scholarly journals Employing photoluminescence to rapidly follow aggregation and dispersion of cellulose nanofibrils

The Analyst ◽  
2020 ◽  
Vol 145 (14) ◽  
pp. 4836-4843 ◽  
Author(s):  
Marcus A. Johns ◽  
Anna E. Lewandowska ◽  
Ellen Green ◽  
Stephen J. Eichhorn
Keyword(s):  
Emission Intensity ◽  
Cellulose Nanofibrils ◽  
Time Dependent ◽  
Spatially Resolved ◽  
Intensity Ratios ◽  
Confocal Spectroscopy

Multichannel confocal spectroscopy enables tracking of time dependent, spatially resolved changes in the physicochemical environment of cellulose nanofibrils due to variation in emission intensity ratios.

scholarly journals A physico-chemical model to study the ion density distribution in the inner coma of comet C/2016 R2 (Pan-STARRS)

2020 ◽  
Author(s):  
Susarla Raghuram ◽  
Anil Bhardwaj ◽  
Damien Hutsemékers ◽  
Cyrielle Opitom ◽  
Jean Manfroid ◽  
...  
Keyword(s):  
Density Distribution ◽  
Electron Impact ◽  
Emission Intensity ◽  
Impact Ionization ◽  
Excitation Source ◽  
Resonance Fluorescence ◽  
Ion Density ◽  
Physico Chemical ◽  
Intensity Ratios ◽  
Ion Emission

Abstract The recent observations show that comet C/2016 R2 (Pan-Starrs) has a unique and peculiar composition when compared with several other comets observed at 2.8 au heliocentric distance. Assuming solar resonance fluorescence is the only excitation source, the observed ionic emission intensity ratios are used to constrain the corresponding neutral abundances in this comet. We developed a physico-chemical model to study the ion density distribution in the inner coma of this comet by accounting for photon and electron impact ionization of neutrals, charge exchange and proton transfer reactions between ions and neutrals, and electron-ion thermal recombination reactions. Our calculations show that CO$_2^+$ and CO+ are the major ions in the inner coma, and close to the surface of nucleus CH3OH+, CH3OH$_2^+$ and O$_2^+$ are also important ions. By considering various excitation sources, we also studied the emission mechanisms of different excited states of CO+, CO$_2^+$, N$_2^+$, and H2O+. We found that the photon and electron impact ionization and excitation of corresponding neutrals significantly contribute to the observed ionic emissions for radial distances smaller than 300 km and at larger distances, solar resonance fluorescence is the major excitation source. Our modelled ion emission intensity ratios are consistent with the ground-based observations. Based on the modelled emission processes, we suggest that the observed ion emission intensity ratios can be used to derive the neutral composition in the cometary coma only when the ion densities are significantly controlled by photon and photoelectron impact ionization of neutrals rather than by the ion-neutral chemistry.

Spatially resolved optical emission of cubic GaN/AlN multi-quantum well structures

2014 ◽  
Vol 1736 ◽  
Author(s):  
D.J. As ◽  
R. Kemper ◽  
C. Mietze ◽  
T. Wecker ◽  
J.K.N. Lindner ◽  
...  
Keyword(s):  
Optical Properties ◽  
Low Temperature ◽  
Film Thickness ◽  
Quantum Wells ◽  
Emission Intensity ◽  
Optical Emission ◽  
Quantum Well Structures ◽  
Spatially Resolved ◽  
Scanning Transmission ◽  
Cubic Gan

ABSTRACTIn this contribution we report on the optical properties of cubic AlN/GaN asymmetric multi quantum wells (MQW) structures on 3C-SiC/Si (001) substrates grown by radio-frequency plasma-assisted molecular beam epitaxy (MBE). Scanning transmission electron microscopy (STEM) and spatially resolved cathodoluminescence (CL) at room temperature and at low temperature are used to characterize the optical properties of the cubic AlN/GaN MQW structures. An increasing CL emission intensity with increasing film thickness due to the improved crystal quality was observed. This correlation can be directly connected to the reduction of the linewidth of x-ray rocking curves with increasing film thickness of the c-GaN films. Defects like stacking faults (SFs) on the {111} planes, which also can be considered as hexagonal inclusions in the cubic crystal matrix, lead to a decrease of the CL emission intensity. With low temperature CL line scans also monolayer fluctuations of the QWs have been detected and the observed transition energies agree well with solutions calculated using a one-dimensional (1D) Schrödinger-Poisson simulator.

