Functionalized g-C3N4 Nanosheets Research Articles

Functionalized g-C3N4 nanosheet interlayer enables enhanced separation performance of nanofiltration membranes

Thin film nanocomposite membrane with a nanomaterial interlayer (TFNi) has attracted extensive attention in recent years. Herein, for the first time, tannic acid (TA) functionalized g-C3N4 nanosheets are used to construct an interlayer for the fabrication of TFNi nanofiltration membranes with enhanced separation performance. The TA-C3N4 nanosheet interlayers possess high hydrophilicity, low resistance for water transport, and strong structural stability, which is conducive to improving water permeance of the TFNi membranes. Meanwhile, the uniformity of interfacial polymerization on the interlayers is improved by virtue of the smooth surface of the interlayer, enabling the formation of an integral and dense polyamide layer with a thickness of only about 10 nm. The TFNi membranes exhibit excellent performance with water permeance of 34.25 L m−2 h−1 bar−1 and Na2SO4 rejection of 98.53%, which are obviously higher than those of the corresponding membrane without TA-C3N4 nanosheets (21.03 L m−2 h−1 bar−1 and 92.04%). The TFNi membranes also show significant selectivity improvement toward divalent/monovalent ions. This work gives inspiration for designing advanced nanofiltration membranes with functionalized nanomaterials acting as interlayers.

Synthesis of metal-free functionalized g-C3N4 nanosheets for enhanced photocatalytic activity

A new visible-light active polymeric semiconductor was fabricated covalently functionalizing the g-C3N4 using halogenated phenyl groups. 4-bromobenzonitrile was employed to introduce organic motifs into g-C3N4 networks through a convenient one-pot thermally induced process. The functionalization of the g-C3N4 with the halogenated phenyl group extended the original π-conjugation system, leading to the enhancement of visible-light absorption, and the separation of charge carriers. Introducing the new group, the g-C3N4 pore structure was enriched, resulting in a larger specific surface area and an increase in active sites. The functionalization led to an easier exfoliation of the g-C3N4 framework into thinner layers, enhancing its dispersion ability in the water. Under visible-light irradiation, the as-prepared semiconductor exhibited increased photocatalytic activity to the pristine g-C3N4. The photocatalytic performances were investigated on a simple organic compound, methanol, a model dye, rhodamine B, and an emergent contaminant, 4-nitrophenol. This research provided new insights on metal-free modified g-C3N4 as a visible-light photocatalyst.

An “on-off” electrochemiluminescence immunosensor for PIVKA-II detection based on the dual quenching of CeO2–Au-g-C3N4 hybrids by Ag nanocubes-VB2

Herein, we report a novel dual-quenching electrochemiluminescence (ECL) immunosensor for detecting protein induced by vitamin K absence or antagonist-II (PIVKA-II) based on ECL resonance energy transfer (ECL-RET). In this protocol, self-accelerated ECL hybrids of CeO2 and Au nanoparticles functionalized g-C3N4 nanosheets (CeO2–Au-g-C3N4) were prepared, which exhibited high ECL emission in the presence of S2O82− as a coreactant for “signal on” state. Concretely, CeO2 with a reproducible redox couple of Ce3+ and Ce4+ could act as an efficient co-reaction accelerator to generate more oxidizing intermediate (SO4•−) to significantly self-promote the ECL emission of g-C3N4 NSs/S2O82− ECL system. Besides, Au nanoparticles not only accelerated electron transfer in the ECL process, but also provided massive active sites for biomolecules immobilization. The dual quenching labels of Ag nanocubes modified with vitamin B2 (AgNCs-VB2) were firstly proposed towards g-C3N4 NSs/S2O82− ECL system by ECL-RET, resulting in the remarkable ECL decrease for “signal off” state. Based on the sandwich immunoreaction, the “on-off” PIVKA-II ECL immunosensor gratifyingly possessed excellent detection sensitivity with the linear range of 0.4 pg mL−1–10 ng mL−1 and the low detection limit of 28.46 fg mL−1 (S/N = 3). This presented strategy might provide a potential alternative tool for PIVKA-II detection in medical research and early clinical diagnostics of hepatocellular carcinoma.

