Mustafa M. Aslan

Characterization of Individual Cotton Fibers via Light-Scattering Experiments

A detailed experimental/theoretical study is conducted to explore the fundamental nature of individual cotton fibers via light-scattering experiments. For this purpose, a new precision nephelometer is built and calibrated with quartz fibers. In the experiments, iris opening (viewing angle) and scanning range and rate were determined to be the key parameters for precision measurements. The experimental results are compared against the theoretical predictions based on a finite element model. It is shown that the scattered intensity profiles as a function of scattering angle (0) can be related to the quality (fineness) of cotton. At small scattering angles of θ < 10 deg, these profiles can be used to infer the shape (cross section) of cotton fibers. On the other hand, within the range of 30 deg < θ < 50 deg they may be used to evaluate single-fiber cotton quality (fineness)

Surface Plasmon Scattering by Gold Nanoparticles and Two-Dimensional Agglomerates

There has long been an interest in nanosized metallic particles for numerous novel applications, from the productions of colored glass in medieval times to the molecular-level sensors of today. These particles are known to display considerably different, and size-dependent, optical properties than those of their bulk counterparts. Yet it is very difficult to determine the size and structure of these particles in situ, such as monitoring the actual self-assembly process, because of their small size. In this paper, we present a methodology to predict the patterns of nanosized particles and agglomerates subjected to surface plasmon waves. For this characterization, the scattering patterns of different types of particles and agglomerates on or near the surface are needed. A combination of the T-matrix method, image theory, and a double interaction model are considered. The incident and scattered fields are expanded by employing spherical harmonic functions. The surface effects are incorporated using the Fresnel equations, in the incident-field expansion coefficients, and by including particle-surface interaction fields. The premise of the method is that the T-matrix is independent of incident and scattered fields and hence can be used effectively for cases involving incident surface waves. By obtaining the T-matrix for clusters or agglomerates of metallic particles, the scattering matrix elements (M 1 , M 12 , M 33 , and M 34 ) of agglomerated structures on the surface are calculated using an additional T-matrix operation. The effect of size, shape, and orientation of gold nanosized particles on their scattering patterns are explored both in the visible spectrum and at resonance wavelengths. The results show that the normalized scattering matrix elements at certain observation angles and incident wavelengths provide significant information to monitor the structural change of gold nanosized particles on a gold substrate.

EFFECT OF FAT AND CASEIN PARTICLES IN MILK ON THE SCATTERING OF ELLIPTICALLY POLARIZED LIGHT

In this article, we present an experimental approach to determine the milk fat content using scattered light intensity profiles. The elements of the scattering (Mueller) matrix have been shown to provide valuable information about variation of the optical properties of scattering particles. The scattering behavior of fat and casein in terms of the scattering matrix elements was experimentally determined for milk with varying fat levels ranging from 0.05 wt% (skim) to 3.20 wt% (whole). Three of the scattering Mueller matrix elements, specifically S11, S12/S11, and S33/S11, were found to be sensitive to the number of fat particles in milk. These results indicate that it should be possible to develop a reliable sensor based on the measurement of these scattering elements, which will allow for the development of a robust, in-line sensor to be used in food processing. In addition, an attempt was made to model the phenomena using a relatively simple approach based on single scattering with a size distribution. The disagreement between the model and experiments suggests that a more comprehensive model is needed which can account for multiple scattering.

The Surface Plasmon Scattering Patterns of Gold Nanoparticles and Agglomerates

Metallic nanoparticles display considerably different optical properties than those of their bulk counterparts. They have long been of interest in several novel applications, from colored glass production of medieval times to molecular-level sensors of today. Recently, there has been significant interest in characterization of such small particles via surface plasmons, for example for monitoring of the actual self-assembly purposes. For such characterization, we need scattering patterns by different type of particles and agglomerates on or near the surface. Here we present a methodology to predict the required scattering patterns of single particles and agglomerates on or near a surface subjected to surface plasmon waves. We investigate the effect of size, shape and orientation of gold nano particles on their scattering patterns both in the visible spectrum and at resonance wavelengths. The results show that the normalized scattering matrix elements (Mij) at certain observation angles and incident wavelengths provide significant information to monitor self-assembly process of gold nanoparticles on a gold substrate.© 2005 ASME

CHARACTERIZATION OF METALLIC NANO-PARTICLES VIA SURFACE WAVE SCATTERING: A. THEORETICAL FRAMEWORK AND FORMULATION

Characterization of nano-size particles and structures are crucial for successful application of selfassembly processes that lead to bottom-up machining and manufacturing concepts. Conventional lightbased approaches cannot be used for these purposes, mainly because the particle and structure sizes are much smaller than the wavelength of visible light. To overcome this problem, we are in the process of developing a diagnostic tool based on surface-wave scattering. In this paper, we outline the governing equations required to describe the scattering of the electromagnetic field by a particle located near a film. The formulation given here is for a general case; a special application of this work to surface waves can be obtained by considering the fields propagating at near grazing angles. This work constitutes the theoretical frame work needed for the characterization of nano-particles on or above a thin metallic film via scattered surface waves, which is outlined in Part B (JQSRT (2004)). Published by Elsevier Ltd.

Surface-Wave-Scattering-Based Characterization of Nano-Particles

In this paper, we introduce a novel methodology to determine the size and structure of nano-particles on a surface. We present an analysis, dubbed Elliptically Polarized Surface-Wave Scattering (EPSWS) approach, to show that 5–10 nm size particles on or above an interface can be characterized by using the scattered surface plasmon (SP) or evanescent waves. We present an analysis to show that the scattering matrix elements of the evanescent waves scattered by the nano-particles on or near an interface can be used for characterization of nano-size particles.Copyright