Surface-engineered natural fibers: Emerging alternative substrates for chemical sensor applications: A review.

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.

Fire Performance of Cotton Fabrics Coated with 10-(2,5-Dihydroxyphenyl)-9,10-dihydro-9-xa-10-phosphaphenanthrene-10-oxide (DOPO-HQ) Zr-Based Metal-Organic Frameworks.

We investigated the performance of cotton fabrics coated with DOPO-HQ and Zr-based Metal-organic Frameworks when exposed to fire. The chemical structure of the cotton fabrics before and after the coating was characterized using FTIR spectroscopy, and the surface morphology of cotton and their combustion residues was probed via scanning electron microscopy. In our experiments, we used flammability tests and thermogravimetric methods to understand the burning behavior of the coated fibers, as well as their thermal stability. The cotton fabrics coated with DOPO-HQ and Zr MOFs exhibited shorter combustion times, had better thermal degradation properties, promoted the creation of heat-insulating layers, and exhibited improved smoke suppression behavior.

Preparation of SERS active filter paper for filtration and detection of pesticides residue from complex sample.

The selectivity is needed mostly in SERS sensing because analytes of interest are commonly present in a complex mixture containing particles and impurities, which hinder the interactions between the laser and analyte being detected. In this manuscript, we describe our efforts developing a simple and instant. method to prepare a filter paper SERS sensor. Colloidal Ag nanoparticles were immobilized on one side of filter paper via an in-situ growth method. The fabrication process of the sensor could be finished in several minutes, and no special facility needed. The filter paper SERS sensor demonstrated a spectra uniformity with a 7.0 % point-by-point signal deviation. And the filter function of the sensor could effectively filter out interferences from samples in 1 min, that allowing the direct detection of thiram in ketchup by SERS with detection limit of 93 ppb. Furthermore, we used a Quick Easy Cheap Effective Rugged and Safe (QuEChERS) sample preparation method to detect malachite green (MG) in soil with a sensitivity as low as 0.01 ppm without any sample pre-treatment or purification. A SERS filter paper may open a new avenue for rapid testing of food quality during manufacturing as well as fast detection of potential contaminants in a myriad of substrates.

Impact of Vegetable Oil Type on the Rheological and Tribological Behavior of Montmorillonite-Based Oleogels.

We formulated and characterized oleogels based on montmorillonite clay and vegetable oils that could serve as eco-friendly semi-solid lubricants. In particular, we studied the influence of the physical-chemical properties of olive, castor, soybean, linseed, and sunflower oils on the rheological, chemical, thermal, and tribological properties of the semi-solid lubricants. We prepared the oleogels via the highly intensive mixing of vegetable oils with clay at a concentration of 30 wt.%. The oleogels exhibited shear-thinning, thixotropy, structural recovery, and gel-like behavior commonly related to that of a three-dimensional network. The results were corroborated via XRD measurements showing the presence of intercalated nanoclay structures well-dispersed in the vegetable oil. Empirical correlations between the content of saturated (SFAs), unsaturated (UFAs), mono-unsaturated (MUFAs) and poly-unsaturated (PUFAs) fatty acids and the plateau modulus of the aerogels were found. From these experimental results, we can conclude that the fatty acid profile of the vegetable oils exerts an important influence on the rheological and tribological properties of resulting clay and vegetable oil oleogels.

Planar or Biaxial Stretching of Poly(ethylene terephthalate) Fiber Webs Prepared by Laser-Electrospinning.

In this work, laser-heated electrospinning (LES) process using carbon dioxide laser was explored as an eco-friendly method for producing ultrafine fibers. To enhance the thinning of fibers and the formation of fiber structure, planar or equibiaxial stretching and subsequent annealing processes were applied to poly(ethylene terephthalate) (PET) fiber webs prepared by LES. The structure and properties of the obtained webs were investigated. Ultrafine fiber webs with an average diameter of approximately 1 µm and a coefficient of variation of 20-25% were obtained when the stretch ratios in the MD (machine direction) × TD (transverse direction) were 3 × 1 and 3 × 3 for the planar and equibiaxial stretching, respectively. In the wide-angle X-ray diffraction analysis of the web samples, preferential orientation of crystalline c-axis were confirmed along the MD for planar stretching and only along the web plane for equibiaxial stretching, which was in contrast to the stretching of film samples, where additional preferential orientation of benzene ring along the film plane proceeded. The results obtained suggest that PET fiber webs fabricated through LES and subsequent planar or biaxial stretching processes have potential for a wide variety of applications, such as packaging and battery separator materials.

