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1.
A dual‐emission ratiometric fluorescent sensing film for metal ion detection is designed. This dual‐emission film is successfully prepared from chitosan, graphitic carbon nitride (g‐C3N4), and gold nanoclusters (Au NCs). Here, it is shown that the g‐C3N4 not only serves as the fluorescence emission source, but also enhances the mechanical and thermal stability of the film. Meanwhile, the Au NCs are adsorbed on the surface of chitosan film by the electrostatic interaction. The as‐prepared dual‐emission film can selectively detect Cu2+, leading to the quench of red fluorescence of Au NCs, whereas the blue fluorescence from g‐C3N4 persists. The ratio of the two fluorescence intensities depends on the Cu2+ concentration and the fluorescence color changes from orange red to yellow, cyan, and finally to blue with increasing Cu2+ concentration. Thus, the as‐prepared dual‐emission film can be worked as ratiometric sensing paper for Cu2+ detection. Furthermore, the film shows high sensitivity and selectivity, with low limit of detection (LOD) (10 ppb). It is observed that this novel gold‐cluster‐based dual‐emission ratiometric fluorescent sensing paper is an easy and convenient way for detecting metal ions. It is believed that this research work have created another avenue for the detection of metal ions in the environment.  相似文献   

2.
The fabrication of well-ordered nanoporous graphitic carbon nitride by condensation of cyanamide (CN-NH2) as a molecular precursor using a colloidal silica crystalline array as a template is described. The resulting sample exhibited a three-dimensionally extended highly ordered pore array as shown by transmission electron microscopy, scanning electron microscopy and nitrogen isotherms. The carbon nitride structure revealed high graphitic nature with C3N4 stoichiometry. In particular, the C3N4 network structure consists of tri-s-triazine rings (C6N7) cross-linked by trigonal N atoms.  相似文献   

3.
In this study, a novel graphene/g‐C3N4 microwave absorber is developed to solve the electromagnetic wave interference problem. Graphene/g‐C3N4 composite is synthesized by loading g‐C3N4 nanosheets on graphene through a simple liquid‐phase approach. High‐performance electromagnetic absorption performance can be achieved. The optimal reflection loss value is up to ?29.6 dB under a thin coating layer of 1.5 mm. At the same time, the corresponding absorption bandwidth of this composite can reach 5.2 GHz (12.8–18 GHz). Excellent electromagnetic absorption property may be attributed to the current attenuation theory which has been proven by replacing graphene with porous graphene or graphene oxide. The results reveal that free electron numbers and loading mass of g‐C3N4 on graphene play the key roles in the intensity of current attenuation and resistance value.  相似文献   

4.
The electronic properties of an experimentally realized graphitic carbon nitride (g-C3N3) layer has been studied via first-principles calculations. Unlike the recently reported ferromagnetic g-C4N3 structure, the g-C3N3 system is nonmagnetic. Based on the two-dimensional g-C3N3 structure, we predicts a new graphitic hydrogenated carbon nitride (g-H3C3N3) for the first time, which shows 100% half-metallic property around Fermi energy. It would be a kind of important material in spintronics if it could be synthesized experimentally in the future.  相似文献   

5.
Catalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are at the heart of water oxidation reactions. Despite continuous efforts, the development of OER/HER electrocatalysts with high activity at low cost remains a big challenge. Herein, a composite material consisting of TC@WO3@g‐C3N4@Ni‐NiO complex matrix as a bifunctional electrocatalyst for the OER and HER is described. Though the catalyst has modest activity for HER, it exhibits high OER activity thereby making it a better nonprecious electrocatalyst for both OER and HER and is further improved by g‐C3N4. The catalytic activity arises from the synergetic effects between WO3, Ni‐NiO, and g‐C3N4. A Ni‐NiO alloy and WO3 nanoparticles decorated on the g‐C3N4 surface supported toray carbon (TC) matrix (TC@WO3@g‐C3N4@Ni‐NiO) by a facile route that show an excellent and durable bifunctional catalytic activity for OER and HER in the alkaline medium are developed. This carbon nitride with binary metal/metal‐oxide matrix supported with TC exhibit an overpotential of 0.385 and 0.535 V versus RHE at a current density of 10 mA cm?2 (Tafel slopes of 0.057 and 0.246 V dec?1 for OER and HER, respectively), in 0.1 m NaOH . The catalyst is tested in water electrolysis for 17 h.  相似文献   

