Ordered mesoporous carbon for electrochemical sensing: A review

Screen-Printed Sensors Modified with Nafion and Mesoporous Carbon for Electrochemical Detection of Lead in Blood

Lead (Pb) has long been acknowledged as a systemic toxicant, with pronounced health impacts observed even at low exposure levels, particularly in children. Adverse effects include diminished cognitive function, altered behavior, and developmental delays. Consequently, it is imperative to conduct regular monitoring of Blood Lead Levels (BLLs). In this work, we report on an electrochemical sensor based on screen-printed carbon electrode (SPCE) coated with Nafion and mesoporous carbon (MC). The sensor system uses simple sample preparation (acidification and dilution of whole blood), minimal sample volume (a few blood drops, 200 μl), and swift time-to-results (1 h). A limit of quantitation (LOQ) of 0.3 μg dL-1 Pb was achieved in whole blood. To demonstrate the practical utility of our sensor system, we evaluated its performance in the analysis of blood samples collected from children (n = 25). Comparative analysis with the laboratory-based gold standard method of inductively coupled plasma mass spectrometry (ICP-MS) demonstrated approximately 77% accuracy and 94% precision. We anticipate that our approach will serve as a valuable tool for more frequent BLL monitoring, particularly in communities where access to laboratory testing is impractical or expensive.

Optimizing surfactant removal from a soft-templated ordered mesoporous carbon precursor: an in situ SAXS study

In situ small-angle X-ray scattering (SAXS) was employed to identify critical parameters during thermal treatment for template removal of an ordered mesoporous carbon precursor synthesized via a direct soft-templating route. The structural parameters obtained from the SAXS data as a function of time were the lattice parameter of the 2D hexagonal structure, the diameter of the cylindrical mesostructures and a power-law exponent characterizing the interface roughness. Moreover, detailed information on contrast changes and pore lattice order was obtained from analysis of the integrated SAXS intensity of the Bragg and diffuse scattering separately. Five characteristic regions during heat treatment were identified and discussed regarding the underlying dominant processes. The influence of temperature and O₂/N₂ ratio on the final structure was analyzed, and parameter ranges were identified for an optimized template removal without strongly affecting the matrix. The results indicate that the final structure and controllability of the process are optimum for temperatures between 260 and 300°C with a gas flow containing 2 mol% of O₂.

M. SK, Baek KH. Assessing the Food Quality Using Carbon Nanomaterial Based Electrodes by Voltammetric Techniques

The world is facing a global financial loss and health effects due to food quality adulteration and contamination, which are seriously affecting human health. Synthetic colors, flavors, and preservatives are added to make food more attractive to consumers. Therefore, food safety has become one of the fundamental needs of mankind. Due to the importance of food safety, the world is in great need of developing desirable and accurate methods for determining the quality of food. In recent years, the electrochemical methods have become more popular, due to their simplicity, ease in handling, economics, and specificity in determining food safety. Common food contaminants, such as pesticides, additives, and animal drug residues, cause foods that are most vulnerable to contamination to undergo evaluation frequently. The present review article discusses the electrochemical detection of the above food contaminants using different carbon nanomaterials, such as carbon nanotubes (CNTs), graphene, ordered mesoporous carbon (OMC), carbon dots, boron doped diamond (BDD), and fullerenes. The voltammetric methods, such as cyclic voltammetry (CV) and differential pulse voltammetry (DPV), have been proven to be potential methods for determining food contaminants. The use of carbon-based electrodes has the added advantage of electrochemically sensing the food contaminants due to their excellent sensitivity, specificity, large surface area, high porosity, antifouling, and biocompatibility.

A Facile Fabrication of Ordered Mesoporous Carbons Derived from Phenolic Resin and Mesophase Pitch via a Self-Assembly Method

Ordered and disordered mesoporous structures were synthesized by a self-assembly method using a mixture of phenolic resin and petroleum-based mesophase pitch as the starting materials, amphiphilic triblock copolymer F127 as a soft template, hydrochloric acid as a catalyst, and distilled water as a solvent. Then, mesoporous carbons were obtained via autoclave method at low temperature (60 °C) and then carbonization at a relatively low temperature (600 °C), respectively. X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM) analyses revealed that the porous carbons with a mesophase pitch content of approximately 10 wt% showed a highly ordered hexagonal mesostructure with a highly uniform pore size of ca. 5.0 nm. In addition, the mesoporous carbons prepared by self-assembly and low-temperature autoclave methods exhibited the amorphous or crystalline carbon structures with higher specific surface area (SSA) of 756 m2/s and pore volume of 0.63 cm3/g, depending on the synthesis method. As a result, mesoporous carbons having a high SSA were successfully prepared by changing the mixing ratio of mesophase pitch and phenolic resin. The electrochemical properties of as-obtained mesoporous carbon materials were investigated. Further, the OMC-meso-10 electrode delivered the maximum SC of about 241 F/g at an applied current density of 1 A/g, which was higher than those of the MC-10 (~104 F/g) and OMC-20 (~115 F/g).

