‘Loops of light’ promising for optical detection of individual molecules
Loops of light
In order to overcome these limitations, Dr. Valev and his colleagues sought out to nanoengineer larger spots. They began by shining circularly polarised light rather than linearly polarised light on the nanostructures and found that this could increase the useful area of these nanostructures. More importantly, when shone on square-ring shaped gold nanostructures, the scientists observed that the entire surface of the nanostructures was successfully activated.
Dr. Valev explains: “Essentially, light is constituted of electric and magnetic fields moving through space. While with linearly polarised light, the fields move in a linear, forward direction, with circularly polarised light, they rotate in a spiral-like motion." The circularly polarised light imparts a sense of rotation on the electron density in ring-shaped gold nanostructures, thus trapping the light in the rings and forming ‘loops of light’. The loops of light cause excited electrons to oscillate coherently on the full surface of the square-ringed nanostructures – rather than in a few concentrated hotspots. This increases the opportunity for interaction with molecules: “The trick is to try to activate the whole surface of the nanostructure so that whenever a molecule attaches, we will be able to see it,” says Dr. Valev. “That is precisely what we did.”
The method has a broad range of potential applications in nanoscale photochemistry and could assist in the advancement of technologies for visualising single molecules and multiple-molecule interactions. The findings were published in the scientific journal Advanced Materials.
Original publication
Other news from the department science
Get the chemical industry in your inbox
From now on, don't miss a thing: Our newsletter for the chemical industry, analytics, lab technology and process engineering brings you up to date every Tuesday and Thursday. The latest industry news, product highlights and innovations - compact and easy to understand in your inbox. Researched by us so you don't have to.