Carboxyl-functionalized Multi-walled Carbon Nanotubes Research Articles

Smartphone-based portable sensor with Bi-MOF nanocomposite for Cd (II) in vegetable samples

The accumulation of heavy metal cadmium (Cd) in the food chain poses a serious threat to human health, necessitating the development of rapid, on-site, and portable detection methods for Cd (II). Herein, we developed a smartphone-based electrochemical sensor for portable determination of Cd (II) in vegetables using a bismuth metal–organic framework (Bi-MOF) nanocomposite. Prismatic rod-like Bi-MOF was hydrothermally synthesized using trimesic acid as organic ligands, and subsequently, carboxyl-functionalized multi-walled carbon nanotubes (COOH-MWCNTs) were incorporated to form Bi-MOF nanocomposite network. The smartphone-based electrochemical sensor enables rapid, sensitive, and portable detection of Cd (II) in vegetable samples using Bi-MOF/COOH-MWCNTs-modified screen-printed carbon electrodes (SPCE). A comparative analysis of traditional electrochemical sensors coupled with desktop computer for linear voltametric responses for Cd (II) in the range of 0.2–500 ng/mL with a limit of detection (LOD) of 0.07 ng/mL using Bi-MOF/COOH-MWCNTs-modified glassy carbon electrodes (GCE), the portable sensor demonstrated good linear range in 0.7–350 ng/mL with a LOD of 0.22 ng/mL. This work introduces a novel approach for on-site and portable detection of Cd (II) in agricultural products.

Submersible voltammetric sensing probe for rapid and extended remote monitoring of opioids in community water systems

The intensifying global opioid crisis, majorly attributed to fentanyl (FT) and its analogs, has necessitated the development of rapid and ultrasensitive remote/on-site FT sensing modalities. However, current approaches for tracking FT exposure through wastewater-based epidemiology (WBE) are unadaptable, time-consuming, and require trained professionals. Toward developing an extended in situ wastewater opioid monitoring system, we have developed a screen-printed electrochemical FT sensor and integrated it with a customized submersible remote sensing probe. The sensor composition and design have been optimized to address the challenges for extended in situ FT monitoring. Specifically, ZIF-8 metal–organic framework (MOF)-derived mesoporous carbon (MPC) nanoparticles (NPs) are incorporated in the screen-printed carbon electrode (SPCE) transducer to improve FT accumulation and its electrocatalytic oxidation. A rapid (10 s) and sensitive square wave voltammetric (SWV) FT detection down to 9.9 µgL−1 is thus achieved in aqueous buffer solution. A protective mixed-matrix membrane (MMM) has been optimized as the anti-fouling sensor coating to mitigate electrode passivation by FT oxidation products and enable long-term, intermittent FT monitoring. The unique MMM, comprising an insulating polyvinyl chloride (PVC) matrix and carboxyl-functionalized multi-walled carbon nanotubes (CNT-COOH) as semiconductive fillers, yielded highly stable FT sensor operation (> 95% normalized response) up to 10 h in domestic wastewater, and up to 4 h in untreated river water. This sensing platform enables wireless data acquisition on a smartphone via Bluetooth. Such effective remote operation of submersible opioid sensing probes could enable stricter surveillance of community water systems toward timely alerts, countermeasures, and legal enforcement.Graphical abstract

Synthesis, characterization and evaluation of a pH-responsive molecular imprinted polymer for Matrine as an intelligent drug delivery system

