The development of synthetic techniques for metal oxides and doped metal oxides is an area of active research within the Larese group. Using a patented technique, nanosized metal oxide materials with controlled size and morphology are synthesized for adsorption and neutron studies. The ability to control morphology and size distribution allows us to systematically study the influence of surface conditions on the adsorption/desorption process, and the storage and catalytic properties of these materials.
We are able to expand the group’s repertoire by adapting current synthetic methodologies from the literature. Along with metal oxide synthesis, we are interested in studying confinement and adsorption in uniform porous materials such as amorphous carbon, hollow meso-porous silica spheres, nanotubes, and porous aluminum oxide.
About ten years ago Walter Kunnmann and John Larese began experimenting at Brookhaven National Laboratory with ways to produce molar quantities of highly pure, homogenous, nanometer scale MgO powders for use in neutron scattering investigations of molecular adsorption. They tried a number of typical wet chemistry and chemical vapor deposition (CVD) routes before stumbling upon the method depicted in the movie clip above. This led to a very exciting time for the group, which continues to this day. You can read more about the details of the process by clicking the following link, U.S. Patent No. 6,179,897, which leads to the US patent office record of our discovery.
We synthesize MgO nanocubes using the patented technique shown in the movie above. We then use MgO as a substrate to examine the thermodynamics and structure of various molecules. We are currently interested in the homologous series of small chain alkanes, hydrogen, cyclic alkanes, benzene, and nitromethane as possible adsorbates. Pictured to the left is a TEM image of a MgO cube. The edge of the cube is approximately 200 nm long.
ZnO needles, plates, and tetrapods
Our group’s efforts have concentrated on developing the synthesis and growth conditions necessary for cultivating single morphology nanoparticles of ZnO. A variety of ZnO morphologies can be produced by varying the parameters inside the solid state reaction vessel. ZnO nanostructures are very promising for applications in field emission displays and photonic devices operating in blue and UV spectral ranges, due to its wide band gap (3.37 eV) and large exciton binding energy (60 meV). ZnO currently finds a variety of uses in cosmetics because of its high opacity to UV light and mild deodorant properties; it is protective, astringent, and non-toxic. Pictured is a ZnO tetrapod, one of many morphologies that can be produced in our group.
Decorated/Doped Metal Oxides
Small metal clusters on metal oxides have the potential of being excellent catalytic sites. We are able to decorate our metal oxides (MgO, ZnO, SiO2) with nickel, palladium, tin oxide, gold, and other metals through the same patented process used to synthesize MgO, and also through a second, solution-based chemical process. Pictured is MgO decorated with palladium nanoparticles.
Anodized Aluminum Oxide
Through an electrochemical technique the Larese group is able to make highly ordered nanoporous anodized aluminum oxide (AAO). Porous AAO can be used as a template to make nanorods or nanowires. The tunable pore size of AAO makes it ideal for studying confinement effects in various pore diameters. Pictured is a template with pores having an average diameter of 50 nm.
Hollow mesoporous silica spheres are a great candidate for a drug delivery mechanism because of their high storage capacity, biocompatability, penetrating pore channels, and ability to be functionalized due to surface hydroxyl groups. Producing spheres of varying size, and studying gas adsorption and confinement in this system are of great interest. We are currently optimizing the reaction conditions to yield more uniform spheres of tunable diameter. Pictured is an SEM image of spheres with diameters of 150 – 500 nm, and pores of approximately 3 nm.