Comparative first principles investigation on the structural, optoelectronic and vibrational properties of strain-engineered graphene-like AlC3, BC3and C3N monolayers.

Three cardinal two-dimensional semiconductorsviz., AlC3, BC3and C3N, closely resembling the graphene structure, are intriguing contenders for emerging optoelectronic and thermomechanical applications. Starting from a critical stability analysis, this density functional theory study delves into a quantitative assessment of structural, mechanical, electronic, optical, vibrational and thermodynamical properties of these monolayers as a function of biaxial strain(ε)in a sublinear regime(-2%⩽ε⩽4%)of elastic deformation. The structures with cohesive energies slightly smaller than graphene, manifest exceptional mechanical stiffness, flexibility and breaking stress. The mechanical parameters have been deployed to further cultivate acoustic attributes and thermal conductivity. The hexagonal structures with mixed ionic-covalent molecular bonds have indirect electronic band-gap and work-function acutely sensitive toε. Dispersions of optical dielectric function, energy loss, refractive index, extinction coefficient, reflectivity, absorption coefficient and conductivity are deciphered in the UV-Vis-NIR regime against strain, where particular frequency bands featuring high polarization, dissipation, absorbance or reflectance are identified. Phonon band-structure and density of states testify dynamic stability in the ground state for all systems except the compressed ones. A comprehensive group theoretical analysis is performed to cultivate rotational; infrared and Raman-active modes, and the nature of molecular vibrations is delineated. The red-shifting of phonon bands andE2g/A1gRaman peaks with increasingε, associates estimation of Grüneisen parameter. Finally, strain-induced alterations of thermodynamic quantities such as entropy, enthalpy, free energy, heat capacity and Debye temperature are studied, followed by a molecular dynamics-based stability assessment under canonical ensemble.

CsPbI3-PVDF Composite-Based Multimode Hybrid Piezo-Triboelectric Nanogenerator: Self-Powered Moisture Monitoring System.

For several decades, the development of potential flexible electronics, such as electronic skin, wearable technology, environmental monitoring systems, and the internet of Things network, has been emphasized. In this context, piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs) are highly regarded due to their simple design, high output performance, and cost-effectiveness. On a smaller scale, self-powered sensor research and development based on piezo-triboelectric hybrid nanogenerators have lately become more popular. When a material in the TENG is a piezoelectric material, these two distinct effects can be coupled. Herein, we developed a multimode hybrid piezo-triboelectric nanogenerator using the CsPbI3-PVDF composite. The addition of CsPbI3 to PVDF significantly enhances its electroactive phase and dielectric property, thereby enhancing its surface charge density. 5 wt % CsPbI3 incorporation in poly(vinylidene difluoride) (PVDF) results in a high electroactive phase (FEA) value of >90%. Moreover, CsPbI3-PVDF composite-based PENGs were fabricated in three modes, viz., nanogenerators in contact-separation mode (TECS), single electrode mode (TESE), and sliding mode (TES), and the output performance of all the devices was investigated. The fabricated TECS, TESE, and TES reveal peak output powers of 3.08, 1.29, and 0.15 mW at an external load of 5.6 MΩ. Through analysis of the contact angle measurement and experimental quantification, the hydrophilicity of the composite film has been identified. The hydrophobicity and moisture absorption capacity of CsPbI3-PVDF film make it an attractive option for self-powered humidity monitoring. The TENGs effectively powered several low-powered electronic devices with just a few human finger taps. This study offers a high-performance PTENG device that is reliant on ambient humidity, which is a helpful step toward creating a self-powered sensor.

Strong non-linear optical response of Sb2Se3 nanorods in a liquid suspension based on spatial self-phase modulation and their all-optical photonic device applications.

