...where electrons and photons run naked and free
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Chemically Responsive Photonic Lattices for Chemical Sensing
Goal: To develop diffraction-based sensing schemes that employ chemically responsive gratings for trace-level, gas-phase and aqueous-phase analyte detection.

Studies:

  • Facile fabrication of gratings via non-conventional lithographic techniques – e.g., microtransfer molding (mTM) coupled with electrochemical deposition methods.
  • Design of grating materials that impart superior analyte sensitivity and selectivity.
  • Establishment of robust, low-cost chemical sensing technologies for field portable, remote sensing applications.


(Left) schematic illustration of the patterning of metal oxides via mTM and electrodeposition process. (Right) WO3 gratings prepared by process depicted at left.
Our detection  strategy exploits the use of micropatterned mesoporous sensor material to modulate the complex refractive index of the sensing material. The refractive index, ñ, consists of two parts: real part, n, that alters the phase of the light wave and imaginary part, ik, that effects amplitude of the wave. As a result, refractive index, ñ = n + ik, can be modulated by changes in either real or imaginary part. The intensity of diffraction pattern (referred as diffraction efficiency, DE) changes with change in refractive index contrast between the patterned material and the surrounding medium (i.e., refractive index of analyte). Note that the diffraction efficiency expression relates to the two components of the refractive index:


(Left) Scheme of experimental cell used for refractive index modulation of patterned metal oxides shown at center. (Right) Digital image of actual diffraction pattern obtained from the patterned metal oxide.

(Left) Diagram of waveform for double potential step chronoamperometry used for the refractive index modulation via Li+ insertion/deinsertion  into WO3 pattern. (Center) Plot of the diffraction intensity changes during Li+ insertion/deinsertion into WO3 pattern. (Right) Digital images of the diffraction pattern during Li+ insertion/deinsertion into WO3 pattern.
Significance: Essential to the production of functional and efficient chemical sensors is the miniaturization of sensor materials, interconnects and interfaces along with simplification of the signal transduction and detection schemes. Ideally, this project will provide critical sensing technology advances in the creation of next-generation chemical sensors. Furthermore, we are exploring innovative approaches for developing advanced chemically-responsive and electrochemically-responsive materials and interfaces.
Students currently involved in this project: Lilia Kondrachova