g-C3N4 Quantum Dots Research Articles

Amorphous CoFePOx hollow nanocubes decorated with g-C3N4 quantum dots to achieve efficient electrocatalytic performance in the oxygen evolution reaction.

Simultaneously enriching active sites and enhancing intrinsic activity in a simple way is of great importance for the design of highly active electrocatalysts for the oxygen evolution reaction (OER), but it still faces challenges. Herein, g-C3N4 quantum dot decorated amorphous hollow CoFe bimetallic phosphate nanocubes (a-CoFePOx@CNQD) are prepared as an efficient OER electrocatalyst by a simple in situ etching-phosphating process. Research shows that their unique hollow architecture and amorphous structure can help provide generous exposed active sites for OER, and the incorporation of g-C3N4 quantum dots can effectively adjust the electronic structure to improve the intrinsic activity. Therefore, a-CoFePOx@CNQD exhibits excellent OER performance with a low overpotential (239 mV) at 10 mA cm-2 and a small Tafel slope (58.4 mV dec-1), surpassing the commercial RuO2. Furthermore, a-CoFePOx@CNQD as an electrode catalyst for a water electrolyzer and zinc-air battery also shows higher performance and stability than RuO2 + Pt/C catalysts. This study provides a feasible strategy for preparing efficient and stable amorphous hollow heterostructure OER electrocatalysts.

A novel TFNi pervaporation membrane with g-C3N4 quantum dots for high-efficiency IPA dehydration

Pervaporation (PV) shows significant potential for the highly selective isopropanol (IPA). The pursuit of developing PV membranes with outstanding separation effect and enduring high purity permeation is an indispensable goal. Based on polyamide (PA) separation layers, a polydopamine (PDA) mixed g-C3N4 quantum dots (gCNQDs) coating as the interlayer was deposited onto a porous ceramic hollow fiber substrate to fabricate thin-film nanocomposite membranes with an interlayer (TFNi). The nanocomposite interlayer enabled the formation of a smoother and highly separated selective polyamide layer. The separation factor exhibited a 31-fold enhancement with the augmentation of the blending fraction of gCNQDs during the PDA coating process. The resulting TFNi membrane attained an exceedingly high separation factor of 10270 ± 90 with a permeate water concentration of 99.9% and demonstrated a satisfactory flux of 1.40 ± 0.08 kg⋅m-2⋅h-1 during the PV process of 90 wt% IPA dehydration at 60 °C. This study presents a fresh perspective on the implementation of nanocomposite interlayers, which is expected to expand the application of high-performance TFNi membranes in PV dehydration processes.

Electroluminescent white quantum dot light-emitting diodes based on high pressure synthesis of graphitic C3N4 semiconductor

Graphitic carbon nitride (g-C3N4) has shown promising potentials for quantum dot light-emitting diodes (QLEDs), which might be an effective alternative of the mostly used Cd(Se,S)/Zn(S,Se) emitting layers and can achieve both low toxicity and high stability, meeting the goal of sustainable development. Herein, we for the first report a white electroluminescent QLED device with blue and orange dual-color emissions, which were attributed to the σ*-LP, π*- π, and π*-LP transitions, respectively, from a single-compound g-C3N4 quantum dots (QDs) by synthesizing the precursor at 0.8 Mpa high-pressure N2. By selectively exciting the δ and π bonds with X-ray, the luminescence mechanism was approved with the synchrotron radiation techniques of X-ray absorption near edge structure (XANES) and the X-ray excited optical luminescence (XEOL).The chromaticity coordinate changes from cayan color space with CIE (0.2034, 0.1939) to white color space with CIE (0.3009, 0.2697) as pressure increases from 0.06 to 0.8 Mpa, with the increased overlap of the δ* and π* orbital upon the contraction of crystal lattice. The breakthrough achieved in this work will promisingly promote the development of future white light sources as thin as paper for human home and office lighting by using direct current-driven electroluminescence of QDs, instead of photoluminescence of phosphors.

