Study of Laser-Stimulated Heating of Aqueous Suspensions of Titanium Nitride Nanoparticles for Biomedical Applications

We report an experimental study of optical and photothermal properties of aqueous suspensions of titanium nitride (TiN) nanoparticles (NPs), exhibiting plasmon resonance in the visible and near-IR spectral regions. Dependences of the rate of photoinduced heating and the value of photothermal conversion efficiency (PCE) on the concentration of TiN NPs are obtained for exciting laser wavelengths of 532, 665, and 808 nm. It is found that under irradiation at 808 nm, the PCE is 1.5-2.5 times greater than that under irradiation in the visible range of the spectrum, and for all studied laser wavelengths, an increase in the PCE is observed with increasing NP concentration, reaching a value of 0.55 for an NP concentration on the order of 1 mg/ml under irradiation at a wavelength of 808 nm. The concentration dependence of the PCE is explained by the contribution of multiple scattering in combination with light absorption in ensembles of TiN NPs. The results may be useful for biomedical applications of TiN NPs in the method of local photohyperthermia under multifrequency laser excitation.