Gas Sensors Based on Electrospun Nanofibers

Nanofibers fabricated via electrospinning have specific surface approximately one to two orders of the magnitude larger than flat films, making them excellent candidates for potential applications in sensors. This review is an attempt to give an overview on gas sensors using electrospun nanofibers comprising polyelectrolytes, conducting polymer composites, and semiconductors based on various sensing techniques such as acoustic wave, resistive, photoelectric, and optical techniques. The results of sensing experiments indicate that the nanofiber-based sensors showed much higher sensitivity and quicker responses to target gases, compared with sensors based on flat films

Microfabricated Formaldehyde Gas Sensors

Formaldehyde is a volatile organic compound that is widely used in textiles, paper, wood composites, and household materials. Formaldehyde will continuously outgas from manufactured wood products such as furniture, with adverse health effects resulting from prolonged low-level exposure. New, microfabricated sensors for formaldehyde have been developed to meet the need for portable, low-power gas detection. This paper reviews recent work including silicon microhotplates for metal oxide-based detection, enzyme-based electrochemical sensors, and nanowire-based sensors. This paper also investigates the promise of polymer-based sensors for low-temperature, low-power operation

Nanocrystalline tin oxide nanofibers deposited by a novel focused electrospinning method. Application to the detection of TATP precursors

A new method of depositing tin dioxide nanofibers in order to develop chemical sensors is presented. It involves an electrospinning process with in-plane electrostatic focusing over micromechanized substrates. It is a fast and reproducible method. After an annealing process, which can be performed by the substrate heaters, it is observed that the fibers are intertwined forming porous networks that are randomly distributed on the substrate. The fiber diameters oscillate from 100 nm to 200 nm and fiber lengths reach several tens of microns. Each fiber has a polycrystalline structure with multiple nano-grains. The sensors have been tested for the detection of acetone and hydrogen peroxide (precursors of the explosive triacetone triperoxide, TATP) in air in the ppm range. High and fast responses to these gases have been obtained. © 2014 by the authors; licensee MDPI, Basel, Switzerland.This work has been supported by the Spanish Science and Innovation Ministry under the projects TEC2010-21357-C05-04 and TEC2013-48147-C6-4-R. Authors want to thank University of Extremadura for SEM and XRD analysis. We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)Peer Reviewe

Cellulose-Based Polymer Composite with Carbon Black for Tetrahydrofuran Sensing

This work focused on studying the sensing efficiency of tetrahydrofuran (THF) by composite films made of thin layers of a cellulose-based polymer and carbon black. We analyze the reproducibility, durability, desorption time, and the sensitivity percent as a function of the amount of solvent. Two types of experiments were conducted, (1) progressive sensing test (PST) which consisted of progressively increasing the amount of solvent from 0.1 mL increments up to 1.0 mL and (2) multiple sensing test (MST) where the layers were subjected to consecutive pulses of the same amount of solvent, with a minimum of 0.1 mL and a maximum of 0.4 mL. The response and desorption times were a few seconds, and the sensitivity percent ranged from 1% to 170% and was dependent on the solvent quantity

Green Synthesis of Nanofiber and Its Affecting Parameters

Nanofibers, the widely applied in various field of science research, is one of the important area in nanotechnology research. Nanofibers can be classified into polymeric, ceramic and composite nanofibers depending upon the material used. A variety of nanofibers are applied in field of energy storage, biotechnology and healthcare industry, environmental engineering, as well as security and defense. The wide uses of nanofibers are mainly due to low density, high porosity, tight pore size and large surface area per unit mass. Synthesis of nanofibers depends upon various parameters of solution like molecular weight of polymer, concentration, electrical conductivity, surface tension and viscosity. The process parameters affecting nanofibers synthesis are distance between needle tip and collector, feeding rate of polymer material and electric field

NANOFIBRAS DE POLI(ÁLCOOL VINÍLICO) COM ÓXIDO DE GRAFENO REDUZIDO PARA APLICAÇÃO EM SENSOR DE GÁS

Considerando o avanço da nanotecnologia e que os nanomateriais possuem uma variedade de aplicações e que a descoberta do grafeno promete revolucionar a tecnologia, devido as suas propriedades e diversas aplicações, é de grande importância realizar estudos deste material juntamente com o polímero poli (álcool vinílico) (PVA), importante para a fabricação de nanofibras, objetivando a aplicação em sensor de gás amônia, pois sensores a base de grafeno já vêm sendo desenvolvidos com o intuito de detectar uma variedade de moléculas, entre elas a amônia. Dessa forma, neste trabalho foram produzidas nanofibras de poli (álcool vinílico) (PVA) com o óxido de grafeno reduzido (rGO) em diferentes concentrações, por meio da técnica de eletrofiação, com o intuito de analisar a influência do rGO nas nanofibras de PVA para aplicação em sensor de gás amônia. Para isso, as nanofibras de rGO/PVA foram caracterizadas por microscopia óptica (MO) e foram testadas na presença de gás amônia

