QCM-Based MgFe2O4@CaAlg Nanocomposite as a Fast Response Nanosensor for Real-Time Detection of Methylene Blue Dye.

Methylene blue (MB) dye is a common colorant used in numerous industries, particularly the textile industry. When methylene blue is discharged into water bodies without being properly treated, it may seriously damage aquatic and human life. As a result, a variety of methods have been established to remove dyes from aqueous systems. Thanks to their distinguishing features e.g., rapid responsiveness, cost-effectiveness, potential selectivity, portability, and simplicity, the electrochemical methods provided promising techniques. Considering these aspects, a novel quartz crystal microbalance nanosensors based on green synthesized magnesium ferrite nanoparticles (QCM-Based MgFe2O4 NPs) and magnesium ferrite nanoparticles coated alginate hydrogel nanocomposite (QCM-Based MgFe2O4@CaAlg NCs) were designed for real-time detection of high concentrations of MB dye in the aqueous streams at different temperatures. The characterization results of MgFe2O4 NPs and MgFe2O4@CaAlg NCs showed that the MgFe2O4 NPs have synthesized in good crystallinity, spherical shape, and successfully coated by the alginate hydrogel. The performance of the designed QCM-Based MgFe2O4 NPs and MgFe2O4@CaAlg NCs nanosensors were examined by the QCM technique, where the developed nanosensors showed great potential for dealing with continuous feed, very small volumes, high concentrations of MB, and providing an instantaneous response. In addition, the alginate coating offered more significant attributes to MgFe2O4 NPs and enhanced the sensor work toward MB monitoring. The sensitivity of designed nanosensors was evaluated at different MB concentrations (100 mg/L, 400 mg/L, and 800 mg/L), and temperatures (25 °C, 35 °C, and 45 °C). Where a real-time detection of 400 mg/L MB was achieved using the developed sensing platforms at different temperatures within an effective time of about 5 min. The results revealed that increasing the temperature from 25 °C to 45 °C has improved the detection of MB using the MgFe2O4@CaAlg NCs nanosensor and the MgFe2O4@CaAlg NCs nanosensor exhibited high sensitivity for different MB concentrations with more efficiency than the MgFe2O4 NPs nanosensor.