Hydroxyl Multi-walled Carbon Nanotubes Research Articles

Collagen composite fibers with various functionalized carbon nanotubes fabricated via microfluidic spinning

AbstractCollagen (Col) composite fibers containing various functionalized multiwalled carbon nanotubes (MWNTs) were prepared via microfluidic spinning, and the influences of MWNT content and type on the performances of the composite fibers were investigated by transmission electron microscope, UV–vis, SEM, Fourier Transform Infrared Spectrometer, differential scanning calorimetry, X‐ray diffraction, and tensile testing. The Col composite fibers showed tightly packed bundle structures on surfaces originated from the high shear rates in the microfluidic channels, and MWNT facilitates the self‐assembly of Col molecules, leading to the ordered arrangement of Col fibrils along the fiber axis. When the loading of carboxylated MWNT (cMWNT) was 0.5 wt%, the tensile strength of Col/cMWNT achieved the maximum of 1.94 cN/dtex owing to the excellent hydrogen bond and electrostatic interactions between the carboxyl groups in cMWNT and amino groups in Col molecules, which is significantly higher than those composite fibers made from unfunctionalized and hydroxylated MWNT. Moreover, with the incorporation of MWNT the thermal stability and water resistance of Col fibers were improved due to the enhanced interfacial interactions between Col and MWNT. The fabrication method in this work enables the controlled formation of Col fibers and demonstrates huge potential for use in Col‐based biomaterials.Highlights Novel collagen (Col)/multiwalled carbon nanotube (MWNT) composite fibers were prepared via microfluidic spinning. The Col composite fibers showed tightly packed bundle surface structures. Col/carboxylated MWNT achieved the maximum tensile strength of 1.94 cN/dtex. MWNT enhanced thermal stability and water resistance of Col fibers.

Cost-efficient and ultrasensitive sensor for electrochemical detection and cytotoxicity assessment of tetracyclines

The uncontrolled overuse of tetracyclines (TCs) has contributed to a significant rise in the levels of not only antibiotic residues in the environmental but also drug- and multidrug-resistant bacteria, necessitating a convenient, sensitive, and rapid assay for the quantitative determination and health risk assessment of TCs. This study presents the development of a nanocomposite sensor which integrates hydroxylated multiwalled carbon nanotubes (MWCNTs-OH), tungsten disulfide quantum dots (WS2QDs), and prussian blue (PB). This sensor was capable of measuring the concentrations of tetracycline (TC), oxytetracycline (OTC), doxycycline (DC), and tigecycline (TEC) at levels ranging from 0.10 to 125.00 μM, with detection limits of 0.010, 0.015, 0.020, and 0.060 μM, respectively (S/N = 3). The excellent electrochemical performance enabled the sensor to measure TC concentrations in real water samples. Importantly, the sensor was also used to evaluate the cytotoxicity of TCs on human hepatocarcinoma (HepG2) cells. The 48 h half-inhibitory concentrations (IC50) for TC, OTC, DC, and TEC were 344.91 μM, 365.14 μM, 349.59 μM, and 604.66 μM, respectively, indicating that TC was the most cytotoxic. The sensing platform described herein not only facilitates the quantitative determination of TCs but also allows for the assessment of their cytotoxicity in the water environment, which greatly simplifies the comprehensive evaluation process and reduces the cost, thus holding great promise for TCs testing.

