Essentially by turning the AuNPs to just the right size - researchers from BU have developed a catalyst which selectively converts CO2 into carbon monoxide (CO). CO is an active carbon molecule which can be employed to make alternative fuels and commodity chemicals.
As stated by Professor Shouheng Sun - "our study shows potential of carefully designed gold nanoparticles to recycle CO2 into useful forms of carbon," - and "the work we've done here is preliminary, but we think there's great potential for this technology to be scaled-up for commercial applications."
The principle of recycling CO2 is extremely enticing, but there are practical obstacles. CO2 is an extremely stable molecule that needs to be reduced to an active form like CO to make it useful. CO can help make synthetic natural gas, methanol and other alternative fuels.
Unfortunately, converting CO2 into CO is not so easy. Prior-art has shown that catalysts made from gold (Au) foil can perform an active conversion, but the drawback is that they do not do an effective job. The Au tends to react both with the CO2 and with the water in which the CO2 is dissolved - creating hydrogen (H2) as a by-product rather than the desired CO.
The BU research group - Sun and Wenlei Zhu (graduate student in Sun's group) - wanted to investigate if shrinking the Au down to nanoparticle dimensions might make it more selective for CO2. Subsequently it was found out that the AuNPs were more selective, but the exact size of the particles was extremely important. Eight nanometer (nm) particles had the optimum selectivity - achieving a 90% conversion rate from CO2 to CO. Other nanoparticle sizes tested by the team were 4, 6 and 10 nm, but they did not perform nearly as well.
Professor Andrew Peterson stated - "at first, that result was confusing," - and "as we made the particles smaller we got more activity, but when we went smaller than eight nanometers, we got less activity."
Paterson continues to state - "when you take a sphere and you reduce it to smaller and smaller sizes, you tend to get many more irregular features - flat surfaces, edges and corner," - and "what we were able to figure out is that the most active sites for converting CO2 to CO are the edge sites, while the corner sites predominantly give the by-product, which is hydrogen. So as you shrink these particles down, you'll hit a point where you start to optimise the activity because you have to high number of these edge sites but still a low number of these corner sites. But if you go too small, the edges start to shrink and you're left with just corners."
Sun concludes with stating - "because we're using nanoparticles, we're using a lot less gold than in a bulk metal catalyst," - and "that lowers the cost for making such a catalyst and gives the potential to scale up." Original article available here
Please Note the research findings are published in the Journal of the American Chemical Society. 
The BU research clearly demonstrates the potential of AuNPs for catalysis, and DCN Corp believes it can provide a nano-fabrication methodology easily facilitating the above optimum nanoparticle size (8 nm). Therefore, if you and/or your colleagues are interested in making the above research findings reality - please ensure to contact the company as soon as practicably possible.
 Zhu, W., Michalsky, R., Metin, O., Lv, H., Guo, S., Wright, C.J., Sun, X., Peterson, A.A. and Sun, S. Monodisperse Au Nanoparticles for Selective Electrocatalytic Reduction of CO2 to CO. Journal of the American Chemical Society 135, 45, 16833-36 (2013) Journal citation available here