Synthesis of Sb2S3 nanosphere layer by chemical bath deposition for the photocatalytic degradation of methylene blue dye

An antimony tri-sulfide Sb₂S₃ nanosphere photocatalyst was effectively deposited utilizing sodium thiosulfate and antimony chloride as the starting precursors in a chemical bath deposition process. This approach is appropriate for the large-area depositions of Sb₂S₃ at low deposition temperatures without the sulfurization process since it is based on the hydrolytic decomposition of starting compounds in aqueous solution. X-ray diffraction patterns and Raman spectroscopy analysis revealed the formation of amorphous Sb₂S₃ layers. The scanning electron microscopy images revealed that the deposited Sb₂S₃ has integrated small nanospheres into sub-microspheres with a significant surface area, resulting in increased photocatalytic activity. The optical direct bandgap of the Sb₂S₃ layer was estimated to be about 2.53 eV, making amorphous Sb₂S₃ appropriate for the photodegradation of organic pollutants in the presence of solar light. The possibility of using the prepared Sb₂S₃ layer in the photodegradation of methylene blue aqueous solutions was investigated. The degradation of methylene blue dye was performed to evaluate the photocatalytic property of Sb₂S₃ under visible light. The amorphous Sb₂S₃ exhibited photocatalytic activity for the decolorization of methylene blue solution under visible light. The mechanism for the photocatalytic degradation of methylene blue has been proposed. Our results suggest that the amorphous Sb₂S₃ nanospheres are valuable material for addressing environmental remediation issues.

A facile chemical synthesis of nanoflake NiS2 layers and their photocatalytic activity

A single-phase and crystalline NiS₂ nanoflake layer was produced by a facile and novel approach consisting of a two-step growth process. First, a Ni(OH)₂ layer was synthesized by a chemical bath deposition approach using a nickel precursor and ammonia as the starting solution. In a second step, the obtained Ni(OH)₂ layer was transformed into a NiS₂ layer by a sulfurization process at 450 °C for 1 h. The XRD analysis showed a single-phase NiS₂ layer with no additional peaks related to any secondary phases. Raman and X-ray photoelectron spectroscopy further confirmed the formation of a single-phase NiS₂ layer. SEM revealed that the NiS₂ layer consisted of overlapping nanoflakes. The optical bandgap of the NiS₂ layer was evaluated with the Kubelka-Munk function from the diffuse reflectance spectrum (DRS) and was estimated to be around 1.19 eV, making NiS₂ suitable for the photodegradation of organic pollutants under solar light. The NiS₂ nanoflake layer showed photocatalytic activity for the degradation of phenol under solar irradiation at natural pH 6. The NiS₂ nanoflake layer exhibited good solar light photocatalytic activity in the photodegradation of phenol as a model organic pollutant.

COVID-19 related posttraumatic stress disorder in children and adolescents in Saudi Arabia

INTRODUCTION

The COVID-19 pandemic resulted in quarantine/lockdown measures in most countries. Quarantine may create intense psychological problems including post-traumatic stress disorder (PTSD) especially for the vulnerable critically developing children/adolescents. Few studies evaluated PTSD associated with infectious disasters but no Saudi study investigated PTSD associated with COVID-19 in children/adolescents. This study was undertaken to screen for PTSD in children/adolescent in Saudi Arabia to identify its prevalence/risk factors during COVID-19 pandemic and its quarantine.

METHODS

A cross-sectional survey was conducted after 2 months form start of quarantine for COVID-19 pandemic utilizing the original English version and an Arabic translated version for the University of California at Los Angeles Brief COVID-19 Screen for Child/Adolescent PTSD that can be parent-reported or self-completed by older children/adolescents. Participants (Saudi citizens/non-Saudi residents) were approached online via social media.

RESULTS

Five hundred and thirty seven participants were enrolled. The participants were 262 boys and 275 girls with a mean age of 12.25±3.77 years. Symptoms of no, minimal, mild and potential PTSD were identified in 15.5%, 44.1%, 27.4% and 13.0% of children/adolescents, respectively. The age, gender, school grade, and residence were not predictive of PTSD symptoms. Univariate analysis of risk factors for PTSD revealed that work of a close relative around people who might be infected was significantly different between groups of PTSD symptoms, but this difference disappeared during multivariate analysis. Children/adolescents of Saudi citizens had significantly lower median total PTSD score than children/adolescents of expatriate families (p = 0.002).