A Solid-State Pathway towards the Tunable Carboxylation of Cellulosic Fabrics: Controlling the Surface's Acidity.

We report on a tunable solid-state approach to modify the acidity of cotton substrates using citric, oxalic, and fumaric acids. The first stage of the method involves soaking the cotton swatches in an ethanolic saturated solution of the corresponding acid. After drying, the carboxylation reaction proceeds at high temperature (T > 100 °C) and in solid state. We quantified the effect of temperature and reaction time on the solid-state carboxylation reaction, which allowed us to tune the carboxylation degree and the acidity of the surface. We characterized the modified cotton by performing adsorption isotherms and by determining the kinetics of adsorption of a cationic dye: methylene blue (MB). We found that the MB uptake kinetics varied as a function of the acidic strength of the surface, which is closely related to the strength of the acid used for surface modification. The proposed solid-state cotton carboxylation procedure allows us to achieve sustainable cotton modification, which constitutes a starting point for several applications using cotton as the substrate.

Surface Modification of Polyester Fabrics by Ozone and Its Effect on Coloration Using Disperse Dyes.

Polyester fibers (PES) are the most consumed textile fibers due to their low water absorption; non-ionic character and high crystallinity. However, due to their chemical structure, the chemical interactions between polyester, finishing products, and dyes are quite challenging. We report on the use of ozone to modify the surface of polyester fibers with the goal of improving the interaction of the modified surface with finishing compounds and dyes. We used C.I. Disperse Yellow 211 to dye ozone-treated polyester fabrics and evaluated the effects of ozone treatment using FTIR-ATR, Raman spectroscopy, SEM imaging, rubbing tests, and capillarity measurements. We evaluated the dyeing performance via color analysis, and determined the dyeing kinetics. Experimental results indicate that the modification of polyester fabrics with ozone is a feasible pre-treatment that improves dyeing efficiency allowing better solidity of color and a decrease in the amount of dye required.

Effect of the Ethanol/BTC Ratio on the Methane Uptake of Mechanochemically Synthesized MOF-199.

We report on a detailed textural analysis of mechanochemically synthesized MOF-199 including N2 adsorption-desorption and CO2 adsorption isotherms data at 77 K and 273 K (up to atmospheric pressure), respectively, and CH4 adsorption data at 298 K (up to 35 bar). We used the isotherm adsorption data to determine the micropore volume of the MOF-199 structures, to establish their methane uptake capacity and to understand how these properties depended on the Ethanol/BTC ratio used during the synthesis. The maximum methane uptake capacity for our specimens was recorded at 130 v/v at 35 bars. These results open an avenue for a better understanding of alternative manufacturing processes of MOF structures for gas storage applications.

Structure and Properties of Poly(ethylene terephthalate) Fiber Webs Prepared via Laser-Electrospinning and Subsequent Annealing Processes.

Melt-electrospinning is an eco-friendly method for producing ultra-fine fibers without using any solvent. We prepared webs of poly(ethylene terephthalate) (PET) through melt-electrospinning using CO2 laser irradiation for heating. The PET webs comprised ultra-fine fibers of uniform diameter (average fiber diameter = 1.66 µm, coefficient of variation = 19%). The co-existence of fibers with high and low molecular orientation was confirmed through birefringence measurements. Although the level of high orientation corresponded to that of commercial highly oriented yarn, crystalline diffraction was not observed in the wide-angle X-ray diffraction (WAXD) analysis of the webs. The crystallinity of the webs was estimated using differential scanning calorimetry (DSC). The fibers with higher birefringence did not exhibit any cold crystallization peak. After annealing the web at 116 °C for 5 min, a further increase in the birefringence of the fibers with higher orientation was observed. The WAXD results revealed that the annealed webs showed crystalline diffraction peaks with the orientation of the c-axis along the fiber axis. In summary, the formation of fibers with a unique non-crystalline structure with extremely high orientation was confirmed.

