Separation and concentration of natural products by fast forced adsorption using well-dispersed velvet-like graphitic carbon nitride with response surface methodology optimisation

Enhanced detection of 4-nitrophenol in drinking water: ECL sensor utilizing velvet-like graphitic carbon nitride and molecular imprinting

In this work, a molecularly imprinted electrochemiluminescence (ECL) sensor was developed for selective detection of 4-nitrophenol (4-NP) in drinking water for the first time. By synthesizing velvet-like graphitic carbon nitride (V-g-C3N4) via one-step thermal polycondensation and integrating it with a molecularly imprinted polymer (MIP), the ECL sensor was fabricated. The MIP-modified V-g-C3N4 composites (MIP/V-g-C3N4) were synthesized using a sol-gel method with 4-NP as the template molecule. Under optimal conditions, the ECL sensor exhibited a wide detection range (5 × 10-10-1 × 10-5 mol/L) and a low detection limit (1.8 × 10-10 mol/L). In testing with actual drinking water samples, it displayed high accuracy (recoveries for intraday and inter-day: 93.50-106.2% and 97.00-107.3%, separately) and precision (RSDs for intraday and inter-day: 1.54-4.59% and 1.53-4.28%, respectively). The developed MIP-based ECL sensor demonstrated excellent selectivity, stability, and reproducibility, offering a promising and reliable approach for highly sensitive and selective determination of 4-NP in drinking water.

Self-Supporting g-C3N4 Nanosheets/Ag Nanoparticles Embedded onto Polyester Fabric as “Dip-Catalyst” for Synergic 4-Nitrophenol Hydrogenation

Herein, we report the design of a cost-effective catalyst with excellent recyclability, simple recuperation and facile recovery, and the examination between the reaction cycles via the development of self-supporting g-C3N4 nanosheets/Ag NPs polyester fabric (PES) using a simple, facile and efficient approach. PES fabrics were coated via a sono-coating method with carbon nitride nanosheets (GCNN) along with an in situ setting of Ag nanoparticles on PES coated GCNN surface producing PES-GCNN/Ag0. The elaborated textile-based materials were fully characterized using FTIR, 13C NMR, XRD, TGA, SEM, EDX, etc. Catalytic performance of the designed “Dip-Catalyst” demonstrated that the as-prepared PES-GCCN/Ag0 has effectively catalyzed the hydrogenation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of NaBH4. The 3 × 3 cm2 PES-GCNN/Ag0 showed the best catalytic activity, displaying an apparent rate constant (Kapp) equal to 0.43 min−1 and more than 10 reusability cycles, suggesting that the prepared catalyst-based PES fabric can be a strong nominee for sustainable chemical catalysis. Moreover, the coated fabrics exhibited appreciable antibacterial capacity against Staphylococcus epidermidis (S. epidermidis) and Escherichia coli (E. coli). The present study opens up new opportunities for the future design of a low cost and large-scale process of functional fabrics.

Adsorption of lindane (γ-hexachlorocyclohexane) on nickel modified graphitic carbon nitride: a theoretical study

Adsorption of lindane (HCH) on nickel modified graphitic carbon nitride (Ni-gCN) was investigated using a novel, accurate and broadly parametrized self-consistent tight-binding quantum chemical (GFN2-xTB) method. Two graphitic carbon nitride (gCN) models were used: corrugated and planar, which represent the material with different thicknesses. Electronic properties of the adsorbates and adsorbent were estimated via vertical ionization potential, vertical electron affinity, global electrophilicity index and the HOMO and LUMO. Adsorption energy and population analyses were carried out to figure out the nature of the adsorption process. The results reveal that the introduction of the nickel atom significantly influences the electronic properties of gCN, and results in the improvement of adsorption ability of gCN for lindane. Lindane adsorption on Ni-gCN is considered as chemisorption, which is primarily supported by the interaction of the nickel atom and chlorine atoms of HCH. The effect of solvents (water, ethanol, acetonitrile) was investigated via the analytical linearized Poisson-Boltzmann model. Due to the strong chemisorption, Ni-gCN can collect lindane from different solvents. The adsorption configurations of HCH on Ni-gCN were also shown to be thermally stable at 298 K, 323 K, 373 K, 473 K, and 573 K via molecular simulation calculations. The obtained results are useful for a better understanding of lindane adsorption on Ni-gCN and for the design of materials with high efficiency for lindane treatment based on adsorption-photocatalytic technology.

