Journal Articles

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12504/113

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A dye-sensitized solar cell based on an in-situ hydrothermally grown hematite photo-anode
(Springer Nature Link, 2025-07-22) Nasejje, Stella; Mukhokosi, Emma Panzi; Mmantsae, Diale
Transition metal-oxides have gained research attention for applications in optoelectronics devices like dye-sensitized solar cells (DSSCs). This contribution presents an α-Fe2O3-Pt DSSC configuration. An in-situ hydrothermal technique was used to grow spherically shaped α-Fe2O3 thin films on an FTO substrate, forming the photo-anode. The surface morphology, structural, and optical properties were characterized by standard techniques, confirming the samples’ purity. Pt was drop-cast on the FTO substrate, forming the counter electrode. The photo-anode was soaked in N719 ruthenium dye for 24 h. The electrodes were assembled using crocodile clips, and the iodide electrolyte was injected into the space between them. At an intensity of 100 mW/cm2, the α-Fe2O3-Pt DSSC yielded a short-circuit photocurrent density, open-circuit voltage, fill factor, and efficiency of 0.098 mAcm−2, 0.410 V, 0.247, and 0.01%, respectively. These results provide a simple, cost-effective strategy for synthesizing spherical nanoporous α-Fe2O3 thin films for potential application as photo-anodes in n-DSSCs.
Assessing the radiological hazards due to radionuclides in sediments and tailings around Kilembe copper mines, Western Uganda
(International Journal of Environmental Analytical Chemistry, 2024-03-19) Evarist, Turyahabwa R. S.; Farooq, Kyeyune; Eric, Mucunguzi; Akisophel, Kisolo; Manny, Mathuthu
Copper mining in Kilembe Valley, Western Uganda, between 1956 and 1982 resulted in multiple tailing sites, raising concerns about potential increases in the natural background radiation. In this study, the radioactivity concentrations of 226Ra, 232Th, and 40K in 31 sediments and tailing samples from the Kilembe copper mines area were determined using HPGe-based gamma spectrometry. The mean activity concentrations of 226Ra, 232Th, and 40K in sediment samples were 38.6 ± 8.9, 37.4 ± 7.8, and 708.0 ± 147.3 Bq kg−1, respectively. While in tailing samples, the mean values were 171.3 ± 31.7, 34.8 ± 14.9, and 792.4 ± 208.2 Bq kg−1, respectively. These values exceeded global averages of 35, 30, and 400 Bq kg−1 for 226Ra, 232Th, and 40K, respectively. To assess the radiological hazards due to radionuclides in sediments and tailings, several parameters such as the radium equivalent activity (Raeq), external hazard index (Hex), internal hazard index (Hin), gamma representative index (Iγ), absorbed dose rate (D), total annual effective dose (Etot), and total excess lifetime cancer risk (ELCRtot) were determined. In sediments, most of these hazard parameters were above the world’s average values, except Raeq, Iγ, Hex, and Hin. While in tailings, all the hazard parameters surpassed the global average values except Raeq and Hex. Pearson correlation coefficient and hierarchical cluster analysis showed that 226Ra was the main contributor to the assessed radiological hazards. The study suggests potential radiological risks linked to natural radioactivity from sediments and mine tailings, especially when used as building materials.
