Search Results (223)

The detection of trace chemicals at low and ultra-low concentrations is critical for applications in environmental monitoring, medical diagnostics, food safety and other fields. Conventional detection techniques often lack the required sensitivity, specificity, or cost-effectiveness, making real-time, in situ analysis challenging. Surface-enhanced Raman spectroscopy (SERS) is a powerful analytical tool, offering improved sensitivity through the enhancement of Raman scattering by plasmonic nanostructures. While noble metals such as Ag and Au are currently the reference choices for SERS substrates, fabrication methods should balance enhancement efficiency, reproducibility and scalability. In this study, we propose a novel approach for SERS substrate fabrication using reactive Aerosol Jet Printing (r-AJP) as an innovative additive manufacturing technique. The r-AJP process enables in-flight Ag seed reduction and nucleation of Ag nanoparticles (NPs) by mixing silver nitrate and ascorbic acid aerosols before deposition, as suggested by computational fluid dynamics (CFD) simulations. The resulting coatings were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses, revealing the formation of nanoporous crystalline Ag agglomerates partially covered by residual matter. The as-prepared SERS substrates exhibited remarkable SERS activity, demonstrating a high enhancement factor (10⁶) for rhodamine (R6G) detection. Our findings highlight the potential of r-AJP as a scalable and cost-effective fabrication strategy for next-generation SERS sensors, paving the way for the development of a new additive manufacturing tool for noble metal material deposition. Full article

Coal-fired power plants exacerbate hazy weather under low winter temperatures, while sulphate ions (SO₄²⁻) in condensable particulate matter (CPM) emitted from ultra-low emission coal-fired power plants accelerate sulphate formation. The transformation of gaseous precursors (SO₂, NOx, NH₃) is the main pathway for sulphate formation by homogeneous or non-homogeneous reactions. For the sustainability of the world, in this paper, the effects of condensation temperature, H₂O, NO_X and NH₃ on the SO₄²⁻ generation characteristics under low-temperature rapid condensation conditions are investigated. With lower temperatures, especially from 0 °C cooling to −20 °C, the concentration of SO₄²⁻ was as high as 26.79 mg/m³. With a greater proportion of H₂SO₄ in the aerosol state, and a faster rate of sulphate formation, H₂O vapour condensation can provide a reaction site for sulphuric acid aerosol generation. SO₄²⁻ in CPM is mainly derived from the non-homogeneous reaction of SO₂. SO₃ is an important component of CPM and provides a reaction site for the formation of SO₄²⁻. SO₂ and SO₃, in combination with Stefan flow, jointly play a synergistic role in the generation of SO₄²⁻. The content of SO₄²⁻ was as high as 36.18 mg/m³. While NO_X sometimes inhibits the formation of SO₄²⁻, NH₃ has a key role in the nucleation process of CPM. NH₃, SO₂ and NO_X have been found to rapidly form sulphate with particle sizes up to 5 µm at sub-zero temperatures and promote the formation of sulphuric acid aerosols. Full article

Recently, vegetable oil-derived monounsaturated fatty acids (MUFAs) have predominantly been utilized in producing bio-based surfactants, resulting in low bioresource utilization and high separation costs. Although polyunsaturated fatty acids (PUFAs) are abundant and often co-exist with MUFAs, bio-based surfactants synthesized from PUFA-rich feedstocks have been less researched due to concerns regarding their interfacial performance. In this study, a novel series of PUFA-based zwitterionic surfactants with strong interfacial activity was synthesized from waste vegetable oils via an eco-friendly three-step process, optimized through an orthogonal experimental design. The structures and conversion rates of the surfactants were confirmed using GC-MS, LC-MS, and ESI-MS. At 0.5 g/L and 3.0 g/L (typical concentrations often used in most oil fields), the bio-based surfactants derived from waste soybean oil (PUFA-to-MUFA ratio ≈ 2.11, C18:2, and C18:1 in large contents) could reduce the interfacial tension between Daqing crude oil and simulated formation groundwater to an ultra-low level of ~10⁻³ mN/m. These results confirm our hypothesis that bio-based zwitterionic surfactants derived from PUFA-rich feedstocks possess excellent interfacial activity, providing a potential sustainable option to be considered for chemically enhanced oil recovery. Full article

Amid the global transition toward sustainable energy, regional power grids with high wind power penetration are increasingly emerging. The implementation of frequency control is critically essential for enhancing the frequency support capability of grid-connected devices. However, existing studies indicate this may induce ULFOs (ultra-low frequency oscillations). Current research on ULFOs have been predominantly concentrated on hydro-dominated power systems, with limited exploration into systems where thermal power serves as synchronous sources—let alone elucidation of the underlying mechanisms. This study focuses on regional power grids where wind and thermal power generation coexist. Eigenvalue analysis reveals that frequency regulation control of doubly-fed induction generators (DFIGs) can trigger ULFOs. Leveraging common-mode oscillation theory, an extended system frequency response (ESFR) model incorporating DFIG frequency control is formulated and rigorously validated across a range of operational scenarios. Moreover, frequency-domain analysis uncovers the mechanism by which inertia control affects ULFO behavior, and time-domain simulations are conducted to validate the influence of DFIG control parameters on ULFOs. Full article

