Carbon Nitride Nanotubes Research Articles

Surface-Controlled Water Flow in Nanotube Membranes.

The independent effect of nanotube surface chemistry and structure on the flow of water under nanoscale confinement is demonstrated in this paper for the first time via the synthesis of novel carbon nitride nanotube (CNNT) membranes. Using a combination of experiments and high-fidelity molecular dynamics (MD) simulations, it is shown here that the hydrophilization of the sp2 carbon structure, induced by the presence of the C-N bonds, decreases the pure water permeance in CNNTs when compared with pristine and turbostratic carbon nanotubes (CNTs). The MD simulations are based on a model true to the chemical structure of the synthesized nanotubes, built from spectroscopy measurements and calibrated potentials using droplet experiments. The effect on permeance is explained in terms of solid-liquid interactions at the nanotube wall with increased water viscosity and decreased surface diffusion near the CNNT wall, when compared to CNTs. A model directly linking the solid-liquid interactions to the water permeance is presented, showing good agreement with both experiments and MD simulations. This work opens the way to tailoring surface chemistry and structure inside nanotube membranes for a wide range of transport and separation processes.

Tunable Type I and II heterojunction of CoOx nanoparticles confined in g-C3N4 nanotubes for photocatalytic hydrogen production

This work reports tunable heterojunction architectures of cobalt oxides (CoOx) nanoparticles confined on well-arrayed graphitic carbon nitride nanotubes (C3N4 NTs) by using a facile one-pot method but under different annealing atmospheres. A Type II heterojunction of cobalt monoxide nanoparticles (CoO NPs)/C3N4 NTs was obtained after annealing under vacuum, and fine CoO NPs less than 8 nm in size were homogeneously anchored on the surface of C3N4 NTs. A Type I heterojunction of tricobalt tetraoxide (Co3O4)/C3N4 NTs were formed under air condition, and Co3O4 NPs in the size range of 20 to 80 nm were aggregated on the surface. The photocatalytic activities of these two heterojunctions were evaluated with hydrogen production from water splitting. The strategically developed CoO/C3N4 NTs with a 7 wt. % CoO shows the highest H2 yield under visible light irradiation and the best stability among the photocatalysts studied in this work. Comprehensive characterization results reveal that the superior performance of CoO/C3N4 NTs may be attributed to the uniformly distributed smaller nanoparticles on the well-arrayed nanotubes, the longer lifetime of excited electrons, the faster charge transfer and the stronger electronic interaction between the heterojunctions. Our Kelvin probe force microscopy results firmly verify that the CoO/C3N4 NT and Co3O4/C3N4 NT nanocomposites form a Type II and Type I heterojunction, respectively, and charge transfer pathways and reaction mechanisms are therefore established.

Localized Surface Plasmon Resonance Enhanced Photocatalytic Hydrogen Evolution via Pt@Au NRs/C3N4 Nanotubes under Visible‐Light Irradiation

AbstractAu nanorods (NRs) decorated carbon nitride nanotubes (Au NRs/CNNTs) photocatalysts have been designed and prepared by impregnation–annealing approach. Localized surface plasmon resonance (LSPR) peaks of Au NRs can be adjusted by changing the aspect ratios, and the light absorption range of Au NRs/CNNTs is extended to longer wavelength even near‐infrared light. Optimal composition of Pt@Au NR769/CNNT650 has been achieved by adjusting the LSPR peaks of Au NRs and further depositing Pt nanoparticles (NPs), and the photocatalytic H2 evolution rate is 207.0 µmol h−1 (20 mg catalyst). Preliminary LSPR enhancement photocatalytic mechanism is suggested. On one hand, LSPR of Au NRs is beneficial for visible‐light utilization. On the other hand, Pt NPs and Au NRs have a synergetic enhancement effect on photocatalytic H2 evolution of CNNTs, in which the local electromagnetic field can improve the photogenerated carrier separation and direct electron transfer increases the hot electron concentration while Au NRs as the electron channel can well restrain charge recombination, finally Pt as co‐catalyst can boost H+ reduction rate. This work provides a new way to develop efficient photocatalysts for splitting water, which can simultaneously extend light absorption range and facilitate carrier generation, transportation and reduce carrier recombination.

