Highly stretchable and strain-insensitive fiber-based wearable electrochemical biosensor to monitor glucose in the sweat

Development of high-performance fiber-shaped wearable sensors is of great significance for next-generation smart textiles for real-time and out-of-clinic health monitoring. The previous focus has been mainly on monitoring physical parameters such as pressure and strains associated with human activities. Development of an enzyme-based non-invasive wearable electrochemical sensor to monitor biochemical vital signs of health such as the glucose level in sweat has attracted increasing attention recently, due to the unmet clinical needs for the diabetic patients. To achieve this, the key challenge lies in the design of a highly stretchable fiber with high conductivity, facile enzyme immobilization, and strain-insensitive properties. Herein, we demonstrate an elastic gold fiber-based three-electrode electrochemical platform that can meet the aforementioned criteria toward wearable textile glucose biosensing. The gold fiber could be functionalized with Prussian blue and glucose oxidase to obtain the working electrode and modified by Ag/AgCl to serve as the reference electrode; and the nonmodified gold fiber could serve as the counter electrode. The as-fabricated textile glucose biosensors achieved a linear range of 0–500 μM and a sensitivity of 11.7 μA mM–1 cm–2. Importantly, such sensing performance could be maintained even under a large strain of 200%, indicating the potential applications in real-world wearable biochemical diagnostics from human sweat

Highly Stretchable Fiber-Shaped Supercapacitors Based on Ultrathin Gold Nanowires with Double-Helix Winding Design

The ability of developing highly durable fiber-shaped electronic devices is crucial for next-generation smart textile electronics. Past several years have witnessed encouraging progress made in stretchable fiber-shaped supercapacitors using carbon materials, transition metal oxides, and conducting polymers. Here, we report a dry-spun strategy to produce scalable ultrathin gold nanowire-based fibers, which can lead to highly stretchable fiber-based supercapacitors using a double-helix winding design. Hildebrand’s and Hansen’s solubility parameters of gold nanowire-binding oleylamine ligands match those of styrene-ethylene/butylene-styrene and tetrahydrofuran, enabling the formation of high-quality dry-spun fibers. In conjunction with conductivity enhancement by electroless plating and pseudocapacitance by polyaniline, we obtained fiber-shaped supercapacitors stretchable up to 360% with a capacitance of 16.80 mF cm–2. The capacitance retention is about 85% after 2000 cycles of 0–200–0% stretching/releasing. Our fiber capacitors can be woven into an everyday glove, with negligible capacitance changes for normal finger movements

Photoelectrochemical Conversion from Graphitic C₃N₄ Quantum Dot Decorated Semiconductor Nanowires

Despite the recent progress of developing graphitic carbon nitride (g-C₃N₄) as a metal-free photocatalyst, the synthesis of nanostructured g-C₃N₄ has still remained a complicated and time-consuming approach from its bulk powder, which substantially limits its photoelectrochemical (PEC) applications as well as the potential to form composites with other semiconductors. Different from the labor-intensive methods used before, such as exfoliation or assistant templates, herein, we developed a facile method to synthesize graphitic C₃N₄ quantum dots (g-CNQDs) directly grown on TiO₂ nanowire arrays via a one-step quasi-chemical vapor deposition (CVD) process in a homemade system. The as-synthesized g-CNQDs uniformly covered over the surface of TiO₂ nanowires and exhibited attractive photoluminescence (PL) properties. In addition, compared to pristine TiO₂, the heterojunction of g-CNQD-decorated TiO₂ nanowires showed a substantially enhanced PEC photocurrent density of 3.40 mA/cm² at 0 V of applied potential vs Ag/AgCl under simulated solar light (300 mW/cm²) and excellent stability with ∼82% of the photocurrent retained after over 10 h of continuous testing, attributed to the quantum and sensitization effects of g-CNQDs. Density functional theory calculations were further carried out to illustrate the synergistic effect of TiO₂ and g-CNQD. Our method suggests that a variety of g-CNQD-based composites with other semiconductor nanowires can be synthesized for energy applications