Diffuse Reflectance Method Research Articles

Insights on the Synthesis, Crystal and Electronic Structures, and Optical and Thermoelectric Properties of Sr1- xSb xHfSe3 Orthorhombic Perovskite.

Single-phase polycrystalline powders of Sr1- xSb xHfSe3 ( x = 0, 0.005, 0.01), a new member of the chalcogenide perovskites, were synthesized using a combination of high temperature solid-state reaction and mechanical alloying approaches. Structural analysis using single-crystal as well as powder X-ray diffraction revealed that the synthesized materials are isostructural with SrZrSe3, crystallizing in the orthorhombic space group Pnma (#62) with lattice parameters a = 8.901(2) Å; b = 3.943(1) Å; c = 14.480(3) Å; and Z = 4 for the x = 0 composition. Thermal conductivity data of SrHfSe3 revealed low values ranging from 0.9 to 1.3 W m-1 K-1 from 300 to 700 K, which is further lowered to 0.77 W m-1 K-1 by doping with 1 mol % Sb for Sr. Electronic property measurements indicate that the compound is quite insulating with an electrical conductivity of 2.9 S/cm at 873 K, which was improved to 6.7 S/cm by 0.5 mol % Sb doping. Thermopower data revealed that SrHfSe3 is a p-type semiconductor with thermopower values reaching a maximum of 287 μV/K at 873 K for the 1.0 mol % Sb sample. The optical band gap of Sr1- xSb xHfSe3 samples, as determined by density functional theory calculations and the diffuse reflectance method, is ∼1.00 eV and increases with Sb concentration to 1.15 eV. Careful analysis of the partial densities of states (PDOS) indicates that the band gap in SrHfSe3 is essentially determined by the Se-4p and Hf-5d orbitals with little to no contribution from Sr atoms. Typically, band edges of p- and d-character are a good indication of potentially strong absorption coefficient due to the high density of states of the localized p and d orbitals. This points to potential application of SrHfSe3 as absorbing layer in photovoltaic devices.

Magnetic, thermodynamic and optical properties of Sb-substituted Ba2PrBiO6 double perovskite oxides

We demonstrated crystal structures, magnetic, thermodynamic and optical properties of the B-site substituted perovskite oxides Ba2Pr(Bi1−x,Sbx) O6 (x=0, 0.1 and 0.2). Polycrystalline samples of Sb-substituted Ba2PrBiO6 were prepared with the conventional solid-state reaction technique. The X-ray diffraction data revealed that the polycrystalline samples are an almost single phase with a monoclinic structure (C2 /m). Substitution of smaller Sb ion at Bi site causes a monotonic decrease in both the lattice parameters and volume. Magnetization measurements at high temperatures above 200 K show that the effective magnetic moment is estimated to be around 3.15 µB, which is close to that for Pr3+ion. The X-ray photoemission spectroscopy analysis revealed that a prominent peak of Pr3+ is dominant with a smaller shoulder structure of Pr4+. A Schottky-like anomaly observed in the low-temperature specific heat measurement is explained by low-lying splitting of Pr ions under the crystal field effect. Optical spectra were measured using a diffuse-reflectance method. The band gaps were estimated from the optical data to be 0.977 eV and 1.073 eV, at x = 0 and 0.2, respectively. The effect of band gap opening due to Sb substitution is examined by using the density functional theory.

Synthesis of ferrocenylazobenzene-functionalized MCM-41 via direct co-condensation method

