Australian researchers have demonstrated an excellent method for generating energy from metal nanocrystals, with benefits in photovoltaics, photocatalysis and optoelectronics.
Based at RMIT University and CISRO, a team led by Exciton Science has developed nano-size “matches” – small objects made of gold nanorods and cadmium selenide tips.
The metal ends of the matchstick structure work as antennae to collect light, and their interaction with the tip causes the collection of electric charges.
By developing (Generating Energy from Metal Nanocrystals) an optimized system, the researchers demonstrated the ability to achieve a charge extraction efficiency of up to 45%.
This study is a demonstration of the promise of this method for important industrial and energy applications, including hydrogen production from the sun.
The results were published in the journal ACS Nano and are available here.
Led by RMIT PhD student Lesly Melendez and associate Professor Daniel Gomez, the project focused on charge extraction by plasmons, a term for collective oscillations of electrons in metals.
When a photon of light with a certain energy is passed through a material, it promotes the movement of electrons from the metal to the semiconductor, which is called “hot electron transfer”.
However, collecting charges effectively from plasmons (and understanding their behavior) is difficult, because they “degenerate” and lose their energy quickly.
The team used a technique called single-particle electron energy loss spectroscopy (EELS) to better understand the relationship between the structure and function of metal-semiconductor systems.
EELS is a technique based on high-resolution electron microscopy useful for studying nanocrystals because it provides functional correlations as well as detailed information about size, geometry, and composition.
A few previous studies have demonstrated the power of EELS to investigate electron and energy transfer between nanoparticle and semiconductor materials.
By applying it to the gold nanorod structure, the researchers were able to achieve some of the highest levels of plasmonic heat generation reported to date.
EELS helped them determine the parameters that control the efficiency of charge separation, including the quality of the interface between gold and cadmium selenide and the size of the metal rods.
The results should support the best future methods for these structures, which can demonstrate a sophisticated design process that can create highly functional nanostructures.
Source: Exciton Science
