Reflectance Curves Research Articles

Monitoring biological degradation of historical stone using hyperspectral imaging

ABSTRACT Stone is one of the most common materials used as a building material in central Europe for centuries. Historical objects are endangered by degradation procedures coming from physical, chemical and biological weathering agents.The weathering process itself should be analysed in detail in order to prevent historical objects by application of proper restoration cleaning techniques. Within our research, a historical sandstone block was analysed during time to monitor biological changes on the surface. The object of interest is situated in the immediate vicinity of Charles Bridge in Prague, which is protected as a UNESCO heritage site. This site was chosen due to high overall humidity all year long. For investigation of the year- round process of biodegradation hyperspectral sensor was used. In the first place, data were processed using four vegetation indices (NDVI, RGRI, CRI1 and VREI1). All vegetation indices indicate that vegetation is thriving and subject to normal seasonal change. The second chosen method of data processing is to use spectral reflectance curves and their subsequence processing by Spectral Angle Mapper (SAM) classification algorithms. A decline in vegetation with the onset of autumn and during the winter months was detected.

Designing the Structure of a One-Dimensional Photonic Crystal with a Given Spectrum of the Reflection Coefficient

A method for solving the inverse problem of designing the structure of a one-dimensional photonic crystal is proposed and experimentally implemented. It is known that a one-dimensional photonic crystal with a spatial sinusoidal modulation of the refractive index, has a narrow photonic bandgap at a frequency related to the spatial frequency of this sinusoid. A reverse engineering method is proposed for one-dimensional photonic crystals with an arbitrary given reflection spectrum by expanding this spectrum into elementary photonic band gaps and then summing them. The application of this method to fabricate examples of photonic crystals with simple shapes of spectral reflection curves is demonstrated.

A surface plasmon resonance nanostructure containing graphene and BaTiO3 layers for sensitive defection of organic compounds.

Organic compound-based sensors are used in a variety of significant fields, including medical research, azeotropic calibration, vegetable oil extraction, the shoe industry and geothermal power plants. Here, a high-performance, two-dimensional material-based organic compound sensor has been proposed using a surface plasmon resonance (SPR) nanostructure consisting of a BK7 glass prism, Ag, BaTiO3, Ag, graphene and sensing layer. The reflectivity curves of the SPR device have been investigated when the sensing media are Pentane, n-Hexane, n-Heptane and n-Octane. The thickness of the BaTiO3 layer and the number of graphene sheets have been optimized to maximize the sensitivity. The highest sensitivity attained is 220.83 deg/RIU for n-Octane with 45 nm silver/10 nm BaTiO3/8 nm silver and four layers of graphene. We believe that the SPR-based sensors are simple and can replace the spectrometry, chromatography and electrochemical based sensors. The proposed design is extremely effective for diverse applications in biological, industrial and chemical detection because of its simple structure and great performance.

Designing the Structure of a One-Dimensional Photonic Crystal with a Given Spectrum of the Reflection Coefficient

A method for solving the inverse problem of designing the structure of a one-dimensional photonic crystal is proposed and experimentally implemented. It is known that a one-dimensional photonic crystal with a spatial sinusoidal modulation of the refractive index, has a narrow photonic bandgap at a frequency related to the spatial frequency of this sinusoid. A reverse engineering method is proposed for one-dimensional photonic crystals with an arbitrary given reflection spectrum by expanding this spectrum into elementary photonic band gaps and then summing them. The application of this method to fabricate examples of photonic crystals with simple shapes of spectral reflection curves is demonstrated.

Performance Enhancement of an Ag–Au Bimetallic SPR Sensor: A Theoretical and Experimental Study

