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A new broad-band atmospheric dispersion corrector for HROS-TMT
Atmospheric dispersion causes light from celestial objects with different wavelengths to refract at varying angles as it passes through Earths atmosphere. This effect results in an elongated image at the focal plane of a telescope and diminishes fibre coupling efficiency into spectrographs. We propose an optical design that incorporates a Rotational Atmospheric Dispersion Corrector (RADC) to address the broad-band dispersion for the multi-object mode of the High-Resolution Optical Spectrograph (HROS) on the Thirty Meter Telescope (TMT). The RADC corrects the dispersion across the entire wavelength range (0.311 ?m), using Amici prisms optimized for over 90 per cent transmission efficiency and minimal angular deviation of the beam from the optical axis after dispersion correction. For enhanced accuracy, particularly in the blue region, we have, for the first time, implemented the Filippenko model in Zemax via a custom Dynamic-Link Library (DLL) file. The Author(s) 2025. Published by Oxford University Press on behalf of Royal Astronomical Society. -
Evidence fora slim accretion disc in GX 17+2: a polarimetric study of super-Eddington flows
This study presents a time-resolved spectro-polarimetric analysis of GX 17+2 using IXPE, NICER, and NuSTAR observations. Spectral modelling with (Formula presented) (Formula presented) (Formula presented) (Formula presented) (Formula presented) (Formula presented) (Formula presented) (Formula presented) (Formula presented) ) indicates that the source was in a soft spectral state, and accreting at super-Eddington luminosity. Time-resolved PCUBE analysis shows that the polarization degree (PD) and polarization angle (PA) remain nearly constant across the 2.0(Formula presented) 8.0?keV energy range, suggesting an aligned geometry between the spin and the binary orbital axes of the neutron star. Energy-resolved PCUBE analysis further indicates that the blackbody emission component most likely originates from the boundary layer. The spectro-polarimetric analysis confirms that the reflected emission contributes a PD <20per?cent, consistent with theoretical expectations. In contrast, the Comptonizing medium exhibits a PD of (Formula presented) 1.4per?cent, while the accretion disc shows a PD of (Formula presented) 3.2per?cent in the 2.0(Formula presented) 8.0?keV energy range, exceeding theoretical predictions. Energy-resolved spectro-polarimetric analysis hints at excess disc polarization, possibly associated with the formation of a slim disc and the presence of disc wind under super-Eddington accretion conditions. Both time- and energy-resolved polarization measurements reveal a rotation of the PA for the (Formula presented) and (Formula presented) components in the 3.5(Formula presented) 8.0?keV energy range, suggesting a coupling between the soft and hard polarized emission components. Our results indicate that while the geometry of GX 17+2 is aligned, the emergent hard X-ray emission is significantly influenced by inner disc outflows. The nearly constant PD across energy and time further points to a complex interplay among the accretion disc, Comptonization, and reflection components. The Author(s) 2026. Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. -
The broad-band spectral energy distribution of candidate neutrino blazars
Blazars, the jet-dominated class of active galactic nuclei comprising flat-spectrum radio quasars (FSRQs) and BL Lacertae objects (BL Lacs), are now increasingly identified as potential sources of high-energy neutrinos. Such neutrino blazars are ideal targets to investigate the high-energy emission processes and to understand their role as neutrino sources. We report results on four candidate neutrino blazars, PKS 0446+112, TXS 0506+056, PKS 1424(Formula presented) 418, and PKS 1502+106. We carried out (Formula presented) -ray spectral and timing analysis on three time periods that comprise a quiescent epoch, an epoch that corresponds to neutrino detection, and a flaring epoch. We also carried out modelling of the broad-band spectral energy distribution (SED) on those three epochs. We found that the (Formula presented) -ray spectra of the BL Lac TXS 0506+056 can be adequately described by a power law, while the spectra of the other three FSRQs require a log-parabola model. On shorter time-scales, we observed flux variability with doubling/halving time-scales of 4.70, 9.24, 30.76, and 15.42 h for PKS 0446+112, TXS 0506+056, PKS 1424(Formula presented) 418, and PKS 1502+106, respectively. The SEDs of most of the epochs for the sources are well explained by a leptonic scenario. However, the quiescent epoch of PKS 1502+106 and the neutrino-emission epoch of PKS 0446+112 required an additional hadronic component to reproduce the observed SEDs. Our analysis reveals a complex interplay of leptonic and hadronic processes. While certain neutrino-associated epochs align with a leptonic model, others necessitate a hadronic component to explain the emission features. The Author(s) 2026. Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. -
