Enhancing Electrochemical Performance with g-C3N4/CeO2 Binary Electrode Material.

An innovative form of 2D/0D g-C3N4/CeO2 nanostructure was synthesized using a simple precursor decomposition process. The 2D g-C3N4 directs the growth of 0D CeO2 quantum dots, while also promoting good dispersion of CeO2QDs. This 2D/0D nanostructure shows a capacitance of 202.5 F/g and notable rate capability and stability, outperforming the g-C3N4 electrode, reflecting the state-of-the-art g-C3N4 binary electrodes. The binary combination of materials also enables an asymmetric device (g-C3N4/CeO2QDs//AC) to deliver the highest energy density (9.25 Wh/kg) and power density (900 W/kg). The superior rate capacity and stability endorsed the quantum structural merits of CeO2QDs and layered g-C3N4, which offer more accessible sites for ion transport. These results suggest that the g-C3N4/CeO2QDs nanostructure is a promising electrode material for energy storage devices.

CdSe/CdS/CdTe Core/Barrier/Crown Nanoplatelets: Synthesis, Optoelectronic Properties, and Multiphoton Fluorescence Upconversion.

Colloidal two-dimensional (2D) nanoplatelet heterostructures are particularly interesting as they combine strong confinement of excitons in 2D materials with a wide range of possible semiconductor junctions due to a template-free, solution-based growth. Here, we present the synthesis of a ternary 2D architecture consisting of a core of CdSe, laterally encapsulated by a type-I barrier of CdS, and finally a type-II outer layer of CdTe as so-called crown. The CdS acts as a tunneling barrier between CdSe- and CdTe-localized hole states, and through strain at the CdS/CdTe interface, it can induce a shallow electron barrier for CdTe-localized electrons as well. Consequently, next to an extended fluorescence lifetime, the barrier also yields emission from CdSe and CdTe direct transitions. The core/barrier/crown configuration further enables two-photon fluorescence upconversion and, due to a high nonlinear absorption cross section, even allows to upconvert three near-infrared photons into a single green photon. These results demonstrate the capability of 2D heterostructured nanoplatelets to combine weak and strong confinement regimes to engineer their optoelectronic properties.

Epitaxial Synthesis of Monolayer PtSe2 Single Crystal on MoSe2 with Strong Interlayer Coupling.

PtSe2, a layered two-dimensional transition-metal dichalcogenide (TMD), has drawn intensive attention owing to its layer-dependent band structure, high air stability, and spin-layer locking effect which can be used in various applications for next-generation optoelectronic and electronic devices or catalysis applications. However, synthesis of PtSe2 is highly challenging due to the low chemical reactivity of Pt sources. Here, we report the chemical vapor deposition of monolayer PtSe2 single crystals on MoSe2. The periodic Moiré patterns from the vertically stacked heterostructure (PtSe2/MoSe2) are clearly identified via annular dark-field scanning transmission electron microscopy. First-principles calculations show a type II band alignment and reveal interface states originating from the strong-weak interlayer coupling (SWIC) between PtSe2 and MoSe2 monolayers, which is supported by the electrostatic force microscopy imaging. Ultrafast hole transfer between PtSe2 and MoSe2 monolayers is observed in the PtSe2/MoSe2 heterostructure, matching well with the theoretical results. Our study will shed light on the synthesis of Pt-based TMD heterostructures and boost the realization of SWIC-based optoelectronic devices.

Anisotropic visible photoluminescence from thermally annealed few-layer black phosphorus.

Black phosphorus, a two-dimensional material, with high carrier mobility, tunable direct bandgap and anisotropic electronic properties has attracted enormous research interest towards potential application in electronic, optoelectronic and optomechanical devices. The bandgap of BP is thickness dependent, ranging from 0.3 eV for bulk to 1.3 eV for monolayer, while lacking in the visible region, a widely used optical regime for practical optoelectronic applications. In this work, photoluminescence (PL) centered at 605 nm is observed from the thermally annealed BP with thickness ≤20 nm. This higher energy PL is most likely the consequence of the formation of higher bandgap phosphorene oxides and suboxides on the surface BP layers as a result of the enhanced rate of oxidation. Moreover, the polarization-resolved PL measurements show that the emitted light is anisotropic when the excitation polarization is along the armchair direction. However, if excited along zigzag direction, the PL is nearly isotropic. Our findings suggest that the thermal annealing of BP can be used as a convenient route to fill the visible gap of the BP-based optoelectronic and optomechanical devices.

Evaluation of Effect of Irrigants with or without Surfactant on Root Canal Transportation by Cone Beam Computed Tomography-An In vitro Study.

INTRODUCTION: Maintenance of original canal anatomy with proper disinfection is our primary goal to achieve during root canal instrumentation. Surfactants are added to irrigating solution to promote deeper penetration into dentinal tubules. AIM: The aim of this study was to evaluate the influence of addition of surfactants to Sodium Hypochlorite (NaOCl) and Ethylenediaminetetraacetic Acid (EDTA) on transportation of root canal. MATERIALS AND METHODS: Fifty human mandibular molars with mesial root curvatures of 10° - 40° were selected and embedded in silicone impression material to simulate mandibular arch form to facilitate imaging process and maintain reproducibility of images. Before instrumentation, root canals were scanned by using Cone Beam Computed Tomography (CBCT) imaging (Carestream, India). The canals were then prepared with the ProTaper Next (PTN) system (Dentsply Maillefer, Ballaigues, Switzerland), using one of the following irrigation regimens during the instrumentation and were divided into five groups based on irrigation regimens followed: G1 (n=10)-irrigation with saline solution(control); G2 (n=10)-irrigation with 2.5% NaOCl; G3 (n=10)-irrigation with 2.5% NaOCl added with surfactant; G4 (n=10)-irrigation with 17% EDTA; G5 (n=10)-irrigation with 17% EDTA added with surfactant. Post-instrumentation scans were obtained with similar parameters and position as pre-instrumentation scans by CBCT imaging. Transportation of the root canals were then analysed at three cross-sectional planes of pre-instrumentation and post-instrumentation images at 2 mm, 5 mm, 8 mm from the apical end of the root. The data was statistically analyzed using Analysis of Variance (ANOVA) and Tukey post hoc test (p<0.05). RESULTS: The mean transportation values were higher in G5. Transportation in G3 and G5 was not significantly different compared to G2 and G4 respectively (p<0.05). CONCLUSION: Instrumentation using irrigating solutions added with surfactant like 1% cetrimide maintained the canal curvature well.

