Investigating Graphene Manufacturing Towards Biosensing

Abstract

Dopamine is a crucial neurotransmitter in the central nervous system, and its dysregulated level is implicated in a spectrum of neurological disorders, including Parkinson's disease. Thus, precise and timely dopamine level assessments are critical for early diagnosis and treatment efficacy monitoring. Various nanomaterials are explored for biosensor receptors in dopamine detection. Graphene has significantly contributed to biosensor receptor development because of its remarkable properties, including superior electrical and thermal conductivity, large specific surface area, ease of functionalisation, chemical stability and biocompatibility. The CVD graphene production study investigates the effect of temperatures ranging from 900 °C to 1050 °C, total chamber pressure and annealing gases on growth quality. The data demonstrates that graphene formed on copper was continuous and of higher quality at higher temperatures, with monolayers to few layers, whereas on nickel, the majority were covered by multilayer graphitic structures. Other fabrication alternatives are explored in parallel, including electrochemical exfoliation, pyrolysis, and reduced graphene oxide. The graphene devices' surface characteristics and chemistry were assessed using Raman spectroscopy, SEM, XPS, and UV-Vis spectroscopy. The study next evaluates the efficacy of monolayer graphene surfaces as GFET sensors using drain-source current measurements, indicating their capacity to detect dopamine concentrations as low as 5nM. Other graphene-based materials are employed in RF filter-based microstrip lines to facilitate dopamine binding. The work employs empirical analysis to evaluate the impact of biomolecule attachment on filter response parameters involving attenuation and phase shift. It gives information about material compatibility for RF biosensing applications. Overall, this thesis work explores graphene's unique properties and the effectiveness of surface modification approaches in increasing sensor sensitivity and specificity and emphasises the potential of RF-based biosensors and GFETs in neurotransmitter detection, paving the path for more effective diagnostics and therapeutic interventions in neurological illnesses.