The field of nonlinear optics is constantly expanding and gaining new impetus through the discovery of fresh nonlinear materials. Herein, for the first time, we have performed spatial self-phase modulation (SSPM) experiments with an emerging anisotropic Sb2Se3 layered material in a liquid suspension for an all-optical diode and all-optical switching application. The third-order broadband nonlinear optical susceptibility (χ(3)single layer ∼ 10-9 esu) and nonlinear refractive index (n2 ∼ 10-6 cm2 W-1) of Sb2Se3 have been determined using a 671 nm laser beam. This result could be unambiguously explained by the anisotropic hole mobility of Sb2Se3. The linear relationship of χ(3) and carrier mobility emphasizes the establishment of nonlocal hole coherence, the origin of the diffraction pattern. Consequently, the time evolution of diffraction rings follows the 'Wind-Chime' model. A novel photonic diode based on Sb2Se3/SnS2 has been demonstrated using the nonreciprocal propagation of light. The self-phase modulation (SPM) technique uses laser lights of different wavelengths and intensities to demonstrate the all-optical logic gates, particularly OR logic gates. The exploration of nonlinear optical phenomena in Sb2Se3 opens up a new realm for optical information processing and communication. We strongly believe that this result will help to underpin the area of optical nonlinearities among its various applications.

Highly exfoliated graphitic carbon nitride for efficient removal of wastewater pollutants: Insights from DFT and statistical modelling.

The present work entails the synthesis of thermally modified graphitic carbon nitride (GCN) using a two-step thermal treatment procedure and its subsequent use in the photocatalytic reduction of toxic pollutants such as rhodamine B dye (RhB) and chromium (VI) (Cr(VI)) from aquatic environments. The as-synthesised exfoliated GCN (GCNX) is characterised by X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), Brunauer-Emmett-Teller analysis (BET), diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). These characterisations helped to elucidate the phase formation, chemical structure, composition, surface area, optical properties, and morphology of the sample. With assistance from a visible light source, GCNX can degrade RhB dye within 30 min in the presence of hydrogen peroxide (H2O2) and reduce Cr(VI) to Cr(III) in under 2 h in the presence of formic acid (FA/HCOOH). Variations in different catalytic parameters, including catalyst amount, pH of the solution, initial RhB or Cr(VI) concentration, and variation in H2O2 or FA concentration, are performed to inspect their effects on the photodegradation activity of GCNX. Moreover, the GCNX catalyst exhibits impressive stability and reusability. A thorough statistical evaluation follows the response surface methodology to understand the complex interaction between the factors contributing to the catalytic activity. The band alignment of differently functionalised GCN blocks in their pristine form and their H2O2/FA-adsorbed states is investigated using first-principles calculations to provide a further understanding of the RhB and Cr(VI) reduction mechanisms. The modified GCN can thus be effectively employed as a low-cost material for removing contamination from aquatic environments.

Self-Charging Piezo-Supercapacitor: One-Step Mechanical Energy Conversion and Storage.

With the contemplations of ecological and environmental issues related to energy harvesting, piezoelectric nanogenerators (PNGs) may be an accessible, sustainable, and abundant elective wellspring of energy in the future. The PNGs' power output, however, is dependent on the mechanical energy input, which will be intermittent if the mechanical energy is not continuous. This is a fatal flaw for electronics that need continuous power. Here, a self-charging flexible supercapacitor (PSCFS) is successfully realized that can harvest sporadic mechanical energy, convert it to electrical energy, and simultaneously store power. Initially, chemically processed multimetallic oxide, namely, copper cobalt nickel oxide (CuCoNiO4) is amalgamated within the poly(vinylidene fluoride) (PVDF) framework in different wt % to realize high-performance PNGs. The combination of CuCoNiO4 as filler creates a notable electroactive phase inside the PVDF matrix, and the composite realized by combining 1 wt % CuCoNiO4 with PVDF, coined as PNCU 1, exhibits the highest electroactive phase (>86%). Under periodic hammering (∼100 kPa), PNGs fabricated with this optimized composite film deliver an instantaneous voltage of ∼67.9 V and a current of ∼4.15 µA. Furthermore, PNG 1 is ingeniously integrated into a supercapacitor to construct PSCFS, using PNCU 1 as a separator and CuCoNiO4 nanowires on carbon cloth (CC) as the positive and negative electrodes. The self-charging behavior of the rectifier-free storage device was established under bending deformation. The PSCFS device exhibits ∼845 mV from its initial open-circuit potential ∼35 mV in ∼220 s under periodic bending of 180° at a frequency of 1 Hz. The PSCFS can power up various portable electronic appliances such as calculators, watches, and LEDs. This work offers a high-performance, self-powered device that can be used to replace bulky batteries in everyday electronic devices by harnessing mechanical energy, converting mechanical energy from its environment into electrical energy.

