Sonatan Das

The utility of planar optical waveguides constructed from a novel thiol-ene-epoxy polymer has been demonstrated for refractive index sensing. The propagating modes supported by this planar structure were excited as well as taken out of the waveguide using the prism coupling method, and detected using an indigenously developed photodetector system comprising a commercial charge-coupled device (CCD) array and an Arduino microcontroller. The mode-dependent refractive index sensitivity was established by considering a monochromatic laser light excitation at 632.8 nm wavelength. The highest sensitivity of this waveguide sensor was found to be 21.84/RIU (refractive index units) and the corresponding refractive index resolution was 4.92 × 10 ⁻⁴ RIU. The miniaturized version of this optical waveguide sensor has the potential to be integrated within a photonic system for plasmonic-based point-of-care device development.

The thiol–ene–epoxy polymer-based planar-type photodetector has been fabricated by varying stoichiometric ratios of constituent monomers. This device exhibits light intensity-dependent photo-response that has enormous potential for photonic applications.

The development of a nanoparticle-based optical platform has been presented as a biosensor for detecting target-specific plant virus DNA. The binding dynamics of gold nanoparticles has been studied on the amine-functionalized surface by the attenuated total reflection (ATR)-based evanescent wave absorption method monitoring the localized surface plasmon resonance (LSPR). The developed surface was established as a refractive index sensor by monitoring the LSPR absorption peak of gold nanoparticles. This nanoparticle-immobilized surface was explored to establish as a biosensing platform with target-specific immunoglobulin (IgG) antibody–antigen interaction. The IgG concentration-dependent variation of absorbance was correlated with the refractive index change. After successfully establishing this ATR configuration as an LSPR-based biosensor, the single-stranded DNA of the chilli leaf curl virus was detected using its complementary DNA sequence as a receptor. The limit of detection of this sensor was determined to be 1.0 μg/mL for this target viral DNA. This ATR absorption technique has enormous potential as an LSPR based nano-biosensor for the detection of other begomoviruses.

We demonstrate the reduction mechanism of graphene oxide (GO) using prism-based attenuated total reflection platform. The connection between the change in current and reflectance of GO film during reduction was studied along with device photo-response.