Digital holographic microscopy of spiropyran-based dynamic materials.

Spiropyran (SP)-based dynamic materials undergo structural changes in response to external stimuli. In this paper, we show that digital holographic microscopy (DHM) is an effective candidate for characterisation of SPs (embedded in polymer matrices) and for monitoring of their dynamical changes. The polymer matrices are polylactic acid (PLA) and poly(methyl methacrylate) (PMMA) films, which are decorated with SPs and immobilised on graphene quantum dots (GQDs). GQDs are modified by benzylamines prior to the loading of SP species because of the enhancement of hydrophobic characteristics. UV irradiation is used as the external stimulus and the dynamical changes of the samples before and after UV irradiation are measured. DHM is arranged on a novel self-referencing setup, which substantially reduces the sensitivity of DHM to environmental vibrations. Morphometric information for characterisation of the samples is obtained by analysis of the recorded digital holograms. The experimental results demonstrate the potential of the presented technique to serve as an alternative technique for surface measurement methodologies such as atomic force microscope and stylus profiler for surface characterisation of similar materials.

Direct coupling of CO2 with epoxides catalyzed by lanthanum(III) supported on magnetic mesoporous organosilica nanoparticles.

Lanthanum(III) supported on the magnetic mesoporous organosilica nanoparticle (La@MON) has been described as an efficient, simple, and durable heterogeneous catalyst for the synthesis of 5-membered cyclic carbonates from carbon dioxide (CO2) and epoxides. Under optimized reaction conditions, various terminal epoxides have been converted to the corresponding carbonates in the presence of 0.3 mol% La@MON and 0.5 mol% tetrabutylammonium iodide (TBAI) as co-catalyst at relatively mild reaction conditions. It was also found that La@MON catalysts had significantly higher catalytic activity than some selected reference catalysts, which can be explained by the abundance of lanthanum(III) species acting as Lewis acidic sites for activating both carbon dioxide and epoxide molecules, along with the fact that the catalyst channels are short and provided facile mass transfer. The catalyst showed good reusability for at least five reaction cycles while the magnetic core of the catalyst helps the easy separation of the catalyst by just using an external magnet.