05 Feb 2015

Imitating plant cells to build tiny reactors

SASKATOON – Living cells are a hive of activity, full of tiny structures making proteins, breaking down junk, and creating energy. All of this happens through a series of chemical reactions made possible largely because of the humble cell wall. 

“If you remove the cell wall, keeping exactly the same molecules that were inside the cell, then the same reactions will not occur or will occur very, very, slowly,“ says Cecile Malardier - Jugroot, Associate Professor in chemistry and chemical engineering at the Royal Military College of Canada.

Inspired by the reactive power of cells, her team and collaborators are working to develop nanoreactors that mimic natural biosystems and their very high efficiency within a confined space. Their hope is to produce something more stable than biosystems offer, harnessing their advantages and using their structure and function as a model. 

By introducing confinement to nanosystems, researchers mimic the effect of the cell wall on reactions. Suddenly, reactions that would not occur normally in bulk materials start to form. They’re fairly slow reactions, but they are special because no heat, pressure, nor catalysts need to be added to the mix to get the activity going. 

Biosystems are inherently efficient in both thermodynamic and kinetic terms, but how best to maximize their nanoreactor cousins will take a great deal of study. The goal is to make more efficient fuel cells than anything currently on the market, working with carbon nanotubes and sheets, on the scale of individual atoms. 

One of the first variables to test is the introduction of platinum crystals within their nanoreactor templates — a design also inspired by nature, since many cells use a metal centre as a reactive site. This first nanoreactor provided a 3 fold increase in the reaction rate within the template in the presence of the metal center compare to the empty nanoreactor. The researchers also plan to test gold and gold-platinum alloys to open up more potential applications. 

The function of these metal-reactive site systems is still relatively new territory, and called for new research methods. 

To achieve the fine detail needed to analyze these systems, the team used the Canadian Light Source synchrotron, transmission electron microscopy, and the Canadian Centre for Electron Microscopy.

“When we started this four years ago, we did the characterization using transmission electron microscopy, however with this technique, the samples have to be in the dry state and you get only the sense of one part of the sample, not the average of the sample which we needed to find out if we had the same number of clusters distributed everywhere in our sample.”

The Malardier-Jugroot team is most specialized in modelling, so they were grateful to work with the CLS crystallography scientists, who performed the X-Ray Diffraction analysis for the researchers. 

“We’re trying to understand at a the atomic level what’s happening inside the nanoreactor templates, so having a link with experimentalists at that level, and being able to send them our models and trying to understand the interactions going on — that was very very helpful.” 

There were surprises in store. For one thing, the templates, which were normally only stable at pH 7, remained stable from pH 3-13 with the addition of platinum. How and why that occurs is a major question. 

In fact, the field remains full of mysteries: the nanoreactors can be light sensitive, so how can that be harnessed? What creates specific crystal structures? How do these structures affect function? Fuel cells are only one potential application for these mimic of biosystems — more wait to be uncovered. 

The authors would like to thank the National Science and Engineering Research Council of Canada (NSERC) (NSERC Discovery Grant, 355595), the Canadian Centre for Electron Microscopy (McMaster University), the NIST-CNR supported in part by the National Science Foundation under Agreement DMR-0944772 and the Canadian Macromolecular Crystallography Facility at the Canadian Light Source for their generous support.

Artificial nanoreactors with 1D and 2D confined environment, the Pt metal center observed by transmission electron microscopy is shown on the left (a) with an average diameter of 1.89 nm. The X-Ray spectra of the system presented in blue (b) shows the Pt nanoparticle peaks at 2q of 17.49 and 20.22o
Cite: Groves, Michael N., Cecile Malardier-Jugroot, and Manish Jugroot. "Environmentally friendly synthesis of supportless Pt based nanoreactors in aqueous solution." Chemical Physics Letters 612 (2014): 309-312. doi:10.1016/j.cplett.2014.08.017
This photo and others to accompany this story are available in the CLS image gallery for use with a Creative Commons licence.

About the CLS:

The Canadian Light Source is Canada’s national centre for synchrotron research and a global centre of excellence in synchrotron science and its applications. Located on the University of Saskatchewan campus in Saskatoon, the CLS has hosted over 2,000 researchers from academic institutions, government, and industry from 10 provinces and 2 territories; delivered over 32,000 experimental shifts; received over 8,300 user visits; and provided a scientific service critical in over 1,000 scientific publications, since beginning operations in 2005. The CLS has over 200 full-time employees.

CLS operations are funded by Canada Foundation for Innovation, Natural Sciences and Engineering Research Council, Western Economic Diversification Canada, National Research Council of Canada, Canadian Institutes of Health Research, the Government of Saskatchewan and the University of Saskatchewan.

Synchrotrons work by accelerating electrons in a tube to nearly the speed of light using powerful magnets and radio frequency waves. By manipulating the electrons, scientists can select different forms of very bright light using a spectrum of X-ray, infrared, and ultraviolet light to conduct experiments.

Synchrotrons are used to probe the structure of matter and analyze a host of physical, chemical, geological and biological processes. Information obtained by scientists can be used to help design new drugs, examine the structure of surfaces in order to develop more effective motor oils, build more powerful computer chips, develop new materials for safer medical implants, and help clean up mining wastes, to name a few applications.

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mark.ferguson@lightsource.ca

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