Assessment of indoor radon (222Rn) levels and associated radiological risks in occupational buildings and dwellings in Kampala, Uganda
(The European Physical Journal Plus, 2025-08-09) Farooq, Kyeyune; Ivan Ssikubwabo; Thomas Baluku; Evarist R. S. Turyahabwa
Radon-222 (222Rn) is a naturally occurring radioactive gas and the second leading cause of lung cancer after smoking, posing a public health concern. Assessing indoor 222Rn levels in occupational and residential environments is essential for radiological risk evaluation. In this study, indoor 222Rn concentrations were measured using a continuous radon monitor (CRM) in 20 buildings across Kampala City, Uganda. In occupational buildings, 222Rn concentrations ranged from 8.7 ± 1.5 to 95.8 ± 8.0 Bq m−3, with a mean of 30.8 ± 4.5 Bq m−3. Poorly ventilated storage rooms showed elevated levels, with a maximum of 194.8 ± 21.2 Bq m−3, exceeding the WHO reference level of 100 Bq m−3. In dwellings, concentrations ranged from 15.3 ± 2.3 to 188.2 ± 8.2 Bq m−3, averaging 71.7 ± 17.5 Bq m−3. Some dwellings recorded values above the WHO threshold. The average annual effective doses were 0.32 ± 0.05 mSv y−1 in occupational buildings and 0.75 ± 0.18 mSv y−1 in dwellings, both below the recommended public limit of 1.0 mSv y−1. Additional radiological parameters, including annual equivalent dose, excess lifetime cancer risk and potential lung cancer cases, were also evaluated. Statistical analysis revealed a strong positive correlation between 222Rn concentrations and radiological hazard indices, as well as a positive correlation with indoor humidity and a weak negative correlation with temperature. These findings highlight the importance of controlling humidity and enhancing ventilation to mitigate indoor radon risks. Although indoor 222Rn levels in the surveyed buildings were generally low and unlikely to pose significant health risks, continued monitoring is recommended to capture seasonal variability and ensure long-term radiological protection for occupants.
Biomarker Raman bands of estradiol, follicle-stimulating, luteinizing, and progesterone hormones in blood
(Vibrational Spectroscopy, 2022-08) Annah, M. Ondieki; Zephania, Birech; Kenneth, A. Kaduki; Catherine, K. Kaingu; Anne, N. Ndeke; Loyce, Namanya
Variation of the levels of reproductive hormones outside the normal range indicates health problems that include cancer, infertility, and menstrual difficulties. This work reports on a potentially novel method of screening four (estradiol, follicle-stimulating hormone, FSH; luteinizing hormone, LH; and progesterone) hormones. The work involved first determining the characteristic Raman spectra of their standards. Thereafter, the Raman marker bands of the respective hormones in blood were determined experimentally. Simulate samples were prepared by mixing, at varying concentrations, the respective standard hormone samples with male mouse’s blood and concentration-sensitive Raman bands identified upon 785 nm laser excitation. The samples were applied, separately, onto prepared conductive silver paste smeared microscope glass slides. Spectral data analyses were done using both Principal Component Analysis (PCA) and Analysis of variance (ANOVA). The spectral profiles of respective standard hormones (with no blood) displayed common bands at 483, 1005, 1244, and 1455 cm−1 which were tentatively attributed to C-C stretching of glucose, lipid bands, and CH2/CH3 scissoring respectively. Other bands were observed at 542 cm−1 (for LH and progesterone), 859 cm−1 (for estradiol and FSH), 837 cm−1 (for FSH and LH) and at 1360 cm−1 (for progesterone). In blood, a large comparative Raman spectral intensity variation was observed at around 483 and 1450 cm−1 in LH; 902 and 1569 cm−1 in estradiol. These bands could be used as biomarker Raman bands for the respective hormones. The bands centered at 668 and 1219 cm−1 displayed almost identical intensity variation in the four hormones (estradiol, FSH, LH, and progesterone) and could be used as marker bands for level determination for the four combined. This work has shown the power of Raman spectroscopy in potential hormone concentration level determination when respective biomarker bands are employed.
Co-sensitization effect of chlorophyll and anthocyanin on optical absorption properties and power conversion efficiency of dye-sensitized solar cells
(Springer, 2024-04) Mukhokosi, Emma Panzi; Mohammed, Tibenkana; Loyce, Namanya; Botha, Nandipha L.; Maaza, Maliki; Velauthapillai, Dhayalan
In this article, the chemical structure, optical absorption and photoluminescence properties of un/adsorbed dyes of hibiscus flower (H), pumpkin leaf (P), sweet potato leaf (S) and their composites (H: P & H: S) have been studied. The chemical structural properties revealed the O–H, C–C and C = O as the main anchoring functional groups. The optical absorption properties revealed two definite bands in between 450–500 nm and 600–680 nm wavelength for chlorophyll-based dyes and a peak at 526 nm for anthocyanin based dye extract. The composite dye extracts revealed optical absorption bands corresponding to chlorophyll and anthocyanin pigments with enhanced absorption of light. Five different solar cells based on H, P, S, H:P-3:1 and H:S-3:1 were developed and revealed an efficiency of ~ 0.08, 0.3, 0.5, 0.7 and ~ 1% respectively. The efficiency was reduced by half after 30 days. The composites had the highest power conversion efficiency due to more O–H, C–C and C = O binding sites on TiO2 nanoparticles, reduced rate of electron–hole pair recombination and a wide range of optical absorption. These studies suggest that co-pigmentation can be an alternative strategy to increasing the power conversion efficiency in DSSCs.
