Hepatitis E virus (HEV) is one of the leading causes of acute viral hepatitis worldwide. In this work, a pulse-triggered ultrasensitive electrochemical sensor was fabricated using graphene quantum dots and gold-embedded polyaniline nanowires, prepared via an interfacial polymerization and then self-assembly approach. Introducing an external electrical pulse during the virus accumulation step increases the sensitivity towards HEV due to the expanded surface of the virus particle as well as the antibody-conjugated polyaniline chain length, compared to other conventional electrochemical sensors. The sensor was applied to various HEV genotypes, including G1, G3, G7 and ferret HEV obtained from cell culture supernatant and in a series of fecal specimen samples collected from G7 HEV-infected monkey. The sensitivity is similar to that detected by real-time quantitative reverse transcription-polymerase chain (RT-qPCR). These results suggests that the proposed sensor can pave the way for the development of robust, high-performance sensing methodologies for HEV detection.

The good stability, low cytotoxicity, and excellent photoluminescence property of graphene quantum dots (GQDs) make them an emerging class of promising materials in various application fields ranging from sensor to drug delivery. In the present work, the dopamine-functionalized GQDs (DA-GQDs) with stably bright blue fluorescence were successfully synthesized for low level Fe(3+) ions detection. The as-synthesized GQDs are uniform in size with narrow-distributed particle size of 4.5 ± 0.6 nm and high quantum yield of 10.2%. The amide linkage of GQDs with dopamine, confirmed by using XPS and FTIR spectra, results in the specific interaction between Fe(3+) and catechol moiety of dopamine at the interfaces for highly sensitive and selective detection of Fe(3+). A linear range of 20 nM to 2 μM with a detection limit of 7.6 nM is obtained for Fe(3+) detection by DA-GQDs. The selectivity of DA-GQDs sensing probe is significantly excellent in the presence of other interfering metal ions. In addition, the reaction mechanism for Fe(3+) detection based on the complexation and oxidation of dopamine has been proposed and validated. Results obtained in this study clearly demonstrate the superiority of surface functionalized GQDs to Fe(3+) detection, which can pave an avenue for the development of high performance and robust sensing probes for detection of metal ions and other organic metabolites in environmental and biomedical applications.

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Graphene quantum dots (GQDs) are a newly developed graphene family with good electrical conductivity and high theoretical capacitance, while halloysite nanotubes (HNTs) are naturally occurring layered mineral materials containing high active sites for energy storage support. The combination of HNTs and GQDs can offer a new strategy on the fabrication of eco-friendly electrode materials for high performance supercapacitor applications. Herein, an environmentally friendly GQD-HNT nanocomposite is fabricated in the presence of (3-aminopropyl)-triethoxysilane to provide increased charge storage sites as well as to allow for the fast charge transport for supercapacitor application. Morphological and surface analytical results show that 5–10 nm GQDs are homogeneously distributed on the surface of APTES-coated HNTs via amide linkage. This new and novel layered nanocomposite can provide accessible electroactive sites and low resistance to accelerate the electrons and electrolyte ion transport, resulting in excellent specific capacitance and high energy density. The specific capacitances of 363–216 F/g at current densities of 0.5–20 A/g are obtained. In addition, the GQD-HNTs exhibit excellent energy density of 30–50 Wh/kg. Results obtained in this study clearly demonstrate the feasibility of using GQD-HNTs as alternative energy storage materials with increased charge storage sites and fast charge transport for high energy density supercapacitor applications.