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The TiO₂ thin film was grown on a $64^{\circ }$ Y-axis cut, X-axis propagation lithium niobate substrate by radio frequency magnetron sputtering to fabricate a surface acoustic wave device. The sputtering ratios of argon to oxygen at 20% and post-annealing temperature at $500^{\circ }$C for 3 h were controlled to improve the photocatalytic activity of TiO₂ thin film. The effects of work frequency and input voltage of the surface acoustic wave device on the methylene blue photocatalytic degradation efficiency of the TiO₂ thin film were investigated. The TiO₂ thin film was vibrated at radio frequency by surface acoustic wave device to increase the scattering and reactive frequency for methylene blue in liquid. The surface acoustic wave device operated at 28.65 MHz work frequency and 0.95 V input voltage revealed the highest photocatalytic degradation efficiency of methylene blue. Compared to the TiO₂ thin film combined with and without surface acoustic wave device, the surface acoustic wave device enhanced the TiO₂ thin film photocatalytic degradation efficiency to 46%.

The scattering layer in the TiO₂ photoanode (PAs) of dye-sensitized solar cells (DSSCs) is doped with single-layer graphene (G), and DSSC is prepared by doctor blade coating method. A small amount of graphene (0.0016 wt.%) in a graphene aqueous solution (G-AS) and a G-TiO₂ paste was prepared to make 2–20 wt.% of G-AS in the deionized water (DIW). The UV-Vis measurement results show that the TiO₂ scattering layers doped with graphene effectively improve the visible light absorption intensity of DSSC PAs and increase the current density (Jsc) from 13.84 mA/cm² to 16.20 mA/cm². The Electrochemical Impedance Spectroscopy (EIS) measurement showed that the internal structural impedance Rk $(\mathrm{\Omega })$ decreased from 12.086 $(\mathrm{\Omega })$ (without graphene doping) to 9.875 $(\mathrm{\Omega })$ at 5 wt.% of the graphene doping. The photoelectric conversion efficiency (PCE) increased from 6.56% of the original un-doped graphene to the maximum PCE value of 7.57% at 5 wt.%. The results show that the best PCE is obtained when the concentration of G-AS is 5 wt.%.

It is well known that electron transport layer (ETL) plays an indispensable role in the planar heterojunction perovskite solar cells (PSCs). TiO₂ is widely used as an ETL material due to its excellent transport properties, however, the presence of defects in the TiO₂ layer diminishes the power conversion efficiency (PCE) of the devices. Herein, we introduce a method of low-temperature TiCl₄ treatment to deposit a TiO_x layer on the surface of TiO₂ film, which can effectively passivate trap states at the TiO₂ surface. Moreover, the treating process is optimized to be 30min using a 40mM TiCl₄ aqueous solution. Benefiting from this, we obtain the champion device with the highest PCE of 18.47%, which is mainly due to the reduction of surface defects and the deposition of the well-crystallized perovskite films. Besides, the modified PSCs exhibit an average PCE of 17.59%, which is much better than the control devices.

Decreasing the scale of vanadium dioxide (VO₂) structures is one of the ways to enhance the switching speed of the material. We study the properties of VO₂ films of altered thicknesses in the range of 20–170nm prepared on c-sapphire substrates with a TiO₂ sublayer by pulsed laser deposition (PLD) method. The synthesis regime to design a TiO₂ film was preliminarily optimized based on XRD data. XRD patterns reveal an epitaxial growth of the VO₂ films with distortion of the monoclinic cell to hexagonal symmetry. The positions of the lattice vibration modes in Raman spectra are similar to those in bulk VO₂ when the film thickness is greater than $\sim 30$nm. For VO₂ films thicker that $\sim 20$nm, a lattice strain results in the modes’ positions and intensity change. However, the electrically triggered transition in a $\sim 50$nm thick VO₂ film reveals forward and reverse switching times as short as 20ns and 400ns, correspondingly.

N-doped titanium dioxide (TiO${}_2)$ hollow nanospheres with abundant oxygen vacancies were successfully synthesized by coupling urea treatment and annealing in an N₂ atmosphere. The pristine TiO₂ hollow nanospheres exhibit a shallow donor level for electron trapping, while the urea treatment generates a N 2p acceptor level for hole trapping. After annealing in N₂, the sufficient N atoms generate abundant oxygen vacancies for trapping electrons, resulting in further improved charge separation efficiency. The N-doped TiO₂ exhibits the highest H₂ evolution rate, reaching 2867$\mu$molg${}^{-1}$h${}^{-1}$, which is six times higher than that of pristine TiO₂ hollow nanospheres. The introduction of oxygen vacancies by interstitial N provides a promising way to improve the photocatalysis activity of photocatalysts.

The aim of this study is to develop a non-continuous droplet manipulation technology in contrast to conventional continuous flow micro-fluidic systems. The droplets were manipulated based on the proposed opto-wetting effect. In addition, an experimental ultraviolet (UV) light actuated droplet manipulation system was developed for verifying the opto-wetting droplet manipulation. The proposed opto-wetting effect was achieved by utilizing ultraviolet to activate oxidation-reduction mechanism of nano-TiO₂ photo catalyst coated base material. The water-affinity of the base material will changed due to the decreased free-energy of the material surface. Therefore, the contact angle between the liquid droplet and base material will also be changed which facilitates droplet manipulability. The main components of the proposed ultraviolet (UV) light actuated droplet manipulation system include ultraviolet masking device, moving platform and main frame structure. System software and user interface were designed by using Microsoft Visual Basic 6.0 toolkit. Upon completion of the proposed system, experiments were carried out to verify system functionalities. Follow by the controlled variable optimization using Taguchi method and liquid droplet manipulation experiments. The experiment results indicate that by exposure to 6.8mW UV light, the surface tension and hydrophilic property of nano-TiO₂ (anatase type, 3.5% concentration, PH 1.5, and with average particle size of 69 nm) coated base material will changed. The change of surface tension and hydrophilic property were critical for droplet manipulation. The moving speed of the liquid droplet was measured as 3.33mm/sec. The results suggest that the opto-wetting system may be effective to overcome the shortcoming of traditional opto-electrowetting technique. The proposed opto-wetting droplet manipulation system could potentially applied for manipulating biomedical or pathological test specimens in the future.