Search

The prepared NVOY electrode achieves high stability and excellent cycle performance for AZIBs by embedding polypyrrole in ammonium vanadate layers to remove excess ammonium ions, expand the interlayer spacing, and enhance electronic conductivity. [Display omitted] Ammonium vanadate with stable bi-layered structure and superior mass-specific capacity have emerged as competitive cathode materials for aqueous rechargeable zinc-ion batteries (AZIBs). Nevertheless, fragile N H...O bonds and too strong electrostatic interaction by virtue of excessive NH 4 + will lead to sluggish Zn2+ ion mobility, further largely affects the electro-chemical performance of ammonium vanadate in AZIBs. The present work incorporates polypyrrole (PPy) to partially replace NH 4 + in NH 4 V 4 O 10 (NVO), resulting in the significantly enlarged interlayers (from 10.1 to 11.9 Å), remarkable electronic conductivity, increased oxygen vacancies and reinforced layered structure. The partial removal of NH 4 + will alleviate the irreversible deammoniation to protect the laminate structures from collapse during ion insertion/extraction. The expanded interlayer spacing and the increased oxygen vacancies by the virtue of the introduction of polypyrrole improve the ionic diffusion, enabling exceptional rate performance of NH 4 V 4 O 10. As expected, the resulting polypyrrole intercalated ammonium vanadate (NVOY) presents a superior discharge capacity of 431.9 mAh g−1 at 0.5 A g−1 and remarkable cycling stability of 219.1 mAh g−1 at 20 A g−1 with 78 % capacity retention after 1500 cycles. The in-situ electrochemical impedance spectroscopy (EIS), in-situ X-ray diffraction (XRD), ex-situ X-ray photoelectron spectroscopy (XPS) and ex-situ high resolution transmission electron microscopy (HR-TEM) analysis investigate a highly reversible intercalation Zn-storage mechanism, and the enhanced the redox kinetics are related to the combined effect of interlayer regulation, high electronic conductivity and oxygen defect engineering by partial substitution NH 4 + of PPy incorporation. [ABSTRACT FROM AUTHOR]

[Display omitted] • First report on C-dots derived from beetroot and Fabrication of 0D/0D C-dots@CdS heterostructured photocatalysts. • C-dots@CdS showed superior activity with H 2 evolution rates of 1582 µmolg−1 than the pristine CdS (849 µmolg−1). • Achieved 97.3 % degradation efficiency of CV dye under visible light for C-dots@CdS. • The presence of C-dots in heterojunction increases the charge carrier separation leading to highest photocatalytic activity. Carbon dots (C-dots) developed from beetroot is used for the rational design of cadmium sulphide based heterojunction photocatalysts (C-dots@CdS) using hydrothermal technique. The crystal structure, phase, morphology and optical characteristics of the synthesised materials are determined using X-ray diffraction (XRD), High resolution transmission electron microscopy (HR-TEM), Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray analysis (EDAX), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, UV–Visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence spectroscopy (PL spectroscopy), BET adsorption, X-ray photoelectron spectroscopy (XPS) and electrochemical studies. Using C-dots@CdS catalytic system, a superior photocatalytic activity relative to the undecorated CdS is observed. Among the C-dots@CdS samples, the CdS loaded with 6 wt% of C-dots exhibited enhanced hydrogen evolution rate compared with other samples considered for the study. CdS nanospheres modified with C-dots (6 wt%) resulted in the photocatalytic hydrogen evolution rate of 1582 µmolg−1 against 849 µmolg−1 evolution rate obtained for CdS nanospheres within 3 h. In spite of being 0D/0D type nano-heteroarchitecture, C-dots@CdS system obtained an apparent quantum yield of 6.37 % for the catalytic dosage of 20 mg under the irradiation of visible light. CdS in the C-dots@CdS system serves as the light harvester while C-dots with discernible edges can maintain the continuous supply of photo-excited charge carriers and hence can reduce the charge-carrier recombination. Further, the photodegradation of crystal violet dye