Aptasensor for Mycobacterium tuberculosis antigen MPT64 detection using anthraquinone derivative confined in ordered mesoporous carbon as a new redox nanoprobe

Rapid and sensitive tuberculosis (TB) diagnoses remain big challenges to current detection tools. In this work, a sensitive electrochemical aptasensor was constructed for the determination of Mycobacterium tuberculosis antigen MPT64 using a new redox nanoprobe. We found that anthraquinone derivative, anthraquinone-2-carboxylic acid (AQCA), a redox mediator, could be confined in ordered mesoporous carbon material of CMK-3. Due to the large loading amount of AQCA, as well as the confined space and electron transfer promotion effect of CMK-3, the obtained AQCA/CMK-3 nanohybrid with mass ratio of 2:1 showed excellent electroactivity and was employed as a new redox nanoprobe for signal amplification for the first time. Additionally, urchin-like Ce-MOFs were used to load a large amount of deposited gold nanocrystals (dep-Au), leading to dense immobilization of capture probe. The proposed electrochemical aptasensor for MPT64 detection showed a good linear relationship in the range from 100 fg/mL to 10 ng/mL with a low detection limit of 67.6 fg/mL. Besides, the aptasensor was utilized to detect MTP64 in human serum samples for TB diagnosis and presented satisfactory results.

Simultaneous electrochemical determination of morphine and methadone by using CMK-5 mesoporous carbon and multivariate calibration

For the first time, a sensitive electrochemical sensor using a glassy carbon electrode modified with CMK-5 Ordered mesoporous carbon was fabricated for simultaneous analysis of morphine and methadone. Modern electrochemical FFT-SWV techniques and partial least-squares as a multivariable analysis were used in this method. CMK-5 nanostructures were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and Raman spectroscopy. Variables such as accumulation time and pH for the proposed sensor were optimized before quantitative analysis. To train the proposed sensor, standard mixtures of morphine (MOR), and methadone (MET) were prepared in the established linear ranges of the analyzes. The results obtained from training samples were used for PLS modeling. The efficiency of the model was determined using test and real matrix samples. The root mean square error of prediction and the squared correlation coefficients (R2p) for MET and MOR were estimated to be 0.00772 and 0.00892 and 0.948 to 0.990, respectively. The recoveries in urine samples were reported to be 97.0 and 105.6% for both MOR and MET, respectively.

Research on Adsorption and Desorption Performance of Gas-Phase Naphthalene on Hydrophobic Modified FDU-15

Naphthalene (NAP) is a typical gaseous polycyclic aromatic hydrocarbons (PAHs) pollutant that displays toxicological effects on biosystems. Ordered mesoporous carbon has relatively adequate adsorption capacity; however, the attached hydrophilic functional groups were proven to affect the adsorption performance in the presence of moisture. In this paper, trimethylchlorosilane (TMCS) is used to carry out the hydrophobic modification of ordered mesoporous carbon FDU-15, and the adsorption and desorption properties of FDU-15 were studied. Furthermore, the adsorption isotherms of naphthalene on FDU-15 and modified FDU-15 were fitted by L-F equation, and the kinetic parameters of desorption of naphthalene on modified FDU-15 were analyzed based on the method of temperature programming desorption (TPD). The results showed that the micropore volume and specific surface area of FDU-15 were significantly increased after hydrophobically modified by TMCS, and the polar functional groups of the hydrophobically modified FDU-15 were significantly reduced. Furthermore, the adsorption of naphthalene by FDU-15 before and after modification conformed to the L-F equation (R2 > 99%), and the adsorption of naphthalene by modified FDU-5 at low concentration was significantly improved due to the increase of micropores. Based on desorption kinetic performance study of modified FDU-15, it can be seen that the adsorption kinetic characteristics of naphthalene on the modified FDU-15 conform to the mechanical function of the JMA equation. When the mass ratio of TMCs to FDU-15 is 1:10 in the modification process, the pore structure and surface hydrophobicity of the modified FDU-15 reach an excellent balance. At this time, the adsorbent had the optimum desorption performance under experimental conditions, and the desorption activation energy was decreased from 60.98 kJ/mol of FDU-15 to 50.28 kJ/mol.

