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T. A. King - One of the best experts on this subject based on the ideXlab platform.
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effect of pmma impregnation on the Fluorescence Quantum Yield of sol gel glasses doped with quinine sulfate
Optical Materials, 2001Co-Authors: M A Menesesnava, Sabino Chavezcerda, L A Diaztorres, O Barbosagarcia, M Torrescisneros, T. A. KingAbstract:Abstract The Fluorescence Quantum Yield of quinine sulfate in sol–gel and PMMA impregnated glasses is measured. The observed Quantum Yield improvement in the sol–gel matrix, compared to ethanol, is interpreted as a reduction of non-radiative relaxation channels by isolation of the molecules by the cage of the glass. PMMA impregnated sol–gel glasses show an extra improvement of the Fluorescence Yield, which is interpreted as a reduction of the free space and the rigid fixation of the molecules to the matrix.
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Effect of PMMA impregnation on the Fluorescence Quantum Yield of sol–gel glasses doped with quinine sulfate
Optical Materials, 2001Co-Authors: Marco-antonio Meneses-nava, Sabino Chávez-cerda, Oracio Barbosa-garcía, Miguel Torres-cisneros, Luis A. Diaz-torres, T. A. KingAbstract:Abstract The Fluorescence Quantum Yield of quinine sulfate in sol–gel and PMMA impregnated glasses is measured. The observed Quantum Yield improvement in the sol–gel matrix, compared to ethanol, is interpreted as a reduction of non-radiative relaxation channels by isolation of the molecules by the cage of the glass. PMMA impregnated sol–gel glasses show an extra improvement of the Fluorescence Yield, which is interpreted as a reduction of the free space and the rigid fixation of the molecules to the matrix.
V. P. N. Nampoori - One of the best experts on this subject based on the ideXlab platform.
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variations in Fluorescence Quantum Yield of basic fuchsin with silver nanoparticles prepared by femtosecond laser ablation
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2014Co-Authors: Bini Pathrose, V. P. N. Nampoori, P. Radhakrishnan, H Sahira, A. MujeebAbstract:Nano structured noble metals have very important applications in diverse fields such as photovoltaics, catalysis, electronic and magnetic devices, etc. In the present work, the application of dual beam thermal lens technique is employed for the determination of the absolute Fluorescence Quantum Yield of the triaminotriphenylmethane dye, basic fuchsin in the presence of silver sol is studied. Silver sol is prepared by femtosecond laser ablation. It is observed that the presence of silver sol decreases the Fluorescence Quantum efficiency. The observed results are in line with the conclusion that the reduction in Quantum Yield in the quenching region is essentially due to the non-radiative relaxation of the absorbed energy. It is also observed that the presence of silver sol enhances the thermal lens signal which makes its detection easier at any concentration.
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Measurement of Absolute Fluorescence Quantum Yield of Basic Fuchsin Solution Using a Dual-Beam Thermal Lens Technique
Journal of Fluorescence, 2014Co-Authors: Bini Pathrose, V. P. N. Nampoori, P. Radhakrishnan, A. MujeebAbstract:The dual beam thermal lens technique is an effective method for the measurement of Fluorescence Quantum Yield of dye solutions. The concentration-dependent Quantum Yield of a novel dye of triaminotriphenylmethane family in ethanol is studied using this technique. The absolute Fluorescence Quantum Yield is measured and is observed that the reduction in the Quantum Yield is due to the non-radiative relaxation of the absorbed energy.
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Thermal lens technique to evaluate the Fluorescence Quantum Yield of a schiff base
Applied Physics B, 2004Co-Authors: A. Santhi, P. Radhakrishnan, U.l. Kala, Ritty J. Nedumpara, Achamma Kurian, M.r.p. Kurup, V. P. N. NampooriAbstract:The Fluorescence spectrum of the schiff base obtained from salicylaldehyde and 2-aminophenol is studied using an argon-ion laser as the excitation source and its Fluorescence Quantum Yield (Qf) is determined using a thermal lens method. This is a nondestructive technique that gives the absolute value of Qf without the need for a Fluorescence standard. The Quantum-Yield values are calculated for various concentrations of the solution in chloroform and also for various excitation wavelengths. The value of Qf is relatively high, and is concentration dependent. The maximum value of Qf obtained is nearly 0.78. The high value of the Fluorescence Quantum Yield will render the schiff base useful as a fluorescent marker for biological applications. Photostability and gain studies will assess its suitability as a laser dye.
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effect of silver nano particles on the Fluorescence Quantum Yield of rhodamine 6g determined using dual beam thermal lens method
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2004Co-Authors: A. Santhi, P. Radhakrishnan, M Umadevi, V Ramakrishnan, V. P. N. NampooriAbstract:Nano structured noble metals have very important applications in diverse fields as photovoltaics, catalysis, electronic and magnetic devices, etc. Here, we report the application of dual beam thermal lens technique for the determination of the effect of silver sol on the absolute Fluorescence Quantum Yield (FQY) of the laser dye rhodamine 6G. A 532 nm radiation from a diode pumped solid state laser was used as the excitation source. It has been observed that the presence of silver sol decreases the Fluorescence Quantum efficiency. This is expected to have a very important consequence in enhancing Raman scattering which is an important spectrochemical tool that provides information on molecular structures. We have also observed that the presence of silver sol can enhance the thermal lens signal which makes the detection of the signal easier at any concentration. © 2003 Elsevier B.V. All rights reserved.