using the optimised dosage of C-dots@CdS-6 exhibited an efficiency of 97.3 % in 120 min of visible light irradiation under neutral conditions. The detailed kinetic study reveals that the mechanism of photodegradation of crystal violet dye using C-dots@CdS system can be described using pseudo-second-order kinetics. The presence of oxygen rich hydrophilic surface functionalities of C-dots, the formation of near-surface heterojunction and the suitable band structure of C-dots@CdS system leading to the optimum charge carrier separation kinetics can be attributed to the enhanced photocatalytic performance. This work offers a promising strategy to develop bio-derived C-dots based heterojunction photocatalyst to address the burgeoning energy and environmental demands. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reaction orders and rates for the water-gas shift reaction on Au catalysts as a function of Au particle size and support. • DFT calculations performed on the catalyst with the lowest (alumina) and highest (titania) rates allowed us to understand the catalytic role that the support plays in activating water. • Non-porous, high surface area supports have permitted preparation of samples with tight Au particle distributions fully accessible by TEM. • Full reaction kinetics presented to understand the relation between the chemical and physical characteristics of the catalysts and their performance. • DFT calculations to examine the adsorption and reaction of CO, water and relevant intermediates over a range of different sites on model unsupported cubo-octahedral Au clusters (Au 55) as well as on model Au nano-rods supported on rutile TiO 2 (1 1 0) and α-Al 2 O 3 (0 0 0 1) surfaces. The water–gas shift (WGS) reaction rates per total mole of Au at 120 °C, 7% CO, 22% H 2 O, 8.5% CO 2 , 37% H 2 decrease in the order Au/Anatase ∼ Au/Anatase001 (uniform anatase TiO 2 single crystals with 64 per cent of the more {0 0 1} facets) ∼ Au/P25 ∼ Au/P25-WGC (obtained from the World Gold Council) ∼ Au/Rutile > Au/ZrO 2 > Au/CeO 2 > Au/ZnO when compared at the same number average Au particle size (d) and vary as ∼ d -3. From high resolution transmission electron microscopy images, the geometry of Au nanoparticles on these catalysts resembled truncated cubo-octahedra. A physical model of Au nanoparticles as truncated cubo-octahedra was used to calculate that the fractions of surface, perimeter and corner sites to the total Au sites vary as d -0.7, d -1.8 and d -2.9, respectively. Thus, the variation in the WGS reaction rate per total mole of Au (∼ d -3) correlates well with the corner sites (d -2.9) allowing us to determine that the dominant active sites for these catalysts are the low coordinated metallic corner Au sites. In addition, as the apparent H 2 O order increases and the apparent activation energy decreases, the WGS reaction rate per total mole of Au systematically decreases for Au nanoparticles supported on anatase, anatase001, P25, rutile, ZrO 2 , CeO 2 , ZnO and Al 2 O 3 at near 120 °C. Density functional theory calculations were carried out over Au nano-rods supported on rutile TiO 2 (1 0 0) and α-Al 2 O 3 (0 0 0 1) surfaces to elucidate the differences in reactivity for the most reactive (Au/TiO 2) and least reactive (Au/Al 2 O 3) catalysts. Water preferentially adsorbs and dissociates at the Lewis acid- Lewis base Ti4+-O b and Al3+-O b site pairs at the Au/TiO 2 (1 1 0) and Au/α-Al 2 O 3 interfaces with activation energies of 0.25 eV and 0.20 respectively. These barriers are significantly lower than those to activate water on the corner sites of unsupported Au nanoparticles (1.48 eV). The prediction that both the TiO 2 and Al 2 O 3 readily dissociate water supports the experimental findings that the support plays an important role in activating the water in the WGS reaction. The subsequent oxidation of CO appears to proceed at the Au/support interface via the reaction of CO adsorbed on Au with the OH on the support. DFT results indicate that OH binds 0.4 eV stronger to Al3+ sites at the Au/Al 2 O 3 interface perimeter than to Ti4+ sites at the Au/TiO 2 interface perimeter. As such, the barrier for OH to react with CO at an adjacent Au site is 0.52 eV higher for Au/Al 2 O 3 (0.85 eV) than for Au/TiO 2 (0.33 eV). The theoretical results suggest that the oxidation of CO is rate-limiting on Al 2 O 3 whereas both the water dissociation as well as CO oxidation limit the rate on TiO 2. This is consistent with the near first order CO dependence of the measured rates over both Au/TiO 2 and Au/Al 2 O 3 as well as the changes in the water reaction orders over Au/TiO 2 (−0.2 to −0.5) and Au/Al 2 O 3 (0.5 to 0.8). [ABSTRACT FROM AUTHOR]

