The Origin of Green Emission of ZnO Microcrystallites:  Surface-Dependent Light Emission Studied by Cathodoluminescence

The excitonic blue emission, excimeric green emission and energy transfer-mediated red emission of Nile red lead to bright white light emission upon the photoexcitation of Nile red-doped DPA nanoaggregates.

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Optical studies of Poly[p-(2,5-didodecylphenylene)ethynylene] in Thin Films

MRS Proceedings ◽

10.1557/proc-0937-m03-14 ◽

2006 ◽

Vol 937 ◽

Author(s):

Lynn Rozanski ◽

David A. Vanden Bout ◽

Uwe H.F. Bunz

Keyword(s):

Thin Films ◽

Light Emission ◽

Emission Spectra ◽

Green Emission ◽

Blue Shift ◽

Polymer Chains ◽

Emission Characteristic ◽

Brick Wall ◽

Interchain Interaction ◽

Polymer Backbone

ABSTRACTUnlike many other conjugated polymers popular for use in LEDs, poly[p-(2,5-didodecylphenylene)ethynylene] (DPPE), shows less interchain interaction between polymer chains after annealing to an ordered film. Evidence of this decreased interchain interaction can be seen in the emission spectra of pristine and annealed films. Thin films of pristine DPPE show a broad featureless green emission, characteristic of an excimer-like state, whereas annealed films blue-shift and become structured, resembling dilute solution emission. DPPE packs into ordered domains after annealing, shown by birefringence, polarization anisotropy NSOM, and x-ray crystallography data. The lack of chromophore interaction in the ordered domains can be explained through a brick-wall-type packing motif, where the polymer backbone is insulated by the side chains of offset neighboring polymers. Electroluminescence spectra of pristine and annealed LEDs are nearly identical, both having green emission, unlike their different photoluminescence spectra. This is evidence that light emission in LEDs comes only from excimer sites within the film, which would indicate a decreased performance for the annealed devices compared to pristine devices. Preliminary data of pristine and annealed LEDs supports this theory, with most pristine devices having a slightly higher electroluminescence intensity compared to annealed devices.

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On the Origin of Color Degradation in Polyfluorenes – Block Copolymer Approach for Stable Blue Light Emission

MRS Proceedings ◽

10.1557/proc-856-bb2.9 ◽

2004 ◽

Vol 856 ◽

Author(s):

Christos L. Chochos ◽

Joannis K. Kallitsis ◽

Vasilis G. Gregoriou

Keyword(s):

Light Emission ◽

Green Emission ◽

Spectroscopic Studies ◽

Light Emitting ◽

Light Emitting Devices ◽

Green Emission Band ◽

Blue Emitters ◽

Color Degradation ◽

Excimer Formation ◽

Rigid Segment

ABSTRACTSpectroscopic studies on a series of rod-coil block copolymers with terfluorene as the rigid segment demonstrate that the main cause of color instability in fluorene oligomers and polymers is aggregate and/or excimer formation and not the presence of keto defects alone (fluorenone formation) along the molecular chain. Keto defects when are present contribute to the appearance of the undesirable ‘green’ emission band but are not the leading cause of color instability. Thus, the synthesis of materials where aggregation and/or inter-chain, inter-segment interactions are inhibited is the key approach for the production of stable polymeric light-emitting devices (PLED's). The potential of this method is verified by the synthesis of photo-oxidative stable fluorene/styrene diblock copolymer blue emitters.

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Fabrication and Characterisation of Organic EL Devices in the Presence of Cyclodextrin as an Interlayer

Sensors ◽

10.3390/s21113666 ◽

2021 ◽

Vol 21 (11) ◽

pp. 3666

Author(s):

Michihiro Hara ◽

Takao Umeda ◽

Hiroyuki Kurata

Keyword(s):

Indium Tin Oxide ◽

Organic Molecules ◽

Light Emission ◽

Green Emission ◽

Coated Glass Substrate ◽

Organic Electroluminescence ◽

Cyclodextrin Polymer ◽

Electroluminescence Device ◽

Potential Energy Saving ◽

Self Association

This study examined glass-based organic electroluminescence in the presence of a cyclodextrin polymer as an interlayer. Glass-based organic electroluminescence was achieved by the deposition of five layers of N,N’-Bis(3-methylphenyl)N,N’-bis(phenyl)-benzidine, cyclodextrin polymer (CDP), tris-(8-hydroxyquinolinato) aluminium LiF and Al on an indium tin oxide-coated glass substrate. The glass-based OEL exhibited green emission owing to the fluorescence of tris-(8-hydroxyquinolinato) aluminium. The highest luminance was 19,620 cd m−2. Moreover, the glass-based organic electroluminescence device showed green emission at 6 V in the curved state because of the inhibited aggregation of the cyclodextrin polymer. All organic molecules are insulating, but except CDP, they are standard molecules in conventional organic electroluminescence devices. In this device, the CDP layer contained pores that could allow conventional organic molecules to enter the pores and affect the organic electroluminescence interface. In particular, self-association was suppressed, efficiency was improved, and light emission was observed without the need for a high voltage. Overall, the glass-based organic electroluminescence device using CDP is an environmentally friendly device with a range of potential energy saving applications.

