Supramolecular self-assembly of layer-by-layer graphene film driven by the synergism of π–π and hydrogen bonding interaction

The Heptazine-Based Materials through Intrinsically Modification for the Cycloaddition of CO2 and Bisepoxides

For the efficient utilization of CO2 into valuable product, the attractive carbon nitride catalysts have been widely studied. In this work, heptazine-related materials with varying degree of polymerization were designed by an intrinsically modification strategy and employed in the cycloaddition of CO2 with the bisepoxide 1, 4-butanediol diglycidyl ether (BDODGE). We initially figured out that the sample prepared at 450 °C contained more melem hydrate, exhibiting the best performance. The epoxides conversion and corresponding cyclic carbonates selectivity could achieve 93.1 % and 99.3 % at 140 °C for 20 h without any cocatalyst and solvent, respectively. Results of the catalytic tests suggested that the high catalytic activity was dependent on big size porous structure and the synergetic effect of active amino groups and -OH groups. The role of water in maintaining the specific structure and providing active site has been proved. Moreover, the CN-450-W catalyst exhibited outstanding recycling stability. And finally, a plausible reaction mechanism was proposed.

Enhancing Pollutant Mineralization through Organic-Inorganic Defect-Transit Dual S-scheme with a Robust Internal Electric Field

Achieving superior photomineralization of pollutants relies on a rational design of a dual S-scheme with a robust internal electric field (IEF). In this study, to tackle the low mineralization rate in type-II In2 O3 /In2 S3 (IO/IS) systems, an organic-inorganic dual S-scheme In2 O3 /PDI/In2 S3 (IO/PDI/IS) nanostructured photocatalyst is synthesized via a method combining solvent-induced self-assembly and electrostatic forces. Due to the unique energy band position and strong IEF, the photoinduced defect-transit dual S-scheme IO/PDI/IS facilitates the degradation of lignin and antibiotics. Notably, a promising mineralization rate of 80.9% for sodium lignosulfonate (SL) is achieved. The charge transport pathway of IO/PDI/IS are further validated through the analysis of in situ X-ray photoelectron spectroscopy (in situ XPS), density functional theory calculations, and radical trapping experiments. In-depth, two possible pathways for the photocatalytic degradation of lignin are proposed based on the intermediates monitored by liquid chromatography-mass spectrometry (LC-MS). This study presents a new strategy for the design of organic-inorganic dual S-scheme photocatalysts with a robust IEF for pollutant degradation.

An electrochemical sensor based on carbon composites derived from bisbenzimidazole biphenyl coordination polymers for dihydroxybenzene isomers detection

Co-based coordination polymers (CoCP) based on 4,4'-bis(1H-benzo[d]imidazol-1-yl)-1,1'-biphenyl (BMB) ligand have been synthesized for the first time by the solvothermal method. The CoCP was carbonized at 700 °C under a nitrogen atmosphere to obtain carbide coordination polymer (C-CoCP) with a unique two-dimensional layered network structure. C-CoCP@GO was obtained by binding with GO and C-CoCP, its morphology and structure were investigated by XRD, SEM, EDS, FTIR, and TGA, which confirmed its two-dimensional stacked layered structure with high catalytic activity and large specific surface area. A highly sensitive electrochemical sensor was constructed for the simultaneous detection of hydroquinone and catechol based on the prepared carbon-based composite. Under optimized conditions, the working potentials (vs. Ag/AgCl) of HQ and CC are at 0.097 V and 0.213 V, respectively. The sensor exhibited an extremely wide linear range of 3-600 μM and 3-1750 μM for hydroquinone (HQ) and catechol (CC), respectively, with limits of detection (LOD) of 0.46 μM and 0.27 μM. The electrode material demonstrated stability over 14 days without significant attenuation of the response signal. Impressively, the sensor shows high stability, reproducibility, and selectivity due to the stable carbon skeleton structure of the C-CoCP material. In addition, it can be applied to the detection of hydroquinone in real samples with high interference immunity and high recovery. Hence, the C-CoCP@GO composite proved to be a great prospect and highly sensitive sensing platform for the detection of phenolic isomers.

