Simultaneous detection of SARS-CoV-2 S1 protein by using flexible electrochemical and Raman enhancing biochip

Flexible laser-scribed graphene (LSG) substrates with gold nanoislands have been developed as biochips for in situ electrochemical (EC) and surface-enhanced Raman scattering (SERS) biodetection (biomolecules and viral proteins). A flexible biochip was fabricated using CO2 laser engraving polyimide (PI) films to form a 3D porous graphene-like nanostructure. Gold nanoislands were deposited on the LSG substrates to enhance the intensity of the Raman signals. Moreover, the addition of auxiliary and reference electrodes induced a dual-function EC-SERS biochip with significantly enhanced detection sensitivity. The biochip could selectively and easily capture SARS-CoV-2 S1 protein through the SARS-CoV-2 S1 antibody immobilized on EC-SERS substrates using 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The grafted antibody specifically bound to SARS-CoV-2, resulting in a significant increase in the SERS signal of the target analyte. The limit of detection (LOD) of the SARS-CoV-2 S1 protein was 5 and 100 ng/mL by using EC and SERS detection, respectively. Although the LOD of the SARS-CoV-2 S1 protein detected using SERS is only 100 ng/mL, it can provide fingerprint information for identification. To improve the LOD, EC detection was integrated with SERS detection. The three-electrode detection chip enables the simultaneous detection of SERS and EC signals, which provides complementary information for target identification. The dual-functional detection technology demonstrated in this study has great potential for biomedical applications, such as the rapid and sensitive detection of SARS-CoV-2.

Tin dioxide-based nanomaterials as anodes for lithium-ion batteries

The development of new electrode materials for lithium-ion batteries (LIBs) has attracted significant attention because commercial anode materials in LIBs, like graphite, may not be able to meet the increasing energy demand of new electronic devices. Tin dioxide (SnO2) is considered as a promising alternative to graphite due to its high specific capacity. However, the large volume changes of SnO2 during the lithiation/delithiation process lead to capacity fading and poor cycling performance. In this review, we have summarized the synthesis of SnO2-based nanomaterials with various structures and chemical compositions, and their electrochemical performance as LIB anodes. This review addresses pure SnO2 nanomaterials, the composites of SnO2 and carbonaceous materials, the composites of SnO2 and transition metal oxides, and other hybrid SnO2-based materials. By providing a discussion on the synthesis methods and electrochemistry of some representative SnO2-based nanomaterials, we aim to demonstrate that electrochemical properties can be significantly improved by modifying chemical composition and morphology. By analyzing and summarizing the recent progress in SnO2 anode materials, we hope to show that there is still a long way to go for SnO2 to become a commercial LIB electrode and more research has to be focused on how to enhance the cycling stability.

Insight into the capacity fading of layered lithium-rich oxides and its suppression via a film-forming electrolyte additive

The capacity fading of layered lithium-rich oxide (Li_1.2Mn_0.54Ni_0.13Co_0.13O₂, LLO) cathodes greatly hinders their practical application in next generation lithium ion batteries. It has been demonstrated in this work that the slow capacity fading of a LLO/Li cell within 120 cycles is mainly caused by electrolyte oxidation and LLO phase transformation with Ni dissolution. After 120 cycles, the dissolution of Mn becomes worse than that of Ni, leading to structural destruction of the generated spinel phase structure of LLO and fast capacity fading. Tripropyl borate (TPB) is proposed as a film-forming electrolyte additive, which shows a great capability to enhance the cycling stability of LLO/Li, with a capacity retention improvement from 21% to 78% after 250 cycles at 0.5C. Electrochemical and physical characterization demonstrated that the TPB-derived SEI film shows great capability to suppress electrolyte oxidation and the structural destruction of the generated spinel phase of LLO.

The capacity fading of layered lithium-rich oxide (Li_1.2Mn_0.54Ni_0.13Co_0.13O₂, LLO) cathodes greatly hinders their practical application in next generation lithium ion batteries.