A Novel Polycatechol/Ordered Mesoporous Carbon Composite Film Modified Electrode and Its Electrocatalytic Application

Polycatechol (PCC) was prepared by electropolymerizing catechol (CC) on the surface of an ordered mesoporous carbon (OMC) modified electrode for the first time. Scanning electron microscopy (SEM) and cyclic voltammetry (CV) were used to characterize the structure and electrochemical behaviors of PCC/OMC nanocomposite film. Compared with the bare GC and OMC/GC electrodes, the PCC/OMC/GC electrode exhibits a good electrocatalysis toward the oxidation of NADH at 0.0 V with a high sensitivity (8.7 mA/mM). These make PCC/OMC/GC electrode a promising candidate for stable and efficient electrochemical sensors for the detection of NADH.     

功能化有序介孔碳对重金属离子Cu(II)、Cr(VI)的选择性吸附行为

以三嵌段共聚物F127为模板剂, 酚醛树脂为碳源, 正硅酸乙酯为硅源, 三组分共组装合成介孔碳?氧化 硅纳米复合物, 再经HF去除氧化硅, 得到有序介孔碳(OMC). X射线衍射(XRD)、透射电子显微镜(TEM)、低温 N2吸脱附(BET)等测试表明, 所得样品具有高度有序的介孔结构, 比表面积和孔容分别为1330 m²·g^-1和2.13 cm³·g^-1, 平均孔径6.4 nm. 对其先氧化、后氯化、再胺化, 得到不同胺基接枝量的胺化介孔碳(C-NH₂(m), m为加入的乙二胺的质量(g)). 傅里叶变换红外(FT-IR)光谱表征结果证实, 胺基官能团成功接枝到有序介孔碳表面.TEM测试表明介孔碳的有序孔道结构得到了较好的保持. 以有序介孔碳、胺化介孔碳作吸附剂对Cu(II)、Cr(VI)进行选择性吸附研究. 结果表明: 功能化修饰前, 样品对Cu(II)、Cr(VI)饱和吸附量分别为213.33、241.55 mg·g^-1; 修饰后饱和吸附量可分别达到495.05、68.21 mg·g^-1. 功能化介孔碳表现了较强的选择性吸附Cu(II)的能力.     

Screen-printed voltammetric sensor for TNT

Screen-printed carbon electrodes have been developed as disposable voltammetric sensors for 2,4,6-trinitrotoluene (TNT). Thick-film electrodes based on various conventional and modified inks have been compared for this task. The operation is based on placing the selected thick-film carbon sensor in the non-deaerated/quiescent sample and using a fast (<1 s) and sensitive square-wave voltammetric scan. Different experimental variables have been optimized to yield a detection limit of 200 ppb TNT and a wide linear range. The high selectivity, demonstrated in assays of various untreated environmental samples, is attributed to the facts that the reducible nitro group is rare in nature and that most electroactive organic compounds require higher potentials. The new single-use sensor strips should facilitate the on-site environmental screening of TNT.     

In situ synthesis of ceria nanoparticles in the ordered mesoporous carbon as a novel electrochemical sensor for the determination of hydrazine

A novel ceria (CeO₂)–ordered mesoporous carbon (OMC) modified electrode for the sensitive amperometric determination of hydrazine was reported. CeO₂–OMC composites were synthesized via a hydrothermal method at a relatively low temperature (180 °C) and characterized by scanning electron microscopy (SEM), transmission electron microcopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The CeO₂–OMC modified glassy carbon electrode was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) and indicated good electrocatalytic effect to the oxidation of hydrazine. Under the optimized conditions, the present sensor could be used to measure hydrazine in wide linear range from 40 nM to 192 μM (R² = 0.999) with a low detection limit of 12 nM (S/N = 3). Additionally, the sensor has been successfully applied to detect hydrazine in real water samples and the recoveries were between 98.2% and 105.6%. Eventually, the sensor exhibited an excellent stability and reproducibility as a promising method for determination of hydrazine.     

