Fig. 2

Synthesis and characterization of nanoparticles. a A schematic illustration of the procedure for preparing colloidal carbon sphere (CCS) nanoparticles using glucose, producing silica-carbon (SC) nanoparticles using the CCS and tetraethyl orthosilicate (TEOS), modifying the SC nanoparticles with (3-Aminopropyl) trimethoxysilane (APTMS) to form SC-A nanoparticles, and coating the SC-A nanoparticles with phospholipid dipalmitoylphosphatidylcholine (DPPC) to produce LSC nanoparticles. The pyruvate group can be formed during the hydrothermal process. b, c Scanning (SEM, b) and transmission (TEM, c) electron microscopy images of the CCS and SC nanoparticles synthesized with different reaction times showing that SC nanoparticles of ~35 nm with a homogeneous size distribution can be obtained after 6 h of reaction. Since the SC nanoparticles do not have core–shell structure, the silica should not cover the whole surface of the nanoparticles. Therefore, the lipid membrane should not completely cover the surface of the LSC nanoparticles because the lipid only interacts with silica through APTMS. Scale bar: 500 nm in b and 100 nm in c. d TEM image of lipid membrane-coated SC (LSC) nanoparticles showing the lipid membrane on the surface of the nanoparticles (indicated by arrows). Scale bar: 50 nm. e The production of singlet oxygen by the LSC nanoparticles under NIR irradiation as compared with LSC nanoparticles without NIR laser irradiation (w/o laser, 1 mg ml⁻¹). f The NIR irradiation (1.0 W cm⁻²) time and LSC nanoparticle concentration (0.06–0.5 mg ml⁻¹) dependent increase of temperature. g UV-Vis absorbance of LSC nanoparticles and DOX-laden LSC (LSC-D) nanoparticles showing successful encapsulation of DOX in the LSC nanoparticles with an absorbance peak at ~480 nm