compare the thermal performance of two thermal insulating materials for domestic heating applications
(European Journal of Physics, 2025-07-22) Abedigamba, Oyirwoth Patrick; Obia, Pius; Mawire, Ashmore; Rukaaya, Musa; Okullo, Michael
Thermal insulating materials are very essential in thermal energy storage. There are both imported and locally/homemade thermal insulation materials. However, the imported thermal insulation materials are expensive compared to the locally made ones due to the high importation cost and taxes imposed on them. This paper aims to compare two thermal insulators for domestic solar heating applications. The two insulators are a wonderbag (imported from South Africa) and a hay basket (locally made in Uganda). Two identical cooking pots with a capacity of 1 litre each are separately placed on identical Photovoltaic Direct Current (PV DC) cookers inside a wonderbag and hay basket, respectively. Water heating experiments are performed in the morning and noon. Results show that when a 0.5 kg water load is used, a higher maximum temperature of 96.3 oC is achieved by the water in a wonderbag insulator compared to 94.8 oC achieved for a hay basket, within 24 min of the experiments during solar noon. A slightly higher water heating efficiency of 3.9% is shown when in the wonderbag compared to that of 3.7% attained when the hay basket is used. No significant difference in the maximum water load temperatures and heating efficiencies are observed when using a wonderbag and hay basket as thermal insulating materials for domestic solar cooking applications during solar noon. Longer heating times are taken during morning experiments (32 – 34 min) than during noon experiment (26 – 30 min). The work demonstrates that a cheaply available and locally made heat retention vessel (hay basket) can substitute the imported and expensive heat retention vessel (wonderbag). The experimental setup can be used to introduce the ideas of heat retention, solar cooking, and photovoltaics to senior undergraduate students pursuing courses in thermal physics and semiconductor physics, respectively.
Computational Insights for interactions between NsP2 and NsP3 of CHIKV and Hormones through DFT computations and Molecular Dynamics Simulations
(Chemistry & Biodiversity, 2024-08-13) Raman, Anirudh Pratap Singh; Kumar, Durgesh; Kumari, Kamlesh; Jain, Pallavi; Bahadur, Indra; Abedigamba, Oyirwoth P.; Preetam, Amreeta; Singh, Prashant
The non-structural protein (nsP2 & nsP3) of the CHIKV is responsible for the transmission of viral infection. The main role of nsp is involved in the transcription process at an early stage of the infection. In this work, authors have studied the impact of nsP2 and nsP3 of CHIKV on hormones present in the human body using a computational approach. The ten hormones of chemical properties such as 4-Androsterone-2,17-dione, aldosterone, androsterone, corticosterone, cortisol, cortisone, estradiol, estrone, progesterone and testosterone were taken as a potency. From the molecular docking, the binding energy of the complexes is estimated, and cortisone was found to be the highest negative binding energy (-6.57 kcal/mol) with the nsP2 protease and corticosterone with the nsP3 protease (-6.47 kcal/mol). This is based on the interactions between hormones and NsP2/NsP3, which are types of noncovalent intermolecular interactions categorized into three types: electrostatic interactions, van der Waals interactions, and hydrogen-bonding. To validate the docking results, molecular dynamics simulations and MM-GBSA methods were performed. The change in enthalpy, entropy, and free energy were calculated using MM-GBSA methods. The nsP2 and nsP3 protease of CHIKV interact strongly with the cortisone and corticosterone with free energy changes of -20.55 & -36.08 kcal/mol, respectively.
