Conductive hydrogels have emerged as promising candidate materials for fabricating wearable electronics because of their fascinating stimuli-responsive and mechanical properties. However, the inherent instability of hydrogels seriously limits their application scope. Herein, the stable, ultrastretchable (upon to 1330% strain), self-healing, and transparent organohydrogel was exploited as a novel gas-responsive material to fabricate NH3 and NO2 gas sensors for the first time with extraordinary performance. A facile solvent substitution method was employed to convert the unstable hydrogel into the organohydrogel with a remarkable moisture retention (avoid drying within a year), frost resistance (freezing point below −130 °C), and unimpaired mechanical and gas sensing properties. First-principles simulations were performed to uncover the mechanisms of antidrying and antifreezing effects of organohydrogels and the interactions between NH3/NO2 and organohydrogels, revealing the vital role of hydrogen bonds in enhancing the stability and the adsorption of NH3/NO2 on the organohydrogel. The organohydrogel gas sensor displayed high sensitivity, ultralow theoretical limit of detection (91.6 and 3.5 ppb for NH3 and NO2, respectively), reversibility, and fast recovery at room temperature. It exhibited the capabilities to work at a highly deformed state with nondegraded sensing performance and restore all the electrical, mechanical, and sensing properties after mechanical damage. The gas sensing mechanism was understood by considering the gas adsorption on functional groups, dissolution in the solvent, and the hindering effect on the transport of ions.

With the advent of the 5G era and the rise of the Internet of Things, various sensors have received unprecedented attention, especially wearable and stretchable sensors in the healthcare field. Here, a stretchable, self-healable, self-adhesive, and room-temperature oxygen sensor with excellent repeatability, a full concentration detection range (0-100%), low theoretical limit of detection (5.7 ppm), high sensitivity (0.2%/ppm), good linearity, excellent temperature, and humidity tolerances is fabricated by using polyacrylamide-chitosan (PAM-CS) double network (DN) organohydrogel as a novel transducing material. The PAM-CS DN organohydrogel is transformed from the PAM-CS composite hydrogel using a facile soaking and solvent replacement strategy. Compared with the pristine hydrogel, the DN organohydrogel displays greatly enhanced mechanical strength, moisture retention, freezing resistance, and sensitivity to oxygen. Notably, applying the tensile strain improves both the sensitivity and response speed of the organohydrogel-based oxygen sensor. Furthermore, the response to the same concentration of oxygen before and after self-healing is basically the same. Importantly, we propose an electrochemical reaction mechanism to explain the positive current shift of the oxygen sensor and corroborate this sensing mechanism through rationally designed experiments. The organohydrogel oxygen sensor is used to monitor human respiration in real-time, verifying the feasibility of its practical application. This work provides ideas for fabricating more stretchable, self-healable, self-adhesive, and high-performance gas sensors using ion-conducting organohydrogels.

Respiratory monitoring plays a pivotal role in health assessment and provides an important application prospect for flexible humidity sensors. However, traditional humidity sensors suffer from a trade-off between deformability, sensitivity, and transparency, and thus the development of high-performance, stretchable, and low-cost humidity sensors is urgently needed as wearable electronics. Here, ultrasensitive, highly deformable, and transparent humidity sensors are fabricated based on cost-effective polyacrylamide-based double network hydrogels. Concomitantly, a general method for preparing hydrogel films with controllable thickness is proposed to boost the sensitivity of hydrogel-based sensors due to the extensively increased specific surface area, which can be applied to different polymer networks and facilitate the development of flexible integrated electronics. In addition, sustainable tapioca rich in hydrophilic polar groups is introduced for the first time as a second cross-linked network, exhibiting excellent water adsorption capacity. Through the synergistic optimization of structure and composition, the obtained hydrogel film exhibits an ultrahigh sensitivity of 13,462.1%/%RH, which is unprecedented. Moreover, the hydrogel film-based sensor exhibits excellent repeatability and the ability to work normally under stretching with even enhanced sensitivity. As a proof of concept, we integrate the stretchable sensor with a specially designed wireless circuit and mask to fabricate a wireless respiratory interruption detection system with Bluetooth transmission, enabling real-time monitoring of human health status. This work provides a general strategy to construct high-performance, stretchable, and miniaturized hydrogel-based sensors as next-generation wearable devices for real-time monitoring of various physiological signals.

