Abdominal aortic aneurysm (AAA), a medical complication, occurs when the aortic area becomes swollen and very large. It is mandatory to identify AAA to avoid the breakdown of aneurysms. C-reactive protein (CRP) has been recognized as one of the biomarkers for identifying AAA due to the possibility of CRP produced in vascular tissue, which contributes to the formation of an aneurysm, and it is elevated in patients with a ruptured AAA. This research work was designed to develop an immunosensor on a multiwalled carbon nanotube (MWCNT)-modified surface to quantify the CRP level. Anti-CRP specificity was constructed on the MWCNT surface through a silane linker to interact with CRP. The detection limit of CRP was calculated as 100 pM with an R2 (determination coefficient) value of 0.9855 (y = 2.3446x - 1.9922) on a linear regression graph. The dose-dependent linear pattern was registered from 200 to 3000 pM and attained the saturation level during binding at 3000 pM. Furthermore, serum-spiked CRP showed a clear increase in the current response, proving the specific recognition of CRP in biological samples. This designed biosensor identifies CRP at a lower level and can help diagnose AAA.
The carbon dioxide (CO2) crisis is one of the world's most urgent issues. Meeting the worldwide targets set for CO2 capture and storage (CCS) is crucial. Because it may significantly reduce energy consumption compared to traditional amine-based adsorption capture, adsorption dependant CO2 capture is regarded as one of the most hopeful techniques in this paradigm. The expansion of unique, critical edge adsorbent materials has received most of the research attention to date, with the main objective of improving adsorption capacity and lifespan while lowering the temperature of adsorption, thereby lowering the energy demand of sorbent revival. There are specific materials needed for each step of the carbon cycle, including capture, regeneration, and conversion. The potential and efficiency of metal-organic frameworks (MOFs) in overcoming this obstacle have recently been proven through research. In this study, we pinpoint MOFs' precise structural and chemical characteristics that have contributed to their high capture capacity, effective regeneration and separation processes, and efficient catalytic conversions. As prospective materials for the next generation of energy storage and conversion applications, carbon-based compounds like graphene, carbon nanotubes, and fullerenes are receiving a lot of interest. Their distinctive physicochemical characteristics make them suitable for these popular study topics, including structural stability and flexibility, high porosity, and customizable physicochemical traits. It is possible to precisely design the interior of MOFs to include coordinatively unsaturated metal sites, certain heteroatoms, covalent functionalization, various building unit interactions, and integrated nanoscale metal catalysts. This is essential for the creation of MOFs with improved performance. Utilizing the accuracy of MOF chemistry, more complicated materials must be built to handle selectivity, capacity, and conversion all at once to achieve a comprehensive solution. This review summarizes, the most recent developments in adsorption-based CO2 combustion capture, the CO2 adsorption capacities of various classes of solid sorbents, and the significance of advanced carbon nanomaterials for environmental remediation and energy conversion. This review also addresses the difficulties and potential of developing carbon-based electrodes for energy conversion and storage applications.
This paper presents a functionalized, horizontally oriented carbon nanotube network as a sensing element to enhance the sensitivity of a pressure sensor. The synthesis of horizontally oriented nanotubes from the AuFe catalyst and their deposition onto a mechanically flexible substrate via transfer printing are studied. Nanotube formation on thermally oxidized Si (100) substrates via plasma-enhanced chemical vapor deposition controls the nanotube coverage and orientation on the flexible substrate. These nanotubes can be simply transferred to the flexible substrate without changing their physical structure. When tested under a pressure range of 0 to 50 kPa, the performance of the fabricated pressure sensor reaches as high as approximately 1.68%/kPa, which indicates high sensitivity to a small change of pressure. Such sensitivity may be induced by the slight contact in isolated nanotubes. This nanotube formation, in turn, enhances the modification of the contact and tunneling distance of the nanotubes upon the deformation of the network. Therefore, the horizontally oriented carbon nanotube network has great potential as a sensing element for future transparent sensors.
