Integrating nanodiamonds into a polymer can advance quantum computing and biological studies

A nitrogen vacancy (NV) center is a defect in the crystal structure of diamond, where a nitrogen atom replaces a carbon atom in the diamond lattice and a neighboring site in the lattice is vacant. This and other fluorescent defects in diamond, called color centers, have attracted the attention of researchers due to their quantum properties, such as emitting a single photon at room temperature and with a long dwell time. consistency. Their many applications include quantum information coding and processing, as well as cell labeling in biological studies.

Microfabrication in diamond is technically challenging, and nanodiamonds with colored centers have been integrated into custom-designed structures to integrate these quantum emitters into photonic devices. A study conducted at the São Carlos Institute of Physics (IFSC-USP) at the University of São Paulo in Brazil established a method for this, as described in a paper published in the journal Nanomaterials.

“We have demonstrated a method for integrating fluorescent nanodiamonds into purpose-built microstructures, using two-photon polymerization (2PP),” said Cleber Mendonça, professor at IFSC-USP and last author of the paper. article, at Agência FAPESP. “We investigated the ideal concentration of nanodiamonds in the photoresist to obtain structures with at least one fluorescent NV center and good structural and optical quality.” Photoresist is a light-sensitive material used in the manufacturing process to transfer nanoscale patterns onto the substrate.

Mendonça and his group have widely used 2PP to fabricate three-dimensional microstructures. Simply put, 2PP is a direct laser writing technique in which a high-intensity laser beam is focused onto a light-sensitive polymer resin that has not yet solidified to produce the microstructure of interest.

In the study, a solution of nanodiamonds in deionized water was added to the mixture of monomers making up the photoresist, and once all the required physicochemical procedures were completed, microfabrication was carried out by subjecting the sample to the pulses from a powerful controlled titanium-sapphire laser. by dedicated software to define the exact coordinates of the beam.

“Fluorescence and Raman spectroscopy measurements were used to confirm the presence and location of the nanodiamonds, while absorbance measurements assessed diffusion losses at higher concentrations. Our results show the feasibility of making nanodiamonds microstructures integrated into fluorescent nanodiamonds via 2PP for photonics and quantum technology applications,” the authors write in the paper.

The study was part of the Ph.D. research of first author Filipe Assis Couto, with Mendonça as thesis director.