g-C3N4 Quantum Dots Research Articles

G-C3N4 quantum dots and Au nano particles co-modified CeO2/Fe3O4 micro-flowers photocatalyst for enhanced CO2 photoreduction

Wide-light absorption performance and efficient carrier separation ability are the necessary conditions for excellent photocatalytic materials. In this research, g-C3N4 QDs (CN QDs) and Au nano-particles (NPs) co-modified CeO2/Fe3O4 micro-flowers (MFs) photocatalyst (CACeF) has been prepared. CO2 photoreduction experiments showed that the composite had obviously enhanced photoreduction activity and photocatalytic stability. The yields of CO and CH4 over it as catalyst in 4 h is about 5 and 8 times greater than that of pure CeO2. Photoelectrochemical tests showed that the heterojunction between CN QDs and Au NPs can greatly improve the carrier separation ability and the light-utilization efficiency of photocatalysts. Besides, the excellent electronic transmission performance of Au NPs provided a specific channel for the electron transmission, and the strong local surface plasmon resonance (LSPR) of Au NPs resulted in a lot of hot-electrons can directly take part in the CO2 photoreduction. The synergistic effect between CN QDs and Au NPs can further enhance the photocatalytic activity of the photocatalyst. Fe3O4 QDs can ensure the effective recovery and reuse of the composite without affecting the photocatalytic performance of composite. Finally, a potential photoreduction mechanism of CN QDs and Au NPs co-modified CeO2/Fe3O4 MFs photocatalyst were discussed in total.

0D/3D coupling of g-C3N4 QDs/hierarchical macro-mesoporous CuO-SiO2 for high-efficiency norfloxacin removal in photo-Fenton-like processes

Photo-Fenton process is an advanced oxidation technology, which is used to eliminate organic pollutants in environmental pollution. In this paper, g-C3N4 quantum dots incorporated hierarchical macro-mesoporous CuO-SiO2 (MM SC-QDs) composite was successfully fabricated by a dual-template method combined with polystyrene sphere (PS) crystal and copolymer F127. With the presence of H2O2, MM SC-QDs exhibited excellent degradation performance against the antibiotic pollutant norfloxacin (NOR) under visible-light assisted heterogeneous Fenton process at neutral condition, which was 27 times higher than that of the Bulk CuO-SiO2. Interconnected macropores, together with abundant mesopores effectively expand specific surface area and improve mass transfer. In addition, the g-C3N4 QDs served as the separation center for photogenerated charges, promoting the separation and migration of the charge carriers. Wherein, the long-lived photogenerated electrons were effectively separated and transferred to the surface of CuO-SiO2, which accelerated the reduction rate of Cu2+ to Cu+, enhancing the photo-Fenton-like catalytic activity. This stable, efficient, and environmentally friendly Cu-based heterogeneous photo-Fenton-like catalyst is expected to become an effective implementation in organic pollution removal. Meanwhile, this paper proves that Cu-based materials can activate H2O2 to generate singlet oxygen (1O2) for the degradation of organic pollutants. The transformation mechanism of 1O2 was clarified, which is helpful to better understand the Fenton-like reaction process of Cu-based materials.

An ultrasensitive photoelectrochemical sensor with layer-by-layer assembly of chiral multifarene[3,2,1] and g-C3N4 quantum dots for enantiorecognition towards thyroxine

