Carbon Nitride Nanospheres Research Articles

Efficient Photodegradation of Methylene Blue using WLED with Nanosphere Graphitic Carbon Nitride Compared with its Bulk Counterpart

Herein, a simple solvothermal synthesis of graphitic carbon nitride nanosphere (g-CNN) at 180 ºC is reported. The photocatalytic activity of g-CNN was studied under an in-house developed white light emitting diode (WLED) reactor and characterized by FESEM, PXRD, FTIR, EDX, UV-visible spectroscopy and BET isotherm. The g-CNN has absorbance in visible light region and exhibits enhanced photocatalytic activity compared to bulk graphitic carbon nitride (BGCN) for photodegradation of methylene blue, which attributes to its lower surface area. The photocatalytic performance of g-CNN as function of pH of dye solution and catalyst amount were also studied. The g-CNN can be used for three repeated cycles with minimal change in photocatalytic efficiency. The solvothermal synthesis method at relative low temperature introduces terminal oxygen functionalities in g-CNN, which enhance light absorption and accelerate electron transfer results in improvement of photocatalytic efficiency of g-CNN. The results demonstrated the effectiveness of g-CNN as a photocatalyst for the treatment of water using visible light from WLED.

Aptamer-Based Fluorescence Detection and Selective Disinfection of Salmonella Typhimurium by Using Hollow Carbon Nitride Nanosphere.

Hollow carbon nitride nanosphere (HCNS) was synthesized via the hard template method to improve the fluorescence characteristics, drug delivery ability, and photocatalytic activity. Blue fluorescent HCNS was utilized as a quenching agent and an internal reference to combine with Cy5-labelled aptamer (Cy5-Apt), resulting in an off-on fluorescence aptasensing method for the detection of Salmonella typhimurium (S. typhimurium). Under optimum conditions, this fluorescence assay presented a linear range from 30 to 3 × 104 CFU mL−1 with a detection limit of 13 CFU mL−1. In addition, HCNS was also used as a drug carrier to load chloramphenicol (Cap) molecules. The Cap-loading amount of HCNS could reach 550 μg mg−1 within 24 h, whereas the corresponding Cap-release amount is 302.5 μg mg−1 under acidic and irradiation conditions. The integration of photocatalyst with antibiotic could endow HCNS-Cap with better disinfection performance. The bactericidal efficiency of HCNS-Cap (95.0%) against S. typhimurium within 12 h was better than those of HCNS (85.1%) and Cap (72.9%). In addition, selective disinfection of S. typhimurium was further realized by decorating aptamer. Within 4 h, almost all S. Typhimurium were inactivated by HCNS-Cap-Apt, whereas only 13.3% and 48.2% of Staphylococcus aureus and Escherichia coli cells were killed, respectively. Therefore, HCNS is a promising bio-platform for aptamer-based fluorescence detection and selective disinfection of S. typhimurium.

Infrared-to-visible energy transfer photocatalysis over black phosphorus quantum dots/carbon nitride

• BP QDs decorated hollow S doping carbon nitride nanospheres are synthesized. • The hollow porous structures generate more active sites for photocatalytic reaction. • BP/S-HC 3 N 4 exhibits remarkable photocatalytic amino acids and H 2 production rates. • The charge separation and exciton–exciton energy transfer are greatly promoted. Polymeric photocatalysts have been considered as promising candidates for the photocatalytic biomass conversion and H 2 evolution, but they suffer from the fast charge recombination and the short light absorption range. Herein, for the first time, a novel energy-transfer-mediated photocatalyst is facilely fabricated by anchoring black phosphorus quantum dots on sulfur-doped graphitic carbon nitride hollow nanospheres (BP/S-HC 3 N 4 ). Doping of S element not only inhibits the recombination of photogenerated carriers, but also promote exciton dissociation by trap states. In addition, black phosphorus quantum dots extend the light response range to the near-infrared region, and the near-infrared light energy can be transferred to S-HC 3 N 4 through exciton mediated energy transfer, so as to improve the photocatalytic performance, and this energy transfer mechanism is not limited by the heterojunction type Ⅰ energy band structure. In this conceptual photocatalytic system, energy transfer is different from the traditional carrier transfer mechanism, which is not restricted by the energy band structure. Consequently, the photocatalytic amino acids and hydrogen production rates of BP/S-HC 3 N 4 reach 643 mmol h −1 and 102 μmol h −1 under visible-NIR light, which are 58.5 and 51.0 times larger than that of the pristine g-C 3 N 4 , respectively. This work provides a new strategy for constructing high-efficient and wide-spectral response photocatalysts.