Adsorption and catalytic degradation of tetracycline hydrochloride by HCNTs /MnFe2O4

Developing efficient, stable and selective materials is essential for removing antibiotics from aquatic systems. In this study, one composite is prepared via loading of magnetic MnFe2O4 onto hydroxylated multi-walled carbon nanotubes (HCNTs) through co-precipitation, named as HCNTs/MnFe2O4. The characterization of materials was performed using various methods, such as Vibrating Sample Magnetometer (VSM), Electron Paramagnetic Resonance (EPR), etc. There are larger surface and good magnetic property, which are useful to bind adsorbate and easy separation from mixtures. The as-synthesized composite exhibited excellent adsorption capacity and ability to activate potassium persulfate (KPS) for the efficient removal of Tetracycline hydrochloride (TC) from solution. The results showed that the adsorption capacity of HCNTs/MnFe2O4 towards TC was 341 mg·g–1 at 303 K. The kinetic process can be elucidated using pseudo-second-order kinetic model while the adsorption equilibrium can be fitted by Freundlich model. The mechanism of adsorption may include electrostatic attraction, complexation, π-π stacking, etc. To initiate Fenton-like heterogeneous catalytic degradation, KPS was added to the adsorption system to degrade and remove TC from solution. The experimental results showed that HCNTs/MnFe2O4 as a catalyst could achieve up to 89 % degradation of TC in the range of pH=3–8 due to its ability to generate active species such as ‧OH, SO4‧-, ‧O2- and 1O2 as confirmed from radical capturing experiments and EPR analysis. The removal efficiency after three adsorption regeneration or degradation cycles could reach up to 56 %, confirming its good reusability properties. There are good prospects of HCNTs/MnFe2O4 for the practical removal of antibiotics from aqueous solutions.

Highly sensitive detection of multiple antiviral drugs using graphitized hydroxylated multi-walled carbon nanotubes/ionic liquids-based electrochemical sensors

Global outbreaks and the spread of viral diseases in the recent years have led to a rapid increase in the usage of antiviral drugs (ATVs), the residues and metabolites of which are discharged into the natural environment, posing a serious threat to human health. There is an urgent need to develop sensitive and rapid detection tools for multiple ATVs. In this study, we developed a highly sensitive electrochemical sensor comprising a glassy carbon electrode (GCE) modified with graphitized hydroxylated multi-walled carbon nanotubes (G-MWCNT-OH) and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6, IL) for the detection of six ATVs including famciclovir (FCV), remdesivir (REM), favipiravir (FAV), hydroxychloroquine sulfate (HCQ), cepharanthine (CEP) and molnupiravir (MOL). The morphology and structure of the G-MWCNT-OH/IL nanocomposites were characterized comprehensively, and the electroactive surface area and electron conductivity of G-MWCNT-OH/IL/GCE were determined using cyclic voltammetry and electrochemical impedance spectroscopy. The thermodynamic stability and non-covalent interactions between the G-MWCNT-OH and IL were evaluated through quantum chemical simulation calculations, and the mechanism of ATV detection using the G-MWCNT-OH/IL/GCE was thoroughly examined. The detection conditions were optimized to improve the sensitivity and stability of electrochemical sensors. Under the optimal experimental conditions, the G-MWCNT-OH/IL/GCE exhibited excellent electrocatalytic performance and detected the ATVs over a wide concentration range (0.01–120 μM). The limit of detections (LODs) were 42.3 nM, 55.4 nM, 21.9 nM, 15.6 nM, 10.6 nM, and 3.2 nM for FCV, REM, FAV, HCQ, CEP, and MOL, respectively. G-MWCNT-OH/IL/GCE was also highly stable and selective to the ATVs in the presence of multiple interfering analytes. This sensor exhibited great potential for enabling the quantitative detection of multiple ATVs in actual water environment.

Preparation and properties of oxidized multi-walled carbon nanotube superhydrophobic composites modified by bio-fatty acids

In this paper, a preparation method of superhydrophobic composites of oxidized multi-walled carbon nanotubes modified by stearic acid (SA) is proposed. Hydroxylated multi-walled carbon nanotubes (HMWCNTs) were obtained by oxidizing multi-walled carbon nanotubes with potassium dichromate to give them hydroxyl groups on the surface. Subsequently, the carboxyl group in the SA molecule was esterified with the hydroxyl group on the HMWCNTs. SA molecules were grafted onto the surface of multi-walled carbon nanotubes. SA modified oxidized multi-walled carbon nanotubes (SMWCNT) superhydrophobic composites were obtained. The results show that the water contact angle (WCA) of superhydrophobic composites can reach up to 174°. At the same time, the modified nanocomposites have good anti-icing and corrosion resistance. After low temperature delayed freezing test, the freezing extension time of the nanocomposite film is 30 times that of the smooth surface. Under strong acid and alkali conditions, the superhydrophobic nanocomposites still maintain good superhydrophobicity. The nanocomposites may have potential applications in the preparation of large-scale superhydrophobic coatings.

