Search Results (8,676)

The aim of this paper is the analysis of the main elements of the patinas of an outdoor bronze monument by using portable energy-dispersive X-ray fluorescence (ED-XRF) equipment designed and assembled at the University of Salento. Thanks to the versatility of the ED-XRF portable apparatus, we carried out a scan based on a limited set of measurements that was representative of the studied surface of the monument before the restoration in a relatively short time and in a completely non-invasive way. We investigated the concentrations of copper, zinc, lead, chlorine, iron, tin and sulphur in the statue dedicated to the emperor Caesar Augustum, which was created in 1935 and later placed in Brindisi (Apulia, Southern Italy). Moreover, X-ray diffraction (XRD) and Raman spectroscopy were carried out for a sample of patina in order to identify its chemical composition. The information obtained can be helpful for restoration work on this statue and possible future monitoring. Full article

Chlorophyll, a natural photosynthetic pigment, is gaining interest for its sustainable and eco-friendly applications in renewable energy, particularly as a photosensitizer in dye-sensitized solar cells (DSSCs). This study investigates the feasibility of chlorophyll extracted from Moringa oleifera as a natural photosensitizer in DSSCs, building on our previous work demonstrating its high chlorophyll content and long-term stability. Chlorophyll was extracted using acetone under optimal conditions (45 °C, 60 min) and applied in DSSCs comprising a TiO₂ photoanode, iodide/triiodide electrolyte, and platinum counter electrode. The TiO₂ photoanode was characterised using UV-Vis spectroscopy, FE-SEM, XRD, and Raman spectroscopy, confirming the presence of pure anatase phase TiO₂ with uniform spherical nanoparticle morphology. The fabricated DSSCs achieved a short-circuit current density of 0.197 mA cm⁻², an open-circuit voltage of 0.44 V, a fill factor of 32%, and a photoconversion efficiency (PCE) of 0.027%. While this performance is lower than the highest reported chlorophyll-based DSSC efficiency (4.6%), the results demonstrate that M. oleifera is a viable and sustainable source of chlorophyll for DSSC applications. The findings highlight the importance of dye–semiconductor interactions and suggest that further optimisation through co-sensitization, TiO₂ surface modification, and improved dye anchoring could enhance device performance. Full article

ZnS is one of the most promising wide-bandgap semiconductors for optoelectronic and sensing applications owing to its efficient ultraviolet–blue emission, high exciton binding energy, and chemical stability. However, the synthesis of ZnS nanocrystals in silicon-compatible porous matrices remains largely unexplored. In this work, ordered arrays of ZnS nanocrystals were synthesized for the first time in SiO₂/Si track templates fabricated by swift heavy ion irradiation followed by selective chemical etching. ZnS nanocrystals were deposited by electrochemical deposition from aqueous solutions containing ZnCl₂ and thiourea precursors. The structural, optical, and electrical properties of the resulting ZnS/SiO₂/Si nanocomposites were investigated using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, photoluminescence spectroscopy, and electrical measurements. The fabricated templates contained vertically aligned pores with a density of approximately 10⁸ cm⁻² and an average diameter of about 500 nm. Electrochemical deposition resulted in a pore filling efficiency of approximately 88%. X-ray diffraction analysis confirmed the formation of crystalline ZnS with a cubic zinc blende structure. The nanocomposites exhibit intense ultraviolet–blue photoluminescence in the 335–477 nm range, with pronounced emission peaks at 372 and 400 nm characteristic of ZnS nanocrystals. Current–voltage measurements indicate predominantly electronic conductivity, with a conductivity of 1.54 × 10⁻⁶ Ohm⁻¹·cm⁻¹, comparable to values reported for polycrystalline ZnS films. To support the experimental observations, the electronic structure of ZnS was analyzed using density functional theory within the LCAO framework. The calculated bandgap of 3.4 eV is consistent with previously reported theoretical and experimental data. The obtained results demonstrate that SiO₂/Si track templates provide a promising platform for the fabrication of ordered ZnS nanoarrays with potential applications in silicon-compatible optoelectronic and sensing devices. Full article

