Carbon nanotube based biosensors

The use of carbon nanotubes (CNT) for fabrication of sensors and biosensors has increased considerably over the past decade. This review covers the progress and advances made during the years (2014-2018) in the utilisation of carbon nanotubes for fabrication of electrochemical biosensors. The focus of the review is on reported CNT-based biosensors for detection of, important substances, such as glucose, H2O2, (DNA), ascorbic acid, uric acid, dopamine, metal ions, and pesticides. The review starts by first discussing the structures and properties of CNTs, followed by discussion of some of the synthetic methods for CNTs preparation. The working principles and performances of CNT-based biosensors are then discussed. Considerations for future developments in CNT-based biosensors are also outlined.

Multiwalled carbon nanotubes bound beta-galactosidase: It's activity, stability and reusability.

One of the crucial properties of Carbon NanoTubes (CNTs) is their conductivity. They can be metallic, semiconducting or insulating in nature [6]. Therefore, their conducting properties are closely related to the existence and width of CNTs energy band gap – quantity which is (relatively) easily calculable. From a theoretical point of view, CNTs have been studied by various methods. Many results have been obtained; however, their status is quite diverse. The widespread rule claims that (n,m) CNT is metallic if $$n-m = 0$$ mod 3 [2, 6]. This rule was based on ‘gluing’ of graphene sheets into tubes (or the ‘zone folding’ method). Moreover, the geometry of all hexagons has been assumed to be identical – the structure optimization hasn’t been performed. Such an approach can be reliable for large-diameter CNTs, where curvature effects are small. However, it is at least disputable for its applicability to small-diameter CNTs. For these reasons, we undertook a systematic exploration of small-diameter CNTs to examine the significance of the ‘deviation’ effects (i.e. the deviation from planar regular hexagon geometry) on properties of CNTs. In particular, we wanted to check explicitly the validity of the claim that ‘CNTs (n,m), where $$n-m$$ = 0 mod 3, possess zero energy gap’. In our paper, we present the results of calculations for (2, m) and (3, m) series of CNTs. These are optimized geometries, densities of states, energy gaps, and electronic band structures. The general conclusion is that the ‘zone-folding’ based rule predicting metallicity for those CNTs where $$n-m=0$$ mod 3 is fulfilled, besides the find that hexagons forming CNTs are not planar and possess non-equal bond lengths. So this ‘zone-folding’ based law describes conductivity aspects of CNTs amazingly well.

Colorectal and pancreatic cancers represent significant global health challenges, contributing to high morbidity and mortality rates, largely due to limitations in early-stage detection. While traditional diagnostic methods are often invasive and costly, biosensors utilizing carbon nanotubes (CNTs) offer a transformative approach for detecting key cancer biomarkers. This review discusses the potential of CNT-based biosensors for the detection of established cancer biomarkers, specifically carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9), two critical biomarkers for gastrointestinal cancers. We analyze various sensor configurations, including electrochemical, optical, and piezoelectric platforms, which leverage the exceptional properties of CNTs – such as high surface area and electrical conductivity – to achieve superior analytical performance. Key findings from the reviewed literature demonstrate that these advanced biosensors can achieve ultra-low limits of detection, often in the picogram/mL (pg/mL) and even femtogram/mL (fg/mL) range, surpassing conventional immunoassays by orders of magnitude. Furthermore, the integration of CNTs with other nanomaterials such as gold nanoparticles and quantum dots, further enhances signal amplification and sensor sensitivity. Despite existing challenges in industrial-scale fabrication and clinical integration, CNT-based biosensors hold promise for developing non-invasive diagnostic tests that could significantly improve early detection and monitoring of gastrointestinal cancers, leading to better patient outcomes.

The discovery of carbon nanotubes (CNT) in 1991 has brought many scientific breakthroughs. These breakthroughs resulted from the superior properties of CNTs. The remarkable properties of CNTs were the center of attraction for many researchers around the globe. This study was performed using molecular dynamic simulations, where the primary focus was to compare the mechanical properties of single-walled CNTs with multi-walled CNTs. However, the CNT models considered the influence of waviness as it is a very prominent characteristic associated with CNT growth. To clarify the influence of waviness on CNTs a comparison was done between straight and wavy structures at various temperatures from 300 K to 1200 K. The comparison resulted in a significant decrease in total strength where straight CNT structures had higher Tensile strength and Modulus of elasticity of 121.67 GPa and 1106.09 GPa, respectively. Whereas, compared to MWCNT, where it had a Tensile strength and Modulus of elasticity of 64.33 GPa and 584.81 GPa.