Ordered mesoporous carbon film as an effective solid-phase microextraction coating for determination of benzene series from aqueous media

The present work reports preparation of ordered mesoporous carbon (OMC) film supported on a graphite fiber as a new type of solid-phase microextraction (SPME) fiber for determination of benzene series from aqueous media. The strategy for the supported OMC film preparation was combined dip-coating technology with solvent evaporation-induced self-assembly (EISA) approach. A graphite fiber was immersed in an ethanol solution containing phenolic resin and Pluronic triblock copolymer. Upon solvent evaporation and subsequent pyrolysis under 700 °C, the phenolic resin and the surfactant self-assembled on the surface of the graphite fiber to form smooth OMC film. X-ray diffraction (XRD), transmission electron microscopy (TEM) and nitrogen isothermal adsorption results indicate that the resultant OMC film possesses well-ordered two dimensional hexagonal mesostructure with pore diameters of 4.5 nm and BET surfaces of 630 m²/g. Scanning electron microscopy (SEM) studies show the supported OMC film with thickness at 8.5 μm is continuous and defect-free. The SPME efficiency of the OMC fiber was evaluated by analysis of five benzene series (benzene, toluene, ethylbenzene, p-xylene and m-xylene) from water samples by gas chromatography-flame ionization detection (GC-FID). The analysis results indicate that the prepared OMC fiber has wide linear ranges (0.5–500 μg/L), low detection limits (0.01–0.05 μg/L) and good repeatabilities (4.0–5.8% for one fiber, 2.9–8.7% for fiber-to-fiber). Compared with commercial counterparts, the OMC fiber exhibits improved extraction efficiency for benzene series and PAHs.     

Electrochemical sensors based on binuclear cobalt phthalocyanine/surfactant/ordered mesoporous carbon composite electrode

A new ordered mesoporous carbon (OMC) composite modified electrode was fabricated for the first time. Binuclear cobalt phthalocyaninehexasulfonate sodium salt (bi-CoPc) can be adsorbed onto didodecyldimethylammonium bromide (DDAB)/OMC film by ion exchange. UV-vis spectroscopy, scanning electron microscopy (SEM) and electrochemical methods were used to characterize the composite film. The cyclic voltammograms demonstrate that the charge transfer of bi-CoPc is promoted by the presence of OMC. Further study indicated that bi-CoPc/DDAB/OMC film is the excellent electrocatalyst for the electrochemical reduction of oxygen in a neutral aqueous solution and hemoglobin (Hb) at lower concentrations. Additionally, as an amperometric 2-mercaptoethanol (2-ME) sensor, this modified electrode shows a wider linear range (2.5 × 10⁻⁶ to 1.4 × 10⁻⁴ M), high sensitivity (16.5 μA mM⁻¹) and low detection limit of 0.6 μM (S/N = 3). All these confirm the fact that the new composite film may have wide potential applications in biofuel cells, biological and environmental sensors.     

Gold Nanoparticles Electrodeposited on Ordered Mesoporous Carbon as an Enhanced Material for Nonenzymatic Hydrogen Peroxide Sensor

A facile and controllable electrodeposition method was developed to directly attach gold nanoparticles (GNPs) on ordered mesoporous carbon (OMC). The GNPs on OMC substrate were characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD) and X‐ray photoelectron spectrometer (XPS), respectively. A nonenzymatic hydrogen peroxide (H₂O₂) sensor was fabricated on GNPs‐OMC/GCE. The sensor demonstrated a fast amperometric response (2.5 s), a wide linear range toward H₂O₂ concentrations between 2.0×10^?6 and 3.92×10^?3 M (R=0.999), and a low detection limit of 0.49 µM (S/N=3). Moreover, it exhibited good reproducibility and long‐term stability. The excellent electrocatalytical activity might be attributed to the synergistic effect of OMC and GNPs.     

有序介孔碳负载NiCo2O4电极的制备及其超电容性能

以有序介孔碳(OMC)为载体,采用共沉淀法制备了OMC/NiCo2O4复合物.用X射线衍射(XRD)、傅里叶变换红外(FT-IR)光谱和透射电镜(TEM)研究其结构与形貌,发现NiCo2O4纳米颗粒均匀地负载在有序介孔碳上.循环伏安和恒流充放电测试表明,NiCo2O4质量分数为40%时,在1A·g-1的电流密度下,复合物电极的比电容可以达到577.0F·g-1,电流密度为8A·g-1时,比电容可以达到470.8F·g-1,并具有良好的循环稳定性.在2A·g-1的电流密度下,经过2000次循环后,比电容还可达到508.4F·g-1,电容保持率为92.7%.     