CONCLUSION

PTSD associated with the COVID-19 and its resultant quarantine shouldn't be overlooked in different populations as it is expected in a considerable proportion of children/adolescents with variable prevalence, risk factors and severity. Parents/healthcare providers must be aware of PTSD associated with COVID-19 or similar disasters, so, they can provide children/adolescent with effective coping mechanisms.

Modifications of the CZTSe/Mo back-contact interface by plasma treatments

Molybdenum (Mo) is the most commonly used back-contact material for copper zinc tin selenide (CZTSe)-based thin-film solar cells. For most fabrication methods, an interfacial molybdenum diselenide (MoSe₂) layer with an uncontrolled thickness is formed, ranging from a few tens of nm up to ≈1 μm. In order to improve the control of the back-contact interface in CZTSe solar cells, the formation of a MoSe₂ layer with a homogeneous and defined thickness is necessary. In this study, we use plasma treatments on the as-grown Mo surface prior to the CZTSe absorber formation, which consists of the deposition of stacked metallic layers and the annealing in selenium (Se) atmosphere. The plasma treatments include the application of a pure argon (Ar) plasma and a mixed argon–nitrogen (Ar–N₂) plasma. We observe a clear impact of the Ar plasma treatment on the MoSe₂ thickness and interfacial morphology. With the Ar–N₂ plasma treatment, a nitrided Mo surface can be obtained. Furthermore, we combine the Ar plasma treatment with the application of titanium nitride (TiN) as back-contact barrier and discuss the obtained results in terms of MoSe₂ formation and solar cell performance, thus showing possible directions of back-contact engineering for CZTSe solar cells.

Molybdenum (Mo) is the most commonly used back-contact material for copper zinc tin selenide (CZTSe)-based thin-film solar cells. The effect of a pure Ar plasma and a mixed Ar–N₂ plasma on the back-contact interface of CZTSe solar cells is reported in this study.

A vapor-phase-assisted growth route for large-scale uniform deposition of MoS2 monolayer films

In this work a vapor-phase-assisted approach for the synthesis of monolayer MoS₂ is demonstrated, based on the sulfurization of thin MoO_3-x precursor films in an H₂S atmosphere. We discuss the co-existence of various possible growth mechanisms, involving solid-gas and vapor-gas reactions. Different sequences were applied in order to control the growth mechanism and to obtain monolayer films. These variations include the sample temperature and a time delay for the injection of H₂S into the reaction chamber. The optimized combination allows for tuning the process route towards the potentially more favorable vapor-gas reactions, leading to an improved material distribution on the substrate surface. Raman and photoluminescence (PL) spectroscopy confirm the formation of ultrathin MoS₂ films on SiO₂/Si substrates with a narrow thickness distribution in the monolayer range on length scales of a few millimeters. Best results are achieved in a temperature range of 950-1000 °C showing improved uniformity in terms of Raman and PL line shapes. The obtained films exhibit a PL yield similar to mechanically exfoliated monolayer flakes, demonstrating the high optical quality of the prepared layers.

Arsenic in drinking water and pregnancy outcomes

We studied a group of women of reproductive age (15-49 years) who were chronically exposed to arsenic through drinking water to identify the pregnancy outcomes in terms of live birth, stillbirth, spontaneous abortion, and preterm birth. We compared pregnancy outcomes of exposed respondents with pregnancy outcomes of women of reproductive age (15-49 years) who were not exposed to arsenic-contaminated water. In a cross-sectional study, we matched the women in both exposed and nonexposed groups for age, socioeconomic status, education, and age at marriage. The total sample size was 192, with 96 women in each group (i.e., exposed and nonexposed). Of the respondents in the exposed group, 98% had been drinking water containing [Greater and equal to] 0.10 mg/L arsenic and 43.8% had been drinking arsenic-contaminated water for 5-10 years. Skin manifestation due to chronic arsenic exposure was present in 22.9% of the respondents. Adverse pregnancy outcomes in terms of spontaneous abortion, stillbirth, and preterm birth rates were significantly higher in the exposed group than those in the nonexposed group (p = 0.008, p = 0.046, and p = 0.018, respectively).