Revisiting wideband pulsar timing measurements
In the wideband paradigm of pulsar timing, the time of arrival of a pulsar pulse is measured simultaneously with the corresponding dispersion measure from a frequency-resolved integrated pulse profile. We present a new method for performing wideband measurements that rigorously accounts for measurement noise. We demonstrate this method using observations of PSR J2124?3358 made as part of the Indian Pulsar Timing Array experiment using the upgraded Giant Metre-wave Radio Telescope, and show that our method produces more realistic measurement uncertainty estimates compared to the existing wideband measurement method. The Author(s) 2026. Published by Oxford University Press on behalf of Royal Astronomical Society. -
DESI DR2 meets cosmography: a comparative study of Pad Chebyshev, and Taylor expansions
We perform a comprehensive cosmographic analysis of the late-time Universe using the latest Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2) baryon acoustic oscillation (BAO) measurements, comparing Taylor, Pad and Chebyshev expansions as model-independent reconstructions of the background expansion. We consider Padapproximants of order (2,1) and (2,2), a Chebyshev expansion, and a third-order Taylor series. Due to its limited radius of convergence, the Taylor expansion is constrained using only the low-redshift DESI sub-set (z < 1), while the rational Padforms and the Chebyshev expansion are applied over the full DESI DR2 redshift range. Cosmographic parameters are inferred through a Bayesian Markov chain Monte Carlo (MCMC) analysis, and the resulting best-fitting reconstructions of H(z), dL(z), and BAO distance indicators are compared with the predictions of the Lambda cold dark matter (CDM) model. All methods are consistent with CDM at low redshift, but the Chebyshev expansion exhibits noticeable deviations at higher redshifts, while the Pad2,1) and Pad2,2) reconstructions remain closely aligned with CDM across the DESI DR2 range. A model-selection analysis based on Akaike Information Criterion and Bayesian Information Criterion shows a clear statistical preference for the Taylor expansion over low-zCDM, and a strong preference for Padcosmography over CDM when the full DESI DR2 data set is used. These results demonstrate the constraining power of DESI DR2 for cosmographic studies and highlight the utility of rational approximants, especially Padforms, in extending cosmography reliably to higher redshifts beyond the domain of traditional Taylor series. The Author(s) 2026. Published by Oxford University Press on behalf of Royal Astronomical Society. -
Analysis of forbidden neon emission lines in HAeBe stars using Spitzer IRS spectra
We analysed high-resolution mid-infrared spectra of 78 well-known Herbig Ae/Be (HAeBe) stars using Spitzer InfraRed Spectrograph data, focusing on the detection of [Ne ii] and [Ne iii] emission lines as indicators of ionized outflows or disc winds. Emission from [Ne ii] at 12.81 m or [Ne iii] at 15.55 m was identified in 25 sources, constituting the largest sample of HAeBe stars with these detected lines. Our analysis revealed a higher detection frequency of [Ne ii] in sources with lower relative accretion luminosity (Lacc/L?< 0.1), suggesting a connection to the disc dispersal phase. We examined correlations between neon lines and various spectral features and investigated [Ne iii]-to-[Ne ii] line flux ratios to explore potential emission mechanisms. Neon emission is predominantly observed in Group I sources (75 per cent), where their flared disc geometry likely contributes to the observed emission, potentially originating from the irradiated disc atmosphere. Interestingly, we also find that Group II sources exhibit a higher median relative [Ne ii] line luminosity (L/L), suggesting enhanced photoevaporation rates possibly associated with their more settled disc structures. However, larger samples and higher-resolution spectra are required to confirm this trend definitively. The high detection rate of the [Fe ii] and [S iii] lines, commonly associated with EUV-dominated regions, alongside a [Ne iii]-to-[Ne ii] emission ratio greater than 0.1 in sources where both lines detected, suggests that EUV radiation is the primary driver of neon emission in our sample. 2025 The Author(s). -