Hydrogen Evolution Reaction Monitored by Electrochemiluminescence Blinking at Single-Nanoparticle Level.

Monitoring and characterization methods that provide performance tracking of hydrogen evolution reaction (HER) at the single-nanoparticle level can greatly advance our understanding of catalysts' structure and activity relationships. Electrochemiluminescence (ECL) microscopy is implemented for the first time to identify HER activities of single nanocatalysts and to provide a direction for further optimization. Here, we develop a novel ECL blinking technique at the single-nanoparticle level to directly monitor H2 nanobubbles generated from hollow carbon nitride nanospheres (HCNSs). The ECL ON and OFF mechanisms are identified being closely related to the generation, growth, and collapse of H2 nanobubbles. The power-law distributed durations of ON and OFF states demonstrate multiple catalytic sites with stochastic activities on a single HCNS. The power-law coefficients of ECL blinking increase with improved HER activities from modified HCNSs with other active HER catalysts. Besides, ECL blinking phenomenon provides an explanation for the low cathodic ECL efficiency of semiconductor nanomaterials.

Stable and Monochromatic All-Inorganic Halide Perovskite Assisted by Hollow Carbon Nitride Nanosphere for Ratiometric Electrochemiluminescence Bioanalysis.

Lead halide perovskites have been promising electrochemiluminescence (ECL) candidates because of their excellent photophysical attributes, but their poor stability has severely restricted ECL applications. Herein, the in situ assembly of all-inorganic perovskite CsPbBr3 nanocrystals (CPB) into hollow graphitic carbon nitride nanospheres (HCNS) were described as a novel ECL emitter. The architecture guaranteed not only improved stability because of the peripheral HCNS protecting shell but also high-performance ECL of CPB because of a matching band-edge arrangement. Dual-ECL readouts were obtained from the nanocomposite including an anodic ECL from CPB and a cathodic ECL from HCNS. The former displayed prominent color purity to construct an efficient ECL resonance energy transfer system, and the latter served as an internal standard for a ratiometric analysis. A well-designed DNA probe was further utilized for the targeting of CD44 receptors on the MCF-7 cell surface and the double signal amplification. The sensing strategy exhibited good analytical performance for MCF-7 cells, ranging from 1.0 × 103 to 3.2 × 105 cells mL-1 with a detection limit of 320 cells mL-1. Sensitive and accurate evaluation of CD44 expression was finally achieved at 0.22 pM. This work is the first attempt to use halide perovskite for reliable ECL bioanalysis and provides a perspective to design a perovskite-based nanocomposite as a high-performance ECL emitter for its exclusive ECL system.

Highly active metal-free carbon dots/g-C3N4 hollow porous nanospheres for solar-light-driven PPCPs remediation: Mechanism insights, kinetics and effects of natural water matrices

Pharmaceuticals and personal care products (PPCPs) are increasingly being scrutinized by the scientific community due to their environmental persistence. Therefore, the development of novel environmentally compatible and energy-efficient technologies for their removal is highly anticipated. In this work, a novel metal-free photocatalytic nanoreactor was successfully synthesized by anchoring carbon dots to hollow carbon nitride nanospheres (HCNS/CDs). The unique structure of these hollow nanospherical HCNS/CDs hybrids endowed them with a high population of reactive sites, while enhancing optical absorption due to internal light reflection. Simultaneously, the CDs served as “artificial antennas” to absorb and convert photons with low energy, due to their superior up-converting properties. Consequently, the HCNS/CDs demonstrated excellent photodegradation activities for the degradation of PPCPs under broad-spectrum irradiation. Remarkedly, 10 mg/L of naproxen (NPX) was completely degraded following 5 min of natural solar irradiation. It was further revealed that the O2•- played a significant role during the photocatalytic process, which could lead to the decomposition of NPX. The effects of natural water matrices and the degradation of trace PPCPs further supported that this photocatalytic system may be efficaciously applied for the remediation of PPCPs contamination in ambient waterways.

Building MOF Nanocomposites with Oxidized Graphitic Carbon Nitride Nanospheres: The Effect of Framework Geometry on the Structural Heterogeneity.

