Comparative Study Of Optical Properties Based On The Gold Nanostars And Gold Nanorods

Nanomaterials hold particular ability in physical adsorption, chemical reaction andphotochemical catalysis, because of their specific volume effect, size effect, surfaceeffect and tunnel effect, which make them widely used in the biomedical field and thechemical engineering realm. As the strong surface plasmon resonance (SPR) in the nearinfrared region (NIR), gold nanomaterials have unique advantages in converting energy.Among various kinds of gold nanomaterials, the photothermal effect of goldnanorod (GNR) is outstanding. GNR has two SPR peaks, the tranverse peak and thelongitudinal peak, and the longitudinal SPR peak can be tuned from the visible region tothe NIR. And this tunability makes GNR useful for the photothermal therapy and theformation of various functional composite materials. In recent years, gold nanostar(GNS), as a novel kind of nanomaterial, catches a lot of research interest. Because of theirregular branch structure and the large surface-to-volume ratio, GNS has notablescattering feature. At the same time, GNS holds large molar extinction coefficient, andthe branch structure of GNS can be easily penetrated by the incident electromagneticradiation, which makes the whole parts of GNS involve generating heat.The aim of this master project is to compare the optical properties of GNS andGNR, evaluate the photothermal properties of GNS, and offer basic support for theapplication of GNS in the photothermal therapy field. There are four tasks in this project,including synthesis, simulation, measurement and comparison. Firstly, GNSs and GNRswere synthesized using seed-mediated method, and they were characterized by theextinction spectra and electronic microscopy. Through changing the experimentalconditions, the well-monodispersed GNSs and GNRs were obtained. And we studied theinfluence of different components of the growth solution on the growth of goldnanostructures by the control variate method. After that, the optical properties of GNSand GNR were simulated by discrete dipole approximation method. We used thesphere-parabolic model to simulate the optical properties of GNSs. While for GNRs, thecylindroid model, the cylindroid-cap model and the cylindroid-semisphere model wereemployed. And then, the photothermal effect of these two kinds of gold nanomaterialswere measured, and several typical optical parameters were calculated, including molar heating rate, photothermal conversion efficiency and molar extinction coefficient. Atlast, we calculated the extinction efficiency and absorption efficiency of goldnanostructures through the optical parameters obtained from the photothermalmeasurement, and these efficiencies were contrasted with the simulation results. Andthe optical properties of GNSs and GNRs were compared both theoretically andexperimentally. Through the comparison, for the gold nanostructures, whose centralSPR peaks are in the NIR, GNS displays more advantages in the photothermal effect,which indicates that GNS has a promising future in the application of the photothermaltherapy of tumors.