Acid-functionalized Multi-walled Carbon Nanotubes Research Articles

Polycaprolactone-Based Composite Electrospun Nanofibers as Hybrid Biomaterial Systems Containing Hydroxyl- or Carboxylic Acid-Functionalized Multiwall Carbon Nanotubes

Composite electrospun nanofibers based on polycaprolactone (PCL) have shown promise in various biomedical applications due to their unique properties. This study investigates the effects of incorporating hydroxyl (–OH)- or carboxylic acid (–COOH)-functionalized multiwall carbon nanotubes (MWCNTs) into PCL matrices. Two types of functionalized additives, MWCNT-OH and MWCNT-COOH, were used at different concentrations (0.06 and 0.12 wt%). Various characterization techniques including FTIR, XRD, AFM, SEM, water contact angle analysis, and tensile strength testing were employed to evaluate changes in nanofiber morphology, crystallinity, surface topography, wettability, and mechanical properties. In addition, in vitro cytotoxicity assays were conducted using HUVECs and L929 fibroblasts over 1-, 3-, and 5-day intervals. This study represents a novel examination of (–OH)- and (–COOH)-functionalized MWCNTs as additives in electrospun PCL biopolymer matrices. The findings indicate that incorporating small amounts of (–OH)- or (–COOH)-functionalized MWCNTs enhances the physicochemical characteristics of PCL nanofibers, making them more suitable for biomedical applications. While both types of functionalized MWCNT additives improved properties compared to pure PCL nanofibers, (–COOH)-functionalized MWCNT-incorporated nanofibers exhibited the most favorable features. In conclusion, this research highlights the potential of tailored PCL-based composite nanofibers containing functionalized MWCNTs as advanced biomaterial systems for biomedical applications, contributing to the development of innovative biomaterials for diverse biomedical contexts.

Redox-active cerium-based metal–organic layers coordinated on carbon nanotubes as materials for supercapacitors

In this work, the redox-active, two-dimensional (2D), and highly dispersible metal–organic layers (MOLs) constructed from hexa-cerium(IV) clusters, CeBTB (BTB = 1,3,5-benzenetribenzoate), were directly coordinated onto the surface of carboxylic acid-functionalized multi-walled carbon nanotubes (CNTs) by utilizing a post-synthetically grafting approach. Nanocomposites with various MOL-to-CNT ratios can be synthesized. Crystallinity, porosity, morphology, electrical conductivity, and electrochemical behaviors of CeBTB and all nanocomposites as well as the chemical interaction between CeBTB and CNT in the composite are investigated. Thin films of materials with the same mass loading are then fabricated for measuring their capacitive performances in neutral aqueous solutions of Na2SO4. With the electrical conductivity provided by carbon nanotubes and the redox activity of CeBTB between Ce(IV) and Ce(III), the optimal CeBTB-CNT nanocomposite can show a better capacitive performance compared to the pristine CeBTB, pristine CNT, and the physical mixture of both of them with the same MOL-to-CNT ratio. With such a simple post-synthetically grafting approach that can precisely control the ratio between the 2D MOLs and CNTs, the findings here open opportunities for designing numerous composites composed of MOLs and nanocarbons with tunable conductivity, redox activity, and functionality, which are potential candidates for a range of applications.

Electrochemical detection of myeloperoxidase (MPO) in blood plasma with surface-modified electroless nickel immersion gold (ENIG) printed circuit board (PCB) electrodes

Printed circuit board (PCB) based biosensors have often utilized hard gold electroplating, that nullifies the cost advantages of this technology as compared to screen printed electrodes. Electroless nickel immersion gold (ENIG) is a popular gold deposition process widely used in PCB manufacturing, but vulnerable to pinhole defects and large surface roughness, which compromises biosensor performance. In this work, we present a method to address these challenges through electrodeposition of methylene blue (MB) to cover surface defects and improve electroactivity of ENIG PCB electrodes. We also demonstrate a process to realize in situ synthesis of gold nanoparticles (AuNPs) using acid-functionalized multi-walled carbon nanotubes (MWCNTs) as scaffold, that are used to immobilize antibody for the target molecule (myeloperoxidase: MPO, early warning biomarker for cardiovascular diseases) through a modified cysteamine/gluteraldehyde based process. The processing steps on the electrode surface are developed in a manner that do not compromise the integrity of the electrode, resulting in repeatable and reliable performance of the sensors. Further, we demonstrate a cost-effective microfluidic packaging process to integrate a capillary pump driven microfluidic channel on the PCB electrode for seamless introduction of samples for testing. We demonstrate the ability of the sensor to distinguish clinically abnormal concentrations of MPO from normal concentrations through extensive characterization using spiked serum and blood plasma samples, with a limit of detection of 15.79 ng/mL.

