Sweat pH monitoring is a routine indicator in wearable biotechnology. The state-of-the-art wearable pH sensors mostly rely on organic materials but face the risk of biological toxicity. WO 3 is a typical H + -sensitive inorganic material with chemical stability, biocompatibility, and low cost but low sensitivity and slow response. Lattice H + intercalation is herein proposed as an efficient approach that can greatly improve the sensitivity and selectivity of WO 3based pH sensors. Specifically, lattice H + intercalation can promote WO 3 from the monoclinic phase to cubic phase, which enhances the ion exchange capacity between WO 3 and H + . The resistance decreases more than two orders of magnitudes, which improves the interfacial charge transport. The occupancy of lattice H + leads to ion exchange only with H + , thus increasing the H + recognition. The intercalated H x WO 3 exhibits much improved sensitivity, reversibility, and response time. Additionally, the H x WO 3 is integrated with a solid reference electrode on a miniaturized chip for wearable sweat pH monitoring. The pH sensor exhibits good potential response even at curving over 270°. On-body sweat pH measurments show high accuracy compared with ex situ analyses. This work emphasizes the concept of lattice proton intercalation to regulate the H + recognition of solid contacts.

Current solid potentiometric ion sensors mostly rely on polymeric-membrane-based, solid-contact, ion-selective electrodes (SC-ISEs). However, anion sensing has been a challenge with respect to cations due to the rareness of anion ionophores. Classic metal/metal insoluble salt electrodes (such as Ag/AgCl) without an ion-selective membrane (ISM) offer an alternative. In this work, we first compared the two types of SC-ISEs of Cl− with/without the ISM. It is found that the ISM-free Ag/AgCl electrode discloses a comparable selectivity regarding organic chloride ionophores. Additionally, the electrode exhibits better comprehensive performances (stability, reproducibility, and anti-interference ability) than the ISM-based SC-ISE. In addition to Cl−, other Ag/AgX electrodes also work toward single and multi-valent anions sensing. Finally, a flexible Cl− sensor was fabricated for on-body monitoring the concentration of sweat Cl− to illustrate a proof-of-concept application in wearable anion sensors. This work re-emphasizes the ISM-free SC-ISEs for solid anion sensing.

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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.

Reaction of a imidazole phenol ligand 4-(imidazlo-1yl)phenol (L) with 3d metal salts afforded four complexes, namely, [Ni(L) 6 ]·(NO 3 ) 2 (1), [Cu(L) 4 (H 2 O)]·(NO 3 ) 2 ·(H 2 O) 5 (2), [Zn(L) 4 (H 2 O)]·(NO 3 ) 2 ·(H 2 O) (3), and [Ag 2 (L) 4 ]·SO 4 (4). All complexes are composed of monomeric units with diverse coordination arrangements and corresponding anions. All the hydroxyl groups of monomeric cations are used as hydrogen-bond donors to form O-H···O hydrogen bonds. However, the coordination habit of different metal ions produces various supramolecular structures. The Ni II atom shows octahedral arrangement in 1, featuring a 3D twofold inclined interpenetrated network through O-H···O hydrogen bond and π-π stacking in-* Dr. L.-L. Zheng E-Mail: zsuzhengll@163.com [a] Guangzhou Vocational College of Technology and Business 511442,