CuO/ZnO composites are synthesized using a simple mechanochemical combustion method. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared (FTIR) are used to characterize the prepared oxides. X-ray diffraction reveals that the prepared CuO/ZnO exhibit a wurtzite ZnO crystal structure and the composites are composed of CuO and ZnO. The strong peaks of the Cu, Zn, and O elements are exhibited in the EDX spectrum. The FTIR spectra appear at around 3385 cm⁻¹ and 1637 cm⁻¹, caused by O–H stretching, and 400 cm⁻¹ to 590 cm⁻¹, ascribable to Zn–O stretching. The photocatalytic performances of CuO/ZnO nanocomposites are investigated for the degradation of methylene blue (MB) aqueous solution in direct solar irradiation. The degradation value of MB with 5 wt % CuO/ZnO is measured to be 98%, after 2 h of solar irradiation. The reactive ^•O₂⁻ and ^•OH radicals play important roles in the photodegradation of MB. Mineralization of MB is around 91% under sunlight irradiation within 7 h. The photodegradation treatment for the textile wastewater using sunlight is an easy technique—simply handled, and economical. Therefore, the solar photodegradation technique may be a very effective method for the treatment of wastewater instead of photodegradation with the artificial and expensive Hg-Xe lamp.

Undoped and N-doped ZnO nanocomposites are produced by a simple and low-cost mechanochemical method. The characterizations of all nanocomposites are examined by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), scanning electron microscopy (SEM) and UV-Vis-NIR spectroscopy. The XRD measurements show that the crystal sizes of undoped and N-doped ZnO nanocomposites are ~29 and ~28 nm, respectively. The UV-Vis-NIR spectroscopy results illustrate that the transmittance of the 7 wt% N/ZnO in the visible and infrared region is a bit higher than the undoped ZnO. The photocatalytic activity of undoped and N-doped ZnO nanocomposites is investigated for the degradation of Methylene Blue (MB) and Rhodamine B (RhB) aqueous solution with direct sunlight irradiation. The photocatalytic degradation percentages with 7 wt% N/ZnO for 5 and 10 mg/L MB dye solution are found to be 93.70% and 98.11%, respectively, whereas 78.40% and 89.15% degradation percentages are found with undoped ZnO, after 3 h sunlight irradiation. Under the same conditions, the photocatalytic degradation value of RhB dye (10 mg/L) solution is measured to be 86.21% for 7 wt% N/ZnO and 64.75% for undoped ZnO. The N-doped ZnO nanocomposites are found to exhibit enhanced photocatalytic performance for both dyes’ degradation under sunlight irradiation in comparison with the undoped ZnO. Therefore, the photocatalytic degradation treatment of wastewater including dye pollutants with sunlight is an easy and simple technique, and cost-effective.

To elucidate the factors that induce phase transitions in biomembranes due to interactions of proteins/peptides at the lipid membrane-interface, the effects of positively charged peptides on the cubic phase (Q²²⁹) of Dioleoylphosphatidylglycerol (DOPG)/Monoolein (MO) membranes were investigated. Small angle X-ray Scattering (SAXS) results revealed that 12 mol% DOPG/88 mol % MO membranes in excess water at 25°C is body centered cubic phase of crystallographic space group Im3m (Q²²⁹). In presence of peptide LLKKK, the lattices constant of Q²²⁹ phase was gradually decreased with an increase of peptide concentration and a phase transition from cubic (Q²²⁹) to cubic (Q²²⁴) phase occurred at R=0.080; (R= molar ratio of peptide to lipid). On the other hand the designed peptide WLFLLKKK and antimicrobial peptide Magainin-2 induced lamellar phase (L_α) in the same mixture membranes. These results indicate that the interactions of the these peptides with this mixture membrane are different: LLKKK induces electrostatic attractive interactions and that of WLFLLKKKK and Magainin-2 bound with the lipid membranes induce electrostatic repulsive interaction at the membrane-interface, might be the major factor inducing different phase transitions in 12 mol% DOPG/88mol% MO mixture membranes. Key words: Antimicrobial peptide Magain-2; Dioleoylphosphatidylglycerol; Monoolein; Cubic phases; Small angle X-ray Scattering DOI: 10.3329/bjsir.v45i3.6530 Bangladesh J. Sci. Ind. Res. 45(3), 219-224, 2010