CN Components Research Articles

Triangle CeO2/g-C3N4 heterojunctions: Enhanced light-driven photocatalytic degradation of methylparaben

In this work, an efficient photocatalytic system for methylparaben (MP) removal, using solar (λ > 360 nm) and visible (λ > 420 nm) light-driven CeO2/g-C3N4 (CeO2/CN) heterojunctions is reported for the first time. The physicochemical properties of pure CeO2, CN, and CeO2/CN composites were investigated using characterization techniques, such as XRD, FESEM-EDS, TEM, UV–Vis, PL, XPS, and electrochemical spectroscopy. Among the catalysts with different mass ratios of CeO2, 10 %CeO2/CN showed the best photocatalytic performance. This is attributed to the enhanced charge carrier’s separation because of the proper band-edge alignment between CN and CeO2 components, and the strong visible light absorbance. The photocatalytic degradation of MP followed the first-order kinetics, and the 10 %CeO2/CN catalyst exhibited a 3.8- and 11.3-times higher reaction rate (k) constant than that of pure CN, investigated under solar and visible light illumination, respectively. Further, scavenger trapping experiments confirmed that hydroxyl radicals (OH.) and dissolved oxygen are the predominant active species in MP oxidation over 10 %CeO2/CN composite catalyst. 1H NMR and LCMS-HPLC results and observations showed complete degradation of MP (0.1 g/L) to CO2 and H2O after 7 h of solar irradiation, due to the absence of the representative peaks of MP and its organic degradation products (e.g. phenols, benzoates).

2D/2D BiOIO3/g-C3N4 S-scheme hybrid heterojunction with face-to-face interfacial contact for effective photocatalytic H2 production and norfloxacin degradation

A two-dimensional (2D)/2D hybrid heterojunction with face-to-face interfacial assembly is a desirable dimensionality design with significant potential for various photocatalytic applications due to the large interfacial contact area, which facilitates charge migration and separation. Herein, we developed an efficient 2D/2D hybrid heterojunction consisting of BiOIO3 nanoplates (BIO) and g-C3N4 nanosheets (CN) using a simple but effective in situ growth method for photocatalytic aqueous antibiotic degradation and H2 generation. The face-to-face interfacial assembly of the BIO and CN components in the BIO/CN hybrid heterojunction was verified using electron microscopy. Remarkably, the BIO/CN hybrid heterojunction outperformed both the BIO and CN counterparts in terms of norfloxacin degradation and H2 generation under simulated solar light irradiation. Moreover, the photocatalytic performance of the hybrid catalyst remained nearly unchanged throughout five consecutive test runs. The exceptional performance and stability of the hybrid catalyst are attributable to its extended optical absorption range, large interfacial contact area provided by the face-to-face assembly in the 2D/2D hybrid configuration, and enhanced photoexcited charge separation efficiency and redox power of the separated charges, which are supported by an efficient S-scheme charge transfer mechanism. This study illuminates the rational construction of novel 2D/2D S-scheme hybrid heterojunction photocatalysts with practical applications in environmental remediation and sustainable energy generation.

Maximizing the expected number of components in an online search of a graph

The following optimal stopping problem is considered. The vertices of a graph G are revealed one by one, in a random order, to a selector. He aims to stop this process at a time t that maximizes the expected number of connected components in the graph G˜t, induced by the currently revealed vertices. The selector knows G in advance, but different versions of the game are considered depending on the information that he gets about G˜t. We show that when G has N vertices and maximum degree of order o(N), then the number of components of G˜t is concentrated around its mean, which implies that playing the optimal strategy the selector does not benefit much by receiving more information about G˜t. Results of similar nature were previously obtained by M. Lasoń for the case where G is a k-tree (for constant k). We also consider the particular cases where G is a square, triangular or hexagonal lattice, showing that an optimal selector gains cN components and we compute c with an error less than 0.005 in each case.

