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The precise monitoring of H2S has aroused immense research interest in the biological and biomedical fields since it is exposed as a third endogenous gasotransmitter. Hence, there is an urgent requisite to explore an ultrasensitive and economical H2S detection system. Herein, we report a simple strategy to configure an extremely sensitive electrochemical sensor with a 2D nanosheet-shaped layered double hydroxide (LDH) wrapped carbon nanotubes (CNTs) nanohybrid (CNTs@LDH), where a series of CNTs@CuMn-LDH nanohybrids with varied amounts of LDH nanosheets grafted on a conductive CNTs backbone has been synthesized via a facile coprecipitation approach. Taking advantage of the unique core–shell structure, the integrated electrochemically active CuMn-LDH nanosheets on the conductive CNTs scaffold, the maximum interfacial collaboration, and the superior specific surface area with a plethora of surface active sites and ultrathin LDH layers, the as-prepared CNTs@CuMn-LDH nanoarchitectures have exhibited superb electrocatalytic activity toward H2S oxidation. Under the optimum conditions, the electrochemical sensor based on the CNTs@CuMn-LDH nanohybrid shows remarkable sensing performances for H2S determination in terms of a wide linear range and a low detection limit of 0.3 nM (S/N = 3), high selectivity, reproducibility, and durability. With marvelous efficiency achieved, the proposed sensing platform has been practically used in in situ detection of abiotic H2S efflux produced by sulfate reducing bacteria and real-time in vitro tracking of H2S concentrations from live cells after being excreted by a stimulator which in turn might serve as early diseases diagnosis. Thus, our core–shell hybrid nanoarchitectures fabricated via structural integration strategy will open new horizons in material synthesis, biosensing systems, and clinical chemistry.

Herein, we have summarized and argued about biomarkers and indicators used for the detection of SARS-CoV-2. Antibody detection methods are not considered suitable to screen individuals at early stages and asymptomatic cases. The diagnosis of COVID-19 using biomarkers and indicators at point of care level is much crucial. Therefore, it is urgently needed to develop rapid and sensitive detection methods which can target antigens. We have critically elaborated key role of biosensors to cope the outbreak situation. In this review, the importance of biosensors including electrochemical, surface enhanced Raman scattering, field-effect transistor and surface plasmon resonance biosensors in the detection of SARS-CoV-2 has been underscored. Finally, we have outlined pros and cons of diagnostic approaches as-well-as future directions.

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The development of structurally modified metal oxide heteroarchitectures with higher energy facets exposed has been of extensive research interests because of their unique construction and synergy effect of multifunctioning characteristics. In this study, we reported for the first time the development of a distinct type of gold nanoislands (AuNIs) on metal oxides (i.e., Cu 2 O−CuO) octadecahedral (ODH) heterostructures through the galvanic exchange reaction, where Cu 2 O not only acts as a stabilizer but also functions as a reductant. The electrocatalytic performance of the resultant core−shell Cu 2 O− CuO@AuNI ODH-based electrochemical sensing platform has been evaluated in ultrasensitive detection of sulfide as early disease diagnostics and bacterial marker. Owing to the synergistic collaboration of enhanced surface active sites, exposed {110} crystallographic facets, mixed valances of copper that encourage redox reactions at electrode material/analyte interface, and the polarization effect provide by AuNIs decorated onto the Cu 2 O surface, Cu 2 O−CuO@AuNI ODH-modified electrode has demonstrated striking electrochemical sensing performance toward sulfide oxidation in terms of broad linear range, real detection limit down to 1 nM (S/N = 3), and incredible durability and reproducibility. In virtue of marvelous efficiency, the proposed electrochemical sensor based on Cu 2 O−CuO@AuNI ODH has been employed in in situ sensitive detection of a ubiquitous amount of sulfide engendered by sulfate-reducing bacteria and real-time tracking of sulfide efflux from live cells as early diagnostic strategies.

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