Significant enhancement of lattice thermal conductivity of monolayer AlN under bi-axial strain: a first principles study.

Using rigorous ab initio calculations within the framework of phonon Boltzmann transport theory, we have carried out a detailed investigation to probe the effects of uniform bi-axial strain and finite size on the lattice thermal conductivity (κ) of monolayer AlN. We show that implementation of bi-axial tensile strain can shoot up the value of κ of monolayer AlN by a large amount unlike in the case of analogous 2D materials. The value of κ for monolayer AlN is calculated to be 306.5 W m-1 K-1 at room temperature (300 K). The value of κ can be raised by one order of magnitude to up to 1500.9 W m-1 K-1 at 300 K by applying a bi-axial strain of about 5%. A similar trend persists when the finite size effect is incorporated in the calculation. As the sample size is varied from 10 nm to 10 000 nm along with increasing tensile strain, a huge variation of κ (from 20.7 W m-1 K-1 to 558.9 W m-1 K-1) is observed. Our study reveals that the major part of the lattice thermal conductivity of monolayer AlN comes from the contribution of the flexural acoustic (ZA) phonon modes. The anomalous trend of drastic increment in the value of κ with tensile strain is found to be a direct effect of interaction between nitrogen lone-pair electrons and bonding electrons in the ionic lattice which results in the reduction of phonon anharmonicity with increasing tensile strain. Our study provides a detailed analysis of the strain modulated and size-tuned thermal transport properties of monolayer AlN revealing that it is an impactful 2D material to be used in thermal management devices.

Solution-processed light-induced multilevel non-volatile wearable memory device based on CsPb2Br5 perovskite.

Despite the recent advancements in memory devices, the quest for building materials with low power consumption is still on, with the ultimate focus on the durability of the system and reliability and reproducibility of its performance. Halide perovskites (HPs), which have several intriguing photoelectrical traits, have recently been utilized for memory applications; one of the highlights of these materials is the ionic-motion-based fast switching in their crystal structure. In this work, a CsPb2Br5 film is applied as a switching layer to implement memory devices with a flexible Al/CsPb2Br5/ITO-PET structure. The device exhibits a pronounced bipolar resistive switching (RS) characteristic at low operating voltage. The as-fabricated flexible device presented RS features with no initial forming process, concentrated distributions of high and low resistance states (HRS and LRS), uniform switching, endurance over 100 cycles, and a long retention time of 103 s with a high on/off ratio of around 102. Multilevel data-storage capability was also observed via subtle control of the compliance current (CC). Considering the current demand for smart, wearable, and flexible electronic gadgets, the current-voltage (I-V) characteristics of the as-fabricated all-inorganic halide-perovskite-based memory device were further explored under different bending conditions to determine its electrical reliability and mechanical stability. This flexible device exhibited no discernible difference in device performance under flat or bent conditions, and the performance remained nearly the same even after 500 bending cycles. In addition to control of the RS effect of the device using an electrical field, the performance of the device under light was also explored. Blue light modulates the resistive states by regulating the condition of photo-generated electron-hole pairs, and the SET and RESET voltages are changed from 2.34 to 2.14 V and from -2.04 to -1.90 V, respectively. The observed RS behavior is explained on the basis of the creation and partial annihilation of conductive multifilaments, which is dominated by the migration of bromine ions and their associated vacancies in the HP layer. We believe that this work will offer a new context to understand the intrinsic characteristics of HPs for RS applications at low voltage and validate their potential in the design of next-generation stable and nonvolatile memory devices for future flexible electronic systems.

Amalgamation of MnWO4 nanorods with amorphous carbon nanotubes for highly stabilized energy efficient supercapacitor electrodes.

