Defect-Induced Self-Poling in a W18O49/PVDF Piezoelectric Energy Harvester.

W18O49 nanostructures, previously used for electrocatalysis, energy storage, electrochromic, and gas sensing applications, are incorporated in poly(vinylidene fluoride) (PVDF) in this work for mechanical energy-harvesting applications. X-ray diffraction spectroscopy (XRD), high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, differential scanning calorimetry (DSC), and the polarization-electric (P-E) field loop test prompts the addition of W18O49 nanorods in PVDF nucleates and stabilizes the piezoelectric polar γ-phase in the nanocomposite. Electrochemical experiments were employed for the first time to relate the event of the evolution of crystalline phases in PVDF to the transfer of electrons to the electrolyte from PVDF using the data from cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). High dielectric constant (ε') and low dielectric loss (ε″) values were obtained proportionately for different weight percentage additions of W18O49 nanorods in PVDF. DSC was employed to study the crystallization kinetics of γ-phase evolution. Piezoresponse force microscopy (PFM) was used to compare the piezoelectric responses from the PVDF nanocomposites. The W18O49/PVDF nanocomposite could generate a peak open circuit voltage of ∼6 V and a peak short circuit current of ∼700 nA. The W18O49/PVDF nanocomposite could light two commercial blue-light-emitting diodes (LEDs) with hand impulse imparting.

Transformation of Battery to High Performance Pseudocapacitor by the Hybridization of W18O49 with RuO2 Nanostructures.

Defects such as oxygen vacancy in the nanostructures have paramount importance in tuning the optical and electronic properties of a metal oxide. Here we report the growth of oxygen deficit tungsten oxide (W18O49) nanorods modified with ruthenium oxide (RuO2) using a simple and economical hydrothermal approach for energy storage application. In this work, a novel approach of hybridizing the W18O49 nanostructure with RuO2 to control the electrochemical performance for energy storage applications has been proposed. The result displays that the hybridization of the nanostructures plays an important role in yielding high specific capacitance of the electrode material. Due to the augmentation of W18O49 and RuO2 nanostructures, the galvanostatic charging and discharging (GCD) mechanism exhibited the transformation from the battery type characteristics of W18O49 into the typical pseudocapacitor feature of hybrid architect nanostructure due to defect creations. The electrochemical measurement of hybrid nanomaterial shows the doubling of specific capacitance to 1126 F/g and 1050 F/g in cyclic voltammetry (CV) and GCD, respectively, in comparison with W18O49 and RuO2 and earlier reports. The enhancement in the stability performance up to 3000 cycles of hybrid is indebted to the stable nature of W18O49 and the high conductivity of RuO2.

Synthesis, characterization and application of intracellular Ag/AgCl nanohybrids biosynthesized in Scenedesmus sp. as neutral lipid inducer and antibacterial agent.

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 AgNO3 precursor, respectively and Scenedesmus sp. as reducing agent. Total lipid content of the cells treated with 0.5 mM and 1 mM AgNO3 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 AgNO3 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.

Effect of Cu intercalation on humidity sensing properties of Bi2Se3 topological insulator single crystals.

Here we report the self-flux method-based synthesis of CuxBi2Se3 (x = 0, 0.13 and 0.25) topological insulator (TI) single crystals with high phase purity for humidity sensing for the first time. The samples were thoroughly characterized using XRD, FESEM, Raman, etc. The chemi-resistive humidity sensing performance of the obtained Cu0.25Bi2Se3 single crystal exhibits high sensitivity (∼849%) with decent response time (24 s) and recovery (25 s) time, negligible hysteresis (<1%) and excellent stability within an 8-97% relative humidity (RH) range at room temperature. The Freundlich isotherm model shows improved adsorption parameters (k and α) for CuxBi2Se3 (x = 0.25) over the entire RH region demonstrating the improved sensing performance of Bi2Se3 TIs with Cu intercalation. The effect of Cu intercalation in Bi2Se3 was investigated using the Langmuir adsorption isotherm (LA) model signifying the role of faster conduction of water vapour over the surface with a single active site for the adsorption-desorption process. The current experimental results suggest that CuxBi2Se3 TIs hold immense potential for important applications related to sensing.

Enhancement of field electron emission in topological insulator Bi2Se3 by Ni doping.