In situ Magnesiothermal Synthesis of Mesoporous MgO/OMC Composite for Sensitive Detection of Lead Ions

Mesoporous materials have exceptional properties for application owing to their ability to absorb and interact with guest species. A novel MgO/OMC composite with mesoporous structure was successfully synthesized via in situ magnesiothermic reduction. The structure was confirmed by N₂ sorption isotherms, X‐ray diffraction pattern (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). By using nafion and bismuth films as co‐modifiers, the MgO/OMC composite material shows high sensitivity of 0.113 μA ? L μg^?1 and lower background current for electrochemical determination of lead ion (Pb²⁺) by using anodic stripping voltammetry. The high specific surface area and good mass transfer on the proposed mesoporous material, as well as the outstanding adsorption abilities of MgO to metal ions and the excellent conductivity of the carbon skeleton contribute to the enhanced electrochemical response of Pb²⁺. As the stripping response of Bi/MgO/OMC‐Nafion/PGE is highly linear (R²=0.998) over a Pb²⁺ concentration range of 2 to 300 μg/L, it was successfully used to analyse Pb²⁺ in real tap‐water samples with good recoveries.     

Simultaneous and Sensitive Detection of Cd(II) and Pb(II) Using a Novel Bismuth Film/Ordered Mesoporous Carbon‐molecular Wire Modified Graphite Carbon Paste Electrode

An electrochemical sensor for the simultaneous and sensitive detection of Cd(II) and Pb(II) is proposed on the basis of square‐wave anodic stripping voltammetry (SWASV) experiments using a novel bismuth film/ordered mesoporous carbon‐molecular wire modified graphite carbon paste electrode (Bi/OMC‐MW/GCPE). Ordered mesoporous carbon (OMC) and molecular wire (MW) (diphenylacetylene) were used as the modifier and binder, respectively. The Bi/OMC‐MW/GCPE was prepared with the addition of graphite powder, OMC and DPA at the ratio of 2 : 1 : 1. The electrochemical properties and morphology of the electrode were characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), SWASV and scanning electron microscopy (SEM). The parameters affecting the stripping current response were investigated and optimized. The experimental results show that the prepared electrode exhibited excellent electrochemical performance, good electrical conductivity and a high stripping voltammetric response. Under optimized conditions, a linear range was achieved over a concentration range from 1.0 to 70.0 μg/L for both Cd(II) and Pb(II) metal ions, with detection limits of 0.07 μg/L for Cd(II) and 0.08 μg/L for Pb(II) (S/N=3) with the deposition time 150 s. Moreover, the sensor exhibited improved sensitivity and reproducibility compared to traditional CPEs. The fabricated electrode was then successfully used to satisfactorily detect Cd(II) and Pb(II) in real soil samples.     

High‐Loading Nano‐SnO2 Encapsulated in situ in Three‐Dimensional Rigid Porous Carbon for Superior Lithium‐Ion Batteries

Tin oxide nanoparticles (SnO₂ NPs) have been encapsulated in situ in a three‐dimensional ordered space structure. Within this composite, ordered mesoporous carbon (OMC) acts as a carbon framework showing a desirable ordered mesoporous structure with an average pore size (≈6 nm) and a high surface area (470.3 m² g^?1), and the SnO₂ NPs (≈10 nm) are highly loaded (up to 80 wt %) and homogeneously distributed within the OMC matrix. As an anode material for lithium‐ion batteries, a SnO₂@OMC composite material can deliver an initial charge capacity of 943 mAh g^?1 and retain 68.9 % of the initial capacity after 50 cycles at a current density of 50 mA g^?1, even exhibit a capacity of 503 mA h g^?1 after 100 cycles at 160 mA g^?1. In situ encapsulation of the SnO₂ NPs within an OMC framework contributes to a higher capacity and a better cycling stability and rate capability in comparison with bare OMC and OMC ex situ loaded with SnO₂ particles (SnO₂/OMC). The significantly improved electrochemical performance of the SnO₂@OMC composite can be attributed to the multifunctional OMC matrix, which can facilitate electrolyte infiltration, accelerate charge transfer, and lithium‐ion diffusion, and act as a favorable buffer to release reaction strains for lithiation/delithiation of the SnO₂ NPs.     

Electrochemical Properties of Ordered Mesoporous Carbon Film Adsorbed onto a Self‐Assembled Alkanethiol Monolayer on Gold Electrode

A stable ordered mesoporous carbon (OMC) film electrode was successfully constructed by adsorbing OMC onto a self‐assembled monolayer (SAM) of C₁₈H₃₇SH chemisorbed on the Au electrode. Transmission electron microscopy (TEM), atomic force microscopy (AFM), and electrochemical methods were used to characterize the properties of the OMC film electrode. The adsorbed OMC can restore the heterogeneous electron transfer almost totally blocked by the alkanethiol monolayer. Nyquist plots show a sharply decrease of the charge transfer resistance (R_ct) of the Fe(CN) couple at the OMC film electrode. Furthermore, the OMC film electrode is found to possess a significantly reduced interfacial capacitance and largely enhanced current response of hydrogen peroxide. This novel approach to the fabrication of stable OMC film electrode with excellent electrochemical properties is believed to be very attractive for electrochemical studies and electroanalytical applications.     

