Rutile titanium dioxide nanoparticles and ordered acicular aggregates of same

A method for preparing calcined rutile TiO2 nanoparticles from rutile TiO2 nanoparticles which are aggregates of elongated TiO2 crystallites comprising:

• (a) forming an aqueous solution of a soluble titanium compound at a titanium concentration of from 0.5 to 1.0 moles per liter, optionally in the presence of a mineral acid;
• (b) introducing a morphology controlling agent or a mixture of said morphology controlling agents selected from (i) an a-hydroxy carboxylic acid of the formula R—CH(OH)COOH, (ii) an a-hydroxy carboxamide of the formula R—CH(OH)CONH2 or (iii) an α-amino acid of the formula R—CH(NH2)COOH, wherein said R group in each formula is an alkane, alkene, alkyne, arene, or cycloalkane group having 6 or more carbon atoms, into the solution at an acid- or carboxamide-to-titanium molar ratio of from 0.02 to 0.2 while simultaneously heating the solution to a temperature in the range of from 60° C. to 80° C. with constant stirring;
• (c) introducing TiO2 seeds into the stirred solution at a seed-to-TiO2 molar ratio of from 0.0005 to 0.0015 and maintaining the stirred solution including said TiO2 seeds at a temperature in the range of from 60° C. to 80° C. for a period of from one to 3 hours;
• (d) elevating the temperature of the stirred solution from step (d) to a value of from 100° C. to the refluxing temperature of the aqueous solution and maintaining said temperature for a period of from 2 hours to 4 hours to form a reaction product;
• (e) cooling the reaction mixture which results from step (e) to room or ambient temperature;
• (f) optionally neutralizing the reaction mixture;
• (g) separating and drying the reaction product;
• and
• (h) calcining the reaction product.