scholarly journals Терагерцевое поглощение в композитных пленках на основе металлоорганического перовскита и смешанного эфира целлюлозы

2020 ◽  
Vol 46 (10) ◽  
pp. 51
Author(s):  
А.В. Андрианов ◽  
А.Н. Алешин
Keyword(s):  
Composite Films ◽  
Low Frequency ◽  
Cellulose Ester ◽  
Terahertz Time Domain Spectroscopy ◽  
Absorption Bands ◽  
Cellulose Esters ◽  
Terahertz Region ◽  
The Stability ◽  
Thz Absorption ◽  
Mixed Cellulose Esters

Composites based on the organometallic perovskite CH3NH3PbI3 and mixed cellulose ester were studied by terahertz time-domain spectroscopy. It is shown that the introduction of mixed cellulose esters into the precursor of organometallic perovskite CH3NH3PbI3 significantly modifies the parameters of perovskite in the terahertz region and also improves the stability of such composite films. It is found that the addition of mixed cellulose ester to the perovskite film leads to a significant weakening of the THz absorption bands in the frequency range of the order of 1 and 2 THz, which are caused by the excitation of low-frequency vibrational modes in CH3NH3PbI3 perovskite molecules. This can be explained by the fact that cellulose ester molecules enveloping perovskite molecules dampen low-frequency vibrations in them.

scholarly journals Фотоэлектрические свойства композитных пленок на основе металлоорганического перовскита CH-=SUB=-3-=/SUB=-NH-=SUB=-3-=/SUB=-PbBr-=SUB=-3-=/SUB=- модифицированного смешанным эфиром целлюлозы

2021 ◽  
Vol 63 (1) ◽  
pp. 152
Author(s):  
Н.К. Исаев ◽  
А.Н. Алешин
Keyword(s):  
Composite Films ◽  
Perovskite Solar Cells ◽  
Cellulose Ester ◽  
Simulated Sunlight ◽  
Cellulose Esters ◽  
Light Emitting ◽  
Photoelectric Properties ◽  
The Stability ◽  
Mixed Cellulose Esters ◽  
Main Factor

It is shown that the introduction of a mixed cellulose esters with acetrimethyl acetate into films of organometallic perovskite CH3NH3PbBr3 significantly increases their stability while maintaining the optical and photoelectric properties of perovskite. It was found that with the introduction of 10-20 wt% mixed cellulose ester in CH3NH3PbBr3, the resistivity of the composite increases by 5-10 times within 60-70 days, while in pure perovskite films such changes are observed within 10-15 days. When the films are irradiated with a simulated sunlight, the resistance of the samples drops by 2-3 orders of magnitude, and the effect of photosensitivity persist for more than 2 months. The formation of hydrogen bonds between mixed cellulose ester and organometallic perovskite is, in our opinion, the main factor that increases the stability of the composite film in comparison with pure perovskite. The investigated composite films are promising for the design of degradation-resistant perovskite solar cells and light-emitting diodes.

scholarly journals Characterization of Nucleobases in Broadband Terahertz Spectra from 0.5 to 10 THz with the Air-Biased-Coherent-Detection Technique

Sensors ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 1148 ◽  
Author(s):  
Miao Yu ◽  
Shihan Yan ◽  
Yong-qiang Sun ◽  
Wang Sheng ◽  
Fu Tang ◽  
...  
Keyword(s):  
Low Frequency ◽  
Frequency Region ◽  
Coherent Detection ◽  
Detection Technique ◽  
Terahertz Time Domain Spectroscopy ◽  
High Frequency Region ◽  
Characteristic Absorption ◽  
Thz Range ◽  
Thz Absorption

Terahertz time-domain spectroscopy (THz-TDS) is an effective coherent detection technique for deeply understanding the structures and functions of biomolecules. However, generally not full information in the whole THz range can be obtained due to the limited detection bandwidth (usually less than 5 THz) of the traditional THz-TDS systems. In this paper, effective THz absorption spectra in 0.5–10 THz range of five typical nucleobases of DNA/RNA are characterized with a super broadband THz detection technique, called the air-biased- coherent-detection (THz-ABCD) technique. Few unexpected characteristic absorption peaks appeared in the low-frequency region and meanwhile a series of anticipated characteristic absorption peaks are found in the high-frequency region. The fingerprint spectra of these nucleobases are helpful for further analysis on the vibration and twisting behavior of hydrogen bonds, van der Waals and electrostatic forces etc. between and within DNA/RNA biomolecules.

