Highly sensitive smartphone-integrated colorimetric glucose sensor based on MnFe2O4 – graphitic carbon nitride hybrid nanostructure

Abstract An extremely sensitive colorimetric glucose sensor was fabricated using a novel hybrid nanostructure comprised of manganese ferrite oxide– graphitic carbon nitride (MnFe2O4/g-C3N4). A neural network-based glucose analytical smartphone application can be used to easily monitor the glucose concentration with a high accuracy by only taking images with the smartphone camera. The as-synthesized MnFe2O4/g-C3N4 exhibited a very high affinity toward 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2, as calculated via Michaelis-Menten kinetics. The glucose sensors using as-synthesized MnFe2O4/g-C3N4 exhibit a wide linear range and very low detection limits of 20.5 nM for H2O2 and 17.3 nM for glucose, which are one of the lowest values ever reported. The instrumental analysis with XPS, XRD, and TEM revealed that MnFe2O4/g-C3N4 had a highly crystalline structure of MnFe2O4 and g-C3N4 with abundant oxygen vacancies and well-developed hybrid structures, which might result in excellent catalytic activity and glucose sensitivity.