Growth and Functionalization of Particle-Based Mesoporous Silica Films and Their Usage in Catalysis

Abstract

We report the formation of mesoporous films consisting of SBA-15 particles grown directly onto substrates and their usage as catalysts in esterification of acetic acid and ethanol. The film thickness was altered between 80 nm and 750 nm by adding NH4F to the synthesis solution. The salt also affects the formation rate of the particles, and substrates must be added during the formation of the siliceous network in the solution. Various substrate functionalizations were tested and hydrophobic substrates are required for a successful film growth. We show that large surfaces (> 75 cm2), as well as 3D substrates, can be homogenously coated. Further, the films were functionalized, either with acetic acid through co-condensation, or by coating the films with a thin carbon layer through exposure to furfuryl alcohol fumes followed by carbonization and sulfonation with H2SO4. The carbon-coated film was shown to be an efficient catalyst in the esterification reaction with acetic acid and ethanol. Due to the short, accessible mesopores, chemical variability, and possibility to homogenously cover large, rough surfaces. the films have a large potential for usage in various applications such as catalysis, sensing, and drug delivery.

Cell adherence and drug delivery from particle based mesoporous silica films

“…No free particles are observed on the substrate aer ultrasonication treatment. The particle width and lm thickness decreases with an increasing salt concentration (Table 1), which is consistent with the data previously shown by Wu et al 23 The micrographs clearly shows that a vast majority of the particles are well attached to the substrate. It has been suggested that this type of lms is formed through nucleation of silica coated micelles on the hydrophobic substrate, and that the particles grow from these sites.…”

“…This defect yields a particle that is only partly bound to the substrate and can thus inuence the particle detachment rate. The time for adding the substrates to the synthesis solution increased with decreasing salt content to gain the desired lm morphology since the material formation rate is signicantly increased by the addition of NH 4 F. 23,27 The salt affects the condensation rate of the silica precursor, and also the structure of the silica network, and therefore it is of great importance that the substrates are added during a time window in the formation of the siliceous network where micelles can nucleate onto the substrate, but prior to the micelle aggregation. In order to demonstrate that DiG lms can also be grown on rough, 3D surfaces, a DiG_0.00 was synthesized onto an alumina sand blasted silicon wafer.…”

“…25 By varying the particle size using various NH 4 F concentration in the synthesis solution, the lm thickness can be altered to preserve ne structures of the substrate. 23 We show in this study that it is possible to functionalize the lms with^Si-R-COOH aer synthesis and to load the lms with a hydrophobic, small molecule model drug, DiO, conrming the accessibility of the pores. Cells can adhere to all lms, and the particles are taken up by the cells prior to release of their cargo.…”

“…The protocol for synthesizing the lms followed the DiG method presented in literature. 22,23 In the synthesis P123 (0.414 mmol) was dissolved in HCl (1.84 M, 80 mL) at 20 C. Simultaneously, 0, 0.189, or 0.756 mmol of NH 4 F was added to the solution. Subsequently, 1 mL of heptane was mixed with 5.5 mL of TEOS and added to the P123 solution.…”

“…22 Using the described method, it has previously been shown that it is possible both to grow lms with controlled thickness and on 3D-substates. 23 This is of great importance for fabricating porous coatings on implants without compromising the ne structures of the substrate. The particles themselves in powder form have been shown to efficiently immobilize enzymes, 24 and to act as a potential drug carrier.…”