Ferrocenylazobenzene-functionalized mesoporous MCM-41 material (Fc-Az-M14), was synthesized directly through co-condensation of 4-triethoxysilyl-3′-ferrocenylazobenzene (TEFA) and tetraethyl orthosilicate (TEOS), under basic conditions, using cetyltrimethylammmonium bromide (CTAB) as structure-directing agent. The template was removed through solvent extraction, to yield the ferrocenylazobenzene-containing ordered mesoporous organosilicas Fc-Az-M41. The prepared material was characterized by nitrogen adsorption, X-ray diffraction (XRD), solid state 29Si MAS NMR and 13C CP-MAS NMR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Thermogravimetric analysis (TGA) and diffuse reflectance UV-Vis spectroscopy (DR UV). The results showed that Fc-Az-M41 had an ordered two-dimensional hexagonal mesostructure, high BET surface area and pore volume. The pore diameter, BET surface area, and pore volume of the extracted material were 3.8 nm, 1070 m2/g and 0.80 cm3/g, respectively. The mean pore diameters of MCM-41 clearly decreased by ca. 0.65 nm upon incorporation of Fc-Az groups. UV-Vis spectrum of Fc-Az-M41 was determined by a diffuse reflectance method after UV irradiation. The presence of the azobenzene chromophores in this material can be clearly observed in the DR UV-Vis spectra of surfactant-free Fc-Az-M41. This spectra shows that the framework of this material is formed predominantly by trans isomer, and the π-π* and the n-π* absorption bands were affected by metal-to-ligand charge transfer (MLCT).

Rapid identification of oral solid dosage forms of counterfeit pharmaceuticals by discrimination using near-infrared spectroscopy.

Since it can take an enormous amount of time and cost to discriminate counterfeit medicines by using conventional methods, counterfeit medicines has been spread in the world markets. The purpose of this study was to develop a rapid and simple analytical method to discriminate counterfeit drugs using near infrared (NIR) spectroscopy. Seven types of brand name tablet and generic tablets containing atorvastatin calcium sesquihydrate (AT) preparations were used as simulated counterfeit medicines. NIR spectra of 35 AT tablet products were measured using a diffuse reflection method. The NIR spectral data were analyzed by principal component analysis (PCA). The PCA results suggested that the model had sufficient accuracy to discriminate the 7 types for AT tablets. The NIR spectral data were also analyzed using a soft independent modeling of class analogy (SIMCA) method. Predicting the classification of the AT tablet samples was performed based on all the validated AT tablet data using the SIMCA model, and the probability of classification of 7 types was 100%. The discrimination power spectrum of the SIMCA model indicated significant patterns based on diluents. The PCA and SIMCA classification of the AT tablets were depended on the major excipient combinations.

Modification method to reduce the impact of blood vessel on noncontact discrimination of human blood based on “M+N” theory

Noncontact discriminating human blood is significantly crucial for import-export ports and inspection and quarantine departments. We had already demonstrated that visible diffuse reflectance spectroscopy combining PLS-DA method can successfully realize noncontact human blood discrimination. However, the circulated blood vessels may be produced with different materials. The use of various kinds of blood tubes may have a negative effect on the discrimination, based on “M+N” theory (Li et al., 2016). In this research, we explored the impact of different material of blood vessels, such as glass tube and plastic tube, on the prediction ability of the discrimination model. Furthermore, we searched for the modification method to reduce the influence from the blood tubes. Our work indicated that generalized diffuse reflectance method can greatly improve the discrimination accuracy. This research can greatly facilitate the application of noncontact discrimination method based on visible and near-infrared diffuse reflectance spectroscopy.

Diclofenac degradation by heterogeneous photocatalysis with Fe3O4/TixOy/activated carbon fiber composite synthesized by ultrasound irradiation

