Zinc ferrite (ZnFe2O4) nanoparticles were synthesized using a hydrothermal method and annealed at various temperatures ranging from 250 degrees C-750 degrees C. Comprehensive characterization was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), Fourier transform infrared (FTIR) spectroscopy, photoluminescence (PL), and vibrating sample magnetometry (VSM). XRD confirmed the formation of a cubic spinel structure, with crystallite sizes varying between 30 and 40 nm for the annealed nanoparticles. It is observed from the BET analysis that the surface area and pore volume are indirectly proportional to the annealing temperature of the ZnFe2O4 nanoparticles. The FTIR spectra confirmed the presence of metal-oxygen vibrations, particularly Zn-O and Fe-O bonds, and the PL studies revealed emission peaks indicating charge carrier recombination. Magnetic measurements revealed that the 750 degrees C annealed ZnFe2O4 nanoparticles had a saturation magnetization (Ms) of 4.04 emu/g, coercivity (Hc) of 14.28 Oe, and retentivity (Mr) of 0.0029 emu/g. ESR spectroscopy provided a g-value of 2.00 and a peak-to-peak linewidth (Delta Hpp) of 67.008 mT. The photocatalytic activity of the nanoparticles was evaluated for the degradation of methylene blue under visible light irradiation, where TA = 500 degrees C and TA = 750 degrees C ZnFe2O4 nanoparticles exhibited the highest degradation efficiencies of 53 %. Antibacterial studies demonstrated that the 750 degrees C annealed ZnFe2O4 nanoparticles were effective against B. subtilis and P. aeruginosa, with zones of inhibition of 22 mm and 24 mm, respectively, comparable to those of the control. Density functional theory (DFT) calculations were performed to obtain insights into the electronic and optical properties of the ZnFe2O4 system. The DFT results imply that the electronic structure is fully dominated by the 3d electrons of the transition metal atoms and the 2p of the oxygen atoms. The calculated optical band gap of 1.74 eV closely aligns with the optical properties observed experimentally 1.82 eV for TA = 500 degrees C, thereby validating the accuracy of the experimental findings. Additionally, the DFT analysis highlights the isotropic nature of the material with respect to the optical response, offering deeper insight into its suitability for photocatalytic applications. The combination of superior optical, magnetic, and structural properties, along with strong photocatalytic and antibacterial activities, makes zinc ferrite nanoparticles annealed at 750 degrees C promising candidate for environmental and biomedical applications.

Abstract To investigate solar activity dependence of the coupling between medium-scale traveling ionosphere disturbance (MSTID) and sporadic E (Es) layer, we analyzed the total electron content (TEC) obtained from a Japanese global positioning system (GPS) receivers and ionosonde at Kokubunji (35.7° N, 139.5° E) in Japan during the summer period of May–August from 1998 to 2019. To obtain perturbation TEC caused by MSTIDs, the detrended TEC is calculated by subtracting 1-h moving averages from the measured TEC for each pair of GPS satellite and receiver. The detrended TEC data are mapped on to the geographical coordinates to make detrended 2-D maps with spatial resolution of 0.15° × 0.15° in longitude and latitude. The MSTID activity is defined as a ratio of the standard deviation to the background TEC over Kokubunji in Japan. Day-to-day variations of the MSTID activity during summer nights was compared to Es layer parameters [critical frequency ( $${f}_{o}Es$$ f o E s ) and $${\Delta f}_{o-b}\equiv {f}_{o}Es-{f}_{b}E$$ Δ f o - b ≡ f o E s - f b E , where $${f}_{{\text{b}}}Es$$ f b E s is blanketing frequency] derived from ionosonde station at Kokubunji. We have found that the correlation coefficient between the MSTID activity and $${f}_{o}Es$$ f o E s ( $${\Delta f}_{o-b}$$ Δ f o - b ) between 1998 and 2019 is 0.5 3 (0.46) on average, suggesting that there is an electrodynamical coupling between the Es layer and F region could generate nighttime MSTIDs. We also have found that the correlation coefficient positively correlates with solar activity. This finding indicates that in the high solar activity conditions, when the growth rate of Perkins instability is relatively low, generation of the polarization electric fields in the $$Es$$ Es layer could play a more important role to grow MSTIDs than in the low solar activity conditions. Graphical Abstract

