Study of the Diffusion Behavior of Seawater Absorption in Multi-Walled Carbon Nanotubes/Halloysite Nanotubes Hybrid Nanofillers Modified Epoxy-Based Glass/Carbon Fiber Composites

In the maritime industry, cost-effective and lightweight Fiber Reinforced Polymer (FRP) composites offer excellent mechanical properties, design flexibility, and corrosion resistance. However, their reliability in harsh seawater conditions is a concern. Researchers address this by exploring three approaches: coating fiber surfaces, hybridizing fibers and matrices with or without nanofillers, and interply rearrangement. This study focuses on evaluating the synergistic effects of interply rearrangement of glass/carbon fibers and hybrid nanofillers, specifically Multi-walled carbon nanotubes (MWCNT) and Halloysite nanotubes (HNT). The aim is to enhance impact properties by minimizing moisture absorption. Hybrid nanocomposites with equal-weight proportions of two nanofillers: 0 wt.%, 1 wt.%, and 2 wt.% were exposed to seawater for 90 days. Experimental data was subjected to modelling through the application of Predictive Fick’s Law. The study found that the hybrid composite containing 2 wt.% hybrid nanofillers exhibited a 22.10% increase in impact performance compared to non-modified counterparts. After 90 days of seawater aging, the material exhibited enhanced resistance to moisture absorption (15.74%) and minimal reduction in impact strength (8.52%) compared to its dry strength, with lower diffusion coefficients.

Electroless deposition of Cu on multiwalled carbon nanotubes

Copper has been deposited on the surface of multiwailed carbon nanombes （MWNTs） and inside MWNTs by electroless deposition. The as-prepared Cu-MWNT composite materials have been characterized by X-ray diffractometer （XRD）, transmission electron microscopy （TEM）, and electrochemical measurement. XRD analyses showed that Cu was a face-centered cubic （fcc） structure. The average size of Cu was calculated by Scherrer＇s formula from XRD data, and it was 11 nm. TEM revealed that Cu grains on the surface of MWNTs were uniform with the sizes of about 30-60 nm. The electrochemical measurement indicated that Cu-MWNT composite materials possessed fine electron conductivity.

Sensitive determination of fenpropathrin,cyhalothrin and deltamethrin in environmental water samples using multiwalled carbon nanotubes cartridge prior to HPLC

This paper described a new method for the trace determination of fenpropathrin, cyhalothrin and deltamethrin using multiwalled carbon nanotubes （MWCNTs） cartridge. Important parameters, such as the sample pH, eluent and its volume, sample flow rate and sample volume were investigated in detail. The linear ranges, the detection limits, and precisions （R.S.D.） were in the range of 0.1- 40 μg L^-11, 1.34.3 ng L^-1 and 2.3-2.8%, respectively. The performance of the proposed method was validated with real water samples, and the spiked recoveries were in the range of 91.7-117.8%, respectively. The experimental results demonstrated that the proposed method was an excellent alternative for the routine analysis of such pollutants in environmental samples. 2007 Qing Xiang Zhou. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Photoluminescence of multiwalled carbon nanotubes excited at different wavelengths

In this paper the multiwalled carbon nanotubes （MWNTs） were synthesized by a chemical vapour deposition and the SEM graph shows that the sample has good construction. The micro-Raman spectrum shows the characteristic line of the MWNTs and an additional line produced by the defects on the outer surface of MWNTs. The photoluminescence （PL） spectra observed experimentally are variable under different excitation wavelengths and the strong excitation wavelength dependence of luminescence indicates a distribution of emitters which include electron π in excited states and the Van Hove singularities. The absorption spectra confirm the transition channels which are consistent with the PL emission.

