Determination of refractive indices and thicknesses of Ba0.7Sr0.3TiO3 films with and without MgO (001) buffer layer on silicon substrate

2009 ◽  
Vol 106 (7) ◽  
pp. 074103 ◽  
Author(s):  
Y. Yin ◽  
H. Ye ◽  
C. Zhang ◽  
W. D. Shen ◽  
X. Liu
Keyword(s):  
Buffer Layer ◽  
Silicon Substrate ◽  
Refractive Indices

Οπτικοί βιοαισθητήρες για την ανίχνευση βιομορίων χωρίς τη χρήση ιχνηθετών

2015 ◽  
Author(s):  
Αιμιλία Ψαρούλη
Keyword(s):  
Light Source ◽  
Silicon Substrate ◽  
Serum Samples ◽  
Fully Integrated ◽  
Monolithically Integrated ◽  
Immunochemical Determination ◽  
Wide Range ◽  
Myocardial Infraction ◽  
Biological Recognition

Recent developments in the fields of bioanalytical chemistry and microelectronics have resulted in a growing trend of transferring the classical analytical methods from the laboratory bench to the field through the development of portable devices or microsystems based on biosensors. Biosensors are self-contained integrated devices capable to provide analytical information using biological recognition molecules in direct spatial contact with a transducer. Biosensors using antibodies or antigens as biological recognition elements are termed as immunosensors and they are based on the same principle as the classical solid-phase immunoassays.The aim of this thesis was to develop and evaluate an optical immunosensor based on Mach-Zehnder Interferometry and integrated on silicon substrate for the immunochemical determination of clinical analytes. The optical sensor developed is fabricated entirely by mainstream silicon technology by the Optical Biosensors group of the Institute of Nanoscience and Nanotechnology of NCSR “Demokritos” and combines arrays of ten sensors in a single silicon chip. Each sensor consists of an integrated on silicon light source that emits a broad spectrum in visible-near ultraviolet range and it is coupled to an integrated silicon nitride waveguide which has been patterned into Mach-Zehnder interferometer. The signal is recorded either through a photodetector monolithically integrated onto the same silicon chip (fully integrated configuration) or through an external spectrometer (semi-integrated configuration). In the fully integrated configuration, the signal recorded is the total photocurrent across the whole spectral range, while in semi-integrated configuration the whole transmission spectrum is continuously recorded and is mathematically transformed (Fourier Transform) to phase shift. As in the classical Mach-Zehnder interferometers, the waveguide in the proposed sensor is split into two arms, the sensing one which is appropriately modified with recognition biomolecule and the reference arm that is covered by a protective layer. The specific binding of the analyte with the immobilized onto the surface recognition biomolecule causes an effective refractive index change at the surface of the sensing arm thus affecting the phase of the waveguided light with respect to the reference arm. Thus, when the two arms converge again, an interference spectrum is generated that is altered during bioreaction providing the ability of monitoring in real-time and without using labels. The main difference of the sensor developed with respect to classical Mach-Zehnder interferometers is that the light source is monolithically integrated on the same silicon substrate with the waveguides and the waveguided light is not monochromatic, but broad spectrum.At first in this study, the method for chemical activation of biofunctionalization of chips was optimized. It was found that the highest signals were obtained when chips where activated by (3-aminopropyl)triethoxysilane and deposition of biomolecules solutions using a microarray spotter. Then, a comparison of the two sensor configurations, i.e. the fully and the semi-integrated configuration was performed using a model binding assay namely the streptavidin-biotin reaction. Semi-integrated configuration provided higher detection sensitivities mainly due to lower between-sensor signal variation in the same chip and between different chips. Thus, this configuration was selected for further evaluation with respect to the determination of analytes of clinical interest and especially of immunochemical determination of C-reactive protein in human serum samples. CRP is a marker of inflammation widely used in everyday clinical practice for diagnosis and therapy monitoring of inflammatory situations. Nevertheless, CRP has been also proposed as a prognostic marker of myocardial infraction and three risk levels have been established; low risk for serum CRP concentrations < 1 μg/mL; medium risk for concentrations in the range 1-3 μg/mL; and high risk for concentrations >3 μg/mL. In the frame of the present thesis, enzyme immunoassays for the determination of CRP in microtitration plates both competitive and non-competitive were developed in order to select the most appropriate reagents and define the immunoassay conditions. Then both assay format were transferred and evaluated on the sensor. It was found that the non-competitive format offered higher responses and ability for regeneration of immobilized onto the sensor antibody against CRP and was therefore selected for the final sensor evaluation. The assay developed following the competitive format was sensitive and accurate as was demonstrated through recovery and dilution linearity experiments, and provided for analysis of samples with a wide range of CRP concentrations since it was immune to the presence of serum. In addition, the CRP values determined with the immunosensor developed in serum samples from unknown donors were in good agreement with those determined for the same samples by commercially available kits and instruments showing the reliability of the determinations performed with the immunosensor developed and its potential for analysis of clinical samples.

scholarly journals Refractive index evaluation of porous silicon using Bragg reflectors

2018 ◽  
Vol 64 (1) ◽  
pp. 72 ◽  
Author(s):  
D. Estrada-Wiese ◽  
J.A. Del Río
Keyword(s):  
Refractive Index ◽  
Porous Silicon ◽  
Simple Procedure ◽  
Merit Function ◽  
Refractive Indices ◽  
Bragg Reflectors ◽  
Photonic Bandgaps ◽  
Photonic Structures ◽  
Index Evaluation

