A Study on the Graphitic Carbon and Metal/Metal Oxide Hybrid Structures for the Glucose Sensing Materials

Abstract

Diabetes mellitus is one of the most serious issues worldwide, causes serious damage to the eyes, kidneys, nerves, and heart. To reduce the health risk, early diagnosis and effective self-monitoring are crucial to controlling the glucose levels in the blood. Therefore, the development of suitable materials for the precise and reliable determination of glucose concentration is very important in many areas, including the food industry, biotechnology, and clinical diagnostics. Considerable efforts on glucose sensing have been made, consisting mainly of electrochemical, fluorescence and colorimetric methods. In Part II related to enhance graphitic carbon sensing material by decorating transition metal/metal oxide based on non-enzymatic electrochemical glucose sensor, i.e. hybridizing silver – Ag, nickel oxide–NiO with reduced graphene oxide (rGO), decorating nickel manganese oxide-NiMn2O4 on rGO, and incorporating nickel oxide-NiO with graphitic carbon nitride (g-C3N4). The multi-dimensional Ag/NiO/rGO hybrid nanostructure exhibited good glucose sensing properties with sensitivity as high as 1869.4 A mM1 cm2. The synergistic effect of each component improved its electrocatalytic activity by enhancing electron transfer and increasing the specific surface area. Meanwhile, the presence of rGO in the composite inhibited the agglomeration of Ag and NiO nanoparticles regardless of the Ag and NiO content. rGO also played an important role as well as a charge transfer. In the other hand, the 3-dimensional rGO hydrogel (rGOH) network with NiMn2O4 was fabricated using a facile solvothermal synthesis, where the porous rGOH and NiMn2O4 provided a large surface are and excellent ion transportation. Moreover, rGOH provided numerous dispersion sites of NiMn2O4 and conductive pathways for electrons that are generated during the electrochemical reaction on an NiMn2O4 catalyst, which results in excellent glucose sensitivity. Recently, the g-C3N4 has become a potential candidate and replaced rGO based on its charge transfer ability in a range of applications, due to its unique electronic and optical properties, thermal/chemical stability, that improves the charge transfer in the electrochemical reaction. The NiO/g-C3N4 hybrid (NC) exhibited extremely high glucose sensitivity, up to 5387.1 A mM1 cm2, which is one of the highest values ever reported. These also show excellent selectivity, good-long term stability, and rapid response towards glucose. In Part III studied of g-C3N4 quantum dot (g-CNQDs) and boronic acid for a highly selective and sensitive fluorescence glucose sensor, where g-CNQDs as a fluorescent and boronic acid as a quencher and receptor during glucose sensing. The g-CNQDs/phenylboronic acid (PBA) was prepared by a simple hydrothermal process, exhibited the high quantum yields, high glucose sensitivity and selectivity, low toxicity and good biocompatibility in the cell imaging test. The fluorescence quenching mechanism of this sensor can be attributed to some molecular interactions such as  stacking interaction between triazine rings of CNQDs and benzene rings of PBA, and hydrogen bonding between functional groups. Then, the fluorescence intensity (PL) was recovered in the presence of glucose due to PBA was released from g-CNQDs. On the other hand, the development of multi-chemical sensor was further investigated by introducing the covalent bonds between g-CNQDs and boronic acid groups. The functionalized of 3-amino phenylboronic acid (3APBA) on g-CNQDs caused strong enhancement of the fluorescence intensity, which acted as a fluorescent. When adding the glucose, the PL quenching of g-CNQDs/3APBA can be due to the formation of glucoboronate ester, meanwhile, the PL intensity of glucose added g-CNQDs/3APBA increased with increasing 1,2-propanediol concentration, which can be owing to the hydrolysis of glucoboronate ester in the presence of 1,2-propanediol at the boronic acid sites of g-CNQDs/3APBA. The g-CNQDs/3APBA exhibited high sensitivity and excellent selectivity with low detection limit towards glucose. This also can be applied to an effective multi-chemical sensor