A proof-of-principle prototype of a volumetric 3Ddisplaying system is demonstrated by utilizing the photoactivated phosphorescence of two long-lived phosphorescent metal-porphyrins in dimethyl sulfoxide (DMSO), a photochemically deoxygenating solvent. The first phosphorescent sensitizer, Pt(TPBP), absorbs a light beam with a wavelength of 635 nm, and the sensitized singlet oxygen is scavenged by DMSO. The second phosphorescent emitter, Pt(OEP), absorbs a light beam with a wavelength of 532 nm and visibly phosphoresces only in the deoxygenated zone generated by the first sensitizer. The phosphorescent voxels, 3D images, and animations are well-defined by the intersections of the 635-nm and 532-nm light beams that are programmable by tuning of the excitation-power densities, the beam shapes, and the kinetics. As a pivotal selection rule for the phosphorescent molecular couple used in this 3D-displaying system, their absorptions and emissions must be orthogonal to each other, so that they can be excited and addressed independently.Volumetric three-dimensional display technologies, which provide static or dynamic scenes in 3D spaces to the observer, [1] have been under investigation for many years but still remain one of the most intriguing research fields with potential applications in medical imaging as well as architectural and military modelling. [2] The challenge of realizing volumetric 3D images is to define and to optically address a voxel (volumetric pixel) in a real 3D space. Light-scattering, light-absorbing, and light-emitting surfaces are indispensable for the construction of voxels. In this context, an individual micro-particle or micro-bubble suspended in air by controllable photophoretic [3] or acoustic trapping [4] has been demonstrated to generate a voxel upon photo-illumination, and the 3D arrays of such voxels could be rendered into volumetric 3D images in air upon fast laser scanning.Molecular spectroscopic or photochemical approaches could be promising for volumetric 3D display in condensed phases where photophoretic and acoustic trapping are inapplicable. [5] As a representative example, in 1996, [6] two high-power infrared pump-laser beams traveled through rareearth-ion-doped glass and defined a voxel at their intersection, where only the rare-earth ions became light-emitting due to two-photon absorption or photon upconversion. [7] Later, in 2017, Lippert and co-workers used a dichloromethane (CH 2 Cl 2 ) solution of a photochromic dye (N-phenyl spirolactam rhodamine) as the medium for a volumetric 3D display. [8] The initially non-emissive dye undergoes a ring-opening photoreaction upon illumination with UV light at 385 nm and then becomes fluorescent in the green-yellow region upon excitation with a digitally processed 525 nm light. The fluorescent voxels and 3D images in their setup were defined by the intersection of the 385-nm and 525-nm light beams. An optical filter was needed to visualize the 3D images due the small Stokes shift caused by the fluorescent nature of the photochromic dye...

For an efficient triplet–triplet annihilation photon upconversion (TTA-UC) process, the matrices in which the sensitizers and emitters are dispersed should allow molecular diffusions but also protect triplet excited states from...

No abstract

No abstract