Typical Non–TiO2-Based Visible-Light Photocatalysts

Photocatalysis has received much attention as a potential solution to the worldwide energy shortage and for counteracting environmental degradation. However, the traditional photocatalyst, TiO2, cannot make use of visible light that accounts for 45% of solar spectrum because of a large bandgap (3.2 eV). Therefore, it is urgent to develop visible-light-driven photocatalysts. On the one hand, some modification technologies were explored to extend the light absorption of TiO2 to visible-light region, such as doping of metal and non-metal elements, dye sensitization, and so on. On the other hand, much effort has been directed toward the development of new visible-light photocatalysts. The good news is, some novel and efficient non-TiO2-based photocatalysts have been discovered, such as WO3, Ag3PO4, BiVO4, g-C3N4. In this chapter, these four typical visible light–driven semiconductor photocatalysts were highlighted. WO3 is a visible light–responsive photocatalyst that absorbs light up to ca. 480 nm. Besides that, WO3 has some advantages, such as low cost, harmlessness, and stability in acidic and oxidative conditions. Preparation of WO3 films with the deposition of noble metal is considered to be a promising approach for the photocatalytic applications. In addition, the characteristic morphology and improved photocatalytic performance of Ag3PO4-based and BiVO4-based have been raised up. New methods for fabrication Ag3PO4 with exposed high-energy facets and novel heterogeneous Ag3PO4 co-catalysts have been developed. Monoclinic BiVO4 is a promising photo-anode material for photocatalytic water splitting to produce hydrogen. Co-catalysts loaded on BiVO4 could improve the surface charge transfer efficiency. Furthermore, g-C3N4 is a promising visible-light photocatalyst due to its unique electronic structure. To date, g-C3N4-based photocatalysis has become a very hot research topic. The synthesis, bandgap engineering, and semiconductor composites of g-C3N4-based photocatalysts are highlighted

Near-infrared quantum cutting in Ho3+, Yb3+-codoped BaGdF5 nanoparticles via first- and second-order energy transfers

Infrared quantum cutting involving Yb(3+) 950–1,000 nm ((2) F(5/2) → (2) F(7/2)) and Ho(3+) 1,007 nm ((5)S(2),(5)F(4) → (5)I(6)) as well as 1,180 nm ((5)I(6) → (5)I(8)) emissions is achieved in BaGdF(5): Ho(3+), Yb(3+) nanoparticles which are synthesized by a facile hydrothermal route. The mechanisms through first- and second-order energy transfers were analyzed by the dependence of Yb(3+) doping concentration on the visible and infrared emissions, decay lifetime curves of the (5) F(5) → (5)I(8), (5)S(2)/(5)F(4) → (5)I(8), and (5) F(3) → (5)I(8) of Ho(3+), in which a back energy transfer from Yb(3+) to Ho(3+) is first proposed to interpret the spectral characteristics. A modified calculation equation for quantum efficiency of Yb(3+)-Ho(3+) couple by exciting at 450 nm was presented according to the quantum cutting mechanism. Overall, the excellent luminescence properties of BaGdF(5): Ho(3+), Yb(3+) near-infrared quantum cutting nanoparticles could explore an interesting approach to maximize the performance of solar cells

Effects of different bicarbonate on spirulina in CO2 absorption and microalgae conversion hybrid system

According to the characteristics of power plant flue gas emission and the requirements of reducing CO2 capture cost. CO2 absorption hybrid with microalgae conversion (CAMC) can avoid the challenges of heat consumption during absorbent desorption and nutrient consumption during microalgae culture. In this study, the bicarbonate solution (represents the products of CO2 absorption by Na2CO3 and K2CO3) is used as carbon source for mutagenic Spirulina platensis cultivation, and different concentrations of bicarbonate were set to explore the best carbon source. The results showed that NaHCO3 was a better medium for the CO2 absorption hybrid with microalgae conversion system, which was beneficial for the growth of mutagenic Spirulina, compared with K2CO3. When .3 mol/L NaHCO3 was added to the CO2 absorption hybrid with microalgae conversion system, the highest biomass dry weight, carbon fixation rate and carbon utilization efficiency were obtained, which were 2.24 g/L, 230.36 mg/L/d and 26.71%, respectively. In addition, .3 mol/L NaHCO3 was conducive to protein synthesis, reaching 1,625.68 mg/L. This study provided a feasible idea for power system to achieve carbon neutrality in the future

Robust magnetism against pressure in non-superconducting samples prepared from lutetium foil and H2/N2 gas mixture

Recently, the claim of "near-ambient superconductivity" in a N-doped lutetium hydride attracted enormous following-up investigations in the community of condensed matter physics and material sciences. But quite soon, the experimental results from different groups indicate consistently that no evidence of near-ambient superconductivity is found in the samples synthesized by the same method as the reported one, or by the other alternative methods. From our extended high-pressure heat capacity and magnetic susceptibility measurements on the samples prepared with the lutetium foil and H2/N2 gas mixture, we report the finding of a magnetic transition at the temperature about 56 K. Our results show that this magnetic phase is robust against pressure up to 4.3 GPa, which covers the critical pressure of boosting the claimed near room temperature superconductivity.Comment: 14 pages, 4 figure

Smart Growth in Two Contrastive Metropolitan Areas: A Comparison between Portland and Los Angeles

This study compares urban landscapes in the Portland and Los Angeles metropolitan areas at the neighborhood level by operationalizing six smart growth indices and mapping their spatial distribution patterns and time trends. Analysis results show that the two metropolitan areas have both strengths and weaknesses in different aspects of smart growth. Most neighborhoods in both regions do not excel in all six smart growth measures: they are at the high ends of some smart growth indices but at the low ends of others. Some smart growth features such as mixed land use and mixed housing are already pervasive in suburban areas. Density in some mature suburban neighborhoods is also relatively high. A large number of neighborhoods in suburban and exurban areas exhibit high levels of socioeconomic diversity. Time trend analyses suggest that in both regions, older neighborhoods tend to be “smarter ” than newer ones, except for racial/ethnic diversity

Do Residents of Smart Growth Neighborhoods in Los Angeles, California, Travel Smarter ?

With the individual trip diary from the recent 2009 National Household Travel Survey, a study was done on the effect of neighborhood-level smart growth patterns and socioeconomic diversity on commute mode choice, daily work travel mode choice, and nonwork travel mode choice for individuals living in neighborhoods in the Los Angeles, California, metropolitan statistical area. Model results consistently showed that nonauto transportation infrastructure diversity and quality were the most important aspects of smart growth patterns that affected the choice of nonauto travel modes. Moreover, housing mix in a neighborhood increased the likelihood of choosing walking and cycling for daily work trips and daily nonwork trips. The socioeconomic diversity of a neighborhood reduced the likelihood of choosing walking and cycling for daily nonwork trips. The remaining two factors—residential density and mixed use—insignificantly affected travel mode choice. Overall, people living in smart growth neighborhoods in Los Angeles do travel smarter, in that they use environmentally more sustainable (bus and train) and healthier (walking and cycling) travel modes