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Optics Express, Vol. 21, Issue 17, pp. 20260-20267 (2013)
Takashi Hiroi and Mitsuhiro Shibayama.
The Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan.
Abstract
We developed a new technique that conducts dynamic light scattering (DLS) under a microscope with high spatial resolution. This technique dramatically extends the range of DLS application from transparent to opaque samples. The total scattered electric field contains both electric field generated from the samples and time-independent reflected electric field. These two components are decomposed by applying a partial heterodyne method. By using this technique, we successfully calculate the characteristic size distribution of both multiple-scattering samples and strong light-absorbing samples. This is the first study to observe the collective motion of particles in a highly concentrated solution by using DLS.
© 2013 OSA
Additional Information
We measured the particle size distribution of milk without dilution by using our dynamic light scattering (DLS) microscope. The result is shown in Fig. A1 with that of diluted milk. Diluted milk shows two peaks. Small particles are considered to be proteins such as casein and large particles are fat globules. In contrast to this, the data without dilution shows wide distribution of particles. This result corresponds to the result obtained from Transmission Electron Microscope (TEM). Fig. A2 is the picture of original milk obtained by TEM, kindly provided by Meiji Co., Ltd. Black particles are proteins and white particles are fat globules. It is clear that the size of both particles is widely distributed. By using our DLS microscope, we can obtain such a wide distribution easily and quantitatively.
Fig. A1. Particle size distribution of milk. Solid line: Data of milk without dilution obtained from the DLS microscope. Dashed line: Data of milk with 1000 times dilution obtained from a typical DLS system (DLS/SLS 5000 compact goniometer, ALV).
Fig. A2. TEM picture of original milk provided by Meiji Co., Ltd. Magnification ratio is 10200. One side of the picture corresponds to 10 mm.
