The effect of interlayer distance and oxygen content on proton conductivity of graphite oxide is presented. Bulk-state proton conductivities were measured using coin-shaped pellets of three different graphite oxide samples, namely, H-GO, S-GO, and B-GO, generated respectively from the techniques of Hummers, Staudenmaier, and Brodie. The extent of oxidation, nature of functional groups, interlayer distances, and morphologies are studied through Raman spectroscopy, XPS, powder XRD pattern, and SEM images. The proton conductivities follow the trend H-GO > S-GO > B-GO. In the XPS study, the total oxygen contents were found to follow the trend H-GO > B-GO > S-GO, whereas the interlayer distances obtained from the powder XRD patterns show the trend H-GO > S-GO > B-GO. Beside the nature of the functional groups and extent of oxidation, the interlayer distance displays a significant effect on the proton conductivity values. The temperature-dependent Arrhenius plots reveal the activation energy (E a ) of the samples as 0.274, 0.291, and 0.296 eV. These low E a values imply the Grotthuss mechanism for proton conduction. The high conductivity value and low activation energy of H-GO with a maximum interlayer distance indicate that hydronium ion's rotational movement and re-formation of hydrogen bonds by the Grotthuss mechanism are supported by a more flexible interlayer. We propose that this physical insight might be considered to improve the proton conductivity through modulating layer distances not only in carbon allotropes but also in other materials.

The development of n-type single-walled carbon nanotubes (SWCNTs) stable under an air atmosphere is a key issue to prepare an efficient and stable thermoelectric conversion device using SWCNTs. Doping of SWCNT sheets with 2-(2-methoxyphenyl)-1,3-dimethyl-2,3-dihydro-1H-benzo­[d]­imidazole (o-MeO–DMBI) offers air-stable n-type SWCNT sheets. However, a clear mechanism of the stabilization in air has not been clarified yet. In this study, air stability is found to largely depend on the doping concentration. Adsorption isotherm experiments of the dopant onto SWCNT sheet reveal that the entire coverage of the SWCNT surface by o-MeO–DMBI cation is the key requirement to realize the air stability, which is well-supported by the theoretical calculation. This finding provides useful guidelines to develop air-stable n-type SWCNTs with various n-dopants.

The rapid transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-driven infection signifies an ultimate challenge to global health, and the development of effective strategies for preventing and/or mitigating its effects are of the utmost importance. In the current study, an in-depth investigation for the understanding of the SARS-CoV-2 inactivation route using graphene oxide (GO) is presented. We focus on the antiviral effect of GO nanosheets on three SARS-CoV-2 strains: Wuhan, B.1.1.7 (U.K. variant), and P.1 (Brazilian variant). Plaque assay and real-time reverse transcription - polymerase chain reaction (RT-PCR) showed that 50 and 98% of the virus in a supernatant could be cleared following incubation with GO (100 μg/mL) for 1 and 60 min, respectively. Transmission electron microscopy (TEM) analysis and protein (spike (S) and nucleocapsid (N) proteins) decomposition evaluation confirm a two-step virus inactivation mechanism that includes (i) adsorption of the positively charged spike of SARS-CoV-2 on the negatively charged GO surface and (ii) neutralization/inactivation of the SARS-CoV-2 on the surface of GO through decomposition of the viral protein. As the interaction of S protein with human angiotensin-converting enzyme 2 (ACE2) is required for SARS-CoV-2 to enter into human cells, the damage to the S protein using GO makes it a potential candidate for use in contributing to the inhibition of the worldwide spread of SARS-CoV-2. Specifically, our findings provide the potential for the construction of an effective anti-SARS-CoV-2 face mask using a GO nanosheet, which could contribute greatly to preventing the spread of the virus. In addition, as the effect of surface contamination can be severe in the spreading of SARS-CoV-2, the development of efficient anti-SARS-CoV-2 protective surfaces/coatings based on GO nanosheets could play a significant role in controlling the spread of the virus through the utilization of GO-based nonwoven cloths, filters, and so on.

Colostrum has enough humoral and cellular elements to protect babies. Therefore, immune protection derived from breastfeeding depends on the immunoglobulin level of the colostrum as well as the amount of colostrum ingested.