A cleaner, better way to produce single-photon emitters
Introducing organic color centers to air-suspended nanotubes using vapor-phase reaction. a A schematic of a functionalized SWCNT suspended across a trench on a Si substrate. b A scanning electron micrograph of a tube after the functionalization and the series of PL measurements. Particles on the top are patterned catalysts for growing SWCNTs and the nanotube is indicated by an arrow. c Representative PL spectra of an identical air-suspend (10,5) SWCNT before and after the functionalization taken with a laser power of 10 μW and an excitation energy of 1.59 eV. PL intensity maps of (d) E11, (e) E11, and (f) E−∗11 emission from a (9,7) tube where the intensity is integrated within a window of 37.4, 32.5, and 28.5 meV centered at each emission peak, respectively. The color scales are normalized to the maximum intensities in the respective maps. The dim features on the right of the tube are caused by reflection of the excitation laser from the bottom of the trench. The white broken lines indicate the edges of the trench. g A reflection image in the same area, where brighter and darker regions correspond to the surface of the substrate and the bottom of the trench, respectively. The scale bars in panels (b, d–g) are 1.0 μm. Credit: Nature Communications (2022). DOI: 10.1038/s41467-022-30508-z

In order to create an effective source of single photons for emerging quantum technologies, researchers at Riken have created a reaction that occurs in the Vapor phase.

The benefits of quantum technology are promising, such as secure communication, ultrasensitive sensor and parallel computing. The smallest packets of light possible can be generated by light sources.

A promising source of single photons in the wavelength range used in telecommunications is carbon nanotubes, which have been functionalized by adding an organic molecule.

The best way to do this is to use carbon nanotubes suspended across an air gap, but this isn't compatible with the usual approach of functionalizing carbon nanotubes. "Carbon nanotubes functionalized in solution tend to be short and have defects all over them," says Yuichiro Kato of the RAP.

A method for functionalizing carbon nanotubes that can be done in the vapor phase has been developed by RAP and their co-workers.

A cleaner, better way to produce single-photon emitters
A carbon nanotube suspended across a trench in a silicon substrate. By developing a method that allows such suspended nanotubes to be functionalized with organic molecules, RIKEN researchers have enhanced their usefulness for sources of single photons. Credit: Reproduced from Ref. 1 and licensed under CC BY 4.0  © 2022 D. Kozawa et al.

"We functionalized them in the vapor phase, so they had no contact with solutions, which contain a lot of impurities." The method allowed us to introduce organicmolecules.

A pre-pandemic interaction led to the creation of the study. The team at RAP produced the suspended nanotubes and sent them to the University of Maryland to be functionalized. The one who got curious about the possibility of doing these reactions in the vapor phase was a chemist at the University of Maryland. It took us a while, but we were able to see good emission from the nanotubes.

In order to verify the optical performance of their carbon nanotubes, the team had to do a lot of tests. They were able to model this effect in terms of the greater reactivity of narrower nanotubes after they discovered that the number of organic molecules introduced pernanotube increased with smaller diameter nanotubes.

The team wants to make the functionalization process more efficient so that only one organic molecule is introduced per tube.

Daichi Kozawa and his team formed organic color centers in air-suspended carbon nanotubes using a vapor-phase reaction. There is a DOI titled " 10.1038/s41467-022 30508-z".

Journal information: Nature Communications