Kinematic study of molecular gas in cometary globule - LBN 437
Bright-rimmed, cometary-shaped star-forming globules, associated with H ii regions, are remnants of compressed molecular shells exposed to ultraviolet radiation from central OB-type stars. The interplay between dense molecular gas and ionizing radiation, analysed through gas kinematics, provides significant insights into the nature and dynamic evolution of these globules. This study presents the results of a kinematic analysis of the cometary globule, Lynds' Bright Nebula (LBN) 437, focusing on the first rotational transition of CO and CO molecular lines observed using the Taeduk Radio Astronomy Observatory. The averaged CO spectrum shows a slightly skewed profile, suggesting the possibility of a contracting cloud. The molecular gas kinematics reveals signatures of infalling gas in the cometary head of LBN 437, indicating the initial stages of star formation. The mean infall velocity and mass infall rate towards the cometary head of LBN 437 are 0.25 km s and 5.08 10 M yr, respectively, which align well with the previous studies on intermediate or high-mass star formation. 2025 The Author(s). -
Unveiling the bulge-disc structure, AGN feedback, and baryon landscape in a massive spiral galaxy with Mpc-scale radio jets
We study the bulge-disc components and stellar mass distribution in the fast-rotating, highly massive spiral galaxy 2MASX J23453268-0449256, which is distinguished by extraordinary radio jets extending to Mpc scales. Using high-resolution multiwavelength Hubble Space Telescope (HST) observations and multiparameter panchromatic spectral energy distribution (SED) fitting, we derive estimates of key properties, such as the star formation rate, total baryonic mass in stars, and the characteristics of warm dust. Our findings, validated at a spatial resolution of approximately 100 pc, reveal a pseudo-bulge rather than a classical bulge, as well as a small nuclear bar and resonant ring, challenging traditional models of galaxy formation. Furthermore, the absence of tidal debris and the highly symmetric spiral arms within a rotationally supported stellar disc suggest a peaceful co-evolution of the galactic disc and its central supermassive black hole (SMBH). Notably, the galaxy exhibits suppressed star formation in its central region, which may be influenced by feedback from the central accreting SMBH, producing powerful radio jets. Detailed multiwavelength studies of potential star-forming gas show that while hot X-ray gas cools in the galaxy's halo, new stars do not form in the centre, likely due to this feedback. This study raises important questions about the efficient fuelling and sustained collimated jet activity in J2345-0449, highlighting the need for a better understanding of the central black hole's properties. The exceptional rarity of galaxies like 2MASX J23453268-0449256 presents intriguing challenges in uncovering the physical processes behind their unique characteristics. 2025 The Author(s). -
High-resolution spectroscopy of HE 0225?0546 and HE 1153?0518: probing the progenitors through abundance patterns and kinematics
We present the results of a high-resolution (SUBARU/HDS, R ? 50 000) spectroscopic study of two metal-poor stars, HE 0225 ?0546 and HE 1153 ?0518. This marks the first such detailed analysis for both objects. Our findings reveal that HE 0225 ?0546 is extremely metal-poor with [Fe/H] ??3.03, while HE 1153 ?0518 is very metal-poor with [Fe/H] ??2.80. Both stars exhibit enhancements in carbon and neutron-capture elements and formally satisfy the criteria for carbon-enhanced metal- poor (CEMP) classification. Although their [Ba/Eu] and [La/Eu] ratios do not allow a secure assignment to any specific CEMP sub-class, the estimated [Ba/Eu] and [Eu/Fe] ratios indicate that both stars fall into the r-II star category. Distinct abundance patterns between the two stars suggest different nucleosynthetic histories. HE 0225 ?0546 shows strong enhancement in Fe-peak elements, while HE 1153 ?0518 is mildly deficient in the same. Both stars are ?