Dynamics of the photoexictation of azo dye-doped liquid crystals probing by pumped attenuated total reflection

2007 ◽  
Author(s):  
Kuang Yao Lo ◽  
Chia Yi Huang
Keyword(s):  
Liquid Crystals ◽  
Azo Dye ◽  
Total Reflection ◽  
Attenuated Total Reflection

scholarly journals Solar photodegradation of a textile azo dye using synthesized ZnO/Bentonite

2016 ◽  
Vol 75 (5) ◽  
pp. 1211-1220 ◽  
Author(s):  
B. Boutra ◽  
M. Trari
Keyword(s):  
Azo Dye ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Impregnation Method ◽  
Order Kinetic ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Order ◽  
Optical Gap ◽  
Optimal Ph

The present work is devoted to the synthesis of a new photocatalyst ZnO (7.5%)/Bentonite prepared by impregnation method and its successful application for the degradation of Solophenyl Red 3BL (SR 3BL) under solar light (∼660 W/m2). The X-ray diffraction (XRD) indicates mixed phases of the nanocomposite catalyst (ZnO/Bentonite), characterized by scanning electron microscopy, X-ray fluorescence and attenuated total reflection. The optical properties confirm the presence of the Wurtzite ZnO phase with an optical gap of 3.27 eV. The catalyst dose (0.25–1 gL−1), pH solution (2.5–11) and initial dye concentration (5–75 mg/L) are optimized. The optimal pH (∼6.7) is close to the natural environment. The photodegradation yield increases with decreasing the SR 3BL concentration. The equilibrium is reached within 160 min and the data are well fitted by the Langmuir-Hinshelwood model; the SR 3BL disappearance obeys to a first-order kinetic with an apparent rate constant of 10−2 mn−1. The best yield of SR 3BL photodegradation (92%) is achieved for a concentration of 5 mg/L and a catalyst dose of 0.75 gL−1 at free pH.

Attenuated total reflection and emission due to surface plasmon excitation of layer-by-layer ultrathin films containing azo-dye

2003 ◽  
Vol 438-439 ◽  
pp. 101-107 ◽  
Author(s):  
Keizo Kato ◽  
Junichi Kawashima ◽  
Akira Baba ◽  
Kazunari Shinbo ◽  
Futao Kaneko ◽  
...  
Keyword(s):  
Surface Plasmon ◽  
Ultrathin Films ◽  
Azo Dye ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Layer By Layer ◽  
Plasmon Excitation ◽  
Surface Plasmon Excitation

VARIATION OF ATTENUATED TOTAL REFLECTION AND SECOND HARMONIC GENERATION OF MIXED NEMATIC LIQUID CRYSTALS

2001 ◽  
Vol 10 (04) ◽  
pp. 441-457 ◽  
Author(s):  
R. L. DONG ◽  
T. S. LIN ◽  
J. T. LUE
Keyword(s):  
Liquid Crystals ◽  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
Second Harmonic ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Nonlinear Susceptibility ◽  
Layered System ◽  
Flexoelectric Effect ◽  
Angle Shift

Optical second harmonic generation from nematic and cholesteric liquid crystals attributing to quadrupole, flexoelectric effect and electric field induced nonlinear susceptibility is detected. The measured second harmonic generation (SHG) intensity is proportional to the square of the applied field irrespective of whether the field is alternate or direct current. The SHG intensity can be enhanced by the surface plasmons generated by attenuated total reflection (ATR) installed by the Kretcshmann–Raether configurations. The small angle shift of the ATR minimum under various change of bias as large as 40 V can be satisfactorily expressed by the three layered system in which the indices of two outer layers retained in their original values by the strong anchoring effect.

scholarly journals Competitive Dye Adsorption-Desorption on the Isotropic Surface at the Early Stage of the Photoexcitation of Azo Dye-Doped Liquid Crystals

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 802
Author(s):  
Wei-Ting Chen ◽  
Sheng-Chung Ji ◽  
Shih-Hsuan Chen ◽  
Chia-Yi Huang ◽  
Kuang Yao Lo
Keyword(s):  
Azo Dye ◽  
Early Stage ◽  
Dye Adsorption ◽  
Adsorbed Layer ◽  
Structural Evolution ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Pump Light ◽  
In Situ Observation ◽  
Adsorption Desorption

The instantaneous response of liquid crystal (LC) molecules near the dye-adsorbed layer of azo dye-doped LCs (ADDLCs) in early-stage photoexcitation was observed through the pumped-attenuated total reflection (PATR) method. As the sensing depth of the attenuated total reflection (ATR) method is in the order of hundreds of nm, in situ observation using the PATR method directly inspected the restructuring of the adsorbed layer in the early-stage photoexcitation, which demonstrated the competition between adsorption and desorption on the isotropic surface without the interference of the elastic continuum in the bulk of a cell. Analyzing the frequency of the oscillation-like PATR signal, which reflects the evolution of the orientation of the LC molecules, revealed that, depending on the dose of the pump light, the structural evolution of the adsorbed layer is fast at the beginning of photoalignment in ADDLCs and slows down with the accumulation of the adsorbed layer. A suitable intensity of the pump light in the early stage of the photoalignment process can improve the reform of the adsorbed layer to strengthen its anchoring.

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