One-step chemically vapor deposited hybrid 1T-MoS2/2H-MoS2 heterostructures towards methylene blue photodegradation

The photocatalytic degradation of methylene blue is a straightforward and cost-effective solution for water decontamination. Although many materials have been reported so far for this purpose, the proposed solutions inflicted high fabrication costs and low efficiencies. Here, we report on the synthesis of tetragonal (1T) and hexagonal (2H) mixed molybdenum disulfide (MoS2) heterostructures for an improved photocatalytic degradation efficiency by means of a single-step chemical vapor deposition (CVD) technique. We demonstrate that the 1T-MoS2/2H-MoS2 heterostructures exhibited a narrow bandgap ∼ 1.7 eV, and a very low reflectance (<5%) under visible-light, owing to their particular vertical micro-flower-like structure. We exfoliated the CVD-synthesised 1T-MoS2/2H-MoS2 films to assess their photodegradation properties towards the standard methylene blue dye. Our results showed that the photo-degradation rate-constant of the 1T-MoS2/2H-MoS2 heterostructures is much greater under UV excitation (i.e., 12.5 × 10-3 min-1) than under visible light illumination (i.e., 9.2 × 10-3 min-1). Our findings suggested that the intermixing of the conductive 1T-MoS2 with the semi-conducting 2H-MoS2 phases favors the photogeneration of electron-hole pairs. More importantly, it promotes a higher efficient charge transfer, which accelerates the methylene blue photodegradation process.

The Role of Otorhinolaryngological Manifestations of Mild Covid-19 Disease in Hilly Terrain: Lessons Learnt at a Secondary Care Hospital

We conducted the study to find the prevalence of ENT symptoms amongst mild Covid-19 patients from the hilly region of North India and attempted to propose a solution to curb the spread of Covid-19 through early identification, isolation, and treatment. A retrospective, cross-sectional study at a secondary healthcare center in a hilly region of North India covered 423 mildly symptomatic Covid-19 patients from April 2020 to March 2022. These patients were telephonically contacted or called in person at the outpatient department to answer a preset questionnaire with various parameters such as age, gender, ENT symptoms, and time to recover. The data obtained were statistically analyzed. 207 out of 423 mild Covid-19 patients complained of different ENT symptoms. Cough was the most common ENT symptom and was reported by 162 patients. Dizziness was the least common ENT symptom and was reported by 9 patients. Recovery time for tinnitus was maximum (persistent till six months in 5 patients). A high index of suspicion for Covid-19 disease in patients with ENT symptoms must be practiced. As the Covid-19 restrictions are gradually relaxed, widespread community education for strict adherence to Covid-19 appropriate behaviour and sensitization of General Practitioners a well as Otorhinolaryngologists regarding the importance of ENT symptoms in mild Covid19 disease will play a pivotal role in the early identification, isolation, and treatment of mild Covid-19 disease, which eventually may curb the future waves.

Large area growth of vertically aligned luminescent MoS2 nanosheets

Vertically aligned MoS₂ nanosheets (NSs) with exposed edges were successfully synthesized over a large area (∼2 cm²). The NSs were grown using an ambient pressure chemical vapor deposition technique via rapid sulfurization of sputter deposited thick molybdenum films. Extensive characterization of the grown MoS₂ NSs has been carried out using high resolution scanning and transmission electron microscopy (SEM & TEM). A special care was given to the TEM lamella preparation process by means of a focused ion beam to preserve the NS growth direction. The cross-section TEM measurements revealed the growth of densely packed, vertically aligned and straight MoS₂ NSs. Additional characterization techniques such as atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and photoluminescence (PL) were used to evaluate the MoS₂ NSs. These studies revealed the high crystallinity and quality of the synthesized NSs. The MoS₂ NSs show visible light emission similar to mechanically exfoliated monolayer MoS₂ NSs. The striking PL signal comes from the exposed edges as shown by experimental and theoretical calculations. The vertical MoS₂ NSs also exhibit a hydrophobic character with a contact angle of 114°. The as-grown MoS₂ NSs would be highly useful in the development of catalysis, nano-optoelectronics, gas-sensing and bio-sensing device applications.