Light scattering near and from interfaces using evanescent wave and ellipsometric light scattering

The broad range of interface light scattering investigations in recent years shows the power and the versatility of these techniques to address new and open questions in colloid and interface science and the soft condensed matter field. Structural information for polymers, liquid crystals, or colloids close to planar or spherical colloidal interfaces are either captured with long range light scattering resolution, or in a complementary approach by high resolution ellipsometric techniques. Of special interest is the dynamic behavior close to or in interfaces, since it determines material properties and responses to external fields. Due to the broad dynamical range and the high scattering contrast for visible light, interface light scattering is a key to elucidate soft matter interfacial dynamics. This contribution reviews experimental and related theoretical approaches for interface light scattering and further gives an overview of achievements based on such techniques.     

Raman scatterings of colloidal silver and gold prepared in the presence of a nonionic surfactant,Surfynol 465

The FT-Raman and resonance Raman scatterings of colloidal silver or gold formed in the presence of a nonionic surfactant, Surfynol 465, were studied. The intensity of Raman scattering of colloidal solution was strongly affected by the power of laser for excitation. At the low power, the intensity of scattering and the spectrum of colloidal solution were normal. However, at the high power, the intensity of Raman scattering anomalously increased over the whole frequency region, suggesting the surface enhanced Raman scattering (SERS) on colloidal silver or gold. And in the Raman spectra new bands were found in addition to bands of starting materials. Through the assignment of new bands, the working mechanism of Surfynol 465 for the formation of colloidal silver or gold was discussed.     

Differential dynamic microscopy for the characterization of polymer systems

This review summarizes recent progress in investigating polymer systems by using Differential dynamic microscopy (DDM), a rapidly emerging approach that transforms a commercial microscope by combining real-space information with the powerful capabilities of conventional light scattering analysis. DDM analysis of a single microscope movie gives access to the sample dynamics in a wide range of scattering wave-vectors, enabling contemporary polymer science experiments that would be difficult or impossible with standard light scattering techniques. Examples of application include the characterization of polymer solutions and networks, of polymer based colloidal systems, of biopolymers, and of cellular motility in polymeric fluids. Further applications of DDM to a variety of polymer systems are suggested to be just behind the corner and it is thus likely that DDM will become a tool of choice of the modern experimental polymer scientists.     

Studies on microemulsions

The microemulsions formed in the 4-component system water-potassium oleate-hexanol-dodecane have been investigated by time-average light scattering and small angle neutron scattering. A constant volume fraction ratio water: potassium oleate of 1.44 was used and at this constant composition, which gave a pseudo 3-component system, a wide region of the microemulsion domain was examined. In order to interpret the scattering data at finite volume fractions of the dispersed phase, water, allowance had to be made for interactions between the water-in-oil microemulsion droplets. This was carried out using a hard sphere model for the interaction. It is shown that using this model self-consistent results are obtained by light scattering and neutron scattering and an estimate can be made of the size of the particles in concentrated colloidal dispersions.     

Suppression of Multiple Scattering in a Depolarized Light-Scattering Experiment Using the One-Beam Setup

We have performed depolarized dynamic light-scattering measurements of suspensions of colloidal spherical particles made of tetrafluoroethylene copolymerized with perfluoromethylvinylether (MFA). Measurements on highly concentrated turbid suspensions of 17 wt% MFA in water show that the one-beam cross-correlation technique successfully suppresses the multiple scattering contributions. This is the first time that a cross-correlation technique has been used in a depolarized scattering experiment.     

