This research makes use of tetraethylortho-silicate (TEOS) to synthesize silicon dioxide (SiO 2 ) nanoparticles with the sol-gel process. During the discussions of reactants (TEOS, NH 3 , H 2 O, solvent) and reaction conditions (temperature, reaction time), the size of the silicon dioxide particle will be subjected to change with the variation of these preparation parameters. When the concentrations of TEOS and NH 3 are reduced and the reaction temperature is increased, the particle size diminishes immediately. The particle size rises first and then declines along with the water concentration increment. Because of the rise in the value of the solvent's dielectric constant, the synthesized silicon dioxide particles are smaller. The concentrations of NH 3 and H 2 O increment will achieve a more uniform particle size. To synthesize the silicon dioxide particles in the nano class, the concentrations of TEOS, H 2 O, and NH 3 need to be reduced. The preparation parameters should be chosen under the relatively higher reaction temperature, and solvents with lower dielectric constants should not be chosen. The aim of this experiment is to understand the influence of particular factors (NH 3 concentration, H 2 O concentration, reaction temperature) on the target function (particle size and its distribution) and to determine the interaction between factors by using the response surface methodology (RSM). It is shown that the above three factors have notable influences on particle size and that the concentration of NH 3 has a more notable influence on the particle size distribution.

A variety of visible-light-driven silver vanadates, including α-AgVO3, β-AgVO3, and α-Ag3VO4, were synthesized using a microwave-assisted hydrothermal synthesis method. UV−vis spectroscopy indicated that each of the silver vanadate particles obtained in the study had strong visible-light absorption with associated band gaps in the range of 2.2−2.5 eV. The α-Ag3VO4 crystalline sample with rich hydroxyl functional groups on the surface exhibited the highest degree of photocatalytic activity. The reaction rates of the photodegradation of isopropanol (IPA) and benzene vapors were approximately 8 times higher than those of P25 under visible-light irradiation. Furthermore, the active sites at which catalysts play a role as proton donors (Brønsted acidity) in the photodegradation of VOC were characterized by the temperature-programmed desorption (TPD) method in conjunction with the diffuse reflectance infrared Fourier transform (DRIFT) technique. In addition, the photocatalytic activities of microwave-assisted hydrothermal samples were higher than those of samples produced by conventional hydrothermal techniques. This was due to an increase in the specific surface area and additional hydroxyl functional groups on the surface. These results demonstrate that the microwave-assisted hydrothermal method is an efficient technique for the fabrication of visible-light-responsive silver vanadates with outstanding performance in the photocatalysis of VOCs.

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Conventional nanorod-based dye-sensitized solar cells (DSSCs) are fabricated by growing nanorods on top of a transparent conducting oxide (TCO, typically fluorine-doped tin oxide—FTO). The heterogeneous interface between the nanorod and TCO forms a source for carrier scattering. This work reports on a new DSSC architecture without a TCO layer. The TCO-less structure consists of ZnO nanorods grown on top of a ZnO film. The ZnO film replaced FTO as the TCO layer and the ZnO nanorods served as the photoanode. The ZnO nanorod/film structure was grown by two methods: (1) one-step chemical vapor deposition (CVD) (2) two-step chemical bath deposition (CBD). The thicknesses of the nanorods/film grown by CVD is more uniform than that by CBD. We demonstrate that the TCO-less DSSC structure can operate properly as solar cells. The new DSSCs yield the best short-current density of 3.96 mA/ and a power conversion efficiency of 0.73% under 85 mW/ of simulated solar illumination. The open-circuit voltage of 0.80 V is markedly higher than that from conventional ZnO DSSCs.

The process of absorbing water vapor into triethylene glycol (TEG) solutions is achieved in two steps. In the first step, water vapor is condensed into water droplets on the gas-liquid interface. The second step involves the dissolution of water droplets into the TEG solution as a result of the change in surface tension in the surface thin film. This study is focused on the effects of the surface tension gradient on mass transfer performance of the absorption process. An investigation of the disturbance induced by the surface tension gradient and an evaluation of the mass transfer behavior were conducted. As noted, the phenomenon of fluid flow in the surface thin film due to the surface tension gradient is termed the Marangoni effect, and the induced convection is usually termed Marangoni convection. To discuss the relationship between the Marangoni effect and the mass transfer performance, the surface tension of the liquid desiccant was measured under different temperatures and concentrations during experimental runs. The conventional mass transfer correlation was modified by using the term of the M index, which combines the surface tension gradient and the driving force of mass transfer to explain Marangoni effects. This improves the average error between predicted values and experimental data significantly.