Measurements Of Optical Absorption Spectra Research Articles

Nanodiamond-promoted white light emission in Eu, Dy, and Cu-containing phosphate glass: quantitative analysis and colorimetric study.

A thorough analysis of glass containing Eu2 O3 and Dy2 O3 , or Eu2 O3 , Dy2 O3 , and CuO melted together with nanodiamond powder was pursued based on measurements of optical absorption, photoluminescence (PL) emission and excitation spectra, and colorimetry. Nanodiamond facilitated the stabilization of Cu+ and Eu2+ ions with blue-emitting characteristics that, along with yellow-emitting Dy3+ and red-emitting Eu3+ led to the white light-emitting glass. Novel intensity notations implemented in intensity-based spectral ratios, and difference intensity correlation analysis were proposed for the assessment of PL properties. The chromaticity and correlated colour temperature of the emission were ultimately investigated as a two-parametric problem based on: (1) the different ionic components; and (2) the various excitation wavelengths employed. The optical analysis approach adds to the characterization methods to further fundamental understanding and provide helpful analytical tools for designing materials for tunable white light-emitting devices.

Appreciably optimization of PVA/PVP nanocomposite blend for enhanced optoelectronics properties and multifunctional applications

The optical and electrical properties of PVA/PVP were manipulated by optimizing the blend ratio between those polymers. The (40/60) wt.% of PVA/PVP achieved the lowest energy gap and the highest electrical conductivity. After that, the optical and electrical properties of blend films were engineered using Ni(OAc)2 for enhanced optoelectronic properties. The doping impact on the semicrystalline and molecular structures of the prepared blend was investigated. The optical properties of the doped blend films were examined using optical transmission and absorption spectra measurements. The nonlinear optical parameters such as nonlinear refractive index and third-order optical susceptibility were estimated. The prepared films showed a pronounced laser cut-off performance. The electrical properties of the fabricated films showed a tunable behavior with the variation of doping level. The engineered doped polymer blend films exhibited good sensitivity to visible light with promising values of responsivity and specific detectivity ∼5.89 mA/W, and 4.31 × 109 Jones, respectively.

