Nano-plasmonic biosensors and an analysis of surface plasmon resonance towards an optimal nano-optofluidic device

Wednesday, March 2, 2016

12:00pm | 125 Hudson Hall

Presenter

Dr. Jianjun Wei , Associate Professor, Department of Nanoscience, Joint School of Nanoscience and Nanoengineering

Nano-plasmonics, an emerging branch field of nanophotonics concerning properties of collective electronic excitations (surface plasmon, SP) in nanostructures of noble metals (e.g. silver and gold), has attracted intense attention due to its versatility for optical sensing and chip-based device integration. This lecture will cover our recent work in this field, including a plasmonic nano-probe for bio-sensing, a semi-analytical approach for analysis of SP generation and experimental testing of a new nanostructured thin metal films towards an optimal nano-optofluidic device. Firstly, localized surface plasmon resonance (LSPR)-coupled fiber-optic (FO) nanoprobe is reported as a biosensor that is capable of label-free, sensitive detection of cancer protein biomarkers. The results present the improvement of a robust plasmonic nano-disk array and its incorporation to fiber tip towards a miniaturized, multifunctional technology that integrates informational communication and sensing function for a high performance point-of-care (POC) Instrument.

Secondly, since understanding the underlying physics and developing applications of nanoplasmonic devices with desirable optical properties, e.g. intensity of light scattering, high refractive index (RI) sensitivity and reproducibility, is crucial for practical uses in physics, biomedical detection, and environmental monitoring, a semi-analytical model that enables decomposition and quantitative analysis of SP under plane-wave illumination is used to a new complex nanoledge aperture structure, enlightening a little on how to design such plasmonic devices for optimal surface plasmon polariton (SPP) generation, thus the optical transmission and RI sensitivity. In concert with the analytical treatment, a finite-difference time-domain (FDTD) simulation and testing of the fabricated devices were performed to validate the optical transmission spectra and RI sensitivity as a function of the nanoledge device’s geometric parameters, and it shows good agreement with the analytical model. Furthermore, we tried to address the challenge of efficient delivery of bio-molecules to the subwavelength nanoledge cavity. An analytical model based on the underlying diffusion and viscoelastic force knowledge is applied to analyze the friction rotation of a number of interesting molecules (disease protein biomarkers regarding the size and weight) into the nanoledge structure. Experimental measurements, including nano-confined dye solution flow-through the nanochannel and near-field fluorescence correlation spectroscopy (FCS) of labeled proteins in the nano-cavity, have been carried out to visualize the transportation of molecules and migration in nanoscale.

Dr. Jianjun Wei is Associate Professor of Nanoscience at the Joint school of Nanoscience and Nanoengineering (JSNN), the University of North Carolina at Greensboro where he is leading a group conducting interdisciplinary research with focus on functional nanomaterials, nanoplasmonics, bioelectronics, and applications in biosensing, nanomedicine, energy conversion and storage. Prior to joining JSNN, he had worked in an industrial research corporation (CFDRC) from 2006 to 2013, and led as a Principal Scientist (PI and co-PI) for a number of BAA, SBIR/STTR Phase I, II, and III US government contracts, primarily through NIH, NASA and DOD research grants. His work has won the US DOD SBIR Phase II Achievement Award, NASA Tech Brief Award. Currently his research is sponsored by a NSF grant and JSNN research funding.

Dr. Wei obtained his Ph.D. in chemistry in 2004 at the University of Pittsburgh, followed with one year postdoctoral fellowship at the same university. He was a lecture and researcher at Shanghai University during 1995-2000, and graduated with degrees of M.E. in 1995 and BS in 1992 in Applied Chemistry from East China University of Science and Technology, Shanghai, China.