The influence of particle size of TiO2 on the photocatalytic degradation of methylene blue (MB)
in a suspended aqueous solution has been studied. The results suggested that the adsorption
rate and adsorbability of MB on suspended TiO2 particles increased as the particle sizes of TiO2
decreased. Photocatalytic activity of TiO2 also increased as the particle size of TiO2 became
smaller, especially when the particle size is less than 30 nm. The half-life (t
0.5) of the
photocatalytic degradation of MB also decreased as the particle sizes of TiO2 decreased. The
first-order reaction rate constant for photodegradation of MB increased as the particle size of
TiO2 decreased. The initial degradation rate of MB in a suspended model was higher than that
of a fixed-bed model. This will overcome the difficulty of preparation of ultrafine TiO2 catalyst
particles. Once the problem of separation of fine TiO2 particles is solved, a TiO2 suspended
photoreactor could be provided on an industrial basis.
In response to the demands for energy and the concerns of global warming and climate change, energy efficient and environmentally friendly solid-state lighting, such as white light-emitting diodes (WLEDs), is considered to be the most promising and suitable light source. Because of their small size, high efficiency, and long lifetime, WLEDs based on colloidal semiconductor nanocrystals (or quantum dots) are emerging as a completely new technology platform for the development of flat-panel displays and solid-state lighting, exhibiting the potential to replace the conventionally used incandescent and fluorescent lamps. This replacement can cut the ever-increasing level of energy consumption, solve the problem of rapidly depleting fossil fuel reserves, and improve the quality of the global environment. In this review, the recent progress in semiconductor-nanocrystals-based WLEDs is highlighted, the different approaches for generating white light are compared, and the benefits and challenges of the solid-state lighting technology are discussed.
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