Carboxylic acid-functionalized multiwalled carbon nanotubes (COOH-MWCNTs) improved production of atropine in callus of Datura inoxia by influencing metabolism, gene regulation, and DNA cytosine methylation; an in vitro biological assessment

Atropine is a well-known tropane alkaloid commonly employed in medicine class called anticholinergics. This study intends to address biochemical and molecular responses of Datura inoxia calluses to fortifying culture medium with carboxylic acid-functionalized multi-walled carbon nanotubes (COOH-MWCNTs). The application of MWCNTs influenced callogenesis performance and biomass in a dose-dependent manner. The MWCNT at 5 mgL−1 resulted in the highest biomass of calluses by 57%. While, MWCNTs at high concentrations were accompanied by cytotoxicity. On the other hand, MWCNTs at concentrations above 100 mgL−1 exhibited cytotoxicity, decreased callogenesis performance, and reduced Atropine biosynthesis. The MWCNTs increased the activity of phenylalanine ammonia-lyase (PAL) and catalase enzymes. The concentrations of proline and soluble phenols displayed upward trends in response to using MWCNTs. According to the HPLC assessment, enriching culture medium with MWCNTs at 5 mgL−1 elicited Atropine production in calluses by 64%. The quantitative PCR assessment referred to the upregulation in the transcription of the PAL gene. The expression of ornithine decarboxylase (ODC) and putrescine N-methyltransferase 1 (PMT) genes were also upregulated in calluses cultured in a medium supplemented with MWCNTs. Methylation Sensitive Amplification Polymorphism (MSAP) technique indicated that employing MWCNTs altered the DNA methylation profile, reflecting epigenetic modification. Overall, engineering plant cells with MWCNTs as a nano-elicitor can be suggested for large-scale synthesis of industrially-valuable secondary metabolites.

Novel electrochemical biosensor for Escherichia coli using gold-coated tungsten wires and antibody functionalized short multiwalled carbon nanotubes

Rapid and easy detection of pathogens, especially bacteria, plays an important role in daily life in the face of increasing environmental pollution. Nanosensors focus on carbon nanotubes, which can bind various molecules to large surfaces and have high electron conductivity. They are widely used in the development of electrochemical biosensors. In this study, a new design of electrochemical biosensors is presented by integrating gold-coated tungsten wires (GC-TW) and acid-functionalized multi-walled carbon nanotubes (MWCNTs) in a two-step coating process. GC-TWs are coated with acid-functionalized short MWCNTs. Fourier transforms infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) results show efficient immobilization of the electrodes. The performance for Escherichia coli (E. coli) K-12 is evaluated based upon the change in current following antibody-antigen interactions. Bioimpedance measurements are performed from 50 Hz to 10 MHz to achieve optimal coverage of impedance changes. The measurements show that the electrode has a detection limit of 0.8 CFU/mL. The response of the electrode saturates when the bacterial concentration is increased to 1.70 x 102 CFU/mL. The biosensor is capable of detecting E. coli between 0.8 and 1.70 × 102 CFU/mL. The data show that this MWCNT-based biosensor can be developed into a highly sensitive device for E. coli.

Co(II) Porphyrin-MWCNT Nanoconjugate as an Efficient and Durable Electrocatalyst for Oxygen Reduction Reaction.