-enhanced, though the level of enhancement varies. These results indicate pollution by multiple progenitor channels. Abundance ratios imply that HE 0225 ?0546 is likely enriched by fast-rotating massive stars (FRMS), whereas HE 1153 ?0518 shows signatures consistent with asymptotic giant branch (AGB) star enrichment. Kinematic analyses place both stars in the high-energy, prograde component of the Galactic halo. HE 0225 ?0546 has an apogalactic distance (rapo ) of ?31.8 kpc, placing it in the outer halo, while HE 1153 ?0518 lies closer to the boundary of the inner and outer halo with rapo ?13.8 kpc. Both stars show kinematic coherence with the Sagittarius substructure, suggesting a possible extragalactic origin. The Author(s) 2025. Published by Oxford University Press on behalf of Royal Astronomical Society. -
Discovery of fullerenes in the shell of candidate luminous blue variable WRAY 16-232
We report the discovery of fullerene in the circumstellar environment of WRAY 16-232, a strong candidate luminous blue variable. Multiple pointings of archival Spitzer Infrared Spectrograph spectra reveal, for the first time, the presence of prominent vibrational bands of C60 at 17.4 and 18.9 ?m in a luminous blue variable (LBV) envelope, along with the strong polycyclic aromatic hydrocarbon features. These observations suggest that, despite the harsh radiative conditions, large carbonaceous molecules can form, process, and survive in the ejecta of massive stars. Complementary optical spectroscopy with South African Large Telescope High-Resolution Spectrograph shows multiple P Cygni profiles in H ?, He i, and Fe ii lines, which are indicative of a dense, expanding wind and substantial mass-loss. Furthermore, analysis of decade long photometric data shows short-term brightness variations of ?0.5 mag. These results not only reinforce the classification of WRAY 16-232 as a strong LBV candidate but also provide new insights into the mechanisms of dust formation and the chemical enrichment of the interstellar medium by massive stars. We discuss various scenarios for fullerene formation in such environments, and find that shock processing due to wind-wind interactions could be playing a vital role. The shell of WRAY 16-232 has an ideal UV field strength and the time-scales appear to match with shock processing time-scales. The results highlight the need for further high spatial/spectral resolution and temporal observations to confirm the formation and survival scenario of C60 in its shell. The Author(s) 2025. Published by Oxford University Press on behalf of Royal Astronomical Society. -
Thermonuclear X-ray bursts across the eclipse transitions in the LMXBs EXO 0748?676 and XTE J1710?281
The primary radiation from thermonuclear X-ray bursts observed in the neutron star low-mass X-ray binary (LMXB) systems can interact with various parts of the binary system. This interaction gives rise to secondary radiation in different wavelength ranges, known as reprocessed emission. In eclipsing LMXBs, the reprocessed emission from the bursts can be examined during eclipses, as the primary emission is blocked and only the reprocessed emission is visible. We searched for bursts during eclipses in the archival RXTE data of the eclipsing LMXBs and found them in EXO 0748?676 and XTE J1710?281. In EXO 0748?676, seven bursts were found to occur near eclipse egress, with their tails extending beyond the eclipse, and one such burst was found for XTE J1710?281. We estimate the reprocessing fraction at orbital phases near eclipse egress by modelling the peculiar eclipse bursts detected in both systems, which have tails extending beyond the eclipses. We observe an increasing trend in reprocessing fraction as these eclipse bursts occur closer to the eclipse egress. We discuss the possibilities of reprocessing in the ablated wind from the companion star, the accretion disc, and the disc wind in EXO 0748?676 and XTE J1710?281. Additionally, we observe two decay components in the bursts in EXO 0748?676, which could suggest a complex composition of the accreting fuel. From the burst rise time-scales, we place an upper limit on the size of the reprocessing regions in both EXO 0748?676 and XTE J1710?281, finding it comparable to the size of the respective X-ray binaries. The Author(s) 2025. Published by Oxford University Press on behalf of Royal Astronomical Society. -
Investigation of the Axe-shaped Radio Galaxy J1051+5523 with uGMRT