The corrosion behavior of ferritic–martensitic 17Cr stainless steel in CO₂-saturated brine was investigated using static autoclave immersion tests in 4.12 wt% NaCl solution at 230 °C under CO₂ partial pressures of 6.36, 18.28, and 24.57 MPa. The calculated in situ pH values obtained using the OLI System were 3.79, 3.55, and 3.49, respectively. Corrosion morphology, microstructural evolution, and corrosion products were characterized by SEM, EDS, EBSD, and Raman spectroscopy. The average mass-loss corrosion rate increased from 0.138 ± 0.0221 mm/year at 6.36 MPa pCO₂ to 0.326 ± 0.0142 mm/year at 24.57 MPa pCO₂. Although the specimens did not show severe macroscopic pitting, localized attack preferentially occurred in fine-grained martensitic banded regions. EBSD analysis revealed that these regions exhibited higher local misorientation and defect density, which may reduce the stability of Cr-rich surface films. Raman spectra identified Cr(OH)₃ in the corrosion products, and the Cr(OH)₃ signal became more evident with increasing CO₂ partial pressure. The results indicate that, under fixed temperature and salinity, the corrosion behavior of 17Cr stainless steel is governed by CO₂ partial pressure and microstructural heterogeneity. Full article

Raman spectroscopy is a non-destructive, label-free analytical technique that can probe biochemical alterations in tissues and cells. Raman spectroscopy, being sensitive to biochemical perturbations, can potentially provide early and real-time identification of changes preceding morphological changes, allowing early diagnosis as well as disease monitoring. Recent research has demonstrated its broad utility across diverse clinical domains, including cancers, neurological conditions, and infections. Raman spectroscopy combined with machine learning algorithms allows rapid assessment and automated pipelines and can act as a clinical adjunct, enhanced by integrating tools like principal component analysis (PCA), linear discriminant analysis (LDA), random forests, and deep-learning architectures. These models allow interpretation of complex spectra, and decipher meaningful biomarkers in heterogeneous clinical samples. This review highlights the earliest and most recent progress in Raman-based non-destructive diagnosis, underscoring advances in cancer diagnosis and challenges faced in clinical settings. Full article

The increasing demand for materials with enhanced properties and high-performance devices has driven substantial research into nanomanufacturing, particularly using carbon nanotubes (CNTs), because of their exceptional properties and high sensitivity to chemical doping. In this way, this work summarizes nanomanufacturing methods for CNT-based devices developed in Brazil, covering the complete cycle from nanocomposite production to functional device assembly across cellulosic, polymeric, and metallic matrix systems. For cellulosic matrices, vacuum filtration enables the production of buckypaper, which is subsequently assembled into chemiresistive, thermoresistive, and thermoelectric devices. For polymeric matrices, 3D printing combined with surface functionalization techniques (spray coating, inverted immersion, and direct immersion) produces piezoresistive robotic sensors, metal-free thermal sensors, and biomedical scaffolds for tissue engineering. For metallic matrices, electrodeposition can produce Cu-CNT-coated aluminum comparable to traditional copper power transmission cables, while arc welding produces stainless steel composites with properties comparable to commercial high-grade steels. These devices have commercial and industrial applications, with low-cost and scalable production methods in comparison with conventional materials. Characterization results demonstrate that CNT integration into diverse matrices successfully bridges nanoscale properties to macroscopic functional devices. Current challenges include uniform CNT dispersion and structural defect control, laboratory to industry scale transition, and long-term device stability under environmental conditions. Future perspectives encompass lab-on-chip systems, wearable devices, 3D-printed smart structures, Internet of Things integration, and machine learning-enhanced analytics. Full article