In this study, we consider Bi-directional Long Short Term Memory (Bi-LSTM) model based Vertical Total Electron Content (VTEC) prediction over Thanjavur (Geographic 10.72˚ N, 79.01˚ E, Geomagnetic 2.34˚ N, 152.19˚ E) Global Positioning System (GPS) station. This station is located at low latitude Equatorial Ionization Anomaly (EIA) region of 2˚ geomagnetic dip latitude and has unique ionospheric dynamics. In this region, the VTEC prediction is crucial and challenging for space weather and the Sixth Generation (6G) Internet of Space (IoS) application to support early warning systems and future spatial data transmissions. A Deep Learning (DL) model based on Bi-LSTM was developed and trained for F10.7 and Dst index for predicting the VTEC. This study highlights the prediction of VTEC for any day that includes solstice and equinox time frames. The Bi-LSTM has an improvement of 28 % in mean absolute error (MAE), 48% in mean square error (MSE) and 24% in root mean square error (RMSE) as compared to the conventional Long Short Term Memory (LSTM) network. Hence, this Bi-LSTM model can be helpful to predict the VTEC in the EIA region and may be helpful to extrapolate over the unmeasured grid region of ocean and land.

The ionosphere’s dynamic fluctuations are a persistent challenge to satellite navigation and communication. The total electron content (TEC) information from global navigation satellite system (GNSS) signals provides the status of the ionosphere for fail-safe transionospheric communication. The equatorial ionization anomaly (EIA) and equatorial plasma bubble (EPB) dominate in low latitude and equatorial ionosphere. The low solar activity's fast varying pre-reversal enhancement is low, and slow varying gravity waves can seed ionospheric disturbances. This study analyses the vertical TEC (VTEC) variations using a ground-based global positioning system (GPS) receiver at Thanjavur (10.72° N, 79.02° E), Tamil Nadu, India, for the years 2019 and 2020, with specific emphasis on the Equinox and Solstice conditions during low solar activity. The suitability of global ionospheric models such as IRI-Plas and NeQuick2 models is investigated with low solar activity GPS VTEC observations. VTEC variations are more during the Vernal Equinox compared to other seasons. The NeQuick2 model underestimates the VTEC content during the night hours and overestimates the day's evening hours regardless of the month, perhaps due to higher ITU-R coefficients. The results help us improve IRI-Plas and NeQuick prediction models' accuracy.

The influence of Cr-doping on mono/bilayer MoTe2 nanostructures is studied within the framework of density functional theory (DFT) since doping may be used to effectively tailor the electronic and optical characteristics in a desired manner. Chromium (Cr) seems to modify the electronic properties and energy band gap of MoTe2 considerably. At first, we confirmed the stability of the proposed structure with the support of cohesive formation energy and phonon-band-spectrum. Moreover, doping with Cr on MoTe2 produces a red shift towards far infrared region in the absorption coefficient, thus making it suitable for far infra-red region applications. Hence, Cr doping is employed in this work. When Cr impurities are substituted in pristine MoTe2 nanostructures, the band structure gets modified. Additionally, the band gap of mono/bilayer MoTe2 nanostructures reduces from 1.143/ 0.74 eV for pristine MoTe2 to 0.807/0.621 eV for 8 % substitution of Cr. By examining absorption spectra, it was found that the optical characteristics of mono/bilayer MoTe2 changed significantly with doping of Cr impurities. The results of this study provide insight into the band structure, optical, and electronic attributes of mono/ bilayer MoTe2 nanostructures that could be further fine-tuned for optoelectronic applications using substitution of Cr impurities.

Enzymes derived from earthworm (Eudrilus eugeniae) excretes (vermiwash) were used as supporting bio-catalysts with SnO2/g-C3N4 nanocomposites for photocatalytic dye degradation of toxic organic dyes. The results were compared to those of the composite partners SnO2 and g-C3N4. The enzyme supported nanocomposite has superior photocatalytic efficiency of 95%, 93%, 83% and 97% against the test dyes Methylene Blue (MB), Malachite Green (MG), Methyl Orange (MO) and Rose Bengal (RB) whereas the partners SnO2 (62%, 81%, 36% & 73%) and g-C3N4 (76%, 84%, 80% & 89%) exhibited lower efficiencies. The enzymes phosphatase, amylase, urease and protease present in the synthesized nanocomposite play supporting role as co-catalyst in enhancing the photocatalytic ability of the nanocomposite. The mechanism involving the charge carrier recombination delay due to the formation of g-C3N4 sheets beneath the SnO2 particles is illustrated. The partnering mechanism with g-C3N4 having lower bandgap (2.8 eV) leads to a reduction in the bandgap from 3.5 eV for SnO2 to 2.6 eV for the nanocomposite making the nanocomposite as visible light responsive photocatalyst. The XRD, FTIR, SEM-EDX, UV-vis-NIR, XPS and DFT results support the discussion on photocatalytic mechanism. The near complete dye degradation is confirmed by phenotypic test on earthworm (Eudrilus eugeniae).

