Carbon nitride reinforced chitosan/sodium alginate hydrogel as high-performance adsorbents for free hemoglobin removal in vitro and in vivo

Removing free hemoglobin generated during extracorporeal circulation remains a challenge. Currently, there is no adsorbent with specificity and good biosafety for removing hemoglobin. In this study, a new chitosan/sodium alginate/carbon nitride (CS/SA/C3N4) hydrogel adsorbent was prepared by blending SA with C3N4 to drop into CS/CaCl2 solution. The physicochemical properties of CS/SA/C3N4 hydrogel were evaluated using some techniques, including scanning electron microscope, Zeta potential measurement, and thermogravimetric analysis. Hemoglobin adsorption in vitro, stability, hemocompatibility, cell compatibility, inflammatory reaction and blood extracorporeal circulation in vivo were also evaluated. The findings revealed that the CS/SA/C3N4-0.4 % hydrogel exhibited an impressive adsorption capacity of 142.35 mg/g for hemoglobin. The kinetic data of hemoglobin adsorption were well-described by pseudo second-order model, while the isothermal model data conformed to the Langmuir model. The hardness and modulus of CS/SA/C3N4-0.4 % was 11.7 KPa and 94.66 KPa respectively, which indicated robust resistance to breakage. CS/SA/C3N4 demonstrated excellent hemocompatibility, biocompatibility and anti-inflammatory properties. In addition, the results of in vivo rabbit extracorporeal blood circulation experiment demonstrated that CS/SA/C3N4 could adsorb free hemoglobin from blood while maintaining high biosafety standard. Consequently, CS/SA/C3N4 hydrogel emerges as a promising candidate for use as a hemoglobin adsorbent in extracorporeal blood circulation system.

Boosting Electrochemiluminescence Performance of a Dual-Active Site Iron Single-Atom Catalyst-Based Luminol-Dissolved Oxygen System via Plasmon-Induced Hot Holes

Due to the commonly low content of biomarkers in diseases, increasing the sensitivity of electrochemiluminescence (ECL) systems is of great significance for in vitro ECL diagnosis and biodetection. Although dissolved O2 (DO) has recently been considered superior to H2O2 as a coreactant in the most widely used luminol ECL systems owing to its improved stability and less biotoxicity, it still has unsatisfactory ECL performance because of its ultralow reactivity. In this study, an effective plasmonic luminol-DO ECL system has been developed by complexing luminol-capped Ag nanoparticles (AgNPs) with plasma-treated Fe single-atom catalysts (Fe-SACs) embedded in graphitic carbon nitride (g-CN) (pFe-g-CN). Under optimal conditions, the performance of the resulting ECL system could be markedly increased up to 1300-fold compared to the traditional luminol-DO system. Further investigations revealed that duple binding sites of pFe-g-CN and plasmonically induced hot holes that disseminated from AgNPs to g-CN surfaces lead to facilitate significantly the luminous reaction process of the system. The proposed luminol-DO ECL system was further employed for the stable and ultrasensitive detection of prostate-specific antigen in a wide linear range of 1.0 fg/mL to 1 μg/mL, with a pretty low limit of detection of 0.183 fg/mL.

Efficient CO2 methanation using nickel nanoparticles supported mesoporous carbon nitride catalysts

The CO₂ methanation technique not only gives a solution for mitigating CO₂ emissions but can also be used to store and convey low-grade energy. The basic character and large surface area of mesoporous carbon nitride, (MCN), are considered promising properties for the methanation of CO₂. So, a series (5-20 wt.%) of Ni-doped mesoporous carbon nitride catalysts were synthesized by using the impregnation method for CO₂ methanation. the prepared catalysts were characterized by several physicochemical techniques including XRD, BET, FT-IR, Raman spectroscopy, TEM, TGA analysis, Atomic Absorption, H₂-TPR, and CO₂-TPD. The catalytic performance was investigated at ambient pressure and temperature range (200-500 °C) using online Gas chromatography system. The prepared catalysts showed good performance where 15%Ni/MCN exhibited the best catalytic conversion and methane yield with 100% methane selectivity at 450 °C for investigated reaction conditions.

Hierarchical Porous Carbon Nitride-Crumpled Nanosheet-Embedded Copper Single Atoms: An Efficient Catalyst for Carbon Monoxide Oxidation

Rational design of metal single-site embedded porous graphitic carbon nitride (P-g-C₃N₄) nanostructures exploiting maximum atom utilization is warranted to enhance the thermal CO oxidation (CO_Ox) reaction. Herein, a facile, green, one-pot, and template-free approach is developed to fabricate the hierarchical porous P-g-C₃N₄-crumpled ultrathin nanosheets atomically doped with copper single atoms (Cu-P-g-C₃N₄). Mechanistically, the quick protonation of melamine and pyridine under acidic conditions induces deamination to form melem, which is polycondensed under heating. The interconnected pores, high surface area (240 m²g^-1), and maximized exposed isolated Cu atomic active sites (1.8 wt %) coordinated with nitrogen atom P-g-C₃N₄ are the salient features of Cu- P-g-C₃N₄ that endowed complete conversion to CO₂ at 184 °C. In contrast, P-g-C₃N₄ only converted 3.8% of CO even at 350 °C, implying the electronic effect of Cu single atoms. The abundant Cu-nitrogen moieties can drastically weaken the binding affinity of the CO-oxidation (CO_Ox) intermediates and products, thus accelerating the reaction kinetics at a low temperature. This study may promote the fabrication of P-g-C₃N₄ doped with various single atoms for the oxidation of CO.

