An optical probe was constructed to simultaneously measure both OSM types (Fig. 2). The two OSM types are spectrally separated. PtTFPP OSMs have multiple absorption peaks at 390, 504, and 538 nm and emission peaks at 647 and 710 nm.22 PtTPTBP OSMs have multiple absorption peaks at 430 and 614 nm and an emission peak at 770 nm.22 The optical probe can selectively excite either type of OSM with two pairs of light emitting diode (LEDs) (Rebel LED, Luxeon Star, Brantford, Canada) centered at 530 nm (green) and 617 nm (red) for PtTFPP and PtTPTBP, respectively. The LEDs are mounted onto a custom three-dimensional printed conical mount designed to pitch the LEDs such that emitted light converges onto samples placed just above the surface of the cone. The conical mount is glued onto the distal surface of a 2-in. long lens tube (Thorlabs, Newton) containing a 6.4-mm diameter image conduit (Edmund Optics, Barrington) and a focusing lens (). The distal end of the lens tube is mounted onto a filter cube holder (Thorlabs) containing a long-pass dichroic beam splitter (FF740-Di01, Semrock, Rochester) to reflect PtTFPP and transmit PtTPTBP emissions, respectively. Two amplified photodiode detectors (PDA100A, 9.8-mm diameter, , Thorlabs) are mounted onto the cube to detect emissions from each OSM type. LED emission and digitalization of photodiode signals are conducted by a National Instruments data acquisition device (USB6361 DAQ, National Instruments, Austin) controlled by LabView (National Instruments).