“The near-field-optics community has realized that optics with a single nano-emitter [such as a single molecule at low temperature] as light source is possible,” Serge Huant of the University Joseph Fourier told nanotechweb.org. “This opens the way to optics at true molecular resolution, i.e. far beyond the classical limit due to light diffraction. Our goal was to propose easy-to-produce alternative active tips able to work at room temperature for easier manipulation.”

Huant and colleagues added nanocrystals or nanorods of cadmium selenide to optical tips made of chemically etched pure silica optical fibres coated with aluminium. To create the layers they dissolved ZnSe-capped CdSe nanocrystals or ZnSe/ZnS-coated CdSe nanorods in chloroform and then mixed them with a PMMA polymer.

Next the researchers dipped an aluminium-coated silica probe tip into the solution and allowed the solvent to evaporate. This left a thin PMMA coating on the apex of the tip that contained nanoparticles or nanorods.

According to the scientists, the spectral and temporal behaviour of the active tips indicated that only a limited number of nanoparticles were active at the tip apex. They say that their research opens the way to near-field optics using a single semiconductor nanoparticle as light source - a material that is potentially much more photostable than a single molecule.

Now the team plans to investigate the spatial resolution that the tips can achieve and whether they can use them to map out the near-field optical properties of nanostructures. “We are planning to use our tips to control fluorescence-resonance-energy transfer at the nanometre scale,” added Huant. “This could be of interest to nanobiological applications.”

The researchers reported their work in Nanotechnology.