Copper(II) immobilized on silica extracted from foxtail millet husk: a heterogeneous catalyst for the oxidation of tertiary amines under ambient conditions

Direct Stepwise Oxidation of Methane to Methanol over Cu–SiO2

“…Surface mixtures of highly dispersed and bulk CuO were also previously reported on SiO 2 -supported catalysts. , Further increase in the O 2 activation temperature to 650 °C resulted in the complete disappearance of the CuO reflections in the XRD pattern. At 650 °C, a small peak assigned to cristobalite phase was observed in line with the literature on Cu–SiO 2 treated at similar temperatures. , We hypothesize that the disappearance of CuO crystal peaks might be due a number of phenomena including the formation of dispersed Cu species, doping of Cu into the SiO 2 matrix due to partial crystallization of the support, or formation of amorphous islands. At 800 °C, peaks associated with (002) and (111) planes of CuO at 2θ angles of 35.4° and 38.7°, respectively were observed with a very small intensity, indicating that a small portion of copper formed CuO crystals.…”

“…°C resulted in the complete disappearance of the CuO reflections in the XRD pattern. At 650 °C , a small peak assigned to cristobalite phase was observed in line with the literature on Cu-SiO2 treated at similar temperatures [52][53] . We hypothesize that the disappearance of CuO crystal peaks might be due a number of phenomena including the formation of dispersed Cu species, doping of Cu into the SiO2 matrix due to partial crystallization of the support or the formation of amorphous islands.…”

Copper containing nanosilica thioalated dendritic material: A recyclable catalyst for synthesis of benzimidazoles and benzothiazoles

“…Each of the Cu 2p peaks in the spectrum of the catalyst was fitted using two Gaussian–Lorentzian peaks with energies of 934.32 and 932.99 eV for Cu 2p 3/2 , and 953.89 and 952.72 eV for Cu 2p 1/2 (Figure b). The peak at 934.32 eV (90.36%) corresponds to Cu(II) ions while the lower peak at 932.99 eV (9.64%) corresponds either to Cu(I) or Cu(0), though the chemical states of Cu(I) and Cu(0) are not distinguishable by XPS analysis . The presence of reduced forms of Cu(II) has been described by Hwang and Woo who have reported that Cu(II) is reduced to the lower oxidation states under X–ray irradiation in Ultrahigh vacuum (by calcination followed by heating in He).…”

Synthesis of biogenic nano-silica hydrogel from foxtail millet ashes husk via greener approach

“…Foxtail millet husk ash seemed white a peak noticed at 1098 cm − 1 for displays the silicon carbide groups an evidence of sharpness peak were obtained. [10,12,16]. The formation of effective nano silica hydrogel with an abundance of hydroxyl bonds affords further evidence for its amorphous nature.…”

“…Though, the number of investigated hydrogel nanocomposites such as; sodium alginateg-poly(acrylic acid-co-Acrylamide)/RH(rice husk) as the super adsorbent hydrogel, Poly(AAm-co-AC)/RHA, silica modi ed RHA hydrogel, Si-C/H 3 PO 4 composite, metallic impurities removal of amorphous silica NPs/rice husk for high puri cation [8][9][10][11]. Sivasubramanian et al have also revealed foxtail millet used to silica synthesizing heterogeneous catalyst [12]. So, many types of research have also been indicated, the present work based on the purpose of foxtail millet husk is to study the in uence in hydrogel nanocomposite applications [13][14][15].…”