Interference Effect of Silica Colloidal Crystal Films and Their Applications to Biosensing.

With the aim to develop better and more reliable interference effective substrates, silica colloidal crystal films with different sphere diameters and film thicknesses were successfully made by an improved vertical deposition method and a systematic investigation of their reflectometric interference spectroscopy (RIfS) properties are presented in this work. The influence of silica sphere diameter and film thickness on the RIfS signals was studied. The results showed that the film thickness is the key factor of RIfS signals. An RIfS system was set up by using a silica colloidal crystal film as an interference effective substrate. The influence of film thickness on the response to refractive index changes of the proposed system was also investigated. When the influence of film thickness on RIfS signals and refractive index response we considered together, silica colloidal crystal films with a thickness between 4 and 6 μm were chosen for sensor construction. Monitoring the digestive process of gelatin with trypsin was also demonstrated by combining gelatin-modified silica colloidal crystal films with RIfS. The system showed excellent sensitivity with a wide linear range and could achieve real-time measurement of each process. It has been proved that this is a promising method to construct biosensors using silica colloidal crystal films as interference-sensitive substrates.