Polyaniline (PANI) is an important conductive-polymer gas-sensing material with working temperature and mechanical flexibilities superior to those of conventional metal oxide sensing materials. However, its applicability is limited by its low sensitivity, high detection limits, and long response/recovery times. In this study, we prepared PANI/WS₂ composites via chemical oxidative polymerization and mechanical blending. A multilayer sensor structure—sequentially printed silver-paste heating electrodes, fluorene polyester insulating layer, silver interdigitated electrodes, and sensing material layer—was fabricated on a polyimide substrate via flexible microelectronic printing and systematically characterized using scanning electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. The optimized 5 wt% WS₂ composite showed enhanced gas-sensing performance, with 219.1% sensitivity to 100 ppm ammonia (2.4-fold higher than that of pure PANI) and reduced response and recovery times of 24 and 91 s, respectively (compared to 81 and 436 s for pure PANI, respectively). Notably, the PANI/WS₂ sensor detected an ultralow ammonia concentration (100 ppb) with 0.104% sensitivity. The structural characterization and performance analysis results were used to deduce a mechanism for the enhanced sensing capability. These findings highlight the application potential of PANI/WS₂ composites in flexible gas sensors and provide fundamental insights for PANI-based sensing materials research. Full article

The widespread use of formaldehyde in both industrial and household products has raised significant health concerns, emphasizing the need for highly sensitive sensors to monitor formaldehyde concentrations in the environment in real time. In this study, we report the fabrication of a highly sensitive formaldehyde gas sensor based on Ag₂O and PtO₂ co-decorated LaFeO₃ nanofibers, prepared by electrospinning, with an ultra-low detection limit of 10 ppb. Operating at an optimal temperature of 210 °C, the sensor exhibits high sensitivity, with a response value of 283 to 100 ppm formaldehyde—nearly double the response of the Ag-only decorated LaFeO₃ sensor. Additionally, the sensor demonstrated good selectivity, repeatability, and long-term stability over 80 days. The enhanced sensitivity is attributed to the strong adsorption ability of Ag towards both oxygen and formaldehyde, Ag’s catalytic oxidation of formaldehyde, PtO₂’s catalytic action on oxygen, and the spillover effect of PtO₂ on oxygen. This sensor holds significant potential for environmental monitoring due to its ultrahigh sensitivity and ease of fabrication. Full article

Chemical nanosensors based on tin dioxide (SnO₂) and zinc oxide (ZnO) nanoparticles (NPs) were developed and characterized for the detection of low concentrations of atmospheric pollutants, such as nitrogen dioxide (NO₂) and carbon monoxide (CO). The sensing layers were prepared using three fabrication methods: drop-casting, electrospray, and spark ablation coupled with an inertial impaction printer, to compare their performance. Multiple surface characterization techniques were carried out to investigate the surface morphology and elemental composition of the deposited layers such as SEM (scanning electron microscopy) and XPS (X-ray photoelectron spectroscopy) analyses. UV light photoactivation enabled the sensors to detect ultra-low concentrations of the target gases at room temperature (100 ppb NO₂ and 1 ppm CO). The measurements were conducted at 50% relative humidity to simulate real environmental conditions. All sensors were capable of detecting the target gases. Drop-casting is the simplest and most cost-effective technique, but it is also the least reproducible. In contrast, sensors based on the spark ablation technique achieved more homogeneous sensing layers, with practically no nanoparticle agglomeration, resulting in devices with lower noise and drift in their electrical response. Full article

Low-density lipoprotein cholesterol (LDL-C) plays a central role in lipid metabolism and is a well-established therapeutic target for the prevention of atherosclerotic cardiovascular diseases (CVDs). In recent years, increasingly aggressive lipid-lowering strategies have been adopted to achieve ultra-low LDL-C concentrations (<55 mg/dL or even <30 mg/dL) in high-risk patients. While the benefits of LDL-C reduction in lowering the incidence of myocardial infarction and ischemic stroke are well documented, emerging clinical evidence has raised concerns about a potential association between very low LDL-C levels and an increased risk of bleeding, particularly hemorrhagic stroke and gastrointestinal hemorrhage. This review critically examines the molecular mechanisms by which reduced LDL-C levels may influence the hemostatic system and vascular integrity. It explores the complex interplay between cholesterol availability and platelet function, endothelial barrier stability, and coagulation pathways. In addition, we assess experimental and clinical studies supporting this association and discuss how these findings may inform risk stratification and personalized lipid-lowering strategies. A deeper understanding of the biological basis of this paradoxical risk is essential for achieving a safe, balanced, and effective approach to cardiovascular prevention. Full article