The performance of a semiconducting carbon nanotube (CNT) is assessed and tabulated for parameters against those of a metal-oxide-semiconductor field-effect transistor (MOSFET). Both CNT and MOSFET models considered agree well with the trends in the available experimental data. The results obtained show that nanotubes can significantly reduce the drain-induced barrier lowering effect and subthreshold swing in silicon channel replacement while sustaining smaller channel area at higher current density. Performance metrics of both devices such as current drive strength, current on-off ratio (Ion/Ioff), energy-delay product, and power-delay product for logic gates, namely NAND and NOR, are presented. Design rules used for carbon nanotube field-effect transistors (CNTFETs) are compatible with the 45-nm MOSFET technology. The parasitics associated with interconnects are also incorporated in the model. Interconnects can affect the propagation delay in a CNTFET. Smaller length interconnects result in higher cutoff frequency.
We demonstrate a simple and low cost mode-locked erbium-doped fiber laser (EDFL) operating in the nanosecond region using a single-walled carbon nanotube (SWCNT)-based saturable absorber (SA). A droplet of SWCNT solution is applied on the end of a fiber ferrule, which is then mated to another clean connector ferrule to construct an SA. Then the SA is integrated into a ring EDFL cavity for nanosecond pulse generation. The EDFL operates at around 1570.4 nm, with a soliton-like spectrum with small Kelly sidebands, which confirms the attainment of the anomalous dispersion. It produces a soliton pulse train with a 332 ns width, repetition rate of 909.1 kHz, an average output power of 0.31 mW, and energy of 0.34 nJ at the maximum pump power of 130.8 mW.
The development of easy to use, rapid and sensitive methods for direct detection of foodborne bacterial pathogens has become significantly important due to their impact on human health. In recent years, carbon nanomaterials have been adapted in the fabrication of electrochemical biosensors due to their exceptional combination of intrinsic properties such as high conductivity, stability and biocompatibility that render them as a promising candidate for bio-sensing material. The scope of this review is to provide a brief history of the current methods and different types of electrochemical biosensors used for the detection of bacterial pathogens. We primarily focus on the recent progress and applications of graphene, carbon nanotubes and their derivatives in electrochemical biosensors for foodborne bacterial pathogens detection. Finally, the status and future prospects of carbon-based electrochemical biosensors are also reviewed and discussed.
The fabrication of TiO2 nanotubes (TNT) was carried out by electrochemical anodization of Ti in aqueous electrolyte containing NH4F. The effect of electrolyte pH, applied voltage, fluoride concentration and anodization duration on the formation of TNT was investigated. It was observed that self-organized TNT can be formed by adjusting the electrolyte to pH 2-4 whereby applied voltage of 10-20 V can be performed to produce highly ordered, well-organized TNT. At 20 V, TNT can be fabricated in the concentration range of 0.07 M to 0.20 M NH4F. Higher fluoride concentration leads to etching of Ti surface and reveals the Ti grain boundaries. The prepared TNT films also show an increase in depth and in size with time and the growth of TNT films reach a steady state after 120 minutes. The morphology and geometrical aspect of the TNT would be an important factor influencing the photoelectrochemical response, with higher photocurrent response is generally associated with thicker layer of TNT. Consequently, one can tailor the resulting TNT to desired surface morphologies by simply manipulating the electrochemical parameters for wide applications such as solar energy conversion and photoelectrocatalysis.
Since the discovery of carbon nanotubes (CNTs) in 1991, a fundamental question still remained on how to control morphologically the synthesis of CNTs. This task has always been a challenge. In this paper, we report the results that we have published previously with the aim of sharing the possible controlled synthesis approach via this novel production method. Findings demonstrated that various CNTs could be synthesized by using specially developed supported catalysts from the catalytic decomposition of methane. These synthesized CNTs include carbon nanofibres, single-walled and multi-walled CNTs, Y-junction CNTs and CNTs with special morphologies. It was also revealed that catalyst composition and reaction parameters played an important role in controlling the morphology and type of CNTs formed. The synthesis of CNTs with various morphologies is important because this can enrich the nanostructures of the carbon family. This finding also provides useful data for better understanding of the parameters that govern the growth mechanism of CNTs which may be required in the near future for enhanced controlled synthesis of CNTs.