One-pot derivatization/magnetic solid-phase extraction coupled with liquid chromatography-fluorescence detection for the rapid determination of sulfonamide residues in honey

Consuming foods with excess sulfonamide residues threatens human health, underscoring the importance of their detection in food. This study presents an innovative one-pot derivatization/magnetic solid-phase extraction (OPD/MSPE) method for sulfonamides analysis. This approach integrates the derivatization and extraction steps into a single process. The sample solution, along with the derivatization reagent fluorescamine and the sorbent magnetic hydroxyl multi-walled carbon nanotubes, is mixed and vortexed for 3 min. This procedure simultaneously conducts derivatization and extraction, with easy phase separation using an external magnet. This streamlined sample preparation method is completed in only 5 min and, when combined with liquid chromatography-fluorescence detection (LC-FLD), demonstrates excellent linearity (R2 > 0.99) and satisfactory detection limits (0.004–0.04 ng/g) for the quantification of nine sulfonamides in honey samples. The proposed OPD/MSPE-LC-FLD method is distinguished by its simplicity, rapidity, high sensitivity, and specificity, making it an outstanding advancement in the field of food safety analysis.

Enhanced thermal conductive and moisturizing hydrogels by constructing 3D networks of BN-OH and CNT-OH in alignment for burn therapy

Hydrogel treatment as a common cooling method could effectively ease pain and promote wounds healing by reducing thermal injury to the skin. However, the inherent low thermal conductivity of polymers limits the improvement of hydrogels’ cooling performance. The present study reports a simple method by combining thermal conductive fillers 1D hydroxylated multiwall carbon nanotubes (CNT-OH) and 2D hydroxylated hexagonal boron nitride (BN-OH) to construct 3D conductive networks in hydrogels for cooling treatment and burn therapy. It is interesting that the thermal conductive fillers are aligned via varying the mass ratios of CNT-OH to BN-OH. Hence, the utilization efficiency of the thermal conductive fillers is improved; and the thermal conductivity of the hydrogels is enhanced up to 1.31 W*m−1*K−1, which is 226 % to the pristine hydrogel of 0.58 W*m−1*K−1. Consequently, the optimized hydrogel exhibits rapid cooling abilities that the heated porcine skin only takes 168 s to decrease 30 °C with the treatment of the hydrogel. More importantly, the thermal conductivity enhanced hydrogel exhibits the capacities of rapid cooling, reducing heat injury and pain relieving, and promoting wound healing in vivo tests, which prove that the enhanced thermal conductive and moisturizing hydrogel can be a good alternative for burn therapy.

Synergistic Effect of Water-Soluble Hydroxylated Multi-Wall Carbon Nanotubes and Graphene Nanoribbons Coupled with Tetra Butyl Ammonium Bromide on Kinetics of Carbon Dioxide Hydrate Formation