Band Engineering of Carbon Nanotubes for Device Applications

Single-wall carbon nanotubes (SWCNTs) have unique electrical properties, making them potential silicon and copper replacements in semiconductors and nanointerconnects. Current research focuses on single vacancy defects, needing expansion to other topological defects. In this study, we account for the presence of topological defects and develop a model that demonstrates their impact on the electrical properties of carbon nanotubes (CNTs) by using a degradation coefficient for the conductivity. This study employs density functional theory combined with the nonequilibrium Green’s function method to systematically analyze the influence of various topological defects on the electronic structure and transport characteristics of SWCNTs, using I–V curves, transmission spectra, and 3D transmission spectra. The results indicate that defects of the same type substantially degrade the electronic transport properties of CNTs, with the degree of degradation varying based on the defects’ positions and quantities. This degradation can result in a reduction of over 20% in the electronic transport capacity compared with ideal CNTs. A linear positive correlation exists between the extent of degradation and the magnitude of the defects. Furthermore, the presence of a small number of 5–8–5 defects and Stone–Wales defects can induce bandgap opening from 0.109 to 0.549 eV for the bandgap of (6,6) CNTs. However, a high defect concentration reduces the bandgap, potentially to zero. Notably, regardless of whether the bandgap increases or decreases, the bandgap of (6,6) CNTs remains smaller than the bandgap of (11,0) semiconductor CNTs, leading to the transition of SWCNTs to metallic conductors. Finally, the differential conductivity diagram of CNTs with topological defects was analyzed, demonstrating that introducing specific 5–8–5 defects can effectively regulate the electrical properties of the CNTs. This paper analyzes the effects of defects on the CNTs electrical properties and finds a regulatory effect, providing a reference for carbon-based transistor manufacturing.

Carbon nanotube (CNT) is a material widely chosen for object of research in nano technology. Apart from its good absorbent property, CNT also has a unique structure, superior mechanic and electric properties and its high strength. The property of CNT above is to be expected to improve performance of Titania nanotube (TiNT) composite. Properties of pure CNT are hydrophobic at the surface and low dispersion stability. To improve dispersability of CNT then modification need to be modified. Adding Cetyl trimethyl ammonium bromide (CTAB) surfactant on CNT is a way to increase dispersion stability of TiNT-CNT. The objective of the research was to study influence of adding of Cetyl trimethyl ammonium bromide (CTAB) surfactant to synthesis of TiNT-CNT composite in degrading phenol compound. Pure CNT was added with CTAB surfactant in liquid, then was sonificated and dried. Surfactant Cetyl trimethyl ammonium bromide (CTAB) added CNT then composited with TiNT. Phenol degradation then tested by using TiNT-CNT (CTAB) in reactor for 4.5 hours. Then sample was characterized by employing Field Emission Scanning Electron Microscopy (FESEM), X-ray Diffraction (XRD), Fourier Transform Infra-Red (FTIR) and UV-vis Spectroscopy. The result of experiments from FESEM characterization showed forming of TiNT-CNT composites morphology. From X–ray Diffraction (XRD) characterization showed crystal formed on TiNT-CNT only of anatase crystal. Degradation of TiNT-NT composite (CTAB) to phenol was also studied.

Metallic–semiconducting transition of single-walled carbon nanotubes under high axial strain

The use of carbon nanotubes (CNTs) in the field of biosensing technology is considered a revolution, as it aims to produce faster and more sensitive biosensor devices. Both the physical and mechanical properties of CNTs make them highly suitable to be utilized as biosensors. Surface functionalizations and modifications of CNTs make them even more versatile, giving rise to various types of CNT-based biosensors. Though CNT-based biosensors find wide operations in the field of biomedical sciences, some major issues regarding their toxicity and biocompatibility need to be acknowledged before commercializing them completely. This review article focuses on the properties of CNTs which make them one of the prominent candidates to be used for biosensing purposes, chemical modifications of CNTs, and types and working of CNT-based biosensors.KeywordCarbon nanotubesChemical functionalizationBiosensorsToxicityBiocompatibility

