Thermal Polycondensation Research Articles

Highly efficient isomerization of glucose to fructose over a novel aluminum doped graphitic carbon nitride bifunctional catalyst

Glucose isomerization to fructose is a crucial step for the efficient production of fuel and valuable chemicals from renewable carbohydrates. Aluminum (Al) was introduced into the structure of a graphitic carbon nitride (g-C3N4) by a simple thermal polycondensation of urea and aluminum chloride, and thereby, provided a series of Al-doped g-C3N4 (xAl-UCN) catalysts for the isomerization reaction. A high fructose yield of 48.29%, comparable to the quantitative yields (ca. 50%) by enzymatic routes, was achieved with the 0.5Al–UCN catalyst. Detailed characterizations of a series of Al–UCN catalysts, with different Al loadings, showed that 1) the Al loading amount has a profound effect on the physical-chemical properties of Al–UCN catalysts; 2) excess Al loading can inhibit the formation of a crystalline g-C3N4 structure; and 3) at lower Al loadings, the Al appears to be doped into the g-C3N4 framework possibly via coordination bonds. The mechanism for glucose isomerization to fructose may involve both Lewis acid and base catalyzed routes, with the coordinated Al species (Al[6]) providing Lewis acidity, and N-containing groups on g-C3N4 providing basicity. The additive effect of this dual-functionality is likely responsible for the high catalytic activity. The 0.5Al–UCN catalyst was readily recycled, demonstrating near-constant activity after 5 cycles of use. Altogether, glucose isomerization to fructose over the readily synthesized and recyclable Al–UCN catalyst could provide a highly-efficient and cost-effective step in lignocellulosic biomass valorization.

Investigating the role of ultrasound in improving the photocatalytic ability of CQD decorated boron-doped g-C3N4 for tetracycline degradation and first-principles study of nitrogen-vacancy formation

Graphitic carbon nitride (CN) is recognized as a promising photocatalyst for energy and environmental remediation. However, challenges persist due to limited CN surface-active sites and poor electronic properties. To overcome such challenges, we have synthesized Carbon Quantum Dots decorated Boron-doped Exfoliated CN (CQD@B-ECN) via ultrasound-assisted thermal polycondensation method. The substitutional boron doping favored nitrogen-vacancy as evident from experimental results and DFT calculations, which accelerated the charge separation/transfer and the CQD incorporation broadens the light-harvesting ability through photon upconversion. Moreover, the specific surface area of 2CQD-2B-ECN (685 m2/g) was significantly greater than CN providing enormous active sites. 2CQD-2B-ECN were evaluated using Tetracycline (TC) antibiotic, where photocatalysis and sonocatalysis showed 68% and 0.2% degradation in 120 min, respectively. Remarkably, sonophotocatalysis exhibited 84% TC degradation with a synergy index of 1.2 and complete degradation within 180 min. This work reveals an insight into CQD-B-ECN as a novel sonophotocatalyst for the degradation of diverse recalcitrant pollutants.

One-step supramolecular preorganization constructed crinkly graphitic carbon nitride nanosheets with enhanced photocatalytic activity

• Crinkly graphitic carbon nitride nanosheets are prepared by a one-step polycondensation process using urea and melamine as the precursors. • The conversion of urea to cyanuric acid during polycondensation enables the formation of melamine-cyanuric acid. • The obtained crinkly graphitic carbon nitride nanosheets exhibit much better optoelectronic properties compared to its bulk counterpart. • The photocatalytic hydrogen production rate of crinkly graphitic carbon nitride nanosheets is increased by 7 times. Here we report a new one-step thermal polycondensation process to form crinkly graphitic carbon nitride nanosheets (CGCNNs) via supramolecular preorganization, using a mixture of urea and melamine as the starting material. Systematical studies reveal that the newly developed CGCNNs significantly strengthen the optical absorption, widen the bandgap, and increase the Hall mobility and carrier density compared to that of its bulk counterpart, regardless of the similar chemical composition and structure. As a result, the photocatalytic hydrogen production rate is improved by 7 times. Moreover, Na doping of CGCNNs can further promote its photocatalytic activity, leading to an excellent photocatalytic hydrogen production rate of 250.9 µmol h –1 , which is approximately 10.5 times higher than its bulk counterpart. Moreover, an impressive apparent quantum efficiency of 19.12% is achieved at 420 nm. This study provides a facile strategy for the design of efficient low-cost carbon-nitride-based photocatalysts for solar fuel production.

