Chemical functionalization of single-walled carbon nanotube field-effect transistors as switches and sensors
ABSTRACT Because of the one-dimensional (1D) nanostructural nature of single-walled carbon nanotubes (SWNTs) and their advantages of chemical flexibility and sensitivity arising from the susceptibility of their active surfaces to interacting species, great effort has been made to integrate carbon nanotube field-effect transistors (NTFETs) into functional optoelectronic devices capable of converting external stimuli to easily detectable electrical signals. In this Review article, we aim to capture recent advances of rational design and chemical functionalization of NTFETs for the purpose of switching or biosensing applications. To provide a deeper understanding of the device responses to analytes, this review will also survey the proposed sensing mechanisms. As demonstrated by these remarkable examples, the concept of combining the proper selection of functional molecular materials and molecular self-assembly with device micro/nanofabrication offers attractive new prospects for constructing NTFET-based molecular optoelectronic devices with desired functionalities.
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ABSTRACT: We investigated top-contact pentacene-based organic thin-film transistor (OTFTs) with bi-layer MoO3/Au electrodes. The device performance including field effect mobility, threshold voltage, and On/Off ratio was highly improved in a device with 5 nm MoO3 layer which showed the highest field-effect mobility of 0.72 cm2 V-1s-1. In addition, from temperature dependence characteristics, we observed that the barrier height was dramatically decreased from 0.12 eV (without MoO3) to 0.03 eV in device with 5 nm MoO3 layer. This improved device performance was attributed to significant reduction in barrier height at Au/pentacene interfaces and surface roughness of pentacene layer after inserting a suitable MoO3 layer between pentacene and gold electrodes.Current Nanoscience 05/2013; 9(3):407. · 1.36 Impact Factor
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ABSTRACT: Interactions between selective factors (hypertension and tuberculosis) and environmental effects (vitamin D deficiency [VDD], temperature, and altitude) largely explain cystic fibrosis (CF) carrier geography. For VDD sequelae such as hypertension and tuberculosis vulnerability, clinical evidence of carrier protection is supported by indications that decreased CF arylsulfatase B activity suppresses tuberculosis, and that excess CF salt loss decreases blood pressure. A need for salt retention in the tropics selected against CF carriers despite possible advantages against cholera, typhoid, and other factors, but salt retention was less important elsewhere. Increased hypertension with cold selected for carriers with increasing latitude, and with altitude, where hypertensive complications of pregnancy also rise. ΔF508 rates especially seem to follow these parameters, and may be particularly protective against hypertension, while lower rates in Ashkenazi Jews are consistent with a greater role for tuberculosis in this group. This scenario suggests geographical correlations of CF with other genes affecting blood pressure, and significant carrier levels, especially of ΔF508, in mountainous areas of Asia with VDD.Journal of cystic fibrosis: official journal of the European Cystic Fibrosis Society 10/2011; 11(1):68-70. · 3.19 Impact Factor
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ABSTRACT: Solidly mounted resonators (SMRs) with a top carbon nanotubes (CNTs) surface coating that doubles as an electrode and as a sensing layer have been fabricated. The influence of the CNTs on the frequency response of the resonators was studied by direct comparison to identical devices with a top metallic electrode. It was found that the CNTs introduced significantly less mass load on the resonators and these devices exhibited a greater quality factor, Q (>2000, compared to ∼1000 for devices with metal electrodes), which increases the gravimetric sensitivity of the devices by allowing the tracking of smaller frequency shifts. Protein solutions with different concentrations were loaded on the top of the resonators and their responses to mass-load from physically adsorbed coatings were investigated. Results show that resonators using CNTs as the top electrode exhibited a higher frequency change for a given load (∼0.25 MHz cm2 ng−1) compared to that of a metal thin film electrode (∼0.14 MHz cm2 ng−1), due to the lower mass of the CNT electrodes and their higher active surface area compared to that of a thin film metal electrode. It is therefore concluded that the use of CNT electrodes on resonators for their use as gravimetric biosensors is a significant improvement over metallic electrodes that are normally employed.Sensors and Actuators B Chemical 01/2011; B160:1386. · 3.54 Impact Factor