[Display omitted] • Cobalt-bismuth nanoparticles in carbon nanotubes supported catalysts. • Noticeable increase in catalyst stability on the promotion. • Migration of metallic bismuth occurring leading to its redispersion. • Enhancement of cobalt reduction on the promotion. • Preferential bismuth localization at the steps and edges of cobalt nanoparticles. Metal nanoparticles on the surface of porous supports have found numerous applications in different areas of science. Fischer-Tropsch synthesis, which proceeds on the surface of cobalt metal nanoparticles, is an efficient way to convert renewables and fossil feedstocks into alternative fuels. The stability of cobalt catalysts is an essential and even crucial parameter and can be significantly improved by promotion. In this paper, a combination of operando Quick-XAS, NAP-XPS, high resolution electron microscopy imaging, DFT modeling alongside with Fischer-Tropsch catalytic experiments has provided deep insights into the evolution of bismuth promoter and structure of cobalt-bismuth nanoparticles in the catalysts supported by carbon nanotubes. We uncovered noticeable migration of metallic bismuth occurring during the reduction step, which leads to bismuth redispersion over the surface of cobalt nanoparticles. Cobalt reduction is facilitated in the presence of bismuth. The working Fischer-Tropsch catalyst contains cobalt-bismuth bimetallic nanoparticles, with bismuth located in the nanoparticle shell. The promotion with bismuth has resulted in a noticeable increase in catalyst stability. Characterization and DFT modeling suggest preferential localization of bismuth mobile promoter at the steps and edges of cobalt nanoparticles, which hinders cobalt sintering and carbon deposition and improves the catalyst stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Diffusion limitations are present in aryl thioethers oxidation with H 2 O 2 on UiO-66. • Mass transfer limitations can be minimized using nanoscale UiO-66 samples. • Basic sites in UiO-66 determine intrinsic catalytic activity in thioether oxidation. • Basic sites are represented by Zr-OH terminal groups at defect open sites. • Adsorption of isobutyric acid allows reliable quantification of Zr-OH groups. Zr-based metal–organic frameworks (Zr-MOFs) have attracted significant attention as selective oxidation catalysts due to their stability in aqueous and oxidative media and high activity in H 2 O 2 activation. Oxidation of thioethers with aqueous H 2 O 2 over Zr-MOFs reveals extremely high selectivity toward the formation of sulfones even at low conversions. Herein, the main factors determining activity of Zr-MOF in the thioether oxidation have been investigated using zirconium terephthalate UiO-66 as a model catalyst and methyl phenyl sulfide (MPS) as a model substrate. Samples of UiO-66 differing in the particle size, number of defects, and composition have been synthesized. The particle size was evaluated based on high resolution transmission electron microscopy images. Thermogravimetric analysis (TGA), proton nuclear magnetic resonance spectroscopy (1H NMR), and inductively coupled plasma atomic emission spectroscopy (ICP-OES) were employed for quantification of defects and determination of the composition of the UiO-66 samples. The number of basic sites was determined by liquid-phase adsorption of isobutyric acid. It was demonstrated that this characteristic depends on both the number of defects and specific composition of UiO-66 and can be affected by dehydration/hydration procedures. The number of basic sites turned out close to the number of terminal Zr–OH 2 /OH groups in the Zr-MOF defects determined by combinations of 1H NMR/TGA and 1H NMR/ICP-OES, suggesting that the basic sites are represented by Zr-OH groups at open Zr sites. Kinetic studies implicated that catalytic activity of UiO–66 in MPS oxidation is proportional to the number of basic sites provided that the particle size of the Zr-MOF does not exceed 10–20 nm. Acid additives suppress both the thioether oxidation and H 2 O 2 dismutation, pointing to the key role of basic Zr–OH groups in these two catalytic reactions. [ABSTRACT FROM AUTHOR]

