Investigation for regulation of DNA-programmed nanoflower-shaped gold nanozymes and its multi-mode detection of ascorbic acid.

As nanozymes are more advantageous than natural enzymes, the development of their excellent catalytic properties has become a research hotspot. However, it is still challenging to design and adjust the morphology and structure in order to obtain nanozymes with better enzyme-like activities. Here, we report a DNA programming seed growth strategy, which successfully generate gold nanozymes with a flower-like morphology and enhanced peroxidase-like activity through precise regulation by coding a 30-base polyA sequences (A30-AuNFs). A30-AuNFs provide excellent peroxidase-like (POD) activity for the substrates 3,3'-5,5'tetramethylbenzidine (TMB) and H2O2, of which the Michaelis-constant (Km) value of TMB is approximately 5 times lower than that of horse radish peroxidase (HRP), and hydroxyl radicals (•OH) was the main reactive oxygen species (ROS) in the oxidation reaction of TMB. Based on the good colorimeter performance of A30-AuNFs and the excellent photothermal conversion performance of TMB oxidation products (ox TMB), the multi-mode detection method of Ascorbic acid (AA) has been successfully established, including colorimetric, photothermal and paper-based methods, with corresponding detection limits of 1.14 μM (colorimetric mode), 19.11 μM (photothermal mode) and 4.74 μM (paper-based mode). This work provides an effective strategy for regulating the preparation of the gold nanozymes and established the multi-mode detection of AA.