Self-Decoration of PtNi Alloy Nanoparticles on Multiwalled Carbon Nanotubes for Highly Efficient Methanol Electro-Oxidation

A simple one-pot method was developed to prepare Pt Ni alloy nanoparticles,which can be self-decorated on multiwalled carbon nanotubes in [BMIm][BF4] ionic liquid.The nanohybrids are targeting stable nanocatalysts for fuel cell applications.The sizes of the supported Pt Ni nanoparticles are uniform and as small as 1–2 nm.Pt-to-Ni ratio was controllable by simply selecting a Pt Ni alloy target.The alloy nanoparticles with Pt-to-Ni ratio of 1:1 show high catalytic activity and stability for methanol electro-oxidation.The performance is much higher compared with those of both Pt-only nanoparticles and commercial Pt/C catalyst.The electronic structure characterization on the Pt Ni nanoparticles demonstrates that the electrons are transferred from Ni to Pt,which can suppress the CO poisoning effect.

New modified multiwalled carbon nanotubes paste electrode for electrocatalytic oxidation and determination of warfarin in biological and pharmaceutical samples

A novel sensor for the determination of warfarin based on a simple and sensitive method was developed on multiwalled-carbon-nanotube modified ZnCrFeO4 carbon paste electrodes（MWCNT/ZnCrFeO4/CPEs）. Cyclic voltammetry, differential pulse voltammetry, chronoamperometry, and electrochemical impedance spectroscopy were used to investigate the electrochemical behavior of warfarin at the chemically modified electrode. According to the results, MWCNT/ZnCrFeO4/CPEs showed high electrocatalytic activity for warfarin oxidation, producing a sharp oxidation peak current at about ＋0.97 vs Ag/AgCl reference electrode at pH = 4.0. The peak current was linearly dependent on warfarin concentration over the range of 0.02–920.0 μmol/L with a detection limit of 0.003 μmol/L. In addition, chronoamperometry was also used to determine warfarin＇s catalytic rate constant and diffusion coefficient at MWCNT/ZnCrFeO4/CPEs.

New amperometric glucose biosensor by entrapping glucose oxidase into chitosan/nanoporous ZrO_2/multiwalled carbon nanotubes nanocomposite film

A new nanocomposite material for construction of glucose biosensor was prepared. The biosensor was formed by entrapping glucose oxidase(Gox) into chitosan/nanoporous ZrO2/multiwalled carbon nanotubes nanocomposite film. In this biosensing thin film, the multiwalled carbon nanotubes can effectively catalyze hydrogen peroxide and nanoporous ZrO2 can enhance the stability of the immobilized enzyme. The resulting biosensor provides a very effective matrix for the immobilization of glucose oxidase and exhibits a wide linear response range from 8 μmol/L to 3 mmol/L with a correlation coefficient of 0.994 for the detection of glucose. And the response time and detection limit of the biosensor are determined to be 6 s and 3.5 μmol/L, respectively. Another attractive characteristic is that the biosensor is inexpensive, stable and reliable.

Laccase biosensor using magnetic multiwalled carbon nanotubes and chitosan/silica hybrid membrane modified magnetic carbon paste electrode

A simple and rapid strategy to construct laccase biosensor for determination of catechol was investigated. Magnetic multiwalled carbon nanotubes (MMCNT) which possess excellent capability of electron transfer were prepared by chemical coprecipitation method. Scanning electron microscope (SEM) and vibrating sample magnetometer (VSM) were used to identify its surfacetopography and magnetization, respectively. Laccase was immobilized on the MMCNT modified magnetic carbon paste electrode by the aid of chitosan/silica (CS) hybrid membrane. Using current-time detection method, the biosensor shows a linear response related to the concentration of catechol in the range from 10-7 to 0.165×10-3 mol/L. The corresponding detection limit is 3.34×10-8 mol/L based on signal-to-noise ratios (S/N) ≥3 under the optimized conditions. In addition, its response current retains 90% of the original after being stored for 45 d. The results indicate that this proposed strategy can be expected to develop other enzyme-based biosensors.

