Carbon Nanotubes and Graphite Doped Nano Hydroxyapatite Gas Sensor

Abstract

Sensing matrices based on Calcium Hydroxyapatite (HAp) and Graphite and CNT newlinecomposite materials are prepared as thick films using screen printing techniques. Six newlinedifferent composites of HAp doped with variable weight concentrations of Graphite newlineand CNT are prepared for sensor material. Structural and morphological newlinecharacterizations are performed using X-Ray Diffraction (XRD), Brunauer-Emmett- newlineTeller (BET), Scanning Electron Microscopy (SEM) and Energy Dispersive newlineSpectroscopy (EDX). Ideal performance of the sensor is important from a device newlinepoint of view. It includes various parameters such as sensitivity, response/recovery newlinetime and uptake limit of these films. These parameters are investigated in the newlinepresence of atmospheric air and test vapors using two probe electrical methods. The newlineexperimental study involves detection of alcoholic vapors / volatile pollutants like newlinemethanol, ethanol, and propanol at lower concentration level (100ppm) and newlineammonia at 5ppm. The study of gas sensing characteristics of (i) HAp, (ii) Graphite newlinedoped HAp and (iii) CNT doped HAp material reveals the enhanced role of dopant newlinein the detection of volatile pollutant (VOCs). An addition of Graphite and CNT newlineshows much (six times) higher sensitivity for alcoholic vapors and ammonia vapors newlinethan synthesized HAp. The quantity of Graphite and CNT as the doping material newlinealso makes a noticeable effect on sensing performance of the device. Such material newlinecan be incorporated to monitor alcoholic vapors discharged in the environment at newlinetheir meagre concentrations. The uniqueness of the sensor substrate lies in selectivity newlineof the vapours. It detects individual species viz., methanol, ethanol, and propanol newlineseparately at their respective temperatures even when all these vapors are newlinecollectively present in the ambient air. Literature servey reveals that there are many newlinedifferent types of alcohol sensors designed and developed for the detection of the newlinealcohol concentration in the ambient atmosphere. A novel electrochemical sensor is newlinedeveloped by Liang Yan to moni