research

Interfacing nanomaterials with biology

nano-bio

Our group is interfacing nanomaterials with biological systems, such as central neuronal system, to address critical challenges in in vivo biomedical applications. We discovered unique intensive and intrinsic nonlinear optical signal of nanowires and applied this property for in vitro and in vivo imaging of silicon nanowires for the first time (Nano Letters, 2009, 9, 2440). We visualized the interaction between nanowires in real time and demonstrated specific targeting of cancer cells (Nano Letters, 2012, 12, 1002). We recently have shown endocytosis of nanowires is through a membrane mechanism, which is one of the first experimental evidences supporting theoretical prediction (Journal of Nanobiotechnology, 15:17, 2017).

In addition, we have demonstrated a novel label-free imaging in vitro and in vivo imaging graphene oxide, a promising nanomedicine system proposed (Scientific Reports, 5:12394, 2015). We have also demonstrated graphene as a biocompatible protection layer from corrosion for in vivo biomedical devices, for example, to improve success of implants with metal surface (Scientific Reports, doi: 10.1038/srep04097, 2014). Such anti-corrosion film can be significant and broadly needed in many important biomedical applications, such as brain-machine interface which will be studied.

Such nano-bio interface is a powerful tool allowing us to recently promote directional neuron growth and regeneration over 1 mm distance (ACS Biomaterial,  2018, 4, 3, 1037-1045>). Our 2D and 3D nanoladder scaffolds mimicking the native organization of axons demonstrate the potential in facilitating and guiding neuronal development and functional restoration, significant for injured central neuronal system repair. In addtion, our 2D and 3D structure will serve as a platform for a test-bed cortical neuronal co-culture system and neuronal circuits.

Understanding and designing new nanomaterials with unique photonics properties for solar energy applications

new mater energy

We have great interest in understanding and designing nanomaterials with unique physical chemistry properties. We have demonstrated a novel label-free imaging of single wall carbon nanotubes with single tube sensitivity and ability to distinguishing metallic and semiconducting tubes (Physical Review Letters, 105, 217401, 2010) and of graphene with single layer sensitivity (Scientific Reports, 5:12394, 2015) and domain boundary contrast as well as and high speed meeting the large scale production needs (2018).

Nanowires have offered an elegant improvement or solution for addressing solar energy challenges, in photovoltaic, photo electrochemical cells and photosynthesis. Our contribution is to explore semiconductor-metal-semiconductor core-multishell (CMS) nanowires for novel photonic and energy applications such as negative reflective index materials, white LEDs and photoelectrochemical cells. (Scientific Reports, 4:4931, 2014;  ACS Photonics, 2018, 5, 5, 1853-1862; Nano Letters, 14, 4517-4522, 2014, Journal of Material Science and Technology, Special issue on 1D nanomaterial, invited review, 2015).

 

Nanowire architecture for electronics and photonics applications

nanoelectronics

In the area of novel nanomaterial for nanoelectronics, we have been consistently exploring the ideal nanowire architecture, including new materials, doping, orientation and structural complexity, for large scale, high performance and low power consumption nanoelectronics. We have achieved GaSb (Nano Letters, 15, 4993-5000, 2015) and InSb nanowires, conventionally considered to be fundamental challenging through thin film growth, and pioneered doped GaSb nanowires through the in-situ doping (invited paper, ChemPhysChem, 2012, 13, 2585-2588). We have established the fundamental understanding in controlling the orientation of nanowires in large arrays particularly for two systems, homoepitaxial and heteroepitaxial growth of IV nanowires vertical arrays (Journal of Materials Research, 26, 2744-2748, 2011Nanomaterials and Nanotechnology, doi: 10.5772/58317 2014) and self-aligned planar growth (Nano Letters, 13, 2786–2791, 2013) and self-catalyzed growth (Nano Letters, DOI: 10.1021/acs.nanolett.6b04046, 2017) of III-V nanowires. My group has demonstrated insights of device physics in core-shell nanowires– a suitable platform for tunneling device applications for low power consumptions (Nano letters, 2011, 11, 1406) and small band gap nanowire devices (Nano Letters, 12, 5331–5336, 2012).