Research Articles (Physics)
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Item Spatially resolved polarization swings in the supermassive binary black hole candidate OJ 287 with first Event Horizon Telescope observationsGómez, Jose L.; Cho, Ilje; Traianou, Efthalia; Krichbaum, Thomas P.; Zhao, Guangyao; Lico, Rocco; Fuentes, Antonio; Foschi, Marianna; Dahale, Rohan; Georgiev, Boris; Moriyama, Kotaro; Wielgus, MacIek Iej; Gold, Roman; Pesce, Dominic W.; Müller, Hendrik; Jorstad, Svetlana G.; Toscano, Teresa; Röder, Jan; Martí, Josep María; Perucho, Manuel; Kovalev, Y.Y.; Komossa, Stefanie; Gopakumar, Achamveedu; Valtonen, Mauri J.; Bruni, Gabriele; Chandra, Sunil; Akiyama, Kazunori; Albentosa-Ruíz, Ezequiel; Alberdi, A.; Alef, Walter; Algaba Marcos, Juan Carlos; Anantua, Richard J.; Asada, Keiichi; Azulay, Rebecca; Bach, Uwe; Baczko, Anne Kathrin; Ball, David; Baloković, Mislav; Bandyopadhyay, Bidisha; Barrett, John P.; Bauböck, Michi; Benson, Bradford A.; Bintley, Dan I.; Blackburn, Lindy L.; Blundell, Raymond; Bouman, Katherine L.; Bower, Geoffrey C.; Bremer, Michael A.R.; Brissenden, Roger J.V.; Britzen, Silke; Broderick, Avery E.; Broguière, Dominique; Bronzwaer, Thomas; Bustamante, Sandra; Carlos, Douglas Ferreira; Carlstrom, John E.; Chael, Andrew A.; Chan, Chikwan; Chang, Dominic O.; Chatterjee, Koushik; Chatterjee, S.; Chen, Mingtang; Chen, Yongjun; Cheng, Xiaopeng; Christian, Pierre; Conroy, Nicholas S.; Conway, John E.; Crawford, Thomas M.; Crew, Geoffrey B.; Cruz-Osorio, A.; Cui, Yuzhu; Curd, Brandon; Davelaar, Jordy R.J.; De Laurentis, Mariafelicia; Deane, Roger; Dempsey, Jessica T.; Desvignes, Grégory; Dexter, Jason; Dhruv, Vedant; Dihingia, Indu Kalpa; Doeleman, Sheperd S.; Dzib, Sergio Abraham; Eatough, Ralph P.; Emami, Razieh; Falcke, Heino D.; Farah, Joseph R.; Fish, Vincent L.; Fomalont, Edward B.; Ford, H. Alyson; Fraga-Encinas, Raquel; Freeman, William T.; Friberg, Per; Fromm, Christian M.; Galison, Peter Louis; Gammie, Charles F.; García, Roberto; Gentaz, Olivier; Geertsema, Gertie T.; Goddi, Ciriaco; Gómez-Ruiz, Arturo I.; Gu, Minfeng; Gurwell, Mark; Hada, Kazuhiro; Haggard, Daryl; Hesper, Ronald; Heumann, Dirk; Ho, Luis C.; Ho, Paul; Honma, Mareki; Huang, Chih-Wei L.; Huang, Lei; Hughes, David H.; Ikeda, Shiro; Impellizzeri, C.M. Violette; Inoue, Makoto; Issaoun, Sara; James, David J.; Jannuzi, Buell T.; Janssen, Michael; Jeter, Britton; Jiang, Wu; Jiménez-Rosales, Alejandra; Johnson, Michael D.; Jones, Adam C.; Joshi, Abhishek V.; Jung, Taehyun; Karuppusamy, Ramesh; Kawashima, Tomohisa; Keating, Garrett K.; Kettenis, Mark; Kim, Dong-Jin; Kim, Jae-Young; Kim, Jongsoo; Kim, Junhan; Kino, Motoki; Koay, Jun Yi; Kocherlakota, Prashant; Kofuji, Yutaro; Koch, Patrick M.; Koyama, Shoko; Kramer, Carsten; Kramer, Joana A.; Kramer, Michael; Kuo, Cheng-Yu; La Bella, Noemi; Lee, Sang-Sung; Levis, Aviad; Li, Zhiyuan; Lindahl, Greg; Lindqvist, Michael; Lisakov, Mikhail; Liu, Jun; Liu, Kuo; Liuzzo, Elisabetta; Lo, Wen-Ping; Lobanov, Andrei P.; Loinard, Laurent; Lonsdale, Colin J.; Lowitz, Amy E.; Lu, Ru-Sen; MacDonald, Nicholas R.; Mao, Jirong; Marchili, Nicola; Markoff, Sera; Marrone, Daniel P.; Marscher, Alan P.; Martí-Vidal, Ivàn; Matsushita, Satoki; Matthews, Lynn D.; Medeiros, Lia; Menten, Karl M.; Mizuno, Izumi; Mizuno, Yosuke; Montgomery, Joshua; Moran, James M.; Moscibrodzka, Monika; Mulaudzi, Wanga; Müller, Cornelia; Mus, Alejandro; Musok, Gibwa; Myserlis, Ioannis; Nagai, Hiroshi; Nagar, Neil M.; Nai, Dhanya G.; Nakamura, Masanori; Narayanan, Gopal; Natarajan, Iniyan; Nathanail, Antonios; Navarro Fuentes, Santiago; Neilsen, Joey; Ni, Chunchong; Nowak, Michael A.; Oh, Junghwan; Okino, Hiroki; Olivares Sánchez, Héctor Raúl; Oyama, Tomoaki; Özel, Feryal; Palumbo, Daniel