scholarly journals Fluorescence Quenching Studies on the Interactions between Chosen Fluoroquinolones and Selected Stable TEMPO and PROXYL Nitroxides

2021 ◽  
Vol 22 (2) ◽  
pp. 885
Author(s):  
Krzysztof Żamojć ◽  
Irena Bylińska ◽  
Wiesław Wiczk ◽  
Lech Chmurzyński
Keyword(s):  
Fluorescence Quenching ◽  
Rate Constants ◽  
Quenching Rate ◽  
Time Resolved ◽  
Radiative Processes ◽  
Diffusion Limited ◽  
Fluoroquinolone Antibiotics ◽  
Quenching Efficiency ◽  
Bimolecular Quenching ◽  
The Impact

The influence of the stable 2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPO) nitroxide and its six C4-substituted derivatives, as well as two C3-substituted analogues of 2,2,5,5-tetramethylpyrrolidynyl-N-oxyl (PROXYL) nitroxide on the chosen fluoroquinolone antibiotics (marbofloxacin, ciprofloxacin, danofloxacin, norfloxacin, enrofloxacin, levofloxacin and ofloxacin), has been examined in aqueous solutions by UV absorption as well as steady-state and time-resolved fluorescence spectroscopies. The mechanism of fluorescence quenching has been specified and proved to be purely dynamic (collisional) for all the studied systems, which was additionally confirmed by temperature dependence experiments. Moreover, the selected quenching parameters—that is, Stern–Volmer quenching constants and bimolecular quenching rate constants—have been determined and explained. The possibility of electron transfer was ruled out, and the quenching was found to be diffusion-limited, being a result of the increase in non-radiative processes. Furthermore, as the chosen nitroxides affected the fluorescence of fluoroquinolone antibiotics in different ways, an influence of the structure and the type of substituents in the molecules of both fluoroquinolones and stable radicals on the quenching efficiency has been determined and discussed. Finally, the impact of the solvent’s polarity on the values of bimolecular quenching rate constants has been explained. The significance of the project comes from many applications of nitroxides in chemistry, biology and industry.

A study on fluorescence quenching of a laser dye by aromatic amines in alcohols

2015 ◽  
Vol 93 (4) ◽  
pp. 469-474 ◽  
Author(s):  
H.R. Deepa ◽  
J. Thipperudrappa ◽  
H.M. Suresh Kumar
Keyword(s):  
Fluorescence Quenching ◽  
Aromatic Amines ◽  
Room Temperature ◽  
Static Quenching ◽  
Laser Dye ◽  
Approximation Model ◽  
Positive Deviation ◽  
Quenching Rate ◽  
Time Resolved ◽  
Bimolecular Quenching

The fluorescence quenching of 1,2,3,8-tetrahydro-1,2,3,3,8-pentamethyl-5-(trifluoromethyl)-7H-pyrrolo[3,2-g]quinolin-7-one (LD-473) by aromatic amines, namely, aniline, dimethyl aniline, and diethyl aniline, in methanol, ethanol, propanol, and butanol has been studied at room temperature using steady-state and time-resolved methods. A positive deviation from linearity has been observed in Stern–Volmer (S–V) plots. Various quenching rate parameters have been determined using the extended S–V equation and are found to be dependent on the dielectric constant of alcohols. The quenching ability of amines increases with increasing their ionization energies. Further, with the use of the sphere of action, static quenching model, and finite sink approximation model, it is concluded that the bimolecular quenching reactions are due to the combined effect of both dynamic and static quenching processes.

scholarly journals Spectroscopic Study on the Reaction of Singlet-Excited Nile Blue with Certain Antioxidants

2021 ◽  
Author(s):  
C. Manivannan ◽  
S. Baskaran ◽  
Anbazhagan V
Keyword(s):  
Antioxidant Activity ◽  
Fluorescence Quenching ◽  
Electronic Properties ◽  
Nile Blue ◽  
Quenching Rate ◽  
Visible Absorption ◽  
Time Resolved ◽  
Fluorescence Measurements ◽  
Different Temperatures ◽  
Bimolecular Quenching

Abstract The photoinduced interaction of nile blue (NB) with various antioxidant molecules was investigated by fluorescence quenching technique and lifetime measurements. The various substituted catecholic compounds are employed as quenchers to evaluate their antioxidant activity. The formations of ground state complex between NB and quencher molecules observed from the UV-Visible absorption spectroscopy. The bimolecular quenching rate constants (kq) values depend on presence of substituent and its electronic properties of quencher molecules. Fluorescence quenching experiments have been performed at three different temperatures to assess the thermodynamic parameters. Time resolved fluorescence measurements suggest that the fluorescence quenching of NB with antioxidant molecules undergoes static quenching mechanism. The bond dissociation enthalpy (BDE) values reveal the discharge of HTfrom the antioxidant molecules. The electronic properties play an important role in the antioxidant activity of quencher molecules. The mechanism of fluorescence quenching between NB and quencher molecules are analysed based on the fluorescence quenching experiments, cyclic voltammetry experiments and BDE calculations.