Device architectures for photoelectrochemical water splitting based on hematite: a review
(Discover Materials, 2024-08-21) Stella, Nasejje; Emma Panzi Mukhokosi; Mmantsae Diale; Dhayalan Velauthapilla
Hydrogen production by photoelectrochemical (PEC) water splitting is a sustainable means that can avert the effects of global warming caused by fossil fuels. For decades, a suitable semiconductor that can absorb solar radiation in the visible region has been a focal research question. Hematite has a theoretical Solar-To-Hydrogen efficiency of 15% which is higher than the 10% benchmark for PEC water splitting. Despite being cheap, chemically stable, and bearing a desired band gap, hematite has not reached this projection due to challenges like band edge mismatch, short hole diffusion length and charge recombination. Various articles have shown hetero-structuring is a reliable solution to some challenges due to enhanced spectral range, enhanced carrier mobility, strong built-in electric field and thus increase in efficiency. However, these articles lack scientific rationale on the performance of hematite and its hetero-structures on different substrates, which is the basis for this review. Our analysis suggests that hetero-structure improves hematite’s PEC performance due to increased spectral range, enhanced carrier mobility and built-in electric field. This review article is organized as follows: a brief PEC background, performance parameters, Physical and Crystallographic properties of hematite, device configurations, performance of hematite and its hetero-structures on different substrates.
Enhancing infrared solar absorption efficiency through plasmonic solar absorber using machine learning-assisted design
(Springer Link- Plasmonics, 2024-10-18) Muheki, Jonas; Patel, Shobhit K.; Ainembabazi, Fortunate; Al-Zahrani, Fahad Ahmed
This research introduces the architecture of an infrared solar energy absorber coupled with absorption prognosis employing machine learning techniques. Our approach involves creating an efficient absorber tailored for infrared wavelengths complemented by a machine learning model for accurately predicting absorption levels. The absorber's design focuses on maximizing absorption within the 0.7 µm to 4.0 µm range. We optimized the absorber's parameters, including resonator thickness, substrate thickness, and angle of incidence. Simulation results demonstrate excellent absorption performance, capturing over 90% of light within the specified range. At angles between 0° and 40°, the average absorptance exceeds 80%, peaking at 97.16%. However, at an 80° angle of incidence, absorptance drops to 23.3%. The study employs a 1D-CNN regression model to estimate absorption at various wavelengths, which greatly decreases the time required for simulations and experiments. The findings demonstrate the promise of combining metamaterial structures with machine learning approaches to boost the efficiency of solar energy harvesting and conversion processes.
Experimental comparison of erythritol and erythritol-granite pebble mixtures as heat storage materials for solar cooking
(Green Technology & Innovation, 2025-02-19) Mawire, Ashmore; Abedigamba, Oyirwoth P.
In this article, a comparison is presented between a pure latent heat storage system (erythritol) and a mixed storage system consisting of equal mass ratios of erythritol and granite pebbles (5 – 10 mm) for a solar cooking application. Two small black stainless cooking pots with a capacity of 1 L were placed inside two larger 5 L cooking pots to form simple storage cooking pots. The space between the pots was filled with thermal energy storage (TES) material. In the first configuration, the space between the pots was filled with 2 kg of erythritol. In the second configuration, the storage system consisted of 1 kg of erythritol and 1 kg of granite pebbles in the same space. The first experimental tests involved charging the storage cooking pots without any load for 4 h, followed by discharging them using heating loads in insulated wonder bags to evaluate off-sunshine cooking performance for another 4 h. The second experimental test involved simultaneous cooking and heat storage alternating between charging and discharging cycles. Experimental results showed that the mixed storage system achieved higher temperatures than the erythritol storage system during charging without cooking. During discharging cycles, the heat utilization rate was faster for the mixed storage system than for the erythritol storage system. Both storage systems enabled the cooking of multiple meals within an 8-h cooking period. However, at the end of the experiments, the erythritol storage system retained higher temperatures than the mixed storage system. Future work will focus on characterizing the thermophysical properties of the mixed storage system, optimizing the erythritol-to-granite mixing ratio for improved thermal performance, and investigating alternative, locally available TES materials – such as sandstone, marble, limestone, and xylitol – for potential use in mixed storage systems.
