scholarly journals Elucidating the Photoluminescence Quenching in Ensulizole: An Artificial Water Soluble Sunscreen

2021 ◽  
Author(s):  
Muhammad Mubeen ◽  
Muhammad Adnan Khalid ◽  
Maria Mukhtar ◽  
Saba Shahrum ◽  
Shanila Zahra ◽  
...  
Keyword(s):  
Dominant Mode ◽  
Water Soluble ◽  
Premature Aging ◽  
Absorption Feature ◽  
Dynamic Mode ◽  
Quenching Rate ◽  
Polar Solvents ◽  
Quenching Rate Constant ◽  
Bimolecular Quenching ◽  
Steady State Absorption

Abstract Employing natural or artificial sunscreens is essential to protect the skin from ultraviolet radiations that cause premature aging and develop melanoma and other forms of skin cancer. The 2-Phenylbenzimidazole-5-sulfonic acid, commonly known as ensulizole is a water-soluble artificial sunscreen that absorbs mostly UV-B (280 nm − 315 nm) radiations and protects the skin against the harmful effects of these radiations. Steady-state absorption indicates a strong absorption feature at 303 nm and a weak at 316 nm that have been identified as π → π* and n → π* transitions, respectively. The photoluminescence (PL) spectra indicate that the PL of ensulizole is less Stokes-shifted in polar solvents and more Stokes-shifted in non-polar solvents. The average PL lifetime of ensulizole is longer in non-polar solvents as compared to polar solvents and it exhibits the shortest PL lifetime in aqueous medium that signifies its efficiency in water. This suggests in non-polar solvents intersystem crossing is the dominant mode of relaxation of the excited ππ* state. Furthermore, an increase of pH of ensulizole solution decreases the PL intensity and the lifetime. Stern-Volmer equation is employed to evaluate bimolecular quenching rate constant kq that suggests the diffusional dynamic mode of PL quenching is operative.

scholarly journals Photodynamic Effect of 5,10,15,20-Tetrakis[4-(3-N,N-dimethylaminopropoxy)phenyl]chlorin towards the Human Pathogen Candida albicans under Different Culture Conditions

Photochem ◽  
2021 ◽  
Vol 1 (3) ◽  
pp. 505-522
Author(s):  
Paula V. Cordero ◽  
Darío D. Ferreyra ◽  
María E. Pérez ◽  
María G. Alvarez ◽  
Edgardo N. Durantini
Keyword(s):  
Candida Albicans ◽  
Culture Conditions ◽  
Oxygen Species ◽  
Type Ii ◽  
Planktonic Cells ◽  
Quenching Rate ◽  
Log Reduction ◽  
Quenching Rate Constant ◽  
Bimolecular Quenching ◽  
Human Pathogen Candida Albicans

Photocytotoxic activity sensitized by 5,10,15,20-tetrakis[4-(3-N,N-dimethylaminopropoxy)phenyl]chlorin (TAPC) was investigated in Candida albicans under different culture conditions. Planktonic cells incubated with 2.5 μM TAPC were eradicated after 5 min irradiation with white light. Studies in the presence of reactive oxygen species scavengers indicated the involvement of mainly a type II mechanism. Furthermore, cell growth of C. albicans was suppressed in the presence of 5 μM TAPC. A decrease in pseudohyphae survival of 5 log was found after 30 min irradiation. However, the photokilling of this virulence factor reached a 1.5 log reduction in human serum. The uptake of TAPC by pseudohyphae decreased in serum due to the interaction of TAPC with albumin. The binding constant of the TAPC-albumin complex was ~104 M−1, while the bimolecular quenching rate constant was ~1012 s−1 M−1, indicating that this process occurred through a static process. Thus, the photoinactivation of C. albicans was considerably decreased in the presence of albumin. A reduction of 2 log in cell survival was observed using 4.5% albumin and 30 min irradiation. The results allow optimizing the best conditions to inactivate C. albicans under different culture conditions.

scholarly journals Photoinduced Electron Transfer Reactions of Water Soluble Porphyrins in Zeolite Environment

2021 ◽  
Author(s):  
Anbazhagan Venkattappan ◽  
Kandavelu Velappan ◽  
Renganathan Rajalingam
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Water Solution ◽  
Total Concentration ◽  
Water Soluble ◽  
Bet Surface Area ◽  
X Ray Diffraction ◽  
Quenching Rate ◽  
Glycerol Water ◽  
Quenching Rate Constant

