In the proposed DLS system, the information on the nanoparticle size in sample solution is basically acquired by measuring its movement-induced scattering light intensity fluctuations over time.

Experimental results are in good accordance with the nominal values of the measured nanoparticles, verifying good feasibility of the system. Moreover, the rational incorporation of multimode fiber elements with single-mode fiber elements in the processing of light improves the spatial coherence and thus the measuring ability of the system. Since the fiber probes are used and directly embedded in sample solutions, they provide more flexible measurement for nanoparticles. In this work, we proposed and demonstrated a novel optical fiber dynamic light scattering nanometer particle sizing system. Although this design had the potential to work with high performance and direct contact with the samples, the fabrication of the probe was time consuming and more expensive. Dhadwal used a fiber ferrule design containing single-mode and multimode fiber probes to enhance light collecting capacity. However, the usage of single-mode fiber reduced the ability of the probes to collect the scattering light, and the scattering angle of the probes was fixed, which to a large extent limited the inflexibility of constructing the instrumentations. The construction of the instrumentations permitted the sample volumes to be miniaturized. In recent studies, Chastek presented several miniaturized dynamic light scattering instrumentations comprising two single-mode fiber probes directly embedded into the sample. But in these works, there are few about directly embedding fiber probes in sample solutions, thereby eliminating complexity and inflexibility of goniometers and glass sample holding arrangements in traditional methods. Afterwards, many researchers have attempted to carry out similar experiments of replacing optical lens with fiber probes.

Pioneering work by Brown adopted a couple of single-mode fiber probes, terminated with gradient refractive index lens, to deliver laser light and collect scattering light, respectively. An effective resolution is to use optical fiber probes to deliver and receive light in DLS system instead of using traditional optical lens. In complicated systems, however, local detection of scattering light using DLS technology is sometimes hard to be realized. In practical applications, the laser is generally launched on the particles in suspension, and the generating scattering light is detected using standard optical components. Now, it has become a standard method for submicron particle sizing. Specifically speaking, the translational diffusion coefficient for the particles in suspension can be derived from the line width of its scattering light. The basic principle of DLS is that the broadening of the intensity line of scattering light can be demodulated for some velocity-related information. It has been discussed theoretically in and was first used for particle size measurement in 1972. Introductionĭynamic light scattering (DLS), called photon correlation spectroscopy (PCS), was first found in the early 1960s and has been widely used in various scientific and engineering fields. Experimentation shows the measured sizes of the nanoparticles are well consistent with the nominal ones, verifying the feasibility of the system. By using this system, four kinds of polystyrene nanoparticles are evaluated. This design not only improves the measuring ability of the system but also provides flexibility in choosing scattering angle for measurement. A multimode fiber probe is used to highly efficiently couple and deliver laser light, while a single-mode fiber probe is used to only receive single scattering light. We present a novel optical fiber dynamic light scattering measurement system for nanometer particle size.

Dynamic light scattering detector