Nanostructures of bismuth selenide (Bi2Se3), a 3D topological insulator material, and nickel (Ni) doped Bi2Se3 samples were prepared by a hydrothermal method to explore the field emission properties. An enrichment in the field electron emission (FE) properties in terms of the threshold and turn-on field values of Bi2Se3 and Ni doped Bi2Se3 nanostructures was measured at a base pressure of ∼1 × 10-8 mbar. Using the background of the Fowler-Nordheim (FN) theory a field enhancement factor (ß) of 5.7 × 103 and a threshold field value of 2.5 V µm-1 for 7.5% Ni doped Bi2Se3 were determined by investigating the J-E plot of the FE data. The value of ß is three times higher than that of pure Bi2Se3 confirming the superior FE properties. The emission current was found to be very stable with the property of long standing durability as a negligible amount of variation was observed when measured at a constant value of 5 mA for 3 hours. The experimental results signify many opportunities for potential applications of Ni doped Bi2Se3 as a source of electrons in scanning as well as transmission electron microscopy, flat panel displays and as an X-ray generator, etc.

Enhancement of superconducting critical current density by Fe impurity substitution in NbSe2 single crystals and the vortex pinning mechanism.

Magnetization measurements have been used to determine the effect of magnetic impurities (Fe) on the Larkin-Ovchinnikov (LO) 3D collective pinning model in NbSe2 single crystals. Upon increasing the concentration of Fe impurities, the superconducting critical current density enhances appreciably compared to pure NbSe2 reflecting the fact that the addition of magnetic impurities assists in improving the practical applicability of NbSe2. The random pinning potential that is introduced by the Fe impurities also shows a considerable change in the interaction between the vortices and the core region, resulting in a competitive nature of single vortex, small bundle and large bundle pinning regimes in the H-T phase diagram. The intrinsic disorder in pure NbSe2 single crystals shows δTc flux pinning; however, the extrinsic disorder created by Fe atoms in NbSe2 shows δl flux pinning. Furthermore, the field dependence of the pinning force on both NbSe2 and Fe-incorporated NbSe2 represents the existence of point pinning and the surface pinning mechanism with a broadening of the fp curves in the Fe-incorporated single crystals.

Synthesis, Morphology, Optical and Electrical Properties of Cu(1−x) Fe(x) O Nanopowder.

The pure and Fe-doped CuO nanoparticles of the series Cu(1−x) Fe(x)O (x = 0, 0.027, 0.055, 0.097 and 0.125) were synthesized by a simple low temperature sol­gel method. Synthesized samples were characterized by a series of techniques including Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-ray electron spectroscopy (EDX), Diffuse Reflectance Spectroscopy (DRS), Fourier Transform Infrared Spectroscopy (FTIR), Hall Effect Set-up and Current­Voltage (I­V) characteristics. FESEM analysis shows formation of disc type structure increasing in grain size with Fe concentration in CuO. EDX confirmed the incorporation of iron in CuO. FTIR results of pure and Fe doped CuO samples have confirmed the formation of monoclinic CuO. The optical band gap estimated using Diffuse Reflectance Spectroscopy (DRS) shows the increment in the band gap values with Fe substitution. The Hall measurements show predominantly p-type conduction in all the samples and carrier densities decrease with increased Fe substitution. I­V characteristics of pure and Fe doped CuO nanoparticles show rectification behaviour of Schottky diodes.

Advancements in lanthanide-based perovskite oxide semiconductors for gas sensing applications: a focus on doping effects and development.

Lanthanide-based perovskite oxide semiconductors have garnered significant attention due to their exceptional electrical and sensing properties, making them promising candidates for gas sensing applications. This review paper focuses on developments and the impact of doping in lanthanide-based perovskite oxide semiconductors for gas sensing purposes. The review explores the factors influencing gas sensing performance, such as operating temperature, dopant selection, and target gas species. The role of dopants in enhancing gas sensing selectivity, sensitivity, response/recovery times, and stability is discussed in detail. Comparisons are drawn between doped perovskite oxide semiconductors, undoped counterparts, and other gas-sensing materials. Practical applications of lanthanide-based perovskite oxide semiconductor gas sensors are outlined, including environmental monitoring, industrial process control, and healthcare. The review also identifies current challenges and future perspectives in the field, such as the exploration of novel doping strategies and integration with emerging technologies like the Internet of Things (IoT). The findings emphasize the potential of these materials in advancing gas sensing technology and the importance of continued research in this field.

Disappearance of superconductivity in the solid solution between (Ca4Al2O6)(Fe2As2) and (Ca4Al2O6)(Fe2P2) superconductors.

