Green synthesized 2D/3D SnO2 semiconductor ultrasensitive sensors for electrochemical sensing of hydrogen peroxide

Electrochemical behaviour of green derived SnO₂ (G-SnO₂) was used to sense H₂O₂ and determine their levels in an alkaline medium (pH = 12). Plectranthusamboinicus (P.A.) extract derived SnO₂ showed a novel hybrid structure of 2D nanostructures distributed over 3D microbars (dimensions of 3D microbars: B ≈ 1 µm × L ≈ 10 µm × T ≈ 1 µm; 2D nanostructures ranging < 100 nm). Unlike, chemical synthesis of SnO₂ where NaOH is used, here the strong alkali is replaced with the P.A. plant extract which acts as the stabilizing and precipitating agent, making the synthesis process greener. This is the first time hybrid morphology with 2D/3D structures of SnO₂ is developed. G-SnO₂ modified glassy carbon electrode (GCE) was used on a three-electrode system to study the electrocatalytic redox activity for sensing of H₂O₂ in concentrations ranging 2.45 to 24.5 μM. A good electron transfer rate of 3.01 s⁻¹ was observed. The active surface area of material deposited over the working electrode was displaying a diffusion coefficient of 0.042 cm²/s. Limit of detection (LOD) was observed as 1.03 μM within the measured range. Sensors exhibited an ultrahigh sensitivity of 231 mA.mM⁻¹.cm⁻², unlike μA level sensitivity by other sensors. It should be noted that electrochemical sensing of SnO₂ alone is tested depicting better properties compared to many other hybrid, composite sensors. This green extraction method to synthesis electrocatalytic sensors is promising for non-enzymatic sensing of H₂O₂.