scholarly journals 4,4′-Dimethylazobenzene as a chemical actinometer

2022 ◽  
Author(s):  
Lorenzo Casimiro ◽  
Leonardo Andreoni ◽  
Jessica Groppi ◽  
Alberto Credi ◽  
Rémi Métivier ◽  
...  
Keyword(s):  
Quantitative Analysis ◽  
Light Source ◽  
Visible Region ◽  
Experimental Methods ◽  
Photon Flux ◽  
Total Conversion ◽  
Data Treatment ◽  
Uv Visible

AbstractChemical actinometers are a useful tool in photochemistry, which allows to measure the photon flux of a light source to carry out quantitative analysis on photoreactions. The most commonly employed actinometers so far show minor drawbacks, such as difficult data treatment, parasite reactions, low stability or impossible reset. We propose herewith the use of 4,4′-dimethylazobenzene as a chemical actinometer. This compound undergoes a clean and efficient E/Z isomerization, approaching total conversion upon irradiation at 365 nm. Thanks to its properties, it can be used to determine the photon flux in the UV–visible region, with simple experimental methods and data treatment, and with the possibility to be reused after photochemical or thermal reset. Graphical abstract

Costing out light source and product collection during evaluation of materials for renewable fuels

2011 ◽  
Vol 1326 ◽  
Author(s):  
Karthikayini Palanivelu ◽  
Meenakshi Ramalingam ◽  
Ramnarayanan Ramanathan
Keyword(s):  
Electron Microscopy ◽  
Light Source ◽  
Diffuse Reflectance Spectroscopy ◽  
Photon Flux ◽  
Source Spectrum ◽  
Mercury Vapour ◽  
Renewable Fuels ◽  
Silicon Photodiode ◽  
Analytical Technique ◽  
Uv Visible

ABSTRACTWe examined LEDs as a cheap and test lamp source to simulate monochromatic laser radiation to help us cost out optics while evaluating materials for renewable fuels. The light source spectrum was recorded using a fiber optic spectrophotometer and a calibrated silicon photodiode was used to determine the intensity. Photon flux from the LEDs was recorded using actinometry. We chose CdS and Fe3O4 as photocatalysts. The as-prepared and annealed samples were characterised using X-Ray Diffraction, UV-Visible spectroscopy, UV-Visible Diffuse reflectance spectroscopy, Fourier Transform Infra-red spectroscopy, Attenuated Total Reluctance -FTIR spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). CdS and Fe3O4 were evaluated for hydrogen evolution using DI water, sacrificial agents and an electron donor (methyl viologen) using three light sources (LEDs, sunlight and mercury vapour lamp). Products were collected by an inverted burette (Generation1), balloons with a B-14 adapter (Generation2) and septum cells (Generation3). Developing an analytical technique to quantify products continues to remain a challenge.

Hydrothermal Synthesis of Nanosized Titania Photocatalysts Using Novel Water-Soluble Titanium Complexes

2007 ◽  
Vol 124-126 ◽  
pp. 723-726 ◽  
Author(s):  
Makoto Kobayashi ◽  
Koji Tomita ◽  
Valery Petrykin ◽  
Shu Yin ◽  
Tsugio Sato ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Specific Surface ◽  
Single Phase ◽  
Visible Region ◽  
Water Soluble ◽  
No Oxidation ◽  
Nano Particles ◽  
Titanium Complexes ◽  
Uv Visible

Highly crystalline titania nano-particles were synthesized by hydrothermal method using novel stable water-soluble titanium complexes. It was confirmed that single phase anatase, rutile and brookite, which can be rarely synthesized as a single phase, can be obtained by varying the ligand in the complex and pH of the aqueous solution. TEM observations and BET specific surface area measurements had shown that these samples consisted of nanosized particles of 5~200 nm and had high specific surface areas of 25~150 m2/g. According to UV-visible diffuse reflectance spectra, these titania samples absorbed light in the visible region (λ > 400 nm). Photocatalytic activities in NO oxidation reaction exhibited by synthesized titania powders under the irradiation by UV- visible light were higher than the activity of the commercial TiO2 photocatalyst P25 (Degussa). Especially, under illumination by only visible light of above 510 nm wavelength, photocatalytic activity of the obtained specimens exceeded that of P25 more than four times. We also clearly demonstrated that single phase brookite had high photocatalytic activity for NO oxidation.

