Label-free imaging methods for single bio-NP detection.
(A) (i) Schematic representation of the experimental setup for TIRDFM: ND, neutral density filter; BE, beam expander; FS, field stop; M1, mirror; L1 lens; PM, perforated mirror; L2, objective lens. (ii) Pictorial representation of the detection event. Adapted from Ref. . (B) (i) Schematic representation of the iSCAT optical setup: O, objective; QWP, quarter wave plate; PBS, polarizing beam splitter; AOD, acousto-optic deflector. (ii) Pictorial representation of the sample region, where the incident Einc, reflected by the substrate Eref, and scattered by the biomolecule Esca, are also shown. Adapted from Ref. . (C) (i) Schematic representation of the optical setup for IRIS: XC, x-cube used to combine the beam of three different LED sources; BS, cube beam splitter. (ii) Pictorial representation of the layered substrate and of the optical paths leading to the interference signal. Adapted with permission from Ref. . Copyright (2010) American Chemical Society. (D) Schematic representation of the SPRM experimental setup. Adapted from Ref. .