scholarly journals Wavelength Dependence of the Transformation Mechanism of Sulfonamides Using Different LED Light Sources and TiO2 and ZnO Photocatalysts

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 49
Author(s):  
Máté Náfrádi ◽  
Tünde Alapi ◽  
Luca Farkas ◽  
Gábor Bencsik ◽  
Gábor Kozma ◽  
...  
Keyword(s):  
Excited State ◽  
Formation Rate ◽  
Wavelength Dependence ◽  
Light Sources ◽  
Tio2 Photocatalyst ◽  
High Quantum Yield ◽  
Reaction Parameters ◽  
Transformation Mechanism ◽  
Photogenerated Electrons ◽  
Dissolved O2

The comparison of the efficiency of the commercially available photocatalysts, TiO2 and ZnO, irradiated with 365 nm and 398 nm light, is presented for the removal of two antibiotics, sulfamethazine (SMT) and sulfamethoxypyridazine (SMP). The •OH formation rate was compared using coumarin, and higher efficiency was proved for TiO2 than ZnO, while for 1,4-benzoquinone in O2-free suspensions, the higher contribution of the photogenerated electrons to the conversion was observed for ZnO than TiO2, especially at 398 nm irradiation. An extremely fast transformation and high quantum yield of SMP in the TiO2/LED398nm process were observed. The transformation was fast in both O2 containing and O2-free suspensions and takes place via desulfonation, while in other cases, mainly hydroxylated products form. The effect of reaction parameters (methanol, dissolved O2 content, HCO3− and Cl−) confirmed that a quite rarely observed energy transfer between the excited state P25 and SMP might be responsible for this unique behavior. In our opinion, these results highlight that “non-conventional” mechanisms could occur even in the case of the well-known TiO2 photocatalyst, and the effect of wavelength is also worth investigating.

scholarly journals Driving high quantum yield NIR emission through proquinoidal linkage motifs in conjugated supermolecular arrays

2020 ◽  
Vol 11 (31) ◽  
pp. 8095-8104
Author(s):  
Erin J. Viere ◽  
Wei Qi ◽  
Ian N. Stanton ◽  
Peng Zhang ◽  
Michael J. Therien
Keyword(s):  
Excited State ◽  
Quantum Yield ◽  
Structural Relaxation ◽  
Ground State ◽  
Building Blocks ◽  
High Quantum Yield ◽  
High Quantum ◽  
Nir Emission

Incorporation of proquinoidal BTD building blocks into conjugated porphyrin oligomers minimizes the extent of excited-state structural relaxation relative to the ground-state conformation, elucidating new classes of impressive NIR fluorophores.

Kinetics model for the wavelength-dependence of excited-state dynamics of hetero-FRET sensors

2017 ◽  
Author(s):  
Ahmed A. Heikal ◽  
Jacob Schwarz ◽  
Ryan Leighton ◽  
Hannah Leopold ◽  
Megan Currie ◽  
...  
Keyword(s):  
Excited State ◽  
Wavelength Dependence ◽  
Kinetics Model ◽  
Excited State Dynamics

Electronic Relaxation and Dissociation Dynamics in Formaldehyde: Pump Wavelength Dependence

2021 ◽  
Author(s):  
Tomoyuki Endo ◽  
Simon Neville ◽  
Philippe Lassonde ◽  
Chen Qu ◽  
Hikaru Fujise ◽  
...  
Keyword(s):  
Excited State ◽  
First Principles ◽  
Wavelength Dependence ◽  
Pump Wavelength ◽  
Electronic Relaxation ◽  
Excited State Dynamics ◽  
Dissociation Dynamics

The effect of the incident UV pump wavelength on the subsequent excited state dynamics, elec- tronic relaxation, and ultimate dissociation of formaldehyde is studied using first principles simu- lation and...