Samarium vanadate affixed sulfur self doped g-C3N4 heterojunction; photocatalytic, photoelectrocatalytic hydrogen evolution and dye degradation

The Thermal polycondensation method was used to make sulfur self-doped graphitic-carbon nitride (SCN) sheets that were anchored with samarium vanadate (SmV). The decorating of SmV nanoparticles on sheets of SCN is confirmed by X-ray diffraction, spectroscopic, and microscopic characterizations. When compared to the bandgap of pure SmV (2.16 eV) and SCN (2.44 eV), SmV decorating decreased the bandgap of SCN to 1.89 eV. The lowered bandgap in SmV/SCN and the formation of type II heterostructure resulted in improved performance in photoelectrochemical and photochemical hydrogen evolution and photocatalytic degradation experiments. The amount of hydrogen evolution was high in SmV/SCN which was found to be 22,618 μmol g −1 of H 2 in 4 h under photochemical conditions. The obtained onset potential at 10 mA cm 2 is −190 mV under photoelectrochemical studies. The SmV/SCN was able to absorb visible light and degraded Methyl orange (MO). The reaction conditions were thoroughly optimized, found pH 8, 10 mg L −1 initial concentration of dye and 25 mg of SmV/SCN as an optimum condition under visible light. The degradation efficiency was up to 90% in just 80 min. Scavenger investigations were used to identify the active species (OH . and . O 2 − ) and indicate which were then confirmed by electron spin resonance spectroscopic (ESR) experiments. The mechanism of photocatalysis has been well explored. The obtained results show that the SmV/SCN nanocomposite is capable of serving a choice of material for energy and environmental applications. • SmVO 4 decorated on S doped g-C 3 N 4 sheets. • Decrease in the bandgap of g-C 3 N 4 upon decoration of SmVO 4 (1.89 eV). • Enhanced H 2 evolution both in photoelectrochemical and photochemical. • Visible light driven degradation of Methyl orange (90%). • Detailed mechanism of photocatalysis based on heterostructure of Type-II.

Improvement in Structure and Visible Light Catalytic Performance of g-C3N4 Fabricated at a Higher Temperature

A highly-efficient graphitic carbon nitride (g-C3N4) photocatalyst for visible light photodegradation of rhodamine B (RhB) and methyl orange (MO) simulating dyeing wastewater was synthesized by the thermal polycondensation of melamine. The photocatalysts were characterized by TG-DTG-DSC, XRD, EA, XPS, FT-IR, SEM, TEM, BET, PL and UV-vis DRS. The results showed that the photocatalytic performance of g-C3N4 at a higher calcination temperature was significantly enhanced, and its photocatalytic activities for the photodegradation of RhB and MO were remarkably improved by 64.91% and 41.83%, respectively, which was mainly attributed to the satisfactory crystallinity, stable graphene-like structure, large surface area, and excellent optical properties. It was found that •O2− radicals and •OH radicals were the main active species for the photodegradation process by the free radicals trapping experiments and ESR analysis. The photodegradation mechanism of g-C3N4 was proposed predicated using the characterization results.