A photoelectrochemical sensor was developed with stepwise decoration of g-C 3 N 4 quantum dots and chiral multifarene[3,2,1] to achieve the ultrasensitive enantiorecognition for L -thyroxine. • A facile method for preparation of g-C 3 N 4 quantum dots was discovered. • A photoelectrochemical sensor built with g-C 3 N 4 QDs and chiral macrocycle was developed. • The ultrasensitive enantiorecognition for thyroxine was reached with the proposed photoelectrochemical sensor. With a facile preparation for graphitic carbon nitride quantum dots (g-C 3 N 4 QDs), an ultrasensitive photoelectrochemical (PEC) sensor was developed with the supramolecular affinity of chiral multifarene[3,2,1] (CMF) to a hormone drug, thyroxine (T 4 ), for efficient identification of thyroxine enantiomers. In the principle that g-C 3 N 4 QDs was employed to achieve the photocurrent response and the macrocyclic compound served as the supramolecular enantiorecognition for thyroxine, the photoelectrochemical electrode was constructed by layer-by-layer assembly of g-C 3 N 4 QDs and CMF on the surface of ITO (ITO-g-C 3 N 4 -CMF QDs). The proposed PEC sensor produced the limits of detection low to 67 pM towards L -T 4 and 85 pM towards D -T 4 in a concentration range from 0.1 nM to 10 nM, which was superior to the values in pioneering reports with colorimetric or electrochemical methods. With good stability, reproducibility, repeatability anti-interference ability, and acceptable recoveries, the proposed PEC sensor was employed for quantitative determination of L/D -T 4 in water, human serum and commercial tablet.

An investigation on development of a molecular imprinted sensor with graphitic carbon nitride (g-C3N4) quantum dots for detection of acetaminophen

An investigation on development of a molecular imprinted sensor with graphitic carbon nitride (g-C3N4) quantum dots for detection of acetaminophen

Tuning the reactivity of tri-s-triazine, trinitro-tri-s-triazine and ternary tri-s-triazine graphitic C3N4 quantum dots through H-functionalized and B-doped complexes: A density functional study

Modifying the structures and doping are proven to be effective methods to tune the structural and electrical properties of g-C3N4 quantum dots. Hence, in this study, tri-s-triazine and tri-nitro tri-s-triazine have been studied by functionalizing their edges with hydrogen. The H-functionalized tri-nitro tri-s-triazine quantum dot displays a buckled structure with a band gap of 1.988 eV, whereas the tri-s-triazine demonstrates a planner structure with a band gap of 1.636 eV. The obtained results have been compared with the previous results. The absorbance spectrum of H-functionalized trinitro tri-s-triazine falls under the visible region with a peak value of 488 nm, and the absorption spectrum of tri-s-triazine falls at 790 nm. The planarity of the tri-nitro tri-s-triazine structure is improved by doping the B atom in the N site, and the band gap of H-functionalized B doped tri-nitro tri-s-triazine is 1.143 eV. The absorbance spectrum of H-functionalized B doped tri-nitro tri-s-triazine is 508 nm. The reactivity of the structure is increased by doping B atoms, and it is confirmed by the electrophilicity index. Similarly, the H-functionalized B doped tri-s-triazine exhibits a band gap of 1.328 eV. Further, the tri-s-triazine structures are arranged in ternary form, and the properties are studied by increasing the number of B atoms in the tri-s-triazine rings. The outcome presents that the structures are planar, and band gap values are reduced further. Also, the reactivity of the sheets is increased, which is confirmed by the electrophilicity index. It is proposed that the sheets with a high reactivity can be used for the removal of hazardous ions and molecules from the industrial wastage.

B-Doped g-C3N4 Quantum Dots-Modified Ni(OH)2 Nanoflowers as an Efficient and Stable Electrode for Supercapacitors

For increasing the specific capacitance of supercapacitors, boron-doped g-C3N4 quantum dots (B-CNQDs) were synthesized by KOH cutting and further adsorbed on the surface of Ni(OH)2 nanoflowers (B-C...

The synthesis and application progress of g-C3N4 quantum dots photocatalytic composite materials

The synthesis and application progress of g-C3N4 quantum dots photocatalytic composite materials

Molten-based defect engineering polymeric carbon nitride quantum dots with enhanced hole extraction: An efficient photoelectrochemical cell for water oxidation

