Transcription-polymerase chain reaction (RT-qPCR) is the golden standard to detect viral RNA. However, it suffers from several inherent defects such as high false-negative rates, time-consuming and expensive. To exploit better analytical methods for future global pandemics, it is vital to develop rapid, sustainable, and environmentally-friendly sensing methods. Here, a one-step, regenerated nanosensor assembled by DNA tweezers is developed for rapid and sustainable detection of viral RNA. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA is selected as model analyte. The DNA tweezer is designed with a central strand and two arm strands containing overhangs complementary to SARS-CoV-2 RNA. The SARS-CoV-2 RNA hybridizes with the two arm overhangs and strains the DNA tweezer to closed conformation, resulting in the close proximity of the donor and acceptor fluorophores. With the addition of an anti-strand complementary to the SARS-CoV-2 RNA, the closed DNA tweezer is relaxed to open conformation through a strand displacement process, leading to the separation of the dual fluorophores. Thus, the DNA tweezer is revived for fresh SARS-CoV-2 RNA. The proposed nanosensor can be regenerated for three cycles with the same performance. Moreover, the viral RNA can be detected within 30 min with a detection limit of 0.04 nM. By altering the sequences of the DNA tweezer, rapid, sensitive, and sustainable detection of Hg 2 + is achieved. The proposed nanosensor provides a novel approach for rapid, flexible, and sustainable detection of viral RNA and Hg 2 + , exhibiting great potential for routine preliminary coronavirus disease tests, epidemic control, and environmental monitoring.

Two-dimensional transition-metal dichalcogenides (TMDs) have attracted widespread interests owing to their attractive physical and chemical properties. In particular, they are especially attractive in the field of electrochemical biosensors. In this study, the properties of TMDs ((molybdenum sulfide (MoS2), molybdenum diselenide (MoSe2) and molybdenum telluride (MoTe2)) on the glucose sensing were explored and compared. Exfoliated MoS2, MoSe2 and MoTe2 nanosheets with basically the same size were fabricated through controlling the ultrasonic power. The structure and morphological characteristics of MoS2, MoSe2 and MoTe2 were examined through scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and powder X-ray diffractometer. Electrochemical properties were analyzed through cyclic voltammetry and differential pulse voltammetry. Results showed that all the three kinds of TMDs can enhance the electroconductibility of the electrodes. When incorporated into the construction of electrochemical biosensors for glucose detection, all of the three kinds of exfoliated TMDs modified electrodes possessed achieved analytical requirements of selectivity, wide linear ranges, as well as low limits of detection and quantification. In particular, MoS2-based biosensor generated a higher specificity and lower detection limit than that of MoSe2 and MoTe2. This is imperative to showcase the real potential of TMDs in electrochemical biosensors.