Fabrication Of Electrospinning Polypyrrole/Copper Composite Nanotube For Nitrite Detection

Polypyrrole（PPy）is one of the typical conductive polymers with redox reversibility,good stability,high conductivity and prepared easily,and can be prepared by electrochemical method and chemical oxidation polymerization of pyrrole monomer（Py）.In recent years,with the vigorous development of nanomaterials,polypyrrole nanomaterials with different structural shapes have been successively prepared,such as nanospheres,nanorods,and nanotubes,etc.,and exhibit specific light and electricity,magnetic,thermal,mechanical,and other properties,having a broad application prospects.Compared with other morphologies,nanotube materials have the advantages of large specific surface area,many active sites and excellent conductivity,and are suitable for the development and application of electrochemical devices.Electrospinning technology can efficiently produce nanofibers with large specific surface area,high porosity,continuous and uniform.The use of electrospinning nanofibers as templates can effectively produce conductive polymer nanotubes with high aspect ratio,uniform and large specific surface area,which greatly promotes the development of hollow nanomaterials.In this paper,polystyrene（PS）nanofibers were prepared using electrospinning and PPy nanotubes were fabricated using Py polymerization on an electrospun PS nanofiber followed by solvent etching.Polypyrrole-copper nanotubes（PPy-Cu）were fabricated on the surface of PPy nanotubes by loading the ultrafine copper nanoparticles.The resulting materials were characterized by different characterization techniques and electrochemical means.Nitrite（NO₂^-）electrochemical sensors were successfully developed by optimizing operating conditions.The main conclusions are as follows:1.With as PS precursor,N,N-dimethylformamide（DMF）as solvent and tetrabutylammonium bromide（TBAB）as conductive,the PS nanofibers with the size of 150 nm were prepared by electrospinning.Following sulfonation,PPy was coated on the sulfonated PS fiber by chemical polymerization.And PPy nanotubes were obtained after removal of PS template.Scanning electron microscopy（SEM）and Fourier transform infrared spectroscopy（FT-IR）demonstrate the formation of PPy nanotubes.And the form of PPy nanotubes depends on Py monomer concentration.When Py concentration is 0.6%（PPy（0.6%））,the PPy nanotubes with the uniform wall thickness of 80±7nm and inner diameter of 110±26 nm are achieved.Cyclic voltammetry（CV）analysis using a three-electrode system reveals that the PPy/GCE with uniform particle distribution and the high redox activity have the highest redox activity,improving the electron transportation in electrochemical sensors.2.The ultrafine Cu nanoparticles were successfully deposited onto the PPy nanotube surface using a convenient constant potential deposition at-0.7V.Transmission electron microscopy（TEM）,energy dispersive X-ray from TEM（TEM-EDX）and X-ray photo spectroscopy（XPS）analysis indicate that Cu particles exist majorly in the form of zero-valent copper,and these particles uniformly distribute along the nanotube inner and outer wall without any agglomeration.As the electrodeposition time increases,the Cu nanoparticle size and copper content increase slightly.Particles size of Cu varies from 2.5 nm to 5.0 nm.It proves that PPy with the tubular structure facilitates the deposition of Cu due to high surface area and rich active sites on the PPy tube to interact with Cu atom.3.The PPy-Cu/GCE shows an excellent catalytic activity to the reduction of nitrite via cyclic voltammetry technique.The catalytic performance of the obtained PPy-Cu/GCE was optimized by varying the morphology of the PPy,the deposition amount of copper and concentration of H₂SO₄solution.PPy（0.6）-Cu/GCEs with Cu particle size of 4.2±1.2 nm（200s deposition time）have the best electrocatalytic performance for the reduction of nitrite at 0.1 M H₂SO₄ solution.There is a good linear relationship between the reduction current value and NO₂^-concentration in the range of 0.1-0.7μM and 0.7-1040.7μM,respectively.The corresponding linear calibration equation is:Ip（μA）=-1.5688C-0.01487（R²=0.9911）and Ip（μA）=-0.0458C-0.77763（R²=0.9996）,with a detection limit of approximately 0.03μM（S/N>3）.Obviously,the current PPy（0.6）-Cu/GCE has a wider linear range and lower detection limit than the prior art.It has been successfully applied to real-life water sample analysis.The high selectivity,stability and repeatability of PPy-Cu/GCEs demonstrate the great potential of nitrite sensing applications.