My Work
I began working directly with nano research shortly after my arrival at UB in 1998. Prior to joining the engineering faculty here I conducted post-doctoral research in aerosol science and technology at the University of Minnesota. There I studied small particles in the gas phase and how to prevent such particle formation. My transition to nano research roughly coincided with the rise of nanotechnology as a distinct research field, which led to the launching of the National Nanotechnology Initiative (NNI) in 2001.
My work at UB initially involved silicon particle modeling and experimentation. Currently I am mostly focused on the experimental side of this project, or the intentional synthesis of these silicon particles (and others). My research attempts to exploit the size-dependent optical and electronic properties of silicon particles, specifically silicon nanocrystals, for use in medical and environmental applications such as biomedical imaging, solar cells, and solid-state lighting. The stability of silicon particles, and more importantly, their low toxicity, makes this type of research and its applications extremely important areas of investigation for crucial issues within our society today.
In addition to collaborating with Paras Prasad and other members of UB’s Institute for Lasers, Photonics, and Biophotonics, on the biomedical imaging applications of nanomaterials, I have similarly contributed to others’ research endeavors, both within and outside of the university. Some of these projects have included advising InnovaLight, a California-based company pursuing cost-effective solar power, and collaborating with faculty in our own School of Dental Medicine on use of nanomaterials in the tissue engineering of bone. Such collaborations are essential to making advances of practical importance in nanotechnology applications.
My Research
Silicon Nanocrystals
Silicon nanocrystals, like other semiconductor nanocrystals, exhibit size-dependent optical and electronic properties. Despite the fact that bulk silicon is a very poor light-emitter, silicon nanocrystals show efficient emission at wavelengths from the near-infrared to green as their size decreases from about 5 nm to 1.5 nm in diameter. These properties, along with low toxicity and low cost, make silicon nanocrystals more practical than other semiconductor nanocrystals in many applications. The downside is that they are much less amenable to solution phase synthesis than CdSe and other semiconductor nanocrystals; thus, developing improved methods of preparing these nanocrystals and modifying their surfaces is an ongoing research challenge.
Our research team has in fact developed a unique, patented three-step approach to preparing dispersions of light-emitting silicon nanoparticles in solvents (sometimes called luminescent silicon nano-ink) that allows us to prepare macroscopic quantities of photoluminescent silicon nanocrystals and modify their surface for subsequent processing and applications. First, we use a laser-driven gas-phase process to produce small but highly agglomerated (stuck together in clumps) nanoparticles. These are formed at high temperature, which allows them to have high crystalline quality. Then, we use a mixture of acids to break up the clumps of nanoparticles and slowly etch them, making them smaller. Because the color of light emitted by the particles depends on their size, we can simply etch them until they have the color emission that we desire. Finally, we react organic molecules with the surface of the nanoparticles, which makes the particles dispersible in organic solvents and stabilizes them against further reaction. Ultimately this allows them to be processed by low-cost technologies like ink jet printing.
If we are able to continue improving silicon nanocrystal preparation methods, they will be extremely useful in significant medical and environmental applications such as biomedical imaging, biomedical assays, solid-state lighting, displays, and photovoltaics.