Search Results (87)

Defect engineering and metal–support coupling provide an effective route to tune interfacial charge dynamics for selective photocatalytic CO₂ reduction. Here, Ti-vacancy-rich Bi₄Ti₃O₁₂ (BTvO) nanosheets were prepared and decorated with Au nanoparticles (Au NPs) to build Au-BTvO junctions that favor multi-electron/proton transfer toward deep hydrogenation. The optimized 3%Au-BTvO achieved high hydrocarbon productivity under visible light (λ > 420 nm), delivering CH₄ and C₂H₆ formation rates of 92.66 and 17.96 μmol g⁻¹ h⁻¹, respectively, with stable performance over 25 h. Spectroscopic analyses reveal higher CO₂ uptake and more effective surface activation, increased water adsorption with a more favorable interfacial hydration environment, and time-dependent formation of key C₁ and C₂ intermediates. In situ light-irradiation XPS, PL mapping, and KPFM collectively demonstrate directional electron transfer from Bi₄Ti₃O₁₂ to Au and amplified surface band bending, enabling efficient charge separation and accelerated surface reduction. This work highlights defect–metal synergy as a general strategy to boost activity, selectivity, and durability in visible-light CO₂-to-methane conversion. Full article

The aim of the study was to develop hybrid nanomaterials based on monodisperse silica spheres as carriers for silver nanoparticles (AgNPs) or bismuth nanoparticles (BiNPs) and to evaluate their antimicrobial properties. Silica spheres were synthesized using a modified Stöber method, either unmodified or functionalized with (3-aminopropyl)triethoxysilane (APTES), prior to AgNP or BiNP deposition. The materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy (ICP-OES), and zeta potential measurements, while antimicrobial activity was assessed by microdilution against Gram-positive (Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Enterococcus faecium) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa), with Helicobacter pylori as a clinical model. The results show that both SiO₂-AgNP and SiO₂-BiNP composites completely inhibited H. pylori and showed high activity against other pathogens, although P. aeruginosa remained less susceptible. Functionalization of AgNP-coated samples with APTES promoted uniform distribution of AgNPs, with the minimum bactericidal concentration (MBC) to minimum inhibitory concentration (MIC) ratios ranging from 1 to 4, confirming a bactericidal rather than bacteriostatic effect. In contrast, BiNP-coated samples without APTES exhibited lower MIC values from 74 to 595 μg mL⁻¹, consistent with increased Bi³⁺ release from amorphous phases. This indicates the antimicrobial potential, highlighting the role of surface functionalization in regulating ion release and biological performance, and suggesting applications in the biomedical and food industries. Full article

Multilayer heterostructures of [(BiFeO₃)_m/(SrTiO₃)_n]_p were synthesized on ITO-coated quartz substrates via pulsed laser deposition, with varying thickness ratios (r = n/m) and periodicities (p = 1–3). Structural, electrical, and piezoelectric properties were systematically investigated using X-ray diffraction, AFM, and PFM. The BiFeO₃ layers crystallized in a distorted rhombohedral phase (R3c), free of secondary phases. Compared to single-layer BiFeO₃ films, the multilayers exhibited markedly lower leakage current densities and enhanced piezoelectric response. Electrical conduction transitioned from space-charge-limited current at low fields (E < 100 kV/cm) to Fowler–Nordheim tunneling at high fields (E > 100 kV/cm). Optimal performance was achieved for r = 0.30, p = 1, with minimal leakage (J = 8.64 A/cm² at E = 400 kV/cm) and a peak piezoelectric coefficient (d₃₃ = 55.55 pm/V). The lowest coercive field (Ec = 238 kV/cm) occurred in the configuration r = 0.45, p = 3. Saturated hysteresis loops confirmed stable ferroelectric domains. These findings demonstrate that manipulating layer geometry in [(BiFeO₃)_m/(SrTiO₃)_n]_p stacks significantly enhances functional properties, offering a viable path toward efficient, lead-free piezoelectric nanodevices. Full article

