A non-invasive textile-based colorimetric sensor for the simultaneous detection of sweat pH and lactate was created by depositing of three different layers onto a cotton fabric: 1.) chitosan, 2.) ...sodium carboxymethyl cellulose, and 3.) indicator dye or lactate assay. This sensor was characterized using field emission scanning electron microscopy and fourier transform infrared spectroscopy. Then, this sensor was used to measure pH and lactate concentration using the same sweat sample. The sensing element for sweat pH was composed of a mixture of methyl orange and bromocresol green while a lactate enzymatic assay was chosen for the lactate sensor. The pH indicator gradually shifted from red to blue as the pH increased, whereas the purple color intensity increased with the concentration of lactate in the sweat. By comparing these colors with a standard calibration, this platform can be used to estimate the sweat pH (1−14) and the lactate level (0–25 mM). Fading of the colors of this sensor was prevented by using cetyltrimethylammonium bromide (CTAB). The flexibility of this textile based sensor allows it to be incorporated into sport apparels and accessories hence potentially enabling real-time and continuous monitoring of sweat pH and lactate. This non-invasive sensing platform might open a new avenue for personal health monitoring and medical diagnosis as well as for determining of the physiological conditions of endurance athletes.
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•Non-invasive textile-based colorsensor for detection of sweat pH and lactate was created.•This sensor was simplifyfabricated by coating of cotton with chitosan, sodium carboxymethyl cellulose,indicator dye or lactate assay.•The sensor was able to differentiate sweat pH and lactate levels in human sweat.•This sensor was applied for simultaneous detection of sweat pH and lactate in human volunteers.
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•CNFs/chitosan-GO modified thread was prepared as non-invasive glucose and urea sensor.•CNFs improved the absorption behavior for chitosan-GO on the cotton thread surface.•Chitosan-GO ...increased thread surface area for enzymatic immobilization and thus sensor performances.•This sensor was applied for simultaneous detection of glucose and urea in sweat.•This platform can successfully differentiate between the normal and abnormal people.
Thread has become a promising substrate for non-invasive wearable sensor. Herein, we create a modified cotton thread-based colorimetric sensor for non-invasive and simultaneous detection of glucose and urea excreted from human sweat. Cellulose nanofiber/chitosan-graphene oxide was selected to modify the cotton thread surfaces for enhancing of enzymatic immobilization efficiency and sensor performance. The modified thread surfaces were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. This sensing platform exhibits a linear range of 0.1–3 mM with a detection limit of 0.1 mM for glucose and a linear range of 30–180 mM with a detection limit of 30 mM for urea. Interestingly, this colorimetric sensor can determine the cut-off levels for both glucose (0.3 mM) and urea (65 mM) in human sweat, thus it can effectively distinguish between normal and abnormal people. Due to the thread flexibility nature, this sensor can be readily integrated with the clothes and accessories for real-time and continuous monitoring of diabetes and kidney failure from the wearer’s sweat. This platform might open a new road for blood-free diagnosis in healthcare applications.
We present a review of current research endeavors that merge relatively new chemical structures: metal–organic frameworks (MOFs), and one of the most studied and abundant molecules: cellulose. We ...analyze how cellulosic substrates have been modified to enable the growth of diverse MOFs, and we offer some insight on the myriad of applications for these new materials which include removal of pesticides, capture of pollutants, creation of antibacterial surfaces, decomposition of toxic compounds, selective gas adsorption and water purification. We believe that this unique combination between traditional and emerging materials—between natural and synthetic ones—can significantly expand the performance of cellulosic substrates.
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This work proposes a new approach to fabricate highly transparent and flexible composite films that exhibit enhanced UV-shielding properties. Lignin has innate UV-shielding properties. However, when ...purified lignin, which is conventionally extracted through chemical treatment, is mixed with polymeric materials, its presence negatively influences the transparency of the resulting composite. High transparency and UV-shielding are desirable properties for many applications. In this study, composites were made by mixing lignocellulose particles and polyvinyl alcohol (PVA), where lignocellulose particles were obtained from ball-milled waste hemp hurd without chemical treatments. The UV-shielding properties of the resulting composite film, as a function of hemp/PVA weight ratios, were investigated. The intermolecular interactions between the hemp particles and the PVA were characterized using infrared spectroscopy with the presence of -C=O group at 1655 cm
, providing evidence that the chemical structure of lignin was preserved. The fabricated hemp/PVA films exhibit stronger UV-shielding, in the UVA-I range (340-400 nm) than TiO
/PVA films. The composite films also showed comparable water vapor permeability (WVP) with commercial packaging plastic film made of HDPE (high-density polyethylene). The optimization experiments were reported, with aim at understanding the balance between the UV-shielding and mechanical properties of the hemp/PVA films. The findings of this work can be applicable to the packaging, food and cosmetic industries where UV shielding is of utmost importance, hence adding value to hemp hurd waste.
A Zn-imidazolate metal–organic framework, ZIF-8, was synthesized using ZnO nanorods grown on cotton fibers as precursors. We monitored the synthesis path via X-ray diffraction, scanning electron ...microscopy, and thermogravimetric analysis. The fibers were evaluated by their capacity to absorb arsenate from aqueous solutions and we used scanning transmission electron microscopy–high angle annular dark-field (STEM–HAADF) imaging to observe the transport gradient of arsenate across the ZIF layer and the ZnO interface. The uptake of arsenate in the fibers coated with ZIF-8 on top of the ZnO rods, at pH 7, was of 70% while the uptake of the fibers coated only with ZnO rods was 38%. In addition to the enhanced uptake capacity, the fibers containing ZIF-8 also exhibited lower amounts of Zn leaching into the arsenate solutions. These results provide insights on the synthesis of Zn-imidazole metal–organic frameworks and confirm the potential use of ZIF-8 in the removal of arsenate from contaminated water streams.
