Search Results (5)

Black phosphorene quantum dots (BPQDs) were prepared by ultrasonic-assisted liquid-phase exfoliation and centrifugation with morphologies proved by TEM results. Furthermore, an electrochemical enzyme sensor was prepared by co-modification of BPQDs with horseradish peroxidase (HRP) on the surface of a carbon ionic liquid electrode (CILE) for the first time. The direct electrochemical behavior of HRP was studied with a pair of well-shaped voltammetric peaks that appeared, indicating that the existence of BPQDs was beneficial to accelerate the electron transfer rate between HRP and the electrode surface. This was due to the excellent properties of BPQDs, such as small particle size, high interfacial reaction activity, fast conductivity, and good biocompatibility. The presence of BPQDs on the electrode surface provided a fast channel for direct electron transfer of HRP. Therefore, the constructed electrochemical HRP biosensor was firstly used to investigate the electrocatalytic behavior of trichloroacetic acid (TCA) and potassium bromate (KBrO₃), and the wide linear detection ranges of TCA and KBrO₃ were 4.0–600.0 mmol/L and 2.0–57.0 mmol/L, respectively. The modified electrode was applied to the actual samples detection with satisfactory results. Full article

The embedded immobilized enzymes (Rhizopus-oryzae) on the magnetic nanoparticles (Fe₃O₄-NPs) is a new application for the sustainable production of high-quality biodiesel. In this study, biodiesel is derived from Kapok oil via ultrasonication (US)-assisted catalytic transesterification method. A novel attempt is made to prepare magnetic nanoparticles embedded by an immobilized enzyme to solve the problem of enzyme denaturation. This innovative method resulted in optimum biodiesel conversion of 89 ± 1.17% under reactant molar ratio (methanol: oil) of 6:1, catalyst loading 10 wt% with a reaction time of 4 h at 60 °C. The kinetic and thermal study reveals that conversion of Kapok oil to biodiesel follows a pseudo first-order reaction kinetic with a lower ΔE of 30.79 kJ mol⁻¹. The ΔH was found to be 28.06 kJ mol⁻¹ with a corresponding ΔS of −237.12 J mol⁻¹ K⁻¹ for Fatty Acid Methyl Ester formation. The ΔG was calculated to be from 102.28 to 109.40 kJ mol⁻¹ for temperature from 313 K to 343 K. The positive value of ΔH and ΔG is an indication of endothermic and non-spontaneous reaction. A negative ΔS indicates the reactant in the transition state possesses a higher degree of ordered geometry than in its ground state. The immobilized catalysts provided great advantages towards product separation and efficient biodiesel production. Highlights: 1. Effective catalytic transesterification assisted by the ultrasonication method was used for bi-odiesel production. 2. Magnetite nanoparticles synthesized by the co-precipitation method were used as heteroge-neous catalysts. 3. An immobilized enzyme (Rhizopus-oryzae) was embedded in the heterogeneous catalyst, as it is reusable and cost-effective. 4. The maximum biodiesel yield obtained from Kapok oil was 93 ± 1.04% by catalytic trans-esterification reactions. Full article

Flavonoid-rich leaves of the Ficus carica L. plant are usually discarded as waste. In this work, ultrasonic enzyme-assisted aqueous two-phase extraction (UEAATPE) was proposed as an innovative method to estimate the total flavonoids present in F. carica L. leaves. Total flavonoids were analyzed qualitatively and quantitatively by UPLC-QTOF-MS. At 38% (w/w) ethanol/18% (w/w) ammonium sulfate, we achieved the optimum conditions in which to establish an easy-to-form aqueous two-phase extraction (ATPE) as the final system. The optimal UEAATPE conditions were set at an enzymatic concentration of 0.4 U/g, 150 min enzymolysis time, an enzymolysis temperature of 50 °C, a liquid–solid ratio of 20:1 (mL/g), and 30 min ultrasonic time. The yields of the total flavonoids, i.e., 60.22 mg/g, obtained by UEAATPE were found to be 1.13-fold, 1.21-fold, 1.27-fold, and 2.43-fold higher than those obtained by enzyme-assisted ATPE (EAATPE), ultrasonic-assisted ATPE (UAATPE), ATPE, and soxhlet extraction (SE) methods, respectively. Furthermore, eleven flavonoids from the leaves of the F. carica L. plant were completely identified and fully characterized. Among them, ten flavonoids have been identified for the first time from the leaves of the F. carica L. plant. These flavonoids are quercetin 3-O-hexobioside-7-O-hexoside, 2-carboxyl-1,4-naphthohydroquinone-4-O-hexoside, luteolin 6-C-hexoside, 8-C-pentoside, kaempferol 6-C-hexoside-8-C-hexoside, quercetin 6-C-hexobioside, kaempferol 6-C-hexoside-8-C-hexoside, apigenin 2″-O-pentoside, apigenin 6-C-hexoside, quercetin 3-O-hexoside, and kaempferol 3-O-hexobioside. Therefore, F. carica L. leaves contain new kinds of unidentified natural flavonoids and are a rich source of biological activity. Therefore, this research has potential applications and great value in waste handling and utilization. Full article

A novel nano-silicon oxides (SiOx)/chitosan complex film was prepared using ultrasonic assistant in the process of dissolving chitosan and silicon oxides (SiOx), and characterized by transmission electron microscopy. Its effect on quality preservation of tomatoes (Solanum lycopersicum L. cv. Zheza 205) was investigated under ambient temperature. The results revealed that the nano-SiOx/chitosan complex (NSCC) film retarded weight loss and softness, delayed the titratable acids and total soluble solids loss, and thus markedly extended shelf life of green tomatoes. The antimicrobial activity of tomatoes coated with NSCC film was also recorded higher compared to chitosan (Ch) films and control. In addition, the NSCC film-coated tomatoes prevent the increase of malondialdehyde content and total polyphenol content. Moreover, the peroxidase activity, phenylalanine ammonia-lyase activity, and polyphenoloxidase activity of tomatoes coated with NSCC film were found lower than that in other treatments. These data indicated that the beneficial effects of nano-SiOx/chitosan complex coating on postharvest quality were possibly associated with the lower rate of O₂/CO₂ transmission coefficient, limiting food-borne pathogenic bacterial growth, higher antioxidant activities, and also higher reactive oxygen species (ROS) scavenging and anti-browning activities of related enzymes in the tomatoes. Further, the results of the study could be used to successfully develop a novel nano-SiOx/chitosan complex film for improving the postharvested quality of tomatoes and thus effectively utilized by the food packaging industry. Full article

Graphene oxide/Fe₃O₄ (GO/Fe₃O₄) nanoparticles were synthesized by an ultrasonic-assisted reverse co-precipitation method, and then horseradish peroxidase (HRP) was covalently immobilized onto GO/Fe₃O₄ with 1-ethyl-3-(3-dimethyaminopropyl)carbodiimide (EDC) as a cross-linking agent. In order to enhance the phenol removal efficiency and prevent the inactivation of the enzyme, the polyethylene glycol with highly hydrophilicity was added in this reaction, because the adsorption capacity for the polymer by degradation was stronger than the HRP. The results showed that the immobilized enzyme removed over 95% of phenol from aqueous solution. The catalytic condition was extensively optimized among the range of pH, mass ratio of PEG/phenol as well as initial concentration of immobilized enzyme and H₂O₂. The HRP immobilized on GO/Fe₃O₄ composite could be easily separated under a magnetic field from the reaction solution and reused. Full article