Visible fingerprints

The reaction of amino acids with ninhydrin can detect amino acids on a wide variety of substrates. For example, if a kidnapper touches a ransom note with his fingers, the dermal ridges on his fingers leave traces of amino acids from skin secretions. Treatment of the paper with ninhydrin and pyridine causes these secretions to turn purple, forming a visible fingerprint. 

Treatment of the paper with ninhydrin and pyridine causes these secretions to turn purple, forming a visible fingerprint. 

In this Section we want to present one of the fingerprints of noble-metal cluster formation, that is the development of a well-defined absorption band in the visible or near UV spectrum which is called the surface plasma resonance (SPR) absorption. SPR is typical of s-type metals like noble and alkali metals and it is due to a collective excitation of the delocalized conduction electrons confined within the cluster volume [15]. The theory developed by G. Mie in 1908 [22], for spherical non-interacting nanoparticles of radius R embedded in a non-absorbing medium with dielectric constant s i (i.e. with a refractive index n = Sm ) gives the extinction cross-section a(o),R) in the dipolar approximation as ... 

In addition to the characteristic XRD patterns and photoluminescence, UV-visible and X-ray absorption spectra, another fingerprint thought to indicate lattice substitution of titanium sites was the vibrational band at 960 cm-1, which has been recorded by infrared and Raman spectroscopy (33,34). Although there is some controversy about the origin of this band, its presence is usually characteristic of a good TS-1 catalyst, although it turned out to be experimentally extremely difficult to establish quantitative correlations between the intensity of the 960 cm-1 band and the Ti content of a Ti silicate and/or its catalytic activity. 

Silylenes are short-lived intermediates, and their detection requires fast methods such as ultraviolet (UV)24 or laser-induced fluorescence spectroscopy.25 The characteristic absorption maxima in the UV-visible spectra of these species, which are assigned to n - p transitions of electrons at the silicon atom, were used as a fingerprint to prove the occurrence of silylenes in matrices or solution. In addition, these transient species, which under normal conditions are too short lived to be observed by a slow detection method such as infrared (IR) spectroscopy, can be isolated in inert hydrocarbon or noble gas matrices, thus allowing the accurate measurement of their IR spectra. 

The identification and quantitative determination of specific organic compounds in very complex samples is an area of intense current research activity in analytical chemistry Optical spectroscopy (particularly UV-visible and infrared absorption and molecular fluorescence and phosphorescence techniques) has been used widely in organic analysis. Any optical spectroscopic technique to be used for characterization of a very complex sample, such as a coal-derived material, should exhibit very high sensitivity (so that trace constituents can be determined) and extremely great selectivity (so that fractionation and separation steps prior to the actual analysis can be held to the minimum number and complexity). To achieve high analytical selectivity, an analytical spectroscopic technique should produce highly structured and specific spectra useful for "fingerprinting purposes," as well as to minimize the extent of overlap of spectral bands due to different constituents of complex samples. 

Each one of us is a unique and complex waveform, though we also share many of the same "harmonics." Like fingerprints, we are unique but all related. Modem science takes advantage of this fact in order to identify materials by their vibratory nature in the form of spectral resonances in visible light, infrared, microwaves, etc. Einstein once said, "Everything is energy, beyond that is divine."... 

The haemoproteins are highly coloured, usually red but occasionally green or brown. This colour arises from strong absorption bands in the visible region, attributable to the haem group. These bands are quite sensitive to the structure and environment of the chromophore, and have been used in the characterisation of haemoproteins for nearly a century. Some spectroscopically identical haemoproteins have been shown to be chemically distinct, but the visible and near-ultraviolet absorption spectrum remains the most convenient fingerprint for haemoproteins. 

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