Spontaneous Ion Migration via Mechanochemical Ultrasonication in Mixed Halide Perovskite Phase Formation: Experimental and Theoretical Insights

We present a simple yet powerful synthesis process to prepare compound-phase perovskite nanoparticles (MAPbX_3-nY_n; MA = CH₃NH₃⁺ and X/Y = I, Br, or Cl). This is achieved by mixing two pure-phase perovskites (MAPbX₃ and MAPbY₃) by using ultrasonic vibration as a mechanochemical excitation. Unlike conventional methods, this procedure does not require any effort in designing a reaction or choosing any particular precursor. X-ray diffraction and TEM studies confirm compound-phase formation in all possible stoichiometries. The origin behind ultrasonic mixing lies in the generation of mechanical stress and high temperature arising from acoustic cavitation during reaction. Long-term experimental stability of the compound-phase is comprehended theoretically by simulating the temperature-dependent Gibbs free energy. Negative mixing entropy plays a crucial role during the synthesis which leads to better stabilization of the compound-phase perovskite over the pure-phase. The ease of synthesis and remarkable phase stability make this process effective and less cumbersome for perovskite nanoparticle synthesis.

Effect of postprandial triglycerides on DDT/ppDDE levels in subjects with varying degree of glucose intolerance

BACKGROUND

Organochlorine pesticides such as DDT as well as postprandial hypertriglyceridemia have been linked with insulin resistance and diabetes mellitus. The cardiometabolic risk of PPhTg could also be due to its potential to increase the serum levels of this highly lipophilic pesticide. We studied the effect of postprandial triglyceride responses to a standard oral fat challenge on the levels of DDT and its metabolites in subjects with varying degree of glucose intolerance METHODS: A standard fat challenge was performed in 60 subjects who were categorized as NGT, prediabetes, and NDDM based on an earlier OGTT. Fasting and postprandial levels of serum triglycerides, plasma DDT and its metabolites were estimated and compared in the 3 groups and their association with each other, and measures of glycemia and insulin resistance were also determined.

RESULTS

Peak Tg and TgAUC levels were significantly higher in NDDM group as compared to NGT and PD groups. TgAUC showed positive correlation with fasting plasma glucose (r=0.33, p=0.01), postprandial plasma glucose (r=0.39, p=0.002) and HOMA IR(r=0.63, p=0.001). ppDDE levels were found to be significantly higher in NDDM subjects compared with NGT group. ppDDE-AUC was significantly higher in the NDDM group compared with the other two study groups. Mean ppDDE levels also showed strong positive correlation with peak Tg (r=0.295 p=0.022), TgAUC (r=0.303 p=0.018), iPPTgAUC(r=0.57 p≤0.001) and iPPpeakTg(r=0.51 p≤0.001) as well as with FPG (r=0.269 p=0.038) PPPG (r=0.424 p=0.001) and HbA1c (r=0.321 p=0.012).

CONCLUSION

The findings of this study support the concept that the cardiometabolic risk associated with PPhTg may at least in part be related to the associated increase in serum levels of lipophilic OCPs like DDT.

Synthesis, characterization and photocatalytic performance of W6+ impregnated g-C3N4 for the removal of chlorophenol derivatives in natural sunlight exposure