6.
陈刚  高尚鹏 《中国物理 B》2012,21(10):107101-107101
The structures of the heptazine-based graphitic C3N4 and the S-doped graphitic C3N4 are investigated by using the density functional theory with a semi-empirical dispersion correction for the weak long-range interaction between layers.The corrugated structure is found to be energetically favorable for both the pure and the S-doped graphitic C3N4.The S doptant is prone to substitute the N atom bonded with only two nearest C atoms.The band structure calculation reveals that this kind of S doping causes a favorable red shift of the light absorption threshold and can improve the electroconductibility and the photocatalytic activity of the graphitic C3N4.  相似文献   

7.
Raman characteristics of carbon nitride films synthesized by nitrogen-ion-beam-assisted pulsed laser deposition were investigated. In addition to the D (disorder) band and G (graphitic) band commonly observed in carbon nitride films, two Raman bands located at 1080–1100 and 1465–1480 cm-1 were found from our carbon nitride films. These two bands were well matched with the predicted Raman frequencies for βC3N4 and the observed Raman bands reported for carbon nitride films, indicating their relation to carbon-nitrogen stretching vibrations. Furthermore, the relative intensity ratio of the two Raman bands to the D and G bands increased linearly with increasing nitrogen content of the carbon nitride films. Received: 30 October 2000 / Accepted: 5 February 2001 / Published online: 2 October 2001  相似文献   

8.
A novel network-like magnetic nanoparticle was fabricated on a graphitic carbon nitride through a facile sonochemical route at frequency 20 kHz and power 70 W. To enhance the electrocatalytic activity of the modified materials, the graphitic carbon nitrides (g-C3N4) was prepared from melamine. Monitoring of xanthine concentration level in biological fluids is more important for clinical diagnosis and medical applications. As modified CuFe2O4/g-C3N4 nanocomposite exhibits better electrochemical activity towards the oxidation of xanthine with higher anodic current compared to other modified and unmodified electrode for the detection of xanthine with larger linear range (0.03–695 µM) and lower limit of detection (13.2 nM). To compare with these methods, the electrochemical techniques may be an alternative high sensitive method due to their simplicity and rapid detection time. In addition, the practical feasibility of the sensor was inspected with biological samples, reveals the acceptable recovery of the sensor in real samples.  相似文献   

9.
Hydrophobic forms of the N,N‐dialkyl‐4‐nitroaniline (DNAP) (p‐O2NC6H4NR2) ( 1a–f ) and alkyl‐4‐nitrophenyl ether (p‐O2NC6H4OR) ( 2a–c ) solvatochromic π* indicators have been characterized and compared with respect to: (a) solvatochromic bandshape, (b) sensitivity expressed as ?s , ( / d π * ), and (c) trends in ? s with increasing length of alkyl chain(s) on the probe molecule. ? Octyl 4‐nitrophenyl ether (p‐O2NC6H4OC8H17) ( 2b ) and ? decyl 4‐nitrophenyl ether (p‐O2N C6H4 OC10H21) ( 2c ) were synthesized and their solvatochromic UV/Vis absorption bands were found to maintain a Gausso‐Lorentzian bandshape for the indicators in non‐polar and alkyl substituted aromatic solvents, for example, hexane(s) and mesitylene. Corresponding absorption bands for 1a–f display increasing deviation from a Gausso‐Lorentzian shape in the same solvents as the alkyl chains on the indicator are increased in length all the way to C10 and C12, for example, N,N‐didecyl‐4‐nitroaniline (p‐O2NC6H4N (C10H21)2) and N,N‐didodecyl‐4‐nitroaniline (p‐O2NC6H4N (C12H25)2) ( 1d–f ). A plot of ? s versus Cn follows a 1st order decay for the DNAP indicators but is linear for the alkyl 4‐nitrophenyl ethers. A discussion of how the long alkyl chains on the two types of indicators affect the orientation and overlap of n and π * orbitals, and resulting solvatochromic bands is presented. For DNAP, overextending the alkyl chains to obtain greater hydrophobic character may cause the alkane component to dominate solute‐solvation processes at the expense of the probe's fundamental solvatochromic character. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

