scholarly journals Optical and Electrochemical Characterization of Nanoporous Alumina Structures: Pore Size, Porosity, and Structure Effect

2020 ◽  
Vol 10 (14) ◽  
pp. 4864
Author(s):  
Ana Laura Cuevas ◽  
A. Silvia González ◽  
Víctor Vega ◽  
Víctor M. Prida ◽  
Juana Benavente
Keyword(s):  
Pore Size ◽  
Near Infrared ◽  
Electrochemical Characterizations ◽  
Refraction Index ◽  
Solution Concentration ◽  
Asymmetric Structure ◽  
Transport Numbers ◽  
Optical Parameters ◽  
Nanoporous Alumina ◽  
Charge Concentration

Three nanoporous alumina structures (NPASs) obtained by the two-step anodization method were optically and electrochemically characterized. Two of the structures were symmetric (NPAS-Sf and NPAS-Ph) and one was asymmetric (NPAS-And); pore size ranged from 10 nm to 100 nm and porosity was 12% in the case of the symmetrical NPAS and 23% and 30% for each surface of the asymmetric structure NPAS-And(A) and (B), respectively. Optical parameters of the studied samples (refraction index and extinction coefficient) were obtained from ellypsometric spectroscopy measurements carried out for wavelengths ranging between 250 nm and 1700 nm (visible and near infrared regions), with the total average refraction indices being 1.54, 1.52, 1.14, and 1.05 for NPAS-Sf, NPAS-Ph, NPAS-And(A), and NPAS-And(B), respectively, which indicates porosity control of refraction index values. Electrochemical characterizations (concentration potential and impedance spectroscopy measurements) were performed with NaCl solutions, and they allowed us to estimate samples of effective fixed charge concentration (1.22 × 10−2 M, 1.13 × 10−3 M, and 1.15 × 10−3 M), ion transport numbers, permselectivity (33.0%, 3.1%, and 9.6%), and the electrical resistance of each solution/sample system as well as the interfacial effects associated to solution concentration–polarization, which seems to be mainly controlled by pore size and sample symmetry.

scholarly journals Nanoporous Alumina Membranes for Sugar Industry: An Investigation of Sintering Parameters Influence onUltrafiltration Performance

2021 ◽  
Vol 13 (14) ◽  
pp. 7593
Author(s):  
Farooq Khan Niazi ◽  
Malik Adeel Umer ◽  
Ashfaq Ahmed ◽  
Muhammad Arslan Hafeez ◽  
Zafar Khan ◽  
...  
Keyword(s):  
Mechanical Strength ◽  
Pore Size ◽  
Sugar Industry ◽  
Average Pore Size ◽  
Research Work ◽  
Homogeneous Distribution ◽  
Alumina Membrane ◽  
Average Pore ◽  
Nanoporous Alumina ◽  
Alumina Membranes

Ultrafiltration membranes offer a progressive and efficient means to filter out various process fluids. The prime factor influencing ultrafiltration to a great extent is the porosity of the membranes employed. Regarding membrane development, alumina membranes are extensively studied due to their uniform porosity and mechanical strength. The present research work is specifically aimed towards the investigation of nanoporous alumina membranes, as a function of sintering parameters, on ultrafiltration performance. Alumina membranes are fabricated by sintering at various temperatures ranging from 1200–1300 °C for different holding times between 5–15 h. The morphological analysis, conducted using Scanning electron microscopy (SEM), revealed a homogeneous distribution of pores throughout the surface and cross-section of the membranes developed. It was observed that an increase in the sintering temperature and time resulted in a gradual decrease in the average pore size. A sample with an optimal pore size of 73.65 nm achieved after sintering at 1250 °C for 15 h, was used for the evaluation of ultrafiltration performance. However, the best mechanical strength and highest stress-bearing ability were exhibited by the sample sintered at 1300 °C for 5 h, whereas the sample sintered at 1250 °C for 5 h displayed the highest strain in terms of compression. The selected alumina membrane sample demonstrated excellent performance in the ultrafiltration of sugarcane juice, compared to the other process liquids.

scholarly journals Fabrication of Nanoporous Alumina Ultrafiltration Membrane with Tunable Pore Size Using Block Copolymer Templates

2017 ◽  
Vol 27 (34) ◽  
pp. 1701756 ◽  
Author(s):  
Chun Zhou ◽  
Tamar Segal-Peretz ◽  
Muhammed Enes Oruc ◽  
Hyo Seon Suh ◽  
Guangpeng Wu ◽  
...  
Keyword(s):  
Block Copolymer ◽  
Pore Size ◽  
Ultrafiltration Membrane ◽  
Nanoporous Alumina

scholarly journals Multi-layered tissue head phantoms for noninvasive optical diagnostics

