Abstract The persistent presence of antibiotic contaminants in water bodies poses a significant environmental and public health challenge, as their stability contributes to antimicrobial resistance. In this study, nanocomposites (NCs) composed of CuWO 4 (CW) and g-C 3 N 4 (GCN), referred to as GCN/CW, were synthesized and tested as photocatalysts driven by visible light to degrade tetracycline (TC) in an aqueous system. Graphitic carbon nitride (GCN) nanosheets were prepared through thermal polymerization, while copper tungstate (CW) nanoparticles were synthesized through a co-precipitation approach. The NCs with varying CW loadings (5–50 wt.%) were subsequently fabricated using a hydrothermal method followed by calcination. Characterization of the morphological and structural properties confirmed that CW nanoparticles successfully formed on GCN nanosheets, maintaining the original crystal structure of CW. Optical analysis showed increased visible-light absorption in the NCs compared with the respective pristine materials. Photocatalytic experiments demonstrated that the heterojunction catalysts exhibited significantly improved TC degradation efficiency under visible light, attributed to enhanced charge separation and synergistic interactions between CW and GCN. The photocatalytic performance increased with CW loading, with the optimized composite achieving over 93% degradation within 90 min under alkaline conditions. Reaction parameters, including catalyst dosage, pollutant concentration, and pH, were also investigated, revealing optimal performance at pH 10 with a catalyst loading of 20 mg and a TC concentration of 20 mg l −1 . Radical scavenging experiments indicated that • OH, •O 2 - , and h + are the key reactive species responsible for the degradation process. The catalyst also exhibited good stability, retaining significant activity after repeated cycles. Optimization could also enable the NC to degrade a wider range of pharmaceutical pollutants in water systems.
Calcium carbonate (CaCO _3 ) nanoparticles mediated by Petroselinum crispum (parsley) followed by comparison with commercial CaCO _3 nanoparticles. UV–Vis and FTIR analyses confirmed the presence of phytochemicals containing hydroxyl, carbonyl, and aliphatic functional groups, which acted as reducing, capping, and stabilizing agents. XRD confirmed predominantly calcite in both samples, with mean crystallite sizes of 51.97 nm and 60.90 nm for commercial and green-synthesized nanoparticles, respectively, while transmission electron microscopy showed mean particle diameters of 66.11 nm and 76.45 nm. SEM revealed morphological differences caused by phytochemical surface functionalization. Green-synthesized CaCO _3 nanoparticles showed a greater colloidal stability (−26.05 mV vs −18.25 mV), whereas commercial nanoparticles had a higher specific surface area (17.926 m ^2 g ^−1 vs 15.61 m ^2 g ^−1 ) due to their smaller size. Antibacterial testing against Streptococcus mutans and Staphylococcus aureus showed that green-synthesized nanoparticles had a fourfold lower Minimum Inhibitory Concentration against S. mutans (125 μ g ml ^−1 vs 500 μ g ml ^−1 ) and larger inhibition zones at all tested concentrations, suggesting enhanced synergistic bactericidal activity. In contrast, commercial nanoparticles showed stronger concentration-independent antibiofilm activity, likely due to their smaller size and higher surface area, which promoted penetration of the extracellular polymeric matrix. These complementary effects indicate that P. crispum -mediated green synthesis can produce biofunctional CaCO _3 nanoparticles with improved antibacterial potential against clinically important oral pathogens, supporting their use in dental caries prevention and broader biomedical applications.
Obtaining a uniform coverage of ultrathin dielectrics on two-dimensional (2D) materials by atomic layer deposition (ALD) commonly requires oxidative pretreatments that damage the underlying crystals. While ALD nucleation on chemically inert 2D surfaces such as MoS _2 has been studied extensively, 2D materials that inherently carry an oxide surface have been examined far less often as ALD growth platforms. Here, an identical Al _2 O _3 ALD process is applied to representatives of three classes of 2D materials: an inert sulfide (MoS _2 ), a native-oxide-forming sulfide (TaS _2 ), and an intrinsic oxide (RuO _2 nanosheets). Film growth and uniformity are quantified by atomic force microscopy, referenced to the growth per cycle on the surrounding SiO _2 . On inert MoS _2 , growth is strongly suppressed unless the surface is activated by air plasma. In contrast, TaS _2 and RuO _2 nanosheets support morphologically uniform, low-roughness growth without any pretreatment. Electrical measurements, used as a probe of process-induced damage, show that TaS _2 and RuO _2 nanosheets retain their conductivity through the ALD process far better than MoS _2 . Across the three classes, morphologically uniform pretreatment-free growth correlates with the presence of a surface oxide, native or intrinsic.
Two-dimensional semiconductors, and particularly MoS _2 , are promising active materials for room-temperature gas sensing devices because their channel conductance is strongly modulated by surface adsorption. Here we report a systematic study of the electrical transport properties of back-gated MoS _2 field-effect transistors (FETs) under controlled atmosphere and pressure. Transferred MoS _2 devices show stable n-type operation with a pronounced dependence of conductance, threshold voltage and hysteresis on ambient conditions, consistent with adsorption/desorption and trap dynamics at the MoS _2 /SiO _2 interface. To further clarify the microscopic kinetics underlying these macroscopic electrical variations, we performed low-frequency noise (LFN) measurements. This combined transport–noise approach provides access to microscopic fluctuation mechanisms that cannot be distinguished from conventional DC characterization alone. The spectra exhibit a 1/ ${f^{\;\gamma}}$ background and Lorentzian components whose characteristic frequencies are in the tens-of-hertz range (≈40–60 Hz) and at ∼2.0 kHz. The slow component shows thermally activated behavior with ${E_a} \approx 0.19{\text{ }}$ eV, consistent with physisorption-controlled dynamics, while the faster component is compatible with contact-related fluctuations. Measurements on CVD-grown MoS _2 FETs reproduce the same slow fluctuations, supporting the generality of the adsorption-driven process. Overall, this work establishes a solid transport baseline for MoS _2 FETs in controlled atmospheres and demonstrates that LFN spectroscopy provides a powerful tool to disentangle surface-adsorption kinetics from contact and interface effects.
Abstract Hybrid organic–inorganic perovskites are emerging as key materials for next-generation photodetectors, where the compositional and structural tunability and exceptional optoelectronic properties provide a powerful strategy to tune the microscopic mechanisms governing the photoresponse. Here, 3D MAPbI 3 and quasi-2D (PEA) 2 (MA)Pb 2 I 7 single-crystal photodetectors are comparatively investigated under dark and illuminated conditions. The devices employ two lateral Ag-paste contacts and therefore operate as photoconductors, in which illumination increases the crystal conductivity through the generation of mobile charge carriers under an applied bias. Both devices exhibit a nearly ohmic behavior in the dark and under illumination. The photocurrent increases almost linearly with the incident optical power, with a power-law exponentia of α ≈ 0.9 for both crystals. The 3D perovskite shows higher conductivity, with a dark current of 10 −10 A at V bias = 1 V, whereas the quasi-2D device exhibits a strongly suppressed dark current of 10 −12 A under the same bias condition. Prompt and reversible photocurrent switching is observed in both devices within the temporal resolution of the experimental setup; however, the 3D crystal also displays an additional slow current rise, suggesting the activation of a secondary light-induced process. Spectral measurements further reveal a widened bandgap in the quasi-2D perovskite, consistent with its layered structure. Overall, this comparative study highlights the key role of dimensionality and organic-cation engineering in balancing efficient photogeneration, dark-current suppression, and low-noise photodetection.