Enhanced electrochemical performance of supercapacitors can be achieved through optimal hybridization of electroactive nanomaterials, as it effectively increases the overall surface area and ensures greater electrolyte-electrode interaction. This work reports the realization of a manganese tungstate and amorphous carbon nanotube (MnWO4-aCNT) hybrid and its utilization as the electrodes for a solid-state asymmetric supercapacitor. Large-scale synthesis of aCNTs was carried out via an economical solid-state reaction at low temperature and the walls of these nanotubes were decorated with MnWO4 nanorods via a surfactant-free in situ hydrothermal process. The as-fabricated electrode based on this hybrid over nickel foam delivered a high specific capacitance of 542.18 F g-1 at a scan rate of 2 mV s-1, which is much superior to the values of the structural units separately. This MnWO4-aCNT based electrode showed a high-rate capacity with ∼100% capacitance retention and a coulombic efficiency of ∼100% even after operation for 15 000 cycles. A solid-state asymmetric supercapacitor based on this hybrid attained an energy density of 5.6 W h kg-1 and a power density as high as 893.6 W kg-1. Significantly enhanced electrochemical behaviour registered from the hybrid sample is accounted for by its enhanced surface area and thereby greater number of redox reaction sites along with the positive synergetic effect of the building blocks. This study unlocks further exploration possibilities with other types of aCNT-based hybrid materials for the development of highly stable, non-toxic and cost-effective sustainable energy storage systems.

Incorporation of V2O5 nanorods into perovskite photodetectors as an alternative approach to enhance device performance: a step towards stability against ambient water species.

Numerous reports have been made in the literature on the usability of a halide perovskite, namely methyl ammonium lead iodide (CH3NH3PbI3), as a light harvesting material. Suitable optimization in material composition and synthesis has led to an improvement in device performance. However, the susceptibility of CH3NH3PbI3 towards atmospheric water is an alarming issue which hinders its long-term application in day-to-day life. Herein, low temperature synthesized V2O5 nanorods are incorporated into the CH3NH3PbI3 matrix to facilitate carrier dynamics by interface engineering. The optimized hybrid sample exhibits a much improved and stable photo-response behaviour than the pristine building blocks. Additionally, the modified perovskite shows improved hydrophobicity in the form of small-scale surface undulations due to the incorporation of V2O5 nanorods into it. This way, we have solved two problems with one single action, firstly by improving the device performance and secondly by stabilizing the sample against ambient water species.

In-Situ Grown ZnS Nanoparticles on Amorphous Carbon Nanotubes Improved Cold Cathode Emission and Photoluminescence.

The current work reveals notable increase in field emission and photoluminescence characteristics of amorphous carbon nanotubes after forming its composite with In-Situ grown zinc sulfide (ZnS) nanoparticles. An easy chemical technique was employed to synthesize amorphous carbon nanotubes (ACNTs) and then ZnS nanoparticles were grown on them through an In-Situ solvothermal process. The morphology of the ZnS-ACNTs hybrid material was investigated through scanning electron microscope. Photoluminescence and field emission studies of the material were carried out as well in order to realize the applications. Substantial increase in photoluminescence intensity was found for ZnS-ACNTs hybrid material in comparison with pure amorphous carbon nanotubes, the hybrid also turned out as a better field-emitter than pure amorphous carbon nanotubes. Turnon field for ZnS-ACNTs composite decreased to 6 Vµm-1 which was 8 Vµm-1 in case of pure amorphous carbon nanotubes. A simulation analysis following finite element modelling method was carried out which ensured the improvement as field emitter for amorphous carbon nanotubes after ZnS nanoparticles were grown on them. Altogether the hybrid material proved to be a potential candidate for luminescent and cold cathode applications.

Size-modulation of functionalized Fe3O4: nanoscopic customization to devise resolute piezoelectric nanocomposites.