Nitrogen-defect induced trap states steering electron-hole migration in graphite carbon nitride

Defect structures of semiconductors intrinsically regulate the trap states, excitons and active charge carriers for artificial photosynthesis systems. A g-C3N4 system with abundant nitrogen defects was prepared through a thermal polycondensation strategy to reveal the role of trap states and exhibited a 20-fold enhanced H2 evolution efficiency relative to bulk g-C3N4 under visible light irradiation. Subsequent femtosecond transient absorption spectroscopy study found that the N-defect induced shallow trap states can capture photogenerated electrons to inhibit deep trapping and direct recombination of photogenerated charges. The active electrons in shallow trap states can enhance the photocatalytic H2 evolution when compared with the inactive electrons in deep trap states. Mid-infrared transient absorption spectroscopy also confirmed the increased quantity of shallow-trapped electrons without interference of other signals. This work provides new insights for steering depth of trap states and photocatalytic processes through N defects to achieve high photocatalytic performance using femtosecond transient absorption spectroscopy.

Precursor-modified strategy to synthesize thin porous amino-rich graphitic carbon nitride with enhanced photocatalytic degradation of RhB and hydrogen evolution performances

The photocatalytic activity of carbon nitride (CN) materials is mainly limited to small specific surface areas, limited solar absorption, and low separation and mobility of photoinduced carriers. In this study, we developed a precursor-modified strategy for the synthesis of graphitic CN with highly efficient photocatalytic performance. The precursor dicyandiamide reformed by different acids undergoes a basic structural change and transforms into diverse new precursors. The thin porous amino-rich HNO3-CN (5H-CN) was calcined by dicyandiamidine nitrate, formed by concentrated nitric acid modified dicyandiamide, and presented the best photocatalytic degradation rate of RhB, more than 34 times that of bulk graphitic CN. Moreover, the photocatalytic hydrogen evolution rate of 5H-CN significantly improved. The TG-DSC-FTIR analyses indicated that the distinguishing thermal polymerization process of 5H-CN led to its thin porous amino-rich structure, and the theoretical calculations revealed that the negative conduction band potential of 5H-CN was attributed to its amino-rich structure. It is anticipated that the thin porous structure and the negative conduction band position of 5H-CN play important roles in the improvement of the photocatalytic performance. This study demonstrates that precursor modification is a promising project to induce a new thermal polycondensation process for the synthesis of CN with enhanced photocatalytic performance.

Hematite decorated functional porous graphitic carbon nitride binary nanohybrid: Mechanistic insight into the formation and arsenic adsorption study

Here, hydroxyl functionalized porous graphitic carbon nitride (gCN) decorated with hematite (α-Fe2O3) nanoparticles (NPs) (P-gCN-OH/α-Fe2O3) were synthesized by an eco-friendly hydrothermal and thermal polycondensation process. The physicochemical investigation and mechanistic approach signified that glucose is responsible for porosity formation and potassium (K) ions from KCl are responsible for breaking the periodic chemical structure of gCN; while a trace amount of H2O in melamine helps in introducing hydroxyl groups in the P-gCN matrix. Apart from this, α-Fe2O3 NPs were also successfully introduced into the P-gCN-OH. The synthesized P-gCN-OH/α-Fe2O3 binary nanohybrid shows enhanced adsorption performance towards both arsenite (As(III)) and arsenate (As(V)) ions due to their greater specific surface area (242.5 m2/g). About > 96% and > 98% of As(III) and As(V) were adsorbed with an adsorption capacity of 22.22 mg/g and 27.80 mg/g respectively. The proposed adsorption mechanism was supported by the combined results of Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). It is demonstrated that arsenic (As) adsorption onto the P-gCN-OH/α-Fe2O3 surface was due to electrostatic attraction, simultaneous As(III) oxidation & adsorption, and monodentate & bidentate complex formation.

