Self-assembled natural biomacromolecular fluorescent hydrogels with tunable red edge effects

Biomimetic Wearable Sensors: Emerging Combination of Intelligence and Electronics

Owing to the advancement of interdisciplinary concepts, for example, wearable electronics, bioelectronics, and intelligent sensing, during the microelectronics industrial revolution, nowadays, extensively mature wearable sensing devices have become new favorites in the noninvasive human healthcare industry. The combination of wearable sensing devices with bionics is driving frontier developments in various fields, such as personalized medical monitoring and flexible electronics, due to the superior biocompatibilities and diverse sensing mechanisms. It is noticed that the integration of desired functions into wearable device materials can be realized by grafting biomimetic intelligence. Therefore, herein, the mechanism by which biomimetic materials satisfy and further enhance system functionality is reviewed. Next, wearable artificial sensory systems that integrate biomimetic sensing into portable sensing devices are introduced, which have received significant attention from the industry owing to their novel sensing approaches and portabilities. To address the limitations encountered by important signal and data units in biomimetic wearable sensing systems, two paths forward are identified and current challenges and opportunities are presented in this field. In summary, this review provides a further comprehensive understanding of the development of biomimetic wearable sensing devices from both breadth and depth perspectives, offering valuable guidance for future research and application expansion of these devices.

Quinoxaline-probe embedded injectable fluorogenic hydrogels: Comparative detection of mesitylene in guar gum and i-carrageenan hydrogels

The innovation of novel chemosensor probes for the recognition of trace volatile organic compounds is critical due to their hazardous effect on the environment and human health. A nitro-group integrated quinoxaline probe with a profound discriminative fluorescence 'turn-on' response to mesitylene was fabricated into guar gum and i-carrageenan, two biopolymer-based hydrogel matrices, to develop compact, portable fluorogenic hydrogel sensors and assess their fluorescence properties. A comparative characterization-based analysis of native, probe-associated, and probe-analyte-associated hydrogels, (comprising of FT-IR, XRD, TGA) was investigated to ascertain the overall compatibility of the hydrogel-based sensors for use as a smart rapid detection tool. Dynamic rheological measurements also validated the mechanical stability and robustness of the developed hydrogel matrices. Fluorescence spectroscopic investigations yielded promising results of 0.15 ppm limit of detection (LOD) in guar gum and 0.29 ppm LOD in i-carrageenan hydrogels respectively. FESEM and Fluorescence microscopy studies represented the morphological variations of the hydrogel sensors on interaction with mesitylene. The practical feasibility of the chemosensor in hydrogel form for mesitylene detection in the vapor phase was also explored. Probe-embedded hydrogels with injectable property was shown, depicting its use as security ink for information encryption functions. This approach of incorporating chemosensors into biobased hydrogel networks has the potential to broaden its opportunities in the field of chemical, biomedical, and environmental sensing sectors.

Fabrication of lignin reinforced hybrid hydrogels with antimicrobial and self-adhesion for strain sensors

Ionic conductive hydrogels prepared from various biological macromolecules are ideal materials for the manufacture of human motion sensors from the perspective of resource regeneration and environmental sustainability. However, it is still challenging to prepare hydrogels with both high toughness and self-healing ability. In this study, lignin-based β-CD-PVA (LCP) self-healing conductive hydrogels with high tensile properties were prepared by one-step method using alkali lignin as a plasticizer. Compared with PVA hydrogel, the maximum storage modulus and elongation were increased by 2.5 and 20.0 times, respectively. Uniform distribution of lignin can increase the fluidity and distance of polymer molecular chains, thus improving the viscoelastic and tensile properties of the LCP self-healing hydrogel. LCP hydrogels can maintain self-healing ability in both high (45 °C) and low temperature (0 °C) environments, and the self-healing ability is not affected by pH. Moreover, it also has good conductivity, anti-bacterial, thermostability, and anti-UV property, which has a good application prospect in the field of 3D printing and wearable electronic devices, which expands the efficient utilization of lignin in biorefinery.

