Synthesis of boron carbon nitride oxide (BCNO) from urea and boric acid

A solid state synthesis of boron carbon nitride oxide (BCNO) material was carried out starting from urea and boric acid treated at 600°C. The X-ray diffraction pattern corresponded to amorphous BCNO with an interlayer distance of 3.49 Å. The material had a layered structure similar to that of graphite and hexagonal boron nitride (h-BN). Infrared spectroscopy (IR) showed bands which were similar to those typical of BN and carbon nitride. The presence of boron was also confirmed by energy dispersive spectroscopy in an amount compatible with the IR spectrum. The spectra obtained by X-ray photoelectron spectroscopy (XPS) corresponded to those of a BCNO family with a considerable content of oxygen too. The optical band gap was estimated to be 3.22 eV, typical of a wide band-gap semiconductor. The particle size was very dispersed from micro to nanosize. The material dispersed in polar solvents formed stable suspensions due to the presence of hydroxyl groups.     

Synthesis and characterization of Cu-doped polymeric carbon nitride

Polymeric carbon nitride doped with copper through a solid-state reaction was characterized by several techniques, among them are UV-visible spectroscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, etc. The material is a semiconductor with a wide band gap of 2.74 eV. Sites of both Cu(I) and Cu(II) were detected, apparently only coordinated by the polymer. The material comprises crumpled nanosheets, and is substantially an amorphous layered material with a prevalent 2D structure with low inter-planar interactions, as shown by X-ray diffractometry and TeraHertz spectroscopy. Photo-oxidation of benzyl alcohol was used to probe the active sites of the material, comparing them with the non-doped material. The higher activity and selectivity toward salicylic alcohol of the non-doped material can be due to both a more localized electron transfer and a longer lifetime of the hole–electron pair. Cu-CN favored the oxidation of hydroxymethyl group. Therefore, the presence of copper can favor different reaction pathways with respect to the non-doped material.     

Effects of carbon nanotubes additions on flash ignition characteristics of Fe and Al nanoparticles

The influences of carbon nanotubes (CNTs) additions on the flash ignition characteristics of Iron (Fe) and aluminum (Al) nanoparticles (NPs) were presented. CNTs can be used as the additive to these metal nanoparticles for improving the flash ignition and burning processes. Different mass fractions of CNTs additions were considered. The mixture of Al and CNTs could combust in air with obvious giant flame, whereas the mixture of Fe and CNTs combusted under a relative stable condition with slight red light. The temperature distributions were measured using non-contact optical method and showed that Al NPs mixed with CNTs were burning at a higher temperature level than Fe NPs. Although different mass fractions of CNTs cannot significantly change the overall flash ignition phenomenon, CNTs additions influenced the minimum ignition energy (MIE) of mixtures. The appropriate content of CNTs addition can decrease the Fe NPs MIE significantly. However, the Al NPs MIE decreased all along with the increase of CNTs content. The micro- and nano- structures of Fe and Al NPs with CNTs additions before and after ignitions were examined by scanning electron microscope and high-resolution transmission electron microscopy. It was found that the special thermal conductive characteristics of CNTs and the cross-connected features for metal particles with CNTs caused the enhancement of flash ignition.     

Enhanced catalytic activity of monodispersed AgPd alloy nanoparticles assembled on mesoporous graphitic carbon nitride for the hydrolytic dehydrogenation of ammonia borane under sunlight

We address the composition-controlled synthesis of monodispersed AgPd alloy nanoparticles (NPs),their assembly for the first time on mesoporous graphitic carbon nitride (mpg-C3N4),and the unprecedented catalysis of mpg-C3N4@AgPd in the hydrolytic dehydrogenation of ammonia borane (AB) at room temperature.Monodispersed AgPd alloy NPs were synthesized using a high-temperature organic-phase surfactant-assisted protocol comprising the co-reduction of silver(Ⅰ) acetate and palladium(Ⅱ) acetylacetonate in the presence of oleylamine,oleic acid,and 1-octadecene.This protocol allowed the synthesis of four different compositions of AgPd alloy NPs.The AgPd alloy NPs were then assembled on mpg-C3N4,reduced graphene oxide,and Ketjenblack using a liquid-phase self-assembly method.Among the three supports tested,the mpg-C3N4@AgPd catalysts provided the best activity because of the Mott-Schottky effect,which was driven by the favorable work function difference between mpg-C3N4 and the metal NPs.Moreover,the activity of the mpg-C3N4@AgPd catalyst was further enhanced by an acetic acid treatment (AAt),and a record initial turnover frequency of 94.1 mol(hydrogen)·mol(catalyst)-1·min-1 was obtained.Furthermore,the mpg-C3N4@Ag42Pd58-AAt catalyst also showed moderate durability for the hydrolysis of AB.This study also includes a wealth of kinetic data for the mpg-C3N4@AgPd-catalyzed hydrolysis of AB.     