Polymeric carbon nitride (g-C3N4) has emerged as a promising material for energy-related applications. However, the utilization of g-C3N4 in photoelectrochemical cells is still limited by poor exciton mobility, sluggish hole extraction, and short electron diffusion length. Here, we report a molten-based defect engineering strategy to prepare nitrogen-deficient g-C3N4 quantum dots (SxCNQD) for photoelectrochemical water splitting. This novel strategy requires no chemical etching or secondary treatments like recent state-of-the-art defect introduction methods, and for the first time achieves the in-situ integration of nitrogen-vacancy defects (NVs) during the polymerization of g-C3N4. Theoretical evaluation and experimental validation identified that the involved structural NVs redistribute the electrons on the delocalized π-conjugated networks of g-C3N4 and creates an additional sub-band on the optical bandgap, which can effectively improve carrier separation, facilitate charge transport dynamics, and boost hole extraction. Beneficial from its featured topological structures and electronic properties, the S600CNQD@ZnO photoanode exhibits a markedly high photocurrent density of 193.8 μA cm−2 at 1.23 V vs. RHE, long-term durability, as well as an impressive IPCE value in an alkaline solution in the absence of sacrificial agent under visible light illumination.

Fabrication of g-C3N4 Quantum Dots/MnCO3 Nanocomposite on Carbon Cloth for Flexible Supercapacitor Electrode

In this study, the nanocomposite of g-C3N4 quantum dots/MnCO3 on carbon cloth (q-MC//CC) is prepared via a simple hydrothermal method. The obtained q-MC//CC composite is employed for a flexible supercapacitor electrode. The g-C3N4 quantum dots could effectively improve the interface electrical conductivity and ion transportation of the MnCO3 electrode, which results in superior electrochemical performance. The q-MC//CC electrode delivers a high specific capacity of 1001 F·g−1 at a current density of 1 A·g−1 and a good cycling performance of 96% capacity retention after 5000 cycles. Moreover, an asymmetric flexible supercapacitor (ASC) is assembled with q-MC//CC and carbon cloth as a positive and negative electrode, respectively, which exhibits a high energy density of 27.1 Wh·kg−1 at a power density of 500 W·kg−1. In addition, the fabricated ASC device demonstrates the ability to power the light-emitting diode effectively under mechanical bending.

G-C3N4 quantum dots-modified mesoporous CeO2 composite photocatalyst for enhanced CO2 photoreduction

g-C3N4 quantum dots (CN QDs)-decorated mesoporous CeO2 composite photocatalyst was prepared by hydrothermal method. The characterized results exhibit that the CN QDs are successfully coupled with mesoporous CeO2, and the photoelectronic response is effectively enhanced. The photocatalytic activity was tested by CO2 reduction, and the results showed that when the loading of CN QDs was 0.75 wt%, the composite photocatalyst has the best photocatalytic activity. After 10 h of UV irradiation, the yields of CO and CH4 were 22.48 µmol/g and 15.81 µmol/g, respectively. Some of the electrons generated within m-CeO2 participated in the CO2 reduction reaction and some were transferred to CN QDs through the two-phase interface to participate in the CO2 catalytic reaction. The oxygen vacancies in m-CeO2 can adsorb CO2 and the introduced CN QDs can excite more oxygen vacancies with m-CeO2 heterostructure, thereby adsorbing more CO2 and photoreduction electrons.

Surface-engineering of decahedron shaped bismuth vanadate for improved photoelectrochemical water oxidation by indium doping coupled with graphitic carbon nitride quantum dots

Surface of a photocatalyst critically determines the efficiency of water oxidation by providing suitable reaction sites and energetics. Manipulating the properties of semiconductor surface for better charge extraction and efficiency forms the basis of present study. We chose monoclinic BiVO4 as a model system, due to its suitable band structure and stability with a theoretical current density approaching 7 mA/cm2 is a promising material for photoelectrochemical water oxidation. An in-situ growth procedure yields, indium doped BiVO4 (BiVO4:In) photoanode with distinctive morphology. This photoanode forms a type II heterojunction (BiVO4:In)-CNQD) with g-C3N4 quantum dots (CNQD) loading to address the shortcomings. A photocurrent density of ~2.42 mA/cm2 with a solar to hydrogen conversion of 2.66% with an average Faradaic yield of 90% is yielded, which is ~4-folds higher than its bare counterpart. (BiVO4:In)-CNQD photoanode shows a significant cathodic shift of 136 mv than bare BiVO4 photoanode. Indium in BiVO4 favors the creation of oxygen vacancies, which improves charge separation and charge carrier density in BiVO4:In photoanode. It is also observed that the BiVO4:In photoanode shows higher surface hydrophilic characteristics, results in more polar surface and water adsorption on the surface, leading to more active water at the reaction site.