The surface of the g-C₃N₄ was altered by impregnating W⁶⁺ ions that transformed to homogeneously coated oxide layer by a calcination process. An enhanced absorption and the suppressed de-excitation in the emission spectra, with the increasing W⁶⁺ loading, exposed the supporting role of the coated layer in extending the spectral response as well as the prolonged life span of excitons. The same was further supported by electrochemical impedance spectroscopy (EIS). The XRD and XPS analysis revealed the coated layer as highly crystalline pure phase monoclinic WO₃ with the majority of impregnated tungsten ions in 6+ oxidation state respectively, whereas the FESEM and HRTEM analysis substantiated the uniformity of the coated layer with the interlayer spacing of the 0.369 nm. Additionally, the probable formation of individual WO₃ nanoparticles or clusters was ruled out. The as-synthesized impregnated photocatalysts, in comparison to pure g-C₃N_4, were subjected to natural sunlight exposure for the photocatalytic removal of chlorophenol derivatives (2-CP, 3-CP, 4-CP, 2,3-DCP, 2,4-DCP, 2,4,6-TCP and PCP) that revealed the 5 wt% coating as the optimum level for significant removal. The progress of the photocatalytic process was monitored by periodic HPLC analysis whereas ion chromatography (IC) was used for the estimation of released ions. The mineralization capability of the as-synthesized W⁶⁺ coated catalysts was measured by the time scale TOC measurements. As the formation of intermediates was indicated in HPLC analysis, selected samples were subjected to GC-MS analysis for the identification of the nature of intermediates. The variable degree of removal of chlorophenol derivatives signified the role of the position and orientation of Cl group. The kinetics of the removal process was evaluated with the calculation of rate constants. The results extracted from the analytical tools and the associated band edge potentials were correlated to speculate the probable mechanism as well as the identification of major reactive oxygen species (ROS) involved in the removal process.

Erosive assessment of dry mouth lozenges and tablets on enamel and dentin

OBJECTIVES

To assess the erosive potential of dry mouth lozenges and tablets on enamel and dentin.

MATERIALS AND METHODS

The following lozenges and tablets were tested: Salese, Oracoat Xylimelts, Cotton Mouth, TheraBreath, DenTek OraMoist, SmartMouth, ACT, CVS Health, Rite Aid, Med Active, and Hager Pharma. pH Analysis: Each lozenge or tablet was crushed with a pestle and mortar and 5 g of the resultant powder was dissolved in 10 ml of distilled water (pH 7.02) The pH of each lozenge solution was assessed by using a calibrated pH meter. Titratable Acidity (TA) was determined by adding 0.1 M of NaOH to each homogenous tablet solution until the pH reached 7.0. Gravimetric Analysis was measured with freshly extracted molars crown/roots were sectioned at the CEJ and enamel and dentin specimens were fabricated. The specimens were then submerged in 5 ml of solution containing 2.5 gm of crushed tablets for 24 h, 48 h, 96 h and 14 days with measurements performed at each interval after drying. The solutions were renewed at each interval.

RESULTS

Significant correlation between pH and TA was observed for lozenges and tablets evaluated (p < 0.0001). Both variables were strongly correlated with enamel and dentin loss (p < 0.0001). For enamel, DenTek resulted in significantly more substance loss (p < 0.05) than with the other tested products, while Xylimelts presented the lowest percentage of substance loss. For dentin, Cotton Mouth resulted in the highest substance loss, and Xylimelts presented the lowest percentage of substance loss.

CONCLUSIONS

There is a strong correlation between the pH, tritatable aciditiy, and erosive potential of these products. DenTek and Cotton Mouth reported erosive effect to the enamel and dentin, respectively. Xylimelts performed better than the rest of the products in relationship to enamel and dentin.

The efficacy of Co3O4 loaded WO3 sheets for the enhanced photocatalytic removal of 2,4,6-trichlorophenol in natural sunlight exposure

Owing to the promising photocatalytic performance, the sheet-like WO₃ was modified by depositing nanostructured Co₃O₄ at the surface. The appearance of the varying dual absorption edges in the optical analysis exposed the composite nature of the synthesized materials. The structural analysis revealed the deposition of Co₃O₄ particles at the surface without altering the lattice of WO₃ however, during the processing the cracking of disc was also evidenced. The FESEM and HRTEM analysis corroborated the uniform surface dispersion of Co₃O₄ nanoparticles. The co-existence of 2+ and 3+ oxidation states of Co in the deposited Co₃O₄ was examined by XPS analysis. The efficient trapping of excitons by Co₃O₄ surface entities was witnessed in the emission measurements whereas the same was authenticated by the photo-electrochemical chronopotentiometry. The Co₃O₄ loaded sheets exhibited substantially enhanced activity for the removal of 2,4,6-trichlorophenol as compared to pure WO₃ in the complete spectrum and visible region of natural sunlight exposure. The progress of the degradation process was monitored by HPLC whereas the degradation products were identified by GC-MS. The measurement and identification of the ion released during the photocatalytic process facilitated the estimation of the probable route and role of reactive oxygen species involved in the removal process. Although, the careful analysis of the findings from the analytical tools revealed the major involvement of hydroxyl radicals however, the role of superoxide anions was also exposed. An alternative mechanism of the generation of the superoxide radical involving the 2+ and 3+ oxidation states of Co was also proposed. The effect of the pH and the added concentration of H₂O₂ on the ease of removal process was also investigated.