Abstract Excited state interactions of zeolite adsorbed porphyrins have been investigated by steady state luminescence quenching technique with certain antioxidants such as reduced glutathione, ascorbic acid and L-cysteine. The zeolite supported porphyrins, meso-tetra (N-methyl-4-pyridyl) porphyrin (H2TMPyP4+) and zinc tetra(N-methyl-4-pyridyl) porphyrin (ZnTMPyP4+) was prepared and characterized by various techniques such as Diffuse Reflectance Spectra (DRS), Scanning Electron Microscope (SEM), powder X-Ray Diffraction (XRD) and BET surface area. The interaction of zeolites with porphyrins are shown to increase the lifetime of the singlet excited state of porphyrins and decays are biphasic in nature. The splitting of the emission band of porphyrins occurs in 1:1 glycerol: water solution due to the changes in the dielectric of the solvation sphere associated with porphyrin. The Stern-Volmer plots of I0/I vs quencher total concentration [Q] were linear in the whole range of [Q] used. This study revealed effective quenching for zinc porphyrin compared to free base porphyrin. The effect of quenchers and zeolite acidity has also been studied. Quenching rate constant (kq) is on the order of 109 M−1 s−1. The quenching reaction obeys Rehm-Weller Equation and is shown to be due to thermodynamically favoured electron transfer from quenchers to the excited singlet state of porphyrins (reductive quenching).

Interaction of Nitroglycerin with Bovine Serum Albumin and the Influence of Metal Ions on the Binding

2020 ◽  
Vol 42 (2) ◽  
pp. 180-180
Author(s):  
Chengman Bao Chengman Bao ◽  
Jialian Wang Jialian Wang ◽  
Xuehong Tong Xuehong Tong ◽  
Chunli Zhang Chunli Zhang ◽  
Xinhui Tang Xinhui Tang
Keyword(s):  
Bovine Serum Albumin ◽  
Serum Albumin ◽  
Metal Ions ◽  
Bovine Serum ◽  
Binding Constants ◽  
Entropy Change ◽  
Quenching Rate ◽  
Different Temperatures ◽  
Quenching Rate Constant ◽  
Bimolecular Quenching

The effect of Cu2+, Ca2+, Mg2+and Zn2+ on the interaction between nitroglycerin and bovine serum albumin was investigated. The bimolecular quenching rate constant, the Stern-Volmer quenching constant, the binding constants and the number of binding sites were calculated in the absence and presence of Cu2+, Ca2+, Mg2+and Zn2+. The quenching constants of nitroglycerin to bovine serum albumin were increased in the presence of metal ions. Static quenching mechanism was also confirmed. The binding constants of nitroglycerin to bovine serum albumin were influenced by different metal ions. The enthalpy change, free energy chang, entropy change and the distance between the donor and the acceptor at different temperatures were calculated. The results indicated that energy transfer from bovine serum albumin to nitroglycerin occurs with high probability.

A Spectroscopic Approach with Theoretical Studies to Study the Interaction of 9-aminoacridine with Certain Phenols

2017 ◽  
Vol 231 (5) ◽  
Author(s):  
Chandrakumar Manivannan ◽  
Rajadurai Vijay Solomon ◽  
Ponnambalam Venuvanalingam ◽  
Rajalingam Renganathan
Keyword(s):  
Steady State ◽  
Bathochromic Shift ◽  
Acetonitrile Solution ◽  
Theoretical Studies ◽  
Time Resolved Fluorescence ◽  
Quenching Rate ◽  
Time Resolved ◽  
Fluorescence Measurements ◽  
Quenching Rate Constant ◽  
Bimolecular Quenching

AbstractThe influence of phenols upon the fluorescence quenching of 9-aminoacridine (9-AA) was examined in acetonitrile solution by employing steady state and time-resolved fluorescence measurements. On increasing the concentration of quencher molecules the absorption spectra of 9-AA change with significant bathochromic shift. The fluorescence intensity of 9-AA change in presence of quencher molecules were measured at various temperatures as a function of the quencher concentrations. The observed bimolecular quenching rate constant (k

Lifetime of Singlet Oxygen and Quenching by NaN3 in Mixed Solvents

1982 ◽  
Vol 37 (5) ◽  
pp. 649-652 ◽  
Author(s):  
N. Miyoshi ◽  
M. Ueda ◽  
K. Fuke ◽  
Y. Tanimoto ◽  
M. Itoh ◽  
...  
Keyword(s):  
Activation Energy ◽  
Charge Transfer ◽  
Singlet Oxygen ◽  
Mixed Solvents ◽  
Solvent Polarity ◽  
Thermal Lensing ◽  
Partial Charge ◽  
Partial Charge Transfer ◽  
Quenching Rate ◽  
Quenching Rate Constant