In this work, the thermodynamics and kinetics of hydrate formation in 9.01 wt% tetra butyl ammonium bromide (TBAB) mixed with water-soluble hydroxylated multi-wall carbon nanotube (MWCNTol) systems were characterized by measuring hydrate formation conditions, induction time, and final gas consumption. The results showed that MWCNTols had little effect on the phase equilibrium of CO2 hydrate formation. Nanoparticles (graphene nanoribbons (GNs) and MWCNTols) could significantly shorten the induction time. When the concentration was ≤0.06 wt%, MWCNTols had a better effect on the induction time than the GN system, and the maximum reduction in induction time reached 44.22%. The large surface area of MWCNTols could provide sites for heterogeneous nucleation, thus shortening the induction time of hydrate formation. Furthermore, adding different concentrations of nanoparticles to the 9.01 wt% TBAB solution effectively increased the final gas consumption, and the maximum increase was 10.44% of the 9.01 wt% TBAB + 0.08 wt% GN system. Meanwhile, the suitable initial pressure and experimental temperature could also promote the hydrate formation and increase the motivation in hydrate formation. The 9.01 wt% TBAB + 0.02 wt% MWCNTol system had the best effect at 3.5 MPa and 277.15 K. The induction time was reduced by 66.67% and the final gas consumption was increased by 284.11% compared to those of the same system but at a different initial pressure and experimental temperature. This work helps to promote the industrial application of hydrate technology in CO2 capture and storage.

Ni3S4 combined hydrophilic hydroxylated MWCNTs for high performance asymmetric supercapacitors

A composite material (Ni3S4-Q) of Ni3S4 combined with hydrophilic hydroxylated multi-walled carbon nanotubes (MWCNTs) was prepared by one-step method in the reactor. For comparison, hydrophilic MWCNTs were replaced by hydrophobic MWCNTs (Ni3S4-S), and pure Ni3S4 was synthesized without adding MWCNTs, so as to study the influence of the hydrophilicity and hydrophobicity of MWCNTs on the capacitive performance of Ni3S4. The contact Angle analysis shows that Ni3S4-Q has better hydrophilicity. The electrochemical cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy show that Ni3S4-Q has the highest specific capacitance and the lowest ion diffusion resistance. In addition, the asymmetric supercapacitor assembled by Ni3S4-Q and activated carbon has a maximum energy density of 51 Wh kg−1. This work strongly validated that hydrophilicity can improve the electrochemical properties of supercapacitors.

Construction of superhydrophobic alkyl siloxane-modified carbon nanotubes/epoxy coating

In this study, the superhydrophobic epoxy resin coating with siloxane-modified carbon nanotubes was prepared. Hydroxylated multi-walled carbon nanotubes (HMWCNTs) were modified with siloxane to make them superhydrophobic, which were mixed with epoxy resin to prepare an excellent superhydrophobic coating on the surface of AH36 carbon steel. Highly silanized HMWCNTs (HSHMWCNTs) were added to hydrophobic isobutyl groups and amino groups that can bond with epoxy resin. The results show that the water contact angle (WCA) of HSHMWCNTs is >170°. The coating has a WCA of 157.2° and a water sliding angle of 6° when the addition of the HSHMWCNTs reaches 70 %. The coating has excellent self-cleaning properties and remains superhydrophobicity under tape-peeling for 90 times. When the coating has a superhydrophobic effect, there is an air layer on the surface, improving the corrosion resistance of the coating.

Effect of Tube Diameters and Functional Groups on Adsorption and Suspension Behaviors of Carbon Nanotubes in Presence of Humic Acid

The adsorption and suspension behaviors of carbon nanotubes (CNTs) in the water environment determine the geochemical cycle and ecological risk of CNTs and the compounds attached to them. In this study, CNTs were selected as the research object, and the effect of tube diameters and functional groups (multiwall CNTs (MWNTs) and hydroxylated MWNTs (HMWNTs)) on the adsorption and suspension behaviors of the CNTs in the presence of humic acid (HA) was systematically analyzed. The results indicate that HA adsorption decreased with the increase in the solution pH, and the adsorption amount and rate were negatively correlated with the tube diameter of the CNTs. The surface hydroxylation of the CNTs prevented the adsorption of HA, and the maximum adsorption amounts on the MWNTs and HMWNTs were 195.95 and 74.74 mg g−1, respectively. HA had an important effect on the suspension of the CNTs, especially for the surface hydroxylation, and the suspension of the CNTs increased with the increase in the tube diameter. The characteristics of the CNTs prior to and after adsorbing HA were characterized by transmission electron microscopy, fluorescence spectroscopy, Fourier-transform infrared spectroscopy and Raman spectroscopy. The results indicate that surface hydroxylation of the CNTs increased the adsorption of aromatic compounds, and that the CNTs with a smaller diameter and a larger specific surface area had a disordered carbon accumulation microstructure and many defects, where the adsorption of part of the HA would cover the defects on the CNTs’ surface. Density functional theory (DFT) calculations demonstrated that HA was more easily adsorbed on the CNTs without surface hydroxylation. This investigation is helpful in providing a theoretical basis for the scientific management of the production and application of CNTs, and the scientific assessment of their geochemical cycle and ecological risk.