Hydrogenated amorphous carbon and carbon nitride films deposited at low pressure by plasma enhanced chemical vapor deposition

Hydrogenated amorphous carbon (a-C:H) films were deposited by plasma enhanced chemical vapor deposition from methane, argon diluted methane, and nitrogen diluted methane at 26.7 Pa with a 13.56 MHz RF power supply. In this pressure regime, multiple-scattering of carbon species within the plasma phase is expected during the transport to the substrates placed on both the driven and the earthed electrodes. These films were analyzed using UV-VIS optical transmittance, monochromatic ellipsometry, Raman spectroscopy and current-voltage measurements. From these results, the effect of the plasma conditions and the effective flux of the carbon species controlled by the input power through the negative self bias are found to be important in the deposition process. The growth conditions at the higher pressure regime are important to synthesize a-C:H films from low energetic carbon species, since it reduces the defect density and improves the quality of the films. Furthermore, the effect of nitrogen on the growth conditions of a-C:H:N films is observed.     

Molecular dynamics simulations of nanosheets of polymeric carbon nitride and comparison with experimental observations

A computational study of the properties of polymeric carbon nitride using molecular dynamics is presented. The analysis of ideal infinite-extent sheets permits to evaluate the effect of temperature on the network of hydrogen bonds responsible for the linkage of the material. The weakening of this binding mechanism at sufficiently high temperatures, together with the inter-layer interactions characteristic of this type of 2D materials, is shown to determine the conformation properties of polymeric carbon nitride at the nanoscale. The results obtained from the simulation of finite samples in the canonical ensemble at varying temperatures are consistent with those from the characterization of our experimentally synthesized samples. Hydrogen bonding between adjacent polymer ribbons leads this process and is the cause of the typical crumpled structure of this material.     

无机酸刻蚀多孔氮化碳的合成及光催化性能

通过合理的形貌调控使石墨相氮化碳(g-C_3N_4)低维化和多孔化,是提高其光催化活性的有效途径.采用高温煅烧方法制备了HCl、HNO_3和H_2SO_4刻蚀的g-C_3N_4,并对它们进行了结构形貌表征、形成机理探究和光催化降解罗丹明B测试,还给出了活性增强机理.结果显示:酸刻蚀g-C_3N_4具有和g-C_3N_4相同的基本晶体结构,但是呈薄片状,且表面出现了大量纳米孔,这些孔是由无机酸阻碍前驱体中N—H键参与热缩聚反应所致,按照HCl、HNO_3、H_2SO_4的顺序阻碍作用依次增强,对应的孔径依次增大,结构边缘(C)_2—N—H基团的XPS特征峰强度也依次增加;经过40 min光反应,g-C_3N_4和HCl、HNO_3、H_2SO_4刻蚀的g-C_3N_4对罗丹明B的降解率分别为45%、 56%、 52%和95%,H_2SO_4刻蚀的g-C_3N_4光催化活性最高;酸刻蚀引起的薄片和多孔结构不仅增加了g-C_3N_4的比表面积,促进了暗条件下对罗丹明B的吸附,还通过量子限域效应提高了其光吸收能力,拓宽了禁带宽度,有效促进了光生电荷的分离.因此,酸刻蚀克服了g-C_3N_4的缺点,为探寻其光催化活性的提高方法提供了有价值的启发.     

