Fluorescent probe – which can detect metal ions, pH, and other analytical species through spectroscopic approaches – have recently attracted significant research attention in the fields of analytical and biological chemistry. For this study, two novel colorimetric and fluorescent probes, named RP1 and RP2, were designed and synthesized. Their structural confirmations were then achieved through elemental analysis, FT‐IR, NMR (¹H and ¹³C) spectroscopies, and tandem MS spectrometry. To gain full understanding of the photophysical properties and chemosensory performances of these two dyes, both the UV‐Vis absorption and fluorescence titration experiments were carefully performed in aqueous media. Notably, upon treatment of RP1 and RP2 in solutions with each competitive metal ion, neither increases in absorption and fluorescence spectra above 400 nm nor any changes in color were observed. However, at lower pH (i. e.,<7.0), those two sensors exhibited a drastic change in color from colorless to pink, followed by broadened absorption bands. As expected, upon excitation at 510 nm, a strong enhancement of the fluorescence emissions was obtained. By conducting ¹H NMR and optical titrations, the spirolactam‐ring opening reaction of these receptors, induced by H⁺ ions at lower pH, was approved. The results demonstrate that the fluorescent dyes RP1 and RP2 can be effectively used as reversible pH‐responsive chromogenic and fluorogenic “Off‐On” switches in real samples.

中文翻译：

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两个比色和荧光双通道化学传感器，用于水溶液中的pH选择性检测

荧光探针可以通过光谱方法检测金属离子，pH和其他分析物质，最近在分析和生物化学领域引起了广泛的研究关注。为进行这项研究，设计并合成了两种新颖的比色和荧光探针，称为RP1和RP2。然后通过元素分析，FT-IR，NMR（¹ H和¹³ C）光谱和串联MS光谱法获得了结构确认。为了全面了解这两种染料的光物理性质和化学感应性能，我们在水性介质中仔细进行了UV-Vis吸收和荧光滴定实验。值得注意的是，含有竞争性金属离子的溶液中的RP1和RP2，在400 nm以上的吸收光谱和荧光光谱均未增加，也未观察到颜色变化。但是，在较低的pH（即＜7.0）下，这两个传感器显示出从无色到粉红色的急剧颜色变化，随后吸收带变宽。如所预期的，在510nm处激发时，获得了荧光发射的强烈增强。通过¹ H NMR和光学滴定，这些受体的螺内酰胺开环反应在较低pH下由H ⁺离子诱导而被批准。结果表明荧光染料RP1和RP2可有效用作真实样品中可逆的pH响应发色和荧光“关闭”开关。