An electrochemical sensor based on oxygen-vacancy cobalt–aluminum layered double hydroxides and hydroxylated multiwalled carbon nanotubes for catechol and hydroquinone detection

A sensitive electrochemical sensor based on oxygen vacancy Co-Al layered double hydroxides (OV-LDHs) and hydroxylated multi-walled carbon nanotubes (H-MWCNTs) was developed by self-assembly method. The existence of oxygen vacancy improved the poor electrochemical performance of original LDHs. In addition, the surface of the hydroxylated MWCNTs was rich in hydroxyl functional groups, which enabled them to form hydrogen bonds with the oxygen containing groups on the surface of the OV-LDHs, thus leading to the formation of stable nanocomposite. The electrode modified with OV-LDHs/H-MWCNTs was used for detection of hydroquinone (HQ) and catechol (CT). Under optimum experimental condition, the detection linear range of the electrochemical sensor was both 0.5–150 μM. The limit of detection (S/N = 3) for CT and HQ were as low as 0.074 μM and 0.076 μM, respectively. In addition, the OV-LDHs/H-MWCNTs sensor was explored to determine the content of HQ and CT in industrial wastewater, and satisfying recoveries were obtained. Therefore, this innovative sensor with excellent electrochemical performance is indeed an option for practical detection of organic pollutants in the environment.

A novel foam system stabilized by hydroxylated multiwalled carbon nanotubes for enhanced oil recovery: Preparation, characterization and evaluation

Carbon nanotube (CNT) is one of promising materials for stabilizing foam. However, the aggregation of CNT seriously affects its foam-stabilizing performance. Herein, this study employed the ultrasonic waves to improve the dispersity of hydroxylated multiwalled carbon nanotube (HMCNT) in SDBS solution. The ultrasonic treatment can disentangle the HMCNT through cavitation and chip effects and the SDBS molecules adsorbed on the HMCNT may increase the electrostatic repulsion between nanotubes, leading to a good dispersion of HMCNT. Besides the conventional evaluations in bulk phase, this study developed a visualized cylinder filled with quartz glass beads to estimate the foam properties in porous media. Experimental results indicate that the novel SDBS/HMCNT foam has a good foaming and foam-stabilizing performance both in bulk solution and porous media. A series of analysis experiments have been conducted to reveal the foam-stabilizing mechnism of HMCNT, including the surface tension and dilational viscoelastic modulus measurements, and the optical microscope and fluorescence microscope observations. This study found that the SDBS-modified HMCNT can adsorb on the gas-liquid interface and gather around the bubbles. As a result, the dilational viscoelasticity and thickness of foam films increase, which help to slow down the gas diffusion rate and restrain the film drainage. Finally, the fractured-core flooding tests showed that the SDBS/HMCNT foam system can effectively plug the millimeter-sized cracks in low-permeability cores and have a good potential in enhanced oil recovery.

