scholarly journals Efficient Molecular Aggregation of Rhodamine 6G and Pseudoisocyanine by Light-Induced Force

2020 ◽  
Vol 10 (10) ◽  
pp. 3563
Author(s):  
Masayuki Shirakawa ◽  
Takayoshi Kobayashi ◽  
Eiji Tokunaga
Keyword(s):  
Thermal Equilibrium ◽  
Room Temperature ◽  
Rhodamine 6G ◽  
Gradient Force ◽  
Molecular Aggregation ◽  
Benzenesulfonic Acid ◽  
Absorbance Changes ◽  
Lock In ◽  
Induced Aggregation ◽  
Force Potential

A highly efficient light-induced aggregation of porphyrin molecules in solution was recently reported for 4-[10,15,20-tris(4-sulfophenyl)-21,24-dihydroporphyrin-5-yl]benzenesulfonic acid (TPPS). Here, we demonstrate that rhodamine 6G (R6G) and pseudoisocyanine (PIC) also show efficient light-induced aggregation in unsaturated aqueous solution, being detected with a multichannel lock-in amplifier as the absorbance decrease/increase in the monomers/aggregates, induced by a laser at 633 nm, which is non-resonant off their main monomer absorption wavelengths. The light-induced aggregation states are H-aggregates that are hardly formed in the thermal equilibrium. The similar absorbance changes are absent in the monomer molecules fixed in polyvinyl alcohol (PVA) films. The aggregation efficiency defined as ( Δ A / A ) / ( U t r a p / k B T ) , where A is the absorbance of the monomers, Δ A is the absorbance increase in the aggregates, U t r a p is the optical gradient force potential, and k B T is the thermal energy at room temperature, is approximately 100 for R6G and 500 for PIC, which are much smaller than that of TPPS.

scholarly journals Solvent Effects in Highly Efficient Light-Induced Molecular Aggregation

2019 ◽  
Vol 9 (24) ◽  
pp. 5381 ◽  
Author(s):  
Masayuki Shirakawa ◽  
Takayoshi Kobayashi ◽  
Eiji Tokunaga
Keyword(s):  
Aqueous Solution ◽  
Ethanol Solution ◽  
Gradient Force ◽  
Molecular Aggregation ◽  
Irradiation Intensity ◽  
Dipole Interactions ◽  
Absorbance Change ◽  
Irradiation Volume ◽  
Induced Aggregation ◽  
Close Distance

It has been reported that when irradiated with laser light non-resonant with the main absorption peaks, porphyrin molecules (4-[10,15,20-tris(4-sulfophenyl)-21,24-dihydroporphyrin-5-yl]benzenesulfonic acid, TPPS) in an aqueous solution become 10,000 to 100,000 times more efficient in light-induced molecular aggregation than expected from the ratio of gradient force potential to the thermal energy of molecules at room temperature. To determine the mechanism of this phenomenon, experiments on the light-induced aggregation of TPPS in alcohol solutions (methanol, ethanol, and butanol) were performed. In these alcohol solutions, the absorbance change was orders of magnitude smaller than in the aqueous solution. Furthermore, it was found that the absorbance change in the aqueous solution tended to be saturated with the increase of the irradiation intensity, but in the ethanol solution, the absorbance change increased linearly. These results can be qualitatively explained by the model in which intermolecular light-induced interactions between molecules within a close distance among randomly distributed molecules in the laser irradiation volume are highly relevant to the signal intensity. However, conventional dipole–dipole interactions, such as the Keesom interaction, are not quantitatively consistent with the results.

Room-Temperature Near-Infrared Metastable Species Measured by Phase-Sensitive Lock-in and Fourier Transform Techniques

1998 ◽  
Vol 45 (4) ◽  
pp. 503-508 ◽  
Author(s):  
Pi-Tai Chou ◽  
Youn-Chan Chen ◽  
Shu-Juan Chen ◽  
Min-Zen Lee ◽  
Ching-Yen Wei ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Room Temperature ◽  
Near Infrared ◽  
Phase Sensitive ◽  
Lock In

scholarly journals Spectral Properties of Hybrid of Rhodamine (6G) Dyes Doped Epoxy Resin Dissolved in Chloroform

2019 ◽  
Vol 16 (3(Suppl.)) ◽  
pp. 0764 ◽  
Author(s):  
Al-Hamdani Et al.
Keyword(s):  
Epoxy Resin ◽  
Quantum Efficiency ◽  
Fluorescence Spectra ◽  
Room Temperature ◽  
Rhodamine 6G ◽  
Energy Gap ◽  
Radiative Lifetime ◽  
Stokes Shift ◽  
Fluorescence Emission ◽  
Absorption And Fluorescence Spectra

            The research is dealing with the absorption and fluorescence spectra for the hybrid of  an Epoxy Resin doped with organic dye Rhodamine (R6G) of different concentrations (5*10-6, 5*10-5, 1*10-5, 1*10-4, 5*10-4) Mol/ℓ at room temperature. The Quantum efficiency Qfm, the rate of fluorescence emission Kfm (s-1), the non-radiative lifetime τfm (s), fluorescence lifetime τf and the Stokes shift were calculated. Also the energy gap (Eg) for each dye concentration was evaluated. The results showed that the maximum quantum efficiency 62 % and maximum stokes shift 96 nm was obtained in dye concentration 5*10-6 and 1*10-4. The energy gap ranges between 1.066 eV to 1.128 eV depending proportionally on the dye concentrations.

scholarly journals The Impact of Cold Storage on Adenosine Diphosphate-Mediated Platelet Responsiveness

