Abstract
Core-shell nanomaterials have received promising attention in chemical sensing due to their potential as enzyme mimics, particularly with peroxidase-like properties. However, osmium (Os)-based core-shell systems have not been extensively explored for their role in sensing and other potential applications. Herein, a leap forward approach is successfully devised to strategically design Au@Os nanoparticles (NPs) by tuning the molar ratios of Au@Os (1:1, 1:3, 1:6, 1:9) and investigating their peroxidase-like activity and sensitivity towards cysteine (Cys) detection. The hierarchy in morphological and structural changes were understood with physicochemical characterizations. It is revealed that Au@Os (1:6) NPs, resulted in the development of a well-intact, thick, and homogeneous Os shell around the Au core and possess excellent peroxidase activity to oxidize 3, 3', 5, 5'-tetramethylbenzidine (TMB)-H2O2 system to ox-TMB with a characteristic peak at 652nm. The detection mechanism relies on the inhibition of Au@Os NP catalytic activity by Cys through Os-S bond formation, causing a visible color change from greenish to colorless. The Au@Os NPs demonstrated ultrasensitive visual detection of Cys, with a detection limit of 9.02nM within a linear range of 0-50μM. As a proof-of-concept, the Au@Os colorimetric nanozyme was successfully applied to detect Cys in milk samples, validated by HPLC method. The proposed work will open up new avenues to strategically correlate the morphological changes for point-of-care detection of analytes in foods.
Published Version
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