No abstract

To develop new lanthanide single-molecule m a g n e t s ( S M M s ) , t w o n e w c o m p l e x e s o f [Dy 2 (MeOH) 2 (HL 1 ) 2 (NO 3 ) 2 ]•2MeOH (1) and [Dy 6(2) were obtained by reacting Dy(NO) 3 •6H 2 O with 3-amino-1,2-propanediol in the presence of 2-hydroxynaphthaldehyde for 1 and by reacting DyCl 3 •6H 2 O with 1,1-di-(hydroxymethyl)ethylamine in the presence of 2-hydroxynaphthaldehyde for 2, respectively, in which the Schiff base ligands of 3-(((2-hydroxynaphthaen-1-yl)methylene)amino)propane-1,2-diol (H 3 L 1 ) and 2-(β-naphthalideneamino)-2-(hydroxylmethyl)-1-propanol (H 3 L 2 ) were in situ formed. The two Dy(III) ions in 1 are linked by two O alkoxy atoms of two (HL 1 ) 2− ligands to build a dinuclear skeleton. Complex 2 presents a nearly planar hexanuclear skeleton constructed from four edge-shared triangular Dy 3 units with the two peripheral Dy 3 units consolidated by two μ 3 -O bridges and the two central Dy 3 units consolidated by one μ 3 -O bridge. Obviously, they exhibit a different topological arrangement resulting from the linkage of the Schiff base ligands. Both of them are typical SMMs under zero dc fields, with a U eff /k B value of 34 K for 1 and 40 K for 2, respectively. Multiple processes are involved in the relaxation processes of 1 and 2. The different SMM performances of the two titled complexes reveal a tuning effect of Schiff base ligands through tuning the coordination environments and topological arrangements of dysprosium(III) ions, which is supported by the theoretical calculations.

No abstract

During the long‐term operation of temperature sensors, periodical calibration is required to achieve accurate readings, which usually requires bulky and costly heating facilities for calibration. Herein, a new kind of self‐calibrated thermistors using embedded microheaters as a self‐heating platform are proposed for in situ, convenient, cost‐effective, and fast self‐calibration. Furthermore, the thermal sensing properties of 3D reduced graphene oxide hydrogel (RGOH) is explored for the first time based on this microheater platform. It is found that the a 3D sulfonated RGOH (S‐RGOH) based thermistor displays high sensitivity (2.04% K−1), extraordinary resolution (0.2 °C), a broad detection range (26–101 °C), good repeatability, and stability. The thermal sensitivity of S‐RGOH is far superior to that of pristine RGOH, revealing the remarkable role of chemical modification in enhancing temperature sensing performance. In addition to self‐calibration, the microheaters are also used for characterizing temperature‐dependent properties and thermal annealing of S‐RGOH in situ. The thermal sensing mechanism is proposed and the high sensitivity is discussed by considering the abundant functional groups, defects, and 3D porous structure of S‐RGOH. The flexible S‐RGOH thermistor fabricated on a liquid crystal polymer substrate is immune to mechanical flexion, allowing for various practical applications in future wearable electronics.

Summary In this study, a novel, highly efficient, and magnetically responsive demulsifier, namely, Fe3O4@hyperbranched polyamidoamine‐graphene oxide (MKh‐GO), was synthesized. First, Fe3O4 was synthesized, and Fe3O4 was wrapped in hyperbranched polyamidoamine (h‐PAMAM) by γ‐(methacryloyl oxide) propyltrimethoxysilane (kh570), and MKh‐GO was synthesized by condensation reaction. The chemical structures and morphologies of the samples were characterized by Fourier transform‐infrared spectroscopy (FTIR) and transmission electron microscope (TEM). The magnetic response of the sample was tested by vibrating sample magnetometer (VSM). The MKh‐GO was used to separate crude oil in water emulsion; the effects of MKh‐GO dosage, temperature, and pH value on the demulsifying efficiency were investigated. Possible demulsification mechanisms were summarized. The results show that MKh‐GO is successfully synthesized, and MKh‐GO exhibits excellent demulsification performance; MKh‐GO is recycled seven times, and the demulsification efficiency is 97%.