Mesoporous metal oxide microspheres and method for forming same
The present disclosure provides a method for forming populations of monodisperse porous silica particles. Also provided are monodisperse populations of porous silica particles, an array of physically connected monodisperse porous silica particles and a microfluidic device for forming populations of monodisperse porous silica particles.
1. A method for forming a monodisperse population of mesoporous metal oxide particles comprising:
providing a microfluidic device comprising one central and two side channels, a point of convergence between the three inlet channels and an outlet channel extending away from the point of convergence;
hydrolyzing 5.2 g of tetraethylorthosilicate (TEOS, Purum >98%) in 3 g of ethanol (99.7%), and 2.7 g of 0.01 N hydrochloric acid (pH=2) under vigorous stirring at room temperature for 30 min to form a sol-dispersed aqueous phase;
delivering the sol-dispersed aqueous phase to the central inlet channel in the microfluidic device;
delivering an oil continuous phase to the two side inlet channels in the microfluidic device;
allowing the aqueous phase and oil continuous phase to emulsify at the junction and form droplets within the microfluidic device;
collecting the droplets;
allowing the droplets to polymerize, thereby forming particles;
separating the particles from the oil; and
removing the templating molecule to form a monodisperse population of mesoporous metal oxide beads.
2. The method of claim 1 wherein the droplets are allowed to form bridges during polymerization such that an array of monodisperse mesoporous beads is formed.
3. The method of claim 2 wherein the array is a two-dimensional array.
4. The method of claim 2 wherein the array is a three-dimensional array.
5. The method of claim 1 further comprising preventing bridges from being formed during polymerization such that a population of unconnected monodisperse mesoporous beads is formed.
6. The method of claim 5 wherein the microfluidic device further comprises additional side inlets, the method comprising delivering oil to the additional inlets so as to provide greater spacing between the droplets.
7. The method of claim 1 further comprising control the flow rate of the sol-dispersed aqueous phase and continuous phases in order to control the size of the beads.
8. The method of claim 1 wherein the population of beads consists of beads having a diameter that is within 0.01 standard deviations of the mean bead diameter.
9. The method of claim 1 wherein 1.4 g of an amphiphilic, triblock copolymer templating molecule (Pluronic, BASF: P104) is dissolved in 5.43 g of DI water and subsequently mixed with the hydrolyzed TEOS solution.