**2. Experiment**

### *2.1. Materials*

The reagents used in this paper included: polyacrylonitrile (PAN) (solid, molecular weight 150,000, Macklin), graphene (commercially available), N, N-dimethylformamide (DMF) (liquid, analytical purity, Macklin), nano silicon particles (Si) (50 nm) and polymethylmethacrylate (PMMA) (solid, Macklin). These reagents were analytically pure so could be used directly.
