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Carbon Nanotube–Based Electrochemical Biosensors
Published in Li Jun, Wu Nianqiang, Biosensors Based on Nanomaterials and Nanodevices, 2017
Carbon nanotubes, particularly vertically aligned carbon nanotube arrays (VA-CNTs), have been demonstrated to be useful for the development of various electrochemical biosensors, including glucose, protein, enzyme, and DNA sensors as well as biosensor chips. However, it is essential to functionalize and/or micropattern VA-CNTs for biosensing applications. Several innovative functionalization approaches, including in situ functionalization during the nanotube growth, post-functionalization by chemical doping, plasma modification, and electrochemical and physical deposition of polymers, have been developed for chemical modification of VA-CNTs while largely retaining their structural integrity. We have provided a brief overview on the progress toward the synthesis and construction of aligned and micropatterned carbon nanotubes for electrochemical sensors by spotlighting some important work in the field. As can be seen, aligned/patterned nanotube growth, in conjunction with controlled functionalization of the resultant carbon nanotubes, could provide various vertically aligned carbon nanotube arrays with tailormade surface characteristics useful for construction of many advanced electrochemical biosensors.
Novel multiwalled carbon nanotube (MWCNT) modified metal oxide semiconductor field effect transistor (MOSFET) based electrode for electrophysiological measurements on human skin
Published in Instrumentation Science & Technology, 2019
Mustafa Istanbullu, Mutlu Avci
As shown in Figure 4, the gate terminal of n-channel depletion type MOSFET is covered with vertically aligned carbon nanotube arrays. Due to the depletion-type transistor characteristics, the channel between the drain and the source is conducting and current flows even though there is no voltage at the gate terminal. When the proposed electrode is attached to the skin surface, the carbon nanotubes at the gate terminal sense the biopotential signal. Oscillations of electrophysiological signals sensed by carbon nanotubes appear on the current flowing through drain to source.
Role of supercritical carbon dioxide (scCO2) in fabrication of inorganic-based materials: a green and unique route
Published in Science and Technology of Advanced Materials, 2021
Hao Liu, Biao-Qi Chen, Yu-Jing Pan, Chao-Ping Fu, Ranjith Kumar Kankala, Shi-Bin Wang, Ai-Zheng Chen
Finally, the reduction of the inorganic precursor to its metal elementary substance form (or oxidized to metal-oxide form) is the last procedure of the SCD process after solubility and deposition of the surface. The eventual properties of the supported nanoparticles and films in the end-product (for instance, particle size, distribution range, thickness of the film, and morphology) are often dependent on the reduced or oxidized forms of the nanoparticles and the processing conditions (reaction temperature and time). Typically, the first reduction of the metal precursor is performed using the reducing agents, such as the H2 reducing agent added to scCO2 and the metal precursor in contact with the substrate. In this vein, Rincón and colleagues fabricated diverse nanoparticles, such as Pb, Pt, and Cu-supported onto the carbon nanotubes by reducing the inorganic precursor using H2 [67,85,86]. Contrarily, in the case of the metal precursor being oxidized, the precursor organic solution was usually added dropwise to scCO2. Accordingly, previous reports indicated the utilization of different metal oxide nanoparticles supported onto various core substrates. In a case, Cheng and colleagues prepared the NiO nanoparticle-supported vertically-aligned carbon nanotube arrays (VACNTs) through the scCO2-assisted deposition after the annealing approach [87]. The nickelocene precursor was deposited in the gaps of VACNTs, demonstrating that the VACNTs/NiO composite arrays could result in a high capacitance of 1088.44 F·g−1. In another case, Rybaltovsky and coworkers explored the influence of laser irradiation at different wavelengths on the supported Ag nanoparticles generated using the SCD process and the Ag nanoparticles deposition behavior on silica aerogel [68,69]. The Ag precursor of the Ag(hfac)COD disposed of through the laser irradiation, demonstrating that the minimum size of the particles would be obtained using off-resonant irradiation, and the irradiation dosage could tune the particle concentration.