The focus of current advances in nanotechnology has shifted significantly towards environmentally conscious methods that use harmless ingredients and moderated reaction circumstances to promote equitable development. Zinc oxide nanoparticles (NPs) currently grabbed attention of multiple medical fields owing to their unique ability to safeguard against cellular damage and alleviate serious human diseases via processes related to metabolism. This work focused on the generation of ZnO NPs using the peel of Cucumis melo fruit. The NPs were then analyzed and characterized using UV-Vis spectroscopy. The results indicated that at a wavelength of 352 nm, it was proven that the biosynthesis of ZnO NPs had occurred. The XRD pattern indicated the presence of dense crystal structures. The field emission scanning electron microscope (FE-SEM) picture confirmed the existence of polygonal-shaped ZnO NPs. The findings indicate that the produced ZnO NPs possess tough antibacterial properties against Gram-positive and Gram-negative microorganisms. When the ZnO NPs were exposed to direct sunshine for 80 min, they showed an 89% dye breakdown efficiency. This research specifically focused on the decomposition of reactivity dyes, with methylene blue dye being used as the target dye. The work demonstrates that the biosynthesis of ZnO NPs has a crucial and versatile role in the biological and environmental sectors.

In this study, different configuration of lightweight aluminum hybrid composite foam core sandwich panel using Kevlar and Carbon fibers as a face sheet has been investigated under flexural loading. The flexural rigidity ( 10 times of bare foam) and flexural strength ( 7 times of bare foam) were found significantly high for double layer Carbon fiber sandwich panel. Whereas the energy absorption ( 22 times of bare foam) and specific energy absorption ( 16 times of bare foam) is high for double layer Kevlar fiber sandwich panels. Double layer hybrid fiber sandwich panel shows inclusive properties of both double layer Kevlar fiber sandwich panels and double layer carbon fiber sandwich panels making it suitable for crashworthiness and structural application. Detailed analysis on deformation mechanism was carried out with the help of videography. The contribution of individual failure modes to flexural properties was calculated empirically and compared with experimental data. The results are encouraging for using high-performance foam-core sandwich panels in structural and blast mitigation applications. Graphical abstract of aluminum hybrid composite foam core sandwich panel

This research work presents the photocatalytic activities of pristine and Zn-doped V2O5 nanoparticles for the degradation of Methylene Blue (MB), Methyl Violet (MV), and Malachite Green (MG) dyes. The nanoparticles of V2O5 pure and Zn with different atomic ratios (1–5 at%) were prepared by sol–gel method. X-ray diffraction (XRD) studies confirm the orthorhombic phase. X-ray Photoelectron spectroscopy (XPS) confirms the presence of V, O, and Zn elements along with their oxidation states. Further, decreased photoluminescence (PL) intensity spectra confirm the reduced recombination rate. Band structure analysis were studied with valance band XPS (VB-XPS), Mott-Schottky (M−S) curves, and Kubelka-Munk (K-M). The Time resolved photoluminescence (TRPL) and Electrochemical impedance spectroscopy (EIS) studies showed that the charge carrier life time was increased and charge transfer resistance was lowered with increasing Zn concentration. The photocatalytic studies show excellent degradation efficiencies against MB, MV, and MG dyes. The results from the present work show the degradation time decreases as the Zn concentration increases. The reusability test was performed and the dye degradation (DD) mechanism with their kinetics are discussed in detail with the radical test. The consistency of the samples were tested by taking XRD, FTIR and BET analysis after three trials of usage.

Metal oxide based semiconductors play a vital role in the development of cost-effective gas sensors. In this study, undoped and Mo-doped SnO2 films were deposited using nebulizer spray by varying Mo doping concentrations from 0 to 1.5 wt% (in steps of 0.5 wt%) at the substrate temperature of 350 degrees C. Ammonia vapour was used as the test gas. The effect of Mo doping concentration on the gas sensing ability of SnO2 films was investigated. Among the tested samples, the SnO2: Mo film with 1 wt% of Mo doping exhibits the best response (21 s) and recovery (31 s) times. The XRD results revealed the tetragonal structure and a decrease in the crystallite size upon doping. The Mo doping caused noticable changes in oxygen vacancies (as observed from PL), surface morphology, grain size and surface roughness which are found to be favourable for effective gas sensing.

