Cu1.4Mn1.6O4 as a bifunctional transducer for potentiometric Cu2+ solid-contact ion-selective electrode.

Current potentiometric Cu2+ sensors mostly rely on polymer-membrane-based solid-contact ion-selective electrodes (SC-ISEs) that constitute ion-selective membranes (ISM) and solid contact (SC) for respective ion recognition and ion-to-electron transduction. Herein, we report an ISM-free Cu2+-SC-ISE based on Cu-Mn oxide (Cu1.4Mn1.6O4) as a bifunctional SC layer. The starting point is simplifying complex multi-interfaces for Cu2+-SC-ISEs. Specifically, ion recognition and signal transduction have been achieved synchronously by an ion-coupled-electron transfer of crystal ion transport and electron transfer of Mn4+/3+ in Cu1.4Mn1.6O4. The proposed Cu1.4Mn1.6O4 electrode discloses comparable sensitivity, response time, high selectivity and stability compared with present ISM-based potentiometric Cu2+ sensors. In addition, the Cu1.4Mn1.6O4 electrode also exhibits near Nernstian responses toward Cu2+ in natural water background. This work emphasizes an ISM-free concept and presents a scheme for the development of potentiometric Cu2+ sensors.

A Solid-Contact Reference Electrode Based on Silver/Silver Organic Insoluble Salt for Potentiometric Ion Sensing.

Solid-contact ion-selective electrodes are a type of ion measurement devices that have been focused in wearable biotechnology based on the features of miniaturization and integration. However, the solid-contact reference electrodes (SC-REs) remain relatively less focused compared with numerous working (or indicator) electrodes. Most SC-REs in wearable sensors rely on Ag/AgCl reference electrodes with solid electrolytes, for example, the hydrophilic electrolyte salts in polymer matrix, but face the risk of electrolyte leakage. Herein, we report a type of SC-REs based on the silver/silver tetraphenylborate (Ag/AgTPB) organic insoluble electrode. The SC-RE consists of a Ag substrate, a solid contact (AgTPB), and a plasticized poly(vinyl chloride) (PVC) membrane containing the hydrophobic organic salt of tetrabutylammonium tetraphenylborate (TBATPB). The potentiometric measurements demonstrated that the SC-RE of Ag/AgTPB/PVC-TBATPB showed a reproducible standard potential in various electrolytes and disclosed high long-term stability. This SC-RE was further fabricated on a flexible substrate and integrated into all-solid-state wearable potentiometric ion sensor for sweat Cl- monitoring.

An SPR Sensor Chip Based on Peptide-Modified Single-Walled Carbon Nanotubes with Enhanced Sensitivity and Selectivity in the Detection of 2,4,6-Trinitrotoluene Explosives.

In this study, we developed a surface plasmon resonance (SPR) sensor chip based on 2,4,6-trinitrotoluene (TNT) recognition peptide-modified single-walled carbon nanotubes (SWCNTs). The carboxylic acid-functionalized SWCNTs were immobilized on a 3-aminopropyltriethoxysilane (APTES)-modified SPR Au chip surface. Through π-stacking between the aromatic amino acids and SWCNTs, the TNT recognition peptide TNTHCDR3 was immobilized onto the surface of the SWCNTs. The peptide⁻SWCNTs-modified sensor surface was confirmed and evaluated by atomic force microscope (AFM) observation. The peptide⁻SWCNTs hybrid SPR sensor chip exhibited enhanced sensitivity with a limit of detection (LOD) of 772 ppb and highly selective detection compared with commercialized carboxymethylated dextran matrix sensor chips.