Rational Design of Phase-Engineered WS2/WSe2 Heterostructures by Low-Temperature Plasma-Assisted Sulfurization and Selenization toward Enhanced HER Performance.

Efficient hydrogen generation from water splitting underpins chemistry to realize hydrogen economy. The electrocatalytic activity can be effectively modified by two-dimensional (2D) heterostructures, which offer great flexibility. Furthermore, they are useful in enhancing the exposure of the active sites for the hydrogen evolution reaction. Although the 1T-metallic phase of the transition metal dichalcogenides (TMDs) is important for the hydrogen evolution reaction (HER) catalyst, its practical application has not yet been much utilized because of the lack of stability of the 1T phase. Here, we introduce a novel approach to create a 1T-WS2/1T-WSe2 heterostructure using a low-temperature plasma-assisted chemical vapor reaction (PACVR), namely plasma-assisted sulfurization and plasma-assisted selenization processes. This heterostructure exhibits superior electrocatalytic performance due to the presence of the metallic 1T phase and the beneficial synergistic effect at the interface, which is attributed to the transfer of electrons from the underlying WS2 layer to the overlying WSe2 layer. The WS2/WSe2 heterostructure catalyst demonstrates remarkable performance in the HER as evidenced by its small Tafel slope of 57 mV dec-1 and exceptional durability. The usage of plasma helps in replacing the top S atoms with Se atoms, and this ion bombardment also increases the roughness of the thin film, thus adding another factor to enhance the HER performance. This plasma-synthesized low-temperature metallic-phase heterostructure brings out a novel method for the discovery of other catalysts.

Enhanced Electrical Transport Properties of Molybdenum Disulfide Field-Effect Transistors by Using Alkali Metal Fluorides as Dielectric Capping Layers.

The electronic properties of 2D materials are highly influenced by the molecular activity at their interfaces. A method was proposed to address this issue by employing passivation techniques using monolayer MoS2 field-effect transistors (FETs) while preserving high performance. Herein, we have used alkali metal fluorides as dielectric capping layers, including lithium fluoride (LiF), sodium fluoride (NaF), and potassium fluoride (KF) dielectric capping layers, to mitigate the environmental impact of oxygen and water exposure. Among them, the LiF dielectric capping layer significantly improved the transistor performance, specifically in terms of enhanced field effect mobility from 74 to 137 cm2/V·s, increased current density from 17 µA/µm to 32.13 µA/µm at a drain voltage of Vd of 1 V, and decreased subthreshold swing to 0.8 V/dec The results have been analytically verified by X-ray photoelectron spectroscopy (XPS) and Raman, and photoluminescence (PL) spectroscopy, and the demonstrated technique can be extended to other transition metal dichalcogenide (TMD)-based FETs, which can become a prospect for cutting-edge electronic applications. These findings highlight certain important trade-offs and provide insight into the significance of interface control and passivation material choice on the electrical stability, performance, and enhancement of the MoS2 FET.

Phase/Interfacial-Engineered Two-Dimensional-Layered WSe2 Films by a Plasma-Assisted Selenization Process: Modulation of Oxygen Vacancies in Resistive Random-Access Memory.

Here, we propose phase and interfacial engineering by inserting a functional WO3 layer and selenized it to achieve a 2D-layered WSe2/WO3 heterolayer structure by a plasma-assisted selenization process. The 2D-layered WSe2/WO3 heterolayer was coupled with an Al2O3 film as a resistive switching (RS) layer to form a hybrid structure, with which Pt and W films were used as the top and bottom electrodes, respectively. The device with good uniformity in SET/RESET voltage and high low-/high-resistance window can be obtained by controlling a conversion ratio from a WO3 film to a 2D-layered WSe2 thin film. The Pt/Al2O3/(2D-layered WSe2/WO3)/W structure shows remarkable improvement to the pristine Pt/Al2O3/W and Pt/Al2O3/2D-layered WO3/W in terms of low SET/RESET voltage variability (-20/20)%, multilevel characteristics (uniform LRS/HRS distribution), high on/off ratio (104-105), and retention (∼105 s). The thickness of the obtained WSe2 was tuned at different gas ratios to optimize different 2D-layered WSe2/WO3 (%) ratios, showing a distinctive trend of reduced and uniform SET/RESET voltage variability as 2D-layered WSe2/WO3 (%) changes from 90/10 (%) to 45/55 (%), respectively. The electrical measurements confirm the superior ability of the metallic 1T phase of the 2D-layered WSe2 over the semiconducting 2H phase. Through systemic studies of RS behaviors on the effect of 1T/2H phases and 2D-layered WSe2/WO3 ratios, the low-temperature plasma-assisted selenization offers compatibility with the temperature-limited 3D integration process and also provides much better thickness control over a large area.

