Porous Si can be synthesized from diverse silica (SiO₂) via magnesiothermic reduction technology and widely employed as potential anode material in lithium ion batteries. However, concerns regarding the influence of residual silicon oxide (SiO_x) component on resulted Si anode after reduction are still lacked. In this work, we intentionally fabricate a cauliflower-like silicon/silicon oxide (CF-Si/SiO_x) particles from highly porous SiO₂ spheres through insufficient magnesiothermic reduction, where residual SiO_x component and internal space play an important role in preventing the structural deformation of secondary bulk and restraining the expansion of Si phase. Moreover, the hierarchically structured CF-Si/SiO_x exhibits uniformly-dispersed channels, which can improve ion transport and accommodate large volume expansion, simultaneously. As a result, the CF-Si/SiO_x-700 anode shows excellent electrochemical performance with a specific capacity of ~1,400 mA·h·g^-1 and a capacity retention of 98% after 100 cycles at the current of 0.2 A·g^-1.

Recently, increasing attention has been paid to magneto-conjugated polymer core–shell nanoparticles (NPs) as theranostic platforms. However, the utilization of surfactants and extra oxidizing agents with potential toxicity in synthesis, the lack of general methods for the controlled synthesis of various kinds of magnetic NP (MNP)@conjugated polymer NPs, and the difficulty of obtaining balanced magneto-optical properties have greatly limited the applications of magneto-conjugated polymers in theranostics. We developed an in situ surface polymerization method free of extra surfactants and oxidizing agents to synthesize MNP@polypyrrole (PPy) NPs with balanced, prominent magneto-optical properties. MNP@PPy NPs with an adjustable size, different shapes, and a controlled shell thickness were obtained using this method. The method was extended to synthesize other MNP-conjugated polymer core–shell NPs, such as MNP@polyaniline and MNP@poly(3, 4-ethylenedioxythiophene): poly(4- styrenesulfonate) (PEDOT: PSS). We discuss the formation mechanism of the proposed method according to our experimental results. Finally, using the optical and magnetic properties of the obtained MNP@PEDOT: PSS NPs, in vivo multimodal imaging-guided hyperthermia was induced in mice, achieving an excellent tumor-ablation therapeutic effect. Our work is beneficial for extending the application of MNP-conjugated polymer core–shell NPs in the biomedical field.