Development of graphitic carbon nitride quantum dots-based oxygen self-sufficient platforms for enhanced corneal crosslinking

Keratoconus, a disorder characterized by corneal thinning and weakening, results in vision loss. Corneal crosslinking (CXL) can halt the progression of keratoconus. The development of accelerated corneal crosslinking (A-CXL) protocols to shorten the treatment time has been hampered by the rapid depletion of stromal oxygen when higher UVA intensities are used, resulting in a reduced cross-linking effect. It is therefore imperative to develop better methods to increase the oxygen concentration within the corneal stroma during the A-CXL process. Photocatalytic oxygen-generating nanomaterials are promising candidates to solve the hypoxia problem during A-CXL. Biocompatible graphitic carbon nitride (g-C3N4) quantum dots (QDs)-based oxygen self-sufficient platforms including g-C3N4 QDs and riboflavin/g-C3N4 QDs composites (RF@g-C3N4 QDs) have been developed in this study. Both display excellent photocatalytic oxygen generation ability, high reactive oxygen species (ROS) yield, and excellent biosafety. More importantly, the A-CXL effect of the g-C3N4 QDs or RF@g-C3N4 QDs composite on male New Zealand white rabbits is better than that of the riboflavin 5’-phosphate sodium (RF) A-CXL protocol under the same conditions, indicating excellent strengthening of the cornea after A-CXL treatments. These lead us to suggest the potential application of g-C3N4 QDs in A-CXL for corneal ectasias and other corneal diseases.

When 2D g-C3N4 meets 0D CNQDs and 1D CNTs: A strategy for photocatalytic hydrogen production over a ternary non-metallic catalyst

Utilizing solar energy to facilitate photocatalytic hydrogen production holds great promise in addressing the energy crisis. One material that shows tremendous potential in this field is two-dimensional graphitic carbon nitride (2D g-C3N4). However, the fast recombination rate of photogenerated carriers and the limited specific surface area impede its photocatalytic activity. This research endeavors to address these limitations by developing a ternary composite photocatalyst, CNQDs/g-C3N4/CNTs, by employing the microwave hydrothermal method. g-C3N4 was co-modified with zero-dimensional g-C3N4 quantum dots (0D CNQDs) and one-dimensional carbon nanotubes (1D CNTs). Incorporating CNQDs and the g-C3N4 interface facilitates the separation of photogenerated carriers, while the tubular channel of CNTs provides favorable conditions for transferring photogenerated electrons. Additionally, the introduction of CNQDs and CNTs significantly increases the specific surface area of the sample, thereby enhancing the number of reaction active sites available for the photocatalytic production of hydrogen. The hydrogen generation rate of the CNQDs/g-C3N4/CNTs is 1109.388 μmol⋅g−1⋅h−1, surpassing that of the single g-C3N4 specimen by 3.62 times. The application of density functional theory (DFT) calculations reinforces the enhanced performance of the composite through the synergistic effect of CNQDs and CNTs. This effect optimizes the adsorption behavior of the active intermediate (H*) and reduces the Gibbs free energy ΔG(H*) associated with the photocatalytic hydrogen evolution reaction.

Expression of Concern: “Synergistic visible light assisted photocatalytic degradation of p-chlorophenol and rifampicin from aqueous solution using a novel g-C3N4 quantum dots incorporated α-MoO3 nanohybrid – Mechanism, Pathway and toxicity studies” (Chemosphere, Volume 339, October 2023, 139529)

Expression of Concern: “Synergistic visible light assisted photocatalytic degradation of p-chlorophenol and rifampicin from aqueous solution using a novel g-C3N4 quantum dots incorporated α-MoO3 nanohybrid – Mechanism, Pathway and toxicity studies” (Chemosphere, Volume 339, October 2023, 139529)