Gamma-Ray Irradiation Induced Ultrahigh Room-Temperature Ferromagnetism in MoS2 Sputtered Few-Layered Thin Films.

Defect engineering is of great interest to the two-dimensional (2D) materials community. If nonmagnetic transition-metal dichalcogenides can possess room-temperature ferromagnetism (RTFM) induced by defects, then they will be ideal for application as spintronic materials and also for studying the relation between electronic and magnetic properties of quantum-confined structures. Thus, in this work, we aimed to study gamma-ray irradiation effects on MoS2, which is diamagnetic in nature. We found that gamma-ray exposure up to 9 kGy on few-layered (3.5 nm) MoS2 films induces an ultrahigh saturation magnetization of around 610 emu/cm3 at RT, whereas no significant changes were observed in the structure and magnetism of bulk MoS2 (40 nm) films even after gamma-ray irradiation. The RTFM in a few-layered gamma-ray irradiated sample is most likely due to the bound magnetic polaron created by the spin interaction of Mo 4d ions with trapped electrons present at sulfur vacancies. In addition, density functional theory (DFT) calculations suggest that the defect containing one Mo and two S vacancies is the dominant defect inducing the RTFM in MoS2. These DFT results are consistent with Raman, X-ray photoelectron spectroscopy, and ESR spectroscopy results, and they confirm the breakage of Mo and S bonds and the existence of vacancies after gamma-ray irradiation. Overall, this study suggests that the occurrence of magnetism in gamma-ray irradiated MoS2 few-layered films could be attributed to the synergistic effects of magnetic moments arising from the existence of both Mo and S vacancies as well as lattice distortion of the MoS2 structure.

Rational Design on Controllable Cation Injection with Improved Conductive-Bridge Random Access Memory by Glancing Angle Deposition Technology toward Neuromorphic Application.

A conductive-bridge random access memory (CBRAM) has been considered a promising candidate for the next-generation nonvolatile memory technology because of its excellent performance, for which the resistive switching behavior depends on the formation/dissolution of conducting filaments in an electrolyte layer originated by the cation injection from the active electrode with electrochemical reactions. Typically, the controllability of cations into the electrolyte layer is a main issue, leading to stable switching reliability. In this work, an architecture combining spike-shaped Ag electrodes created by Al2O3 nanopillar arrays as a physical diffusion barrier by glancing angle deposition technology was proposed to localize Ag cation injection for the formation of controllable filaments inside TiOx as the switching layer. Interestingly, the dimension of the Ag plugs defined by the topography of Al2O3 nanopillar arrays can control Ag cation injection to influence the dimensionality of conductive filaments. Compared to the typical planar-Ag/TiOx/Pt device, the spiked-Ag/Al2O3 nanopillar arrays/TiOx/Pt device shows improvement of endurance and voltage disturbance. With enhanced multilevel characteristics, the spiked active-metal-based CBRAM device can be expected to serve as an analogue synapse for neuromorphic applications.

Correction: Consequences of gamma-ray irradiation on structural and electronic properties of PEDOT:PSS polymer in air and vacuum environments.

[This corrects the article DOI: 10.1039/D1RA03463D.].

Consequences of gamma-ray irradiation on structural and electronic properties of PEDOT:PSS polymer in air and vacuum environments.

In this work, the effects of gamma-ray irradiation (up to 3 kGy) on the structural and electronic properties of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), irradiated in air and vacuum environments are systematically investigated. Raman spectroscopy indicates that there is no significant change in structural conformation of PEDOT:PSS film after gamma-ray irradiation. However, the conductivity of the film decreases as a function of dose in both air and vacuum environments, which can be deduced as a result of defects created in the structure. Hall effect measurements showed higher carrier concentration when the samples are irradiated under vacuum in comparison to the air environment, whereas mobility decreases as a function of dose irrespective of the environment. Furthermore, the electron spin resonance spectra provided evidence of the evolution of polaron population after gamma-ray exposure of 3 kGy, due to the decrease in charge delocalization and molecular ordering of the molecules. This decrease in conductivity and mobility of the PEDOT:PSS films irradiated in air and vacuum environments can be mainly ascribed to the defects and radical formation after gamma-ray exposure, favoring chain scission or cross-linking of the polymers.

Influence of gamma-ray irradiation and post-annealing studies on pentacene films: the anisotropic effects on structural and electronic properties.

