Plasmon-Enhanced Nanoscale Metamaterial Sensors

Plasmon-enhanced Nanoscale Metamaterial Sensors

 

Presenting Author: D. Keith Roper. University of Arkansas, dkroper@uark.edu

Nano Bio Photonics Lab, Chemical Engineering, http://comp.uark.edu/~dkroper/

Microelectronics/Photonics Graduate Program, http://microep.uark.edu/

Coauthors: Phillip Blake; Gyoung Jang; Braden Harbin

Nanoscale metamaterials exhibit coupling between plasmon-active elements that creates strong, local electromagnetic fields.  These fields enhance sensitivity more than 10-fold relative to localized surface plasmon (nanoparticle) or plasmon polariton (BIACore) sensors.   Plasmons are oscillating free electrons confined to metal surfaces excited by incident electromagnetism at specific wavelengths (l).  But sensitivity gains from plasmon field enhancements are in limited regions of the electromagnetic spectrum and only occur in close proximity to plasmon-active nanostructures.  These limitations arise from the wavelength-specificity and nanometer-scale localization of plasmon resonances, respectively.  Metamaterials, whose tunable electromagnetic functionality derives from three-dimensional (3D) structuring of suitable condensed-matter composites, can provide delocalization of plasmon effects as well as tunability across the electromagnetic spectrum to permit far-field, broad-spectrum, plasmon enhancement.  However, progress in developing plasmon-active nano-scale metamaterials for sensing is limited by (1) lack of comprehensive, multi-scale models to evaluate plasmon-exciton coupling and design ordered plasmon-active, 3D metamaterial nanostructures; (2) limited availability of inexpensive, bottom-up methods to fabricate plasmon-active metamaterials for sensing applications; and (3) scant analytic and experimental evaluation of plasmon-active nanoscale metamaterials sensing. We present the first sensor data from nanoscale metamaterials fabricated using inexpensive, scale-able methods guided by solutions of Navier Stokes[1] and Maxwell-Stefan equations.  We characterize sensor properties using TEM, SEM, T-UV, and Raman spectroscopy.  Data corresponds to theoretical sensor results based on analytic and finite difference time domain (FDTD) solutions to Maxwell's[2] equations.  A new, refined metric is introduced to compare sensitivity of nanoscale metamaterials with nanoparticle and BIAcore sensors on an equivalent basis.

 

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[1] Jang, G.-G. and D.K. Roper.  Continuous flow electroless plating enhances optical features of Au films and nanoparticles. J. Phys. Chem C.  (2009) 113:19228-19236.

[2] Roper, D.K.,  Ahn, W., Taylor, B., D'Asen, Y.  Enhanced spectral sensing by electromagnetic coupling with localized surface plasmons on subwavelength structures.  IEEE Sensors (2010) 10(3) 531-540.