Parambath Mithun, Hanley Quentin S, Martin-Martinez Francisco J, Giesa Tristan, Buehler Markus J, Perry Carole C
School of Science and Technology, Nottingham Trent University, Nottingham, NG11 8NS, UK.
Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, USA.
Phys Chem Chem Phys. 2016 Feb 17;18(8):5938-48. doi: 10.1039/c5cp05105c.
PDMPO (2-(4-pyridyl)-5-((4-(2-dimethylaminoethylaminocarbamoyl)methoxy)phenyl)oxazole), has unique silica specific fluorescence and is used in biology to understand biosilicification. This 'silicaphilic' fluorescence is not well understood nor is the response to local environmental variables like solvent and pH. We investigated PDMPO in a range of environments: using UV-vis and fluorescence spectroscopy supported by computational data, (SPARC, molecular dynamics simulations, density functional theory calculations), dynamic light scattering and zeta potential measurements to understand the PDMPO-silica interaction. From absorption data, PDMPO exhibited a pKa of 4.20 for PDMPOH2(2+) to PDMPOH(+). Fluorescence emission measurements revealed large shifts in excited state pKa* values with different behaviour when bound to silica (pKa* of 10.4). PDMPO bound to silica particles is located in the Stern layer with the dye exhibiting pH dependent depolarising motion. In aqueous solution, PDMPO showed strong chromaticity with correlation between the maximum emission wavelength for PDMPOH(+)* and dielectric constant (4.8-80). Additional chromatic effects were attributed to changes in solvent accessible surface area. Chromatic effects were also observed for silica bound dye which allow its use as a direct probe of bulk pH over a range far in excess of what is possible for the dye alone (3-5.2). The unique combination of chromaticity and excited state dynamics allows PDMPO to monitor pH from 3 to 13 while also reporting on surface environment opening a new frontier in the quantitative understanding of (bio)silicification.
2-(4-吡啶基)-5-((4-(2-二甲基氨基乙氨基甲酰基)甲氧基)苯基)恶唑（PDMPO）具有独特的二氧化硅特异性荧光，在生物学中用于理解生物硅化作用。这种“亲硅”荧光尚未得到充分理解，其对溶剂和pH等局部环境变量的响应也不清楚。我们在一系列环境中研究了PDMPO：使用紫外可见光谱和荧光光谱，并辅以计算数据（SPARC、分子动力学模拟、密度泛函理论计算）、动态光散射和zeta电位测量，以了解PDMPO与二氧化硅的相互作用。从吸收数据来看，PDMPO从PDMPOH2(2+)到PDMPOH(+)的pKa为4.20。荧光发射测量显示，与二氧化硅结合时，激发态pKa值有很大变化，且行为不同（pKa为10.4）。与二氧化硅颗粒结合的PDMPO位于斯特恩层，染料表现出pH依赖性的去极化运动。在水溶液中，PDMPO表现出强烈的色度，PDMPOH(+)*的最大发射波长与介电常数（4.8 - 80）之间存在相关性。额外的色度效应归因于溶剂可及表面积的变化。对于与二氧化硅结合的染料也观察到了色度效应，这使得它能够在远超单独染料可能的范围（3 - ！5.2）内直接探测整体pH。色度和激发态动力学的独特组合使PDMPO能够监测3到13的pH值，同时还能报告表面环境，为定量理解（生物）硅化作用开辟了新的前沿领域。 （注：原文中“3 - ！5.2”疑似有误，翻译时保留原文形式）