Detection of antipersonnel landmines containing ANFO-based explosive: A review / Detección de minas antipersonal que contienen explosivos tipo ANFO: una revisión / Detecção de minas terrestres antipessoal contendo explosivo à base de ANFO: Uma revisão

Resumen After an internal conflict that lasted over half a century, the detection and removal of antipersonnel landmines in Colombia have become cumbersome challenges. Antipersonnel landmines remain scattered in Colombia and with a considerable impact on the central-western region. Most of these devices are handmade (therefore, they can also be classified as improvised explosive devices) and composed of ammonium nitrate and fossil fuel blend, a mixture known as ANFO. Due to several unique factors, including concealment tactics and non-conventional manufacturing techniques employed by guerrilla fighters, the most efficient method for the detection of ANFO-based antipersonnel landmines is the use of trained canines. This review aims at describing the current chemical strategies used in the detection of ANFO-based antipersonnel landmines. First, a detailed description of the different techniques used in the detection of explosives is made. Then, all the strategies reported in the world for antipersonnel landmines detection are described. Finally, the importance of the use of canines for antipersonnel landmines detection is explained.

Abstract Después de un conflicto interno que duró más de medio siglo, la detección y eliminación de minas antipersonales en Colombia se han convertido en desafíos engorrosos. Las minas antipersonales siguen dispersas en la región centro-occidental de Colombia. La mayoría de estos dispositivos están hechos a mano (hecho que puede clasificarlos como artefactos explosivos improvisados, AEI) y están compuestos por una mezcla de nitrato de amonio y un combustible fósil, una mezcla conocida como ANFO. Debido a varios factores únicos, que incluyen tácticas de ocultación y técnicas de fabricación no convencionales empleadas por guerrilleros, el método más eficiente para la detección minas antipersonales basadas en ANFO es el uso de caninos entrenados. Esta revisión tiene como objetivo describir las estrategias químicas actuales utilizadas en la detección de minas antipersonales basadas en ANFO. En primer lugar, se hace una descripcion detallada de las diferentes técnicas utilizadas en la detección de explosivos; luego, se describen todas las estrategias reportadas en el mundo para la detección de minas antipersonales y, finalmente, se explica la importancia del uso de caninos para la detección de minas antipersonales.

Resumo Após um conflito interno que durou mais de meio século, a detecção e remoção de minas antipessoal na Colômbia se tornaram desafios complexos. As minas antipessoal continuam espalhadas na região centro-oeste da Colômbia. A maioria desses dispositivos é feita à mão (fato que pode classificá-los como dispositivos explosivos improvisados, DEI) e composta de uma mistura de nitrato de amônio e um combustível fóssil - uma mistura conhecida como ANFO. Devido a vários fatores únicos, incluindo táticas de ocultação e técnicas de fabricação não convencionais empregadas por guerrilheiros, o método mais eficiente para a detecção de minas antipessoal baseadas em ANFO é o uso de caninos treinados. Esta revisão visa descrever as estratégias químicas atuais usadas na detecção de minas antipessoal baseadas em ANFO. Primeiro, é feita uma descrição detalhada das diferentes técnicas utilizadas na detecção de explosivos; Em seguida, são descritas todas as estratégias relatadas no mundo para a detecção de minas antipessoal e, finalmente, é explicada a importância do uso de caninos para a detecção de minas antipessoal.

Transparent Ultraviolet (UV)-Shielding Films Made from Waste Hemp Hurd and Polyvinyl Alcohol (PVA).

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-1, 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 TiO2/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.

Non-invasive textile based colorimetric sensor for the simultaneous detection of sweat pH and lactate.

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.

Enhanced biosorption of Cr(VI) using cotton fibers coated with chitosan - role of ester bonds.

