Size control of mesoporous silica nanoparticles by metal-chelating surfactant micelle templates

In this work is reported the facile synthesis of highly ordered mesoporous silica nanoparticles by transition metal-chelating micelle templates such as Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ in the Pluronic P123 surfactant micellar solution. The transition metal salts are formed the metal complex through the coupling with Pluronic P123 surfactant at aqueous hydrophilic domain as a chelation. The different complexation of each metal salt played an important role to determine the formation of nano-sized ordered mesoporous silica particles due to the different stabilization constant. The characterization of the materials was achieved by SAXS, SEM, TEM analysis, ¹³C-NMR, solid-state ²⁹Si-NMR, XPS, ICP-OES and Adsorption/Desorption analyzer (BET). As a result, the transition metal chelated mesoporous silica particles showed the reduced particle length in the range of 700−250 nm and the pores can be reduced from 8.8 to 6.6 nm. Especially, Cu²⁺ chelated mesoporous silica particle showed 250 nm of particle length. The stability constants of four mesoporous silicas chelated with transition metals which are Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ were observed to 0.286, 0.316, 0.439, and 0.376, respectively. This propensity is attributed to Irving-Williams´ the stability constant series: Co < Ni ≤ Cu > Zn.