  The practical use of nanoparticle superlattices (NPSLs) which are of great
interest as materials with designed functionalities is often limited by their
lack of structural stability under various utilization conditions. Here, we
report a new method for directly synthesizing NPSL fully embedded in
hierarchically porous silica which provides exceptional stability and efficient
pathways for reactant molecules, making the NPSL highly efficient catalyst. The
superlattices made of 12 nm gold nanoparticles exhibit exceptionally high
catalytic activity for CO oxidation at low temperature, showing higher activity
than that of small gold nanoparticles (ca. 3 nm) supported on metal oxides. The
gold NPSL also shows unprecedented stability, maintaining its structural
stability and catalytic activity without any signature of degradation over a
month of continuous catalytic reaction, which present one significant step
forward to realizing the great potentials of gold catalysts in automotive
emission control and green chemistry industry.
