We studied the formation of a composite from an aqueous dispersed medium with albumin and carbon nanotubes under the action of laser radiation in continuous wave (CW) mode and pulsed mode with a repetition rate of 10 Hz and pulse duration of 16 ns. During the experiments, the temperature was monitored at the site of exposure, as well as its distribution in the liquid. Pulsed solid-state Nd:YAG laser and CW diode laser with an irradiation power of ∼500 mW were used as radiation sources. However, a three-dimensional composite was formed only with constant exposure. The effect of pulsed laser radiation with an intensity corresponding to nonlinear interaction with water dispersion led only to its enlightenment. Thus, it is important not only the energy parameters of radiation but also the frequency of energy portions exposure for the fabrication of tissue-engineered structures (composites). As a result, it was found that the curing of the dispersion and the composite formation occurs under the action of continuous or pulsed (with a high pulse repetition rate) laser radiation at a temperature in the range from 45°C to 50°C; in case the pulse repetition rate is insufficient, composite formation is not observed even under the action of high intensity radiation and heating occurs only to a temperature of ∼40 ° C. This formation process can be generated both in the visible 532 nm and in the infrared 810-nm wavelength ranges. In this case, one of the main conditions is the absence of albumin or cells absorption at these wavelengths so that absorption occurs mainly with single-walled carbon nanotubes. Studies of the surface and internal structure of the composite made it possible to demonstrate the binding of nanotubes to each other. This happened under the influence of laser radiation. This led to high hardness values of the composites. The average value of hardness was 0.26 ± 0.02 GPa.
At present, laser sources are widely used in many fields. Not only in laboratories, but also in sphere of medicine, manufacturing and military. Lasers are potentially dangerous to the eyes or sensitive optical devices, therefore it is necessary to develop optical limiters. One of the significant properties of carbon nanotubes is their optical limitation of laser radiation. Many works of scientific groups are devoted to materials for limiters, which include carbon nanotubes. However, they still have an increased interest. A particular role is given to such mechanism of nonlinear attenuation as scattering and absorption. Moreover, it is important not only their combined effect to increase the effectiveness of the limiters as a whole, but also the contribution of each of them with their combined effect. It is equally important to accurately determinate the concentration in which there is a strong attenuation of high-intensity laser radiation and minimal attenuation at low intensity. The nonlinear and linear optical properties of water-dispersed media with different concentrations of single-walled carbon nanotubes (SWCNTs) were obtained by optical density spectra, experimental Zscan data with an open aperture and a fixed location of the limiter. Radiation in single mode with duration of 16 ns at wavelength of 1064 nm from Nd:YAG laser was used. The linear transmittance of the prepared water dispersions of the SWCNTs ranged from 60% to 70%. Limiter with such working substances had attenuation coefficient 10 and 14 for the concentration of nanotubes 3.125 mg/l and 6.25 mg/l, respectively.
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