Thesis Title : "Advanced Nanoscale Sensing: From Plasmonic Nanogaps to Micropore-Based Detection"
Name of the Student   : Mr. Avisekh Pal
Degree Registered : Ph.D. Engineering
Advisor : Prof. Manoj Varma, CeNSE
Date : 14th August 2026 (Friday)
Time : 4:00 PM
Venue: CeNSE Seminar Hall (Hybrid)

Abstract:
Advances in nanoscale sensing have enabled unprecedented sensitivity in the detection of 
chemical and biological species, driven by the development of novel transduction mechanisms 
that operate at molecular length scales. This thesis explores complementary optical and electrical 
approaches to nanoscale sensing, focusing on plasmonic nanogap-based platforms and micropore ionic 
current-based sensing, with the aim of advancing high-sensitivity and real-time analytical capabilities.
The work begins with an overview of nanopore-based measurement techniques, highlighting the 
principles of ionic current blockade, instrumentation requirements, and challenges associated 
with low-current detection and signal-to-noise limitations. This provides a foundation for understanding 
electrical transduction mechanisms and their role in single-entity detection. Besides electrical, 
there are several optical and hybrid measurement methods which are recently being explored to provide highly efficient readouts.

Subsequently, plasmonic nanostructures fabricated via metal de-wetting are investigated 
for surface-enhanced Raman scattering (SERS)-based sensing. These substrates enable both static 
and dynamic detection of analytes, demonstrating strong electromagnetic field enhancement and 
reproducible sensing performance. The capability of transport-assisted detection is further explored, 
establishing a link between molecular motion and optical signal variation.

Building on this, the thesis examines near-field vibrational energy transfer in plasmonic nanogaps, 
introducing mid-infrared (MIR) upconversion as a mechanism for extending the spectral capabilities of
plasmonic sensing. Molecularly defined nanogap systems are utilized to study donor–acceptor interactions, 
with particular emphasis on the role of functional groups and nanoscale orientation in governing energy 
transfer dynamics. A rate equation model is developed to describe the observed processes, providing theoretical 
insight into near-field coupling phenomena.

Finally, the practical applicability of micropore sensing is demonstrated through the real-time detection 
of antimicrobial resistance (AMR). By analyzing changes in bacterial properties under antibiotic exposure, 
including optical characteristics, charge, and translocation behaviour, the study establishes a rapid and 
label-free method for assessing resistance. This highlights the potential of micropore-based systems for 
clinically relevant diagnostics.

Overall, this thesis demonstrates that integrating optical and electrical transduction mechanisms provides 
a comprehensive approach to nanoscale sensing. By combining the chemical specificity of plasmonic platforms 
with the temporal resolution of micropore detection, the work lays the foundation for next-generation multimodal 
sensing technologies for chemical analysis and biomedical applications.