Infrared spectrometry.

  Fourier-transform spectroscopy

    Infrared spectra of absorption, reflectance and scattering convey extremely comprehensive information on the sample composition and characteristics. By comparing the sample infra-red spectrum with the spectra of known substances, one can identify the unknown substance, determine the basic composition of the substance and perform a fractional and group analysis. In the up-to-date devices the infrared spectrum is determined by scanning along the phase displacement between the two parts of a divided light beam (Fourier-transform spectroscopy). This method is significantly more accurate photometrically and in wavelength reading.

Fourier-transform spectroscopy is a method of optical spectroscopy, in which spectra are obtained in two stages:
 1. First, interferogram is recorded;
 2. The spectrum is calculated using Fourier inversion (by path difference).

    The second part requires rather extensive calculations; therefore the method became widely used only with the arrival of up-to-date computers.

    However, the difficulty of obtaining spectra using Fourier spectrometers is significantly compensated by the advantages over other spectral devices:

 1. Using Fourier spectrometers one can record the whole spectrum simultaneously. Thanks to the permissibility of a larger-sized inlet in the interferometer, as compared to the slit of spectral devices with a dispersion element of the same resolution, Fourier spectrometers in comparison to the latter have advantage in luminosity which makes it possible:
      • reduce the time of spectra recording;
      • increase the signal-noise ratio;
      • increase the resolution;
      • decrease the dimension of the device.

 2. Fourier spectrometer also has advantage in the accuracy of wavelength reading.
 3. In diffraction devices the wavelength can be determined only indirectly, while Fourier spectrometers make it possible to determine it directly.

     Most often Fourier-spectrometers are used in the research where other methods are low-effective or inapplicable, for example in the infrared spectrum. Fourier spectrometers have significant advantage over diffraction devices in photometric accuracy. In diffraction devices the light falls on the receiver only in a narrow spectral interval which falls on the outlet slit of the monochromator. In Fourier spectrometers the entire source light arrives into the photoreceiver, and all spectral lines are recorded simultaneously. Consequently, the signal-noise ratio increases.

There are other methods of analysis of nanomaterials:

• Mass spectrometry
• X-ray structural analysis
• Spectrofotomery in ultra-violet and visible areas of the spectrum
• Highly effective solution chromatography
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