C.M.; Paraschos, Georgios Filippos; Park, Jongho; Parsons, Harriet; Patel, Nimesh; Pen, Ue-Li; Piétu, Vincent; PopStefanija, Aleksandar; Porth, Oliver; Prather, Ben; Principe, Giacomo; Psaltis, Dimitrios; Pu, Hung-Yi; Ramakrishnan, Venkatessh; Rao, Ramprasad; Rawlings, Mark G.; Rezzolla, Luciano; Ricarte, Angelo; Ripperda, Bart; Roelofs, Freek; Romero-Cañizales, Cristina; Ros, Eduardo; Roshanineshat, Arash; Rottmann, Helge; Roy, Alan L.; Ruiz, Ignacio; Ruszczyk, Chet; Rygl, Kazi L.J.; Sánchez, Salvador; Sánchez-Argüelles, David; Sánchez-Portal, Miguel; Sasada, Mahito; Satapathy, Kaushik; Saurabh; Savolainen, Tuomas; Schloerb, F. Peter; Schonfeld, Jonathan; Schuster, Karl-Friedrich; Shao, Lijing; Shen, Zhiqiang; Silpa, Sasikumar; Small, Des; Sohn, Bong Won; SooHoo, Jason; Salas, León D.S.; Souccar, Kamal; Stanway,; Sun, He Joshua S.; Tazaki, Fumie; Tetarenko, Alexandra J.; Tiede, Paul; Tilanus, Remo P.J.; Titus, Michael; Toma, Kenji; Torne, Pablo; Trent, Tyler; Trippe, Sascha; Turk, Matthew; Van Bemmel, Ilse; Van Langevelde, Huib Jan; Van Rossum, Daniel R.; Vos, Jesse; Wagner, Jan; Ward-Thompson, Derek; Wardle, John; Washington, Jasmin E.; Weintroub, Jonathan; Wharton, Robert; Wiik, Kaj; Witzel, Gunther; Wondrak, Michael F.; Wong, George N.; Wu, Qingwen; Yadlapalli, Nitika; Yamaguchi, Paul; Yfantis, Aristomenis; Yoon, Doosoo; Young, André; Younsi, Ziri; Yu, Wei; Yuan, Feng; Yuan, Ye-Fei; Zeng, Ai-Ling; Zensus, J. Anton; Zhang, Shuo; Zhao, Shan-Shan (EDP Sciences, 2026-01)We present the first Event Horizon Telescope 1.3 mm observations of the supermassive binary black hole candidate OJ 287. The observations achieved an unprecedented angular resolution of 18 μas and reveal significant structural and polarization variability over just five days, marking the shortest timescale on which such changes have been directly imaged in this source. The inner jet exhibits a twisted ridgeline structure, with features displaying apparent superluminal motions up to about 22 c. The linear polarization maps reveal three main polarized features whose electric-vector position angles (EVPAs) change substantially over the time span of our observations, including a component with a radial polarization consistent with being produced by a recollimation shock. Most notably, we directly resolved two innermost jet components whose EVPAs rotate in opposite directions. The faster component, moving at 2.4 ± 0.9 μas/day (17.4 ± 6.5 c), exhibits counterclockwise EVPA swings of roughly 3.7° per day, while the slower component, with a proper motion of 1.4 ± 0.3 μas/day (10.2 ± 2.2 c), rotates clockwise at approximately 2.5° per day. Previous studies inferred helical magnetic fields in AGN jets from time-resolved or integrated polarization variability but lacked the angular resolution to directly image this effect. Our results provide spatially resolved evidence that a helical magnetic field threads the jet’s collimation and acceleration zone, ruling out models based on the superposition of unresolved components. Our analysis suggests that propagating shocks interact with a Kelvin–Helmholtz plasma instability, illuminating different phases of the helical magnetic field and producing the observed polarization spatial and temporal variability. Moreover, our model naturally accounts for the more rapid polarization rotation observed in the faster moving component. Our model predicts even more rapid swings in polarization, which could be tested with future observations featuring a more densely sampled time coverage.Item A possible challenge for cold and warm dark matterVegetti, Simona; White, Simon D.M.; McKean, John P.; Powell, Devon M.; Spingola, Cristiana; Massari, Davide; Despali, Giulia; Fassnacht, Christopher