Microplasmas are a special class of electrical discharges formed in geometries where at least one dimension is less than 1 mm. As a result of their unique scaling, microplasmas operate stably at atmospheric pressure and contain large concentrations of energetic electrons (1-10 eV). These properties are attractive for a range of nanomaterials synthesis and nanostructure engineering [1-3]. Recently the development of carbon nanomaterials such as carbon nanotubes (CNTs) and graphene has been leading us to an exciting direction for both fundamental science and commercial applications because of their exceptional properties. While researchers have achieved significant progress in CNT synthesis, precise control of structure including diameter, wall number, and chirality remains a critical technological challenge due to the unclear role of the catalyst in controlling the CNT structure. Surface enhance Raman scattering (SERS) is a promising technology for various applications including plasmonic devices, photo energy generation and conversion, biomedical detection and chemical sensing. However, this conventional approach to fabricate SERS-active materials is usually time-consuming and laborious. In this presentation, I will discuss these topics in detail, highlighting the advantages of microplasma-based systems for the synthesis of well-defined nanomaterials. These experiments will aid in the rational design and fabrication of nanoparticle alloys for selective growth of CNT structures and may also have significant impact in other catalytic applications including nanowire growth, gas conversion, and fuel cells. Moreover I will present a facile synthesis of silver (Ag) nanoparticles (NPs)/graphene composites using a unique atmospheric-pressure microplasma-assisted electrochemistry. The systematic micro Raman study indicates that the AgNP/graphene composites show superior SERS performance with low detection concentration of 10^-10 M of R6G and high enhance factor (EF) about 1×10⁹.

Reference:

[1] W-H. Chiang and R. M. Sankaran, Appl. Phys. Lett. 91, 121503 (2007)

[2] W-H. Chiang and R. M. Sankaran, Adv. Mater. 20, 4857 (2008)

[3] W-H. Chiang and R. M. Sankaran, Nature Mater. 8, 882 (2009)