Solution, Solid-State Two Step Synthesis and Optical Properties of ZnO and SnO2 Nanoparticles and Their Nanocomposites with SiO2

Visible-light driven photocatalytic performance of eco-friendly cobalt-doped ZnO nanoarrays: Influence of morphology, cobalt doping, and photocatalytic efficiency

In order to remove the organic pollution from water environment, Co²⁺-doped ZnO nanoarray photocatalyst was prepared through a hydrothermal process. The influences of Co²⁺ doping amount and hydrothermal temperature on the nanostructure and photocatalytic performance of Co²⁺-doped ZnO nanoarray were discussed in detail. The standard ZnO structure and nanoarray morphology of Co²⁺-doped ZnO samples were achieved and the absorption of visible light was also realized through Co²⁺ doping. The 2% Co²⁺-doped ZnO nanoarray prepared at 95 °C exhibited excellent photocatalytic activity and could degrade 96% of methylene blue solution within 120 min under visible light. Furthermore, the as-prepared 2% Co²⁺-doped ZnO nanoarray still maintained 91% for removal rate after 3 cycles of photocatalytic degradation, showed good photocatalytic activity and recyclability. All results indicate that ZnO nanoarray with Co²⁺ doping has a potential application in visible light photocatalysis for environmental protection and pollution control.

Solid-State Preparation of Metal and Metal Oxides Nanostructures and Their Application in Environmental Remediation

Nanomaterials have attracted much attention over the last decades due to their very different properties compared to those of bulk equivalents, such as a large surface-to-volume ratio, the size-dependent optical, physical, and magnetic properties. A number of solution fabrication methods have been developed for the synthesis of metal and metal oxides nanoparticles, but few solid-state methods have been reported. The application of nanostructured materials to electronic solid-state devices or to high-temperature technology requires, however, adequate solid-state methods for obtaining nanostructured materials. In this review, we discuss some of the main current methods of obtaining nanomaterials in solid state, and also we summarize the obtaining of nanomaterials using a new general method in solid state. This new solid-state method to prepare metals and metallic oxides nanostructures start with the preparation of the macromolecular complexes chitosan·Xn and PS-co-4-PVP·MXn as precursors (X = anion accompanying the cationic metal, n = is the subscript, which indicates the number of anions in the formula of the metal salt and PS-co-4-PVP = poly(styrene-co-4-vinylpyridine)). Then, the solid-state pyrolysis under air and at 800 °C affords nanoparticles of M°, M_xO_y depending on the nature of the metal. Metallic nanoparticles are obtained for noble metals such as Au, while the respective metal oxide is obtained for transition, representative, and lanthanide metals. Size and morphology depend on the nature of the polymer as well as on the spacing of the metals within the polymeric chain. Noticeably in the case of TiO₂, anatase or rutile phases can be tuned by the nature of the Ti salts coordinated in the macromolecular polymer. A mechanism for the formation of nanoparticles is outlined on the basis of TG/DSC data. Some applications such as photocatalytic degradation of methylene by different metal oxides obtained by the presented solid-state method are also described. A brief review of the main solid-state methods to prepare nanoparticles is also outlined in the introduction. Some challenges to further development of these materials and methods are finally discussed.

Solventless Preparation of Thoria and Its Inclusion into SiO2 and TiO2: A Luminescence and Photocatalysis Study

Thoria was prepared using a solid-state method from the macromolecular precursor Chitosan·Th(NO3)4 (chitosan) and PS-co-4-PVP·Th(NO3)4 (PVP). The morphology and the average size of ThO2 depend of the chitosan and PS-co-4-PVP polymer forming the precursor. Their photoluminescent properties were investigated, finding a dependence of their intensity emission maxima, with the nature of the precursor polymer. The photocatalytic activity of ThO2 toward the degradation of methylene blue was measured for the first time, finding a degradation of about 66% in 300 min. The inclusion of ThO2 into SiO2 and TiO2 was achieved by the solid-state pyrolysis of the macromolecular composites Chitosan·Th(NO3)4//MO2 and PS-co-4-PVP·Th(NO3)4//MO2, MO2 = SiO2 or TiO2. The ThO2 exhibits a homogeneous dispersion inside the silica, showing sizes of about 40 and 50 nm for the chitosan and PVP polymer precursors, respectively. The luminescent properties of the ThO2/SiO2 and ThO2/TiO2 composites were also studied, finding a decrease in intensity when introducing the SiO2 or TiO2 matrices. The photocatalytic behavior to methylene blue degradation of ThO2 and their composites ThO2/SiO2 and ThO2/TiO2 was investigated for the first time, with them in the following order: ThO2 > ThO2/TiO2 > ThO2/SiO2.