Synthesis and Characterization of Needle Coke Produced from Thermal Modified Ethylene Residue Pitch

ABSTRACT Ethylene residue pitch (ETP) is the by-product in the process of producing ethylene from the pyrolysis of crude oil. ETP is a kind of complex organic matrix with a lower aromaticity, a larger number of aliphatic chain hydrocarbons, and a higher content of carbon. To study the effects of thermal polycondensation on the quality of derived needle coke, 5 types of thermally modified ETPs have been used as the feedstock for needle coke production. Thermal modification is a favorable method to adjust the molecular structure parameters of ETP (especially on Iar and CH3/CH2). Iar is also a key parameter to determine the quality of ETP-based needle coke. Thermal modification treatment of ETP followed by liquid-phase carbonization is a feasible strategy to obtain high-quality ETP-based needle coke with the content of tended regular carbon microcrystals higher than 74%, the specific area (SBET) lower than 6 m2·g−1, the microstrength higher than 61%, and the resistance lower than 5.747 Ω. Therefore, moderate thermal modification of ETP significantly enhances the properties of the derived needle coke.

Development of graphitic carbon nitride supported novel nanocomposites for green and efficient oxidative desulfurization of fuel oil

The catalysts utilized for oxidative desulfurization have acquired significant attention and ability to improve the quality of the fuel oil by removing sulfur. In this work, the catalysts used for oxidative desulfurization include CoWO4 and Bi2WO6 with graphitic carbon nitride (g-C3N4) as support were synthesized by the one-pot hydrothermal method. Graphitic carbon nitride was obtained by thermal polycondensation of melamine at 550°C for 5 h. These catalysts were homogeneously dispersed on the surface of the support and their structure, morphology, and properties were determined by different characterization techniques (Powder X-Ray Diffractometer, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy and Energy Dispersive X-Ray Spectroscopy, Specific Surface Area (Brunauer, Emmett and Teller (SBET)). The parameters that affect the efficiency of the desulfurization process such as catalyst amount, amount of oxidizing agent, and reaction temperature have been optimized thoroughly. The oxidative desulfurization reaction was studied in terms of kinetics which shows that reaction is pseudo first order. The thermodynamic studies revealed that the reaction is endothermic and spontaneous in nature. The results determined that the catalytic efficiency for the removal of sulfur (as dibenzothiophene) is more than 90% in the presence of support (g-C3N4) to obtain sulfur free fuel.

Biomass porous carbon as the active site to enhance photodegradation of oxytetracycline on mesoporous g-C3N4.

Graphitic carbon nitride (g-C3N4) is widely used in photocatalytic adsorption and degradation of pollutants, but there are still some problems such as low adsorption performance and high electron–hole recombination efficiency. Herein, we propose a new molten salt assisted thermal polycondensation strategy to synthesize biomass porous carbon (BPC) loaded on g-C3N4 composites (designated as BPC/g-C3N4) with a hollow tubular structure, which had a high surface area and low electron–hole recombination rate. The study shows that the morphology of g-C3N4 changes dramatically from massive to hollow tubular by molten salt assisted thermal polycondensation, which provides a base for the loading of BPC, to construct a highly effective composite photocatalyst. BPC loaded on g-C3N4 could be used as the active site to enhance Oxytetracycline (OTC) removal efficiency by adsorption and with higher electron–hole separation efficiency. As a result, the BPC(5%)/g-C3N4 sample presented the highest photocatalytic degradation efficiency (84%) for OTC degradation under visible light irradiation. The adsorption capacity and photocatalytic reaction rate were 3.67 and 5.63 times higher than that of the g-C3N4, respectively. This work provided a new insight for the design of novel composite photocatalysts with high adsorption and photocatalytic performance for the removal of antibiotic pollutants from wastewater.

