The role of anions in adsorbate-induced anchoring transitions of liquid crystals on surfaces with discrete cation binding sites

Soft Matter ◽  
2018 ◽  
Vol 14 (5) ◽  
pp. 797-805 ◽  
Author(s):  
Tibor Szilvási ◽  
Nanqi Bao ◽  
Huaizhe Yu ◽  
Robert J. Twieg ◽  
Manos Mavrikakis ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Response Times ◽  
Fast Response ◽  
Cation Binding ◽  
Dynamic Responses ◽  
Free Energies ◽  
Exponential Relationship ◽  
Anchoring Transitions ◽  
Nitrate Anions

A universal exponential relationship is found between calculated displacement free energies and adsorbate-induced dynamic responses of liquid crystals for a range of metal salts. Nitrate anions provide fast response times.

scholarly journals Dynamic Grating Recording by a Light-Induced Modification of the Order Parameter in Dye-Doped Chiral Nematic Liquid Crystals

2019 ◽  
Vol 64 (4) ◽  
pp. 293 ◽  
Author(s):  
A. Iljin ◽  
D. Wei ◽  
U. Bortolozzo ◽  
S. Residori
Keyword(s):  
Liquid Crystals ◽  
Order Parameter ◽  
Response Times ◽  
Nematic Liquid Crystals ◽  
Helical Structure ◽  
Fast Response ◽  
Optical Nonlinearity ◽  
Chiral Structure ◽  
Chiral Nematic ◽  
Dynamic Grating

The dynamic grating recording in dye-doped chiral nematic liquid crystals is studied. It is shown that the mechanism responsible for the grating recording can be ascribed to a photoinduced modification of the order parameter of a liquid crystal within the range of optical intensities, for which the orientational nonlinearity remains quenched by the structural order of the chiral structure. The two-wave mixing dynamic behavior is analyzed for different intensities of the recording beams, by comparing the self-diffraction regime with the probe diffraction. This allows us to distinguish a particular mechanism of optical nonlinearity. The photo-induced modulation of the order parameter and the respective changes of medium’s refractive indices determine the relatively fast response times, local nonlinear response, and quite high diffraction efficiency within an extremely wide intensity range (more than three orders of magnitude) The chiral helical structure hinders the nematic director reorientation, prevents the appearance of surface effects, and is very favorable for the manipulation of a nonlinear polarization. Such new mechanism could also be extended to the recording of arbitrary phase profiles as requested in several applications for the manipulation of a light-beam.

Control of free volume through size exclusion in the formation of smectic C phases for display applications

2015 ◽  
Vol 3 (17) ◽  
pp. 4333-4344 ◽  
Author(s):  
R. J. Mandle ◽  
E. J. Davis ◽  
J. P. Sarju ◽  
N. Stock ◽  
M. S. Cooke ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Free Volume ◽  
Response Times ◽  
Fast Response ◽  
Size Exclusion ◽  
Ferroelectric Liquid Crystals ◽  
Display Devices ◽  
Smectic C

Ferroelectric liquid crystals are of interest in display devices because of their bistable operation and fast response times.

Nanostructure of semiconductor quantum dots in a borosilicate glass matrix by complementary use of HREM and AEM

1990 ◽  
Vol 48 (4) ◽  
pp. 728-729
Author(s):  
M.J. Kim ◽  
L.C. Liu ◽  
S.H. Risbud ◽  
R.W. Carpenter
Keyword(s):  
Quantum Dots ◽  
Borosilicate Glass ◽  
Glass Matrix ◽  
Optical Switching ◽  
Response Times ◽  
Fast Response ◽  
Processing Technique ◽  
Internal Stresses ◽  
Electron Hole ◽  
Spatial Dimensions

When the size of a semiconductor is reduced by an appropriate materials processing technique to a dimension less than about twice the radius of an exciton in the bulk crystal, the band like structure of the semiconductor gives way to discrete molecular orbital electronic states. Clusters of semiconductors in a size regime lower than 2R {where R is the exciton Bohr radius; e.g. 3 nm for CdS and 7.3 nm for CdTe) are called Quantum Dots (QD) because they confine optically excited electron- hole pairs (excitons) in all three spatial dimensions. Structures based on QD are of great interest because of fast response times and non-linearity in optical switching applications.In this paper we report the first HREM analysis of the size and structure of CdTe and CdS QD formed by precipitation from a modified borosilicate glass matrix. The glass melts were quenched by pouring on brass plates, and then annealed to relieve internal stresses. QD precipitate particles were formed during subsequent "striking" heat treatments above the glass crystallization temperature, which was determined by differential thermal analysis.