A review on positive and negative impacts of nanotechnology in agriculture

Nanotechnology holds huge potentials in several fields and is envisaged as a technology to lead the way toward sustainable environment-friendly development in the coming years. The basic theme of nanotechnology is to use particles having size in nanometer range for various applications in medical fields, cosmetics industry, and agriculture and food technologies. The benefits associated with nanotechnology include among others increase in yield and quality of produce in agriculture, improved cosmetic products, directed delivery of medicines and sensor applications. Advancement in the development of nanosensors has made recognition of disease causing elements, toxins and nutrients in foods, and elements in environmental samples, easier and cost effective. However, immense focus on nanotechnology in past few decades has led to its unrestricted development and consequently enormous use of nanoparticles (NPs). It is considered that NPs may pose risks to the environment and biological systems. It is also becoming evident that the size, structure and type of nanomaterials, such as graphene/graphene oxide with gold NPs, carbon and carbon nitride nanotubes, have different effects on plants and environment. Hence, long-term life cycle analyses are needed to assess impacts of NPs. This review presents a brief overview of applications of nanomaterials in agriculture and discusses its positive and negative aspects in agricultural field. The review emphasizes that future development of nanotechnology must be based on scientific evaluations of benefits and risks associated to it in long term.

Bimetallic PtNi/g-C3N4 nanotubes with enhanced photocatalytic activity for H2 evolution under visible light irradiation

Bimetallic PtNi-decorated graphitic carbon nitride (g-C3N4) nanotubes were prepared through calcining the mixture of urea and thiourea in the presence of Pluronic F127, followed by deposition of bimetallic PtNi nanoparticles (NPs) via chemical reduction. It is found that the photocatalytic activity of PtNi/g-C3N4 nanotubes is strongly dependent on the molar ratio of Pt/Ni and the highest activity is observed for Pt1Ni1/g-C3N4. Under visible light (λ > 420 nm) irradiation, the H2 generation rate over Pt1Ni1/g-C3N4 nanotubes is 104.7 μmol h−1 from a triethanolamine (10 vol%) aqueous solution, which is higher than that of Pt/g-C3N4 nanotubes (98.6 μmol h−1) and is about 47.6 times higher than that of pure g-C3N4 nanotubes. The cyclic photocatalytic reaction indicates that our Pt1Ni1/g-C3N4 nanotubes function as a stable photocatalyst for visible light-driven H2 production. The effect of bimetallic PtNi NPs in the transfer and separation of photogenerated charge carriers occurring in the excited g-C3N4 nanotubes was investigated by performing photo-electrochemical and photoluminescence measurements. Our results reveal that bimetallic PtNi could replace Pt as a promising cocatalyst for photocatalytic H2 evolution with better performance and lower cost.

Wall-Mesoporous Graphitic Carbon Nitride Nanotubes for Efficient Photocatalytic Hydrogen Evolution.

Graphitic carbon nitride (g-CN) has attracted tremendous attention as visible-light photocatalyst. However, for further improving the catalytic activity, multilevel and hierarchical nanostructuring of g-CN is highly desirable to effectively expose active sites and facilitate separation and migration of photoexciteded charge carriers for largely enhanced photocatalytic behavior. Here, we prepare wall-mesoporous graphitic carbon nitride nanotubes (g-CNNTs) by in situ annealing of urea microrod arrays preformed in virtue of a vertical gradient freeze growth (VGFG) method. Benefiting from the distinctive structural features, the hierarchical g-CNNTs exhibit a high photocatalytic H2 production rate of 8789 μmol h-1 g-1 with an excellent apparent quantum yield of 6.3 % under visible-light irradiation and long-term cycling stability. This work provides a facile and eco-friendly strategy to prepare a new type of carbon nitride-based nanostructural material for photocatalysis and environmental remediation.