In English

The aim of the work is synthesis and study on the properties of polyfunctional magnetosensitive nanocomposites (NC) and target-directed magnetic fluids (MF) based on physiological solution (PS), magnetite, gemcitabine (GEM) and HER2 antibodies (AB), promising for use in targeted antitumor therapy against MDA-MB-231 aggressive tumor cells of triple-negative human breast cancer (BC) with high proliferative and metastatic activity. The specific surface area (Ssp) of samples was determined by the method of thermal desorption of nitrogen using a device KELVIN 1042 of “COSTECH Instruments”. The size of nanoparticles (NP) has been estimated by the formula DBET = 6/(ρSBET), where ρ is the density of NC particle, SBET is the value of the specific surface area calculated by the polymolecular adsorption theory of Brunauer, Emmett and Teller (BET). The surface condition of nanodispersed samples was studied by IR spectroscopy (“Perkin Elmer” Fourier spectrometer, a model 1720X). To calculate the concentration of hydroxyl groups on the surface of nanostructures, the method of differential thermal analysis was used in combination with differential thermogravimetric analysis. The thermograms were recorded using a derivatograph Q-1500D of MOM firm (Hungary) in the temperature range of 20–1000 °C at a heating rate of 10 deg/min. X-ray phase analysis of nanostructures was performed using a diffractometer DRON-4-07 (CuKα radiation with a nickel filter in a reflected beam, the Bragg-Brentano focusing). The size and shape of NP were determined by electron microscopy (a transmission electron microscope (TEM) JEM-2100F (Japan)). The hysteresis loops of the magnetic moment of the samples were measured using a laboratory vibration magnetometer of Foner type at room temperature. Measurement of optical density, absorption spectra and GEM concentration in solutions was performed by spectrophotometric analysis (Spectrometer Lambda 35 UV/Vis Perkin Elmer Instruments). The amount of adsorbed substance on the surface of magnetite was determined using a spectrophotometer at λ = 268 nm from a calibration graph. The thickness of the adsorbed layer of GEM in the composition of Fe3O4@GEM NC was determined by magnetic granulometry. To study the direct cytotoxic/cytostatic effect of a series of experimental samples of MF based on PS, Fe3O4 NP, GEM, HER2 AB, as well as MF components in mono- or complex use, onto MDA-MB-231 cells in vitro, IC50 index was determined. MF were synthesized on the basis of single-domain Fe3O4 and PS, stabilized with sodium oleate (Ol.Na) and polyethylene glycol (PEG), containing GEM and HER2 (Fe3O4@GEM/Ol.Na/PEG/HER2+PS). The cytotoxic/cytostatic activity of MF against MDA-MB-231 cells was studied. It was found that as a result of application of synthesized MF composed of Fe3O4@GEM/Ol.Na/PEG/HER2+PS at the concentration of magnetite of 0.05 mg/mL, GEM - 0.004 mg/mL and HER2 AB - 0.013 μg/mL, a synergistic effect arose, with reduction of the amount of viable BC cells to 51 %. It has been proved that when using MF based on targeted Fe3O4/GEM/HER2 complex, the increased antitumor efficacy is observed compared to traditional use of the drug GEM, with a significant reduction (by four times) of its dose. The high cytotoxic/cytostatic activity of Fe3O4/GEM/HER2 complexes is explained by the fact that endogenous iron metabolism disorders play a significant role in the mechanisms of realization of the apoptotic program under the influence of nanocomposite. Thus, when the nanocomposite system contains Fe3O4/GEM/HER2 complexes in MDA-MB-231 cells, a significant increase is observed in the level of “free iron”, which favours formation of reactive oxygen species and causes oxidative stress (Fenton reaction). The consequences of oxidative stress are induction of apoptosis, enhancement of lipid peroxidation processes, as well as structural and functional rearrangement of biological membranes. The prospects have been shown of further studies of Fe3O4@GEM/Ol.Na/PEG/HER2+PS MF in order to create on their basis a magnetically carried remedy for use in targeted antitumor therapy.

Experimental investigation of temperature and angular dependence of plasmonic structures on resonance and absorption properties

A metallic microcones array-based plasmonic strcture is presented as an example for the purpose of experimentally exploring the dependence of ambient temperature and incident angle on resonance and absorption properties. The microcones array is fabricated using the technique of heavy ion tracking. The technique has advantages of large-area patterning, high-aspect ratio of unit dimension, controllable length, and multichoice of materials. Fabrication steps, mathematical fitting, and experimental measurements of optical absorption spectra are presented. To analyze the experimental data regarding thetemperature-dependence effect, a theoretical formula, a quasi-Gauss model, is applied to describe the relationship between temperature (T) and plasmonic wavelength (λSP). Our experimental results demonstrate that the variation of temperature and incident angle strongly affect the sensitivity of λSP and its absorption properties. Our experimental results indicate that this structure is capbale of acting as an optical sensor for detection of temperature and angular denpendence.

Simultaneous measurement of optical rotation dispersion and absorption spectra for chiral substances.

We present a new method based on optical null methods for simultaneously measuring the optical rotatory dispersion (ORD) and absorption spectra of chiral substances. The optical rotation angle at a specific wavelength can be obtained from the optical nulls of the Malus curves with and without the sample. We use the optical nulls of the two curves as benchmark points and the readings to the right of the benchmark points by a certain angular offset to eliminate the influence of the analyzer on the light intensity and obtain the absorbance of the chiral substance at a specific wavelength. The 4096 pixels of the line scan CCD can measure multiple wavelengths simultaneously so that continuous ORD and absorption spectra can be obtained. The experimental results show that the standard deviation of the specific optical rotation is 0.11 deg mL g-1 dm-1 , the standard deviation of the maximum absorption wavelength is 0.45 nm, and that absorbance of the sample varies linearly with the concentration. This method is helpful for simplifying the experiment and has a profound influence on the analysis of the contents and molecular configurations of chiral substances in the future.