D. (Nature Research, 2026)Measuring the density profile and mass concentration of dark-matter haloes is a key test of the standard cold dark matter paradigm. Such objects are dark and thus challenging to characterize, but they can be studied via gravitational lensing. Recently, a million-solar-mass object was discovered superposed on an extended and extremely thin gravitational arc. Here we report on extensive tests of various assumptions for the mass density profile and redshift of this object. We find that models that best describe the data have two components: an unresolved point mass of radius ≤10 pc centred on an extended mass distribution with an almost constant surface density out to a truncation radius of 139 pc. These properties do not resemble any known astronomical object. However, if the object is dark matter dominated, its structure is incompatible with cold dark matter models but may be compatible with a self-interacting dark-matter halo where the central region has collapsed to form a black hole. This detection could thus carry substantial implications for our current understanding of dark matter.Item Investigating the influence of radio-faint active galactic nuclei on the infrared-radio correlation of massive galaxiesPeluso, Giorgia; Delvecchio, Ivan; Radcliffe, Jack Frederick; Daddi, Emanuele; Deane, Roger; Jarvis, Matt; Zamorani, Giovanni; Prandoni, Isabella; Gitti, Myriam; Spingola, Cristiana; Ubertosi, Francesco; Sargent, Mark; Smolcic, Vernesa; Wang, Wuji; Delhaize, Jacinta; Jin, Shuowen; Deller, Adam (EDP Sciences, 2026-02)Please read abstract in the article.Item Therapeutic switching of metformin using heteroleptic Cu(II) and Zn(II) complexes : a combined experimental and computational studyAlem, Mamaru B.; Koobotse, Moses O.; Demissie, Taye B.; Desalegn, Tegene; Kruger, T.P.J. (Tjaart); Damena, Tadewos; Mmereki, Baagi T.; Ngwira, Kennedy J.; Zachariah, Matshediso (American Chemical Society, 2026-02-02)Please read abstract in the article.Item Spectral modelling of Cygnus A between 110 and 250 MHz : impact on the LOFAR 21-cm signal power spectrumCeccotti, E.; Offringa, A.R.; Koopmans, L.V.E.; Mertens, F.G.; Mevius, M.; Acharya, A.; Brackenho, S.A.; Ciardi, B.; Gehlot, B.K.; Ghara, R.; Chege, J.K.; Ghosh, S.; Höfer, C.; Hothi, I.; Iliev, I.T.; McKean, John P.; Munshi, S.; Zaroubi, S. (EDP Sciences, 2025-04)Studying the redshifted 21-cm signal from the neutral hydrogen during the Epoch of Reionisation and Cosmic Dawn is fundamental for understanding the physics of the early universe. One of the challenges that 21-cm experiments face is the contamination by bright foreground sources, such as Cygnus A, for which accurate spatial and spectral models are needed to minimise the residual contamination after their removal. In this work, we develop a new, high-resolution model of Cygnus A using Low Frequency Array (LOFAR) observations in the 110–250 MHz range, improving upon previous models by incorporating physical spectral information through the forced-spectrum method during multi-frequency deconvolution. This approach addresses the limitations of earlier models by providing a more accurate representation of the complex structure and spectral behaviour of Cygnus A, including the spectral turnover in its brightest hotspots. The impact of this new model on the LOFAR 21-cm signal power spectrum is assessed by comparing it with both simulated and observed North Celestial Pole datasets. Significant improvements are observed in the cylindrical power spectrum along the Cygnus A direction, highlighting the importance of having spectrally accurate models of the brightest foreground sources. However, this improvement is washed out in the spherical power spectrum, where