Ammonium Ion-Sensing Skin Patch Based on Three-Dimensional Nanoarchitecture of Polystyrenesulfonate:Polyaniline/Copper Microflowers Deposited on Flexible Graphene Electrodes

A flexible ammonium ion-sensing skin patch was developed based on a three-dimensional (3D) polystyrenesulfonate:polyaniline/copper microflower (PSS:PANI/CuMF) nanoarchitecture deposited on a flexible graphene electrode. The hierarchical 3D nanostructure integrates CuMF with a PSS:PANI network, providing a high-density electroactive surface, enhanced charge-transfer pathways, and stable ion-doping sites for NH4+ detection. The transducer was fabricated via a two-step electrochemical process and characterized using SEM and FTIR, confirming the formation of nanostructured CuMF and uniform nanopolymer coating. Coupled with adsorptive stripping voltammetry (AdSV), the sensor exhibited dual linear ranges (0.01–20 mM and 20–60 mM), high sensitivity (127.9 μA mM–1 cm–2 in the low range), and a low detection limit of 3.3 μM. The nanoscale PSS:PANI framework enables reversible NH4+ doping/dedoping through fixed sulfonate sites, while CuMF enhances electron-transfer kinetics. Integration into a wearable patch platform demonstrated reliable detection of NH4+ in artificial sweat using a skin-mimicking model. This work presents a nanostructured, flexible electrochemical platform for noninvasive ammonium monitoring, with potential applications in wearable bioanalysis.