Fabricating BiOI nanostructures armed catalytic strips for selective electrochemical and SERS detection of pesticide in polluted water

We have constructed a dual mode catalytic strip equipped with 2D BiOI nanostructures and deployed for dual mode detection sensing of hazardous trichlorophenol (TCP). Synthesized BiOI nanostructures are investigated for its crystal architecture, morphology and chemical composition. The BiOI are loaded onto the catalytic strips with the assistance of gravity offered drying process. The BiOI nanostructures offers a very less charge transfer resistance indicating its superior catalytic properties upon the electrochemical impedance studies. It reflected on providing an excellent limit of detection (LOD) and linear sensing range for TCP in electrochemical mode. For SERS, a thin plasmonic Au layer is sputter coated on BiOI equipped catalytic strips (Au@BiOI) for the TCP detection. An impressive enhancement factor of 10⁷ is obtained for SERS detection of TCP with good LOD of 10^-10 M. Fabricated dual mode BiOI based strips are thoroughly examined for operational stability and performance in real time conditions. The fabricated high performance dual mode platform for the detection of hazardous pesticides appears to be a promising prospect for the on-the-spot investigation.

Recent progress in the development of porous carbon-based electrodes for sensing applications

Electrochemical (bio)sensors are considered clean and powerful analytical tools capable of converting an electrochemical reaction between analytes and electrodes into a quantitative signal. They are an important part of our daily lives integrated in various fields such as healthcare, food and environmental monitoring. Several strategies including the incorporation of porous carbon materials in its configuration have been applied to improve their sensitivity and selectivity in the last decade. The porosity, surface area, graphitic structure as well as chemical composition of materials greatly influence the electrochemical performance of the sensors. In this review, activated carbons, ordered mesoporous carbons, graphene-based materials, and MOF-derived carbons, which are used to date as crucial elements of electrochemical devices, are described, starting from their textural and chemical compositions to their role in the outcome of electrochemical sensors. Several relevant and meaningful examples about material synthesis, sensor fabrication and applications are illustrated and described. The closer perspectives of these fascinating materials forecast a promising future for the electrochemical sensing field.

Polyaniline nanowire arrays generated through oriented mesoporous silica films: effect of pore size and spectroelectrochemical response

Indium-tin oxide electrodes modified with vertically aligned silica nanochannel membranes have been produced by electrochemically assisted self-assembly of cationic surfactants (cetyl- or octadecyl-trimethylammonium bromide) and concomitant polycondensation of the silica precursors (tetraethoxysilane). They exhibited pore diameters in the 2-3 nm range depending on the surfactant used. After surfactant removal, the bottom of mesopores was derivatized with aminophenyl groups via electrografting (i.e., electrochemical reduction of in situ generated aminophenyl monodiazonium salt). These species covalently bonded to the ITO substrate were then exploited to grow polyaniline nanofilaments by electropolymerization of aniline through the nanochannels. Under potentiostatic conditions, the length of polyaniline wires is controllable by tuning the electropolymerization time. From cyclic voltammetry characterization performed either before or after dissolution of the silica template, it appeared that both the polyaniline/silica composite and the free polyaniline nanowire arrays were electroactive, yet with much larger peak currents in the latter case as a result of larger effective surface area offered to the electrolyte solution. At identical electropolymerization time, the amount of deposited polyaniline was larger when using the silica membrane with larger pore diameter. All polyaniline deposits exhibited electrochromic properties. However, the spectroelectrochemical data indicated more complete interconversion between the coloured oxidized form and colourless reduced polyaniline for the arrays of nanofilaments in comparison to bulky films. In addition, the template-free nanowire arrays (i.e., after silica dissolution) were characterized by faster electrochromic behaviour than the polyaniline/silica hybrid, confirming the potential interest of such polyaniline nano-brushes for practical applications.

Modification of ordered mesoporous carbon for removal of environmental contaminants from aqueous phase: A review

Contamination of water bodies by potentially toxic elements and organic pollutants has aroused extensive concerns worldwide. Thus it is significant to develop effective adsorbents for removing these contaminants. As a new member of carbonaceous material families (activated carbon, biochar, and graphene), ordered mesoporous carbon (OMC) with larger specific surface area, ordered pore structure, and higher pore volume are being evaluated for their use in contaminant removal. In this paper, modification techniques of OMC were systematically reviewed for the first time. These include nonmetallic doping modification (nitrogen, sulfur, and boron) and the impregnation of nano-metals and metal oxides (iron, copper, cobalt, nickel, magnesium, and rare earth element). Reaction conditions (solution pH, reaction temperature, sorbent dosage, and contact time) are of critical importance for the removal performance of contaminants onto OMC. In addition, the pristine and modified OMC have been investigated for the removal of a range of contaminants, including cationic/anionic toxic elements and organic contaminants (synthetic dye, phenol, and others), and involving different and specific mechanisms of interaction with contaminants. The future research directions of the application of pristine and modified OMC were proposed. Overall, this review can provide sights into the modification techniques of OMC for removal of environmental contaminants.