Photocatalytic self-cleaning carbon nitride nanotube intercalated reduced graphene oxide membranes for enhanced water purification

Crumpled laminar nanostructures with nanoscale water transport channels constructed by two-dimensional (2D) reduced graphene oxide nanosheets (rGO NS) have been considered as a promising membrane separation layer for water purification. However, efficient tuning of rGO laminar structures with enhanced membrane performance remains challenging. In this work, we report a novel 1D graphitic carbon nitride nanotube (g-C3N4 NT) intercalated rGO nanofiltration (NF) membrane with enhanced photo-induced self-cleaning performance. The g-C3N4 NT photocatalyst could not only enlarge the rGO interlayer spacing for improved water permeability, but also endow the composite membrane with visible-light photocatalytic activity for efficient removal of organic dyes from polluted water. Our g-C3N4 NT/rGO membrane exhibits superior water permeability (4.87 L·m−2·h−1·bar−1) and synergetic Rhodamine B (RhB) removal rate (>98%) for long-term operation, compared with pristine rGO membrane and 2D g-C3N4 NS intercalated rGO membrane prepared by the same method. The RhB removal mechanism on the as-prepared composite membranes under integrated photocatalytic filtration process is presented. Our findings offer new insights into designing and tuning laminar structures of photocatalytic graphene-based NF membranes for enhanced water purification.

Synthesis and Characterization of Graphitic Carbon Nitride Nanotubes Using Porous Anodic Alumina Templates

In the present paper, we reported the preparation of Graphitic carbon nitride (GCN) nanotubes using porous anodic aluminium oxide membranes as templates through thermal condensation of cynamide at 500 °C. Structural analysis of synthesized nanotubes was systematically carried out by scanning electron microscope (SEM), X-ray powder diffraction (XRD) and results confirmed the growth of GCN inside the nanochannels of anodic alumina templates. Optical features of GCN were carried out using UV visible spectroscopy and photoluminescence. PL analysis showed that a strong emission peak occurs in the wavelength range of 350–600 nm in blue region. Thermal behaviour of GCN was studied using differential scanning calorimetry (DSC).

Phosphorus Doped Carbon Nitride Nanotubes by Sequential Cation-Exchanging Reaction with Enhanced Photocatalytic Hydrogen Evolution

In this work, a novel and facile sequential cation-exchanging strategy was developed to synthesize phosphorus doped g-C3N4 nanotubes, and resulted nanotubes were composed of small nanorods with length of several hundred nanometers by oriented aggregation. As obtained products exhibit greatly enhanced photocatalytic hydrogen evolution with rate of 4.59 mmol h-1 g-1, which is 16 times higher than that of the bulk g-C3N4 under visible light irradiation. Mechanism investigation reveals that the superior photocatalytic property could be attributed to its improved visible light absorbance, well suppressed charges recombination and nanostructural construction.

The Activation of Methane on Ru, Rh, and Pd Decorated Carbon Nanotube and Boron Nitride Nanotube: A DFT Study

Methane decomposition catalyzed by an Ru, Rh, or Pd atom supported on a carbon or boron nitride nanotubes was analyzed by means of the density functional theory with the M06-L hybrid functional. The results suggested that the dissociative reaction of methane was a single-step mechanism. Based on the calculated activation energy, the Ru-decorated carbon nanotube showed superior catalytic activity with an activation barrier of 14.5 kcal mol−1, followed by the Rh-decorated carbon nanotube (18.1 kcal mol−1) and the Pd-decorated carbon nanotube (25.6 kcal mol−1). The catalytic performances of metals supported on a boron nitride nanotube were better than those on a carbon nanotube. The total activation barrier for the Ru, Rh, and Pd atoms on boron nitride nanotube was 10.2, 14.0, and 20.5 kcal mol−1, respectively. Dissociative adsorption complexes on the Ru–boron nitride nanotube were the most stable. The anionic state of the supported metal atom was responsible for decreasing the activation energy of methane decomposition. Our finding provides a crucial point for further investigation.