G-C3N4 quantum dots decorated on urchin-like TiO2 nanostructures for the photoelectrochemical water splitting

g-C3N4 quantum dots decorated on urchin-like TiO2 nanostructures for the photoelectrochemical water splitting

Enhancing photoelectrochemical surface reactivity through interface grafting of g-C3N4 quantum dots with BiVO4

Due to the high photosensitivity, quantum dots (QDs) offer promise in establishing heterojunctions to improve the photoelectrochemical (PEC) water oxidation process and enhance the solar-to-hydrogen conversion efficiency. However, apart from their catalytic capacity, additional protection strategies should be considered to eliminate the destruction of QDs from electrolytes and photo-corrosion. Here, we present a facile strategy to fabricate heterojunction by employing graphitic carbon nitride QDs (g-C3N4 QDs) coupled with BiVO4, referred to CNQDs/BiVO4. With the help of CNQDs, a gradient energy band alignment has been established in CNQDs/BiVO4, leading to facilitated hole migration driven by an upward force. The optimal CNQDs/BiVO4 sample shows significantly enhanced PEC performance for water oxidation, with a photocurrent of 2.2 mA/cm2 at 1.23 V vs. RHE (reversible hydrogen electrode), which is about 2.26 times better than that of BiVO4 (0.97 mA/cm2). The enhanced PEC performance could be attributed to the increased surface-active area and facilitated surface oxidation kinetics.

Vesicular BiVO4 nanostructures modified by g-C3N4 quantum dots for enhanced photocatalytic activity

Photocatalysis technology has been an available method to alleviate the improper discharge of dye wastewater by employing light energy to degrade the dye pollutants. Here, the vesicular BiVO4 hollow structures were modified by graphite phase carbon nitride quantum dots (CNQDs) to construct the BiVO4-based photocatalyst (BiVO4/CNQDs) for the enhanced removal of dye molecules. The CNQDs with a diameter of 2–5 nm evenly decorate on BiVO4 vesicles to construct the close interface of the BiVO4/CNQDs heterojunctions. Compared with vesicular BiVO4, the enhanced visible-light decomposition of methyl orange (MO) comes down to the coordination of different components, the C and/or N doping and hollow structure. This is helpful to increase surface area of bulk BiVO4, broaden light response, narrow band gap and obstruct charge combination. Especially, the up-conversion luminescence of the CNQDs can induce BiVO4 to generate more photo-excited electrons to participate in the MO photo-degradation reaction. The BiVO4/CNQDs heterojunctions with the unique hollow structure and excellent photocatalytic activity display the promising utilization in wastewater treatment.

One stone two bird: Reduced oxide graphene supported g-C3N4 quantum dots implements efficient capturing/catalytic polysulfides conversion and high sulfur loading for lithium-sulfur battery

One stone two bird: Reduced oxide graphene supported g-C3N4 quantum dots implements efficient capturing/catalytic polysulfides conversion and high sulfur loading for lithium-sulfur battery

The effect of dopant P[dbnd]O functional group and OH, O, H2O adsorption on the structural, electronic, and optical properties of triangular g-C3N4 quantum dots by first-principles study

The effect of dopant PO functional group and OH, O, H2O adsorption on the structural, electronic, and optical properties of triangular g-C3N4 QDs has been studied by first-principle calculations. Negative formation energies indicate that the formation processes of these systems are exothermic. PO doping can enhance the stability of C3N4–H QD and weaken the stability of C3N4–F QD. O–C3N4–H QD presents a chemisorption process, whereas the adsorption of OH group or H2O molecule on the C3N4–H QD is proposed to be a physisorption process. The substitutional PO group significantly deforms the geometric structure of the tri-s-triazine unit and induces charge redistribution in the PO-C3N4–H and PO-C3N4–F QDs. For C3N4–H QD, PO-C3N4–H QD, C3N4–F QD, and PO-C3N4–F QD, the calculated HOMO-LUMO gaps are 3.248, 1.583, 2.821 and 1.478 eV, respectively. The charge transfer between the O radical and the C3N4–H QD is +0.522 e, indicating a strong chemical bonding interaction. The tiny charge transfers of +0.107 e and +0.003 e indicate weak interaction between OH or H2O and C3N4–H QD. The study will provide an effective theoretical foundation for the development of new g-C3N4 QDs sensors or catalysis systems.

