Exploring dielectric and AC conduction characteristics in elemental selenium glass modified with silver halides.

In this research work, we have examined the influence of silver halide doping on the dielectric dispersion and AC conduction of elemental selenium. The in-depth investigation shows that when the dopant silver halides are incorporated, there are noticeable changes in the parent selenium's dielectric constant (ε'), dielectric loss (ε''), and AC conductivity (σ ac). When we frame the discussion of the obtained results with the relevant transport models, we found that in pure selenium and Se95(AgI)5, conduction is primarily due to polaron hopping and follows the correlated barrier hopping (CBH) model. In contrast, Se95(AgBr)5 predominantly exhibits non-overlapping small polaron tunneling (NSPT). Interestingly, Se95(AgCl)5 demonstrates both NSPT and CBH conduction mechanisms, depending on the temperature range: NSPT is dominant between 303 K and 313 K, while CBH prevails from 318 K to 338 K. Additionally, our findings revealed the presence of both the Meyer-Neldel rule (MNR) and its reverse in the prepared silver halide chalcogenide alloys. The best optimization of dielectric constant and loss is observed for silver iodide as compared to silver chloride and silver bromide. Comparison with other silver-containing chalcogenide glasses indicates the better dielectric performance of the present silver halides containing selenium.

Correction: Optimized Cu-doping in ZnO electro-spun nanofibers for enhanced photovoltaic performance in perovskite solar cells and photocatalytic dye degradation.

[This corrects the article DOI: 10.1039/D4RA01544D.].

The structural, optical and photovoltaic properties of Zn-doped MAPbI2Br perovskite solar cells.

The spin coating method was used to deposit MAPbI2Br films on FTO-glass substrates. Zn2+ (zinc) doping was used for these films at intensity rates of 2% and 4%, respectively. XRD analysis proved that MAPbI2Br films had a cubic structure and a crystalline character. 2% Zn doping into the MAPbI2Br film had a modest large grain size (38.09 nm), Eg (1.95 eV), high refractive index (2.66), and low extinction coefficient (1.67), according to XRD and UV-vis analyses. To facilitate and enhance carrier transit, at contacts as well as throughout the bulk material, the perovskite's trap-state densities decreased. The predicted MAPbI2Br valence and conduction band edges are -5.44 and -3.52, respectively. The conduction band (CB) edge of the film that was exposed to Zn atoms has been pressed towards the lower value, assembly it a better material for solar cells. EIS is particularly useful for understanding charge carrier transport, recombination mechanisms, and the influence of different interfaces within the device structure. Jsc is 11.09 mA cm-2, Voc is 1.09, PCE is 9.372% and FF is 0.777. The cell made with the 2% Zn doped into the MAPbI2Br film demonstrated a superior device.

Green synthesis of novel spiropyrazoline-indolinones in neutral deep eutectic solvents and DFT studies.

Novel spiropyrazoline-indolinones (4a-t) have been synthesized successfully in neutral deep eutectic solvents by reacting 5-Cl/Br-isatin (1a-b) with aromatic ketones (2a-b) and a variety of substituted hydrazines (3a-e) in good to excellent yields. This eco-friendly straightforward synthetic protocol discloses good functional group compatibility. The conventional synthetic approach was compared with the greener route of microwave-assisted synthesis of spiropyrazolines using ethanol. This approach utilized mild reaction conditions which furnished high yields in short reaction time employing one pot two-step multicomponent. All new compounds were structurally confirmed by detailed spectroscopic analysis and density functional theory calculations. This method provides efficient access to spiropyrazole derivatives using biodegradable and green solvent.

Correlation between the density of defect states (DDS) and cross-linking of corner/edge sharing GeSe4 tetrahedral structural units.

We have estimated the DDS in the STSG [Se78-xTe20Sn2Gex (x = 0, 2, 4, 6)] system by using the Correlated Barrier Hopping (CBH) model by performing A.C. conduction measurements in the frequency range (1 kHz-10 kHz) and temperature underneath the glass transition temperature (303-333) K. The detailed analysis reveals that bi-polaron hopping is a leading conduction mechanism over single-polaron hopping. Further, there is a noticeable reduction in DDS with increasing concentration of Ge beyond the composition x = 2. A close inspection indicates that cross-linking of Se with Ge has an important role in controlling the DDS in terms of the corner/edge sharing configurations in the structural unit of GeSe4 tetrahedral.

Contemporary innovations in two-dimensional transition metal dichalcogenide-based P-N junctions for optoelectronics.

Two-dimensional transition metal dichalcogenides (2D-TMDCs) with various physical characteristics have attracted significant interest from the scientific and industrial worlds in the years following Moore's law. The p-n junction is one of the earliest electrical components to be utilized in electronics and optoelectronics, and modern research on 2D materials has renewed interest in it. In this regard, device preparation and application have evolved substantially in this decade. 2D TMDCs provide unprecedented flexibility in the construction of innovative p-n junction device designs, which is not achievable with traditional bulk semiconductors. It has been investigated using 2D TMDCs for various junctions, including homojunctions, heterojunctions, P-I-N junctions, and broken gap junctions. To achieve high-performance p-n junctions, several issues still need to be resolved, such as developing 2D TMDCs of superior quality, raising the rectification ratio and quantum efficiency, and successfully separating the photogenerated electron-hole pairs, among other things. This review comprehensively details the various 2D-based p-n junction geometries investigated with an emphasis on 2D junctions. We investigated the 2D p-n junctions utilized in current rectifiers and photodetectors. To make a comparison of various devices easier, important optoelectronic and electronic features are presented. We thoroughly assessed the review's prospects and challenges for this emerging field of study. This study will serve as a roadmap for more real-world photodetection technology applications.

