Data_Sheet_1_Biomass Juncus Derived Nitrogen-Doped Porous Carbon Materials for Supercapacitor and Oxygen Reduction Reaction.pdf

Juncus is a perennial herb aquatic plant found worldwide, with high reproductive ability in warm regions. It has three-dimensional hierarchical porous triangular networks structures composited of tubular fibers. Here, juncus derived nitrogen-doped porous carbon (NDPC) was prepared by mixing juncus and ZnCl2 through one-step pyrolysis and activation which is a low-cost, simple, and environmentally friendly method. The NDPC had hierarchical porous structures and a high specific surface area and was applied for supercapacitor and oxygen reduction reaction (ORR). The resulted NDPC-3-800 was prepared by mixing juncus with ZnCl2 at a mass ratio of 1:3 and then carbonized at 800°C, it was used as electrode material of a supercapacitor. The supercapacitor exhibited excellent specific capacitance of 290.5 F g−1 and 175.0 F g−1 in alkaline electrolyte at the current densities of 0.5 A g−1 and 50 A g−1, respectively. The supercapacitor showed good cycle stability, and the capacitance was maintained at 94.5% after 10,000 cycles. The NDPC-5-800 was prepared by mixing juncus with ZnCl2 at a mass ratio of 1:5 and then carbonized at 800°C. It exhibited outstanding ORR catalytic activity and stability attributing to their high specific surface area and abundant actives sites. The juncus can derive various materials for application in different fields.</p

Simple Preparation Method of Multilayer Polymer Films Containing Pd Nanoparticles

A simple route to the fabrication of multilayer films containing Pd nanoparticles is described. Following layer-by-layer assembly of PdCl42- and polycation, QPVP−Os (a quaternized poly(4-vinylpyridine) complexed with [Os(bpy)2Cl]2+/+), on 4-aminobenzoic acid-modified glassy carbon electrodes, the three-dimensional Pd nanoparticle multilayer films are directly formed on electrode surfaces via electrochemical reduction of PdCl42- sandwiched between polymers. The growth of PdCl42- is easy on electrode surfaces by electrostatic interaction, and the assembly processes are monitored by cyclic voltammetry and UV−vis spectroscopy. The depth profile analyses by X-ray photoelectron spectroscopy verify the constant composition of the Pd nanoparticle multilayer films. Atomic force microscopy proves that the as-prepared Pd nanoparticles are uniformly distributed with an average particle diameter of 3−7 nm. The resulting Pd nanoparticle multilayer-modified electrode possesses high catalytic activity for the reduction of dissolved oxygen and oxidation of hydrazine compounds in aqueous solution

Self-Exfoliating Double-Emission N‑Doped Carbon Dots in Covalent Organic Frameworks for Ratiometric Fluorescence “Off–On” Cu²⁺ Detection

Covalent organic frameworks (COFs) usually have weak emission because of π–π stacking between layers, linkage bond rotation, or photoinduced electron transfer (PET) between monomer parts, which gives a chance to prepare “off–on” fluorescent sensors based on these weakly emissive COFs. Here, nitrogen-doped carbon dots (NCDs) encapsulated in COFTAPT‑TT (NCCOFTAPT‑TT) are successfully prepared by a one-pot method, in which COFTAPT‑TT is synthesized by ammonaldehyde condensation between 2,4,6-tris­(4-aminophenyl)-1,3,5-triazine (TAPT) and thieno­[3,2-b]­thiophene-2,5-dicarboxaldehyde (TT) in the presence of NCDs. NCCOFTAPT‑TT emits a strong NCD peak at 445 nm and a weak peak of COFTAPT‑TT at 337 nm due to PET between electron-deficient TAPT and electron-rich TT. The NCDs lead spherical stacked COFTAPT‑TT to self-exfoliate into NCCOFTAPT‑TT nanosheets, which greatly improves the dispersion and stability of NCCOFTAPT‑TT. In the presence of Cu2+ (0–10.0 μM), the fluorescence of NCDs is quenched but the fluorescence of COFTAPT‑TT remains unchanged. The linear range is 51.9 nM to 0.75 μM, and the detection limit is 17.3 nM. Then, Cu2+ inhibits the PET process to result in an enhancement of COFTAPT‑TT fluorescence and the fluorescence of NCDs remains unchanged, thus realizing a Cu2+ off–on ratiometric fluorescent sensor with high sensitivity, good selectivity, and good stability. This off–on fluorescent sensor has a linear range of 18–26 μM. This work provides a new idea for application of COFs with weak emission to construct off–on fluorescent sensors

An Immunosensor Using Electroactive COF as Signal Probe for Electrochemical Detection of Carcinoembryonic Antigen

