RSC Advances最新文献

The phosgene-free synthesis of methylene diphenyl diisocyanate (MDI) from dimethyl carbonate (DMC) involves the acid-catalyzed condensation of methyl N-phenylcarbamate (MPC) with formaldehyde (HCHO) to produce methylene diphenyl carbamate (MDC). This study investigates the catalytic properties of a commercial acidic clay (HM-X), with a focus on its acidity and Brønsted/Lewis (B/L) balance. Characterization by XRD, N₂ adsorption, NH₃-TPD, and pyridine-IR shows that HM-X has a high density of medium and strong acid sites, with a notable Brønsted component. Under certain reaction conditions in DMC with co-fed water, HM-X achieved an 88.1% MDC yield at 90 °C after 6 hours. However, excessive acidity promoted side reactions, decreasing MDC selectivity. These findings highlight the importance of optimizing Brønsted and Lewis sites to balance activity and selectivity, providing insights for designing efficient, recyclable solid acids for sustainable, phosgene-free MDI production.

The development of a reliable, sensitive, and economical gas sensor is crucial for effective environmental monitoring. In this study, we present the development of an interdigitated electrode (IDE) based graphene nanoplatelet (GnP) and GnP-TiO₂ composite NH₃ gas sensor operated at room temperature. Firstly, for the synthesis of GnPs, tea extract was used as a green alternative without the use of organic solvents using a kitchen mixer, whereas TiO₂ and GnP-TiO₂ were prepared via a simple hydrothermal process. An IDE-based chemiresistive sensor of GnPs and GnP-TiO₂ was tested for NH₃ detection over a wide concentration range of 100 ppb to 100 ppm at room temperature. The GnP-TiO₂ composite exhibited a response nearly eight times higher than that of the GnP sensor at 100 ppm NH₃. Additionally, the GnP sensor exhibited response and recovery times of 249 and 107 s, respectively, whereas the GnP-TiO₂ composite achieved 15 and 30 s, corresponding to an ∼17 fold faster response time and ∼3.5 fold quicker recovery at 100 ppb NH₃. Overall, this study advocates the applicability of a grown GnP-TiO₂ based composite for NH₃ sensing application in ppb level concentration.

Nitric oxide (NO) is a pleiotropic signaling molecule fundamentally involved in regulating skeletal muscle physiology, including blood flow, contractility, and metabolism. For decades, the synthesis of NO was attributed solely to the l-arginine-dependent nitric oxide synthase (NOS) enzymes. However, the discovery and characterization of the nitrate-nitrite-NO pathway have revealed an alternative, NOS-independent mechanism for NO generation. This pathway is particularly significant under hypoxic and acidic conditions, which are characteristic of exercising skeletal muscle. Dietary inorganic nitrate, abundant in green leafy vegetables and beetroot, is sequentially reduced to nitrite and then to bioactive NO. This review critically examines the intricate chemistry underpinning this pathway, from the initial enzymatic reduction of nitrate by both mammalian and microbial reductases to the diverse chemical routes of nitrite reduction to NO within the muscle milieu. We delve into the specific roles of key proteins such as xanthine oxidoreductase, deoxyhemoglobin/deoxymyoglobin, and mitochondrial complexes in catalyzing these transformations. Furthermore, we explore how NO generated via this pathway modulates muscle oxygenation through vasodilation and regulation of mitochondrial respiration. The ergogenic potential of dietary nitrate supplementation is discussed in the context of human exercise performance, highlighting the significant controversies, methodological challenges, and sources of inter-individual variability, including genetics and the microbiome. This review aims to provide a comprehensive, chemistry-focused perspective on the nitrate-nitrite-NO pathway, bridging fundamental biochemical mechanisms with their physiological consequences in exercise.

