基板表面张力对量子点胶体及其聚氨酯复合膜荧光性能的影响

Effect of Substrate Surface Tension on Fluorescence Properties of Quantum Dot Colloids and Quantum Dots/Polyurethane Composite Films

通过离子共沉积法、一锅法分别制备水相CdS@ZnS核壳结构量子点和水性聚氨酯,将量子点与聚氨酯以1:1的质量比均匀混合后,滴在具有不同表面张力的基板上,经自然干燥后形成量子点/聚氨酯薄膜。研究表明,基板的表面张力大小能直接影响量子点以及量子点薄膜的荧光性能。文中通过测量接触角来表征基板的表面张力。接触角越大,表面张力越小。表面张力较大时,会引起量子点大范围聚集,导致区域量子点浓度过大,引起浓度猝灭,所以,基板表面张力增大虽然能提升量子点的色纯度但也会导致其荧光强度下降。在365 nm紫外灯照射下可以明显看出基板与量子点分散液接触面荧光强度明显高于其它区域。通过荧光光谱仪测试量子点/聚氨酯复合膜发现,复合膜荧光强度也随表面张力的增大而减小。

Aqueous CdS@ZnS core-shell quantum dots(QDs)and water-based polyurethane(PU)were prepared by ion co-deposition method and one-pot method,respectively.After the QDs and PU were uniformly mixed at the mass ratio of 1:1,they were dropped on substrates with different surface tensions in order to form QDs/PU composite film after natural drying.The studies show that the surface tension of the substrate can directly affect the fluorescence properties of QDs and QDs/PU films.In this paper,the surface tension of the substrate was characterized by measuring the contact angle.The larger the contact angle is,the smaller the surface tension is.When the surface tension is large,it will cause a large-scale aggregation of QDs,resulting in an excessive concentration of regional QDs,and causing the concentration to be quenched.Although the increase of the surface tension of the substrate can improve the color purity of the quantum dots,it will also lead to a decrease in its fluorescence intensity.Under the 365 nm of UV lamp,it can be clearly seen that the fluorescence intensity of the interface between the substrate and the quantum dot dispersion is significantly higher than that of other areas.The QDs/PU composite film was tested by fluorescence spectrometer,and it is found that the fluorescence intensity of the composite films also decreases with the increase of surface tension.