Abstract To address the undesirable reactions associated with matrine (MAT) injection in clinical settings, a high-loading drug delivery system (DDS) based on pH-sensitive molecularly imprinted polymer (MAT@MIPs) was prepared for the first time. The imprinted materials containing recognition sites for the matrine were formed by using carboxyl-functionalized multiwalled carbon nanotubes as a supportive matrix and dopamine as a cross-linker due to its exceptional biocompatibility. Subsequently, the optimal reaction conditions and adsorption performance of MAT@MIPs were systematically investigated. The obtained polymers were characterized and evaluated by Fourier transform infrared spectrometry, scanning electron microscopy, elemental analysis, and thermogravimetric analysis. Results indicated that the MIPs demonstrated a favorable imprinting factor (2.36) and a high binding capacity (21.48 mg·g−1) for matrine. In vitro studies, we performed cell counting kit-8 assays in HepG2 cells, then the drug delivery capabilities of MAT-loaded MIPs were validated through light microscopy analyses, and the matrine content in culture medium was quantified using ultra high-performance liquid chromatography-mass spectrum synchronously. The facile fabrication of MAT@MIPs presents a viable solution for designing high-loading and pH-responsive DDS, which can offer a novel administration approach for drugs requiring injection in clinical applications.

Dopamine Measurement Using Engineered CNT-CQD-Polymer Coatings on Pt Microelectrodes.

This study aims to develop a microelectrode array-based neural probe that can record dopamine activity with high stability and sensitivity. To mimic the high stability of the gold standard method (carbon fiber electrodes), the microfabricated platinum microelectrode is coated with carbon-based nanomaterials. Carboxyl-functionalized multi-walled carbon nanotubes (COOH-MWCNTs) and carbon quantum dots (CQDs) were selected for this purpose, while a conductive polymer like poly (3-4-ethylene dioxythiophene) (PEDOT) or polypyrrole (PPy) serves as a stable interface between the platinum of the electrode and the carbon-based nanomaterials through a co-electrodeposition process. Based on our comparison between different conducting polymers and the addition of CQD, the CNT-CQD-PPy modified microelectrode outperforms its counterparts: CNT-CQD-PEDOT, CNT-PPy, CNT-PEDOT, and bare Pt microelectrode. The CNT-CQD-PPy modified microelectrode has a higher conductivity, stability, and sensitivity while achieving a remarkable limit of detection (LOD) of 35.20 ± 0.77 nM. Using fast-scan cyclic voltammetry (FSCV), these modified electrodes successfully measured dopamine's redox peaks while exhibiting consistent and reliable responses over extensive use. This electrode modification not only paves the way for real-time, precise dopamine sensing using microfabricated electrodes but also offers a novel electrochemical sensor for in vivo studies of neural network dynamics and neurological disorders.

Synergistic design of high-performance symmetric supercapacitor based on iron oxide nanoplatelets/COOH-MWCNTs heterostructures: DFT computation and experimental analysis

Here, we employed facile methods to develop a symmetric supercapacitor based on a heterostructure consisting of iron oxide (III) (hematite) nanoplatelets dispersed on carboxyl-functionalized multiwalled carbon nanotubes (Fe2O3/COOH-MWCNTs). The Fe2O3/COOH-MWCNTs supercapacitor effectiveness was evaluated using a 3-electrode system, demonstrating an outstanding specific capacitance of 250 F/g at 1 A/g and preserved 98.41% of its capacitance after 5000 cycles, indicating excellent cycling stability. Moreover, the symmetric Fe2O3/COOH-MWCNTs device achieved an ultrahigh energy density of 44 Wh/kg while maintaining a power density of 325 W/kg, showcasing its capability to provide substantial energy output. Furthermore, we employed Density Functional Theory (DFT) to determine the quantum capacitance of Fe2O3, both with and without functionalized-MWCNTs. These results were utilized to assess the impact of functionalized MWCNTs on enhancing the energy storage performance of the heterostructures, as well as estimating the double layer capacitance in these structures.

Electrochemical Nanoaptasensor Based on Graphitic Carbon Nitride/Zirconium Dioxide/Multiwalled Carbon Nanotubes for Matrix Metalloproteinase-9 in Human Serum and Saliva.