Fluorescence Quenching of Aminodiphenylamines with Chloromethanes

2002 ◽  
Vol 67 (8) ◽  
pp. 1154-1164 ◽  
Author(s):  
Nachiappan Radha ◽  
Meenakshisundaram Swaminathan
Keyword(s):  
Charge Transfer ◽  
Fluorescence Quenching ◽  
Ground State ◽  
Rate Constants ◽  
Quenching Mechanism ◽  
Quenching Rate ◽  
Charge Transfer Interaction ◽  
Electronically Excited ◽  
A Charge

The fluorescence quenching of 2-aminodiphenylamine (2ADPA), 4-aminodiphenylamine (4ADPA) and 4,4'-diaminodiphenylamine (DADPA) with tetrachloromethane, chloroform and dichloromethane have been studied in hexane, dioxane, acetonitrile and methanol as solvents. The quenching rate constants for the process have also been obtained by measuring the lifetimes of the fluorophores. The quenching was found to be dynamic in all cases. For 2ADPA and 4ADPA, the quenching rate constants of CCl4 and CHCl3 depend on the viscosity, whereas in the case of CH2Cl2, kq depends on polarity. The quenching rate constants for DADPA with CCl4 are viscosity-dependent but the quenching with CHCl3 and CH2Cl2 depends on the polarity of the solvents. From the results, the quenching mechanism is explained by the formation of a non-emissive complex involving a charge-transfer interaction between the electronically excited fluorophores and ground-state chloromethanes.

Resonance energy transfer study of laser dyes LD 489 and LD 473 with rhodamine 6G

2014 ◽  
Vol 92 (4) ◽  
pp. 302-306 ◽  
Author(s):  
H.R. Deepa ◽  
J. Thipperudrappa ◽  
H.M. Suresh Kumar
Keyword(s):  
Energy Transfer ◽  
Rhodamine 6G ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Laser Dyes ◽  
Rate Parameter ◽  
Quenching Rate ◽  
Range Interaction ◽  
Time Resolved ◽  
Bimolecular Quenching

The energy transfer using two laser dyes 6,7,8,9-tetrahydro-6,8,9-trimethyl-4-(trifluoromethyl)-2H-pyrano[2,3-b][1,8]naphthyridin-2-one (LD-489) and 1,2,3,8-tetrahydro-1,2,3,3,8-pentamethyl-5-(trifluoromethyl)-7H-pyrrolo[3,2-g]quinolin-7-one (LD-473) as donors and rhodamine 6G (Rh6G) as acceptor was investigated in methanol using steady state and time resolved fluorescence spectroscopy. The bimolecular quenching rate parameter, kq, and the translation diffusion rate parameter, kd, were calculated and these values indicated that the diffusion process alone does not operate in energy transfer process. The mean diffusion length, d1, is found to be less than the Förster distance, R0, supporting the dominance of long-range interaction. The critical transfer distances determined from both the Förster equation and the half quenching concentration are close to one another, revealing that the Förster mechanism plays an important role in overall energy transfer of the donors.

Effect of fluorescence quenching on 6BAAC in different solvents

2014 ◽  
Vol 92 (1) ◽  
pp. 41-45 ◽  
Author(s):  
N.R. Patil ◽  
R.M. Melavanki
Keyword(s):  
Fluorescence Quenching ◽  
Empirical Relation ◽  
Static Quenching ◽  
Einstein Relation ◽  
Positive Deviation ◽  
Quenching Rate ◽  
R And D ◽  
Diffusion Limited ◽  
Quenching Mechanisms ◽  
Static And Dynamic Quenching