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Facial hydrothermal route of graphene and titanium dioxide nanotube composite with enhanced green light emission at ~ 530 nm

VNU Journal of Science Mathematics - Physics ◽

10.25073/2588-1124/vnumap.4252 ◽

2018 ◽

Vol 34 (2) ◽

Author(s):

Sang Nguyen Xuan

Keyword(s):

Titanium Dioxide ◽

Light Emission ◽

Green Light ◽

Green Emission ◽

Excited Electron ◽

Photoluminescence Spectra ◽

Defect States ◽

Hydrothermal Route ◽

Trap Hole ◽

Green Light Emission

Herein we report a simple fabrication of graphene and titanium dioxide nanotube composite using hydrothermal method. Photoluminescence emission of the composite were investigated to study defect states in bandgap of nanotubes when the content of graphene varied from 1 wt% to 8 wt%. With the content of graphene lower than 5 wt%, the photoluminescence spectra form of the composite showed similar to that of pristine titanium dioxide nanotube. When the content of graphene reached 8 wt%, the emission positions were unchanged. However the spectrum form was dramatically changed, the intensity of green emission at about 530 nm was dominated. Thanks to the formation of graphene and titanium dioxide nanotube, excited electron was easy to diffuse from nanotube to graphene. The recombination of excited electron and trap hole on nanotube surface induced by oxygen vacancy in titanium dioxide anatas phase was enhanced which was attributed to the 530 nm emission.

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Tunable white light emission by variation of composition and defects of electrospun Al2O3–SiO2 nanofibers

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.6.29 ◽

2015 ◽

Vol 6 ◽

pp. 313-320 ◽

Cited By ~ 12

Author(s):

Jinyuan Zhou ◽

Gengzhi Sun ◽

Hao Zhao ◽

Xiaojun Pan ◽

Zhenxing Zhang ◽

...

Keyword(s):

Electron Microscopy ◽

White Light ◽

Composite Nanofibers ◽

Light Emission ◽

Blue Emission ◽

Green Emission ◽

White Light Emission ◽

Transmission Electron ◽

The Individual ◽

White Luminescence

Composite nanofibers consisting of Al2O3–SiO2 were prepared by electrospinning in combination with post-calcination in air. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used to investigate the crystalline phase and microstructure of the composite nanofibers. Photoluminescence experiments indicated that the resulting white light emission can be tuned by the relative intensity of the individual spectral components, which are related to the individual defects such as: violet-blue emission from O defects, green emission from ≡Si(Al)–O–C∙=O, and red emission from intersystem radiative crossing. White light emission was realized at a Al/(Al–Si) ratio of 40 and 60 mol %. This research may offer a deeper understanding of the preparation of efficient and environmentally friendly, white luminescence materials.

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Carrier excitation dynamics in black silicon nano pillar arrays

10.21203/rs.3.rs-81652/v1 ◽

2020 ◽

Author(s):

SEREF KALEM

Keyword(s):

Time Constant ◽

Radiative Recombination ◽

Surface Defects ◽

Light Emission ◽

Slow Component ◽

Green Emission ◽

Recombination Process ◽

Black Silicon ◽

Defect States ◽

Pillar Arrays

Abstract Black silicon has attracted a great deal of interest for its promising photonic applications and exciting physical properties. Several approaches have been used to demonstrate the possibility of producing black silicon with CW light emission, but the investigation of a detailed radiative dynamical properties of the recombination process is still lacking. Here, we present ultrafast radiative recombination phenomena from black silicon consisting of quantum pillars produced by plasma ion etching. An ultrafast blue luminescence component competing with non-radiative recombination at surface defects was identified as no-phonon recombination process. This component involves two decay processes with a peak energy at around 480 nm, which have the fast component of about 10 ps followed by a component of around 50 ps decay time constant. The emission exhibits slow component in red spectral region with time constant ranging from 1.5 to 2.5 ns. When the surface of nano pillars is smoothed, the slow component at around 600 nm is enhanced to the detriment of blue-green emission, increasing the lifetime of carriers within the Si core of the quantum pillars. This process results in a slower sates assuming a 3-component exponential decay as measured by Streak camera. The ultrafast PL decay leads to a transfer of carriers to long-lived defect states as evidenced by a red emission at around 2 eV. The results are interpreted through the presence of quantum confinement at the tip regions of the pillars and surface defects originating from the oxide environment surrounding the nanometer size pillars.

