Phosphate
is an important anion in both the aquatic environment
and biological systems. The search for a selective and sensitive phosphate
ratiometric fluorescent probe to quantify the phosphate level in water
samples and body fluids is of great significance for the protection
of the ecological environment and human health. Here, a porphyrin-based
nano metal–organic framework (NMOF), PCN-224, was successfully
exploited as a simple but highly sensitive and selective single-component
ratiometric fluorescent probe with accurate composition and measurable
structure for the quantitative determination of phosphate, based on
the interesting double-emission fluorescence of the porphyrin ligand
itself. Compared with other zirconium-based NMOF probes for phosphate,
the reduced number of connections for ZrO clusters with the ligand
in PCN-224 obtained by a linker-elimination strategy simultaneously
provides more active recognition sites for phosphate, which effectively
improves the sensitivity of the zirconium-based NMOF probes. The detection
limit of the probe is only 54 nM. Additionally, the accuracy of the
ratiometric detection based on this probe was further proved by the
detection of phosphate in human serum and drinking water.
A novel synthetic strategy toward a series of tetraphenylethene (TPE)functionalized polyethylene-based homo/copolymers is presented. Tris(3-(4-(1,2,2triphenylvinyl)phenoxy)propyl)borane, synthesized by hydroboration of (2-(4-(allyloxy)phenyl)ethene-1,1,2-triyl)tribenzene with BH3, was used to initiate the polyhomologation of dimethylsulfoxonium methylide to afford well-defined TPE-terminated linear polyethylene (PE). Combining this efficient strategy with ring-opening polymerization (ROP) or atom transfer radical copolymerization (ATRP) TPE-functionalized PE-based block copolymers have been synthesized. All synthesized polymers showed aggregation-induced emission (AIE)-behavior either in solution or in bulk. Self-assembly of the PE-based block copolymer in DMF resulted in strong emission due to the AIE effect of the aggregated TPE-PM core, the fluorescence intensity of the solution is directly related to the composition of block copolymers and the size of the micelle. The response of the AIE-operative fluorescence behavior toward the concentration of the block copolymer solutions has also been used to locate the CMC value of the block copolymers. The non-emissive dilute solutions of block copolymers became fluorescent when increasing concentrations above CMC. ASSOCIATED CONTENT Supporting Information. Additional figures are presented in the supporting inforamtion. This material is available free of charge via the Internet at http://pubs.acs.org.
A novel synthetic strategy gives reversible crosslinked polymeric materials with tunable fluorescence properties. Dimaleimide-substituted tetraphenylethene (TPE-2MI), which is non-emissive owing to the photo-induced electron transfer (PET) between maleimide (MI) and tetraphenylethene (TPE) groups, was used to cross-link random copolymers of methyl (MM), decyl (DM) or lauryl (LM) methacrylate with furfuryl methacrylate (FM). The mixture of copolymer and TPE-2MI in DMF showed reversible fluorescence with "on/ off" behavior depending on the Diels-Alder (DA)/retro-DA process, which is easily adjusted by temperature. At high temperatures, the retro-DA reaction is dominant, and the fluorescence is quenched by the photo-induced electron transfer (PET) mechanism. In contrast, at low temperatures, the emission recovers as the DA reaction takes over. A transparent PMFM/TPE-2MI polymer film was prepared which shows an accurate response to the external temperature and exhibited tunable fluorescent "turn on/off" behavior. These results suggest the possible application in areas including information security and transmission. An example of invisible/visible writing is given.
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