Emergent chiroptical properties in supramolecular and plasmonic assemblies

2021 ◽  
Author(s):  
N. S. Shahana Nizar ◽  
Meleppatt Sujith ◽  
K. Swathi ◽  
Cristina Sissa ◽  
Anna Painelli ◽  
...  
Keyword(s):  
Visible Region ◽  
Electromagnetic Spectrum ◽  
Comprehensive Description ◽  
Chiroptical Properties ◽  
Uv Visible

This tutorial provides a comprehensive description of the origin of chiroptical properties of supramolecular and plasmonic assemblies in the UV–visible region of the electromagnetic spectrum.

scholarly journals Determination of X-ray flux using silicon pin diodes

2009 ◽  
Vol 16 (2) ◽  
pp. 143-151 ◽  
Author(s):  
Robin L. Owen ◽  
James M. Holton ◽  
Clemens Schulze-Briese ◽  
Elspeth F. Garman
Keyword(s):  
Light Source ◽  
Energy Deposition ◽  
Photon Flux ◽  
Macromolecular Crystallography ◽  
Pin Diodes ◽  
Web Based ◽  
X Ray ◽  
Swiss Light Source ◽  
Flux Incident

Accurate measurement of photon flux from an X-ray source, a parameter required to calculate the dose absorbed by the sample, is not yet routinely available at macromolecular crystallography beamlines. The development of a model for determining the photon flux incident on pin diodes is described here, and has been tested on the macromolecular crystallography beamlines at both the Swiss Light Source, Villigen, Switzerland, and the Advanced Light Source, Berkeley, USA, at energies between 4 and 18 keV. These experiments have shown that a simple model based on energy deposition in silicon is sufficient for determining the flux incident on high-quality silicon pin diodes. The derivation and validation of this model is presented, and a web-based tool for the use of the macromolecular crystallography and wider synchrotron community is introduced.

scholarly journals Effect of Supplementary Light Source on Quality of Grafted Tomato Seedlings and Expression of Two Photosynthetic Genes

Agronomy ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 207 ◽  
Author(s):  
Hao Wei ◽  
Jiangtao Hu ◽  
Chen Liu ◽  
Mengzhao Wang ◽  
Jin Zhao ◽  
...  
Keyword(s):  
Light Source ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Light Sources ◽  
Seedling Production ◽  
White Leds ◽  
Tomato Seedlings ◽  
Photosynthetic Genes ◽  
Supplementary Lighting

Supplementary lighting is commonly used in high-quality seedling production. In this study, grafted tomato seedlings were grown for 10 days in a glasshouse with 16-h daily supplementary lighting at 100 μmol·m−2·s−1 PPFD (Photosynthetic photon flux density) from either high-pressure sodium (HPS), metal halide (MH), far-red (FR), white LEDs (Light emitting diodes) (W), or mixed LEDs (W1R2B1, where the subscript numbers indicate the ratio of the LED chips) to determine which light sources improve the seedling quality. The control seedlings did not receive any supplementary light. Physiological parameters and the expression of genes related to photosynthesis were analyzed. The results showed that root length, biomass, number of leaves, chlorophyll (SPAD), scion dry weight to height ratio (WHR), and specific leaf weight (SLW) were the greatest for grafted seedlings grown in W1R2B1. The level of root ball formation was the greatest for seedlings grown in W1R2B1, followed by those grown in W, HPS, and MH. Seedlings grown in FR did not fare well, as they were very thin and weak. Moreover, the expression of two photosynthetic genes (PsaA and PsbA) was significantly increased by W1R2B1 and W, which suggests that the plastid or nuclear genes might be regulated. The overall results suggest that W1R2B1 was the most suitable light source to enhance the quality of grafted tomato seedlings. The results of this study could be used as a reference for seedling production in glasshouses, and may provide new insights in the research on lights affecting the development of plants.

Eco-Friendly Green Synthesis of MgO Nanoparticles from Zingiber Officinale(Ginger) Root Extract and its Antibacterial Application

2021 ◽  
Vol 9 (VI) ◽  
pp. 4219-4222
Author(s):  
R. D. More
Keyword(s):  
Green Synthesis ◽  
Pathogenic Bacteria ◽  
Visible Region ◽  
Cost Effective ◽  
Zingiber Officinale ◽  
Band Gap Energy ◽  
Root Extract ◽  
Mgo Nanoparticles ◽  
Medicinal Value ◽  
Uv Visible

In this study preparation of MgO nanoparticles using Zingiber officinale (ginger) aqueous root extract by using green method. The green synthesis approaches are recognized by many scientists due to its cost effective, simple, eco-friendly. The stability and reduction of Mg+2 ions to MgO nanoparticles were characterized by UV-Visible spectroscopic analysis. From UV-Visible spectroscopy, higher band gap energy of 7.8 eV is obtained in the near visible region at the wavelength of 300 nm. The Zingiber officinale (ginger) root extract act as reducing agent for stabilization of particle size as well as medicinal value result showed a significant antibacterial activity against pathogenic bacteria, E.Coli.and S.aureus. The present investigation deals with the green synthesis of MgO nanoparticles and its antibacterial effect on selected bacteria.

