Metal Nanomaterials Synthesis And Their Biomedical Application

Nanomaterials have gained a continous and remarkable interest in the past several years, due to their unique physical and chemical properties substantially different from bulk materials, and their great potential in the application of electronics, photonics, catalysis, and biomedicine. In this thesis, we described the synthesis of silver nanostructures, and their spectral properties along with their aplicaiton in the areas of catalysis, sensing, and biomidince. We also reported the autophagy-mediated chemosensitization in cancer cells by fullerence C60 nanocrystals.In the first section, we introduced three new methods to synthesize silver nanocubes. In the first method, Argon was employed into a NaHS-mediated polyol synthesis, which allowed for the production of silver nanocubes on a scale of 0.1 g per batch. The use of argon protection was the key to the success of this scale-up synthesis, suggesting the importance of controlling oxidative etching during synthesis. The second approach described a new protocol to synthesize silver nanocubes of 30 to 70 nm in the edge length with the use of CF3COOAg as a precursor to the element of silver. The controllable growing pace of silver nanocubes over the course of synthesis and the linear relationship between the edge length of silver nanocubes and the postion of localized surface plasmon resonance peak (LSPR) provided a powerful method to accurately control the size of every bath of silver nanocubes by monitoring the UV/Vis spectra of the reaction at different times. The third method described a seed-mediated mothod to produce silver nanocubes with an edge length from 30 to 200 nm. Both the spherical and cubic silver single-crystal seeds could be used as the original seeds. The key to the success of this synthesis were the use of sinlge-crystal silver seeds to direct the growth and the use of AgNO3 as a precursor to elemental silver,as the presence of HNO3 could help block homogeneous nucleation from the added AgNO3, which might lead to the production of twinned seeds and polydispersed samples. The edge length of silver nanocubes could be controlled by varying the amnout of silver seeds used, the amount of AgNO3 added and stopping the reaction at different time.The synthesis of silver nanobars was discussed in the second part. Two new approaches were developed to synthesize silver nanobars with different aspect ratios. From the previous study, we knew that silver nanobars also envolved from the single-crsytal seeds as the silver nanocubes did, and sodium bromides was used to promote the anisotropic growth of silver nanobars. In the seed-mediated method, different bromides were tested, and the added ionic bromides could efficiently transform the seeds into silver nanbars than the added convalent bromides. Three kinds of Ag nanocrystals, Ag nanocubes, square Ag nanobars and oblate Ag nanobars, coexisted in the final products due to the different expanding rates of Ag nanocrystals in the three (100) orientations of x, y and z axis. However, previous work and the seed mediated approach only could produce the silver nanobars with a largest average aspect ratio less than 5,which because that the used silver precursor was AgNO3. The by-product of HNO3 inhibited the further growth of silver nanobars. The second method was developed on the basement of the synthesis of silver nanocubes with CF3COOAg as a precursor to the element of silver, and the as-synthesized silver nanobars were with an average aspect ratio over 50 and a length over 2μm. The spectal properties of silver nanostructures with different shapes, different sizes were also investigated.In the following paragraph, we discussed the synthesis of gold hollow nanostructures using the galvanic replacement reaction with different silver nanostructures as templates. H2O2 was investigated as an oxditave ething agent to produce silver nanocages with the super thin wall-thickness and the LSPR peak position in the infared region. Cholorides, bromides, and iodides were demonstrated that they could more or less etch silver nanostructures into different shapes.Finally, we described autophagy induced by fullerene C60 nanocrystals, and their great potential in cancer treatment. The authentic autophagy induced by fullerene C60 was reactive oxygen species (ROS)-dependent and photo-enhancedment. The chemosensitization effect of fullerene C60 was autphagy-mediated and required a functional Atg 5 gene.