Fully automated graphitic carbon nitride-based disposable pipette extraction-gas chromatography-mass spectrometric analysis of six polychlorinated biphenyls in environmental waters

A fully automated online emulsification-enhanced disposable pipette extraction-gas chromatography-mass spectrometry (EE-DPX-GC-MS) method has been developed for the extraction of six polychlorinated biphenyls (PCBs) from environmental waters. An in-house prepared material, graphitic carbon nitride (g-C₃N₄), was used as sorbent in a home-packed DPX device. The six PCBs studied include PCB 10, 28, 52, 153, 138 and 180. g-C₃N₄ was characterized successfully by X-ray diffraction, elemental analysis, scanning electron microscopy, Fourier-transform infrared and Raman spectroscopy. As a C-N analogue of graphite, the two-dimensional structure of g-C₃N₄ allows rapid analyte adsorption and desorption to take place. With a significant number of nitrogen functionalities in g-C₃N₄, the material dispersed well in aqueous sample, increasing the active surface area of contact between the sorbent and the sample. When coupled with a pre-emulsification step, PCBs in each portion of sample could be efficiently extracted by g-C₃N₄ within 20 s of gentle turbulence. Under the most favorable conditions, the automated online EE-DPX-GC-MS method achieved wide dynamic working ranges with good linearity (r² ≥ 0.998) for all analytes. Limits of detection ranging between 4.35 and 7.82 ng L^-1 were attained, with enrichment factors of between 34 and 57 and relative standard deviations (RSDs) for intra- and inter-day precision of ≤ 8.95% and ≤ 12.6%, respectively. Absolute recoveries were between 69.3% and 109%. The fully automated online EE-DPX-GC-MS approach was applied to industrial wastewaters and reservoir waters where good relative recoveries of PCBs of between 89.3% and 105% were obtained, with RSDs ≤ 11.6%.

Insights into the structure-performance relationships of extraction materials in sample preparation for chromatography

Sample preparation is one of the most crucial steps in analytical processes. Commonly used methods, including solid-phase extraction, dispersive solid-phase extraction, dispersive magnetic solid-phase extraction, and solid-phase microextraction, greatly depend on the extraction materials. In recent decades, a vast number of materials have been studied and used in sample preparation for chromatography. Due to the unique structural properties, extraction materials significantly improve the performance of extraction devices. Endowing extraction materials with suitable structural properties can shorten the pretreatment process and improve the extraction efficiency and selectivity. To understand the structure-performance relationships of extraction materials, this review systematically summarizes the structural properties, including the pore size, pore shape, pore volume, accessibility of active sites, specific surface area, functional groups and physicochemical properties. The mechanisms by which the structural properties influence the extraction performance are also elucidated in detail. Finally, three principles for the design and synthesis of extraction materials are summarized. This review can provide systematic guidelines for synthesizing extraction materials and preparing extraction devices.

Emerging Chemical Functionalization of g-C3N4: Covalent/Noncovalent Modifications and Applications

Atomically 2D thin-layered structures, such as graphene nanosheets, graphitic carbon nitride nanosheets (g-C₃N₄), hexagonal boron nitride, and transition metal dichalcogenides are emerging as fascinating materials for a good array of domains owing to their rare physicochemical characteristics. In particular, graphitic carbon nitride has turned into a hot subject in the scientific community due to numerous qualities such as simple preparation, electrochemical properties, high adsorption capacity, good photochemical properties, thermal stability, and acid-alkali chemical resistance, etc. Basically, g-C₃N₄ is considered as a polymeric material consisting of N and C atoms forming a tri-s-triazine network connected by planar amino groups. In comparison with most C-based materials, g-C₃N₄ possesses electron-rich characteristics, basic moieties, and hydrogen-bonding groups owing to the presence of hydrogen and nitrogen atoms; therefore, it is taken into account as an interesting nominee to further complement carbon in applications of functional materials. Nevertheless, g-C₃N₄ has some intrinsic limitations and drawbacks mainly related to a relatively poor specific surface area, rapid charge recombination, a limited light absorption range, and a poor dispersibility in both aqueous and organic mediums. To overcome these shortcomings, numerous chemical modification approaches have been conducted with the aim of expanding the range of application of g-C₃N₄ and enhancing its properties. In the current review, the comprehensive survey is conducted on g-C₃N₄ chemical functionalization strategies including covalent and noncovalent approaches. Covalent approaches consist of establishing covalent linkage between the g-C₃N₄ structure and the chemical modifier such as oxidation/carboxylation, amidation, polymer grafting, etc., whereas the noncovalent approaches mainly consist of physical bonding and intermolecular interaction such as van der Waals interactions, electrostatic interactions, π-π interactions, and so on. Furthermore, the preparation, characterization, and diverse applications of functionalized g-C₃N₄ in various domains are described and recapped. We believe that this work will inspire scientists and readers to conduct research with the aim of exploring other functionalization strategies for this material in numerous applications.

The transport of graphitic carbon nitride in saturated porous media: Effect of hydrodynamic and solution chemistry

Understanding transport behavior of graphitic carbon nitride (g-C₃N₄) in porous media plays an important role in preventing its possible causing the underground environmental problems. The transport behavior of g-C₃N₄ in porous media were investigated by packed column experiments at different flow rates, ionic strengths (ISs), pHs and multivalent cations. The experimental results showed that the transport ability of g-C₃N₄ decreased with the IS increasing, and most of the g-C₃N₄ was retained in the sand column for the IS greater than 0.0001 M. The flow rate had little effect on the transport behavior of g-C₃N₄, and the recovery of g-C₃N₄ increased slightly with increasing flow rate. In addition, the migration ability of g-C₃N₄ under acidic conditions was drastically reduced compared with neutral alkaline conditions. Moreover, it was found that 1.51%, 30.33%, 34.91%, and 60.54% of g-C₃N₄ was retained in the column when g-C₃N₄ was leached through the quartz sand column at Al³⁺, Ca²⁺, Mg²⁺, and K⁺, which was consistent with the Schulze-Hardy rule. Finally, FTIR spectrum showed that the infrared absorption peak of the g-C₃N₄ mixed quartz sand were shifted to certain degrees under different conditions, which confirmed that hydrogen bond was formed in the transport of carbon nitride with the quartz sand surface. This study provides a new perspective on the role of hydrogen bond in the transport and fate of nanomaterials.

