Advances in electrospun nanofibrous membrane sensors for ion detection

Harmful metal ions and toxic anions produced in industrial processes cause serious damage to the environment and human health. Chemical sensors are used as an efficient and convenient detection method for harmful ions. Electrospun fiber membranes are widely used in the field of solid-state chemical sensors due to high specific surface area, high porosity, and strong adsorption. This paper reviews the solid-state chemical sensors based on electrospinning technology for the detection of harmful heavy metal ions and toxic anions in water over the past decade. These electrospun fiber sensors have different preparation methods, sensing mechanisms, and sensing properties. The preparation method can be completed by physical doping, chemical modification, copolymerization, surface adsorption and self-assembly combined with electrospinning, and the material can also be combined with organic fluorescent molecules, biological matrix materials and precious metal materials. Sensing performance aspects can also be manifested as changes in color and fluorescence. By comparing the literature, we summarize the advantages and disadvantages of electrospinning technology in the field of ion sensing, and discuss the opportunities and challenges of electrospun fiber sensor research. We hope that this review can provide inspiration for the development of electrospun fiber sensors.

Functionalized Electrospun Nanofibers as a Versatile Platform for Colorimetric Detection of Heavy Metal Ions in Water: A Review

The increasing heavy metal pollution in the aquatic ecosystem mainly driven by industrial activities has raised severe concerns over human and environmental health that apparently necessitate the design and development of ideal strategies for the effective monitoring of heavy metals. In this regard, colorimetric detection provides excellent opportunities for the easy monitoring of heavy metal ions, and especially, corresponding solid-state sensors enable potential opportunities for their applicability in real-world monitoring. As a result of the significant interest originating from their simplicity, exceptional characteristics, and applicability, the electrospun nanofiber-based colorimetric detection of heavy metal ions has undergone radical developments in the recent decade. This review illustrates the range of various approaches and functional molecules employed in the fabrication of electrospun nanofibers intended for the colorimetric detection of various metal ions in water. We highlight relevant investigations on the fabrication of functionalized electrospun nanofibers encompassing different approaches and functional molecules along with their sensing performance. Furthermore, we discuss upcoming prospectus and future opportunities in the exploration of designing electrospun nanofiber-based colorimetric sensors for real-world applications.

Conjugated Copolymers through Electrospinning Synthetic Strategies and Their Versatile Applications in Sensing Environmental Toxicants, pH, Temperature, and Humidity

Conjugated copolymers (CCPs) are a class of polymers with excellent optical luminescent and electrical conducting properties because of their extensive π conjugation. CCPs have several advantages such as facile synthesis, structural tailorability, processability, and ease of device fabrication by compatible solvents. Electrospinning (ES) is a versatile technique that produces continuous high throughput nanofibers or microfibers and its appropriate synchronization with CCPs can aid in harvesting an ideal sensory nanofiber. The ES-based nanofibrous membrane enables sensors to accomplish ultrahigh sensitivity and response time with the aid of a greater surface-to-volume ratio. This review covers the crucial aspects of designing highly responsive optical sensors that includes synthetic strategies, sensor fabrication, mechanistic aspects, sensing modes, and recent sensing trends in monitoring environmental toxicants, pH, temperature, and humidity. In particular, considerable attention is being paid on classifying the ES-based optical sensor fabrication to overcome remaining challenges such as sensitivity, selectivity, dye leaching, instability, and reversibility.

Switchable Wettability of Poly(NIPAAm-co-HEMA-co-NMA) Coated PET Fabric for Moisture Management

In this study, we synthesized a random poly[(N-isopropylacrylamide)-co-(2-hydroxyethylmethacrylate)-co-(N-methylolacrylamide)] [poly(NIPAAm-co-HEMA-co-NMA)] copolymer through free-radical polymerization. The NIPAAm, HEMA and NMA moieties were framed to provide thermoresponsiveness, water absorption and retention control, and chemical cross-linking to achieve stability in aqueous medium, respectively. The copolymer showed a significant change in optical transmittance with a variation in temperature due to the change in volume (i.e., hydrophilic/hydrophobic) between 25 °C and 40 °C, attributed to the lower critical solution temperature property of the NIPAAm moiety. The copolymers were wire-bar-coated onto polyethylene terephthalate (PET) fabric. Variation in the water contact angle affirmed the switchable wettability due to the change in temperature. We tested the coated fabrics for moisture absorption and release at different temperatures. The results at 20 °C and 37 °C indicated that the P2 copolymer had the highest moisture absorption and release capability. Therefore, the copolymers with tailored properties can be used as smart textiles for activity specific clothing.

A comprehensive review of electrospinning block copolymers

Electrospinning provides a versatile and cost-effective route for the generation of continuous nanofibres with high surface area-to-volume ratio from various polymers. In parallel, block copolymers (BCPs) are promising candidates for many diverse applications, where nanoscale operation is exploited, owing to their intrinsic self-assembling behaviour at these length scales. Judicious combination of BCPs (with their ability to make nanosized domains at equilibrium) and electrospinning (with its ability to create nano- and microsized fibres and particles) allows one to create BCPs with high surface area-to-volume ratio to deliver higher efficiency or efficacy in their given application. Here, we give a comprehensive overview of the wide range of reports on BCP electrospinning with focus placed on the use of molecular design alongside control over specific electrospinning type and post-treatment methodologies to control the properties of the resultant fibrous materials. Particular attention is paid to the applications of these materials, most notably, their use as biomaterials, separation membranes, sensors, and electronic materials.

Installing a functional group into the inactive ω-chain end of PMMA and PS-b-PMMA by terminal-selective transesterification

Various functional groups were incorporated into the inherently inactive ω-chain end of polymethacrylate-based polymers by terminal-selective transesterification.

Recent Advances of Electrospun Nanofibrous Membranes in the Development of Chemosensors for Heavy Metal Detection

It is critical to detect and analyze the heavy metal pollutions in environments and foods. Chemosensors have been widely investigated for fast detection of analytes such as heavy metals due to their unique advantages. In order to improve the detection sensitivity of chemosensors, recently electrospun nanofibrous membranes (ENMs) have been explored for the immobilization of chemosensors or receptors due to their high surface-to-volume ratio, high porosity, easiness of fabrication and functionalization, controllability of nanofiber properties, low cost, easy detection, no obvious pollution to the detection solution, and easy post-treatment after the detection process. The purpose of this review is to summarize and guide the development and application of ENMs in the field of chemosensors for the detection of analytes, especially heavy metals. First, heavy metals, chemosensors, and four types of preparation methods for ENM-immobilized chemosensors/receptors are briefly introduced. And then, ENM-immobilized chemosensors/receptors and their application progresses for optical, electro, and mass detections of heavy metals are reviewed according to the four types of preparation methods. Finally, the application of ENM-immobilized chemosensors/receptors is summarized and an outlook is provided. The review will provide an instruction to the research and development of ENM-immobilized chemosensors/receptors for the detection of analytes.

A PEGylated colorimetric and turn-on fluorescent sensor based on BODIPY for Hg(ii) detection in water

We herein reported a click strategy to fabricate two kinds of colorimetric and turn-on fluorescent dual-modal mercury sensors (PEG-DMS), which could detect mercury ion in pure water with high selectivity and sensitivity.