Bispropylurea bridged polysilsesquioxane: A microporous MOF-like material for molecular recognition

Microporous organosilicas assembled from polysilsesquioxane (POSS) building blocks are promising materials that are yet to be explored in-depth. Here, we investigate the processing and molecular structure of bispropylurea bridged POSS (POSS-urea), synthesised through the acidic condensation of 1,3-bis(3-(triethoxysilyl)propyl)urea (BTPU). Experimentally, we show that POSS-urea has excellent functionality for molecular recognition toward acetonitrile with an adsorption level of 74 mmol/g, which compares favourably to MOFs and zeolites, with applications in volatile organic compounds (VOC). The acetonitrile adsorption capacity was 132-fold higher relative to adsorption capacity for toluene, which shows the pores are highly selective towards acetonitrile adsorption due to their size and arrangement. Theoretically, our tight-binding density functional and molecular dynamics calculations demonstrated that this BTPU based POSS is microporous with an irregular placement of the pores. Structural studies confirm maximal pore sizes of ∼1 nm, with POSS cages possessing an approximate edge length of ∼3.16 Å.

ZVI impregnation altered arsenic sorption by ordered mesoporous carbon in presence of Cr(Ⅵ): A mechanistic investigation

It is challenging to efficiently remove arsenate (As(Ⅴ)) and chromate (Cr(Ⅵ)) simultaneously. Herein, ordered mesoporous carbon (OMC) was fabricated with averaged pore diameter of 6.5 nm and surface area of 997 m² g^-1. Zerovalent iron (ZVI) impregnation reduced surface area of ZVI/OMC (432 m² g^-1) and increased I_D/I_G ratio by 13%. Maximal Cr(Ⅵ) and As(Ⅴ) sorption capacities at pH 3 were 0.66 and 0.019 mmol g^-1 by OMC, and 0.71 and 0.39 mmol g^-1 by ZVI/OMC, respectively. Reduction accounted for over 55% for Cr(Ⅵ) and As(Ⅴ) removal followed by complexation and precipitation. Better ZVI/OMC performance was ascribed to higher electron transfer rate and lower electrical resistance than OMC as per electrochemical analysis. Upon Cr(Ⅵ) introduction, As(Ⅴ) removal increased to 0.28 mmol g^-1 by OMC, but decreased to 0.16 mmol g^-1 by ZVI/OMC. OMC could preferably reduce CrO₄^2- to Cr³⁺ by hydroxyl group, which enhanced its zeta potential facilitating As(Ⅴ) sorption. Regarding ZVI/OMC, Fe⁰ and Fe oxide in ZVI/OMC exhibited better affinity to As(Ⅴ), but the competition for the similar active sites resulted in compromised As(Ⅴ) and Cr(Ⅵ) removal. Thus, the novel OMC is advantageous for removal of binary As(Ⅴ) and Cr(Ⅵ), but ZVI/OMC is robust to detoxify single heavy metal.

Supramolecular assemblies of carbon nanocoils and tetraphenylporphyrin derivatives for sensing of catechol and hydroquinone in aqueous solution

Non-enzymatic electrochemical detection of catechol (CC) and hydroquinone (HQ), the xenobiotic pollutants, was carried out at the surface of novel carbon nanocoils/zinc-tetraphenylporphyrin (CNCs/Zn-TPP) nanocomposite supported on glassy carbon electrode. The synergistic effect of chemoresponsive activity of Zn-TPP and a large surface area and electron transfer ability of CNCs lead to efficient detection of CC and HQ. The nanocomposite was characterized by using FT-IR, UV/vis. spectrophotometer, SEM and energy dispersive X-ray spectroscopy (EDS). Cyclic voltammetry, differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy were used for the electrochemical studies. CNCs/Zn-TPP/GCE nanosensor displayed a limit of detection (LOD), limit of quantification (LOQ) and sensitivity for catechol as 0.9 µM, 3.1 µM and 0.48 µA µM-1 cm-2, respectively in a concentration range of 25-1500 µM. Similarly, a linear trend in the concentration of hydroquinone detection was observed between 25 and 1500 µM with an LOD, LOQ and sensitivity of 1.5 µM, 5.1 µM and 0.35 µA µM-1 cm-2, respectively. DPV of binary mixture pictured well resolved peaks with anodic peak potential difference, ∆Epa(CC-HQ), of 110 mV showing efficient sensing of CC and HQ. The developed nanosensor exhibits stability for up to 30 days, better selectivity and good repeatability for eight measurements (4.5% for CC and 5.4% for HQ).