The effect of alloying the two perovskite-type iron-based superconductors (Ca(4)Al(2)O(6))(Fe(2)As(2)) and (Ca(4)Al(2)O(6))(Fe(2)P(2)) was examined. While the two stoichiometric compounds possess relatively high T(c)'s of 28 and 17 K, respectively, their solid solutions of the form (Ca(4)Al(2)O(6))(Fe(2)(As(1-x)P(x))(2)) do not show superconductivity over a wide range from x = 0.50 to 0.95. The resultant phase diagram is thus completely different from those of other typical iron-based superconductors such as BaFe(2)(As,P)(2) and LaFe(As,P)O, in which superconductivity shows up when P is substituted for As in the non-superconducting "parent" compounds. Notably, the solid solutions in the non-superconducting range exhibit resistivity anomalies at temperatures of 50-100 K. The behavior is reminiscent of the resistivity kink commonly observed in various non-superconducting parent compounds that signals the onset of antiferromagnetic/orthorhombic long-range order. The similarity suggests that the suppression of the superconductivity in the present case also has a magnetic and/or structural origin.

Transition metal oxides as a cathode for indispensable Na-ion batteries.

The essential requirement to harness well-known renewable energy sources like wind energy, solar energy, etc. as a component of an overall plan to guarantee global power sustainability will require highly efficient, high power and energy density batteries to collect the derived electrical power and balance out variations in both supply and demand. Owing to the continuous exhaustion of fossil fuels, and ever increasing ecological problems associated with global warming, there is a critical requirement for searching for an alternative energy storage technology for a better and sustainable future. Electrochemical energy storage technology could be a solution for a sustainable source of clean energy. Sodium-ion battery (SIB) technology having a complementary energy storage mechanism to the lithium-ion battery (LIB) has been attracting significant attention from the scientific community due to its abundant resources, low cost, and high energy densities. Layered transition metal oxide (TMO) based materials for SIBs could be a potential candidate for SIBs among all other cathode materials. In this paper, we discussed the latest improvement in the various structures of the layered oxide materials for SIBs. Moreover, their synthesis, overall electrochemical performance, and several challenges associated with SIBs are comprehensively discussed with a stance on future possibilities. Many articles discussed the improvement of cathode materials for SIBs, and most of them have pondered the use of Na x MO2 (a class of TMOs) as a possible positive electrode material for SIBs. The different phases of layered TMOs (Na x MO2; TM = Co, Mn, Ti, Ni, Fe, Cr, Al, V, and a combination of multiple elements) show good cycling capacity, structural stability, and Na+ ion conductivity, which make them promising cathode material for SIBs. This review discusses and summarizes the electrochemical redox reaction, structural transformations, significant challenges, and future prospects to improve for Na x MO2. Moreover, this review highlights the recent advancement of several layered TMO cathode materials for SIBs. It is expected that this review will encourage further development of layered TMOs for SIBs.

Correction: Transition metal oxides as a cathode for indispensable Na-ion batteries.

[This corrects the article DOI: 10.1039/D2RA03601K.].

Enhancement of CO gas sensing performance by Mn-doped porous ZnSnO3 microspheres.

This work reports the synthesis of Mn-doped ZnSnO3 microspheres (Zn1-x Mn x SnO3) using a simple co-precipitation method with (x = 0 to 0.15) and characterized for structural, morphological, surface area, and sensing properties. X-ray diffraction (XRD) analysis revealed the face-centered cubic structure of Mn-doped ZnSnO3 samples. Brunauer-Emmett-Teller (BET) analysis demonstrated the variation in surface area from 15.229 m2 g-1 to 42.999 m2 g-1 with x = 0 to 0.15 in Zn1-x Mn x SnO3. XPS indicates the change in the defect levels by Mn doping, which plays a crucial role in chemical sensors. Indeed a significant increase (≈311.37%) in CO gas sensing response was observed in the x = 0.10 sample compared to pure ZnSnO3 with a simultaneous reduction in operating temperature from 250 to 200 °C. Moreover, remarkable enhancements in response/recovery times (≈6.6/34.1 s) were obtained in the x = 0.10 sample. The Mn-doped ZnSnO3 could be a promising candidate for CO gas sensing devices used for maintaining air quality.

Emergence of superconductivity in "32522" structure of (Ca3Al2O(5-y))(Fe2Pn2) (Pn = As and P).