Composite of two MOFs, copper-based Cu-BTC (HKUST-1) and zirconium-based Zr-BDC (UiO-66), with oxidized graphitic carbon nitride nanospheres were synthesized. For comparison, pure MOFs were also obtained. The surface features were analyzed using x-ray diffraction (XRD), sorption of nitrogen, thermal analysis, and scanning electron microscopy (SEM). The incorporation of oxidized g-C3N4 to the Cu-BTC framework caused the formation of a heterogeneous material of a hierarchical pores structure, but a decreased surface area when compared to that of the parent MOF. In the case of UiO-66, functionalized nanospheres were acting as seeds around which the crystals grew. Even though the MOF phases were detected in both materials, the porosity analysis indicated that in the case of Cu-BTC, a collapsed MOF/nonporous and amorphous matter was also present and the MOF phase was more defectous than that in the case of UiO-66. The results suggested different roles of oxidized g-C3N4 during the composite synthesis, depending on the MOF geometry. While spherical units of UiO-66 grew undisturbed around oxidized and spherical g-C3N4, octahedral Cu-BTC units experienced geometrical constraints, leading to more defects, a disturbed growth of the MOF phase, and to the formation of mesopores at the contacts between the spheres and MOF units. The differences in the amounts of CO2 adsorbed between the MOFs and the composites confirm the proposed role of oxidized g-C3N4 in the composite formation.

Defectous UiO-66 MOF Nanocomposites as Reactive Media of Superior Protection against Toxic Vapors

The composites of UiO-66 with nanographite or oxidized graphitic carbon nitride nanospheres (∼10 wt %) were synthesized and used as CEES decontamination media from a vapor phase. The materials were characterized using XRD, nitrogen adsorption, SEM, potentiometric titration, FTIR, and thermal analysis. The results showed a marked improvement of the detoxification capability against the vapors of CEES compared to those of pristine UiO-66, either in terms of the amount adsorbed or surface reactivity. The maximum weight uptake for the composites reached 632 mg g-1, which was higher than that on UiO-66. The improved adsorption and catalytic activity were linked to the new interface between the modifiers and MOF units/defects, which provided additional active sites formed as a result of modifiers' surface groups acting as MOF linkers. The morphology and porosity were also altered, positively affecting the sites' accessibility and their dispersion in the MOF particles. Dehydrohalogenation and oxidation were the predominant pathways of the composites' surface reactivity. The detoxification mechanisms involving CEES vapor-UiO-66 surface interactions differ from those reported for CEES liquid/dissolved liquid-UiO-66 interactions, and dehydrohalogenation, fragmentation, and oxidation predominate.

Cover Feature: Polydopamine and Barbituric Acid Co‐Modified Carbon Nitride Nanospheres for Highly Active and Selective Photocatalytic CO2 Reduction (Eur. J. Inorg. Chem. 15/2019)

Cover Feature: Polydopamine and Barbituric Acid Co‐Modified Carbon Nitride Nanospheres for Highly Active and Selective Photocatalytic CO₂ Reduction (Eur. J. Inorg. Chem. 15/2019)

Plasmonic AuPd-based Mott-Schottky photocatalyst for synergistically enhanced hydrogen evolution from formic acid and aldehyde

Plasmonic AuPd alloy nanoparticles supported on super small carbon nitride nanospheres (AuxPdy/CNS) for the design of Mott-Schottky catalysts were successfully synthesized and further applied for the photocatalytic hydrogen evolution from formic acid. A high turnover frequency (TOF) value of 1017.8 h−1 was obtained for the AuPd/CNS catalyst under visible-light irradiation (λ > 420 nm) at 298 K. XPS analysis, photoelectrochemical characterization and density functional theory (DFT) calculation indicate that the remarkable photocatalytic activities are mainly attributed to the optimized electronic structure of Pd in the AuPd/CNS composite resulting from the alloying, plasmonic and Mott-Schottky effects. These effects can efficiently accelerate the electron transfer from photoresponsive super small carbon nitride nanospheres and plasmonic Au to the active Pd sites. We also infer that the alloying effect is the main factor on the high activity, which is mainly due to weakened adsorption of hydrogen atoms on Pd sites according to the DFT calculation. Moreover, the Mott-Schottky AuPd/CNS catalyst presents a good universality for the photocatalytic hydrogen evolution from a series of aldehyde aqueous solutions.

Mitochondria and Nuclei Dual-Targeted Hollow Carbon Nanospheres for Cancer Chemophotodynamic Synergistic Therapy.