Green synthesis of hematite nano flakes and their application as a counter electrode in dye-sensitized solar cells
(Scientific Reports, 2025-06-05) Mukhokosi, Emma Panzi; Mushebo, Emmanuel; Nassejje, Stella; Botha, Nandipha L.; Velauthapillai, Dhayalan; Maaza, Malik
This study pioneers using hematite nanoflakes as a viable alternative to traditional platinum counter-electrodes in dye-sensitized solar cells (DSSCs), demonstrating its effectiveness for the first time. Besides such a novelty, the used hematite nanoflakes were bio-engineered using ginger extract as an effective chelating reducing agent. From the X-ray diffraction studies, it was observed that the sample annealed at 700 °C formed a highly crystalline α-Fe2O3, with a crystallite nano-scaled size of the order of 46.3 nm. The scanning electron microscopy investigations indicated a preferred layered nanoflakes morphology while the optical properties revealed a direct band gap of 2.30 eV. Using N-719 dye as a sensitizer on TiO2 photoanode and I−/I3− as electrolyte, the DSSC was fabricated. Such a cell exhibited significant DSSC responses, namely; a short circuit current density (JSC) of 7.0 mAcm−2, an open circuit voltage (VOC) of 389 mV, and a fill factor (FF) of 75.3% in addition to an efficiency (η) of 2.05%. Based on such a significant photo-conversion response using bio-engineered active counter electrodes, this study provides a cost-effective approach for synthesizing hematite NFs that have potential applications not only in DSSC but also in sensors, water splitting, and electrochemical devices.
Influence of device architectures and mobility on response/recovery time of metal halide perovskites: A review
(Journal of Materials Science, 2022-01) Emma, Panzi Mukhokosi; Maliki, Maaza
Organic–Inorganic perovskite materials have attracted great interest in the research community for photo-detector and solar energy applications. For various photo-detector applications, the response time is a very important parameter. In telecommunication, a high response speed is required and for this special class of materials, a fast response time in the order of ns has been realized by some authors. The main challenge is their stability. It is established that the response time is primarily controlled by the electron/hole mobility, electrode spacing and the depletion width. In this review, we discuss the recent developments of photo-detector devices composed of mixed halide perovskites and their performance with the main emphasis on the role played by mobility and internally generated electric field to the response/recovery speed. We discuss how the response speed clear relates to charge carrier mobility and depletion width. We further suggest ways on how to improve the response speed to match those of the conventional commercial photo-detectors like Si and InGaAs. We hope this article will find a suitable audience who will utilize this knowledge in the design and construction of ultra-fast photo-detectors.
Optical absorption and photoluminescence properties of Cucurbita maxima dye adsorption on TiO2 nanoparticles
(IOP Publishing Materials Research Express, 2023-04) Emma, Panzi Mukhokosi; Maliki, Maaza; Muhammed, Tibenkana; Nandipha, L Botha; Loyce, Namanya; Madiba, I G; Michael, Okullo
Dye-sensitised solar cells (DSSCs) are 3rd generation photovoltaic device that imitate photosynthesis in plants. The fundamental concept of a DSSCs is that the photoanode is covered by the dye as a sensitiser. Natural dyes from plant-based extracts have gained attention as alternatives to toxic and expensive commercial dye sensitisers. Various studies have been conducted on the use of natural plant dye extracts for DSSCs . However, more fundamental studies on their adsorption on TiO2 photoanode nanoparticles are still not well understood. In this study, we investigated the crystal structure, optical absorption, and photoluminescence properties of TiO2, Cucurbita maxima, and Cucurbita maxima dyes adsorbed on TiO2 nanoparticles as potential materials for DSSCs. Raman spectra confirmed the anatase phase of the TiO2 nanoparticles. The particle size of 12 ± 2 nm was confirmed through the transmission electron microscope. The optical absorption properties of Cucurbita maxima show two distinct absorption bands: blue visible (450–500 nm) and red visible (635–674 nm). The photoluminescence spectra of the dye extract and its adsorption onto the TiO2 nanoparticles showed two prominent peaks in the blue and red regions of the electromagnetic spectrum. No significant peak is observed in the green region of the electromagnetic spectrum. These studies shed more light on the fundamental properties of chlorophyll adsorption on TiO2 nanoparticles and their optical and photoluminescence properties for applications as sensitisers in DSSCs.