we measure differences of a few hundred mK at k < 0.63 h cMpc−1, but not statistically significant. The results suggest that other systematic effects must be mitigated before a substantial impact on 21-cm power spectrum can be achieved.Item Investigation of mass substructure in gravitational lens system SDP 81 with ALMA long-baseline observationsStacey, H.R.; Powell, D.M.; Vegetti, S.; McKean, John P.; Wen, D. (EDP Sciences, 2025-11)The prevalence and properties of low-mass dark matter haloes serve as a crucial test for understanding the nature of dark matter, and may be constrained through the gravitational deflection of strongly lensed arcs. Previous studies found evidence for the presence of low-mass dark matter haloes in observations of the gravitationally lensed, dusty star-forming galaxy SDP.81, using the Atacama Large Millimetre/sub-millimetre Array (ALMA). In this work, we analyse these observations to assess the robustness of these reported results. While our analysis indicates that the data support additional angular structure in the lensing mass distribution beyond an elliptical power-law density profile, we do not find evidence for two previously reported sub-halo detections. However, we verify with realistic mock data that we could have found evidence in favour of a previously reported sub-halo with a log Bayes factor of 29, should it exist in the real data. After testing various systematics, we find that this previous sub-halo inference was most likely spurious and resulted from an inadequate smooth model, specifically, poorly fitting multipoles. While we do not find evidence in favour of any individual sub-halo, we find evidence for similarity in the lensing signatures of multipoles () and single massive sub-haloes, consistent with other recent work. We suggest that future searches for low-mass haloes in lensed arcs include lens angular structure in the form of multipoles up to 4th order and require a good-fitting smooth model as a prerequisite. Overall, our findings demonstrate the suitability of ALMA data of this quality to simultaneously constrain the abundance of low-mass haloes and lens angular structure.Item Discovery of a z ∼ 0.8 ultra steep spectrum radio halo in the MeerKAT-South Pole Telescope SurveyMagolego, Isaac; Deane, Roger; Thorat, Kshitij; Heywood, Ian; Rasakanya, William; Aravena, Manuel; Bleem, Lindsey E.; Campitiello, Maria Giulia; Phadke, Kedar A.; Spilker, Justin S.; Vieira, Joaquin D.; Zhou, Dazhi; Benson, Bradford A.; Chapman, Scott C.; Posses, Ana C.; Schrabback, Tim; Stark, Anthony A.; Vizgan, David (Oxford University Press, 2026-01)Please read abstract in the article.Item The effect of Y element on the properties of cobalt-based full-Heusler ZrCo2Y (Y=Sb, Bi, As) as a potential thermoelectric contact electrodeAllan, Lynet; Mulwa, Winfred M.; Mapasha, Refilwe Edwin; Mwabora, Julius M.; Musembi, Robinson J. (Elsevier, 2025-12)Please read abstract in the article.Item Controlling the migration of implanted cesium in silicon carbide using zirconium nanolayerAbdelbagi, Hesham Abdelbagi Ali; Mtshali, Christopher B.; Hossain, M.K.; Ronning, C.; Jafer, Tasabeeh A.O.; Ismail, Mahjoub Yagoub Abdalla; Abdalla, Zaki Adam Yousif; Malherbe, Johan B.; El-Said, A.S.; Hlatshwayo, Thulani Thokozani; Ntshangase, S.S. (Elsevier, 2025-12)Please read abstract in the article.Item Growth and characterization of orthorhombic cesium lead tri-iodide perovskite thin-films by sequential physical vapor deposition for solar cellsSibiya, Sizwe Bhekithemba (Elsevier, 2025-12)This study used the sequential physical vapor deposition (SPVD) technique to grow poly-crystalline yellow phase cesium lead triiodide (γ-CsPbI3). The effect of CsI thickness on structural, optical, morphological, and