Structural and analytical studies of silica accumulations in <Emphasis Type="Italic">Equisetum hyemale</Emphasis>

Horsetail (Equisetum spp.) is known as one of the strongest accumulators of silicon among higher terrestrial plants. We use the combination of position-resolved analytical techniques, namely microtomography, energy-dispersive X-Ray elemental mapping, Raman microscopy, as well as small-angle and wide-angle scattering of X-rays, to study the type, distribution and nanostructure of silica in the internodes of Equisetum hyemale. The predominant silicification pattern is a thin continuous layer on the entire outer epidermis with the highest density in particular knob regions of the long epidermal cells. The knob tips contain up to 33 wt% silicon in the form of pure hydrated amorphous silica, while the silica content is lower in the inner part of the knobs and on the continuous layer. In contrast to the knob tips, the silica in these regions lacks silanol groups and is proposed to be in close association with polysaccharides. No mentionable amount of crystalline silica is detected by wide-angle X-ray scattering. The small-angle X-ray scattering data are consistent with the presence of colloidal, sheet-like silica agglomerates with a thickness of about 2 nm. From these results we conclude that there are at least two distinct forms of silica in E. hyemale which may have different functions. The close association of silica with cell wall polymers suggests that they may act as a polymeric template that controls the shape and size of the colloidal silica particles similar to many other biominerals and mineralised tissues. We propose that owing to its specific distribution in E. hyemale, a protective role and possibly also an important biomechanical role are among the most likely functions of silica in these plants. Figure 3D rendering of X-ray microtomography data from a dry Equisetum hyemale stalk. The red colour indicates high X-ray absorption values due to local silica accumulations     

Angle‐dependent light scattering by highly uniform colloidal rod‐shaped microparticles: Experiment and simulation

While extensive theoretical work has been devoted to analyzing scattering behavior for nonspherical particles, few experimental studies of the light‐scattering properties of such particles are available, largely because of the difficulty of synthesizing such particles with uniform geometries. Here we report the synthesis of highly uniform, volume‐equivalent rod‐shaped colloidal particles prepared from their commercial spherical counterparts, on which we performed light scattering experiments as a function of scattering angle for micro rods with varying aspect ratio and volume. These results were compared to values calculated using the T‐Matrix method. Good agreement with theoretical predictions was found for the experimentally measured scattering cross sections and the angular dependence of the scattering intensity. An increase in the forward scattering intensity is observed and predicted for particles with larger aspect ratios relative to their volume equivalent spheres, with only minor differences observed at both mid‐range and backscattering angles. Furthermore, the light scattering results for the rod‐shaped particles did not show the scattering fringes seen in scattering by the spheres, indicating that as three‐dimensional symmetry is broken, the associated Lorenz–Mie resonances are strongly attenuated. This observation also was predicted by theory. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1889–1895     

Evanescent Wave Light Scattering A Fusion of the Evanescent Wave and Light Scattering Techniques to the Study of Colloids and Polymers Near the Interface

The evanescent wave light scattering technique, which is produced by a fusion of the evanescent wave technique and light scattering technique, is a very powerful and useful tool for investigation of colloidal particles and polymers near the surface and interfaces. We have developed two kinds of evanescent wave light scattering apparatuses. One is the evanescent wave dynamic light scattering (EVDLS) technique and the other is the evanescent wave light scattering microscope (EVLSM). By EVDLS, the diffusion behavior of a colloidal particle near the interface can be extracted quantitatively as a function of the distance from the interface. The diffusion coefficient was smaller than those for particles in bulk, reflecting electrostatic and hydrodynamic interactions. By EVLSM, the interaction potential profile between a colloidal particle and the surface in dispersion can be evaluated directly. EVLSM will play an important role in colloidal interaction studies, especially at a low ionic strength. It is also pointed out that a particle dynamics study is also possible by the EVLSM technique. A new field will be developed in colloid science and polymer science by application of the evanescent wave light scattering technique, i. e. a fusion of the evanescent light and a light scattering techniques.     

