In chemical engineering, Da is defined as the characteristic mixing time (diffusion rate) divided by the characteristic chemical time (reaction rate). This number is used to describe the relative time scale of chemical reactions compared to other phenomena in the same system. From the engineering viewpoint, this task is related to the creation of the point-like reaction conditions and to the successful realization of the physical reagents’ micromixing and conducting process at low Damkohler numbers Da ≤ 1. Therefore, preparation of the monodispersed colloids becomes essential for the understanding of the nucleation-growth mechanisms and definition of the most stable material building unit-the nucleus. The electrons and holes diffuse to the surface of the particle, thus creating a strong redox potential to induce the photocatalytic reaction.įundamentally, if the particle size distribution is polydisperse, size determination will be disturbed, which hinders the size evolution kinetics. When the energy of the photon is larger than the band gap of semiconductor nanoparticles, the electrons in its valence band will be excited to the conduction band leaving the holes in the valence band. For photocatalytic reactions, the generation of a hole-electron pair is a significant stage of photo reactions. Since the photo-induced decomposition of water on TiO 2 electrodes was discovered, MONs (e.g., TiO 2, ZnO, Fe 3O 4, V 2O 5 and CeO 2 ) photocatalysis has attracted extensive interest. In particular, semiconductor MONs have been widely used for the photocatalytic degradation of various organic pollutants. It has been shown that the size and shape of nanocatalysts have a main impact of catalytic reactions by tailoring the nanoparticle at molecular level. Nanoparticles, especially metal oxide nanoparticles (MONs) are currently of great interest to scientists and engineers due to their prospective uses in the majority of industrial chemical processes, mainly in catalysis, electronics and optics. By increasing the rate of chemical reaction, catalysts have become the core of chemical technology and more than 90% of chemical industrial processes cannot be separated from catalysts. Modern industrial production pursues high efficiency and energy saving. The MONs preparation monitored by DLS was presented, taking into consideration both ex situ and in situ configuration. Ex-situ and in situ configuration of DLS, sample preparations, measurement conditions and reaction cell design for in situ configuration were studied. The instrument design was then investigated. The measuring principle, including an overview of sizing techniques, advantages and limitations and theories of DLS were first discussed. In this review, we focus on the in situ sizing of nanomaterial preparation in the form of colloids, especially for metal oxide nanoparticles (MONs). Dynamic light scattering (DLS) is a fast and non-invasive tool used to measure particle size, size distribution and stability in solutions or suspensions during nanomaterial preparation. The measurement and control of this parameter are crucial for nanomaterial synthesis. The particle size distribution plays an important role in chemical and physical properties. For the volume scattering of particles of the same kind,shape deformation has significant influence on side and backforward scattering,but has little on the for-ward scattering.Due to surface effects and quantum size effects, nanomaterials have properties that are vastly different from those of bulk materials due to surface effects. Equivalent Mie scattering errors of sand and maritime aerosols are bigger than those of smoke and dissolvable aerosols. A great discrepancy exists in volume scattering phase functions of aerosols with different physical characteristics. Result shows that the shape deformation has great effects on the space distribution of seattering energy the relationship between equivalent Mie scattering error and shape deformation is more complex than that ever has assumed.The dynamic range of equivalent Mie scattering error found that shape deformation influences the scattering phase functions more at 0° than at 180°,while at 35°,the effect is small for the sphere- equivalent methods,surface- area equivalent method is more applicable in calculating the scattering characteristics of non-spherical particles. In addition,the variation law between shape deformation and equivalent Mie scattering error is also discussed in this paper. To analyze the influence of shape deformation on the scattering property of atmospherical aerosols,T-Martrix method is used to calculate the scattering phase functions of particles with different types and shapes at a wavelength of 633 nm( unpolarized light).
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