Carbon Nanotube−Metal Cluster Composites:  A New Road to Chemical Sensors?

Abstract

Novel carbon nanotube−metal cluster structures are proposed as prototype systems for molecular recognition at the nanoscale. Ab initio calculations show that already the bare nanotube cluster system displays some specificity because the adsorption of ammonia on a carbon nanotube−Al cluster system is easily detected electrically, while diborane adsorption does not provide an electrical signature. Since there are well-established procedures for attaching molecular receptors to metal clusters, these results provide a "proof-of-principle" for the development of novel, high-specificity molecular sensors.Since their discovery in 1991, carbon nanotubes (CNTs) have become one of the most exciting nanomaterials, combining a range of extraordinary physical properties, such as extremely small size and high aspect ratio, high stiffness and excellent flexibility under different mechanical stimuli, high structural and chemical stability, and a rich spectrum of electrical properties. Many potential applications have been proposed: superstrong composites, energy storage and energy conversion devices, field emission displays, mechanical, chemical and biological probes and sensors, radiation sources, nanoelectronic devices, and more. 1 In this letter we concentrate on the possibility of using carbon nanotubes as chemical sensors and probes. Pioneering experiments from Dai's group 2,3 have shown that at room temperature the resistance of an individual single wall carbon nanotube is very responsive to the adsorption of molecules, such as NO 2 and NH 3 . These measurements demonstrate the excellent sensing capabilities of CNTs, in particular their fast response time, high selectivity, and reversibility. It has also been shown that CNT-based single-molecule biosensors 4-6 can compete with other nanowire nanosensors 7 in detecting biological and chemical molecules. If appropriately functionalized, carbon nanotubes even have the ability to recognize proteins and DNA. [8][9][10] Moreover, their intrinsic strength and resilience makes them ideally suited for ultrasmall sensors capable of exploring complicated geometries at the nanoscale. 5,6 Real-world applications, such as CNTbased resonant-circuit wireless ammonia sensors, have been developed by different groups. 11,12 Due to their strong sp 2 bonding and near perfect hexagonal network, carbon nanotubes are chemically stable and do not form strong chemical bonds with most molecules. However, since experiments have shown that the properties of a CNT can change when it is immersed in a specific chemical or biological environment, there has been a substantial effort toward the development of techniques to enhance the sensing capability of CNTs. The most common route to improvement in reactivity and sensitivity is through functionalization of CNT sidewalls with specific bio/chemical molecules. [4][5][6]8 In fact, chemical functionalization can both ensure better chemical bonding between the nanotube and a specific chemical species as well as improve the selectivity of the adsorptio...

Improving gas sensing properties of graphene by introducing dopants and defects: a first-principles study

“…As indicated by the previous theoretical calculations [20,26], GGA methods tend to underestimate the adsorption energies. For example, GGA suggested that almost no interaction between two graphene layers.…”

Applications of Al Modified Graphene on Gas Sensors and Hydrogen Storage

“…The high sensitivity of boron doped SWCNT to CO and H 2 O absorptions has been also demonstrated (Peng & Cho, 2003). Most recently, Al-cluster and Al doped SWCNT assembly were suggested to be promising systems for novel molecular sensors to NH 3 (Zhao et al, 2005) and CO (Wang et al, 2007), and the B doped SWCNTs are highly sensitive to the gaseous cyanide and formaldehyde molecules (Zhang et al, 2006). However, the devices with higher sensitivity to these toxic gases are apparently required for environmental safety issues both in workplaces and residential areas, especially in some industrial and military fields.…”

Experimental Analysis of Modified CNTs-Based Gas Sensor

“…Literature [70] shows we can get more accurate calculation results on CNTs (8, 0) brillouin zone 2 K points. All the calculation procedures completed on the Dmol 3 .…”

“…P polarized function is used for modified hydroxyl (OH)-wall (8, 0) SWNT in presence of gas molecule adsorption density functional calculations. Previous theoretical calculations [70] show that the generalized gradient approximation (GGA) method can accurately describe the geometric structure and electronic structure of CNTs, and the process of interaction with molecules. To avoid the interaction between the nanotubes, we designed a large lattice of 20 Å × 20 Å × 85 Å, and use the periodic boundary conditions.…”