Planet population synthesis: the role of stellar encounters
(Monthly Notices of the Royal Astronomical Society, 2022-03) Ndugu, N; Abedigamba, O P; Andama, G
Depending on the stellar densities, protoplanetary discs in stellar clusters undergo: background heating; disc truncation-driven by stellar encounter; and photoevaporation. Disc truncation leads to reduced characteristic sizes and disc masses that eventually halt gas giant planet formation. We investigate how disc truncation impacts planet formation via pebble-based core accretion paradigm, where pebble sizes were derived from the full grain-size distribution within the disc lifetimes. We make the best-case assumption of one embryo and one stellar encounter per disc. Using planet population synthesis techniques, we find that disc truncation shifts the disc mass distributions to the lower margins. This consequently lowered the gas giant occurrence rates. Despite the reduced gas giant formation rates in clustered discs, the encounter models mostly show as in the isolated field; the cold Jupiters are more frequent than the hot Jupiters, consistent with observation. Moreover, the ratio of hot to cold Jupiters depend on the periastron distribution of the perturbers with linear distribution in periastron ratio showing enhanced hot to cold Jupiters ratio in comparison to the remaining models. Our results are valid in the best-case scenario corresponding to our assumptions of: only one disc encounter with a perturber, ambient background heating, and less rampant photoevaporation. It is not known exactly of how much gas giant planet formation would be affected should disc encounter, background heating, and photoevaporation act in a concert. Thus, our study will hopefully serve as motivation for quantitative investigations of the detailed impact of stellar cluster environments on planet formations.
Structural and mechanical properties of non-glazed ceramic tiles developed from selected mineral deposits in Uganda
(Nano-Horizons: Journal of Nanosciences and Nanotechnologies, 2023-07) George, William Mukwaya; Ben, Enjiku; Emma, Panzi Mukhokosi
Uganda is well endowed with clay resources; however, comprehensive knowledge about the composition, structure and suitability of these clays for ceramic tile production is lacking. In this study, we provide a comprehensive characterisation of locally sourced clays in Uganda and their suitability for ceramic tile production. In the study, we developed ceramic tiles using feldspar, kaolin, ball clay and sand from four different sites in Uganda. We focused on analysing the surface morphology, crystallographic structure and mineralogical composition of the raw materials. In addition, we examined the mechanical properties of the developed tiles with the different mixture ratios of the clay types. The surface morphology of the raw materials was analysed by using a scanning electron microscope. The structural analysis of the raw clay materials was done using X-ray diffraction. The mineralogical composition of the raw materials was investigated using energy dispersive X-ray spectroscopy and X- ray fluorescence spectroscopy. The results indicated that the strength and rapture modulus are influenced by the composition of kaolin and feldspar. We concluded that the selected mineral deposits can be used in the production of ceramic tiles in Uganda.
Structural, chemical, and mechanical properties of concrete developed from a binder composite of sugarcane bagasse ash and Portland cement
(Discover Materials, 2025-06-05) Nzugua, Michael Evans; Mukhokosi, Emma Panzi; Kinyera, Sam Obwoya
The East Africa Community (EAC) countries have immense sugarcane cane bagasse ash (SCBA) which remains unexploited as a supplementary-cementitious material (SCM). This study delved into using EAC SCBA as a pozzolan. SCBA investigated was collected from Kenya’s coastal area. Raw SCBA, processed SCBA, Portland cement (PC) and the developed concrete were characterised by various techniques to determine the surface morphology, chemical composition, structural properties and mineralogical composition. The raw SCBA was calcined at 600 °C then used to design the concrete mix. PC was replaced with SCBA from 0 to 30% in steps of 10%. The flexural and compressive strengths were determined in the hardened state after 28 days of concrete curing. The compressive and flexural strengths of the mix containing 20% SCBA were higher than the control mix by 9.65 and 6.51%, respectively. The microstructural properties of the developed concrete revealed dense particle distribution, indicating good micro/nanofiller effects of the interfacial transition zone (ITZ). The processed SCBA was found to meet class N and F of natural pozzolan as per ASTM C 618. This study suggests that the Kenya coastal SCBA can be used as a supplementary cementitious material.
