scholarly journals Luminance Conversion Property of Er and Yb Doped KZnF3Nanocrystal Synthesized by Hydrothermal Method

2015 ◽  
Vol 2015 ◽  
pp. 1-8
Author(s):  
Weidong Lai ◽  
Xinzheng Li ◽  
Lu Han ◽  
Huiqing Liu ◽  
Yingjuan Chen ◽  
...  
Keyword(s):  
Hydrothermal Method ◽  
Green Light ◽  
Average Diameter ◽  
Photon Absorption ◽  
Rare Earth Doping ◽  
Xenon Lamp ◽  
Nonlinear Phenomenon ◽  
Two Photon ◽  
Photon Excitation ◽  
Exposure Energy

In order to make full use of exposure energy, one feasible way is to modify the luminance of crystal by rare earth doping technique. KZnF3:Er3+and KZnF3:Er3+/Yb3+nanocrystals of uniform cuboid perovskite type morphology, with average diameter of 130 nm, has been synthesized by hydrothermal method. When Yb3+ions were codoped with Er3+, absorption peak at 970 nm has been heightened and widened, and the photon absorption cross section increased. The common xenon lamp exposure cannot initiate obvious nonlinear phenomenon of the doped Er3+and Yb3+, and exposing at 245 nm only excites the fluorescence around 395 nm. Contrarily, under high power IR exposure at 980 nm, obvious upconversion photoluminescence (PL) has been observed due to the two-photon process. The PL mechanism of the doped Er3+ion in KZnF3:Er3+/Yb3+nanocrystals is confirmed. Furthermore, Yb3+codoped as sensitizer has modified the PL intensity of Er3+from green light range to red range, and the primary channel is changed from4S3/2(Er3+) →4I15/2(Er3+) of only Er3+doped KZnF3nanocrystal to4F9/2(Er3+) →4I15/2(Er3+) of Er3+/Yb3+codoped sample. With exposure energy increasing, such primary transition channel after two-photon excitation is unchanged.

Two-Photon Excitation Imaging of Glucose Metabolism in Living Tissue

1997 ◽  
Vol 3 (S2) ◽  
pp. 305-306
Author(s):  
David W. Piston
Keyword(s):  
Confocal Microscopy ◽  
Collection Efficiency ◽  
Three Dimensional ◽  
Spatial Filter ◽  
Input Power ◽  
Photon Absorption ◽  
Focal Volume ◽  
Two Photon ◽  
Photon Excitation ◽  
Two Photon Excitation

Two-photon excitation microscopy (TPEM) provides attractive advantages over confocal microscopy for three-dimensionally resolved fluorescence imaging and photochemistry. It provides three-dimensional resolution and eliminates background equivalent to an ideal confocal microscope without requiring a confocal spatial filter, whose absence enhances fluorescence collection efficiency. This results in inherent submicron optical sectioning by excitation alone. In practice, TPEM is made possible by the very high local instantaneous intensity provided by a combination of diffraction-limited focusing of a single laser beam in the microscope and the temporal concentration of 100 femtosecond pulses generated by a mode-locked laser. Resultant peak excitation intensities are 106 times greater than the CW intensities used in confocal microscopy, but the pulse duty cycle of 10−5 limits the average input power to less than 10 mW, only slightly greater than the power normally used in confocal microscopy. Because of the intensity-squared dependence of the two-photon absorption, the excitation is limited to the focal volume.

Fluorescence anisotropy in indole under two-photon excitation in the spectral range 385–510 nm

2018 ◽  
Vol 20 (30) ◽  
pp. 19922-19931 ◽  
Author(s):  
M. E. Sasin ◽  
A. G. Smolin ◽  
K.-H. Gericke ◽  
E. Tokunaga ◽  
O. S. Vasyutinskii
Keyword(s):  
Propylene Glycol ◽  
Excited States ◽  
Spectral Range ◽  
Ground State ◽  
Fluorescence Anisotropy ◽  
Photon Absorption ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Photon Excitation ◽  
Molecular Ground State

This paper presents the detailed study of two-photon excited fluorescence in indole dissolved in propylene glycol produced by two-photon absorption from the molecular ground state to several high lying excited states.

scholarly journals Two-Photon–NIR-II Antimicrobial Graphene-Nanoagent for Ultraviolet–NIR Imaging and Photoinactivation

2021 ◽  
Author(s):  
WEN-SHUO KUO ◽  
Chia-Yuan Chang ◽  
Ping-Ching Wu ◽  
Jiu-Yao Wang
Keyword(s):  
Photodynamic Therapy ◽  
Quantum Yield ◽  
Chemical Modification ◽  
Near Infrared ◽  
Photon Absorption ◽  
Excitation Wavelength ◽  
Strong Electron ◽  
Two Photon ◽  
Photon Excitation ◽  
Two Photon Excitation

