Controlling Plasmon-Aided Reduction of p-Nitrothiophenol by Tuning the Illumination Wavelength

ACS Catalysis ◽  
2021 ◽  
pp. 14898-14905
Author(s):  
Binbin Zhou ◽  
Weihui Ou ◽  
Junda Shen ◽  
Chenghao Zhao ◽  
Jing Zhong ◽  
...  
Keyword(s):  
Illumination Wavelength

scholarly journals HONO and NO<sub>2</sub> evolution from irradiated nitrate-doped ice and frozen nitrate solutions

2006 ◽  
Vol 6 (5) ◽  
pp. 10713-10731 ◽  
Author(s):  
T. Bartels-Rausch ◽  
D. J. Donaldson
Keyword(s):  
High Temperature ◽  
Gas Phase ◽  
Water Surface ◽  
Wavelength Dependence ◽  
Surface Fluxes ◽  
Strong Temperature Dependence ◽  
Adsorption Processes ◽  
Illumination Wavelength ◽  
Monolayer Coverage ◽  
Nitrate Solutions

Abstract. Nitrate photolysis in the wavelength range 250–1200 nm was studied on ice in a controlled laboratory experiment. Monolayer coverage of nitrate was achieved by dosing well-known amounts of HNO3 from the gas phase onto a frozen water surface. Fluxes of HONO and NO2 into the gas phase with time were quantified at temperatures between 193 K and 258 K and as a function of illumination wavelength in the range: 250–345 nm. Whereas HONO release showed a strong temperature dependence at colder temperatures, attributed to reversible adsorption processes, NO2 fluxes were independent of temperature. The observed fluxes of HONO and NO2 at high temperature were not affected by diffusion or adsorption processes, and could be used to estimate a quantum yield for HONO formation of (3.8±0.6)×10−4. A different wavelength dependence for HONO and NO2 fluxes indicates that additional reactions besides nitrate photolysis and subsequent release of the products contribute to the emission of nitrogen oxides.

Quantum efficiency of the photo-induced electronic transfer in dye–TiO2 complexes

2018 ◽  
Vol 20 (41) ◽  
pp. 26280-26287
Author(s):  
Dalma M. Marquez ◽  
Cristián G. Sánchez
Keyword(s):  
Charge Transfer ◽  
Quantum Efficiency ◽  
Electronic Transfer ◽  
Illumination Wavelength

The quantum efficiency of charge transfer in a dye–titania complex is calculated as a function of illumination wavelength.

scholarly journals Towards shifted position-diffuse reflectance imaging of anatomically correctly scaled human microvasculature

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Moritz Späth ◽  
Martin Hohmann ◽  
Clemens Roider ◽  
Benjamin Lengenfelder ◽  
Florian Stelzle ◽  
...  
Keyword(s):  
Diffuse Reflectance ◽  
Optical Methods ◽  
Reference Image ◽  
Core Diameter ◽  
Non Invasive ◽  
Evaluation Algorithm ◽  
Examination Methods ◽  
Illumination Wavelength ◽  
Diffuse Reflectance Imaging ◽  
Reflectance Data

Abstract Due to significant advantages, the trend in the field of medical technology is moving towards minimally or even non-invasive examination methods. In this respect, optical methods offer inherent benefits, as does diffuse reflectance imaging (DRI). The present study attempts to prove the suitability of DRI—when implemented alongside a suitable setup and data evaluation algorithm—to derive information from anatomically correctly scaled human capillaries (diameter: $$10\,\upmu \hbox {m}$$ 10 μ m , length: $$45\,\upmu \hbox {m}$$ 45 μ m ) by conducting extensive Monte–Carlo simulations and by verifying the findings through laboratory experiments. As a result, the method of shifted position-diffuse reflectance imaging (SP-DRI) is established by which average signal modulations of up to 5% could be generated with an illumination wavelength of $$\lambda =424\,\hbox {nm}$$ λ = 424 nm and a core diameter of the illumination fiber of $$50\,\upmu \hbox {m}$$ 50 μ m . No reference image is needed for this technique. The present study reveals that the diffuse reflectance data in combination with the SP-DRI normalization are suitable to localize human capillaries within turbid media.

scholarly journals Cytomat-R: a computer-controlled multiple laser source multiparameter flow cytophotometer system.