Properly aligned band structures in B-TiO2/MIL53(Fe)/g-C3N4 ternary nanocomposite can drastically improve its photocatalytic activity for H2 evolution: Investigations based on the experimental results

The development of new tools that could meet the demand of sustainable energy production has attracted worldwide scientific attention. Over the past few decades, significant research efforts have been carried out to efficiently reduce water to H2 (green fuel) over semiconductor photocatalysts. Numerous semiconductor photocatalysts have been employed in photocatalysis for optimum H2 production. All the techniques were chosen based on their flexibility, cost-effectiveness, and ease of availability. Recently, polymeric carbon nitride (g-C3N4) received worldwide attention in visible light photocatalysis for energy and environmental applications due to its low price, robust nature, and superior thermal stability. Nevertheless, g-C3N4 (CN) exhibits shortfalls such as high charge carrier's recombination rate and weak reduction ability. To overcome these drawbacks, herein, for the first time we have fabricated B-TiO2/MIL-53(Fe)/CN ternary composite via hydrothermal and wet-chemical methods. The resultant B-TiO2/MIL53(Fe)/CN ternary composite shows drastically improved photocatalytic activity for hydrogen evolution compared to the bare CN, B-TiO2, and MIL53(Fe) components. The B-TiO2/MIL53(Fe)/CN ternary composite produced approximately 166.3 and 581.2 μmol h−1 g−1 of hydrogen under visible light and UV–visible light irradiations, respectively, with the assistance of co-catalyst Pt. Photo-luminescence (PL) and the fluorescence (FL) spectroscopy measurements reveal that the enhanced photoactivity is due to the greatly promoted charge carrier's separation and transfer at the interfacial contact of the well-aligned three-component systems. This work will promote the design and development of efficient photocatalyst based on CN for clean energy production and environmental purification.

Evaluation of cross-reactivity between casein components using inhibition assay and in silico analysis.

We previously reported that the specific IgE levels to αs1-casein (CN) and β-CN in patients with cow's milk allergy decreased with similar dynamics during oral immunotherapy. Therefore, we hypothesized that αs1- and β-CN have strong cross-reactivity among CN components, despite the low similarity in the full-length amino acid sequences. The αs1-, β-, and κ-CN were purified from commercial cow's milk. We recruited 39 patients with cow's milk allergy, and the serum IgE levels for each CN component were measured by enzyme-linked immunosorbent assay (ELISA). Cross-reactivity between CN components was investigated by competitive ELISA against αs1-CN. Sequence homology between CN components at the peptide level was calculated using in silico analysis and quantified by the property distance (PD) value. The αs1-CN-specific IgE levels exhibited a strong positive correlation with the β-CN-specific IgE (r=0.945, P<.001). Complete competition was observed by β-CN against αs1-CN, suggesting the presence of common epitopes between them. In silico analysis detected 24 peptide sets with PD values lower than 10 between αs1- and β-CN, and 14 sets between αs1- and κ-CN. The amino acid sequences of αs1-CN (E61-E70) and β-CN (I12-E21) that showed the lowest PD value (5.30) were present in the characteristic sequence known as casein phosphopeptide (CPP). We detected strong cross-reactivity between CN components. Furthermore, we found highly homologous sequences in the CPP region, which contains a core sequence of "SSSEE" with phosphorylated serine residues.

Magnetically responsive SnFe2O4/g-C3N4 hybrid photocatalysts with remarkable visible-light-induced performance for degradation of environmentally hazardous substances and sustainable hydrogen production

SnFe2O4/g-C3N4 (SFO/CN) hybrids were fabricated as efficient magnetically recoverable and visible-light-responsive photocatalysts via a facile in situ precipitation method. The photocatalytic activities of the fabricated SFO/CN hybrids were assessed on the basis of their ability to degrade environmentally hazardous dyes (Rhodamine B, methylene blue, and methyl orange) and to produce H2 under visible light. The SFO/CN hybrids displayed outstanding performance toward both the elimination of dye pollutants and the production of H2, demonstrating several-fold enhancements compared with the performances of the hybrids’ CN and SFO components and a commercial P25 catalyst. This enhancement in the photocatalytic performance of the SFO/CN hybrids predominantly corresponds to the synergetic effect between CN and SFO that improves not only their specific surface area and optical absorption capability but also the separation efficiency of photoexcited electrons and holes. Total organic carbon analysis further demonstrated the efficient mineralization of model dye molecules over the SFO/CN hybrids. In addition, the SFO/CN hybrids could be easily recovered magnetically and exhibited notable recyclability without obvious loss of activity after five consecutive photocatalytic test cycles, demonstrating their strong potential for use in practical applications, especially pollutant elimination and sustainable H2 production.

