Carbon Dioxide Proves Useful in Nanotech
March 3, 2014
Carbon dioxide is mostly known for being a greenhouse gas and hence a major environmental problem. For Warsaw chemists, however, carbon dioxide (CO2) has become something else: a key to the development of nanomaterials with unprecedented properties.
Researchers from the Polish Academy of Sciences’ Institute of Physical Chemistry in Warsaw and the Warsaw University of Technology’s Faculty of Chemistry used specially designed chemicals combined with carbon dioxide to develop a range of unprecedented nanomaterials. The new materials are highly porous and can be used for the storage of gases that are an important source of energy and for the production of sensing devices, for example. Moreover, microporous fluorescent materials obtained using carbon dioxide emit light with a quantum yield significantly higher than those of standard materials used in organic light-emitting diodes (OLEDs).
“Our research is not confined to the development of materials,” says Janusz Lewiński, a professor at the Warsaw Institute of Physical Chemistry. “Its particular importance comes from the fact that it opens a new route for the synthesis of nanomaterials based on zinc carbonate and zinc oxide, a route where carbon dioxide plays a key role.”
Research papers reporting on the accomplishments of Lewiński’s group have been published in prestigious international chemical journals such as Angewandte Chemie and Chemical Communications.
Carbon dioxide is a natural component of the Earth’s atmosphere. It is the most abundant carbon-based building block and plays a role in the synthesis of glucose, an energy carrier and building unit of paramount importance for living organisms.
Kamil Sokołowski, a doctoral student at the Institute of Physical Chemistry, says, “Carbon dioxide has for years been used in the industrial synthesis of polymers. However, there has been very few research papers focusing on the development of inorganic functional materials using carbon dioxide.”
Lewiński’s group has demonstrated that appropriately designed precursor compounds, in reaction with carbon dioxide, can be used to produce microporous material (with a pore diameter of less than 2 nm) resulting from the self-assembly of luminescent nanoclusters. This novel microporous material, composed of building blocks with a zinc carbonate core encapsulated in an appropriately designed organic shell (hydroxyquinoline ligands), is highly luminescent.
Sokołowski says, “Using carbon dioxide as a building block we were able to construct a highly porous and highly luminescent material. Can it be used for the construction of luminescent diodes or sensing devices? The discovery is new, the research work on the innovative material is in progress, but we are deeply convinced that the answer is yes.”
The new material has attracted considerable interest. Both Polish and international patent applications have been filed for the invention and work is in progress to put it to practical use in a project involving a joint venture company.
The design of the precursors was inspired by nature, the researchers say, in particular by the binding of carbon dioxide in enzymatic systems of carbonic anhydrase, an enzyme responsible for the fast metabolism of carbon dioxide in the human body. Effective enzyme activity hinges on its active center, where a hydroxyzinc (ZnOH) type reaction system is located.
A hydroxyzinc reaction system also occurs in molecules of the alkylzinc compounds designed by the researchers and used for the fixation of carbon dioxide. These compounds are particularly interesting, because, in addition to hydroxyl compounds, they also contain a reactive metal-carbon bond. This means that both the first and the second reaction system can participate in consecutive chemical transformations of such precursors.
Research involving the chemistry of alkylhydroxyzinc compounds is more than 150 years old and its beginnings are related to the birth of organometallic chemistry. However, it was only in 2011 and 2012 that Lewiński’s group presented the first examples of stable alkylhydroxyzinc compounds obtained as a result of a rationally designed synthesis.
The strategy for materials synthesis using carbon dioxide and appropriate alkylhydroxyzinc precursors discovered by the Warsaw researchers promises to be a versatile tool for the production of various functional materials. Depending on the composition of the reagents and the process conditions, a mesoporous material (with a pore diameter of 2 to 50 nm) composed of zinc carbonate nanoparticles or multinuclear zinc nanocapsules for prospective applications in supramolecular chemistry can be obtained.
Further research by Lewiński’s group showed that the mesoporous materials based on ZnCO3-nanoparticles can be transformed into zinc oxide (ZnO) aerogels. Mesoporous materials made of ZnO nanoparticles with an extended surface can be used as catalytic fillings allowing for and accelerating reactions of various gaseous reagents. Other potential applications are related to the semiconducting properties of zinc oxide. That’s why in the future the innovative materials can be used in photovoltaic cells or as a major component of semiconductor sensing devices.