A Thermochromic Thin Film Based on Host−Guest Interactions in a Layered Double Hydroxide

Abstract

Optically transparent thin films with thermochromic properties have been fabricated by means of cointercalation of different molar ratios of 4-(4-anilinophenylazo)benzenesulfonate (AO5) and sodium dodecylbenzene sulfonate (SDS) into the galleries of a ZnAl layered double hydroxide (LDH). The X-ray diffraction (XRD) patterns of these thin films show that they are assembled in a highly c-oriented manner, and the basal spacing ranges from 2.95 to 2.63 nm with varying AO5/SDS molar ratio. The preferential orientation of AO5 in the galleries of 10% AO5-LDH (AO5/SDS = 10:90, molar percentage) was evaluated by the fluorescence polarization technique; the results show that AO5 anions are accommodated between sheets of ZnAl-LDH as monomeric units with a tilt angle Psi (defined as the angle between the transition dipole moment of the AO5 anion with respect to the normal to the LDH layer) of 74 degrees. It was found that the composite film exhibits marked thermochromic behavior (light yellow <==> reddish-orange) in the temperature range of 35-65 degrees C, which is reversible over a number of heating-cooling cycles. It has been demonstrated that the thermochromic behavior results from tautomerism of interlayer AO5 and furthermore that both the host-guest and guest-guest interactions are key factors, since pristine AO5 shows no thermochromic performance. The 10% AO5-LDH film shows the highest thermochromic efficiency of all the films examined. Furthermore, a reversible contraction and expansion of the LDH basal spacing was also observed for this thin film over the same temperature range.

Recent Advances in Stimuli‐Responsive Photofunctional Materials Based on Accommodation of Chromophore into Layered Double Hydroxide Nanogallery

“…An effective way to enhance the thermochromic performances of this dye is to choose a suitable host matrix for tuning its molecular environment. Wang et al [25] have fabricated transparent thin films based on AO5 and sodium dodecylbenzene sulfonate (SDS) cointercalated in LDH, which show a fast and repeatable thermochromic behavior. By the use of temperature-dependent UV/visible absorption spectrophotometer, it was observed that the 10% AO5-LDH thin film shows the highest thermochromic efficiency.…”

“…This is one of the main bottlenecks in developing optical devices with superior optical properties based on the molecular isomerization. LDH nanosheets can provide the organic Journal of Nanomaterials The correlation between the absorbance of the band at 445 nm and temperature over a heating-cooling cycle [25]. chromophores with a rigid and ordered microenvironment, in which the severe interpenetration of the cis-trans groups may be restrained by the isolating effect of the 2D nanosheets.…”

Layered Double Hydroxide Materials: Assembly and Photofunctionality

“…It was well known that this tautomerism is very sensitive to the surrounding environment; therefore, it has been widely used as thermal sensors and in molecular memory storage. In order to further modulate the environment in an inorganic matrix, AO5 was co-intercalated with sodium dodecylbenzene sulfonate (SDS) into the interlayer of LDH [112]. The absorption [99] band at 363 nm at room temperature is attributed to the absorption of A-form, and the intensity increases with elevated temperature (Fig.…”

“…However, the research on piezochromic luminescent (PCL) materials remains relative seldom The correlation between the absorbance of the band at 445 nm and temperature over a complete heating-cooling cycle (inset shows the corresponding digital photographs) [112] Scheme 3 Tautomeric equilibrium between the A-Form and H-Form of AO5 [112] compared with other environment-responsive materials (such as temperature-, pHand HMI-sensitive materials). Therefore, the investigation on PCL materials with excellent reversibility, repeatability, and rapid responsiveness is still a challenge [168,169].…”

Photoresponsive thin films containing an azobenzene derivative intercalated with a layered double hydroxide

“…Therefore, it can be anticipated that the incorporation of an anionic azo dye into an LDH matrix will give rise to a new kind of photoresponsive material with the following features: first, the LDH host layers provide an ordered microenvironment for the distribution and alignment of the azobenzene groups within the available free space, which may reduce the barrier for isomerization; second, the presence of the inorganic LDH host matrix can improve the thermal and optical stability of the intercalated organic dye. In our previous work, transparent thin films were fabricated that contained AO5 and sodium dodecylbenzene sulfonate (SDS) co-intercalated in LDH, which showed reversible and repeatable thermochromic behavior based on the tautomerism of the AO5 between the azo A-form and the hydrazone H-form [24]. In this work, we further studied the photochromic behavior of an interlayer of AO5 based on its trans-cis isomerization.…”