2015 ◽  
Vol 08 (03) ◽  
pp. 1541005 ◽  
Author(s):  
M. S. Wróbel ◽  
A. P. Popov ◽  
A. V. Bykov ◽  
M. Kinnunen ◽  
M. Jędrzejewska-Szczerska ◽  
...  
Keyword(s):  
Optical Properties ◽  
Near Infrared ◽  
Optical Measurement ◽  
Human Head ◽  
Medical Diagnostics ◽  
Optical Parameters ◽  
Measurement Systems ◽  
Tissue Phantoms ◽  
Optical And Mechanical Properties

Extensive research in the area of optical sensing for medical diagnostics requires development of tissue phantoms with optical properties similar to those of living human tissues. Development and improvement of in vivo optical measurement systems requires the use of stable tissue phantoms with known characteristics, which are mainly used for calibration of such systems and testing their performance over time. Optical and mechanical properties of phantoms depend on their purpose. Nevertheless, they must accurately simulate specific tissues they are supposed to mimic. Many tissues and organs including head possess a multi-layered structure, with specific optical properties of each layer. However, such a structure is not always addressed in the present-day phantoms. In this paper, we focus on the development of a plain-parallel multi-layered phantom with optical properties (reduced scattering coefficient [Formula: see text] and absorption coefficient μa) corresponding to the human head layers, such as skin, skull, and gray and white matter of the brain tissue. The phantom is intended for use in noninvasive diffuse near-infrared spectroscopy (NIRS) of human brain. Optical parameters of the fabricated phantoms are reconstructed using spectrophotometry and inverse adding-doubling calculation method. The results show that polyvinyl chloride-plastisol (PVCP) and zinc oxide ( ZnO ) nanoparticles are suitable materials for fabrication of tissue mimicking phantoms with controlled scattering properties. Good matching was found between optical properties of phantoms and the corresponding values found in the literature.

scholarly journals Dopping Effect on Optical Constant of Poly (Vinyl Chloride)

2011 ◽  
Vol 8 (4) ◽  
pp. 976-981
Author(s):  
Baghdad Science Journal
Keyword(s):  
Dielectric Constant ◽  
Absorption Coefficient ◽  
Vinyl Chloride ◽  
Maxwell Equation ◽  
Extinction Coefficient ◽  
Refraction Index ◽  
Optical Parameters ◽  
Optical Studies ◽  
Poly Vinyl Chloride ◽  
Salt Complex

Thick films of poly(vinyl chloride)(PVC)& PVC doped with Zn(etx)2 salt complex have been prepared by cast method with fixed thickness almost (120±5) Microns. Optical studies were carried out in the wavelengths region(200-900)nm based on absorption & transmition measurement. Optical parameters such as absorption coefficient(?) ,refraction index(n) and extinction coefficient(K) were observed to be effected by adding the dopant.Electrical parameters such as real(?)& imaginary(?) part of dielectric constant were also calculated part of dielectric constant were also calculated from the optical parameters using Maxwell equation.

scholarly journals Influence of Detector Size and Positioning on Near-Infrared Measurements and Iso-pathlength Point of Turbid Materials

2021 ◽  
Vol 9 ◽  
Author(s):  
Hamootal Duadi ◽  
Idit Feder ◽  
Dror Fixler
Keyword(s):  
Critical Parameter ◽  
Near Infrared ◽  
Tissue Oxygenation ◽  
Experimental System ◽  
Optical Path ◽  
Optical Parameters ◽  
Infrared Measurements ◽  
Profile Changes ◽  
Physical Phenomena ◽  
Crossing Point

Measuring physical phenomena in an experimental system is commonly limited by the detector. When dealing with spatially defined behaviors, the critical parameter is the detector size. In this work, we examine near-infrared (NIR) measurements of turbid media using different size detectors at different positions. We examine cylindrical and semi-infinite scattering samples and measure their intensity distribution. An apparent crossing point between samples with different scatterings was previously discovered and named the iso-pathlength point (IPL). Monte Carlo simulations show the expected changes due to an increase in detector size or similarly as the detector’s location is distanced from the turbid element. First, the simulations show that the intensity profile changes, as well as the apparent IPL. Next, we show the average optical pathlength, and as a result, the differential pathlength factor, are mostly influenced by the detector size in the range close to the source. Experimental measurements using different size detectors at different locations validate the influence of these parameters on the intensity profiles and apparent IPL point. These findings must be considered when assessing optical parameters based on multiple scattering models. In cases such as NIR assessment of tissue oxygenation, size and location may cause false results for absorption or optical path.

scholarly journals Near-Infrared Spatial Self-Phase Modulation in Ultrathin Niobium Carbide Nanosheets

2021 ◽  
Vol 9 ◽  
Author(s):  
Si Xiao ◽  
Yi-lin He ◽  
Yu-lan Dong ◽  
Yi-duo Wang ◽  
Li Zhou ◽  
...  
Keyword(s):  
Phase Modulation ◽  
Light Propagation ◽  
Near Infrared ◽  
Niobium Carbide ◽  
Infrared Region ◽  
Hybrid Structure ◽  
Optical Parameters ◽  
Self Phase Modulation ◽  
Non Linear ◽  
Linear Optical

