Hydroperoxyl intermediate is a vital component in the mechanism of electrochemical oxygen reduction reaction (ORR) and several other important chemical reactions. The selectivity and kinetics of ORR are controlled by the energetics of *OOH intermediate (* represents the active site). The present work integrates iron phthalocyanine (FePc) with sulfonic acid-functionalized multiwalled carbon nanotubes (MWCNTs-SO 3 H). The resulting composite (FePc@MWCNTs-SO 3 H) demonstrates significantly improved kinetics and higher four-electron selectivity for the electrochemical reduction of oxygen compared to its counterpart without functionalization (FePc@MWCNTs) in alkaline, neutral, and acidic media. Based on the in situ electrochemical shell-isolated nanoparticle-enhanced Raman spectroscopy (EC-SHINERS) results and DFT calculations, it is proposed that sulfonate groups are involved in the water-assisted hydrogen-bonding interaction with the FeOOH intermediate. This interaction causes a substantial increase in selectivity and kinetics of ORR. Apart from the ORR, the findings of the current work strongly recommend that the functional groups on carbon support can be manipulated to get improved kinetics and selectivity of several important chemical transformations.

Two-dimensional nanostructures (2DNS) attract tremendous interest and have emerged as potential materials for a variety of applications, including biomolecule sensing, due to their high surface-to-volume ratio, tuneable optical and electronic properties. Advancements in the engineering of 2DNS and associated technologies have opened up new opportunities. Surface-enhanced Raman scattering (SERS) is a rapid, highly sensitive, non-destructive analytical technique with exceptional signal amplification potential. Several structurally and chemically engineered 2DNS with added advantages (e.g., π–π* interaction), over plasmonic SERS substrates, have been developed specifically towards biomolecule sensing in a complex matrix, such as biological fluids. This review focuses on the recent developments of 2DNS-SERS substrates for biomolecule sensor applications. The recent advancements in engineered 2DNS, particularly for SERS substrates, have been systematically surveyed. In SERS substrates, 2DNS are used as either a standalone signal enhancer or as support for the dispersion of plasmonic nanostructures. The current challenges and future opportunities in this synergetic combination have also been discussed. Given the prospects in the design and preparation of newer 2DNS, this review can give a critical view on the current status, challenges and opportunities to extrapolate their applications in biomolecule detection.

Investigating the behavior of analytes at the electrode surface is crucial in understanding the electrochemical and electrocatalytic reactions. Although Surface Enhanced Raman Scattering (SERS) is sensitive to minor chemical changes in the analyte, it is not widely used to study the reaction mechanisms on nonplasmonic surfaces because of the interference from plasmonic SERS substrates. In this study, we have investigated the redox reaction of Nile Blue A on a glassy carbon surface using pinhole-free silica-coated silver nanoparticles for Raman signal enhancement. The silver nanostructures were synthesized by a chemical reduction method, and the quality of the silica layer was confirmed using microscopic and electrochemical method. The in situ spectroelectrochemical data reveals the catalytic interference from silver which considerably alters the native reaction mechanism. The pinhole-free silica layer prevents the hot electron transfer and yields an interference-free enhancement to the Raman signals.