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Zn 1−x Mg x S (x = 0, 0.2 and 0.4) quantum dots (QDs) were prepared by co-precipitation method. The Mg dopant did not modify the cubic blende structure of ZnS QDs. The Mg related secondary phase was not detected even for 40% of Mg doping. The size mismatch between host Zn ion and dopant Mg ion created distortion around the dopant. The creation of distortion centres produced small changes in the lattice parameters and diffraction peak position. All the QDs showed small sulfur deficiency and the deficiency level were increased by Mg doping. Band gap of the QD was decreased due to the dominated quantum confinement effect over compositional effect at initial doping of Mg. But at higher doping the band gap was increased due to compositional effect, since there was no change in average crystallite size. The prepared QDs had three emission bands in the UV and Visible regions corresponding to near band edge emission and defect related emissions. The electron transport reaction chain which forms free radicals was broken by sulfur vacancy trap sites. Therefore, the ZnS QDs had better antioxidant activity and the antioxidant behaviour was enhanced by Mg doping. The enhanced UV absorption and emission of 20% of Mg doped ZnS QDs let to maximize the zone of inhibition against E. Coli bacterial strain. [ABSTRACT FROM AUTHOR]

In the present study, the pure ZnS and MgS quantum dots (QDs) were synthesized by co-precipitation method and the ZnS:MgS nanocomposites were prepared from these QDs in the ratios, 4:1, 1:1 and 1:4. The synthesized nanocomposite were characterized by structural, morphological, compositional and optical by X-Ray Diffraction (XRD), Transmission Electron Microscope (TEM), Energy Dispersive X-ray (EDAX), and UV–visible absorption techniques. The ZnS and MgS were in cubic crystalline structure with high phase purity. The average crystallite structure had been calculated as 1.8 and 4.8 nm for ZnS and MgS quantum dots, respectively. The absorption was increasing by the increase of MgS concentration in composite and the band gap is narrowing due to the compositional and size effects. The ZnS:MgS nanocomposites have been used as a photocatalyst for the reduction of methylene blue dye. Though, all the nanocomposites possessed with photocatalytic activity, ZnS:MgS (4:1) showed excellent efficiency and rapid decolourization. Moreover, reusability of these nanocomposite were analysed. The Antioxidant activity of the pure ZnS and MgS and their composites was evaluated by DPPH radical scavenging method and vitamin E (Vit. E) was used as a standard drug. • The ZnS:MgS nanocomposite was prepared in the ratios, 4:1,1:1 and 1:4. • Increase in MgS concentration enhance the optical absorption. • Increase in MgS concentration broaden the optical absorption. • The ZnS:MgS (4:1) nanocomposite had excellent photocatalytic activity. • The ZnS:MgS (1:4) nanocomposite had greater antioxidant activity. [ABSTRACT FROM AUTHOR]

Zn 0.96− x Cu 0.04 Ni x O (0 ⩽ x ⩽ 0.04) nanoparticles were synthesized by co-precipitation method. The X-ray diffraction pattern showed the crystalline nature of prepared nanoparticles with hexagonal wurtzite structure. The average crystal size is decreased from 27 to 22.7 nm when Ni concentration is increased from 0% to 2% due to the suppression of nucleation and subsequent growth of ZnO by Ni-doping. The increased crystal size from 22.7 to 25.8 nm (Δ D ∼ 3.1 nm) by Ni-doping from 2% to 4% is due to the creation of distortion centers and Zn/Ni interstitials. The cell parameters and volume of the lattice showed solubility limit at 2% of Ni doping. The energy dispersive X-ray spectra confirmed the presence of Cu and Ni in Zn–O. The optical absorption spectra showed that the absorption was increased up to Ni = 2% due to the creation of carrier concentration by Ni-doping and decreased beyond 2% due to the presence of more defects and interstitials in the Zn–Ni–Cu–O lattice. The observed red shift of energy gap from 3.65 eV (Ni = 0%) to 3.59 eV (Ni = 2%, Δ E g ≈ 0.06 eV) is explained by sp–d exchange interactions between the band electrons and the localized d-electrons of the Ni 2+ ions. The blue shift of energy gap from 3.59 eV (Ni = 2%) to 3.67 eV (Ni = 4%, Δ E g ≈ 0.08 eV) is explained by Burstein–Moss effect. Presence of chemical bonding was confirmed by FTIR spectra. [ABSTRACT FROM AUTHOR]

Abstract: Zn0.96−xCu0.04CrxO nanoparticles with different Cr concentrations from 0 to 4% were successfully synthesized by co-precipitation method. The X-ray diffraction pattern showed the crystalline nature with hexagonal wurtzite structure. The diminution in activation energy and the enhanced strain by Cr-doping from 0 to 3% reduced the average crystal size from 27 to 23.8nm while the formation of secondary phase such as spinel ZnCr2O4 enhanced it to 25.6nm after Cr=3% via increasing the activation energy. The solubility limit of Cr in the present system is fixed as 3%. The energy dispersive X-ray spectra confirmed the presence of Cu and Cr in Zn-O. The optical absorption spectra showed the three distinct bands corresponding to UV region (305–324nm) due to electronic transition between the bands; blue region (382–386nm) mainly due to the Zn/Cr interstitials and bluish green (481–482nm) region due oxygen vacancies and interstitials. The noticed poor transmittance throughout the region and the broader absorption bands in Cr=1% doped Zn0.96Cu0.04O confirmed that it had more defects such as oxygen vacancies, Zn interstitials and other defects. The blue shift of energy gap from 3.68eV (Cr=0%) to 3.71eV (Cr=1%) was due to the creations of more defects. The red shift of Eg from 3.71eV (Cr=1%) to 3.6eV (Cr=3%) was explained by sp–d exchange interactions between the band electrons and the localized d-electrons of the Cr3+ ions. Presence of chemical bonding was confirmed by FTIR spectra. [Copyright &y& Elsevier]

