This paper summarizes recent research dealing with development of titanium dioxide (TiO2) used for environmental applications. TiO2 plays the most important role owing to its excellent chemical and physical properties. However, the TiO2 band edge lies in the UV region that makes them inactive under visible irradiation. In this regard, considerable efforts have been made to increase the visible light activity of TiO2 via the modification of its electronic and optical properties. Doping TiO2 using either anions or cations is one of the typical approaches that has been largely applied. Coupling TiO2 with a narrow bad gap semiconductor (MxOy/TiO2 or MxSy/TiO2) represents another approach. This work aims to encompass the new progress of TiO2 for an efficient application in water and wastewater treatment under visible light, emphasizes the future trends of TiO2 in the environment, and suggests new research directions, including preparation aspects for the development of this promising material.

Modified TiO2 For Environmental Photocatalytic Applications: A Review

The dynamics of the piezo inkjet printhead operation

The presence of both organic and inorganic pollutants in water due to industrial, agricultural, and domestic activities has led to the global need for the development of new, improved, and advanced but effective technologies to effectively address the challenges of water quality. It is therefore necessary to develop a technology which would completely remove contaminants from contaminated waters. TiO2 (titania) nanocatalysts have a proven potential to treat "difficult-to-remove" contaminants and thus are expected to play an important role in the remediation of environmental and pollution challenges. Titania nanoparticles are intended to be both supplementary and complementary to the present water-treatment technologies through the destruction or transformation of hazardous chemical wastes to innocuous end-products, that is, CO2 and H2O. This paper therefore explores and summarizes recent efforts in the area of titania nanoparticle synthesis, modifications, and application of titania nanoparticles for water treatment purposes.

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Recent developments in environmental photocatalytic degradation of organic pollutants: the case of titanium dioxide nanoparticles—a review

The fabrication and characterization of highly flexible textiles are reported. These textiles can harvest thermal energy from temperature gradients in the desirable through-thickness direction. The tiger yarns containing n- and p-type segments are woven to provide textiles containing n-p junctions. A high power output of up to 8.6 W m(-2) is obtained for a temperature difference of 200 °C.

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Woven-Yarn Thermoelectric Textiles.

Fabrication of Fe-doped TiO2 nanoparticles and investigation of photocatalytic decolorization of reactive red 198 under visible light irradiation

A three-dimensional computer-aided analysis system has been developed in this study to simulate the formation, ejection, and impact of a liquid droplet in a squeeze-type piezoelectric inkjet printing device. The computer simulation system is based on a solution algorithm (SOLA) scheme for the solution of velocity and pressure fields. It is coupled with volume-of-fluid (VOF) and piecewise-linear interface construction (PLIC) techniques for the transport of F values, which are the volume fractions of liquid in the cells, and construction of the interface. For the treatment of surface tension effects, a CSF (continuum surface force) model is employed. The pressure at the nozzle inlet, which is related to the applied voltage, imposed on the simulation system is determined by the propagation theory of acoustic waves. The simulated results are rather consistent with the experimental observations in terms of droplet morphology, break-up time, flying distance, and droplet volume.

Development of a three-dimensional simulation system for micro-inkjet and its experimental verification

Optical and photocatalytic properties of Fe3+-doped TiO2 thin films prepared by a sol–gel spin coating

Kinetics of anatase transition to rutile TiO2 from titanium dioxide precursor powders synthesized by a sol-gel process

The aim of this study is to investigate the formation and ejection behavior of droplets created by a squeeze mode piezoelectric inkjet printing device using a single pulse voltage pattern. The test liquids are de-ionized (DI) water and ethylene glycol. The experimental results and acoustic wave theory are used to discuss the effects of operating frequency, positive voltage keeping time and pulse voltage magnitude on the volume and velocity of the droplets. For this study, a squeeze mode piezoelectric printhead is employed. By coordinating an LED flash with droplet ejection, a CCD camera could be used to capture images of the droplets at different points in the formation and ejection process. These images were then used to estimate the volume and velocity of the droplets. The experimental results are consistent with the propagation theory of acoustic waves. The maximum allowable pulse frequency in DI water and ethylene glycol are 1500 Hz and 14000 Hz respectively. If the positive voltage keeping time equals the time required for the acoustic wave to propagate through the printhead, optimal ejection behavior is achieved. As the pulse voltage increases, both the velocity and volume of the droplet become larger.

Huey-Jiuan Lin

Papers

Development of a three-dimensional simulation system for micro-inkjet and its experimental verification

Optical and photocatalytic properties of Fe3+-doped TiO2 thin films prepared by a sol–gel spin coating

Kinetics of anatase transition to rutile TiO2 from titanium dioxide precursor powders synthesized by a sol-gel process

Study of Micro-Droplet Behavior for a Piezoelectric Inkjet Printing Device Using a Single Pulse Voltage Pattern

Effects of annealing temperature on the photocatalytic activity of N-doped TiO2 thin films