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A sensitive and portable on-thread pre-concentration and colorimetric detection method of copper ions was proposed. Commercial cotton thread was proposed as a solid sorbent for effectively extracting copper ions (Cu2+) from solution. The adsorbed Cu2+ was converted to Cu+ by ascorbic acid. The Cu+ on the threads was visualized by horseradish-peroxidase-catalyzed color changes of a chromogenic oxidized tetramethylbenzidine substrate. The adsorption of Cu2+ on the plasma- and Na2CO3-treated thread was verified by scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and zeta potential characterization. The Cu+-induced dysfunction of HRP on the thread was verified by X-ray photoelectron spectroscopy. With optimized reaction conditions, the concentration-dependent colorimetric response plot was characterized, where the linear detection range was 2–400 nM and the detection limit was about 0.15 nM. Measurements of a group of possible interfering ions and spiked real-water samples demonstrated the good selectivity of the proposed method. The proposed on-thread pre-concentration and colorimetric detection offers a low-cost and effective alternative for detecting of copper ions in real applications.

The root system of plants is a major component of their bodies in terms of both function and bulk. The investigation of root system development is greatly assisted by microfluidic devices, which improve the spatial and temporal resolution of observations without destroying tissue. In the present study, a multi-chamber petaloid root-growth chip was developed for studying the development and physiology of root systems that have thin branching structures (i.e., fibrous root systems). The petaloid root-growth chip includes a central seed germination chamber and five root-growth chambers for observing the development of fibrous roots. The proposed device was applied for investigating the root system development of Oryza sativa. The phenotype and growth kinetics of O. sativa root systems grown in the proposed device were compared with those obtained during growth in a conventional conical flask with agar-based medium, and the results indicated that cultivation in the miniaturized device did not delay root system growth in the early stage (≤2 weeks). In addition, the transparent device enabled the non-destructive observation of the developmental and microstructural characteristics of the roots, such as the root caps, root border cells, and root hairs. Moreover, the ability to control the microenvironment in each of the five root-growth chambers individually facilitated the investigation of specific adaptations in the fibrous root growth of single O. sativa seedlings to different drought stresses. Accordingly, five polyethylene glycol (PEG)6000-induced drought stress conditions were established in the five root-growth chambers to investigate the root development of a single O. sativa seedling in the central germination chamber. In situ observations demonstrated that the different PEG6000-induced conditions affected the root growth responses and root microstructural adaptations of the single seedlings in each root-growth chamber. Therefore, the petaloid root-growth microfluidic chip can eliminate the effects of variations in different plant seeds to reveal the responses of plants to different environmental conditions more objectively while concurrently allowing for non-destructive observations at very high spatial and temporal resolution.

Cotton thread has been proposed as a new, economically affordable material for the fabrication of microfluidic circuits for use in fast, low-cost, point-of-care diagnostic testing devices. In this work, chitosan, a biocompatible polymer, was used to modify cotton thread to improve its fluidic properties for microfluidic applications. Electrostatic-interaction-mediated adsorption of chitosan on alkaline-scoured thread can effectively increase thread’s solution hydrophilicity and wicking rate. Moreover, the proposed process conserves the thread’s hydrophilicity and fluidic properties even when stored for several months. As a microfluidic platform for enzymatic-reaction-associated colorimetric measurement, the suggested chitosan modification results in the accumulation of more analyte in the detection zone because of the improved flow rate, which enhances the colorimetric signal intensity. In this study, a glucose oxidase-mediated colorimetric glucose assay was demonstrated on a chitosan-modified microfluidic thread-based analytical device (μTAD). A linear range of 1–7.5 mM, a low detection limit of 0.2 mM, and a recovery rate between 93 and 98% was achieved in detecting glucose in artificial urine samples.

CoSb3 thermoelectric thin films were prepared on polyimide flexible substrate by radio frequency (RF) magnetron sputtering technology using a cobalt antimony alloy target. Ti and In were added into CoSb3 thin films by co-sputtering. The influence of Ti and In on the thermoelectric properties of CoSb3 thin films was investigated. X-ray diffraction result shows that the major diffraction peaks of all the thin films match the standard peaks related to the CoSb3 phase. The sample has best thermoelectric properties when the Ti sputtering time was 1min and In sputtering time was 30 seconds.

In this study, copper selenide thin films were fabricated by ion beam sputtering deposition by using a fan-shaped target of Cu and Se. The influence of heat treatment on thermoelectric properties of copper selenide thin films was investigated. X-ray diffraction results demonstrate that the as-deposited and annealed thin films are both amorphous. The SEM images show that the thin films are discontinuous and just like island structure. The thin films are crystalline when the substrate temperature is added at the deposition process. The thin film exhibits the dominating CuSe phase at the substrate temperature of 250 °C and it transforms to single CuSe2 phase at the temperature of 300 °C. When the substrate temperature further increased to 350 °C, the mixed Cu2−xSe phase is dominated. The thin film with Cu2−xSe phase has a high electrical conductivity of 2.02 × 104 Scm−1 at 423 K and thin film with CuSe2 phase has a high Seebeck coefficient of 37.3 μVK−1 at 316 K.

Delafossite-type CuCr1−x Zn x O2 (x = 0, 0.03, 0.05, 0.07, 0.1) conductive oxides were synthesized by sol–gel method, and the effects of Zn-doping on morphology, structure, and electrical properties of the CuCr1−x Zn x O2 oxides were investigated. Based on X-ray diffraction (XRD) and Raman spectrum, the crystalline quality of the oxides is improved by the suitable substitution of Cr by Zn. The X-ray photoelectron spectroscopy (XPS) spectra reveal the chemical state of Zn is +2. The Hall and Seebeck coefficients of the pellet samples display a positive sign, indicating p-type conductive characteristics of the obtained oxides. The temperature-dependent resistivity of the oxides is proven to be consistent with small polaron hopping. For the three oxide samples with x = 0, 0.05, and 0.1, the activation energies for the polaron hopping between Zn2+ and Cr3+ sites are 54, 41.5, 32 meV, respectively, which is found to decrease with the increase of Zn content. The electrical conductivity can be remarkably improved by Zn-doping due to the small polaron hopping activation energy. These properties render this material promising as transparent electrode in optoelectronic industry.

In this study, we investigated the effect of carbon nanotubes (CNTs) and performance of the prepared membranes. Thin film composite (TFC) forward osmosis (FO) membranes were fabricated based on the polyacrylonitrile (PAN) substrate, incorporating carbon nanotubes (CNTs) in the active skin layer. The CNTs can improve the water flux through added the hydrophilic groups. The mean surface roughness and hydrophilicity increased with the concentration of carbon nanotubes increased. The TFC membranes incorporated CNTs (0.2 wt%) exhibited the best FO performance with water flux of 25.14 L/m2·h and reverse salt flux of 8.64 g/m2·h using 0.5 M NaCl as draw solution and DI water as feed solution during FO test. The research provides us a promising approach to fabricate the high flux FO membranes.