Abstract BackgroundNitrogen doping and amino-group functionalization, which result in strong electron donation, can be achieved through chemical modification. Large π-conjugated systems of graphene quantum dot (GQD)-based materials acting as electron donors can be chemically manipulated with low two-photon excitation energy in a short photoexcitation time for improving the charge transfer efficiency of sorted nitrogen-doped amino acid–functionalized GQDs (sorted amino-N-GQDs). ResultsIn this study, a self-developed femtosecond Ti-sapphire laser optical system (222.7 nJ pixel−1 with 100-170 scans, approximately 0.65-1.11 s of total effective exposure times; excitation wavelength: 960 nm in the near-infrared II region) was used for chemical modification. The sorted amino-N-GQDs exhibited enhanced two-photon absorption, post-two-photon excitation stability, two-photon excitation cross-section, and two-photon luminescence through the radiative pathway. The lifetime and quantum yield of the sorted amino-N-GQDs decreased and increased, respectively. Furthermore, the sorted amino-N-GQDs exhibited excitation-wavelength-independent photoluminescence in the near-infrared region and generated reactive oxygen species after two-photon excitation. An increase in the size of the sorted amino-N-GQDs boosted photochemical and electrochemical efficacy and resulted in high photoluminescence quantum yield and highly efficient two-photon photodynamic therapy. ConclusionThe sorted dots can be used in two-photon contrast probes for tracking and localizing analytes during two-photon imaging in a biological environment and for conducting two-photon photodynamic therapy for eliminating infectious microbes.

Two-photon excitation spectroscopy of photosynthetic light-harvesting complexes and pigments

2019 ◽  
Vol 216 ◽  
pp. 494-506 ◽  
Author(s):  
Alexander Betke ◽  
Heiko Lokstein
Keyword(s):  
Spectral Region ◽  
Protein Complexes ◽  
Photosynthetic Pigment ◽  
Photon Absorption ◽  
Light Harvesting Complexes ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Photon Excitation ◽  
Pigment Protein Complexes ◽  
Two Photon Excitation

Two-photon excitation (TPE) profiles of LHCII samples containing different xanthophyll complements were measured in the presumed 11Ag− → 21Ag− (S0 → S1) transition region of xanthophylls. Additionally, TPE profiles of Chls a and b in solution and of WSCP, which does not contain carotenoids, were measured. The results indicate that direct two-photon absorption by Chls in the presumed S0 → S1 transition spectral region of carotenoids is dominant over that of carotenoids, with negligible contributions of the latter. These results suggest the re-evaluation of previously published TPE data obtained with photosynthetic pigment–protein complexes containing (B)Chls and carotenoids.

Two-Photon Excitation of Potentiometric Probes Enables Optical Recording of Action Potentials From Mammalian Nerve Terminals In Situ

2008 ◽  
Vol 99 (3) ◽  
pp. 1545-1553 ◽  
Author(s):  
Jonathan A. N. Fisher ◽  
Jonathan R. Barchi ◽  
Cristin G. Welle ◽  
Gi-Ho Kim ◽  
Paul Kosterin ◽  
...  
Keyword(s):  
Action Potentials ◽  
Optical Recording ◽  
Photon Absorption ◽  
Nerve Terminals ◽  
Electrode Arrays ◽  
Two Photon ◽  
Photon Excitation ◽  
Mammalian Nerve ◽  
Two Photon Excitation

We report the first optical recordings of action potentials, in single trials, from one or a few (∼1–2 μm) mammalian nerve terminals in an intact in vitro preparation, the mouse neurohypophysis. The measurements used two-photon excitation along the “blue” edge of the two-photon absorption spectrum of di-3-ANEPPDHQ (a fluorescent voltage-sensitive naphthyl styryl-pyridinium dye), and epifluorescence detection, a configuration that is critical for noninvasive recording of electrical activity from intact brains. Single-trial recordings of action potentials exhibited signal-to-noise ratios of ∼5:1 and fractional fluorescence changes of up to ∼10%. This method, by virtue of its optical sectioning capability, deep tissue penetration, and efficient epifluorescence detection, offers clear advantages over linear, as well as other nonlinear optical techniques used to monitor voltage changes in localized neuronal regions, and provides an alternative to invasive electrode arrays for studying neuronal systems in vivo.

scholarly journals Dual Near Infrared Two-Photon Microscopy for Deep-Tissue Dopamine Nanosensor Imaging

2017 ◽  
Author(s):  
Jackson T. Del Bonis-O’Donnell ◽  
Ralph H. Page ◽  
Abraham G. Beyene ◽  
Eric G. Tindall ◽  
Ian McFarlane ◽  
...  
Keyword(s):  
Near Infrared ◽  
Photon Absorption ◽  
Deep Tissue ◽  
Biologically Relevant ◽  
Two Photon Microscopy ◽  
Two Photon ◽  
Tissue Phantom ◽  
Photon Excitation ◽  
Photon Absorption And Scattering ◽  
Two Photon Excitation