Ag-Au bimetallic surface plasmon resonance (SPR) sensors operating in the Kretschmann configuration were investigated by numerical modelling and experiment. While Ag-based sensors have good sensitivity, they suffer from poor stability, and the addition of an Au capping layer offers improved chemical resistance and reliable analyte bonding via thiol-gold interactions. Sensors were evaluated with an Ag-Au combined thickness of 50 nm but different thickness ratios, and SPR reflectivity curves were obtained for 632.8 nm wavelength light incident over a range of angles. Numerical modelling using the transfer matrix method showed the SPR response improving as Au thickness decreased, giving the best results for 45 nm of Ag and 5 nm of Au. Experimental characterisation of fabricated Ag-Au bimetallic sensors was carried out with a custom SPR testbed. Performance parameters, including minimum reflectivity, FWHM, stability, and sensitivity were measured and the results were compared to those of single-layer Ag and Au sensors. A 5 nm Au coating was unable to preserve stable bimetallic sensor performance; however, increasing the Au thickness to 10 nm was sufficient to protect the Ag sensing layer, allowing only a small variation in the minimum reflectivity and FWHM when exposed to analytes for multiple hours. The sensitivity of the single-layer Ag, bimetallic Ag-Au, and Au sensors was measured as 3041%/Refractive Index Unit (RIU), 1817%/RIU, and 1229%/RIU, respectively. The sensitivity of the thickness-optimized bimetallic layer was ~1.5× that of the single-layer Au sensor.

Oil Palm Health Estimation Using Low Altitude Remote Sensing

Unmanned Aerial Vehicle (UAV), Unmanned Aerial System (UAS), or drones are small autonomous airplane that does not need a pilot on board (CAR, 2016). UAS is increasingly becoming widely known for its capability to bring many innovations to the world. UAVs are also utilized as geospatial technology tools, providing benefits to environmental monitoring. Therefore, this study aims to estimate oil palm health using UAV payload remote sensing compact sensors. Two remote sensing compact sensors were used in this study which is visible (RGB) and Near Infrared (NIR) to get the reflectance curve of the oil palm. Analysing oil palm condition from reflectance curve by using a spectroradiometer are the first objective while analysing extraction oil palm condition by using sensors is the second objective. Some policy and regulation were involved to follow the guideline that has been implemented by the agency. Instead of using a UAV, the spectroradiometer was used to visualize the spectral response curve of an oil palm. As a result, the oil palm condition at study area is in healthy condition where the reflectance curve for multispectral compact sensors (0.84) and spectrometer (0.82) which are above healthy indicator (0.5) whereby favourable to determine the growth stability of oil palm trees. As a summary, these techniques are potential to support the development of modernization technology in environmental monitoring for oil palm plantations and give an alternative way to give good result on oil palm health condition.

A Highly Sensitive Sensing Technique via Surface Plasmons With Tunable Prism Refractive Index

A new perspective using Kretschmann configuration is presented to excite surface plasmon polaritons (SPP) at liquid crystal (LC)/metal interface. The excitation of SPP takes place through the electrical tuning of the prism refractive index instead of the commonly used angular interrogation. The results show that the proposed methodology is 30% superior to the traditional angular interrogation. The 5CB (4-pentyl-4’-cyanobiphenyl) is one of the best suited nematic LC material for the proposed detection framework. Its refractive index is linearly tunable in the range 1.55 ~ 1.78 (at wavelength 1.55 μm) via an external applied electric field. In that range of refractive index variation, the SPP modes are efficiently excited; and hence any minute variation in the analyte refractive index can be detected reliably and accurately through a simple tuning of the refractive index of the prism LC material. The fundamental characteristics of the sensor are assessed through the evaluation of the linearity, sensitivity (S), the full width at half maximum (FWHM) of the reflectivity curve and the figure of merit (FOM). The variation of these characteristics over a whole range of analyte refractive index (1.3–1.4) are presented as well. The electrical tuning provides a well-matched design with micro-scale devices.

Employing Surface Curvature for Spatially Resolved X‐Ray Reflectivity: Graphene Domains on Liquid Copper

AbstractHere the possibility of utilizing X‐ray reflectivity for visualization with ≈µm spatial resolution of a surface with a heterogeneous electron density due to a partial coverage by another nanometrically thin material is demonstrated. It requires the sample to be convexly bent, thus reflecting the collimated incident beam onto a magnified image recorded by a position‐sensitive detector. By the use of a small, intense, and parallel beam such as provided by the most recent synchrotron sources, one can record such spatially resolved X‐ray reflectivity with 0.1–1 kHz frame rate. The use of the method for in situ, time‐resolved characterization of single‐layer graphene domains during their chemical vapor deposition on a naturally curved surface of a liquid copper drop is demonstrated. This method can follow the growth kinetics, including the coverage ratio, 2D crystal (flake) sizes, and distances between flakes. By taking a single scan, the individual X‐ray reflectivity curves can be reconstructed, of both covered and noncovered parts of the surface, allowing to deduce the corresponding electron density profiles perpendicular to the surface. The technique has a promising perspective for in situ study of 2D materials, ultrathin films, and self‐assemblies on liquid as well as solid surfaces.