In the present work, open-cell aluminum-reduced graphene oxide composite (Al-rGO) foam with varying concentrations of reduced graphene oxide (rGO) was fabricated through the template method and foam's electrical, mechanical, and electromagnetic shielding behavior was studied. The reticulated Al-rGO foam allows the electromagnetic wave (EMW) to go inside the structure and resulting in multiple scattering which enhances the wave absorption capacity of the material. Adding rGO into open-cell aluminium foam (OCAF) enhances its shielding properties, particularly the absorption component. The Al-rGO3 foam shows a total EMI shielding of similar to 62 dB at 8.4 GHz frequency and out of which 61.34 dB (> 99% of total shielding) is the absorption component. The Al-rGO foam also exhibited maximum compressive strength of 2.96 MPa and EMI shielding of similar to 62 dB at 1.5 wt% rGO, even though the electrical conductivity reduces with rGO content. This may be due to a greater degree of multiple scattering of EMW inside the cellular structure and different energy losses at rGO-Al interfaces. This work shows a new way to use the lightweight metallic structure for high EMW absorption applications with good mechanical stability in the defense and aerospace sectors.

In this work, we have investigated the potential of zigzag phosphorene antidot nanoribbons (ZPANRs) for biosensing applications. ZPANRs were created from the optimized structures of phosphorene nanoribbons by using a density functional theory tool. Utilizing the generalized gradient approximation half method for improving the accuracy of calculations, we have studied the electronic and sensing behavior of ZPANRs based devices wherein nucleobases were inserted into the device. We have compared the device performance of ZPANRs with and without nucleobases and found that using ZPANRs devices, we are able to identify different nucleobases with considerable sensitivity. In a quantitative manner, a max sensitivity of 45[Formula: see text] is achieved while identifying adenine nucleobase using the ZPANRs based devices. From these simulation results, it is predicted that the ZPANR based two-terminal device can work as a possible biosensor.

In the current investigation, L-Proline Potassium pentaborate octahydrate single crystals are successfully grown from aqueous solution by slow evaporation technique at ambient conditions. Single-crystal X-ray Diffraction technique proves that the LPPPB crystal belongs to monoclinic crystal system. The optical transparency is analyzed by UV–Vis–NIR spectroscopic technique. It exhibits 92.7% transparency of the title compound with a wide band gap of 6.4 eV. The different types of vibrations such as symmetric stretching, asymmetric stretching, wagging, rocking, intramolecular hydrogen bond interaction, and scissoring vibrations are well established by FTIR technique. The Z-scan technique is employed to assess the nonlinear absorption and refraction behavior of the LPPPB crystal. It declares the saturable absorption and self-defocussing behavior. The hardness number of the LPPPB crystal is calculated by Microhardness Study. The creditability of the LPPPB crystal for nonlinear optical device applications is proved by simultaneous TG–DSC analysis.

The mechanical properties of Tungsten(W), Re doped W (W-Re), La-doped W-Re and Cu doped W-Re nanostructures of BCC phase were explored using Density Functional Theory (DFT). For exploring the mechanical characteristics, elastic constants, Young's modulus, Shear modulus and Bulk modulus were observed. The ductility and hardness of the nanostructures have also been studied at the atomistic level. Furthermore, the density of states spectrum was analyzed for these nanostructures. The findings reveal that W0.81Re0.14Cu0.05 show the best combination when compared to factors like ductility and Young's modulus.

The stir casting technique was used to produce A356 alloy composite foams reinforced with different volume fractions of mullite (5, 7.5, 10, and 12.5%) and SiC (5, 7.5, 10, and 12.5%) particles. The microstructure of the fabricated foams reveals a uniform distribution of these particles within the cell walls, as well as good interfacial interaction with the alloy matrix. Compressive stress–strain curves of the composite foam increase smoothly with strain, and there is very marginal stress oscillation occurred in the plateau region of foam throughout the test. It is worth noting that, regardless of foam composition, plateau stress and energy absorption of foams follow power-law relationships with relative density, while densification strain follows a linear trend with relative density. Furthermore, as compared to the SiC particles reinforced composite foams, the mullite reinforcement exhibits higher plateau stress and energy absorption.