The presence of pharmaceuticals in treated wastewater has become an environmental concern due to their persistence, biological activity, and incomplete removal in conventional wastewater treatment systems. In this study, a g-C₃N₄/rGO nanocomposite was synthesized via thermal polycondensation of melamine in the presence of reduced graphene oxide and evaluated as a photocatalyst for the degradation of selected pharmaceuticals in membrane bioreactor (MBR)-treated wastewater. The obtained materials were characterized using Fourier-transform infrared spectroscopy (FTIR–ATR), X-ray diffraction (XRD), nitrogen adsorption–desorption measurements (BET), Raman spectroscopy, scanning electron microscopy (SEM), and UV–Vis spectroscopy to evaluate their chemical structure, crystallinity, textural properties, morphology, and optical characteristics. Photocatalytic experiments were performed under UV irradiation using real wastewater spiked with carbamazepine, diclofenac, ibuprofen, and sulfamethoxazole at an initial concentration of 50 mg/L, selected to ensure reliable quantification under laboratory conditions. The complete removal of diclofenac and sulfamethoxazole was achieved within 30 min of treatment, while the presence of the nanocomposite enhanced the degradation efficiency of ibuprofen and carbamazepine by approximately 19% and 13%, respectively, compared to UV irradiation alone. The obtained results demonstrate the applicability of the investigated g-C₃N₄/rGO system for pharmaceutical degradation in real wastewater matrices and indicate its potential as a preliminary photocatalytic post-treatment approach. Full article

The selective gas-phase oxidation of γ-picoline (γ-P) to isonicotinic acid (INA)—a key precursor for the anti-tuberculosis drug isoniazid—was investigated over a V–Mn oxide catalyst as a solvent-free, waste-minimizing alternative to conventional liquid-phase synthesis routes. XRD and Raman spectroscopy confirmed the formation of a stable manganese vanadate crystalline phase with a high concentration of terminal vanadyl groups (V=O), providing well-defined redox-active sites. Water vapour proved essential for sustainable process performance: at an optimal H₂O/substrate molar ratio of 98, γ-picoline conversion reached 94.8% with INA selectivity of 86.5%, eliminating the need for hazardous solvents or additives. NH₃-TPD and kinetic analysis revealed that water vapour acts as a competitive adsorbent at vanadium Lewis acid sites, accelerating target product desorption and suppressing deep oxidation to COx—directly reducing carbon waste. Long-term stability was assessed over 96 h of continuous operation: the 23.4% decline in specific surface area correlated with an equivalent reduction in total acidity, while pore diameter expansion from 2.07 to 3.25 nm mitigated diffusion limitations, partially compensating for deactivation. These findings establish the V–Mn oxide system as a promising green catalytic platform for upgrading petrochemical fractions into high-value pharmaceutical intermediates with reduced environmental impact. Full article

Sickle cell disease (SCD), the most common inherited blood disorder in the United States, affects approximately 100,000 individuals annually. A major complication of SCD is sickle cell bone disease, which results in substantial bone loss comparable to osteoporosis. Previous work showed that treatment with GBT1118, a sickle hemoglobin polymerization inhibitor, improved bone formation and reduced bone resorption in humanized SCD mice. However, its effects on bone material and mechanical properties were unknown. To address this, four-month-old control and SCD mice were fed vehicle or GBT1118 chow for two months. Hematocrit levels, significantly reduced in SCD mice of both sexes, were restored by GBT1118 treatment, confirming its efficacy in improving anemia. Raman spectroscopy revealed increased mineral-to-organic matrix ratios in SCD femurs of both sexes and elevated carbonate-to-phosphate ratios in males, none of which were altered by GBT1118. Mechanical testing showed decreases in ultimate stress and Young’s modulus in female SCD femurs, with no significant differences in males nor rescue by GBT1118. Thus, while GBT1118 improved hematological parameters, it failed to restore the impaired bone material properties observed in SCD mice, highlighting the need for additional therapeutic strategies to address bone fragility in sickle cell disease. Full article