In-situ construction of g-C3N4/carbon heterostructure on graphene nanosheet: An efficient polysulfide barrier for advanced lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) have been considered as the future potential energy storage system with advantages of high energy density (2600 Wh kg−1), eco-friendliness and low cost. However, the poor conductivity and serious shuttle effects of polysulfides block their application. Herein, g-C3N4/carbon heterostructure on graphene nanosheet (PCNG) is constructed via phenyl-modified strategy and in-situ thermal polycondensation, which has a unique electron cloud distribution with excellent sulfur immobilization ability as well as good electroconductivity. As a result, Li-S cells with simple S/C cathodes and PCNG interlayers show a high initial capacity of 1192 mAh g−1 at 0.1C, and an ultra-long lifespan with a slow capacity attenuation of 0.050% per cycle after 800 cycles. The cell with PCNG/PP separator also has a stable cycle performance at high area sulfur loading of 7 mg cm−2. These findings provide a new sight on functionalizing g-C3N4 for application in Li-S electrochemistry.

Dual plasmonic Au and TiN cocatalysts to boost photocatalytic hydrogen evolution

Employing a suitable cocatalyst is very important to improve photocatalytic H2 evolution activity. Herein, two plasmonic cocatalysts, Au nanoparticles and TiN nanoparticles were in-situ coupled over the g-C3N4 nanotube to form a ternary 0D/0D/1D Au/TiN/g-C3N4 composite via a successive thermal polycondensation and chemical reduction method. The g-C3N4 nanotube acted as a support for the growth of Au and TiN nanoparticles, leading to intimate contact between g-C3N4 nanotube with Au nanoparticles and TiN nanoparticles. As a result, multiple interfaces and dual-junctions of Au/g-C3N4 Schottky-junction and TiN/g-C3N4 ohmic-junction were constructed, which helped to promote the charged carriers’ separation and enhanced the photocatalytic performance. Furthermore, loading plasmonic cocatalysts of Au nanoparticles and TiN nanoparticles can enhance the light absorption capacity. Consequently, the Au/TiN/g-C3N4 composite exhibited significantly enhanced photocatalytic H2 evolution activity (596 μmol g−1 h−1) compared to g-C3N4 or binary composites of Au/g-C3N4 and TiN/g-C3N4. This work highlights the significant role of cocatalysts in photocatalysis.

An efficient and unique route for the fabrication of highly condensed oxygen-doped carbon nitride for the photodegradation of synchronous pollutants and H2O2 production under ambient conditions

N2-assisted thermal polycondensation of a novel supramolecular self-assembly based on melamine, cyanuric acid, and thiourea produced S-doped carbon nitride. Molecular dynamics simulation estimated nonbonding energies between the melamine-cyanuric acid adduct and thiourea. The C–S functional group was efficiently converted to C–O by facile calcination in a static air atmosphere, which gave a highly condensed O-doped carbon nitride nanosheet (O-CN). Density functional theory (DFT) calculations and experimental results confirmed that the oxygen-doped site is more stable and provides midgap states near the conduction band position of CN compared with sulfur doping. O-CN exhibited excellent visible light harvesting and photocatalytic activities toward removal of tetracycline and rhodamine B in an initial 15 min while producing a highly stable amount of H2O2 under an open atmosphere without a sacrificial agent. These outstanding performances result from synergistic approaches that lead to the modified polycondensation process, unprecedented reduction ability, and enhanced optical properties.

Facile preparation of a novel modified biochar-based supramolecular self-assembled g-C3N4 for enhanced visible light photocatalytic degradation of phenanthrene

The rational design of a novel and environmentally friendly photocatalytic composite for persistent pollutant removal, energy production and catalytic applications have attracted widespread interest. In this study, the new composite composed of KOH-modified biochar and g-C3N4 with different morphologies was successfully prepared with facile supramolecular self-assembly and thermal poly-condensation method. The characterization results of the as-prepared composites suggested that KOH-modified biochar had been well combined with g-C3N4 with different morphologies. These synthesized catalysts were used to degrade phenanthrene under visible light radiation. A-BC/g–C3N4–D performed best and removed 76.72% phenanthrene. Its first-order reaction rate constant was 0.355 h−1, which was 3.7 times higher than that of g-C3N4. A-BC/g–C3N4–D still exhibited a high photocatalytic activity after four cycles. Radical quenching results showed that superoxide radical (·O2−), hydroxyl radical (·OH) and hole (h+) could be used as active species in the redox reaction with phenanthrene. Based on the exploration results of gas chromatography-mass spectrometer (GC-MS), a possible reaction pathway of phenanthrene degradation was also proposed. This study provides a novel strategy for fabricating various high-performance photocatalysts and the removal of persistent organic pollutants.

