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Information × Registration Number 0219U001218, 0118U001357 , R & D reports Title Characterization of the nonlinear optical properties of harmonic nanoparticles: impact of size, shape and interface state. popup.stage_title Head Gayvoronsky Volodymyr Yaroslavovych, Доктор фізико-математичних наук Registration Date 18-01-2019 Organization Institute of physics NASU popup.description2 Harmonic nanoparticles (HNPs) are a new class of nanoparticles that effectively convert laser radiation and generate second, third, and higher optical harmonics. HNPs are very promising for use in the field of bioimaging due to the possibility of excitation wavelengths tuning, high imaging depth, photostability for long-term observations and increased sensitivity due to their specific high harmonics signatures on the background of the biological tissues components optical response ("biological markers"). Experimental techniques for rapid characterizing of the optical harmonics generation efficiency of nanoparticle colloidal suspensions and for the studying of the individual ZnO nanoparticles response have been introduced for the studying of nanoparticles. The influence of the size and functionalization of the HNPs surface on the harmonic generation efficiency were studied. A NLO diagnostics of bulk ZnO single crystals with different concentration of defects has been studied and different types of optical responses of ZnO were analyzed. It was shown that there is a correlation between the values of the real and imaginary parts of the cubic NLO susceptibility with the photoluminescence data and FTIR spectra in the region of defective bands, as well as the efficiency of elastic optical scattering - with the concentration of intrinsic defects. The excitation spectra of the second and the third optical harmonics, as well as the photoluminescence of individual NPs were studied by the multiphoton microscopy technique under fs laser excitation in spectral range ?ex = 710-1300 nm. For the ZnO NPs with a size of ~ 150 nm it was shown that there are three excitation ranges with the most characteristic type of response: ?ex < 800 nm for SH, 800 < ?ex <950 nm for PL, and 950 < ?ex <1200 nm for TG. Excitation of NPs in one of these ranges gives the opportunity to work mainly with one type of response and to improve the accuracy of the identification of NPs in biological tissues. Also, the effect of optical harmonics generating in ZnO NPs (~ 150nm) with a functionalized surface by a small ZnO NPs has been studied. It was shown that the surface functionalization leads to the expansion of the spectra efficiency range of the second and third harmonics. On the basis of the experimental equipment of the SYMME laboratory, Annecy, France, a multiphoton microscopy technique was realized for the second and the third optical harmonics generation efficiencies studying from individual nanoparticles under femtosecond laser pulses excitation in the wide spectral range ?ex = 710-1300 nm. Within the framework of the approach, it was realized: (i) optimization of the polarization of the pump laser beam for each HNP from a large ensemble of NPs on the substrate; (ii) optimization of the optical harmonics spectra readout, taking into account the thermal drift of the ensemble of HNPs on the substrate with long measurements; (iii) the separation of contributions from the generation of harmonics on the background of photoluminescence bands (PL), when multiphoton resonances result in the multiphoton virtual and real transitions superimposed upon the excitation of the HNPs. With this technique, for the first time, the excitation spectra of the second and third optical harmonics were studied, and the photoluminescence of individual ZnO HNPs in such a wide spectral range. For "large" ZnO HNPs with a typical diameter of ~ 150 nm it has been shown that there are three ranges of wavelengths of excitation ?ex with the most effective manifestation of a certain type of response: ?ex <800 nm for generation of the second harmonic (SG), 800 <?ex <950 nm for the manifestation of the PL response close to the fundamental absorption edge, and 950 <?ex <1200 nm for the generation of the third harmonic (TG). Laser excitation of the HNPs in a certain mentioned spectral range implements the registration of the signal with the optimal contribution of a certain type of optical response SG / PL / TG, which increases the accuracy of the identification of the NPs in biological tissues. Comparison of the data analysis of the diagnostics results for nanoparticle colloidal suspensions and the individual ZnO HNPs response studying showed a decrease of the optical harmonics generation efficiency in the transition from a HNPs with a characteristic size of 150 nm to a HNPs with a size of ~ 40 nm. On the background of a general decrease in the efficiency of harmonic generation, the expansion of the excitation spectra of SG and TG in the range 900 < ?ex <1100 nm was observed. It was shown that the surface functionalization by the gas-phase epitaxy technique of the "large" ZnO HNPs (~ 150nm) by the "small" ZnO HNPs with a characteristic size below 10 nm leads to a significant expansion of the excitation spectra of SH and TG with increasing efficiency of the laser radiation frequency conversion in certain ranges. The obtained result is important for the creation of high-efficient HNPs with optimal size for the study of biological systems. The results of the work are recommended for implementation in scientific and industrial fields in the development of biomarkers based on harmonic nanoparticles, in particular GAP-biophotonics (University of Geneva, Switzerland), V.E. Lashkaryov Institute of Semiconductor Physics NAS of Ukraine and M.G. Kholodny Institute of Botany of the NAS of Ukraine. Product Description popup.authors Гайворонський Володимир Ярославович Мультян Володимир Вікторович Уклеін Андрій Володимирович popup.nrat_date 2020-04-02 Close