In this work, γ-ray irradiation effects on pentacene thin films are investigated in terms of the change in the crystallinity, and electronic structure as well as chemical states of the film. The pentacene films are γ-irradiated up to 3 kGy and then characterized using synchrotron X-ray diffraction, near edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy. We found that γ-ray irradiation creates defects, resulting in a decrease of X-ray diffraction intensity both in the plane normal and in-plane directions. From angle dependent NEXAFS; the transition of C 1s to π* orbital for irradiated samples increases; suggesting that the unoccupied π* states enhance due to defects or radical formation in pentacene thin films. Additionally, the in-plane resistivity shows a decreasing trend of resistance after irradiation. This trend of increase in conductivity is also consistent with C 1s to π transition, which manifests the increase in carrier concentration. Hall effect measurements further confirmed the increase in carrier concentration as a function of dose; however, the mobility of the sample decreases as the dose rate increases due to the defects created. By post-irradiation annealing, the thin film phase diffraction intensity can be recovered. Altogether, the anisotropic studies on pentacene films disclosed that the irradiation leads to defect formation along in-plane and plane normal directions. Overall, these results suggest that pentacene is one of the robust organic electronic materials; whose structure remains mostly intact even after irradiation up to a dose of 3 kGy.

Reactive hyperplastic lesions of the oral cavity: A retrospective survey study and literature review.

CONTEXT: The reactive lesions are relatively common in the oral cavity because of the frequency with which the tissues are injured. They often result from a known stimulus or injury such as dental plaque, calculus, or foreign material. AIMS:: The aim of this study was to review the clinicopathologic features of reactive hyperplastic lesions (RHLs) of the oral cavity at MIDSR, Dental College and Hospital, Latur, Maharashtra, and to compare these data with those of previously reported studies. SETTINGS AND DESIGN: The patient case files from the Department of Oral and Maxillofacial Pathology from June 2010 to May 2016 were reviewed for cases of RHLs of the oral cavity. SUBJECTS AND METHODS: Both clinical and histopathological diagnosis of reactive lesions was selected for the study. Data including the type of the lesion, age, gender, and the site involved were collected. STATISTICAL ANALYSIS USED: Descriptive statistics was applied to the data and differences in frequencies among groups were evaluated using SPSS (IBM Corporation) software. RESULTS:: A total of 155 histologically diagnosed cases of RHLs were obtained with a prevalence of 11.7%. The data consist of 56 (36.1%) males and 99 (63.9%) females. The most common lesion clinically was traumatic fibroma (36.5%) and histologically fibrous hyperplasia (37.4%). The reactive lesions clinically presented as either sessile (51%) or pedunculated (49%) lesions. CONCLUSIONS: The clinical features of reactive hyperplasia among our patients were similar to those reported previously with divergence in some analyzed data. The novelty in our study was the correlation between histopathology and clinical features which were not reported in literature till date.

Effectiveness of integrated teaching module in pharmacology among medical undergraduates.

CONTEXT: Over the years with advancement of science and technology, each subject has become highly specialized. Teaching of medical students has still remained separate in various departments with no scope of integration in majority of medical institutes in India. Study was planned to have an experience of integration in institute and sensitize faculty for integrated teaching-learning (TL) method. AIMS: To prepare and test effectiveness of integrated teaching module for 2(nd) year MBBS student in pharmacology and to sensitize and motivate faculties toward advantages of implementing integrated module. SETTINGS AND DESIGN: Education intervention project implemented 2(nd) year MBBS students of Government Medical College and New Civil Hospital, Surat. SUBJECTS AND METHODS: Students of second MBBS were divided into two groups. One group was exposed to integrated teaching sessions and another to traditional method. Both the groups were assessed by pre- and post-test questionnaire, feedback and focus group discussions were conducted to know their experience about process. RESULTS: A total of 165 students of the 2(nd) year MBBS were exposed to the integrated teaching module for two topics in two groups. One group was taught by traditional teaching, and another group was exposed to the integrated TL session. Both the groups have shown a significant improvement in posttest scores but increase in mean score was more in integrated group. During analysis of feedback forms, it was noted that students preferred integrated TL methods since they help in better understanding. Faculty feedback shows consensus over the adaptation of integrated TL methods. CONCLUSIONS: Integrated TL sessions were well-appreciated by students and faculties. To improve the critical reasoning skills and self-directed learning of students, integrated TL is highly recommended for must know areas of curriculum.

Evaluation and co-relation of the Oratest, colorimetric Snyder's test and salivary Streptococcus mutans count in children of age group of 6-8 years.

