A biosensor based on Coriolopsis gallica laccase immobilized on nitrogen-doped multiwalled carbon nanotubes and graphene oxide for polyphenol detection

Abstract

The use of nanomaterials allows the design of ultrasensitive biosensors with advantages in the detection of organic molecules. Catechol and catechin are molecules that occur naturally in fruits, and their presence in products like dyes and wines affects quality standards. In this study, catechol and catechin were measured at the nanoscale by means of cyclic voltammetry. The oxidation of Coriolopsis gallica laccase immobilized on nitrogen-doped multiwalled carbon nanotubes (Lac/CN_x-MWCNT) and on graphene oxide (Lac/GO) was used to measure the concentrations of catechol and catechin. Nitrogen-doped multiwalled carbon nanotubes (CN_x-MWCNT) were synthesized by spray pyrolysis and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy (XPS). Covalently bonded hybrids with laccase (Lac/CN_x-MWCNT and Lac/GO) were generated. Catalytic activity of free enzymes determined with syringaldazine yielded 14 584 UmL^?1. With Lac/CN_x-MWCNT at concentrations of 6.4 mmol L^?1 activity was 9326 U mL^?1, while enzyme activity measured with Lac/GO at concentration of 6.4 mmol L^?1 was 9 234 U mL^?1. The Lac/CN_x-MWCNT hybrid showed higher stability than Lac/GO at different ethyl alcohol concentrations. The Lac/CN_x-MWCNT hybrid can measure concentrations, not previously reported, as low as 1 × 10^?8 mol L^?1 by measuring the electric current responses.     

New Polymeric Phase in Low‐Doped Lithium Intercalated Fullerides

Abstract

The low‐doped Li _x C₆₀ compounds (x≤6) were investigated using laboratory X‐ray and synchrotron radiation diffraction, ¹³C NMR and Raman spectroscopy. Li₄C₆₀ shows an unusual 2D polymerisation in which the C₆₀ units are connected both by [2+2] cycloaddition and by single carbon–carbon bonds, a unique feature among the known polymerised fullerene compounds. This picture is fully supported also by static NMR and Raman measurements. The charge transfer to C₆₀ in the polymeric phase was evaluated from the shift of the A_g(2) mode. The depolymerisation process was investigated as well; despite the presence of two different bonds, the polymer‐to‐monomer transition induced by thermal treatments is a single‐step phenomenon.     

The New Method for the Synthesis of Fullerols Based on Radical Reaction

Abstract

The method for the synthesis of fullerols C₆₀(OH) _x was developed, allowing to obtain products with low number of hydroxy groups attached to fullerene molecule. At the first stage, product C₆₀(tert‐BuO) _x was obtained by the radical reaction of C₆₀ with tert‐butyl‐peroxide under heating or UV‐irradiation. At the second stage, fullerol C₆₀(OH) _x was synthesized after the elimination of tert‐butyl groups by acid treatment. Several samples C₆₀(OH) _x containing different numbers (x = 2–5) of hydroxy groups were obtained, the main product had x = 2. The structure of the fullerols was confirmed by UV‐ and Fourier‐transform infrared (FTIR)‐spectroscopy and MALDI‐TOF mass‐spectrometry.     

Y-junction bamboo-like CN<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> nanotubes

The method for the production of multiwall Y-junction bamboo-like CN _x nanotubes by the resistive heating of graphite is described. Different branched bamboo-like CN _x nanotubes have been observed. The possible mechanism of the formation of branched nanotubes is proposed.     

