Characterization of amide and ester functionalized multiwalled carbon nanotubes

Multi-walled carbon nanotubes (MWCNT) were functionalized by different functional group via amidation and esterification process. The MWCNT were treated with H2SO4/HNO3 first to introduce carboxylic acid functional group on the surface of MWCNT. This carboxylic group was used as reaction precursor in the functionalization. There are two functionalizing reactant were used which is dodecylamine, CH3(CH2)11NH2 and 1-octadecanol, CH(CH)17OH. Electron microscopy revealed that the morphology of amide and ester functionalized MWCNT exhibit decrease in their diameter size due to insertion of amide and ester functional group. Raman measurements showed that G-band (graphitic structure) of amide and ester functionalized MWCNT slightly shifted downfield about 6-8 cm–1 due to presence of new functional group on the surface of MWCNT. Multi-walled carbon nanotubes attached to organofunctional element have greater flexibility for further usage in various application fields such as nanocomposite material, biology and chemical sensor and environmental monitoring

Characterizations of MWCNTs nanofluids on the effect of surface oxidative treatments

In this study, multi-walled carbon nanotubes (MWCNTs) were chemically modified using three acid treatment methods to introduce the surface oxygen functional group (SOFG). The presence of SOFG on the MWCNTs has been characterized by Fourier Transform Infrared (FTIR) spectroscopy. Morphology, structural and thermal properties were performed using Field Emission Scanning Electron Microscopy (FESEM), Raman spectroscopy, and Thermogravimetric analysis (TGA), respectively. The result shows that the modification with acid treatment significantly affects the degree of defects and surface group functionality of surface oxidized MWCNTs from method B. The preparation of nanofluids using MWCNTs produced from method B (MWCNT-MB) was prepared using two different parameters: with and without polyvinylpyrrolidone (PVP) as surfactant. The experiment was conducted by setting variable carbon particle concentration from 0.1 wt.% to 1.0 wt.%, and the amount of PVP is 10% of carbon particles at different temperatures (6 ◦C, 25 ◦C, 40 ◦C). Based on visual observation, the dispersion of carbon particles was enhanced by the presence of PVP as the stabilizing agent. The thermal conductivity performance of nanofluids revealed that the surface oxidized MWCNTs with PVP show enhanced thermal conductivity compared to the nanofluid containing MWCNTs without PVP. The improvement contributes to this in terms of stability and homogenization of nanoparticles. Hence the improved distribution of MWCNTs in water-based media improves thermal conductivity. These promising properties of MWCNTs in water-based fluids would enable the nanofluids to be used in heat transfer fluid and cooling applications

Surface-oxidised carbon nanofibre-based nanofluids: Structural, morphological, stability and thermal properties

The reputation of nanofluids as a convenient heat transfer media has grown in recent years. The synthesis of nanofluids is often challenging, particularly carbon-based nanofluids, due to the rapid agglomeration of the nanoparticles and the instability of the nanofluids. In this regard, surface modification and surfactant addition are potential approaches to improve the physical and thermal properties of carbon-based nanofluids that have been studied and the structural, morpho-logical, and thermal characteristics of surface-oxidised carbon nanofibre (CNF)-based nanofluids has been characterised. Commercial CNF was first subjected to three different acid treatments to introduce surface oxygen functional groups on the CNF surface. Following the physical and thermal characterisation of the three surface-oxidised CNFs (CNF-MA, CNF-MB, and CNF-MC), including Raman spectroscopy, Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FESEM), the CNF-MB was selected as the best method to synthesise the surface-oxidised CNF-based nanofluid. A total of 40 mL of ultrapure water was used as a pure base fluid and mixed with the surface-oxidised CNF at a concentration range of 0.1– 1.0 wt.%, with a fixed of 10 wt.% amount of polyvinylpyrrolidone (PVP). The thermal conductivity of CNF-based nanofluid was then characterised at different temperatures (6, 25, and 40 °C). Based on the results, surface oxidation via Method B significantly affected the extent of surface defects and effectively enhanced the group functionality on the CNF surface. Aside from the partially defective and rough surface of CNF-MB surfaces from the FESEM analysis, the presence of surface oxygen functional groups on the CNF wall was confirmed via the Raman analysis, TGA curve, and FTIR analysis. The visual sedimentation observation also showed that the surface-oxidised CNF particles remained dispersed in the nanofluid due to the weakened van der Waals interaction. The dispersion of CNF particles was improved by the presence of PVP, which further stabilised the CNF-based nanofluids. Ultimately, the thermal conductivity of the surface-oxidised CNF-based nanofluid with PVP was significantly improved with the highest enhancement percentage of 18.50, 16.84, and 19.83% at 6, 25, and 40 °C, respectively, at an optimum CNF concentration of 0.7 wt.%

Emerging development of nanocellulose as an antimicrobial material: An overview

The prolonged survival of microbes on surfaces in high-traffic/high-contact environments drives the need for a more consistent and passive form of surface sterilization to minimize the risk of infection. Due to increasing tolerance to antibiotics among microorganisms, research focusing on the discovery of naturally-occurring biocides with low-risk cytotoxicity properties has become more pressing. The latest research has centred on nanocellulosic antimicrobial materials due to their low-cost and unique features, which are potentially useful as wound dressings, drug carriers, packaging materials, filtration/adsorbents, textiles, and paint. This review discusses the latest literature on the fabrication of nanocellulose-based antimicrobial materials against viruses, bacteria, fungi, algae, and protozoa by employing variable functional groups, including aldehyde groups, quaternary ammonium, metal, metal oxide nanoparticles as well as chitosan. The problems associated with industrial manufacturing and the prospects for the advancement of nanocellulose-based antimicrobial materials are also addressed