scholarly journals Photoluminescence and Photoconductivity of Lead Halide Perovskite Films Modified with Mixed Cellulose Esters-=SUP=-1-=/SUP=-

2021 ◽  
Vol 91 (6) ◽  
pp. 985
Author(s):  
A.N. Aleshin ◽  
P.P. Shirinkin ◽  
A.K. Khripunov ◽  
N.N. Saprykina ◽  
I.P. Shcherbakov ◽  
...  
Keyword(s):  
Composite Films ◽  
Optical Excitation ◽  
Excitation Power ◽  
Solar Simulator ◽  
Cellulose Esters ◽  
Exciton Recombination ◽  
Halide Perovskite ◽  
Mixed Cellulose Esters ◽  
Lead Halide ◽  
Selection Of

We have investigated the photoluminescence (PL) and photoconductivity of lead halide perovskite (CH3NH3PbBr3) films modified with different mixed cellulose esters (CEs). It was shown that the absorbance and PL spectra of CH3NH3PbBr3 : CE films contain contributions of both the CH3NH3PbBr3 and CE with the dominant contribution to the PL from perovskite component. The dependences of the integral PL intensities of the CH3NH3PbBr3 : CE films on the optical excitation power turned out to be sublinear. This indicates that exciton recombination, as well as recombination via impurity levels, occur in CH3NH3PbBr3 : CE films at high excitation power levels. The conductivity of CH3NH3PbBr3 : CE films at 300 K increases up to ~90 times when illuminated by a solar simulator, and this effect is environmentally stable due to the formation of hydrogen bonds between CE and the lead halide perovskite CH3NH3PbBr3. It is expected that appropriate selection of CE and optimization of CE inclusion will improve the optoelectronic properties and stability of composite films based on lead halide perovskite-CE composites.

scholarly journals Low-frequency optical phonon modes and carrier mobility in the halide perovskite CH3NH3PbBr3 using terahertz time-domain spectroscopy

2017 ◽  
Vol 111 (20) ◽  
pp. 201903 ◽  
Author(s):  
Daming Zhao ◽  
Jonathan M. Skelton ◽  
Hongwei Hu ◽  
Chan La-o-vorakiat ◽  
Jian-Xin Zhu ◽  
...  
Keyword(s):  
Time Domain ◽  
Optical Phonon ◽  
Carrier Mobility ◽  
Low Frequency ◽  
Terahertz Time Domain Spectroscopy ◽  
Phonon Modes ◽  
Time Domain Spectroscopy ◽  
Halide Perovskite

Resonance in a mathematical model of baroreflex control: arterial blood pressure waves accompanying postural stress

2005 ◽  
Vol 288 (6) ◽  
pp. R1637-R1648 ◽  
Author(s):  
Peter E. Hammer ◽  
J. Philip Saul
Keyword(s):  
Blood Pressure ◽  
Mathematical Model ◽  
Blood Volume ◽  
Low Frequency ◽  
Pressure Waves ◽  
Central Blood Volume ◽  
Arterial Baroreflex ◽  
Arterial Blood ◽  
Gain Margin ◽  
The Stability

A mathematical model of the arterial baroreflex was developed and used to assess the stability of the reflex and its potential role in producing the low-frequency arterial blood pressure oscillations called Mayer waves that are commonly seen in humans and animals in response to decreased central blood volume. The model consists of an arrangement of discrete-time filters derived from published physiological studies, which is reduced to a numerical expression for the baroreflex open-loop frequency response. Model stability was assessed for two states: normal and decreased central blood volume. The state of decreased central blood volume was simulated by decreasing baroreflex parasympathetic heart rate gain and by increasing baroreflex sympathetic vaso/venomotor gains as occurs with the unloading of cardiopulmonary baroreceptors. For the normal state, the feedback system was stable by the Nyquist criterion (gain margin = 0.6), but in the hypovolemic state, the gain margin was small (0.07), and the closed-loop frequency response exhibited a sharp peak (gain of 11) at 0.07 Hz, the same frequency as that observed for arterial pressure fluctuations in a group of healthy standing subjects. These findings support the theory that stresses affecting central blood volume, including upright posture, can reduce the stability of the normally stable arterial baroreflex feedback, leading to resonance and low-frequency blood pressure waves.

scholarly journals Evolution of a narrow-band spectrum of random surface gravity waves