Optical Properties of Dyes Confined into Carbon and Boron Nitride Nanotubes for Multimodal Bio-Imaging

Nanotubes attracted a lot of interest as 1D nano-porous materials for the encapsulation and aggregation control of organic dyes molecules. Indeed, the 1D confinement drives the stacking of the molecules inside and enables original aggregation effects on their optical properties (1,2). When encapsulated inside carbon nanotube, organics dyes such as 6T, exhibits for example a strong and specific Raman scattering but their luminescence is efficiently quenched by the nanotube (3). Here we show that the same dyes, when encapsulated inside boron nitride nanotubes (6T@BNNT) exhibits strong luminescence (4). Photoluminescence imaging experiments on individualized 6T@BNNT show that the encapsulation also circumvent the photobleaching issue over days under continuous photo-excitation. Finally we show that these hybrid materials, with specific luminescence and/or Raman fingerprints, can act as robust nanoprobes with reduced toxicity in living system such as Daphnia Pulex, for multimodal imaging from the visible to the near infrared range. (4) (1) E. Gaufrès et al Nature Photon. (2014) (2) S. Cambré et al Nature Nano (2015) (3) E. Gaufrès et al ACS Nano (2016) (4) E. Gaufrès et al (submitted)

A selective ion replacement strategy for the synthesis of copper doped carbon nitride nanotubes with improved photocatalytic hydrogen evolution

Developing new strategy to efficiently improve the photocatalytic activity of graphitic carbon nitride (g-C3N4) for hydrogen evolution is critical for its application in solar energy utilization. In this work, an innovative selective cation replacement process is developed to synthesize copper doped g-C3N4 nanotubes driven by the ion–dipole interaction of metal ions in g-C3N4. The tri-s-triazine units may act as stable frameworks in the sequential cation exchange reaction process, which subsequently leads to the formation of Cu doped g-C3N4 with high specific surface area and nanotube structures. The obtained g-C3N4 exhibits greatly enhanced visible-light-driven hydrogen evolution of 3.02 mmol h−1 g−1, which is about 13 times higher than that of pristine one. Detailed characterization reveals the underlying mechanism of the improved photocatalytic performance on the newly developed g-C3N4, which can provide valuable guides to rationally design new efficient photocatalysts.

Halloysite-derived mesoporous g-C3N4 nanotubes for improved visible-light photocatalytic hydrogen evolution

Abstract Hydrogen evolution via visible-light photocatalytic water splitting is an ideal solution to the worldwide energy and environmental crisis, while the key challenge is to develop efficient and cheap photocatalysts. Here, mesoporous graphitic carbon nitride (g-C3N4) nanotubes were synthesized using modified halloysite as template via a facial vapor deposition method. The halloysite-derived mesoporous g-C3N4 nanotubes exhibited an excellent photocatalytic hydrogen evolution efficiency of 633 μmol g−1 h−1 under visible light irradiation, which was 14.3 times that of bulk g-C3N4. The improvement of photocatalytic activity mainly benefits from the enlarged specific surface area and the reduced recombination rate of photoinduced electron-hole pairs of the mesoporous g-C3N4 nanotubes. The strategy established here may be valuable for synthesizing efficient g-C3N4 photocatalysts with other tailor nanostructures utilizing diverse raw clay minerals.

Sodium-doped carbon nitride nanotubes for efficient visible light-driven hydrogen production

Sodium-doped carbon nitride nanotubes (Na x -CNNTs) were prepared by a green and simple two-step method and applied in photocatalytic water splitting for the first time. Transmission electron microscopy (TEM) element mapping and X-ray photoelectron spectroscopy (XPS) measurements confirm that sodium was successfully introduced in the carbon nitride nanotubes (CNNTs), and the intrinsic structure of graphitic carbon nitride (g-C3N4) was also maintained in the products. Moreover, the porous structure of the CNNTs leads to relatively large specific surface areas. Photocatalytic tests indicate that the porous tubular structure and Na+ doping can synergistically enhance the hydrogen evolution rate under visible light (λ > 420 nm) irradiation in the presence of sacrificial agents, leading to a hydrogen evolution rate as high as 143 μmol·h−1 (20 mg catalyst). Moreover, other alkali metal-doped CNNTs, such as Li x -CNNTs and K x -CNNTs, were tested; both materials were found to enhance the hydrogen evolution rate, but to a lower extent compared with the Na x -CNNTs. This highlights the general applicability of the present method to prepare alkali metal-doped CNNTs; a preliminary mechanism for the photocatalytic hydrogen evolution reaction in the Na x -CNNTs is also proposed.

Bimetallic Ag-Cu Supported on Graphitic Carbon Nitride Nanotubes for Improved Visible-Light Photocatalytic Hydrogen Production.

