2.5.4. SEM observation
For scanning electronic microscope observation, the air-dried BC membrane was mounted on a copper stub using double adhesive carbon conductive tape and coated with platinum for 30 s using a platinum coating facility (Auto Fine Coater JFC-1300, Jeol, Japan). The SEM photographs were obtained by scanning electron microscope (JSM-6360LV, Jeol, Japan) at room temperature at 15 kV.