Dual-targeted nanoparticles are gaining increasing importance as a more effective anticancer strategy by attacking double key sites of tumor cells, especially in chemophotodynamic therapy. To retain the nuclei inhibition effect and enhance doxorubicin (DOX)-induced apoptosis by mitochondrial pathways simultaneously, we synthesized the novel nanocarrier (HKH) based on hollow carbon nitride nanosphere (HCNS) modified with hyaluronic acid (HA) and the mitochondrial localizing peptide D[KLAKLAK]2 (KLA). DOX-loaded HKH nanoparticles (HKHDs) showed satisfactory drug-loading efficiency, excellent solubility, and very low hemolytic effect. HA/CD44 binding and electrostatic attraction between positively charged KLA and A549 cells facilitated HKHD uptake via the endocytosis mechanism. Acidic microenvironment, hyaluronidase, and KLA targeting together facilitate doxorubicin toward the mitochondria and nuclei, resulting in apoptosis, DNA intercalation, cell-cycle arrest at the S phase, and light-induced reactive oxygen species production. Intravascular HKHD inhibited tumor growth in A549-implanted mice with good safety. The present study, for the first time, systemically reveals biostability, targetability, chemophotodynamics, and safety of the functionalized novel HKHD.

C3N4-digested 3D construction of hierarchical metallic phase MoS2 nanostructures

Metallic MoS2 with a controllable hierarchical spherical structure has been achieved via a hydrothermal strategy by using the carbon nitride nanospheres as a self-sacrificed template.

Nanopore enriched hollow carbon nitride nanospheres with extremely high visible-light photocatalytic activity in the degradation of aqueous contaminants of emerging concern

Nanopore enriched hollow carbon nitride nanospheres exhibit extremely high visible-light photocatalytic activity in the degradation of aqueous contaminants of emerging concern.

Polydopamine and Barbituric Acid Co‐Modified Carbon Nitride Nanospheres for Highly Active and Selective Photocatalytic CO2 Reduction

Carbon nitride nanospheres modified with polydopamine and barbituric acid (BA‐CNS‐PDA) were successfully prepared by following a template‐copolymerization and post‐modification strategy. The photocatalytic CO2 reduction was carried out using BA‐CNS‐PDA as photocatalyst, Co(bpy)32+ as the cocatalyst and TEOA as the sacrificial electron donor. The productivity and selectivity for photocatalytic reduction of CO2 to CO on BA20‐CNS‐PDA15 under visible‐light for 4 h were measured to be 158 µmol and 86.0 %, respectively, and are nearly 5 and 1.5 times, respectively, that of unmodified CNS. Optical characterization indicates that the outstanding photocatalytic CO2 reduction performance is a result of improved charge separation and transfer due to copolymerization with barbituric acid and enhanced visible light absorption due to polydopamine. The adsorption isotherm of CO2 demonstrates that polydopamine increase CO2 adsorption capacity and promote CO2 activation due to the presence of the amino groups.

Cyano-rich mesoporous carbon nitride nanospheres for visible-light-driven photocatalytic degradation of pollutants

Visible-light-responsive photocatalysis offers exciting opportunities for sustainable environmental pollution control, but the unsatisfactory photoactivity of the existing photocatalysts impedes its practical application.

Super Small Polymeric Carbon Nitride Nanospheres with Core‐Shell Structure for Photocatalysis

AbstractNovel uniform super small carbon nitride nanospheres with core‐shell structure were prepared in a one step procedure by using SiO2 hollow nanospheres as hard templates. The as‐prepared carbon nitride nanospheres with the average size of 20 nm displayed enhanced activities and durability in photocatalytic hydrogen production and the degradation of methyl orange (MO), compared to the conventional carbon nitride with bulky morphology under visible light (λ > 420 nm) irradiation. The enhancement is attributed to the nano‐scaled carbon nitride spheres with unique core‐shell structures and large surface areas, which facilitate the photogenerated charge separation and fast transport.

