Nanoscale chemical imaging: Tools and techniques for localised infrared spectroscopy of nanostructured polymers and biomaterials.

All living things are, in essence, formed by nanoscale self-assembly. Chemical interactions control the physical ordering of individual molecules, combining them to build ordered structures that form the basis of macroscopic organisms. The overall structures formed can, therefore, be seen as arising from molecular-level chemical programming . Although these processes have been occurring in nature for billions of years, science has recently started to catch up. The investigation of artificial self-assembled materials, both wholly synthetic and biologically inspired, is an extremely active area of research within the wider field of nanoscience. Such materials are widely recognised as key to a range of future technologies. At the same time, the restrictive dimensions of nanoscale structures often cause chemical processes in to proceed in a markedly different manner to those in bulk materials, thus offering a way to control, for example, the underlying molecular causes of some diseases.Studying structures of such nanoscale dimensions, perhaps only a few tens of atoms in diameter, presents new challenges for scientific instrumentation. Ordinary microscopes are fundamentally incapable of seeing such small structures due to the wavelength of light being many times these dimensions. While electron microscopes are widely used, a more recently developed technique is the atomic force microscope (AFM). An AFM uses a fine probe, in some cases having a tip only a few atoms in diameter, to build a mechanically profiled image of a sample. Effectively the AFM feels rather than sees the surface. The small probe tip dimensions allow AFMs to easily resolve nanoscale features, and they have rapidly become ubiquitous research tools in the field.However, abandoning the light microscope has a major disadvantage. Optical spectroscopy, detecting particular chemical compounds by their absorption or emission of light, is not possible with an AFM. Many molecules involved in nanoscale self assembly have characteristic spectroscopic fingerprints in the infrared. It would, therefore, be of immense value to combine the techniques of infrared spectroscopy with the nanoscale imaging capabilities of the AFM. Such techniques would give researchers important new insights into the chemical processes at work in individual nanostructures, allowing significant advances in the field. It is the aim of this project to develop precisely such an instrument.Promising early work to achieve this is limited by the lack of suitable infrared lasers able to precisely tune their wavelength far enough to collect the spectroscopic fingerprint of chemical compounds. In this project, novel laser-like sources will be developed, based on so-called nonlinear optical techniques, which effectively shift the output of a laser from wavelengths where the desired tuning properties are available to infrared wavelengths, where they are not.To test the techniques developed, several nanoscale chemical processes will be studied. The first is nanoscale control of the natural self-assembly of certain proteins thought to be associated with the progress of Alzheimer's disease. The second will examine chemical changes occurring during self-assembly of designer proteins, which may form the foundation of artificial tissues. Finally, the behaviour of structures forming functional surfaces that change their physical properties in response to the local chemical environment will be investigated. In all cases, as well as testing the new analytical techniques developed in the project, it is anticipated that new insights, unobtainable by other methods, will be gained into the systems under study.