| Abstract [eng] |
In this thesis two type silica composite coatings were investigated which includes (i) silica-single-walled carbon nanotube (SWCNT) and (ii) silica-silver nanoprism (AgNPR) coatings. Research results showed, that the highest colloidal stability of SWCNTs in ethanol is obtained with surfactant P4VP. Saturable absorption experiments showed better performance of semiconductive SWCNT compared to unsorted ones – they have lower non-saturable loses and lower saturation power. SWCNT-silica composite coatings show higher thermal stability compared to polymeric SWCNT-P4VP coatings. Smaller AgNPRs are found to show positive nonlinear absorption, which was identified as two photon absorption and positive nonlinear refraction in the NIR spectral region. Nanoparticles, which LSPR peak was nearer to the excitation wavelength have negative nonlinear absorption and behave as saturable absorbers. It was found, that in prepared hybrid silica-APTES coatings amount of used APTES is crucial for deposition rate and behaviour of AgNPRs on surface - high APTES concentration leads to rapid aggregation and particle precipitation. Nevertheless, deposition and aggregation rates can be slightly adjusted when moderate amount of APTES is used. SERS study revealed, the highest enhancement occurs on coatings containing large particles where LSPR band is near laser excitation wavelength. |
