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Povzetek: Single metal atom catalysts (SACs) are receiving widespread attention in electrochemical energy conversion reactions due to the rational use of metal resources and maximum atom utilization efficiency. The role of the support in stabilizing the single atoms is crucial for their catalytic stability. Carbon nitride (CN) is an excellent support for SACs but its low electrical conductivity is not appropriate for electrochemical applications. Here, we report an engineered composite material based on multiwall carbon nanotubes (MWCNTs) and single nickel atoms stabilized on CN (Ni–CN) as efficient and robust electrocatalyst for the oxygen evolution reaction (OER). Composites with different mass Ni–CN:MWCNT ratios have been prepared to optimize the contribution of both materials, and characterized by X-ray diffraction, transmission electron microscopy, X-ray absorption, and X-ray photoemission spectroscopy. Results confirmed the self-assembly of both materials and the condensation of the triazine-based structure of CN into heptazine-based onto the MWCNTs’ surface during the synthesis, as well as the presence of single Ni atoms in the composites. The co-presence of NiO nanoparticles was detected for the samples with the highest Ni content. The ratio of NiO nanoparticles to single-atom Ni centers was governed by the Ni–CN:MWCNT ratio employed during synthesis. Electrochemical characterization showed a synergistic effect between Ni–CN and MWCNTs that boosted the OER activity of the composites respect to the individual components. The 1:2 ratio turned out to be the optimal one for the composite preparation, maximizing the combined effects of the catalytic activity of the Ni centers and the electrical conductivity of MWCNTs. The mass activity obtained by this composite was 30 times higher than that of the Ni–CN starting material, attributable to its superior electrical conductivity and improved accessibility of Ni active sites. This study underscores the potential of composite materials to advance SACs toward large-scale application.
Ključne besede: carbon nanotubes, carbon nitride, single atom catalysts, nickel oxygen evolution reaction
Objavljeno v DiRROS: 18.09.2025; Ogledov: 325; Prenosov: 127
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Povzetek: Children’s lead exposure in three mining-impacted residential areas (Črna, Mežica and Žerjav) was modelled using the Integrated Exposure Uptake Biokinetic Model for Lead in Children (IEUBK). Site-specific environmental and dietary Pb source values were determined for modelling. For the first time, dietary exposure from both market and local foods was studied in detail. Children (Group 1: 24–36 and Group 2: 36–48 months) geometric mean blood lead levels (BLLs) were predicted and lead uptake from multiple sources was quantified according to the different dietary exposure scenarios. Biomonitoring data were used for validation. Site-specific soil, house dust and local food Pb contents are higher than legislative and background levels, remaining a cause for concern. Drinking tap water concentrations and outdoor air contents were found in acceptable levels. The determined dietary exposures, ranging from 0.7 to 3.3 µg/kg bw/day, were above the benchmark dose level of 0.5 µg/kg bw/day for developmental neurotoxicity set for Pb in children, indicating a health concern. In general, the estimated BLLs matched reasonably well with the observed BLLs in the Črna and Mežica area for both age groups and in the Žerjav area for Group 2. For Group 1, in the Žerjav area, the output of the IEUBK model overestimated the actual BLLs of the children. For both groups, the primary exposure pathway in Žerjav is from soil/dust, ranging from 55.3 to 84.8%. In Črna and Mežica, soil/dust exposure ranged between 24.2 and 57.8% and between 26.4 and 61.7%, respectively, indicating that dietary exposure predominates when local foods are included. The results of our study also suggest that using the IEUBK default diet value would reduce the dietary exposure up to 25.2% in Črna, 24.2% in Mežica and 8.6% in Žerjav. One of the main findings is that a diet containing local foods can be an important source of lead in mining-contaminated areas.
Ključne besede: IEUBK model, blood lead level, soil, house dust, dietary exposure, risk assessment
Objavljeno v DiRROS: 18.09.2025; Ogledov: 322; Prenosov: 114
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Povzetek: Recently, we have demonstrated that dye-doped soap and smectic bubbles can be used as lasers. Here we investigated smectic bubble lasers for their potential to measure pressure changes in both air and water and as microphones. Smectic bubbles consist of a very thin smectic liquid crystal film. In contrast to ordinary soap bubbles, smectic bubbles are highly stable. When illuminated with a pump laser, they exhibit whispering gallery mode lasing with sharp, regularly spaced peaks in the emission spectrum. The bubbles enable extremely precise measurement of pressure changes based on wavelength shifts of the lasing peaks. We have demonstrated that smectic bubbles can be inflated under water and used as water pressure sensors. Additionally, we have used smectic bubble lasers in air as highly sensitive microphones to detect sound waves across different frequencies with advantages over conventional microphones. Their extremely thin walls result in negligible acoustic impedance. Furthermore, bubble size changes due to pressure variations depend only on bubble volume, eliminating the need for calibration and making performance independent of manufacturing precision or defects. This also leads to a linear amplitude response, and a flat frequency response over a wide range of frequencies. Unlike most microphones, bubble lasers can measure arbitrarily small frequencies down to static pressure, making them promising candidates for acoustic wave detection in various applications.
Ključne besede: smectic bubbles, liquid crystal lasers, smectic liquid crystals, water pressure
Objavljeno v DiRROS: 18.09.2025; Ogledov: 263; Prenosov: 139
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Povzetek: Laboratory and field assessments of low-cost sensors (LCS) are essential for ensuring the accuracy of PM2.5 measurements collected by citizens in air quality campaigns. Evaluation of Sensirion SPS30 (LCS SPS30) in controlled laboratory setting showed a coefficient of determination (R2) ranging from 0.81–0.99 and a root mean square error (RMSE) from 0.81–61.72 μg m−3, at average concentration of 21.5 μg m−3. In contrast, co-location assessment at an average concentration of 9 μg m−3 resulted in R2 of 0.5 and a RMSE of 6.82 μg m−3. The results demonstrated that the sensor met micro-environmental monitoring standards (accuracy < 25%) and United States Environmental Protection Agency's performance criteria (RMSE ≤ 7 μg m−3, R2 > 0.7) only at relative humidity (RH) levels below 60%, emphasising its strong sensitivity to RH and the need for RH-dependent data corrections. The observed underestimation or overestimation of PM2.5 readings was primarily attributed to variations in particle composition and concentration. Despite accuracy variations, LCSs can effectively capture spatiotemporal urban air quality patterns and identify pollution hotspots in community monitoring, particularly in low-pollution environments. In a citizen-led PM2.5 monitoring campaign in Maribor, Slovenia, the lowest concentrations were recorded at 15:00 (2.9 μg m−3), while the highest occurred during the morning rush-hour (4.8 μg m−3), likely attributed to the planetary boundary layer’s impact on atmospheric particulate dispersion. Spatial analysis revealed that hotspots clustered near intersections, where vehicle waiting time is the longest.
Ključne besede: particulate matter, low-cost sensor, Sensirion SPS30, citizen science, calibration
Objavljeno v DiRROS: 18.09.2025; Ogledov: 280; Prenosov: 190
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Objavljeno v DiRROS: 17.09.2025; Ogledov: 343; Prenosov: 171
Celotno besedilo (1,74 MB)
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