In the present work, the suitability of Aloe vera (AV) as a ‘green reducing agent’ has been investigated for the reduction of graphene oxide (GO). The extent of reduction was studied by varying the amount of AV. The physical and chemical properties of the GO and reduced graphene oxide (rGO) were investigated using UV-Vis spectrophotometry, FT-IR spectroscopy, High Resolution Transmission Electron Microscopy (HRTEM) and Selected Area Electron Diffraction (SAED). Partially reduced graphene oxide sheets obtained with 7.5 g of AV (rGO-7.5) demonstrated a maximum reduction efficiency of about 73% as evident from FT-IR data. Cyclic voltammetry and electrochemical impedance spectroscopy studies revealed a significant enhancement in current density and a decrease in charge transfer resistance for the rGO-7.5 sample. Moreover, the as prepared rGO-7.5 sample showed a remarkable dye removal ability with a maximum efficiency of ∼98%. The enhanced surface area, π–π interaction and strong electrostatic attraction were correlated with the dye removal capability. The adsorption kinetics were also studied and pseudo second order adsorption phenomena were confirmed. The recyclability of the rGO-7.5 sample was further investigated and an excellent desorption capability was established.

Thermoelectric materials have been extensively used in space satellites, automobiles, and, more recently, in solar thermal application as power generators. Solar thermoelectric generators (STEGs) have enjoyed rapidly improving efficiency in recent years in both concentrated and non-concentrated systems. However, there is still a critical need for further research and development of their materials and systems design before this technology can deployed for large-scale power generation.

By exploiting the presence of abundant carboxylic groups (–COOH) on graphene oxide (GO) and using EDC–NHS (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride–N-hydroxysuccinimide) chemistry to covalently conjugate protein molecules, we demonstrate a novel electrochemical immunosensor for detection of antibody–antigen (Rabbit IgG–AntiRabbit IgG) interactions. The interactions were verified using Electrochemical Impedance Spectroscopy (EIS). Although GO is known to be a poor conductor, the charge transfer resistance (R_P) of a GO modified glassy carbon electrode (GCE) was found to be as low as 1.26 Ω cm². This value is similar to that obtained for reduced graphene oxide (RGO) or graphene and an order of magnitude less than bare GCE. The EIS monitored antibody–antigen interactions showed a linear increase in R_P and the overall impedance of the system with increase of antibody concentration. Rabbit IgG antibodies were detected over a wide range of concentrations from 3.3 nM to 683 nM with the limit of detection (LOD) estimated to be 0.67 nM. The sensor showed high selectivity towards Rabbit IgG antibody as compared to non-complementary myoglobin. RGO modified GCE showed no sensing properties due to the removal of carboxylic groups which prevented subsequent chemical functionalization and immobilization of antigen molecules. The sensitivity and selectivity achievable by this simple label free technique hint at the possibility of GO becoming the electrode material of choice for future electrochemical sensing protocols.

Significant enhancement in supercapacitor performance was achieved via the synthesis of nanocrystalline RuO₂ on vertically aligned Few Layered Graphene (FLG) nanoflakes, synthesized on bare n-type heavily doped silicon substrates by microwave plasma chemical vapour deposition. The RuO₂ nanoparticles (diameter <2 nm) were deposited using a combination of low base pressure radio frequency magnetron sputtering and subsequent electrochemical cycling in acidic media. The well-dispersed RuO₂ nanoparticles on FLGs achieve a specific capacitance of the order of 650 F g⁻¹. The specific capacitance of RuO₂–FLGs is significantly higher than pristine sputtered RuO₂ (∼320 F g⁻¹) and FLGs (∼6 F g⁻¹) indicative of the synergistic effect between the FLGs and RuO₂. In addition, the fabricated RuO₂–FLG supercapacitors show excellent cycling capability with approximately 70% retention of initial specific capacitance over 4000 cycles at high charging–discharging rates of 500 mV s⁻¹. The superior electrochemical performance is attributed to the good electronic conductivity of the FLGs as well as high utilization of well-dispersed RuO₂ nanoparticles on FLGs.