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The high concentration of antibiotics in aquatic environments is a serious environmental issue. In response, researchers have explored photocatalytic degradation as a potential solution. Through chemical vapor deposition (CVD), we synthesized copper selenide (β-Cu 2-x Se) and found it an effective catalyst for degrading tetracycline hydrochloride (TC-HCl). The catalyst demonstrated an impressive degradation efficiency of approximately 98% and a reaction rate constant of 3.14 × 10 -2 min -1 . Its layered structure, which exposes reactive sites, contributes to excellent stability, interfacial charge transfer efficiency, and visible light absorption capacity. Our investigations confirmed that the principal active species produced by the catalyst comprises O 2- radicals, which we verified through trapping experiments and electron paramagnetic resonance (EPR). We also verified the TC-HCl degradation mechanism using high-performance liquid chromatography-mass spectrometry (LC-MS). Our results provide valuable insights into developing the β-Cu 2-x Se catalyst using CVD and its potential applications in environmental remediation.

Transition-metal dichalcogenides (TMDCs) are unique layered materials with exotic properties. So, examining their structures holds tremendous importance. 2H-MoSe 2 (analogous to MoS 2 ; Gr. 6 TMDC) is a crucial optoelectronic material studied extensively using Raman spectroscopy. In this regard, low-frequency Raman (LFR) spectroscopy can probe this material's structure as it reveals distinct vibration modes. Here, we focus on understanding the microstructural evolution of different 2H-MoSe 2 morphologies and their layers using LFR scattering. We grew phase-pure 2H-MoSe 2 (with variable microstructures) directly on a Mo foil using a two-furnace ambient-pressure chemical vapor deposition (CVD) system by carefully controlling the process parameters. We analyzed the layers of exfoliated flakes after ultrasonication and drop-cast 2H-MoSe 2 of different layer thicknesses by choosing different concentrations of 2H-MoSe 2 solutions. Further detailed analyses of the respective LFR regions confirm the presence of newly identified Raman signals for the 2H-MoSe 2 nanosheets drop-cast on Raman-grade CaF 2 . Our results show that CaF 2 is an appropriate Raman-enhancing substrate compared to Si/SiO 2 as it presents new LFR modes of 2H-MoSe 2 . Therefore, CaF 2 substrates are a promising medium to characterize in detail other TMDCs using LFR spectroscopy., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Recently, graphene and its derivatives have been extensively investigated for their interesting properties in many biomedical fields, including tissue engineering and regenerative medicine. Nonetheless, graphene oxide (GO) and reduced GO (rGO) are still under investigation for improving their dispersibility in aqueous solutions and their safety in different cell types. This work explores the interaction of GO and rGO with different polymeric dispersants, such as glycol chitosan (GC), propylene glycol alginate (PGA), and polydopamine (PDA), and their effects on human chondrocytes. GO was synthesized using Hummer's method, followed by a sonication-assisted liquid-phase exfoliation (LPE) process, drying, and thermal reduction to obtain rGO. The flakes of GO and rGO exhibited an average lateral size of 8.8 ± 4.6 and 18.3 ± 8.5 µm, respectively. Their dispersibility and colloidal stability were investigated in the presence of the polymeric surfactants, resulting in an improvement in the suspension stability in terms of average size and polydispersity index over 1 h, in particular for PDA. Furthermore, cytotoxic effects induced by coated and uncoated GO and rGO on human chondrocytes at different concentrations (12.5, 25, 50 and 100 µg/mL) were assessed through LDH assay. Results showed a concentration-dependent response, and the presence of PGA contributed to statistically decreasing the difference in the LDH activity with respect to the control. These results open the way to a potentially safer use of these nanomaterials in the fields of cartilage tissue engineering and regenerative medicine.

Among the most reliable techniques for exfoliation of two-dimensional (2D) layered materials, sonication-assisted liquid-phase exfoliation (LPE) is considered as a cost-effective and straightforward method for preparing graphene and its 2D inorganic counterparts at reasonable sizes and acceptable levels of defects. Although there were rapid advances in this field, the effect and outcome of the sonication frequency are poorly understood and often ignored, resulting in a low exfoliation efficiency. Here, we demonstrate that simple mild bath sonication at a higher frequency and low power positively contributes to the thickness, size, and quality of the final exfoliated products. We show that monolayer graphene flakes can be directly exfoliated from graphite using ethanol as a solvent by increasing the frequency of the bath sonication from 37 to 80 kHz. The statistical analysis shows that ∼77% of the measured graphene flakes have a thickness below three layers with an average lateral size of 13 μm. We demonstrate that this approach works for digenite (Cu 9 S 5 ) and silver sulfide (Ag 2 S), thus indicating that this exfoliation technique can be applied to other inorganic 2D materials to obtain high-quality few-layered flakes. This simple and effective method facilitates the formation of monolayer/few layers of graphene and transition metal chalcogenides for a wide range of applications.

We report a facile and robust room-temperature NO 2 sensor fabricated using bi- and multi-layered 2H variant of tungsten di-selenide (2H-WSe 2 ) nanosheets, exhibiting high sensing characteristics. A simple liquid-assisted exfoliation of 2H-WSe 2 , prepared using ambient pressure chemical vapor deposition, allows smooth integration of these nanosheets on transducers. Three sensor batches are fabricated by modulating the total number of layers (L) obtained from the total number of droplets from a homogeneous 2H-WSe 2 dispersion, such as ∼2L, ∼5-6L, and ∼13-17L, respectively. The gas-sensing attributes of 2H-WSe 2 nanosheets are investigated thoroughly. Room temperature (RT) experiments show that these devices are specifically tailored for NO 2 detection. 2L WSe 2 nanosheets deliver the best rapid response compared to ∼5-6L or ∼13-17L. The response of 2L WSe 2 at RT is 250, 328, and 361% to 2, 4, and 6 ppm NO 2 , respectively. The sensor showed nearly the same response toward low NO 2 concentration even after 9 months of testing, confirming its remarkable long-term stability. A selectivity study, performed at three working temperatures (RT, 100, and 150 °C), shows high selectivity at 150 and 100 °C. Full selectivity toward NO 2 at RT confirms that 2H-WSe 2 nanosheet-based sensors are ideal candidates for NO 2 gas detection.

We report a facile two-furnace APCVD synthesis of 2H-WSe 2 . A systematic study of the process parameters is performed to show the formation of the phase-pure material. Extensive characterization of the bulk and exfoliated material confirm that 2H-WSe 2 is layered (i.e., 2D). X-ray diffraction (XRD) confirms the phase, while high-resolution scanning electron microscopy (HRSEM), high-resolution transmission electron microscopy (HRTEM), and atomic force microscopy (AFM) clarify the morphology of the material. Focused ion beam scanning electron microscopy (FIB-SEM) estimates the depth of the 2H-WSe 2 formed on W foil to be around 5-8 μm, and Raman/UV-vis measurements prove the quality of the exfoliated 2H-WSe 2 . Studies on the redox processes of lithium-ion batteries (LiBs) show an increase in capacity up to 500 cycles. On prolonged cycling, the discharge capacity up to the 50th cycle at 250 mA/g of the material shows a stable value of 550 mAh/g. These observations indicate that exfoliated 2H-WSe 2 has promising applications as an LiB electrode material., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)