1977 ◽  
Vol 25 (7) ◽  
pp. 836-844 ◽  
Author(s):  
H M Shapiro ◽  
E R Schildkraut ◽  
R Curbelo ◽  
R B Turner ◽  
R H Webb ◽  
...  
Keyword(s):  
Flow Chamber ◽  
General Purpose ◽  
Optical Measurements ◽  
Laser Source ◽  
Flow Cytometric ◽  
Laser Wave ◽  
Laser Sources ◽  
Computer Controlled ◽  
Illumination Wavelength ◽  
Classification Procedures

A multiple illumination wavelength multiparameter flow cytophotometer system, using laser sources and controlled by a small, general-purpose digital computer, has been produced for use in the development of new flow cytometric techniques. Three different laser wave-lengths can be used simultaneously to illuminate different regions of the flow chamber; as many as five measurements of light scattering at various angles, extinction, and fluorescence at one or more wavelengths can be made at each illuminated station. Cells in suspension may be examined at rates of 1000 cells/sec, with seven correlated optical measurements being recorded for each cell. A library of programs for data manipulation and statistical analysis make it possible to use the system to develop and implement cell characterization, counting and classification procedures for basic and clinical research applications.

Electro-optical Wavelength Selection Enables Confocal Ratio Imaging at Low Light Levels

1995 ◽  
Vol 1 (1) ◽  
pp. 1-11
Author(s):  
Roland Nitschke ◽  
Kenneth R. Spring
Keyword(s):  
Epithelial Cells ◽  
Fluorescent Dyes ◽  
Fluorescence Emission ◽  
Argon Laser ◽  
Tunable Filter ◽  
Transmitted Light ◽  
Light Levels ◽  
Mechanical Filter ◽  
Ratio Imaging ◽  
Illumination Wavelength

A confocal attachment (Odyssey) to an inverted microscope was modified to better study living cultured epithelial cells stained with fluorescent dyes. Improvements to the instrument included elimination of light leaks, improved electronic shielding, reduction of thermal effects, and use of low dark current detectors. In addition, rapid changes in illumination wavelength and power were accomplished by replacing the original mechanical filter changer by an acousto-optic tunable filter attached to the argon laser light source. The addition of a liquid crystal tunable filter to one of the two photomultiplier detectors also permitted rapid spectral scanning of the fluorescence emission. High-resolution, differential interference contrast transmitted light images were formed simultaneously by replacement of the photodiode-based transmitted light detector with a photomultiplier tube and dichroic mirror assembly. An illumination intensity of only 40 μW/cm2 at the back focal plane of the microscope objective allowed high-quality fluorescence and transmitted light images of living cells at video rates with minimal bleaching and photodynamic damage. Both excitation ratio imaging and emission spectral scanning of living epithelial cells were accomplished. The system performance was evaluated by optical sections of fluorescent beads and thin films.

Photoconductive behavior of binary porphyrin crystalline assemblies

2017 ◽  
Vol 21 (09) ◽  
pp. 569-580 ◽  
Author(s):  
Bryan Borders ◽  
Morteza Adinehnia ◽  
Naomi Rosenkrantz ◽  
Marshall van Zijll ◽  
K. W. Hipps ◽  
...  
Keyword(s):  
Laser Light ◽  
Soret Band ◽  
Charge Carriers ◽  
Water Molecules ◽  
Persistent Photoconductivity ◽  
Temperature Dependent ◽  
Recombination Mechanism ◽  
Laser Illumination ◽  
Proposed Model ◽  
Illumination Wavelength

The mechanism of photoconductivity in a crystalline photoconductor synthesized from 1:1 ratio of meso-tetra(4-pyridyl)porphyrin (TPyP) and meso-tetra(4-sulfonatophenyl)porphyrin (TSPP) ionic tectons was examined. The rod-like crystals of TPyP:TSPP insulate in the dark but become photoconducting on illumination and a portion of the photoinduced current persists after the laser light is turned off. This persistent photoconductivity (PPC) is investigated as a function of laser illumination wavelength, laser power, and sample temperature. The primary charge carriers in the TPyP:TSPP upon photoexcitation are electrons and the charge recombination mechanism follows monomolecular kinetics. The number of electrons contributing to the photocurrent is directly proportional to the number of photons absorbed thus, the mechanisms of the photoconductivity resulting from excitations within the Soret band and the Q-band are the same. The PPC is interpreted to be the result of the formation of photoinduced metastable defects that allow for Miller–Abrahams-like hopping conductivity. The TPyP:TSPP has an incommensurately modulated crystal lattice and its proposed model structure is based on both ionic and neutral porphyrin tectons. The thermogravimetric analysis shows that the porphyrin crystals undergo dehydration on heating (˜50 ∘C) by losing water molecules located in the crystalline channels. Temperature dependent XRD indicates that dehydration causes irreversible changes to the crystal structure. The loss of crystallinity observed with heating the TPyP:TSPP crystals above 90 ∘C causes approximately 25% loss in photoconductivity but has little effect on the lifetime associated with the persistent photoconductivity.

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