Two kinds of two-dimensional (2D) covalent-organic frameworks (COF) were used to construct a sandwich-type electrochemical immunosensor for a proof-of-concept study. Vinyl-functionalized COFTab-Dva could be linked with Ab1 by the thiol–ene “click” reaction. Electroactive COFTFPB-Thi was modified with gold nanoparticles (AuNPs) to ensure the successful connection with Ab2 through Au–S bond. Meanwhile, electroactive COFTFPB-Thi was used to as signal probe to realize both the detection of carcinoembryonic antigen (CEA) and the amplification of detection signal. In detection process of the sandwich-type electrochemical immunosensor, glassy carbon electrode (GCE) was modified with 2D COFTab-Dva first then connected with Ab1 by the thiol–ene “click” reaction, next quantitative CEA was captured, followed by specificially capturing signal probe of Ab2/AuNPs/COFTFPB-Thi where AuNPs acted as nanocarriers of Ab2 and COFTFPB-Thi served as the signal producers. As the amount of CEA was increased, the amount of signal probe captured to the electrode was also increased, and the peak signal intensity of the redox reaction of COFTFPB-Thi was enhanced accordingly. Thus, the quantitative detection of CEA could be realized according to the peak signal intensity of electroactive COFTFPB-Thi. The electrochemical immunosensor owned wide detection range of 0.11 ng/mL-80 ng/mL, low detection limit of 0.034 ng/mL and good practicability. This study opens up a new revelation for quantitative detection of CEA using electroactive COF as enhanced signal probe

Simple and Large-Scale Strategy to Prepare Flexible Graphene Tape Electrode

A simple and large-scale strategy to prepare flexible graphene tape electrode (GTE) was proposed. The flexible GTE was prepared by a facile peeling method in which a piece of commercial graphite foil was first covered by a commercial acrylic transparent tape and then the transparent adhesive tape was quickly torn off from the graphite foil. Scanning electron microscopy results showed that some folded and wrinkled graphene layers stood up on the GTE surface to form three-dimensional (3D) porous graphene foam. The 3D porous flexible GTE was proposed as a novel supporting matrix to load Ni–Co nanoparticles (Ni-CoNPs) and glucose oxidase (GOD) as examples to test its applications for electrochemical glucose sensing. The Ni-CoNPs/GTE showed the linear range of 0.6 μM–0.26 mM and 1.360–5.464 mM with a detection limit of 0.16 μM. The GOD/AuNPs-CHIT/GTE had a linear range of 0.616–14.0 mM and a detection limit of 0.202 mM. These results were similar or superior to the printable electrodes by nanocarbon and electrodes modified with graphene, carbon nanotubes, or porous carbon materials, but the flexible GTE was more easier to prepare in large-scale and the 3D porous graphene foam were not easy to drop off from the tape because they were glued on acrylic transparent tape firmly. Therefore, the 3D porous flexible GTE should be promising candidates for electrochemical sensors and other electrochemical applications

Terbium-Based Coordination Polymer Nanoparticles for Detection of Ciprofloxacin in Tablets and Biological Fluids

The metal–organic coordination polymers with tunable structures and properties have been rapidly emerging as very important functional materials. In this work, we prepared terbium (Tb³⁺)-based coordination polymer nanoparticles (CPNPs) by employing adenine (Ad) as bridging ligands. The CPNPs was further used as a receptor reagent for ciprofloxacin (CF) detection in aqueous solution. Addition of CF induces a typical emission of Tb³⁺ due to the formation of Ad/Tb-CF complex and the sensitization of CF. The fluorescent intensity of Tb³⁺ was enhanced linearly with increasing the CF concentration from 60 nM to 14 μM. The detection limit for CF in aqueous solution is 60 nM. The Ad/Tb CPNPs was successfully applied to detect CF in tablet and urine samples and showed a satisfactory result. Compared with other methods, the proposed method is advantageous because that it provides a very simple strategy for CF detection, which does not require complicated sample pretreatment processes or special reaction media. The proposed strategy could be contributed to expand the potential applications of lanthanide coordination polymers in biological and environmental fields

H₂O₂ Ratiometric Electrochemical Sensors Based on Nanospheres Derived from Ferrocence-Modified Covalent Organic Frameworks

A uniform nanosphere derived from ferrocence-modified covalent-organic frameworks (COFETTA‑TPAL-Fc­(COOH)2) with 200 nm in diameter was prepared by dehydration condensation reaction between 4,4′,4′,4′- (ethane-1,1,2,2-tetrayl) tetraaniline and terephthalaldehyde in the presence of electroactive Fc­(COOH)2. The Fc­(COOH)2 was embedded into the layers of COFETTA‑TPAL to result in the formation of nanospheres, which increased the specific surface area of the available COFETTA‑TPAL to provide more active sites due to the increase in interlayer distance. The Fc­(COOH)2 could interact with H2O2 which might undergo self-disproportionation process to produce O2 and be reduced into H2O simultaneously, whereas the generated O2 was directly reduced into H2O by COFETTA‑TPAL. The reduction peak current of the generated O2 at −0.5 V (j–0.5 V) was gradually enhanced, whereas that of Fc­(COOH)2 around 0.45 V (j0.45 V) was decreased with continuous adding of H2O2. Thus, the COFETTA‑TPAL-Fc­(COOH)2 nanospheres were used to fabricate a “on–off” nonenzymatic H2O2 ratiometric electrochemical sensor. The proposed “on–off” ratiometric electrochemical sensor showed good performance with a wide linear range of 1.1–500 μM, high sensitivity of 0.009 μM–1, and lower detection limit of 0.33 μM. The work would offer insights for design and preparation of electroactive COF and accelerate the practical application of COF in electroanalysis