Truly Multicolor Emissive Hyperbranched Polysiloxane: Synthesis, Mechanism Study, and Visualization of Controlled Drug Release

Unconventional fluorescent polymers have attracted increasing attention due to their facile synthesis, excellent biocompatibility, and novel photophysical properties. In this work, a truly multicolor emissive hyperbranched polysiloxane (HBPSi-β-CD) is obtained through adjusting the distribution of electron-rich atoms and grafting β-cyclodextrin; the quantum yields of HBPSi-β-CD after being excited by 360, 420, 450, and 550 nm are 19.36, 31.46, 46.14 and 44.84%, respectively. The density functional theory calculations reveal that the truly multicolor emission is derived from the formed electron delocalization among the hydroxyl, amine, ether, and -Si(O)₃ groups due to the strong intermolecular interaction, high density of electron-rich atoms, and low steric hindrance among functional groups. The prepared polymers could serve as a multisensitivity sensor in detecting Fe³⁺, Cu²⁺, and Co²⁺. The HBPSi-β-CD shows low cytotoxicity and excellent cellular imaging capability. The self-assembly of HBPSi-β-CD also possesses high drug loading capacity and pH-controlled drug release, especially, the drug delivery system could be applied in the visualization of controlled drug delivery.

Preparation and application of chitosan-based fluorescent probes

Biomass materials have abundant natural resources, renewability and good biochemical compatibility, so biomass-based fluorescent materials prepared from biomass materials have gradually become a research hotspot.

Preparation of Agarose Fluorescent Hydrogel Inserted by POSS and Its Application for the Identification and Adsorption of Fe3

After entering in water, Fe3+ is enriched in the human body and along the food chain, causing chronic poisoning and irreversible harm to human health. In order to solve this problem, we synthesized citric acid POSS (CAP) from aminopropyl POSS (OAP) and citric acid. Then, we synthesized fluorescent hydrogels (CAP-agarose hydrogel, CAHG) with CAP and agarose. The luminescence mechanism of CAP was investigated by theoretical calculation. CAP plays a dual role in composite hydrogels: one is to give the gels good fluorescence properties and detect Fe3+; the second is that the surface of CAP has a large content of carbonyl and amide groups, so it can coordinate with Fe3+ to enhance the adsorption properties of hydrogels. The experimental results show that the lowest Fe3+ concentration that CAHG can detect is 5 μmol/L, and the adsorption capacity for Fe3+ is about 26.75 mg/g. In a certain range, the fluorescence intensity of CAHG had an exponential relation with Fe3+ concentration, which is expected to be applied to fluorescence sensors. Even at a lower concentration, CAHG can effectively remove Fe3+ from the solution. The prepared fluorescent hydrogel has great potential in the field of fluorescent probes, fluorescent sensors, and ion adsorption. Besides, CAHG can be used as photothermal material after adsorbing Fe3+, allowing for material recycling and reducing material waste.

Chitosan based macromolecular probes for the selective detection and removal of Fe3+ ion

Chitosan has been widely used due to its biodegradable, cost-effective and environmentally friendly properties. Modification of chitosan attracts much attention as promising methods to detect and remove organic and inorganic pollutants. In this work, chitosan-based macromolecular probes were designed and synthesized. The probes can detect Fe³⁺ in the presence of other metal ions. The detection mechanism is investigated as well. The probe's fluorescence quenching upon the addition of Fe³⁺ ion could be ascribed to the complexation between the electron-deficient ion Fe³⁺ and "C=N" (electron-rich group) of fluorescent chitosan probes. What's more, the obtained fluorescent macromolecular probes can be used for the removal of Fe³⁺ in solution. The probes could adsorb the Fe³⁺ in solution and the removal efficiency can reach as high as 62.0% while the removal efficiency of original chitosan is only 16.0%. The probes have good selective detection for Fe³⁺ and the detection limit reaches 1.2 μM.

Inversing supramolecular chirality and boosting circularly polarized luminescence of pyrene moieties via a gel matrix

Alkyl-substituted l/d-glutamide derivatives (L/D-SG) were designed as gelators to fabricate host gel matrices. Pyrene-appended l/d-glutamide derivatives (Py-LG/Py-DG) were employed as guest luminophores to investigate chiral packing and emission behavior in gel matrices. It was found that Py-LG and Py-DG are prone to form P- and M-chirally packed assemblies in DMSO gels, respectively. However, the chiral packing was inversed, and CPL was boosted after Py-LG/Py-DG was embedded in the L/D-SG gel matrix. M-chiral packing together with left-handed excimer emission ((-)-CPL) was observed in the Py-LG immobilized L-SG gel matrix, while P-chiral packing together with right-handed excimer emission ((+)-CPL) was found in the Py-DG immobilized L-SG gel matrix. It is more interesting to find that the molecular chirality of the matrix gelator did not affect the supramolecular chirality of pyrene assemblies. Either l or a d-matrix gelator can inverse the supramolecular chirality of the pure gel, but did not follow the chirality of the matrix. It was found that the gel matrix converts intralayer pyrene-pyrene (Py-Py) packing in the pure pyrene gel to interlayer Py-Py packing, thus giving an opposite chirality. The study not only deepened our understanding of the supramolecular chirality transfer but also unveiled the effects of an inert gel matrix in regulating the chiroptical properties.