Mesoporous Materials-Based Electrochemical Biosensors from Enzymatic to Nonenzymatic

Mesoporous materials have drawn more and more attention in the field of biosensors due to their high surface areas, large pore volumes, tunable pore sizes, as well as abundant frameworks. In this review, the progress on mesoporous materials-based biosensors from enzymatic to nonenzymatic are highlighted. First, recent advances on the application of mesoporous materials as supports to stabilize enzymes in enzymatic biosensing technology are summarized. Special emphasis is placed on the effect of pore size, pore structure, and surface functional groups of the support on the immobilization efficiency of enzymes and the biosensing performance. Then, the development of a nonenzymatic strategy that uses the intrinsic property of mesoporous materials (carbon, silica, metals, and composites) to mimic the behavior of enzymes for electrochemical sensing of some biomolecules is discussed. Finally, the challenges and perspective on the future development of biosensors based on mesoporous materials are proposed.

An overview of palladium supported on carbon-based materials: Synthesis, characterization, and its catalytic activity for reduction of hexavalent chromium

Palladium plays a pivotal role in most of the industrial heterogeneous catalysts, because of its unique properties such as well-defined structure, great intrinsic carrier, outstanding electronic, mechanical and thermal stability. The combination of palladium and various porous carbons (PCs) can widen the use of heterogeneous catalysts. This review highlights the advantages and limitations of carbon supported palladium-based heterogeneous catalyst in reduction of toxic hexavalent chromium (Cr^(VI)). In addition, we address recent progress on synthesis routes for mono and bimetallic palladium nanoparticles supported by various carbon composites including graphene-based materials, carbon nanotubes, mesoporous carbons, and activated carbons. The related reaction mechanisms for the Cr^(VI) reduction are also suggested. Finally, the challenge and perspective are proposed.

Enhanced Electrochemical Characteristics of the Glucose Oxidase Bioelectrode Constructed by Carboxyl-Functionalized Mesoporous Carbon

This research revealed the effect of carboxyl-functionalization on the mesoporous carbon (MC)-fixed glucose oxidase (GOx) for promoting the properties of bioelectrodes. It showed that the oxidation time, temperature and concentration, can significantly affect MC carboxylation. The condition of 2 M ammonium persulfate, 50 °C and 24 h was applied in the study for the successful addition of carboxyl groups to MC, analyzed by FTIR. The nitrogen adsorption isotherms, and X-ray diffraction analysis showed that the carboxylation process slightly changed the physical properties of MC and that the specific surface area and pore size were all well-maintained in MC-COOH. Electrochemical characteristics analysis showed that Nafion/GOx/MC-COOH presented better electrocatalytic activity with greater peak current intensity (1.13-fold of oxidation peak current and 4.98-fold of reduction peak current) compared to Nafion/GOx/MC. Anodic charge-transfer coefficients (α) of GOx/MC-COOH increased to 0.77, implying the favored anodic reaction. Furthermore, the GOx immobilization and enzyme activity in MC-COOH increased 140.72% and 252.74%, leading to the enhanced electroactive GOx surface coverage of Nafion/GOx/MC-COOH electrode (22.92% higher, 1.29 × 10-8 mol cm-2) than the control electrode. Results showed that carboxyl functionalization could increase the amount and activity of immobilized GOx, thereby improving the electrode properties.

Amperometric determination of hydrazine using a CuS-ordered mesoporous carbon electrode

An electrocatalytic sensor for hydrazine using copper sulfide-ordered mesoporous carbon (CuS-OMC) is described. A facile solvothermal synthetic strategy was adopted for CuS-OMC and the ordered mesoporous carbon was obtained through nanocasting method. The synthesized CuS-OMC was characterized using microscopic and spectrochemical techniques. CuS-OMC was immobilized on GCE and evaluated for its electrochemical sensing of hydrazine using cyclic voltammetry and amperometry. CuS-OMC modified GCE exhibited better hydrazine sensing at an optimized pH 7.4 in terms of oxidation potential and current compared with that of GCE, CuS, and OMC. The observed sensing performance of CuS-OMC was attributed to the presence of Cu (I/II) in CuS dispersed in OMC which acts as an electrocatalytic center for the sensing of hydrazine. Amperometry under optimized experimental condition with an applied potential of 270 mV was employed to obtain a linear calibration plot in the range 0.25 to 40 μM (R² = 0.9908) with a detection limit of 0.10 μM with a sensitivity of 0.915 (± 0.02) μA cm^-2 μM^-1. Real sample analyses were carried out by spiking of hydrazine in different water samples and the recoveries were in the range of 97 ± 2.1% (n = 3). Graphical abstract.

Electrochemical strategy with zeolitic imidazolate framework-8 and ordered mesoporous carbon for detection of xanthine

An accurate, safe, environmentally friendly, fast and sensitive electrochemical biosensors were developed to detect xanthine in serum. The metal-organic framework ZIF-8 was synthesised and elemental gold was supported on the surface of ZIF-8 by reduction method to synthesise Ag-ZIF-8. The mesoporous carbon material and the synthesised Ag-ZIF-8 were, respectively, applied to a glassy carbon electrode to construct biosensors. The constructed biosensor has a good linear relation in the range of 1-280 μmol l^-1 of xanthine and the detection limit is 0.167 μmol l^-1. The relative standard deviation value in serum samples was <5%, and the recoveries were 96-106%, indicating the good selectivity, stability and reproducibility of this electrochemical biosensor.

