RESUMEN
An emerging strategy in the design of efficient gas storage technologies is the development of stimuli-responsive physisorbents which undergo transformations in response to a particular stimulus, such as pressure, heat or light. Herein, we report two isostructural light modulated adsorbents (LMAs) containing bis-3-thienylcyclopentene (BTCP), LMA-1 [Cd(BTCP)(DPT)2 ] (DPT=2,5-diphenylbenzene-1,4-dicarboxylate) and LMA-2 [Cd(BTCP)(FDPT)2 ] (FDPT=5-fluoro-2,diphenylbenzene-1,4-dicarboxylate). Both LMAs undergo pressure induced switching transformations from non-porous to porous via adsorption of N2 , CO2 and C2 H2 . LMA-1 exhibited multi-step adsorption while LMA-2 showed a single-step adsorption isotherm. The light responsive nature of the BTPC ligand in both frameworks was exploited with irradiation of LMA-1 resulting in a 55 % maximum reduction of CO2 uptake at 298â K. This study reports the first example of a switching sorbent (closed to open) that can be further modulated by light.
RESUMEN
Photo-switching of the NIR emission of gold nanoparticles (GNP) upon photo-isomerization of azobenzene ligands, bound to the surface, is demonstrated. Photophysical results confirm the occurrence of an excitation energy transfer process from the ligands to the GNP that produces sensitized NIR emission. Because of this process, the excitation efficiency of the gold core, upon excitation of the ligands, is much higher for the trans form than for the cis one, and tâc photo-isomerization causes a relevant decrease of the GNP NIR emission. As a consequence, photo-isomerization can be monitored by ratiometric detection of the NIR emission upon dual excitation. The photo-isomerization process was followed in real-time through the simultaneous detection of absorbance and luminescence changes using a dedicated setup. Surprisingly, the photo-isomerization rate of the ligands, bound to the GNP surface, was the same as measured for the chromophores in solution. This outcome demonstrated that excitation energy transfer to gold assists photo-isomerization, rather than competing with it. These results pave the road to the development of new, NIR-emitting, stimuli-responsive nanomaterials for theranostics.
RESUMEN
Controllable host-guest assemblies play a key role in developing supramolecular materials. This review highlights recent research progress for a type of host-guest systems based on cucurbiturils (CBs) and their derivatives, in which their structural states and related properties can be tuned in response to relative movements of CBs driven by a variety of external stimuli. By taking advantage of unique stimuli-responsive features, these CB-based host-guest systems have been grafted into applicable materials, such as biosystems, nanoarchitectures, and functional nanoparticles. In addition to discussing the preparation methodology and structural characterizations of several CB-based host-guest materials, their charming functionalities, accompanied by variation in the in situ controlled manner and resulting property changes were highlighted. Future studies on the applications of CB-based, smart, tunable materials are also predicted.