In this study, a nanocomposite was synthesized by incorporating graphitic carbon nanosheets, carboxyl-functionalized multiwalled carbon nanotubes, and zirconium oxide nanoparticles. The resulting nanocomposite was utilized for the modification of a glassy carbon electrode. Subsequently, matrix metalloproteinase aptamer (AptMMP-9) was immobilized onto the electrode surface through the application of ethyl-3-(3-(dimethylamino)propyl)carbodiimide hydrochloride-N-hydroxysuccinimide (EDC-NHS) chemistry. Morphological characterization of the nanomaterials and the nanocomposite was performed using field-emission scanning electron microscopy (FESEM). The nanocomposite substantially increased the electroactive surface area by 205%, facilitating enhanced immobilization of AptMMP-9. The efficacy of the biosensor was evaluated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under optimal conditions, the fabricated sensor demonstrated a broad range of detection from 50 to 1250 pg/mL with an impressive lower limit of detection of 10.51 pg/mL. In addition, the aptasensor exhibited remarkable sensitivity, stability, excellent selectivity, reproducibility, and real-world applicability when tested with human serum and saliva samples. In summary, our developed aptasensor exhibits significant potential as an advanced biosensing tool for the point-of-care quantification of MMP-9, promising advancements in biomarker detection for practical applications.

CNT incorporation improves the resolution and stability of porous 3D printed PLGA/HA/CNT scaffolds for bone regeneration

In this study, 3D printed porous poly(lactide-co-glycolide) (PLGA) and its nanocomposites with 5 wt. % hydroxyapatite (HA) and 0.5, 1 and 2 wt. % carboxyl-functionalized multi-walled carbon nanotube (CNT) scaffolds were fabricated by using extrusion-based printing. The printing parameters were optimized by rheological studies. The rheological studies demonstrated shear thinning properties for all compositions and an increase in storage modulus was observed after the addition of CNT. Porous PLGA/HA/CNT scaffolds were printed by applying a pressure of 4.76 bar at 125 °C. The addition of 0.5 wt. % of CNT reduced the strut size and increased the porosity from 42% to 60%. The increase in storage modulus and decrease in strut size were related to hydrogen bonding between CNT, HA and PLGA which ultimately improved shape fidelity. The scaffolds were characterized by analysis of their chemical structure, water contact angle measurement, in vitro bioactivity test, biodegradation test, mechanical analysis, and in vitro cell studies. The scaffolds were found to be more hydrophilic by the incorporation of CNTs. Also, degradation studies showed that the microstructure of the scaffold became more stable with the addition of HA and CNT. The compressive modulus of PLGA/HA/CNT2 scaffold was found to be 548.5 MPa, which is found suitable to replace cancellous bone. The scaffolds were found to be highly biocompatible which is possibly due to alignment of CNT and PLGA during 3D printing process. Alizarin red staining indicated improvement of mineralization of MC3T3-E1 cells on the CNT incorporated porous 3D scaffolds. The results suggest that the produced porous 3D printed PLGA/HA/CNT scaffolds are promising for bone regeneration applications.

Simple Immunosensor Based on Carboxyl-Functionalized Multi-Walled Carbon Nanotubes @ Antimony-Doped Tin Oxide Composite Membrane for Aflatoxin B1 Detection.

This paper presents a novel nano-material composite membrane for detecting aflatoxin B1 (AFB1). The membrane is based on carboxyl-functionalized multi-walled carbon nanotubes (MWCNTs-COOH) @ antimony-doped tin oxide (ATO)-chitosan (CS). To prepare the immunosensor, MWCNTs-COOH were dissolved in the CS solution, but some MWCNTs-COOH formed aggregates due to the intertwining of carbon nanotubes, blocking some pores. ATO was added to the solution containing MWCNTs-COOH, and the gaps were filled by adsorbing hydroxide radicals to form a more uniform film. This greatly increased the specific surface area of the formed film, resulting in a nano-composite film that was modified on screen-printed electrodes (SPCEs). The immunosensor was then constructed by immobilizing anti-AFB1 antibodies (Ab) and bovine serum albumin (BSA) on an SPCE successively. The assembly process and effect of the immunosensor were characterized using scanning electron microscopy (SEM), differential pulse voltammetry (DPV), and cyclic voltammetry (CV). Under optimized conditions, the prepared immunosensor exhibited a low detection limit of 0.033 ng/mL with a linear range of 1 × 10-3-1 × 103 ng/mL. The immunosensor demonstrated good selectivity, reproducibility, and stability. In summary, the results suggest that the MWCNTs-COOH@ATO-CS composite membrane can be used as an effective immunosensor for detecting AFB1.

