ACS Omega最新文献

Photocatalytic materials for hydrogen generation are typically categorized into UV-absorbing metal oxides and visible-range semiconductors such as chalcogenides or perovskites, which often incorporate toxic elements. To address environmental concerns of the latter group, indium phosphide (InP)-based quantum dots (QDs) have recently emerged as a less toxic alternative. These nanocrystals (NCs) benefit from a broadband and tunable absorption spectrum, which is well matched for solar photochemistry, and offer suitable electronic characteristics to drive photoinduced charge separation. This perspective provides a comprehensive summary of the recent advancements in developing InP-based NCs with a focus on photocatalytic hydrogen production. We discuss synthetic strategies that enhance the catalytic activity of these materials and highlight key challenges that must be addressed to enhance their performance. Finally, we explore future research directions aimed at improving photocatalytic efficiency and integrating InP-based QDs into practical solar-to-fuel conversion systems.

Hydrogen-ammonia fuels combine the high hydrogen storage density and zero carbon emissions of ammonia with the rapid combustion kinetics of hydrogen, yet their markedly different physicochemical properties pose significant challenges in cylinder mixing. To enhance mixture uniformity and ignition stability, this study employs three-dimensional (3D) CFD simulations to analyze the flow and mixing behavior of hydrogen-ammonia blends under low pressure direct injection (DI) conditions using an auxiliary injection system. The results demonstrate that shear layer instabilities and baroclinic vorticity generation act synergistically to drive vortex formation and trigger a turbulence cascade, thereby strengthening the mixing of fuel and air. In the later stages of injection, the primary vortex ring decays and releases fuel from its core outward, expanding the mixing region and further improving the homogeneity. Applying the Q criterion to identify vortical structures within the jet, the flow field is partitioned into strong, weak, and no vortical regions. Notably, the weak vortex region maintains an equivalence ratio (Φ) near the stoichiometric mixture (Φ ≈ 1.0–1.2) and moderate turbulent kinetic energy throughout the injection, creating ideal conditions for flame kernel development and marking it as the optimal ignition region. These findings provide a theoretical foundation for ignition prediction and mixture optimization in DI hydrogen-ammonia engines.

Gas separation employing polymeric membranes is limited by the permeability–selectivity trade-off, which has driven the development, among numerous technologies, of mixed matrix membranes (MMMs) that combine highly permeable polymers with fillers capable of enhancing gas selectivity. The compatibility in the filler/polymer interface is therefore essential to design materials with superior separation performances. In this work, MMMs were produced with Pebax-2533, incorporating synthetic silico-metallic mineral particles (SSMMPs) and SSMMP-NH₂ fillers, both with and without PIM-1 surface coating, and were evaluated in the separation of CO₂/CH₄ and CO₂/N₂. The membranes were prepared in two types: dense and thin-film composite (TFC). These MMMs were characterized through several techniques, and gas permeation assessments of the dense membranes were conducted at pressures ranging from 1 to 10 bar. The findings demonstrated enhanced thermal, mechanical, and gas separation properties following the addition of the fillers. Specifically, the sample containing 20 wt % SSMMP-NH₂@PIM-1 achieved a permeability of 501.7 Barrer at 10 bar, representing a 129.8% increase relative to the pure membrane. Additionally, the TFC membrane was fabricated using a self-made porous polysulfone (PSF) support, which was subsequently coated with a selective layer and a protective layer of polydimethylsiloxane (PDMS), achieving a CO₂ permeance of 575 GPU and selectivities of 12 for CO₂/CH₄ and 33 for CO₂/N₂. The results demonstrated the beneficial effects of functionalizing the amine groups (−NH₂) in the fillers, particularly when employing the nonsolvent-induced surface deposition (NISD) technique to coat PIM-1 on the filler surface. The developed materials exhibit promising performance as visualized in the Robeson graph and TFCs target regions, suggesting that they could be suitable for industrial-scale CO₂ separation with additional development.

