Preparation Of Copper Oxide Based Nanocomposites And Gas Sensing Properties Of NH 3

It is necessary to detect and monitor the content of NH₃ in the environment and industry.In this work,one dimensional?ID?Co₃O₄/CuO nanochains and In₂O₃/CuO nanorods with different molar ratios have been successfully prepared combining the electrospinning and calcinations method.The structure and morphology of the samples are characterized by XRD,FT-IR,RAMAN,XPS,BET,SEM and TEM techniques,and the response to ammonia gas at room temperature?RT?has been investigated.In addition,the gas sensing mechanism is also discussed.Firstly,the pristine CuO nanomaterials are fabricated by electrospinning approach and controlled annealing route.The gas sensitivity of the pristine CuO to NH₃ at different calcination temperatures is also studied.The calcined?600 ??samples are composed of CuO particles whose size is?100 nm and there are many smaller CuO nanoparticles?-23 nm?on the surface of particls.The 1D pristine CuO nanorods have many P-P homojunctions and lots of defect oxygen,which displayed the excellent gas sensing properties towards NH₃ at RT.The highest sensing response of the best sample is 24.2%with a fast response time of 22.7 s for 100 ppm NH₃.Secondly,Co₃O₄/CuO nanochains with P-P homojunctions are forming after calcination at the optimum calcination temperature?600 ??with doped P-type semiconductor Co₃O₄ into the pristine CuO nanocomposites.The addition of Co₃O₄ can improve the oxygen content in the composites and increase the carrier density of the Co₃O₄/CUO nanochains which endly enhance the gas response to ammonia at RT.The gas detection of NH₃ results show that CCNC-2?Cu:Co molar ratios of 5:2?has the best gas response toward NH₃ among the samples,the highest sensing response is up to 4.72 for 100 ppm NH₃ with a fast response time of 1.3 s,and its detection limit is only 1 ppm.Finally,In₂O₃/CuO nanorods are forming after calcination at 600? with doped N-type semiconductor In₂O₃ into the pristine CuO,which displays excellent gas sensing properties toward NH₃ at RT.The enhanced gas sensing properties of the best sample ICCN-5?Cu:In molar ratios of 100:5?shows the highest sensing response?1.57?,the fastest response time?2.0 s?for 100 ppm NH₃ and good stability after 30 days for 10 ppm NH₃,and its detection limit is 0.3 ppm.This may be attributed to P-N?CuO-In₂O₃?heterojunctions and P-P?CuO-CuO?homojunctions,which are favorable to form more electronic transfer channels,and ultimately resulting in faster electron transport.