Wavelength Dependence of the Non-Linear Transmission of Hitci Using the Z-Scan Technique

1994 ◽  
Vol 374 ◽  
Author(s):  
Stewart Swatton ◽  
Kevin Welford ◽  
Cameron Ray ◽  
Steven Till
Keyword(s):  
Excited State ◽  
Laser Pulses ◽  
Wavelength Dependence ◽  
Equation Model ◽  
Induced Absorption ◽  
Third Harmonic ◽  
Optical Parametric ◽  
Carbocyanine Dye ◽  
Non Linear ◽  
Linear Behaviour

AbstractThe excited state properties of dyes become important under intense illumination of a short laser pulse. The pulse induces a significant population in an excited state which will have different absorptive properties, this causes a change in absorption of the incident pulse within its duration. An increase in absorption arises from molecules in an excited state having an absorption greater than the corresponding ground state.The z-scan technique has been used to measure the induced absorption of a carbocyanine dye 1,1′,3,3,3′,3′- Hexamethylindtricarbocyanine Iodide (HITCI) for laser pulses of different wavelengths. An optical parametric oscillator pumped by the third harmonic of a Q-switched Nd:YAG laser was used. Z-scans were taken at a number of different wavelengths between 460 and 630 nm. Data is presented which shows the spectral region where induced absorption occurs. An eight level rate equation model is used to predict the non-linear behaviour and to fit to the experimental data, good correlation is found between the model and data.

scholarly journals Wavelength dependence of isotope fractionation in N<sub>2</sub>O photolysis

2003 ◽  
Vol 3 (2) ◽  
pp. 303-313 ◽  
Author(s):  
J. Kaiser ◽  
T. Röckmann ◽  
C. A. M. Brenninkmeijer ◽  
P. J. Crutzen
Keyword(s):  
Cross Sections ◽  
Vacuum Ultraviolet ◽  
Isotopic Fractionation ◽  
Theoretical Models ◽  
Wavelength Dependence ◽  
Light Sources ◽  
Actinic Flux ◽  
Comprehensive Picture ◽  
Ultraviolet Photolysis ◽  
Linear Fit

Abstract. In previous reports on isotopic fractionation in the ultraviolet photolysis of nitrous oxide (N2O) only enrichments of heavy isotopes in the remaining N2O fraction have been found. However, most direct photolysis experiments have been performed at wavelengths far from the absorption maximum at 182 nm. Here we present high-precision measurements of the 15N and 18O fractionation constants (ε) in photolysis at 185 nm. Small, but statistically robust depletions of heavy isotopes for the terminal atoms in the linear N2O molecule are found. This means that the absorption cross sections σ(15N 14N 16O) and σ(14N218O) are larger than σ(14N216O) at this specific wavelength. In contrast, the central N atom becomes enriched in 15N. The corresponding fractionation constants (±1 standard deviation) are 15ε1 = σ(15N 14N 16O)/σ(14N2 16O) - 1 = (3.7±0.2) %o 18ε = σ(14N218O)/σ(14N216O) - 1 = (4.5±0.2) %o  and 15ε2 = σ(14N 15N 16O)/σ(14N216O) - 1 = (-18.6±0.5) %o To our knowledge, this is the first documented case of such a heavy isotope depletion in the photolysis of N2O which supports theoretical models and pioneering vacuum ultraviolet spectroscopic measurements of 15N substituted N2O species that predict fluctuations of ε around zero in this spectral region (Selwyn and Johnston, 1981). Such a variability in isotopic fractionation could have consequences for atmospheric models of N2O isotopes since actinic flux varies also strongly over narrow wavelength regions between 175 and 200 nm due to the Schumann-Runge bands of oxygen. However, the spacing between maxima and minima of the fractionation constants and of the actinic flux differ by two orders of magnitude in the wavelength domain. The wavelength dependence of fractionation constants in N2O photolysis can thus be approximated by a linear fit with negligible consequences on the actual value of the spectrally averaged fractionation constant. In order to establish this linear fit, additional measurements at wavelengths other than 185 nm were made using broadband light sources, namely D2, Hg/Xe and Sb lamps. The latter lamp was used in conjunction with various interference filters to shift the peak photolysis rate to longer wavelengths. From these experiments and existing data in the literature, a comprehensive picture of the wavelength dependence of N2O photolysis near room-temperature is created.

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