We report a detailed theoretical investigation into the electronic, mechanical, and hydrogen adsorption behaviors of zigzag dodecanophene nanotubes (Dode-NTs) with chiralities (n,0) and (0,n). Using density functional theory (DFT) and classical reactive molecular dynamics (MD) simulations, we demonstrate that chirality and curvature strongly modulate the physical behavior of these nanotubes. The Dode-NTs (n,0) maintain a robust metallic character even under uniaxial strain, whereas Dode-NTs (0,n) with odd chiral indices exhibit a tunable semiconducting behavior, with frontier orbitals spatially separated along transverse and longitudinal directions. Mechanically, Dode-NTs (n,0) exhibit higher stiffness and tensile strength, confirmed by both DFT and MD, while Dode-NTs (0,n) show a more ductile response with distributed strain accommodation. These features highlight a pronounced mechanical anisotropy. The hydrogen adsorption studies reveal that the Dode-NTs (n,0), particularly at a specific adsorption site and at larger diameters, exhibit adsorption free energy values near the catalytic optimum for the hydrogen evolution reaction (HER). In contrast, Dode-NTs (0,n) present lower reactivity and weaker site selectivity. MD results confirm a more efficient surface functionalization for the Dode-NTs (n,0) configuration under elevated temperatures. These findings highlight that Dode-NTs, especially those with (n,0) chirality, are highly tunable nanostructures with potential applications in catalysis, hydrogen storage, nanoelectronics, and nanomechanical systems.

C₇–C₁₀ aromatics are indispensable components of aviation fuels to meet the swelling need for sealing rings in aero engines. Aromatics with a short and single substituent have weak low-temperature reactivity, yet this may be enhanced under a fuel blend environment. In this work, we investigated low-temperature oxidation chemistry of n-propylbenzene, a representative C₉ aromatic in a blend with n-heptane, in a jet-stirred reactor. Time-of-flight molecular beam mass spectrometry using synchrotron vacuum ultraviolet radiation as a photon ionization source was used for product analysis and species identification. Thirty-six species were identified by comparison of measured photoionization efficiency curves and calculated species ionization energies, and six of them are key reaction intermediates of n-propylbenzene oxidation. Kinetic model simulations captured the measured mole fractions of reactants, main products, and intermediates with some discrepancies. Furthermore, many oxygenated aromatics are missing in the model, reflecting insufficient understanding of n-propylbenzene low-temperature chemistry. Low-temperature oxidation pathways were proposed based on molecular structures of reaction intermediates. This work explored low-temperature oxidation of n-propylbenzene under a fuel blend environment, which might be useful to unravel the low-temperature chemistry of C₇–C₁₀ aromatics in practical jet fuels.

The industrial viability of chemical looping technology is directly linked to the development of oxygen carriers (OCs) that meet the operational requirements of the process. This study investigates the optimization, characterization, and selection of iron ores from different regions of Brazil as potential OCs for chemical looping applications. A total of 13 samples were analyzed, including 11 predominantly composed of hematite and 2 of ilmenite. These materials were characterized through physicochemical, morphological, and structural analyses using techniques such as X-ray diffraction (XRD), X-ray fluorescence (XRF), temperature-programmed reduction (TPR), and scanning electron microscopy–energy-dispersive spectroscopy (SEM-EDS). The samples exhibited good mechanical strength (≥2.2 N), oxygen transport capacity ranging from 1.21% to 4.90%, and high reactivity during redox cycles with methane and hydrogen. Notably, the FeHP, FeHJ, FeHC, FeLC, FeTiHL, and FeTiHM samples demonstrated outstanding performance in terms of reactivity, cyclic stability, and oxygen transport capacity, showing suitability for operation in the typical temperature range of 800–1100 °C for CL processes. These findings highlight the potential of applying the selected materials in chemical looping technologies, offering sustainable and cost-effective alternatives for CO₂ capture and utilization.

Controlling the activity of synthetic catalysts over time remains a key challenge for designing adaptive chemical systems. Supramolecular phosphodiesterase mimics can be particularly sensitive to pH, with some of them presenting active species that operate only under basic conditions. In this work, we have focused on a dissipative strategy that exploits activated carboxylic acids (ACAs) to temporally modulate pH and, consequently, the activity states of these catalysts. ACAs undergo combined acid–base and decarboxylation processes, enabling transient acidification followed by a spontaneous return to higher pH. We first analyze the acid–base behavior of a selected ACA through potentiometric studies to identify the parameters governing the lifetime of the dissipative state in semiaqueous media. Guided by these insights, we investigate the time-dependent catalytic performance of metal complexes based on a cyclic polyamine and a bifunctional calix[4]arene bearing both a cyclic polyamine and a guanidinium group. This approach provides a programmable way to regulate phosphodiester cleavage catalysis, laying the foundations for future adaptive and temporally controlled chemical systems.