Preparation and characterization of dried cellulose nanofibrils

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jianping Ni ◽  
Chen Gong ◽  
Zhenghua Su ◽  
Chao Tian
Keyword(s):  
Spray Drying ◽  
Freeze Drying ◽  
Cellulose Nanofibrils ◽  
Time Dependent ◽  
X Ray ◽  
Original State ◽  
Final Mass ◽  
Freeze Dried ◽  
Spray Dried

Abstract One of the main manufacturing challenges is to obtain dried cellulose nanofibrils (CNFs) so that they can be cost effectively transported to customers. This work presents a study on using two methods of drying: freeze drying and spray drying; these dried CNFs were then characterized. The dried CNFs from either freeze drying or spray drying could not recover their original state after simple re-dispersion in water. Compared to spray dried CNFs, the microstructure of the freeze dried CNFs remained in a better shape. This was because the packing of nanofibrils as a result of freeze drying was not as tight as that from spray drying. It was demonstrated by the lower final mass residue and crystallinity of the freeze-dried CNFs, which led to better re-dispersion in water. X-ray diffractometry proved the occurrence of aggregation/hornification of the dried CNFs with increased crystallinity. Time-dependent sedimentation confirmed that the dried CNFs were incapable of forming stable water-re-dispersible suspensions.

Molecular orientation in ultrathin films of α-sexithiophene on silicon dioxide revealed by spatially resolved confocal spectroscopy

2005 ◽  
Vol 155 (2) ◽  
pp. 287-290 ◽  
Author(s):  
Enrico Da Como ◽  
Maria Antonietta Loi ◽  
Franco Dinelli ◽  
Mauro Murgia ◽  
Fabio Biscarini ◽  
...  
Keyword(s):  
Silicon Dioxide ◽  
Ultrathin Films ◽  
Molecular Orientation ◽  
Spatially Resolved ◽  
Confocal Spectroscopy

scholarly journals Semianalytical solution for the transient temperature in a scattering and absorbing slab consisting of three layers heated by a light source

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Dominik Reitzle ◽  
Simeon Geiger ◽  
André Liemert ◽  
Alwin Kienle
Keyword(s):  
Heat Conduction ◽  
Light Propagation ◽  
Time Dependent ◽  
Transient Temperature ◽  
Moderate Increase ◽  
Eigenvalues And Eigenvectors ◽  
Spatially Resolved ◽  
Fem Method ◽  
Collimated Beam ◽  
Fourier Equation

AbstractWe derived a semianalytical solution for the time-dependent temperature distribution in a three-layered laterally infinite scattering and absorbing slab illuminated by an obliquely incident collimated beam of light. The light propagation was modeled by the low-order $$P_1$$ P 1 and $$P_3$$ P 3 approximations to the radiative transfer equation with closed form expressions for eigenvalues and eigenvectors, yielding a quickly computable solution, while the heat conduction was modeled by the Fourier equation. The solution was compared to a numerical solution using a Monte Carlo simulation for the light propagation and an FEM method for the heat conduction. The results showed that using the $$P_3$$ P 3 solution for the light propagation offers a large advantage in accuracy with only a moderate increase in calculation time compared to the $$P_1$$ P 1 solution. Also, while the $$P_3$$ P 3 solution is not a very good approximation for the spatially resolved absorbance itself, its application as a source term for the heat conduction equation does yield a very good approximation for the time-dependent temperature.

scholarly journals Equivalence Ratio Measurements in CH4/Air Gases Based on the Spatial Distribution of the Emission Intensity of Femtosecond Laser-Induced Filament

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 2022
Author(s):  
Ming Li ◽  
Jiangpeng Gu ◽  
Dayuan Zhang ◽  
Qiang Gao ◽  
Bo Li
Keyword(s):  
Spatial Distribution ◽  
Flow Field ◽  
Femtosecond Laser ◽  
Emission Intensity ◽  
Equivalence Ratio ◽  
Femtosecond Lasers ◽  
Diagnostic Techniques ◽  
Spatially Resolved ◽  
Combustion Diagnostics ◽  
Laser Filamentation

Femtosecond lasers have been used in combustion diagnostics. Based on the characteristics of femtosecond laser filamentation, many diagnostic techniques have been developed. Here, we propose a method, based on femtosecond laser filamentation, for equivalence ratio measurements in CH4/air gases. By measuring the spatially resolved spectra of the femtosecond laser-induced filament, we found that the variation of the equivalence ratio in the flow field would affect the spatial distribution of the emission intensity of femtosecond laser-induced filament. On this basis, the equivalence ratio was calibrated by using the relative spatial positions of N2 (337 nm) and C2 (516.5 nm) signals in the filament. This method overcomes the interference of local air disturbance, having lower measurement uncertainty.

scholarly journals Hydroxyl (6–2) airglow emission intensity ratios for rotational temperature determination

2000 ◽  
Vol 18 (10) ◽  
pp. 1293-1303
Author(s):  
W. J. R. French ◽  
G. B. Burns ◽  
K. Finlayson ◽  
P. A. Greet ◽  
R. P. Lowe ◽  
...  
Keyword(s):  
Emission Intensity ◽  
Rotational Temperature ◽  
Airglow Emission ◽  
Temperature Determination ◽  
Intensity Ratios
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