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•Multifunctional absorbent cotton-Ag composite was fabricated via electroless deposition Ag NPs on surface of cotton fiber.•The high absorbency of cotton could enrich the analyte on ...the SERS substrate.•SERS performance depending on the concentration of AgNO3 in growth media.•The plasmonic absorbent cotton were used for adsorption and detection of pesticide residue by SERS with good selectivity.
We report on a simple method for fabricating plasmonic absorbent cotton fibers conformally dyeing with Ag NPs to be used as surface-enhanced Raman scattering (SERS) substrates. The Ag NPs were integrated on the surface of cotton by a process in which Ag-NP seeds were immobilized on cotton via electroless deposition. Scanning electron microscope, transmission electron microscopy imaging as well as elemental mapping analysis provided evidence that the Ag NPs were densely immobilized on the surface of cotton. By controlling the amount of AgNO3 in growth media, the optimal SERS absorbent cotton-Ag was obtained by using 20 mM of AgNO3. The high absorbency of cotton could enrich the analyte concentration within 3 min, which brings additional enhancement sensitivity in SERS sensing. In addition, the mechanical flexibility of plasmonic cotton-Ag SERS substrate makes it suitable for swiping the SERS substrate on the surface of apple, the limit of detection of thiram from apple was lower than 0.1 ppm. Finally, the multiplex sensing capability of the plasmonic cotton was demonstrated by identifying pesticides from their mixture.
The stabilizing role of carboxymethyl groups on the conformal deposition of Ag NPs over cellulosic fibers was elucidated while developing a method for the deposition of silver nanoparticles (NPs) on ...cellulose acetate (CA), cellulose and partially carboxymethylated cellulose (CMC) electrospun fibers. CMC fibers were prepared through judicious anionization of deacetylated cellulose acetate fibers. Ag NPs were chemically reduced from silver nitrate using sodium borohydride and further stabilized using citrate. Ag NPs were directly deposited onto CA, cellulose and CMC electrospun fibers at pH conditions ranging from 2.5 to 9.0. The resulting composites of Ag/fiber were characterized by field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX). The results revealed that the amount of Ag agglomerates and NPs deposited on CMC fibers was higher than that deposited on cellulose fibers at similar pH conditions, and that barely any Ag agglomerates or NPs were deposited on the CA fibers. These results implied that functional groups on the cellulose backbone played two important roles in the deposition of NPs as follows: (1) Hydrogen bonding was the main driving force for agglomeration of NPs when the medium pH was below 4.4, which corresponds to the
pKa
of carboxylic acid groups; (2) Carboxymethyl groups could replace citrate groups as stabilizers allowing the fabrication of a uniform and evenly distributed Ag NPs layer over CMC fibers at higher pH values. This report also highlights the importance of the substrate’s surface charge and that of the pH of the medium used, on the deposition of NPs. The composite of Ag NPs on CMC electrospun fibers appears to be a promising candidate for wound dressing applications due to its superior antibacterial properties originated by the uniform and even distribution of Ag NPs on the surface of the fibers and the wound healing aptness of the CMC fibers.
Natural fiber has become one of the most widely used alternative materials for chemical sensor fabrication due to its advantages, such as biocompatibility, flexibility, and self-microfluidic ...properties. Enhanced natural fiber surface has been used as a substrate in colorimetric and electrochemical sensors. This review focuses on improving the natural fiber properties for preparation as a substrate for chemical sensors. Various methods for natural fiber extraction are discussed and compared. Bleaching and decolorization is important for preparation of colorimetric sensors, while carbonization and nanoparticle doping are favorable for increasing their electrical conductivity for electrochemical sensor fabrication. Also, example fabrications and applications of natural fiber-based chemical sensors for chemical and biomarker detection are discussed. The selectivity of the sensors can be introduced and improved by surface modification of natural fiber, such as enzyme immobilization and biorecognition element functionalization, illustrating the adaptability of natural fiber as a smart sensing device, e.g., wearable and portable sensors. Ultimately, the high performances of natural fiber-based chemical sensors indicate the potential uses of natural fiber as a renewable and eco-friendly substrate material in the field of chemical sensors and biosensors for clinical diagnosis and environmental monitoring.
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We report on simple and low-cost active SERS substrates made using regenerated fibers from wood products. Glycidyltrimethylammonium chloride (GTAC) was used to graft ammonium groups on the fibers’ ...surfaces under strong alkaline conditions. After GTAC treatment, citrate-stabilized nanoparticles were assembled via electrostatic interaction. X-ray diffraction, Scanning electron microscopy images and optical photographs indicated that the surfaces of the fibers were conformally coated with metal nanoparticles. We also observed that after being cationized, the fibers experienced significant swelling and shrinking under dry and wet conditions. Rhodamine 6G was used as probe molecule to test the SERS performance of the substrates- concentrations as low as 10⁻⁹ M were detected. Furthermore, the modified fibers were used to detect melamine, illustrating their potential as viable substrates for applications such as markers for the quality and shelf-life of food products and detection of toxins.
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