and C=O bonds.