Photochromic TiO2/PEGDA organogels

Abstract

Photochromic materials can be used for modulation of the visible and infrared light transmittance for providing privacy or energy saving by blocking the heat. Titanium dioxide (TiO 2 ) nanoparticles has been well reported as a promising photochromic material. However, a high photochromic response from TiO 2 can be observed only when the nanoparticles are dispersed in a strong photogenerated hole scavenger at a liquid state, but polymer composites are less responsive due to lack of hole scavenging capability. However, it is intricate to apply suspensions in real window devices because of possible leaking. Here, we describe the preparation of TiO 2 quantum dot (QD)-based gels from polyethylene glycol diacrylate (PEGDA), N,N-Dimethylformamide (DMF), and ethanol (EtOH). Photochromic gels with TiO 2 contents (1-5 volume%) show performance comparable to their colloidal counterparts with capable of photodarkening within 30 min with a transmittance change ranging from 35.8 to 84.5% at 550 nm. These gels were capable of fully recovering the initial transmittance when not exposed to ultraviolet (UV) light within 3-8 h. The photochromic gel systems with ethanol shows reasonable stability by decreasing in transmittance recovery only by less than 10% in 10 cycles. A potential application for the developed photochromic gels can be photochromic windows.

Stretchable photochromic hydrous TiO2‐embedded glycerol‐poly(dimethylsiloxane) film for rewritable information storage

“…Moreover, the Δ E of the 40 phr film exceeded that of the 20 phr film, signifying that the films with higher hydrous TiO 2 ‐glycerol content exhibited superior color‐changing ability to those with a lower content. Compared to TiO 2 /polyethylene glycol diacrylate (PEGDA), the N , N dimethylformamide (DMF), and ethanol (EtOH) organogels as prepared by Eglītis and Šutka 24 who reported an 86% decrease in transmittance after 30 min, the color change experienced by the glycerol‐PDMS was not as significant, but the response time was nevertheless low (<5 min). Photochromic materials that fade quickly could be utilized for “Read and Burn” applications, which require instantaneous and temporary information display, whereas materials with a lower fading speed could function as rewritable films.…”

“…UV radiation induces the formation of Ti 3+ , 23 resulting in a color change from white to blue, albeit this has been found to fade quickly due to the oxidation of Ti 3+ with the consequent reformation of Ti 4+ . 9,24 Several strategies have been employed to enhance the photoresponsiveness of TiO 2containing materials, such as doping TiO 2 21 and adding alcohols. 25 TiO 2 particles, for example, have been doped with Nb, 21 silver nanoparticles, 26 graphene oxide, 6 and other kinds of oxides 9 to reduce oxygen vacancies and decrease the charge recombination rate, subsequently enhancing photochromism.…”

“…Among these inorganic compounds, TiO 2 particles have several attractive features, such as rapid responses to UV light, low toxicity, high stability, resistance to photocorrosion, and abundance in the earth. UV radiation induces the formation of Ti 3+ , 23 resulting in a color change from white to blue, albeit this has been found to fade quickly due to the oxidation of Ti 3+ with the consequent reformation of Ti 4+ 9,24 . Several strategies have been employed to enhance the photoresponsiveness of TiO 2 ‐containing materials, such as doping TiO 2 21 and adding alcohols 25 .…”