Synergistic visible light assisted photocatalytic degradation of p-chlorophenol and rifampicin from aqueous solution using a novel g-C3N4 quantum dots incorporated α-MoO3 nanohybrid – Mechanism, pathway and toxicity studies

In this work, a simple g-C3N4 quantum dots enriched MoO3 nanohybrid was formulated for the synergistic photocatalytic degradation of an industrially active organic pollutant, p-chlorophenol (PCP) and a widely prescribed antibiotic, rifampicin (RIF). The nanohybrid was synthesised via a facile ultrasonic assisted hydrothermal method and characterized using various characterization analysis. The efficient Z-scheme charge transfer of the nanohybrid resulted in the elimination of 98% PCP and 89% RIF under visible light with a rate constant of 0.012 and 0.006 min−1 respectively. The photocatalysis was attributed to the formation of both hydroxyl (OH•) and superoxide (O2•-) radicals in the resulting nanohybrid. The intermediates formed in the course of reaction were estimated through gas chromatography-mass spectroscopy/mass spectroscopy (GC-MS/MS) analysis and a suitable degradation pathway was constructed. The structural stability and reusability of the nanohybrid was affirmed through X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis to outweigh the industrial potential of the catalyst, with 85% PCP and 80% RIF removal efficiency after six cycles of degradation. In addition, the mineralization of the pollutants was confirmed by total organic carbon analysis. Further, the toxicity of the drug and the formed intermediates was determined using ecological structure activity relationships (ECOSAR) software. On the whole, this work provides an excellent insight for the development of environment-friendly materials in a large scale for the degradation of water-based pollutants.

AHMT functionalized g-C3N4 quantum dots/Au based localized surface plasmon resonance sensors for ultrasensitive and rapid detection of adrenaline

Adrenaline (ADR) is a neurotransmitter/hormone responsible for stress syndrome and the concentration level in blood is an indication of health consequences. Herein, a simple and cost-effective nanosensors based on the interaction between highly fluorescent g-C3N4 quantum dots (CNQDs) and surface plasmon resonance gold nanoparticles (AuNPs) in the presence of 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (AHMT) was developed for ultra-sensitive and selective detection of ADR. After functionalization of AHMT onto both CNQDs and AuNPs, AHMT can serve as the recognizer to link with ADR by hydrogen bond, resulting in the non-radiative energy transfer from CNQD to AuNP to quench the fluorescence intensity. The quenching efficiency is highly dependent on ADR concentration and the size of AuNPs. When 45 nm AuNPs is combined with CNQDs, an excellent linear relationship with a wide dynamic range of (10 pM – 100 µM) and a low limit of detection of 7 pM is obtained for ADR detection. Moreover, the developed sensor exhibits high selectivity towards ADR detection over 25 potential interferences. These findings have demonstrated the superiority of AHMT-conjugated CNQD-AuNP sensing probe for ADR detection, which can be applied to design of a newly developed nanosensing platform for the early detection and therapeutic diagnosis of ADR associated diseases in biomedical applications.

