Intermixing of MoS2 and WS2 photocatalysts toward methylene blue photodegradation.

Visible-light-driven photocatalysis using layered materials has garnered increasing attention regarding the degradation of organic dyes. Herein, transition-metal dichalcogenides MoS2 and WS2 prepared by chemical vapor deposition as well as their intermixing are evaluated for photodegradation (PD) of methylene blue under solar simulator irradiation. Our findings revealed that WS2 exhibited the highest PD efficiency of 67.6% and achieved an impressive PD rate constant of 6.1 × 10-3 min-1. Conversely, MoS2 displayed a somewhat lower PD performance of 43.5% but demonstrated remarkable stability. The intriguing result of this study relies on the synergetic effect observed when both MoS2 and WS2 are combined in a ratio of 20% of MoS2 and 80% of WS2. This precise blend resulted in an optimized PD efficiency and exceptional stability reaching 97% upon several cycles. This finding underscores the advantageous outcomes of intermixing WS2 and MoS2, shedding light on the development of an efficient and enduring photocatalyst for visible-light-driven photodegradation of methylene blue.

Photodetection Properties of MoS2, WS2 and MoxW1-xS2 Heterostructure: A Comparative Study.

Layered transition metals dichalcogenides such as MoS2 and WS2 have shown a tunable bandgap, making them highly desirable for optoelectronic applications. Here, we report on one-step chemical vapor deposited MoS2, WS2 and MoxW1-xS2 heterostructures incorporated into photoconductive devices to be examined and compared in view of their use as potential photodetectors. Vertically aligned MoS2 nanosheets and horizontally stacked WS2 layers, and their heterostructure form MoxW1-xS2, exhibit direct and indirect bandgap, respectively. To analyze these structures, various characterization methods were used to elucidate their properties including Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectrometry and high-resolution transmission electron microscopy. While all the investigated samples show a photoresponse in a broad wavelength range between 400 nm and 700 nm, the vertical MoS2 nanosheets sample exhibits the highest performances at a low bias voltage of 5 V. Our findings demonstrate a responsivity and a specific detectivity of 47.4 mA W-1 and 1.4 × 1011 Jones, respectively, achieved by MoxW1-xS2. This study offers insights into the use of a facile elaboration technique for tuning the performance of MoxW1-xS2 heterostructure-based photodetectors.

Reusable Sensor for Strontium Sulfate Scale Monitoring in Seawater.

The onset of scaling in oil pipelines can halt or drastically reduce oil production, causing huge financial losses and delays. Current methods used to monitor scaling can take weeks, while the scaling process only takes few hours. The proposed sensor is designed for online monitoring of strontium ions concentration in seawater as an early scaling indicator. The sensor operates in the GHz range by probing the shift in the resonance frequency due to changes in the ionic concentrations of the medium. The results show selective sensitivity to changes in the strontium ions concentration even in the presence of many other ions found in seawater. The measured sensitivity is found to be stable and linear with a detection level of better than 0.08% (0.042 mol/L) of strontium ions in seawater. This work demonstrates a robust GHz sensor for strontium sulfate scale monitoring and early detection, which could be used in the oil industry to prevent huge production losses. These results could also be extended further to target the monitoring of other ions in different industrial sectors.