The RGO-supported HoVO 4 -ZnO nanocomposite was synthesized using the ultra sonication process. X-ray diffraction patterns, Field emission scanning electron microscopy, high resolution transmission electron microscopy, Diffractive Reflectance spectroscopy, and photoluminescence spectroscopy were employed to examine the heterostructured photocatalyst in this research study. The photocatalytic efficiency of the RGO-supported HoVO 4 -ZnO nanoparticles, under UV light irradiation, in the degradation of Rhodamine-B dye was investigated. Undoped ZnO, bare HoVO4, and HoVO 4 -ZnO, degraded at 55.6, 57.5, and 74.33 percent in 45 min, respectively. This new RGO coupled HoVO 4 -ZnO exhibits enhanced photocatalytic efficiency compared to the bare ZnO and HoVO 4 -ZnO nanocomposite. [Display omitted] • RGO coupled HoVO 4 -ZnO exhibits enhanced photocatalytic efficiency. • SEM images display existence of cavities in the lattice structure. • Incorporation of RGO into the crystal structure minimizes aggregation and crystal size. • HR TEM indicates concentric ring with occasional brilliant spots. • Narrower photoluminescence spectrum for new Nanocomposite. [ABSTRACT FROM AUTHOR]

This study was aimed on the eco-friendly synthesis of silver nanoparticles (AgNPs), reduced graphene oxide (rGO) and AgNPs decorated rGO (rGO/AgNPs) nanocomposite and appraisal of their bioactivities and toxicity. As-prepared nanomaterials were established through high resolution X-ray diffraction (HR-XRD), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV–Vis. spectroscopy and Fourier transform infrared spectroscopy (FT-IR). In this study, leaves extract, graphene oxide (GO) and rGO did not show antibacterial and anticancer activities; no significant embryo toxicity was recorded. On the other hand, AgNPs displayed good antibacterial and anticancer activities; however, higher toxic effects were observed even at the lowest test concentration (0.7 μg/ml). In case of rGO/AgNPs nanocomposite, significant antibacterial activity together with low cytotoxicity was noticed. Interestingly, the embryo toxicity of AgNPs was significantly reduced by rGO, implying the biocompatible nature of as-synthesized nanocomposite. Taken together, these results clearly suggest that rGO/AgNPs nano hybrid composite could be developed as the promising biomaterial for future biomedical applications. [Display omitted] • In this study, AgNPs, rGO and rGO/AgNPs composites were prepared. • AgNPs showed good antibacterial and anticancer activities. • However, higher toxicity was observed even at 0.7 μg/ml of AgNPs. • rGO/AgNPs displayed good antibacterial activity with low cytotoxicity. • Interestingly, the toxic effects of AgNPs were significantly reduced by rGO. [ABSTRACT FROM AUTHOR]

Tunable white light-emitting Ca (2-x) Sb 2 O 7 :xDy3+ phosphors were synthesized via high temperature solid-state reaction method. The crystal structure, morphology, luminescence characteristics, and energy transfer mechanism of the phosphors were investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), high resolution transmission electron microscopy (HR-TEM), UV–Visible spectroscopy, photoluminescence (PL) spectroscopy, and Fluorescence lifetime analysis. The XRD, EDS, and TEM analysis confirmed the phase purity and orthorhombic weberite structure of the samples with an average particle size in the range of 0.2 to 0.3 ​μm. Under ultraviolet (UV) excitation of 330/351 ​nm, the prepared phosphors exhibit characteristic emission bands of Dy3+ ions along with the blue emission band of the host. The broad band peaking at 440 ​nm corresponds to Sb5+ to O2− transition