Alkali metal ion-doped heptazine-based g-C3N4 quantum dots for efficient adsorption of methyl blue: A DFT perspective

Organic effluents disposed of by industrial plants have created a serious impact on the availability of potable water, disturbed environmental sanity, and hampered the natural thriving of aquatic animals. In particular, the concentrations of methyl blue (MB) dye in different water bodies has lately risen to an alarming level. In the present study, the adsorption performance of metal ion-doped heptazine-based graphitic carbon nitride (g-C3N4) quantum dots towards MB was investigated using first-principles calculations. The computed electronic properties associated with the MB∙∙∙g-C3N4 and MB∙∙∙M+−g-C3N4 clusters in the aqueous medium indicated that doping the carbon nitride sheets with lithium ions exhibits the smallest HOMO-LUMO gap and the highest charge potential, as compared to the potassium and sodium counterparts. The interaction in MB∙∙∙Li+-g-C3N4 was shown to become weaker in acidic media. The effective adsorption of the metal-doped nanosheets was predicted to increase in the order K+-g-C3N4 < Na+-g-C3N4 < Li+-g-C3N4. Protonation of the nanoclusters resulted in a stronger attraction of the dye molecule while the same order for the non-protonated analogs is retained, suggesting that electrostatic attraction is the key factor that controls the adsorption behavior in such systems.

UV light driven high-performance room temperature surface acoustic wave NH3 gas sensor using sulfur-doped g-C3N4 quantum dots

UV light driven high-performance room temperature surface acoustic wave NH3 gas sensor using sulfur-doped g-C3N4 quantum dots

Insights into engineered graphitic carbon nitride quantum dots for hazardous contaminants degradation in wastewater

Increased environmental pollution is a critical issue that must be addressed. Photocatalytic, adsorption, and membrane filtration methods are suitable in environmental governance because of their high selectivity, low cost, environment-friendly nature, and excellent treatment efficiency. Graphitic carbon nitride (g-C3N4) quantum dots (QDs) have been considered as photocatalysts, adsorbents, and membrane materials for wastewater treatments, owing to their stability, adsorption capacity, photochemical properties, and low toxicity and cost. This review summarizes g-C3N4 QD synthesis techniques, operating parameters affecting the removal performance in the treatment process, modification effects with other semiconductors, and benefits and drawbacks of g-C3N4 QD-based materials. Furthermore, this review discusses the practical applications of g-C3N4 QDs as adsorbents, photocatalysts, and membrane materials for organic and inorganic contaminant treatments and their value-added product formation potential. Modified g-C3N4 QD-based material adsorbents, photocatalysts, and membranes present potentially applicable effects, such as removal of most waterborne contaminants. Excellent results were obtained for the reduction of methyl orange, bisphenol A, tetracycline, ciprofloxacin, phenol, rhodamine B, E. coli, and Hg. Overall, this paper provides comprehensive background on g-C3N4 QD-based materials and their diverse applications in wastewater treatment, and it presents a foundation for the enhancement of similar unique materials in the future.

Reduced electron relaxation time of perovskite films via g-C3N4 quantum dot doping for high-performance perovskite solar cells.

Perovskite film-quality is a crucial factor to improve the photovoltaic properties of perovskite solar cells, which is closely related to the morphology of crystallization grain size of the perovskite layer. However, defects and trap sites are inevitably generated on the surface and at the grain boundaries of the perovskite layer. Here, we report a convenient method for preparing dense and uniform perovskite films, employing g-C3N4 quantum dots doped into the perovskite layer by regulating proper proportions. This process produces perovskite films with dense microstructures and flat surfaces. As a result, the higher fill factor (0.78) and a power conversion efficiency of 20.02% are obtained by the defect passivation of g-C3N4QDs.

Boron doped g-C3N4 quantum dots based highly sensitive surface acoustic wave NO2 sensor with faster gas kinetics under UV light illumination