Singlet oxygen was generated by the photosensitization of erythrosine. The lifetime of singlet oxygen and the quenching rate constant for singlet oxygen by NaN3 were measured by a thermal lensing method in MeOH-H2O mixed solvents. The reciprocal of the lifetime increased linearly with the increase of the H2O mole fraction. Semi-log plot of the quenching constant against the reciprocal of the solvent polarity exhibited a linear relation. The quenching of the singlet oxygen by NaN3 may proceed through a partial charge-transfer intermediate. The activation energy for the quenching reaction of N3- + 1O2 →[N3·1O2-] increased with the increase of the solvent polarity. The lifetime was also measured in MeOH-ethyleneglycol mixed solvents, and its relation with viscosity was obtained

scholarly journals Спектральное исследование фотодинамических процессов в системе C-=SUB=-60-=/SUB=--(н-метилпирролидон)-кислород

2021 ◽  
Vol 129 (12) ◽  
pp. 1493
Author(s):  
И.М. Кисляков ◽  
И.М. Белоусова ◽  
В.М. Киселев ◽  
И.В. Багров ◽  
А.М. Стародубцев ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Singlet Oxygen ◽  
Transient Absorption ◽  
Rapid Quenching ◽  
Quenching Rate ◽  
Broadband Absorption ◽  
Laser Pumping ◽  
Time Dependencies ◽  
Quenching Rate Constant

The processes of photoexcitation and energy transfer in an air-saturated solution of fullerene C60 in n-methylpyrrolidone are studied. With femtosecond laser pumping at a wavelength л(p) = 520 nm, transient absorption spectra were obtained in the range 470-750 nm. Broadband absorption is observed at л > 650 nm as a result of aggregation of fullerene molecules, characterized by a short decay time of the picosecond scale. The analysis of the time dependencies indicates the presence of several processes. Within the proposed interpretation, we state a remarkable reduction in the time of singlet-triplet intersystem crossing with an increase of nanocluster size while the rapid quenching of the singlet state varies only slightly. The quantum yield of the triplet state can therefore increase, reaching 0.14. The phosphorescence spectra of singlet oxygen with a maximum at л = 1276 nm were measured with LED excitation at various wavelengths in the range 370-625 nm. The lifetime and quenching rate constant of singlet oxygen in n-methylpyrrolidone are determined. The combined quantum yield of triplet fullerene and singlet oxygen in n-methylpyrrolidone is estimated as 0.74. The efficiency spectra of the singlet oxygen photosensibilization in the C60-(n-methylpyrrolidone)-oxygen system are obtained, indicating the increasing role of large nanoclusters in this process during aging of the solution.

scholarly journals Particle size-dependent fluorescence properties of water-soluble organic compounds (WSOC) and their atmospheric implications on the aging of WSOC

2021 ◽  
Author(s):  
Juanjuan Qin ◽  
Jihua Tan ◽  
Xueming Zhou ◽  
Yanrong Yang ◽  
Yuanyuan Qin ◽  
...  
Keyword(s):  
Particle Size ◽  
Organic Compounds ◽  
Fine Particles ◽  
Stokes Shift ◽  
Bimodal Distribution ◽  
Dominant Mode ◽  
Water Soluble ◽  
Atmospheric Particle ◽  
Humification Degree ◽  
Transformation Processes

Abstract. Water-soluble organic compounds (WSOC) are essential in atmospheric particle formation, migration, and transformation processes. Size-segregated atmospheric particles were collected in a rural area of Beijing. Excitation-emission matrix (EEM) fluorescence spectroscopy was used to investigate the sources and optical properties of WSOC. Sophisticated data analysis on EEM data was performed to characteristically estimate the underlying connections among aerosol particles in different sizes. The WSOC concentrations and average fluorescence intensity (AFI) showed monomodal distribution in winter and bimodal distribution in summer, with dominant mode between 0.26 to 0.44 µm for both seasons. The EEM spectra of size-segregated WSOC were different among variant particle sizes, which could be the results of changing sources and/or chemical transformation of organics. Size distributions of fluorescence regional intensity (region Ⅲ and Ⅴ) and HIX indicate that humification degree or aromaticity of WSOC was highest between 0.26 to 0.44 µm. The Stokes shift (SS) and the harmonic mean of the excitation and emission wavelengths (WH) reflected that π-conjugated systems were high between 0.26 to 0.44 µm as well. The parallel factor analysis (PARAFAC) results showed that humic-like substances were abundant in fine particles (< 1 µm) and peaked at 0.26–0.44 µm. All evidence supported that the humification degree of WSOC increased in submicron mode (< 0.44 µm) and decreased gradually. Thus, it was conjectured that condensation of organics still goes on in submicron mode, resulting in the highest humification degree exhibit in particle size between 0.26 to 0.44 µm rather than < 0.26 µm. Synthetically analyzing 3-dimensional fluorescence data could efficiently present the secondary transformation processes of WSOC.