Carbon quantum dots functionalized g-C3N4 nanosheets as enhanced visible-light photocatalysts for water splitting

Graphitic carbon nitride (g-C3N4) is a representative photocatalyst, but the photocatalytic activity is often limited because of the easy recombination and slow migration of photogenerated charges. Herein, we have successfully prepared carbon quantum dots (CQDs) functionalized g-C3N4 (CCN) by a simple thermal polymerization method. Besides, the CQDs serving as a photosensitizer can enlarge the absorption range of visible light of the composite material. As a result, under the irradiation of visible light, the optimized CCN showed superior catalytic activity with a high H2 production rate of 2321 μmol·g−1·h−1, which was almost about 7.4 times higher than that of bulk g-C3N4. Based on the systematic characterization and density functional theory (DFT) calculation, it was proved that the efficiencies of the separation and transfer of photogenerated charges were enhanced by the micro-regional heterostructure of CQDs and g-C3N4.

Functionalized g-C3N4 nanosheets for potential use in magnetic resonance imaging-guided sonodynamic and nitric oxide combination therapy

The oxygen consumption-induced hypoxia and the high concentration of glutathione in tumor microenvironment limit the treatment outcomes of sonodynamic therapy (SDT). SDT needs to be combined with other treatment modalities to achieve the desired therapeutic efficiency. In this study, an oxidized g-C3N4 (OCN) nanosheet-based theranostic nanoplatform is developed for sonodynamic and nitric oxide (NO) combination therapy of cancer. The OCN nanosheets are successively modified with amino-terminated 6-armed polyethylene glycol, chlorin e6, and Gd3+ ions, and then the as-prepared OCN-PEG-(Ce6-Gd3+) nanosheets are loaded with the NO donor N,N′-di-sec-butyl-N,N′-dinitroso-1,4-phenylenediamine (BNN6). Upon ultrasound (US) irradiation, the OCN-PEG-(Ce6-Gd3+)/BNN6 nanocomposite can induce the generation of reactive oxygen species (ROS) and simultaneously release NO molecules to effectively kill the cancer cells, thereby significantly suppressing the tumor growth. Moreover, a good in vivo T1-weighted magnetic resonance imaging (MRI) contrast effect is achieved after intravenous injection of OCN-PEG-(Ce6-Gd3+)/BNN6 due to remarkably enhanced contrast performance of the nanocomposite. Therefore, the OCN-PEG-(Ce6-Gd3+)/BNN6 formulation can serve as a promising theranostic agent for MRI-guided sonodynamic-NO combination therapy.

Aminated flower-like ZnIn2S4 coupled with benzoic acid modified g-C3N4 nanosheets via covalent bonds for ameliorated photocatalytic hydrogen generation

To ameliorate the photocatalytic activity of g-C3N4 samples, through covalent bonds, we coupled aminated flower-like ZnIn2S4 (AZIS) with functionalized g-C3N4 nanosheets by benzoic acid (BCN) to establish an integral structure, BCN/AZIS. A series of photocatalytic tests and characterization results confirmed that the conjunct catalyst is able to give superior photocatalytic properties for H2 generation (485.4 μmol h−1), about 15.1 times that of pure g-C3N4 (32.1 μmol h−1). The improvement in photocatalysis of BCN/AZIS could be ascribed to the intimately interfacial contact and well-matched band gaps structure between BCN and AZIS, both of which bring about effective photoinduced charge separation and migration.

Novel functionalized graphitic carbon nitride incorporated thin film nanocomposite membranes for high-performance reverse osmosis desalination

In this study, a series of hydrophilic graphitic carbon nitride (g-C3N4) nanosheets was synthesized with various oxygen donor compounds to produce OH, COOH and SO3H groups on the surface of g-C3N4 and incorporated in polyamide layer (PA) of thin film nanocomposite (TFN) membrane to fabricate reverse osmosis (RO) membranes with excellent antifouling and desalination properties. The results of FTIR and EDX analysis indicated the successful introduction of functional groups on the g-C3N4 nanosheets surface. The average surface roughness of the modified membranes with COOH functionalized g-C3N4 nanosheets decreased to 3.2 nm with 82% decrease compared with g-C3N4 modified membranes. The effect of incorporated g-C3N4 nanosheets on the performance of the membranes was studied using pure water flux, NaCl and BSA solution filtration. The outcomes showed that introducing of the functionalized g-C3N4 nanosheets in the PA active layer of the membranes improved considerably the membrane permeation without decrease in rejection performance. The modified membrane with COOH functionalized g-C3N4 nanosheets showed maximum pure water flux of 91.8 L/m2 h with 54% increase compared with g-C3N4 modified membranes.