In this work, a photocatalytic system to degrade diclofenac was developed using a composite Fe3O4/TixOy on an activated carbon fiber. Diclofenac is widely used as an anti-inflammatory compound worldwide and it is constantly being added as waste in the environment (Heberer 2002 J. Hydrol. 266 175–89), exceeding the permissible maximum concentration in the wastewater (GEO-3 2002 Programa de las Naciones Unidas para el Medio Ambiente; Golet et al 2003 Environ. Sci. Technol. 37 3243–9; Oviedo et al 2010 Environ. Toxicol. Pharmacol. 29 9–43; Le-Minh et al 2010 Water Res. 44 4295–323; Legrini et al 1993 Chem. Rev. 1093 671–98). The composite was synthesized by sol-gel technique with and without ultrasound irradiation (Singh and Nakate 2014 J. Nanopart. 2014 326747). The solids were deposited by ultrasound irradiation on active carbon fiber in order to optimize the diclofenac degradation. The solids were characterized by x-ray diffraction (XRD), nitrogen physisorption (BET), and scanning electron microscopy with EDS microanalysis (SEM-EDS). The crystal size was calculated with the Debye-Scherrer equation, and the band gap values by the diffuse reflectance method. The evaluation process was studied by UV–vis spectroscopy (Rizzoa et al 2009 Water Res. 43 979–88). It was found that in this synthesis method (ultrasound), textural properties such as porosity, specific surface area and morphology depend on the ultrasound irradiation. The proposed system, Fe3O4/titanium oxide hydrate showed better degradation profile than TiO2 anatase phase; the increase of diclofenac degradation was attributed to the textural properties of the composite, it avoids the filtering process since the separation can be achieved by magnetizing and/or decantation.

Rectangular Illumination Based on Diffuse Reflective Off-Axis Surface

Diffuse reflective LED lighting system is widely used in many areas, while rectangular illumination is also widely used in various lighting fields because of its regular lighting shapes, but traditional diffuse reflection method can only produce circular spot. This paper first introduced rectangular illumination into design of the diffuse reflective surface, combined the merits of both. A mathematical model of a diffuse reflective off-axis surface based on a single LED chip, desired value of the target plane and energy conservation is established and the shape of the illumination facula is used as the constraint condition. By solving the nonlinear equations, a number of two-dimensional (2-D) curves are obtained and combine these 2-D curves into off-axis surface. The results show that the shape of the illumination facula is close to the standard rectangle, and the efficiency and the uniformity of illumination is higher than traditional diffuse reflectors.

Analytical study of the XIV century wall painting and lime mortars in the "St. George" church in Staro Nagoričane, Republic of Macedonia

This work presents the first comprehensive study of the wall painting in the “St. George” church accomplished mainly by means of Fourier Transform Infrared Spectroscopy using Diffuse Reflectance and Micro-Infrared method (FTIR/DRS/Micro-IR) and the other analytical techniques Optical microscopy (OM), X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD) and Inductively Coupled Plasma – Mass Spectrometry (ICP-MS). The main research objective was characterization of the artistic palette and painting technique, but also determination of the degradation products and observed alterations to the wall painting. Additionally, the lime mortars (plaster and renders) located immediately behind the studied wall painting were analyzed. The analysis demonstrated that mainly natural/mineral pigments were used in the artwork and the majority of painting was executed in combination of fresco and lime-painting technique. The major risk factor in the painting deterioration was found to be the salt efflorescence, which mostly occurred as oxalates and sulfates.

Complementary analyses of infrared transmission and diffuse reflection spectra of macerals in low-rank coal and application in triboelectrostatic enrichment of active maceral

Fourier infrared analyses of coal mostly adopted KBR compression method currently. However, infrared spectra obtained by this technique will suffer the interference of water absorption band. For a comprehensive knowledge of macerals in low-rank coal, complementary analyses of KBR compression and diffuse reflection methods were conducted in this investigation. Other researches of coal liquefaction have shown that vitrinite and inertinite are the active and inert component respectively in the coal liquefaction and improvement of vitrinite content in coal will enhance the liquefaction efficiency. Triboelectrostatic separation was performed to easily liquefied low-rank coal, and the active component vitrinite content of negative coal flow was increased markedly. This study compared surface structures of vitrinite and inertinite based on quantitative analysis of diffuse reflectance spectra and researched their triboelectrostatic separation behavior from the surface functional groups angle. Inertinite possesses high concentrations of oxygen-containing groups and hydrophilic groups (phenolic hydroxyl and carboxyl) while vitrinite has high content of hydrophobic groups (alkyl groups and long carbon chain), which indicate they could be separated and enriched at some degree by triboelectrostatic beneficiation at the condition of high-temperature and low relative humidity.

