Microwave synthesis of boron- and nitrogen-codoped graphene quantum dots and their detection to pesticides and metal ions.

Through developing a highly efficient solid-phase microwave-assisted (SPMA) synthesis technique, we were able to synthesize graphene quantum dots (GQDs) that were doped with nitrogen and boron atoms. The as-synthesized GQDs were employed as sensing probes for detecting pesticides and iron ions within aqueous solutions. The SPMA approach is very versatile for in-situ doping of multiple atoms within the graphitic structure of GQDs. The maximal B/C and N/C atomic ratios within the GQD structures were reached as high as 28.6 and 86.4 at.%, respectively. For the B-/N-codoped GQDs, the N dopants comprises of pyrrolic/pyridinic N and graphitic N, whereas the B doping mainly involves two bonding types (i.e., B4C and BCO2) inserted into or decorated on the GQD skeleton structure. Based on the analysis of the Stern-Volmer plots, the B-/N-codoped GQDs can be employed as probing nanomaterials toward Fe2+ and paraquat detection thanks to their incredible sensitivity throughout the photoluminescent quenching. The PL quenching mechanism of GQDs is usually governed by the GQD‒(paraquat)x intermediates formation and the resulting π-π stacking that can easily quench and aggregate. The findings of this work pave the pathway to engineering the chemical compositions as well as the crystalline structures of GQDs, used for energy and other sensing devices.

Employing functionalized graphene quantum dots to combat coronavirus and enterovirus.

The ongoing COVID-19 (i.e., coronavirus) pandemic continues to adversely affect the human life, economy, and the world's ecosystem. Although significant progress has been made in developing antiviral materials for the coronavirus, much more work is still needed. In this work, N-functionalized graphene quantum dots (GQDs) were designed and synthesized as the antiviral nanomaterial for Feline Coronavirus NTU156 (FCoV NTU156) and Enterovirus 71 (EV71)) with ultra-high inhibition (>99.9%). To prepare the GQD samples, a unique solid-phase microwave-assisted technique was developed and the cell toxicity was established on the H171 and H184 cell lines after 72 h incubation, indicating superior biocompatibility. The surface functionality of GQDs (i.e., the phenolic and amino groups) plays a vital role in interacting with the receptor-binding-domain of the spike protein. It was also found that the addition of polyethylene glycol is advantageous for the dispersion and the adsorption of functionalized GQDs onto the virus surface, leading to an enhanced virus inhibition. The functionality of as-prepared GQD nanomaterials was further confirmed where a functionalized GQD-coated glass was shown to be extremely effective in hindering the virus spread for a relatively long period (>20 h).

Hierarchical Carbon Composites for High-Energy/Power-Density and High-Reliability Supercapacitors with Low Aging Rate.

A facile method for preparing hierarchical carbon composites that contain activated carbon (AC), carbon nanospheres (CNSs), and carbon nanotubes (CNTs) for use as the electrode material in supercapacitors (SCs) was developed. The CNS/CNT network enabled the formation of three-dimensional conducting pathways within the highly porous AC matrix, effectively reducing the internal resistance of an SC electrode. The specific capacitance, cyclability, voltage window, temperature profile during charging/discharging, leakage current, gas evolution, and self-discharge of the fabricated SCs were systematically investigated and the optimal CNS/CNT ratio was determined. A 2.5 V floating aging test at 70 °C was performed on SCs made with various hierarchical carbon electrodes. Electrochemical impedance spectroscopy, postmortem electron microscopy, Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analyses were conducted to examine the electrode aging behavior. A hierarchical carbon architecture with an appropriate AC/CNS/CNT constituent ratio could significantly improve charge-discharge performance, increase cell reliability, and decrease the aging-related degradation rate.