Magnetite (Fe3O4), a representative relaxor multiferroic material, possesses fundamentally appealing multifaceted size-dependent properties. Herein, to evaluate a prototype spinel transition metal oxide (STMO), monodispersed and highly water-dispersible spherical magnetite nanoparticles (MNPs) with an enormous size range (3.7-242.8 nm) were synthesized via a facile microwave-assisted and polyol-mediated solvothermal approach at a controlled temperature and pressure using unique crystallite growth inhibitors. The excellent long-term colloidal stability of the MNPs in a polar environment and increase in their zeta potential confirmed the coordinative effect of the carboxylate groups derived from the covalent surface functionalization, which was also validated by FTIR spectroscopy, TGA and XPS analysis. The optical bandgap (Eg) between the crystal field split-off bands, which was calculated using the absorption spectra, increased gradually with a decrease in size of the MNPs within a broad UV-Vis range (1.59-4.92 eV). The red-shifting of the asymmetric Raman peaks with a smaller size and short-range electron-phonon coupling could be explained by the modified phonon confinement model (MPCM), whereas ferrimagnetic nature rejigged by superparamagnetism was verified from Mössbauer analysis. These stoichiometric, non-toxic, polar and magnetic nanocrystals are not only ideal for biomedical applications, but also suitable as electroactive porous host networks. Finally, the size-modulated MNPs were incorporated in poly(vinylidene fluoride) [PVDF]-based polytype nanogenerators as an electret filler to demonstrate their piezoelectric performance (VOC∼115.95 V and ISC∼1.04 µA), exhibiting substantial electromagnetic interference shielding.

Negative capacitance switching in size-modulated Fe3O4 nanoparticles with spontaneous non-stoichiometry: confronting its generalized origin in non-ferroelectric materials.

Persistent low-frequency negative capacitance (NC) dispersion has been detected in half-metallic polycrystalline magnetite (Fe3O4) nanoparticles with varying sizes from 13 to 236 nm under the application of moderate dc bias. Using the Havriliak-Negami model, 3D Cole-Cole plots were employed to recapitulate the relaxation times (τ) of the associated oscillating dipoles, related shape parameters (α, ß) and resistivity for the nanoparticles with different sizes. The universal Debye relaxation (UDR) theory requires a modification to address the shifted quasi-static NC-dispersion plane in materials showing both +ve and -ve capacitances about a transition/switching frequency (f0). A consistent blue-shift in 'f0' is observed with increasing external dc field and decreasing particle size. Based on this experimental data, a generalized dispersion scheme is proposed to fit the entire positive and negative capacitance regime, including the diverging transition point. In addition, a comprehensive model is discussed using phasor diagrams to differentiate the underlying mechanisms of the continuous transition from -ve to +ve capacitance involving localized charge recombination or time-dependent injection/displacement currents, which has been adequately explored in the scientific literature, and the newly proposed 'capacitive switching' phenomenon. An inherent non-stoichiometry due to iron vacancies [Fe3(1-δ)O4], duly validated from first principles calculations, builds up p-type nature, which consequently promotes more covalent and heavier dipoles and slows the dipolar relaxations; this is incommensurate with Maxwell-Wagner interfacial polarization (MWIP) dynamics. This combinatorial effect is likely responsible for the sluggish response of the associated dipoles and the stabilization of NC.

Blue Emitting BaAl2O4:Ce3+ Nanophosphors with High Color Purity and Brightness for White LEDs.

In this work, strongly blue emitting Ce3+-activated BaAl2O4 nanophosphors were successfully synthesized by a sol-gel technique. The crystal structure, morphology, and microstructure of the nanophosphors have been studied by X-ray powder diffraction, field emission scanning electron microscopy, and high-resolution transmission electron microscopy. The photoluminescence spectra show the impact of concentration variation of Ce3+ on the photoluminescence emission of the phosphor. These nanophosphors display intense blue emission peaking at 422 nm generated by the Ce3+ 5d → 4f transition under 350 nm excitation. Our results reveal that this nanophosphor has the capability to take part in the emergent domain of solid-state lighting and field-emission display devices.

CsPbBrCl2/g-C3N4 type II heterojunction as efficient visible range photocatalyst.