Construction of S-scheme 1D/2D rod-like g-C3N4/V2O5 heterostructure with enhanced sonophotocatalytic degradation for Tetracycline antibiotics

Pharmaceutically active compounds are an emerging water contaminant that resists conventional wastewater treatments. Herein, the sonophotocatalytic degradation of Tetracycline (TC) antibiotics as a model contaminant was carried out over a rod-like g-C3N4/V2O5 (RCN-VO) nanocomposite. RCN-VO nanocomposite was synthesized via ultrasound-assisted thermal polycondensation method. The results showed that the RCN-VO nanocomposite could completely remove the TC in water within 60 min under simultaneous irradiation of visible light and ultrasound. Moreover, the sonophotocatalytic TC degradation (a synergy index of ∼1.5) was superior to the sum of individual sonocatalytic and photocatalytic degradation using RCN-VO nanocomposite. Besides, the enhanced sonophotocatalytic activity of RCN-VO can be attributed to the 1D/2D nanostructure and the S-scheme heterojunction formation between RCN and VO where the electrons migrated from RCN to VO across the RCN-VO interface. Under irradiation, the built-in electric field, band edge bending and Coulomb interaction can synergistically facilitate the unavailing electron-hole pair recombination. Thereby, the cumulative electron in RCN and holes in VO can actively take part in the redox reaction which generates free radicals and attack the TC molecules. This study provides insight into a novel S-Scheme heterojunction photocatalyst for the removal of various refractory contaminants via sonophotocatalytic degradation.

Complete removal of Tetracycline by sonophotocatalysis using ultrasound-assisted hierarchical graphitic carbon nitride nanorods with carbon vacancies

Tuning a graphitic carbon nitride (CN) structure is an effective strategy to advance its physicochemical and electronic properties. Herein, hierarchical CN nanorods with carbon vacancy were synthesized via ultrasound-assisted thermal polycondensation method wherein melamine-HONH2·HCl complex acts as a template. The hierarchical CN nanorods can facilitate multiple light scattering, provide large specific surface area with extensive reactive sites and endow abundant mass-transport channels for charge migration. The existence of carbon vacancies can serve as shallow charge trapping sites and prompt charge separation. Consequently, hierarchical CN nanorod possessed excellent sonophotodegradation efficiency of ∼100% towards Tetracycline (TC) antibiotic within 60 min under ultrasonic irradiation and visible light illumination. Moreover, the sonophotocatalytic degradation was higher than the sum of sonocatalytic and photocatalytic TC degradation using hierarchical CN nanorods due to its synergistic performance. A plausible sonophotocatalytic mechanism and TC degradation pathway using hierarchical CN nanorod were proposed. Lastly, hierarchical CN nanorod is durable and stable which can withstand the sonophotocatalytic condition even after the fifth run. This work offers an insight into hierarchical CN nanorod to advance sonophotocatalytic degradation performance for highly efficient removal of various recalcitrant pollutants.

Impact of graphitic carbon nitrides synthesized from different precursors on Schottky junction characteristics.

