THE AMMONIA VAPORS INFLUENCE ON THE ELECTRICAL CHARACTERISTICS OF NANOSIZED TIN DIOXIDE FILMS OBTAINED USING A POLYMER

In the presented paper the effect of ammonia vapors on the electrical properties of nanosized tin dioxide films obtained using polymers was investigated to assess the possibility of their use as an ammonia sensor’s sensitive element at room temperature. Ammonia vapor leads to a decrease in the conductivity of the studied SnO2 films. This is due to the fact that the adsorbed ammonia molecules increase the height of the intergranular potential barriers, and the surface shut-off bend of the energy bands. The main role in this is played by the processes of physical adsorption of ammonia molecules. The sensitivity of the films to ammonia vapor is in the range of 0.35-0.63 and reaches a maximum at a voltage of 300 V. The processes of adsorption and desorption take place in two stages and are reversible, as evidenced by the calculated time constants of adsorption and desorption.

Comparison of Optical Ammonia-Sensing Properties of Conducting Polymer Complexes with Polysulfonic Acids

Thin films of conducting polymer complexes with polysulfonic acids of various structures were electrochemically deposited onto transparent FTO electrodes. The behavior of the polymer-based optical ammonia vapor sensors in response to various concentrations of ammonia vapors, ranging from 5 to 135 ppm, was investigated, including the response time and response amplitude. It was found that the nature of the conducting polymers (poly (3,4-ethylenedioxythiophene), polypyrrole, polyaniline), as well as the structure of the polyacids, affected the sensing performance of the obtained complexes.

Detection of aflatoxin producing Aspergillus flavus from animal feed in Karnataka, India.

Aflatoxins are toxic carcinogenic secondary metabolite produced by Aspergillus flavus and are responsible for contamination in animal feed. The aim of the study was to determine the prevalence of aflatoxin contamination in animal feed in Karnataka state, India. The screening was performed by desiccated coconut agar and quantification of aflatoxin by liquid ammonia vapor test, TLC and ELISA. A total of 29 samples received from different places of Karnataka were analysed for aflatoxin B1. Out of 29 animal feed sample aflatoxin B1 detected in 12 samples representing 41.38% at average concentration of 288.50 μg/kg. Out of 42 isolates screened in animal feed, Aspergillus flavus was found to be in 86.2% and Aspergillus niger was 24.1%. It was observed that out of 42 isolates analyzed from animal feed, aflatoxin B1 was detected in 12 samples. Aflatoxin B1 is the most common contaminant and the method is more sensitive in screening and detection of aflatoxin B1 in the animal feed.

Fabrication of Reproducible and Selective Ammonia Vapor Sensor-Pellet of Polypyrrole/Cerium Oxide Nanocomposite for Prompt Detection at Room Temperature

Polypyrrole (PPy) and polypyrrole/cerium oxide nanocomposite (PPy/CeO2) were prepared by the chemical oxidative method in an aqueous medium using anhydrous ferric chloride (FeCl3) as an oxidant. The successful formulation of materials was confirmed by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmittance electron microscopy (TEM). A four-in-line probe device was used for studying DC electrical conductivity and ammonia vapor sensing properties of PPy and PPy/CeO2. The significant improvement in both the conductivity and sensing parameters of PPy/CeO2 compared to pristine PPy reveals some synergistic/electronic interaction between PPy and cerium oxide nanoparticles (CeO2 NPs) working at molecular levels. The initial conductivity (i.e., conductivity at room temperature) was found to be 0.152 Scm−1 and 1.295 Scm−1 for PPy and PPy/CeO2, respectively. Also, PPy/CeO2 showed much better conductivity retention than pristine PPy under both the isothermal and cyclic ageing conditions. Ammonia vapor sensing was carried out at different concentration (0.01, 0.03, 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5 vol %). The sensing response of PPy/CeO2 varied with varying concentrations. At 0.5 vol % ammonia concentration, the % sensing response of PPy and PPy/CeO2 sensor was found to be 39.1% and 93.4%, respectively. The sensing efficiency of the PPy/CeO2 sensor was also evaluated at 0.4. 0.3, 0.2, 0.1, 0.05, 0.03, and 0.01 vol % ammonia concentration in terms of % sensing response, response/recovery time, reversibility, selectivity as well as stability at room temperature.

Simple Preparations and Characterizations of Activated-Carbon- Clothes from Palm-Kernel-Shell for Ammonia Vapor Adsorption and Skim-Latex-Odor Removal

This study explored a simple preparation and characterization of the activated carbon and cloth from the palm kernel shell and compared it to the commercial-water-filter-carbon specification. A new pyrolysis chamber that is easily scaled up using the palm kernel shell itself as a heat source was tested. Two different steps were compared: the alkaline activation process performed before or after the carbonation process in the palm-kernel-shell carbon preparation. The palm-kernel-shell activated carbons prepared with the current method fulfilled the standard quality of activated charcoal except for the ash content. The sequencing step of the preparation affected the adsorption capacity. Instead of the reverse sequence, the soaking palm kernel shells in NaOH before the carbonation process lead to a higher adsorption capacity. The carbon particle stability on the cloth surface was affected by both the adhesive concentration and its size. The ammonia adsorption capacity of activated carbon cloth (ACC) was between 1–4 mg ammonia per g stuck carbon. The preparation and the carbon type source on ACC affected the adsorption capacity. The ACC absorbed and lessened the skim latex odor vapor, nearly odorless depending on the ACC area and the volume of odor vapor.