With the depletion of conventional light crude oil reserves in China, the demand for heavy oil exploitation has grown, highlighting the increasing significance of enhanced heavy oil recovery. Surfactants reduce oil–water interfacial tension, modify the wettability of reservoir rocks, and facilitate the emulsification of heavy oil. Consequently, investigating the adsorption behavior of surfactants at oil–water interfaces and the underlying mechanisms of wettability alteration is of considerable importance. In this study, the surface tension of four surfactants and their interfacial tension with Gudao heavy oil were measured. Among these, BS-12 exhibited a critical micelle concentration (CMC) of 6.26 × 10⁻⁴ mol·dm⁻³, a surface tension of 30.15 mN·m⁻¹ at the CMC, and an adsorption efficiency of 4.54. In low-salinity systems, BS-12 achieved an ultralow interfacial tension on the order of 10⁻³ mN·m⁻¹, demonstrating excellent surface activity. Therefore, BS-12 was selected as the preferred emulsifier for Gudao heavy oil recovery. Additionally, FT-IR, SEM, and contact angle measurements were used to elucidate the interfacial adsorption mechanism between BS-12 and aged cores. The results indicate that hydrophobic interactions between the hydrophobic groups of BS-12 and the adsorbed crude oil fractions play a key role. Core flooding experiments, simulating the formation of low-viscosity oil-in-water (O/W) emulsions under reservoir conditions, showed that at low flow rates, crude oil and water interact more effectively within the pores. The extended contact time between heavy oil and the emulsifier led to significant changes in rock wettability, enhanced interfacial activity, improved oil recovery efficiency, and increased oil content in the emulsion. This study analyzes the role of surfactants in interfacial adsorption and the multiphase flow behavior of emulsions, providing a theoretical basis for surfactant-enhanced oil recovery. Full article

Alkyl sulfobetaine shows a strong advantage in the compounding of surfactants due to the defects in the size matching of hydrophilic and hydrophobic groups. The interfacial tensions (IFTs) of alkyl sulfobetaine (ASB) and xylene-substituted alkyl sulfobetaine (XSB) with oil-soluble (Span80) and water-soluble (Tween80) nonionic surfactants on a series of n-alkanes were studied using a spinning drop tensiometer to investigate the mechanism of IFT between nonionic and betaine surfactants. The two betaine surfactants’ IFTs are considerably impacted differently by Span80 and Tween80. The results demonstrate that Span80, through mixed adsorption with ASB and XSB, can create a relatively compacted interfacial film at the n-alkanes–water interface. The equilibrium IFT can be reduced to ultra-low values of 5.7 × 10⁻³ mN/m at ideal concentrations by tuning the fit between the size of the nonionic surfactant and the size of the oil-side vacancies of the betaine surfactant. Nevertheless, Tween80 has minimal effect on the IFT of betaine surfactants, and the betaine surfactant has no vacancies on the aqueous side. The present study provides significant research implications for screening betaine surfactants and their potential application in enhanced oil recovery (EOR) processes. Full article

Copper-thiolate nanostructures, formed through the self-assembly of cysteine (Cys) and glutathione (GSH) with copper ions, offer a versatile platform for redox-active applications due to their structural stability and chemical functionality. In this study, Cu-Cys-GSH nanoparticles were synthesized and employed to develop a capacitive biosensor for the ultralow concentration detection of hydrogen peroxide (H₂O₂). The detection mechanism leverages a Fenton-like reaction, where H₂O₂ interacts with Cu-Cys-GSH nanoparticles to generate hydroxyl radicals (·OH) through redox cycling between Cu²⁺ and Cu⁺ ions. These redox processes induce changes in the sensor’s surface charge and dielectric properties, enabling highly sensitive capacitive sensing at gold interdigitated electrodes (IDEs). The influence of chirality on sensing performance was investigated by synthesizing nanoparticles with both L- and D-cysteine enantiomers. Comparative analysis revealed that the stereochemistry of cysteine impacts the catalytic activity and sensor response, with Cu-L-Cys-GSH nanoparticles exhibiting superior performance. Specifically, the biosensor achieved a linear detection range from 1.0 fM to 1.0 pM and demonstrated an ultra-sensitive detection limit of 21.8 aM, outperforming many existing methods for H₂O₂ detection. The sensor’s practical performance was further validated using milk and saliva samples, yielding high recovery rates and confirming its robustness and accuracy for real-world applications. This study offers a disposable, low-cost sensing platform compatible with sustainable healthcare practices and facilitates easy integration into point-of-care diagnostic systems. Full article