10.
We have evaluated a small portable Raman instrument on loan from B&W Tek, Inc., and have determined that it can successfully be used in the classroom both as a visual aid for teaching the fundamentals of Raman spectroscopy and for a variety of undergraduate experiments as a normal component of an instrumental analysis class. Having portable Raman instrumentation would allow the instructor to demonstrate the principles of Raman spectroscopy, as well as the concepts of calibration curves, blank subtraction, detection limits, and regression analysis. Both qualitative and quantitative types of experiments were done for solid Tylenol tablets, aqueous solutions of isopropyl alcohol, dimethyl sulfoxide, methanol, and ethanol, and gaseous CO2 and N2O4. Additionally, surface‐enhanced resonance Raman spectra of Rhodamine 6G were obtained using a chloride ion–activated silver colloid. Spectra from the B&W Tek, Inc., instrument were comparable to literature Raman spectra.  相似文献   

11.
Graphitic carbon nitride (g-C3N4) has been synthesized via a two-step pyrolysis of melamine (C3H6N6) at 800°C for 2 h under vacuum conditions. X-ray diffraction (XRD) patterns strongly indicate that the synthesized sample is g-C3N4. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) morphologies indicate that the product is mainly composed of graphitic carbon nitride. The stoichiometric ratio of C:N is determined to be 0.72 by elemental analysis (EA). Chemical bonding of the sample has been investigated by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Electron energy loss spectroscopy (EELS) verifies the bonding state between carbon and nitrogen atoms. Optical properties of the g-C3N4 were investigated by PL (photoluminescence) measurements and UV–Vis (ultraviolet–visible) absorption spectra. We suppose its luminescent properties may have potential application as component of optical nanoscale devices. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were also performed.  相似文献   

12.
In this study, based on the first-principles calculations, we systematically investigated the electronic and magnetic properties of the transition metal–oxide-incorporated 2D g-C3N4 nanosheet (labeled C3N4–TM–O, TM = Sc–Mn). The results suggest that the TM–O binds to g-C3N4 nanosheets strongly for all systems. We found that the 2D C3N4–TM–O framework is ferromagnetic for TM = Sc, Ti, V, Cr, while it is antiferromagnetic for TM = Mn. All the ferromagnetic systems exhibit the half-metallic property. Furthermore, Monte Carlo simulations based on the Heisenberg model suggest that the Curie temperatures (T c ) of the C3N4–TM–O (TM = Sc, Ti, V, Cr) framework are 169 K, 68 K, 203 K, and 190 K, respectively. Based on Bader charge analysis, we found that the origin of the half-metallicity at Fermi energy can be partially attributed to the transfer of electrons from TM atoms to the g-C3N4 nanosheet. In addition, we found that not only electrons but also holes can induce half-metallicity for 2D g-C3N4 nanosheets, which may help to understand the origin of half-metallicity for graphitic carbon nitride.  相似文献   