Conductive and Thermo-Responsive Composite Hydrogels with Poly(N-isopropylacrylamide) and Carbon Nanotubes Fabricated by Two-Step Photopolymerization.

Biocompatible and conductive polymer hydrogels are the subject of intensive research in the bioengineering field because of their use in bioelectronic devices and for the fabrication of electro-responsive tissues and drug delivery systems. In this study, we report the synthesis of conductive composite hydrogels consisting of a poly(N-isopropylacrylamide) (PNIPAM) matrix embedding carboxyl-functionalized multi-walled carbon nanotubes (MWCNT-COOH) using a two-step photopolymerization method. Thermo-responsive hydrogels with controlled hydrophilicity and conductivity were prepared by varying the carbon nanotube concentration in the range 0.5-3 wt%. The thermal response of the PNIPAM-based composite hydrogels was measured by differential scanning calorimetry with both ultrapure water and PBS solution as swelling liquid. Results show that the endothermic peak associated with the temperature-induced volume phase transition (VPT) shifts to higher temperatures upon increasing the concentration of the nanotubes, indicating that more energy is required to dissociate the hydrogen bonds of the polymer/filler network. In PBS solution, the swelling ratios and the VPT temperatures of the composite hydrogels are reduced because of salt-induced screening of the oppositely charged polymer/filler assembly, and the electrical resistivity decreases by a factor of 10 with respect to the water-swollen hydrogels.

Development and Characterization of a Sustainable Bio-Polymer Concrete with a Low Carbon Footprint.

Polymer concrete (PC) has been used to replace cement concrete when harsh service conditions exist. Polymers have a high carbon footprint when considering their life cycle analysis, and with increased climate change concerns and the need to reduce greenhouse gas emission, bio-based polymers could be used as a sustainable alternative binder to produce PC. This paper examines the development and characterization of a novel bio-polymer concrete (BPC) using bio-based polyurethane used as the binder in lieu of cement, modified with benzoic acid and carboxyl-functionalized multi-walled carbon nanotubes (MWCNTs). The mechanical performance, durability, microstructure, and chemical properties of BPC are investigated. Moreover, the effect of the addition of benzoic acid and MWCNTs on the properties of BPC is studied. The new BPC shows relatively low density, appreciable compressive strength between 20-30 MPa, good tensile strength of 4 MPa, and excellent durability resistance against aggressive environments. The new BPC has a low carbon footprint, 50% lower than ordinary Portland cement concrete, and can provide a sustainable concrete alternative in infrastructural applications.

Effect of ultrasonication on carboxyl-functionalized multiwalled carbon nanotubes in fresh and hardened Portland cement pastes

abstract: The effects of chemical and physical methods on multiwalled carbon nanotube (MWCNT) dispersion in Portland cement pastes were investigated. Consistency, rheology, compressive strength, dynamic elastic modulus, flexural strength, water absorption, and void content tests were performed to evaluate these effects. Changes in the rheology of the cement pastes and surfactants resulted in a significant reduction in apparent viscosity and yield strength. Additionally, cement pastes containing carboxyl- functionalized MWCNTs (MWCNT-COOH) and surfactant showed higher compressive strengths at 28 d. However, the ultrasonic dispersion method did not significantly influence the properties of hardened Portland cement compared with Portland cement produced using the non-sonicated aqueous solution.

