Nanoimprinted Hybrid Platforms for Sensing, Optical Modulation, and Multifunctional Interfaces

Abstract

This thesis investigates the design, fabrication, and functional evaluation of nanoimprinted platforms for sensing, optical modulation, and multifunctional interfacial applications. Nanoimprinting is employed throughout as a unifying strategy for generating deterministic nanoscale architectures across multiple material systems, enabling systematic investigation of the relationships between surface geometry, materials integration, and measurable performance.

The thesis first establishes the theoretical and methodological framework underpinning nanoimprinted functional surfaces and their Raman, surface-enhanced Raman scattering (SERS), and optical behaviour. It then presents a connected series of nanoimprinted composite and hybrid platforms based on graphene oxide/cellulose acetate, cellulose acetate/titanium dioxide (TiO2), piezoelectric poly(vinylidene fluoride) (PVDF), poly(vinylidene fluoride)/multi-walled carbon nanotube (PVDF/MWCNT) nanocomposites, and humidity-responsive 9-

fluorenylmethoxycarbonyl-L-phenylalanine/polydimethylsiloxane (Fmoc-Phe- OH/PDMS) films. Across these systems, the effects of nanoscale patterning on

structural fidelity, optical response, interfacial behaviour, analyte accessibility, and signal reproducibility are examined using complementary spectroscopic, microscopic, and thermo -mechanical characterization methods.

The graphene oxide/cellulose acetate and cellulose acetate/TiO2 platforms

demonstrate that nanoimprinted biopolymer-based and hybrid semiconductor- containing substrates can improve Raman enhancement, analytical sensitivity, and

reproducibility through the combined effects of surface structuring, plasmonic coupling, and interfacial charge-transfer processes. The piezoelectric PVDF and PVDF/MWCNT platforms extend this approach by integrating mechanically tunable Raman enhancement, nanotube-induced surface roughening, UV-assisted signal amplification, and flexible label-free sensing. The final experimental stage develops humidity-responsive Fmoc-Phe-OH/PDMS nanocomposite films that retain patterned

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submicron features after prolonged water exposure, exhibit hydration-induced swelling, produce a reversible reflectance red shift of approximately 30 nm, show a surface potential increase of more than 500 mV under humid conditions, and support SERS enhancement factors of up to 108 after silver coating.

Overall, this thesis shows that nanoimprinted geometry is not merely a pattern-transfer route, but a powerful design variable for controlling optical response, interfacial function, spectroscopic enhancement, and stimulus-responsive behaviour across multiple material platforms. It therefore establishes a coherent framework for the development of reproducible, multifunctional, and environmentally responsive

nanoimprinted interfaces for sensing, optical modulation, and advanced surface- based applications