Porous Semiconducting Polymer Nanoparticles as Intracellular Biophotonic Mediators to Modulate the Reactive Oxygen Species Balance.

The integration of nanotechnology with photoredox medicine has led to the emergence of biocompatible semiconducting polymer nanoparticles (SPNs) for the optical modulation of intracellular reactive oxygen species (ROS). However, the need for efficient photoactive materials capable of finely controlling the intracellular redox status with high spatial resolution at a nontoxic light density is still largely unmet. Herein, highly photoelectrochemically efficient photoactive polymer beads are developed. The photoactive material/electrolyte interfacial area is maximized by designing porous semiconducting polymer nanoparticles (PSPNs). PSPNs are synthesized by selective hydrolysis of the polyester segments of nanoparticles made of poly(3-hexylthiophene)-graft-poly(lactic acid) (P3HT-g-PLA). The photocurrent of PSPNs is 4.5-fold higher than that of nonporous P3HT-g-PLA-SPNs, and PSPNs efficiently reduce oxygen in an aqueous environment. PSPNs are internalized within endothelial cells and optically trigger ROS generation with a >1.3-fold concentration increase with regard to nonporous P3HT-SPNs, at a light density as low as a few milliwatts per square centimeter, fully compatible with in vivo, chronic applications.

Resembling Graphene/Polymer Aerogel Morphology for Advancing the CO2/N2 Selectivity of the Postcombustion CO2 Capture Process.

The separation of CO2 from N2 remains a highly challenging task in postcombustion CO2 capture processes, primarily due to the relatively low CO2 content (3-15%) compared to that of N2 (70%). This challenge is particularly prominent for carbon-based adsorbents that exhibit relatively low selectivity. In this study, we present a successfully implemented strategy to enhance the selectivity of composite aerogels made of reduced graphene oxide (rGO) and functionalized polymer particles. Considering that the CO2/N2 selectivity of the aerogels is affected on the one hand by the surface chemistry (offering more sites for CO2 capture) and fine-tuned microporosity (offering molecular sieve effect), both of these parameters were affected in situ during the synthesis process. The resulting aerogels exhibit improved CO2 adsorption capacity and a significant reduction in N2 adsorption at a temperature of 25 °C and 1 atm, leading to a more than 10-fold increase in selectivity compared to the reference material. This achievement represents the highest selectivity reported thus far for carbon-based adsorbents. Detailed characterization of the aerogel surfaces has revealed an increase in the quantity of surface oxygen functional groups, as well as an augmentation in the fractions of micropores (<2 nm) and small mesopores (<5 nm) as a result of the modified synthesis methodology. Additionally, it was found that the surface morphology of the aerogels has undergone important changes. The reference materials feature a surface rich in curved wrinkles with an approximate diameter of 100 nm, resulting in a selectivity range of 50-100. In contrast, the novel aerogels exhibit a higher degree of oxidation, rendering them stiffer and less elastic, resembling crumpled paper morphology. This transformation, along with the improved functionalization and augmented microporosity in the altered aerogels, has rendered the aerogels almost completely N2-phobic, with selectivity values ranging from 470 to 621. This finding provides experimental evidence for the theoretically predicted relationship between the elasticity of graphene-based adsorbents and their CO2/N2 selectivity performance. It introduces a new perspective on the issue of N2-phobicity. The outstanding performance achieved, including a CO2 adsorption capacity of nearly 2 mmol/g and the highest selectivity of 620, positions these composites as highly promising materials in the field of carbon capture and sequestration (CCS) postcombustion technology.

Innovative Strategy for Developing PEDOT Composite Scaffold for Reversible Oxygen Reduction Reaction.