electrical properties of γ-CsPbI3 was investigated. Crystallographic parameters of γ-CsPbI3 as-deposited and 100 °C annealed pure-phase were determined using X-ray diffraction (XRD). Computed lattice constants were a = 4.88, b = 9.96, and c = 16.5 Å, with an average crystallite size increasing from 170 − 243 nm, and micro-strain decreasing with an increase of cesium iodide (CsI) thickness from 200 to 500 nm. Field-emission scanning electron microscopy (FE-SEM) images showed uniform surface coverage with polycrystalline grains. Average grain size increased from 168 to 235 nm with increasing CsI thickness, resulting in large, pinhole-free, and tightly packed grains. Furthermore, atomic force microscopy (AFM) surface analysis demonstrated a reduction in surface roughness from 44.0 to 38.3 nm as CsI thickness increased from 200 to 500 nm. The ultraviolet–visible (UV–Vis) spectra showed an increase in bandgap from 2.24 to 2.38 eV for as-deposited and a decrease from 2.37 to 2.05 eV for annealed films as the thickness of CsI increased. Current–voltage (J-V) measurements revealed a correlation between the trap-filled limit voltage (VTFL) and defect density. For electron-only devices with film thicknesses of 300, 400, 500, and 600 nm, the trap state densities were found to be 1.40 × 1015, 1.95 × 1015, 2.12 × 1015, and 2.39 × 1015 cm−3, respectively. The corresponding electron mobilities were 2.34 × 101, 6.30 × 101, 4.72 × 102, and 1.07 × 102 cm2/V·s. Additionally, perovskite solar cells (PSCs) fabricated under ambient air conditions revealed an improvement in power conversion efficiency (PCE) from 2.0 to 4.93 % for the FTO/c-TiO2/CsPbI3/Au architecture. This work suggests a way of improving precursor’s reaction using SPVD by controlling the film thickness, reducing defect density through SPVD, and therefore highlighting film thickness optimization in perovskites.Item Effects of the physisorption properties of human hair-derived activated carbon as a potential electrode for symmetric supercapacitorAdam, Rashed Ali Mohamed; Tarimo, Delvina Japhet; Maphiri, Vusani Muswa; Mirghni, Abdulmajid Abdallah; Fasakin, Oladepo; Manyala, Ncholu I. (Springer, 2025-04)Herein, human hair-derived activated carbon (HH-AC) with remarkable physisorption properties such as high surface area and well-balanced micro- and mesopores, is synthesized by chemical activation method using potassium hydroxide (KOH). The activated carbon is synthesized at different ratio of charred human hair and activator as 1:1, 1:2 and 1:3 for HH AC(11), HH-AC(12) and HH-AC(13), respectively. These activated materials are characterized by a powder X-ray diffraction (XRD), Laser Raman spectroscopy, Scanning electron microscope (SEM), and N2 adsorption/desorption isotherms. To examine the influence of the micro-mesopore ratio with high surface area on supercapacitor behavior, all samples are tested in a three-electrode using 2.5 moles of potassium nitrate (2.5 M KNO3) as electrolyte solution. The results show that HH-AC(12) sample which has micro to mesopore-balanced (50 : 50) exhibited superior electrochemical performance with specific capacitance of 215 F g−1 and 125.8 F g−1 in the negative and positive potential, respectively at 1A g−1. The sample HH-AC(11), which is dominated by micropores, showed lower rate capability and specific capacitance despite the huge surface area. Whereas the HH-AC(13) sample with mostly mesopores achieved higher rate capability compared to the others. The HH-AC(12) is further examined in a 2-electrode setup to form a symmetric device. The results show a specific energy of 16Wh kg−1 and a specific power of 375Wkg−1 at 0.5 A g−1. The device demonstrates outstanding capacitance retention of 