Project title: Self-assembled Nanowires as Building Blocks for Tip Enhanced Raman Spectroscopy (TERS) Probes

Raman spectroscopy (RS) is widely used for chemical characterization of molecular species, however, the low efficiency of RS limits its applications to large samples and the spatial resolution is limited to that of optical microscopes (~ 0.5 mm). In Tip Enhanced Raman Spectroscopy (TERS) both limitations are resolved using a metallic, or metal-coated, scanning probe microscope (SPM) tip. The SPM provides large spatial resolution while the metallic termination provides large Raman enhancement (RE) resulting from localized surface plasmon resonances in the vicinity of low-dimension metals. Theoretical predictions suggest that TERS can achieve RE of 107-1012 and high (<5 nm) spatial resolution, however, such capabilities are still far from being realized.  The major limitation in the progress of TERS, and its wide use in non-specialized research laboratories, is the lack of reproducible tips with high enhancing factors. This proposal will study a new approach, namely, the use of self-assembled nanostructures as building blocks for the assembly of TERS tips.  A wide range of nanostructures are suitable to be used for this purpose; in particular, Si, ZnO, ZnS and CdS nanowires with a reproducible and well-defined metallic tip (20 to 200 nm in diameter).  The ability to fabricate such tips, systematically and reproducibly, is will become a major contribution towards the development of reliable TERS with vast applications in fields like semiconductor, biological, and biomedical technologies.

Supervisor: Dr J. Antonio Zapien (apjazs@cityu.edu.hk)

Suitable for: M. Phil. /Ph.D.

Number of students: 2.