Search Results (4)

With the growing severity of air pollution, monitoring harmful gases that pose risks to both human health and the ecological environment has become a focal point of research. Titanium dioxide (TiO₂) demonstrates significant potential for application in SO₂ gas detection. However, the performance of pure TiO₂ is limited. In this study, TiO₂ nanospheres and MoSe₂ nanosheets were synthesized using a hydrothermal method, and the gas-sensing properties of TiO₂/MoSe₂ nanostructures for SO₂ detection were investigated. The TiO₂/MoSe₂ composites (with a TiO₂-to-MoSe₂ volume ratio of 2:1) were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The TiO₂/MoSe₂ sensor exhibited high sensitivity to SO₂; the response to 100 ppm of SO₂ reached as high as 59.3, with a significantly shorter response and recovery time (15 s/13 s), as well as excellent repeatability, selectivity, and long-term stability. The experimental results suggest that the enhanced SO₂ adsorption capacity of the TiO₂/MoSe₂ composite can be attributed to the formation of an n-n heterojunction and the unique microstructural features of TiO₂/MoSe₂. Therefore, the TiO₂/MoSe₂ sensor represents a promising candidate for rapid SO₂ detection, providing a theoretical foundation for the development and application of high-performance SO₂ sensors. Full article

In this research study, the effects of different parameters on the electron transfer rate from three quantum dots (QDs), CdSe, CdS, and CdTe, on three metal oxides (MOs), TiO₂, SnO₂, and SnO₂, in quantum-dot-sensitized solar cells (QDSSCs) with porous structures in the presence of four types of blocking layers, ZnS, ZnO, TiO₂, and Al₂O₃, are modeled and simulated using the Marcus theory and tunneling between two spheres for the first time. Here, the studied parameters include the change in the type and thickness of the blocking layer, the diameter of the QD, and the temperature effect. To model the effect of the blocking layer on the QD, the effective sphere method is used, and by applying it into the Marcus theory equation and the tunneling method, the electron transfer rate is calculated and analyzed. The obtained results in a wide range of temperatures of 250–400 °K demonstrate that, based on the composition of the MO-QD, the increase in the temperature could reduce or increase the electron transfer rate, and the change in the QD diameter could exacerbate the effects of the temperature. In addition, the results show which type and thickness of the blocking layer can achieve the highest electron transfer rate. In order to test the accuracy of the simulation method, we calculate the electron transfer rate in the presence of a blocking layer for a reported sample of a QDSSC manufacturing work, which was obtained with an error of ~3%. The results can be used to better interpret the experimental observations and to assist with the design and selection of the appropriate combination of MO-QD in the presence of a blocking layer effect. Full article

Even in the 21st century, water contamination has been a big problem and industrial processes are to be blamed for polluted water supplies. The use of sunlight in the process of photocatalysis is an efficient way to purify wastewater. Composites of TiO₂/activated carbon/two-dimensional selenides performed better than either of the individual material or binary composites for this application. A straightforward hydrothermal technique was employed in the synthesis of photocatalysts. The synthesized photocatalytic composites were verified with the help of UV-Visible spectroscopy, FTIR, XRD, and SEM. The heterostructures absorbed nearly all of the sun’s UV and visible light. These photons are then converted into usable reducing electrons and oxidizing species such as ^•O₂ and OH^• to decompose organic pollutants from industrial wastewater. Since there were additional pathways available for charge transfer along with several active edge sites, the composite photocatalysts are proven more active than individual TiO₂ and 2D MoSe₂ components. With the help of a cascade-driven mechanism of electrons, these channels can transmit more charges than single-component heterojunctions. The results provided a realistic method for developing photocatalyst composites powered by solar light for use in industrial wastewater treatment. Results of degradation of methylene blue suggest that the synthesized composites possess better photocatalytic activity. This enhanced photocatalytic activity is not limited to organic dyes. Other hazardous organic pollutants present in industrial wastewater can be decomposed by using this approach. Full article

Indoor and outdoor ultrafine, accumulation mode, and coarse fractions collected at two preschools (S1 and S2) in Hanoi capital, Vietnam were characterized in terms of mass-size distribution and elemental composition to identify major emission sources. The sampling campaigns were performed simultaneously indoors and outdoors over four consecutive weeks at each school. Indoor average concentrations of CO₂ and CO at both schools were below the limit values recommended by American Society of Heating, Refrigerating and Air-Conditioning Engineers (1000 ppm for CO₂) and World Health Organization (7 mg/m³ for CO). Indoor concentrations of PM_2.5 and PM₁₀ at S1 and S2 were strongly influenced by the presence of children and their activities indoors. The indoor average concentrations of PM_2.5 and PM₁₀ were 49.4 µg/m³ and 59.7 µg/m³ at S1, while those values at S2 were 7.9 and 10.8 µg/m³, respectively. Mass-size distribution of indoor and outdoor particles presented similar patterns, in which ultrafine particles accounted for around 15–20% wt/wt while fine particles (PM_2.5) made up almost 80% wt/wt of PM₁₀. PM_2.5–10 did not display regular shapes while smaller factions tended to aggregate to form clusters with fine structures. Oxygen (O) was the most abundant element in all fractions, followed by carbon (C) for indoor and outdoor particles. O accounted for 36.2% (PM_0.5–1) to 42.4% wt/wt (PM_0.1) of indoor particles, while those figures for C were in the range of 14.5% (for PM_0.1) to 18.1% (for PM_1–2.5). Apart from O and C, mass proportion of other major and minor elements (Al, Ca, Cr, Fe , K, Mg, Si, Ti) could make up to 50%, whereas trace elements (As, Bi, Cd, Co, Cr, Cu, La, Mn, Mo, Ni, Pb, Rb, Sb, Se, Sn, Sr, and Zn) accounted for less than 0.5% of indoor and outdoor airborne particles. There were no significant indoor emission sources of trace and minor elements. Traffic significantly contributed to major and trace elements at S1 and S2. Full article