Using a high-pressure technique, we have successfully synthesized (Ca(3)Al(2)O(5-y))(Fe(2)Pn(2)) (Pn = As and P), the first iron-based superconductors with the perovskite-based "32522" structure to be reported. The transition temperature (T(c)) is 30.2 K for Pn = As and 16.6 K for Pn = P. The emergence of superconductivity is ascribed to the small tetragonal a-axis lattice constant of the materials. From these results, an empirical relationship is established between the a-axis lattice constant and T(c) in iron-based superconductors, which offers a practical guideline for exploring new superconductors with higher T(c).

Discharge State of Layered P2-Type Cathode Reveals Unsafe than Charge Condition in Thermal Runaway Event for Sodium-Ion Batteries.

A sol-gel process followed by heat treatment derived a layered P2-type NaCoO2 cathode, which depicted unit cell parameters values of a = 2.8389 Å, c = 10.9899 Å, and V = 76.71 Å3 in powder X-ray diffraction pattern. The synthesized cathode exhibited hexagonal, 2D platelets with an ∼300 nm thickness. During the anodic and cathodic sweeps, the cyclic voltammograms revealed multiple redox peaks with the same current densities, shapes, and peak positions, associated with the highly reversible phase transition mechanism of the layered P2-type NaCoO2 cathode. The sodium cells yielded the capacities of 93/92 mAh g-1 at 0.5 C and 87/87 mAh g-1 at 1 C for the 50th charge-discharge cycles. The in situ multimode calorimetry (MMC) studies of sodium cells demonstrated a thermal explosion event, which occurred by sodium melting, short-circuit, electrode decomposition reaction, gas generation, exothermic reaction, released heat energy ,and cell gasket melting. Ultimately, the calculated released total heat energies of ∼550/740 J g-1 for in situ MMC studies and ∼312/594 J g-1 for ex situ DSC analyses (charge state at 4 V and discharge state at 2 V) show that the discharged state of sodiated layered P2-type NaCoO2 cathode material is more unsafe than the charge state. Furthermore, the ex situ differential scanning calorimetry (DSC) spectrum of a discharge state at 2 V of layered P2-type NaCoO2 revealed a decreased onset temperature (DOT) at 141 °C with two pronounced exothermic peaks at 197 and 266 °C with a released higher total heat energy of 594 J g-1 than the charge state heat energy at 312 J g-1, attributed to the higher charge onset temperature (COT) at 191 °C. Thus, the observed higher heat energy and decreased onset temperature for the discharge state at 2 V is associated with the higher Na+ ion in the discharge state of the layered P2-type NaxCoO2 cathode than that of the pristine cathode, showcasing that the layered P2-type NaCoO2 cathode is unsafe at the discharged condition for sodium-ion batteries.

Absence of an appreciable iron isotope effect on the transition temperature of the optimally doped SmFeAsO(1-y) Superconductor.

We report the iron (Fe) isotope effect on the transition temperature (T(c)) in oxygen-deficient SmFeAsO(1-y), a 50-K-class, Fe-based superconductor. For the optimally doped samples with T(c) = 54 K, a change of the average atomic mass of Fe (M(Fe)) causes a negligibly small shift in T(c), with the Fe isotope coefficient (α(Fe)) as small as -0.024 ± 0.015 (where α(Fe)=-d lnT(c)/dlnM(Fe)). This result contrasts with the finite, inverse isotope shift observed in optimally doped (Ba,K)Fe2As2, indicating that the contribution of the electron-phonon interaction markedly differs between these two Fe-based high-T(c) superconductors.

Gold nanoparticle-cellulose/PDMS nanocomposite: a flexible dielectric material for harvesting mechanical energy.

Cellulose is an abundant natural piezoelectric polymer and is also a renewable resource of significant importance. Here in this work we realize an enhanced piezoelectric response with cellulose in a polydimethylsiloxane (PDMS) matrix by forming a nanocomposite with the incorporation of gold nanoparticles (Au NPs). In the Au NP-cellulose/PDMS nanocomposite an enhancement in the dielectric constant is recorded due to the presence of cellulose alone and a reduction of dielectric loss is found owing to the presence of Au NPs. This opens the possibility of realizing a nanodielectric material from the nanocomposite under current study. This also indicates the significant potential of the nanocomposite towards energy conversion applications. Subsequently, a mechanical energy harvesting device was fabricated using the Au NP-cellulose/PDMS nanocomposite, which is named as a piezoelectric nanogenerator (PNG). The PNG delivered an enhanced open circuit voltage of ∼6 V, short circuit current of ∼700 nA and a peak power density of 8.34 mW m-2 without performing any electrical poling steps. The PNG could charge a 10 µF capacitor to 6.3 V in 677 s and could light two commercial blue light emitting diodes (LEDs) simultaneously. The PNG exhibited a good energy conversion efficiency of 1.8%. A touch sensor application of the PNG is also shown.