Correction: Semiconducting quaternary chalcogenide glasses as new potential thermoelectric materials: an As-Ge-Se-Sb case.

Correction for 'Semiconducting quaternary chalcogenide glasses as new potential thermoelectric materials: an As-Ge-Se-Sb case' by A. Dahshan, et al., Dalton Trans., 2015, 44, 14799-14804.

Semiconducting quaternary chalcogenide glasses as new potential thermoelectric materials: an As-Ge-Se-Sb case.

The performance of thermoelectric materials may be improved via complex structures, impurities, disorder etc. Chalcogenide glasses possess such properties. In the present paper, we report the electrical and thermoelectric properties of As14Ge14Se72-xSbx (where x = 3, 6, 9, 12, 15 at%) chalcogenide glasses in the temperature range of 300 K-450 K. The electrical conductivity has been observed to increase from 1.46 × 10(-9) Ω(-1) cm(-1) to 1.80 × 10(-6) Ω(-1) cm(-1) for x = 3 at% to x = 15 at%. The addition of Sb increases the Seebeck coefficient to a large value of 1124 µV K(-1) for x = 15 at% at 333 K. As a result of increased electrical conductivity and Seebeck coefficient for enhanced values of Sb, the power factor (a measure of the performance of the thermoelectric energy converters) has been observed to increase strongly. Results indicate that the investigated chalcogenide glassy compositions may be potential candidates for incurring high action thermoelectric materials.

Management of ingested foreign bodies in children.

This paper reviews the presentation, diagnosis, and management of ingested foreign bodies in children. It may help primary care physicians to recognize the wide spectrum of presentations of ingested foreign bodies in children, therefore emphasizing considering ingested foreign bodies in the differential diagnosis of many respiratory and vague gastrointestinal complaints. It also proposes an approach to handling asymptomatic children with foreign body ingestion and points out certain types of foreign bodies that require special consideration.

Correlation of endoscopy and histology in the gastroesophageal mucosa in children: are routine biopsies justified?

Guidelines for obtaining biopsies during endoscopy in children are needed. The endoscopic evaluation may be considered deficient on many occasions if not accompanied by a histopathologic evaluation. A retrospective review of our endoscopic records and biopsies was undertaken to determine the correlation of the visualized endoscopic appearance and the histopathologic findings in the upper gastrointestinal (GI) tract in children. Over a 1-year period, 204 patients, all of whom had esophageal biopsies and 59 of whom had gastric biopsies as well, were evaluated by an upper GI endoscopy. Endoscopic findings included erythema, granularity, abnormal vascular pattern, friability, erosions, plaques, ulceration, and strictures. Histologic evaluation of biopsies was undertaken by one pathologist according to the presence of and type of cellular infiltrate and cellular morphologic abnormalities in the mucosa and submucosa where available. In this study, the correlation of endoscopic appearance with histology was rather limited in both the esophagus and the gastric mucosa. Low specificity and sensitivity of endoscopy in both locations (41% and 81% for the esophagus; and 43% and 86% for the gastric mucosa, respectively) illustrated the discrepancy. The overall accuracy of endoscopic evaluation in matching the histologic diagnosis was not more than two out of three (63.8%). No single endoscopic finding had a reliable correlation with histologic diagnosis but some had higher predictive value than others. Of the multiple indications for endoscopy in children, recurrent abdominal pain had the least diagnostic yield. Endoscopic appearance correlates poorly with histologic diagnosis in the gastroesophageal mucosa in children. Regardless of the appearance of the mucosa, routine biopsy during upper GI endoscopy in children should be encouraged.

A randomized, prospective study to evaluate the efficacy and acceptance of three bowel preparations for colonoscopy in children.

OBJECTIVE: We performed a prospective, randomized, single-blind study in children undergoing colonoscopy to evaluate the acceptance and efficacy of three different bowel preparations. METHODS: Seventy patients (ages 3-20 yr, 38 males) were randomly assigned to one of the three study preparations: Magnesium citrate with X-prep and clear liquid diet for 2 days (group A); Dulcolax for 2 days and Fleet enema without dietary restriction (group B); and Golytely 20 ml/kg (up to 1 L) per hour for 4 h with clear liquid diet for 1 day (group C). Endoscopists blinded to bowel preparation graded the adequacy of colon cleansing. The preparations were rated by patients for tolerance, willingness to retake them, adverse effects, and compliance. RESULTS: Data analysis using Fisher exact test and trend test showed that colon cleansing in groups A and C was superior to that in group B (p < 0.0001) and better in group C than A (p < 0.075). Overall tolerance and compliance were significantly better for groups A and B than group C (p < 0.003), but not different between A and B. More of group B patients were willing to retake the preparation than in group C (p < 0.002) and group A (p < 0.05), but this was not different between groups A and C. Adverse effects were reported more frequently by patients in group C than in groups A and B (p < 0.01). CONCLUSIONS: Although the least well tolerated, Golytely provided the best cleansing. Dulcolax without dietary restriction provided unsatisfactory colon cleansing. Magnesium citrate with X-prep was acceptable and provided good cleansing.