19 research outputs found
Indefinite and Bidirectional Near Infrared Nanocrystal Photoswitching
Materials whose luminescence can be switched by optical stimulation drive
technologies ranging from superresolution imaging1-4, nanophotonics5, and
optical data storage6-8, to targeted pharmacology, optogenetics, and chemical
reactivity9. These photoswitchable probes, including organic fluorophores and
proteins, are prone to photodegradation, and often require phototoxic doses of
ultraviolet (UV) or visible light. Colloidal inorganic nanoparticles have
significant stability advantages over existing photoswitchable materials, but
the ability to switch emission bidirectionally, particularly with NIR light,
has not been reported with nanoparticles. Here, we present 2-way, near-infrared
(NIR) photoswitching of avalanching nanoparticles (ANPs), showing full optical
control of upconverted emission using phototriggers in the NIR-I and NIR-II
spectral regions useful for subsurface imaging. Employing single-step
photodarkening10-13 and photobrightening12,14-18, we demonstrate indefinite
photoswitching of individual nanoparticles (>1000 cycles over 7 h) in ambient
or aqueous conditions without measurable photodegradation. Critical steps of
the photoswitching mechanism are elucidated by modeling and by measuring the
photon avalanche properties of single ANPs in both bright and dark states.
Unlimited, reversible photoswitching of ANPs enables indefinitely rewritable 2D
and 3D multi-level optical patterning of ANPs, as well as optical nanoscopy
with sub-{\AA} localization superresolution that allows us to distinguish
individual ANPs within tightly packed clusters.Comment: 15 pages, 5 figure
Conductivity-type anisotropy in molecular solids
Thin polycrystalline films of perylenetetracarboxylic dianyhydride (PTCDA), an organic molecular solid, exhibits substantial anisotropies in its electronic transport properties. Only electrons transport in the directions along molecular planes, while mainly holes transport in the direction normal to molecular planes. A series of measurements on both field effect transistors with PTCDA active layers and light emitting diodes with PTCDA transport layers documents the anisotropy seen in the electronic transport in thin films of PTCDA. (C) 1997 American Institute of Physics
Conductivity-type anisotropy in molecular solids
Thin polycrystalline films of perylenetetracarboxylic dianyhydride (PTCDA), an organic molecular solid, exhibits substantial anisotropies in its electronic transport properties. Only electrons transport in the directions along molecular planes, while mainly holes transport in the direction normal to molecular planes. A series of measurements on both field effect transistors with PTCDA active layers and light emitting diodes with PTCDA transport layers documents the anisotropy seen in the electronic transport in thin films of PTCDA. (C) 1997 American Institute of Physics
Indefinite and bidirectional near-infrared nanocrystal photoswitching
Materials whose luminescence can be switched by optical stimulation drive technologies ranging from superresolution imaging(1-4), nanophotonics(5), and optical data storage(6,7), to targeted pharmacology, optogenetics, and chemical reactivity(8). These photoswitchable probes, including organic fluorophores and proteins, can be prone to photodegradation and often operate in the ultraviolet or visible spectral regions. Colloidal inorganic nanoparticles(6,9) can offer improved stability, but the ability to switch emission bidirectionally, particularly with near-infrared (NIR) light, has not, to our knowledge, been reported in such systems. Here, we present two-way, NIR photoswitching of avalanching nanoparticles (ANPs), showing full optical control of upconverted emission using phototriggers in the NIR-I and NIR-II spectral regions useful for subsurface imaging. Employing single-step photodarkening(10-13) and photobrightening(12,14-16), we demonstrate indefinite photoswitching of individual nanoparticles (more than 1,000 cycles over 7 h) in ambient or aqueous conditions without measurable photodegradation. Critical steps of the photoswitching mechanism are elucidated by modelling and by measuring the photon avalanche properties of single ANPs in both bright and dark states. Unlimited, reversible photoswitching of ANPs enables indefinitely rewritable two-dimensional and three-dimensional multilevel optical patterning of ANPs, as well as optical nanoscopy with sub-A localization superresolution that allows us to distinguish individual ANPs within tightly packed clusters.11Nsciescopu