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1.
J Nanosci Nanotechnol ; 20(2): 840-851, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31383079

RESUMO

A mixture of Cu (10%) and Fe (1 to 9%) was deposited on multiwalled carbon nanotubes (MWCNTs) and mesoporous carbon (MC). The catalytic activity was investigated in a reaction between carboxylic acids/esters and aromatic amines. The physico-chemical properties of the materials were characterized by different analytical techniques such as powder XRD (X-ray diffraction), BET (brunauer emmett teller) surface area, XPS (X-ray photoelectron spectroscopy), TPD-NH3 (thermal desorption spectroscopy), SEM-EDS (scanning electron microscopy-energy dispersive spectroscopy) and TEM (transmission electron microscopy). The catalytic activity was investigated in the synthesis of aliphatic and aromatic amides from aliphatic/aromatic carboxylic acids and esters with aniline/benzyl amine. The yields of the product/s were in the range 30 to 92% with 100% selectivity. The percentage yield of amides from esters was found to be less than that of corresponding acids. Cu along with 5% of Fe supported on MWCNTs was found to be a better catalyst than when supported on MC, with respect to the isolated yield of the product/s and recyclability. The catalytic activity of the materials had a good correlation with their surface acidity. A plausible reaction mechanism has been proposed.

2.
J Nanosci Nanotechnol ; 18(1): 202-214, 2018 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-29768832

RESUMO

Sulphate ion modified multiwalled carbon nanotubes (S-CNTs), mesoporous carbon (S-MC), zirconia (S-ZrO2), alumina (S-Al2O3) and silica (S-SiO2) were prepared by wet impregnation technique. The physico-chemical properties of the prepared materials were investigated by Powder-XRD, BET-Surface area and SEM-EDS analysis. Surface acidity of the materials was analyzed using TPD-NH3 and n-butyl amine titration methods. Catalytic activity of these materials was investigated in liquid phase transesterification of diethyl malonate with benzyl alcohol. Effect of various reaction parameters on product yield as well as recyclability of the catalysts was investigated. Kinetics of the reactions was studied and activation energy was evaluated. All the catalysts investigated in this reaction were found to be catalytically active except S-Al2O3, for the formation of transester products; benzyl ethyl malonate (BEM) and dibenzyl malonate (DBM). S-ZrO2 and S-MC resulted good % yield (70 and 73% respectively) of total transester products where as S-CNTs showed 100% selectivity towards the formation of only BEM. Acid sites with moderate acid strength are found to be catalytically active for the transesterification reaction. The catalysts were recyclable up to 5 times without significant loss in their catalytic activity except in the case of S-MC. The reaction followed first order kinetics and the energy of activation of the reaction with different catalysts was in the range of 12-58 kJ mol-1.

3.
J Nanosci Nanotechnol ; 18(1): 426-433, 2018 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-29768864

RESUMO

Sulphate modified multiwalled carbon nanotubes (S-MWCNT) and Mesoporous carbon (S-MC) catalysts were prepared by wet impregnation method. These materials were characterized by different analytical techniques such as Powder-XRD, BET surface area analysis, SEM-EDS and TEM analysis to evaluate their bulk and surface properties. Surface acidity of the catalyst was measured by TPD-NH3 technique, as well as n-butyl amine titration. The estimated surface acidity of S-MWCNT and S-MC using n-butyl amine titration was found to be 0.82 and 1.75 mmol/g respectively. The catalytic activity of these materials was investigated in the synthesis of acetamide derivatives using aromatic acids with substituted aromatic amines in a liquid phase reaction. The reaction conditions were optimized to achieve good % yield of the products. In general S-MC catalyst exhibited good catalytic activity and gave higher % yield of the respective acetamides than S-MWCNT. This is attributed to higher surface acidity of S-MC, however the catalyst was found to be non-recyclable. S-MWCNT exhibited moderate % yield and 100% selectivity towards the formation of products. S-MWCNT catalyst was recycled up to 5 times with a consistent % yield of the respective acetamide derivatives. The synthesized acetamide derivatives were analyzed by M.P, 1HNMR techniques.

4.
Photochem Photobiol ; 88(2): 414-22, 2012 Mar-Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22145679

RESUMO

The mechanism of biocidal action of nano titania on Escherichia coli and Staphylococcus aureus has been evaluated by various biochemical techniques like lipid peroxidation, hydrolysis of orthonitrophenol ß-D-galactopyranoside, estimation of protein-amino acid and bacterial nucleic acids leakage into solution, in addition to morphology studies by electron microscopy (TEM and SEM) and K(+) ion leakage by inductively coupled plasma optical emission spectrometry. The active anatase phase of nano titania has been synthesized by sol-gel and pulverization techniques to obtain particle sizes averaging around 11 nm. The nano semiconductor with a bandgap of 3.2 eV responds well to the UV source to liberate reactive oxygen species (ROS). Gram negative bacteria easily succumb to the ROS at a faster rate than gram-positive bacteria with an observable difference in the mode of attack. The use of analytical techniques revealed the release of peroxidized lipid (26 nmol mL(-1) ) and protein content (370 µg mL(-1)) with a K(+) ion concentration of 22 000 ppb on complete destruction of E. coli.


Assuntos
Escherichia coli/efeitos da radiação , Nanopartículas Metálicas/química , Viabilidade Microbiana/efeitos da radiação , Staphylococcus aureus/efeitos da radiação , Titânio/farmacologia , Escherichia coli/efeitos dos fármacos , Escherichia coli/crescimento & desenvolvimento , Hidrólise/efeitos dos fármacos , Hidrólise/efeitos da radiação , Peroxidação de Lipídeos , Nanopartículas Metálicas/ultraestrutura , Viabilidade Microbiana/efeitos dos fármacos , Microscopia Eletrônica de Transmissão , Tamanho da Partícula , Processos Fotoquímicos , Potássio/metabolismo , Proteólise/efeitos dos fármacos , Proteólise/efeitos da radiação , Espécies Reativas de Oxigênio/metabolismo , Espectrofotometria Atômica , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/crescimento & desenvolvimento , Titânio/química , Raios Ultravioleta
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