The Use of Multiwalled Carbon Nanotubes Mini Column for Preconcentration of Trace Metal Ions in Tap Water of Khartoum City and Their Determination by Flame Atomic Absorption Spectrometry （FAAS）

The adsorption behavior of multiwalled carbon nanotubes （MWNTs） toward heavy elements has been investigated systemically, and a new method has been developed for the determination of trace elements in water samples based on preconcentration with mini-column packed with MWNTs prior to its determination by flame atomic absorption spectrometry （FAAS） The recommended parameters of proposed method influencing the preconcentration of the analytes, such as pH of the sample, sample flow rate and volume, elute solution and interfering ions, have been used. Under the optimized conditions, the calibration graphs were linear with the correlation coefficient range 0.9981-0.9995. According to the results, the metals were found 0.019-0.051, 0.011-0.031, 0.00-0.081, 0.00-0.0002, 0.007-0.0925, 0.00-0.0104 μg/L in water samples for Pb, Mn, Zn, Cd, Fe, Cu respectively. The percentage relative standard deviation （%RSD） for five replicate samples were 〈 5% in all cases. The method has been successfully applied to the determination of trace elements in some environmental samples with satisfactory results.

Determination of Pb, Cr, Ni and Mn in Tap Water of Riyadh Metropolitan City Using ICP-MS after Preconcentration with Multiwalled Carbon Nanotubes

The determination of toxic metals in water using multiwalled carbon nanotubes （MWNTs） as a solid-phase extraction adsorbent prior to their determination by inductively coupled plasma mass spectrometry （ICP-MS） has been investigated. Standard addition method was applied for the calibration using aqueous solutions. Multiwalled carbon nanotubes （MWNTs） absorb these metals at pH 8.0, HNO3 of 1.0 mol-Ll is used for complete elusion of these metals from MWNTs. Previously investigated parameters have been applied for the determination of Pb, Cr, Ni and Mn in tap water samples. Fifteen tap water samples from different locations of Riyadh metropolitan area have been determined by ICP-MS after preconcentration with MWNTs.

Highly conjugated water soluble CdSe quantum dots to multiwalled carbon nanotubes

Highly conjugated multiwalled carbon nanotube-quantum dot heterojunctions were synthesized by ethylene carbodiimide coupling procedure. The functional multiwalled carbon nanotube with carboxylic groups on sidewall could react with the amino group of L-cysteine capped CdSe quantum dots and then resulted in nanotube-quantum dot heterojunctions. Scanning electron microscopy was used to characterize the heterojunctions.

Electrochemical Determination of Reduced Glutathione at Multiwalled Carbon Nanotubes/Poly(bromocresol green) Modified Glassy Carbon Electrode

A multiwalled carbon nanotubes/poly(bromocresol green) modfied glassy carbon electrode (MWNTs-PBG/GCE) was used to investigate the electrochemical behavior of reduced glutathione(GSH). GSH showed an irreversible oxidation process on MWNTs-PBG/GCE with an oxidation peak at 0.77 V(vs. SCE) in a phosphate buffer solution(pH=4.0). The kinetic parameters of the electrochemical behavior of GSH on MWNTs-PBG/GCE were calculated. Under the optimal conditions and with the help of amperometric method, a linear relationship was obtained between the oxidation peak current and GSH concentration in the range from 2×10-7 mol/L to 5×10-6 mol/L with the detection limit as 1×10-8 mol/L(signal-to-noise ratio of 3). The current reached the steady-state current within about 5 s. The modified electrode surface had very good reproducibility and stability.

Adsorption of Silver Nanoparticles from Aqueous Solution by Multiwalled Carbon Nanotubes

Silver nanoparticles (AgNPs) are becoming an emerging pollutant of the environment. In this study, the efficacy of Multiwalled carbon nanotubes (MWCNTS) to remove AgNPs from aqueous solution at a concentration of 250 and 500 mg/100 ml MWCNTS was investigated. The results showed that the adsorption of AgNPs by 250 and 500 mg/100 ml MWCNTS after a contact time of 10 min., 30 min., 60 min., 120 min. and 240 min was 33.95%, 34.36%, 40.32%, 45.33%, 58.53% and 57.29%, 61.27%, 64.89%, 87.21%, 88.58%, respectively. The statistical analysis of data showed that, after adding 250 and 500 mg/100 ml MWCNTS, the total residues of AgNPs were significantly reduced in all MWCNTS exposed samples when compared to the control groups (P < 0.05). Moreover, at the two used concentrations, there were significant differences between 240 min. and all other contact times. The result concluded that the removal percent of AgNPs from aqueous solution was increased with the increase in contact time and concentrations of MWCNTS. Additionally, MWCNTS are expected to be potential adsorbent in the future due to their high removal capacity of nano-sized silver.