Effect of the Electrodeposition Potential on the Physical Properties of Rapid Thermal Processing‐Annealed CuInSe2 Films

Herein, the effect of the bath reference potential during the one‐step electrodeposition process of chalcopyrite CuInSe2 (CIS) films on “ITO‐coated glass” substrate is reported. Electrodeposited films are annealed by rapid thermal processing (RTP) under argon atmosphere. The deposition potential ranges between −0.85 and −0.65 V. The surface morphology and crystalline structure are investigated by scanning electron microscopy and X‐ray diffraction (XRD), respectively. Obtained results from XRD are supported by cyclic voltammetric measurements. Values of the extinction coefficient and refractive index are determined by fitting curves of theoretical reflectance and transmittance to experimental ones using the Fresnel matrix method. Results show that the deposition potential affects the physical properties of electrodeposited CIS films. Furthermore, using the Mott–Schottky analysis, it is shown it is possible to grow n‐ or p‐type CIS semiconductor by adjusting the cathodic voltage. This switching can be attributed to the effect of a metastable hole trap in CIS films.

Hyperspectral Signatures and Volumetric Study of Iron Ore from Kemmanagundi, Bababudan Hill Ranges of Karnataka State, India

Iron is one among the oldest metals known to man and is quite rich in our country. 95% of the total iron reserves of India were accounted from few states such as Jharkhand, Orissa, Madhya Pradesh, Chhattisgarh, Karnataka and Goa. Kudremukha and Donimalai is known for producing high grades of iron in Karnataka state. The present study aims to analyze the spectral signatures and volumetric determinations of iron ore deposits which were well developed and was being mined in Kemmanagundi of Bababudan hills in Chikmagalur district. Field random samples were collected for laboratory work and analysis in determining the spectral signature curves and volumetric content. The spectral signatures of any mineral will discriminated based on their characteristics features of absorption and reflectance curves. Volumetric analysis is generally one of the quantitative methods that deal with determination of amount of particular elements in tested sample. As demand of iron in India is expected to increase day by day this deposit has to be considered as an important one for its rich iron content of 69.8 percent of iron content occurring around Kemmanagundi of Bababudanhill range, Chikmagalur district, Karnataka. The final results show the presence of rich iron content around the study area.

Modification of ZIF-8 nanocomposite by a Gd atom doped TiO2 for high efficiency photocatalytic degradation of neutral red dye: An experimental and theoretical study

The sol–gel method was used to prepare the rare earth element Gd-doped TiO2, and the solvothermal synthesis method was used to prepare ZIF-8@TiO2 (0.3% Gd). A neutral red solution was used as the degradation object to evaluate the photocatalytic degradation ability of the material. The structure, element distribution, crystallite morphology, specific surface area, element valence, light response range, and electrochemical properties of the material were analyzed by XRD, EDX, SEM, TEM, BET, XPS, UV–Vis, and EIS. The neutral red solution was degraded by a photocatalytic test. The effects of the Gd doping amount, initial concentration of the neutral red solution, photocatalyst dose, and recycling times on the catalytic efficiency were tested. The results show that TiO2 (0.3% Gd) has an anatase structure, and Gd element doping inhibits crystal growth. The composite of ZIF-8 and TiO2 (0.3% Gd) dramatically improves the specific surface area of the material. When Gd is doped in TiO2, the UV diffuse reflectance curve is shifted by a redshift. After 0.3% Gd (molar ratio), doped TiO2 has the best photocatalytic degradation effect of neutral red. ZIF-8@TiO2 (0.3% Gd) UV irradiation for 1 h, the degradation rate of neutral red was 96.55%. The optimum concentration of the neutral red solution is 20 mg/L. After four times of recycling, the catalytic efficiency is 69.41%. The content of total organic carbon after photocatalysis was analyzed, and the degradation products of neutral red dye were analyzed. The main active substances in the process of photocatalysis are analyzed, and the principle of photocatalysis is expounded. This work provides a new strategy for the field of photocatalytic degradation of organic pollutants.