W18O49 Frameworks Decorated with Graphitic Carbon Nitride Quantum Dots for Photocatalytic Hydrogen Production

Quantum dots (QDs) have exhibited remarkable advantages for photocatalytic H2 evolution. Unfortunately, despite their unique quantum size effects and abundant catalytic active sites, many applications of QDs have been hindered in that they are prone to aggregation and easy to leach off from the substrate. Therefore, it is highly desirable to fabricate a special nanostructure with confinement effects to conquer their intrinsic drawbacks. Herein, we present a direct g-C3N4–x/W18O49 Z-scheme nanocomposite for enhanced photocatalytic H2 production. This system is composed of a W18O49 framework with several microporous slits and g-C3N4 QDs with a rich nitrogen vacancy. These several microporous slits can fix QDs and avoid their aggregation. Besides, the microporous slit surface can be functionalized by adjusting the pH value, thus ensuring intimate contact between W18O49 framework and g-C3N4–x QDs. The unique Z-scheme confinement structure facilitates photoinduced carrier transfer and improves the photocatalytic H2 production performance. The g-C3N4–x/W18O49 nanocomposite exhibits an exceedingly high H2 evolution rate and super stability because of the confinement structure and effective charge channel. This study provides a strategy to design the high-efficiency catalysts for solar H2 production.

Graphitic Carbon Nitride Quantum Dots Embedded in Carbon Nanosheets for Near-Infrared Imaging-Guided Combined Photo-Chemotherapy.

Rational design of metal-free multifunctional therapeutic reagents offers great opportunities for cancer treatment in the clinic. Here, graphitic carbon nitride (g-C3N4) quantum dots embedded in carbon nanosheets (CNQD-CN) are in situ prepared via a one-pot hydrothermal approach with formamide as carbon and nitrogen source. The CNQD-CN not only serves as an excellent near-infrared (NIR) fluorescent marker but also acts as a pH-responsive nanocarrier. Moreover, the CNQD-CN possesses both light-to-heat conversion and singlet oxygen generation capabilities under a single NIR excitation wavelength. Further investigations show that systemic delivery of doxorubicin (DOX) using the multifunctional CNQD-CN nanocarrier under NIR irradiation was highly effective to cause cancer cell apoptosis in vitro and inhibit tumor growth in vivo. CNQD-CN represents a multifunctional therapeutic platform for synchronous cancer imaging and treatment through the synergistic effect of phototherapy and chemotherapy.

Long-lasting CaAl2O4:Eu2+,Nd3+ phosphor-coupled g-C3N4 QDs composites for the round-the-clock photocatalytic methyl orange degradation

Long-lasting phosphors are a type of important materials that can release their stored energy in form of light after tuning off the excitation light source. Due to this unique luminescent property, combining a long-lasting phosphor and a suitable photocatalyst can keep the photocatalytic activity in the absence of the excitation light source. Here, a novel round-the-clock photocatalyst, combined the CaAl2O4:Eu2+,Nd3+ (CAOED) blue long-lasting phosphor with the g-C3N4 quantum dots (QDs), is reported for the first time. Our results reveal that when the excitation light is off, the photocatalytic degradation of methyl orange (MO) in the CAOED-coupled g-C3N4 QDs composites can continue for > 3 h, and come back its initial state after several time. Although the light intensity emitted from the CAOED is decreased with the increase of the delay time, the stored energy of the obtained photocatalyst can be recharged and recovered basing on the long-lasting decay curve, exhibiting the round-the-clock behavior. Our discussion reveal that this external irradiation-free photocatalytic activity is due to the long-lasting luminescence of the CAOED caused by the crystal lattice defects and the visible-light utilization and recombination rate of photo-generated carriers in the CAOED-coupled g-C3N4 QDs photocatalyst.