Spatial self-phase modulation (SSPM) as a purely coherent non-linear optical effect (also known as Kerr effect) can support strong broadband phase modulation, which is essential for all-optical applications. Besides this, the increasing use of two-dimensional (2D) materials opens up new prospects in this field of research. In this work, we report a broadband SSPM response from 2D transition metal carbonitrides (MXenes) and Nb2C, arising in the near-infrared (1,550 nm) range. Based on the SSPM measurements of few-layer Nb2C nanosheets, the third-order non-linear optical parameters of Nb2C, including the non-linear refractive index n2 and susceptibility χ(3), were determined at 400, 800, 1,300, and 1,550 nm. Moreover, the physics mechanism of the dynamic formation process of SSPM diffraction rings was exploited. The formation time of SSPM diffraction rings can be divided into two typical parts which correspond to the polarization and reorientation of 2D Nb2C nanosheets. As a proof of concept, we demonstrate the nonreciprocal light propagation at wavelengths of 1,300 and 1,550 nm by constructing an Nb2C/water hybrid structure. Our results reveal strong optical phase modulation of Nb2C in the infrared region, thus showing the great potential of MXene materials for use in passive photonic devices.

Laterally Graded Rugate Filters in Porous Silicon

2003 ◽  
Vol 797 ◽  
Author(s):  
Sean E. Foss ◽  
Terje G. Finstad
Keyword(s):  
Refractive Index ◽  
Porous Silicon ◽  
Near Infrared ◽  
Reflectance Spectrum ◽  
Voltage Drop ◽  
Optical Parameters ◽  
Filter Surface ◽  
Strong Reflection ◽  
Discrete Layer ◽  
Reflectance Peak

ABSTRACTRugate optical reflectance filters with position dependent reflectance peaks in the visible to near infrared spectrum were realized in porous silicon (PS). Filters with strong reflection peaks, near 100%, no detectable higher order harmonics and suppressed sidebands compared to discrete layer filters were obtained by varying the current density continuously and periodically during etching. An in-plane voltage up to 1.5 V was used to obtain refractive index and periodicity change along the filter surface resulting in reflectance peak shifts of up to 100 nm/mm in the direction of the voltage drop. The effect of the lateral change in optical parameters on the filter characteristics is studied by varying the gradient and comparing measurements at different positions with measurements on a non-graded filter. We have observed extra features in the reflectance spectrum of these graded filters compared with reflectance from a non-graded filter which is likely caused by the gradient.

scholarly journals precision: a fast python pipeline for high-contrast imaging – application to SPHERE observations of the red supergiant VX Sagitariae

2020 ◽  
Vol 494 (3) ◽  
pp. 3200-3211
Author(s):  
P Scicluna ◽  
F Kemper ◽  
R Siebenmorgen ◽  
R Wesson ◽  
J A D L Blommaert ◽  
...  
Keyword(s):  
Near Infrared ◽  
Extrasolar Planets ◽  
Asymmetric Structure ◽  
High Contrast ◽  
Contrast Imaging ◽  
Near Ir ◽  
High Contrast Imaging ◽  
Infrared Imager ◽  
Imaging Application ◽  
Efficient Reduction

ABSTRACT The search for extrasolar planets has driven rapid advances in instrumentation, resulting in cameras such as SPHERE at the VLT, GPI at Gemini South and SCExAO at Subaru, capable of achieving very high contrast (∼106) around bright stars with small inner working angles (${\sim}0.1\,{\rm arcsec}$). The optimal exploitation of data from these instruments depends on the availability of easy-to-use software to process and analyse their data products. We present a pure-python pipeline, precision, which provides fast, memory-efficient reduction of data from the SPHERE/IRDIS near-infrared imager, and can be readily extended to other instruments. We apply precision to observations of the extreme red supergiant VX Sgr, the inner outflow of which is revealed to host complex, asymmetric structure in the near-IR. In addition, optical polarimetric imaging reveals clear extended polarized emission on ∼0.5 arcsec scales that varies significantly with azimuth, confirming the asymmetry. While not conclusive, this could suggest that the ejecta are confined to a disc or torus, which we are viewing nearly face on, although other non-spherical or clumpy configurations remain possible. VX Sgr has no known companions, making such a geometry difficult to explain, as there is no obvious source of angular momentum in the system.

Photoluminescent Silicon in Nanoporous Aluminium Oxide

1997 ◽  
Vol 486 ◽  
Author(s):  
Andreas Heilmann ◽  
Peter Jutzi ◽  
Andreas Klipp ◽  
Uwe Kreibig ◽  
Rolf Neuendorf ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Pore Size ◽  
Aluminium Oxide ◽  
Silicon Nanostructures ◽  
Pore Surface ◽  
Nanoporous Alumina ◽  
Inner Pore

AbstractThermal decomposition of a metastable silane in nanoporous alumina leads to the formation of luminescent silicon nanostructures. While varying the pore size of the transparent membranes the luminescence can be shifted from 504 nm up to 537 nm by building up a sheet-like structure of siloxene on the inner pore surface.

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