Global warming is a serious threat to the planet and the living beings. One of the main cause of global warming is the increase in the atmospheric CO2 level. The main source of this CO2 is from the burning of fossil fuels in our daily day life (electricity, vehicles, industry and many more).

We have developed the solution phase synthesis of dendritic plasmonic colloidosomes with varying interparticle distances between the gold NPs using a cycle-by-cycle growth approach by optimizing the nucleation-growth step. These DPCs absorbed the entire visible and near-infrared region of solar light, due to interparticle plasmonic coupling as well as the heterogeneity in the Au NP sizes, which transformed golden gold material to black gold. Raman thermometry and SERS provided information about the thermal and electromagnetic hotspots and local temperatures which was found to be dependent on the interparticle plasmonic coupling. The spatial distribution of the localized surface plasmon modes by STEM-EELS plasmon mapping confirmed the role of the interparticle distances in the SPR of the material.

We observed the significant effect of the plasmonic hotspots on the performance of these DPCs for the oxidation reaction of cinnamyl alcohol using pure oxygen as the oxidant, hydrosilylation of aldehydes as well as for temperature jump assisted protein unfolding and purification of seawater to drinkable water via steam generation.They also catalyzed CO2 to methane (fuel) conversion at atmospheric pressure and temperature, using solar energy.

This was attributed to varying interparticle distances and particle sizes in these dendritic plasmonic colloidosomes. The results indicate the synergistic effects of EM and thermal hotspots as well as hot electrons on DPC-Cx performance. Thus, DPC-Cx catalysts can effectively be utilized as Vis-NIR light photo-catalysts, and the design of new plasmonic nanocatalysts for a wide range of other chemical reactions may be possible using the concept of plasmonic coupling.

Thus, in this work, by using the techniques of nanotechnology, we transformed golden gold to black gold, by simply changing the size and gaps between gold nanoparticles. Like real trees, where they use CO2, sunlight and water to produce food, our developed black gold act like an artificial tree and use CO2, sunlight and water to produce fuel, which we can be used to run our car. Notably, black gold can also use to convert sea water into drinkable water using the heat that black gold generates after it captures sunlight.

 This work is way forward to develop artificial trees which capture and convert CO2 to fuel and useful chemicals. Although at this stage, their production is low, in coming years, these challenges can be resolved and we may able to convert CO2 to fuel using sunlight at atmospheric condition, at a commercially viable scale. CO2 will then become our friend again and will become our main source of clean energy, and we will have CO2 based Civilisation. 

Reference: Plasmonic Colloidosomes of Black Gold for Solar Energy Harvesting and Hotspots Directed Catalysis for CO2 to Fuel Conversion. "Cover Page”  "Pick of the Week" M. Dhiman, A. Maity, A, Das, R. Belgamwar, B. Chalke, Y. Lee, Kyunjong Sim, Jwa-Min Nam and Vivek Polshettiwar*, Chemical Science, 2019, 10, 6694-6603. 

More information about this project can be found on the Nanocat webpage