Colorimetric Textile Sensor for the Simultaneous Detection of NH3 and HCl Gases.

For the immediate detection of strong gaseous alkalis and acids, colorimetric textile sensors based on halochromic dyes are highly valuable for monitoring gas leakages. To date, colorimetric textile sensors for dual-gas detection have usually been fabricated by electrospinning methods. Although nanofibrous sensors have excellent pH sensitivity, they are difficult to use commercially because of their low durability, low productivity, and high production costs. In this study, we introduce novel textile sensors with high pH sensitivity and durability via a facile and low-cost screen-printing method. To fabricate these textiles sensors, Dye 3 and RhYK dyes were both incorporated into a polyester fabric. The fabricated sensors exhibited high detection rates (<10 s) and distinctive color changes under alkaline or acidic conditions, even at low gas concentrations. Furthermore, the fabricated sensors showed an outstanding durability and reversibility after washing and drying and were confirmed to contain limited amounts of hazardous materials. Thus, our results show that the fabricated textile sensors could be used in safety apparel that changes its color in the presence of harmful gases.

A Highly Porous Nonwoven Thermoplastic Polyurethane/Polypropylene-Based Triboelectric Nanogenerator for Energy Harvesting by Human Walking.

: A highly porous nonwoven thermoplastic polyurethane (TPU)/Polypropylene (PP) triboelectric nanogenerator (N-TENG) was developed. To fabricate the triboelectric layers, the TPU nanofiber was directly electrospun onto the nonwoven PP at different basis weights (15, 30, and 50 g/m2). The surface morphologies and porosities of the nonwoven PP and TPU nanofiber mats were characterized by field-emission scanning electron microscopy and porosimetry. The triboelectric performance of the nonwoven TPU/PP based TENG was found to improve with an increase in the basis weight of nonwoven PP. The maximum output voltage and current of the TPU/PP N-TENG with 50% PP basis weight reached 110.18 ± 6.06 V and 7.28 ± 0.67 µA, respectively, due to high air volume of nonwoven without spacers. In order to demonstrate its practical application as a generator, a TPU/PP N-TENG-attached insole for footwear was fabricated. The N-TENG was used as a power source to turn on 57 light-emitting diodes through human-walking, without any charging system. Thus, owing to its excellent energy-conversion performance, simple fabrication process, and low cost, the breathable and wearable nonwoven fiber-based TENG is suitable for large-scale production, to be used in wearable devices.

Nano- And Microfiber-Based Fully Fabric Triboelectric Nanogenerator For Wearable Devices.

The combination of the triboelectric effect and static electricity as a triboelectric nanogenerator (TENG) has been extensively studied. TENGs using nanofibers have advantages such as high surface roughness, porous structure, and ease of production by electrospinning; however, their shortcomings include high-cost, limited yield, and poor mechanical properties. Microfibers are produced on mass scale at low cost; they are solvent-free, their thickness can be easily controlled, and they have relatively better mechanical properties than nanofiber webs. Herein, a nano- and micro-fiber-based TENG (NMF-TENG) was fabricated using a nylon 6 nanofiber mat and melt blown nonwoven polypropylene (PP) as triboelectric layers. Hence, the advantages of nanofibers and microfibers are maintained and mutually complemented. The NMF-TENG was manufactured by electrospinning nylon 6 on the nonwoven PP, and then attaching Ni coated fabric electrodes on the top and bottom of the triboelectric layers. The morphology, porosity, pore size distribution, and fiber diameters of the triboelectric layers were investigated. The triboelectric output performances were confirmed by controlling the pressure area and basis weight of the nonwoven PP. This study proposes a low-cost fabrication process of NMF-TENGs with high air-permeability, durability, and productivity, which makes them applicable to a variety of wearable electronics.

Thiol-functionalized cellulose nanofiber membranes for the effective adsorption of heavy metal ions in water.

This work reports the fabrication of a thiol-functionalized cellulose nanofiber membrane that can effectively adsorb heavy metal ions. Thiol was incorporated onto the surface of cellulose nanofibers, which were fabricated by the deacetylation of electrospun cellulose acetate nanofibers and subsequent esterification of a thiol precursor molecule. Adsorption mechanism was investigated using adsorption isotherms. Adsorption capacity as a function of adsorbate concentration was described well with Langmuir isotherm, suggesting that metal ions form a surface monolayer with a homogenously distributed adsorption energy. Maximum adsorption capacities in the Langmuir isotherm for Cu(II), Cd(II), and Pb(II) ions were 49.0, 45.9, and 22.0 mg·g-1, respectively. The time-dependent adsorption capacities followed a pseudo-second-order kinetic model, suggesting that chemisorption of each doubly charged metal ion occurs with two thiol groups on the surface. These results highlight the significance of surface functionality on biocompatible, nontoxic, and sustainable cellulose materials to expand their potential and applicability towards water remediation applications.

Thiol-based chemistry as versatile routes for the effective functionalization of cellulose nanofibers.

We demonstrate effective functionalization chemistry for cellulose nanofiber modification using thiol functionality. Electrospun cellulose acetate nanofibers were deacetylated to obtain cellulose nanofibers, which were modified further to incorporate thiol on their surface by the esterification of hydroxyl groups with 3,3'-dithiodipropionic acid and further reductive cleavage of the disulfide bond. The thiol functionality was highly versatile to bring simple and efficient chemical reactions to attain (i) Ag nanoparticle-adsorbed cellulose nanofibers by Ag ion reduction at surface, (ii) various amine (primary amine and quaternary amine) functionalized cellulose nanofibers by Michael addition, and (iii) complex polymer functionalized cellulose nanofibers by a radical-based thiol-ene reaction, under mild conditions, i.e. in any reaction media, at room temperature, and under ambient atmosphere, evidenced by a variety of characterization methods including a quantitative analysis with X-ray photoemission spectroscopy. These scalable thiol-based chemistries should offer a new generation of well-tailored cellulose nanofiber materials with complex inorganic, organic, and polymeric functionalities, potentially expanding to functionalized surfaces of other carbohydrate-based materials to achieve the desired properties.