Tissue-Like Phantoms as a Platform for Inserted Fluorescence Nano-Probes.

Tissue-like phantoms are widely used as a model for mimicking the optical properties of live tissue. This paper presents the results of a diffusion reflection method and fluorescence lifetime imaging microscopy measurements of fluorescein-conjugated gold nanorods in solution, as well as inserted in solid tissue-imitating phantoms. A lack of consistency between the fluorescence lifetime results of the solutions and the phantoms raises a question about the ability of tissue-like phantoms to maintain the optical properties of inserted contrast agents.

Redistribution of Soil Organic Carbon Triggered by Erosion at Field Scale Under Subhumid Climate, Hungary

Soil organic carbon (SOC) has primary importance in terms of soil physics, soil fertility and even of climate change control. One hundred soil samples were taken from an intensively cultivated Cambisol to quantify SOC redistribution triggered by soil erosion under a subhumid climate, by the simultaneous application of diffuse reflectance (240–1 900 nm) and traditional physico-chemical methods. The representative sample points were collected from the solum along the slopes at the depth of 20–300 cm with a mean SOC content of 12 g kg−1. Hierarchical cluster analyses were performed based on the determined SOC results. The spatial pattern of the groups created were similar, and even though the classifications were not the same, diffuse reflectance had proven to be a suitable method for soil/sediment classification even within a given arable field. Both organic and inorganic carbon distributions were found to be a proper tool for estimations of past soil erosion processes. The SOC enrichment was found on two sedimentary spots with different geomorphological positions. Soil organic matter composition also differed between the two spots due to selective deposition of the delivered organic matter. The components with low-molecular-weight reached the bottom of the slope where they could leach into the profile, while the more polymerised organic matter compositions were delivered and deposited even before on a higher segment of the slope in an aggregated form. This spatial difference appeared below the uppermost tilled soil layer as well, referring the lower efficiency of conventional ploughing tillage in soil spatial homogenisation.

Noninvasive assessment of hemodynamic and brain metabolism parameters following closed head injury in a mouse model by comparative diffuse optical reflectance approaches.

Optical techniques have gained substantial interest over the past four decades for biomedical imaging due to their unique advantages, which may suggest their use as alternatives to conventional methodologies. Several optical techniques have been successfully adapted to clinical practice and biomedical research to monitor tissue structure and function in both humans and animal models. This paper reviews the analysis of the optical properties of brain tissue in the wavelength range between 500 and 1000nm by three different diffuse optical reflectance methods: spatially modulated illumination, orthogonal diffuse light spectroscopy, and dual-wavelength laser speckle imaging, to monitor changes in brain tissue morphology, chromophore content, and metabolism following head injury. After induction of closed head injury upon anesthetized mice by weight-drop method, significant changes in hemoglobin oxygen saturation, blood flow, and metabolism were readily detectible by all three optical setups, up to 1h post-trauma. Furthermore, the experimental results clearly demonstrate the feasibility and reliability of the three methodologies, and the differences between the system performances and capabilities are also discussed. The long-term goal of this line of study is to combine these optical systems to study brain pathophysiology in high spatiotemporal resolution using additional models of brain trauma. Such combined use of complementary algorithms should fill the gaps in each system's capabilities, toward the development of a noninvasive, quantitative tool to expand our knowledge of the principles underlying brain function following trauma, and to monitor the efficacy of therapeutic interventions in the clinic.

