Rhodamine-Based Ratiometric Fluorescent Probe For The Determination Of Pd²⁺ Ions

Palladium, one of the platinum-group elements, is ideally suited for catalysts (chemical synthesis catalysts and automobile exhaust catalysts), dental materials, electrical equipments, fuel cells, and jewelry. Howerer, the extensive use of palladium increases the risks associated with health hazards. It has been shown that palladium can coordinate with DNA, thiol-containing amino acids, proteins, and vitamin B6, and disturb several cellular processes, thereby leading to health problems. Thus, the threshold for palladium in drugs is set at5ppm (mg/kg) to10ppm, and the proposed maximum dietary intake of palladium is<1.5μg to15μg per person per day. Consequently, effective methods to detect trace palladium are necessary.Traditional analytical methods (atomic absorption spectrometry, plasma emission spectroscopy, solid-phase microextraction-high-performance liquid chromatography, and X-ray fluorescence) can quickly detect palladium with high sensitivity but need expensive instrumentation and highly skilled individuals. Fluorescence methods, however, can avoid these shortcomings while maintaining the efficiency and accuracy of the traditional methods and therefore have been exploited by researchers.In this study, An aniline-rhodamine-based ratiometric fluorescent probe (RI) was designed and synthesized. The probe RI exhibits both fluorometric and colorimetric responses to Pd2+ions with high selectivity and sensitivity, thus providing a method for visual detection of Pd2+ions. The detection limit for Pd2+ions with RI was73.8nM (nmol/L), the response time was10min. And then, the aniline moiety of RI was replaced by naphthylamine to obtain an improved ratiometric fluorescent probe (RN). This improvement increases the emission wavelength of the short wavelength and remains the highly selective and sensitive detection of Pd2+ions, makes the probe has a wider range of applications. The detection limit for Pd2+ions with RN was45.9nM and the response time was still10min. Furthermore, the probe RN can be used to monitor Pd2+ions in live mice by fluorescence imaging.