Simões Mónica Gaspar, Schennach Robert, Hirn Ulrich
AlmaScience CoLAB, Instituto RAIZ - Quinta de São Francisco, Rua José Estevão 221, 3800-783 Eixo-Aveiro, Portugal.
Institute of Solid-State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
J Colloid Interface Sci. 2024 Jan;653(Pt B):1642-1649. doi: 10.1016/j.jcis.2023.09.192. Epub 2023 Oct 2.
Interfacial adhesion caused by intermolecular forces only occur between surfaces at nano-scale contact (NSC), i.e., 0.1-0.4 nm and can be evaluated using Forster resonance energy transfer spectroscopy (FRET). For this, a suitable pair of fluorescent dyes must be selected, which spectroscopic properties will determine the FRET system performance. Here, we present a brand-new FRET dye system specifically designed to measure NSC in the distance range relevant for van-der-Waals and hydrogen bonding, i.e., below 1 nm.
We propose the FRET pair: 7-Amino-4-methyl-cumarin (C120) and 5(6)-Carboxy-2',7'-dichlor-fluorescein (CDCF) with high quantum yield (QY, QY = 0.91 and QY = 0.64) and a distance detection range of 0.6-2.2 nm (0.1 mM). Adhered-thin films with increasing NSC degrees are produced with ascending pressure from 1.5 to 150 bar. To validate the proposed FRET measurement, we are correlating the bonded films interfacial adhesion (separation energy) to the measured FRET intensity, indicating its degree of NSC.
We find that the proposed dyes are producing the desired FRET signal in adhered-thin films, for an interaction range of 0.6-2.2 nm, with high sensitivity due to the dye's high quantum yields. The increasing adhesion in these films is only caused by its increase in NSC. We find that the adhesion strength, measured as the separation energy between the films, is correlated to the measured FRET signal. Hence, the introduced FRET system is accurately able to measure the degree of NSC between soft surfaces.
由分子间力引起的界面粘附仅发生在纳米级接触（NSC）的表面之间，即0.1 - 0.4纳米，并且可以使用福斯特共振能量转移光谱（FRET）进行评估。为此，必须选择合适的一对荧光染料，其光谱特性将决定FRET系统的性能。在此，我们提出一种全新的FRET染料系统，专门设计用于测量范德华力和氢键相关距离范围内（即低于1纳米）的NSC。
我们提出FRET对：7-氨基-4-甲基香豆素（C120）和5(6)-羧基-2',7'-二氯荧光素（CDCF），其具有高量子产率（QY，QY = 0.91和QY = 0.64）以及0.6 - 2.2纳米（0.1 mM）的距离检测范围。通过从1.5到150巴的递增压力制备具有增加的NSC程度的粘附薄膜。为了验证所提出的FRET测量，我们将粘结薄膜的界面粘附（分离能）与测量的FRET强度相关联，表明其NSC程度。
我们发现所提出的染料在粘附薄膜中产生了所需的FRET信号，作用范围为0.6 - 2.2纳米，由于染料的高量子产率而具有高灵敏度。这些薄膜中粘附力的增加仅由其NSC的增加引起。我们发现，作为薄膜之间分离能测量的粘附强度与测量的FRET信号相关。因此，引入的FRET系统能够准确测量软表面之间的NSC程度。