The fluorescence quenching studies of 6-bromo-3-azidoacetyl coumarin (6BAAC) by aniline in four different solvents, namely acetonitrile, benzene, dioxane, and toluene, were carried out at room temperature to understand quenching mechanisms. The Stern–Volmer plots have been found to be nonlinear with a positive deviation for all the solvents studied. To interpret these results we have invoked the ground state complex formation and sphere of action static quenching models. Using these models various quenching rate parameters have been determined. The magnitudes of these parameters suggest that the sphere of action static quenching model agrees well with the experimental results. Hence the positive deviation is attributed to the static and dynamic quenching. Further, with the use of the finite sink approximation model, it was possible to check these bimolecular reactions as diffusion-limited and to estimate independently distance parameter R′ and mutual diffusion coefficient D. Finally an effort has been made to correlate the values of R′ and D with the values of the encounter distance R and the mutual coefficient D determined using Edward’s empirical relation and the Stokes–Einstein relation.

Nonlinear quenching rates in SrI2 and CsI scintillator hosts

2011 ◽  
Vol 1341 ◽  
Author(s):  
Joel Q. Grim ◽  
Qi Li ◽  
K.B. Ucer ◽  
R.T. Williams ◽  
A. Burger ◽  
...  
Keyword(s):  
Rate Constants ◽  
Light Yield ◽  
Detailed Comparison ◽  
Integrating Sphere ◽  
Excitation Density ◽  
Spatial Gradient ◽  
Quenching Rate ◽  
Time Resolved ◽  
Light Emitting ◽  
Laser Measurements

ABSTRACTUsing 0.5 ps pulses of 5.9 eV light to excite electron-hole concentrations varied up to 2x1020 e-h/cm3 corresponding to energy deposition within electron tracks, we measure dipole-dipole quenching rate constants K2 in SrI2 and CsI. We previously reported determination of K2 directly from the time dependence of quenched STE luminescence in CsI. The nonlinear quenching rate decreases rapidly within a few tens of picoseconds as the host excitation density drops below the Förster threshold. In the present work, we measure the dependence of integrated light yield on excitation density in the activated scintillators SrI2:Eu2+ and CsI:Tl+. The “z-scan” method of yield vs. irradiance is applicable to a wider range of materials, e.g. when the quenching population is not the main light-emitting population. Furthermore, because of using an integrating sphere and photomultiplier for light detection, the signal-to-noise is substantially better than the time-resolved method using a streak camera. As a result, both 2nd and 3rd orders of quenching (dipole-dipole and Auger) can be distinguished. Detailed comparison of SrI2 and CsI is of fundamental importance to help understand why SrI2 achieves substantially better proportionality than CsI in scintillator applications. The laser measurements, in contrast to scintillation, allow evaluating the rate constants of nonlinear quenching in a population which has small enough spatial gradient to suppress the effect of carrier diffusion.

Polyoligopeptides functionalized zinc(II)porphyrins: Step towards artificial hemes

2011 ◽  
Vol 15 (09n10) ◽  
pp. 871-882 ◽  
Author(s):  
Shawkat M. Aly ◽  
Hannah Guernon ◽  
Brigitte Guérin ◽  
Pierre D. Harvey
Keyword(s):  
Fluorescence Quenching ◽  
Click Chemistry ◽  
Computer Modeling ◽  
Rate Constant ◽  
Steric Hindrance ◽  
Rate Constants ◽  
Emission Spectra ◽  
Quenching Rate ◽  
Photophysical Parameters ◽  
Quenching Rate Constant

Two new zinc(II)porphyrin oligopeptide conjugates (zinc(II)-5,10,15,20-bis[4-(peptide)- phenyl]porphyrin (5) and -tetrakis[3,5-di(peptide)phenyl]porphyrin (9; peptide = -CH2(CO)Gly-Phe-Ala-CNH2) were prepared using the click chemistry with azides and ethynyl-containing precursors. The spectroscopic signature (S0→S1 and transient T1→Tn absorption, excitation and emission spectra) are typical for zinc(II)porphyrin and shows no perturbation upon anchoring the oligopeptides, whereas some small decreases in the photophysical parameters (𝜏F and ΦF), and larger decrease in T1 lifetimes are noted, which are attributable to the known "loose bolt" effect. The structure for 9 in solution was addressed qualitatively using computer modeling and the comparison of the bimolecular fluorescence quenching rate constants between 5 and 9 using C60 as a photooxidative agent. While 5 exhibits a totally accessible zinc(II)porphyrin unit for a C60 approach, 9 shows a slower quenching rate constant meaning some steric hindrance must be present.

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