“…They can be easily prepared in different morphologies (nanowires, nanofibers, nanoflowers, nanotubes, nanorods, etc.) by various facile and low-cost methods [ 8 , 10 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ], making them adequate for a broad range of applications, such as photovoltaics [ 26 ], electronic devices [ 27 ], photocatalysis [ 28 ], water purification [ 29 ], dye-sensitized solar cells [ 30 ], sensors [ 31 ], and renewable energy [ 32 ].…”