We report on the role of ester bonds in the enhanced removal of hexavalent chromium from water using cotton fibers coated with chitosan. Adsorption capacities up to five times higher than those of the unmodified fibers were observed when the cotton fibers were exposed to an NaOH, followed by citric acid (0.97 M), and a chitosan solution (2%). We found that the use of NaOH favors the formation of ester bonds over amide bonds on the surface of the cotton fibers. This increase in the surface density of ester bonds generates an increase in the amount of exposed amino groups from the chitosan, hence increasing the removal capacity of the modified fibers. Experimental results also reveal that the adsorption is induced by the electrostatic attraction between the protonated amino groups on the surface and the negatively charged chromium ions in the water. Adsorption isotherms and kinetic studies indicated that the adsorption process fits the Langmuir and the Freundlich isotherm models as well as the pseudo-first and pseudo-second order kinetic models. These results can open a new avenue for the manufacturing of fibers with enhanced removal capacities for hexavalent chromium.

In Situ and Real-Time Studies, via Synchrotron X-ray Scattering, of the Orientational Order of Cellulose Nanocrystals during Solution Shearing.

In this manuscript, we report on the ordering of the cellulose nanocrystals (CNCs) as they experience shear forces during the casting process. To achieve these measurements, in situ and in real time, we used synchrotron-based grazing incidence wide-angle X-ray scattering (GIWAX). We believe that the GIWAX technique, although not commonly used to probe these types of phenomena, can open new avenues to gain deeper insights into film formation processes and surface-driven phenomena. In particular, we investigated the influence of solution concentration, shear-cast velocity, and drying temperature on the ordering of cellulose nanocrystals (CNCs) using GIWAXS. The films were prepared from aqueous suspensions of cellulose nanocrystals at two concentration values (7 and 9 wt %). As the films were cast, the X-ray beam was focused on a fixed position and GIWAXS patterns were recorded at regular time intervals. Structural characterization of the dry films was carried out via polarized optical microscopy and scanning electron microscopy. In addition, a rheological study of the CNC suspensions was performed. Our results show that the morphology of the CNC films was significantly influenced by shear velocity, concentration of the precursor suspension, and evaporation temperature. In contrast, we observed that the orientation parameter of the films was not significantly affected. The scattering intensity of the peak (200) was analyzed as a function of time, following a sigmoidal profile, hence indicating short- and long-range interactions within the anisotropic domains as they reached their final orientation state. A model capable of describing the resulting film morphologies is also proposed. The results and analysis presented in this manuscript provide new insights into the controlled alignment of cellulose nanocrystals under shear. This controlled alignment has significant implications in the development of advanced coatings and films currently used in a myriad of applications, such as catalysis, optics, electronics, and biomedicine.

Acid-Base Polymeric Foams for the Adsorption of Micro-oil Droplets from Industrial Effluents.

Separation of toxic organic pollutants from industrial effluents is a great environmental challenge. Herein, an acid-base engineered foam is employed for separation of micro-oil droplets from an aqueous solution. In acidic or basic environments, acid-base polymers acquire surface charge due to protonation or dissociation of surface active functional groups. This property is invoked to adsorb crude oil microdroplets from water using polyester polyurethane (PESPU) foam. The physicochemical surface properties of the foam were characterized using X-ray photoelectron spectroscopy, inverse gas chromatography, electrokinetic analysis, and micro-computed tomography. Using the surface charge of the foam and oil droplets, the solution pH (5.6) for maximum separation efficacy was predicted. This optimal pH was verified through underwater wetting behavior and adsorption experiments. The droplet adsorption onto the foam was governed by physisorption, and the driving forces were attributed to electrostatic attraction and Lifshitz-van der Waals forces. The foam was regenerated and reused multiple times by simple compression. The lowest trace oil content in the retentate was 3.6 mg L-1, and all oil droplets larger than 140 nm were removed. This work lays the foundation for the development of a new class of engineered foam adsorbents with the potential to revolutionize water treatment technologies.

Oriented Growth of α-MnO2 Nanorods Using Natural Extracts from Grape Stems and Apple Peels.