Processing, Structure, and Properties of Nanostructured Multifunctional Tribological Coatings

Nanostructured, nanocomposite binary (TiC-a:C), ternary (Cr-Al-N), quaternary (Ti-B-C-N) and quinternary (Ti-Si-B-C-N) multicomponent films have been deposited using unbalanced magnetron sputtering (UBMS) and closed field unbalanced magnetron sputtering (CFUBMS) from both elemental and composite targets. Approaches to control the film chemistry, volume fraction and size of the multicomponent species, and pulsed ion energy (ion flux) bombardment to tailor the structure and properties of the films for specific tribological applications, e.g., low friction coefficient and low wear rate, are emphasized. The synthesized films are characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), nanoindentation, and microtribometry. The relationships between processing parameters (pulsed ion energy and ion flux), thin film microstructure, mechanical and tribological properties are being investigated in terms of the nanocrystalline-nanocrystalline and nanocrystalline-amorphous composite thin film systems that are generated. In the Ti-Si-B-C-N films, nanocomposites of solid solutions, e.g., nanosized (Ti,C,N)B2 and Ti(C,N) crystallites are embedded in an amorphous TiSi2 and SiC matrix including some carbon, SiB4, BN, CN(x), TiO2 and B2O3 components. The Ti-Si-B-C-N coating with up to 150 W Si target power exhibited a hardness of about 35 GPa, a high H/E ratio of 0.095, and a low wear rate of from approximately 3 to approximately 10 x 10(-6) mm3/(Nm). In another aspect, using increased ion energy and ion flux, which are generated by pulsing the power of the target(s) in a closed field arrangement, to provide improved ion bombardment on tailoring the structure and properties of TiC-a:C and Cr-Al-N coatings are demonstrated. It was found that highly energetic species (up to hundreds eV) were found in the plasma by pulsing the power of the target(s) during magnetron sputtering. Applying higher pulse frequency and longer reverse time (lower duty cycle) will result in higher ion energy and ion flux in the plasma, which can be utilized to improve the film structure and properties. For example, optimum properties of the TiC-a:C coating were a hardness of 35 to 40 GPa and a COF of 0.2 to 0.22 for moderate maximum ion energies of 70 to 100 eV, and a super high hardness of 41 GPa and low wear rate of 3.41 x 10(-6) mm3N(-1) m(-1) was obtained for Cr-Al-N coatings deposited with a maximum ion energy of 122 eV. These conditions can be achieved by adjusting the pulsing parameters and target voltages. However, the pulsed ion energy together with the applied substrate bias are need to be carefully controlled in order to avoid excessive ion bombardment (e.g., the maximum ion energy is larger than 180 eV in the current study), which will responsible for an increase in point and line defects, and high residual stress in the crystalline structure.

2D IR photon echo spectroscopy reveals hydrogen bond dynamics of aromatic nitriles

The CN vibrations of two aromatic nitriles, cinnamonitrile, PhCH CH–CN and benzonitrile, PhCN, representative of components of common enzyme inhibitors, are examined by two-dimensional infrared spectroscopy. In methanol, these spectra display cross peaks between the two CN components whose evolution exposes the few picosecond (4.5 ps for CIN and 5.3 ps for BN) equilibrium dynamics of hydrogen bond making and breaking. The main features of the 2D IR spectra are reproduced by simulations only when exchange is incorporated. The lowest free energy state is the non-hydrogen bonded form. Both alkyl and aryl nitriles have now shown this picosecond exchange process.

Spectroscopic studies of nitrogenated amorphous carbon films prepared by ion beam sputtering

Spectroscopic analysis of the unhydrogenated amorphous carbon nitride (a-CNx) films, prepared by ion beam sputtering, was done by ellipsometry, Raman scattering and x-ray photoelectron spectroscopic (XPS) studies. The optical gap of the films was estimated from the Tauc’s analysis of the (n,k) data obtained from spectroscopic ellipsometry. In addition to the commonly observed D and G bands at ∼1350 cm−1 and 1550 cm−1, respectively, we detected a separate band at ∼1450 cm−1 in the Raman spectrum of a-CNx films. This intermediate peak was unambiguously identified as the N band arising out of the nitrogen–nitrogen bonding, due to the incorporation of nitrogen in the a-C network. High resolution XPS C 1s and N 1s peaks were used to estimate the nitrogen content in the films and various bonding configurations were identified from their Gaussian deconvolution. An increase in the intensity ratio of CN and CC components, I(CN)/I(CC), in the C 1s spectra signified increasing nitrogenation of the carbon network. Deconvolution of the N 1s spectra revealed that the sp3-hybridized C–N component remained unchanged at ∼40%, however, the sp1-hybridized C≡N component increased in intensity when the nitrogen content in the network increased systematically. Increasing nitrogenation led to the graphitization of the network and resulted in a gradual decrease in the optical gap, along with simultaneous increase in the ID/IG and IN/IG intensity ratios in the Raman band.

