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

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

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

Effect of Functionalized Carbon Nanotubes in the Detection of Benzene at Room Temperature

In this paper, carbon nanotubes (CNTs) were functionalized by acid treatment and further functionalized with dodecylamine and were designated as CNT-carboxylic and CNT-amide, respectively. Then, functionalized CNTs produced were characterized with various methods to verify the attachment of a functional group. Performance of the functionalized CNTs in the detection of benzene gas was monitored at room temperature. The sample was dropped cast on the interdigitated transducer (IDT), and the changes in resistivity were recorded by a digital multimeter in a customized chamber under controlled humidity (∼55%) environment. Based on the findings, it showed that the functionalized CNTs provide an extra active area for interaction between the gas analyte and CNTs, thus increasing their response and improving the sensitivity of the sensing material

The Frontiers of Functionalized Nanocellulose-Based Composites and Their Application as Chemical Sensors

Chemical sensors are a rapidly developing technology that has received much attention in diverse industries such as military, medicine, environmental surveillance, automotive power and mobility, food manufacturing, infrastructure construction, product packaging and many more. The mass production of low-cost devices and components for use as chemical sensors is a major driving force for improvements in each of these industries. Recently, studies have found that using renewable and eco-friendly materials would be advantageous for both manufacturers and consumers. Thus, nanotechnology has led to the investigation of nanocellulose, an emerging and desirable bio-material for use as a chemical sensor. The inherent properties of nanocellulose, its high tensile strength, large specific surface area and good porous structure have many advantages in its use as a composite material for chemical sensors, intended to decrease response time by minimizing barriers to mass transport between an analyte and the immobilized indicator in the sensor. Besides which, the piezoelectric effect from aligned fibers in nanocellulose composites is beneficial for application in chemical sensors. Therefore, this review presents a discussion on recent progress and achievements made in the area of nanocellulose composites for chemical sensing applications. Important aspects regarding the preparation of nanocellulose composites using different functionalization with other compounds are also critically discussed in this review