Patent ID: 8574536

Claim:
Method to produce diamonds containing Nitrogen-Vacancy centers from diamonds having a size above 0.1 micrometers grown by a high pressure and high temperature process and containing isolated substitutional nitrogen, comprising: generating vacancies in the diamonds by irradiating said diamonds by an electron beam such that the irradiation dose is comprised between 10 17 and 10 19 electrons per square centimeter, said electron beam having an acceleration energy above 7 MeV; combining the vacancies generated by irradiation with nitrogen atoms by annealing the irradiated diamonds in an inert gas at atmospheric pressure at a temperature comprising between 800° C. and 850° C. and for at least 1 hour and less than 2 hours; after annealing, grinding said diamonds to nano-particles of diamonds having a size of less than 20 nanometers, generating nano-particles of diamonds containing 4 to 16 Nitrogen-Vacancy centers in a 20-nanometer particle or 10 Nitrogen-Vacancy centers in a 10- nanometer particle or 8 Nitrogen-Vacancy centers in a 15-nanometer particle.