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Evidence for structural phase transitions and large effective band gaps in quasi-metallic ultra-clean suspended carbon nanotubes

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Nano Research 2013年第10期6卷 736-744页

作者： Shun-Wen Chang Rohan Dhall moh amer Kentaro Sato Riichiro Saito Stephen Cronin Department of Physics and Astronomy University of Southern California Los Angeles CA 90089 USA Department of Electrical Engineering University of Southern California Los Angeles CA 90089 USA Department of Chemistry University of Southern California Los Angeles CA 90089 USA Department of Physics Tohoku University Sendai 980-8578 Japan

We report evidence for a structural phase transition in individual suspended metallic carbon nanotubes by examining their Raman spectra and electron trans- port under electrostatic gate potentials. The current-gate voltage characteristics reveal anomalously large quasi-metallic band gaps as high as 240 meV, the largest reported to date. For nanotubes with band gaps larger than 200 meV, we observe a pronounced M-shape profile in the gate dependence of the 2D band （or G＇ band） Raman frequency. The pronounced dip （or softening） of the phonon mode near zero gate voltage can be attributed to a structural phase transition （SPT） that occurs at the charge neutrality point （CNP）. The 2D band Raman intensity also changes abruptly near the CNP, providing further evidence for a change in the lattice symmetry and a possible SPT. Pronounced non-adiabatic effects are observed in the gate dependence of the G band Raman mode, however, this behavior deviates from non-adiabatic theory near the CNP. For nanotubes with band gaps larger than 200 meV, non-adiabatic effects should be largely suppressed, which is not observed experimentally. This data suggests that these large effective band gaps are primarily caused by a SPT to an insulating state, which causes the large modulation observed in the conductance around the CNP. Possible mechanisms for this SPT are discussed, including electron-electron （e.g., Mott） and electron-phonon （e.g., Peierls） driven transitions.

关键词： carbon nanotube Raman spectroscopy phase transition bandgap energy

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Highly sensitive,scalable,and rapid SARS-CoV-2 biosensor based on In_(2)O_(3)nanoribbon transistors and phosphatase

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Nano Research 2022年第6期15卷 5510-5516页

作者： Mingrui Chen Dingzhou Cui Zhiyuan Zhao Di Kang Zhen Li Shahad Albawardi Shahla Alsageer Faisal Alamri Abrar Alhazmi moh.R.amer Chongwu Zhou Mork Family Department of Chemical Engineering and Materials Science University of Southern CaliforniaLos AngelesCalifornia 90089USA Ming Hsieh Department of Electrical Engineering University of Southern CaliforniaLos AngelesCalifornia 90089USA Department of Physics and Astronomy University of Southern CaliforniaLos AngelesCalifornia 90089USA Center of Excellence for Green Nanotechnologies King Abdulaziz City for Science and TechnologyRiyadhSaudi Arabia Department of Electrical Engineering 420 Westwood Plaza5412 Boelter HallUniversity of CaliforniaLos AngelesLos AngelesCalifornia 90095USA eDNA Biotech PasadenaCalifornia 91107USA

Developing convenient and accurate SARS-CoV-2 antigen test and serology test is crucial in curbing the global COVID-19 *** this work,we report an improved indium oxide(In2O3)nanoribbon field-effect transistor(FET)biosensor platform detecting both SARS-CoV-2 antigen and *** FET biosensors,which were fabricated using a scalable and cost-efficient lithography-free process utilizing shadow masks,consist of an In_(2)O_(3)channel and a newly developed stable enzyme *** the biosensing process,the phosphatase enzymatic reaction generated pH change of the solution,which was then detected and converted to electrical signal by our In_(2)O_(3)*** biosensors applied phosphatase as enzyme reporter,which has a much better stability than the widely used urease in FET based *** proof-of-principle studies,we demonstrate the detection of SARS-CoV-2 spike protein in both phosphate-buffered saline(PBS)buffer and universal transport medium(UTM)(limit of detection[LoD]:100 fg/mL).Following the SARS-CoV-2 antigen tests,we developed and characterized additional sensors aimed at SARS-CoV-2 IgG antibodies,which is important to trace past infection and *** spike protein IgG antibody tests exhibit excellent detection limits in both PBS and human whole blood((LoD):1 pg/mL).Our biosensors display similar detection performance in different mediums,demonstrating that our biosensor approach is not limited by Debye screening from salts and can selectively detect biomarkers in physiological *** newly selected enzyme for our platform performs much better performance and longer shelf life which will lead our biosensor platform to be capable for real clinical diagnosis usage.

关键词： biosensor indium oxide transistor phosphatase SARS-CoV-2 spike protein SARS-CoV-2 spike IgG antibody

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