Spectroscopic ellipsometry characterization of amorphous carbon and amorphous, graphitic and fullerene-like carbon nitride thin films

Carbon nitride (CN_x) and amorphous carbon (a-C) thin films are deposited by reactive magnetron sputtering onto silicon (001) wafers under controlled conditions to achieve amorphous, graphitic and fullerene-like microstructures. As-deposited films are analyzed by Spectroscopic Ellipsometry in the UV-VIS-NIR and IR spectral ranges in order to get further insight into the bonding structure of the material. Additional characterization is performed by High Resolution Transmission Electron Microscopy, X-ray Photoelectron Spectroscopy, and Atomic Force Microscopy. Between eight and eleven resonances are observed and modeled in the ellipsometrically determined optical spectra of the films. The largest or the second largest resonance for all films is a feature associated with C-N or C-C modes. This feature is generally associated with sp³ C-N or sp³ C-C bonds, which for the nitrogen-containing films instead should be identified as a three-fold or two-fold sp² hybridization of N, either substituted in a graphite site or in a pyridine-like configuration, respectively. The π→π? electronic transition associated with sp² C bonds in carbon films and with sp² N bonds (as N bonded in pyridine-like manner) in CN_x films is also present, but not as strong. Another feature present in all CN_x films is a resonance associated with nitrile often observed in carbon nitrides. Additional resonances are identified and discussed and moreover, several new, unidentified resonances are observed in the ellipsometric spectra.     

A novel approach to the formation of amorphous carbon nitride film on silicon by ECR-CVD

Amorphous carbon nitride films have been synthesized on silicon by using an ECR-CVD system equipped with a DC bias and a mixture of C₂H₂, N₂ and Ar. Excess argon together with the application of DC bias can increase the ratio of nitrogen to carbon in the film up to 41% as determined by XPS. FTIR spectrum shows an absorption band between 1000 and 1700 cm⁻¹ which proves the incorporation of nitrogen atoms into the amorphous network of carbon. The plasma chemistry of the system was also analyzed by OES to investigate the active chemical species that were involved in the formation of carbon nitride. The result indicated that the addition of excess argon (four times more than nitrogen) can effectively enrich the excited-state CN radicals which subsequently promotes the concentration of nitrogen in the amorphous carbon nitride film. This observation is likely due to the lower ionization energy of argon (15.8 eV), argon's larger cross-section area for collision and its massive weight in comparison with the indispensable hydrogen gas as employed in the synthesis of other related materials.     

Coating of carbon nanotubes with amorphous carbon nitride thin films and characterization of long-term emission stability

The effects of amorphous carbon nitride (CN) thin films that were coated on carbon nanotubes (CNTs) and their thermal treatment were investigated, in terms of the chemical bonding and morphologies of the CNTs and their field emission properties. CNTs were directly grown on conical tip-type tungsten substrates via the inductively coupled plasma-chemical vapor deposition (ICP-CVD) system, and the CNTs were coated with CN films using the RF magnetron sputtering system. The CN-coated CNTs were thermally treated using the rapid thermal annealing (RTA) system by varying the temperature (300-700 °C). The morphologies, microstructures, and chemical compositions of the CN-coated CNTs were analyzed as a function of the thickness of the CN layers and the RTA temperatures. The field emission properties of the CN/CNT hetero-structured emitters, and the fluctuation and long-term stability of the emission currents were measured and compared with those of the conventional non-coated CNT-emitter. The results showed that the electron emission capability of CNT was noticeably improved by coating a thin CN layer on the surface of the CNT. This was attributed to the low work function and negative electron affinity nature of the CN film. The CN-coated CNT-emitter had a more stable emission characteristic than that of the non-coated one. In addition, the long-term emission stability of the CN-coated emitter was further enhanced by thermal treatment, which was verified by x-ray photoelectron spectroscopy (XPS) analysis.     