Photocatalytic activity of low band gap semiconductor largely restrained by high recombination rate of photogenerated charge carriers. To enhance the catalytic performance numerous protocols were adopted amongst which designing of novel hybrid via coupling of semiconductors are very intriguing from modest application point of view. Here, we report facile realization of type II heterojunctions embracing polymeric graphitic carbon nitride (g-C3N4/GCN) and all-inorganic cesium lead halide perovskite (CsPbBrCl2) for degradation complex organic effluents under visible-light illumination. Synthesized hybrid presented much improved performance in toxic cationic and anionic dyes degradation as compared to individual building units. Signature of favorable staggered gap junction's formation at interface was confirmed via Mott-Schottky analysis. Such kind of junctions delay the recombination of photogenerated electron holes and facilitates active radical generation at catalyst surface thereby ensures improved photocatalytic performance. Charge transfer process in heterojunction further illustrated via Density functional theory (DFT) based calculations. Several scavenger tests have been performed to examine the impact of different active radicals in the photocatalysis which suggests manifold performance improvement in the presence of very small concentrations of EDTA. A plausible photocatalytic mechanism in accordance with the type II junction has been proposed.

Enhanced Photoluminescence Properties of Low-Dimensional Eu3+-Activated Y4Al2O9 Phosphor Compared to Bulk for Solid-State Lighting Applications and Latent Fingerprint Detection-Based Forensic Applications.

In recent years, nanoscale phosphors have become vital in optoelectronic applications and to understand the improved performance of nanophosphors over bulk material, detailed investigation is essential. Herein, trivalent europium-activated Y4Al2O9 phosphors were developed by solid-state reaction and solvothermal reaction methods and their performance as a function of their dimension was studied for various applications. Under 394 nm optical excitation, the photoluminescence (PL) emission, excited state lifetime of the nanophosphor, exhibits greater performance than its bulk counterpart. The homogeneous spherical structure of the nanophosphors as compared with solid lumps of bulk phosphors is the basis for almost 40% of the enhancement in nanophosphors' intense red emission compared to the bulk. Moreover, the thermal stability of the nanophosphor is much better than the bulk phosphor, which clearly indicates a key advantage of nanophosphor. The superior performance of Eu3+-doped Y4Al2O9 nanophosphors over their bulk counterparts has been demonstrated for industrial phosphor-converted light-emitting diodes and visualization of latent fingerprint.

Resonant energy transfer in a van der Waals stacked MoS2 - functionalized graphene quantum dot composite with ab initio validation.

Graphene-based van der Waals (vdW) heterostructures can facilitate exciting charge transfer dynamics in between structural layers with the emission of excitonic quasi-particles. However, the chemical formation of such heterostructures has been elusive thus far. In this work, a simple chemical approach is described to form such van der Waals (vdW) heterostructures using few layer MoS2 sheet embedded quantum dots (QDs) and amine-functionalized graphene quantum dots (GQDs) to probe the energy transfer mechanism for tunable photoluminescence (PL). Our findings reveal an interesting non-radiative Förster-type energy transfer with the quenching of functional GQD PL intensity after GQD/MoS2 composite formation, which validates the existing charge transfer dynamics analogous to 0D and 2D systems. The non-radiative type of energy transfer characteristic from GQD into the MoS2 layer through vdW interactions has been confirmed by photoluminescence, time decay analyses and ab initio calculations with the shifting of the Fermi level in the density of states towards the conduction band in the stacked configuration. These results are encouraging for the fundamental exploration of optical properties in other chemically prepared QD/2D based heterostructures to understand the charge transfer mechanism and fingerprint luminescence quenching for future optoelectronic device and optical sensing applications.

White light emitting MgAl2O4:Dy3+,Eu3+ nanophosphor for multifunctional applications.

Feeble white emission with a low Colour Rendering Index (CRI) has become the principal gridlock for the extensive commercialization of phosphor converted white LEDs (pc-WLEDs). Fusion of red, green and blue emitting rare-earth (RE) ions in a suitable host can overcome these drawbacks but the energy migration between multiple RE ions at single excitation wavelength defines the key standpoint in designing such white light emitting phosphors. Apart from the abovementioned obstacles, recently traditional optical temperature sensors based on RE ions have faced difficulties due to their low relative sensitivity and large detection error. Keeping these points in mind, in this work, a series of MgAl2O4:Dy3+,Eu3+ nanophosphors are synthesized among which 2% Dy3+,0.2% Eu3+ doped MgAl2O4 nanophosphors demonstrate strong white emission with CIE co-ordinates of (0.31, 0.33), and high quantum yield (∼67%), which could be directly utilized for pc-WLED based solid state lighting devices. Detailed investigation of PL properties reveals that Eu3+ ions can be well sensitized by Dy3+ under near-ultraviolet excitation of 351 nm. Dexter's theory & Reisfeld's approximation are employed for an in-depth analysis of the inter-RE energy transfer (ET) mechanism, which signposts that the dipole-quadrupole interaction phenomenon is responsible for the ET process from Dy3+ to Eu3+. Additionally, the validated ET plays a pivotal role in demonstrating the self-referencing ratiometric temperature sensor behaviour supported by a distinct high temperature thermal quenching trend between Dy3+ and Eu3+ ions. Hence the obtained nanophosphors are highly promising for utilizing in WLED based solid state lighting and self-referencing ratiometric temperature sensor applications.