Rod-like Co based metal-organic framework embedded into mesoporous carbon composite modified glassy carbon electrode for effective detection of pyrazinamide and isonicotinyl hydrazide in biological samples

Herein, we report a novel composite fabricated via embedding rod-like Co based metal-organic framework (Co-MOF-74) crystals into MC matrix for the first time. The introduction of MC astricts the size of Co-MOF-74 crystals, enlarges the pore size and improves the electrical conductivity, which lead to the good electrochemical properties of the composite. The fabricated sensor based on Co-MOF-74@MC exhibits superior electrocatalytic activity toward the reduction of pyrazinamide (PZA) and the oxidation of isonicotinyl hydrazide (INZ). Under optimized conditions, the sensor shows two linear ranges from 0.3 to 46.5 μM and 46.5-166.5 μM with a high sensitivity of 7.2 μA μM^-1 cm^-2 and a detection limit of 0.21 μM for the determination of PZA. The electroanalytical sensing of INZ also gives two linear ranges of 0.15-1.55 μM and 1.55-592.55 μM with a detection limit of 0.094 μM. The mechanism involved was also discussed, briefly. The sensor is assessed toward the detection of PZA and INZ in human serum and urine samples. Recovery values varied from 97.08 to 103.20% for PZA sensing and 96.67-102.90% for INZ sensing, revealing the promising practicality of sensor for PZA and INZ detection.

Novel Electrochemical Sensor Fabricated for Individual and Simultaneous Ultrasensitive Determination of Olaquindox and Carbadox Based on MWCNT-OH/CMK-8 Hybrid Nanocomposite Film

A hybrid nanocomposite consisting of hydroxylated multi-walled carbon nanotubes (MWCNTs-OH) and cube mesoporous carbon (CMK-8) was applied in this study to construct an MWCNT-OH/CMK-8/gold electrode (GE) electrochemical sensor and simultaneously perform the electro-reduction of olaquindox (OLA) and carbadox (CBX). The respective peak currents of CBX and OLA on the modified electrode increased by 720- and 595-fold relative to the peak current of GE. The performances of the modified electrode were investigated with electrochemical impedance spectroscopy, cyclic voltammetry, and differential pulse voltammetry. Then, the modified electrodes were used for the individual and simultaneous determination of OLA and CBX. The fabricated sensor demonstrated a linear response at 0.2-500 nmol/L in optimum experimental conditions, and the detection limits were 104.1 and 62.9 pmol/L for the simultaneous determination of OLA and CBX, respectively. As for individual determination, wide linear relationships were obtained for the detected OLA with levels of 0.05-500 nmol/L with LOD of 20.7 pmol/L and the detected CBX with levels of 0.10-500 nmol/L with LOD of 50.2 pmol/L. The fabricated sensor was successfully used in the independent and simultaneous determination of OLA and CBX in spiked pork samples.

RAFT-photomediated PISA in dispersion: mechanism, optical properties and application in templated synthesis

Diblock copolymer nanoparticles were prepared by photomediated polymerization-induced self-assembly (“photo-PISA”) in dispersion.

Ordered mesoporous carbon-covered carbonized silk fabrics for flexible electrochemical dopamine detection

Flexible dopamine sensors were fabricated with ordered mesoporous carbon-covered carbonized silk fabrics (OMC/CSFs) as the working electrodes, which exhibited high sensitivity, good selectivity, a large linear detection range of 0.2–80 μM, and a low limit detection of 0.11 μM.

Lanthanum Hydroxide Nanorod-Templated Graphitic Hollow Carbon Nanorods for Supercapacitors

Lanthanum hydroxide nanorods were employed as both a template and catalyst for carbon synthesis by chemical vapor deposition. The resulting carbon possesses hollow nanorod shapes with graphitic walls. The hollow carbon nanorods were interconnected at some junctions forming a mazelike network, and the broken ends of the tubular carbon provide accessibility to the inner surface of the carbon, resulting in a surface area of 771 m²/g. The hollow carbon was tested as an electrode material for supercapacitors. A specific capacitance of 128 F/g, an energy density of 55 Wh/kg, and a power density of 1700 W/kg at 1 A/g were obtained using the ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, as the electrolyte.

