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Nanoporous oxides have been established as key materials for constructing electrodes for energy conversion and storage devices, offering high surface area and a large number of active sites for electrochemical reactions. Herein, we mainly focus on the characteristics, synthesis, and application of various nanoporous oxide electrodes for energy conversion and storage devices. Features of various nanoporous oxides by dimensionality and their functionalities in electrodes are presented. The synthesis strategies for nanoporous oxide electrodes to control their morphology are introduced, including top-down and bottom-up methods. Recent advances in nanoporous oxide electrodes in energy conversion and storage devices, such as fuel cells, water splitting electrodes, solar cells, light-emitting diodes, batteries, and supercapacitors, are summarized. The roles of nanoporous oxides tailored to the specific requirement for high performance of each device are further discussed. This review provides valuable insights into the design of nanoporous oxide electrodes from a materials point of view, contributing to renewable energy technologies.

Photocatalysis, due to its operability under sustainable and green energy conditions, is one of the cardinal branches of the environmental remediation domain. To date, a significant amount of work has been carried out in the design and development of various photocatalysts for applications such as dye degradation, CO2 and NOx reduction, organic transformation and hydrogen generation. Among several factors leading to enhancement of the photocatalytic activity, decreasing the electron–hole (exciton) recombination is regarded as one of the prime factors. Typically, the lifetime of the excitons can be increased by combining two or more semiconductors via forming a heterojunction. Various types of heterojunctions, such as the Schottky barrier, p–n (or non-p–n), van der Waals and facet heterojunctions, can be fabricated depending on specific applications. Each type of heterojunction has its advantages and limitations; hence, proper choice of heterojunction is essential. Almost all classes of semiconductor materials, for instance, metal oxide, perovskites, chalcogenides, metal–organic frameworks (MOFs), covalent organic frameworks (COFs) and MXenes, with a suitable band gap, have been studied for photocatalysis. This review details different classes of materials and types of heterojunctions from the recent literature to provide the reader with a deeper understanding of the same. Initially, the fundamentals of photocatalysis and its basic mechanism are discussed, followed by a detailed discussion on the various types of heterojunctions based on the charge transfer mechanism, such as types I, II and III, with representative examples from recent reports. This panoramic review attempts to encourage a rational design of heterojunctions by choosing the proper candidates to push the process efficiency to its limit.

Biodiesel has emerged as a sustainable renewable energy option and a promising substitute for traditional fossil fuel-derived petroleum. However, its current industrial production is financially impractical requiring novel approaches to ensure sustainability and commercial viability. Carbon dots (CDs) have recently been reported as promising heterogeneous catalysts for transesterification of oil to biodiesel yet the role of the surface chemistry remains vaguely understood. Here, we present amine-passivated CDs (N-CDs) as a model in which their surface chemistry, namely the degree of carboxylic acid to amine and amide functionalization, can be controlled by modifying the amine passivating agent. We thoroughly investigated the N-CDs physico-chemical properties and applied them as heterogeneous catalysts to transesterify canola oil to biodiesel. We report biodiesel conversions of ≥97% using 1 wt% catalyst loading at 100 °C for 3 hours even when the catalyst is reused for five reaction cycles. Lastly, we investigate the effects of modifying the carbon dot surface groups and postulate a plausible governing mechanism for the N-CD-catalyzed transesterification of canola oil to biodiesel. Our findings suggest that both carboxylic acids and amines can act as active catalytic sites, and depending on their concentration, two different reaction mechanisms are possible.