Hybridization of g-C3N4 quantum dots with 1D branched TiO2 fiber for efficient visible light-driven photocatalytic hydrogen generation

The hybrid 1D branched TiO2 loaded with g-C3N4 QDs was successfully fabricated that plays a significant role in photocatalysis. The 1D branched TiO2 prepared by electrospinning followed by alkali-hydrothermal process, and g-C3N4 QDs were grafted over it by a chemical vapor deposition method. The composite display enhancement in photocatalytic hydrogen evolution is about 10.57 mmol. g−1.h−1 in comparison to the g-C3N4 sample that only produces 0.32 mmol. g−1.h−1 while the HBTiO2 sample evolved a negligible amount of hydrogen under visible light. The composite sample shows quantum efficiency for HER at 420 nm light is 18.6% that is much higher than the other two samples. The specific surface area of the composite sample is 92.39 m2g-1 that is about 13 times more than bulk g-C3N4. The bandgap of HBTiO2/g-C3N4 QDs, g-C3N4, and HBTiO2 samples calculated as 2.71 eV, 2.67eV, and 3.24eV, respectively. The TRPL spectra imply that the duration of the lifetime of composite becomes longer which effectually overwhelm the electron-hole recombination. The 1D branched TiO2 fiber reduces the charge recombination by fast transfer of electron while g-C3N4 QDs facilitate the visible light absorption by improving the optical properties. The formation of the type II heterostructure system remarkably promotes the separation and transfer of electron holes and facilitates the photo-reduction reaction.

Polyaniline supported g-C3N4 quantum dots surpass benchmark Pt/C: Development of morphologically engineered g-C3N4 catalysts towards “metal-free” methanol electro-oxidation

In spite of being one of the most promising energy conversion devices, the state of the art in the efficient application of direct methanol fuel cell is far from being optimal mostly because of its heavy reliance on expensive Pt anode that suffers from easy CO poisoning. Here, in this work for the first time in literature, we have explored the catalytic efficacy and improved mass activity of morphologically engineered metal-free graphitic carbon nitride towards methanol oxidation. The 2D nano-sheets, 1D nano-rods, and 0D quantum dots of graphitic carbon nitride are successfully prepared from bulk by a thermo-chemical etching process. The materials are thoroughly characterized with the help of X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, luminescence study and are studied for methanol oxidation reaction in basic condition with the help of cyclic voltammetry. Among the three different dimensional g-C3N4 materials, the quantum dots show higher methanol oxidation activity due to its abundant edges in nano morphology and maximum atomic percentages of active site of pyridinic N. The 0D g-C3N4 when supported on conducting polyaniline, not only shows higher electrocatalytic methanol oxidation activity than the commercial Pt/C but also demonstrates excellent CO tolerance to be a suitable and applicable metal-free anode catalyst in direct methanol fuel cell applications. The electrostatic interaction between 0D g-C3N4 and conducting polyaniline (PANI) fibres may have improved the electrical conductivity and methanol adsorption of CNQD-PANI electrocatalyst and also played a role in oxidizing the adsorbed CO to upsurge the CO tolerance.

In situ decoration of g-C3N4 quantum dots on 1D branched TiO2 loaded with plasmonic Au nanoparticles and improved the photocatalytic hydrogen evolution activity

The hybrid 1D branched TiO2 loaded with surface plasmonic Au and decorated with g-C3N4 QDs were successfully fabricated which played a significant role in photocatalysis. The 1D branched TiO2 prepared by electrospinning followed by an alkali-hydrothermal process. The Au particles decorated by photo deposition and after that g-C3N4 QDs were grafted over it by a chemical vapor deposition method. The composite shows great improvement in photocatalytic hydrogen evolution and evolved about 2.22 mmol g−1 h−1 hydrogen. The composite sample has a quantum efficiency of 19.5% for hydrogen production at 420 nm light that depicts the performance behavior of the composite. The 1D branched TiO2 fiber facilitates the fast transfer of electrons and Au reduces the charge recombination due to its surface plasmonic effect while g-C3N4 QDs facilitate the visible light absorption by improving the optical properties and reduces the bandgap. The formation of the type II heterostructure system remarkably promotes the separation and transfer of electron holes and facilitates the photo-reduction reaction.