Selection and screening of drought tolerant high yielding chickpea genotypes based on physio-biochemical indices and multi-environmental yield trials

BACKGROUND

Chickpea is one of the major legume crops being cultivated in the arid and semi-arid regions of Pakistan. It is mainly grown on the marginal areas where, terminal drought stress is one of the serious threats to its productivity. For defining the appropriate selection criteria for screening drought tolerant chickpea genotypes, present study was conducted. Distinct chickpea germplasm was collected from different pulses breeding institutes of Pakistan and evaluated for drought tolerance at germination and early seedling stages, furthermore, at late vegetative growth stages physiochemical traits and multi-environment yield performance were also tested.

RESULTS

Chickpea genotypes under different environments, were significantly varied for different seedling traits, physio-chemical attributes and seed yield. Genotypes showing drought tolerance by performing better at an early seedling stages were not correspondingly high yielding. Screening for drought tolerance on seed yield basis is the most appropriate trait to develop the drought tolerant as well as high yielding chickpea genotypes. Results confirmed that traits of early growth stages were not reflecting the drought tolerance at terminal growth stages and also did not confer high yielding. NIAB-rain fed environment proved ideal in nature to screen the chickpea genotypes whereas, NIAB-lysimeter and Kalur Kot was least effective for selecting genotypes with high seed yield. Genotypes D0091-10, K010-10, D0085-10, K005-10, D0078-10, 08AG016, 08AG004, D0080-10, 09AG002, K002-10 and D0099-10 were high yielding and drought tolerant based on their performance across multiple hotspot environments.

CONCLUSIONS

The selected genotypes are intended for further evaluation for varietal approval to recommend for general cultivation on farmer fields in drought hit areas of Pakistan. Among physio-biochemical traits, higher proline, glycine betain, RWC and CMS were reflecting the higher capability to tolerate the drought stress in chickpea. Drought sensitive genotypes (K0037-10, 2204, K0052-10, 09AG015, K0042-10, CM709/06, K0068-10, K004-10, K0026-10 and K0063-10) were also identified in present study which were resourceful asset for using as contrasting parents in hybridization programs. To our knowledge, this is first report using an integrated approach involving, physio-biochemical indices, and multi-environmental yield trials, for comparison, screening and selection of chickpea genotypes for drought tolerance.

Construction of a ternary g-C3N4/TiO2@polyaniline nanocomposite for the enhanced photocatalytic activity under solar light

The combination of two or more semiconductor materials for the synthesis of new hybrid photocatalyst could be a good approach to enhance the visible light absorption, electron-hole (e^-/h⁺) pair separation rate and photocatalytic decomposition of the organic contaminants. Herein, a facile in situ oxidative polymerization method has been used for the synthesis of visible light active g-C₃N₄/TiO₂@polyaniline (g-C₃N₄/TiO₂@PANI) nanocomposite for the decomposition of the congo red (CR) under the solar light irradiation. Prior to making the composite of TiO₂ (P25) with g-C₃N₄ and polyaniline, a lamellar structure was generated onto the TiO₂ brim by alkali hydrothermal treatment to enhance the surface area and adsorption properties. The PL and UV-visible analysis clearly showed the fast separation of the e^-/h⁺ pair, and reduction in the bandgap energy of the g-C₃N₄/TiO₂@PANI nanocomposite. The results revealed TiO₂, PANI and g-C₃N₄ showed the synergestic behavior in the g-C₃N₄/TiO₂@PANI nanocomposite and greatly enhanced the photocatalytic degradation of the CR. The photocatalytic decomposition of the CR was almost 100% for 20 mg/L at pH 5, 7 and 180 min. The reusability study of the spent catalyst showed the 90% degradation of CR after four consecutive cycles indicate that g-C₃N₄/TiO₂@PANI nanocomposite is a stable and efficient catalyst. The high efficiency and reusability of the g-C₃N₄/TiO₂@PANI nanocomposite could be attributed to the higher visible light absorption and sensitizing effect of the g-C₃N₄ and PANI.