Excessive usage of surfactants in daily life and industry and their undesirable high foamability have caused serious environmental pollution and economic loss. Improving cleaning efficiency and reducing foam stability concurrently is a delicate strategy but a challenging task. Herein, we mixed the most widely used surfactant sodium dodecyl sulfate (SDS) with cyclic amines (CnN, n = 6, 8, 12), by which the self-assembly ability of SDS at the air/water interface and in bulk is significantly enhanced, while spherical micelles, vesicles and wormlike micelles are formed at appropriate total surfactant concentration (CT) and molar fraction of SDS (XSDS). Especially around XSDS = 0.50 and above critical micellar concentration (CMC), the stronger self-assembly ability leads to a higher contact angle of machine oil on stainless-steel plates and lower oil–water interfacial tension in CnN/SDS solution, thus the oil-fouling removal efficiency of CnN/SDS solutions is remarkably improved. Meanwhile, the foamability and foam stability dramatically decline at smaller XSDS and slightly above CMC, attributed to the rapid molecular migration from liquid film of foams to the bulk between the films when the limited surfactant molecules in the films prefer to aggregate in bulk. As a result, C8N/SDS exhibits the best oil cleaning and lowest foaming simultaneously at low XSDS and just above the CMC. This study opens an efficient avenue to eliminate the contradiction between cleaning ability and foamability, thereby obtaining a high-efficiency and low-foam detergent.

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Micellar surfactants with amphiphilic chemical structures are mostly used to disperse single-walled carbon nanotubes (SWCNTs) in water. However, there is little systematic knowledge regarding the use of low-molecular-weight nonmicellar adsorbates as efficient surfactants for colloidal SWCNT dispersions, which limits the number of available solvents. In this article, we present an empirical rule for adsorbate-based dispersants required for SWCNT dispersion in polar organic solvents and water. First, we demonstrate that SWCNTs can be dispersed in aqueous media with the aid of the non-aqueous stilbene backbone compound amsonic acid. The impact of nonmicellar physical adsorption on dispersion was systematically examined using low-molecular-weight compounds, including Fluorescent Brighteners 28 and 220. This discovery has increased the availability of solvents such as water, polar organic solvents such as alcohols, and surfactants such as widely used organic dyes. The results of our study indicate that effective nonmicellar dispersants should include acid–base-carrying structures. The present findings have elucidated the colloidal chemistry of nanocarbon materials with significant potential for application as low-molecular-weight adsorbate-enhanced multifunctional inks.

This work describes the preparation, characterization, and antimicrobial properties of bioactive silver(I) and copper(II) coordination polymers (bioCPs) and derived biopolymer materials. Two bioCPs, [Ag2(μ6-sdba)]n (1) and [Cu(μ4-sdba)H2O]n·1.5nH2O (2), were assembled from metal salt precursors and 4,4′-sulfonyldibenzoic acid (H2sdba). Both compounds were used as dopants for preparing hybrid biopolymer films based on agarose (AGR) or potato starch (PS) as model polysaccharide biopolymers with varying rates of degradability and silver/copper release. BioCPs and derived biopolymer films (1@[AGR]n, 2@[AGR]n, 1@[PS]n, and 2@[PS]n) with a low loading of dopant (1–5 wt%) show promising antibacterial activity against Gram-positive (S. aureus and S. epidermidis) and Gram-negative (E. coli and P. aeruginosa) bacteria. Silver-doped biopolymer films also totally impair the formation of bacterial biofilms, with undetectable biofilm cells in several cases (∼7.5 log or 99.99999% inhibition). By reporting new bioCPs and biopolymer films obtained from renewable polysaccharides, this multidisciplinary work extends the application of coordination compounds as components of hybrid functional materials with antimicrobial properties and prospective biomedical relevance.

We present newly developed buffer systems that significantly improve the efficiency of a photochemically induced surface modification at the single molecule level. Buffers with paramagnetic cations and radical oxygen promoting species facilitate laser-assisted protein adsorption by photobleaching (LAPAP) of single fluorescently labelled oligonucleotides or biotin onto multi-photon-lithography-structured 2D and 3D acrylate scaffolds. Single molecule fluorescence microscopy has been used to quantify photopainting efficiency. We identify specific cation interaction sites for members of the cyanine, coumarin and rhodamine classes of fluorophores using quantum mechanical calculations. We show that our buffer systems provide an up to three-fold LAPAP-efficiency increase for the cyanine fluorophore, while keeping excitation parameters constant.

