Research On Sensors Based On Hydroxyapatite Film

In recent years,people pay more and more attention to environmental problems.It mainly involves the pollutions of water environment and air environment.Accumulation of Pb²⁺can cause various deleterious effects in human bodies such as kidney injury,anemia,memory loss and even cancer.Although Cu²⁺is essential for human bodies,its excess will cause health problems such as lung cancer and liver damage.The low-level Hg²⁺can damage the central nervous system,brain,kidney and lungs.Ammonia,the toxic and corrosive indoor air pollutants,is severe threat to human skin,eye and respiratory tract.In this paper,two kinds of hydroxyapatite（HAp）film sensors are designed for the detection of Pb²⁺,Cu²⁺and Hg²⁺and the testing of NH₃,which is very meaningful for solving environmental problems.The main work is as follows:Firstly,a novel electrochemical sensor basing on an indium tin oxide（ITO）glass electrode modified by HAp film was fabricated by electrodeposited method for simultaneous detection of Pb²⁺,Cu²⁺and Hg²⁺using differential pulse voltammetry（DPV）.Various experimental parameters such as supporting electrolyte and pH were optimized.Under the optimal conditions,the electrode needs no accumulate time.The electrode showed linear correlation in the ranges of 1×10^-7 to 1×10^-6 M and 3×10^-6 to1×10^-5 M for Pb²⁺,1×10^-7 to 1×10^-6 M and 1×10^-6 to 1×10^-5 M for Cu²⁺,and 1×10^-7 to1×10^-5 M for Hg²⁺.the limits of detection（S/N=3）were 1×10^-12,1×10^-12 and 8×10^-8M for Pd²⁺,Cu²⁺and Hg²⁺,respectively.Meanwhile,the developed electrode showed excellent anti-interference capabilities and selectivity with other heavy metal ions and common ions.The electrode has been successfully applied to the detection of above heavy metal ions in tap water.Above all,two major detection mechanisms of developed electrode were also researched in this work.Secondly,a room-temperature high-performance NH₃ gas sensor based on hydroxyapatite（HAp）film with three-dimensional network structure was reported in this paper.The gas sensor was fabricated on the indium tin oxide glass（ITO）interdigital electrode via simple electrochemical deposition technique.The HAp film gas sensor shows good sensitivity,high reproducibility and excellent selectivity to NH₃ gas under dry and relative humidity（RH）conditions at room temperature.The response and recovery time of the HAp film gas sensor to 1000 ppm NH₃ gas are 23 s and 14 s under N₂（dry）condition,and are 4 s and 11 s under air（RH≈30）condition,respectively.The HAp film gas sensor has no considerable deviation in the 1000 ppm NH₃ gas for 3 cycles under N₂（dry）,and so is air（RH≈30）conditions.The HAp film gas sensor shows excellent selectivity to methanol,acetone and ethanol under N₂（dry）and air（RH≈30）conditions.Above all,two sensing mechanisms of the HAp film gas sensor to NH₃ gas have been also researched in this work.