13.
Imidazolium ionic liquids (IMILs) with a piperidine moiety appended via variable length methylene spacers (with n = 1–4) were studied computationally to assess their potential to act as internal base for N‐heterocyclic carbene (NHC) generation. Proton transfer energies computed by B3LYP/6‐311+G(2d,p) were least endothermic for the basic‐IL with n = 3, whose optimized structure showed the shortest C2‐H‐‐‐‐N(piperidine) distance. Inclusion of counter anion (Cl or NTf2) caused dramatic conformational changes to enable close contact between the acidic C2‐H and the anions. To examine the prospect for internal C2‐H‐‐‐‐N coordination, multinuclear NMR data (1H, 15N, and 13C) were computed by gauge independent atomic orbitals–density functional theory (GIAO‐DFT) in the gas phase and in several solvents by the PCM method for comparison with the experimental NMR data for the basic ILs (with n = 2–4) synthesized in the laboratory. These studies indicate that interactions with solvent and counter ion are dominant forces that could disrupt internal C2‐H‐‐‐‐N coordination/proton transfer, making carbene generation from these basic‐ILs unlikely without an added external base. Therefore, the piperidine‐appended IMILs appear suitable for application as dual solvent/base in organic/organometallic transformations that require the use of mild base, without the necessity to alkylate at C‐2 to prevent N‐heterocyclic carbene formation. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

14.
We investigate the surface‐enhanced Raman scattering (SERS) spectra of flavin monoucleotide (FMN) in its different redox states and in a redox active enzyme, nitric oxide synthase. Incubated with silver nanoparticles coated with silica, spectra for oxidized and reduced FMN are obtained at different electrochemical potentials. Dominate Raman mode shifts at 1623/1610, 1567/1550, and 1502/1492 cm−1, belonging to typical redox‐sensitive region of FMN, are observed and analyzed, and they show a consistence with the results of spectral calculation by using the density function theory (DFT) method. We assign mode at 1500 cm−1, composed of N5―H bending, N1C10a stretching and the asymmetric C4a―N5―C5a stretching, as a spectroscopic indicator for the redox states of FMN, because it shows a significant downshift (1502/1492 cm−1) and non‐linearly correction with potentials when FMN gets reduced from its full oxidized state electrochemically. Isolated FMN domain from a wild type neuronal nitric oxide synthase enzyme (nNOS) is also studied with the same experimental approach. We have observed similar Raman mode down‐shifting as that of the pure FMN, which further supports our conclusion that the mode at ~1500 cm−1 indicates redox states for FMN, the coenzyme of nNOS, even in redox protein matrix. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

15.
Four L ‐valine (L ‐Val) phosphonate dipeptides that are potent inhibitors of zinc metalloproteases, namely, L ‐Val‐C(Me)2‐PO3H2 (V1), L ‐Val‐CH(iP)‐PO3H2 (V2), L ‐Val‐CH(iB)‐PO3H2 (V3), and L ‐Val‐C(Me)(iP)‐PO3H2 (V4), are studied by Fourier‐transform infrared (FT‐IR) spectroscopy, Fourier‐transform Raman spectroscopy (FT‐RS), and surface‐enhanced Raman scattering (SERS). The band assignment (wavenumbers and intensities) is made based on (B3LYP/6‐311 + + G**) calculations. Comparison of theoretical FT‐IR and FT‐RS spectra with those of SERS allows to obtain information on the orientation of these dipeptides as well as specific‐competitive interactions of their functionalities with the silver substrate. More specifically, V1 and V4 appear to interact with the silver substrate mainly via a  CsgCH3 moiety localized at the  NamideCsg(CH3)P molecular fragment. In addition, the  POH and isopropyl units of V4 assist in the adsorption process of this molecule. In contrast, the  CαNH2 and  PO3H groups of V2 and V3 interact with the silver nanoparticles, whereas their isopropyl and isobutyl fragments seem to be repelled by the silver substrate (except for the  CH2  of V3), similar to the  Cβ(CH3)2 fragment of L ‐Val for all L ‐Val phosphonate dipeptides investigated in this work. The adsorption mechanism of these molecules onto the colloidal silver surface is also affected by amide bond behavior. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