Metal-air batteries are an emerging technology with great potential to satisfy the demand for energy in high-consumption applications. However, this technology is still in an early stage, facing significant challenges such as a low cycle life that currently limits its practical use. Poly(3,4-ethylenedioxythiophene) (PEDOT) conducting polymer has already demonstrated its efficiency as catalyst for oxygen reduction reaction (ORR) discharge as an alternative to traditional expensive and nonsustainable metal catalysts. Apart from that, in most electrochemical processes, three phenomena are needed: redox activity and electronic and ionic conduction. Material morphology is important to maximize the contact area and optimize the 3 mechanisms to obtain high-performance devices. In this work, porous scaffolds of PEDOT-organic ionic plastic crystal (OIPC) are prepared through vapor phase polymerization to be used as porous self-standing cathodes. The scaffolds, based on abundant elements, showed good thermal stability (200 °C), with potential ORR reversible electrocatalytic activity: 60% of Coulombic efficiency in aqueous medium after 200 cycles.

Tailoring of Textural Properties of 3D Reduced Graphene Oxide Composite Monoliths by Using Highly Crosslinked Polymer Particles toward Improved CO2 Sorption.

The main constraint on developing a full potential for CO2 adsorption of 3D composite monoliths made of reduced graphene oxide (rGO) and polymer materials is the lack of control of their textural properties, along with the diffusional limitation to the CO2 adsorption due to the pronounced polymers' microporosity. In this work, the textural properties of the composites were altered by employing highly crosslinked polymer particles, synthesized by emulsion polymerization in aqueous media. For that aim, waterborne methyl methacrylate (MMA) particles were prepared, in which the crosslinking was induced by using different quantities of divinyl benzene (DVB). Afterward, these particles were combined with rGO platelets and subjected to the reduction-induced self-assembly process. The resulting 3D monolithic porous materials certainly presented improved textural properties, in which the porosity and BET surface area were increased up to 100% with respect to noncrosslinked composites. The crosslinked density of MMA polymer particles was a key parameter controlling the porous properties of the composites. Consequently, higher CO2 uptake than that of neat GO structures and composites made of noncrosslinked MMA polymer particles was attained. This work demonstrates that a proper control of the microstructure of the polymer particles and their facile introduction within rGO self-assembly 3D structures is a powerful tool to tailor the textural properties of the composites toward improved CO2 capture performance.

Experimental and theoretical study of the effect of different functionalities of graphene oxide/polymer composites on selective CO2 capture.

There is a constant need for versatile technologies to reduce the continuously increasing concentration of CO2 in the atmosphere, able to provide effective solutions under different conditions (temperature, pressure) and composition of the flue gas. In this work, a combination of graphene oxide (GO) and functionalized waterborne polymer particles was investigated, as versatile and promising candidates for CO2 capture application, with the aim to develop an easily scalable, inexpensive, and environmentally friendly CO2 capture technology. There are huge possibilities of different functional monomers that can be selected to functionalize the polymer particles and to provide CO2-philicity to the composite nanostructures. Density functional theory (DFT) was employed to gain a deeper understanding of the interactions of these complex composite materials with CO2 and N2 molecules, and to build a basis for efficient screening for functional monomers. Estimation of the binding energy between CO2 and a set of GO/polymer composites, comprising copolymers of methyl methacrylate, n-butyl acrylate, and different functional monomers, shows that it depends strongly on the polymer functionalities. In some cases, there is a lack of cooperative effect of GO. It is explained by a remarkably strong GO-polymer binding, which induced less effective CO2-polymer interactions. When compared with experimental results, in the cases when the nanocomposite structures presented similar textural properties, the same trends for selective CO2 capture over N2 were attained. Besides novel functional materials for CO2 capture and a deeper understanding of the interactions between CO2 molecules with various materials, this study additionally demonstrates that DFT calculations can be a shorter route toward the efficient selection of the best functionalization of the composite materials for selective CO2 capture.

Toward enhanced catalytic activity of magnetic nanoparticles integrated into 3D reduced graphene oxide for heterogeneous Fenton organic dye degradation.