Compact and efficient gas diffusion electrodes based on nanoporous alumina membranes for microfuel cells and gas sensors

The Analyst ◽  
2020 ◽  
Vol 145 (1) ◽  
pp. 122-131 ◽  
Author(s):  
Wanda V. Fernandez ◽  
Rocío T. Tosello ◽  
José L. Fernández
Keyword(s):  
Response Times ◽  
Hydrogen Oxidation ◽  
Fast Response ◽  
Gas Diffusion ◽  
Limiting Current ◽  
Gas Diffusion Electrodes ◽  
Nanoporous Alumina ◽  
Alumina Membranes ◽  
Current Densities ◽  
Microfuel Cells

Gas diffusion electrodes based on nanoporous alumina membranes electrocatalyze hydrogen oxidation at high diffusion-limiting current densities with fast response times.

scholarly journals FEM Simulation of Frequency-Selective Surface Based on Thermoelectric Bi-Sb Thin Films for THz Detection

Photonics ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 119
Author(s):  
Anastasiia Tukmakova ◽  
Ivan Tkhorzhevskiy ◽  
Artyom Sedinin ◽  
Aleksei Asach ◽  
Anna Novotelnova ◽  
...  
Keyword(s):  
Thin Films ◽  
Response Times ◽  
Fem Simulation ◽  
Film Surface ◽  
Frequency Selective Surface ◽  
Fast Response ◽  
Radiation Absorption ◽  
Thz Radiation ◽  
Frequency Filter ◽  
Frequency Selective

Terahertz (THz) filters and detectors can find a wide application in such fields as: sensing, imaging, security systems, medicine, wireless connection, and detection of substances. Thermoelectric materials are promising basis for THz detectors’ development due to their sensitivity to the THz radiation, possibility to be heated under the THz radiation and produce voltage due to Seebeck effect. Thermoelectric thin films of Bi-Sb solid solutions are semimetals/semiconductors with the band gap comparable with THz energy and with high thermoelectric conversion efficiency at room temperature. Detecting film surface can be transformed into a periodic frequency selective surface (FSS) that can operate as a frequency filter and increases the absorption of THz radiation. We report for the first time about the simulation of THz detector based on thermoelectric Bi-Sb thin-filmed frequency-selective surface. We show that such structure can be both detector and frequency filter. Moreover, it was shown that FSS design increases not only a heating due to absorption but a temperature gradient in Bi-Sb film by two orders of magnitude in comparison with continuous films. Local temperature gradients can reach the values of the order of 100 K·mm−1. That opens new perspectives for thin-filmed thermoelectric detectors’ efficiency increase. Temperature difference formed due to THz radiation absorption can reach values on the order of 1 degree. Frequency-transient calculations show the power dependence of film temperature on time with characteristic saturation at times around several ms. That points to the perspective of reaching fast response times on such structures.

scholarly journals Ultraviolet Spectroscopic Detection of Nitrate and Nitrite in Seawater Simultaneously Based on Partial Least Squares

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3685
Author(s):  
Hu Wang ◽  
Aobo Ju ◽  
Lequan Wang
Keyword(s):  
Least Squares ◽  
Partial Least Squares ◽  
Water Samples ◽  
Spectroscopic Method ◽  
River Estuary ◽  
Fast Response ◽  
Yangtze River Estuary ◽  
Exponential Relationship ◽  
Number Of Factors ◽  
Nitrate And Nitrite

A direct, reagent-free, ultraviolet spectroscopic method for the simultaneous determination of nitrate (NO3−), nitrite (NO2−), and salinity in seawater is presented. The method is based on measuring the absorption spectra of the raw seawater range of 200–300 nm, combined with partial least squares (PLS) regression for resolving the spectral overlapping of NO3−, NO2−, and sea salt (or salinity). The interference from chromophoric dissolved organic matter (CDOM) UV absorbance was reduced according to its exponential relationship between 275 and 295 nm. The results of the cross-validation of calibration and the prediction sets were used to select the number of factors (4 for NO3−, NO2−, and salinity) and to optimize the wavelength range (215–240 nm) with a 1 nm wavelength interval. The linear relationship between the predicted and the actual values of NO3−, NO2−, salinity, and the recovery of spiked water samples suggest that the proposed PLS model can be a valuable alternative method to the wet chemical methods. Due to its simplicity and fast response, the proposed PLS model can be used as an algorithm for building nitrate and nitrite sensors. The comparison study of PLS and a classic least squares (CLS) model shows both PLS and CLS can give satisfactory results for predicting NO3− and salinity. However, for NO2− in some samples, PLS is superior to CLS, which may be due to the interference from unknown substances not included in the CLS algorithm. The proposed method was applied to the analysis of NO3−, NO2−, and salinity in the Changjiang (Yangtze River) estuary water samples and the results are comparable with that determined by the colorimetric Griess assay.

Novel optical oxygen sensing by phosphorescence quenching of palladium porphyrin self-assembled film on alumina plate

2000 ◽  
Vol 04 (02) ◽  
pp. 179-184 ◽  
Author(s):  
YUTAKA AMAO ◽  
KEISUKE ASAI ◽  
ICHIRO OKURA
Keyword(s):  
Oxygen Pressure ◽  
Oxygen Sensor ◽  
Response Times ◽  
Oxygen Sensing ◽  
Fast Response ◽  
Phosphorescence Quenching ◽  
Highly Sensitive ◽  
Optical Oxygen Sensor ◽  
Self Assembled ◽  
Quenching By Oxygen

An optical oxygen sensor based on the phosphorescence quenching of palladium tetrakis(4-carboxyphenyl)porphyrin (PdTCPP) self-assembled film (SAM) on alumina plate was developed. The phosphorescence intensity of PdTCPP film decreased with increasing oxygen pressure, indicating that the film can be used as an optical oxygen-sensing device based on phosphorescence quenching by oxygen. The ratio I0/I100 as a sensitivity measure of the sensing film is estimated to be 17.7, showing that the film is a highly sensitive device for oxygen pressure. The film obeyed Stern–Volmer plots with a multisite model and possessed good operational stability and a fast response. Response times are 36 s for deoxygenated to oxygenated conditions and 148 s for the reverse conditions.

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