| In recent years, there has been a growing research interest in metal micro/nano structures due to their potential application in optics, electronics, and chemical sensing. Metal structures, such as photonic crystal, metamaterial, and plasmonic devices, exhibit unique advantages and are able to realize various interesting electromagnetic phenomena like tailored thermal irradiation, negative refraction, and subwavelength light confinement. Our research mainly aims at laser fabrication technique of 2D and 3D metal structures and trying to research their applications. In our work, firstly a new method based on mass sedimentation was proposed for measuring the two-photon absorption cross section(TPACS) of metal ions in solution.Then silver-palladium alloy nanostructures were successfully fabricated by femtosecond laser two-photon absorption induced co-reduction process and then they were employed as stable substrates for surface enhanced Raman scattering(SERS).Next, femtosecond laser filamentation irradiation of aqueous solution was adopted for synthesis of nickel phosphorus nanoparticles ascribing to the intense optical field induced breakdown of chemical bond. Finally femtosecond laser direct writing of a polymer template followed by subsequent electroplating was used for fabrication of3 D metal structures. More detailedly, the work in this thesis can be summarized as follows:(1) Proposing a new method for measuring the TPACS of metal ions based on masssedimentation.The photo-reduction of metal ions in solution induced by femtosecond laser is an important and novel method for fabricating three-dimensional metal microstructures.However, the nonlinear absorption cross section of metal ions remains unknown because its measurement is difficult. In the present study, a method based on Two-Photon Excited Sedimentation(TPES) is proposed to measure the two-photon absorption cross section(TPACS) of metal ions in solution. The TPACS of silver ion and palladium ion were able to be measured by using this method, which wereapproximately(9.97?0.79)?10-2 GM and(1.69?0.31)GM respectively. The power-squared dependence of the amount of sediment on the excitation intensity was confirmed, revealing that 800 nm femtosecond laser induced reduction of metal ions was a two photon absorption process. Moreover, the accuracy, sensitivity, applicable scope, and suggested laser intensity were also discussed in detail.(2)Facile fabrication of silver-palladium alloy nanostructures as a stable substrate for SERS by using femtosecond laser two-photon absorption induced one-step co-reduction process.Silver nanostructures have been extensively studied as sensors for surface enhanced Raman spectroscopy(SERS) owing to their strong enhancement effect. However,pure silver nanostructures are chemically unstable under ambient conditions, resulting in a considerable weakening of the SERS signal with increasing exposure time, thus hindering their long-term use as an efficient sensor. Herein, we demonstrate a facile one-step procedure for the fabrication of silver-palladium alloy nanostructures using a femtosecond laser induced co-reduction process, which could protect themselves from oxidation, thus rendering them as a stabilized substrate for SERS. The as-fabricated silver-palladium alloy substrate with 18% content of palladium showed the best stability against aerobic oxidation while at the same time maintaining its SERS sensitivity, as it was stable for up to 20 days under ambient aerobic conditions,exhibiting a significant improvement compared to those unprotected silver substrates which had a limited lifetime of only 3 or 4 days.(3) Preparation of size-controllable amorphous nickel phosphide nanoparticles by femtosecond laser filamentation irradiation of aqueous solution.Nickel phosphorus nanoparticles exhibited excellent electric, magnetic, and optical properties, thus enabling them as ideal catalysts for hydrodesulphurization(HDS),hydrodenitrogenation(HDN), hydrogen evolution reaction, magnetic storage, and electrode materials for Li batteries. However, the report about size-controllable synthesis of Ni–P nanoparticles is rare and the existing synthesis methods often suffer from complex procedures and they are always time consuming. Herein, a new alternative which is very simple and fast to be implemented for nickel phosphidessynthesis is proposed based on femtosecond laser filamentation. Nickel phosphide nanoparticles were fabricated by the high intensity femtosecond laser filamentation irradiation of nickel sulfate and sodium hypophosphite aqueous solution. The morphology and size of the as-prepared particles were facilely adjusted by varying the reaction parameters such as reactant concentration, reactant molar ratio, laser power,and irradiation time, through which particles with diameters between 35 nm to 120 nm were successfully fabricated. The XRD and TEM results demonstrated that the particles were in amorphous phase. By the addition of dispersant PVP, the size uniformity was greatly improved. The fabrication mechanism is also discussed in terms of the breakdown of chemical bond in the reactant via the highly intense optical field generated by femtosecond laser filamentation.(4)An approach combining femtosecond laser direct writing of polymer template and electroplating was employed for fabrication of 3D metal structures. A micro-inductor was successfully fabricated by using this technique.Due to the limited application of two-dimentional metal structures, a considerable attention has been paid to 3D metal structures for their application in MEMS,plasmonics, and metamaterials. But the fabrication of 3D metal structures remains technically challenging since traditional fabrication methods were mainly capable of2 D structures fabrication. In our work, a method which utilizes metal infiltration into a polymer template by electroplating was used for the fabrication of 3D metal structures. By using this process, three-dimensional solenoid micro-inductors were fabricated, which could facilitate future on-chip device integration. |
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