Temperature dependent microstructural defects and surface charge effects on antioxidant activity of green synthesized nanoceria
(Scientific Reports, 2025-08-08) Musa Kabagambe; IsaAhuura; Sam Kinyera Obwoya; Emma Panzi Mukhokosi
This study reports a novel eco-friendly route for synthesizing cerium dioxide nanoparticles (nanoceria) that converts waste coffee husks into both reagent and process medium. Polyphenol rich phytochemicals chelate Ce3+, guide hydrolysis, and locally modulate redox conditions, imprinting abundant surface Ce3+ and oxygen vacancies that underpin activity. Reuse of the clarified supernatant in successive cycles boosts yield exponentially without added metal oxide precursor, highlighting intrinsic process efficiency. Subsequent calcination turns the bio templated precipitate into phase pure fluorite CeO₂ whose crystallite size, strain, and defect concentration can be tuned by temperature alone. Higher temperatures enlarge particles and improve crystallinity while removing vacancies and strain. Radical scavenging assays show the highest activity in uncalcined material and a steady decline with increasing temperature that parallels the loss of surface Ce3+ and vacancies. Statistical analysis confirms that antioxidant performance depends on defect density, quantum confinement, and surface charge, whereas external morphology and residual organics are negligible. The unique mechanism is phytochemical-directed defect engineering, which couples the use of agricultural waste with precise control of redox-active sites to deliver tuneable nanoceria for biomedical, agricultural, and environmental remediation applications.
Unveiling the variability and chemical composition of AL Col
(MDPI Galaxies, 2025-08-14) Surath, C. Ghosh; Santosh Joshi; Samrat Ghosh; Athul Dileep; Otto Trust; Mrinmoy Sarkar; Jaime Andrés Rosales Guzmán; Nicolás Esteban Castro-Toledo; Oleg Malkov; Harinder P. Singh; Kefeng Tan; Sarabjeet S. Bedi
In this study, we present analysis of TESS photometry, spectral energy distribution (SED),high-resolution spectroscopy, and spot modeling of the α 2 CVn-type star AL Col (HD 46462). The primary objective is to determine its fundamental physical parameters and investigate its surface activity characteristics. Using TESS short-cadence (120 s) SAP flux, we identified a rotational frequency of 0.09655 d −1(Prot = 10.35733 d). Wavelet analysis reveals that while the amplitudes of the harmonic components vary over time, the strength of the primary rotational frequency remains stable. A SED analysis of multi-band photometric data yields an effective temperature (Teff) of 11,750 K. High-resolution spectroscopic observations covering wavelengthrange 4500–7000 Å provide refined estimates of Teff = 13,814 ± 400 K, log g = 4.09 ± 0.08 dex, and υ sin i = 16 ± 1 km s−1. Abundance analysis shows solar-like composition of O II, Mg II, S II, and Ca II, while helium is under-abundant by 0.62 dex. Rare earth elements (REEs) exhibit over-abundances of up to 5.2 dex, classifying the star as an Ap/Bp-type star. AL Col has a radius of R = 3.74 ± 0.48R⊙, with its H–R diagram position estimating a mass of M = 4.2 ± 0.2M⊙ and an age of 0.12 ± 0.01 Gyr, indicating that the star has slightly evolved from the main sequence. The TESS light curves were modeled using a three-evolving-spot configuration, suggesting the presence of differential rotation. This star is a promising candidate for future investigations of magnetic field diagnostics and the vertical stratification of chemical elements in its atmosphere.

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