Digital validation of bicontinuous concentric lamellar morphology in spherical mesoporous silica particles using SEM image-based lamellae density calculations

Abstract

We developed an SEM image processing technique using ImageJ to overcome the complexity of the bicontinuous concentric lamellar (bcl) morphology. SEM images were converted into ready-to-analyze binary images. From there, the lamellae cross-sectional area ratio AL/Atotal was calculated and used to compare the lamellae density between different bcl silica particles. Based on the comparison of bcl silica synthesized via the reflux method with varying times of synthesis, we found no significant difference in lamellae density, which is in accordance with the qualitative observations of the SEM images. We also compared our results with spherical silica particles synthesized by other research groups within the confidence interval of 48 to 53%. The particles above the confidence interval were considered to have lost their bicontinuity features. Whereas the particles below the interval still demonstrate the bicontinuous lamellar morphology, though with a larger interlamellar distance. To further verify our technique, we calculated the narrowness of the V-groove between the lamellae (θ). The θ value of the particles within the confidence interval showed similar values, ranging from 4.3 to 5.1°. Based on the comparison of the θ value with <AL/Atotal> we established a trend where the smaller the θ value, the higher the lamellae density.