Development Of Ag-Doped (Polyaniline-Benzimidazole And Polyaniline-Polypyrrole/Tio2) Nanocomposite Sensor Materials For The Detection Of E. Coli And Ammonia

Abstract

Metallic oxide and conducting polymers-basedsensors have been investigated for the detection of endotoxin (E. coli) bacteria in horses’blood and ammonia gas in air and humidity. Due to the capability of CPs’ (like PANI, PPy and their composites) intrinsic and redox processes, they have attracted a great deal of attention as a gifted and promising sensor application materials. This is based on the reversible and redox processes, which play pivotal role in enhancing the performance of electrochemical as well as biochemical sensors’ applications. However, they have their own problems (working at high temperature which is not being handled for MOS) and performance problem for CPS based sensors.These problems are in chemical and biochemical performances due to morphology and surface area, etc. effects Besides, there are no effective biochemical and electrochemical sensors that could detect endotoxin (E. coli) bacteria and ammonia gas from adultered and putrefied foods (putrefied juice and poisoned meat respectively), which is detrimental to human health that can be taken as the greatest problem throughout the world especially in African countries including Ethiopia. These putrefied juice and poisoned meat lead to food-borne illness also called food poisoning, an illness caused by consuming contaminated, spoiled or toxic juice and meat which is either naturally poisonous or has been contaminated with toxic chemicals (like ammonia ) and bacteria(like endotoxin, E.coli) etc .The poison juice and meat may lead to different acute health poisoning such as brain and nerve damaged, chronic arthritis as well as hemolytic uremic syndrome which brings kidney failure or long-term health diseases such as cancer. So that in order to tackle this problem, new and novel Ag-doped PANI-benzimidazole nanocomposite biochemical sensor for the detection of endotoxin (E. coli) bacteria, PANI-Nanosphere and Ag-doped PANI PPy/TiO2nanocomposite sensors for the detection of ammonia have been developed via in-situ chemical oxidative polymerization method. The row materials are excellent stability, light weight as well excellent physical and chemical properties which originate from their π-conjugated system having their frivolous, process ability, resistance to corrosion, low-priced, and exceptional electrical, mechanical as well as optical properties. These make them very important regard to developthose anefficient sensor, vi whose detection performance were determined using confocal imaging and CV techniques. A new and active biochemical biosensor material of conductive Silver (Ag) reinforced polyaniline (PANI)-Benzimidazole copolymer nanocomposite was fabricated via in situ chemicaloxidative polymerization method for the detection of endotoxin. The fabricated Ag-doped PANI-Benz.nanocomposite was characterized by FTIR, XRD, UV–visible spectrometer, DSC, TGA, Zetapotential, SEM, TEM, and Confocal fluorescence imaging microscopy. The measured particle size,zeta-potential, and conductivity of the Ag-doped PANI-Benz. nanocomposite was 4.942 nm, -10.4 mV,and 73.7 μS cm-1 respectively. The crystallite size of Ag nanoparticles was around 67 nm calculated byXRD analysis and TGA analysis was carried out to determine weight loss and thermal stabilities ofPANI-Benz and Ag-doped PANI-Benz. nanocomposite. The endotoxin (E. coli) bacteria detection ability ofthe synthesized Ag-doped PANI-Benz. nanocomposite-based biochemical biosensor using DMMB dyedisplacement assay through the hitchhiking method by confocal fluorescence microscopy was foundto be simple and effective. Endotoxin (E. coli) can form a stable interaction with other bioactivemolecules and thus it binds readily with Ag-doped PANI-Benzimidazole nanocomposite. Further, theDMMB dye displacement assay method is more accurate and sensitive than the other existing methodsfor the detection of endotoxin. Polyaniline (PANI) nanosphere electrochemical ammonia (NH3) gas sensor was prepared by chemical oxidative polymerization of aniline with Azobisisobutyronitrile (AIBN) polymerization initiator in p-Toluene sulfonic acid (PTSA) at room temperature. It was characterized by DLS (size and zeta potential), UV-Visible, TGA, SEM, TEM XRD, FTIR and CV techniques. Extremely low (0.5 ppm) to 1000 ppm detection of ammonia gas was observed at 25°C operation condition. The anodic peak current value for ammonium ion detection in NH4Cl was 6.631 E-4A at 1.496 mV while for ammonium ion detection in poised meat was 6.585 E-4 A at 1.495 mV have been recorded. PANI nanosphere particle size and zeta potential values of 499.2 nm and - 4.23 mV respectively measured by DLS. vii Silver doped poly(aniline-co-pyrrole)/Titanium dioxide (Ag-doped PANI-PPy/TiO2) conducting copolymer-based nanocomposite ammonia gas sensor was synthesized with different amounts (4wt.%,5wt.%, 6wt.%, 7wt.% and 8wt.%) of AgTiO2(1:2.13ratio) nanoparticles. The UV-Visible spectroscopic analysis exhibited the absorption bands having band gap of 1.87 eV for the Ag-doped PANI-PPy/TiO2 nanocomposite sensor than PANI-PPy copolymer (3.17eV). The Zetasizer (DLS) results provided the size distribution (2.198 nm), zetapotential of -12.9 mV and also an increase in conductivity of 0.101 mS/cm compared with PPy, PANI, PANI-PPy and Ag-doped PANI-PPy due to synergetic effect which are advantageous and desirable for gas sensor. There was an enhancement in detection sensitivity of Ag-doped PANI-PPy/TiO2 nanocomposite based gas sensor than PANI-PPy copolymer to detect am