NANOFIBRAS DE POLI(ÁLCOOL VINÍLICO) COM ÓXIDO DE GRAFENO REDUZIDO PARA APLICAÇÃO EM SENSOR DE GÁS

Considering the advancement of nanotechnology and that nanomaterials have a variety of applications and that the discovery of graphene promises to revolutionize the technology, due to its properties and diverse applications, it is of great importance to carry out studies of this material together with the poly (vinyl alcohol) (PVA), important for the manufacture of nanofibers, aiming at the application in ammonia gas sensor, as graphene-based sensors have already been developed in order to detect a variety of molecules, including ammonia. Thus, in this work, poly (vinyl alcohol) (PVA) nanofibers were produced with reduced graphene oxide (rGO) at different concentrations, using the electrospinning technique, in order to analyze the influence of rGO on PVA nanofibers to application in ammonia gas sensor. For this, the rGO/PVA nanofibers were characterized by optical microscopy (OM) and tested in the presence of ammonia gas.   Considerando o avanço da nanotecnologia e que os nanomateriais possuem uma variedade de aplicações e que a descoberta do grafeno promete revolucionar a tecnologia, devido as suas propriedades e diversas aplicações, é de grande importância realizar estudos deste material juntamente com o polímero poli (álcool vinílico) (PVA), importante para a fabricação de nanofibras, objetivando a aplicação em sensor de gás amônia, pois sensores a base de grafeno já vêm sendo desenvolvidos com o intuito de detectar uma variedade de moléculas, entre elas a amônia. Dessa forma, neste trabalho foram produzidas nanofibras de poli (álcool vinílico) (PVA) com o óxido de grafeno reduzido (rGO) em diferentes concentrações, por meio da técnica de eletrofiação, com o intuito de analisar a influência do rGO nas nanofibras de PVA para aplicação em sensor de gás amônia. Para isso, as nanofibras de rGO/PVA foram caracterizadas por microscopia óptica (MO) e foram testadas na presença de gás amônia

Amphiphilic oxygenated amorphous carbon-graphite buckypapers with gas sensitivity to polar and non-polar VOCs

To precisely control the emission limit of volatile organic compounds (VOCs) even at trace amounts, reactive nanomaterials of, e.g., carbon are demanded. Particularly, considering the polar/non-polar nature of VOCs, amphiphilic carbon nanomaterials with a huge surface area could act as multipurpose VOC sensors. Here, for the first time, a buckypaper sensor composed of oxygenated amorphous carbon (a-COx)/graphite (G) nanofilaments is developed. Presence of the oxygen-containing groups rises the selectivity of the sensor to polar VOCs, such as ethanol and acetone through formation of hydrogen bonding, affecting the electron withdrawing ability of the group, the hole carrier density, and, thus, the resistivity. On the other hand, the electrostatic interactions between the toluene aromatic ring and the π electrons of the graphitic crystals cause a formation of charge-transfer complexes, which could be the main mechanism of high responsiveness of the sensor towards non-polar toluene. To the best of my knowledge, an amphiphilic carbon nanofilamentous buckypaper has never been reported for gas sensing, and my device sensing polar/non-polar VOCs is state of the art for environmental control

Structural and Morphological Investigation of Cr2O3/WO3Oxides Films Composite Using Modified Spray Pyrolysis Technique

Cr2O3/WO3 oxides film composite was successfully synthesized via advanced controlled chemical spray pyrolysis deposition technique using two nozzles. Two solutions of tungstic acid and chromium chloride was sprayed separately at various ratios of (W: Cr) at the same time on a silicon substrate at 500 °C, the film then heat-treated at 400 °C for the 60s. The crystal structure, microstructure and morphology properties of prepared films were studied. Based on characterization techniques, crystallized Cr2O3/WO3 mixed oxides films were investigated by X-ray diffraction after the annealing process, with film thickness of about 500 nm. The SEM and AFM revealed that rough and porous microstructures of Cr2O3/WO3 were formed. The obtained microstructure has been known as one of the most effective microstructures due to having high surface area particularly in gas detection application

Effect of Wrapped Carbon Nanotubes on Optical Properties, Morphology, and Thermal Stability of Electrospun Poly(vinyl alcohol) Composite Nanofibers

Electrospinning was used to elaborate poly(vinyl alcohol) (PVA) nanofibers in the presence of embedded multiwall carbon nanotubes (MWCNTs) in surfactant and polymer. MWCNTs were dispersed in aqueous solution using both sodium dodecyl sulfate (SDS) as surfactant and Poly(vinyl pyrrolidone) (PVP). Changing the surfactant and polymer concentration reveals that the maximum dispersion achievable is corresponding to the mass ratios MWCNTs : SDS—1 : 5 and MWCNTs : SDS : PVP—1 : 5 : 0.6 in the presence of the PVP. After the optimization of the dispersion process, the SEM image of the PVA/PVP/SDS/MWCNTs electrospun fibers presents high stability of the fibers with diameter around 224 nm. Infrared spectroscopy and thermal gravimetric analysis elucidate the type of interaction between the PVA and the coated carbon nanotube. The presence of PVP wrapped carbon nanotubes reduced slightly the onset of the degradation temperature of the electrospun nanofibers