Dopamine modified layered double hydroxide membranes based on nanofibril architectures: Toward superior tellurium separation properties for water treatment

Two-dimensional (2D) membrane materials are widely employed for the accurate sieving of ionic contaminants and are of great importance for water reuse. However, 2D membrane materials often suffer from uneven thickness and surface defects, which severely limit their application prospects. Herein, a continuous 2D membrane (LCUM/D) was prepared using cellulose nanofibrils (CNFs) as the support backbone for the assembled layered double hydroxides (LDHs) and dopamine (DA) as the adhesive. The results demonstrated that LDHs could be uniformly distributed in the network structure of CNFs, and the defects on the membrane surface could be effectively compensated by DA. Simultaneously, the continuous LCUM/D showed excellent rejection (97.18%) and selectivity of ionic contaminants tellurium. Dopamine not only compensated for the surface defects of the 2D membrane and enhanced the rejection of tellurium, but also caused no significant loss of water permeance. Moreover, the LCUM/D exhibited stability, which facilitated its long-term application. In addition, the improved hydrophilicity allowed LCUM/D satisfactory anti-fouling properties. This study provides new dimensional insights into the fabrication of continuous 2D membranes for the removal of ionic contaminant and enhances their application prospects in wastewater treatment.

Organic Thermoelectric Nanocomposites Assembled via Spraying Layer-by-Layer Method

Thermoelectric (TE) materials have been considered as a promising energy harvesting technology for sustainably providing power to electronic devices. In particular, organic-based TE materials that consist of conducting polymers and carbon nanofillers make a large variety of applications. In this work, we develop organic TE nanocomposites via successive spraying of intrinsically conductive polymers such as polyaniline (PANi) and poly(3,4-ethylenedioxy- thiophene):poly(styrenesulfonate) (PEDOT:PSS) and carbon nanofillers, and single-walled carbon nanotubes (SWNT). It is found that the growth rate of the layer-by-layer (LbL) thin films, which comprise a PANi/SWNT-PEDOT:PSS repeating sequence, made by the spraying method is greater than that of the same ones assembled by traditional dip coating. The surface structure of multilayer thin films constructed by the spraying approach show excellent coverage of highly networked individual and bundled SWNT, which is similarly to what is observed when carbon nanotubes-based LbL assemblies are formed by classic dipping. The multilayer thin films via the spray-assisted LbL process exhibit significantly improved TE performances. A 20-bilayer PANi/SWNT-PEDOT:PSS thin film (~90 nm thick) yields an electrical conductivity of 14.3 S/cm and Seebeck coefficient of 76 μV/K. These two values translate to a power factor of 8.2 μW/m·K², which is 9 times as large as the same films fabricated by a classic immersion process. We believe that this LbL spraying method will open up many opportunities in developing multifunctional thin films for large-scaled industrial use due to rapid processing and the ease with which it is applied.

Voltammetric Detection of Caffeine in Beverages at Nafion/Graphite Nanoplatelets Layer-by-Layer Films

We report for the first time a procedure in which Nafion/Graphite nanoplatelets (GNPs) thin films are fabricated using a modified layer-by-layer (LbL) method. The method consists of dipping a substrate (quartz and/or glassy carbon electrodes) into a composite solution made of Nafion and GNPs dissolved together in ethanol, followed by washing steps in water. This procedure allowed the fabrication of multilayer films of (Nafion/GNPs)n by means of hydrogen bonding and hydrophobic‒hydrophobic interactions between Nafion, GNPs, and the corresponding solid substrate. The average thickness of each layer evaluated using profilometer corresponds to ca. 50 nm. The as-prepared Nafion/GNPs LbL films were characterized using various spectroscopic techniques such as X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), FTIR, and optical microscopy. This characterization highlights the presence of oxygen functionalities that support a mechanism of self-assembly via hydrogen bonding interactions, along with hydrophobic interactions between the carbon groups of GNPs and the Teflon-like (carbon‒fluorine backbone) of Nafion. We showed that Nafion/GNPs LbL films can be deposited onto glassy carbon electrodes and utilized for the voltammetric detection of caffeine in beverages. The results showed that Nafion/GNPs LbL films can achieve a limit of detection for caffeine (LoD) of 0.032 μM and linear range between 20‒250 μM using differential pulse voltammetry, whereas, using cyclic voltammetry LoD and linear range were found to be 24 μM and 50‒5000 μM, respectively. Voltammetric detection of caffeine in beverages showed good agreement between the values found experimentally and those reported by the beverage producers. The values found are also in agreement with those obtained using a standard spectrophotometric method. The proposed method is appealing because it allows the fabrication of Nafion/GNPs thin films in a simple fashion using a single-step procedure, rather than using composite solutions with opposite electrostatic charge, and also allows the detection of caffeine in beverages without any pre-treatment or dilution of the real samples. The proposed method is characterized by a fast response time without apparent interference, and the results were competitive with those obtained with other materials reported in the literature.