Sandwich-like, potassium(I) doped g-C3N4 with tunable interlayer distance as a high selective extractant for the determination of Ba(II)

Natural deep eutectic solvent-functionalized mesoporous graphitic carbon nitride-reinforced electrospun nanofiber: a promising sorbent in miniaturized on-chip thin film micro-solid-phase extraction prior to liquid chromatography-tandem mass spectrometry for measuring NSAIDs in saliva

To meet the needs of developing efficient extractive materials alongside the evolution of miniaturized sorbent-based sample preparation techniques, a mesoporous structure of g-C3N4 doped with sulfur as a heteroatom was achieved utilizing a bubble template approach while avoiding the severe conditions of other methods. In an effort to increase the number of adsorption sites, the resultant exfoliated structure was then modified with thymol-coumarin NADES as a natural sorbent modifier, followed by introduction into a nylon 6 polymer via an electrospinning process. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Brunauer-Emmett-Teller (BET) surface area analysis validated S-doped g-C3N4 and composite production. The prepared electrospun fiber nanocomposite, entailing satisfactory processability, was then successfully utilized as a sorbent in on-chip thin film micro-solid-phase extraction of non-steroidal anti-inflammatory drugs (NSAIDs) from saliva samples prior to liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Utilizing a chip device, a thin film μ-SPE coupled with LC-MS/MS analysis yielded promising outcomes with reduced sample solution and organic solvents while extending lifetime of a thin film sorbent. The DES-modified S-doped g-C3N4 amount in electrospun was optimized, along with adsorption and desorption variables. Under optimal conditions, selected NSAIDs were found to have a linear range of 0.05-100.0 ng mL-1 with an R2 ≥ 0.997. The detection limits were ranged between 0.02 and 0.2 ng mL-1. The intra-day and inter-day precisions obtained were less than 6.0%. Relative recoveries were between 93.3 and 111.4%.

Electrochemiluminescence quenching effect of Cu2O towards flower-like ferric ion-doped g-C3N4 and its application for Cyfra21-1 immunosensing

In this article, ferric ion-doped floral graphite carbon nitride (Fe-CN-3, energy donor) was used to construct the substrate of the immunosensor and copper oxide nanocubes (Cu2O, energy acceptor) were taken as an efficient ECL quenching probe. A sandwich quench electrochemiluminescence (ECL) immunosensor for soluble cytokeratin 19 fragment (Cyfra21-1) detection was preliminarily developed based on a novel resonant energy transfer donor-acceptor pair. Fe-CN-3, a carbon nitride that combines the advantages of metal ion doping as well as morphology modulation, is used in ECL luminophores to provide more excellent ECL performance, which makes a significant contribution to the application and development of carbon nitride in the field of ECL biosensors. The regular shape, high specific surface area and excellent biocompatibility of the quencher Cu2O nanocubes facilitate the labeling of secondary antibodies and the construction of sensors. Meanwhile, as an energy acceptor, the UV absorption spectrum of Cu2O can overlap efficiently with the energy donor's ECL emission spectrum, making it prone to the occurrence of ECL-RET and thus obtaining an excellent quenching effect. These merits of the donor-acceptor pair enable the sensor to have a wide detection range of 0.00005-100 ng/mL and a low detection limit of 17.4 fg/mL (S/N = 3), which provides a new approach and theoretical basis for the clinical detection of lung cancer.

Strategies for improving photocatalytic performance of g-C3N4 by modulating charge separation and current research status

Graphitic carbon nitride (g-C3N4) has been extensively investigated over the past decade for its potential utilizations in photocatalytic energy generation and pollutant degradation. To better meeting the requirements for practical utilizations, it is crucial to address the issue of poor charge separation properties in g-C3N4, which origin from the strong interactions in photogenerated electron-hole pairs. In this review, we summarized the pertinent studies on developing strategies to promote the charge separation properties of g-C3N4. The strategies can be categorized into two categories of promoting the surface migration of charge carriers and prolonging the lifetime of surface charge. Finally, we present potential challenges in promoting charge separation and offer feasible suggestions to face these challenges.