Carbon fiber reinforced epoxy (CFRE) is commonly been used in automotive and aviation industries. However, CFRE composite exhibits the problem of adherence between fiber and matrix. The interface between carbon fiber (CF) and epoxy becomes a weak zone and leads to the debonding defect of fiber and low mechanical properties of composites. The main focus of this study is to fabricate CFRE using carbon nanotubes (CNTs), as the hybrid reinforcement with CF. Ultrasonic method is used to disperse CNTs in distilled water for 20 minutes, followed by deposition of CNTs on CF using electrophoretic deposition (EPD) technique. Hand lay-up assisted vacuum bagging is employed to fabricate CNTs/CF/Epoxy composite. From morphologies, surface topography and peel off testing, it can be confirmed that 30 minutes deposition allowed more CNTs to deposit on CF. The flexural properties shows that 30 minutes deposition inherited high flexural strength, 67.4 MPa and modulus, 8490 MPa.
We had successfully synthesised Mg-doped zinc oxide (MZO) and Cudoped zinc oxide (CZO) nanorod arrays (NRAs) on Al-doped ZnO (ZAO)-coated glass substrates using immersion method and investigated their structural properties. With the incorporation of the Mg dopant, the length and crystallinity of MZO NRAs is higher compared to that of the CZO NRAs. The average optical transmittance of MZO NRAs was slightly lower than that of the CZO NRAs over the visible wavelength region. With the incorporation of the Cu dopant, the morphology of the CZO sample was slightly different from that of the MZO NRAs. The CZO NRAs present granular with small sphere shape. On the other hand, the MZO NRAs exhibit a hexagonal shape structure with a flat-top facet. Rods with a diameter of 58.9-96.7 nm were uniformly grown on the ZAO-coated glass substrate. This paper presents the growth behaviors of the MZO and CZO NRAs.
Carbon nanotube reinforced aluminium matrix composites (Al-CNTs) have been widely used in aerospace and automotive industries where high quality and strength is required. The enhanced mechanical properties of Al-CNTs are closely related to processing technique due to challenges within production of these composite materials. In the current review, solid state processing techniques used for synthesizing Al-CNTs have been reviewed to provide an insight into the features and capabilities of each technique regarding the incorporation of CNT reinforcements. To conclude, the mechanical performance of Al-CNT composites is mainly decided by the capability of each technique in the dispersion of CNTs within the aluminum matrix.
The present study reported for the first time covalent immobilization of protocatechuate 3,4-dioxygenase (3,4-POD) onto functionalized multi-walled carbon nanotubes (F-MWCNT) for degrading the toxic 3,4-dihydroxybenzoic acid (3,4-DHBA) pollutant in water. The F-MWCNTs had a maximum 3,4-POD loading of 1060 μg/mg. Immobilized 3,4 POD had 44% of relative structural changes to its free configurations. Nevertheless, >90% of relative activity and about 50% of catalytic efficiency were retained to the free enzyme. Immobilized 3,4-POD demonstrated higher alkaline stability and thermostability than the free 3,4-POD. The free and immobilized 3,4-POD lost 82% and 66% of relative activities, respectively after 180 min of incubations at 90 °C. Excellent shelf-life was observed for the immobilized 3,4-POD with residual activity of 56% compared with 41% and 39% of the free 3,4-POD at 4 °C and 25 °C over 30 days storage. Immobilized 3,4-POD showed >60% of catalytic activity retention even after ten-cycle uses, defraying the expenses of free 3,4-POD productions for long term uses. Finally, the immobilized 3,4-POD removed 71% of 3,4-DHBA from water in <4 h, paving its future application for water purification with reduced costs and time.
