Preparation of zinc (II) nitrate poly acryl amide (PAAm) and its optoelectronic application for humidity sensing

The present paper reports the investigation of transmitted power through the nanostructured zinc (II) nitrate polyacrylamide deposited substrate to investigate the adsorption/desorption of humidity at room temperature. For this purpose, the precursor of Zn(NO₃)₂·(AAm)₄·2H₂O was prepared and used for the deposition of films on borosilicate flat substrates. The film was then investigated using SEM, XRD and UV–Vis absorption techniques. Scanning Electron Microscope showed the macroporous nature of the film with multiple pores in situ. XRD revealed the nature of monomer and polymer. Energy band-gap of the film was estimated as 3.865 eV by UV–Vis spectrophotometer. SAED confirmed the crystalline nature of the material. From Zeta nanosizer, the minimum range of particles was found as 5–20 nm. The film was employed as transmission based opto-electronic humidity sensor. Maximum sensitivity was found as 1.831 µW/%RH. Response and recovery times of the sensor were found as 250 and 37 s respectively. Experiments were repeated time to time and found that the sensor was ~ 96% stable after a long run. Thus the investigated opto-electronic sensor being polymeric is flexible in nature.