The paper models how pillar-and-scaffold structures couple to nitrogen-vacancy emitters in nanodiamonds. Simulated joint-site peak Purcell factors reach about 4 without silver and 20 with a 50 nm silver coating. Two-photon polymerization produces silver-coated polymer scaffolds; reflectance reveals a 647.69 nm resonance with Q = 16.97 ± 4.70. NV emission enhancement is modeled, while fabrication and resonance are demonstrated experimentally. Fabricated structures are 40 µm wide; simulated structures are 3.1 µm wide.

A tiny diamond needs the right neighborhood to shine. Could a scaffold give it one?

This paper designs a three-dimensional structure that gathers light at its joints. In simulations, these hotspots strengthen emission from a diamond quantum emitter—especially with a thin silver coating.

A diamond can be a light source. An NV center is a nitrogen atom beside a missing carbon atom in diamond. Its red light includes a line at 637 nm.

Its surroundings can change its emission. The Purcell factor compares the emission rate in a structure with the rate for the same emitter in vacuum.

Build a brighter neighborhood.

Add a scaffold. Coat it in silver. Then decide where the emitter belongs.

Give light a place to gather.

Bare pillars have a nearly flat emission-enhancement spectrum. Add the diamond-shaped loops to create new optical hotspots.

Try the bright bent joints of the scaffold.

Alignment with the scaffold’s optical modes changes coupling.

Without scaffolds, there is little emission enhancement across 600–700 nm.

The animated field and light pulses explain the mechanism; they are not a numerical simulation. Joint-site peak factors refer to a parallel dipole across 600–700 nm. The orientation trend is illustrated from the paper’s silicon study at 637 nm. Interior-emitter comparisons use polymer and come from Supplementary Section 5. The simulated lateral size was 3.1 µm.

The shape creates the opportunity.

Every diamond-shaped loop adds two bent joints. These edges and junctions confine the electromagnetic field, creating places where an emitter can couple strongly to the structure’s optical modes.

A silver coating also supports surface plasmon modes—collective motion of electrons coupled to light. Geometry and the metal surface work together to concentrate the field.

Peak enhancement at a joint: polymer ≈2× → ≈20× with silver; silicon up to 4× → ≈17×. These peaks occur across the 600–700 nm spectrum.

A pillar can host strong modes, too.

For an emitter inside a polymer pillar, 20 nm below the central pillar’s top, the silver-coated structures show simulated peaks of approximately 90× without a scaffold and 100× with one. The scaffold shifts the spectrum more than it changes the peak.

This is a separate placement comparison. It explains why the emitter’s location matters—and why adding the scaffold contributes differently at a joint and inside a pillar.

Write it with light. Finish it with silver.

Two-photon polymerization builds the three-dimensional polymer architecture.

A focused 780 nm laser writes inside IP-Dip2 resin. Material solidifies near the focus, letting the researchers build suspended loops in three dimensions.

Design

Five vertical pillars. Four connecting scaffolds.

Write

63× objective. 0.1 µm slicing and hatching.

Coat

50 nm of silver, deposited by sputtering.

Printing changes the scale. Calculations used L = W = 3.1 µm. The fabricated structures were enlarged to 40 µm to preserve curved features within the printer’s resolution.

The curved features of the 3.1 µm model were too small to keep their intended shape in printing. The authors increased the lateral size through 10, 20 and 30 µm to 40 µm, while keeping slicing and hatching at 0.1 µm. The fabrication previews show how shape accuracy improves.

Fig. 2 · Ishaq et al., CC BY 3.0; unmodified.

Can the light find a match?

A measured optical resonance sits near the NV center’s 637 nm emission line.

At the NV line, the reconstructed resonance response is about 0.76 of its maximum. The two spectral features partially overlap.

The fabricated silver-coated polymer structure showed optical resonances in reflectance. A fitted resonance at 647.69 nm had an unloaded Q of about 17.

Move the wavelength probe to see how the response rises toward the center and falls away. A higher Q means a narrower resonance relative to its wavelength.

This curve is a single Lorentzian reconstructed from the paper’s fitted center and Q, using FWHM = 647.69 / 16.97 ≈ 38.17 nm. It is a relative resonance response, not an NV emission-enhancement measurement.

A foothold for three-dimensional sensing.

NV centers connect light to electron spin. Their spin-dependent fluorescence can reveal magnetic fields, electric fields and temperature at small scales.

The paper proposes using a 3D scaffold to place these emitters at useful optical hotspots, with possible applications in biological environments. Here, the structure’s fabrication and optical resonances are demonstrated experimentally; enhanced NV emission is modeled, and integrated sensing is a future aim.

3-D pillar-and-scaffold nanostructures for integrating nitrogen-vacancy doped nanodiamonds ↗

Faisal Ishaq, Sumeer Khanna, Roger Narayan, Joshua Bader, Faraz Ahmed Inam and Stefania Castelletto. RSC Advances 2026, 16, 19397–19411. DOI: 10.1039/d6ra00555a.

Source figures 2, 6, 7 and 8 are reproduced unmodified from Ishaq et al. under CC BY 3.0. Supplement Fig. S5 is resized, with content unchanged. Graphical abstract: AI-generated conceptual illustration informed by Figs. 1, 6 and 7.

The 3D view illustrates mechanisms, with dimensions simplified for clarity. The wavelength applet reconstructs a normalized Lorentzian from the published fit parameters. Supplementary Section 5 informs the interior-emitter comparison.