Cu-doped ZnO nanorods were synthesized by sol-gel method using zinc nitrate tetrahydrate, methenamine and cupric acetate monohydrate as precursors. The as-synthesized ZnO nanorods have a twin-rod structure. The polar (002) surface of ZnO nanorods, which could be either negatively charge (O-terminated) or positively charged (Zn- terminated), was responsible for the formation of twin-rod structure. The results showed that the size, aspect ratio, crystallinity and c-lattice parameter of Cu doped ZnO nanorods decreased with increasing of Cu dopant concentration. In fact, the presence of Cu retarded the growth of ZnO nanorods in its preferred growth direction, i.e. (0001). The XPS analysis indicates that Cu ions were oxidized (Cu2+) and substituted into the ZnO lattice at the Zn2+ site. The presence of Cu reduced the optical bandgap of ZnO from 3.34 eV (undoped ZnO nanorods) to 3.31 eV (20 mol% Cu doped ZnO). Besides, it induced a visible PL emission at 2.97 eV, which could be related to the transition of electrons from conduction band (Ec) to Cu acceptor energy level (Ev + 0.45 eV) radiatively.
The effect of various multi-walled carbon nanotubes (MWNTs) on the tensile properties of thermoplastic natural rubber (TPNR) nanocomposite was investigated. The nanocomposite was prepared using melt blending method. MWNTs were added to improve the mechanical properties of MWNTs/TPNR composites in different compositions of 1, 3, 5, and 7 wt.%. The results showed that the mechanical properties of nanocomposites were affected significantly by the composition and the properties of MWNTs. SEM micrographs confirmed the homogenous dispersion of MWNTs in the TPNR matrix and promoted strong interfacial adhesion between MWNTs and the matrix which was improved mechanical properties significantly.
Nanomaterial-based sensors with high sensitivity, fast response and recovery time, large detection range, and high chemical stability are in immense demand for the detection of hazardous gas molecules. Graphene nanoribbons (GNRs) which have exceptional electrical, physical, and chemical properties can fulfil all of these requirements. The detection of gas molecules using gas sensors, particularly in medical diagnostics and safety applications, is receiving particularly high demand. GNRs exhibit remarkable changes in their electrical characteristics when exposed to different gases through molecular adsorption. In this paper, the adsorption effects of the target gas molecules (CO and NO) on the electrical properties of the armchair graphene nanoribbon (AGNR)-based sensor are analytically modelled. Thus, the energy dispersion relation of AGNR is developed considering the molecular adsorption effect using a tight binding (TB) method. The carrier velocity is calculated based on the density of states (DOS) and carrier concentration (n) to obtain I-V characteristics and to monitor its variation in the presence of the gas molecules. Furthermore, the I-V characteristics and energy band structure of the AGNR sensor are simulated using first principle calculations to investigate the gas adsorption effects on these properties. To ensure the accuracy of the proposed model, the I-V characteristics of the AGNR sensor that are simulated based both on the proposed model and first principles calculations are compared, and an acceptable agreement is achieved.
This study was carried out to investigate the effect of adding 1 vol% of multi-walled carbon nanotubes (MWCNT) into
woven kenaf/epoxy laminated composites on their flexural properties and to compare between two techniques used to
incorporate MWCNT into the composite which are spraying and solution techniques. Furthermore, the effect of MWCNT
addition in woven glass/woven kenaf/epoxy hybrid composites at the same filler concentration on the flexural properties
were also investigated. All the laminated composites with and without MWCNT were fabricated using vacuum bagging
method. The flexural properties of the composite samples with and without MWCNT were evaluated by applying threepoint
bending test. The results were supported by morphological observation. It was found that the addition of MWCNT
using both spraying and solution techniques reduced the flexural strength and flexural modulus of MWCNT/woven kenaf/
epoxy composites, with obvious reduction trend was shown by former technique. The morphological observation of the
composites fracture surface showed that delamination failure occurred in MWCNT/woven kenaf/epoxy laminated composite
prepared by spraying technique. Further investigation on hybrid composites showed that MWCNT/woven glass/woven
kenaf/epoxy laminated hybrid composites exhibited significant improvement in the flexural properties.
