Morphology of Mesoporous Silica Revealed by Low-kV SEM Imaging

Gentle Imaging for Fragile Structures

Porous nanoparticles like SBA-15 are inherently sensitive. Their usefulness in catalysis, drug delivery, and molecular separation depends on pore structure and size, and the resulting surface area. Conventional SEM can damage the uncoated surfaces, and other analytical techniques may not be able to accurately capture surface detail.

Transmission electron microscopy (TEM) offers excellent resolution but often lacks context and requires thinning. Standard SEM, meanwhile, can produce charging artifacts unless the sample is coated. The challenge was to find a way to see SBA-15’s real surface structure without altering it. 

Low-Voltage SEM Imaging of As-Synthesized Mesoporous Powders

The sample was as-synthesized mesoporous silica SBA-15 powder, produced using tetraethoxysilane (TEOS) and a triblock copolymer template. The powder was mounted directly onto a conductive carbon tape without additional coating or processing.

Imaging was performed on a Tescan MIRA XR using BrightBeam™ optics in low-voltage conditions: 800 eV acceleration voltage, 10 pA beam current, and an in-column Axial detector, with each field of view acquired in under one minute—imaging parameters that reduce charging and preserve the synthesized sample.

The resulting images showed both rod-like and curved particle shapes, along with nanoscale pore structure, providing a basis for qualitative and statistical shape assessment.

Native Morphology, Clearly Captured

SEM imaging under these conditions produced high-contrast views of individual SBA-15 particles. Surface porosity, curvature, and length variation were recorded with each image acquisition, delivering sufficient data to support meaningful statistical analysis of the particles.

Notably, no conductive coating was used, and the applied beam parameters suppressed charging artifacts. This indicates that low-voltage SEM imaging, when properly configured, is sufficient for direct analysis of non-conductive nanostructures like mesoporous silica.

Tescan MIRA XR provides a practical tool for labs investigating nanoscale materials properties, connecting micro- and nanoscale structure to synthesis effects, scaling consistency, or application-specific morphology in porous nanomaterials.