Preparation of a novel flame retardant based on diatomite/polyethyleneimine modified MWCNT for applications in silicone rubber composites

A new flame retardant, DM/PEI/MWCNT, was prepared by self-assembly method based on non-covalent interactions between hydroxyl and amino groups on the surface of hydroxyl multi-walled carbon nanotubes (MWCNT), polyethyleneimine (PEI) and diatomite (DM). The flame-retardant composites were prepared by adding DM/PEI/MWCNT to room-temperature vulcanisated silicone rubber (RTV-silicone). The structure of the flame retardant and composites was characterised by polarising light microscope, scanning electron microscopy and Fourier-transform infrared spectroscopy. The flame retardancy of composites was studied by limited oxygen index and cone calorimeter measurement. Results showed that RTV-silicone composites with DM/PEI/MWCNT owned better flame retardancy. In addition, DM/PEI/MWCNT exhibited better compatibility in silicone rubber than that of unmodified DM, and the tensile properties of RTV-silicone/DM/PEI/MWCNT composites were improved compared to pure RTV-silicone.

An Electrochemical Sensor Based on Oxygen-Vacancy Cobalt–Aluminum Layered Double Hydroxides and Hydroxylated Multiwalled Carbon Nanotubes for Catechol and Hydroquinone Detection

An Electrochemical Sensor Based on Oxygen-Vacancy Cobalt–Aluminum Layered Double Hydroxides and Hydroxylated Multiwalled Carbon Nanotubes for Catechol and Hydroquinone Detection

Fracture toughness enhancement of epoxy resin reinforced with graphene nanoplatelets and carbon nanotubes

Graphene nanoplatelets (GNPs)/silane-coupling-agent-treated GNPs (KH- GNPs) and hydroxyl multi-walled carbon nanotubes (MWCNTs-OH) were added as reinforcing agents to an epoxy matrix, diglycidylether of bisphenol-A (DGEBA), to improve the fracture toughness of DGEBA. The influence of the MWCNT-OH fraction on the thermal and flexural properties, fracture toughness, and morphology of the DGEBA/GNP/MWCNT-OH and DGEBA/KH-GNP/MWCNT-OH nanocomposites was investigated. The results indicate that the fracture toughness of the DGEBA/KH-GNP/MWCNT-OH nanocomposites increased from 1.09 to 1.46MPa·m1/2, which is 33.9% greater than that of pristine DGEBA. Analysis of the fracture surfaces of the nanocomposites showed a rough morphology with numerous tortuous and river-like structures. In addition, the MWCNTs-OH were slightly pulled out or broken in the epoxy matrix during the fracture toughness tests.

Highly stretchable, transparent and room-temperature self-healable polydimethylsiloxane elastomer for bending sensor

Highly stretchable and self-healable elastomers are attractive for a variety of applications in the fields of electrical skin and wearable devices. Herein, we proposed a simple one-pot two-step approach to synthesize room-temperature self-healable polydimethylsiloxane (PDMS) elastomers. Excess aminopropyl terminated polydimethylsiloxane was firstly reacted with isophorone diisocyanate to synthesize amino-terminated PDMS with incorporated ureido groups, followed by further reaction with terephthalaldehyde as chain extender to yield self-healing PDMS elastomers. The obtained elastomer exhibited high stretchability of 1670% and transmittance of 92%. Owing to the dynamic intermolecular hydrogen bonds, reversible imine bonds and highly flexible SiO chains, the elastomer showed excellent self-healing capability with a healing efficiency of 95% after healing at room temperature for 24 h. Even in water and artificial sweat, the healing efficiencies also reached 89% and 78%, respectively. In addition, the elastomer supported triple-layer bending sensor was fabricated with a sandwiched hydroxylated multiwalled carbon nanotubes (MWCNTs-OH) film and successfully applied for detecting human motions. Interestingly, the cut sensor was able to be recovered for working after being irradiated under sunlight for only 10 min. Our method to synthesize highly stretchable, transparent and self-healing elastomers is simple and the reaction can be carried out at room temperature, which is beneficial for the large-scale production and the further practical application in functional electronics.