We present a multifrequency study of the bent-tail radio galaxy J1051+5523, located in the galaxy cluster WHL J105147.4+552309. This wide-angle tail (WAT) galaxy exhibits a complex radio morphology, characterized by a right-angled bend in the northern jet, which resembles an axe, and multiple kinks in the southern jet, as observed in the deep uGMRT radio observations. The radio power of J1051+5523 at 150 MHz is estimated to be, placing it in the transition zone between FRI and FRII radio galaxies. The spectral index map reveals a flat core and relatively flat lobes, which may indicate ongoing particle acceleration or a relatively young population of relativistic electrons in the lobes. Further, we estimate the equipartition magnetic fields, and spectral ages of the northern and southern lobes to be approximately 150 and 153 Myr, respectively, suggesting a long-lived radio source with sustained active galactic nucleus (AGN) activity. A relative velocity of 278 2643 is obtained for the host galaxy. Due to the large uncertainty associated with the relative velocity estimates, the contribution of ram pressure to the jet bending remains inconclusive. The low mass of the host cluster () and the lack of diffuse X-ray emission indicate a reduced likelihood of major mergers, but minor mergers or interactions remain possible. We propose that the observed WAT morphology of J1051+5523 is likely shaped by a combination of ram pressure and/or buoyant forces within the cluster environment. 2025 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. -
Padcosmography and its insights into teleparallel gravity
We investigate the viability of a modified teleparallel gravity model, specifically within the framework of gravity, by implementing two complementary approaches for cosmological parameter estimation. In the first approach, we incorporate the model into a Pad(2,1) parametrization of the Luminosity distance, enabling a stable and accurate description of the cosmic expansion history across redshift. In the second, we directly solve the modified first Friedmann equation arising from the same model. Both approaches are subjected to a comprehensive Markov Chain Monte Carlo analysis using the latest cosmological observations, including cosmic chronometers, gravitational wave standard sirens, DESI BAO DR2, the Pantheon + SH0ES compilation, and Union3. We find that the parameter constraints obtained from the Padbased formulation are in close agreement with those from the direct dynamical method, highlighting the internal consistency of the scenario and the effectiveness of Padexpansions in confronting modified gravity theories with data. In fact, both methods exhibit a better fit than the standard lambda cold dark matter (CDM) model in light of the DESI DR2 and Union3 observations. In addition, we present a detailed account of the Bayesian analysis methodology and compile a comprehensive set of the most recent and relevant cosmological data sets used in our study. 2025 The Author(s). -
Non-linear solar EUV-driven sodium release from the lunar surface: a contrast to the linear PSD model
The correlation between solar Extreme Ultra-Violet (EUV) radiation above 8.8eV and the release of sodium from the lunar surface via photon-stimulated desorption (PSD) is investigated. We use simultaneous measurements of EUV photon flux and Na optical spectral line flux (FNa) from the lunar exosphere. Data were acquired with the high-resolution (R?72000) Echelle Spectrograph on the 2.34-m Vainu Bappu Telescope during the lunar first quarter (2024 JanuaryMarch), observing NaI D2 and D1 flux at altitudes below ?590km from the surface. Simultaneous EUV and FUV measurements were acquired from the GOES-R Series Extreme Ultraviolet Sensor (EUVS), while NUV data were obtained from the Total and Spectral Solar Irradiance Sensor-1 (TSIS-1) aboard the ISS. We correlated FNa with EUV photon flux from EUVS across six bands spanning 2561405 (48.58.8eV) and NUV (20004000 from TSIS-1. A non-linear rise in lunar exospheric sodium with increasing EUV and FUV fluxes was observed, contrasting with previous linear PSD models. The EUV radiation above 10eV drives sodium release, with 256-304wavelengths as dominant contributors. Additionally, the NUV flux and FNa are positively correlated, indicating the role of sodium release. The zenith column density averages 3.3 109 atoms cm-2, with Characteristic temperatures averaging at ?6700K and scale heights of ?1500km. Elevated temperatures and sodium densities during solar activity suggest enhanced Na release during flares. These results emphasize the need for a revised PSD model above 8.8 eV and improved constraints on the PSD cross-section. The Author(s) 2025. Published by Oxford University Press on behalf of Royal Astronomical Society. -