Photoreduction of Dye with Noble Metal Gold Permeated with Metal Oxide Titania

2020 ◽  
Vol 20 (6) ◽  
pp. 3896-3901 ◽  
Author(s):  
Jyoti Bansal ◽  
A. K. Hafiz ◽  
Shailesh Narain Sharma
Keyword(s):  
Metal Oxide ◽  
Noble Metals ◽  
Irradiation Time ◽  
Visible Region ◽  
Visible Absorption ◽  
Photo Degradation ◽  
Sunlight Irradiation ◽  
Tunable Bandgap ◽  
Photo Response ◽  
Uv Visible

Photoactive degradation of textile malachite green (MG), methylene blue (MB) dyes has been permeated on metal oxide TiO2 nanoparticles under sunlight. Semiconductor photocatalysis is a promising method for removal of toxic chemicals from wastewater produced by industry. Due to tunable bandgap, TiO2 among various semiconductor studied mostly. Large band gap (UV active) and recombination of exciton in TiO2 less active in photo degradation. Noble metals such as gold nanoparticles deposited on TiO2 surface increased the optical activity and to shift optical response to visible region. Degradation detail has been carried out by characterisation such as XRD, UV-Vis, PL, TEM, and SEM for MG and MB textile dyes under sunlight irradiation. UV-visible absorption spectra and PL spectra shows that photo-response of as prepared sample is extended from UV to visible region. PL intensity decreases with increases in concentration of Au nanoparticles, decreases in intensity in optical spectra of Au–TiO2 composites shows that charge transfer process dominates. Au–TiO2 plays an essential role in enhancing photocatalytical activity. Decolorization optimization depends on catalyst concentration, Dye concentration, light intensity and, irradiation time.

Au Nanostructure-Decorated TiO2 Nanowires Exhibiting Photoactivity Across Entire UV-visible Region for Photoelectrochemical Water Splitting

Nano Letters ◽  
2013 ◽  
Vol 13 (8) ◽  
pp. 3817-3823 ◽  
Author(s):  
Ying-Chih Pu ◽  
Gongming Wang ◽  
Kao-Der Chang ◽  
Yichuan Ling ◽  
Yin-Kai Lin ◽  
...  
Keyword(s):  
Water Splitting ◽  
Visible Region ◽  
Photoelectrochemical Water Splitting ◽  
Tio2 Nanowires ◽  
Uv Visible

Al-Au Heterogeneous Dimer-trimer Nanostructure for SERS

2020 ◽  
Vol 10 (1) ◽  
pp. 21-28
Author(s):  
Jyoti Katyal
Keyword(s):  
Field Distribution ◽  
Enhancement Factor ◽  
Extinction Spectrum ◽  
Visible Region ◽  
Field Enhancement ◽  
Spherical Shape ◽  
Resonance Wavelength ◽  
Time Step ◽  
Plasmonic Material ◽  
Uv Visible

: Tunability in resonance wavelength and the enhancement of the electromagnetic field intensities around the surface are two unique properties which make metal as a plasmonic material. A theoretical investigation on the LSPR and field enhancement for heterogeneous dimer–trimer metallic nanostructure by constituting Al and Au as two different plamsonic materials has been studied. Since electrons in Al exhibit free behavior for LSPR of Au, therefore, they influence the electric field magnitude generated by Au LSPR. Methods: The electromagnetic simulations reported in this paper were performed using the FDTD Solutions (version 7.5.1), a product of Lumerical Solutions Inc., Vancouver, Canada. We adopted a cubic Yee cell of 1 nm side and a time step Δt= 1.31•10-18 s, bounded by Courant condition. Results: The extinction spectrum shows LSPR peak over UV-visible region for isotropic nanostructure which shifts to NIR region for anisotropic shape nanostructure. The spherical shape hetero dimer nanostructure shows enhancement factor ~ 3.9 X 105 whereas it increases to ~ 6.2 X 106 for anisotropic shape at 610 nm. The field distribution corresponding to the trimer nanostructure reveals a large dipolar field distribution on each of the three nanoparticles, oscillating approximately in-phase. The spherical shape Al-Au-Al shows enhancement factor ~ 8.5 X 106 at 571 nm. The anisotropic shape increase the enhancement factor to ~ 2.4 X 107 at peak wavelength 700 nm i.e. tuning the plasmon wavelength towards NIR region. Conclusion: The tunability in plasmon wavelength and field enhancement factor has been evaluated for heterogeneous nanostructure over wider spectrum range i.e. DUV-Visible-NIR using Au-Al dimer and trimer nanostructure. The isotropic shape Au-Al hetero nanostructure shows larger enhancement in the UV-visible region, whereas the anisotropic shape nanostructure contributes towards the NIR region.

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