Neutralizing the Charge Imbalance Problem in Eu3+-Activated BaAl2O4 Nanophosphors: Theoretical Insights and Experimental Validation Considering K+ Codoping.

In recent years, rare-earth-doped nanophosphors have attracted great attention in the field of luminescent materials for advanced solid-state lighting and high-resolution display applications. However, the low efficiency of concurrent red phosphors creates a major bottleneck for easy commercialization of these devices. In this work, intense red-light-emitting K+-codoped BaAl2O4:Eu3+ nanophosphors having an average crystallite size of 54 nm were synthesized via a modified sol-gel method. The derived nanophosphors exhibit strong red emission produced by the 5D0 → 7F J (J = 0, 1, 2, 3, 4) transitions of Eu3+ upon UV and low-voltage electron beam excitation. Comparative photoluminescence (PL) analysis is executed for Eu3+-activated and K+-coactivated BaAl2O4:Eu3+ nanophosphors, demonstrating remarkable enhancement in PL intensity as well as thermal stability due to K+ codoping. The origin of this PL enhancement is also analyzed from first-principles calculations using density functional theory. Achievement of charge compensation with the addition of a K+ coactivator plays an important role in increasing the radiative lifetime and color purity of the codoped nanophosphors. Obtained results substantially approve the promising prospects of this nanophosphor in the promptly growing field of solid-state lighting and field emission display devices.

Amorphous Carbon Nanotubes-Nickel Oxide Nanoflower Hybrids: A Low Cost Energy Storage Material.

Amorphous carbon nanotubes (a-CNTs) have been synthesized by a simple low-temperature process and have been grafted with chemically synthesized nickel oxide microflowers with different concentrations. The phase and morphology of the as-prepared pure and hybrid samples were characterized by X-ray diffraction and field emission scanning and transmission electron microscopes. Thermal properties of the samples were estimated by using thermal gravimetric and differential thermal analysis. The optical properties of the sample were characterized by UV-vis spectroscopic, Raman spectroscopic, and Fourier-transformed infrared spectroscopic analysis. The electrochemical performance of all hybrid samples has been done in detail for different scan rates as well as from charge-discharge analysis. It has been seen that because of the nickel oxide grafting, the electrochemical performance of pure a-CNTs gets enhanced significantly. The value of the specific capacitance of the hybrid comes out to be around 120 F/g for the best sample, which is almost 12 times higher compared to that of the pure a-CNTs. The result has been explained in terms of change in effective surface area as well as change in conductivity of the hybrid samples.

Band edge tuned ZnxCd1-xS solid solution nanopowders for efficient solar photocatalysis.

This work highlights the synthesis of zinc blende ZnxCd1-xS ternary solid solutions with a tunable bandgap. Composition dependent band gaps are realized due to the effective band edge tuning of the solid solutions which in turn show decent photocatalytic behaviour. The bandgap of ZnxCd1-xS increases as Zn composition increases. It is interesting to note that the highest catalytic activity is observed for Zn0.8Cd0.2S (Eg = 2.83 eV) in the visible spectra due to the presence of defect states in the bandgap around 2.35 eV which has been explicated according to the results of photoluminescence spectra. Density of states (DOS) analysis provides further theoretical insight into the more negative conduction band edge for x = 0.8 than other samples. It also determines generation of intermediate states due to sulfur vacancy which is responsible for more electron-hole generation and the highest rate of Methyl Orange (MO) degradation under natural sunlight irradiation.