Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Rice-Like, Hollow, and Rhombohedral Nano-Calcite Synthesis by Carbonization(Elsevier, 2026) Kilic, Sevgi; Toprak, Gorkem; Ozdemir, EkremControlling the morphology and size of calcium carbonate (CaCO3) remains an essential challenge in the production of high-performance fillers and advanced functional materials. Here, we report a continuous carbonization strategy that enables the synthesis of monodisperse nano-calcite particles with tunable rice-like, hollow, and rhombohedral morphologies through precise control of CO2 dissolution into a flowing Ca(OH)2 solution under diffusion-limited conditions. A two-stage reactor was designed to decouple nucleation and growth by separating the gas-liquid interaction zone from a stabilization tank. pH and conductivity analyses revealed that crystallization is primarily governed by the CO2 dissolution kinetics rather than mixing intensity in the stabilization tank. SEM and XRD analyses demonstrate a distinct crystallization sequence such that initial formation of rice-like calcite, subsequent development of hollow nanoparticles through selective tip dissolution, and final transformation into rhombohedral calcite via dissolution-reprecipitation mechanism. The method provides a reproducible, template-free route for fabricating hollow CaCO3 nanoparticles, overcoming limitations of bubbletemplating and additive-mediated techniques. This scalable process provides a robust foundation for producing high-surface-area CaCO3 nanomaterials which have potential applications in thin films, ceramics, protective coatings, lightweight composites, thermal/acoustic insulation, adsorption, and catalysis, where tailored particle morphology and size can significantly enhance performance.Article Lipid Monolayer Composition and Production Efficiency in DSPC/PEG40St Microbubbles for Ultrasound Applications(Elsevier, 2025) Kilic, Sevgi; Ozdemir, EkremLipid-coated microbubbles are widely used as ultrasound contrast agents (UCAs) and are being developed as carriers for drug and gene delivery. These microbubbles typically consist of an inert gas core and a stabilizing monolayer shell of phospholipid and a PEGylated emulsifier. In practice, a 9:1 M ratio of DSPC (a saturated phospholipid) to PEG-40-stearate (PEG40St) is conventionally used, under a long-standing assumption that the final composition of the microbubble shell is identical to the initial mixture composition. In this study, we tested that assumption over a wide range of DSPC/PEG40St ratios. Using sonication-based fabrication, we prepared microbubble suspensions with PEG40St fractions from 10 % up to 90 %. We then quantified the shell composition by proton nuclear magnetic resonance (1H NMR) and measured microbubble yield. Contrary to expectation, the PEG40St content in the bubble shells lower than PEG40St added, indicating selective exclusion or "squeezing out" of PEG40St during formation. Only about 4-6 % of the total lipid mixture ended up in the bubble shells and the rest remained as excess in the sub-phase. Thus, 94-96 % of the costly lipid/emulsifier was wasted in the production process. These results overturn the conventional assumption and highlight a critical inefficiency such that substantial amounts of lipid and PEG40St were lost during production, and the bubble yields were low. The findings have important implications for microbubble manufacturing, suggesting that alternative formulations or other production methods are needed to improve efficiency, and thus reduce costs.