Preparation Of Au/Pani Thin Films And Their Dual-band Electrohcromic Properties Research

Building energy-saving materials such as electrochromic smart windows have become the focus of researchers due to the shortage of energy resources.Electrochromic materials refer to materials whose optical properties such as transmittance,absorptivity,reflectivity and color change under applied voltage.Traditional electrochromic materials only consider the properties of visible light band such as absorbance,transmittance,response time and stability.However,the energy of near infrared band in sunlight accounts for 48% of the total energy.Traditional electrochromic materials can not meet the needs of near infrared adjustable.Therefore,the new smart window material requires that its optical performance can be adjusted in both visible and near infrared bands to achieve independent regulation of solar light and heat.The use of improved electrochromic materials is more conveniently,energy saving and environmental protection.Polyaniline is a common electrochromic material,which doped with protonic acid has the advantages of rich color change and fast response time.However,the wide band gap of polyaniline limits its optical properties in near infrared band.In this paper,we successfully prepared Au/PANI composite films by compounding gold nanoparticles with polyaniline.And we found these gold nanoparticles can broaden the range of band gap in polyaniline making it control the visible and near infrared spectroscopic properties independently.Firstly,polyaniline films were prepared by electrodeposition at different polymerization time.It was found that the electrodeposition time had a significant effect on the optical properties of polyaniline films.Polyaniline films with 500 s of polymerization time had the largest range of visible-near infrared transmittance control.When applied with different voltages to make the films in different redox states,the transmittance ranged from 39% to 31.1% at 540 and 1500 nm.Secondly,gold nanoparticles were synthesized by solution method,and we dropped them on the prepared PANI film,repeating these steps we got the Au/PANI composite film with a layer by layer structure.In order to obtain the optimal composite film,the types,content and preparation technology of gold nanoparticles were studied in this paper.Among them,the transmission of Au/PANI composite films at 540 and 1500 nm ranged from 50.1% to 45.7% when the total content of Au/PANI composite films was 0.35?g in polyaniline films deposited at 500 s.Compared with pure polyaniline films,the solar radiation energy regulation ability in visible and near infrared bands increased by about 10%.The Au/PANI composite film achieves three photothermal control modes: VIS transmission,NIR transmission,VIS transmission,NIR transmission,VIS and NIR transmission,with exhibiting various color changes such as purple,blue,green and yellow.Finally,the mechanism of the optical properties of Au/PANI thin films in the visible-near infrared dual-band was analyzed.It was found that the composite of gold nanoparticles could not only expand the range of the transmittance of PANI in the near-infrared region,but also exhibits multi-color changes.