1：Experimental Design and Method Selection:

TNTs were synthesized by using a hydrothermal method from commercial TiO2 powder in a 10 M NaOH solution at 130 (cid:3)C for 22 hours. The synthesized solid product after synthesis was then treated by three different post washing procedures: (i) distilled water, (ii) 2 M HCl + distilled water, and (iii) 2 M HNO3 + distilled water.

2：Sample Selection and Data Sources:

The morphology, structural, and chemical composition of the washed TNT nanostructures were characterized by using the transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy-dispersive X-ray diffraction (EDX).

3：List of Experimental Equipment and Materials:

Commercial TiO2 powder, 10 M NaOH solution, 2 M HCl, 2 M HNO3, distilled water, TEM, XRD, EDX.

4：Experimental Procedures and Operational Workflow:

The photocatalytic activities of TNTs were evaluated through the photocatalytic degradation of the methylene blue (MB) solution.

5：Data Analysis Methods:

The results reveal that the post washing procedures affect the uniformity, Na impurity of the achieved TNTs and the reduction of Na impurity content, makes for ef?cient photocatalytic properties.