Present work proposes green synthesis of reduced graphene oxide using lemon peel extract(vitamin-c) and its application as an electrochemical nonenzymatic human serum glucose sensor. Improved modified Hummer's method was preferred for the preparation of graphene oxide. X-ray diffraction (XRD), Ultraviolet-visible absorption spectroscopy (UV-Vis) and X-ray photon spectroscopy (XPS) analysis revealed the successful reduction of Graphene oxide (GO) using lemon peel extract. Field emission scanning electron microscopy (FESEM), Fourier transform infra-red spectroscopy (FTIR) and Raman spectroscopy supports the formation of reduced graphene oxide (rGO) nanosheets. The proposed glucose sensor exhibits high sensitivity of 1402 μA•cm −2 mM −1 (S/N=3) along with correlation coefficient of 0.9887 and low detection limit of 0.011 μM. The sensor has detected glucose with RSD of 1.99% in human blood serum. The measured values are well agreed with the values obtained using professional glucose sensor used in hospitals.

The important electrochemical measurements of reduced graphene oxide-titanium oxide (rGO)/TiO2) electrodes for the application of a glucose sensor are reported in the proposed work. Investigating the sensitivity, stability, and reproducibility of sensor electrodes that were made and used to evaluate the concentration of glucose in the serum is one of the novel aspects of this work. This study presents the use of citrus limetta (sweet lime) fruit peel waste to synthesize a green reduction of graphene oxide (rGO). The rGO/TiO2 composite obtained using the microwave heating method is applied for measuring the structural and morphological properties by various means. A conducting fluorine-tin oxide substrate is used to modify the enzymeless glucose sensor electrode. The electrochemical measurements of rGO/TiO2 sensor electrodes are carried out using the technique of cyclic voltammetry. The rGO/TiO2 sensor electrode exhibits a high sensitivity of 1425 µA/mM cm2 towards glucose concentration in the range of 0.1 to 12 mM. The sensor was found to be extremely stable and repeatable with a response time of 5 s along with a minimum detection limit of 0.32 μM of glucose. The rGO/TiO2 sensor shows relative standard deviation (RSD) of 1.14%, 1.34%, and 1.3% which reveals its excellent stability, repeatability, and reproducibility respectively. The sensor was used for glucose level detection in natural blood serum and shows an RSD of 1.88%. which is in good agreement with the commercial glucose sensor values.

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Nano-SnO 2 -based thick-film resistors were fabricated using screen printing technology. To study the effect of firing temperature, sensors were fired in the range 425-8501C. A mixture of tetragonal and orthorhombic SnO 2 was observed in the range 425-7001C. Above 7001C, the presence of majority tetragonal phase was observed. The sheet resistivity and TCR values were one to two orders of magnitude less than the reported values. Sensors fired at 7501C showed the highest sensitivity and selectivity for H 2 , CO, and LPG at 1401C, 2101C, and 1801C, respectively, with a response and recovery time of 12 and 22 s.

The development of biosensors with innovative nanomaterials is crucial to enhance the sensing performance of as-prepared biosensors. In the present research work, we prepared copper (II) oxide (CuO) and graphene oxide (GO) composite nanofibers using the hydrothermal synthesis route. The structural and morphological properties of as-prepared GO/CuO nanofibers were analyzed using an X-ray diffractometer, field-emission scanning, energy dispersive X-ray analysis, Fourier transmission infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The results indicated GO/CuO nanofibers exhibit nanosized diameters and lengths in the order of micrometers. These GO/CuO nanofibers were employed to prepare non-enzymatic biosensors (GO/CuO nanofibers/FTO (fluorine-doped tin oxide)) modified electrodes for enhanced glucose detection. The sensing performance of the biosensors was evaluated using linear sweep voltammetry (LSV) and chronoamperometry in phosphate buffer solution (PBS). GO/CuO/FTO biosensor achieved high sensitivity of 1274.8 μA mM−1cm−2 having a linear detection range from 0.1 to 10 mM with the lower detection limit (0.13 μM). Further, the prepared biosensor showed good reproducibility repeatability, excellent selectivity, and long-time stability. Moreover, the technique used for the preparation of the GO/CuO composite is simple, rapid, cost-effective, and eco-friendly. These electrodes are employed for the detection of glucose in blood serum with RSD ~ 1.58%.