磁性有序介孔炭的制备及药物吸附行为研究

采用纳米共铸法将磁性纳米粒子包埋到有序介孔炭的骨架中, 制成含有磁性纳米粒子的有序介孔炭(Fe/OMCs). 实验通过氮气吸附、扫描电镜、X射线衍射、磁性测试等手段对Fe/OMCs进行了系统的表征. 研究表明, Fe/OMCs基本保持了有序介孔结构, 磁性粒子在材料中以纳米α-Fe粒子的形式存在, 并且具有超顺磁特性. 盐酸四环素(TH)在Fe/OMCs上的吸附研究表明, Fe/OMCs的介孔表面积和介孔孔容是决定TH吸附量的关键因素. 脱附动力学研究表明, Fe/OMCs的孔尺寸是影响脱附速率的关键因素, 孔径越大, TH的脱附速率就越大.     

Non-aerosol detection of explosives with a continuous flow immunosensor

Contamination of groundwater, soil, and the marine environment by explosives is a global issue. Identification, characterization and remediation are all required for a site recognized as contaminated with 2,4,6-trinitrotoluene (TNT) or hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). For each step, a method to accurately measure the contaminant level is needed. This paper reviews some of the current methods with emphasis on a single biosensor developed in our laboratory. Current regulatory methods require samples to be sent off-site to a certified laboratory resulting in time delays up to a month. A continuous flow biosensor for detection of explosives has been developed and tested for the rapid field screening of environmental samples. The detection system is based on a displacement immunoassay in which monoclonal antibodies to (TNT) and RDX are immobilized on solid substrates, allowed to bind fluorescently labeled antigens, and then exposed to explosives in aqueous samples. Explosive compounds present in the sample displace proportional amounts of the fluorescent label, which can then be measured to determine the original TNT or RDX concentration. The system can accurately detect ppb to ppt levels of explosives in groundwater or seawater samples and in extracts of contaminated soil. The biosensor has applications in environmental monitoring at remediation sites or in the location of underwater unexploded ordnance.     

有序介孔碳负载Fe、Co、Ni纳米晶的软模板合成及其表征

报道了在有序介孔碳基体中一步合成负载Fe、Co、Ni纳米晶的方法. 以间二苯酚和甲醛为碳源, F127为模板剂, Fe、Co、Ni的硝酸盐为前驱体, 通过软模板组装路线在酸性条件下合成了负载型有序介孔碳复合材料. 采用X射线衍射(XRD)、透射电镜(TEM)和氮气吸附等手段对所合成材料进行了表征. 结果表明: 合成的材料具有类似于SBA-15的有序介孔结构, 有序介孔碳负载Fe、Co、Ni纳米晶复合材料的比表面积分别为586、626和698 m²·g^-1. XRD和TEM表征结果证实了金属物种以高分散纳米晶的形式分布在介孔碳基体中.     

High-loading Pt nanoparticles on mesoporous carbon with large mesopores for highly active methanol electro-oxidation

High metal-loading Pt/C electrocatalysts are important for the fabrication of thin-layered membrane electrode assemblies (MEAs). However, the preparation of high-loading Pt catalysts with a narrow size distribution of nanoparticles remains a challenge. Herein, ordered mesoporous carbon (OMC) with large mesopores (~15 nm) and a high surface area (1316.0 m² g^?1) was fabricated using a SiO₂ nanosphere array as a template. This material was developed to support a high loading of Pt nanoparticles (60 wt%) and was then used as an electrocatalyst for the methanol oxidation reaction (MOR). The prepared Pt/OMC contains Pt nanoparticles with an average size of ~1.9 nm that are uniformly dispersed on the mesoporous walls of the OMC. The Pt/OMC catalyst exhibits smaller Pt nanoparticle size, greater Pt dispersion, larger specific electrochemically active surface area (ECSA), and higher electrocatalytic activity for the MOR than the carbon black (Vulcan XC-72R)-supported Pt and the commercial Pt/C catalysts.     

