Rare-earth post-modified Zn-based coordination polymer microspheres: Simple room-temperature preparation, fluorescent performances and application for detection of tryptophane

Zn-Hbtc-BPY/Ln(3+) fluorescent microspheres were successfully synthesized via a simple two-step solution route. First, the spherical Zn-Hbtc-BPY microstructures were prepared at room temperature employing zinc nitrate as the metal source, trimesic acid and bipyridine as the mixed ligands. Then, spherical Zn-Hbtc-BPY microstructures were sunk in an ethanol solution containing Ln(3+) ions (Ln(3+) = Eu3+, Tb3+, Eu3+/Tb3+) at room temperature to form Zn-Hbtc-BPY/Ln(3+) fluorescent microspheres. Experiments showed that the obtained Zn-Hbtc-BPY/Ln(3+) microspheres exhibited tunable optical properties under the excitation of the light with various wavelengths; and that white light emission could be achieved under the proper excitation wavelength. It was found that L-tryptophan could cause the characteristic emission increase/decrease at 370/546 nm of the as-prepared Zn-Hbtc-BPY/Tb3+ fluorescent microspheres. As a result, the fluorescence intensity ratio between the above wavelengths (I-370/I-546) could be tuned by the concentration of L-tryptophan. Since the other amino acids did not interfere with the above phenomenon, the as-obtained Zn-Hbtc-BPY/Tb3+ fluorescent microspheres have potential application as the fluorescence probe for the selective detection of L-tryptophan in the aqueous system with a detection limit of 15.2 mu M.