Addressing the underexplored catalytic potential of natural polymetallic sulfide minerals and the unclear structure-activity relationship between symbiotic structures and catalytic performance, this study explores the use of mechanically activated natural copper sulfide ore to construct a bimetallic synergistic Fenton-like system for tetracycline degradation, with a focus on the synergistic role of Cu/Fe/S multi-active sites. By optimizing ball milling parameters (ball-to-powder ratio of 3 : 1, duration of 24 h), the catalyst achieved a remarkable 90.11% tetracycline degradation within 10 minutes. Mechanistic investigations revealed that mechanical activation refined particle size, increased specific surface area, and exposed more Cu/Fe/S active sites, establishing a "homogeneous (66.36%) - heterogeneous (33.64%)" synergistic catalytic mechanism. In the homogeneous phase, dissolved Cu²⁺/Fe²⁺ accelerated H₂O₂ decomposition. In the heterogeneous phase, the Cu⁺/Fe³⁺ redox couple (0.16 V/0.77 V) created an energy level difference. Coupled with reductive sulfur species (S^2-, S₂ ^2-)-mediated electron transfer, this facilitated the Fe³⁺ → Fe²⁺ and Cu²⁺ → Cu⁺ cycles, thereby enhancing radical generation efficiency. Two distinct degradation pathways for tetracycline by the copper sulfide concentrate were identified, with intermediates undergoing deep oxidation and ring-opening reactions to mineralize into H₂O, CO₂, and NO₃ ^-. This study overcomes the limitations of traditional single iron-based sulfide catalysts, revealing the catalytic enhancement mechanism of natural mineral symbiotic structures under mechanical activation. It offers a cost-effective and efficient heterogeneous Fenton-like solution for antibiotic wastewater treatment.

The incorporation of metal nanoparticles can enhance the energy release and ignition performance of high-energy-density fuels; however, the effects of particle aggregation and sedimentation mechanisms on combustion remain insufficiently understood. In this work, reactive molecular dynamics simulations are employed to investigate the ignition and combustion behaviors of JP-10/Al composite systems. A validated JP-10/Al model is constructed, and ignition delay, reaction kinetics, and structural descriptors are analyzed across a temperature range of 2000-3000 K and Al concentrations of 10-40 wt%. The results reveal that Al nanoparticle morphology evolves from chain-like extensions to fragmentation and eventual secondary aggregation. The presence of Al accelerates reactant consumption, shortens ignition delay, and promotes rapid Al-O and Al-C bond formation, which destabilizes JP-10 and facilitates cage ring-opening. The accelerated generation of reactive fragments reduces the apparent activation energy by 49.8%. Increasing Al concentration further emphasizes the trade-off: while low-to-moderate loadings enhance ignition, excessive additions induce severe aggregation and reduce efficiency. An optimal concentration window of 20-25 wt% is identified, balancing ignition promotion with minimal aggregation losses. These findings provide mechanistic insights into the multiscale combustion processes of JP-10/Al systems and offer guidance for the design of high-performance composite fuels in aerospace propulsion.

The growing need for advanced materials with tunable properties has triggered an increasing interest in innovative surface modification techniques. Fluidized-bed atomic layer deposition (FB-ALD) offers a powerful solution for surface engineering and functionalization of powder-based materials for a variety of applications. By relying on its capability for controlling uniformity and conformality of the coatings precisely at the atomic scale, ALD can effectively modify surface characteristics to improve the functionality and durability of the materials. In this review, we will provide comprehensive fundamentals and strategies to improve the fluidization of nanopowders and reveal the potential of FR-ALD in two emerging applications. The first application is in energy devices, where FB-ALD is employed to develop Pt-based electrocatalysts for fuel cells and other catalytic reactions. We demonstrate that FB-ALD enables precise control of size, composition, and dispersion of Pt nanoparticles over the support surface, resulting in a strong enhancement in catalytic performance. We additionally discuss the application of FB-ALD in boosting the stability and durability of catalysts by surface engineering with ultrathin films and ultrasmall nanoparticles without compromising their activity. These capabilities open new avenues for the development of high-performance and durable catalysts for energy applications. The second application is in pharmaceutical research, where FB-ALD is employed to coat active pharmaceutical ingredients with thin films of biocompatible materials, such as Al₂O₃, ZnO, SiO₂, and TiO₂, to control their release profiles and improve their physical properties, such as wettability, dispersibility, flowability, and solubility, which are essential for enhancing therapeutic efficacy and patient compliance. The versatility and precision of FB-ALD position it as a key technology for the development of next-generation materials, addressing the critical challenges of performance, stability, and functionality of powder-based materials for different fields.

Carmoisine (CM) (also called azorubine or Acid Red 14) poses severe environmental and health risks due to its chemical stability, persistence in environment, and generation of toxic aromatic amines. Conventional treatment methods such as coagulation, oxidation, membrane filtration, and biological degradation are ineffective and can lead to secondary pollution and incomplete mineralization. Thus, adsorptive and photocatalytic processes have emerged as efficient and sustainable alternatives for CM removal. Adsorption enables rapid dye capture through surface interactions, while photocatalysis achieves complete degradation through light-induced reactive oxygen species. Their integration in adsorptive-photocatalytic composites enhances dye pre-concentration, promotes in situ degradation, and improves catalyst reusability. This review critically discusses the mechanisms, material types, and factors controlling these processes, with emphasis on the influence of surface chemistry, electronic properties, and operational conditions. It also addresses gaps in previous studies, including poor standardization, lack of real wastewater evaluation, and limited environmental assessment. The novelty of this work lies in its comprehensive analysis linking removal performance with mineralization efficiency, toxicity reduction, and scalability while proposing green synthesis and standardized evaluation approaches. Overall, this review provides a concise yet critical framework for advancing efficient, eco-friendly, and practical adsorptive-photocatalytic technologies for the removal of CM from contaminated water systems.

