ABSTRACT
A novel green source was opted to synthesize silver nanoparticles using dried roasted Coffea arabica seed extract. Bio-reduction of silver was complete when the mixture (AgNO3+extract) changed its color from light to dark brown. UV-vis spectroscopy result showed maximum adsorption at 459 nm, which represents the characteristic surface plasmon resonance of nanosilver. X-ray crystal analysis showed that the silver nanoparticles are highly crystalline and exhibit a cubic, face centered lattice with characteristic (111), (200), (220) and (311) orientations. Particles exhibit spherical and ellipsoidal shaped structures as observed from TEM. Composition analysis obtained from SEM-EDXA confirmed the presence of elemental signature of silver. FTIR results recorded a downward shift of absorption bands between 800-1500 cm(-1) indicting the formation of silver nanoparticles. The mean particle size investigated using DLS was found to be in between 20-30 nm respectively. Anti-bacterial activity of silver nanoparticles on E. coli and S. aureus demonstrated diminished bacterial growth with the development of well-defined inhibition zones.
Subject(s)
Anti-Bacterial Agents/chemistry , Coffea/chemistry , Green Chemistry Technology/methods , Metal Nanoparticles/chemistry , Plant Extracts/chemistry , Seeds/chemistry , Silver/chemistry , Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/pharmacology , Bacteria/drug effects , Plant Extracts/pharmacology , Silver/pharmacology , Spectrophotometry, UltravioletABSTRACT
Carbon nanofibers (CNF) have been synthesized under partial combustion conditions in a flame reactor using different mixtures of hydrocarbon gases in the presence and absence of precursors. The hydrogen (H2) adsorption studies have been carried out using a high pressure Sievert's apparatus maintained at a constant temperature (24 degrees C). The flame synthesized CNFs showed high degree of H2 adsorption capacities at 100 atm pressure. The highest H2 capacities recorded have been 4.1 wt% [for CNF produced by liquefied petroleum gas (LPG)-Air (E-17)], 3.7 wt% [for nano carbons produced by Methane-Acetylene-Air (EMAC-4)] and 5.04 wt% for [Lithium intercalated sample (Li-EMAC-4)] respectively.
ABSTRACT
A simple and facile wet chemistry route was used to synthesize nanophase hydroxyapatite (HaP) crystals at low temperature. The synthesis was carried out at a pH of 11.0 and at a temperature of 37°C. The resulting samples were washed several times and subjected to further analysis. XRD studies revealed that the HaP crystals were polycrystalline in nature with a crystallite size of ~15-60 ± 5 nm. SEM-EDXA images confirmed the presence of calcium (Ca), phosphorous (P), and oxygen (O) peaks. Likewise, FTIR confirmed the presence of characteristic phosphate and hydroxyl peaks in samples. Lastly, HRTEM images clearly showed distinctive lattice fringes positioned in the 100 and 002 planes. TGA analysis shows that HaP crystals can withstand higher calcination temperatures and are thermally stable.
Subject(s)
Cold Temperature , Crystallization/methods , Durapatite/chemical synthesis , Nanoparticles/chemistry , Water/chemistry , Durapatite/chemistry , Hydrogen-Ion Concentration , Nanoparticles/ultrastructure , Solutions , Spectroscopy, Fourier Transform Infrared , Thermogravimetry , X-Ray DiffractionABSTRACT
Densely agglomerated, high specific surface area carbon nano onions with diameter of 30-40 nm have been synthesized. Liquefied petroleum gas and air mixtures produced carbon nano onions in diffusion flames without catalyst. The optimized oxidant to fuel ratio which produces carbon nano onions has been found to be 0.1 slpm/slpm. The experiment yielded 70% pure carbon nano onions with a rate of 5 g/h. X-ray diffraction, high-resolution electron microscopy and Raman spectrum reveal the densely packed sp(2) hybridized carbon with (002) semi-crystalline hexagonal graphite reflection. The carbon nano onions are thermally stable up to 600 °C.
Subject(s)
Carbon/chemistry , Nanostructures/chemistry , Petroleum/analysis , Diffusion , Microscopy, Electron, Transmission , Oxidation-Reduction , Particle Size , Spectrum Analysis, Raman , Temperature , X-Ray DiffractionABSTRACT
Acetone and hexane extracts derived from the root, stem, and leaf of Raphanus sativus were investigated for their antibacterial activity against foodborne and resistant pathogens, such as Bacillus subtilis, Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Salmonella typhimurium, Enterobacter aerogenes, Enterobacter cloacae, and Escherichia coli. Total and individual isothiocyanate (ITC) components and their relationship with the antibacterial activity of R. sativus were also evaluated. Both acetone and hexane fractions of root, stem, and leaf exhibited selective antibacterial activity against the organisms tested. Antibacterial activity was strongest in the acetone fraction of root with larger zone of inhibition and lower minimum inhibitory concentration. The results obtained were comparable to that seen with standard antibiotics. Of the different parts of R. sativus studied, root tended to be more active than the stem and leaf extracts in inhibiting the bacterial growth. Gas chromatographic analysis revealed the presence of variable amounts of five different ITCs such as allyl isothiocyanate (AITC), phenyl isothiocyanate (PITC), benzyl isothiocyanate (BITC), phenethyl isothiocyanate, and 4-(methylthio)-3-butenyl isothiocyanate (MTBITC) in different parts of the plant. The low linear correlation between the total ITC content and antibacterial activity implied that bacterial growth inhibitory ability of R. sativus was not dependent on the total ITC content. However, the antibacterial activity of R. sativus was well correlated with AITC, PITC, and BITC for all organisms except for Enteroc. faecalis, whose inhibitory effect was more related to MTBITC.