Ultrathin MoS2 sheets supported on N-rich carbon nitride nanospheres with enhanced lithium storage properties

Deciphering the structural and volume changes occurring during electrode reactions in lithium-ion batteries is perhaps a boon for high energy density batteries. Here, we report the synthesis of 3D network of dichalcogenide molybdenum disulfide (MoS2) encapsulated over nitrogen rich graphitic carbon nitride nanosphere (g-C3N4) forming an interconnected and uniform g-C3N4/MoS2 scaffolds. The crystallinity, phase purity, morphological features and elemental composition were evaluated through XRD, FESEM, TEM, HRTEM, BET and XPS analyses. The electrochemical properties of N-rich g-C3N4/MoS2 scaffolds were investigated as potential anode materials for lithium-ion batteries. Electrochemical testing of the g-C3N4/MoS2 constructured electrode delivered reversible capacity of 857mAhg−1at 0.1C rate after fifty cycles and exhibited a high rate performance with reversible capacity of 383mAhg−1 at 10C rate (higher than theoretical capacity of graphite, 372mAhg−1). The superior electrochemical property of g-C3N4/MoS2 is attributed to N-rich carbon support which favors better electronic conductivity, and affords more sites for Li+ ions. The nitrogen rich carbon nitride accommodates volume changes caused during repeated charge/discharges and maintains high structural integrity and specific capacity.

Oxidized g-C3 N4 Nanospheres as Catalytically Photoactive Linkers in MOF/g-C3 N4 Composite of Hierarchical Pore Structure.

A unique composite of the copper-based metal-organic framework (Cu-benzene tricarboxylic acid (BTC)) with oxidized graphitic carbon nitride nanospheres is synthesized. For comparison, a hybrid material consisting of g-C3 N4 and Cu-BTC is also obtained. Their surface features are analyzed using Fourier transform infrared spectroscopy, X-ray diffraction, sorption of nitrogen, thermal analysis, scanning electron microscopy, photoluminescence, and diffuse reflectance UV-Vis spectroscopy. The results suggest that the formed nanospheres of oxidized g-C3 N4 act as linkers between the copper sites, playing a crucial role in the composite building process. Their incorporation to the Cu-BTC framework causes the development of new mesoporosity. Remarkable alterations in the optical properties, as a result of the coordination of oxygen containing functional groups of the oxidized graphitic carbon nitride to the copper atoms of the framework, suggest an increase in photoreactivity. On the other hand, for the hybrid material consisting of Cu-BTC and g-C3 N4 , the unaltered pore volume and optical properties support the formation of a physical mixture rather than of a composite. The tests on reactive adsorption and detoxification of G-series organophosphate nerve agent surrogate show the enhanced performance of the composite as catalysts and photocatalyst in visible light.

Hollow porous carbon nitride immobilized on carbonized nanofibers for highly efficient visible light photocatalytic removal of NO.

With the deterioration of air quality, great efforts were devoted to designing various photocatalysts for effective removal of NOx in air. However, the present photocatalysts have a fatal problem of low photocatalytic efficiency. In this work, a hollow porous carbon nitride nanosphere coupled with reduced graphene oxide (HCNS/rGO) was exploited as a visible-light photocatalyst to remove nitrogen monoxide in air at a low concentration (600 ppb level) under irradiation of an energy saving lamp. HCNS/rGO showed a NO removal ratio of 64%, which was superior to that of most other visible-light photocatalysts. The excellent photocatalytic ability of HCNS/rGO originates from the hollow porous morphology of HCNS and the grafted rGO on the surface. HCNS/rGO was immobilized on porous carbonized polymer nanofibers to obtain a photocatalytic membrane without affecting photocatalytic efficiency. Furthermore, the membrane showed excellent photochemical stability and recyclability.

A graphitic hollow carbon nitride nanosphere as a novel photochemical internalization agent for targeted and stimuli-responsive cancer therapy.

As a novel technique, photochemical internalization (PCI) has been employed as a new approach to overcome endo/lysosomal restriction, which is one of the main difficulties in both drug and gene delivery. However, the complicated synthesis procedure (usually requiring the self-assembly of polymers, photosensitizers and cargos) and payload specificity greatly limit its further application. In this paper, we employ a highly fluorescent graphitic hollow carbon nitride nanosphere (GHCNS) to simultaneously serve as a PCI photosensitizer, an imaging agent and a drug carrier. The surface modification of GHCNS with multifunctional polysaccharide hyaluronic acid (HA) endows the system with colloidal stability, biocompatibility and cancer cell targeting ability. After CD44 receptor-mediated endocytosis, the nanosystem is embedded in endo/lysosomal vesicles and HA could be specially degraded by hyaluronidase (Hyal), inducing open pores. In the following, with visible light illumination, GHCNS could produce ROS that effectively induced lipid peroxidation and caused endo/lysosomal membrane break, accelerating the cytoplasmic release of the drug in the targeted and irradiated cells. As a result, significantly increased therapeutic potency and specificity against cancer cells could be achieved.