Page 167 - Synthesis of Functional Nanoparticles Using an Atmospheric Pressure Microplasma Process - LiangLiang Lin

Based on the technical underpinning, Chapter 7 furtherly expanded the plasma-assisted technique to the liquid-phase synthesis of a series of lanthanide doped nanophosphors, with Eu3+ doped yttria being a model case for detailed study. In this manner water was exploited as a soft hydrolyzing agent via hydroxyl ions produced under plasma treatment. As a result, series of high quality crystalline Ln3+ (Ln=Eu, Tb, Dy, Tm) doped Y2O3 nanophosphors were successfully prepared. The photoluminescence properties were influenced by comprehensive factors such as the crystallinity of nanophosphors, the spatial-correlation effect and the Coulombic repulsion between the doping ions in the host lattice. Heat-treatment can enhance their luminescent efficiency, while the gradual increase in dopant concentration shows an initial positive but a final quenching effect. For Y2O3:Eu nanophosphors the optimal doping concentration was 7%, with the most prominent emission peak being observed at 612 nm. Moreover, characteristic emission peaks of Tm3+, Tb3+ and Dy3+ ions were also observed at 455 nm, 543 nm and 572 nm respectively. By choosing proper precursors, this technique can be readily expanded to the synthesis of nanophosphors with spectral characteristics tuned according application demands.
To explore the possibility of using this technique as a promising nanofabrication method for bio-application purpose including novel anti-bacterial and anti-fouling materials, in Chapter 8 we suggested and furtherly investigated the direct synthesis of silver nanoparticles from Tollens’ reagent as well as AgNO3 solution via the plasma-liquid interactions using similar process with AgNO3 solution as a comparative reference case. Complementary anti-bacteria tests of the obtained Ag nanoparticles against E. coli. were performed. It was found that Ag(NH3)2OH based process had considerably faster reaction rate due to the higher reactivity. Meanwhile, the obtained Ag nanoparticles proved to be smaller compared to those generated from AgNO3 reaction system. Antibacterial tests demonstrated that Ag nanoparticles obtained from Ag(NH3)2OH have significantly higher antibacterial activity than those generated from AgNO3 solution.
It can be concluded that the atmospheric pressure microplasma-assisted process should be considered as a new versatile and up-scalable technological platform, having great potential for the production of nanomaterials in a simple, flexible and environmental friendly manner. It was shown that, the product properties can be controlled and tuned by adjusting processing parameters, even enabling fine-tuning for “in-flight” mode. This helps to open new routes for nanofabrication, which may greatly benefit socially important fields including life science and sustainable energetics.
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