Synthesis and Catalytic Performance of Gold Intercalated in the Walls of Mesoporous Silica

Summary

Here, we present a protocol with a sol-gel process to synthesize gold intercalated in the walls of mesoporous materials (GMS), which is confirmed to possess a mesoporous matrix with gold intercalated in the walls imparting great stability and recyclability.

Abstract

As a promising catalytically active nano reactor, gold nanoparticles intercalated in mesoporous silica (GMS) were successfully synthesized and properties of the materials were investigated. We used a one pot sol-gel approach to intercalate gold nano particles in the walls of mesoporous silica. To start with the synthesis, P123 was used as template to form micelles. Then TESPTS was used as a surface modification agent to intercalate gold nano particles. Following this process, TEOS was added in as a silica source which underwent a polymerization process in acid environment. After hydrothermal processing and calcination, the final product was acquired. Several techniques were utilized to characterize the porosity, morphology and structure of the gold intercalated mesoporous silica. The results showed a stable structure of mesoporous silica after gold intercalation. Through the oxidation of benzyl alcohol as a benchmark reaction, the GMS materials showed high selectivity and recyclability.

Introduction

As an emerging technology that has great potential in catalysis applications, nanoscale materials have received intensive research interest in the past decades. Amongst the nanoscale catalysts reported, noble metal catalysts such as Au, Ag, Pd and Pt have attracted world-wide attention ^1-3. Select catalytic reactions include the oxidation of carbon monoxide researchers on Au, Heck reaction on Pd catalysts, and water splitting with Pt. In spite of the promising catalytic potential, nanoscale gold is limited in its applicability due to deactivation from poisoning, coking, thermal degradation, and sintering. It has been reported that gold, as a representa....

Protocol

1. Preparation of GMS

1. Use all chemicals in the following process as received.
2. Prepare 75 ml of 2 M of hydrochloric acid (HCl) solution. Weigh 2.0 g of poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123, MW = 5,800) and transfer into the prepared 75 ml of 2 M HCl solution. At RT, apply magnetic stirring to the solution at a speed of 350 r/min until P123 is completely dissolved. The solution will be clear.
3. Weigh 4 g of tetraethoxysilane (TEOS, MW = 208.33) in a small vial and transfer 180 µl of Bis[3-(triethoxysilyl)propyl]-tetrasulfide (TESPTS, MW = 538.94) into the vial. Slowly shake the vial to mi....

Results

This method was used to compare the levels of heme synthesis in normal (HBEC30KT) vs. cancer (HCC4017) lung cells. Figure 2 shows a higher level of heme synthesis in cancer cells (HCC4017) than normal lung cells (HBEC30KT). The level of heme synthesis was also measured in normal and cancer cells in the presence of mitochondrial uncoupler carbonyl cyanide 3-chlorophenylhydrazone (CCCP). Cells were treated with 10 μM CCCP for 24 hr before the measurement of heme synthesis levels. As expected, the levels of.......

Discussion

Within the synthesis protocol, attention to surfactant concentration, pH of solution and reaction temperature is critical to the successful formation of GMS. The critical steps are 1.2, 1.3, 1.4 and 1.6. The above mentioned parameters control the critical packing parameter and phase of micelles formed from surfactant. The phase and morphology of micelle determines the final state of silica matrix, which serves as the framework for GMS. Also important in the formation process is the sequence and time to add the HAuCl solu.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol)	Aldrich	435465-250ML
tetraethoxysilane	TCI	201-083-8
bis[3-(triethoxysilyl)propyl]-tetrasulfide	GELEST	SIB1825.0-100GM
chloroauric acid	Aldrich	520918-1G
benzyl alcohol	Sigma-Aldrich	305197-1L
nitrogen physisorption	Micromeritics	Tristar II
X-ray diffraction	Philips	X'Pert Pro
transmission electron microscopy	Philips	CM200
gas chromatography	Shimadzu	GC-2010