Composite Fenton nanocatalyst was prepared by water-based in situ creation of Fe3O4 nanoparticles integrated within the self-assembly 3D reduced graphene oxide (rGO) aerogel. The hybrid applied for the degradation of Acid Green 25 (AG-25) organic dye in an aqueous solution, in the presence of H2O2. By investigating the conditions that maximize the dye adsorption by the 3D composite, it was found that the pH of the solution should be adjusted between the pKa of the functional groups present on the rGO surface (carboxylic acid) and that of the dye (sulfonic acid) to promote electrostatic interactions dye-3D structure. Performed under these conditions, Fenton degradation of AG-25 in presence of H2O2 was completed in less than 30 min, including all the intermediate products, as demonstrated by MALDI-TOF-MS analysis of the aqueous solution after discoloration. Moreover, this was achieved in a solution with as high a dye concentration of 0.5 mg/mL, with only 10 mg of 3D composite catalyst, at room temperature and without additional energy input. The high performance was attributed to the creation of charge-transfer complex between rGO and Fe3O4 nanoparticles throughout covalent bond C-O-Fe, the formation of which was promoted by the in situ synthesis procedure. For the first time, up to the authors' knowledge, AG-25 degradation mechanism was proposed.

Highly Conductive Structured Catalytic Reactors for One-Step Synthesis of Dimethyl Ether.

Several structured catalytic reactors for the direct synthesis of the DME reaction are compared with regard to catalyst hold-up, thermal conductivity, and volumetric productivity. Adherent and homogeneous catalyst layers were obtained by washcoating independent of the substrates' shape and alloy. Moreover, the substrate nature (FeCrAl, brass, or aluminum) and shape (parallel cell monoliths and open foams) do not modify in great extent the CO conversion values and selectivity to the different compounds. This is reasonable since the catalytic phases are the same in all cases and the existence of mass and heat-transfer limitations was negligible in the experimental conditions studied. Structuring by washcoating exhibits less catalyst inventory per reactor volume than a packed-bed monolith. However, completely packing a monolith with powder catalyst produced a decrease in the CO conversion of around 25% with respect to the coated monolith. Moreover, by means of using the obtained highest catalyst hold-up by washcoating (0.33 gcat/cm3) in a brass monolith and by increasing the reaction temperature, the temperature profiles are only slightly affected. This allows to work in an almost isothermal reactor with a volumetric productivity up to 0.20 LDME/h·cm3 at 573 K.

A green synthesis of nanocatalysts based on reduced graphene oxide/magnetic nanoparticles for the degradation of Acid Red 1.

The increasing amount of organic dye-polluted wastewater from the textile industry makes the development of techniques for the efficient purification and reuse of wastewater an urgent issue. Accordingly, solid adsorbents based on three-dimensional (3D) reduced graphene oxide (rGO) aerogels combined with magnetic nanoparticles (rGO@Fe3O4) appear to be potential materials, which offer fast and efficient discoloration of dye solutions by dye adsorption, simultaneously acting as Fenton reaction nanocatalysts, and thus may eliminate organic dyes. In this work, 3D rGO@Fe3O4 aerogel nanocatalysts were synthesized via a low-energy, simple, one-step in situ method, in which GO and FeSO4·7H2O were simultaneously reduced. Consequently, monolithic porous nanocatalyst 3D structures were obtained, with a specific surface area of 241 m2 g-1 and pore volume 0.39 cm3 g-1. The nanocatalysts were applied for the degradation of Acid Red 1 azo-dye in aqueous solution in the presence of hydrogen peroxide, without the need for external energy. The effect of the adsorbent dose, and concentration of dye and peroxide on the dye removal was studied. The degradation of the dye was monitored by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. It was found that an increase in the amount of peroxide allowed complete degradation of the dye together with high molar mass side-products with a conjugated aromatic structure. The good nanocatalyst performance was explained based on the charge-transfer complex established between rGO and the magnetic nanoparticles, allowing the regeneration of ferrous ions during the Fenton process.