Solid-state photochromism of spironaphthoxazine loaded microcapsules with photo-patterning and thermo-regulating features.

HYPOTHESIS: One of the biggest challenges in the field of photoresponsive spirooxazines is their fast reverse isomerization. Polar phase change materials beside spirooxazines not only stabilize their colored-form, but also induce thermo-regulating properties to the whole system. Moreover, encapsulation is a key route to protect them and provide safe application of photochromic materials in solid-state matrices. EXPERIMENTS: A solution of spironaphthoxazine in oleic acid was encapsulated through solvent evaporation technique and the obtained microcapsules were incorporated in a transparent polymeric coating and also non-woven cotton fabrics. A systematic study on the reverse isomerization rate of spironaphthoxazine, photo-patterning and thermo-regulating features of the microcapsules was performed. FINDINGS: Comprehensive analyses demonstrated successful encapsulation of oleic acid and spironaphthoxazine. Microcapsules showed reversible color changes upon UV-Vis irradiation below melting point of oleic acid and a 85% decrease in discoloration rate compared to those without oleic acid. They also exhibited excellent photoswitchability, making them suitable for anti-counterfeiting applications. Their thermo-regulating feature in cotton fabrics was studied by using of infrared camera and they represented energy saving potentiality. Optically monitoring of temperature around melting point of oleic acid is another feature of these microcapsules.

High performance cyanide sensing with tunable limit of detection by stimuli-responsive gold nanoparticles modified with poly (N,N-dimethylaminoethyl methacrylate).

Detection of cyanide ion (CN-) and design of new sensors with high sensitivity and selectivity are interesting topics in recent developments. Cyanide ions lead to immediate dissolution of gold nanoparticles (AuNPs) and distinct color changes from red to transparent colorless solution. The presence of any material e.g. stabilizer may affect dissolution mechanism and hence sensing properties. Here, we represent a novel sensor (Au-PDA) based on the AuNPs coated with poly (N,N-dimethylaminoethyl methacrylate) (PDMAEMA) for the detection of CN- with tunable sensitivity. PDMAEMA bearing tertiary amine groups not only induced stimuli-responsivity to the prepared Au-PDA as the sensor, but also influenced the sensing performance like linear response range and limit of detection (LOD). The detection process with the increase in CN- concentration in wide range of pHs as well as high ionic strength of the medium was monitored by reduction of the localized surface plasmon resonance band of AuNPs at 530 nm. In the optimized condition, this sensing approach exhibited excellent selectivity in contrary to other anions and cations. The highest sensitivity was obtained in basic media (i.e. pH 9) with a LOD of 4.7 × 10-6 µM and two linear ranges from 10-5-10-3 µM and 0.04-320 µM. The tunable sensitivity could be considered as the strength point of such sensor with lowest LOD for detection of CN- and such a controlled stimuli-responsivity will open up a promising route toward adjustable detection of other chemicals.