3D-Dynamic light scattering (3D-DLS, LS Instruments AG, Switzerland)
Dynamic light scattering (DLS) is a scattering technique in physics that can be used to determine the size distribution profile of small particles in suspension or polymers in solution. In DLS, light scattered by particles in the suspension are detected by a sensitive detector (PMT or APD). A digital correlator then measures the intensity or photon auto-correlation function from which the particle size can be evaluated. However a conventinal DLS technique requires the suspension to be highly dilute so that there is no multiple scattering and scattering takes place only from single particles.
However, in 3D-dynamic light scattering (3D-DLS), a 3D-cross correlation technique is used which effectively suppresses multiple scattering from the sample allowing measurements of many samples in their natural state without dilution. In this technique, two simultaneous light scattering experiments are performed at the same scattering vector on the same sample volume in order to extract the single scattering information common to both.
The 3D-LS setup consists of a polarized HeNe laser (632.8 nm), a single mode fiber detection system with integrated collimators, and a two channel multiple tau correlator. A sensitive APD detector allows measurements on samples with very weak scattering. Both static and dynamic light scattering experiments at all scattering angles from 15 to 120 degrees with a resolution better than 0.01degree can be performed. Different cuvette holders allow measurements with cylindrical scattering cells of 10 or 5 mm diameter. By using the provision to rotate the samples using an upper sample goniometer, non-ergodic samples like glasses and gels can be also studied using 3D-DLS technique.
90 Plus nanoparticle size and zeta potential analyzer (Brookhaven Instruments, USA)
The 90 Plus performs fast, routine submicron particle size measurements on a wide variety of samples and concentrations. It is an ideal instrument for measuring colloids, latexes, micelles, microemulsions, proteins, and other nanoparticles in the size range 1 nm - 6 microns. Based on the principles of dynamic light scattering, most measurements only take a minute or two. Measurements can be done only at two fixed angles, 15o & 90o. 90 Plus is also equipped with a zeta potential analyzer which meaures the zeta potential of the colloidal particles based on its mobility in an applied electric field.
Confocal Laser Scanning Microscopy (CLSM - Carl Zeiss LSM 710)
Confocal laser scanning microscopy (CLSM) is an optical imaging technique for increasing optical resolution and contrast of a micrograph by means of using a special pinhole to block out-of-focus light in image formation. Capturing multiple two-dimensional images at different depths in a sample enables the reconstruction of three-dimensional structures (optical sectioning) within an object. This technique is used extensively in the scientific and industrial communities and typical applications are in life sciences, semiconductor inspection and material science.
In our laboratory we have Carl Zeiss LSM 710 with a Zeiss AXIO observer Z1 inverted microscope. It can collect transmitted light images (bright field and DIC) as well as conventional and confocal fluorescence images. The scope has 10x, 20x, 40x (dry), 40x (water), 63x and 100x (oil) objectives. The filters used are DAPI, Rhodomine (red) and FITC (green) and the laser lines used are: 405 nm Diode laser, Argon/2 (458, 488, 514 nm), HeNe1 (543/561 nm) and HeNe2 (633 nm). ZEN 2011 software is used to control the microscope, scanning, laser module, tools and the image acquisition and processing. We also have an upright microscope, AXIO observer Z2 that can be interchanged with the inverted microscope Z1.
Small and wide angle x-ray scattering (SAXS/WAXS - Rigaku, Japan)
SAXS/WAXS measurement system is a x-ray scattering instrument designed for nano-structure analysis. This unit can be used in small angle scattering (SAXS) geometry and wide angle scattering (WAXS) geometry separately or simulteaneously, which makes it possible to evaluate multi-scale structures from sub-nanometer to nano-order (0.1 nm to 100 nm). SAXS/WAXS measurement system is applicable to a variety of materials, such as: solids, liquids, liquid-crystals, gels etc. Diverse aplications include: nano-particle size distribution analyses, 3D protein molecule structure analyses, identification of molecular assembly or disassembly, and research of advanced materials, such as carbon fiber-reinforced plastics (CFRP).
Rheometers (Anton Paar MCR 301 & TA Instruments ARES G2)
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Rheology is the science of deformation and flow of matter, especially liquid and soft matter. Fluids flow at different speeds and solids can be deformed to a certain extent. Oil, honey, hair shampoo, hand cream, sweet jelly, toothpaste, plastic materials, wood and metals- depending on their physical behaviour, they can be put in an order. On one side there are liquids and on the other side there are solid materials and in between highly viscous semi-solid substances. Rheological characterization of materials gives an overall idea about the viscoelastic flow behaviour of the system. It is well known that the rheology is very important to every material because the rheological responses are closely related to final structures of the system. Complex systems, such as polymeric and disperse systems, show mechanical responses intermediate between those of liquids and solids because they are composed of both viscous and elastic components. Viscoelastic and nonlinear features depend upon both type and magnitude of the field conditions, like a strain or local stresses so also on their extent and variation over time. Accordingly, several material functions must be used to fully characterize the viscoelastic responses even under simple kinematic conditions. Concerning polymers, rheology is the science of their flow in the melting state for thermoplastics and prior to cross-linking for the thermosets and elastomers. The rheological behaviour of polymers is specifically studied in order to investigate the structure and spatial arrangement of the macromolecules that tell us about the different intra- and intermolecular interactions. Moreover, rheological measurements are performed on polymers in order to assess their behaviour during processing. Rheological characterization can be used to fix the optimum processes.
A rheometer is a laboratory device used to measure the way in which a liquid, suspension or slurry flows in response to external applied forces. It is used for those fluids which cannot be defined by a single value of viscosity and therefore require more parameters to be set and measured than is the case for a viscometer. There are two distintively different types of rheometers. Rheometers that control the applied shear stress or shear strain are called rotational or shear rheometers, whereas those that apply extensional stress or extensional strain are called extensional rheometers. Rotational or shear type rheometers are usually designed as a stress controlled instrument (control and applya user defined shear stress and measure the resulting shear strain) or a strain controlled instrument (control and apply a user defined shear strain which can then measure the resulting shear stress). In our laboratory we have both stress controlled and strain controlled rheometers.
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