Removal of Lead Ions from Wastewater Using Functionalized Multiwalled Carbon Nanotubes with Tris(2-Aminoethyl)Amine

Recently, many attempts have been made to use carbon nanotubes in analytical chemistry, especially in adsorption of heavy metal ions from water. In this study, multiwalled carbon nanotubes (MWCNTs) were functionalized with tris(2-aminoethyl) amine. The functionalized nanoparticles were characterized using Fourier transform infrared (FTIR), thermal gravimetric analyzer (TGA), elemental analysis, and Raman spectroscopy. The results revealed that the functionalization reaction was successfully accomplished. Lead adsorption from water was carried out using functionalized MWCNTs and measured by flame atomic absorption spectrometry (FAAS). The effects of pH, shaking time, initial metal ion concentration, and adsorbent dosage on the adsorption process were studied via batch method. The results obtained showed that removal of lead ions strongly depended on the pH. Desorption study revealed that lead ions adsorbed on the functionalized MWCNTs could be desorbed at pH 3 due to breakage of complexes formed on the sorbent surface. Maximum adsorption capacity of the sorbent under the optimal conditions was 43 mg/g. This favorable adsorption capacity suggests that functionalized carbon nanotubes can be applied for removal of lead from water solutions. The data obtained were fitted with the Langmuir and Freundlich isotherm adsorption models and Langmuir model showed better agreement with the experimental data.

Development of a reversed dispersive based graphene functionalized with multiwalled carbon nanotubes for detection ofβ2-agonists in pork by high-performance liquid chromatography

A reliable and inexpensive pretreatment procedure in the determination ofβ2-agonists in pork was developped.The procedure used a nanocomposite of multiwalled carbon nanotubes(CNTs)functionalized with graphene(rGO)as the reversed dispersive sorbent.It was analyzed after purification by highperformance liquid chromatography,the extraction time and the properties of the nanocomposite were optimized.Under optimized conditions,present method has linear response over concentration range of 0.5–50 ng/mL in pork samples with a satisfactory detection limit close to 0.1 ng/mL.The precisions of the current method(coefficient of variation)are lower than 5%,while recoveries are more than 98.3%.The nanocomposite exhibited high adsorptivity,long-term storage stability,satisfactory anti-interfering activity and high selectivity toward2-agonists compared with those of rGO and CNTs.

Nanostructured multilayer thin films of multiwalled carbon nanotubes/gold nanoparticles/glutathione for the electrochemical detection of dopamine

In the present study, multiwalled carbon nanotubes（MWCNTs）, gold nanoparticles（AuN Ps）, and glutathione（GSH） were used to fabricate multilayer nanoscale thin films. The composite thin films were fabricated by layer-by-layer technique as the films were constructed by the alternate deposition of cationic and anionic polyelectrolytes. The MWCNTs were modified via a noncovalent surface modification method using poly（diallydimethylammonium chloride） to form a cationic polyelectrolyte. An anionic polyelectrolyte was prepared by the chemical reduction of HAuCl_4 using sodium citrate as both the stabilizing and reducing agent to form anionic AuN Ps. GSH was used as an electrocatalyst toward the electro-oxidation of dopamine. The constructed composite electrode exhibits excellent electrocatalytic activity toward dopamine with a short response time and a wide linear range from 1 to 100 mmol/L. The limits of detection and quantitation of dopamine are（0.316 ± 0.081） mmol/L and（1.054 ± 0.081） mmol/L, respectively. The method is satisfactorily applied for the determination of dopamine in plasma and urine samples to obtain the recovery in the range from 97.90% to 105.00%.