Composition-Controlled Synthesis of Hybrid Perovskite Nanoparticles by Ionic Metathesis: Bandgap Engineering Studies from Experiments and Theoretical Calculations

Herein a newly discovered non-polar solvent based synthesis of MAPbX₃ hybrid perovskite nanoparticles (NPs) is presented, where MA=Methylammonium and X=I, Br and Cl, as well as their mixed halide counterparts. The methodology proposed is simple and uses low-cost commercial precursors. The conventional method of hybrid perovskite preparation requires methylammonium halide precursors and highly polar solvents. Mandatory use of polar solvents and a particular perovskite precursor makes an intermediate compound which then requires a non-polar solvent to recover the NPs. In contrast here, a whole range of mixed halide perovskite NPs is fabricated without using a methylammonium halide precursor and a polar solvent. In this method, a non-polar solvent is used, which provides a better platform for the particle recovery. Organic cations on the nanoparticle surface prevent degradation from water, due to their hydrophobic nature, and hence offer a stable colloidal suspension in toluene for more than three months. Ab-initio calculations within density functional theory (DFT) predict lower formation energies compared to previously reported values, confirming better chemical stability for this synthesis pathway. Through the halide compositional tuning, these NPs exhibit a variety of emission and absorption starting from ultraviolet to near infrared (IR). The absorption spectra of various halide perovskite show a sharp band edge over the visible wavelength with high absorption coefficient. High oscillator strengths due to high excitonic binding energies combined with the simulated finite dipole transition probabilities point towards the observed high absorption. The emission spectra of mixed halide perovskites vary from 400 to 750 nm, which covers the whole range of visible spectra with sharp full-width at half maxima. Different halide perovskite exhibit average recombination lifetime from 5 to 227 ns. Ambient synthesis, chemical robustness and tunability of emission with varying halide compositions make MAPbX₃ (X=I, Br and Cl) NPs appealing for the optoelectronic applications.

Enhanced and Faster Potassium Storage in Graphene with Respect to Graphite: A Comparative Study with Lithium Storage

The mechanisms, extent, and rate of K-storage in graphenic and graphitic carbons, as direct comparisons with Li-storage in the same structures/materials, in terms of the effects of dimensional scale and presence of surface and exposed edge sites have been brought to the fore via DFT-based simulations, duly complemented and supplemented by experimental studies. The simulation indicates feasibilities toward K-storage on single-layer graphene (SLG) at a concentration greater than that in graphite ( i. e., beyond KC₈), the formation of more than one layer of K on SLG, and K-storage on both the surfaces of SLG, unlike that for Li-storage. Simulations done with graphene nanoribbons (GNRs) indicate that K can get hosted on the graphene surfaces and at the exposed "stepped" edges, in addition to the "classical" K-intercalation in-between the constituent graphene layers. Accordingly, the computation studies indicate considerably enhanced K-storage "specific capacity" of GNR, as compared to bulk graphite, with the capacity decreasing with the increase in number of graphene layers. Electrochemical potassiation/depotassiation of well-ordered fairly pristine few layers graphene films (FLG; ∼6-7 layers) confirms the simultaneous occurrences of bulk ( i. e., K-intercalation) and surface storage of K, resulting in reversible K-storage capacity being greater than that of thicker bulk graphite films by a factor of ∼2.5. This is in agreement with the predictions from DFT. However, this increment is less compared to that for Li-storage, again in accordance with the DFT results. Our measurements indicate lower diffusivity of K, as compared to Li, in the same graphitic structure by an order of magnitude. Accordingly, the rate capability of K-storage in graphite has been found to be considerably inferior to Li-storage, which renders the reduction in dimensional scale even more important in the case of K-storage, as observed here with FLG.