This review examines the emerging role of manganese-based nanoparticles (Mn-NPs) in detecting heavy metal pollutants in environmental matrices. Heavy metals such as cadmium, lead, zinc, and copper pose serious environmental and health concerns due to their tendency to persist in ecosystems and accumulate in living organisms. As a result, there is a growing need for reliable methods to detect and remove these pollutants. Manganese nanoparticles offer unique advantages that scientists could consider as replacing other metal nanoparticles, which may be more expensive or more toxic. The physicochemical properties of Mn-NPs—including their multiple oxidation states, magnetic susceptibility, catalytic capabilities, and semiconductor conductivity—enable the development of multi-modal sensing platforms with exceptional sensitivity and selectivity. While Mn-NPs exhibit inherently low electrical conductivity, strategies such as transition metal doping and the formation of composites with conductive materials have successfully addressed this limitation. Compared to noble metal nanoparticles (Au, Ag, Pd) and other base metal nanoparticles (Bi, Fe₃O₄), Mn-NPs demonstrate competitive performance without the drawbacks of high cost, complex synthesis, poor distribution control, or significant aggregation. Preliminary studies retrieved from the Scopus database highlight promising applications of manganese-based nanomaterials in electrochemical sensing of heavy metals, with recent developments showing detection limits in the sub-ppb range. Future research directions should focus on addressing challenges related to scalability, cost-effectiveness, and integration with existing water treatment infrastructure to accelerate the transition from laboratory findings to practical environmental applications. Full article

Objective: This study aimed to evaluate the in vitro efficacy of silver nanoparticles (AgNPs) synthesized by bioreduction using lemongrass (Cymbopogon citratus) essential oil against multidrug-resistant (MDR) bacteria isolated from an Intensive Care Unit (ICU). Methods: The essential oil was extracted and characterized by gas chromatography–mass spectrometry (GC-MS). Antioxidant activity was assessed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, the 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay, and total phenolic content. AgNPs (3 mM and 6 mM silver nitrate) were characterized by UV-Vis spectroscopy, dynamic light scattering (DLS), zeta potential, transmission electron microscopy (TEM), and Fourier-transform infrared (FTIR) spectroscopy. Bacterial isolates were obtained from ICU surfaces and personal protective equipment (PPE). Results: The essential oil presented citral A, citral B, and β-myrcene as major components (97.5% of identified compounds). AgNPs at 3 mM showed smaller size (87 nm), lower Polydispersity Index (0.14), and higher colloidal stability (−23 mV). The 6 mM formulation (147 nm; PDI 0.91; −10 mV) was more effective against a strain of Enterococcus spp. resistant to all antibiotics tested. FTIR analysis indicated the presence of O–H, C=O, and C–O groups involved in nanoparticle stabilization. Discussion: The higher antimicrobial efficacy of the 6 mM formulation was attributed to the greater availability of active AgNPs. Conclusions: The green synthesis of AgNPs using C. citratus essential oil proved effective against MDR bacteria and represents a sustainable and promising alternative for microbiological control in healthcare environments. Full article