Rh Particles Supported on Sulfated g-C3N4: A Highly Efficient and Recyclable Heterogeneous Catalyst for Alkene Hydroformylation

The hydroformylation of alkenes with CO and H2 to manufacture aldehydes is one of the most large-scale chemical reactions. However, an efficient and recyclable heterogeneous catalyst for alkene hydroformylation is extremely in demand in academia and industry. In this study, a sulfated carbon nitride supported rhodium particle catalyst (Rh/S-g-C3N4) was successfully synthesized via an impregnation-borohydride reduction method and applied in the hydroformylation of alkenes. The catalysts were characterized by XRD, FTIR, SEM, TEM, XPS, and nitrogen adsorption. The influence of the sulfate content, pressure of syngas, temperature, and reaction time, as well as the stability of Rh/S-g-C3N4, on the hydroformylation was examined in detail. The delocalized conjugated structure in g-C3N4 can lead to the formation of electron-deficient aromatic intermediates with alkenes. The sulphate g-C3N4 has a defected surface owing to the formation of oxygen vacancies, which increased the adsorption and dispersion of RhNPs on the surface of g-C3N4. Therefore, Rh/S-g-C3N4 exhibited an outstanding catalytic performance for styrene hydroformylation (TOF = 9000 h−1), the conversion of styrene could reach 99.9%, and the regioselectivity for the branched aldehyde was 52% under the optimized reaction conditions. The catalytic properties of Rh/S-g-C3N4 were also studied in the hydroformylation of various alkenes and displayed an excellent catalytic performance. Furthermore, the reuse of Rh/S-g-C3N4 was tested for five recycling processes, without an obvious decrease in the activity and selectivity under the optimum reaction conditions. These findings demonstrated that Rh/S-g-C3N4 is a potential catalyst for heterogeneous hydroformylation.

Influences of Calcination Atmosphere on Nickel Catalyst Supported on Mesoporous Graphitic Carbon Nitride Thin Sheets for CO Methanation

Nickel (Ni) catalysts supported on mesoporous graphitic carbon nitride (mpg-C₃N₄) were synthesized through simple impregnation method with air and nitrogen calcination atmosphere for CO methanation. The effects of pretreatment gas on catalyst structure, surface characteristics, and Ni species reducibility were investigated. Under air-calcination condition, the increase in specific surface area of the catalyst can be ascribed to the creation of mesopores and exfoliation of bulk mpg-C₃N₄ to form thin sheets. However, excessive Ni content on the catalyst accelerated the decomposition of the mpg-C₃N₄ support during calcination. The catalysts calcined in nitrogen showed lower surface area and fewer number of pores compared to air-treatment. The Ni/mpg-C₃N₄ catalyst calcined in air with Ni loading 10% exhibited enhanced medium-temperature activity for CO methanation with 79.7% CO conversion and 73.9% CH₄ selectivity. This finding can be explained by the formation of mpg-C₃N₄ thin sheets, which increased the number of catalyst active sites. The CO methanation performance of Ni/mpg-C₃N₄ catalysts calcined in air was superior to those calcined in nitrogen. Interestingly, CO₂ formed by water-gas shift reaction at 320 °C also contributed to the overall methane formation through CO₂ methanation. Therefore, mpg-C₃N₄ thin sheets can be an interesting support for nickel catalyst for CO_x methanation.

Unraveling template-free fabrication of carbon nitride nanorods codoped with Pt and Pd for efficient electrochemical and photoelectrochemical carbon monoxide oxidation at room temperature

The tailored synthesis of carbon nitrides (CNs) is of particular interest in multidisciplinary catalytic applications. However, their fabrication in the form of one-dimensional (1D) nanorods for electrocatalytic carbon monoxide (CO) oxidation is not hitherto reported. Herein, a facile roadmap is presented for the rational design of Pt- and Pd-codoped CN (PtPd/CNs) nanorods via protonation of melamine in an ethylene glycol solution containing Pt and Pd precursors using NaNO3 and HCl and subsequent annealing. The protonation induces the polymerization of melamine to melon nanosheets that consequently roll up to CN nanorods. This tailored the prompt high mass production of uniform 1D CN nanorods (94 ± 2 nm) with a high surface area (155.2 m2 g-1) and they were atomically codoped with Pt and Pd (1.5 wt%) without a template and/or multiple complicated steps. The electrocatalytic CO oxidation activity of PtPd/CNs is 2.01 and 23.41 times greater than that of the commercial Pt/C catalyst and metal-free CNs, respectively, at room temperature. Meanwhile, the UV-vis light irradiation enhanced the CO oxidation activity of PtPd/CNs nanorods by 1.48 fold compared to that in the dark, emanated from the coupling between the drastic inbuilt catalytic merits of PtPd and the inimitable physicochemical properties of CNs. The presented study may pave the way for using CN-based materials in gas conversion reactions.

