Fig. 4: Imaging of NV⁻ centers and surface-attached target molecules and cells in a flow channel.

a Widefield fluorescence microscopy image of a diamond membrane corner containing NV⁻ centers at room temperature. Only a round area in the center was illuminated to avoid back-reflection from membrane edges. b The zoomed-in image of the boxed region shown in a post rotation. c A confocal scan of the same region as b using a separate setup at room temperature. Emitters confirmed to be (not) NV⁻ centers are highlighted in cyan circles (yellow boxes). Same symbols are used in b. d A representative CW-ODMR spectrum from the NV⁻ center labeled with a white arrow in c. Additional studies of NV⁻ spin coherence are included in the Supplementary Section 5.7. e, f Widefield fluorescence microscopy images of (e) Alexa-488-labeled streptavidin protein and (f) streptavidin-conjugated Qdot-525 quantum dots that were immobilized at the same region shown in a via biotinylated surface functionalization. g Schematic illustration of the flow channel structure and a cell illuminated by total internal reflection through the diamond membrane. Fluorescence microscopy images of Alexa-488-labeled TLR2 receptors on RAW cell surfaces, under (h) episcopic and (i) objective-based TIRF illumination. Edges of the diamond membrane are also visible in these images.