Silver nanoparticles belong to a highly versatile group of nanomaterials with an appealing range of potential applications. In the realm of antimicrobial and antioxidant application, silver nanoparticles (AgNPs) exhibit auspicious capabilities. This research, for the very first time, endeavors to carry out biosynthesis of AgNPs coupled with fermentation using Medusomyces gisevii and Origanum vulgare L. (O. vulgare) plant species. Fermentation (F) via Medusomyces gisevii is responsible for chemical, physical, biological, and electrochemical processes. During in vitro study of antioxidant activity, fermented O. vulgare herb extract showed strong reductive activity as evaluated by the cupric reducing antioxidant capacity (CUPRAC), ferric reducing antioxidant power (FRAP), and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS•+) assay, with a value of 1.45 ± 0.048 mmol TE/g, 0.95 ± 0.04 mmol TE/g, and 0.59 ± 0.023 mmol TE/g, respectively. The highest antimicrobial activity was shown by Staphylococcus aureus in the inhibition zone, with values of 1.40 ± 0.12 mm of OrV and of 10.30 ± 0.04 mm and 11.54 ± 0.10 mm for OrV-AgNPs and OrV-F-AgNPs, respectively. Analysis of phenolic compounds revealed that the highest total amount of the apigenin, 87.78 µg/g, was detected in OrV-F-AgNPs and the lowest amount, 16.56 µg/g, in OrV-AgNPs. Moreover, in OrV-F-AgNPs, the collective amount of proanthocyanidins, hydroxycinnamic, and flavonoids was prominently high in all cases, i.e., 145.00 ± 0.02 mg EE/g DW, 2.86 ± 0.01 mg CAE/g DW, and 0.55 ± 0.01 mg RE/g DW, respectively, as compared to the original extract (102.1 ± 0.03 mg EE/g DW, 2.78 ± 0.02 mg CAE/g DW, and 0.47 ± 0.01 mg RE/g DW, respectively). During the characterization of biosynthesized nanoparticles by scanning electron microscopy (SEM), AgNPs demonstrated a uniform spherical shape with even distribution. The sample’s elemental composition was confirmed with a signal of 3.2 keV using energy-dispersive X-ray spectroscopy (EDS) analysis. Transmission electron microscopy (TEM) analysis showed silver nanoparticles that were round and spherical in shape in both stacked and congested form, with a size range of less than 30 nm. Thus, this green and sustainable synthesis of AgNPs, a blend of Medusomyces gisevii and O. vulgare herbal extract, has adequate potential for increased antimicrobial and antioxidant activity. Full article

This study investigates the development of advanced radiation shielding materials incorporating bismuth oxide (Bi₂O₃) nanoparticles (NPs) into polymethyl methacrylate (PMMA) composites, comparing efficacy against I-131 gamma radiation. The NPs exhibit a 1.53-fold reduction in z-average diameter and a significantly higher surface area than Bi₂O₃, ensuring superior dispersion and structural uniformity within the PMMA matrix. These characteristics, validated through SEM, EDX, and XRD analyses, contribute to enhanced gamma radiation attenuation, leveraging the high atomic number and density of Bi₂O₃. Mechanical evaluations reveal that increasing Bi₂O₃-NPs concentrations enhances ductility but reduces tensile strength, likely due to nanoparticle agglomeration and stress concentration. Radiation shielding performance, assessed using XCOM and Phy-X/PSD simulations, demonstrates a direct correlation between Bi₂O₃ content and attenuation efficiency. Notably, composites with 75% Bi₂O₃ content exhibit attenuation properties comparable to, or exceeding, those of PbO₂, achieving superior shielding efficacy at reduced thicknesses across various photon interaction mechanisms. These findings position Bi₂O₃ NPs-enhanced PMMA composites as promising lightweight high-performance alternatives to lead-based shields. By addressing toxicity and environmental concerns associated with lead, this work emphasizes the potential of high-Z nanomaterials in advancing radiation protection applications. This study highlights a transformative approach to designing safer and more efficient shielding solutions, contributing to the next generation of radiation protection materials. Full article

Chemical sensors, relying on electrical conductance changes in a gas-sensitive material due to the surrounding gas, have the (dis-)advantage of reacting with multiple target gases and humidity. In this work, we report CMOS-integrated SnO₂ thin film-based gas sensors, which are functionalized with mono-, bi-, and trimetallic nanoparticles (NPs) to optimize the sensor performance. The spray pyrolysis technology was used to deposit the metal oxide sensing layer on top of a CMOS-fabricated micro-hotplate (µhp), and magnetron sputtering inert-gas condensation was employed to functionalize the sensing layer with metallic NPs, Ag-, Pd-, and Ru-NPs, and all combinations thereof were used as catalysts to improve the sensor response to carbon monoxide and to suppress the cross-sensitivity toward humidity. The focus of this work is the detection of toxic carbon monoxide and a specific hydrocarbon mixture (HC_mix) in a concentration range of 5–50 ppm at different temperatures and humidity levels. The use of CMOS chips ensures low-power, integrated sensors, ready to apply in cell phones, watches, etc., for air quality-monitoring purposes. Full article

