Optical image spectroscopy

The success of fluorescent sensors can be explained by the distinct advantages offered by fluorescence detection in terms of sensitivity, selectivity, response time, local observation (e.g. by fluorescence imaging spectroscopy). Moreover, remote sensing is possible by using optical fibers. The great improvement in the sensitivity... 

Tan W. and Kopelman R. (1996) Nanoscale Imaging and Sensing by Near-Field Optics, in Wang X. F. and Herman B. (Eds), Fluorescence Imaging Spectroscopy and Microscopy, Chemical Analysis Series, Vol. 137, John Wiley Sons, New York, pp. 407-75. 

Many of the most effective constraints set well-defined limits to the data function (or its spectrum) beyond which the correct function is not allowed to go. An important example of this type of constraint is nonnegativity, whereby the correctly restored function is not allowed to extend below the zero baseline and thereby take on nonphysical negative values. This is an appropriate constraint for spectroscopy and optical images. A further example of the constraints of fixed limits is that of an upper bound to the values of the restoration. Another important constraint of this type is that of finite extent, for which no deviations from zero are allowed for the spatial function over those intervals on the spatial axis that lie outside the known... 

Treado, P. J., Levin, I. W. and Lewis, E. N. (1992) Near-infrared acousto-optic filtered spectroscopy a solid state approach to chemical imaging, Appl. Spectrosc. 46, 553-9. 

SECM instruments (77,78) will undoubtedly increase the scope and power of SECM. Further improvements in the power and scope of SECM has resulted from its coupling scanning probe or optical imaging techniques, such as AFM (57,79) or single-molecule fluorescence spectroscopy (80). The combined SECM-AFM technique offers simultaneous topographic and electrochemical imaging in connection to a probe containing a force sensor and an electrode component, respectively. 

Fourier-Transform Infrared (FTIR) spectroscopy as well as Raman spectroscopy are well established as methods for structural analysis of compounds in solution or when adsorbed to surfaces or in any other state. Analysis of the spectra provides information of qualitative as well as of quantitative nature. Very recent developments, FTIR imaging spectroscopy as well as Raman mapping spectroscopy, provide important information leading to the development of novel materials. If applied under optical near-field conditions, these new technologies combine lateral resolution down to the size of nanoparticles with the high chemical selectivity of a FTIR or Raman spectrum. These techniques now help us obtain information on molecular order and molecular orientation and conformation [1],... 

The observation of molecular hydrogen by means of its electronic transitions in a sense follows classical optical interstellar spectroscopy. It is, however, considerably more complex, requiring essentially controlled satellite observatories. Thus, it serves to determine molecular-hydrogen column densities in translucent clouds, but cannot provide images of the dense molecular clouds. For these, carbon monoxide is the generally accepted tool. The reported results are in terms of H2 column densities under the assumption that the H2 CO ratio is the accepted value of 10. CO is observable by means of its many isotopomers. This is extremely useful, as the common isotopomer is frequently optically opaque, making... 

While applying optical imaging detectors to analytical spectroscopy, we gradually began to appreciate their potential for elucidation of those problems of multicomponent analysis where it was desired not only to identify and quantitate each component but also to specify its location in space as well, i.e. when analytical chemistry was to be performed with spatial resolution. It is our belief that analytical chemists will become increasingly concerned with this problem in the next decade (15,16) and that optical imaging detectors will play a major role in its solution. 

T. Basche, W. E. Moerner, M. Orrit, and U. P. Wild, Eds., in Single molecule optical imaging and spectroscopy, Verlag Chemie, Weinheim, 1997. 

Scanning near field optical microscopy (SNOM) opens the perspective to apply optical imaging and spectroscopy techniques to soft matter far below the classical diffraction limit. A use of the novel SNOM technique [6,7] based on an aperture less probe provides a lateral optical resolution in the range of 1-10 nm. 

Hamann et al. were among the first to use the apertureless near-field approach to greatly enhance optical processes in the near-field region. One important result of this investigation is that the spatial resolution of this approach is correlated with the radius of the tip apex, while the high cross section arises from an anteima enhancement provided by the tip volume [118]. This illustrates the high potential of this approach for local spectroscopy and optical imaging on the nanometer scale. 

Pesticide concentration can be readily measured with NIR spectroscopy and optical imaging technology. However the accuracy and precision could be impa-oved. There is a need to develop rapid optical techniques for pesticide determination which could be used in the future for agro-food safety assurance. The optical technique could be one of the most useful tools along with the advancement of spectral instrument for determination of p>esticide residue. 

---