Adsorption of Tannase from Aspergillus ficuum to carboxyl-functionalized multi-walled carbon nanotubes

The immobilization of cross-linked tannase onto carboxyl-functionalized multi-walled carbon nanotubes (MWCNT-COOH) was achieved via physical adsorption. Glutaraldehyde was used to cross-link the enzyme molecules. Spectroscopic and morphological characterizations of the enzyme-nanotubes composite were carried out, which authenticated the successful adsorption event. Enzyme composite is proven equal to, or even superior than free tannase, in terms of catalytic activities and stabilities, when measured under different thermal, pH and recycling conditions. Whilst both free and immobilized tannase preparations exhibited optimum catalysis at pH 5.0 and 35?C, tannase-nanotubes composite possesses better thermal stability. The immobilized preparation retained 75 % of its initial catalytic activity following ten consecutive uses. The study demonstrated a facile method to produce catalytically efficient nanobiocatalyst composite for biotechnological applications.

A metal-free voltammetric sensor for sensitive determination of Rhodamine B using carboxyl-functionalized carbon nanomaterials

Rhodamine B (RhB) is a synthetic xanthine dye that is harmful to environment and human health. Therefore, the development of low cost and efficient analytical techniques for RhB monitoring is very critical for environmental protection and food safety. Herein, a novel metal-free voltammetric sensor was constructed for sensitive detection of RhB using carboxyl-functionalized carbon nanomaterials. To understand the role of carboxyl functionalization in RhB electrooxidation, the electrochemical properties and voltammetric responses of carboxyl-functionalized multi-walled carbon nanotube (f-MWCNT), carboxyl-functionalized reduced graphene oxide (f-RGO), multi-walled carbon nanotube (MWCNT) and reduced graphene oxide (RGO) were compared. Amongst, the f-MWCNT/GCE exhibited the lowest charge transferred resistance and the largest electroactive surface area. The f-MWCNT/GCE showed extraordinary electrocatalytic activity for RhB oxidation, which is primarily attributed to the unique 3D structure and the carboxyl functionalization. The anodic peak current of RhB is linearly correlated to RhB concentration from 0.05 to 100 μM with a low limit of detection (LOD, 2.6 nM). In addition, the f-MWCNT/GCE achieved the selective identification and detection of RhB in presence of common metal ions and other red dyes, and retained a robust and stable voltammetric responses for at least a week. The f-MWCNT/GCE was successfully applied to detect RhB concentration in tomato sauce samples with good recovery.

Super-Coordinated Nickel N4 Ni1 O2 Site Single-Atom Catalyst for Selective H2 O2 Electrosynthesis at High Current Densities.

Electrochemical production of hydrogen peroxide (H2 O2 ) from O2 on single-atom catalysts has attracted great attention, yet the quest for robust catalysts is driven by achieving >90 % Faradaic efficiency (FE) under industrial-relevant current densities (>100 mA cm-2 ). Herein we synthesize a catalyst that contains single nickel site coordinated by four nitrogen and two oxygen atoms (i.e., N4 Ni1 O2 ) via involving carboxyl functionalized multiwall carbon nanotubes as a substrate to provide extra O coordination to the regular NiN4 site. It has a cathodic energy efficiency of approximately 82 % and a H2 O2 FE of around 96 % at 200 mA cm-2 current density, outperforming the reported single-atom catalysts for H2 O2 electrosynthesis.