Piezo-photocatalysis is a promising solution to address both water pollution and the energy crisis. However, the recombination of electron–hole pairs often leads to poor performance, rendering current piezoelectric photocatalysts unsuitable for industrial water treatment. To overcome this issue, oxygen vacancies (V) and Ag nanoparticles (NPs) are introduced into Bi₄Ti₃O₁₂ (BTO) nanosheets, forming Schottky junctions (BTO-V/Ag). These 2D/3D structures offer more exposed active sites, shorter carrier separation distances, and improved piezo-photocatalytic performance. Additionally, the photothermal effect of Ag NPs supplies additional energy to counteract adsorption changes caused by active species, promoting the generation of more active species. The rate constant of the optimized BTO-V/Ag-2 in the piezo-photocatalytic degradation of nizatidine (NZTD) was 4.62 × 10⁻² min⁻¹ (with a removal rate of 98.34%), which was 4.32 times that of the initial BTO. Moreover, the composite catalyst also showed good temperature and pH response. This study offers new insights into the regulatory mechanisms of piezo-photocatalysis at the Schottky junction. Full article

The incorporation of Ag nanoparticles onto BiVO₄ (a known H₂O oxidising photocatalyst) through magnetron sputtering to form a composite was studied. ICP-OES results showed that the loading of Ag on BiVO₄ was below 1% in all cases. UV-Vis DRS and CO₂-TPD analyses demonstrated that upon incorporation of Ag onto BiVO₄, an increase in the extent of visible light absorption and CO₂ adsorption was seen. TEM imaging showed the presence of Ag particles on the surface of larger BiVO₄ particles, while XRD analysis provided evidence for some doping of Ag into BiVO₄ lattices. The effect of the composite formation on the activity of the materials in the artificial photosynthesis reaction was significant. BiVO₄ alone produces negligible amounts of gaseous products. However, the Ag-sputtered composites produce both CO and CH₄, with a higher loading of Ag leading to higher levels of product formation. This reactivity is ascribed to the generation of a heterojunction in the composite material. It is suggested that the generation of holes in BiVO₄ following photon absorption is used to provide protons (from H₂O oxidation), and the decay of an SPR response on the Ag NPs provides hot electrons, which together with the protons reduce CO₂ to produce CH₄, CO, and adsorbed hydrocarbonaceous species. Full article

Bi₂O₃ particles are introduced as foreign additives onto SnO₂ nanoparticles (NPs) surfaces for the efficient detection of oxygenated volatile organic compounds (VOCs). Bi₂O₃-loaded SnO₂ materials are prepared via the impregnation method followed by calcination treatment. The abundant Bi₂O₃/SnO₂ interfaces are constructed by the uniform dispersion of Bi₂O₃ particles on the SnO₂ surface. The results of oxygen temperature-programmed desorption suggest that Bi₂O₃-loaded SnO₂ samples display improved surface oxygen ions than neat-SnO₂ NPs. As a result, the gas sensor based on 1 mol% Bi₂O₃-loaded SnO₂ (1Bi-L-SnO₂) composites shows significantly higher sensitivity and a faster response speed toward various oxygenated VOCs compared with SnO₂, especially at 200 °C and 250 °C. The results of catalytic combustion and temperature-programmed reaction measurements reveal the dominant role of adsorption and partial oxidation during ethanol combustion on SnO₂ and 1Bi-L-SnO₂ surfaces. In this case, the improvement in the sensing performance of the 1Bi-L-SnO₂ sensor can be associated with the increase in surface oxygen ions at Bi₂O₃/SnO₂ interfaces. The results confirm the significant role of surface functionalization for sensing materials. The obtained outstanding sensing performance provides the potential application for the simultaneous detection of total oxygenated VOCs in practice. Full article