TH Open ◽  
2020 ◽  
Vol 04 (03) ◽  
pp. e163-e172
Author(s):  
Juergen Koessler ◽  
Philipp Klingler ◽  
Marius Niklaus ◽  
Katja Weber ◽  
Angela Koessler ◽  
...  
Keyword(s):  
Cold Storage ◽  
Whole Blood ◽  
Room Temperature ◽  
Purinergic Receptor ◽  
Adenosine Diphosphate ◽  
Receptor Expression ◽  
Activation Markers ◽  
Inhibitory Pathways ◽  
The Impact ◽  
Induced Aggregation

Abstract Introduction Cold storage of platelets is considered to contribute to lower risk of bacterial growth and to more efficient hemostatic capacity. For the optimization of storage strategies, it is required to further elucidate the influence of refrigeration on platelet integrity. This study focused on adenosine diphosphate (ADP)-related platelet responsiveness. Materials and Methods Platelets were prepared from apheresis-derived platelet concentrates or from peripheral whole blood, stored either at room temperature or at 4°C. ADP-induced aggregation was tested with light transmission. Activation markers, purinergic receptor expression, and P2Y12 receptor function were determined by flow cytometry. P2Y1 and P2X1 function was assessed by fluorescence assays, cyclic nucleotide concentrations by immunoassays, and vasodilator-stimulated phosphoprotein (VASP)-phosphorylation levels by Western blot analysis. Results In contrast to room temperature, ADP-induced aggregation was maintained under cold storage for 6 days, associated with elevated activation markers like fibrinogen binding or CD62P expression. Purinergic receptor expression was not essentially different, whereas P2Y1 function deteriorated rapidly at cold storage, but not P2Y12 activity. Inhibitory pathways of cold-stored platelets were characterized by reduced responses to nitric oxide and prostaglandin E1. Refrigeration of citrated whole blood also led to the attenuation of induced inhibition of platelet aggregation, detectable within 24 hours. Conclusion ADP responsiveness is preserved under cold storage for 6 days due to stable P2Y12 activity and concomitant disintegration of inhibitory pathways enabling a higher reactivity of stored platelets. The ideal storage time at cold temperature for the highest hemostatic effect of platelets should be evaluated in further studies.

Photovoltaic spectroscopic study of GaN epilayers and InGaN quantum well structures

1999 ◽  
Vol 14 (7) ◽  
pp. 2794-2798 ◽  
Author(s):  
W. Liu ◽  
M. F. Li ◽  
K. L. Teo ◽  
Nakao Akutsu ◽  
Koh Matsumoto
Keyword(s):  
Quantum Well ◽  
Absorption Edge ◽  
Room Temperature ◽  
Carrier Screening ◽  
Free Carrier ◽  
Exciton Absorption ◽  
Quantum Well Structures ◽  
Bulk Absorption ◽  
Lock In ◽  
Reference Phase

Room-temperature photovoltaic spectroscopy was applied to study undoped GaN, n-type GaN, and InGaN quantum well structures. Clear exciton absorption was observed in the photovoltaic spectra of the undoped GaN, and polarization measurements were made to identify the exciton absorption. For the n-type GaN sample, instead of the exciton absorption we observed only bulk absorption edge, which may be due to the free carrier screening effect. For the InGaN quantum well structures, the photovoltaic spectra showed relatively complicated line shape due to the overlap of the signals from different layers. By changing the reference phase of the lock-in amplifier, we were able to suppress some of the signals and thus identify the origin of the corresponding signal.

scholarly journals What type of nanoscopic environment does a cationic fluorophore experience in room temperature ionic liquids?

2015 ◽  
Vol 17 (25) ◽  
pp. 16587-16593 ◽  
Author(s):  
Anup Ghosh ◽  
Chayan K. De ◽  
Tanmay Chatterjee ◽  
Prasun K. Mandal
Keyword(s):  
Energy Transfer ◽  
Ionic Liquids ◽  
Room Temperature ◽  
Rhodamine 6G ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Room Temperature Ionic Liquids ◽  
Cationic Dye

Employing spectral and dynamical resonance energy transfer technique nanoscopic environment experienced by a cationic dye (rhodamine 6G) in room temperature ionic liquids could be revealed.

The anomalous paramagnetism of iron(III) NN-dialkyldithiocarbamates

1964 ◽  
Vol 17 (3) ◽  
pp. 294 ◽  
Author(s):  
AH White ◽  
R Roper ◽  
E Kokot ◽  
H Waterman ◽  
RL Martin
Keyword(s):  
Molecular Weight ◽  
Thermal Equilibrium ◽  
Room Temperature ◽  
Chemical Nature ◽  
Magnetic Moments ◽  
Chloroform Solution ◽  
Exchange Interactions ◽  
Magnetic Behaviour ◽  
Antiferromagnetic Exchange ◽  
Molecular Type

The magnetic moments of a series of 19 NN-disubstituted dithiocarbamates of iron(III), [Fe(S2C.NR?R")3], are anomalous in that their behaviour is neither "high-" nor "low-spin". Values of μeff. at room temperature lie between 2.62 and 5.83 B.M., the datum for each compound depending on the chemical nature of the substituents R' and R". This anomalous situation persists in benzene or chloroform solution. Cryoscopic and ebullioscopic molecular weight determinations establish that all the compounds are monomeric, which excludes the possibility that the magnetic behaviour arises from the presence of antiferromagnetic exchange interactions of either the inter- or intra-molecular type. These observations strongly support the early and generally overlooked work of Cambi who in 1932 proposed a thermal equilibrium between "magnetic isomers" of spins S = � and S = 5/2 to account for the origin of the magnetic anomaly.

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