Nanosciences for Biological and Energy Systems
Hongjie Dai
Stanford University
Department of Chemistry, Stanford, CA 94305
This talk will review our work on carbon nanotube and graphene-based nanoscience with a focus on interfacing these novel nanocarbons with biologicalsystems. I will first briefly review our earlier work of carbon nanotubes for biological applications with a focus on our work onfluorescence imaging in the previously unexplored 1000-1700 nm NIR-II window to benefit from greatly suppressed photon scattering at long wavelengths. We show that NIR-II imaging is novel with up to ~ 4 mm tissue depth capable of sub-10 micron spatial resolution, using a wide range of fluorescent agents including carbon nanotubes, AgS2quantum dots, donor-acceptor conjugated polymers and small organic molecules emitting in the 1000-1700nm range. NIR-II imaging is capable of video-rate imaging with dynamic contrast to quantitate blood flows in both normal and ischemic vessels, fast frame rate for revealing the blood flow pattern within a single cardiac-cycle of a mouse, and through-skull imaging of the brain of a mouse without craniotomy to investigate stroke models. These work clearly showed the advantage of NIR-II imaging over traditional NIR imaging near 800 nm due to much reduced photon scattering of long, up to 1700 nm wavelength light by tissues and ultra-low indigenous background of biological systems in this range, thus opening new possibilities in biological and medical imaging.
The second part of the talk will focus on our work on advancing new types of electrocatalysts for renewable catalyst applications. I will talk about achieving record setting performance of electrocatalysts for water splitting including HER and OER. We have developed a novel Ni/NiO heterostructured hydrogen evolution reaction (HER) catalyst with near zero overpotential. The nanoscale nickel oxide/nickel NiO/Ni hetero-structures formed on carbon nanotube sidewalls are highly effective electrocatalysts for hydrogen evolution reaction with activity similar to Pt with near zero overpotential in HER onset in basic solutions. We have also developed a NiFe layered double hydroxide (NiFe LDH) oxygen evolution reaction (OER) catalyst with ~ 250mV overpotential, which was among the most active OER catalyst in basic solutions. The NiFe LDH exhibited higher OER catalytic activity and stability than commercial Ir based catalysts. Using the highly active Ni/NiO HER and NiFe LDH catalyst, we recently achieved enabling water splitting using a record low voltage of < 1.5 volt, making it possible to make an electrolyzer for hydrogen and oxygen gas generation running on a single AAA alkaline battery cell. Lastly, I will present our latest development of rechargeable Al ion battery.