Sulfur‐Modified Graphitic Carbon Nitride Nanostructures as an Efficient Electrocatalyst for Water Oxidation

There is an urgent need to develop metal‐free, low cost, durable, and highly efficient catalysts for industrially important oxygen evolution reactions. Inspired by natural geodes, unique melamine nanogeodes are successfully synthesized using hydrothermal process. Sulfur‐modified graphitic carbon nitride (S‐modified g‐CN _x ) electrocatalysts are obtained by annealing these melamine nanogeodes in situ with sulfur. The sulfur modification in the g‐CN _x structure leads to excellent oxygen evolution reaction activity by lowering the overpotential. Compared with the previously reported nonmetallic systems and well‐established metallic catalysts, the S‐modified g‐CN _x nanostructures show superior performance, requiring a lower overpotential (290 mV) to achieve a current density of 10 mA cm^?2 and a Tafel slope of 120 mV dec^?1 with long‐term durability of 91.2% retention for 18 h. These inexpensive, environmentally friendly, and easy‐to‐synthesize catalysts with extraordinary performance will have a high impact in the field of oxygen evolution reaction electrocatalysis.     

Defektanalyse von a‐C‐ und CNx‐Schichten mittels Röntgen‐Photoemissions‐Elektronenmikroskopie (X‐PEEM)

Carbon and carbon nitride films are widely used as protective overcoats. Especially in magnetic hard disk drive industry there is a need for wear resistant and corrosion preventing overcoats with a thickness of some few nanometers. X‐ray Photoemission Electron Microscopy is a versatile tool to analyze carbon overcoats among others. Information about local bonding environment can be achieved by recording X‐ray Absorption Near Edge Structures (XANES). CVD DLC, a‐C and CN_x coating have been analyzed. The fractions of sp²‐hybridized carbon atoms have been determined for a‐C overcoats and its correlation to mechanical properties could be shown. A scratch test has been performed on a CN_x overcoat on a magnetic disk and analyzed with X‐PEEM afterwards.     

Sustainable Synthesis of Co@NC Core Shell Nanostructures from Metal Organic Frameworks via Mechanochemical Coordination Self‐Assembly: An Efficient Electrocatalyst for Oxygen Reduction Reaction

Herein, a new type of cobalt encapsulated nitrogen‐doped carbon (Co@NC) nanostructure employing Zn_xCo_1?x(C₃H₄N₂) metal–organic framework (MOF) as precursor is developed, by a simple, ecofriendly, solvent‐free approach that utilizes a mechanochemical coordination self‐assembly strategy. Possible evolution of Zn_xCo_1?x(C₃H₄N₂) MOF structures and their conversion to Co@NC nanostructures is established from an X‐ray diffraction technique and transmission electron microscopy analysis, which reveal that MOF‐derived Co@NC core–shell nanostructures are well ordered and highly crystalline in nature. Co@NC–MOF core–shell nanostructures show excellent catalytic activity for the oxygen reduction reaction (ORR), with onset potential of 0.97 V and half‐wave potential of 0.88 V versus relative hydrogen electrode in alkaline electrolyte, and excellent durability with zero degradation after 5000 potential cycles; whereas under similar experimental conditions, the commonly utilized Pt/C electrocatalyst degrades. The Co@NC–MOF electrocatalyst also shows excellent tolerance to methanol, unlike the Pt/C electrocatalyst. X‐ray photoelectron spectroscopy (XPS) analysis shows the presence of ORR active pyridinic‐N and graphitic‐N species, along with CoN_x? C_y and Co? N_x ORR active (M–N–C) sites. Enhanced electron transfer kinetics from nitrogen‐doped carbon shell to core Co nanoparticles, the existence of M–N–C active sites, and protective NC shells are responsible for high ORR activity and durability of the Co@NC–MOF electrocatalyst.     