Utilizing support vector and kernel ridge regression methods in spectral reconstruction

Two regression methods, namely, Support Vector Regression (SVR) and Kernel Ridge Regression (KRR), are used to reconstruct the spectral reflectance curves of samples of Munsell dataset from the corresponding CIE XYZ tristimulus values. To this end, half of the samples (i.e., the odd ones) were used as training set while the even samples left out for the evaluation of reconstruction performances. Results were reviewed and compared with those obtained from Principal Component Analysis (PCA) method, as the most common context-based approach. The root mean squared error (RMSE), goodness fit coefficient (GFC), and CIE LAB color difference values between the actual and reconstruct spectra were reported as evaluation metrics. However, while both SVR and KRR methodologies provided better spectral and colorimetric performances than the classical PCA method, the computation costs were considerably longer than PCA method.

The effect of Zn2+ ion substitution on nanoparticles of ZnxMn(1-X) Fe2O4 (X = 0.2, 0.4, 0.6, 0.8) towards signal surface plasmon resonance (SPR)

ABSTRACT This study examined the effect of Zn2+ ion substitution on ZnxMn(1-x) Fe2O4 nanoparticles (x = 0.2, 0.4, 0.6, 0.8) towards signal Surface Plasmon Resonance (SPR). The co-precipitation method synthesised the nanoparticles at a temperature of 90°C. The X-Ray Diffraction (XRD) results showed a polycrystalline structure with a crystallite size varied from 19.05 nm to 19.77 nm. In addition, as the Zn element increased in the ZnxMn(1-x)Fe2O4 nanoparticles, the degree of crystallinity increased by 21.72%, respectively. The optical properties of the nanoparticles ZnxMn(1-x) Fe2O4 indicate absorbance at wavelengths of 330.36–331.74 nm. The absorbance level increased as the Zn element decreased, resulting a direct optical gap of 3.47 eV and an indirect optical gap of 3.23 eV. The Attenuated Total Reflection (ATR) curve in the SPR biosensor indicated a shift in the reflective angle of the Prism/Au/Air configuration, which is 47.78° on Prisma/Au/nanoparticle of Zn0.8Mn0.2Fe2O4/air by 50.75°, and the prism/Au/nanoparticle of Zn0.2Mn0.8Fe2 O4/air by 51.04°. The substitution of Zn ions in the compound Zn x Mn(1-x)Fe2O4 affects the resulting ATR curve. The shift in the SPR angle is caused by changes in the refractive index in each layer which is influenced by the concentration of each material which has an impact on the absorbance ability and photon reflectance. This research has the potential to continue with the testing of dielectric and magnetic properties, as well as special testing for biological analytes compatible with ZnxMn(1-x)Fe2O4 nanoparticles.

Inversion of Equivalent Electromagnetic Parameters of Multilayer Absorbing Materials Based on Simulated Annealing Algorithm

Multilayer gradient absorbing materials are difficult to be modeled and simulated in practical applications. To solve this problem, a method of the inversion of equivalent electromagnetic parameters of multilayer absorbing materials based on the simulated annealing algorithm is proposed in this paper. The reflectivity of the multilayer absorbing material in different forms of polarization and obliquely incident at different angles is calculated, and then the simulated annealing algorithm is used to calculate the polarization reflectivity and incidence angle reflectivity of the single-layer material in the same thickness within different combinations of electromagnetic parameters to find out the reflectivity curve that is most similar to the reflectivity curve of the wide angle domain of the multilayer absorbing material, namely the desired equivalent electromagnetic parameters. Finally, the simulation verification is performed. The material within the equivalent electromagnetic parameters should be applied to the simple, wedged, and physically-simulated radar cross-section (RCS), and the result is consistent with that of the application of the multilayer absorbing material to the wedged and physically simulated RCS. This suggests that the absorption property of the material within the equivalent electromagnetic parameters calculated with this algorithm is equivalent to that of the multilayer gradient absorbing material.

Colorimetric characterization of the wide-color-gamut camera using the multilayer artificial neural network.