Graphene and its derivatives, such as graphene nanoplatelets (GNPs), are considered promising materials to be combined with copper for composite foil fabrication. However, the use of GNPs in liquid-phase processes remains challenging due to their hydrophobicity; thus, tailoring their wettability is a subject of rising interest. Among the possible approaches, functionalization with polydopamine (PDA) demonstrated a high degree of versatility. This process, especially the impact of the various process parameters on the final PDA coatings, is still a poorly explored topic. Our contribution investigates the nanostructure of the PDA layer on functionalized GNPs and the impact of the presence of copper ions in the functionalization process. Of all parameters tested, the presence or absence of copper ions in the dopamine polymerization process is revealed to be a key parameter controlling the morphology and thickness of the final PDA coating. Indeed, introducing Cu²⁺ during the functionalization process results in a thicker coating onto GNPs and promotes the formation of free-standing PDA particles alongside GNP functionalization. Such straightforward polymeric addition on GNPs allows for their facilitated dispersion and stability in aqueous media, a step toward enhancing the processability easiness of a promising material.

A low-cost, robust, and easy-to-operate photoreactor with automatic temperature control, achieved through heat sinks, cooling fans, a temperature sensor, and a microcontroller (Arduino Nano), was manually constructed using predominantly discarded materials, without the need for sophisticated instrumentation. The light source employed was a 3 W RGB LED lamp with infrared (IR) remote control. The electromagnetic radiation spectra (white, blue, green, and red) were determined by UV–vis spectroscopy; additionally, the irradiance and luminous flux of these radiations were evaluated. For luminous flux determination, a lux meter was developed based on a BH1750-FVI sensor coupled to the Arduino Nano. The characterizations indicated that red radiation exhibits the highest irradiance and luminous flux values when compared to blue and green radiations. The estimated cost for constructing the photoreactor was US$ 41.50, which is significantly lower than that of commercially available photoreactors, whose prices typically exceed US$ 3000.00. To validate the performance of the photoreactor, the photocatalytic degradation of methylene blue (MB) was carried out using a novel Nb₂O₅@H₂TPP material as the photocatalyst. This material was synthesized by physical mixing of niobium pentoxide (Nb₂O₅) and 5,10,15,20-tetraphenylporphyrin (H₂TPP). The resulting photocatalyst was comprehensively characterized by X-ray diffraction, UV–vis diffuse reflectance spectroscopy (UV–vis/DRS), scanning electron microscopy, zeta potential measurements, infrared spectroscopy, and thermogravimetric analysis. The MB degradation reactions were initially conducted following a factorial experimental design. This analysis identified MB concentration as a negative factor in the degradation percentage, catalyst mass as a positive factor, and reaction time as a nonsignificant variable within the time range explored. Based on these findings, MB degradation reactions were performed under different ranges of incident light wavelengths (white, blue, green, and red). The MB degradation percentages observed were 32% under white light, 34% under blue light, 42% under green light, and 44% under red light exposure.

The effect of pentaerythritol (PERT) as a nucleating agent on the crystallization behavior of poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexannoate] (P(3HB-co-3HH)) was examined. Isothermal crystallizations with and without PERT at various temperatures were monitored in real time using simultaneous synchrotron radiation wide-angle X-ray diffraction and small-angle X-ray scattering techniques. Heterogeneous nucleation was observed at significantly higher temperatures, where the crystallization of pure P(3HB-co-3HH) scarcely occurs. The crystal form and morphological parameters of P(3HB) remained unchanged in the presence of the nucleating agent. However, the induction period for crystallization with PERT was significantly reduced. Structural analysis confirmed that the nucleating agent enhances overall crystallinity due to a higher density of nucleation sites. In addition, the interaction between the molecular chain and the substrate surface was investigated through molecular dynamics (MD) simulations. The MD simulations indicated that the molecular chain tends to interact attractively with the substrate surface, with the carbonyl groups of P(3HB) oriented toward the hydroxy groups of PERT. These results suggested that the formation of hydrogen bonds, rather than crystalline lattice matching, plays a crucial role in the heterogeneous nucleation of P(3HB) on PERT.