Recently, researchers are seeking alternatives to replace Pt-based oxygen reduction reaction (ORR) catalysts used in fuel cells due to their high cost and certain stability and selectivity issues. For this purpose, we have synthesized a nanoconjugate, cobalt(II) porphyrin (5,10,15-triphenyl-20-(4-aminophenyl)porphyrinatocobalt(II), CoTPP-NH2) covalently attached to the acid-functionalized multiwalled carbon nanotubes and characterized by various techniques including UV-vis spectroscopy, FTIR, TGA, FESEM, TEM, and Raman spectroscopy. The oxygen reduction performance of the nanoconjugate is checked in basic medium. The ORR onset potential of the nanoconjugate-modified electrode is nearly the same as that of the state-of-the-art platinum-carbon electrode and stable for more than 3000 CV cycles with a 20 mV difference in the onset potential before and after the 3000 CV cycles. The above extrapolations reveal that the nanoconjugate has efficient performance for the ORR in basic medium.

Experimental and Theoretical Insights into Bienzymatic Cascade for Mediatorless Bioelectrochemical Ethanol Oxidation with Alcohol and Aldehyde Dehydrogenases

The efficient utilization of biomass fuels is a critical component of a sustainable energy economy. Via respiration, acetic acid bacteria can oxidize biomass ethanol into acetic acid using membrane-bound alcohol and aldehyde dehydrogenases (ADH and AlDH, respectively). Focusing on the ability of these enzymes to interact directly and electrically with electrode materials, we constructed a mediatorless bioanode for ethanol oxidation based on a direct electron transfer (DET)-type bienzymatic cascade by ADH and AlDH. The three-dimensional structural data of ADH and AlDH elucidated by cryo-electron microscopy were valuable for effectively designing electrode platforms with multi-walled carbon nanotubes (MWCNTs) and pyrene (Py) derivatives. DET-type bioelectrocatalysis by ADH and AlDH was improved by using 1-pyrene carboxylic acid-functionalized MWCNTs. The catalytic current densities for bienzymatic ethanol oxidation were recorded at the bioanodes modified by various ADH/AlDH ratios. The reaction model was constructed by focusing on the competitive adsorption of two enzymes on the electrode surface and the collection efficiency of the intermediately produced acetaldehyde. The power output of an ethanol/air biofuel cell using the bienzymatic bioanode reached 0.48 ± 0.01 mW cm–2, which is the highest value reported for ethanol biofuel cells. In addition, the Faraday efficiency of acetate production by the cell reached 100 ± 4%. This study will lead to efficient conversion of biomass fuels based on a multi-catalytic cascade system.

Uranium Phthalocyanine-Anchored Acid-Functionalized Multiwalled Carbon Nanotubes for Water Electrolysis

One of the major challenges in the commercial production of hydrogen and oxygen from the electrochemical water splitting reaction is the nonavailability of potential and low-cost electrocatalysts for the enhancement of both the half-cell reactions. The bifunctional catalyst capable of demonstrating lower overpotentials for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) eliminates the usage of a membrane, simplifies the overall system design, reduces the cost, and enhances the electrochemical water splitting activity. Here, a bifunctional hybrid composite catalyst comprising an organic N4 macrocycle and acid-functionalized multiwalled carbon nanotubes (MWCNTs) is fabricated and tested for the water splitting reaction to produce H2 and O2. The uranium tetra[4-(2-{(E)-[(4-bromophenyl)imino]methyl}phenoxy)]phthalocyanine (UTBrImPc) is synthesized via a two-step process of imine and oxy-bridge linkage formation. The synthesized ligands and phthalocyanine macrocycle are characterized using various spectroscopic and analytical techniques. The glassy carbon electrode (GCE) and Ni foam are used as the conducting substrate for the fabrication of the UTBrImPc/MWCNT bifunctional electrode to generate H2 and O2. Surprisingly, the fabricated bifunctional hybrid catalyst on the GCE exhibited a lesser overpotential of 15 mV for the HER, which is close to that of the benchmark Pt/C catalyst. Furthermore, the Ni/UTBrImPc/MWCNT displayed a lower overpotential of 368 (±2) mV at a current density of 10 mA·cm–2 for the OER, which is close to the overpotential shown by the precious benchmark catalyst IrO2. In addition, the fabricated electrodes showed remarkable long-term stability for more than 20 h by a chronoamperometric method. The superior results for both the HER and OER at the composite organic hybrid catalyst may be due to the collusive effect of the acid-functionalized MWCNTs with UTBrImPc, which enhances the electronic conductivity and surface area. The developed state-of-the-art catalyst can be employed as a bifunctional catalyst in water electrolyzers.

