Highly Synergistic Sensor of Graphene Electrode Functionalized with Rutile TiO2 Microstructures to Detect L-Tryptophan Compound.

Electrochemical processes are an effective method for detecting dangerous food ingredients. The synergistic between the reduction-oxidation (redox) processes inspired several papers and spurred research towards studying the new materials that can further adapt to optimize the rapid detection of chemical compounds. In this study, we report the eco-synthesis using graphene/TiO2 rutile (G/TiO2) electrode microstructures easily prepared through the physical method by mixing graphene and TiO2 powder and its application for sensing L-tryptophan (Trp) compound. The material characterization results show that the graphene surface is smoother than the G/TiO2 material. Graphene has been detected using X-ray diffraction (XRD) at a value of 2 thetas 26.39° and TiO2 forms rutile crystals (110). The FTIR spectrum exhibits the functional groups from graphene of -OH, C-H, C=C, C-O, and TiO2 identified with Ti-O bonds. The electrochemical test against G/TiO2 electrode microstructures for Trp compound shows that 0.5 g TiO2 rutile was the best composition functionalized with graphene material under 0.1M K3[Fe(CN)6] + 0.1M NaNO3 electrolyte with a scan rate of 0.1 V/s. Determination of the detection limit was obtained at 0.005 mg/L with a HorRat value of 1.05%. The stability test was carried out for 25 days, and the addition of Pb(NO3)2 as an interference compound had a significant effect on the decrease in electrode performance.

Optimization of OPEFB lignocellulose transformation process through ionic liquid [TEA][HSO4] based pretreatment.

Research on the transformation of Oil Palm Empty Fruit Bunches (OPEFB) through pretreatment process using ionic liquid triethylammonium hydrogen sulphate (IL [TEA][HSO4]) was completed. The stages of the transformation process carried out were the synthesis of IL with the one-spot method, optimization of IL composition and pretreatment temperature, and IL recovery. The success of the IL synthesis stage was analyzed by FTIR, H-NMR and TGA. Based on the results obtained, it showed that IL [TEA][HSO4] was successfully synthesized. This was indicated by the presence of IR absorption at 1/λ = 2814.97 cm-1, 1401.07 cm-1, 1233.30 cm-1 and 847.92 cm-1 which were functional groups for NH, CH3, CN and SO2, respectively. These results were supported by H-NMR data at δ (ppm) = 1.217-1.236 (N-CH2-CH3), 3.005-3.023 (-H), 3.427-3.445 (N-H+) and 3.867 (N+H3). The TGA results showed that the melting point and decomposition temperature of the IL were 49 °C and 274.3 °C, respectively. Based on pretreatment optimization, it showed that the best IL composition for cellulose production was 85 wt%. Meanwhile, temperature optimization showed that the best temperature was 120 °C. In these two optimum conditions, the cellulose content was obtained at 45.84 wt%. Testing of IL [TEA][HSO4] recovery performance for reuse has shown promising results. During the pretreatment process, IL [TEA][HSO4] recovery effectively increased the cellulose content of OPEFB to 29.13 wt% and decreased the lignin content to 32.57%. The success of the recovery process is indicated by the increasing density properties of IL [TEA][HSO4]. This increase occurs when using a temperature of 80-100 °C. The overall conditions obtained from this work suggest that IL [TEA][HSO4] was effective during the transformation process of OPEFB into cellulose. This shows the potential of IL [TEA][HSO4] in the future in the renewable energy sector.