To overcome the limitations of optical pH sensors, the response of which is just ca. one pH unit around the pK_a value of the indicator dye and capitalize on the advantages of red-luminescent Ru(II) complexes for optical sensing, multi-pK_a members of this family are proposed. Bipyridine ligands bearing protonatable groups (amines and carboxylates) are the basis to design and prepare the indicator dyes. Their photophysical properties and response to pH changes were investigated in the pH 3.5 − 9.0 range. The complex [Ru(DCB)₂DEAMB], where DCB and DEAMB stand for 2,2’-bipyridine-4,4’-dicarboxylate and 4,4’-(N,N-diethylaminomethyl)-2,2’-bipyridine, respectively, shows a reversible monotonic change of its emission wavelength maximum (648 – 634 nm), luminescence intensity (1.40x) and lifetime (335 – 429 ns) in solution with increasing pH. This complex and two similar ones were covalently tethered to commercial TentaGel® M Br polymer microbeads for luminescence phase shift fiberoptic pH measurements. The immobilized [Ru(DCB)₂DEAMB] displays the widest pH sensitivity over pH 3.5 to pH 8.5. The stability of this sensor was satisfactory when cycling between pH 3.5 and 8.5 for five days as well as under a three-day cycle between each pH unit. Changes of the buffer type, buffer concentration and osmolarity did not significantly influence the sensor response; however, large variations of dissolved oxygen and, naturally, temperature would require correction by the corresponding sensors. The novel, robust luminescent pH sensor has been tested in phase-sensitive mode for cell cultures monitoring in commercial bioreactors, but its response would also be suitable for in situ monitoring of natural waters.

中文翻译：

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使用共价固定化多质子可 Ru（II） 配合物进行宽范围基于发光寿命的 pH 传感


为了克服光学 pH 传感器的局限性，其响应仅为指示剂染料的 pK_a 值周围大约一个 pH 单位，并利用红光发光 Ru（II） 络合物在光学传感中的优势，提出了该家族的多 pK_a 成员。带有质子化基团（胺和羧酸盐）的双吡啶配体是设计和制备指示染料的基础。在 pH 3.5 − 9.0 范围内研究了它们的光物理特性和对 pH 变化的响应。配合物 [Ru（DCB）₂DEAMB]，其中 DCB 和 DEAMB 分别代表 2,2'-联吡啶-4,4'-二羧酸酯和 4,4'-（N，N-二乙氨基甲基）-2,2'-联吡啶，其发射波长最大值 （648 – 634 nm）、发光强度 （1.40x） 和寿命 （335 – 429 ns） 在溶液中表现出可逆的单调变化，随着 pH 值的增加。将该复合物和两种类似的复合物共价连接到市售 TentaGel® M Br 聚合物微珠上，用于发光相移光纤 pH 值测量。固定化 [Ru（DCB）₂DEAMB] 在 pH 3.5 至 pH 8.5 范围内表现出最广泛的 pH 敏感性。当在 pH 3.5 和 8.5 之间循环 5 天以及每个 pH 单位之间的 3 天循环时，该传感器的稳定性令人满意。缓冲液类型、缓冲液浓度和渗透压的变化对传感器响应没有显著影响;然而，溶解氧和温度的较大变化需要相应的传感器进行校正。 这种新型、耐用的发光 pH 传感器已在相敏模式下进行了测试，用于商业生物反应器中的细胞培养物监测，但其响应也适用于自然水的原位监测。