Combination effect of functionalized high aspect ratio carbonaceous nanofillers and carbon black on electrical, thermal conductivity, dielectric and EMI shielding behavior of co-continuous thermoplastic elastomeric blend composite films

The utilization of conductive hybrid carbonaceous fillers to fabricate highly efficient electromagnetic interference (EMI) shielding materials has become a popular area of research interest recently. Here, we report the facile fabrication of lightweight thermoplastic elastomeric blend composite films by solution mixing technique, taking advantage of both the hybrid carbonic nanofillers (high aspect ratio carbon inclusion and conductive carbon black) and the co-continuous polystyrene (PS)/ethylene-co-methyl acrylate (EMA) blend. Combination of acid-functionalized multiwalled carbon nanotubes (f-CNT) and carbon nanofibers (f-CNF) with conductive Vulcan-XC 72 carbon black (VCB) aids in the more uniform dispersion of hybrid carbonaceous inclusion in this blend system. The selective location of hybrid nanofillers in EMA phase of binary polymer mix enhanced the electrical properties, thermal conductivity, and microwave shielding performance of the resultant blend composites by constructing a dense, co-supportive, double percolated conductive network throughout the blend. The effect of f-CNT or f-CNF concentration in hybrid composites on the above-mentioned properties of blend composites has been investigated in this work. The as-prepared PS/EMA/VCB/f-CNT and PS/EMA/VCB/f-CNF blend composite films exhibited a thermal conductivity of 0.81 and 0.83 W/m.K and absorption-dominated microwave shielding of -31 and -32.5 dB, respectively with 15 wt% hybrid filler loading containing 50 wt% of f-CNT or f-CNF. These conductive thermal management composite films could be excellent choices to mitigate EM pollution.

Direct Electrochemistry of Glucose Dehydrogenase-Functionalized Polymers on a Modified Glassy Carbon Electrode and Its Molecular Recognition of Glucose.

A glucose biosensor was layer-by-layer assembled on a modified glassy carbon electrode (GCE) from a nanocomposite of NAD(P)+-dependent glucose dehydrogenase, aminated polyethylene glycol (mPEG), carboxylic acid-functionalized multi-wall carbon nanotubes (fMWCNTs), and ionic liquid (IL) composite functional polymers. The electrochemical electrode was denoted as NF/IL/GDH/mPEG-fMWCNTs/GCE. The composite polymer membranes were characterized by cyclic voltammetry, ultraviolet-visible spectrophotometry, electrochemical impedance spectroscopy, scanning electron microscopy, and transmission electron microscopy. The cyclic voltammogram of the modified electrode had a pair of well-defined quasi-reversible redox peaks with a formal potential of -61 mV (vs. Ag/AgCl) at a scan rate of 0.05 V s-1. The heterogeneous electron transfer constant (ks) of GDH on the composite functional polymer-modified GCE was 6.5 s-1. The biosensor could sensitively recognize and detect glucose linearly from 0.8 to 100 µM with a detection limit down to 0.46 μM (S/N = 3) and a sensitivity of 29.1 nA μM-1. The apparent Michaelis-Menten constant (Kmapp) of the modified electrode was 0.21 mM. The constructed electrochemical sensor was compared with the high-performance liquid chromatography method for the determination of glucose in commercially available glucose injections. The results demonstrated that the sensor was highly accurate and could be used for the rapid and quantitative determination of glucose concentration.

Synthesis of Chemically Modified Acid-Functionalized Multiwall Carbon Nanotubes with Benzimidazole for Removal of Lead and Cadmium Ions from Wastewater.