A Comprehensive Study on Hydroxyl Multiwalled Carbon Nanotubes Used as Catalysts for VO2+/VO2+ Reaction in Vanadium Redox Flow Battery

A comprehensive study on the hydroxyl multiwalled carbon nanotubes (hydroxyl MWCNTs) as catalysts in a positive reaction was performed to improve the efficiency of the vanadium redox flow battery (VRFB). The physicochemical properties of the hydroxyl MWCNT-modified electrode were characterized by using a scanning electron microscope (SEM), conductivity measurement, Brunner–Emmet–Teller (BET) measurement, X-ray photoelectron spectroscopy (XPS) analysis, cyclic voltammetry (CV) tests, electrochemical impedance spectroscopy (EIS) analysis, and charge-discharge tests. The prepared composite electrode possesses a huge amount of oxygen-containing groups, high-specific surface area, high electrical conductivity, and high catalytic activity towards the VO2+/VO2+ reaction based on physicochemical characterization. The hydroxyl MWCNT-modified graphite felt (hydroxyl MWCNTs/GF) shows the best cell performance with the energy efficiency of 79.74% and remains in high stability after 50 cycles. The improved cell performance is probably ascribed to the increase in active sites, fast charge transfer, and mass transfer rate of the introduced hydroxyl MWCNTs.

Fabrication of polymer composite films with carbon composite nanofibers doped MWNTs-OH for multilevel memory device application

Novel carbon composite nanofibers with hierarchical microstructure were synthesized using electro-spinning and carbonization (SC) techniques, and were combined into polyimide matrix based on in-situ polymerization method. The resulted polyimide composites exhibit multilevel resistive switching behavior (MRSB) for memory storage applications, with a favorable ON/OFF current ratio and a high retention time at an operating voltage less than 3 V. A hierarchical microstructure can be observed by SEM, TEM and SAXS tests, which was formed with different sizes between the hydroxyl multi-walled carbon nanotubes (MWNTs-OH), carbon nanofibers and PI matrix, influencing on the MRSB of the composite films. A physical model based on the molecular orbit energy level was utilized to investigate how the microstructures acting as charge transmission layers affect the MRSB. This result provides a new strategy for further improving the high density storage of polymer multilevel switching memory storage device.

Preparation of ionic liquid modified magnetic metal-organic frameworks composites for the solid-phase extraction of α–chymotrypsin

A novel magnetic solid-phase extraction (MSPE) method based on 1-hexyl-3-methyl imidazolium chloride ionic liquid (IL) modified magnetic Fe3O4 nanoparticles, hydroxylated multiwall carbon nanotubes (MWCNTs-OH) and zeolitic imidazolate frameworks (ZIFs) nanocomposites (Fe3O4-MWCNTs-OH@ZIF-67@IL) were proposed and applied to extract α–chymotrypsin. The magnetic materials were synthesized successfully and characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), thermal gravimetric analysis (TGA), fourier transform infrared spectrometry (FT-IR), vibrating sample magnetometer (VSM) and zeta potentials. Subsequently, the UV–vis spectrophotometer at about 280 nm was utilized to quantitatively analyze the α–chymotrypsin concentration in the supernatant. Furthermore, single factor experiments revealed that the extraction capacity was influenced by initial α–chymotrypsin concentration, ionic strength, extraction time, extraction temperature and pH value. The extraction capacity could reach up to about 635 mg g−1 under the optimized conditions, absolutely higher than that of extraction for Ovalbumin (OVA), Bovine serum albumin (BSA) and Bovine hemoglobin (BHb). In addition, the regeneration studies showed Fe3O4-MWCNTs-OH@ZIF-67@IL particles could be reused several times and kept a high extraction capacity. Besides, the study of enzymatic activity also indicated that the activity of the extracted α–chymotrypsin was well maintained 93% of initial activity. What's more, the proposed method was successfully applied to extract α–chymotrypsin in porcine pancreas crude extract with satisfactory results. All of above conclusions highlight the great potential of the proposed Fe3O4-MWCNTs-OH@ZIF-67@IL-MSPE method in the analysis of biomolecules.