The elegant two-dimensional (2D) graphitic carbon nitride (GCN) holds great promise in the detection of hazardous toxic gases especially NO2, for environmental protection and public health safety. However, the poor sensitivity and low surface area of bulk 2D GCN restrains its practical applicability of room temperature (RT) NO2 sensing. Herein, we present the fabrication of boron-doped GCN quantum dots (B@GCN QD) coated langasite (LGS) based surface acoustic wave (SAW) sensor for the RT NO2 gas detection, and applied UV activation energy (365 nm) as an effective strategy to further enhance the NO2 sensing. Fascinatingly, under UV light, the B@GCN QD/LGS SAW sensor showed an enhanced gas sensing performance to the NO2 gas (500 ppb - 50 ppm) with high sensitivity (Δf=35.97 kHz/50 ppm), good selectivity, ultra-low detection limit (DL∼7.9 ppb), fast response/recovery times (35 s/43 s), excellent long-term stability as compared to dark condition. This could be attributed to the generation of abundant photoinduced charge carriers under UV activation, which leads to the significant enhancement in conductivity and enlarged mass loading effect, also, the device showed robust sensitivity responses to NO2 gas at various temperatures (RT-200 °C) and relative humidity (20–80%) conditions. Moreover, the effective doping of B to the GCN QD exhibited a typical p-type behavior which is good in agreement with density functional theory predictions that can induce structural defects, vacancies, and amine functional groups leading to a high specific surface area, which can remarkably enhance the sensitivity and selectivity of NO2 gas. This work may provide insights into the design and development of 2D GCN nanostructure-based SAW RT gas sensors for environmental monitoring.

Encapsulation of in-situ generated g-CNQDs with up-conversion effect in Zr/Ti-based porphyrin MOFs for efficient photocatalytic hydrogen production and NO removal

In this study, a highly efficient bifunctional porphyrin-based MOFs with uniformly in-situ generated g-C3N4 quantum dots (g-CNQDs) was fabricated for photocatalytic hydrogen evolution and NO removal, in which PtTCPP as the organic ligand and mixed Zr/Ti-oxo clusters as the metal nodes. Compared with most reported Zr-based porphyrin MOFs, the g-CNQDs@Zr-MOFs(Pt)(Zr/Ti) exhibited outstanding hydrogen evolution activity (14511.57 μmol g−1) and NO removal rate (31.9 %) under visible light irradiation. The obviously improved photocatalytic performance could be attributed to the significantly enhanced charge separation and transfer rates by the mixed Zr/Ti-oxo clusters via the rapid Ti3+/Ti4+ process. Moreover, the uniformly in-situ generated g-CNQDs via confinement effect in the cavity of MOFs could also improve the utilization of visible light especially through the up-conversion effect, and promote charge carriers separation. This work provides an idea for us to expand the scope of light utilization and promote charge transfer and separation rates of MOFs via functionalizing host MOFs matrix and coupling guest active species to improve photocatalytic performance further.

0D/3D CNQDs/CuFe2O4/Cu0 heterostructures as broad spectrum photocatalyst for efficient 5-fluorouracil degradation: Structural evolution and relay oxidation process

Undesirable solar energy absorption, poor charge transfer efficiency, and sluggish metallic ions redox cycle are three pressing problems, restricting the application of photocatalysis and peroxymonosulfate (PMS) techniques. Herein, an interface engineering of g-C3N4 quantum dots anchoring on the CuFe2O4/Cu0 hollow microspheres (CNQDs@CFO) was developed to construct a novel 0D/3D broad-spectrum-response photocatalyst. In the relaying PMS-photocatalysis process, 30 μM 5-fluorouracil (5-FLU, 50 mL) was degraded by 99.4 % in 60 min with 0.2 g L−1 1.0CNQDs@C1F1O and 0.3 mM PMS. The reusability test showed that 1.0CNQDs@C1F1O maintained superior performance with a 5-FLU removal of 92.6 % after the fifth run. Meanwhile, this newly-designed material can be applied in a large temperature and pH range, and even actual water bodies with strong environmental adaptability. Theoretic and experimental analysis demonstrated that the CNQDs and Cu0 sites on CNQDs@CFO promoted the earlier PMS activation, and then dual Z-scheme heterostructures (CNQDs/CuFe2O4/CuO) was established, boosting the follow-up photocatalytic activity.