Adsorption and anion exchange insight of indigo carmine onto CuAl-LDH/SWCNTs nanocomposite: kinetic, thermodynamic and isotherm analysis

Two-dimensional layered materials are gaining much attention in the field of wastewater purification. Herein, we report the synthesis and characterization of an anion selective copper–aluminum-layered double hydroxide/single-walled carbon nanotubes (CuAl-LDH/SWCNTs) composite for the scavenging of organic dye indigo carmine (IC) from aqueous solution. A facile urea hydrolysis method was used for the controlled growth of the metal hydroxides over the SWCNTs. Structural characterization of the prepared materials was investigated using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and X-ray diffraction (XRD) techniques. The obtained results revealed that the CuAl-LDH/SWCNTs composite has a higher potential for the removal of IC in comparison to CuAl-LDH and SWCNTs. The enhanced adsorption capacity of the composite revealed that deposition of CuAl-LDH over SWCNTs increases the active adsorption sites and promotes the interactions between the composite and IC dye via anion exchange, electrostatic, π–π, hydrogen bonding etc. Moreover, adsorption kinetics, isotherms, and thermodynamic studies have been also proposed to illustrate the mechanism of the IC adsorption onto the CuAl-LDH/SWCNTs composite. Thermodynamic parameters showed that the adsorption of IC dye onto the CuAl-LDH/SWCNTs composite was exothermic and spontaneous in nature. Intra-particle diffusion was determined to be the rate-limiting step and adsorption of IC followed the Langmuir isotherm model with the maximum monolayer adsorption capacity 294.117 mg g⁻¹ at 20 °C. The results suggest that the CuAl-LDH/SWCNTs composite is a potential material for IC adsorption in aqueous solution.

Two-dimensional layered materials are gaining much attention in the field of wastewater purification.

Prevalence of double diabetes in youth onset diabetes patients from east Delhi and neighboring NCR region

BACKGROUND

It is being increasingly reported that some of the youth onset diabetes patients cannot be classified clearly as type 1 diabetes mellitus (T1DM) or type 2 diabetes mellitus (T2DM) based on usual criteria and the term double diabetes (DD) coined for these cases.

AIM

The objective of the study was to find out the prevalence of DD in youth onset diabetes patients from east Delhi and neighboring NCR region.

METHODS

A total of 200 patients with youth onset diabetes below 25 years of age were recruited from a tertiary care hospital in East Delhi. Clinical history, family history of diabetes and anthropometry of patients were recorded. Fasting serum C-peptide, Anti-IA2-antibody and Anti-GAD-antibody were measured in all patients. Patients positive for Anti-GAD-antibody (>1.05U/ml) and C-peptide level >0.3nmol/l were characterized as DD patients. Patients negative for Anti-GAD-antibody and C-peptide >0.3nmol/l were kept under the category of T2DM. Patients with low C-peptide level along with one of the following, positive Anti-GAD-antibody, positive Anti-IA2-antibody and diabetic ketoacidosis (DKA) were considered as T1DM. Remaining patients were kept under the unknown category.

RESULTS

Mean age of study subjects was 18.2±7.1years. Seven percent (7%) of the subjects were classified as DD, 51% as T1DM, 13% as T2DM and 29% were kept under the unknown category. Mean age of subjects with 22.2±9.7, 16.9±6.7, 20.6±7.7 and 19.4±7.4 years in DD, T1DM, T2DM and unknown category respectively. Mean BMI of subjects with DD, T1DM, T2DM and unknown category was 19.8±5.7, 16.6±3.7, 19.3±4.1 and 18.0±4.6 kg/m² respectively.

CONCLUSION

Double diabetes is an important occurrence among youth onset diabetes subjects. Only half of the subjects with youth onset of diabetes had T1DM.

High prevalence of diabetes, prediabetes and obesity among residents of East Delhi - The Delhi urban diabetes survey (DUDS)

AIM

The burden of diabetes is very high in our country particularly in the urban metros. The present survey was planned to ascertain the current prevalence of diabetes and prediabetes in Delhi since the available prevalence estimates are over a decade old.

