Researchers have optimised the design of laboratory-grown artificial diamonds for use in biosensing applications such as magnetic brain imaging.

In ‘Designing Diamonds for Medical Imaging Technologies’, published in Applied Physics Letters, the researchers from Osaka University, the Tokyo University of Science, the Tokyo Institute of Technology and Kyoto University reported they have developed diamonds with nitrogen-vacancy (NV) centres that can detect changes in magnetic fields. The diamonds could be used in magnetoencephalography (MEG), a neuroimaging technique that is used to map brain activity and trace pathological abnormalities.

“MEG is commercially available and used in some hospitals, but is very expensive so not many MEGs are used,” said Norikazu Mizuochi, one of the paper’s authors.

Through a process called ‘doping’, diamonds can be artificially produced for a significantly lower cost. Chemical processes are used to create large sheets of diamonds, and scientists can manipulate the properties of individual diamonds by altering their composition. Doped diamonds can be produced with NV centres at a much lower price than other diamonds.

The biosensing features of the diamonds also require light activation, which changes the electromagnetic charge in the NV centres. “Only the minus [negative] charge can be used for such sensing applications, therefore stabilising [NV] centres is important for operation,” said Mizuochi.

The team produced doped diamonds with phosphorous to stabilise the NV centres, and over 90% of NV centres were given a negative charge. However, this process introduced noise which could interfere with the imaging process, so the team adapted the design of the diamonds to remove the noise. The new design included a 10 micrometre thick NV centre, which stabilised between 70% and 80% of NV centres while reducing the amount of noise in the system.

Mizuochi’s team is currently testing the sensitivity of the design to changes in magnetic fields to further refine the diamonds for use in MEG.