Structure of CN<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> films (0 ≤ <Emphasis Type="Italic">x</Emphasis> ≤ 0.5) deposited by arc sputtering of graphite

The structure of a-C and CN _x coatings 1–3 μ thick deposited on metal substrates by arc-pulse sputtering of graphite target in nitrogen background at P = (10^?2 ?5) Pa was studied by transmission electron microscopy and scanning electron microscopy. Concentration and depth distribution of nitrogen in CN _x depend on progressive saturation of graphite target. Nitrogen-free coatings (x = 0) consist of amorphous matrix with multiwalled nanotubes. Structure of carbon nitride coatings depends on nitrogen concentration. Over the range of C_N/C_C < 0.15 and C_N/C_C > 0.4 CN _x coatings are amorphous. The structure of CN_0.15<x<0.4 is a mixture of two types of amorphous domains, one of which is decorated by microcrystalline inclusions. The same structured inclusions were found on graphite target modified by electric arc. The obtained results allow understanding the dependence of the CN_0≤x≤0.5 coatings properties on nitrogen concentration.     

A biosensor based on Coriolopsis gallica laccase immobilized on nitrogen-doped multiwalled carbon nanotubes and graphene oxide for polyphenol detection

The use of nanomaterials allows the design of ultrasensitive biosensors with advantages in the detection of organic molecules. Catechol and catechin are molecules that occur naturally in fruits, and their presence in products like dyes and wines affects quality standards. In this study, catechol and catechin were measured at the nanoscale by means of cyclic voltammetry. The oxidation of Coriolopsis gallica laccase immobilized on nitrogen-doped multiwalled carbon nanotubes (Lac/CN_x-MWCNT) and on graphene oxide (Lac/GO) was used to measure the concentrations of catechol and catechin. Nitrogen-doped multiwalled carbon nanotubes (CN_x-MWCNT) were synthesized by spray pyrolysis and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy (XPS). Covalently bonded hybrids with laccase (Lac/CN_x-MWCNT and Lac/GO) were generated. Catalytic activity of free enzymes determined with syringaldazine yielded 14 584 UmL⁻¹. With Lac/CN_x-MWCNT at concentrations of 6.4 mmol L⁻¹ activity was 9326 U mL⁻¹, while enzyme activity measured with Lac/GO at concentration of 6.4 mmol L⁻¹ was 9 234 U mL⁻¹. The Lac/CN_x-MWCNT hybrid showed higher stability than Lac/GO at different ethyl alcohol concentrations. The Lac/CN_x-MWCNT hybrid can measure concentrations, not previously reported, as low as 1 × 10⁻⁸ mol L⁻¹ by measuring the electric current responses.     

Preparation of the hard CNx thin films using NO ambient gas by pulsed laser deposition

Pulsed laser deposition (PLD) technique has been widely used in thin film preparation because of its wonderful and excellent properties and amorphous carbon nitride (CN_x) thin films are recognized to have potential for applications like hard coating and electron field emission device. We have deposited CN_x thin films by KrF excimer laser – (λ= 248 nm) ablation of pure graphite target in pure NO gas ambient condition. In this paper, we have prepared the CN_x thin films at various ambient NO gas pressure of 1.3–26 Pa and laser fluence of 2– 5J cm^?2 on Si (100) substrate. We consider that the hardness of CN_x thin films improves due to the increase the nitrogen/carbon (N/C) ratio. The N/C ratio depended on the ambient NO gas pressure and laser fluence. We obtainedthe maximum N/C ratio of 1.0 at NO 3.3 Pa. The typical absorption of CN bonds such as sp² C–N, sp³ C–N, G band and D band were detected from the infrared absorption measurement by FTIR in the deposited CN_x thin films.     

High-yield preparation of individual nitrogen-containing carbon nanobells

We developed a simple method to prepare individual nitrogen-containing carbon (CN_x) nanobells with high yield. A mass of nanobells were produced from polymerized CN_x nanobells by in situ plasma etching inside a chemical vapor deposition chamber. Scanning electron microscopy and transmission electron microscopy characterization reveals that the polymerized nanobells have been totally separated into individual nanobells, where each nanobell keeps its structure as that before etched. The present method sheds a light in the large-scale production of size-controllable short nanotubes.     

