Research

Nanoscale sensing and manipulation is a strategically important field for the development of nanotechnology. The recent rapid advances in nanotechnology are due in large part to the newly acquired ability to characterize and control single structures on the nanoscale. At present, scanning probe techniques such as scanning tunneling microscopy (STM) and atomic force microscopy (AFM) are the main working horses for nano sensing and manipulation with resolution down to the atomic level. Although STM has been successfully demonstrated for atomic manipulation, this technique is limited to conductive samples with specially prepared smooth and clean surfaces. In this aspect, AFM and related scanning probe microscopies hold bigger promise for the general applications in nanotechnology. In the conventional scanning probe methods, probes comprise two main parts: a force-sensing cantilever and a probing tip at the end of the cantilever. The probe tip determines the spatial resolution and detection capabilities of these methods. However, up to now, the top-down-fabricated (mainly using the lithography and etching processes) probe tip is not very controllable in size and shape and not versatile in terms of detection functionality. Although several scanning sensor techniques such as scanning SQUID microscopy, scanning Hall sensor microscopy, scanning single electron transistor (SET) microscopy, and scanning thermal microscopy have been demonstrated by using various sensor functionalities enabled by the top-down microfabrication processes and micro electromechanical systems (MEMS), the spatial resolutions of such sensors are limited by the ultimate resolution limits of the top-down microfabrication processes (such as lithography and pattern transfer). Besides the drawbacks mentioned above, the present scanning probe techniques lack the chemically specific sensing and manipulation capabilities, which are very important for developing single-molecule detection and manipulation techniques in the emerging fields of nanoscale chemistry and biotechnology.

 

 

project 2

Recently discovered quasi zero-dimensional (0D) nanostructures (such as metal and semiconductor nanoparticles, endohedrally doped fullerenes, and self-assembled core/shell nanoparticles) and one-dimensional (1D) nanostructures (such as nanotubes, nanowires, nanorods, and nanobelts), fabricated by the bottom-up methods, possess many novel and highly tunable mechanical, electrical, magnetic, optical, and chemical properties for nano sensing and manipulation applications. Especially, if we can attach single nanoparticles to the scanning probes (ideally, in the form of composite materials assembled with nanowires or nanotubes), we can obtain various chemically specific capabilities such as chemical force sensing, DNA detection, controlled nanoscale chemical reaction, and local photocatalysis by using the well-known methods of functionalization and surface treatment of nanoparticles. Furthermore, besides the greatly added functionalities, the sizes of the assembled probes are much smaller than that achievable by the present top-down approaches. Up to now, these nanostructured materials have not been fully utilized for the purpose of nano sensing and manipulation. The goal of this proposed research is to incorporate the
bottom-up-fabricated and functionalized 0D and 1D functional nanostructures into the main sensing structures of the scanning probes to enhance their spatial resolution and sensing/manipulation capabilities. We believe that the use of functional 0D nanoparticles and 1D nanostructures for both sensing and manipulation on the nanometer and even atomic scale will revolutionize many developing fields of nanoscale science and technology.