Microwave Synthesis of Au Nanoparticles with the System of AuCl_4-CH_3CH_2OH

Au nanoparticles attract keen research efforts due to their unique optical electronic properties1,2. The preparation of nanoparticles has important significance in nanochemistry, material science, physics and life science3. The technique of microwave has been paid attention by the researchers of chemistry, physics, and materials4-6. But the liquid preparation of Au nanoparticles with both microwave high-pressure and reducing agent of alcohol has not been reported to date. As the HAuCl_4-CH_…     

Characterization of polymer materials by scattering techniques,with applications to block copolymers

The application of six techniques—static and dynamic light scattering, small-angle neutron and X-ray scattering, neutron and X-ray reflectivity—to the characterization of polymer materials is summarized. Emphasis is placed on the similarities and differences among the various techniques, and on recent advances in experimental practice. Twelve examples from the recent literature are described, most of which concern block copolymers. A brief introduction to block copolymer properties is also provided.     

Dynamic Light Scattering Based Microelectrophoresis: Main Prospects and Limitations

Microelectrophoresis based on the dynamic light scattering (DLS) effect has been a major tool for assessing and controlling the conditions for stability of colloidal systems. However, both the DLS methods for characterization of the hydrodynamic size of dispersed submicron particles and the theory behind the electrokinetic phenomena are associated with fundamental and practical approximations that limit their sensitivity and information output. Some of these fundamental limitations, including the spherical approximation of DLS measurements and an inability of microelectrophoretic analyses of colloidal systems to detect discrete charges and differ between differently charged particle surfaces due to rotational diffusion and particle orientation averaging, are revisited in this work. Along with that, the main prospects of these two analytical methods are mentioned. A detailed review of the role of zeta potential in processes of biochemical nature is given too. It is argued that although zeta potential has been used as one of the main parameters in controlling the stability of colloidal dispersions, its application potentials are much broader. Manipulating surface charges of interacting species in designing complex soft matter morphologies using the concept of zeta potential, intensively investigated recently, is given as one of the examples. Branching out from the field of colloid chemistry, DLS and zeta potential analyses are now increasingly finding application in drug delivery, biotechnologies, physical chemistry of nanoscale phenomena and other research fields that stand on the frontier of the contemporary science. Coupling the DLS-based microelectrophoretic systems with complementary characterization methods is mentioned as one of the prosperous paths for increasing the information output of these two analytical techniques.     

Colloidal crystals made of poly(N-isopropylacrylamide) microgel particles

Poly (N-isopropylacrylamide) microgel particles are found to form colloidal crystals similar to those occurring in typical hard-sphere colloids like poly(methylmethacrylate) beads. Samples made of particles with different cross-linker concentrations are investigated and their deswelling ratio is determined using dynamic light scattering. Small-angle neutron scattering data are also presented and analysed in terms of a face-centred-cubic crystal structure. The characteristic length, a, of the elementary cell is found to be 535 ± 16 and 495 ± 15 nm for the two systems investigated. This leads to particle radii of 189 ± 6 and 175 ± 5 nm, respectively. These values compare well to the radii determined using several different methods. Received: 26 July 1999/Accepted: 21 March 2000     

Elastic scattering of gamma rays and X-rays

Studies of elastic gamma ray scattering were pursued independently by the groups of Prof. Ghose and the author for several decades in spite of somewhat meagre support. Several techniques for such studies developed by the two groups and some of the results obtained in the energy range from tens of keV to about 1.5 MeV are described briefly. The theoretical background necessary for understanding these results is also outlined. The results showed the importance of Modified Relativistic Form Factor (MRFF) approximation in the explanation of atomic Rayleigh scattering cross sections in the small angle regime and the necessity for an inclusion of real Delbrück scattering amplitudes at large scattering angles. Dispersion corrections to form factor amplitudes or the so-called anomalous scattering factors are shown to be needed at photon energies close to electron binding energy thresholds. A few promising future extensions of such studies are indicated at the end.     

