Gas sensors are fundamental for continuous online monitoring of volatile organic compounds. Gas sensors based on semiconductor materials have demonstrated to be highly competitive, but are generally ...made of expensive materials and operate at high temperatures, which are drawbacks of these technologies. Herein is described a novel ethanol sensor for room temperature (25 °C) measurements based on hematite (α‑Fe
O
)/silver nanoparticles. The AgNPs were shown to increase the oxide semiconductor charge carrier density, but especially to enhance the ethanol adsorption rate boosting the selectivity and sensitivity, thus allowing quantification of ethanol vapor in 2-35 mg L
range with an excellent linear relationship. In addition, the α-Fe
O
/Ag 3.0 wt% nanocomposite is cheap, and easy to make and process, imparting high perspectives for real applications in breath analyzers and/or sensors in food and beverage industries. This work contributes to the advance of gas sensing at ambient temperature as a competitive alternative for quantification of conventional volatile organic compounds.
A common method used to obtain cellulosic fibers is alkalinization with NaOH. Depending on NaOH content, treatments remove significant quantities of lignin and hemicellulose as small molecules. In ...biorefineries, where the preservation of components is needed, KOH may prevent hemicellulose chain formation. Here, we studied the efficacy of obtaining cellulosic fibers from jute using KOH. Jute fibers are about 84.2% holocellulose, which corresponds to 59.5% alpha cellulose and 24.7% hemicellulose. To obtain high cellulosic fiber yields from jute, effects of pulping with different KOH concentrations and altering reaction times were studied using factorial planning (2
2
). Afterward, in natura and treated fibers were characterized via Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG) and derivative thermogravimetry. Holocellulose sample components were obtained by removing lignin. Factors including concentration and reaction time individually significantly affected cellulose yield. Alpha cellulose was produced when higher levels of the factorial planning conditions were applied. Ideal parameters for cellulose extraction included the addition of 10% (w/v) KOH for 3 h. FTIR analysis was used to ensure that lignocellulosic components were removed by fiber treatment. TG showed that treated fibers were thermally stable at temperatures close to, or higher than, in natura fibers.
This work studied the sheet resistance and conductivity of nanocomposite of regenerated cellulose films (RCFs) and silver nanoparticles (AgNPs). The novelty is associated with obtaining conductive ...nanocomposite films from jute fibers, which can be promising for application in electronic devices. A combination of chemical treatments was conducted to obtain bleached jute cellulose, which was used to obtain RCFs. The fibers were characterized by X-ray diffraction, Fourier-transform infrared (FTIR) spectroscopy and thermal analysis. Nanocomposites films were produced containing 0.070%, 0.145% and 0.290% (w/w) of AgNPs, compared to a pure RCF. Further, FTIR, ultraviolet-visible spectroscopy, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), and sheet resistance using the van der Pauw were used to characterize the films. The chemical treatments removed lignin and hemicellulose present in the fiber, increased the crystallinity index and increased the thermal stability. Additionally, the treated fibers were more thermally stable than raw jute. The RCF thermal stability was approximately 225 °C. SEM-EDS of the films showed dense structures and a homogeneous AgNPs dispersion. The regenerated cellulose/AgNPs films showed an increase in conductivity in the range of 10−2 S/cm and decreased transmittance with increasing nanoparticle content, with the 0.290% AgNPs sample being the most conductive.
Display omitted
•Chemical treatments allowed the removal of lignin and hemicellulose of jute fibers.•Bleached cellulosic fibers enabled the production of regenerated cellulose films.•Bleached cellulose was dissolved in aqueous NaOH to production of nanocomposite films.•Increase of AgNPs in nanocomposite films increased the conductivity of the samples.•The conductivity of the nanocomposite films was in the range of 10−2 S/cm.
Functional or smart coatings (organic, inorganic, or hybrid) are formed by materials that can be adapted for many applications where they should be able to perform a well-defined set of functions, ...such as improving chemical, mechanical, electrical, and magnetic properties of the substrate. This project studied the anticorrosive efficiency of nanoaditivated pigment-free epoxy coating by the addition of rGOL in the contents of 0.1 and 0.5 wt%. XRD, AFM, FTIR, and Raman spectroscopies were employed to obtain relevant information on the molecular structure and interaction between epoxy resin and rGOL. Thermogravimetry results did not indicate a significant change in polymer matrix T
g
. This could be related to an incomplete curing process of the resin and/or the presence of defects in the rGOL sample. All the corrosion tests results indicated that the rGOL addition promotes improvements to the epoxy corrosion resistance reached by a barrier mechanism.
In this project there were prepared solar cells using substrates of ITO on glass. The cell assembly was performed using carbon-ITO as cathode and, fourth types of anodes: (1) ITO-TiO2 commercial ...particles, (2) ITO-TiO2 thin film, (3) ITO-TiO2+SWCNT (functionalized single wall carbon nanotubes), (4) ITO- TiO2+ MWCNT (functionalized multi wall carbon nanotube), as anode respectively. For these types of solar cells was used solution organic dye Congo Red with ethanol, iodine electrolyte solution, between the two electrodes producing a photovoltaic cell Grätzel.
Studies of X-Ray diffraction (XRD) in the synthesized nanoparticles of TiO2 showed peaks corresponding to anatase structure, with particle size of 10nm, and large surface area of 6 m2 / g, too these showed higher stability potential that TiO2 commercial particle.
Preliminary studies showed that dye sensitized solar cell containing TiO2 nanoparticules and SWCNT showed the higher potential. Observed too that, the surface resistance is higher in the MWCNT then in the SWCNT.
PDF