16.
Novel graphitic carbon nitride (C3N4) and bismuth vanadate (BiVO4) composite photocatalysts were successfully synthesized by a facile hydrothermal method. The scanning electron microscopy (SEM) revealed that an intimate interface between C3N4 and BiVO4 formed in the composites. Compared with the pure C3N4 and BiVO4, the C3N4–BiVO4 photocatalysts showed remarkably the higher photocatalytic activities in degrading rhodamine B (Rh B). The best active heterojunction proportion was 0.5C3N4–0.5BiVO4. Over this catalyst, the 100% degradation of Rh B (0.002 mmol L−1) was obtained under visible light irradiation (λ>420 nm) for 40 min. The active species in Rh B degradation were examined by adding a series of scavengers. The study on photocatalytic mechanism revealed that the electrons injected directly from the conduction band of C3N4 to that of BiVO4, resulting in the production of superoxide radical (O2•−) and hydroxyl radical (OH) in the conduction band of BiVO4. Simultaneously, the rich holes in the valence band of g-C3N4 oxidized Rh B directly to promote the photocatalytic degradation reaction.  相似文献   

17.
In this paper, a method for enhancing the analysis of biologic materials was designed. This method incorporated the surface‐enhanced Raman scattering (SERS) technique and an enzyme catalysis‐based bioassay to develop a more efficient analysis procedure. Using this combination, the quick and simple detection of disease‐related molecules (the human cardiac isoform of troponin T, cTnT) in human serum was achieved. This method utilizes enzyme catalysis to develop a H2O2‐horseradish peroxidase (HRP)‐3,3′,5,5′‐tetramethylbenzidine (TMB) chromogenic system, and the final enzymatic product TMB2+ revealed perfect SERS activities. By analyzing a concentration‐dependent SERS spectrum, the quantitative analysis was accomplished. Our findings reveal that the proposed method has a wider linear range and a more sensitive detection limit compared with traditional chromogenic tests. In summary, two existing methods have been combined to create a new model, which has the potential to be used for the bioanalysis and early diagnosis of diseases. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

18.
Infrared (IR) and Raman spectra were obtained for N,N′‐dicyclohexylcarbodiimide (DCC) in the solid state and in CHCl3 solution. Structures and vibrational spectra of isolated, gas‐phase DCC molecules with C2 and Ci symmetries, computed at the B3‐LYP/cc‐pVTZ level, show that the IR and Raman spectra provide convincing evidence for a C2 structure in both the solid state and in CHCl3 solution. Using a scaled quantum‐chemical force field, these density functional theory calculations have provided detailed assignments of the observed IR and Raman bands in terms of potential energy distributions. Comparison of solid‐state and solution spectra, together with a Raman study of the melting behaviour of DCC, revealed that no solid‐state effects were evident in the spectra. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

19.
将有机物三聚氰胺(C3N6H6)高温热解,得到了石墨相C3N4(g-C3N4)。利用同步辐射X射线衍射和金刚石对顶砧(DAC)高压技术,在室温下对g-C3N4进行了结构变化研究。实验结果表明,在16.57 GPa压力范围内,g-C3N4发生了压致结构相变,在6.6 GPa压力下,晶体结构由原来的石墨相转变为三斜相。使用Birch-Murnagha等温状态方程拟合出了样品的等温状态方程。  相似文献   

20.
Abstract

Basing on “ab-initio” calculations, C3N4 was claimed to be an ultra-hard material with a bulk-modulus close to that of diamond. Five different structural varieties were announced: the graphitic form, the zinc blende structure, the α and β forms of Si3N4 and another form, isostructural with the high pressure variety of Zn2Si04.

Using the same strategy as that developed for diamond or c-BN synthesis, it appears that the graphitic form could be an appropriate precursor for preparing the 3D varieties. Two main problems characterize the C3N4 synthesis: (-) the temperature should be reduced in order to prevent nitrogen loss, (-) the reactivity of the precursors should be improved.

Consequently, we have developed a new process using the solvothermal decomposition of organic precursors containing carbon and nitrogen in the presence of a nitriding solvent. The resulting material, with a composition close to C3N4, has been characterized by different physico-chemical techniques.  相似文献   

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