This work, for the first time, reports visible-light active bare graphitic carbon nitride nanotubes (C3N4 NTs) for photocatalytic hydrogen generation, even in the absence of any cocatalyst. Upon uniform dispersion of the cocatalysts, Ag-Cu nanoparticles, on the well-ordered bare C3N4 NTs, they exhibit twice the H2 evolution rate of the bare C3N4 NTs. The improved activity is attributed to their unique tubular nanostructure, strong metal-support interaction, and efficient photoinduced electron-hole separation compared to their bare and monometallic counterparts, evidenced by complementary characterization techniques. This work reveals that the H2 production rates correlate well with the oxidation potentials of the sacrificial reagents used. Triethylamine (TEA) outperforms other sacrificial reagents, including triethanolamine (TEOA) and methanol. Mechanistic studies on the role of various sacrificial reagents in photocatalytic H2 generation demonstrate that irreversible photodegradation of TEA into diethylamine and acetaldehyde via monoelectronic oxidation contributes to the improved H2 yield. Similarly, TEOA is oxidized to diethanolamine and glycolaldehyde, whereas methanol is unable to quickly capture the photoinduced holes and remains intact due to the low oxidation potential.

Electrochemical sensing of ractopamine by carbon nitride nanotubes/ionic liquid nanohybrid in presence of other β-agonists

Ractopamine (RAC) is an important β-agonist. It improves the growth rate and reduces the fat for animals. It is also utilized as nutrient repartitioning agent. Nonetheless, it is not licensed in many countries and RAC is dangerous for human health when it is used illegally. Thus, the development of the sensitive analytical methods for real samples is crucial. Carbon nitride nanotubes (C3N4NTs)/ionic liquid (ILs) nanocomposite was firstly synthesized for RAC detection in this study. n-hexyl-3-methylimidazolium hexafluoro phosphate was used as ionic liquid. The formation of the surfaces was characterized by scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and x-ray photoelectron spectroscopy (XPS). The linearity range and the detection limit (LOD) for RAC were calculated as 1.0 × 10−9–1.0 × 10−12 M and 1.0 × 10−13 M, respectively.

Phosphorus-Doped Graphitic Carbon Nitride Nanotubes with Amino-rich Surface for Efficient CO2 Capture, Enhanced Photocatalytic Activity, and Product Selectivity.

Phosphorus-doped graphitic carbon nitrides (P-g-C3N4) have recently emerged as promising visible-light photocatalysts for both hydrogen generation and clean environment applications because of fast charge carrier transfer and increased light absorption. However, their photocatalytic performances on CO2 reduction have gained little attention. In this work, phosphorus-doped g-C3N4 nanotubes are synthesized through the one-step thermal reaction of melamine and sodium hypophosphite monohydrate (NaH2PO2·H2O). The phosphine gas generated from the thermal decomposition of NaH2PO2·H2O induces the formation of P-g-C3N4 nanotubes from g-C3N4 nanosheets, leads to an enlarged BET surface area and a unique mesoporous structure, and creates an amino-rich surface. The interstitial doping phosphorus also down shifts the conduction and valence band positions and narrows the band gap of g-C3N4. The photocatalytic activities are dramatically enhanced in the reduction both of CO2 to produce CO and CH4 and of water to produce H2 because of the efficient suppression of the recombination of electrons and holes. The CO2 adsorption capacity is improved to 3.14 times, and the production of CO and CH4 from CO2 increases to 3.10 and 13.92 times that on g-C3N4, respectively. The total evolution ratio of CO/CH4 dramatically decreases to 1.30 from 6.02 for g-C3N4, indicating a higher selectivity of CH4 product on P-g-C3N4, which is likely ascribed to the unique nanotubes structure and amino-rich surface.