Highlights: [•] Zn0.96− xCu0.04Fe x O nanocrystals from Fe=0% to 4% were successfully synthesized. [•] Change in lattice parameters confirmed the substation of Fe into Zn Cu O lattice. [•] Red shift of E g was explained by the sp–d spin exchange interaction of band electron with the d-electron of Fe. [Copyright &y& Elsevier]

Highlights: [•] Zn0.96−xCu0.04Co x O nanoparticles were successfully synthesized. [•] Co2+ into Cu Zn O lattice was confirmed by EDX, FTIR and optical studies. [•] Above 80% transparency in visible region is useful for optoelectronic devices. [ABSTRACT FROM AUTHOR]

Zn 0.96− x Cu 0.04 Mn x O (0 ⩽ x ⩽ 0.04) nanoparticles were synthesized by sol–gel method. The X-ray diffraction pattern indicated that doping of Mn and Cu did not change the ZnO hexagonal wurtzite structure. The Mn doped nanoparticles had smaller average crystallite size than un-doped Zn 0.96 Cu 0.04 O nanoparticles due to the distortion in the host ZnO lattice. This distortion prevented the subsequent growth and hence the size reduced by Mn doping. The changes in lattice parameters, average crystallite size, peak position and peak intensity confirmed the Mn substitution in Zn–Cu–O lattice. The Mn and Cu co-doping increased the charge carrier density in ZnO nanoparticles which led to increase the dielectric constant. The dielectric constant also varied by depend the size of the nanoparticles. The change in morphology by Mn-doping was studied by transmission electron microscope. The optical absorption and band gap were changed with respect to both compositional and size effects. The band gap was initially increased from 3.65 to 3.73 eV at 1% of Mn doping, while decreasing trend in band gap was noticed for further increase of Mn. The band gap was decreased from 3.73 to 3.48 eV when Mn concentration was increased from 2% to 4%. Presence of chemical bonding and purity of the nanoparticles were confirmed by FTIR spectra. The antibacterial study revealed that that the antibacterial activity of Zn 0.96 Cu 0.04 O is enhanced by Mn doping. [ABSTRACT FROM AUTHOR]

Sn 0.96− x La 0.04 Cu x O 2 (0 ⩽ x ⩽ 0.03) nanocrystals have been successfully synthesized by employing a simple co-precipitation method. The crystal structure of the synthesized nanocrystals was found to be tetragonal rutile of tin oxide by using X-ray diffraction technique and was not affected by doping. The change in lattice parameters was discussed based on the secondary phase formation and presence of Cu 2+ /Cu 3+ in La SnO 2 lattice. The variation in size and shape of the nanocrystals by Cu-doping was discussed using scanning electron microscope. The chemical stoichiometry of Sn, Cu, La and O was confirmed by energy dispersive X-ray spectra. The best optical transparency and lower absorption observed at Sn 0.97 La 0.02 Cu 0.01 O 2 nanocrystals seems to be optimal for industrial applications especially as transparent electrode. The initial blue shift of energy gap from 3.65 eV (Cu = 0%) to 3.78 eV (Cu = 1%) (Δ E g ≈ 0.13 eV) is due to the distortion in the crystal structure of the host compound and generation of defects. The red shift of energy gap after Cu = 1% is due to the charge-transfer transitions between the metal ions d-electrons and the SnO 2 conduction or valence band. Lattice mode of SnO 2 at 686 cm −1 in Sn 0.98 La 0.02 O 2 nanocrystals and anti-symmetric Sn O Sn stretching mode of the surface bridging oxide around 634–642 cm −1 in Cu doped Sn 0.98 La 0.02 O 2 nanocrystals was confirmed by Fourier transform infrared spectra. [ABSTRACT FROM AUTHOR]

Zn .96 − x Y .04 Cu x O ( x = 0, 0.05, 0.10 and 0.15) nanoparticles were successfully synthesized employing simple sol–gel method. Hexagonal wurtzite structure of the synthesized samples was not affected by Cu-doping. CuO phase was induced after Cu = 5% and it was increased by Cu-doping. The change in crystal size was discussed based on compressive stress, lattice volume and bond length. The chemical stoichiometry of Zn, Cu, Y and O was confirmed by energy dispersive X-ray spectra. The increased oxygen percentage from 57.88 (Cu = 5%) to 64.53% (Cu = 15%) by Cu-doping proved the existence of CuO and oxygen rich phase. The lower absorption and high transmittance in visible region observed at Cu = 5% described the good optical quality of the sample with low scattering or absorption losses which leads to the industrial applications especially as transparent electrode. The high energy gap at Cu = 5% could be attributed to the poor crystallinity of the sample. The red shift in energy gap after Cu = 5% was explained by the p–d spin-exchange interactions between the band electrons and the localized d electrons of Cu 2+ ions. The change in intensity and peak position of infrared (IR) peaks confirmed the presence of Cu in Zn Y O lattice and also expressed the perturbation generated by Cu in Zn Y O lattice. [ABSTRACT FROM AUTHOR]

Highlights: [•] Zn0.96 − x Mn0.04Co x O nanoparticles were successfully synthesized. [•] 2Co2+ into Zn–Mn–O lattice was confirmed by EDX, FTIR and optical studies. [•] Tuning of energy gap and transparency in visible region is useful for industrial application. [ABSTRACT FROM AUTHOR]