AIM: Evaluation and co-relation of the caries susceptibility using Oratest, colorimetric Snyder's test and salivary Streptococcus mutans count amongst children in the age group of 6-8 years. MATERIALS AND METHODS: A total of 120 healthy children were grouped into control and test groups according to their dmft/DMFT scores. Snyder's test, salivary S. mutans count and Oratest were performed for each individual. RESULTS: The relationship of three caries activity tests with each other and with existing caries status was found out. CONCLUSION AND CLINICAL IMPLICATIONS: The present study has shown that Oratest has a definite clinical relationship with caries status and microbiological relationship with S. mutans count of the individual.

Osteosarcoma of jaws.

Tumors of jaw bones are among the most uncommon of all types of neoplasms. Osteosarcoma of jaw bones represents a distinct group of lesions from the conventional type commonly occurring in long bones. Nonetheless, our present knowledge of the tumor allows us to affirm that its clinical behavior and pathologic features differ markedly from those of its homolog in the long bones. The maxillary tumors show predilection for posterior portion of the alveolar process and the antrum, whereas the body is most commonly involved in the mandible followed, by angle, symphysis, and ascending ramus. We have reviewed around 300 cases of osteosarcoma of varied racial origin from PubMed indexed journals spanning from 1967 to 2010 and present their etiology, pathogenesis, features and treatment modalities.

Utility of lead thyroid collar in cephalometric radiography.

OBJECTIVE: To investigate whether the application of thyroid collars (TCs) affects the results of cephalometric study. STUDY DESIGN: The Steiner cephalometric analysis of the patients was performed using lateral cephalometric radiographs, which were taken twice for each patient: Once using TCs (TC group; n = 50) and once without using TCs (NTC group; n = 50). A randomized and observer-blinded diagnostic study with head films taken from the two aforementioned groups was performed and results were evaluated with the t-test and Z-test, using GraphPad Prism 4 software. RESULTS: Statistical analysis using t-test was performed. The values of the line angles used in Steiner cephalometric analysis were compared for which values of each angle remained unchanged when done using TCs and without TC to the same samples. CONCLUSIONS: Lead shielding of the thyroid gland does not affect landmark identification or the specific measurements of the angulations traced during cephalometric analysis. TCs should be routinely applied during cephalometric radiography if cephalometric analyses are limited to the structures above the second cervical vertebra.

An assessment of the cariogenicity of commonly used infant milk formulae using microbiological and biochemical methods.

Dental caries is an important dental public health problem and is the most prevalent oral disease among children in the world. The present study was undertaken to evaluate and comparatively assess the change in plaque and salivary pH after ingestion of various commercially available infant milk formulae, and also to evaluate and comparatively assess plaque and salivary samples for change in colony-forming units of Streptococcus mutans caused due to their ingestion. 36 children in the age group of 1-2 years were fed with infant milk formulae three times a day for 21 days and results quantified. The present study revealed a highly significant increase in the levels of colony-forming units of Streptococcus mutans in both the plaque and salivary samples when assessed at baseline and after a period of 21 days, with the t value being 11.92 for the plaque samples and 11.66 for the salivary samples. It was also observed that all the test samples produced significantly lower plaque pH values than pre-feed pH. Based upon this study, further evaluation of the cariogenicity of infant milk formulae is recommended.

Amelogenesis imperfecta: Report of a case and review of literature.

Amelogenesis imperfecta (AI) is a diverse collection of inherited diseases that exhibit quantitative or qualitative tooth enamel defects in the absence of systemic manifestations. Also known by varied names such as Hereditary enamel dysplasia, Hereditary brown enamel, Hereditary brown opalescent teeth, this defect is entirely ectodermal, since mesodermal components of the teeth are basically normal. The AI trait can be transmitted by either autosomal dominant, autosomal recessive, or X-linked modes of inheritance. Genes implicated in autosomal forms are genes encoding enamel matrix proteins, namely: enamelin and ameloblastin, tuftelin, MMP-20 and kallikrein - 4. This article presents a case reported to Dr. D. Y. Patil, Dental College and Hospital, Pune, India, along with a review of this often seen clinical entity.

Molluscum contagiosum in human immunodeficiency virus infected patients.

Molluscum contagiosum (MC) is a cutaneous lesion caused by a DNA virus from the poxvirus family. Worldwide in distribution, MC is most frequently encountered as an easily treated disease of childhood and has rarely been a cause of serious morbidity. With the advent of new populations of immunocompromised individuals, especially those infected with the human immunodeficiency virus (HIV), MC has emerged as a difficult clinical challenge and the focus of renewed interest for dental professionals. This article presents four cases of HIV positive patients afflicted by MC along with a review of the literature on this dermatopathological lesion.