Novel system using hydrogel with reduced graphite oxide particles as active layer for potential application in smart window

A suspended particle device (SPD) is a type of smart window that can be switched with an electrical stimulus, and its transmittance varies proportionally with the applied voltage. This work presents a new route to produce SPD, using hydrogels based on conventional polymers with trapped reduced graphite oxide (rGO) micrometric particles as an active layer, to make this product more accessible, as it is not yet cost-effective. The trapped rGO particles were produced from the chemical oxidation of graphite, followed by thermal reduction. The results of X-ray photoelectron spectroscopy (XPS) confirmed the production of reduced graphite oxide particles with a low quantity of oxidized carbon groups. X-ray diffraction (XRD) showed the crystalline graphitic structure of the produced rGO particles and proved their incorporation inside the hydrogel's tridimensional polymeric network. The presence of these particles causes a decrease of 28.3% in the degree of swelling of the hydrogel. The devices were assembled in two different configurations: (i) fluorine-doped tin oxide (cFTO); and (ii) silver paint (cAg) by changing the positions of the electrodes. The cAg device displayed better responses, with an immediate increase of 38.6% in transmittance, due to an applied voltage of 220 V, compared to the switched-off device. The voltage applying time also increased the transmittance of the cAg device, with an increase of 36.6% after 20 min under 220 V, compared to the device immediately turned on.