Translucency of monolithic and core zirconia after hydrothermal aging

Objective: To evaluate the hydrothermal aging effect on the translucency of partially stabilized tetragonal zirconia with yttria (Y-TZP) used as monolithic or fully milled zirconia and of core type.Methods: Twenty disc-shaped specimens (1 and 10 mm) for each type of monolithic and core Y-TZP materials were milled and sintered according to the manufacturer’s instruction. The final specimens were divided into two groups according to the type of Y-TZP used. Translucency parameter (TP) was measured over white and black backgrounds with the diffuse reflectance method; X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to analyze the microstructure of both Y-TZP types before and after aging. Data for TP values was statistically analyzed using Student’s t-test.Results: Monolithic Y-TZP showed the highest TP mean value (16.4 ± 0.316) before aging while core Y-TZP showed the lowest TP mean value (7.05 ± 0.261) after aging. There was a significant difference between the two Y-TZP types before and after hydrothermal aging. XRD analysis showed increases in monoclinic content in both Y-TZP surfaces after aging.Conclusion: Monolithic Y-TZP has a higher chance to low-temperature degradation than core type, which may significantly affect the esthetic appearance and translucency hence durability of translucent Y-TZP.

Detection of gold nanorods uptake by macrophages using scattering analyses combined with diffusion reflection measurements as a potential tool for in vivo atherosclerosis tracking.

In this study, we report a potential noninvasive technique for the detection of vulnerable plaques using scatter analyses with flow cytometry (FCM) method combined with the diffusion reflection (DR) method. The atherosclerotic plaques are commonly divided into two major categories: stable and vulnerable. The vulnerable plaques are rich with inflammatory cells, mostly macrophages (MΦ), which release enzymes that break down collagen in the cap. The detection method is based on uptake of gold nanorods (GNR) by MΦ. The GNR have unique optical properties that enable their detection using the FCM method, based on their scattering properties, and using the DR method, based on their unique absorption properties. This work demonstrates that after GNR labeling of MΦ, 1) the FCM scatter values increased up to 3.7-fold with arbitrary intensity values increasing from 1,110 to 4,100 and 2) the DR slope changed from an average slope of 0.196 (MΦ only) to an average slope of 0.827 (MΦ labeled with GNR) (P<0.001 for both cases). The combination of FCM and DR measurements provides a potential novel, highly sensitive, and noninvasive method for the identification of atherosclerotic vulnerable plaques, aimed to develop a potential tool for in vivo tracking.

Nanoparticle uptake by macrophages in vulnerable plaques for atherosclerosis diagnosis.

The composition of atherosclerotic (AS) plaques is crucial concerning rupture, thrombosis and clinical events. Two plaque types are distinguished: stable and vulnerable plaques. Vulnerable plaques are rich in inflammatory cells, mostly only M1 macrophages, and are highly susceptible to rupture. These plaques represent a high risk particularly with the standard invasive diagnosis by coronary angiography. So far there are no non-invasive low-risk clinical approaches available to detect and distinguish AS plaque types in vivo. The perspective review introduces a whole work-flow for a novel approach for non-invasive detection and classification of AS plaques using the diffusion reflection method with gold nanoparticle loaded macrophages in combination with flow and image cytometric analysis for quality assurance. Classical biophotonic methods for AS diagnosis are summarized. Phenotyping of monocytes and macrophages are discussed for specific subset labelling by nanomaterials, as well as existing studies and first experimental proofs of concept for the novel approach are shown. In vitro and in vivo detection of NP loaded macrophages (MΦ). Different ways of MΦ labelling include (1) in vitro labelling in suspension (whole blood or buffy coat) or (2) labelling of short-term MΦ cultures with re-injection of MΦ-NP into the animal to detect migration of the cells in the plaques and (3) in vivo injection of NP into the organism.

Preparation and characterization of cobalt(II) phthalocyanine complex-encapsulated zeolite-X

Cobalt(II) phthalocyanine has been encapsulated into the supercage of X-type zeolite as an active monomer (CoPc-X) by the "ship-in-bottle" synthesis method, and furthermore the CoPc-X has been ion-exchanged with secondary metals ( M n+ = Na +, Ag +, Cu 2+, Zn 2+) to obtain CoPc-Mn+-X. They have been characterized by elemental analysis, fluorescent X-ray, UV-vis, diffuse reflectance, physisorption analysis, and ESR spectroscopic methods, and their deodorant behaviors for smell gasses, 2-nonenal and indole, have been examined.

