Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam, 1098XH, Amsterdam, The Netherlands.
Université de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPRA, Pau, France.
Sci Rep. 2022 Dec 23;12(1):22197. doi: 10.1038/s41598-022-26722-w.
Environmentally sensitive molecular rotors are widely used to probe the local molecular environment in e.g. polymer solutions, polymer glasses, and biological systems. These applications make it important to understand its fluorescence properties in the vicinity of a solid surface, since fluorescence microscopy generically employs cover slides, and measurements are often done in its immediate vicinity. Here, we use a confocal microscope to investigate the fluorescence of (4-DASPI) in glycerol/water solutions close to the interface using hydrophilic or hydrophobic cover slips. Despite the dye's high solubility in water, the observed lengthening of the fluorescence lifetime close to the hydrophobic surface, implies a surprising affinity of the dye with the surface. Because the homogeneous solution and the refractive index mismatch reduces the optical sectioning power of the microscope, we quantify the affinity with the help of a simple model of the signal vs. depth of focus, exhibiting surface and bulk contributions. The model reduces artefacts due to refractive index mismatch, as supported by Monte Carlo ray tracing simulations.
环境敏感分子转子广泛用于探测例如聚合物溶液、聚合物玻璃和生物系统中的局部分子环境。这些应用使得理解其在固体表面附近的荧光性质变得很重要，因为荧光显微镜通常使用盖玻片，并且测量通常在其附近进行。在这里，我们使用共焦显微镜研究了在亲水或疏水盖玻片的情况下，靠近界面的甘油/水溶液中（4-DASPI）的荧光。尽管该染料在水中的溶解度很高，但在靠近疏水面时观察到荧光寿命的延长，这表明该染料与表面具有惊人的亲和力。由于均匀溶液和折射率失配降低了显微镜的光学切片能力，我们借助于一个简单的信号与聚焦深度模型来定量确定亲和力，该模型同时考虑了表面和体相的贡献。该模型通过蒙特卡罗光线追踪模拟支持了折射率失配引起的伪影的减少。