CN<Subscript>x</Subscript>/TiN<Subscript>y</Subscript> films prepared by ion-beam sputtering

CN _x /TiN _y multilayers were prepared by ion-beam sputtering and analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy-dispersive X-ray (EDX). EDX results show that the atom ratios of [N]/([C] + [N] + [Ti]) in the multilayers vary from 20 at.% to 41 at.%. XPS analysis presents that the N content of the CN _x layer in CN _x /TiN _y is about 32.18 at.%. The nature of chemical bonding of the CN _x layer in CN _x /TiN _y was also analyzed. The X-ray and electron diffraction analyses suggest that three kinds of C₃N₄ phases, such as -C₃N₄, graphite-C₃N₄ and cubic-C₃N₄, are embodied in the multilayers. In CN _x /TiN _y bilayers, a hetero-epitaxial relationships, of (1 1 2) cubic-C₃N₄//(1 1 13) Ti₂N, and [42 3¯] cubic-C₃N₄//[1 1¯ 0] Ti₂N, was observed between cubic-C₃N₄ and Ti₂N.     

Optimizing hardness of CNxthin films by dc magnetron sputtering and a statistical approach

We have investigated the effects of seven sputtering control factors on the hardness of carbon nitride (CN _x ) thin films by design of experiments and the analysis of variance (ANOVA) to synthesize hard CN _x thin films. It was determined statistically that the substrate temperature, the sputtering pressure and the target to substrate distance are significant control factors for the hardness of the CN _x thin films within the experimental range of this study. Especially, the distance is the most important control factor of the seven factors; the hardest films are obtained at the distance of 4.5 cm. On the other hand, the effects of the substrate treatment, the dc power, the nitrogen concentration and the sputtering time are not statistically significant. It is suggested that these statistical methods are effective to compare the importance of many sputtering control factors. The CN _x thin films deposited under the optimized sputtering conditions exhibit a relatively high hardness value of 55 ± 11 GPa, Young's modulus of 228 ± 21 GPa and an elastic recovery (%R) of 98%. The compressive stress in the films is a low value of 0.3 GPa.     

Peptide Nanotube‐Templated Biomineralization of Cu2−xS Nanoparticles for Combination Treatment of Metastatic Tumor

1D peptide nanostructures (i.e., peptide nanotubes, PNTs) exhibit tunable chemo‐physical properties and functions such as improved tissue adhesion, increased cellular uptake, and elongated blood circulation. In this study, the application of PNTs as a desirable 1D template for biomineralization of Cu_2?xS nanoparticles (Cu_2?xS NPs, x = 1–2) is reported. Monodisperse Cu_2?xS NPs are uniformly coated on the peptide nanotubes owing to the specific high binding affinity of Cu ions to the imidazole groups exposed on the surface of nanotubes. The Cu_2?xS NP–coated PNTs are further covalently grafted with an oxaliplatin prodrug (Pt–CuS–PNTs) to construct a versatile nanoplatform for combination cancer therapy. Upon 808 nm laser illumination, the nanoplatform induces significant hyperthermia effect and elicits reactive oxygen species generation through electron transfer and Fenton‐like reaction. It is demonstrated that the versatile nanoplatform dramatically inhibits tumor growth and lung metastasis of melanoma in a B16‐F10 melanoma tumor‐bearing mouse model by combined photo‐ and chemotherapy. This study highlights the ability of PNTs for biomineralization of metal ions and the promising potential of such nanoplatforms for cancer treatment.     

Efficient and green oxidative degradation of methylene blue using Mn-doped ZnO nanoparticles (Zn1−xMnxO)

Mn-doped ZnO nanoparticles, Zn_1?xMn_xO, were synthesised by a polyethylene glycol (PEG) sol–gel method and the physicochemical properties of compounds were characterised by atomic absorption spectroscopy (AAS), energy-dispersive X-ray analysis, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The catalytic degradation of an organic dye, methylene blue (MB), in the presence of Zn_1?xMn_xO as the catalyst and hydrogen peroxide (H₂O₂) as the oxidant at room temperature in water has been studied. Effects of oxidant, catalyst amount, catalyst composition, pH value of the solution and an OH-radical scavenging agent on the degree of the decomposition of MB dye were also studied.     