In this work, acid-functionalized multiwalled carbon (MWCNTs-CO2H) nanotube was successfully functionalized with a heterocyclic scaffold, namely benzimidazole, to give novel functionalized multiwalled carbon nanotubes (BI@MWCNTs). Then, FTIR, XRD, TEM, EDX, Raman spectroscopy, DLS, and BET analyses were used to characterize the synthesized BI@MWCNTs. The effectiveness of the adsorption of two heavy metal ions, Cd2+ and Pb2+, in single metal and mixed metal solutions on the prepared material was investigated. Influencing parameters for the adsorption method, for example duration, pH, starting metal concentration, and BI@MWCNT dosage, were examined for both metal ions. Moreover, adsorption equilibrium isotherms fit with the Langmuir and Freundlich models perfectly, while the intra-particle diffusion models provide pseudo-second order adsorption kinetics. The adsorption of Cd2+ and Pb2+ ions onto BI@MWCNTs revealed an endothermic and a spontaneous method with great affinity as a result of the negative values of Gibbs free energy (ΔG) and the positive values of enthalpy (ΔH) and entropy (ΔS). Both Pb2+ and Cd2+ ions were completely eliminated from aqueous solution (100 and 98%, respectively) using the prepared material. Additionally, BI@MWCNTs have a high adsorption capacity and were regenerated in a simple way and reused for six cycles, which make them a cost-effective and efficient absorbent for the removal of such heavy metal ions from wastewater.

Preparation, characterizations, and application of (MWCNTs)-COOH/Fe3O4-CaO hybrid as an effective magnetic catalyst for direct C-glycosylation reactions

Modification of acid-functionalized multiwalled carbon nanotubes (MWCNTs)-COOH with Fe3O4-CaO nanoparticles using FeSO4 and eggshell, produced an efficient magnetic catalyst for the synthesis of some C-glycosides. The condensation of dimedone with unprotected sugars in ethanol in the presence of a catalytic amount of (MWCNTs)-COOH/Fe3O4-CaO gave 3,4,5,6,7,9-hexahydro-1H-xanthene-1,8 (2H)-dione derivatives in good yields. The products were identified by CHN analysis, NMR, and FTIR spectra. Conversely, synthesis of Fe3O4-CaO nanoparticles and their conjugation on the surface of (MWCNTs)-COOH have been confirmed by FTIR, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy.

Optimizing proton exchange membrane fuel cell performance at low-humidity via constructing additional anodic water-retaining membrane layer containing sulfonated multi-walled carbon nanotubes

Membrane electrode assembly (MEA) is the core component of a proton exchange membrane fuel cell (PEMFC), which largely dictates the final performance of the device. When PEMFCs are in operation, the internal water migration greatly affects the performance output, so better water management in MEA is necessary. Herein, an additional membrane layer containing sulfonic acid-functionalized multi-walled carbon nanotubes (SO3-MCNT) has been sandwiched between the commercial Nafion proton exchange membrane and the anode catalyst layer. The newly added composite membrane is able to optimize the water electro-osmotic drag (EOD) and back diffusion (BD) and as well as accelerate the proton transfer, which leads to a substantial improvement in the performance of the MEA. This method is practicable with obvious advantages under the conditions closer to the actual operation of PEMFC.

Mechanically robust and highly elastic thermally induced shape memory polyurethane based composites for smart and sustainable robotic applications

AbstractIn the present study, polyurethane (PU) was prepared using a pre‐polymer (two‐shot) process with a novel phloroglucinol chain extender. PU nanocomposite was prepared by incorporating acid‐FMWCNTs in pristine‐PU. Polystyrene (PS) was functionalized with the nitro group through our previously reported method. The ternary blend composites (PU/PS‐NO2/FMWNTs) were prepared using acid functionalized multiwall carbon nanotubes (FMWCNTs) for enhanced properties and selectivity. Nitro‐functionalized‐PS/PU composite properties were compared with pristine‐PU and its blend composite. The structure of the pre‐designed PU polymer and its composites were confirmed by the FTIR and the degree of crystallinity and amorphous state was determined with XRD analysis. Excellent thermal stabilities were confirmed through a TGA thermogram with an increase in the loading amount of FMWCNTs. Excellent tensile strength 59.2 ± 2.6 MPa with 0.1 g loading amount of FMWCNTs with enhanced flexibilities was achieved. The significant change in surface morphologies and porosity suggested enhanced interaction (physical and chain entanglement) of FMWCNTs and nitrated‐PS with PU chain as the loading amount of filler increased. The resulted porous spongy cluster (as seen in SEM images) provides efficient shape recovery strain with excellent flexibility to the composite material without compromising repeatability. Almost 100% shape recovery was observed for all samples with repeated recoveries. The recovery time of PU nanocomposite observed is shorter than neat polyurethane and PU/PS‐NO2 blends because of their better conductive nature but causes brittleness, which can easily initiate a crack in the sample compared to a blended sample.