Phenomenology and constraints of an extended modified gravity in Weyl geometry
We explore a novel class of modified gravity theories built upon Weyl geometry, where the Weyl connection introduces additional geometric degrees of freedom beyond general relativity. By promoting the Weyl field to a dynamical entity with a generalized potential, the resulting modified gravity theory naturally incorporates degrees of freedom arising from both the Weyl field and the scalaron embedded in the non-linear Ricci scalar function. Crucially, the field equations remain second-order, ensuring stability and avoiding Ostrogradsky instabilities. To test its viability, we confront this theory with observational data from Dark Energy Spectroscopic Instrument, cosmic chronometers, and Type Ia supernovae, constraining its free parameters through statistical analysis. Our results show strong agreement with observations, supporting a quintessence-like accelerating cosmic expansion and alleviating the Hubble tension. These findings establish modified gravity as a compelling extension of standard cosmology. 2025 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. -
Remote and Cross-Cultural Training of Research Assistants Abroad to Conduct Neuropsychological Tests: Lessons Learned
There are no published guidelines regarding remotely training research assistants (RAs) to conduct neuropsychological tests. With technological advances allowing for increased international collaboration within the medical and research communities, challenges often arise from such partnerships, including linguistic, cultural, and physical barriers. A notable challenge for supervising neuropsychologists in international projects is the physical distance from RAs, sites, and materials, making training/supervision of RAs and monitoring test data quite challenging. In the context of a research collaboration between neuropsychologists based in New York and RAs based in Kerala, India, as part of the Kerala-Einstein Study, we explore the obstacles of remotely training RAs and maintaining neuropsychological data integrity. We share lessons learned and systems developed to optimize remote, multilingual, cross-cultural training of RAs in administration/scoring of neuropsychological tests. One-on-one video training sessions mitigated logistical problems (i.e., time differences, internet connection, language comfort). Individualized training in scoring and a centralized individual to double-score protocols addressed quality assurance of test data. Close collaboration between our teams was necessary for cultural competency, particularly when building an appropriate test battery, creating and translating manuals, and adapting protocols. Finally, frequent and ongoing communication channels ensured excellence in study design, information gathering, and data quality. Future studies should continue highlighting strategies for remotely training psychometrics/RAs in neuropsychological administration. 2025 The Author(s). Published by Oxford University Press. All rights reserved. -
Microaggression and Its Impact on Lower Caste Women with Psychiatric Disorders in India
This article presents a collection of personal stories of Dalit women highlighting their daily experiences of microaggressions, which they did not even realize or endured in silence, but how it left deep psychological, emotional, and relational scars. These experiences are examined from a postmodern theory perspective. In addition, the article will describe Anderson Franklin and Nancy Boyd-Franklins theoretical concepts of invisibility and Kenneth Hardys concepts of voicelessness and psychological homelessness. These stories indicated that having mental illness defined these women, leading to a lack of opportunities and resources and further chipping away at their sense of self, capabilities, and value. As a therapist, the primary author felt drawn to connect with these womens humanity, suffering, and pain, but also felt vulnerable to seeing them as different and ignoring the fact that she exercised power by categorizing them as low-income, Dalit, and traumatized. By seeing these women differently, the primary author felt less vulnerable and safer in a therapeutic relationship but also realized how language in therapy reinforces the internal psychological and emotional experience of being invisible and thus unimportant. Mental health professionals should use caste-sensitive language and adopt caste-affirmative therapy to prevent the drop-out of these women from therapy. Copyright 2025, Mary Ann Liebert, Inc., publishers. -