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Solvent Effect on Absolute Fluorescence Quantum Yield of Rhodamine 6G Determined Using Transient Thermal Lens Technique
Modern Physics Letters B, 1999Co-Authors: C V Bindhu, Sivanandan S. Harilal, V. P. N. Nampoori, C. P. G. VallabhanAbstract:Dual beam thermal lens technique is successfully employed for the determination of absolute Fluorescence Quantum Yield of rhodamine 6G laser dye in different solvents. A 532 nm radiation from a Q-switched Nd:YAG laser was used for the excitation purpose. The Fluorescence Quantum Yield values are found to be strongly influenced by environmental effects. It has been observed that Fluorescence Yield is greater for rhodamine 6G in ethylene glycol system than in water or in methanol. Our results also indicate that parameters like concentration of the dye solution, aggregate formation and excited state absorption affect the absolute values of Fluorescence Yield significantly.
Jacek Waluk - One of the best experts on this subject based on the ideXlab platform.
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Goodbye to Quinine in Sulfuric Acid Solutions as a Fluorescence Quantum Yield Standard
Analytical chemistry, 2019Co-Authors: Krzysztof Nawara, Jacek WalukAbstract:Quinine is by far the most popular Fluorescence Quantum Yield standard used nowadays. In this work, we exploit a modified version of a recently developed SAFE (simultaneous absorption and emission measurement) method for investigating the temperature dependence of Fluorescence Quantum Yields. The accuracy of the method was verified using rhodamine 6G and rhodamine B solutions, which have well characterized Quantum Yield temperature dependences. Subsequently, we investigated the Quantum Yield temperature dependence of quinine solutions in 0.05 M sulfuric acid and 0.1 M perchloric acid. The results show a large temperature dependence of Fluorescence Quantum Yield for quinine in 0.05 M sulfuric acid. This temperature dependence is particularly pronounced near room temperature (from 20 to 25 °C), where the Quantum Yield changes by −0.45% per Celsius degree. In contrast, the Fluorescence Quantum Yield of quinine in 0.1 M perchloric acid shows no temperature dependence between 20 and 45 °C, where, in the entire...
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Goodbye to Quinine in Sulfuric Acid Solutions as a Fluorescence Quantum Yield Standard
2019Co-Authors: Krzysztof Nawara, Jacek WalukAbstract:Quinine is by far the most popular Fluorescence Quantum Yield standard used nowadays. In this work, we exploit a modified version of a recently developed SAFE (simultaneous absorption and emission measurement) method for investigating the temperature dependence of Fluorescence Quantum Yields. The accuracy of the method was verified using rhodamine 6G and rhodamine B solutions, which have well characterized Quantum Yield temperature dependences. Subsequently, we investigated the Quantum Yield temperature dependence of quinine solutions in 0.05 M sulfuric acid and 0.1 M perchloric acid. The results show a large temperature dependence of Fluorescence Quantum Yield for quinine in 0.05 M sulfuric acid. This temperature dependence is particularly pronounced near room temperature (from 20 to 25 °C), where the Quantum Yield changes by −0.45% per Celsius degree. In contrast, the Fluorescence Quantum Yield of quinine in 0.1 M perchloric acid shows no temperature dependence between 20 and 45 °C, where, in the entire range, the luminescence Quantum Yield value remains constant and equal to 0.60 ± 0.007. These results clearly indicate that it should be recommended to use quinine in 0.1 M perchloric acid rather than quinine in 0.05 M sulfuric acid as a standard solution for the determination of luminescence Quantum Yields
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Improved Method of Fluorescence Quantum Yield Determination
Analytical chemistry, 2017Co-Authors: Krzysztof Nawara, Jacek WalukAbstract:In the most widely used procedure for luminescence Quantum Yield determination, absorption and emission spectra are measured on two different instruments. This leads to errors caused by wavelength misalignment and different monochromator characteristics of the spectrophotometer and the spectrofluorometer. These errors can be avoided using a method for Fluorescence Quantum Yield determination that relies on simultaneous absorption and Fluorescence emission (SAFE) measurement using a single commercial spectrofluorometer. The method's performance is compared with the standard routinely used procedure for the relative Quantum Yield determination. The advantages of SAFE measurement are discussed. The proposed novel approach eliminates a number of potential errors in Quantum Yield determination protocol and provides higher accuracy.
Ute Reschgenger - One of the best experts on this subject based on the ideXlab platform.