Super‐Coordinated Nickel N4Ni1O2Site Single‐Atom Catalyst for Selective H2O2Electrosynthesis at High Current Densities

AbstractElectrochemical production of hydrogen peroxide (H2O2) from O2on single‐atom catalysts has attracted great attention, yet the quest for robust catalysts is driven by achieving >90 % Faradaic efficiency (FE) under industrial‐relevant current densities (>100 mA cm−2). Herein we synthesize a catalyst that contains single nickel site coordinated by four nitrogen and two oxygen atoms (i.e., N4Ni1O2) via involving carboxyl functionalized multiwall carbon nanotubes as a substrate to provide extra O coordination to the regular NiN4site. It has a cathodic energy efficiency of approximately 82 % and a H2O2FE of around 96 % at 200 mA cm−2current density, outperforming the reported single‐atom catalysts for H2O2electrosynthesis.

Development of Correlations of the Charging and Discharging Times of Carboxyl-Functionalized Multi-Walled Carbon Nanotubes (MWCNT-COOH) and Water with and without Polyethylene Glycol in Spherical Encapsulation

This investigation shows the results of a coupled numerical and experimental study on the solidification and melting of spherical capsules and the development of correlations for solidification time and melting time with parameters that impact the complete phase change time of nanofluids and water with and without polyethylene glycol inside plastic spherical capsules. Experiments included the investigation of different configurations of plastic spherical capsule diameters, external temperature, the initial temperature of phase change material (PCM), and PCMs. The PCMs used were water, water with a concentration of polyethylene glycol from 10% to 50%, and multi-wall carbon nanotubes functionalized with carboxylic acid group (COOH-MWCNT) with MWCNT at 0.125, 0.25, 0.5, and 1.0%. The simplified model was validated with available experimental results from the present work and from the literature, showing maximum deviations in the range of 0.25 to 12%. The simulation results showed that the use of nanoparticles in the base fluid increased the velocity of the solidification and melting processes and shortened the time for complete solidification and melting. The correlations for the complete solidification time and complete melting time followed the experimental results, with a maximum deviation of about 6%, which proves an excellent concordance of the correlations with the experiments.

Comparative assessment of oxygen uptake rate of activated sludge and Escherichia coli exposed to nanomaterials.

The adverse effects of engineered nanomaterials (ENMs) on bacterial populations found in wastewater treatment plants (WWTPs) or natural systems have been studied for more than a decade, but conflicting evidence on the matter still makes it a subject of considerable concern. In this paper, the short-term exposure impact of titanium dioxide nanoparticles (nTiO2), carboxyl-functionalized multiwall carbon nanotubes (f-MWCNT), and zero-valent iron nanoparticles (nZVI) toward activated sludge and Escherichia coli (E. coli) was investigated through respiration inhibition experiments. Microorganisms were exposed to nanoparticle concentrations of 50, 100 and 200 mg/L (nTiO2, f-MWCNT) and 20, 50 and 100 mg/L (nZVI). The experiments showed that nTiO2 produced no inhibition in activated sludge or E. coli; up to 100 mg/L of nZVI did not inhibit the activated sludge respiration but 50 mg/L inhibited 24 ± 3% the respiration of E. coli and damaged its cell membrane. Activated sludge respiration was inhibited 17 ± 3% with 200 mg/L of f-MWCNT while for E. coli the inhibition was 36 ± 15% and the cell membrane was damaged with a 100 mg/L dose. Transmission electron microscopy (TEM) showed nTiO2-bacteria and nZVI-bacteria surface interaction while bacteria appeared punctured by f-MWCNT. E. coli was more susceptible than activated sludge to the nanomaterials and nZVI was more toxic than f-MWCNT for E. coli. These results demonstrated the absence of acute toxicity effects of the studied nanomaterials at those concentrations expected to occur in activated sludge facilities, and it would only be a concern in case of extremely high inputs, underscoring the resilience of WWTPs biological treatment.

