Structurally engineered yolk-shell mesoporous silica rods with liquid and nanoparticle cargo

Yolk-shell-structured nanomaterials provide a versatile platform for encapsulating both solid and liquid substances, making them advanced alternatives to hollow materials. While most studies focus on spherical yolk-shell structures, this study pioneers the synthesis of rod-shaped alternatives. Uniform silica rods (SRs) were synthesized using silica nanoparticles as growth nuclei and employed as sacrificial templates to fabricate hollow mesoporous and yolk-shell-structured silica rods (HMSRs and YSSRs, respectively). Dual-fluorescent silica rods were developed by fluorescently labeling the silica shell and encapsulating fluorescent oil within the hollow core, demonstrating their potential as delivery carriers for lipophilic drugs. YSSRs were engineered by using magnetite nanoparticles (Fe₃O₄) as growth seeds and by modifying the silica surface to attach gold nanoparticles (AuNPs) via electrostatic interactions. By integrating these approaches, multifunctional YSSRs encapsulating both Fe₃O₄ and AuNPs were fabricated. YSSRs exhibit unique functionalities, such as paramagnetism and photothermal effects, depending on the encapsulated nanoparticles. These universal synthesis strategies for HMSRs and YSSRs provide a robust platform for encapsulating diverse substances, paving the way for new application opportunities.