There are two main physical properties needed to fabricate 1D photonic structures and form perfect photonic bandgaps: the quality of thethickness periodicity and the refractive index of their components. Porous silicon (PS) is a nano-structured material widely used to prepare 1Dphotonic crystals due to the ease of tuning its porosity and its refractive index by changing the fabrication conditions. Since the morphologyof PS changes with porosity, the determination of PS’s refractive index is no easy task. To find the optical properties of PS we can usedifferent effective medium approximations (EMA). In this work we propose a method to evaluate the performance of the refractive index ofPS layers to build photonic Bragg reflectors. Through a quality factor we measure the agreement between theory and experiment and thereinpropose a simple procedure to determine the usability of the refractive indices. We test the obtained refractive indices in more complicatedstructures, such as a broadband Vis-NIR mirror, and by means of a Merit function we find a good agreement between theory and experiment.With this study we have proposed quantitative parameters to evaluate the refractive index for PS Bragg reflectors. This procedure could havean impact on the design and fabrication of 1D photonic structures for different applications.

Application of the Solution of the Inverse Light Scattering Problem for Characterization of Mononuclear Cells

2009 ◽  
Vol 4 (2) ◽  
pp. 61-68
Author(s):  
Dmitriy Strokotov ◽  
Yuriy Pichugin ◽  
Maxim Yurkin ◽  
Mariya Gridina ◽  
Oleg Serov ◽  
...  
Keyword(s):  
Stem Cells ◽  
Light Scattering ◽  
Mononuclear Cells ◽  
Human Lymphocytes ◽  
Scattering Problem ◽  
Refractive Indices ◽  
Single Particles ◽  
Differentiation Status

In this manuscript we propose two methods to solve inverse light scattering problem for single particles, which can be described as a coated sphere. The efficiency of the methods is illustrated by characterization of lymphocytes and stem cells using light scattering patterns obtained with scanning flow cytometer. Both methods, spectral and global optimization, were used to obtain diameters and refractive indices of the cytoplasm and the nucleus of mice embryo stem cells and human lymphocytes. These results agree with data obtained from other studies. Determination of these parameters is important for diagnostics of pathological states of lymphocytes and differentiation status of embryo stem cells. Moreover, methods described in this manuscript are applicable to all mononuclear cells. We also considered limitations of these methods and their possible improvements.

The petrology of the Mount Padbury mesosiderite and its achondrite enclaves

1966 ◽  
Vol 36 (276) ◽  
pp. 1029-1060 ◽  
Author(s):  
G. J. H. McCall
Keyword(s):  
Microscopic Analysis ◽  
Host Material ◽  
Refractive Indices ◽  
X Ray Diffraction ◽  
Thin Sections ◽  
X Ray ◽  
Wide Range ◽  
Varied Range ◽  
Optical Determination

SummaryThe petrography of the Mount Padbury meteorite, previously briefly recorded, is described in some detail. Both the metalliferous host material of the mesosiderite and the varied range of silicate-rich, virtually metal-free enclaves (including both familiar achondrite material and unfamiliar achondrite material) are described. Eucrite, brecciated eucrite, and a peculiar ‘shocked’ form of eucrite (resembling some terrestrial flaser-gabbros) are the calcium-rich achondrite types represented; hypersthene achondrite (including typical diogenite material and unfamiliar material) and olivine achondrite (granular aggregates of olivine not entirely similar to the unique chassignite and single crystals up to 4 in. in length) are the calcium-poor achondrite types represented. The eucrite displays more or less uniform mineralogy, but the mineral constituents are present in varying proportions, and there is a wide range of textural variations recognized. The silicate grain fragments enclosed in the metallic reticulation to form the mesosiderite host material are, significantly, entirely of minerals seen within the achondrite enclaves—plagioclase, hypersthene, pigeonite, olivine, and tridymite.These results include microscopic analysis of thin sections and polished sections, X-ray diffraction studies, optical determination of refractive indices using mineral grain mounts, and chemical analyses.The wider implications of this new and unique meteorite find are briefly considered.

Determination of refractive indices of liquids by Fresnel diffraction

2009 ◽  
Vol 41 (7) ◽  
pp. 892-896 ◽  
Author(s):  
Arash Sabatyan ◽  
Mohammad Taghi Tavassoly
Keyword(s):  
Fresnel Diffraction ◽  
Refractive Indices

scholarly journals THE REFRACTIVE INDICES OF WHOLE CELLS

1933 ◽  
Vol 17 (1) ◽  
pp. 41-47 ◽  
Author(s):  
E. S. Castle
Keyword(s):  
Focal Length ◽  
Refractive Indices ◽  
Radius Of Curvature ◽  
Whole Cells

Refractive indices of intact sporangiophores of Phycomyces were computed from measurements of focal length and radius of curvature of the cells. For the six cells studied, effective values of n were obtained ranging from 1.35 to 1.40. The average effective n was 1.38. Senn's determination of refractive indices of other plants cells gave much higher values: n = 1.37 to 1.52. The precision of the method and possible sources of this discrepancy are discussed.

Determination of the refractive indices of layers in a multilayer stack by a guided-wave technique

1999 ◽  
Vol 38 (19) ◽  
pp. 4177 ◽  
Author(s):  
Josep Massaneda ◽  
Francois Flory ◽  
Emile Pelletier
Keyword(s):  
Guided Wave ◽  
Refractive Indices ◽  
Wave Technique
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