A key limitation for achieving deep imaging in biological structures lies in photon absorption and scattering leading to attenuation of fluorescence. In particular, neurotransmitter imaging is challenging in the biologically-relevant context of the intact brain, for which photons must traverse the cranium, skin and bone. Thus, fluorescence imaging is limited to the surface cortical layers of the brain, only achievable with craniotomy. Herein, we describe optimal excitation and emission wavelengths for through-cranium imaging, and demonstrate that near-infrared emissive nanosensors can be photoexcited using a two-photon 1560 nm excitation source. Dopamine-sensitive nanosensors can undergo two-photon excitation, and provide chirality-dependent responses selective for dopamine with fluorescent turn-on responses varying between 20% and 350%. We further calculate the two-photon absorption cross-section and quantum yield of dopamine nanosensors, and confirm a two-photon power law relationship for the nanosensor excitation process. Finally, we show improved image quality of the nanosensors embedded 2 mm deep into a brain-mimetic tissue phantom, whereby one-photon excitation yields 42% scattering, in contrast to 4% scattering when the same object is imaged under two-photon excitation. Our approach overcomes traditional limitations in deep-tissue fluorescence microscopy, and can enable neurotransmitter imaging in the biologically-relevant milieu of the intact and living brain.

Photoisomerization transition state manipulation by entangled two-photon absorption

2021 ◽  
Vol 118 (47) ◽  
pp. e2116868118
Author(s):  
Bing Gu ◽  
Daniel Keefer ◽  
Flavia Aleotti ◽  
Artur Nenov ◽  
Marco Garavelli ◽  
...  
Keyword(s):  
Wave Packet ◽  
Transition State ◽  
Product Yield ◽  
Photochemical Reactions ◽  
Photon Absorption ◽  
Conical Intersection ◽  
Two Photon ◽  
Wave Packet Dynamics ◽  
Photon Excitation ◽  
Two Photon Excitation

We demonstrate how two-photon excitation with quantum light can influence elementary photochemical events. The azobenzene trans → cis isomerization following entangled two-photon excitation is simulated using quantum nuclear wave packet dynamics. Photon entanglement modulates the nuclear wave packets by coherently controlling the transition pathways. The photochemical transition state during passage of the reactive conical intersection in azobenzene photoisomerization is strongly affected with a noticeable alteration of the product yield. Quantum entanglement thus provides a novel control knob for photochemical reactions. The distribution of the vibronic coherences during the conical intersection passage strongly depends on the shape of the initial wave packet created upon quantum light excitation. X-ray signals that can experimentally monitor this coherence are simulated.

One-Photon and Two-Photon Pump-Probe Spectroscopy of Photoactive Yellow Protein

1997 ◽  
Vol 06 (03) ◽  
pp. 295-304
Author(s):  
O. Lyngnes ◽  
H. M. Gibbs ◽  
C. F. Li ◽  
S. B. Devanathan ◽  
T. E. Meyer ◽  
...  
Keyword(s):  
Argon Laser ◽  
Absorption Peak ◽  
Photon Absorption ◽  
Photoactive Yellow Protein ◽  
Optical Pump ◽  
Pump Probe ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Photon Excitation ◽  
Probe Spectroscopy

We present the results of nonlinear optical pump-probe experiments on photoactive yellow protein (PYP). We are able to completely bleach the 446 nm absorption peak of PYP by one-photon excitation using a cw argon laser. We calculate the corresponding index change and find it to be similar to that of bacteriorhodopsin. We also determine an upper limit to the two photon absorption cross-section of PYP by looking for bleaching of the 446 nm absorption peak under irradiation by femtosecond pulses at 820–910 nm. No TPA signal is observed.

scholarly journals Optical Biomedical Diagnostics: Sensors with Optical Response Based on Two-Photon Excited Luminescent Dyes for Biomolecules Detection

2008 ◽  
Vol 2008 ◽  
pp. 1-11 ◽  
Author(s):  
V. M. Yashchuk ◽  
S. M. Yarmoluk ◽  
V. Yu. Kudrya ◽  
M. Yu. Losytskyy ◽  
V. P. Tokar ◽  
...  
Keyword(s):  
Cross Sections ◽  
Fluorescence Emission ◽  
Photon Absorption ◽  
Styryl Dyes ◽  
Dna Complexes ◽  
Two Photon ◽  
Photon Excitation ◽  
Dye Absorption ◽  
Dna Solutions ◽  
Biomolecules Detection

The spectral properties of novel styryl dyes developed for the biomacromolecules (such as DNA) detection and imaging were investigated. The energy structures of dye molecules were examined. The spectral data prove that dyes aggregate and interact with DNA. The essential increase of the fluorescence intensity of dyes in the presence of DNA was observed. The photostability and phototoxic influence on the DNA of several styryl dyes were studied by analyzing absorption, fluorescence, and phosphorescence spectra of these dyes and dye-DNA systems. Changes of the optical density value of dye-DNA solutions caused by the irradiation were fixed in the DNA and dye absorption wavelength regions. Fluorescence emission of dye-DNA complexes upon two-photon excitation at wavelength 1064 nm with the 20-nanosecond pulsed YAG:Nd3+ laser and at 840 nm with the 90 famtosecond pulsed Ti:sapphire laser was registered. The values of two-photon absorption cross-sections of dye-DNA complexes were evaluated.

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