The realistic clusters of InGaAs, InGaP and InGaSb were completely optimized using density functional theory. The stable geometry of different isomers namely bucky ball, nanotube and nanocube were studied using calculated energy, dipole moment and point symmetry. The electronic properties were studied in terms of HOMO-LUMO gap, ionization potential and electron affinity. The bucky ball structures have the high value of HOMO-LUMO gap. Low value of ionization potential was noticed for the nanocube structure. The nanotube structures have high electron affinity. The nanocube isomers have the highest binding energy and embedding energy. The bucky ball isomers have the maximum chemical hardness. The least value of chemical potential was seen for nanocube isomers. The information provided in this study will give a clear picture to tailor new materials which finds its potential application in the optoelectronics.

We report pure potassium penta borate octa hydrate (PPB) and methyl orange dye-doped potassium penta borate octa hydrate (MOPPB) for optical limiting applications. The crystals were grown by slow evaporation solution growth technique at ambient conditions. The single crystal X-ray diffraction (SXRD) evinces the orthorhombic class of the pristine and MOPPB crystals. Formation of PPB and incorporation of MO dye in PPB was confirmed through Fourier transform infrared (FTIR) study. Calculated hardness number and stiffness constant with Vicker’s Micro hardness study portrays the soft nature of the title crystals. The decrease in bandgap of MOPPB is due to the additional energy levels introduced between the valence band and conduction band which in turn increases the net polarizability of the crystal. Relative second harmonic generation (SHG) efficiency of pure PPB and MOPPB is 0.45 times and 0.40 times that of SHG output of KDP. Z-scan studies shows that both crystals show reverse saturable absorption (RSA) ascribed due to two-photon absorption (TPA) process. MOPPB [ β = 1.68 × 10 –5 m/W, n 2 = 10.2 × 10 –12 m 2 /W, χ (3) = 3.5 × 10 –9 m 2 /V 2 ] possess higher NLO coefficients than pure PPB [ β = 0.98 × 10 –5 m/W, n 2 = 4.62 × 10 –12 m 2 /W, χ (3) = 6.1 × 10 –9 m 2 /V 2 ] which assured the superiority of azo dye incorporation in PPB crystals. Pristine and MOPPB crystals depict the optical limiting (OL) behavior under continuous wave (CW) diode laser irradiation at 785 nm. Thus, the linear and nonlinear properties bestow the MOPPB single crystal as a versed material for OL devices used for the safeguard of optical components from laser damage.

GNSS/GPS having wide application in Civil and defence sectors like aviation, transport, navigation, survey, vehicular and secured communications. This GNSS/GPS will be vital for future navigation systems, especially in the intelligent transport system (driverless vehicle) and vehicular communications. Nowadays, spoofing is a significant threat that can divert the route or trajectory of mobile units (ground or airborne). To identify and minimise spoofing, many methods have been tried. Methods such as identifying anomalous carrier-to-noise ratios, the interval amongst the phase changes, the delay in between signal broadcast at various frequencies, spatial data processing, and determining the direction of arrival using an antenna array were all successfully applied. Nevertheless, still, there are challenges to be addressed in spoofing detection. In this short communication, we propose using ionospheric signature as an augmentation to the existing methods to detect spoofing more effectively. By the continuous estimation of the ionospheric parameters from the received signal since the beginning of the navigation and comparing it with the model derived values, one can effectively identify the spoofing signal. When added with the existing spoofing detection methods, this method implemented in real-time will become a powerful tool.

V2O5 nanoparticles were synthesized by using a facile method towards its visible-light photocatalytic dye decomposition of two industrial standard dyes, methylene blue (MB) and methyl violet (MV). From the XRD data, the crystalline phase was identified as orthorhombic, and the particle size was estimated as 52 nm. FTIR and XPS studies were performed to confirm the presence of functional groups, 'V' and '0' elements. The photocatalytic dye degradation efficiency of the prepared nanoparticles against MB and MV was found to be 92% and 85% , respectively. Photocurrent measurement confirms the charge carrier generation during exposure to visible light. A density functional theory (DFT) calculation was performed to uphold the experimental results and to understand the mechanism of photocatalytic degradation of the prepared V2O5 nanoparticles. The obtained results through DFT are compared with experimental results and are discussed.