In this study, two core shell nanohybrids of different morphologies, namely SiO2 coated silver (Ag) with surface-exposed silver seeds (Ag@SiO2@Ag-seed) and SiO2-coated Ag with surface-exposed Ag nanoparticles (Ag@SiO2@Ag-NPs), were fabricated using the Stober method. Potential applications in bioimaging and photothermal therapy (PTT) of the two fabricated nanohybrids were also explored. Upon exposure to visible light (400 nm), Ag@SiO2@Ag-seed with surface-exposed Ag seeds exhibited greater photothermal conversion efficiency than Ag@SiO2@Ag-NPs. In vitro MTT assays in the dark and subsequent bioimaging using HeLa cells proved the potential biocompatibility of the fabricated core-shell nanohybrids. PTT applications of the two fabricated core-shell nanohybrids were studied by incubating HeLa cells with the nanohybrids, exposure to 400 nm laser, and subsequent staining with annexin V and propidium iodide (PI), and the two core-shell nanohybrids gave distinctively different PI staining results. Interestingly, Ag@SiO2@Ag-seed caused higher cell death upon light exposure compared to Ag@SiO2@Ag-NPs as the former generated more heat within the cells. These results demonstrated potential bioimaging and PPT applications of the fabricated core-shell nanohybrids and offer a novel candidate for phototherapy-based biomedical applications. (C) 2018 Elsevier Inc. All rights reserved.