Optimization of Synthesis of Carbon Nanotubes Using Chemical Vapor Deposition Method

Multi walled carbon nanotubes (MWCNTs) were synthesized using floating catalyst-chemical vapor deposition (FC-CVD) with ferrocene and benzene as catalyst and carbon source, respectively. Argon was used as a purging gas while hydrogen was used as a carrier gas. Hydrogen flow rate, reaction time and reactor temperature were varied to obtain high yield and purity of MWCNTs. The morphology and microstructures of MWCNTs produced were studied using Scanning Electron Microscopy (SEM). It was found that the maximum yield and purity of MWCNTs were produced at hydrogen flow rate of 300 ml/min with reactor temperature of 900°C and reaction time 45 minutes. It was observed that the MWCNTs are film-like, randomly oriented and in some cases entangled with uniform diameter.</jats:p

Synthesis of Carbon Nanotubes and Volatile Organic Compounds Detection

In this work, the adsorption effect of volatile organic compounds (chloroacetophenone, acetonitrile and hexane) towards the change of resistance of CNTs pellet as sensor signal was investigated. CNTs used in this research were synthesized using Floating Catalyst – Chemical Vapor Deposition (FC-CVD) method in optimum condition. The synthesized CNTs were characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Raman Spectroscopy. The variation of resistance changes towards the tested gases were recorded using a multimeter. CNTs sensor pellet showed good responses towards the tested gases, however, the sensitivity, response time and recovery time of sensor pellet need to be optimized

Synthesis of carbon nanotubes and volatile organic compounds detection

In this work, the adsorption effect of volatile organic compounds (chloroacetophenone, acetonitrile and hexane) towards the change of resistance of CNTs pellet as sensor signal was investigated. CNTs used in this research were synthesized using Floating Catalyst – Chemical Vapor Deposition (FC-CVD) method in optimum condition. The synthesized CNTs were characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Raman Spectroscopy. The variation of resistance changes towards the tested gases were recorded using a multimeter. CNTs sensor pellet showed good responses towards the tested gases, however, the sensitivity, response time and recovery time of sensor pellet need to be optimized

The Influences of Chemical and Mechanical Treatment on the Morphology of Carbon Nanofibers

Oxidation by acid treatment is one of the chemical methods used to introduce surface oxygen functional group (SOFG) and defects on the surface of carbon nanofibers (CNFs). Therefore, many researchers used this method to improve the dispersion ability of CNFs in aqueous media. However, only few researchers used combination of chemical and mechanical method for oxidation of CNFs. In this work, as-received CNFs were treated using chemical method with an addition of mechanical method. On the first experiment (Method A) concentrated sulphuric acid and nitric acid were used and followed by combinations of mechanical method using ultrasonication water bath under reflux. The addition mechanical method through reflux was eliminated and different times of ultrasonication were used in method B and method C. Outer diameter of each CNFs samples were determined from FESEM images and were found to be in range of 50 nm–190 nm. Whereas, Raman spectroscopy was used to analyse any structural defects of CNFs samples during each treatment methods. From the findings, acid treatment of CNFs with addition of mechanical method using ultrasonication showed remarkably effect on the CNFs morphology.</jats:p

Multi-Walled Carbon Nanotubes Functionalized with Carboxyl and Amide for Acetone detection at Room Temperature

The functionalization of multi-walled carbon nanotubes (CNT) with amide group is reported as an alternative to enhance response time, recovery time and sensitivity of detecting acetone gas. We have fabricated an interdigitated transducer (IDT) deposited with amide-functionalized CNT. The elemental compositional analysis was characterized using Energy Dispersion X-ray spectroscopy and CHNOS elemental analyzer. The detection of acetone gas was performed in room temperature and digital multimeter was employed to record the changes of resistivity of IDT upon exposure of acetone. Results showed that amide functional group increases sensitivity, shortens the response time as well as recovery time of the sensor.</jats:p

Comparison and characterization of acid functionalization of multi walled carbon nanotubes using various methods

Functionalization of multiwalled carbon nanotubes (MWCNT) is one of several methods used to improve the compatibility of CNT. Even though acid functionalised method is effective, the strong acids such as H2SO4/HNO3 were normally employed and long hours of sonication is used to disperse the CNTs in the solution frequently can damage the nanotube, thus limiting their great performance as mechanical and electrical reinforcements. Here we are reporting comparison between three methods used in acid functionalized treatments of MWCNT. The first method, MWCNT was functionalized using ultra sonication water bath and followed by reflux (Method A). The second method, MWCNT was functionalized using ultrasonication water bath only for 2 hours (Method B). Finally, the third method MWCNT was functionalized using ultrasonication water bath only for 6 hours (Method C). Raman spectroscopy measurements were used to examine the general relationship between the chemical treatment and the amount of non-graphitic carbon. Electron microscopy analysis revealed that MWCNT functionalized using Method C suffered the highest degree degradation such as, nanotube shortening and additional defect generation in the graphitic network. Method B proved to be the most effective for this aim