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Conductive hydrogels have been widely studied in many fields, such as wearable electronic materials, soft robotics, and human medical monitoring, due to their good water retention, elasticity, softness, flexibility, and sensory properties. However, it is still a great challenge to make all-in-one hydrogels with good mechanical properties, rapid self-healing ability, self-adhesion, and sensitive sensing abilities like natural skin. Thus, a multifunctional ionic conductive hydrogel containing hydroxypropyl methylcellulose/acrylic acid/acrylamide/tea polyphenol and Al3+ (HPMC/AA/AM/TP/Al3+) was prepared by a simple method. Owing to multiple dynamic noncovalent interactions, such as hydrogen bonds, electrostatic interactions, and metal coordination, in the ionic conductive hydrogel network, the hydrogel exhibited excellent mechanical properties (breaking stress: 0.032 MPa, toughness: 0.689 MJ m−3), skin-like elastic modulus (0.065 kPa), and stretchability (2225%). The electric conductivity could rapidly self-heal in a dramatically short period of time (5.1 s). Stress and strain self-healing efficiencies reached 93.8% and 99.4% in 60 min, respectively. Its adhesion strengths on wood and pigskin were as high as 13.12 kPa and 9.98 kPa, respectively, due to phenolic hydroxyl groups in TP. Moreover, the hydrogel exhibits good conductivity (3.03 S m−1). Hence, the hydrogel was assembled as a human motion sensor and high sensitivity (GF: 5.13) was obtained over the strain range of 200–1000% with a fast response/recovery time (response time: 0.4 s; recovery time: 0.75 s). Furthermore, the hydrogel sensor can monitor various human movements, including joint movement and vocal cord vibration. The as-prepared hydrogel achieved multiple functions in a single hydrogel system (all-in-one) and has great potential for application in flexible wearable sensors. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs) are battery-type supercapacitor electrode materials with application potential due to their abundant active metal sites and surface functional groups. The traditional LDH structure easily aggregates and collapses. In this work, a stable cobalt zeolite imidazole framework (Co-ZIF) was used as the derived template to grow LDH nanosheets in situ to increase the contact area with the electrolyte, and polyaniline (PANI) acted as a conductive bridge to provide a rapid charge transfer pathway. The fabricated NiCo-LDH@PANI hollow structure demonstrated a specific capacity of 1315 C g−1 at 1 A g−1 and achieved a rate capacity of 951 C g−1 at 20 A g−1. Furthermore, the battery–supercapacitor hybrid device (NiCo-LDH@PANI//AC) exhibited an high energy density of 66.2 W h kg−1 at a power density of 800 W kg−1 with 95.5% capacitance retention after 20 000 cycles. [ABSTRACT FROM AUTHOR]

Conductive hydrogels have attracted the attention of researchers due to their similarity to biological tissues and potential application in flexible wearable electronic devices. However, fabrication of hydrogels with high sensitivity in combination with mechanical stretchability and biocompatibility via a simple method remains a great challenge. Here, a novel multifunctional hydrogel with high tensile properties, self-adhesion, strain sensitivity and conductivity is prepared by introducing tannic acid (TA) coated graphitized carbon nanotubes (CNTs) into the network structure composed of polyacrylic acid (PAA) and carboxymethyl cellulose (CMC). The chemical cross-linking constructed the framework for the network of the hydrogel. The dynamic physical cross-linking of the multiple hydrogen bonding among TA, CMC, and PAA together with the π–π stacking between CNTs could dissipate energy effectively. The hybrid of chemical and physical cross-linking endowed the hydrogel with excellent toughness, high stretchability, and self-adhesion. The strain reached 1385% of its original length and self-adhesion force on the wood can reach 16.65 kPa. When the carbon nanotube content was 0.6 wt%, the conductivity of the hydrogel reached 5.13 S m−1. Furthermore, the resultant hydrogel as a strain sensor to detect various physiological human movements was investigated in detail. The results indicated that the multifunctional hydrogel has high strain sensitivity and fast response ability. Therefore, the resultant hydrogel has potential application as a strain sensor for human movement monitoring. [ABSTRACT FROM AUTHOR]

A triazine-based fluorescent COF (MaTa-COF) was synthesized from inexpensive reactants. The obtained MaTa-COF has a large BET-specific surface area of 621.15 m2 g−1 and can be used as a highly sensitive Fe3+ fluorescent probe with a wide linear range of 0–250 μM and a low detection limit of 6.18 × 10−2 μM (Ksv = 2.34 × 108 M−1). Furthermore, the probe presented a good recyclability performance. [ABSTRACT FROM AUTHOR]

Two new polyimide based porous covalent organic frameworks (PI-COF 201 and PI-COF 202) were synthesized in high yields by directly heating mixtures of melamine and pyromellitic dianhydride and naphthalenetetracarboxylic dianhydride in a N2 atmosphere, respectively. Their structures and properties were characterized using elemental analysis, Fourier transform infrared spectra, X-ray photoelectron spectroscopy, X-ray powder diffraction, N2 adsorption–desorption and scanning electron microscopy and their fluorescence properties were studied in detail. These two COFs emitted strong fluorescence in appropriate solvents that originated from the π* → n transition caused by the high electro-delocalization and inherently rigid structure of the COF materials. The strong quenching effects of Fe3+ on the fluorescence of the COFs allowed selective chemosensing for Fe3+. [ABSTRACT FROM AUTHOR]

Two new polyimide based porous covalent organic frameworks (PI-COF 201 and PI-COF 202) were synthesized in high yields by directly heating mixtures of melamine and pyromellitic dianhydride and naphthalenetetracarboxylic dianhydride in a N2 atmosphere, respectively. Their structures and properties were characterized using elemental analysis, Fourier transform infrared spectra, X-ray photoelectron spectroscopy, X-ray powder diffraction, N2 adsorption–desorption and scanning electron microscopy and their fluorescence properties were studied in detail. These two COFs emitted strong fluorescence in appropriate solvents that originated from the π* → n transition caused by the high electro-delocalization and inherently rigid structure of the COF materials. The strong quenching effects of Fe3+ on the fluorescence of the COFs allowed selective chemosensing for Fe3+. [ABSTRACT FROM AUTHOR]