97% after 10,000 cycles. Thus, ACs with micro to mesopores-balanced are potential candidates for supercapacitor applications.Item Sunyaev–Zeldovich detection of hot intracluster gas at redshift 4.3Zhou, Dazhi; Chapman, Scott C.; Aravena, Manuel; Araya-Araya, Pablo; Archipley, Melanie; Cathey, Jared; Deane, Roger; Di Mascolo, Luca; Gobat, Raphael; Greve, Thomas R.; Hill, Ryley; Kim, Seonwoo; Phadke, Kedar A.; Pillai, Vismaya R.; Posses, Ana C.; Reichardt, Christian L.; Solimano, Manuel; Spilker, Justin S.; Sulzenauer, Nikolaus; Dike, Veronica J.; Vieira, Joaquin D.; Vizgan, David; Wang, George C.P.; Weiss, Axel (Nature Research, 2026-01-29)Please read abstract in the article.Item Interface engineering of activated carbon via nitrogen and nitrogen-sulfur doping for high-performance supercapacitors and dye adsorptionKitenge, Vianney Ngoyi; Baloyi, T.; Diop, Ndeye Fatou; Mohamed, H.E.A.; Botha, N.; Thior, Souleymane; ShamsKhameneh, A.; Madiba, I.; Manyala, Ncholu I.; Chaker, M.; Maaza, M. (Elsevier, 2026-02)Please read abstract in the article.Item A critical review on electronic materials properties and multifunctional applicationsMengesha, Wubshet Getachew; Nagessar, Kaveer (Springer, 2026-01)The rapid advancement of electronic technologies necessitates the development of materials with tailored properties for multifunctional applications. However, there are significant challenges include a fundamental gap in connecting quantum-level behavior to macroscopic properties, data scarcity, and difficulties in integrating multidisciplinary datasets. This paper aims to analyze recent advancements and propose integrated frameworks to bridge these gaps by leveraging artificial intelligence (AI) and machine learning (ML) with a comprehensive review methodology and critical analysis of properties, types, their diverse applications coupled with AI-driven approaches, including generative models, physics-informed neural networks, and autonomous laboratories, for predicting and optimizing electronic materials. Key findings highlight their diverse applications and discovery such as perovskites, 2D mate- rials, and high-temperature superconductors—and in optimizing electronic, thermal, and magnetic characteristics. Recent studies indicate that AI-driven approaches can improve prediction accuracy and enable inverse design in selected systems. These approaches have the potential for significant impact on materials discovery and integration, potentially leading to a transformation of the electronic materials landscape. This paper underscores the future potential of AI-driven paradigms to revolutionize the electronic materials landscape by integrating computational prediction with experimental validation for multifunctional real-world applications.Item Structural, electronic, and magnetic properties of N, P, As, Sb, and Bi dopants in 2D monolayer SiC for high-power electronic applicationIgumbor, Emmanuel; Mapasha, Refilwe Edwin; Raji, Abdulrafiu T. (Elsevier, 2026-04)Please read abstract in the article.Item Electrical characterization of sputter-induced deep levels in GaN thin films synthesized by electrodepositionAli, Abdulraoof Idriss Ahmed; Taghizadeh, Fatemeh; Janse van Rensburg, Pieter Johan; Meyer, Walter Ernst; Nel, Jacqueline Margot; Venter, Andre (Elsevier, 2026-01)This paper reports on the presence of deep-level defects in polycrystalline GaN thin films induced during the sputter deposition of Au Schottky barrier diodes (SBDs). The n-GaN films, with a thickness of approximately 300 nm were electrodeposited on (111) Si substrates using a low-cost method and a current density of 3 mA.cm-2 for 3 hours. Structural analysis by X-ray diffraction, scanning electron microscopy, and atomic force microscopy