The Lantana genus, especially L. camara, has emerged as a potential yet underutilized lignocellulosic feedstock for various catalytic thermochemical conversion products and advanced carbon materials. This study reviews recent developments in the valorization of Lantana biomass to generate biofuels, bio-oil, syngas, and engineered biochar materials through pyrolysis, gasification, hydrothermal processing, and integrated biorefinery processes, in a critical manner. Particular focus will be on nanocomposite-modified, metal-doped biochar with catalytic elements such as ZSM-5, Fe₃O₄, TiO₂, and Ni-, Co-, and Zn-based oxides to enhance deoxygenation, catalytic cracking, tar reforming, pollutant remediation, and energy storage. Recent developments in catalyst synthesis techniques, such as impregnation, hydrothermal deposition, and in situ functionalization, are reviewed, along with characterization methods including BET, XRD, SEM/TEM, Raman spectroscopy, and XPS. The review further examines the impact of pore structure, surface chemistry, the presence of redox-active centers, and catalyst stability on product selectivity, syngas quality, and upgrading bio-oil performance. The effects of biochar on microbial immobilization, anaerobic digestion, and integrated biochemical conversion are discussed in detail, excluding thermochemical effects. The challenges of catalyst deactivation, biomass heterogeneities, scalability, techno-economic viability, and decentralized biomass logistics are also discussed. In summary, the development and implementation of catalytic reaction engineering, the design of nanocomposite biochar, and circular bioeconomy strategies have great potential to facilitate the conversion of invasive Lantana biomass into renewable fuels, multifunctional carbon materials, and environmentally friendly bioeconomy products. Full article

This study investigated whether salinity during cultivation of the aquatic plant Lemna minor (duckweed) influences the phytochemical composition of plant extracts and the properties of green-synthesized zinc oxide nanoparticles (ZnO NPs). Duckweed was cultivated under 0, 10, and 100 mM NaCl, followed by Orbitrap metabolomic profiling, nanoparticle synthesis, physicochemical characterization, and evaluation of antioxidant and antimicrobial activities. Orbitrap analysis revealed pronounced salinity-dependent changes in extract composition, including increased abundance of several flavonoids, glycosylated flavones, and hydroxycinnamic acid derivatives in the order 0 < 10 < 100 mM. ZnO nanoparticle formation was supported by UV–Vis spectroscopy, which showed characteristic absorption features around 360 nm, and by powder X-ray diffraction (PXRD), which indicated the predominance of the hexagonal wurtzite ZnO phase in all samples. SEM–EDS analysis revealed Zn- and O-rich materials consisting of micron-scale aggregates and finer submicron structures. Raman spectra were dominated by fluorescence, which increased with salinity treatment and may reflect differences in surface-associated phytochemicals rather than substantial changes in the ZnO crystal structure. Nanoparticles synthesized using extracts from salt-stressed duckweed exhibited higher total phenolic content (up to 66.79 ± 0.15 µM GAE g⁻¹), antioxidant activity (up to 55.01 ± 0.21%), and antimicrobial activity against Staphylococcus haemolyticus D4-2-100/1 (inhibition zone up to 1.55 ± 0.05 cm). Although the mechanisms underlying these differences remain to be fully elucidated, the results suggest that salinity-induced changes in duckweed metabolism may influence the biological properties of the resulting nanomaterials. Overall, this study highlights the potential of manipulating cultivation conditions to modulate plant extract composition and, consequently, influence the characteristics and functionality of green-synthesized ZnO nanoparticles. Full article

Hydrogen–steel interactions remain a critical concern for the safe deployment of hydrogen–natural gas mixtures in pipeline infrastructures. Thermally grown iron oxides may be a good barrier to hydrogen ingress into the crystalline lattice of pipeline steels, but their actual effectiveness depends strongly on their composition and stability under service conditions. Several experimental approaches have been proposed to investigate the correlation between thermally grown oxides and hydrogen permeation. Among these, electrochemical permeation testing offers a more complex but safer methodology compared to pressurized hydrogen gas tests. However, when the oxide is directly exposed to the charging side (cathodic charging conditions), permeation behaviour often appears comparable to that of bare steel, and rapid oxide degradation occurs. This study introduces an alternative permeation testing configuration that enables direct assessment of thin thermally grown oxides while preserving their structural integrity. By deliberately placing the oxide on the anodic detection side, mechanical removal during hydrogen evolution is suppressed, allowing the intrinsic resistance of the oxide to hydrogen transport to be evaluated. Carbon steel samples were thermally oxidized at 250 °C for controlled exposure times, and the resulting oxide scales were characterized by Raman spectroscopy, revealing variations in hematite and magnetite fractions. Hydrogen permeation was evaluated using a Devanathan–Stachurski cell by positioning the oxidized surface either on the cathodic charging side or on the anodic detection side. Under these conditions, significant variations in apparent steady-state permeation current density were observed as a function of oxidation time and oxide composition. Full article

