Visualizing Chemistry: The Progress and Promise of Advanced Chemical Imaging (2006)Board on Chemical Sciences and Technology
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Scientists and engineers have long relied on the power of imaging techniques to help see objects invisible to the naked eye, and thus, to advance scientific knowledge. These experts are constantly pushing the limits of technology in pursuit of chemical imaging--the ability to visualize molecular structures and chemical composition in time and space as actual events unfold--from the smallest dimension of a biological system to the widest expanse of a distant galaxy. Chemical imaging has a variety of applications for almost every facet of our daily lives, ranging from medical diagnosis and treatment to the study and design of material properties in new products. To continue receiving benefits from these technologies, sustained efforts are needed to facilitate understanding and manipulation of complex chemical structures and processes. By linking technological advances in chemical imaging with a science-based approach to using these new capabilities, it is likely that fundamental breakthroughs in our understanding of basic chemical processes in biology, the environment, and human creations will be achieved. This report reviews the current state of chemical imaging technology, identifies promising future developments and their applications, and suggests a research and educational agenda to enable breakthrough improvements. The report highlights advances in chemical imaging that could have the greatest impact on critical problems in science and technology.
- A quantitative understanding of molecular electronic structure is needed to make advances in chemical imaging. Two chief ways in which this understanding can be furthered are through improving probes and better theory.
- Acquisition speeds need to be increased in order to provide improved time resolution. In addition, there is a need to provide more online analysis capabilities to improve the efficiency of imaging by allowing more directed investigations of samples.
- Analysis tools for three-dimensional visualization need to be developed for various microscopies and materials analysis instrumentation.
- Brighter, tunable ultrafast light sources need to be developed, particularly infrared-terahertz vibrational and dynamic imaging, near-field scanning optical microscopy (NSOM), and X-ray imaging.
- Chemical imaging would be invigorated by innovations in basic theory of molecular dynamics. At the same time, the specific needs of chemical imaging should play a role in guiding the development of MD theory.
- Contrast mechanisms that reveal chemical identity and function in surface characterization need to be improved for a wider variety of samples.
- Imaging has a wide variety of applications that have relevance to almost every facet of our daily lives. These applications range from medical diagnosis and treatment to the study and design of material properties in novel products. To continue receiving benefits from these technologies, sustained efforts are needed to facilitate understanding and manipulation of complex chemical structures and processes.
- In order to probe chemical constituents and follow their biochemical reaction in cells and tissues, there is a need to make fluorescent labels more specific, brighter, and more robust. This will require greater understanding of the photophysics and photochemistry of fluorescent probes and the mechanisms of their photobleaching.
- Increasing signal-to-noise ratios should be a chief focus of the efforts to improve the sensitivity of NMR and MRI detectors.
- Integrated real-time analysis needs to be expanded for automated customization of data collection, particularly in multiscale imaging applications.
- MRI probes need to have higher relaxivity, be more specific, and be deliverable to the site of action.
- Nonlinear optical techniques need to be developed with particular emphasis on improved ultrafast laser sources and special fluorophores, novel contrast mechanisms based on nonlinear methods for breaking the diffraction barrier without using proximal probes.
- Novel approaches to funding mechanisms for chemical imaging need to be promoted.
- Researchers should be encouraged to integrate their data analysis with the development of their apparatus.
- Spatial and temporal sensitivity of electron microscopy detectors need to be improved.
- The miniaturization of high-field NMR and MRI magnets is needed to broaden the applicability of these techniques by reducing the need for dedicated facilities.
- Theory needs to be developed and better utilized to address the data storage and search problems associated with the increasingly large datasets generated by chemical imaging techniques.
- There is a need for detectors to be developed that possess all of the following attributes: (1) the ability to measure multiple dimensions in parallel fashion, (2) high time resolution, (3) high sensitivity, and (4) broad spectral range. IR and UV detector improvements, even if incremental, could catalyze new chemical insights.
- There is a need to advance X-ray-absorbing probes to specifically detect and localize chemical signals that are introduced into cells.
- There is a need to develop a better theoretical understanding of the radiation signals of gold and silver nanostructures including Raman scattering, Mie scattering, and fluorescence. New probes composed of metal-based nano-particles or atomic clusters should be developed to provide improved sensitivity, specificity, and spatial localization capabilities.
- There is a need to develop a next generation of readily accessible, easy-to-use MD simulation packages.
- There is a need to develop better analysis and data extraction techniques for elucidating more and different kinds of information from an image. In particular, this should include user-friendly multivariate analysis tools and hyperspectral imaging deconvolution and analysis.
- There is a need to develop higher-quality electron beams in order to broaden and deepen the application of electron microscopy.
- There is a need to develop imaging methods for patterning complex spatial and temporal organization into chemical systems.
- There is a need to develop methods for optical, X-ray, Raman, and other probe regimes that can image at depths of a few nanometers to macroscopic distances beneath a surface, especially for materials science applications.
- There is a need to develop multitechnique correlations for various combinations of imaging techniques.
- There is a need to develop optics for miniaturization and speeding of microscopic imaging instrumentation in order to improve chemical imaging capabilities.
- There is a need to develop standards for chemical image data formatting.
- There is a need to encourage both individual investigator and multidisciplinary team approaches for the development of chemical imaging techniques.
- There is a need to expand the range of techniques useful for hyperpolarizing NMR and MRI signals, as well as the range of molecules that can be hyper-polarized.
- There is a need to improve probe geometries for high-resolution chemical imaging beyond the diffraction limit. This includes design (theory) and realization (reproducibility, robustness, mass production) of controlled geometry near-field optics.
- There is a need to improve zone plate optics, which are presently the limiting factor for scanning transmission X-ray microscopes (STXM) and full-field X-ray microscopes (TXM).
- X-ray detectors including solid-state pixel detectors and detectors for hard X-ray tomography need to be improved through the development of scintillators that convert X-rays to visible light and detectors that image directly onto a CCD chip with column parallel readout, among other detector possibilities. The goal is to improve X-ray detector's resolution, dynamic range, sensitivity, and readout speed.