Spectral properties of ionic derivatives of pyrene and their aggregates with anionic surfactant and polyelectrolyte

1995 ◽  
Vol 73 (11) ◽  
pp. 1948-1954 ◽  
Author(s):  
Pavol Hrdlovič ◽  
Lubica Horinová ◽  
Štefan Chmela
Keyword(s):  
Butyric Acid ◽  
Sodium Salt ◽  
Polyacrylic Acid ◽  
Sodium Dodecylsulfate ◽  
Green Emission ◽  
Water Soluble ◽  
Diffusion Controlled ◽  
Packed Structure ◽  
Bimolecular Quenching ◽  
Derivatives Of

A multifunctional probe based on pyrene, the chloride of the 2,2,6,6-tetramethyl-4-hydroxy-piperidinium ester of 4-(1-pyrene)butyric acid, at a concentration of 5 × 10−5 mol dm−3 exhibits excimer-like green emission with the maximum at 480 nm in the presence of sodium dodecylsulfate below its critical micelle concentration. A similar effect has been observed for this probe in the presence of the sodium salt of polyacrylic acid in the same concentration range. 1-Pyrenemethylammonium chloride exhibits a broad green excimer-like emission for sodium dodecylsulfate but not for the sodium salt of polyacrylic acid. The quenching constants of the monomeric and excimer-like emissions were determined for acrylamide, 1-oxo-2,2,6,6-tetramethyl-4-hydroxypiperidine, potassium iodide, and copper(II) sulfate, representing neutral, ionic, and free-radical types of quenchers. The rate constants of quenching for N-oxyl radicals indicate that the monomeric emission from both water-soluble probes is diffusion controlled. For other types of quenchers the rate constant of bimolecular quenching is lower. The quenching of the excimer-like emission of an aggregate of the chloride of the 2,2,6,6-tetramethyl-4-hydroxypiperidinium ester of 4-(1-pyrene)butyric acid is less efficient than in the case of 1-pyrenemethylammonium chloride, which indicates a more packed structure of the former aggregate. Keywords: pyrene, ionic derivative, emission, micelle, aggregation, quenching.

Temperature dependence of the O+I(P21/2)→O+I(P23/2) quenching rate constant

2009 ◽  
Vol 105 (9) ◽  
pp. 094911 ◽  
Author(s):  
Pavel A. Mikheyev ◽  
David J. Postell ◽  
Michael C. Heaven
Keyword(s):  
Temperature Dependence ◽  
Rate Constant ◽  
Quenching Rate ◽  
Quenching Rate Constant

scholarly journals Halogen-Bond Assisted Photoinduced Electron Transfer

Molecules ◽  
2019 ◽  
Vol 24 (23) ◽  
pp. 4361
Author(s):  
Bogdan Dereka ◽  
Ina Fureraj ◽  
Arnulf Rosspeintner ◽  
Eric Vauthey
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Ground State ◽  
Halogen Bond ◽  
Quenching Rate ◽  
Excited Complex ◽  
Diffusion Controlled ◽  
Donor Acceptor ◽  
Quenching Rate Constant ◽  
Excited State Population

The formation of a halogen-bond (XB) complex in the excited state was recently reported with a quadrupolar acceptor–donor–acceptor dye in two iodine-based liquids (J. Phys. Chem. Lett. 2017, 8, 3927–3932). The ultrafast decay of this excited complex to the ground state was ascribed to an electron transfer quenching by the XB donors. We examined the mechanism of this process by investigating the quenching dynamics of the dye in the S1 state using the same two iodo-compounds diluted in inert solvents. The results were compared with those obtained with a non-halogenated electron acceptor, fumaronitrile. Whereas quenching by fumaronitrile was found to be diffusion controlled, that by the two XB compounds is slower, despite a larger driving force for electron transfer. A Smoluchowski–Collins–Kimball analysis of the excited-state population decays reveals that both the intrinsic quenching rate constant and the quenching radius are significantly smaller with the XB compounds. These results point to much stronger orientational constraint for quenching with the XB compounds, indicating that electron transfer occurs upon formation of the halogen bond.

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