Analysis of SiO2-to-Si3N4 selectivity in reactive ion etching using additional O2 gas

The mechanism for control of the Si3N4 etch rate in a self-aligned contact process when C4F8/Ar/O2 gas is used was investigated. The Si3N4 surfaces after dry etching were analyzed by x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy. After dry etching, a polymer-like residue film less than 15 nm thick and an oxidized layer between the polymer layer and the Si3N4 surface were observed. In the CF polymer layer, the etching product of CN or CNO was characterized. CN or CNO components are widely distributed in the CF polymer layer, while the SiO2 layer is more localized on the Si3N4 surfaces. We found that the thicknesses of the CF polymer and SiO2 layer strongly depend on the Si3N4 etch rate, which is determined by the flow rate of the additional O2 gas. The thickness of the CF polymer, which was decreased from 10.1 to 4.1 nm, is considered to act as an inhibitor. The thickness of the SiO2 layer, which is easy to etch, was increased from 1.4 to 2.7 nm. The CF polymer thickness and the etching path of Si3N4 oxidation are important factors in controlling the Si3N4 etch rate.

Ovine κ-Casein in Milk from Lacha Spanish Sheep: Heterogeneity and Total Content

Ten κ -casein ( κ -CN) components were identified on alkaline polyacrylamide electropherograms (PAGE) of ovine isoelectric casein when stained with specific anti- κ -CN antibodies. After brief chymosin digestion of isoelectric casein, two para- κ -CN were identified in PAGE and three in polyacrylamide isoelectric focussing (PAGIF) gels by specific immunostaining. Selective precipitation followed by affinity chromatography on thiopropyl-Sepharose and PAGE of the sulphydryl (SH) containing fraction allowed the detection, spread along the whole electropherogram, of 14 components positively reacting to anti- κ -CN-antibodies and specifically attacked by chymosin. Eight of these κ -CN forms co-migrated or overlapped with β -CN components. By isoelectric focussing of the purified samples before and after chymosin digestion it was also possible to identify 14 κ -CN components with isoelectric points (Ip) ranging from 4.0 to 6.5 and three para- κ -CN components of Ips 8.4, 8.8 and 9.2. Affinity chromatography on thiopropyl-Sepharose and densitometric analysis of PAGE electropherograms of the SH containing casein fraction stained with Coomassie blue allowed estimation of the κ -CN contribution to total casein (about 17%).

Detection of interstellar NH towards Ophiuchi by means of ultra-high-resolution spectroscopy

We have obtained an ultra-high-resolution (0.38 km s−1 FWHM) spectrum of the R1 (0) (3358.053 Å) line of interstellar NH towards ζ Oph. These observations comprise the first detection of NH towards ζ Oph, and the third reported detection of this molecule by absorption-line spectroscopy towards any star. The equivalent width (0.36 ± 0.05 mÅ) corresponds to a column density of 8.8 ± 1.2 × 1011 cm−2. This is more than an order of magnitude higher than that expected on the basis of equilibrium gas-phase models, but is consistent with models incorporating grain-surface chemistry. The line profile is fully resolved, and has an intrinsic velocity dispersion characterized by b = 1.15 ± 0.12 km s−1. This is sufficiently narrow to exclude the possibility of hot NH formation through the endothermic reaction N + H2 → NH + H. There is evidence that the NH line is split into two velocity components (separation 1.26 ± 0.17 km s−1), with relative strengths mirroring those of the two CN components towards this star. We argue that this correlation also supports the case for grain surface reactions dominating the nitrogen chemistry of diffuse molecular clouds.

First results from the UHRF: ultra-high-resolution observations of interstellar CH, Formula and CN towards Formula Ophiuchi

We present ultra-high-resolution observations (R>700 000) of interstellar CH, CH+ and CN towards ζ Oph obtained with the newly commissioned Ultra-High-Resolution Facility (UHRF) at the AAT. The molecular lines have all been fully resolved, and we discuss their implications for this well-studied molecular sightline. The CH and CN lines each consist of two narrow (b≈0.5 km s−1) components separated by 1.13±0.10 km s−1⁠; an additional broad (b=1.8 km s−1) component is present in CH. We show that the very broad (b=2.1 km s−1) CH+ line profile is consistent with the formation of this molecule in warm haloes surrounding the cold cores responsible for the narrow CH and CN components.