Life Sciences and Bio-Medicine
One of the remarkable exploits of SRIR microspectroscopy is probing single isolated cells and tissues at sub-cellular resolution, collecting broadband molecular information with excellent spectral quality via the diffraction limited microbeam. Studying individual cells is important because it reveals the cell-cell differences (e.g. due to cell cycle or biological variability) which are averaged together in conventional IR imaging or spectroscopy. This is important for identifying the subtle underlying spectral differences of interest in the research.
Applications include developing spectral biomarkers for disease diagnosis - particularly cancer research, location of stem cells within tissues, following effects of natural and synthetic chemicals on stem-cell differentiation and quantifying drug sensitivity.
A key development recently achieved is moving from fixed and dried samples to ex vivo, living conditions in the natural aqueous environment and time-dependent studies of biological processes. The combined requirements of high spatial resolution, rapid data acquisition and high photon flux (due to strong IR absorption by water) make synchrotron radiation an invaluable microanalysis tool.
In the THz part of the spectrum, very bright (coherent) synchrotron radiation (CSR) is useful in the study of low energy modes, especially in highly absorbing samples. The THz properties of biological materials is a rapidly growing field, from the organism level (imaging) down to fundamental spectroscopy at the biochemical level, where, for example, the solvation shell around proteins can be studied via changes in low energy hydrogen bonds.
Solid State Physics and Chemistry
Reactions within organic crystals attract considerable attention, both for developing environment-friendly solvent-free materials and in crystal engineering. The kinetics of solid state reactions and their theoretical modelling depends on the ability to spectroscopically monitor, non-destructively, single crystallites in the microgram to picogram range. As well as mid-infrared studies, bright (coherent) THz synchrotron radiation has been used to study long range ordering via low energy modes in molecular crystals including pharmaceutical compounds and zeolites for catalysis. For electrochemistry experiments, the reaction time-resolution depends on the lateral dimensions of the electrode, so small samples accessible with SRIR provide a significant advantage.
Fine Arts, Cultural Heritage and Archaeometry
IR microspectrometry is a versatile non-destructive method for the scientific investigation of artworks, craftsmanship or archaeological finds. Aims include following the evolution of the production techniques, identifying and provenancing the materials used and understanding degradation processes or effects of preservation treatments.
The enhanced spatial resolution offered by the synchrotron IR source has been crucial for the microscopy of paint layers and fabric sections as well as ancient surface structures. It is vital for improving the signal-to-noise ratio in microanalysis of very small material fragments like mineral particles in archaeological sites or organic residues.
FTIR spectroscopy has emerged as a powerful tool for enhancing the characterisation of forensic materials by simultaneously measuring spectra from thousands of different sample locations. Using complementary techniques broadens the range of IR imaging applications, e.g. from the analysis of organic residues including skin fragments, drugs (and counterfeits), textiles or soils, to the detection of trace materials from fingerprints or gunshots/explosives particles on surfaces.
Infrared spectroscopy gives insight into the local composition, orientation and conformation of polymer chains as well as interface properties in phase separated copolymers and composites. The high brightness of the synchrotron enables rapid acquisition of spectra at high spatial resolution for static measurements, or time-resolved measurements of dynamic properties during external perturbations (e.g. mechanical strain, temperature, chemical). This is essential for following irreversible processes where repeated measurements cannot be averaged to improve spectral quality.
The high brightness of the IR synchrotron source is ideal for the study of phases stable in the Earth at extreme pressures up to 100,000 atmospheres or more which requires the use of microscopic samples in (heated) Diamond Anvil Cells. High pressure/temperature experiments are important for modelling the chemical and physical properties of planetary interiors, such as the role of water within minerals in the deep crust, or chemical dependent viscosity changes in silicates which affect magma extrusion.
Environmental Science and Geo-Biology
SR IR microspectroscopy has opened new possibilities for in situ and ex vivo biomineralization studies of environmental contaminants in biological systems and the impact of changes in biogeochemical environment on microbial cell surfaces (e.g. the effect of metals on binding characteristics of bacteria). Tests on experimentally grown biofilms can help us understand a whole series of systems from bio-corrosion in steel pipes to origin-of-life processes.
Unlike conventional broadband IR sources, Synchrotron Radiation is produced in intense, short pulses (1 to 20 picoseconds at Diamond) which can be synchronised with external stimuli (e.g. laser, magnetic pulses) to follow the ultrafast chemical, biological or electronic response of the sample down from a few picoseconds to nanoseconds. Important areas at this timescale include electron-pair dynamics in high temperature superconductors, fast infrared detectors and emitters, semiconductor optoelectronic devices and dynamic processes in photosynthesis and visual perception.