Review Articles (7)

Citation: Deep Jariwala,a Vinod K. Sangwan,a Lincoln J. Lauhon,a Tobin J. Marksab and Mark C. Hersam*, Chemical Society Reviews 2013, 42, 2824-2860.

Summary: In the last three decades, zero-dimensional, one-dimensional, and two-dimensional carbon nanomaterials (i.e., fullerenes, carbon nanotubes, and graphene, respectively) have attracted significant attention from the scientific community due to their unique electronic, optical, thermal, mechanical, and chemical properties. While early work showed that these properties could enable high performance in selected applications, issues surrounding structural inhomogeneity and imprecise assembly have impeded robust and reliable implementation of carbon nanomaterials in widespread technologies. However, with recent advances in synthesis, sorting, and assembly techniques, carbon nanomaterials are experiencing renewed interest as the basis of numerous scalable technologies. Here, we present an extensive review of carbon nanomaterials in electronic, optoelectronic, photovoltaic, and sensing devices with a particular focus on the latest examples based on the highest purity samples. Specific attention is devoted to each class of carbon nanomaterial, thereby allowing comparative analysis of the suitability of fullerenes, carbon nanotubes, and graphene for each application area. In this manner, this article will provide guidance to future application developers and also articulate the remaining research challenges confronting this field.p>

Citation: Ian Matthew Feigel, Harindra Vedala and Alexander Star, Journal of Materials Chemistry (2011), article in press.

Summary: Over the past decade, one-dimensional nanostructures (1D-NS) have been studied for the detection of biological molecules. These nanometre-scale materials, with diameters comparable to the size of individual biomolecules, offer the advantage of high sensitivity. In this feature article we discuss different techniques of biosensing using 1D-NS, namely electrical, electrochemical, optical, and mechanical methods, with a focus on the advancement of these techniques. Advantages and disadvantages of various synthesis and functionalization methods of 1D-NS, as well as biosensor device fabrication procedures are discussed. The main focus of this review is to demonstrate the progress of protein and DNA sensors based on 1D-NS over the past decade, and in addition we present an outlook for the future of this technology.

Citation: D.W.H. Fama, Al. Palaniappana, A.I.Y. Toka, B. Liedberga and S.M. Moochhala, Sensors and Actuators B: Chemical (2011), article in press.

Summary: Carbon nanotubes (CNTs) are one of the advanced functional materials of today and has been researched extensively since its discovery. Although much is still not known about the physical and chemical properties of CNTs, it has already found potential applications in many industries, from defense to electronics and even in environmental remediation. CNTs possess many desirable mechanical and chemical properties, which supercedes many of the advanced materials of today. It was also found that CNTs have excellent electronic properties like unprecedented mobilities of up to 100,000 cm2/V s, which can potentially result in a quantum leap in the electronics industry. Over the recent years, CNT and their derivatives (decorated/functionalized) were also intensively studied, especially in the field of bio and chemical sensing owing to the size similarity of nanotubes with the analytes such as biospecies that enable strong interactions between them. However, despite intensive research, commercialization of these potential applications still remains elusive mainly due to the lack of control in synthesis of specific chirality, diameter and length of CNTs, which influences the device performance. This short review focuses on addressing recent advances in CNT research especially on aspects such as controlled synthesis, decoration/functionalization for specific recognition, sensor device fabrication and commercialization strategies.

Citation: Sandeep Kumar Vashista, Dan Zhenga, Khalid Al-Rubeaand, John H.T. Luonge and Fwu-Shan Sheu, Biotechnology Advances (2011), 29, 2, 169-188.

Summary: Electrochemical (EC) sensing approaches have exploited the use of carbon nanotubes (CNTs) as electrode materials owing to their unique structures and properties to provide strong electrocatalytic activity with minimal surface fouling. Nanofabrication and device integration technologies have emerged along with significant advances in the synthesis, purification, conjugation and biofunctionalization of CNTs. Such combined efforts have contributed towards the rapid development of CNT-based sensors for a plethora of important analytes with improved detection sensitivity and selectivity. The use of CNTs opens an opportunity for the direct electron transfer between the enzyme and the active electrode area. Of particular interest are also excellent electrocatalytic activities of CNTs on the redox reaction of hydrogen peroxide and nicotinamide adenine dinucleotide, two major by-products of enzymatic reactions. This excellent electrocatalysis holds a promising future for the simple design and implementation of on-site biosensors for oxidases and dehydrogenases with enhanced selectivity. To date, the use of an anti-interference layer or an artificial electron mediator is critically needed to circumvent unwanted endogenous electroactive species. Such interfering species are effectively suppressed by using CNT based electrodes since the oxidation of NADH, thiols, hydrogen peroxide, etc. by CNTs can be performed at low potentials. Nevertheless, the major future challenges for the development of CNT-EC sensors include miniaturization, optimization and simplification of the procedure for fabricating CNT based electrodes with minimal non-specific binding, high sensitivity and rapid response followed by their extensive validation using “real world” samples. A high resistance to electrode fouling and selectivity are the two key pending issues for the application of CNT-based biosensors in clinical chemistry, food quality and control, waste water treatment and bioprocessing.

Citation: Kannan Balasubramanian, Biosensors and Bioelectronics (2010), 26, 4, 1195-1204.

Summary: This review outlines the use of one-dimensional nanostructures (1D-NS) for the detection of biomolecules on a chip. The materials discussed here include carbon nanotubes, metallic and semiconducting nanowires and nanochannels. While nanotubes and naowires have predominantly been used as electrical detectors, nanochannels are promising frameworks for optical detection in applications such as separation, preconcentration and DNA mapping. The primary expectation for all the three types of 1D-NS lies in the promise for ultimate single molecule detection. Furthermore, the electrical double layer governs the physics behind biosensing in all the three systems. The review starts by shedding light on the advantages arising due to the use of 1D nanostructures, followed by a discussion of fundamental aspects such as double layer effects and sensing methodologies. After this, the three kinds of 1D-NS are introduced. The main focus of the review is an in-depth analysis of the current achievements in the field and the major challenges that are to be overcome for the widespread use of such nanostructures in applications such as lab-on-a-chip devices and point-of-care diagnostics.

Citation: Paul Stokes and Saiful I. Khondaker, ACS Nano (2010), 4, 5, 2659–2666.

Summary: We performed low-temperature electron transport spectroscopy to evaluate defects in individual single-walled carbon nanotube (SWNT) devices assembled via dielectrophoresis from a surfactant-free solution. At 4.2 K, the majority of the devices show periodic and well-defined Coulomb diamonds near zero gate voltage corresponding to transport through a single quantum dot, while at higher gate voltages, beating behavior is observed due to small potential fluctuations induced by the substrate. The Coulomb diamonds were further modeled using a single electron transistor simulator. Our study suggests that SWNTs derived from stable solutions in this work are free from hard defects and are relatively clean. Our observations have strong implications on the use of solution-processed SWNTs for future nanoelectronic device applications.

Citation: Mark C. Hersam, Nature Nanotechnology (2008) 3, 387-394.

Summary: This paper discusses the advantages of DGU over other nanotube sorting strategies, such as dielectrophoresis, selective chemistry, controlled electrical breakdown, and chromatography. In brief, the principle advantages of DGU are its:

• Demonstrated scalability
• Compatibility with a wide range of starting materials
• Use of reversible functionalization chemistry
• Iterative repeatability