Highly sensitive humidity sensor based on cadmium selenide quantum dots-polymer composites: synthesis, characterization, and effect of UV/ozone treatment

Abstract

This work describes the rational design of thin film-based cadmium selenide quantum dots (CdSe) mixed with conductive polyvinylidene fluoride (PVDF), inducing PVDF-CdSe composite for potential resistive humidity-sensing applications. The effect of UV/ozone treatment on surface hydrophilicity and sensing properties was investigated. AFM has been performed to examine the prepared films' texture, distribution over the surface, and size. Overall, the hydrophilicity of the developed films increases with UV radiation exposure time, leading to enhanced water vapor absorption without deforming the film surface. The sensor's sensitivity is improved with increasing UV radiation exposure. The electrical response of the PVDF-CdSe humidity sensors after 30 min of UV/ozone treatment reveals that at higher humidity levels (i.e., > 80% RH), the sensors exhibit an irregular response. However, at 20 min, treatment increases sensitivity and a linear change in impedance response concerning humidity level change compared to other samples. The hysteresis response was divided into two regions: the lower region, between 30 and 60% RH—where the maximum hysteresis loss was calculated to be 3%. While the higher area between 60 and 90% RH, where the maximum estimated hysteresis loss of the PVDF-CdSe sensor is around 14%, the UV/ozone treatment of the PVDF-CdSe nanocomposite film was found to enhance the sensing film's hydrophilicity without deforming the surface of the as-prepared PVDF-CdSe as well as the UV-treated films validates a potential for novel humidity sensors.