New insights into the structure-performance relationships of mesoporous materials in analytical science

Mesoporous materials are ideal carriers for guest molecules and they have been widely used in analytical science. The unique mesoporous structure provides special properties including large specific surface area, tunable pore size, and excellent pore connectivity. The structural properties of mesoporous materials have been largely made use of to improve the performance of analytical methods. For instance, the large specific surface area of mesoporous materials can provide abundant active sites and increase the probability of contact between analytes and active sites to produce stronger signals, thus leading to the improvement of detection sensitivity. The connections between analytical performances and the structural properties of mesoporous materials have not been discussed previously. Understanding the "structure-performance relationship" is highly important for the development of analytical methods with excellent performance based on mesoporous materials. In this review, we discuss the structural properties of mesoporous materials that can be optimized to improve the analytical performance. The discussion is divided into five sections according to the analytical performances: (i) selectivity-related structural properties, (ii) sensitivity-related structural properties, (iii) response time-related structural properties, (iv) stability-related structural properties, and (v) recovery time-related structural properties.

A dual-signal amplification strategy for kanamycin based on ordered mesoporous carbon-chitosan/gold nanoparticles-streptavidin and ferrocene labelled DNA

An ultrasensitive electrochemical aptasensor for kanamycin (KAN) detection was constructed with a dual-signal amplification strategy. The aptasensor achieved greatly amplified sensitivity due to the excellent electrical conductivity of the ordered mesoporous carbon-chitosan (OMC-CS)/gold nanoparticles-streptavidin (AuNPs-SA) and DNA2 labelled with ferrocene (Fc-DNA2). The AuNPs-SA was used to immobilize the DNA strand (biotin labelled) with the biotin-streptavidin system. The DNA2 strand containing the KAN aptamer was labelled with ferrocene to increase the current signal on the electrode surface when bound to KAN. Some factors that affect the performance of the aptasensor were optimized, and the proposed aptasensor provided a wide linear range from 1 × 10^-10 M to 4 × 10^-6 M, with a detection limit as low as 35.69 pM for KAN under the optimized conditions. This aptasensor had satisfactory electrochemical performance with good stability, sensitivity and reproducibility. Additionally, it also displayed a good specificity for KAN without interference from competitive analogues. Furthermore, the constructed aptasensor was successfully used to detect KAN in a real milk sample. The proposed method for KAN detection has great potential for the detection of other antibiotics.

Recent advances in functionalized micro and mesoporous carbon materials: synthesis and applications

Functionalized nanoporous carbon materials have attracted the colossal interest of the materials science fraternity owing to their intriguing physical and chemical properties including a well-ordered porous structure, exemplary high specific surface areas, electronic and ionic conductivity, excellent accessibility to active sites, and enhanced mass transport and diffusion. These properties make them a special and unique choice for various applications in divergent fields such as energy storage batteries, supercapacitors, energy conversion fuel cells, adsorption/separation of bulky molecules, heterogeneous catalysts, catalyst supports, photocatalysis, carbon capture, gas storage, biomolecule detection, vapour sensing and drug delivery. Because of the anisotropic and synergistic effects arising from the heteroatom doping at the nanoscale, these novel materials show high potential especially in electrochemical applications such as batteries, supercapacitors and electrocatalysts for fuel cell applications and water electrolysis. In order to gain the optimal benefit, it is necessary to implement tailor made functionalities in the porous carbon surfaces as well as in the carbon skeleton through the comprehensive experimentation. These most appealing nanoporous carbon materials can be synthesized through the carbonization of high carbon containing molecular precursors by using soft or hard templating or non-templating pathways. This review encompasses the approaches and the wide range of methodologies that have been employed over the last five years in the preparation and functionalisation of nanoporous carbon materials via incorporation of metals, non-metal heteroatoms, multiple heteroatoms, and various surface functional groups that mostly dictate their place in a wide range of practical applications.

Surface Characteristics of Microporous and Mesoporous Carbons Functionalized with Pentafluorophenyl Groups

The in situ diazonium reduction reaction is a reliable and well-known approach for the surface modification of carbon materials for use in a range of applications, including in energy conversion, as chromatography supports, in sensors, etc. Here, this approach was used for the first time with mesoporous colloid-imprinted carbons (CICs), materials that contain ordered monodisperse pores (10-100 nm in diameter) and are inherently highly hydrophilic, using a common microporous carbon (Vulcan carbon (VC)), which is relatively more hydrophobic, for a comparison. The ultimate goal of this work was to modify the CIC wettability without altering its nanostructure and also to lower its susceptibility to oxidation, as required in fuel cell and battery electrodes, by the attachment of pentafluorophenyl (-PhF₅) groups onto their surfaces. This was shown to be successful for the CIC, with the -PhF₅ groups uniformly coating the inner pore walls at a surface coverage of ca. 90% and allowing full solution access to the mesopores, while the -PhF₅ groups deposited only on the outer VC surface, likely blocking its micropores. Contact angle kinetics measurements showed enhanced hydrophobicity, as anticipated, for both the -PhF₅ modified CIC and VC materials, even revealing superhydrophobicity at times for the CIC materials. In contrast, water vapor sorption and cyclic voltammetry suggested that the micropores remained hydrophilic, arising from the deposition of smaller N- and O-containing surface groups, caused by a side reaction during the in situ diazonium functionalization process.

