Controlled release of volatile (−)-menthol in nanoporous silica materials

In this work, a series of nanoporous silica materials have been prepared as adsorbents for volatile (−)-menthol, a molecule widely used in food, pharmacy, and cosmetics. The isothermal release properties of (−)-menthol have been investigated and correlated with the structural parameters of nanoporous absorbents. A rotary evaporation method is used to effectively load (−)-menthol into the nanopores of adsorbents and to prevent the whisker growth during the adsorption. It is demonstrated that the pore size, structure, wall thickness and surface functionality of nanoporous adsorbents are four important parameters to influence the isothermal release of (−)-menthol. By tuning these parameters of nanoporous silica adsorbents, controlled release of (−)-menthol can be achieved. A vesicular silica material with thick wall and hydrophobic functional groups is shown to possess the slowest release performance. Our contribution provides important knowledge for the future applications of nanoporous silica materials in pharmacy and cosmetics.