METHODS

The present study was conducted in urban area of east Delhi and followed a multistage random sampling design. The prevalence of known diabetes was ascertained based on self reporting and prevalence of newly detected diabetes and prediabetes was based on oral glucose tolerance test (OGTT).

RESULTS

We surveyed 470 households and included 1317 individuals. Prevalence of diabetes was 18.3% (known 10.8% and newly detected 7.5%). Prevalence of prediabetes was 21% as per WHO criteria and 39.5% as per ADA criteria. The ratio of known to unknown diabetes was 1.44:1. Every third household (35.77%) had at least one known case of diabetes. High rates of obesity and central obesity were also observed in the study population.

CONCLUSION

The present study found a strikingly high prevalence of diabetes, prediabetes and obesity in Delhi. This calls for urgent and effective preventive measures to prevent diabetes.

Evaluation of SnO2 for sunlight photocatalytic decontamination of water

The broad bandgap tin (IV) oxide (SnO₂) is the least investigated semiconductor material for photocatalytic water decontamination in sunlight exposure. A detailed study covering the synthesis, characterization and the evaluation of photocatalytic activity of SnO₂, in the natural sunlight exposure, is presented. The structural characterization by XRD revealed the formation of phase pure tetragonal SnO₂ with the average crystallite size of ∼41.5 nm whereas minor Sn²⁺ states in the material were identified by XPS analysis. As explored by diffuse reflectance (DR) and photoluminescence (PL) spectroscopy, the material exhibited a distinct absorption edge at ∼3.4 eV. The morphological and microstructure analysis of the synthesized SnO₂ was carried out by FESEM and HRTEM. The electrochemical impedance spectroscopy (EIS) and chronopotentiometry (CP) predicted the better charge transport and retention ability of the material under illumination whereas the Mott-Schottky extrapolation prophesied the n-type behavior with the flat-band potential of -0.60 V. The photocatalytic activity of SnO₂ was assessed in the exposure of complete spectrum natural sunlight for the removal of 2,4,6-trichlorophenol. The HPLC and TOC analysis monitored the progress of degradation and mineralization whereas the released chloride ions were evaluated by ion chromatography. The effect of the transition metal ions (Fe³⁺, Cu²⁺, Ni^2+, and Zn²⁺) as electron capture agents and H₂O₂ as ROS generator was explored during the degradation process. The utility of the material for the simultaneous removal of chlorophenols in the mixture was also investigated. The SnO₂ exhibited sustained activity in the repeated use. Based on experimental evidence congregated, the mechanism of the removal process and the efficacy of SnO₂ for sunlight photocatalytic decontamination of water was established.

High prevalence of obesity among nursing personnel working in tertiary care hospital

AIM

To find out the prevalence of obesity and glucose intolerance among nurses working in tertiary care hospital.

METHODS

Study was conducted in 496 apparently healthy females comprising two groups. Group B had 290 nurses and control group A had 206 age matched female subjects of general population. Detailed performa was filled which included anthropometry, systemic examination and other details. Fasting plasma glucose was done followed by oral glucose tolerance test (OGTT). Subjects with body mass index ≥23 kg/m² were categorized as 'overweight' and ≥25 kg/m² as 'obese' as per criteria for Asian Indians. Women with waist circumference of ≥80 cm were categorized as 'centrally obese'.

RESULTS

Mean age of subjects in groups A and B was 40.45 ± 8.64 years and 40.50 ± 6.96 years respectively. Significantly higher number of nurses (80%) were overweight or obese compared to controls (59.71%,P = < .001). Similarly, central obesity was significantly higher in nurses (82.07%) compared to controls (67.96%,P = <.001). The prevalence of glucose intolerance (prediabetes and newly detected diabetes) was significantly higher in controls compared to nurses (45.63% vs 29.66%, P < .001).

CONCLUSION

Every four out of five nurses working in tertiary care hospital have overweight/obesity and central obesity. Despite this they have lower rates of glucose intolerance.