Real-time monitoring of sulphur dioxide (SO2) across both trace (ppb) and higher (ppm) ranges is crucial for efficient environmental, household, and industrial applications. Thus, herein binary and ternary structures derived from In2O3/MoS2, SnO2/MoS2, In2O3/SnO2/MoS2, and SnO2/In2O3/MoS2 were successfully developed to boost optical, structural, and SO2 gas sensing capabilities. Structural analysis confirmed that the individual components integrated successfully, yielding well-defined heterostructures with strong interfacial contact between the metal oxides and the MoS2 layers. Morphological studies showed that porous nanoplatelets and hierarchical structures, especially in the ternary composites, increased the surface area and provided numerous active sites for gas adsorption. The In2O3/SnO2/MoS2 sensor demonstrated the best performance and selectivity for SO2 over a wide concentration range, spanning both ppm and ppb levels, at 100 degrees C, compared with the binary counterparts and the reversed stacking configuration. These improved sensing abilities are due to synergistic effects within the heterostructure, including efficient charge transfer at the In2O3/SnO2 interfaces, the high reactivity of MoS2, and the porous nanoplatelet, which enables fast gas diffusion and adsorption. Multiple heterojunctions modulated the electron-depletion layer during SO2 interaction, thereby enhancing sensitivity and selectivity compared to binary versions. These results emphasize the role of heterointerface engineering and porous nanostructure design in creating high-performance gas sensors for detecting sulfur gases at trace levels.
An azo coupling strategy designed to link 1-naphthol with three differently substituted diazonium chalcones predominantly yielded the 4-substituted naphthol isomers. Comprehensive characterization by NMR, FTIR, UV-Vis spectroscopy, electrochemistry, and DFT calculations demonstrated that the hydrazone (keto) tautomer overwhelmingly predominates over the azo (enol) form. The experimental tautomeric assignment was further supported by calculated vibrational frequencies and DFT-predicted equilibrium distributions. TDDFT calculations showed that the lowest-energy electronic transitions are predominantly hydrazone-centred it -> it* excitations, with the B3LYP functional providing the closest agreement with the experimental UV-Vis spectra. The calculated frontier molecular orbitals explain the nearly identical reduction potentials of compounds 1-3, confirming that electron addition occurs predominantly on the hydrazone-naphthalenone moiety. Furthermore, a clear correlation between the 13C NMR chemical shift of the napthalenone carbonyl carbon and the first reduction potential demonstrates that a lower electron density (deshielding) on this carbon facilitates reduction. These results establish the hydrazone-naphthalenone fragment as the principal structural motif governing the optical absorption and electrochemical behaviour of this class of azo-hydrazone chalcones.
Open-pit mining generates airborne particulate matter that can accumulate on vegetation and potentially influence herbivore foraging behaviour. However, the relative importance of foliar particulate deposition compared with habitat quality in driving habitat selection remains poorly understood in arid ecosystems. We investigated whether semi-quantitative foliar particulate indicators derived from scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) were associated with habitat patch selection by cattle (Bos taurus), sheep (Ovis aries), goats (Capra hircus), and springbok (Antidorcas marsupialis) in an arid shrub-grass savanna adjacent to an operational iron-ore mine in South Africa. Leaf-surface particulate signatures were quantified as elemental weight percentages (wt%) of aluminium (Al), magnesium (Mg), and silicon (Si), and compared between preferred and avoided habitat patches using stratified Wilcoxon (van Elteren) tests with animal identity treated as the stratification variable. Habitat-quality variables were subsequently evaluated alongside the measured foliar particulate indicators. Elemental signatures showed substantial overlap between preferred and avoided habitat patches. Although three element-by-growth-form comparisons were statistically significant, preferred patches consistently exhibited equal or higher elemental values than avoided patches, providing no evidence that the measured foliar particulate indicators were associated with habitat avoidance. In contrast, vegetation height and greenness showed stronger and more consistent relationships with habitat selection across species. These findings indicate that habitat quality outweighed the measured foliar particulate indicators in explaining grazer patch selection within this arid mining landscape. Because the SEM-EDS-derived elemental signatures cannot distinguish mine-derived particulates from natural background dust, these results should not be interpreted as evidence that mining-derived dust has no ecological effects. Rather, they demonstrate that the specific foliar particulate indicators measured in this study were poor predictors of observed habitat use, highlighting the need for future studies incorporating source-resolved dust measurements and quantitative particulate loading.
Macrophomina phaseolina, the causal agent of charcoal rot disease, poses a major threat to Phaseolus vulgaris production, particularly under climate change. Climate-induced environmental extremes, in which elevated temperatures and drought conditions favour disease development and pathogen aggressiveness, pose a major challenge to agricultural productivity globally. This study assessed the plant growth-promoting and biocontrol potential of six bacterial endophytic isolates against M. phaseolina in P. vulgaris, using an integration of biochemical, physiological antifungal, and seed germination assays. All the isolates show significant potential (p < 0.05) for producing ammonia and indole-3-acetic acid (IAA), solubilising nutrients, exhibiting hydrolytic enzyme activity, and demonstrating biocontrol traits. Of the six isolates, Serratia marcescens (PR1AI2) showed the highest IAA production and zinc solubilization activity, whereas Enterobacter sp. L1I9 showed enhanced phosphate solubilization. Protease activity was highest in PR1AI2, while Pseudomonas rhodesiae strain MSG-15 (L3I2) exhibited the strongest amylase activity. Dual culture assays demonstrated significant inhibition (p < 0.05) of M. phaseolina mycelial growth and reduction in sporulation by the endophytic bacterial isolates. Among the isolates, L3I2 had the highest inhibition of mycelial growth (75.93%), whereas PR1AI2 qualitatively showed the greatest sporulation reduction. Seed germination assays further showed variable responses under M. phaseolina, with Streptomyces bikiniensis strain SBM (L2I3) and Enterobacter kobei strain V51 (PR5AI1) showing germination percentages of 80.00% and 75.56%, respectively, compared with 76.67% in the M. phaseolina-treated control. These isolates therefore represent promising candidates for sustainable biological management of charcoal rot disease in P. vulgaris, as they possess multiple traits associated with pathogen suppression and improved plant development.
Metal-containing two-dimensional surfaces were prepared by exposing amine-capped silicon wafers to Mn ((3-diketonato)3 precursors [(3-diketonato = acetylacetonato, dibenzoylmethanato, trifluorofuroylacetonato or hexafluoroacetylacetonato] or M(acac)3 (M = Co, Rh or Ir). X-ray photoelectron spectroscopy (XPS) confirmed metal deposition. For the Mn-containing surfaces, strongly sub-stoichiometric F:Mn ratios for fluorinated precursors and broad, oxide-range Mn 2p envelopes indicate extensive ligand loss and heterogeneous, predominantly oxide-like Mn environments; the spectra do not uniquely establish individual Mn compounds or intact surface complexes. Metal:N ratios were therefore used only to estimate total XPS-detected metal surface densities, not molecular complexes or catalytically active sites. The surfaces promoted the reaction of ethanol with hexamethylenediisocyanate (HDI) to form hexamethylenediurethane (HDU). Total-metal-normalised apparent turnover frequencies (TOFapp) were approximately 5-127 s-1. Rh-derived surfaces gave the highest TOFapp. The qualitative association with precursor-metal Pauling electronegativity in this limited series is not proof of the electronic structure or mechanism of the active species.
