Fabrication of porous nanostructured TiO2 particles by an aerosol templating method

An aerosol templating method was applied to fabricate the spherical nanostructured TiO₂ particles containing both mesopores and macropores using two kinds of colloidal mixture such as polystyrene latex (PSL) particles and TiO₂ nanoparticles (P25), and PSL and a titanium hydroxybislactato (TC315). As the weight ratio of PSL/P25 increased from 0 to 1.30, morphology of the as-prepared particles changed from mesoporous particles to particles containing mesopores and macropores. As the furnace temperature decreased from 800 to 600 °C at the fixed process conditions, the increase of mesopore volume and specific surface area were determined. The TiO₂ particles fabricated from a mixture of TC315 and PSL were composed of lots of mesopores and a few macropores. The width of UV-absorption spectra of the porous particles synthesized from two colloidal mixtures decreased a little with respect to the increase of the weight ratio. The complete decomposition of p-xylene of 97.9 ppm was accomplished within 2 h under the illumination of UV-light by all the porous particles.     

Enhanced visible-light photocatalytic activity of strontium-doped zinc oxide nanoparticles

Strontium-doped zinc oxide nanoparticles (Zn_1−xSr_xO NPs; x=0, 0.02, 0.04, and 0.06) were synthesized by a sol–gel method. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images showed NPs with nearly spherical shapes, with sizes from 27 to 41 nm for high Sr concentration and undoped ZnO NPs, respectively. X-ray diffraction (XRD) patterns, selected area electron diffraction (SAED) patterns, and Raman spectra indicated that the undoped and Sr-doped ZnO NPs were crystallized in a hexagonal wurtzite structure. However, the Raman results revealed a decrease in the crystalline quality with an increase in the Sr concentration in the ZnO structure. Evidence of dopant incorporation is demonstrated by X-ray photoelectron spectroscopy (XPS) of the Sr-doped ZnO NPs. From the results of optical characterizations, the band-gap values of the Zn_0.98Sr_0.02O and Zn_0.96Sr_0.04O NPs decreased, while the band-gap value of the Zn_0.94Sr_0.06O NPs increased in comparison to the band-gap value of the undoped ZnO NPs. Finally, the obtained NPs were used as a photocatalyst to remove methylene blue (MB). Observations showed that the efficiency of the photocatalyst activity of the ZnO NPs was significantly increased by increasing the Sr, but until an optimum concentration.     

Rapid synthesis of ZnO dandelion-like nanostructures and their applications in humidity sensing and photocatalysis

In this study, ZnO dandelion-like nanostructures were rapidly synthesized on Si substrates using a two-step thermal oxidation approach. The ZnO nanostructures were grown at various thermal oxidation temperatures ranging from 400 °C to 700 °C. These nanostructures were then applied to humidity sensing and photocatalysis. The ratio of measured resistances in the humidity sensors for relative humidity (RH) levels of 11% and 95% at room temperature (RT) were found to rise from 10² to 10⁵ times for humidity sensors constructed with the nanostructures grown at temperatures from 400 °C to 700 °C, respectively, and sensor response time decreased from 15 s to 5 s. These results show that the proposed ZnO dandelion-like nanomaterial shows promise as a candidate for fabricating high-performance humidity sensors when the nanostructures are grown at 700 °C. In addition, the photocatalytic effect of the nanostructures was tested with a decomposition of methyl orange (MO) dye under UV illumination. Experimental results show that the ZnO dandelion-like nanomaterial grown at a thermal oxidation temperature of 700 °C exhibits an excellent photocatalytic effect, which degrades to almost 90% of the MO activity over 120 min.     

Cadmium selenide@sulfide nanoparticle composites: Facile precipitation preparation,characterization, and investigation of their photocatalyst activity

We report a two-step synthesis and structural characterization of CdSe/CdS core/shell nanoparticles by the precipitation method. Besides, the effects of preparation parameters such as reaction temperature, the speed of the reaction stirrer, and the rate of adding sulfide source on the size, morphology, and photocatalyst activity of CdSe/CdS core–shell nanoparticles were studied by SEM images and degradation of methyl orange (MO) dye test. The structure and composition of the obtained products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution field-emission transmission electron microscope (HRTEM), photoluminescence spectroscopy (PL), scanning electronic microscopy (SEM), spectra energy dispersive analysis of X-ray (EDS), and ultraviolet–visible (UV–vis) techniques.     

Realizing efficient photocatalytic water splitting over Mg-modified BaNbO2N under visible light illumination

With a light absorption up to 740 nm, BaNbO₂N is promising for solar water splitting but normally owns a low activity due to a high defect concentration. Here, Mg is adopted as a dopant to modify the BaNbO₂N. The presence of Mg not only reduces the defect concentration and enhances surface hydrophilicity but also tunes the bandgap as well as the band edge positions. These modifications greatly promote the charge separation and transfer of BaNbO₂N, boosting the photocatalytic activities for O₂-evolution reactions. An apparent quantum efficiency of 1.65 % at 420 ± 20 nm has been attained for Mg modified BaNbO₂N. Overall water splitting at a stable gas-evolution rate (∼ 2.0 μmol·h⁻¹ for H₂ and ∼ 1.0 μmol·h⁻¹ for O₂) has been realized by integrating Mg-modified BaNbO₂N into a Z-scheme system. These findings justify Mg as an effective dopant to modulate the photocatalytic behavior of Nb-based perovskite oxynitrides.     

Selective coordination activation regulating the selectivity for photocatalytic hydrogenation of α, β-unsaturated aldehyde over Pd/MIL-100(FeaCub)

Here, the mixed metal nodes MOFs, Pd/MIL-100(Fe_aCu_b), were constructed as photocatalysts for hydrogenation of α, β-unsaturated aldehyde (UAL) under visible light. 1 wt% Pd/MIL-100(Fe_0.81Cu_0.19) can convert a range of UAL to saturated aldehydes (SAL) with a high efficiency (≈ 100 %) and selectivity (≈ 98 %). The results of XPS and in situ DRIFTS reveal that UAL can be selectively activated via a coordination of -CC- on Cu²⁺ sites, determining the high selectivity of the photocatalytic reaction. The mixed metal nodes and Pd clusters can improve the transformation and separation of photogenerated electrons-holes. EPR result suggests that photogenerated carriers can facilitate the generation of H·on Pd/MIL-100(Fe_0.81Cu_0.19), enhancing the catalytic activity. A possible mechanism is proposed for elucidating the catalytic processes at the molecular level. This work provides a valuable strategy for tailoring the selectivity of photocatalytic hydrogenation via selective coordination activation.