Silica aerogels exhibit exceptionally low thermal conductivity and a low apparent density, as they are unique porous nanomaterials. They are extensively used in thermal insulation in terms of aerospace and building construction, adsorption processes for environmental applications, concentrating solar power systems, and so on. However, the degradation of the silica aerogel’s nanoporous structure at high temperatures seriously restricts their practical applications. Through a comprehensive review of the high-temperature structural evolution and sintering mechanisms of silica aerogels, this paper introduces two strategies to enhance their thermal stability, including heteroatom doping and surface heterogeneous structure construction. In particular, atomic layer deposition (ALD) of ultra-thin coatings on silica aerogel holds significant potential for enhancing thermal stability, while preserving its ultra-low thermal conductivity. Full article

In this study, we developed a novel SERS-active magnetic substrate (MBs@CS@AuNPs) for detecting malachite green (MG) in aquatic products, including shrimp, cod, and aquaculture water. The substrate combines chitosan-functionalized magnetic nanobeads with dense gold nanoparticles. It efficiently enriches MG through electrostatic and π–π interactions, generates high-density plasmonic hotspots for stable signals, and utilizes a superparamagnetic core to concentrate MG molecules. This design achieved an ultralow detection limit of 10⁻⁹ M for MG in aquaculture samples, with a linear range spanning from 10⁻³ to 10⁻¹⁰ M (R² = 0.999). The substrate demonstrated superior performance in untreated, complex food matrices (e.g., shrimp, cod), outperforming conventional magnetic mass spectrometry systems that are prone to matrix interference. This work introduces an innovative approach for detecting harmful residues in food during environmental safety monitoring. Full article

Silicon-based materials provide a new pathway to break through the energy storage limits of battery systems but their industrialization process is still constrained by inherent diffusion hysteresis and unstable electrode structures. In this work, we propose a novel structural design strategy employing a modified spray freeze drying technique to construct multidimensional carbon nanostructures. The continuous morphological transition from carbon nanowires to carbon nanosheets was facilitated by the inducement of ultralow-temperature phase separation and the effect of polymer self-assembly. The unique wrinkled carbon nanosheet encapsulation effectively mitigated the stress concentration induced by the aggregation of silicon nanoparticles, while the open two-dimensional structure buffered the volume changes of silicon. As expected, the SSC-5M composite retained a reversible capacity of 1279 mAh g⁻¹ after 100 cycles at 0.2 C (1 C = 1700 mAh g⁻¹) and exhibited a capacity retention of 677.1 mAh g⁻¹ after 400 cycles at 1 C, demonstrating excellent cycling stability. This study offers a new strategy for the development of silicon-based energy storage devices. Full article

Polycyclic aromatic hydrocarbons (PAHs) and global warming impact aquatic ecosystems, eventually interacting. Monolayer (2D) cultures of cell lines, such as the rainbow trout liver RTL-W1, are employed for unveiling toxicological effects in fish. Nonetheless, three-dimensional (3D) models constitute an alternate paradigm, better emulating in vivo responses. Here, ultra-low attachment (ULA) plates were used to generate ten-day-old RTL-W1 spheroids for exposure to a control, a solvent control (0.1% DMSO) and the model PAH benzo[k]fluoranthene (BkF) at 10 and 100 nM and at 18 and 23 °C (thermal stress). After a 4-day exposure, spheroids were analyzed for viability (alamarBlue and lactate dehydrogenase), biometry (area, diameter and sphericity), histocytology (optical and electron microscopy), and mRNA levels of the detoxification-related genes cytochrome P450 (CYP)1A, CYP3A27, aryl hydrocarbon receptor (AhR), glutathione S-transferase (GST), uridine diphosphate–glucuronosyltransferase (UGT), catalase (CAT), multidrug resistance-associated protein 2 (MRP2) and bile salt export protein (BSEP). Immunocytochemistry (ICC) was used to assess CYP1A protein expression. Neither temperature nor BkF exposure altered the spheroids’ viability or biometry. BkF modified the cell’s ultrastructure. The expression of CYP1A was augmented with both BkF concentrations, while AhR’s increased at the higher concentration. The CYP1A protein showed a dose-dependent increase. Temperature and BkF concurrently modelled UGT’s expression, which increased in the 100 nM condition at 23 °C. Conversely, CYP3A27, MRP2, and BSEP expressions lowered at 23 °C. CAT and GST mRNA levels were uninfluenced by either stressor. Overall, BkF and temperature impacted independently or interactively in RTL-W1 spheroids. These seem to be useful novel tools for studying the liver-related effects of temperature and PAHs. Full article