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Renilla Bioluminescence: A Morphologic Approach to the Location of Photocytes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100051050 ◽

1974 ◽

Vol 32 ◽

pp. 208-209

Author(s):

Ben O. Spurlock ◽

Milton J. Cormier

Keyword(s):

Excited State ◽

Ground State ◽

Molecular Basis ◽

Light Emission ◽

Chemical Basis ◽

Electronic Excited State ◽

Colonial Form ◽

The Common ◽

Eighteenth And Nineteenth Centuries ◽

Catalyzed Oxidation

The phenomenon of bioluminescence has fascinated layman and scientist alike for many centuries. During the eighteenth and nineteenth centuries a number of observations were reported on the physiology of bioluminescence in Renilla, the common sea pansy. More recently biochemists have directed their attention to the molecular basis of luminosity in this colonial form. These studies have centered primarily on defining the chemical basis for bioluminescence and its control. It is now established that bioluminescence in Renilla arises due to the luciferase-catalyzed oxidation of luciferin. This results in the creation of a product (oxyluciferin) in an electronic excited state. The transition of oxyluciferin from its excited state to the ground state leads to light emission.

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Scanning luminescence x-ray microscopy: Progress toward selective staining using microspheres

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100168104 ◽

1994 ◽

Vol 52 ◽

pp. 74-75

Author(s):

C. Jacobsen ◽

J. Fu ◽

S. Mayer ◽

Y. Wang ◽

S. Williams

Keyword(s):

Visible Light ◽

Active Sites ◽

Light Emission ◽

Chinese Hamster ◽

Polystyrene Spheres ◽

Good Resistance ◽

X Ray ◽

Selective Staining ◽

Visible Light Emission ◽

Specific Labelling

In scanning luminescence x-ray microscopy (SLXM), a high resolution x-ray probe is used to excite visible light emission (see Figs. 1 and 2). The technique has been developed with a goal of localizing dye-tagged biochemically active sites and structures at 50 nm resolution in thick, hydrated biological specimens. Following our initial efforts, Moronne et al. have begun to develop probes based on biotinylated terbium; we report here our progress towards using microspheres for tagging.Our initial experiments with microspheres were based on commercially-available carboxyl latex spheres which emitted ~ 5 visible light photons per x-ray absorbed, and which showed good resistance to bleaching under x-ray irradiation. Other work (such as that by Guo et al.) has shown that such spheres can be used for a variety of specific labelling applications. Our first efforts have been aimed at labelling ƒ actin in Chinese hamster ovarian (CHO) cells. By using a detergent/fixative protocol to load spheres into cells with permeabilized membranes and preserved morphology, we have succeeded in using commercial dye-loaded, spreptavidin-coated 0.03μm polystyrene spheres linked to biotin phalloidon to label f actin (see Fig. 3).

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The Advantages of Cryotechniques: Application To Bioluminescent Cells

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010018118x ◽

1990 ◽

Vol 48 (1) ◽

pp. 486-487

Author(s):

Gisèle Nicolas ◽

Jean-Marie Bassot ◽

Marie-Thérèse Nicolas

Keyword(s):

Endoplasmic Reticulum ◽

Striated Muscle ◽

Light Emission ◽

Stable State ◽

Freeze Substitution ◽

Initial Step ◽

Point Of Interest ◽

Cell Components ◽

Excellent Preservation ◽

External Water

The use of fast-freeze fixation (FFF) followed by freeze-substitution (FS) brings substantial advantages which are due to the extreme rapidity of this fixation compared to the conventional one. The initial step, FFF, physically immobilizes most molecules and therefore arrests the biological reactions in a matter of milliseconds. The second step, FS, slowly removes the water content still in solid state and, at the same time, chemically fixes the other cell components in absence of external water. This procedure results in an excellent preservation of the ultrastructure, avoids osmotic artifacts,maintains in situ most soluble substances and keeps up a number of cell activities including antigenicities. Another point of interest is that the rapidity of the initial immobilization enables the capture of unstable structures which, otherwise, would slip towards a more stable state. When combined with electrophysiology, this technique arrests the ultrastructural modifications at a well defined state, allowing a precise timing of the events.We studied the epithelium of the elytra of the scale-worm, Harmothoe lunulata which has excitable, conductible and bioluminescent properties. The intracellular sites of the light emission are paracrystals of endoplasmic reticulum (PER), named photosomes (Fig.1). They are able to flash only when they are coupled with plasma membrane infoldings by dyadic or triadic junctions (Fig.2) basically similar to those of the striated muscle fibers. We have studied them before, during and after stimulation. FFF-FS showed that these complexes are labile structures able to diffentiate and dedifferentiate within milliseconds. Moreover, a transient network of endoplasmic reticulum was captured which we have named intermediate endoplasmic reticulum (IER) surrounding the PER (Fig.1). Numerous gap junctions are found in the membranous infoldings of the junctional complexes (Fig.3). When cryofractured, they cleave unusually (Fig.4-5). It is tempting to suggest that they play an important role in the conduction of the excitation.

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