Hydroxy-carbonate-assisted synthesis of high porous graphitic carbon nitride with broken of hydrogen bonds as a highly efficient visible-light-driven photocatalyst

Graphite carbon nitride (g-C3N4) is a promising candidate as an efficient, affordable, and sustainable alternative photocatalyst owing to its unique physical and chemical properties. However, the photocatalytic activity of pristine g-C3N4 is still far below what is expected, because of its insufficient active site and high electron–hole recombination rates. Herein, we develop a novel strategy—a one-step hydroxy-carbonate-assisted route—to try to overcome these disadvantages in g-C3N4 nanosheets by creating substantial pores ranging from mesoporous to macropore, which are mainly caused by the partial breaking of hydrogen bonds and removing of magnesium oxide. Luxuriant pores in g-C3N4 not only serve as a reaction center by providing a large number of active sites at pore edges, but also effectively improve the photogenerated carrier separation by shortening their transfer lengths. The highly efficient visible-light photocatalytic activity of porous g-C3N4 nanosheets are demonstrated by degrading methyl blue (MB) and gentian violet (GV) as models, which its degradation rate constant is respectively more than 109 times and 12 times higher than those of pristine g-C3N4. Meanwhile, the high porous g-C3N4 has robust stability. The simple and effective strategy proposed here provides a direct route to highly functionalized g-C3N4 nanosheets and other layered semiconductors for various applications.Highlights:1. A novel one-step hydroxy-carbonate-assisted route to prepare well-developed porous g-C3N4 nanosheets is proposed for the first time.2. The porous structure not only provides abundant active sites, but also accelerate the transfer of electrons to reach the lateral surface of the pores.3. The high porous g-C3N4 have highly efficient and stability for photocatalytic application.4. This work provides a simple and effective strategy to design highly functionalized g-C3N4 nanosheets and other layered semiconductors for various applications.

Developing a new method for synthesizing amine functionalized g-C3N4 nanosheets for application as anti-corrosion nanofiller in epoxy coatings

In this research, the effect of graphitic carbon nitride (g-C3N4) on the corrosion protection performance of solvent-based epoxy coatings is investigated. The g-C3N4 is synthesized by two-step condensation of melamine and is characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and carbon–hydrogen–nitrogen elemental analysis. In order to enhance the dispersion of g-C3N4 in epoxy coating, it is chemically functionalized with ethylenediamine vapor via a simple method. Further, epoxy coatings containing different amounts (0, 0.05, 0.1, 0.3, 0.5, and 0.7 wt%) of amine functionalized g-C3N4 (AF g-C3N4) are spray coated on mild steel substrate. The dispersion quality of nanofillers in coating matrix is studied by field emission scanning electron microscopy. The corrosion resistance of samples is investigated by electrochemical impedance spectroscopy. The results reveal the superior corrosion protection of nanocomposite coatings due to barrier performance of AF g-C3N4. Meanwhile, epoxy coating containing 0.5 wt% AF g-C3N4 shows the highest corrosion protection compared to pure epoxy sample.

Enhanced Peroxidase-Like Activity of MoS₂ Quantum Dots Functionalized g-C₃N₄ Nanosheets towards Colorimetric Detection of H₂O₂.

MoS2 quantum dots (QDs) functionalized g-C3N4 nanosheets (MoS2@CNNS) were prepared through a protonation-assisted ion exchange method, which were developed as a highly efficient biomimetic catalyst. Structural analysis revealed that uniformly-dispersed MoS2 QDs with controllable size and different loading amount grew in-situ on the surface of CNNS, forming close-contact MoS2@CNNS nanostructures and exhibiting distinct surface properties. Compared to MoS2 QDs and CNNS, the MoS2@CNNS nanocomposites exhibited a more than four times stronger peroxidase-like catalytic activity, which could catalyze the oxidation of 3,3’,5,5’-tetramethylbenzidine (TMB) in the presence of H2O2 to generate a blue oxide. Among the MoS2@CNNS nanocomposites, MoS2@CNNS(30) was verified to present the best intrinsic peroxidase-like performance, which could be attributed to the more negative potential and larger specific surface area. A simple, rapid and ultrasensitive system for colorimetric detection of H2O2 was thus successfully established based on MoS2@CNNS, displaying nice selectivity, reusability, and stability. The detection limit of H2O2 could reach as low as 0.02 μM. Furthermore, the kinetic and active species trapping experiments indicated the peroxidase-like catalytic mechanism of MoS2@CNNS. This work develops a novel, rapid, and ultrasensitive approach for visual assay of H2O2, which has a potential application prospect on clinical diagnosis and biomedical analysis.