Highly luminescent metal–organic frameworks (LMOFs) have received great attention for their potential use in energy-efficient general lighting devices such as white-light-emitting diodes (WLEDs); however, achieving strong emission with controllable color, especially high-quality white light, remains a considerable challenge. Herein, we present a new strategy to encapsulate in situ multiple dyes into nanocrystalline ZIF-8 pores to form an efficient dyes@MOF system. Using this strategy, we build three models, namely, multiphase single-shell dye@ZIF-8, single-phase single-shell dyes@ZIF-8, and single-phase multishell dyes@ZIF-8, to systematically and fine-tune the white emission color by varying the components and concentration of encapsulated dyes. The study of these three models demonstrates the importance of the multishell structure, which can effectively reduce the interactions such as Förster resonance energy transfer (FRET) between encapsulated dyes. This energy transfer would otherwise be unavoidable in a single-shell setting, which often reduces the efficiency of white-light emission in the dyes@MOF system. This approach offers a new perspective not only for fine-tuning the emission color within nanoporous dyes@MOFs but also for fabricating MOF nanocrystals that are easily solution-processable. The strategy may also facilitate the development of other types of MOF–guest nanocomposite systems.

No abstract

Luminescent metal–organic frameworks (LMOFs) demonstrate strong potential for a broad range of applications due to their tunable compositions and structures. However, the methodical control of the LMOF emission properties remains a great challenge. Herein, we show that linker engineering is a powerful method for systematically tuning the emission behavior of UiO-68 type metal–organic frameworks (MOFs) to achieve full-color emission, using 2,1,3-benzothiadiazole and its derivative-based dicarboxylic acids as luminescent linkers. To address the fluorescence self-quenching issue caused by densely packed linkers in some of the resultant UiO-68 type MOF structures, we apply a mixed-linker strategy by introducing nonfluorescent linkers to diminish the self-quenching effect. Steady-state and time-resolved photoluminescence (PL) experiments reveal that aggregation-caused quenching can indeed be effectively reduced as a result of decreasing the concentration of emissive linkers, thereby leading to significantly enhanced quantum yield and increased lifetime.

A novel nanosensor was explored for the highly selective detection of intracellular carbon monoxide (CO) by surface enhanced Raman spectroscopy (SERS) on the basis of palladacycle carbonylation. By assembling new synthesized palladacycles (PC) on the surface of gold nanoparticles (AuNPs), SERS nanosensors (AuNP/PC) were prepared with good SERS activity and reactivity with CO. When the AuNP/PC nanosensors were incubated with a CO-containing system, carbonylation of the PC assembled on AuNPs was initiated, and the corresponding SERS spectra of AuNP/PC changed significantly, which allowed the carbonylation reaction to be directly observed in situ. Upon SERS observation of CO-dependent carbonylation, this SERS nanosensor was used for the detection of CO under physiological conditions. Moreover, benefiting from the specificity of the reaction coupled with the fingerprinting feature of SERS, the developed nanosensor demonstrated high selectivity over other biologically relevant species. In vivo studies further indicated that CO in normal human liver cells and HeLa cells at concentrations as low as 0.5 μM were successfully detected with the proposed SERS strategy, demonstrating its great promise for the analytical requirements in studies of physiopathological events involved with CO.