Solvent-volume effects on the structural and textural properties of biosurfactant-assisted mesoporous silica nanoparticles

This study investigated the use of the biosurfactant P34, a low-molecular-weight lipopeptide produced by Bacillus velezensis P34, as a green structure-directing agent for the synthesis of mesoporous silica nanoparticles (MSNs). A modified sol–gel method was employed, in which the water content was varied while keeping constant amounts of ethanol, tetraethyl orthosilicate (TEOS), ammonia, and biosurfactant. In the presence of P34, spherical nanoparticles were obtained under all conditions, whereas control syntheses without the biosurfactant yielded particles only at lower solvent volumes. Solvent volume played a decisive role in particle morphology and porosity: compact non-porous nanoparticles were formed at lower water contents, while mesoporous structures with pore diameters between 4.7 and 12.2 nm appeared at higher dilutions. Small-angle X-ray scattering confirmed quasi-spherical morphologies; however, it also revealed increased heterogeneity and rougher interfaces with higher solvent volumes. Fractal analysis of N2 adsorption isotherms showed that P34 strongly influenced particle texture, enhancing surface roughness at low pressures while reducing the volumetric fractal dimension in mesoporous domains. In addition, zeta potential measurements indicated that all P34-assisted particles were electrostatically stable in suspension (− 41 to − 59 mV), with the highest stability observed for the non-porous sample. These findings demonstrate that P34 functions as an effective and sustainable biotemplate, enabling control over morphology, porosity, and colloidal stability. The resulting nanomaterials are well suited for applications in catalysis, drug delivery, and gas separation, highlighting the potential of biosurfactants as environmentally friendly alternatives to synthetic surfactants in nanotechnology