Selective Voltammetric Determination of Uric Acid in the Presence of Ascorbic Acid at Ordered Mesoporous Carbon Modified Electrodes

A novel chemically modified electrode was fabricated by immobilizing ordered mesoporous carbon (OMC) onto a glassy carbon (GC) electrode. The electrocatalytic behavior of the OMC modified electrode towards the oxidation of uric acid (UA) and ascorbic acid (AA) was studied. Compared to a glassy carbon electrode, the OMC modified electrode showed a faster electron transfer rate and reduced the overpotentials greatly. Furthermore, the OMC modified electrode resolved the overlapping voltammetric responses of UA and AA into two well‐defined voltammetric peaks with peak separation of ca. 0.38 V. All results show that the OMC modified electrode has a good electrocatalytic ability to UA and AA, and has an excellent response towards UA even in the presence of high concentration AA.     

Copolypeptide-doped polyaniline nanofibers for electrochemical detection of ultratrace trinitrotoluene

This paper demonstrates a new electrochemical method for the detection of ultratrace amount of 2,4,6-trinitrotoluene (TNT) with synthetic copolypeptide-doped polyaniline nanofibers. The copolypeptide, comprising of glutamic acid (Glu) and lysine (Lys) units, is in situ doped into polyaniline through the protonation of the imine nitrogen atoms of polyaniline by the free carboxylic groups of Glu segments, resulting in the formation of polyaniline nanofibers of emeraldine salt. The free amino groups of Lys segments at the surface of nanofibers provide the receptor sites of TNT through the formation of charge-transfer complex between the electron-rich amino groups and the electron-deficient aromatic rings. Adsorptive stripping voltammetry results demonstrate that the poly(Glu-Lys)-doped nanofibers confined onto glassy carbon electrodes exhibit a remarkable enriching effect and thus sensitive electrochemical response to TNT with a linear dynamic range of 0.5-10 μM and a detection limit down to 100 nM. Moreover, other kinds of nitro compounds show different redox behaviors from TNT at the doped nanofibers, and thus do not interfere with the electrochemical detection of TNT. This study essentially offers a new and simple method for electrochemical detection of ultratrace TNT.     

Voltammetric detection of riboflavin based on ordered mesoporous carbon modified electrode

The potential application of ordered mesoporous carbon (OMC)-modified glassy carbon electrode (OMC/GCE) in electrochemistry as a novel electrode material was investigated. X-ray diffraction, transmission electron micrographs, and cyclic voltammetry were used to characterize the structure and electrochemical behaviors of this material. Compared to GC electrode, the peak currents of potassium ferricyanide (K₃[Fe(CN)₆]) increase and the peak potential separation (ΔE _p) decreases at the OMC/GC electrode. These phenomena suggest that OMC-modified GC electrode possesses larger electrode area and faster electron transfer rate, as compared with bare GC electrode. Furthermore, riboflavin was detected using OMC/GC electrode in aqueous solutions. The results showed that, under an optimum condition (pH 7.0), the OMC/GC electrode exhibited excellent response performance to riboflavin in the concentration range of 4.0 × 10⁻⁷ to 1.0 × 10⁻⁶ M with a high sensitivity of 769 μA mM⁻¹. The detection limit was down to around 2 × 10⁻⁸ M. With good stability and reproducibility, the present OMC/GC electrode was applied in the determination of vitamin B₂ content in vitamin tablets, and satisfactory results were obtained.     

Synthesis and characterization of ordered mesoporous carbon as electrocatalyst for simultaneous determination of epinephrine and acetaminophen

In this research, we report an easy method for synthesis of ordered mesoporous carbon (OMC) with hexagonal arrays of tubes (CMK-5). The synthesized OMC was characterized using X-ray diffraction (XRD), scanning electronic microscopy (SEM) and nitrogen sorption isotherms techniques. Due to the large surface area and high conductivity of OMC, OMC-modified glassy carbon (OMCs/GC) electrode was prepared. The unique electrochemical activity of OMCs/GC electrode was illustrated using cyclic voltammetry (CV) and electron impedance spectroscopy (EIS) in which OMC showed a faster electron transfer rate, as compared with glassy carbon electrode. The electrochemical behavior of epinephrine (EN) and acetaminophen (AP) at OMC/GC electrode was also investigated using cyclic voltammetry. The OMC/GC electrode exhibited high electrocatalytic activities toward oxidation of EN and AP and displayed good voltammetric peak separation between them. In differential pulse voltammetry technique, both EN and AP give sensitive oxidation peaks at 120?mV and 320?mV, respectively. Therefore, investigated method was applied for simultaneous determination of EN and AP. AP and EN give linear response over the range of 0.2–15?μM and 4–100?μM, respectively. The lower detection limits were found to be 0.07?μM for AP and 0.94?μM for EN.