Enhanced photocatalytic activity by the construction of a TiO<Subscript>2</Subscript>/carbon nitride nanosheets heterostructure with high surface area via direct interfacial assembly

A TiO2 heterostructure modified with carbon nitride nanosheets (CN-NSs) has been synthesized via a direct interfacial assembly strategy.The CN-NSs,which have a unique two-dimensional structure,were favorable for supporting TiO2 nanoparticles (NPs).The uniform dispersion of TiO2 NPs on the surface of the CN-NSs creates sufficient interfacial contact at their nanojunctions,as was confirmed by electron microscopy analyses.In comparison with other reported metal oxide/CN composites,the strong interactions of the ultrathin CN-NSs layers with the TiO2 nanoparticles restrain their re-stacking,which results in a large specific surface area of 234.0 m2·g-1.The results indicate that the optimized TiO2/CN-NSs hybrid exhibits remarkably enhanced photocatalytic efficiency for dye degradation (with k of 0.167 min-1 under full spectrum) and H2 production (with apparent quantum yield =38.4％ for,λ =400 ± 15 nm monochromatic light).This can be ascribed to the improved surface area and quantum efficiency of the hybrid,with a controlled ratio that reaches the appropriate balance between producing sufficient nanojunctions and absorbing enough photons.Furthermore,based on the identification of the main active species for photodegradation,and the confirmation of active sites for H2 evolution,the charge transfer pathway across the TiO2/CN-NSs interface under simulated solar light is proposed.     

Decolourisation of Direct Orange S dye by ultra sonication using iron oxide nanoparticles

Biosynthesised iron oxide nanoparticles (INPs) less than 100 nm were used to decolourise the textile dye, Direct Orange S by the process of ultra sonication. The parameters tested for the decolourisation of the Direct Orange S dye were the INP concentration (0.2–1g/l), pH (3–11) and H₂O₂ concentration (2–8 ml/l). The rate of decolourisation process was performed by both stirrer and ultra sonicator method using the first-order kinetics ln(c/c₀). The percentage of dye removal for the optimum conditions such as INP, 1g/l (87.2%); pH, 9 (85.5%) and H₂O₂ concentration 8 ml/l (86.5%) were observed. The Direct Orange S dye was degraded efficiently by sonolysis (60 min) than by the magnetic stirrer method (120 min). High-performance liquid chromatography results showed that the peak for Direct Orange S dye was not present when the dye sample was treated by either H₂O₂ + INP or INP alone. Use of biosynthesised iron NPs in Direct Orange S dye (azo dye) decolourisation by a simple non-toxic Fenton reaction is a safe and novel approach. Industrialisation of this technique will be an economical way to decolorise the textile dyes present in water systems.     

Amperometric acetylcholinesterase biosensor for pesticides monitoring utilising iron oxide nanoparticles and poly(indole-5-carboxylic acid)

A new electrochemical sensing device was constructed for determination of pesticides. In this report, acetylcholinesterase was bioconjugated onto hybrid nanocomposite, i.e. iron oxide nanoparticles and poly(indole-5-carboxylic acid) (Fe₃O₄NPs/Pin5COOH) was deposited electrochemically on glassy carbon electrode. Fe₃O₄NPs was showed as an amplified sensing interface at lower voltage which makes the sensor more sensitive and specific. The enzyme inhibition by pesticides was detected within concentrations ranges between 0.1–60 and 1.5–70 nM for malathion and chlorpyrifos, respectively, under optimal experimental conditions (sodium phosphate buffer, pH 7.0 and 25?°C). Biosensor determined the pesticides level in water samples (spiked) with satisfactory accuracy (96%–100%). Sensor showed good storage stability and retained 50% of its initial activity within 70 days at 4 °C.     

Chemical vapor deposition of titanium nitride on carbon fibres as a protective layer in metal matrix composites

The significance of carbon fibres for reinforcing metals has increased in the last years, because of their excellent mechanical properties. However, to avoid the weakening reaction during MMC fabrication between the fibre and the liquid metal, a protective coating has to be applied. Continuous carbon fibre roving with 6000 filaments were coated with TiN by thermal induced chemical vapour deposition (CVD) using a gas mixture of TiCl₄, N₂ and H₂ as a precursor. The deposition process in the reactor was simulated by a modified Phoenics-CVD software program using a 2D-axisymmetric model. Carbon fibres reinforced magnesium matrix composites are fabricated by a pressure infiltration casting process. The mechanical properties of the MMCs can be used to demonstrate the efficacy of the coated fibre approach. The rule of mixture is realized to 98% for the coated fibre, and only 48% for the uncoated system. The infiltration pressure during the processing of composites was lowered from 10 to 1 MPa for the TiN coated system.     

