Building multiple cross-links or networks is a favorable way of diversifying applications of the hydrogels, which is also available for the organohydrogels prepared via the solvent replacement way. However, the situations become more complicated for organohydrogels due to the presence of replaced solvents. Therefore, the correlations between the multiple cross-links and final performance need to be better understood for the organohydrogels, which is vital for tailoring their inherent properties to expand final application scenarios. Polyacrylamide (PAM)/poly(vinyl alcohol) (PVA)/MXene composite organohydrogels with dual cross-links, namely, the covalently cross-linked PAM chains as the primary network and the physically cross-linked PVA/PAM chains with MXene particles as the secondary cross-links, were developed here for the study. The occurrence of the secondary cross-links plays multiple roles as sacrificial units endowing the system with ultrastretchability with an excellent strain–resistance effect and as temperature-sensitive units endowing the system with thermosensation ability with an outstanding temperature coefficient of resistance. Thus, the optimized sample can be used as a strain sensor with excellent environmental tolerance for detecting human motion as a pressure sensor to probe compression with weak deformation and as a thermal sensor to capture environmental temperature changes. This work provides valuable information on developing organohydrogels with superior performance for multimodal sensors.

Bilayer hydrogel-based actuators have attracted much interest because inhomogeneous structures are easily constructed in hydrogels. We used three kinds of polysaccharides, including anionic carboxymethyl cellulose (CMC), cationic chitosan (CS), and amphoteric carboxymethyl chitosan (CMCS), as both structure-constructing units and actuation-controlling units in this work to fabricate physically crosslinked poly(vinyl alcohol) bilayer hydrogels. The spatial heterogeneity was tuned by changing the types and concentrations of polysaccharides in different layers, to regulate pH-and humidity-driven actions of bilayer hydrogels. Based on the distortion of the ionic channel during the humidity-motivated deformation of bilayer hydrogels, a two-inone flexible device integrating a humidity-driven actuator and humidity-responsive sensor was then developed, which could detect the alterations of environmental humidity in real time. Moreover, good tensile toughness and interfacial bonding as well as the strain−resistance effect endowed the bilayer hydrogels with the capability of identifying human motion as a strain sensor, unlocking more application scenarios. This work provides an overall insight into the heterogeneity regulation of bilayer hydrogels using polysaccharides as stimulus-responsive units and also proposes an interesting strategy of manufacturing hydrogel-based flexible devices with both actuating and sensing capabilities.

Biodegradable polymersomes that can potentially be employed in drug delivery systems were fabricated by blending poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide) (PLLA-PEG-PLLA) and poly(D-lactide)-b-poly(ethylene glycol)-b-poly(Dlactide) (PDLA-PEG-PDLA) block copolymers in a weight ratio of 1:1 in an aqueous solution. A series of amphiphilic PLLA-PEG-PLLA and PDLA-PEG-PDLA triblock copolymers were synthesized with different hydrophobic chain lengths through ring-opening polymerization. The self-assembly of pure PLLA-PEG-PLLA and an equimolar mixture of enantiomers of PLLA-PEG-PLLA and PDLA-PEG-PDLA was investigated by transmission electron microscopy, X-ray diffraction, and dynamic light scattering. Various nanostructures including spherical micelles, worm-like micelles, and vesicles were obtained by controlling the hydrophobic chain length and the incubation temperature. In the pure PLLA-PEG-PLLA systems, the hydrophobic−hydrophilic balance dominated the self-assembled morphologies. In equimolar enantiomer mixtures, self-assembled morphologies were greatly affected by the formation of the PLLA-PDLA stereocomplex (SC). There was an inverse correlation between the SC crystallinity and the curvature of the selfassembled structuresthe higher the SC content, the smaller the curvature. This rule was not applicable when the SC content was too high (≳50%), which produced spherical micelles as the main nanostructures. Since the SC-induced self-assembly could be controlled by changing the incubation temperature, the polymersomes can potentially be used in many applications, such as nanoreactors and nanovehicles.

The initial Si/Al ratio of supports influences the active metal composition and dispersion, acidity of NiMoC/Hβ-x catalysts, and performance of aromatic hydrogenation.

For applications in the fields of biological imaging and chemical sensing, fluorescent carbon nanodots (CNDs) have excellent possibilities because of their unique structure and performance. In this work, we synthesized a series of nitrogen-doped CNDs (N-CNDs) with different fluorescent emission, ranging from blue to yellow, via one-pot solvothermal strategy. Citric acid and urea were employed as the precursors. Formamide, ethanol and N,N-dimethylformamide were used as the solvent, respectively. The excitation-dependent emission and the optimal emission were measured with the ultraviolet–visible and photoluminescence spectra. The morphology and chemical structure of the prepared N-CNDs were characterized via high-resolution transmission electron microscope (HRTEM), atomic force microscope (AFM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, carbon nuclear magnetic resonance (13C NMR) spectroscopy, and so forth. The influence of reaction time, temperature, and type of solvent on the structure of N-CNDs were systematically investigated. The photoluminescence mechanism was discussed based on the chemical structure, the crystallinity and the sp2/sp3 carbon ratio of the prepared N-CNDs. In addition, a biocompatible amphiphilic copolymer mPEG-b-PLLA was synthesized and self-assembled in an aqueous system. The prepared N-CNDs were introduced into the polymer self-assemblies as a fluorescent probe by an in situ grafting method. The fluorescence imaging performance of N-CNDs in the polymer self-assemblies was investigated by comparing with organic fluorescent dye coumarin-6.