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).

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.

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 Preparation of multifunctional nanocomposites Fe3O4@SiO2–EDTA and its adsorption of heavy metal ions in water solution

2020 ◽  
Vol 81 (1) ◽  
pp. 170-177 ◽  
Author(s):  
Tao Gong ◽  
Yongbai Tang
Keyword(s):  
Heavy Metal ◽  
Metal Ions ◽  
Magnetic Materials ◽  
Heavy Metal Ions ◽  
Water Solution ◽  
Water Soluble ◽  
X Ray Diffraction ◽  
Experimental Conditions ◽  
Good Tolerance ◽  
Multifunctional Nanocomposites

Abstract Novel magnetic Fe3O4@SiO2-ethylenediamine tetraacetic acid (adsorbent) CMS–COOH-modified magnetic materials, CMS was prepared by surface modification of amino-functionalized Fe3O4@SiO2 (-NH2-modified magnetic materials, NMS) with EDTA using water-soluble carbodiimide as the cross-linker in deionized water solution. The phase structure, infrared spectra, thermal analysis and magnetic properties of were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis, and vibrating sample magnetometry and its properties for removal of heavy metal ions under varied experimental conditions were also investigated. The results revealed that CMS had good tolerance to low pH and exhibited good removal efficiency for the metal ions. The maximum adsorption capacities of CMS were found to be 0.11 mmol g−1 for Cu(II) at pH5.0 (30 °C) and 0.14 mmol g−1 for Pb(II) ions at pH2.0 (30 °C).

scholarly journals Studies on the Photoinduced Interaction between Zn(II) Porphyrin and Colloidal TiO2

2010 ◽  
Vol 2010 ◽  
pp. 1-5 ◽  
Author(s):  
Heyong Huang ◽  
Jiahong Zhou ◽  
Yan Zhou ◽  
Yanhuai Zhou ◽  
Yuying Feng
Keyword(s):  
Electron Transfer ◽  
Free Energy ◽  
Rate Constant ◽  
Reduction Potential ◽  
Fluorescence Emission ◽  
Quenching Mechanism ◽  
Quenching Rate ◽  
Absorption And Fluorescence Spectroscopy ◽  
Nanoparticle Surface ◽  
Quenching Rate Constant

The interaction of Zn(II) porphyrin (ZnPP) with colloidal TiO2was studied by absorption and fluorescence spectroscopy. The fluorescence emission of ZnPP was quenched by colloidal TiO2upon excitation of its absorption band. The quenching rate constant (kq) is1.24×1011 M−1 s−1. These data indicate that there is an interaction between ZnPP and colloidal TiO2nanoparticle surface. The quenching mechanism is discussed on the basis of the quenching rate constant as well as the reduction potential of the colloidal TiO2. And the mechanism of electron transfer has been confirmed by the calculation of free energy change(ΔGet)by applying Rehm-Weller equation as well as energy level diagram.

scholarly journals Hydrochloric Acid Modification and Lead Removal Studies on Naturally Occurring Zeolites from Nevada, New Mexico, and Arizona

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1238
Author(s):  
Garven M. Huntley ◽  
Rudy L. Luck ◽  
Michael E. Mullins ◽  
Nick K. Newberry
Keyword(s):  
New Mexico ◽  
Surface Area ◽  
Bet Surface Area ◽  
Lead Removal ◽  
X Ray Diffraction ◽  
Sem Images ◽  
X Ray ◽  
Naturally Occurring ◽  
27Al Mas Nmr ◽  
Modified Zeolites

Four naturally occurring zeolites were examined to verify their assignments as chabazites AZLB-Ca and AZLB-Na (Bowie, Arizona) and clinoptilolites NM-Ca (Winston, New Mexico) and NV-Na (Ash Meadows, Nevada). Based on powder X-ray diffraction, NM-Ca was discovered to be mostly quartz with some clinoptilolite residues. Treatment with concentrated HCl (12.1 M) acid resulted in AZLB-Ca and AZLB-Na, the chabazite-like species, becoming amorphous, as confirmed by powder X-ray diffraction. In contrast, NM-Ca and NV-Na, which are clinoptilolite-like species, withstood boiling in concentrated HCl acid. This treatment removes calcium, magnesium, sodium, potassium, aluminum, and iron atoms or ions from the framework while leaving the silicon framework intact as confirmed via X-ray fluorescence and diffraction. SEM images on calcined and HCl treated NV-Na were obtained. BET surface area analysis confirmed an increase in surface area for the two zeolites after treatment, NM-Ca 20.0(1) to 111(4) m2/g and NV-Na 19.0(4) to 158(7) m2/g. 29Si and 27Al MAS NMR were performed on the natural and treated NV-Na zeolite, and the data for the natural NV-Na zeolite suggested a Si:Al ratio of 4.33 similar to that determined by X-Ray fluorescence of 4.55. Removal of lead ions from solution decreased from the native NM-Ca, 0.27(14), NV-Na, 1.50(17) meq/g compared to the modified zeolites, 30 min HCl treated NM-Ca 0.06(9) and NV-Na, 0.41(23) meq/g, and also decreased upon K+ ion pretreatment in the HCl modified zeolites.

Light-Triggered Switching of Quantum Dot Photoluminescence through Excited-State Electron Transfer to Surface-Bound Photochromic Molecules

Nano Letters ◽  
2021 ◽  
Author(s):  
Suyog Padgaonkar ◽  
Christopher T. Eckdahl ◽  
Jakub K. Sowa ◽  
Rafael López-Arteaga ◽  
Dana E. Westmoreland ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Quantum Dot ◽  
State Electron ◽  
Photochromic Molecules

scholarly journals Silica Monolith for the Removal of Pollutants from Gas and Aqueous Phases

Molecules ◽  
2021 ◽  
Vol 26 (5) ◽  
pp. 1316
Author(s):  
Vanessa Miglio ◽  
Chiara Zaccone ◽  
Chiara Vittoni ◽  
Ilaria Braschi ◽  
Enrico Buscaroli ◽  
...  
Keyword(s):  
Rhodamine B ◽  
Water Solution ◽  
Synthesis Method ◽  
Textural Properties ◽  
Adsorption Properties ◽  
Water Soluble ◽  
Silica Monoliths ◽  
Physico Chemical ◽  
Gaseous Toluene ◽  
Mcm 41

This study focused on the application of mesoporous silica monoliths for the removal of organic pollutants. The physico-chemical textural and surface properties of the monoliths were investigated. The homogeneity of the textural properties along the entire length of the monoliths was assessed, as well as the reproducibility of the synthesis method. The adsorption properties of the monoliths for gaseous toluene, as a model of Volatile Organic Compounds (VOCs), were evaluated and compared to those of a reference meso-structured silica powder (MCM-41) of commercial origin. Silica monoliths adsorbed comparable amounts of toluene with respect to MCM-41, with better performances at low pressure. Finally, considering their potential application in water phase, the adsorption properties of monoliths toward Rhodamine B, selected as a model molecule of water soluble pollutants, were studied together with their stability in water. After 24 h of contact, the silica monoliths were able to adsorb up to the 70% of 1.5 × 10−2 mM Rhodamine B in water solution.

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