Comparison of Sealer Penetration by Using Different Irrigation Techniques - An In-vitro Study.

INTRODUCTION: The main goal of root canal treatment is to eliminate the microorganisms particularly in the apical third area and to prevent re-infection. In order to achieve these goals the instrumentation must be combined with adequate irrigation. AIM: To compare sealer penetration by using different irrigation techniques i.e., apical negative pressure irrigation, Passive Ultrasonic Irrigation (PUI) and combination of apical negative pressure irrigation and PUI. MATERIALS AND METHODS: A total of 48 single rooted maxillary central incisors were taken. Access cavity was prepared and biomechanical preparation was done. The samples were randomly assigned into three experimental groups based on the final irrigation technique used. Group I: Apical negative pressure (Endovac); Group II: PUI; Group III: Combination of apical negative pressure and PUI. All the samples were obturated using AH plus sealer and the sections were observed under confocal laser scanning microscope to evaluate the percentage and maximum depth of sealer penetration at 1mm, 3mm and 5mm levels. Statistical analysis was done by using two way ANOVA and Tukey's post-hoc test to compare the percentage and maximum depth of sealer penetration. RESULTS: Combination group resulted in better sealer penetration at 1mm and 3mm from the working length than the Endovac and PUI group. However, the Endovac group showed significantly better sealer penetration at 1mm from the working length when compared with PUI. There was no significant difference in sealer penetration at 5mm level between PUI and combination group. CONCLUSION: Combination group was the only group to achieve better sealer penetration at 1mm and 3mm levels from the working length.

Intramolecular cycloadditions of photogenerated azaxylylenes: an experimental and theoretical study.

The mechanism of intramolecular cycloadditions of azaxylylenes photogenerated via excited-state intramolecular proton transfer (ESIPT) in aromatic o-amido ketones and aldehydes bearing unsaturated functionalities was studied experimentally and computationally. In time-correlated single-photon counting experiments, no relation was found between lifetimes of singlet species and the nature of the amide pendant, either unsaturated furanpropanamide, capable of photocyclization, or the acetamide control. Steady-state emission for amido-tetralone derivatives showed comparable dual emission bands, but bromo substitution decreased the intensity of the ESIPT band. The most reactive derivatives of amidobenzaldehydes were virtually lacking the ESIPT band. The quantum yield of cycloaddition is decreased in the presence of triplet quenchers, O2 or trans-piperylene, and improved with heavy atom substitution in the aromatic ring, providing further evidence for the initial mechanistic hypothesis in which the fast singlet-state ESIPT is accompanied by the ISC in the tautomer (azaxylylene), which undergoes stepwise addition to the tethered unsaturated pendants.

Dual fluorescence of ellipticine: excited state proton transfer from solvent versus solvent mediated intramolecular proton transfer.

Photophysical properties of a natural plant alkaloid, ellipticine (5,11-dimethyl-6H-pyrido[4,3-b]carbazole), which comprises both proton donating and accepting sites, have been studied in different solvents using steady state and time-resolved fluorescence techniques primarily to understand the origin of dual fluorescence that this molecule exhibits in some specific alcoholic solvents. Ground and excited state calculations based on density functional theory have also been carried out to help interpretation of the experimental data. It is shown that the long-wavelength emission of the molecule is dependent on the hydrogen bond donating ability of the solvent, and in methanol, this emission band arises solely from an excited state reaction. However, in ethylene glycol, both ground and excited state reactions contribute to the long wavelength emission. The time-resolved fluorescence data of the system in methanol and ethylene glycol indicates the presence of two different hydrogen bonded species of ellipticine of which only one participates in the excited state reaction. The rate constant of the excited state reaction in these solvents is estimated to be around 4.2-8.0 × 10(8) s(-1). It appears that the present results are better understood in terms of solvent-mediated excited state intramolecular proton transfer reaction from the pyrrole nitrogen to the pyridine nitrogen leading to the formation of the tautomeric form of the molecule rather than excited state proton transfer from the solvents leading to the formation of the protonated form of ellipticine.

Removal of lead from aqueous effluents by adsorption on coconut shell carbon.

The application of adsorption for removal of heavy metals is quite popular and activated carbon is universally used as an adsorbent. However, high cost of its preparation and regeneration has led to a search for alternative sorbents, especially in the developing countries. A number of sorbents are used to remove metals by adsorption from industrial effluents, which include insoluble starch, xanthates, modified cotton and wool, tree barks, activated carbon, plant leaves and agricultural products. Therefore, as an alternative, coconut shell carbon (CSC), a low cost sorbent derived from organic waste material, was used in the present work, for removal of lead from aqueous effluents. The results of the batch sorption studies indicated that the efficiency of lead removal by coconut shell carbon is comparable to that of commercially available activated carbon. From the kinetic and equilibrium studies, the sorptive capacity of coconut shell carbon for lead was found to be 30 mg/g. Desorption and subsequent recovery of the metal from the surface of the sorbent was successfully demonstrated. Parameters affecting the sorption were evaluated.