Hydrophobically Associated Functionalized CNT-Reinforced Double-Network Hydrogels as Advanced Flexible Strain Sensors

Hydrogels have gained the attention of researchers worldwide and can be widely applied for use in medical technologies in human health and in industrial applications such as robotics. However, producing a hydrogel with proper mechanical properties, low hysteresis energy, quick shape recovery, and long-range strain sensitivity is still an ongoing development. More development into hydrogel technology could also lead to an increase in the effectiveness and lifespan of artificial joint replacements. Our hydrogels can be incorporated into the development of highly sensitive strain sensors for wearable electronic devices. To work toward developing these technologies, multifunctional dual crosslinked hydrogels were developed using lauryl methacrylate, acrylamide, and acid-functionalized multiwalled carbon nanotubes (A-MWCNTs). Due to the dual crosslinking, the synthesized hydrogels display outstanding mechanical performance (high fracture stress, strain, toughness, and tensile strength). In shape recovery, the materials recover their original shape after compression and maintain hydrostaticity. A low hysteresis energy of 11.57 kJ m–3 makes it a suitable candidate for strain sensing with high sensitivity (GF = 9.2 at 500% strain) to monitor different human motions (wrist, neck movements, flexion of the fingers, swallowing, and during speaking). Additionally, due to its good mechanical properties, the cyclic stability was monitored up to 300 cycles and the hydrogel still was mechanically stable and had the fastest response–recovery time of less than 130 ms during mechanical performance studies. Our hydrogels can be used to develop highly sensitive strain sensors for wearable electronic devices.

Carbon nanotubes and carbon nanofibers based co-continuous thermoplastic elastomeric blend composites for efficient microwave shielding and thermal management

Microwave absorbing materials based on polymer blend composites are now receiving great interest to mitigate radiation pollution at ultra-low filler concentrations. Herein, polystyrene (PS)/ethylene-co-methyl acrylate (EMA) thermoplastic elastomeric blend composites were prepared via wet mixing utilizing acid-functionalized multi-walled carbon nanotubes (MWCNTs) and carbon nanofibers (CNFs). The development of a compact spatial conductive network throughout the matrix as a result of selective confinement of these functionalized nanofillers in EMA phase of the PS/EMA co-continuous blend reduces the electrical percolation threshold significantly. Higher aspect ratio of FCNFs helps to construct more interconnected conductive pathway in the composite than FCNTs. The thermal conductivity obtained for PS/EMA/FCNT and PS/EMA/FCNF blend composites with 15 wt% of filler concentration are 0.84, 0.86 W/m.K, respectively. The as-preparedcomposites have an absorption-dominant EMI shielding performance of −36.7 dB for 15 wt% of nanofiber loading. These highly efficient EMI shields may be applied in the future generation wearable electronics.

Preparation, Characterization, and Application of (MWCNTs)-COOH/Eu2O3 as an Efficient Reusable Catalyst

Modification of acid-functionalized multi-walled carbon nanotubes (MWCNTs)-COOH with Eu2O3 nanoparticles using Eu(NO3)3.6H2O, produced an efficient catalyst for the synthesis of some nitrogen-containing heterocycles such as quinoxalines. The products were identified by CHN analysis, NMR, and FT-IR spectra. On the other hand, synthesis of Eu2O3 nanoparticles and their conjugation on the surface of (MWCNTs)-COOH have been confirmed by FT-IR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Energy-dispersive X-ray spectroscopy (EDX).