Determination of Fe, Cu, and Zn in Water Samples by Microcolumn Packed with Multiwalled Carbon Nanotubes as a Solid Phase Extraction Adsorbent Using ICP-MS

The heavy metals determination in tap water samples using microcolumn packed with multiwalled carbon nanotubes （MWNTs） as a solid-phase extraction adsorbent before to their determination by inductively coupled plasma mass spectrometry （ICP-MS） has been studied. Standard addition method was applied for the calibration using aqueous solutions. The metals ions absorption were achieved by multiwalled carbon nanotubes （MWNTs） at pH 8.0, and then these retained metals on MWNTs column were eluted by 1.0 mol.L^-1 HNO3. The analytical parameters for the determination ofFe, Cu, and Zn in tap water samples which have been investigated previously were applied. Fifteen tap water samples were collected from different locations of Riyadh metropolitan area and then determined the concentration ofFe, Cu, and Zn by ICP-MS after preconcentration with MWNTs. The concentration range for Fe, Cu, and Zn measured （μg/L） in water samples are 23.37-137.91, 2.12-121.36, and 14.43-202.47 respectively. The level of Fe exceeded the limits set by WHO and SASO for drinking water.

Development of Chitosan/Poly(L-Lactide)/Multiwalled Carbon Nanotubes Scaffolds for Bone Tissue Engineering

This work focuses to improve the mechanical properties and investigates the growth of osteoblasts on a degradable chitosan/poly(L-lactide)/carbon nanotubes composite for tissue engineering. The morphological and mechanical properties characterizations were performed using scanning electronic microscopy (SEM) and rheometrics analysis system (RSA). Osteoblasts differentiation was determined by alkaline phosphatase activity, total number cells by an Alamar Blue assay, cell attachment and proliferation were visualized qualitatively using SEM, mineralization was characterized by transformed infrared spectroscopy, energy dispersive spectroscopy, and X-ray diffraction. The results suggest that the chitosan/poly(L-lactide)/multiwalled carbon nanotubes composites exhibit the ability to promote cell adhesion, proliferation, and differentiation on their surface.

Synthesis and thermal stability of multiwall carbon nanotubes reinforced aluminum metal matrix composites

Multiwall carbon nanotubes（MWNTs） reinforced aluminum composites were synthesized by hot press sintering. The thermal stability of MWNTs in the composite was investigated by transmission electron microscopy（TEM）. The results show that the impurities drop from 2% to 0.11% after the MWNTs are soaked with 95%H2SO4 and 66%HNO4 acids in an ultrasonator and washed with distilled water. In hot pressed composites, MWNTs distribute between aluminum powders and do not react with aluminum. When the composite was held at 800℃ for 1h, MWNTs react with aluminum and form Al4C3 phase, which are small polygons and distribute in the aluminum grains. Although Al4C3 phase still forms when the composite was held at 1000℃ for 1h, its morphology changes to a continuous band and distributes along the origin aluminum powder boundaries. So MWNTs are unstable in aluminum matrix composites that are kept above the liquidus temperature of aluminum.

Determination of isoproterenol in pharmaceutical and biological samples using a pyrogallol red multiwalled carbon nanotube paste electrode as a sensor

Isoproterenol （ISPR） is an important catecholamine‐based drug that is widely used in the treatment of heart disease. However, overdose of this drug is very dangerous to the human body. In this study, a new sensor based on a pyrogallol red modified‐multiwalled carbon nanotube paste electrode （PGRMMWCNTPE） was prepared and used for high sensitivity determination of ISPR in aqueous solution. Electrocatalytic oxidation of ISPR at the PGRMMWCNTPE was investigated by chronoam‐perometry, cyclic voltammetry, and square‐wave voltammetry. The values of the catalytic rate con‐stant, electron transfer coefficient, and diffusion coefficient for ISPR oxidation were then calculated using voltammetric data. A linear calibration curve was constructed for ISPR concentration in the range 0.8–570μmol/L with a detection limit of 0.47μmol/L ISPR. The sensor was then applied to the determination of ISPR in urine and drug samples with satisfactory results.