A small-angle X-ray scattering study of nanoparticle assembly in an aligned nematic liquid crystal

The assembly of colloidal particles in a nematic liquid crystal has been investigated using small-angle X-ray scattering. The structure and orientation of nanoparticle assemblies in bulk samples of aligned nematic liquid crystal have been determined. The method offers some advantages over optical microscopy, which is usually restricted to investigations of thin cells and micron-sized particles. The scattering from chains of particles has been calculated, and comparison with experimental results has shown that suspensions of 48 and 105 nm diameter silica nanoparticles formed highly ordered structures perpendicular to the liquid crystal director, consistent with quadrupolar defect-induced assembly.     

X-Ray scattering study of ionic colloidal crystals

The scattering study of ionic colloidal crystals by using one- and two-dimensional ultra-small-angle scattering techniques is reviewed with a special reference to dilute dispersions. Because of large lattice constants of colloidal crystals, ultra-small angle regions need to be covered either by long distance optical systems combined with a synchrotron X-ray source or by adopting the Bonse–Hart optics. The crystal structure, lattice constant, and crystal orientation can be precisely determined.     

Structural Characterization of Biomaterials by Means of Small Angle X-rays and Neutron Scattering (SAXS and SANS), and Light Scattering Experiments

Scattering techniques represent non-invasive experimental approaches and powerful tools for the investigation of structure and conformation of biomaterial systems in a wide range of distances, ranging from the nanometric to micrometric scale. More specifically, small-angle X-rays and neutron scattering and light scattering techniques represent well-established experimental techniques for the investigation of the structural properties of biomaterials and, through the use of suitable models, they allow to study and mimic various biological systems under physiologically relevant conditions. They provide the ensemble averaged (and then statistically relevant) information under in situ and operando conditions, and represent useful tools complementary to the various traditional imaging techniques that, on the contrary, reveal more local structural information. Together with the classical structure characterization approaches, we introduce the basic concepts that make it possible to examine inter-particles interactions, and to study the growth processes and conformational changes in nanostructures, which have become increasingly relevant for an accurate understanding and prediction of various mechanisms in the fields of biotechnology and nanotechnology. The upgrade of the various scattering techniques, such as the contrast variation or time resolved experiments, offers unique opportunities to study the nano- and mesoscopic structure and their evolution with time in a way not accessible by other techniques. For this reason, highly performant instruments are installed at most of the facility research centers worldwide. These new insights allow to largely ameliorate the control of (chemico-physical and biologic) processes of complex (bio-)materials at the molecular length scales, and open a full potential for the development and engineering of a variety of nano-scale biomaterials for advanced applications.     

Silica Coating on Colloidal Maghemite Particles

Maghemite colloidal particles are coated with a silica layer using a silicon alkoxide as silica precursor. The coating process is studied by electrophoresis, quasi-elastic light scattering, nitrogen adsorption, and infrared spectrometry analyses. The conditions of complete coverage of the iron oxide particles by silica and the nature of the maghemite–silica interface are discussed.     

Light Scattering Probes of Viscoelastic Fluids and Solids

In this article, we discuss recent advances in static and dynamic light scattering applied to soft materials. Special emphasis is given to light scattering methods that allow access to turbid and solid‐like systems, such as colloidal suspensions, emulsions, glasses, or gels. Based on a combination of single‐ and multispeckle detection schemes, it is now possible to cover an extended range of relaxation times from a few nanoseconds to minutes or hours and length scales below 1 nm up to several microns. The corresponding elastic properties of viscoelastic fluids or solid materials range roughly from below 1 Pa to several 100 kPa. Different applications are discussed such as light scattering from suspensions of highly charged colloidal particles, colloid and protein gels, as well as dense surfactant solutions.     

CHEMICALLY DEPOSITED SILVER FILM USED AS A SERS-ACTIVE OVER-COATING LAYER FOR POLYMER FILM*

When colloidal silver particles were chemically deposited onto polymer film as an over-coating layer, surface-enhanced Raman scattering (SERS) spectra could be collected for the surface analysis. SERS measurements of liquid crystalfilm were successfully performed without disturbing the surface morphology.