Synergistic pseudocapacitive behavior of Cr2CTx MXene and Cu-PTC MOF in CM-II: an Electroactive composite
The increasing global energy demand and a shift towards sustainable energy solutions necessitate the development of advanced energy storage devices, with supercapacitors emerging as key candidates. Achieving high energy density without compromising power density remains a critical challenge, underscoring the need for novel materials with robust pseudocapacitive behavior. This study introduces a novel electroactive composite, CM-II, composed of Cr2CTx MXene and a Cu-based MOF, Cu-PTC. The synthesis, structural, and morphological characterization of CM-II is extensively detailed. Cr2CTx MXene provides a conductive scaffold, while Cu-PTC contributes redox-active sites and porosity, creating a synergistic combination that enhances charge storage. The pseudocapacitive performance of CM-II has been systematically evaluated, with a specific capacitance of 3035 F g?1 and a long cycle-life with a capacitance retention of 96% after 5000 cycles, showcasing its potential as a high-performance material for next-generation supercapacitors. 2025 The Author(s). Published by IOP Publishing Ltd. -
Unveiling the potential: iodide-infused nickel-enhanced MXene composite for high-performance sodium ion hybrid capacitors
2D-MXenes have gained much popularity for energy storage applications such as hybrid capacitors, and they have shown very competitive performance, especially as electrode materials for sodium ion hybrid capacitors. However, they suffer from various problems, such as morphology distortion and fast capacity fading, which results in the poor performance of the battery. As a result, researchers have focused more on MXene-based composite materials to address these issues. In this work, we report a sodium iodide and nickel-decorated MXene-based composite (Ti2C/Ni/NaI) material as an electrode for a sodium ion hybrid capacitor. Ti2C MXene and Ni were able to provide physical and mechanical strength, and iodine was able to produce redox activity. The composite had a rough surface with readily aggregated 2D-MXene sheets and was uniformly covered with Ni, Na, and I atoms. Several vibrational bands and peaks associated with Ti, Ni, Na, C and O in the Raman while XPS spectra confirmed the effective incorporation of dopants into the MXene sheets and successful synthesis of the Ti2C/Ni/NaI composite. The fabricated hybrid capacitor exhibited good capacity retention of 59% after 10,000 cycles at a current density of 0.5 mA g?1; thus, the Ti2C/Ni/NaI composite can be a promising electrode material for sodium-based hybrid capacitors. 2025 The Author(s). Published by IOP Publishing Ltd. -
Direct ink writing of nickel oxide-based thin films for room temperature gas detection
The rapid industrial growth and increasing population have led to significant pollution and deterioration of the natural atmospheric environment. Major atmospheric pollutants include NO2 and CO2. Hence, it is imperative to develop NO2 and CO2 sensors for ambient conditions, that can be used in indoor air quality monitoring, breath analysis, food spoilage detection, etc. In the present study, two thin film nanocomposite (nickel oxide-graphene and nickel oxide-silver nanowires) gas sensors are fabricated using direct ink writing. The nano-composites are investigated for their structural, optical, and electrical properties. Later the nano-composite is deposited on the interdigitated electrode (IDE) pattern to form NO2 and CO2 sensors. The deposited films are then exposed to NO2 and CO2 gases separately and their response and recovery times are determined using a custom-built gas sensing setup. Nickel oxide-graphene provides a good response time and recovery time of 10 and 9 s, respectively for NO2, due to the higher electron affinity of graphene towards NO2. Nickel oxide-silver nanowire nano-composite is suited for CO2 gas because silver is an excellent electrocatalyst for CO2 by giving response and recovery times of 11 s each. This is the first report showcasing NiO nano-composites for NO2 and CO2 sensing at room temperature. 2025 Chinese Institute of Electronics.