Carbonitride Nanomaterials,Thin Films,and Solids

Binary, ternary, and quaternary carbonitride materials, such as CN_x, BCN, SiCN, SiBCN, AlBCN, are of significant industrial interest because of their light weight and multi‐functional properties, combining extreme hardness, oxidation resistance, and chemical inertness. The most exciting material in this family is carbon nitride C₃N₄ with expected ‘superdiamond’ properties. This report describes new approaches to the preparation of CN_x thin films, and nanoscale or bulk solids of C₃N₄ and BCN.     

Anisotropic Nanoclustered Carbon Phases Prepared from Fullerite C60 Under Non‐hydrostatic High Pressure

Abstract

We show that application of the non‐hydrostatic pressure to the cluster‐based molecular material, like fullerite C₆₀, provides a new opportunity to create elastically and structurally anisotropic carbon materials, including 2D polymerized rhombohedral C₆₀ and graphite‐type (sp ²) disordered atomic‐based phases. The elastic anisotropy, detected by the difference in the ultrasound velocities propagating along and across the loading axis, is directly confirmed by the results of x‐ray diffraction.     

Metal Cation‐Assisted Synthesis of Amorphous B,N Co‐Doped Carbon Nanotubes for Superior Sodium Storage

Nearly inexhaustible sodium sources on earth make sodium ion batteries (SIBs) the best candidate for large‐scale energy storage. However, the main obstacles faced by SIBs are the low rate performance and poor cycle stability caused by the large size of Na⁺ ions. Herein, a universal strategy for synthesizing amorphous metals encapsulated into amorphous B, N co‐doped carbon (a‐M@a‐BCN; M = Co, Ni, Mn) nanotubes by metal cation‐assisted carbonization is explored. The methodology allows tailoring the structures (e.g., length, wall thickness, and metals doping) of a‐M@a‐BCN nannotubes at the molecular level. Furthermore, the amorphous metal sulfide encapsulated into a‐BCN (a‐MS_x@a‐BCN; MS_x: CoS, Ni₃S₂, MnS) nanotubes are obtained by one‐step sulfidation process. The a‐M@a‐BCN and a‐MS_x@a‐BCN possess the larger interlayer spacing (0.40 nm) amorphous carbon nanotube rich in heteroatoms active sites, making them exhibit excellent Na⁺ ions diffusion kinetics and capacitive storage behavior. As SIBs anodes, they show high capacity, excellent rate performance, and long cycle stability.     

Fabrication of Pb1‐xSnxTe/PbTe heterojunctions by liquid phase epitaxy

Abstract

Pb_1‐x Sn _x Te epitaxial layers were successfully grown on PbTe substrates by liquid phase epitaxy (LPE) technique. The compositions and surface morphology of the epitaxial Pb_1‐x Sn _x Te layers were controlled in the LPE growth, and p‐Pb_1‐x Sn _x Te/n‐PbTe heterodiodes with a good junction‐perfection factor were made.     

Ferric oxide and ZnFe2O4 nanotubes derived from nano ZnO/FeOx core/shell structures

The ZnO/FeO_x core/shell nanorods were prepared with ZnO nanorods as templates, on which ferric oxide was deposited by thermal decomposition of Fe(acac)₃ in solution. The thickness of the ferric oxide shell could be precisely controlled by the concentration of Fe(acac)₃. The amorphous ferric oxide nanotubes were fabricated by wet-etching the ZnO core nanorods in HAc solution and polycrystalline ZnFe₂O₄ nanotubes were prepared by annealing the core/shell ZnO/FeO_x nanocomposites in air. The obtained ZnFe₂O₄ nanotubes showed paramagnetism at room temperature.