of host and the peaks at 477, 575, and 670 ​nm originates from 4F 9/2 ​→ ​6H 15/2 , 4F 9/2 ​→ ​6H 13/2 and 4 F 9/2 ​→ ​6H 11/2 transitions of Dy3+ ions respectively. There exists efficient energy transfer from Ca 2 Sb 2 O 7 host to Dy3+ ions and the energy transfer efficiency increases with an increase in Dy3+ ion concentration. Using Dexter's theory, the mechanism of energy transfer was found to be dipole-quadrupole interaction and the energy transfer process is explained in detail. The decay lifetime of Dy3+ ions was estimated to be in the microsecond range. The critical distance for concentration quenching is determined to be 13.807 ​Å and the dominant mechanism is dipole-dipole interaction. The calculated Commission International de L'Eclairng (CIE) coordinates and correlated color temperature (CCT) values imply that the emission color can be tuned from blue (0.144, 0.097) to near-white (0.296, 0.292) in the cool CCT region. The results suggest that Dy3+ doped Ca 2 Sb 2 O 7 phosphor is a potential candidate for solid-state lighting and display fields. [Display omitted] • Ca (2-x) Sb 2 O 7 :xDy3+ phosphors with orthorhombic weberite structure were synthesized via solid-state reaction method. • Photoluminescence spectra exhibit characteristic emission bands of Dy3+ ions along with blue emission band of the host. • Efficient energy transfer exists between host and Dy3+ ions via electric dipole-quadrupole interaction. • The emission color of the phosphors can be tuned from blue (0.144, 0.097) to near-white (0.296, 0.292). • The decay lifetime of the Dy3+ ions were found to be in the microsecond range in Ca 2 Sb 2 O 7 host. [ABSTRACT FROM AUTHOR]

Lychee-like Mesoporous Silica Nanoparticles (LMSN) were synthesized and functionalized with 3-Aminopropyltrimethoxysilane (3-APTMS) and a novel binuclear Copper complex. The synthesized materials were characterized by UV-DRS, Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDAX) analysis. The High Resolution Transmission Electron Microscopy (HR-TEM) analysis gives view on retention of structural order after functionalization. Thermogravimetric Analysis (TGA), low angle X-ray diffraction (XRD) and BET-BJH analyses confirmed the presence of schiff base complex moieties inside the pore architecture. Electron Spin Resonance (ESR) analysis provide evidence for the presence of paramagnetic copper and ICP-OES studies details the metal loading. The potential of synthesized material as an enzyme-mimetic catalyst for the synthesis of questiomycin A and Rhodamine B degradation agent was analysed in this work. The catalyst material served best with good yields and reusability. [Display omitted] • The lychee-like Mesoporous Silica Nanoparticles (LMSN) was functionalized with a novel binuclear copper complex. • Its potential towards questiomycin A synthesis and rhodamine B degradation were studied. • The synthesized catalyst showed good ability for degradation of dye and for questiomycin A synthesis. [ABSTRACT FROM AUTHOR]

The current research focuses on the Intracellular biosynthesis of Ag/AgCl nanohybrids in microalgae, Scenedesmus sp. The effect of biosynthesis process on growth and lipid profile of cells is key element of this study. Ag/AgCl nanohybrids synthesized intracellularly were characterized by UV–Vis spectrophotometer, Powder X-Ray Diffraction (P-XRD), Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM). 10–20 nm and 10–50 nm sized spherical shaped nanoparticles of polycrystalline nature were grown using 0.5 and 1 mM of AgNO 3 precursor, respectively and Scenedesmus sp. as reducing agent. Total lipid content of the cells treated with 0.5 mM and 1 mM AgNO 3 was static and found to be 43.2 ± 0.01 μg/mL and 48.2 ± 0.02 μg/mL respectively at 120 h of Ag/AgCl nanoparticles biosynthesis. FAME (Fatty Acid Methyl Ester) profile was improved due to intracellular nanoparticles biosynthesis with maximum C16:0 (palmitic acid) (35.7%) in cells treated with 0.5 mM AgNO 3 used for Ag/AgCl nanohybrids synthesis. Palmitic acid in cells exposed to 0.5 mM concentration of metallic precursor increased by 75.86%. Synthesized nanoparticles were tested on four bacterial strains to