On the abnormal efficiency of the luminescence of submicron-sized phosphor Y2O3 : Eu3+

Samples of the Y2O3 : Eu3+ (5–11 at %) phosphor with a high luminescence efficiency have been synthesized by the sol-gel method. The chemical, substructural, and optical properties of the material have been investigated using the thermal analysis, X-ray powder diffraction, electron microscopy, vibrational and Raman spectroscopy, and diffuse reflection methods. The size effect of particles and crystallites on the luminescence parameters of the phosphor has been analyzed. It has been found that the submicron-sized Y2O3 : Eu3+ phosphor containing 9–11 at % Eu3+ exhibits an abnormally high luminescence intensity. It has been shown that these effects are associated with the enrichment of the surface of particles and crystallites with dopant ions due to the decrease in the local symmetry of their environment.

Diffusion Reflection and Fluorescence Lifetime Imaging Microscopy Study of Fluorophore-Conjugated Gold Nanoparticles or Nanorods in Solid Phantoms.

In this paper we report the optical properties of fluorescein-conjugated gold nanoparticles (GNPs) in solid phantoms using diffusion reflection (DR) and fluorescence lifetime imaging microscopy (FLIM). The GNPs attached with fluorescein in solution were studied by fluorescence correlation spectroscopy. The intensity decays were recorded to reveal the fluorescence lifetime of fluorescein while in the near-field vicinity of the GNPs. The DR method was used to explore the solid phantoms containing GNPs, indicating the light propagation from the surface of solid phantoms. The resulting DR slopes of the reflected intensity showed the higher the GNP concentration, the bigger the slope. Fluorescence intensity, lifetime, and anisotropy images of solid phantoms were investigated by FLIM. The exploration of optical properties and molecular imaging combined with DR and FLIM methods is a new approach that has not been established until now. The combined DR–FLIM technique is expected to provide discrimination based on unique spectroscopic fingerprints of GNPs that could be utilized for cell imaging. This paper includes a combined study with a variety of methods, which may lead to multimodal imaging for surfaces (by FLIM) and deep penetration (up to cm by the DR) together.

Optical and EPR properties of BaAl12O19:Eu2+, Mn2+ phosphor prepared by facile solution combustion approach

The BaAl12O19:Eu, Mn blue–green powder phosphor sample has been synthesized by a solution combustion method at the furnace temperature of 500°C within few minutes. Powder X-ray diffractometry, energy-dispersive X-ray analysis, UV–vis diffuse reflectance, photoluminescence and electron paramagnetic resonance (EPR) methods have been employed to characterize the as-synthesized phosphor. Photoluminescence emission of BaAl12O19:Eu, Mn consists of a peak around 442/511 when excited with 328/342nm. The EPR spectra of BaAl12O19:Eu, Mn phosphor exhibited the signals with the effective g values at g≈4.81 and 1.97 at room and different low temperatures. The signal at g≈4.81 has been attributed to Eu2+ ions. The signal at g≈1.97 has been attributed to Mn2+ ions in tetrahedral symmetry. It is found that the g values are independent of temperature variation. Optical and EPR analysis of the sample confirm the presence of Eu2+ and Mn2+ in the BaAl12O19 matrix.

Processes of microstructural evolution during high-energy mechanical treatment of ZnO and black NiO powder mixture

Kinetics of microstructural evolution in ZnO and NiO black powder mixture during prolonged high-energy mechanical ball milling were investigated by Scanning Electron Microscopy, Laser Particle Sizer, X-ray diffraction, Electron Paramagnetic Resonance, Fourier Transform Infrared Spectroscopy and UV–vis Diffuse Reflection methods. The use of these methods allows us to control the macrostructural processes (ZnO particles and NiO granules grinding, the deagglomeration and “secondary agglomeration”), the microstructural processes (formation and annealing of different native defects in ZnO [VZn−:Zni0 (I), VZn− (II), and (VZn−)2− (III) centers] and NiO black) and the mechanothermal processes in samples. This allows to establish the relationship between microstructural evolution and the properties of the samples depending on the duration of the mechanical processing.