A comparison study of sodium ion- and potassium ion-modified graphitic carbon nitride for photocatalytic hydrogen evolution

It is well known that modifying graphitic carbon nitride (GCN) is an imperative strategy to improve its photocatalytic activity. In this study, Na-doped and K-doped graphitic carbon nitride (GCN-Na and GCN-K) were prepared via the simple thermal polymerization of a mixture of melamine and NaCl or KCl, respectively. The structure characterization showed that both Na⁺ and K⁺ intercalation could reduce the interlayer distance of GCN and introduce cyano defects in GCN, while K⁺ apparently had a stronger influence on the structure variation of GCN. The chemical composition data showed that both Na⁺ and K⁺ could easily interact with GCN, while K-doping caused a greater change in the C/N ratio than Na-doping. Moreover, compared to GCN-Na-5 (5 represents weight ratio of alkali halide to melamine), the conduction and valence bands of GCN-K-5 both shifted upward based on the electronic and optical measurements. Consequently, GCN-K-5 yielded an H₂ evolution rate around 4 times higher than that of GCN-Na-5 under visible light irradiation (>420 nm). The cation size effect on GCN was proposed to be mainly responsible for the variation in the structure, optical and electronic properties of ion-doped GCNs, and hence the enhanced photocatalytic H₂ evolution. The current work can provide new insight into optimizing photocatalysts for enhanced photocatalytic performances.

The ion size effect on graphitic carbon nitride is responsible for variations in its structure, optical and electronic properties, and hence the enhancement in photocatalytic hydrogen evolution.

Magnetic N-rich carbon nitride framework material for the high selectivity extraction and determination of La(III)

A novel magnetic C₃N₅ framework material (Fe₃O₄/C₃N₅) was developed as a high selectivity extractant for La(III) determination in food samples. The Fe₃O₄/C₃N₅ material was synthesized by thermal deammoniation method and has larger surface area (100.3 m² g^-1) and more effective adsorption sites compared with that of individual C₃N₅ material (19.4 m² g^-1). It was proved that Fe₃O₄/C₃N₅ material displayed excellent selectivity and adsorption capacity for La(III). In addition, adsorption isotherm and kinetic data indicated that La(III) adsorption based on Fe₃O₄/C₃N₅ material is a monolayer adsorption which is compatible with Langmuir model and follows a pseudo-second-order kinetic equation. By using Fe₃O₄/C₃N₅ material as extractant, an analytical method was established with low limits of detection (3σ, n = 6) of 10.4 μg L^-1, reasonable recoveries ranged from 86% to 106% and good precision with the RSD less than 10.7%. The analytical method was further applied to the determination of trace La(III) in food sample. It evinced that the concentration of La(III) in sea fish is 13.2 μg kg^-1 and the content of ¹³⁸La is 0.138 μg kg^-1, which is 1.03% of total La(III).

Ratiometric fluorescence detection of anthrax biomarker based on terbium (III) functionalized graphitic carbon nitride nanosheets

Detection of anthrax biomarker dipicolinic acid (DPA) is of great importance upon the crisis of bioterrorism. Development of fluorescent materials for DPA detection, particularly one that fully depends on single luminescent response, faces the challenge of being susceptible to interferences. The accompanying accuracy problems offer great opportunities for the establishment of more reliable ratiometric analysis method. Herein, a ratiometric fluorescent probe based on terbium functionalized graphitic carbon nitride nanosheets (Tb-g-C₃N₄NS) is attempted for quantitative detection of DPA to address the distinct function of g-C₃N₄NS as both carrier and reference fluorophore, which is a so-far unexplored option in fluorescent detection approaches. We achieve the incorporation of Tb³⁺ into framework of g-C₃N₄NS by using a simple synthetic strategy comprised of thermal pyrolysis and ultrasonic exfoliation. Combining the reference signal over g-C₃N₄NS at 440 nm (I₄₄₀) with the response signal of Tb³⁺ at 546 nm (I₅₄₆), concentration of DPA can be easily calculated via its linear correlation with the intensity ratio (I₅₄₆/I₄₄₀), giving a precise measurement towards DPA with a detection limit as low as 9.9 nM. Besides enabling an excellent self-calibrating detection of DPA, this work also inspires broader use of g-C₃N₄NS for relevant process.