Graphitic carbon nitride (g-CN) has gained wide interest in many areas, such as energy and the environmental remediation as a layered polymeric semiconductor that allows the formation of catalytically active Schottky junctions due to its proper electronic band structure. Interestingly, although it is known that the precursors used in the synthesis, can influence the properties of the g-CN, no detailed study on these effects on Schottky junctions could be found in the literature. In this research, the effects of g-CNs synthesized by thermal polycondensation of different precursors on the photocatalytic efficiency of Schottky junctions were investigated. For this purpose, urea, thiourea, melamine, and guanidine hydrochloride were used as different precursors, while the photocatalytic dehydrogenation of formic acid was used as a test reaction. The Schottky junctions were formed by decorating the as-prepared g-CNs with AgPd alloy nanoparticles (NP), which were synthesized by reduction of Ag and Pd salts with NaBH4. The structural, electronic and charge carrier dynamics of all prepared structures have been fully characterized by TEM, XRD, BET, XPS, UV-Vis DRS, PL, and PL life measurements. The results showed that the charge transfer dynamics of g-CNs surface defects are more effective in the photocatalytic performance of Schottky junctions than in structural features such as the size of the metal NPs or the surface area of the catalysts.

Preparation and properties of colorless and transparent semi‐alicyclic polyimide films with enhanced high‐temperature dimensional stability via incorporation of alkyl‐substituted benzanilide units

AbstractTwo colorless and transparent polyimide (CPI) films with enhanced high‐temperature dimensional stability and solution‐processability were prepared from the methyl‐substituted benzanilide containing organo‐soluble polyimide (PI) resins. For this target, a new aromatic diamine, 2,3′‐dimethyl‐4,4′‐diaminobenzanilide (MMDABA) was synthesized. The methyl substituents were expected to endow the derived PI resins good solubility and rigid‐rod benzanilide units can efficiently reduce the coefficients of thermal expansion (CTE) of the derived CPI films. CPI‐a and CPI‐b were prepared by the one‐step thermal polycondensation from MMDABA with hydrogenated pyromellitic dianhydride for CPI‐a and hydrogenated 3,3′,4,4′‐biphenyltetracarboxylic dianhydride for CPI‐b, respectively. The derived PI resins were soluble in polar aprotic solvents. Colorless and transparent CPI‐a and CPI‐b films were prepared from the PI solutions and the subsequent 280°C curing. The CPI films showed good transparency in visible light and transmittances higher than 80% at 450 nm and yellowness index (b*) below 2.0. More importantly, the derived CPI‐a film showed the glass transition temperature (Tg) of 417.5°C and the CTE value of 46.9 × 10−6/K in the range of 50–250°C. Apparently, incorporation of alkyl‐substituted benzanilide units achieved good balance among solution‐processability, high‐temperature dimensional stability, and optical properties.

Photo-assisted simultaneous electrochemical detection of multiple heavy metal ions with a metal-free carbon black anchored graphitic carbon nitride sensor

The simultaneous detection of multiple heavy metal ions in solution is an important yet highly challenging problem. In this work, a metal-free g-C3N4/carbon black (CB) composite electrode was synthesized by a one-step thermal polycondensation method and characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and ultraviolet visible light spectroscopy. In addition, the photoelectrochemical response of the g-C3N4/CB nanocomposite to Cd2+, Pb2+ and Hg2+ both separately and as a mixture of the three analytes was investigated by differential pulse anodic stripping voltammetry. The g-C3N4/CB electrode demonstrated an excellent sensing performance to Cd2+, Pb2+ and Hg2+ in the range of 0–700 nM, 0–300 nM and 0–500 nM, respectively, with limits of detection (LOD) of Cd2+, Pb2+, and Hg2+ of 2.1, 0.26 and 0.22 nM, respectively. The LOD of the combined solution of the three analytes was slightly higher at 3.3 nM. Additionally, the metal-free g-C3N4/CB photoelectrochemical sensor exhibited excellent electrochemical stability and electrode reproducibility. Finally, g-C3N4/CB sensor also showed satisfactory results in the detection of trace analyte ions in real environmental systems. This work provides a novel and promising approach in the simultaneous detection of multiple heavy metal ions in solution for practical applications.