Buckling and vibration analyses of MGSGT double-bonded micro composite sandwich SSDT plates reinforced by CNTs and BNNTs with isotropic foam & flexible transversely orthotropic cores

Because of sandwich structures with low weight and high stiffness have much usage in various industries such as civil and aerospace engineering, in this article, buckling and free vibration analyses of coupled micro composite sandwich plates are investigated based on sinusoidal shear deformation (SSDT) and most general strain gradient theories (MGSGT). It is assumed that the sandwich structure rested on an orthotropic elastic foundation and make of four composite face sheets with temperature-dependent material properties that they reinforced by carbon and boron nitride nanotubes and two flexible transversely orthotropic cores. Mathematical formulation is presented using Hamilton\'s principle and governing equations of motions are derived based on energy approach and applying variation method for simply supported edges under electro-magneto-thermo-mechanical, axial buckling and pre-stresses loadings. In order to predict the effects of various parameters such as material length scale parameter, length to width ratio, length to thickness ratio, thickness of face sheets to core thickness ratio, nanotubes volume fraction, pre-stress load and orthotropic elastic medium on the natural frequencies and critical buckling load of double-bonded micro composite sandwich plates. It is found that orthotropic elastic medium has a special role on the system stability and increasing Winkler and Pasternak constants lead to enhance the natural frequency and critical buckling load of micro plates, while decrease natural frequency and critical buckling load with increasing temperature changes. Also, it is showed that pre-stresses due to help the axial buckling load causes that delay the buckling phenomenon. Moreover, it is concluded that the sandwich structures with orthotropic cores have high stiffness, but because they are not economical, thus it is necessary the sandwich plates reinforce by carbon or boron nitride nanotubes specially, because these nanotubes have important thermal and mechanical properties in comparison of the other reinforcement.

Phenylethanolamine A (PEA) Imprinted Polymer on Carbon Nitride Nanotubes/Graphene Quantum Dots/Core-Shell Nanoparticle Composite for Electrochemical PEA Detection in Urine Sample

Phenylethanolamine A (PEA) is used illegally and deposited in animal tissues. Due to the reason, it causes acute poisoning and symptoms of muscular tremors, nervousness. In present article, Ru@Au core-shell nanoparticles (Ru@Au NPs) involved in carbon nitride nanotubes (C3N4 NTs) functionalized graphene quantum dots (GQDs) nanocomposite based molecular imprinted polymer (MIP) was formed for PEA recognition. Firstly, C3N4 NTs@GQDs nanocomposite was prepared by means of hydrothermal treatment. Secondly, this nanocomposite was functionalized with 2-aminoethanethiol (AET) via the affinity of gold-sulfur for binding Ru@Au NPs. After that, PEA imprinted voltammetric sensor was prepared in presence of 100.0 mM phenol as monomer containing 25.0 mM PEA by cyclic voltammetry (CV). All nanomaterials’ formation and properties were highlighted with scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray analysis (EDX), raman spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). 1.0 × 10−12 - 1.0 × 10−9 M and 2.0 × 10−13 M were founded as the linearity range and the detection limit (LOD). Finally, PEA imprinted glassy carbon electrode (GCE) was used for urine sample analysis in presence of the other competitor agents such as clenbuterol (CLE), ractopamine (RAC) and salbutamol (SAL). In addition, the stability and repeatability of prepared sensor was investigated.

Structural transformations of carbon and boron nitride nanoscrolls at high impact collisions.

The behavior of nanostructures under high strain-rate conditions has been the object of theoretical and experimental investigations in recent years. For instance, it has been shown that carbon and boron nitride nanotubes can be unzipped into nanoribbons at high-velocity impacts. However, the response of many nanostructures to high strain-rate conditions is still unknown. In this work, we have investigated the mechanical behavior of carbon (CNS) and boron nitride nanoscrolls (BNS) colliding against solid targets at high velocities, using fully atomistic reactive (ReaxFF) molecular dynamics (MD) simulations. CNS (BNS) are graphene (boron nitride) membranes rolled up into papyrus-like structures. Their open-ended topology leads to unique properties not found in their close-ended analogs, such as nanotubes. Our results show that collision products are mainly determined by impact velocities and by two orientation angles, which define the position of the scroll (i) axis and (ii) open edge relative to the target. Our MD results showed that for appropriate velocities and orientations, large-scale deformations and nanoscroll fractures could occur. We also observed unscrolling (scrolls going back to quasi-planar membranes), scroll unzipping into nanoribbons, and significant reconstruction due to breaking and/or formation of new chemical bonds. For particular edge orientations and velocities, conversion from open to close-ended topology is also possible, due to the fusion of nanoscroll walls.