By developing a new 3D computational model for laser beams propagating through photo-thermally responsive hydrogels, we investigate the complex feedback that occurs as the propagating beam forms a waveguide, which in turn affects the passage of light through the sample. As the beam passes through a poly-(N-isopropylacrylamide) (pNIPAAm) hydrogel, the pendent spiropyran (SP) chromophores isomerize to a hydrophobic state. In water, the resultant localized collapse of the hydrogel leads to a local increase the refractive index, which alters the spatial distribution of light in the sample and leads to the formation of the waveguide. The system displays self-trapping as the light is confined to propagate within the generated waveguide. Our 3D model captures the cooperative interactions among the light propagation, photochemical reaction, hydrogel dynamics, and local heating due to the absorption of light and thereby allows us to characterize the spatial, temporal and thermal variations in the system as the beam traverses the gels. Consequently, the simulations reveal the spatiotemporal behavior as heating due to absorption of light promotes the waveguide formation and leads to a strong attractive interaction between two beams. The strength of interaction between two beams can be tuned by varying the beam intensity, ambient temperature and inter-beam distance. Our results show that two Gaussian beams can cross each other if the interaction is sufficiently strong. The simulations also reveal the long-time dynamics and further elucidate the evolution of the cooperative behavior that leads to this non-linear optical phenomenon.

Interactions between ammonia gas and graphitic materials, including adsorptions and N-doping at elevated temperatures, are known. However, liquid ammonia has rarely been studied other than for the Birch reduction reaction. Here, we report influences of liquid ammonia on graphite oxide (GO) and reduced graphite oxide (rGO), at both the atomic and macroscopic scales. It is demonstrated that GO and rGO do not disperse in liquid ammonia regardless of charge transfer due to the incompatible surface energy and polarity. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy studies of GO sheets treated with liquid ammonia, and liquid nitrogen as a control, for different time periods demonstrate ∼0.6 at% pyridinic N-doping and non-restoration of conjugation in the absence of thermal energy. Macroscopically, liquid ammonia is incapable of altering the shape or size of assembled GO and single walled carbon nanotube (SWCNT) freestanding membranes. However, loud popping sounds along with the generation of pockets, which leads to lower stiffness within the GO membranes, were observed after treating with liquid ammonia. In addition, shrinkage of porous rGO aerogels and counter-intuitively an increase in electrical resistance of SWCNT/cellulose composite membranes after treatment with liquid ammonia, are reported.

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A graphical abstract is available for this content

A graphical abstract is available for this content

A graphical abstract is available for this content

The popularity of ceria (CeO2) supports has been increasing over the last three decades on account of the rich redox chemistry of such an oxide. The ability to act as an oxygen buffer and switch the oxidation state of Ce depending on conditions implies that the role of this oxide goes beyond the conventional function of stabilizing nanoparticles. In fact, ceria can actively participate in catalytic reactions by interacting with the supported metal, in particular precious metals, promoting various types of dynamic processes that are beneficial for catalysis. This perspective put into light such interfacial synergy, and the effects in several catalytic processes, encompassing the most traditional applications up to the most modern reaction schemes.

Near-infrared (NIR) and shortwave infrared (SWIR) image technologies have gained significant attention for emerging applications. However, the absorption edge of Si CMOS image sensors limits their effectiveness beyond the 1000 nm wavelength range. Solution-processed organic semiconductors, with their unique photon-to-electron responses spanning from ultraviolet (UV) to the NIR/SWIR range offer exceptional versatility in optoelectronic applications. To reduce optical noise, narrow-bandpass filters are commonly employed in front of the image sensor for NIR/SWIR applications. Therefore, the development of an image sensor capable of narrowband–broadband dual-mode switchable operation holds significant convenience. In this work, we present a bias-dependent narrowband NIR organic photodiode (OPD) fabricated by blade-coating in ambient atmosphere. The OPD, featuring a 6 μm photo-active layer (PAL), exhibits narrowband photodetection with a detectivity of 1.9 × 1011 Jones at a wavelength of 1100 nm under a bias of −2 V. However, when a bias exceeding −4 V is applied, it transitions into a broadband detector. Furthermore, the fabrication process for this dual-mode OPD is compatible with semiconductor foundry processes, demonstrating promise for large-scale production.