Adaptation of Multi Walled Carbon Nanotubes on Viscoelastic and Damping Behavior of Flax Fiber Composite

ABSTRACT Damping characteristics and viscoelastic behavior of flax/epoxy composites reinforced with carboxyl-functionalized multi-walled carbon nanotubes (COOH-MWCNT) were investigated in this study. The viscoelastic behavior was studied utilizing dynamic mechanical analysis (DMA), conducted on all the fabricated composite specimens and neat-resin (pure epoxy). The results revealed an improvement in glass transition temperature (T g) for flax epoxy composites with 0 wt.%, 0.5 wt.%, and 1 wt.% reinforcement of MWCNT when compared to the free-resin. From the obtained graphs, C-factor was estimated, adhesion factor and Cole–Cole plots were drawn. The frequency response function (FRF) plot, obtained from free vibration testing, unveils the natural frequencies at mode-I and mode-II vibration, and their respective damping ratios are estimated by half-power bandwidth method. The damping ratios and the natural frequencies increased with the addition of MWCNT. The flax/epoxy composite reinforced with 1 wt.% of MWCNT was found to prevail over the rest by exposing great vibration damping, viscoelastic and mechanical properties.

RAPID ELECTROCHEMICAL DETECTION OF CARBENDAZIM IN VEGETABLES BASED ON CARBOXYL FUNCTIONALIZED MULTI-WALLED CARBON NANOTUBES

At present, the commonly used methods for the detection of benzimidazole fungicides include high performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS), fluorescence spectrometry and so on. These methods have high sensitivity and accurate results, but they have disadvantages such as complicated pretreatment, long time consuming, expensive equipment and professional operators. Electrochemical sensor detection method has the advantages of high sensitivity, simple operation, low cost and easy on-site inspection, etc., which has attracted extensive attention in the field of pesticide residue detection and analysis. In order to realize the rapid detection of carbendazim content in vegetables, an electrochemical rapid detection method was established by using Carboxyl Functionalized Multi-Walled Carbon Nanotubes (MWCNTs-COOH) modified glassy carbon electrode. In this study, MWCNTs-COOH with special functional groups and large specific surface area were used to modify electrodes to improve the adsorption and enrichment of CBZ on the electrode and amplify the electrochemical signal, aiming to establish a highly sensitive electrochemical rapid detection technology for CBZ. The results showed that: the modified electrode functionalized with MWCNTs-COOH could significantly improve the electron transfer rate on the electrode surface, which made the detection sensitivity of carbendazim higher. The linear range of detection was 0,3 μM~20 μM, and the detection limit was determined as low as 0,06 μM. In this study, MWCNT-COOH with better conductivity, adsorption and stability was used to modify electrode, and constructed the MWCNT-COOH/GCE, which improved the adsorption and accumulation of CBZ, effectively promoted the electron transfer on the surface of the electrode, accelerated the response speed of the electrode and improved the current response, to realize the rapid and sensitive detection of trace CBZ in vegetables. This method had high sensitivity, good anti-interference, and detection stability. It was of great significance to detect carbendazim in vegetables.

Experimental study on heat transfer enhancement of carboxylate multi-wall carbon nanotubes in a 3D pulsating heat pipe with a corrugated evaporator

ABSTRACT In this research, the thermal performance of a three-dimensional pulsating heat pipe with 11 turns is investigated experimentally. Carboxyl-functionalized multi-walled carbon nanotubes with 0.1 wt% in a water-based fluid are used as the operating fluid. Experiments are performed at 50% and 60% filling ratios, and the effect of grooving the evaporator tubes has also been investigated. Experiments with distilled water were also performed to compare the effect of the nanofluid. Experimental results show that the heat transfer performance of the device depends mainly on the power input and the filling ratio, working fluid, and also, the corrugated evaporator that significantly improves the thermal performance. The use of nanofluids reduces the thermal resistance by about 13% compared to pure water at a filling ratio of 50%, and an input power of 300 watts. At a filling ratio of 60%, and the use of nanofluid, corrugating the evaporator reduces the thermal resistance by 6% in comparison with non-corrugated tubes. In general, and in all cases, with increasing input power, the thermal resistance also decreases.