confirmed the polycrystalline nature and good quality of the films. Deep-level transient spectroscopy (DLTS) revealed a broad, asymmetric peak around 265 K in the as-deposited SBDs, indicating the presence of multiple defects. Laplace DLTS resolved four distinct defects with energies ranging between 0.40 eV and 0.60 eV. Thermal annealing between 450 - 500 K increased the reverse leakage current with only minor changes in the forward-bias characteristics. However, annealing at 550 K significantly reduced the leakage current by two orders of magnitude and improved the rectification ratio by one order of magnitude. All samples exhibited significant series resistance. Capacitance-voltage measurements revealed a reduction in the free carrier density near the surface, suggesting the sputter process introduced additional deep level defects. Furthermore, the deep-level energy (and therefore the likely defect composition) was found to be sensitive to the annealing temperature. HIGHLIGHTS • Sputtering-induced deep levels identified by Laplace DLTS. • Evolution of these defects during annealing at 450-550 K. • Correlation of the deep-level spectra with important diode parameters (Rs, Φb, n). • Enhanced diode performance after 550 K annealing.Item Unveiling the influence of annealing temperature on properties of CZTSSe nanocrystalsOlaleru, Akin; Olasoji, Adekoya; Kehinde, Adewoyin; Solomon, Mattew; Elegbeleye, Ife; Mapasha, Refilwe Edwin (Wiley, 2025-11)The burgeoning interest in kesterite materials stems from their promising applications in both charge-selective materials and photocathodes for photoelectrochemical water splitting. Kesterites, a complex class of semiconductors, typically contain copper, zinc, tin, and either sulfur or selenium atoms. Despite their prevalent use as photocathodes, a comprehensive understanding of their optoelectronic properties remains elusive. This study delves into the synthesis and characterization of Copper Zinc Tin Sulfide Selenium (CZTSSe) nano powders, aiming to elucidate the impact of annealing temperature on their properties. Solution-based synthes is utilizing copper chloride, zinc acetate, tin(II) chloride, and thiourea/selenium precursors yielded CZTSSe nano powders. Annealing in distilled water at varying temperatures (100 to 350 °C) offers a platform to explore the resulting effects on elemental and phase compositions, morphology, and optical behavior. This research contributes to a deeper understanding of Copper ZincT in Selenium (CZTSe) nano powders and their suitability for photoelectrochemical water splitting, paving the way for further advancements in sustainable energy technologies. This research contributes to a deeper understanding of CZTSSe nano powders and their suitability for photoelectrochemical water splitting, paving the way for further advancements in sustainable energy technologies.Item First principles exploration of N-V point defect complexes in graphane : analysis of energetic stabilities and electronic propertiesMapingire, Hezekia; Fwalo, Chewe; Mapasha, Refilwe Edwin (Springer, 2025-02-07)In this study, we employ first principles calculations within the framework of density functional theory to comprehensively investigate the energetic stabilities and electronic properties of various nitrogen dopant-vacancy complexes: NCVH, NCVCH, NCHVH and NCHVCH in the graphane two-dimensional material. The creation of NCVH and NCHVH complexes require less energy than that of NCVCH and NCHVCH, according to the formation energy analysis. The binding energies analysis reveals that all the considered N-vacancy complexes are stable when compared to their isolated counterparts. Based on U-parameter values derivation, it is easier for NCHVH