The nanomechanical properties of carbon nanotubes particulate-reinforced aluminum matrix nanocomposites (Al-CNTs) have been characterized using nanoindentation. Bulk nanocomposite specimens containing 2 wt % multiwalled CNTs (MWCNTs) were synthesized by a combination of ball milling and powder metallurgy route. It has been tried to understand the correlation between microstructural evolution particularly carbon nanotubes (CNTs) dispersion during milling and mechanical properties of Al-2 wt % nanocomposites. Maximum enhancement of +23% and +44% has been found in Young's modulus and hardness respectively, owing to well homogenous dispersion of CNTs within the aluminum matrix at longer milling time.
Van Hove singularities (VHSs) are a hallmark of reduced dimensionality, leading to a divergent density of states in one and two dimensions and predictions of new electronic properties when the Fermi energy is close to these divergences. In carbon nanotubes, VHSs mark the onset of new subbands. They are elusive in standard electronic transport characterization measurements because they do not typically appear as notable features and therefore their effect on the nanotube conductance is largely unexplored. Here we report conductance measurements of carbon nanotubes where VHSs are clearly revealed by interference patterns of the electronic wave functions, showing both a sharp increase of quantum capacitance, and a sharp reduction of energy level spacing, consistent with an upsurge of density of states. At VHSs, we also measure an anomalous increase of conductance below a temperature of about 30 K. We argue that this transport feature is consistent with the formation of Cooper pairs in the nanotube.
Gold nanoparticles (AuNPs) had been synthesized with various molarities and weights of reducing agent, monosodium glutamate (MSG), and stabilizer chitosan, respectively. The significance of chitosan as stabilizer was distinguished through transmission electron microscopy (TEM) images and UV-Vis absorption spectra in which the interparticles distance increases whilst retaining the surface plasmon resonance (SPR) characteristics peak. The most stable AuNPs occurred for composition with the lowest (1 g) weight of chitosan. AuNPs capped with chitosan size stayed small after 1 month aging compared to bare AuNPs. The ability of chitosan capped AuNPs to uptake analyte was studied by employing amorphous carbon nanotubes (α-CNT), copper oxide (Cu2O), and zinc sulphate (ZnSO4) as the target material. The absorption spectra showed dramatic intensity increased and red shifted once the analyte was added to the chitosan capped AuNPs.
Designing a biosensor for versatile biomedical applications is a sophisticated task and how dedicatedly functionalized fullerene (C60) can perform on this stage is a challenge for today and tomorrow's nanoscience and nanotechnology. Since the invention of biosensor, many ideas and methods have been invested to upgrade the functionality of biosensors. Due to special physicochemical characteristics, the novel carbon material "fullerene" adds a new dimension to the construction of highly sensitive biosensors. The prominent aspects of fullerene explain its outstanding performance in biosensing devices as a mediator, e.g. fullerene in organic solvents exhibits five stages of reversible oxidation/reduction, and hence fullerene can work either as an electrophile or nucleophile. Fullerene is stable and its spherical structure produces an angle strain which allows it to undergo characteristic reactions of addition to double bonds (hybridization which turns from sp(2) to sp(3)). Research activities are being conducted worldwide to invent a variety of methods of fullerene functionalization with a purpose of incorporating it effectively in biosensor devices. The different types of functionalization methods include modification of fullerene into water soluble derivatives and conjugation with enzymes and/or other biomolecules, e.g. urease, glucose oxidase, hemoglobin, myoglobin (Mb), conjugation with metals e.g. gold (Au), chitosan (CS), ferrocene (Fc), etc. to enhance the sensitivity of biosensors. The state-of-the-art research on fullerene functionalization and its application in sensor devices has proven that fullerene can be implemented successfully in preparing biosensors to detect glucose level in blood serum, urea level in urine solution, hemoglobin, immunoglobulin, glutathione in real sample for pathological purpose, to identify doping abuse, to analyze pharmaceutical preparation and even to detect cancer and tumor cells at an earlier stage. Employing fullerene-metal matrix for the detection of tumor and cancer cells is also possible by the inclusion of fullerene in single-walled carbon nanotubes (SWCNTs) known as peapods as well as in double-walled carbon nanotubes (DWCNTs), to augment the effectiveness of biosensors. This review discusses various approaches that have been reported for functionalizing fullerene (C60) derivatives and their application in different types of biosensor fabrication.