Coronavirus disease 2019 (COVID-19) is a newly emerging human infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, previously called 2019-nCoV). Based on the rapid increase in the rate of human infection, the World Health Organization (WHO) has classified the COVID-19 outbreak as a pandemic. Because no specific drugs or vaccines for COVID-19 are yet available, early diagnosis and management are crucial for containing the outbreak. Here, we report a field-effect transistor (FET)-based biosensing device for detecting SARS-CoV-2 in clinical samples. The sensor was produced by coating graphene sheets of the FET with a specific antibody against SARS-CoV-2 spike protein.The performance of the sensor was determined using antigen protein, cultured virus, and nasopharyngeal swab specimens from COVID-19 patients. Our FET device could detect the SARS-CoV-2 spike protein at concentrations of 1 fg/mL in phosphate-buffered saline and 100 fg/mL clinical transport medium. In addition, the FET sensor successfully detected SARS-CoV-2 in culture medium (limit of detection [LOD]: 1.6 × 10 1 pfu/mL) and clinical samples (LOD: 2.42 × 10 2 copies/mL). Thus, we have successfully fabricated a promising FET biosensor for SARS-CoV-2; our device is a highly sensitive immunological diagnostic method for COVID-19 that requires no sample pretreatment or labeling.

A wearable thermoelectric generator, woven on a wristband, consisting of chemically exfoliated n- and p-type transition metal dichalcogenide nanosheets.

The contact resistance between a carbon nanotube and metal electrodes decreases by several orders of magnitude and becomes long-term stable when the nanotube contacted by Ti-Au electrodes was annealed by a rapid thermal annealing method at 600-800 °C for 30 s. The contact resistances of the annealed samples are in the range 0.5-50 kΩ at room temperature, depending on the electrical properties of the nanotube. The short and relatively low-temperature annealing process enables us to make a surface Ti-nanotube contact suitable for electrical measurements. For the samples with relatively low contact resistances (0.5-5 kΩ) at room temperature, the contact resistance remained constant or decreased slightly as the temperature was lowered. Those with a relatively high contact resistance (5-50 kΩ), on the other hand, showed increasing contact resistance with a lowering of the temperature.

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Using oxygen adsorption experiments on poly (dG)-poly (dC) DNA molecules, we found that their conductance can be easily controlled by several orders of magnitudes using oxygen hole doping, which is a characteristic behavior of a p-type semiconductor. It also suggests that the conductance of the DNA under doping results from charge carrier transport, not from an ionic conduction. On the other hand, we will also show that the poly (dA)-poly (dT) DNA molecules behave as an n-type semiconductor. This letter demonstrates that the concentration and the type of carriers in the DNA molecules could be controlled using proper doping methods.

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We have studied the electrical conductivity of DNA film using nanogap electrodes. Current-voltage measurements and alternating current measurements were performed for analysis of conductivity. The electrical conductivity of the DNA films of poly(dG)Ápoly(dC) are found to depend strongly on the humidity. The resistance of poly(dG)Ápoly(dC) decreases dramatically with increasing relative humidity. The contact resistance between DNA film and Au electrodes is also examined by the conventional four-probe technique.

This study reports the electrical transport characteristics of Si(1-x)Gex (x=0-0.3) nanowires. Nanowires with diameters of 50-100 nm were grown on Si substrates. The valence band spectra from the nanowires indicate that energy band gap modulation is readily achievable using the Ge content. The structural characterization showed that the native oxide of the Si(1-x)Gex nanowires was dominated by SiO2; however, the interfaces between the nanowire and the SiO2 layer consisted of a mixture of Si and Ge oxides. The electrical characterization of a nanowire field effect transistor showed p-type behavior in all Si(1-x)Gex compositions due to the Ge-O and Si-O-Ge bonds at the interface and, accordingly, the accumulation of holes in the level filled with electrons. The interfacial bonds also dominate the mobility and on- and off-current ratio. The large interfacial area of the nanowire, together with the trapped negative interface charge, creates an appearance of p-type characteristics in the Si(1-x)Gex alloy system. Surface or interface structural control, as well as compositional modulation, would be critical in realizing high-performance Si(1-x)Gex nanowire devices.