In recent decades, significant advancements have been made in isothiourea (ITU) catalysis, particularly in acyl transfer, silyl transfer, annulations, additions via C(1)-ammonium enolates and [2,3]-sigmatropic rearrangements. Despite these achievements, challenges such as a limited substrate scope of substrates and restricted reaction patterns still remain prevalent. The development of dual catalytic strategies involving secondary catalysts such as electricity, light, transition metals, and Brønsted acids has addressed these issues. This review focuses on the "Isothiourea + X" dual catalytic approach, highlighting recent breakthroughs that extend isothiourea catalysis from classic ionic reactions to radical transformations. Notable advances include the use of ITU-activated ammonium intermediates in asymmetric radical additions, as well as the light-driven generation of ketimine intermediates catalyzed by ITU. Furthermore, the integration of ITU with transition-metal catalysis has expanded its application, enabling reactions with a variety of in situ generated intermediates and promoting chiral cyclization. The review also examines the synergistic effects of ITU in combination with Brønsted acids, which enhance both reaction efficiency and stereocontrol. By summarizing these developments, the review provides valuable insights and directions for future research in ITU catalysis, particularly in the context of green, efficient, and asymmetric radical transformations across multiple fields.

The continuously growing interest in sustainable and innovative materials has driven the production of biochar-based bead adsorbents as recoverable and structurally stable alternatives to powdered biochar. Owing to their tunable physicochemical properties, enhanced mechanical stability, and cost-effectiveness, these materials have emerged as promising material for wastewater treatment applications. This review systematically evaluates recent advancements in the synthesis approaches, surface functionalization, and applications of biochar-based beads in wastewater treatment. The primary focus of the present work is to elucidate the adsorption mechanisms, including electrostatic interactions, surface complexation, π-π electron overlap, hydrogen bonding, ligand exchange, and redox processes that govern the adsorbent performance, with a focus on the oxygen-containing functional groups, polymer-derived functional groups, and aromatic domains in bead matrices that influence these mechanisms. The effects of key experimental parameters such as pH, adsorbent dosage, temperature, contact time, and initial pollutant concentration on adsorption efficiency are critically analyzed. In contrast to other review articles that broadly focus on biochar and its applications in wastewater treatment, the present review specifically focuses on biochar-based bead adsorbents, offering in-depth insights into their synthesis-structure-property relationships, adsorption behaviour, and regeneration potential. Furthermore, the review highlights current limitations and outlines future research directions aimed at enhancing selectivity, stability, scalability, and environmental sustainability.

We report the fabrication and systematic evaluation of three thin-layer graphene oxide (GO) composite membranes prepared by vacuum-filtering a GO dispersion (nominal loading 0.42 mg cm^-2) onto low-cost microporous supports (mixed cellulose ester, nylon, PVDF; 0.45 µm pore, 12 cm²). The membranes (M-GO, N-GO, P-GO) were characterized by AFM, SEM, XPS, and contact angle measurements to reveal support-dependent GO morphology and surface chemistry. At low (0.2 bar) transmembrane pressure (TMP), M-GO exhibited the highest steady-state water flux (425 ± 10 L m^-2 h^-1, n = 3), followed by N-GO and P-GO, while all GO-coated membranes achieved near-complete paraquat rejection (≤ LOD = 0.04 ppm) for feed concentrations of 0.1-1.0 ppm. Reusability tests on M-GO demonstrated ≥95% removal over five consecutive 1 h cycles with a flux recovery ratio (FRR) ≥ 65% after hydraulic flushing. In a 42 h continuous stability test at 0.2 bar, M-GO retained 66% of its initial flux and maintained ≥ 99% paraquat rejection. Tests in a simulated agricultural matrix (paraquat 5 ppm, 100 mM NaCl, 10 ppm humic acid) show a moderate flux decline (stabilizing at ∼55-60% of initial flux) with paraquat rejection > 90%, indicating robustness to ionic strength and natural organic matter. The head-to-head comparison isolates the decisive role of support surface roughness and porosity in governing GO layer formation, flux stability, and antifouling behavior, a pathway to low-pressure, high-flux membranes for cationic pesticide removal.