Incorporation of NiO into SiO2, TiO2, Al2O3, and Na4.2Ca2.8(Si6O18) Matrices: Medium Effect on the Optical Properties and Catalytic Degradation of Methylene Blue

The medium effect of the optical and catalytic degradation of methylene blue was studied in the NiO/SiO₂, NiO/TiO₂, NiO/Al₂O₃, and NiO/Na_4.2Ca_2.8(Si₆O₁₈) composites, which were prepared by a solid-state method. The new composites were characterized by XRD (X-ray diffraction of powder), SEM/EDS, TEM, and HR-TEM. The size of the NiO nanoparticles obtained from the PSP-4-PVP (polyvinylpyrrolidone) precursors inside the different matrices follow the order of SiO₂ > TiO₂ > Al₂O₃. However, NiO nanoparticles obtained from the chitosan precursor does not present an effect on the particle size. It was found that the medium effect of the matrices (SiO₂, TiO₂, Al₂O₃, and Na_4.2Ca_2.8(Si₆O₁₈)) on the photocatalytic methylene blue degradation, can be described as a specific interaction of the NiO material acting as a semiconductor with the M_xO_y materials through a possible p-n junction. The highest catalytic activity was found for the TiO₂ and glass composites where a favorable p-n junction was formed. The isolating character of Al₂O₃ and SiO₂ and their non-semiconductor behavior preclude this interaction to form a p-n junction, and thus a lower catalytic activity. NiO/SiO₂ and NiO/Na_4.2Ca_2.8(Si₆O₁₈) showed a similar photocatalytic behavior. On the other hand, the effect of the matrix on the optical properties for the NiO/SiO₂, NiO/TiO₂, NiO/Al₂O₃, and NiO/Na_4.2Ca_2.8(Si₆O₁₈) composites can be described by the different dielectric constants of the SiO₂, TiO₂, Al₂O₃, Na_4.2Ca_2.8(Si₆O₁₈) matrices. The maxima absorption of the composites (λ_max) exhibit a direct relationship with the dielectric constants, while their semiconductor bandgap (E_g) present an inverse relationship with the dielectric constants. A direct relationship between λ_max and E_g was found from these correlations. The effect of the polymer precursor on the particle size can explain some deviations from this relationship, as the correlation between the particle size and absorption is well known. Finally, the NiO/Na_4.2Ca_2.8(Si₆O₁₈) composite was reported in this work for the first time.

Solvent-free and one-pot synthesis of silver and zinc oxide nanoparticles: Activity toward cell membrane component and insulin signaling pathway in experimental diabetes

OBJECTIVE

To investigate and compare between the effect of both silver nanoparticles (AgNPs) and zinc oxide nanoparticles (ZnONPs) on insulin signaling pathway and insulin sensitivity in experimental diabetes. Preparation of AgNPs and ZnONPs in their solid state were carried out using pullulan (Natural polymer) as both reducing and stabilizing agent. The synthesis of these nanoparticles in a large scale were carried out without using any solvents. The experimental male albino rats received diluted solutions of AgNPs and ZNONPs. After the experimental period, blood was withdrawn; erythrocyte membrane lipids were extracted and fatty acids were determined by HPLC. Oxidant, antioxidant profile and phosphatidylinositol 3-kinase (PI₃K) were estimated.

RESULTS

It was observed that the as synthesized AgNPs and ZnONPs have nearly spherical shape with small size due to the stabilization effect of pullulan as proved by UV-vis spectroscopy (UV-vis), Transmission electron microscy (TEM) and Field emission scanning electron microscopy (FESEM), Zeta potential, Dynamic light scattering (DLS) and X-ray diffraction (XRD) techniques. The average hydrodynamic size of the formed AgNPs was 15 nm which is considered as very small size when compared with that of ZnONPs (above 50 nm). Fasting blood sugar was significantly increased in diabetic group along with elevation of MDA and DNA damage indicating the oxidative properties of streptozotocin. Whereas, the treatment with nanoparticles significantly attenuated these elevations.

CONCLUSION

AgNPs and ZnONPs represent promising materials in attenuating diabetic complications and insulin resistance in experimental diabetes; no Impressive differences were observed between the effect of ZnONPs and AgNPs in this current research.