pH-Switchable Electrochemical Sensing Platform based on Chitosan-Reduced Graphene Oxide/Concanavalin A Layer for Assay of Glucose and Urea

A facile and effective electrochemical sensing platform for the detection of glucose and urea in one sample without separation was developed using chitosan-reduced graphene oxide (CS-rGO)/concanavalin A (Con A) as a sensing layer. The CS-rGO/Con A with pH-dependent surface net charges exhibited pH-switchable response to negatively charged Fe­(CN)₆^3–. The principle for glucose and urea detection was essentially based on in situ pH-switchable enzyme-catalyzed reaction in which the oxidation of glucose catalyzed by glucose oxidase or the hydrolyzation of urea catalyzed by urease resulted in a pH change of electrolyte solution to give different electrochemical responses toward Fe­(CN)₆^3–. It was verified by cyclic voltammograms, differential pulse voltammograms, and electrochemical impedance spectroscopy. The resistance to charge transfer or amperometric current changed proportionally toward glucose concentration from 1.0 to 10.0 mM and urea concentration from 1.0 to 7.0 mM. On the basis of human serum experiments, the sensing platform was proved to be suitable for simultaneous assay of glucose and urea in a practical biosystem. This work not only gives a way to detect glucose and urea in one sample without separation but also provides a potential strategy for the detection of nonelectroactive species based on the enzyme-catalyzed reaction and pH-switchable biosensor

Nitrogen-Doped Carbon Nanotubes Supported by Macroporous Carbon as an Efficient Enzymatic Biosensing Platform for Glucose

Effective immobilization of enzymes/proteins on an electrode surface is very essential for biosensor development, but it still remains challenging because enzymes/proteins tend to form close-packed structures on the electrode surface. In this work, nitrogen-doped carbon nanotubes (NCNTs) supported by three-dimensional Kenaf Stem-derived porous carbon (3D-KSC) (denoted as 3D-KSC/NCNTs) nanocomposites were constructed as the supporting matrix to load glucose oxidase (GOD) for preparing integrated glucose biosensors. These NCNTs are vertically arrayed on the channel walls of the 3D-KSC via the chemical vapor deposition method, which could noticeably increase the effective surface area, mechanical stability, and active sites (originating from the doped nitrogen) of the nanocomposites. The integrated glucose biosensor exhibits some advantages over the traditional GOD electrodes in terms of the capability to promote the direct electron transfer of GOD, enhance the mechanical stability of the biosensor attributed to the strong interaction between NCNTs and GOD, and enlarge the specific surface area to efficiently load a large number of GODs. The as-prepared biosensor shows a good performance toward both oxygen reduction and glucose biosensing. This study essentially offers a novel approach for the development of biosensors with excellent analytical properties

Three-Dimensional Macroporous Carbon/Fe₃O₄‑Doped Porous Carbon Nanorods for High-Performance Supercapacitor

Supercapacitors are considered as potential innovation for energy storage owing to their long charge–discharge life and high power density. Herein, a simple and industry-scalable approach was developed to prepare the hybrid of Fe₃O₄-doped porous carbon nanorods (Fe₃O₄-DCN) supported by three-dimensional (3D) kenaf stem-derived macroporous carbon (KSPC) for high-performance supercapacitor, which was prepared via pyrolyzing the iron fumarate metal organic frameworks (MIL-88A, MIL stands for Materials from Institut Lavoisier)/3D-KSPC. The resulted 3D-KSPC/Fe₃O₄-DCN nanocomposites were carefully characterized by various techniques including scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray powder diffraction and N₂ adsorption/desorption isotherms. The 3D-KSPC/Fe₃O₄-DCN were employed as a promising electrode materials of supercapacitors by combining the advantage of Fe₃O₄-DCN (e.g., high specific capacitance, good rate capability and excellent cycling stability) with the superiority of 3D-KSPC (e.g., large specific surface area and hierarchical pores and high conductivity), exhibiting a high specific capacitance of 285.4 F g^–1 at the current density of 1 A g^–1. The capacitance was kept at 220.5 F g^–1 after 5000 cycles at 2 A g^–1, indicating outstanding cycle performance. This work might provide a new strategy to prepare nanostructures on 3D-KSPC for future applications