Resonant quenching of photoluminescence in porphyrin-nanocarbon agglomerates

By adopting structural conformations with sub-nanometer precision, nature creates highly concentrated pigment-protein arrays to capture solar energy with high efficiency. Synthetic analogs of such systems exhibit concentration-dependent fluorescence quenching when approaching pigment concentrations of that seen in biological systems. Here, we report on systems of acid-functionalized multi-walled carbon nanotubes and aminophenyl tetraporphyrins that create a novel synthetic pigment-scaffold complex. The complex does not follow the trend of typical fluorescence quenching. Our steady-state and time-resolved data suggest an optimal concentration that offers a luminescence enhancement compared with the expected standard Stern-Volmer quenching relationship. The quenching is modified by controlling the pigment-distance via agglomerate size to near the upper limit for Dexter transfer of 10 Å as confirmed by dynamic light scattering measurements and chromophore-chromophore distance calculations. Our results highlight a synthetic complex with facile synthesis to investigate resonant electron transfer processes that do not follow traditional luminescence self-quenching relationships. • Facile synthesis of porphyrin-nanotube complexes with high attachment in solution • The system presents resonant, bio-analogous luminescence self-quenching • Nanoparticle agglomeration drives chromophore-chromophore transfer mechanism crossover • Interplay of distance-dependent Förster and Dexter transfer mechanism overlap Spencer et al. affix porphyrins to acid-functionalized carbon nanotubes to assess the concentration-based quenching of varying nanotube loadings, finding that agglomeration of the complexes limits energy transfer mechanisms and reduces luminescence quenching. This work reveals detail of a hard-to-study distance-dependent transfer regime change with flexible optical attachments.

In-situ growth of cerium-based metal organic framework on multi-walled carbon nanotubes for electrochemical detection of gallic acid

Gallic acid (GA) is a valuable polyphenolic compound. GA has a strong antioxidant effect, and its biological properties are anti-inflammatory, anti-histamine, anti-tumor, scavenging free radicals and protecting cardiovascular disease. Therefore, accurate and fast determination of gallic acid content is of great significance to human health. A simple and responsive electrochemical sensor for the detection of gallic acid was constructed by modifying glassy carbon electrodes with the CeMOF/MWCNTs composites synthesized by in situ growth of Ce metal organic framework (CeMOF) on carboxylic acid-functionalized multi-walled carbon nanotubes. The nanomaterials were characterized accurately by X-ray diffraction (XRD), X-ray photoelectron spectroscop (XPS) and scanning electron microscopy (SEM) and so on. Under the optimized conditions, the linear range of the sensor to detect gallic acid is 1.5 μM-200 μM, and the LOD is 0.14 μM (S/N = 3). The sensor can detect gallic acid in tea with good repeatability, stability and anti-interference.

Enhanced electrochemical hydrogen storage performance of organophosphonic carboxylic acid-modified multiwalled carbon nanotubes/Bi2S3 composite

Hydrogen energy, one of the recognized green energy sources, has many advantages, and electrochemical hydrogen storage has been regarded as one of the outstanding energy storage systems. The present research describes that the organophosphonic carboxylic acid-modified multiwalled carbon nanotubes/Bi2S3 composite (OPCAMCN/BS) has been produced successfully by a facile solution reaction method, and it has been characterized by Fourier transform infrared (FTIR), scanning electron microscope (SEM), energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), and porous structure analysis. Because of the efficient synergistic effect of organophosphonic carboxylic acid-functionalized multiwalled carbon nanotubes and bismuth sulfide, the composite displays excellent electrochemical hydrogen storage and stability performances. The electrochemical hydrogen storage performance of the OPCAMCN/BS electrodes has been measured, and its discharge capacity (950.9 mAh/g) greatly exceeds the relevant values of those two reference materials, and the cycle life of the OPCAMCN/BS electrodes is higher than that of Bi2S3 and MWCNTs/BS. Furthermore, the as-synthesized composite OPCAMCN/BS exhibits very low charge transfer resistance which signifies fast electron transfer. Therefore, OPCAMCN/BS is expected to be used as a kind of excellent electrochemical hydrogen storage material and can be applied in the areas of renewable energy to reduce the use of fossil fuels.