X-ray structural analysis

X-ray structural analysis – is the method of studying the atom-molecule structure of substances, mainly that of crystals, based on studying the diffraction occurring when the investigated sample interacts with X-rays with the wavelength of about 0.1 nm.  Characteristic X-rays are mainly used, produced, as a rule, by an X-ray tube.   
 
The device used for the X-ray structural analysis is usually a diffractometer, which comprises a radiation source, goniometer, detector and measuring-controlling unit.  A goniometer is used to set (with an accuracy of 1-3 seconds of arc) the investigated sample and the detector into a position necessary for obtaining a diffraction picture.  Detectors are scintillation, proportional or semiconductor counters.  Measuring device records (continuously or point by point) the intensity of X-ray diffraction maxima (reflections) depending on the diffraction angle – the angle between the incident beam and the diffracted one.
 
With the help of X-ray structural analysis one can investigate polycrystalline samples and monocrystals of metals, alloys, minerals, liquid crystals, polymers, biopolymers.
 
After having determined the general character of a crystal structure, it is given more accurate definition by means of successive approximation of values of theoretically calculated structural amplitudes to the experimentally determined ones, for example by means of a mathematical method of least-squares.  The atomic structure is represented as an atomic axis set and parameters of their thermal vibrations.  Based on this data, one can calculate the interatomic spacing and valence angles with an error of 10-3-10-4 nm and 0.2-2° respectively.  This ensures more accurate determination of the crystal chemical composition, the type of possible isomorphous replacements (with the reliability and accuracy depending on the element atomic number), the character of the atomic thermal vibrations, etc.

 
There are other methods of analysis of nanomaterials:

• Mass spectrometry
• Ir-spectrometry
• Spectrofotomery in ultra-violet and visible areas of the spectrum
• Highly effective solution chromatography
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