Fabrication of Graphene and Molybdenum disulfide based devices for analytical sensors and energy applications

Determination of biomolecules is of utmost significance in the fields of food-water safety, disease diagnosis and management whereas rapid depletion of fossil fuels and ever-increasing environmental pollution problems necessitate the use of sustainable and clean energy storage-conversion devices like supercapacitors, direct methanol fuel cells (DMFCs). Conventional electrodes used for sensors and energy applications often suffer from low analytical performances because of low electronic conductivity and low specific surface area of the electrode materials. Therefore, there is an urgent need for finding optimal and sustainable solutions to the abovementioned problems through an advanced yet simple technology. In this regard, atomically thin 2D layered materials like graphene (Gr) and molybdenum disulfide (MoS2) are being envisioned as the next generation nanomaterials for highly diversified nano-electronics, sensing and energy applications because of their exceptional electrical, chemical and optical properties which include large surface to volume ration, high electron mobility, highly exposed active sites, large specific surface area, layer dependent band gap, higher ionic conductivity etc. This thesis details simple fabrication methods of Gr and MoS2 composites based electrochemical devices for sensing and energy applications. In specific, GrPolyaniline (PANi) composite based sensor and MoS2 based flexible sensor were fabricated for detection of urea and uric acid, emphasizing the superior sensing performances including enhanced sensitivity, specificity, reproducibility, limit of detection, and their applicability in real samples. Underlying sensing mechanisms have been systematically discussed in order to get better insight into how Gr-PANi and MoS2 contribute to the performance of each sensor. The next part of thesis focuses on the binder-free fabrications of Platinum nanoparticles decorated Gr-PANi composite and Platinum-Palladium/MoS2 based devices for supercapacitor and methanol oxidation reaction respectively. Moreover, reduced Graphene Oxide (rGO) - tin Oxide (SnO2) composite was used in determination of ascorbic acid with high sensitivity and selectivity. This rGO- SnO2 was also used as an efficient supporting material for Pt in methanol oxidation reaction. Detection of priority pollutant, viii phenol using rGO-Zinc Oxide composite based electrode was also demonstrated which successfully eradicates the effect of surface fouling through selecting the appropriate sensing peak. Future directions to this research such as fabrication of other novel 2D nanomaterials based chemi-resistive sensors for plant hormones, biomarkers detection and their bluetooth enabled smart phone integration for wireless monitoring applications etc. have also been discussed at the end of the thesis