complex (1.09 eV) to undergo transition from one charge state to another as compared to NCVCH (2.52 eV). The N-vacancy complexes induce acceptor and donor states within the graphane band gap, which alters during transition states (0 to −1 or 0 to +1). This comparative study has provided fundamental insights into the possibilities of utilizing nitrogen-vacancy centers in graphane for band gap engineering and nano-technology tailored applications.Item Evaluation of manganese chromium metal organic framework and cobalt nickel iron layered double hydroxide composite synthesised by electrodeposition for supercapacitor applicationsRutavi, Gift; Tarimo, Delvina Japhet; Maphiri, Vusani Muswa; Kitenge, Vianney Ngoyi; Otun, Kabir Opeyemi; Mutua, Hellen Ngunya; Manyala, Ncholu I. (Elsevier, 2025-08)Chronopotentiometry electrodeposition was used to synthesize manganese chromite metal organic framework (MnCr-MOF- τ) on nickel foam (NF) where τ represents, the duration of the electrodeposition time in minutes. The same procedure was used to deposit cobalt nickel iron layered double hydroxide (CoNiFe-LDH) on MnCr-MOF-20 min to form the MOF-20 min @ CoNiFe-LDH. The synergetic effect of the highly porous MOF with a metal centre and branches with enhanced conductivity increases the performance of the composite. The high reversible redox kinetics of the LDH endowed the composite electrode with high electrochemical performance. The electrode yielded a specific capacity of 296 ± 5 mAh g−1 at a specific current of 0.5 A g−1 in a 3-electrode set-up with a high-capacity retention of 70.4 % after 5, 000 galvanostatic charge discharge (GCD) cycles in 2 M KOH electrolyte. The composite was incorporated into a supercapacitor device with activated carbon from Amarula husk (AMH) as the negative electrode. The fabricated MOF-20 min @ CoNiFe-LDH//AMH device produced a high electrochemical performance in a 2-electrode set-up with a specific energy of 76.6 ± 0.5 Wh kg−1 at a specific power of 724.9 ± 0.5 W kg−1. The device also showed great stability with a capacity retention of 81.2 ± 0.5 % after 10, 000 GCD cycles at 10 A g−1.Item Nanoarchitectonics with redox active site modulation in bimetallic MIL-125 (Ti, Mn) MOF for enhanced supercapacitor performanceOtun, Kabir Opeyemi; Diop, Ndeye Fatou; Maphiri, Vusani Muswa; Fasakin, Oladepo; Kitenge, Vianney Ngoyi; Thior, Souleymane; Manyala, Ncholu I. (Elsevier, 2025-05-05)Metal-organic frameworks (MOFs) with dual metal centres have received considerable attention as electrode materials for supercapacitor applications due to their redox-active sites and unique structural architecture. Herein, we present a simple one-step solvothermal approach to synthesize and optimize bimetallic MIL-125(Ti,Mn) MOF, where redox active site modulation enhances its electrochemical performance in asymmetric supercapacitors. The unique structure of MIL-125(Ti,Mn), featuring a spindle-like morphology anchored by flake-like sheets, facilitates interaction between active sites and electrolyte ions and modulates the redox active sites, leading to improved electrochemical performance. As such, the optimized MIL-125(Ti)-Mn-2 electrode demonstrates a high specific capacity of 137.2 mAhg−1 at 1 A g–1 and a capacity retention of more than 76.3 % after 5000 cycles. Furthermore, an asymmetric supercapacitor built with Mn-MIL-125(Ti)-2 and activated carbon achieved a high specific energy of 22.74 Wh kg–1 at a specific power of 996 W kg–1, while also demonstrating excellent stability with 71.2 % capacitance retention over 10,000 cycles at 10 Ag−1. This one-pot incorporation strategy offers a novel route to modulate the structure of MIL-125(Ti) via Mn2+ doping for enhanced supercapacitor performance.