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Fluorescence Quantum Yield and single particle emissionof cdse dot cds rod nanocrystals
Journal of Physical Chemistry C, 2019Co-Authors: Alexandra Hinsch, Christian Wurth, Svenhendrik Lohmann, Christian Strelow, Tobias Kipp, Daniel Geisler, Andreas Kornowski, Christopher Wolter, Horst Weller, Ute ReschgengerAbstract:The Fluorescence Quantum Yield (QY) of CdSe dot/CdS rod (DR) nanoparticle ensembles is dependent on the shell growth and excitation wavelength. We analyze the origin of this dependency by comparing the optical properties of DR ensembles to the results obtained in single-particle experiments. On the ensemble level, we find that the QY of DRs with shell lengths shorter than 40 nm exhibits no dependence on the excitation wavelength, whereas for DRs with shell lengths longer than 50 nm, the QY significantly decreases for excitation above the CdS band gap. Upon excitation in the CdSe core, the ensemble QY, the Fluorescence wavelength, and the Fluorescence blinking behavior of individual particles are only dependent on the radial CdS shell thickness and not on the CdS shell length. If the photogenerated excitons can reach the CdSe core region, the Fluorescence properties will be dependent only on the surface passivation in close vicinity to the CdSe core. The change in QY upon excitation above the band gap of C...
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Fluorescence Quantum Yield and single particle emission of cdse
2019Co-Authors: A Hirsch, Christian Wurth, Svenhendrik Lohmann, Christian Strelow, Tobias Kipp, Daniel Geisler, Christopher Wolter, Horst Weller, A Komoski, Ute ReschgengerAbstract:The Fluorescence Quantum Yield (QY) of CdSe dot/CdS rod (DR) nanoparticle ensembles is dependent on the Shell growth and excitation wavelength. We analyze the origin of this dependency by comparing the optical properties of DR ensembles to the results obtained in single-particle experiments. On the Ensemble level, we find that the QY of DRs with shell lengths shorter than 40 nm exhibits no dependence on the excitation wavelength, whereas for DRs with shell lengths longer than 50 nm, the QY significantly decreases for excitation above the CdS band gap. Upon excitation in the CdSe core, the ensemble QY, the Fluorescence wavelength, and the Fluorescence blinking behavior of individual particles are only dependent on the radial CdS shell thickness and not on the CDs shell length. If the photogenerated excitons can reach the CdSe core region, the Fluorescence properties will be dependent only on the surface passivation in close vicinity to the CdSe core. The change in QY upon excitation above the band gap of CdS for longer DRs cannot be explained by nonradiative particles because the ratio of emitting DRs is found to be independent of the DR length. We propose a model after which the decrease in QY for longer CdS shells is due to an increasing fraction of nonradiative exciton recombination within the elongated shell. This is supported by an effective-mass-approximation-based calculation, which suggests an optimum length of DRs of about 40 nm, to combine the benefit of high CdS absorption cross section with a high Fluorescence QY.
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stability and Fluorescence Quantum Yield of cdse zns Quantum dots influence of the thickness of the zns shell
Annals of the New York Academy of Sciences, 2008Co-Authors: Markus Grabolle, Jan Ziegler, Alexei Merkulov, Thomas Nann, Ute ReschgengerAbstract:We investigated the correlation between the thickness of the ZnS shell of CdSe-ZnS Quantum dots (QDs), the stability of the particles, and the Fluorescence Quantum Yield. As a measure for stability, a new shell quality test was developed. This test is based on the reaction of the QDs with photochemically formed thiophenol radicals and communicates an imperfect ZnS shell by a rapid and complete loss of Fluorescence. The Quantum Yield increases from less than 5% for unshelled CdSe up to 50%, with an increase in ZnS shell thickness up to 0.6-0.8 nm. At the same time, the particles become significantly more stable, as revealed by the shell test.
A. Mujeeb - One of the best experts on this subject based on the ideXlab platform.
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variations in Fluorescence Quantum Yield of basic fuchsin with silver nanoparticles prepared by femtosecond laser ablation
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2014Co-Authors: Bini Pathrose, V. P. N. Nampoori, P. Radhakrishnan, H Sahira, A. MujeebAbstract:Nano structured noble metals have very important applications in diverse fields such as photovoltaics, catalysis, electronic and magnetic devices, etc. In the present work, the application of dual beam thermal lens technique is employed for the determination of the absolute Fluorescence Quantum Yield of the triaminotriphenylmethane dye, basic fuchsin in the presence of silver sol is studied. Silver sol is prepared by femtosecond laser ablation. It is observed that the presence of silver sol decreases the Fluorescence Quantum efficiency. The observed results are in line with the conclusion that the reduction in Quantum Yield in the quenching region is essentially due to the non-radiative relaxation of the absorbed energy. It is also observed that the presence of silver sol enhances the thermal lens signal which makes its detection easier at any concentration.
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Measurement of Absolute Fluorescence Quantum Yield of Basic Fuchsin Solution Using a Dual-Beam Thermal Lens Technique
Journal of Fluorescence, 2014Co-Authors: Bini Pathrose, V. P. N. Nampoori, P. Radhakrishnan, A. MujeebAbstract:The dual beam thermal lens technique is an effective method for the measurement of Fluorescence Quantum Yield of dye solutions. The concentration-dependent Quantum Yield of a novel dye of triaminotriphenylmethane family in ethanol is studied using this technique. The absolute Fluorescence Quantum Yield is measured and is observed that the reduction in the Quantum Yield is due to the non-radiative relaxation of the absorbed energy.