Photo-mediated co-loading of highly dispersed MnOx-Pt on g-C3N4 boosts the ambient catalytic oxidation of formaldehyde

Exploration of effective metal/support combinations and new fabrication approaches is attractive in the catalytic oxidation of HCHO. In this study, we proposed graphitic carbon nitride (g-C3N4) as a non-metal oxide based support to co-load Pt and MnOx through room-temperature photodeposition and in turn applied for HCHO oxidation. Here, Pt was the active component, while MnOx was the cocatalyst to compensate the shortage of active oxygen on g-C3N4. g-C3N4 was found as a promising support for the high dispersion of Pt and MnOx. Well dispersed Pt nanoparticles with an average diameter of 1.8 nm were obtained, which were highly favorable for the loading of MnOx as MnOx-Pt/g-C3N4. Catalytic performance results indicated that the limited HCHO conversion over g-C3N4 and Pt/g-C3N4 was significantly promoted with the introduction of MnOx, with an optimum MnOx amount of 3.0 wt%. The developed catalysts remained highly stable for 30 h. The enhanced catalytic activity of MnOx-Pt/g-C3N4 was due to the increased number of active oxygen species with the introduction of MnOx and the efficient transfer of electrons from g-C3N4 to Pt. Compared to the traditional impregnation, photodeposition process avoids the application of H2 and high temperatures, scoring in favor of its green and safe nature. This study can concomitantly provide a new way for the design and fabrication of a non-metal oxide based support for the efficient HCHO catalytic oxidation and the application of the photocatalytic process in catalyst fabrication.

Rational Synthesis of Porous Graphitic-like Carbon Nitride Nanotubes Codoped with Au and Pd as an Efficient Catalyst for Carbon Monoxide Oxidation

The precise fabrication of efficient catalysts for CO oxidation is of particular interest in a wide range of industrial and environmental applications. Herein, a scalable method is presented for the controlled synthesis of graphitic-like porous carbon nitride nanotubes (gC₃N₄NTs) codoped with Au and Pd (Au/Pd/gC₃N₄NTs) as efficient catalysts for carbon monoxide (CO) conversion. This includes the activation of melamine with nitric acid in the presence of ethylene glycol and metal precursors followed by consecutive polymerization and carbonization. This drives the formation of porous one-dimensional gC₃N₄NT with an outstanding surface area of (320.6 m² g^-1) and an atomic-level distribution of Au and Pd. Intriguingly, the CO conversion efficiency of Au/Pd/gC₃N₄NTs was substantially greater than that for gC₃N₄NTs. The approach thus presented may provide new avenues for the utilization of gC₃N₄ doped with multiple metal-based catalysts for CO conversion reactions which had been rarely reported before.

Versatile Synthesis of Pd and Cu Co-Doped Porous Carbon Nitride Nanowires for Catalytic CO Oxidation Reaction

Developing efficient catalyst for CO oxidation at low-temperature is crucial in various industrial and environmental remediation applications. Herein, we present a versatile approach for controlled synthesis of carbon nitride nanowires (CN NWs) doped with palladium and copper (Pd/Cu/CN NWs) for CO oxidation reactions. This is based on the polymerization of melamine by nitric acid in the presence of metal-precursors followed by annealing under nitrogen. This intriguingly drove the formation of well-defined, one-dimensional nanowires architecture with a high surface area (120 m2 g−1) and doped atomically with Pd and Cu. The newly-designed Pd/Cu/CN NWs fully converted CO to CO2 at 149 °C, that was substantially more active than that of Pd/CN NWs (283 °C) and Cu/CN NWs (329 °C). Moreover, Pd/Cu/CN NWs fully reserved their initial CO oxidation activity after 20 h. This is mainly attributed to the combination between the unique catalytic properties of Pd/Cu and outstanding physicochemical properties of CN NWs, which tune the adsorption energies of CO reactant and reaction product during the CO oxidation reaction. The as-developed method may open new frontiers on using CN NWs supported various noble metals for CO oxidation reaction.

g-C3N4 supported metal (Pd, Ag, Pt) catalysts for hydrogen-production from formic acid

Pd/g-C₃N₄ with d–π interaction between Pd NPs and g-C₃N₄ with a π-conjugated system shows high catalytic activity in the dehydrogenation of FA.