The capacity retention of commercially-sourced pouch cells with single crystal Al surface-doped Ni-rich cathodes (LiNi0.834Mn0.095Co0.071O2) is examined. The degradation-induced capacity fade becomes more pronounced as the upper-cut-off voltage (UCV) increases from 4.2 V to 4.3 V (vs. graphite) at a fixed cycling temperature (either 25 or 40 °C). However, cycles with 4.3 V UCV (slightly below the oxygen loss onset) show better capacity retention upon increasing the cycling temperature from 25 °C to 40 °C. Namely, after 500 cycles at 4.3 V UCV, cycling temperature at 40 °C retains 85.5% of the initial capacity while cycling at 25 °C shows 75.0% capacity retention. By employing a suite of electrochemical, X-ray spectroscopy and secondary ion mass spectrometry techniques, we attribute the temperature-induced improvement of the capacity retention at high UCV to the combined effects of Al surface-dopants, electrochemically resilient single crystal Ni-rich particles, and thermally-improved Li kinetics translating into better electrochemical performance. If cycling remains below the lattice oxygen loss onset, improved capacity retention in industrial cells should be achieved in single crystal Ni-rich cathodes with the appropriate choice of cycling parameter, particle quality, and particle surface dopants.

The occurrence of harmful ions in water can damage ecosystems and human health. For this, we reported an Al(III)-based MOF (DUT-5), which was synthesized via the solvothermal method and applied to remove phosphate and arsenate from aqueous solutions. DUT-5 displayed high adsorption capacity and stability in the pH range from 4 to 9, besides a high selectivity for phosphate removal and outstanding reusability. The maximum adsorption capacities for phosphate and arsenate were 233.26 and 131.32 mg g−1, respectively. The modeling of the experimental data indicated that chemical forces were involved in the adsorption process since this followed the PSO and Freundlinch models. In addition, the mechanism was elucidated by FTIR and XPS analysis, confirming the possible interactions of the arsenate and phosphate with DUT-5 during the adsorption process. Hydrogen bonding and electrostatic interactions were exhibited for arsenate and hydrogen bonding for phosphate removal. Furthermore, this study confirms that DUT-5 is a suitable adsorbent, significantly contributing to water treatment.

Pt nanoclusters are a promising catalyst for VOC catalytic combustion, but they have been rarely studied so far. Herein, Pt nanoclusters (Pt NCs) and Pt nanoparticles (Pt NPs) were constructed by an in situ confined-domain encapsulation strategy, and then the reaction mechanism of Pt species on the catalytic combustion of VOCs was studied systematically. Interestingly, the addition process of Pt and Ce components greatly affected the dispersion and surface states of Pt species. The catalytic performance over PtNC@CeO2 (0.01 wt% Pt loadings) was proved to be of outstanding activity and stability, and the reason was related to the contribution of Pt nanoclusters and more lattice oxygen and Ce3+ species, whose formation was inextricably linked to the strong interfacial effect between Pt and CeO2. Notably, the in situ introduction approach of Pt species can effectively build up the point defects on the surface of CeO2 to promote the dispersion and anchoring of Pt species. In situ DRIFT spectroscopy verified that the role of lattice oxygen was significant in accelerating the catalytic oxidation of VOCs, and the oxidation process of toluene followed the reaction path: toluene → benzyl alcohol → benzaldehyde → benzoic acid → phenol → maleic anhydride → carbon dioxide and water. Meanwhile, the rate-determining step in the oxidation of toluene may be the further decomposition of alcohol or carboxylic acid intermediates.