In order to realize colorimetric characterization for the wide-color-gamut camera, we propose using the multilayer artificial neural network (ML-ANN) with the error-backpropagation algorithm, to model the color conversion from the RGB space of camera to theX Y Z space of the CIEXYZ standard. In this paper, the architecture model, forward-calculation model, error-backpropagation model, and the training policy of the ML-ANN were introduced. Based on the spectral reflectance curves of the ColorChecker-SG blocks and the spectral sensitivity functions of the RGB channels of typical color cameras, the method of producing the wide-color-gamut samples for the training and testing of the ML-ANN was proposed. Meanwhile, the comparative experiment employing different polynomial transforms with the least-square method was conducted. The experimental results have shown that, with the increase of the hidden layers and the neurons in each hidden layer, the training and testing errors can be decreased obviously. The mean training errors and mean testing errors of the ML-ANN with optimal hidden layers have been decreased to 0.69 and 0.84 (color difference of CIELAB), respectively, which is much better than all the polynomial transforms, including quartic polynomial transform.

Characterization and Growth of TiO2/ZnO on PTFE Substrates at Different Volumetric Ratios Using Chemical Bath Deposition

Developing non-toxic, semiconductor-doped heterojunction materials for optoelectronic applications on the surface of a flexible substrate is a viable strategy for meeting the world’s energy needs without introducing any environmental issues. In this paper, Ti:TiO2/ZnO nanocomposites were prepared by heat treatment and utilized as an active layer in UV photodetectors. First, a ZnO seed layer was deposited by radio frequency (RF) sputtering on polytetrafluoroethylene (PTFE) substrates. Then, TiO2/ZnO thin films (TFs) were successfully grown by combining volumetric mixtures of TiO2 and ZnO at the ratios of 1:7, 1:3, 3:5, and 1:1 via the chemical bath deposition (CBD) method. The morphological, elemental, and topographical analyses of the grown TFs were investigated through SESEM, EDX, and AFM spectroscopy, respectively. XRD patterns illustrated the presence of the unified (002) peak of the Ti/ZnO hexagonal wurtzite structure in all prepared samples, with intensities indicating a very strong preferential crystallinity with increasing TiO2 ratios. Enhanced diffuse reflectance curves were obtained by UV–Vis spectroscopy, with allowed indirect energy bandgaps ranging from 3.17 eV to 3.23 eV. FTIR characterization revealed wider phonon vibration ranges indicating the presence of Ti–O and Zn–O bonds. Metal–semiconductor–metal (MSM) UV photodetectors were fabricated by thermally evaporating Ag electrodes on the grown nanocomposites. The volumetric ratio of TiO2/ZnO impacted the photodetector performance, where the responsivity, photosensitivity, gain, detectivity, rise time, and decay time of 0.495 AW−1, 247.14%, 3.47, 3.68 × 108 jones, 0.63 s, and 0.99 s, respectively, were recorded at a ratio of 1:1 (TiO2:ZnO). Based on the results, the heterostructure nanocomposites grown on PTFE substrates are believed to be highly promising TF for flexible electronics.

Morphological characteristics and spectral reflectivity of some degraded soils west Fold Makhoul

The study aim to determine the status and the types of degradation in different sites, depending on the interest of the morphological characteristics Evaluation of the selected Soils and using the Remote Sensing Thechniques as a modern and efficient technologies in monitoring and controlling changes as a result of soil degradation and vegetation and knowledge of the spectral behavior of these soils using a measuring device reflectivity spectral Spectroradiometer. The study was conducted in the province of Salah Alddin in the area between the city of Baiji, and Sharqat that represent the western flank of Makhoul fold, the Total area was to 402.20 km2. It has been identified types of Degradation of soils study, which varied between physical degradation District Representative Degradation at Soil Structure build soils and chemical Representative high content of salts and gypsum content and biological Representative down the organic matter content and lack of vegetation. The study also demonstrated through the use of Spectral Reflectance dvice (Spectroradiometer) to show properties of Spectral reflectance curves of degraded Soil, and characterized by a high degree of gypsum soils with situations of deterioration as a result of high gypsum content by distinguished absorb moisture packs at wavelengths (1400-1450) nm. A reflectance spectral increases with the color value of the Value and increases with higher content of Gypsum, which increases with depth, The results showed a linear relationship was positive and strong, a factor determining R2 value of 0.93 between the percentage of reflectivity and spectral values​​, linear relationship positive between reflectance and spectral content of gypsum, a factor determining R2 worth 0.77 Pan Pedons soils study area. And the existence of a relationship between the third-degree reflectivity ratio of the spectral content of organic matter by a factor of determining R2 value of 0.52