Carbon nanotube (CNT) has attracted of great interest as advanced nanoreinforcements in new kinds of polymer nanocomposites because of the combination of its unique extraordinary properties with high aspect ratio and small size (Ebbesen, 1997; Dresselhaus et al., 2001; Schadler et al., 1998; Ajayan, 1999; Bokobza, 2007; Paul & Robesson, 2008). In particular, excellent mechanical strength, thermal conductivity, and electrical properties of CNT have created a high level of activity in materials research and development for potential applications such as fuel cell, hydrogen storage, field emission display, chemical or biological sensor, and advanced polymer nanocomposites (Iijima, 1991; De Heer et al., 1995; Wong et al, 1997; Fan et al., 1999; Kim & Lieber, 1999; Liu et al., 1999; Kong et al., 2000; Ishihara et al., 2001; Alan et al., 2003; Wu & Shaw, 2005). This feature has motivated a number of attempts to fabricate CNT/polymer nanocomposites in the development of highperformance composite materials (Kim et al., 2006; Kim et al., 2007; Kim et al., 2008; Kim, 2009; Kim et al., 2009; Kim et al., 2010). In this regard, much research and development have been performed to date for achieving the practical realization of excellent properties of CNT for advanced polymer nanocomposites in a broad range of industrial applications. However, because of high cost and limited availability, only a few practical applications in industrial fields such as electronic and electric appliances have been realized to date. The CNT consisting of concentric cylinder of graphite layers is a new form of carbon and can be classified into three types (Dresselhaus et al., 2001; Iijima, 1991; Shonaike & Advani, 2003): single-walled CNT (SWCNT), double-walled CNT (DWCNT), and multi-walled CNT (MWCNT). SWCNT consists of a single layer of carbon atoms through the thickness of the cylindrical wall with the diameters of 1.0-1.4 nm, two such concentric cylinders forms DWCNT, and MWCNT consists of several layers of coaxial carbon tubes, the diameters of which range from 10 to 50 nm with the length of more than 10 μm (Dresselhaus et al., 2001; Iijima, 1991; Shonaike & Advani, 2003). The graphite nature of the nanotube lattice results in a fiber with high strength, stiffness, and conductivity, and higher aspect ratio represented by very small diameter and long length makes it possible for CNTs to be ideal nanoreinforcing fillers in advanced polymer nanocomposites (Thostenson et al., 2001). Both theoretical and experimental approaches suggest the exceptional mechanical properties of CNTs ~100 times higher than the strongest steel at a fraction of the weight (Goze et al., 1999; Yao et al., 2001;

Recent decades have witnessed many breakthroughs in research on carbon nanotubes (CNTs), particularly regarding controllable synthesis, production scale-up, and application advances for this material. This sp 2-bonded nanocarbon uniquely combines extreme mechanical strength, exceptionally high electrical conductivity, as well as many other superior properties, making it highly attractive for fundamental research and industrial applications. Synthesis and mass production form the solid basis for high-volume applications of CNTs. During recent decades, CNT production capacity has reached more than thousands of tons per year, greatly decreasing the price of CNTs. Although the unique physiochemical properties of an individual CNT are stated repeatedly, manifestation of such unique properties in a macroscopic material, e.g., realization of high-strength CNT fibers, remains a great challenge. If such challenges are solved, many critical applications will be enabled. Herein we review the critical progress in the development of synthesis and scaled-up production methods for CNTs, and discuss advances in their applications. Scientific problems and technological challenges are discussed together.

In recent years, integrating biological components in analytical instruments especially in biomedical research has become a prerequisite for early diagnosis of many diseases. It is well known that the material properties (electrical and physical) of CNTs is very sensitive to be affected by exposure to biomolecules and this led to the investigation by many researchers. Though the CNT-based biosensors has been widely used due their better performance, it still has many practical concerns in application. For the successful commercialization of the concept of CNT-based biosensors, many hurdles need to overcome. Modifications on CNT biosensors have experienced a dramatic change with outstanding developments. The present article provides an overview on the recent development in CNT biosensors and comprehensive analysis was given on various ways to improve the performance of CNT with new designs. In addition, some of the practical applications and concerns in the field are addressed. The scientific and technological challenges in the field are discussed in the conclusion.

Piezoresistive properties of well-dispersed carbon nanotubes (CNTs) modified cement paste

: The core effort of this project has been the electrical transport and infrared photoresponse properties of carbon nanotube (CNT) systems. The word system is important in the context of our work because we have focused on the properties of materials and devices consisting not of a single CNT, but of assemblies with large numbers of CNTs. In these systems it is often not only the properties of single CNTs that count, but also (and primarily) the way in which they interact with each other and with the other materials comprising the system. Thus a rich interplay between such properties ensues that has been able to generate materials and devices with unprecedented functionality and with rich and interesting electronic properties. Two cases illustrate this. The first is the system that we investigated in the earlier parts of this effort consisting of a macroscopically ordered array of CNTs, all which formed individually electronic-grade heterojuctions with an underlying silicon substrate. This system is comprised essentially of billions of individual CNTs connected in parallel. As such, the properties of individual CNTs were just as important as those of their interaction with each other (cross-talk) and with the other elements of the system. For example, a few dozens of shorts within this billion or so of parallel diodes could potentially render the device useless. Yet, our development of novel sample fabrication and CNT growth strategies made such shorts a non-issue. This allowed us to demonstrate and study the interesting electrical rectification properties of this CNT-Silicon heterojunction system, and led to the discovery that this system could behave as a broad-band detector of infrared radiation, capable of operating in both cooled and uncooled modes. A further extension of this system was then achieved by loading the interior spaces of the CNTs with other materials of interest, including lead sulfide in both quantum dot and nanowire forms.