Antimicrobial functionalization of Ca alginate‐coconut oil latent heat storing microcapsules by Ag nanoparticles

Abstract

Latent heat storage by phase change materials (PCM) is a promising way of thermal energy storage for equilibrating the daily fluctuation of temperature in office-and home buildings. Bio-originated compounds have got great importance to evade further plastic contamination all over the world. Durability of biodegradable natural materials by means of environmentally friendly agents is an exciting challenge. In this study Ca alginate-coconut oil eco-friendly coreshell PCM microcapsules were functionalized with Ag nanoparticles, following their synthesis using harmless reducing agents. Throughout the preparation of the PCM microcapsules by repeated interfacial coacervation/crosslinking procedure, the Ag nanoparticles were homogeneously dispersed in the Ca alginate shell. High coconut oil content was achieved in the Ag nanoparticle-loaded microcapsules, which was not influenced by the Ag nanoparticle content. The high PCM content resulted in correspondingly high latent heat storing capability. The freezing and melting heat storing capacities were in the range of 83.6 and 85.6 J/g, as well as 89.7 to 92.6 J/g, respectively, matching to the extremely high PCM content in the range of 82.7% to 84.8% (m/m). Leaking of the heat storing microcapsules was not observed after 200 heating-cooling cycles. The Ag nanoparticle content did not influence the PCM ratio of the microcapsules, although as expected their antimicrobial potential was significantly enhanced by it. The highest Ag nanoparticle loading, that was 1.3% (m/m) related to the total mass of microcapsules, exerted excellent antibacterial and antifungal impact.

Low temperature energy storage by bio-originated calcium alginate-octyl laurate microcapsules

“…Size distribution of prepared Ag nanoparticles (Fig. 3) with a mean size of 130.0 ± 1.6 nm was very similar to that found in our previous study [23].…”

“…Since it was verified in our previous study [23] that Ag nanoparticles dispersed in the shell of calcium alginate microcapsules exert efficient antibacterial and antifungal influence, they have been included in the shell of octyl laurate-loaded calcium alginate microparticles. The size of prepared Ag nanoparticles synthesized for the use in the microcapsule shell was investigated by photon correlation spectroscopy.…”

“…In our previous studies, paraffin [21] and coconut oil [22] PCMs were microencapsulated by Ca alginate shell with high heat storing capacity for use in building applications. Recently, the eco-friendly and biodegradable Ca alginatecoconut oil microparticles were functionalized by Ag nanoparticles in order to avoid too quick microbial degradation and increase the PCM microcapsule lifetime [23].…”

Calcium Alginate/Silver Nanosheet Microencapsulated Phase Change Materials with Controlled Morphology for Thermal Energy Storage and Antibacterial Application

“…The broadband absorption peak of Alg/Ag-MEPCM in the range 3326–3677 cm –1 is attributed to the O–H bond stretching vibration in alginate, and the absorption peaks at 1628 and 1400 cm –1 are assigned to the asymmetric and symmetric stretching vibrations of COO – in alginate, respectively. Furthermore, the peak at 1030 cm –1 corresponds to the C–O bond stretching vibration of the pyranosyl ring . These characterization results suggest the successful formation of Alg/Ag-MEPCM with the desired chemical compositions and structures based on n-eicosane, calcium alginate, and silver nanosheets.…”