Defect Mediated W18O49 Nanorods Bundle for Nonenzymatic Amperometric Glucose Sensing Application.

In this work, we have successfully proclaimed the importance of defect prone nanostructure on to the electrode surface for the promising glucose sensing applications. Oxygen-deficient W18O49 moieties with multiple valences W6+ and W5+ have been investigated as an efficient electrocatalyst for the nonenzymatic glucose sensing. In order to highlight the importance of the defect, WO3 nanomaterial's electrode has also been synthesized and tested for glucose sensing. W18O49 delivers a larger Brunauer-Emmett-Teller (BET) surface area and mesoporous pores which have contributed to the high sensitivity performances. The oxygen vacant W18O49 nanostructure has been synthesized by a facile solvothermal route and has retained interconnected nanorods morphology. Compared with non-oxygen-deficient WO3, this defect prone version of tungsten oxide (W18O49) possesses a doubled linearity range up to 1.6 mM maximum electrooxidation toward glucose by giving a 1.6 times higher sensitivity of 167 µA mM-1 cm-2, 0.5 times lower detection limit of 0.02 µM (S/N = 3), and a swift response time of 5 s.

Influence of pressure on the transport, magnetic, and structural properties of superconducting Cr0.0009NbSe2 single crystal.

We investigate the superconducting critical current density (J c), transition temperature (T c), and flux pinning properties under hydrostatic pressure (P) for Cr0.0009NbSe2 single crystal. The application of P enhances T c in both electrical resistivity (∼0.38 K GPa-1: 0 ≤ P ≤ 2.5 GPa) and magnetization (∼0.98 K GPa-1: 0 ≤ P ≤ 1 GPa) measurements, which leads to a monotonic increase in J c and flux pinning properties. The field-dependent J c at various temperatures under P is analyzed within the collecting pinning theory and it shows that δT c pinning is the crossover to δl pinning above the critical pressure (P c ∼0.3 GPa). Our systematic analysis of the flux pinning mechanism indicates that both the density of pinning centers and pinning forces greatly increase with the application of P, which leads to an enhancement in the vortex state. Structural studies using synchrotron X-ray diffraction under pressure illustrate a stable hexagonal phase without any significant impurity phase and lattice parameter reduction with P shows highly anisotropic nature.

Inverse iron isotope effect on the transition temperature of the (Ba,K)Fe2As2 superconductor.

We report that the (Ba,K)Fe(2)As(2) superconductor (transition temperature, T(c) approximately 38 K) has an inverse iron isotope coefficient alpha(Fe) = -0.18(3) (where T(c) approximately M(-alphaFe) and M is the iron isotope mass); i.e., the sample containing the large iron isotope mass depicts a higher T(c). Systematic inverse shifts in T(c) were clearly observed between the samples using three types of Fe isotopes ((54)Fe, natural Fe, and (57)Fe). This indicates the first evidence of the inverse isotope effect in high-T(c) superconductors. This anomalous mass dependence on T(c) implies an exotic coupling mechanism in Fe-based superconductors.

A quarter of a century after its synthesis and with >200 papers based on its use, `Co(CO3)0.5(OH)·0.11H2O' proves to be Co6(CO3)2(OH)8·H2O from synchrotron powder diffraction data.

The successful attempt to solve the crystal structure of Co(CO3)0.5(OH)·0.11H2O (denoted CCH), based on synchrotron powder diffraction data, leads to a drastic revision of the chemical formula to Co6(CO3)2(OH)8·H2O [hexacobalt(II) bis(carbonate) octahydroxide monohydrate] and to a hexagonal cell instead of the orthorhombic cell suggested previously [Porta et al. (1992). J. Chem. Soc. Faraday Trans. 88, 311-319]. This results in a new structure-type related to malachite involving infinite chains of [CoO6] octahedra sharing edges along a short c axis, delimiting tunnels having a three-branched star section. All reports discussing cobalt hydroxycarbonates (CCH) without any structural knowledge and especially its topotactic decomposition into Co3O4 have, as a result, to be reconsidered.