Enhanced photocatalytic activity of g-C3N4 quantum dots/Bi3.64Mo0.36O6.55 nanospheres composites

In this research, heterostructured g-C3N4 quantum dots (CNQDs)/Bi3.64Mo0.36O6.55 nanospheres have been fabricated trough an in situ precipitation process. Compared to the pure Bi3.64Mo0.36O6.55, the as-fabricated CNQDs/Bi3.64Mo0.36O6.55 nanocomposites exhibited significantly improved photocatalytic performance for the photodegradation of rhodamine B (Rh B) and bisphenol A (BPA). In addition, 5 ​wt% CNQDs/Bi3.64Mo0.36O6.55 sample showed the highest photocatalytic efficiency under visible-light irradiation (λ ​> ​420 ​nm). The effective separation and transmission of photogenerated electron-hole pairs caused by CNQD loading as well as the improved BET surface area are associated with the enhancement of the photocatalytic activity of the CNQDs/Bi3.64Mo0.36O6.55 photocatalyst.

Tin diselinide a stable co-catalyst coupled with branched TiO2 fiber and g-C3N4 quantum dots for photocatalytic hydrogen evolution

Transitional metal dichalcogenide two-dimensional materials have revealed many astonishing properties including the substitution of noble metals as a co-catalyst for hydrogen evolution reaction. Tin diselenide (SnSe2) is the one who also received substantial consideration in many fields due to low cost, earth-abundant and environment-friendly. However, the great challenge to make heterojunction with other semiconductor material to improve its efficiency for photocatalytic water splitting. For this purpose, we have prepared a 1D nanofiber of TiO2 by electrospinning and produced a needle-like structure on the fiber by following the alkali hydrothermal method. The chemical vapor deposition method (CVD) was adopted, first to load g-C3N4 QDs then nanoflakes of SnSe2 on the branched fiber of TiO2 and make a strong heterojunction. The composite interpreted excellent photocatalytic performance by producing hydrogen about 2375 μmol. g−1.h-1 having a quantum efficiency of HER more than 16 % at 420 nm. The photoluminescence, time decay fluorescent spectra and photoelectrochemical results ratified that SnSe2 not only reduces the charge recombination by increasing the transfer of electron but also provides an active site for hydrogen production as a cocatalyst. This study presents an inexpensive and environmentally friendly cocatalyst for hydrogen production as a substitution of noble metals.

Conductivity tuning of charged triazine and heptazine graphitic carbon nitride (g-C3N4) quantum dots via nonmetal (B, O, S, P) doping: DFT calculations

Chemical doping of graphitic carbon nitride (g-C3N4) quantum dots with nontoxic heteroatoms has proven to be an effective means for tuning the electrical properties of this two-dimensional (2D) nanomaterial. In this investigation, triazine (tg-CN) and heptazine (hg-CN) clusters were doped with the p-block (B, O, S, and P) elements, and were further compared in terms of siting and conductance using density functional theory (DFT) at the HSE06/6-311+G* level. The calculation results predicted that B doping in both types of g-C3N4 was favored in place of carbon atoms while the O, S, and P dopants preferred nitrogen atoms, where P siting was dependent on the type of material. Both the initial HOMO–LUMO gap and global hardness were decreased after the substitution, with the most substantial changes after the O and S doping in the hg-CN and tg-CN structures, respectively. The HOMO–LUMO gap changed most significantly (by up to 3.79 eV) with the [+/−] charge switching for the O-doped nanocluster. In contrast to hg-CN, tg-CN turned from an insulator into metallic or half-metallic material upon electron charging. Finally, both hg-CN and tg-CN became better electrophiles after modification, particularly with B doping.