establish its antibacterial efficiency showing appropriate zone of inhibition at varying concentrations. Present study efficiently demonstrates the utility of microalgae integrating nanoparticles biosynthesis and lipid accumulation. [Display omitted] • 10–20 nm size silver nanoparticles were biosynthesized intracellularly in Scenedesmus sp. • X-ray diffraction and electron microscopy were used to characterize silver nanoparticles. • 75.86% increase in saturated fatty acid was observed during NPs synthesis. • Synthesized nanoparticles showed antibacterial properties against four bacterial strains. [ABSTRACT FROM AUTHOR]

Herein, a series of Pb 1-x Nb x Se QDs were prepared via 4,4-bis(carbazole-9-yl)biphenyl assisted microwave approach for NIR-QLED applications. The structural phases and crystalline dimension were accentuated by XRD. The diffraction patterns showed a cubic phase at all Nb-contents. The TEM measurements scrutinized the increase of the particle size from 2.4 ± 0.2 nm to 9.9 ± 0.3 nm with increasing the Nb-amounts. The high resolution transmission electron microscopy (HRTEM) measurements inspected that the d-spacing increases with the increase of the Nb-atoms concentration and the prepared nanocrystals tend to grow along the (111) direction. The energy-dispersive X-ray spectroscopy (EDS) and the X-ray photoelectron spectroscopy (XPS) measurements revealed the stoichiometry of the prepared nanocrystals and the oxidation states of the Nb, Pb, and Se ions are 2+, respectively. The optical absorbance spectroscopy measurement of Pb 1-x Nb x Se QDs revealed the ability of Nb-atoms to modify the bandgaps of PbSe QDs from 1.62 eV to 1.28 eV. The luminescence intensity is increased by 10 folds and the spectral bandwidth is decreased due to the doping of PbSe QDs with Nb-atoms. The doping of PbSe QDs with Nb-atoms increases the quantum yield to 75% and decreases the Stokes shift by 9 folds. These unique characteristics may enable the Pb 1-x Nb x Se QDs to be employed for the manufacture of highly luminescent NIR-QLED devices. • A new series of Nb 1-x Pb x Se QDs was prepared using microwave approach. • The Nb 1-x Pb x Se nanocrystals have face centered cubic crystal structure. • The Nb 1-x Pb x Se QDs showed high monodisperse nanoparticles. • The Nb-dopant improved the PL intensity and narrowing the emission bandwidth. • The developed Nb 1-x Pb x Se may be served as highly luminescent NIR-QLED. [ABSTRACT FROM AUTHOR]

Chitosan flakes (CF) were modified to chitosan nanopowder (CP), using planetary ball milling for 8 h. Dynamic light scattering (DLS) revealed and high resolution transmission electron microscopy (HRTEM) confirmed the nano size of CP. Least gelation capacity (LGC) of CF (3%) and CP (4%) was manipulated to fabricate gels with 1.5, 2, and 3 fold increase in LGC. The total color difference was higher in CP than CF gels and depended on concentration. Dynamic rheometry under temperature ramping (20–80 °C and 80-20 °C) showed stable viscoelasticity. Besides, optimal structural network was observed in CP8 and CF6. During temperature ramping, the damping factor (tan δ) for all the gels was >0.1 < 1, which confirmed the elastic behavior of the gels. Power law model revealed maximum shear thinning behavior in CP8 and CF6. Rapid increase in temperature of gels during thermogravimetric analysis (TGA) and high temperature differential scanning calorimetry (HDSC) revealed more thermal stability in CP than CF gels. The interconnecting gap of polymer gel matrix revealed through scanning electron microscopy (SEM) was higher in CF than in CP gels. In conclusion, the CP gels have comparable rheology but better thermal and matrix properties that could be explored for food and pharmaceutical applications. • Chitosan powder gels at higher concentration than chitosan flakes. • Chitosan gels remain viscoelastic even under cyclic temperature ramping. • Chitosan powder gels dehydrate faster than chitosan flake gels. • Chitosan powder gels have more thermal stability to rapid heating. • Increase in solvent–particle interaction decreases the interconnecting gap of polymer matrix in powder gels. [ABSTRACT FROM AUTHOR]