碳包覆空心Fe3O4纳米粒子作为锂离子电池负极材料的电化学性能研究

以二茂铁为铁源,石油渣油为碳源,通过加压热解和空气氧化制备了碳包覆空心Fe3O4纳米粒子。采用X射线衍射(XRD)、透射电镜(TEM)以及高倍透射电镜(HRTEM)等测试方法对样品的形貌和结构进行表征。采用恒流充放电和交流阻抗方法测试碳包覆空心Fe3O4纳米粒子作为锂离子电池负极材料的电化学性能。在电流密度为0.2mA/cm2时,首次放电比容量高达1294.7mAh/g,30次循环之后其放电比容量为392.1mAh/g;电流密度为1mA/cm2时,首次放电比容量为216.3mAh/g,30次循环之后其放电比容量为113mAh/g。     

Preparation,characterisation and in vitro cytotoxicity studies of chelerythrine-loaded magnetic Fe3O4@O-carboxymethylchitosan nanoparticles

In this work, a novel, active tumour-targeting system (Fe₃O₄@OCMCS-CHE) was designed by surface-modifying superparamagnetic iron oxide nanoparticles (Fe₃O₄) with O-carboxymethylchitosan (OCMCS) to improve their biocompatibility and ability to target specific tumour cells. The chelerythrine (CHE) was used as the model of anti-tumour drug in this system. The optimised formulation was characterised and confirmed by scanning electron microscopy (SEM), transmission electron microscope (TEM), vibrating sample magnetometer (VSM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), in vitro drug release and so on. It was found that the synthesised nanoparticles were spherical in shape with an average size of 60 nm, the drug loading content and entrapment efficiency were 8.32 ± 0.25% (w/w) and 90.65 ± 0.46% (w/w), respectively, and the saturated magnetisation reached 27.06 emu/g. The in vitro drug-release behaviour from nanoparticles displayed a biphasic drug-release pattern with initial burst release and consequently sustained release. Also, the effect of magnetic targeted nanoparticles on the proliferation of human hepatoma cell line (HepG2) in vitro was investigated. The results from 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and Hochest assays suggested that the Fe₃O₄@OCMCS-CHE nanoparticles could effectively inhibit the proliferation of HepG2 cells, which displayed time-dependent and concentration-dependent manner. All these results indicated that the multifunctional Fe₃O₄@OCMCS nanoparticles possess a high drug loading efficiency, have low cytotoxicity, and are promising candidates for targeted drug delivery.     

多糖涂覆的氧化铁纳米粒子的合成及其药物递送应用研究进展

近年来,氧化铁纳米粒子(Iron Oxide Nanoparticles,IONPs)由于具有超顺磁性、生物相容性、比表面积大、易分离等特点而备受科学界关注.然而,裸露的IONPs容易聚集和氧化而失去其应有的特性,采用多糖进行涂覆不仅能提高IONPs的稳定性和生物相容性,还能通过多糖与其他生物活性物质结合,赋予INOPs新的功能.多糖涂覆的IONPs充分结合了多糖的生化特性与磁芯的理化特性,在药物递送中展现出巨大的应用潜力.本文综述了多糖涂覆IONPs的合成方法、合成过程的影响因素、多糖与IONPs的结合机理及其在药物递送中的应用,最后对多糖涂覆的IONPs的合成及其在药物递送方面的应用进行了总结和展望.     

Synthesis of boron nitride nanotubes from boron oxide by ball milling and annealing process

Boron nitride nanotubes were synthesized from boron oxide by high-energy ball milling and annealing method. The diameter of the nanotubes is in the range of 20-200 nm. The nanotubes show a bamboo-like structure and cylindrical-like structure under low magnification. The shorter bamboo nodes with distinct knots were observed for the bamboo-like nanotubes with larger diameters and the knots can also occasionally be observed in the cylindrical-like BN nanotubes with smaller diameters under high magnification. Al and Si were found to be catalytic materials responsible for the formation of BN nanotubes besides the metallic particles containing Fe, Ni and Cr.