Construction of Nanocrystalline Cellulose-Based Composite Fiber Films with Excellent Porosity Performances via an Electrospinning Strategy

Cellulose nanocrystals (CNCs) not only have environmental protection characteristics of being lightweight, degradable, green, and renewable but also have some nanocharacteristics of high strength, large specific surface area, and obvious small size effect, so they are often used as a reinforcing agent in various polymers. However, the hydrogen bonding between CNC molecules is relatively strong, and they can easily aggregate and get entangled with each other. In this work, several large-porosity composite nanofiber films, KH550-CNC/waterborne polyurethane (WPU)/poly(vinyl alcohol) (PVAL) with KH550-modified CNCs, are prepared using poly(vinyl alcohol) (PVAL) solution and electrospinning technology. A variety of characterization methods are used to discuss and analyze the nanofiber materials, and the effects of the added amount of CNCs modified with KH550, spinning voltage, curing distance, and advancing speed on the morphology and performance of composite fibers are discussed separately. The results show that when the content of KH550-CNC is 1%, the composite fiber film obtained has the most regular morphology and the best spinnability, which is convenient for the specific application of fiber materials in a later period. In addition, the porosity of the obtained composite fiber film is 62.61%. Therefore, this work provides a theoretical basis and research strategy for the preparation of higher-porosity composite films as well as the development of new textile materials.

Synthesis of a New Amino-Furopyridine-Based Compound as a Novel Fluorescent pH Sensor in Aqueous Solution

Development of new fluorescent molecules, especially pH-sensitive fluorescent dyes, is always in high demand due to their wide applications in various fields and the limited number of common chromophores. In this work, a family of 3-amino-N-phenylfuro[2,3-b]pyridine-2-carboxamides (AFP) was synthesized as novel fluorescent compounds. Besides fluorescence in an organic solvent, AFP 1 and AFP 2 exhibit good fluorescence properties in both acidic and basic aqueous solution, which could be explained by protonation or different conformations formed in solution. Density functional theory (DFT) calculations on the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) of various conformations were performed for further support.

Self-Assembled Black Phosphorus-Based Composite Langmuir-Blodgett Films with an Enhanced Photocurrent Generation Capability and Surface-Enhanced Raman Scattering Properties

In this work, Langmuir-Blodgett (LB) composite thin films were successfully prepared using black phosphorus nanosheets (BPNS) and dye molecules. Black phosphorus (BP) was first exfoliated in isopropanol solution to form BPNS, and then, BPNS were modified with 4-azidobenzoic acid (Az-BPNS) to improve their stability. The characterization results showed that the synthesized Az-BPNS-dye LB films have a uniform and ordered structure. In addition, the synthesized Az-BPNS-dye LB films exhibit excellent photoelectrochemical performance, and Az-BPNS-methylene blue (MB) produces higher photocurrent compared to Az-BPNS-Neutral red (NR) films. The current work shows an effective way to prepare functionalized BP-based materials and provide evidence for their application in optoelectronic devices.

Self-Assembled Sandwich-like MXene-Derived Composites as Highly Efficient and Sustainable Catalysts for Wastewater Treatment

Photocatalysts play an increasingly important role in environmental remediation polluted by industrial wastewater. However, the preparation of adsorbents and catalysts with high activity by simple and easy methods is still a great challenge. Here, sandwich-like composite catalyst Cu₂O/TiO₂/Ti₃C₂ was prepared by an easily available solvent reduction measure for the highly efficient catalytic nitro compounds. In particular, sandwich-like composite catalyst Cu₂O/TiO₂/Ti₃C₂ exhibits excellent catalysis for 2-nitroaniline (2-NA) and 4-nitrophenol (4-NP), and its pseudo-first-order reaction rate constants (k) are 0.163 and 0.114 min^-1, respectively. Interestingly, even after eight consecutive cycles of catalytic experiments, the conversion rates of catalytic 2-NA and 4-NP are still greater than 95 and 92%, respectively, demonstrating that the obtained catalyst has excellent catalytic capability and a high reutilization rate. The excellent catalytic performances of Cu₂O/TiO₂/Ti₃C₂ can be attributed to the fact that Ti₃C₂ provides a greater reaction site for the formation of Cu₂O and reduces the aggregation during the formation of Cu₂O by in situ synthesis. Therefore, ternary composite catalyst Cu₂O/TiO₂/Ti₃C₂ prepared by solvent reduction not only supplies a technical method for the catalytic reaction of MXene-based material but also lays the foundation for the development of new photocatalysts.