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jiangcj09

铁杆木虫 (正式写手)

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[交流] Dynamic Light Scattering（DLS）测定纳米颗粒大小的仪器原理已有2人参与

DLS是基于布朗运动（Brownian motion），通过测定颗粒的扩散系数（diffusion coefficient，D）而根据Stokes-Einstein公式计算颗粒的大小。
Malvern zetasizer的手册讲：“It does this by illuminating the particles with a laser and analysing the intensity fluctuations in the scattered light.”
但是，另一本书里描述的DLS原理跟Malvern zetasizer手册上说的不一致：“The precisely defined frequencies associated with laser sources make it possible to exploit light scattering to study the motion of colloidal particles. Light scattered by a moving particle will experience a Doppler shift to slightly higher or lower frequency depending on whether the particle is moving towards or away from the observer. For a collection of particles moving at random by virtue of their Brownian motion, a Doppler frequency broadening will result. Mixing this broadened, scattered signal with incident light produces a pattern of beat frequencies, the measurement of which allows the diffusion coefficient of the particles to be calculated.
......
The width of the Doppler broadened peak at half-height is related to the diffusion coefficient…”
(Duncan J. Shaw (1992), Introduction to Colloid and Surface Chemistry, 4th Edition, page: 61-62)

是不是可以这样理解：第二种说法理论上也对，但是现在的zetasizer都是通过测散射光的强度变化来求扩散系数和颗粒大小，而不是通过测定Doppler展宽来实现？

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