Preparation of silica nanocapsules containing phase change material

Silica nanoparticles (SNPs) can be produced in small diameters with good reproducibility, stability, and biocompatibility for carrying phase changing materials (PCM) to develop a new formulation for heating and cooling applications. In this work, a capsule-like silica structure was obtained to carry nonadecane as a PCM and characterized by dynamic light scattering (DLS), zeta potentials, scanning electron microscopy (SEM), Fourier- transform Infrared (FTIR) and differential scanning calorimetry (DSC). Classically, SNPs are synthesized by Stöber method as empty formulations. To achieve a capsule-like structure with small sizes, we used a modified technique including an oil phase containing dissolved PCM addition to the water phase at lower temperatures. This method ensures a slower and controlled reaction which allows smaller particle sizes. SNPs were synthesized in two types as nanodecane loaded and empty as a control. After the synthesis, characterization steps were performed. First of all, particle size was checked by DLS and found as 50 nm. Zeta potentials were also measured as -30 mV'dir. Which suggests the SNP formulation is stable in water. SEM images showed that particles are synthesized successfully with a spherical shape. Also, SEM images confirm the measured nanoparticle size by DLS. FTIR showed that SNPs were synthesized with the characteristic peaks at 1100, 964 and 796 cm -1. According to DSC results, nonadecane was loaded into SNPs confirmed by the peaks around 25-40 o C while the empty formulation showing no peaks. These results show that nanodecane loaded SNP is a good candidate for PCM applications such as building heating and cooling or heating pads. ii 2023, 58 pages Keywords: Phase changing materials (PCM), Silica nanoparticles (SNP)