Nano Bio Photonics
Electromagnetic
interactions with nanometer-scale architectures have important
applications in healthcare, energy, and the environment. For example, electromagnetic (EM) interactions
resonant with evanescent waves at dielectric interfaces can improve absorption and photocurrent in
silicon and
thin-film solar cells, as well as sensitivity of biological sensing devices. Static, near-field EM
interactions can enhance microscopy, spectroscopy and sensing of
biological entities like protein, deoxyribonucleic acid (DNA), and virus.
The Nano Bio Photonics group under the direction of Prof. D. Keith Roper studies near- and far-field features of EM-coupled surface waves, such as plasmons, and low-frequency modes, like molecular vibrations and optical phonons, on nanoscale structures. The group is particularly interested in photon-plasmon coupling on films, nanoparticles, and both random and periodic assemblies of nanparticles, including metamaterials. Optoplasmonic interactions are examined to distinguish effects of near- and far-field radiative interactions and to design nanoscale architectures with enhanced performance in biosensing, solar energy, optoelectronics, microthermalfluidics, spectroscopy, diagnostics and therapeutics. Advanced techniques are used together with novel adaptations of engineering, physics, and chemistry methods to fabricate architectures that are envisioned by modeling. A variety of complementary analytical techniques are then used to compare experimental data from fabricated structures with predictions from theoretical models. Nanoscale architectures that result from this rational process exhibit photon-plasmon coupling that offers significant improvements to solar photovoltaics, microscopy, spectroscopy and sensing of biological entities.
Modeling, Fabrication, and Characterization
The Nano Bio Photonics group has developed new solutions to Maxwell’s
equations for subwavelength NP ordered structures using both analytical and
finite difference difference time domain (FDTD) approaches to identify
near-field EM interactions responsible for photocurrent and SERS, as
well as radiative far-field photon-plasmon
coupling that dwarfs near-field and induction-zone interactions.
Modeling these EM interactions in 2-D and 3-D structures
has identified nanoscale architectures that optimize specific research
objective in a variety of applications. To fabricate envisioned nano-architectures, the Nano Bio Photonics group uses conventional nano-scale fabrication techniques like electron-beam lithography, vacuum evaporation, and sputtering, and develops new 'bottom-up' approaches like nanosphere lithography, electroless plating, and buffered acid etching to economically create scale-able, stable gold (Au) structures. The structures exhibit extraordinary features such as photocurrent enhancement, sensor sensitivity, and thermal conductivity. Specific advances in areas of solar energy, fuel cells, point-of-care DNA analysis, and optothermal therapies for cancer have yielded improvements in (1) field sensing of chemical/biological agents; (2) optothermal properties in micro-scale opto-electronic and micro-electro-mechanical systems; (3) high-efficiency photovoltaics and fuel cell catalysis; and (4) identification of virus and DNA.
Advanced characterization tools employed by our lab include microscopies (TEM, SEM, AFM, MRI, and cofocal light microscopy), spectroscopies (Raman, SPR, NMR, FTIR, AA, UV, vis, and T-UV), lasers, chromatographies (HPLC, GC) and advanced surface characterization (XPS).
D. Keith Roper is Assistant Director of the Microelectronics-Photonics Graduate Program at University of Arkansas, and the Charles W. Oxford Professor of Emerging Technologies in the Ralph E. Martin Department of Chemical Engineering. Professor Roper holds additional faculty appointments in biomedical engineering and cell and molecular biology. He research studies near- and far-field features of electromagnetically coupled surface waves (e.g. plasmons) and low-frequency modes (e.g. molecular vibrations, optical phonons) on nanoscale structures which are important in biosensing, solar energy, optoelectronics, microthermalfluidics, spectroscopy, diagnostics and therapeutics. He develops novel separation and bioseparation processes and analytical methods for chemical and biologically-derived products. He has developed processes for cell culture, fermentation, biorecovery and analysis of polysaccharide, protein, DNA and adenoviral-vectored antigens at Merck & Co. (West Point, PA), extraction of photodynamic cancer therapeutics at Frontier Scientific, Inc. (Logan, UT), and virus binding methods for Millipore Corp (Billerica, MA). His degrees are in chemical engineering from Brigham Young University (B.S., 1989) and University of Wisconsin (Ph.D., 1994) where he worked with Ed Lightfoot. He is coauthor of 1 textbook. His research has led to 35+ peer reviewed publications and proceedings, 3 U.S. Patents, 5 patent applications, 1 viral and 3 bacterial vaccine products, 7 technical pharmaceutical reports, 5 cGMP process documents, multiple cGMP lab procedures, over a dozen novel process equipment and facility designs and startups, and 100+ presentations. He holds memberships in ACS, AIChE, ASEE, AVS, IEEE, and Tau Beta Pi.