Pathogenic bacteria in the environment pose a significant threat to public health. Titanium dioxide (TiO₂)-based photocatalysts have emerged as a promising solution due to their potent antimicrobial effects under visible light and their generally eco-friendly properties. This review focuses on the antibacterial properties of visible-light-activated, TiO₂-based photocatalysts against pathogenic bacteria and explores the factors influencing their efficacy. Various TiO₂ modification strategies are discussed, including doping with non-metals, creating structure defects, combining narrow-banded semiconductors, etc., to extend the light absorption spectrum from the UV to the visible light region. The factors affecting bacterial inactivation, and the underlying mechanisms are elucidated. Although certain modified TiO₂ nanoparticles (NPs) show antibacterial activities in the dark, they exhibit much higher antibacterial efficacies under visible light, especially with higher light intensity. Doping TiO₂ with elements such as N, S, Ce, Bi, etc., or introducing surface defects in TiO₂ NPs without doping, can effectively inactivate various pathogenic bacteria, including multidrug-resistant bacteria, under visible light. These surface modifications are advantageous in their simplicity and cost-effectiveness in synthesis. Additionally, TiO₂ can be coupled with narrow-banded semiconductors, resulting in narrower band gaps and enhanced photocatalytic efficiency and antibacterial activities under visible light. This information aids in understanding the current technologies for developing visible-light-driven, TiO₂-based photocatalysts and their application in inactivating pathogenic bacteria in the environment. Full article

This study developed a MgBi₂O₆-based photocatalyst via low-temperature hydrothermal synthesis. AgBr was co-precipitated onto MgBi₂O₆, and silver nanoparticles (AgNPs) were photo-reduced onto the surface. The photocatalytic performance, assessed by methylene blue (MB) degradation under white-light LED irradiation (2.5 W, power density = 0.38 W/cm²), showed that Ag/AgBr/MgBi₂O₆ achieved 98.6% degradation in 40 min, outperforming MgBi₂O₆ (37.5%) and AgBr/MgBi₂O₆ (85.5%). AgNPs boosted electron-hole separation via surface plasmon resonance, reducing recombination. A Z-scheme photocatalytic mechanism was suggested, where photogenerated carriers transferred across the p–n heterojunction between AgBr and MgBi₂O₆, producing reactive oxygen species like superoxide and hydroxyl radicals critical for dye degradation. Thus, the Ag/AgBr/MgBi₂O₆ composites possessed excellent photocatalytic performance regarding dyestuff degradation (85.8–99.9% degradation within 40 min) under white-light LED irradiation. Full article

Colloidal bismuth nanoparticles (NPs) were synthesized in sodium chloride (NaCl) solutions at different concentrations using the laser ablation of solids in liquids technique. The obtained materials were characterized using various techniques. The morphology, size, and crystalline phases were determined through scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and Fourier-transform infrared spectroscopy (FTIR). The optical properties were studied using UV–visible spectroscopy, employing the Tauc method to determine the band gap of the particles. Two types of materials were identified depending on the NaCl concentration: spherical nanoparticles of α-Bi₂O₃ and the coexistence of α-Bi₂O₃ and BiOCl particles with irregular morphology. NaCl concentrations higher than 11.6% enable the coexistence of α-Bi₂O₃ and BiOCl. The photocatalytic response of the colloids was evaluated by the degrading rhodamine B under visible light irradiation. The sample synthesized at a NaCl concentration of 31.6% showed the best photocatalytic activity. Full article

In this contribution, we reported the synthesis of the nanocomposites of poly(n-butyl acrylate) with Fe₃O₄ nanoparticles (NPs) via dynamic crosslinking of poly(n-butyl acrylate)-grafted Fe₃O₄ NPs with hindered urea bonds (HUBs). Towards this end, the surfaces of Fe₃O₄ NPs were grafted with poly(n-butyl acrylate-ran-2-(3-tert-butyl-3-ethylureido)ethyl acrylate) chains [denoted as Fe₃O₄-g-P(BA-r-TBEA)] via living radical polymerization. Thereafter, 1,2-bis(tert-butyl)ethylenediamine was used as a crosslinker to afford the organic–inorganic networks with variable contents of Fe₃O₄ NPs and crosslinking densities. It was found that the fine dispersion of Fe₃O₄ NPs in the matrix of poly(n-butyl acrylate) was achieved. The nanocomposites exhibited excellent reprocessing properties, attributed to the introduction of HUBs. Owing to the crosslinking, the nanocomposites displayed excellent shape memory properties. Further, the nanocomposites possessed photo- and magnetic–thermal properties, which were inherited from Fe₃O₄ NPs. These functional properties allow triggering the shape shifting of the nanocomposites in an uncontacted fashion. Full article