We report on the synthesis of alpha manganese dioxide (α-MnO2) nanorods using natural extracts from Vitis vinifera grape stems and Malus domestica 'Cortland' apple peels. We used a two-step method to produce highly crystalline α-MnO2 nanorods: (1) reduction of KMnO4 in the presence of natural extracts to initiate the nucleation process; and (2) a thermal treatment to enable further solid-state growth of the nuclei. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) images provided direct evidence of the morphology of the nanorods and these images were used to propose nucleation and growth mechanisms. We found that the α-MnO2 nanorods synthesized using natural extracts exhibit structural and magnetic properties similar to those of nanoparticles synthesized via traditional chemical routes. Furthermore, Fourier transform infrared (FTIR) shows that the particle growth of the α-MnO2 nanorods appears to be controlled by the presence of natural capping agents during the thermal treatment. We also evaluated the catalytic activity of the nanorods in the degradation of aqueous solutions of indigo carmine dye, highlighting the potential use of these materials to clean dye-polluted water.

Synthesis of silver nanoparticles using aqueous extracts of Heterotheca inuloides as reducing agent and natural fibers as templates: Agave lechuguilla and silk.

Silver nanoparticles (Ag NPs) were synthesized using a one-pot green methodology with aqueous extract of Heterotheca inuloides as a reducing agent, and the support of natural fibers: Agave lechuguilla and silk. UV-Vis spectroscopy, X-Ray photoelectron spectroscopy XPS and transmission electron microscopy TEM were used to characterize the resulting bionanocomposite fibers. The average size of the Ag NPs was 16nm and they exhibited low polydispersity. XPS studies revealed the presence of only metallic Ag in the nanoparticles embedded in Agave. lechuguilla fibers. Significant antibacterial activities against gram-negative Escherichia coli and gram-positive Staphylococcus aureus were determined. AgO as well as metallic Ag phases were detected when silk threads were used as a substrates hinting at the active role of substrate during the nucleation and growth of Ag NPs. These bionanocomposites have excellent mechanical properties in tension which in addition to the antibacterial properties indicate the potential use of these modified natural fibers in surgical and biomedical applications.

Removal of sodium and chloride ions from aqueous solutions using fique fibers (Furcraea spp.).

Fique fibers obtained from the leaves of Furcraea spp., a highly abundant plant in the mountains of South America, may offer an alternative as biosorbents in desalination processes as they exhibit high removal capacities (13.26 meq/g for chloride ions and 15.52 meq/g for sodium ions) up to four times higher than exchange capacities commonly observed in synthetic resins. The ion removal capacity of the fibers was also found to be a function of the pH of the solution with the maximum removal of ions obtained at pH 8. Unlike most commercial ion exchange resins, our results suggest that fique fibers allow simultaneous removal of chloride and sodium ions.

Nanotechnology in Textiles.

Increasing customer demand for durable and functional apparel manufactured in a sustainable manner has created an opportunity for nanomaterials to be integrated into textile substrates. Nanomoieties can induce stain repellence, wrinkle-freeness, static elimination, and electrical conductivity to fibers without compromising their comfort and flexibility. Nanomaterials also offer a wider application potential to create connected garments that can sense and respond to external stimuli via electrical, color, or physiological signals. This review discusses electronic and photonic nanotechnologies that are integrated with textiles and shows their applications in displays, sensing, and drug release within the context of performance, durability, and connectivity. Risk factors including nanotoxicity, nanomaterial release during washing, and environmental impact of nanotextiles based on life cycle assessments have been evaluated. This review also provides an analysis of nanotechnology consolidation in the textiles market to evaluate global trends and patent coverage, supplemented by case studies of commercial products. Perceived limitations of nanotechnology in the textile industry and future directions are identified.

Versatile Molding Process for Tough Cellulose Hydrogel Materials.

Shape-persistent and tough cellulose hydrogels were fabricated by a stepwise solvent exchange from a homogeneous ionic liquid solution of cellulose exposure to methanol vapor. The cellulose hydrogels maintain their shapes under changing temperature, pH, and solvents. The micrometer-scale patterns on the mold were precisely transferred onto the surface of cellulose hydrogels. We also succeeded in the spinning of cellulose hydrogel fibers through a dry jet-wet spinning process. The mechanical property of regenerated cellulose fibers improved by the drawing of cellulose hydrogel fibers during the spinning process. This approach for the fabrication of tough cellulose hydrogels is a major advance in the fabrication of cellulose-based structures with defined shapes.