Abstract
The surface morphology and structural properties of titanium dioxide micro-powders have been investigated by scanning electron microscopy and Raman spectroscopy. The Raman scattering was excited by the green line of a copper vapor laser (λ = 510.6 nm) which operates in a repetitively pulsed mode. Powders, consisting of close-packed particles in the form of spherical particles of specified sizes (29-63 μm), were investigated. The recorded Raman spectra of titanium dioxide powders were characterized by an anomalously high intensity, which was associated with trapping of exciting radiation in the mini-resonators of the cells. It was found that in titanium dioxide micro-powders in mini-resonator cells ( photon traps), the effect of “combination opalescence” is observed, leading to a sharp (by 5–6 orders of magnitude) increase in the Raman scattering intensity within the powder. It was revealed that the intensity of the Raman line of optical phonons at the Eg1 mode (144 cm-1) is more than 1000 times higher than the one of the Raman spectra of TiO2 micro-powders recorded under normal conditions (in a cylindrical cell with a large diameter). The high conversion efficiency of the exciting radiation into the Raman signal is explained by the large value of the total path that the exciting radiation photon travels in the dispersed medium in the photon trap. The developed original method for amplifying weak Raman signals based on mini-resonators (photon traps) opens up great prospects for recording weak signals of secondary radiation of powders of important inorganic and organic substances, as well as for creating small-sized laser analyzers of chemical compounds necessary for solving many applied problems.
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