Gray siliceous concretions represent the most ubiquitous surface deposits on marine-excavated ceramics from the Nanhai No. 1 shipwreck. These concretions obscure decorative motifs and glaze surfaces of the artifacts, posing challenges to archeological interpretation and heritage conservation. This study conducted a multi-technique characterization of one representative gray siliceous concretion using micro-CT, PLM, SEM-EDS, XRD, FTIR, and micro-Raman spectroscopy. The concretion exhibits distinct three-tier density stratification and consists of quartz, muscovite, calcite, pyrite, and Mg-rich authigenic silicates (serpentine and talc), with quartz and muscovite as the dominant crystalline phases. Its mineral components are inferred to originate from terrigenous clastic, biogenic, and authigenic sources. This work provides fundamental mineralogical data to support the development of targeted conservation strategies for analogous marine-excavated ceramic heritage. Full article

Two-electron oxygen reduction reaction (2e⁻-ORR) represents a sustainable and energy-efficient approach for decentralized hydrogen peroxide (H₂O₂) production compared with the conventional anthraquinone process. Among various electrocatalysts, metal–nitrogen–carbon (M–N–C) materials have attracted extensive attention owing to their tunable electronic structures and favorable *OOH adsorption behavior. However, the uncontrolled pyrolysis process generally leads to structurally heterogeneous and ill-defined coordination environments, making it difficult to precisely regulate active sites and understand catalytic mechanisms. Herein, we report a single-atom catalyst (CoN@OCNT) featuring spatially confined pyridinic-N-coordinated Co single sites, synthesized by anchoring a well-defined hexapod terpyridine Co-precursor onto oxidized carbon nanotubes (OCNTs) to suppress metal aggregation during pyrolysis. Benefiting from the optimized coordination environment and enhanced mass/electron transfer, the CoN@OCNT catalyst exhibits nearly 100% H₂O₂ selectivity over a wide potential window from −1.0 to 0.66 V versus RHE in neutral electrolyte. In situ FT-IR and Raman spectroscopy reveal a rapid *OOH-mediated reaction pathway during the 2e⁻-ORR process. Furthermore, membrane electrode assembly (MEA) testing demonstrates an H₂O₂ production rate of 21.8 mol h⁻¹ g_cat⁻¹ with stable operation over 80 h at 60 mA cm⁻². Remarkably, at an industrially relevant current density of 300 mA cm⁻², the catalyst achieves a record H₂O₂ production rate of 70.3 mol h⁻¹ g_cat⁻¹ and a salt-free H₂O₂ concentration of 9.4 mM, highlighting its great potential for practical large-scale H₂O₂ electrosynthesis in neutral media. Full article

The development of sustainable electrode materials for supercapacitors requires a deeper understanding of the relationship between precursor structure, processing, and electrochemical performance. In this work, coconut-fiber-derived activated carbons were synthesized via KOH activation, and the influence of oxidative and hydrothermal pre-treatments was systematically investigated. The materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR), while electrochemical performance was evaluated using cyclic voltammetry and galvanostatic charge–discharge measurements in a three-electrode system with 1 M H₂SO₄ electrolyte. The results show that hydrothermal pre-treatment leads to improved electrochemical performance, with CF-HTC-AC exhibiting a specific capacitance of ~332 F g⁻¹ at 0.5 A g⁻¹ and enhanced rate capability. In contrast, the oxidatively treated sample (CF-OC-AC) presents a higher diffusion-controlled contribution, indicating a stronger pseudocapacitive behavior associated with oxygen-containing functional groups. These findings demonstrate that electrochemical performance is governed by a balance between capacitive and diffusion-controlled processes rather than by a single structural parameter. The hydrothermal pre-treatment provides an effective strategy to optimize this balance, highlighting precursor conditioning as a key factor in the design of biomass-derived carbon electrodes for supercapacitor applications. Full article