2003 ◽  
Vol 478 ◽  
pp. 1-10 ◽  
Author(s):  
KRISTIAN B. DYSTHE ◽  
KARSTEN TRULSEN ◽  
HARALD E. KROGSTAD ◽  
HERVÉ SOCQUET-JUGLARD
Keyword(s):  
Three Dimensional ◽  
Low Frequency ◽  
Three Dimensions ◽  
Band Spectrum ◽  
Nls Equation ◽  
Random Surface ◽  
Narrow Bandwidth ◽  
Quasi Stationary State ◽  
The Stability ◽  
Three Dimensional Simulations

Numerical simulations of the evolution of gravity wave spectra of fairly narrow bandwidth have been performed both for two and three dimensions. Simulations using the nonlinear Schrödinger (NLS) equation approximately verify the stability criteria of Alber (1978) in the two-dimensional but not in the three-dimensional case. Using a modified NLS equation (Trulsen et al. 2000) the spectra ‘relax’ towards a quasi-stationary state on a timescale (ε2ω0)−1. In this state the low-frequency face is steepened and the spectral peak is downshifted. The three-dimensional simulations show a power-law behaviour ω−4 on the high-frequency side of the (angularly integrated) spectrum.

FABRICATION OF NANOPOROUS CHITOSAN MEMBRANES

NANO ◽  
2010 ◽  
Vol 05 (01) ◽  
pp. 53-60 ◽  
Author(s):  
XIAOLIANG WANG ◽  
XIANG LI ◽  
ELEANOR STRIDE ◽  
MOHAN EDIRISINGHE
Keyword(s):  
Low Frequency ◽  
Drug Carriers ◽  
Structural Features ◽  
Wound Dressings ◽  
Ftir Analysis ◽  
Tissue Engineering Scaffolds ◽  
Nanoscale Structures ◽  
Low Frequency Ultrasound ◽  
Chitosan Membranes ◽  
The Stability

Naturally derived biopolymers have been widely used for biomedical applications such as drug carriers, wound dressings, and tissue engineering scaffolds. Chitosan is a typical polysaccharide of great interest due to its biocompatibility and film-formability. Chitosan membranes with controllable porous structures also have significant potential in membrane chromatography. Thus, the processing of membranes with porous nanoscale structures is of great importance, but it is also challenging and this has limited the application of these membranes to date. In this study, with the aid of a carefully selected surfactant, polyethyleneglycol stearate-40, chitosan membranes with a well controlled nanoscale structure were successfully prepared. Additional control over the membrane structure was obtained by exposing the suspension to high intensity, low frequency ultrasound. It was found that the concentration of chitosan/surfactant ratio and the ultrasound exposure conditions affect the structural features of the membranes. The stability of nanopores in the membrane was improved by intensive ultrasonication. Furthermore, the stability of the blended suspensions and the intermolecular interactions between chitosan and the surfactant were investigated using scanning electron microscope and Fourier transform infrared spectroscopy (FTIR) analysis, respectively. Hydrogen bonds and possible reaction sites for molecular interactions in the two polymers were also confirmed by FTIR analysis.

Improving the stability of silver nanowire/polyimide composite films for transparent film heaters

2018 ◽  
Vol 30 (3) ◽  
pp. 2089-2095 ◽  
Author(s):  
Xiaoqing Shi ◽  
Wei Xu ◽  
Wenfeng Shen ◽  
Guoliang Wang ◽  
Runfei Wang ◽  
...  
Keyword(s):  
Composite Films ◽  
Silver Nanowire ◽  
Transparent Film ◽  
The Stability

Effect of Low-Frequency Modulation on Thermal Convection Instability

2001 ◽  
Vol 56 (6-7) ◽  
pp. 509-522 ◽  
Author(s):  
P. K. Bhatia ◽  
B. S. Bhadauria
Keyword(s):  
Asymptotic Solution ◽  
Temperature Difference ◽  
Frequency Modulation ◽  
Thermal Convection ◽  
Low Frequency ◽  
Horizontal Layer ◽  
Time Dependent ◽  
Stability Criteria ◽  
Steady Temperature ◽  
The Stability

Abstract The stability of a horizontal layer of fluid heated from below is examined when, in addition to a steady temperature difference between the horizontal walls of the layer a time-dependent low-frequency per­ turbation is applied to the wall temperatures. An asymptotic solution is obtained which describes the be­ haviour of infinitesimal disturbances to this configuration. Possible stability criteria are analyzed and the results are compared with the known experimental as well as numerical results.

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