Structure and Mechanical Performance of Poly(vinyl Alcohol) Nanocomposite by Incorporating Graphitic Carbon Nitride Nanosheets

Owing to the high aspect ratio, the two-dimensional (2D) inorganic nanofillers have attracted extensive interest in the field of polymer reinforcement. In this work, graphitic carbon nitride (g-C₃N₄) nanosheets were obtained via thermal condensation of melamine and were then ultrasonically exfoliated in water, which was confirmed by atomic force microscopy (AFM) and TEM. Poly(vinyl alcohol) (PVA)/g-C₃N₄ nanocomposites were achieved by solution casting using water as the solvent. The structure and mechanical performance of PVA/g-C₃N₄ nanocomposites were studied. It was found that the g-C₃N₄ nanosheets were well dispersed in the PVA matrix. The introduction of g-C₃N₄ nanosheets increased the glass transition temperature and crystallinity of the nanocomposites, leading to the improved mechanical performance. Compared with the pure PVA, the PVA/g-C₃N₄ nanocomposite with 0.50 wt% g-C₃N₄ nanosheets showed ~70.7% enhancement in tensile strength, up from 51.2 MPa to 87.4 MPa.

Cu- and S- @SnO2 nanoparticles loaded on activated carbon for efficient ultrasound assisted dispersive µSPE-spectrophotometric detection of quercetin in Nasturtium officinale extract and fruit juice samples: CCD-RSM design

A simple, rapid, and efficient method of dispersive micro solid phase extraction (D-μ-SPE) combined with UV-Vis spectrophotometry via ultrasound-assisted (UA) was applied for the determination and preconcentration of quercetin in extract of watercress (Nasturtium officinale), fruit juice and water samples. The sorbent in this method was synthesized by doping copper and sulfide into the tetragonal structure of SnO₂-nanoparticles (Cu- and S- @SnO₂-NPs) and subsequently loading it on activated carbon (AC). The D-μ-SPE parameters with direct effect on the extraction efficiency of the targeted analyte, such as sample pH, volume of eluent, sorbent mass and ultrasound time were optimized using central composite design method. Under optimized conditions, the calibration graph for quercetin was linear in the range of 20-4000 ng mL^-1; the limit of detection and quantitation were 4.35 and 14.97 ng mL^-1, respectively and the enrichment factor was 95.24. Application of this method to analyze spiked extract, fruit juice and water samples resulted in acceptable recovery values ranging from 90.3% to 97.28% with intra-day and inter-day relative standard deviation values lower than 6.0% in all cases. Among the equilibrium isotherms tested, Langmuir was found to be the best fitted model with maximum sorption capacity of 39.37 mg g^-1, suggesting a homogeneous mode of sorption for quercetin.

One-step preparation of a novel SrCO3/g-C3N4 nano-composite and its application in selective adsorption of crystal violet

A novel kind of nanoparticle SrCO₃/g-C₃N₄ was prepared using strontium carbonate (SrCO₃) and melamine (C₃H₆N₆) as raw materials via one-step calcination. The formation of SrCO₃/g-C₃N₄ was confirmed from the X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Brunauer–Emmett–Teller (BET) and X-ray photoelectron spectroscopy (XPS) analysis. Its selective adsorption performance was evaluated towards crystal violet (CV), rhodamine B (RhB) and methylene blue (MB). The results showed that the SrCO₃/g-C₃N₄ had selective adsorption ability of CV. Furthermore, adsorption measurements of CV were conducted to investigate the influences of contact time, initial concentration, initial dye solution pH value and adsorbent dosage. The maximum removal rate of CV was 98.56% when the initial concentration was 1600 mg L⁻¹. The kinetic study indicated the adsorption of CV followed the pseudo-second-second model well. The adsorption efficiency of SrCO₃/g-C₃N₄ was greater (97.46%) than that of g-C₃N₄ (31.30%) and SrCO₃ (17.30%). It could be deduced that the synergistic effect of conjugation interaction of g-C₃N₄ and the electrostatic attraction of SrCO₃ might be the main driving force for the superb adsorption of CV.

A novel kind of nanoparticle SrCO₃/g-C₃N₄ was prepared using strontium carbonate (SrCO₃) and melamine as raw materials via one-step calcination.

An ultrasensitive photoelectrochemical bioanalysis strategy for tumor markers based on the significantly enhanced signal of a bismuth oxyiodine microsphere/graphitic carbon nitride composite

An ultrasensitive PEC bioanalysis strategy was designed based on the significantly enhanced signal of BiOI/g-C₃N₄ and amplified signal variation of CuS NPs.