A Label-Free Electrochemical Aptasensor for the Rapid Detection of Tetracycline Based on Ordered Mesoporous Carbon–Fe3O4

A novel aptasensor based on a tetracycline (TET) aptamer immobilized by physical adsorption on an ordered mesoporous carbon–Fe3O4 (OMC-Fe3O4)-modified screen-printed electrode surface was successfully fabricated. OMC-Fe3O4 was characterized by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The modification procedure of the aptasensor was characterized by cyclic voltammetry. Interaction between the TET aptamer and target was determined by differential pulse voltammetry. Under optimal conditions, the proposed aptasensor exhibited good electrochemical sensitivity to TET in a concentration range of 5 nM to 10 μM, with a detection limit of 0.8 nM (S/N = 3). This aptasensor exhibited satisfactory specificity, reproducibility, and stability.

Synthesis and Electrochemical Behavior of the Molybdenum- Modified Electrode Based on Rice Husk

The article presents the results of electrochemical studies made on carbon paste electrode based on bisorbents powder modified by molybdenum. Bisorbent consists of carbon and SiO2. It was synthesized as a support structure obtained from rice husk thermal decomposition products. The obtained sorption material has surface with high specific area – 200 m2/g. Bisorbent was further modified by (NH4)6Mo7O24 · 4H2O (10 wt.%). The elemental composition of used RH was also determined. The surface morphology of plain and modified BS samples was studied. Recording of voltammetric curves was carried out at рН = 3.80, рН = 6.40 in 0.2 М electrolyte solution of Li2SO4. Cathodic and anodic waves were obtained which related to oxidation and reduction processes of molebdenium compounds in the entire range of the potentials (0.8 ÷ -1.2 V). The range of changing molybdate ions concentrations in solution was 2·10‒4 ÷ 10‒2 M. The dependencies of kinetic and electrochemical parameters on paramolybdate ions concentration were studied for modified electrode. Nature of changes in molybdenum reduction currents and oxidation currents indicates that Mo+6 reduction may occur by different mechanisms depending on the composite electrode properties. Results showed the possibility of further the synthesized composite system use for voltammetric determination of low (10‒4–10‒2) concentrations of ions in a solution.

Self-template synthesis of biomass-derived 3D hierarchical N-doped porous carbon for simultaneous determination of dihydroxybenzene isomers

Nitrogen doped hierarchical porous carbon materials (HPCs) was achieved by the successful carbonization, using pig lung as biomass precursor. Three-dimensional HPCs constituted with sheets and lines were synergistically inherited from original pig lung. Such structure provided a large specific surface area (958.5 g-1 m2) and rich porous, effectively supported a large number of electro-active species, and greatly enhanced the mass and electron transfer. High graphitization degree of HPCs resulted in good electrical conductivity. Furthermore, the different electronegativity between nitrogen and carbon atoms in HPCs could affect the electron cloud distribution, polarity and then the electrochemical oxidation kinetics of dihydroxybenzene isomers. Based on these characteristics of HPCs, the electrochemical sensor for dihydroxybenzene isomers exhibited high sensitivity, excellent specificity and stability. Quantitative analysis assays by differential pulse voltammetry (DPV) technology showed that the sensor has wide linear ranges (0.5-320, 0.5-340 and 1-360 μmol L-1) and low detection limits (0.078, 0.057 and 0.371 μmol L-1) for the catechol, resorcinol and hydroquinone, respectively. This proposed method was successfully applied for simultaneous detection of dihydroxybenzene isomers in river water.

Printable Heterostructured Bioelectronic Interfaces with Enhanced Electrode Reaction Kinetics by Intermicroparticle Network

Printable organic bioelectronics provide a fast and cost-effective approach for the fabrication of novel biodevices, while the general challenge is to achieve optimized reaction kinetics at multiphase boundaries between biomolecules and electrodes. Here, we present an entirely new concept based on a modular approach for the construction of heterostructured bioelectronic interfaces by using tailored functional "biological microparticles" combined with "transducer microparticles" as modular building blocks. This approach offers high versatility for the design and fabrication of bioelectrodes with a variety of forms of interparticle spatial organization, from layered-structures to more advance bulk heterostructured architectures. The heterostructured biocatalytic electrodes delivered twice the reaction rate and a six-fold increase in the effective diffusion kinetics in response to a catalytic model using glucose as the substrate, together with the advantage of shortened diffusion paths for reactants between multiple interparticle junctions and large active particle surface. The consequent benefits of this improved performance combined with the simple means of mass production are of major significance for the emerging printed electronics industry.