Bistable Reflection Assisted by Fano Resonance in DMDMW With Low-Threshold and Large Modulation Depth

Owing to an additional thinner planar waveguide with micron scale is attracted to the symmetrical metal cladding waveguide (SMCW) with sub-millimeter scale, the interference interaction between different Q-value guided modes would generate a Fano reflectivity curve. In our double metal-dielectric-metal waveguides (DMDMW) structure, a Kerr nonlinear medium is located in the guiding layer of the SMCW where the excited oscillating wave is enormously enhanced. Numerical calculations show that a minute variation of the incident light intensity will give rise to a change in the dielectric constant of the Kerr nonlinear medium and lead to positive feedback. A bistable reflection can be achieved with a low threshold and a large modulation depth because of the sharpness and the asymmetricity of the Fano reflectivity curve.

Analysis of Ti nanolayers irradiated with Xeq＋ ions using synchrotron radiation based X-ray reflectometry

To characterize morphology and physicochemical properties of nanolayers the surface-sensitive X-ray spectroscopy techniques are often successfully applied. These techniques are still being developed in order to achieve better depth resolution and detection limits. In this article, we present measurements of morphology of Ti nanolayers (deposited on Si substrate) with thickness of 25 nm, 50 nm and 75 nm, unmodified and irradiated with Xeq＋ ions (where q is the charge state of the ion), which were carried out using synchrotron radiation (SR) based XRR technique. The nanolayers were irradiated with low-energy (of the order of hundreds of keV) highly charged Xeq＋ (q = 25, 30, 35) ions, at the Kielce EBIS facility (Jan Kochanowski University, Kielce, Poland). The SR-XRR measurements were performed at Elettra Synchrotron X-ray fluorescence beamline, using X-ray beam with energy of 6.0 keV. The obtained reflectivity curves were modelled by creating a structure consisting (from the bottom to the top) of silicon substrate (Si), main Ti layer, TiO2 layer, and TiO2(a) amorphous layer, with contamination of hydrocarbons, carboxylates or alkoxides. The experimental results obtained with the SR-XRR technique for the nanolayers, unmodified and irradiated with the Xeq＋, show the dependence of the TiO2 layers morphology on the Xe ions charge state. In the article the sample preparation, measurement using SR-XRR and the data analysis procedures are described in details and the advantages and disadvantages of the SR-XRR technique in the context of nanolayer studies are discussed.

Large-scale fabrication of an ultrathin broadband absorber using quasi-random dielectric Mie resonators.

Ultrathin broadband absorber maintaining a near-uniform low reflectivity over a broadband wavelength is essential for many optical applications, such as light harvesting and nanoscale imaging. Recently, there has been considerable interest in employing arrays of high-index dielectric Mie resonators on surfaces to trap light and reduce the reflectivity. For such Mie-resonant metasurfaces, however, antireflection properties featuring both a flat low reflectance curve and a wide bandwidth are hard to be satisfied simultaneously, and an efficient large-scale nanofabrication technique rarely exists. Here, we present a high-throughput laser interference induced quasi-random patterning (LIIQP) technique to fabricate quasi-random Mie resonators in large scale. Mie resonators with feature sizes down to sub-100 nm have been fabricated using a 1064 nm laser source. Each Mie resonator concentrates light at its shape-dependent resonant frequency, and all such resonators are arranged quasi-randomly to provide both rich (with broadband Fourier components) and strong (with large intensities) Fourier spectra. Specifically, a near-uniform broadband reflectivity over 400-1100 nm spectrum region has been confined below 3% by fabricating a large-scale ultrathin (around 400 nm) absorber. Our concept and high-throughput fabrication technique allows the rapid production of quasi-random dielectric Mie-resonant metasurfaces in a controllable way, which can be used in various promising applications including thin-film solar cells, display, and imaging.