Highly Precise Determination of Structural and Optical Parameters of an Innovative (PVA-VOCl) for Flexible Polymer-Semiconductor Devices

A novel polymer-semiconductor nanocomposites of polyvinyl alcoholoxovanadium chloride (PVA-VOCl) films have been successfully synthesized by the simple solution casting technique. XRD analysis of the prepared films confirms the formation of VOCl nanocrystals with different particle sizes distributed in the PVA polymer resulting in the increment in the crystalline phase of the whole structure of PVA-VOCl polymer nanocomposite. The Fourier transform infrared (FT-IR) spectroscopy measurements indicate the distribution of VOCl in the polymer matrix. The optical absorption spectra measurements exhibit a complete blocking of the UV range (200–400 nm) due to VOCl dispersion in the polymer matrix. The optical gap Eg of the films were determined with a high degree of precision using Tauc relation, Absorption spectra fitting and the new accurate geometric method show a strong decrease from 5.2 eV for pure PVA to 2.85 eV with increasing the VOCl level in the polymer film. In addition, the high-frequency refractive index estimated from the optical gap values exhibits a significant increase from 1.70 to 2.07. Our samples can be considered as an innovative flexible optical material for UV filters, optoelectronics, and photonics applications.

Optical and Depolarization Spectroscopy of Doubly Doped Alkaline‐Earth Fluorides

The process of recharging heterogeneous lanthanides in SrF2 and BaF2 crystals is studied by parallel measurements of optical absorption spectra and thermodepolarization curves. Electron transfer between lanthanides Yb2+–Nd3+, Eu2+–Yb3+ in SrF2, and between Yb2+–Nd3+, Eu2+–Yb3+, and Yb2+–Dy3+ in BaF2 is studied. Electron phototransfer between lanthanides, registered by a change in the absorption bands of divalent lanthanides, is accompanied by a backward migration of charge‐compensating interstitial fluorine, which is detected by a change in the corresponding thermodepolarization peaks of .

Light-Irradiated Electrochemical Direct Construction of Cu2O/CuO Bilayers by Switching Cathodic/Anodic Polarization in Copper(II)-Tartrate Complex Aqueous Solution.

p-CuO with a band gap energy of 1.5 eV, p-Cu2O with a band gap energy of 2.05 eV, and their bilayers were prepared by controlling the potential of anodic and cathodic polarization in a copper(II)–tartrate complex aqueous solution containing copper(II) sulfate hydrate and tartaric acid in the dark and under light irradiation. Electrochemical characteristics of the electrodeposition and the resultant CuO and Cu2O layers were investigated with cyclic voltammetry, chronoamperometry, and Mott–Schottky plots, and the structural and optical characterizations were performed with X-ray diffraction, scanning electron microscopy, and optical absorption spectra measurements. The CuO layer prepared at 0.4–0.7 V was composed of aggregates of granular grains with the monoclinic lattice, and the Cu2O layer composed of coarse grains with the cubic lattice was deposited at −0.4 to 0.6 V. The flat-band potentials were estimated to be 0.145 and −0.1 V (vs Ag/AgCl) for the CuO and Cu2O layers, respectively. The 0.4 μm CuO/1.1 μm Cu2O bilayers could be prepared by switching the electrodeposition potentials of 0.4 and −0.4 V, irrespective of the presence of light irradiation. The photoelectrodeposition under light irradiation enabled the preparation of continuous and dense 1.1 μm Cu2O/0.4 μm CuO bilayer by controlling the potential, while electrodeposition in the dark led to sparse, isolated, and coarse Cu2O grains being deposited. The mechanism for the photoelectrodeposition of the bilayers was discussed based on the energy band alignment at the heterointerface to the Cu–tartrate complex solution.

Study of the influence of the ZnO:Al polycrystalline film morphology on the silver nanoparticles formation

The paper presents the results of the optical and structural properties studies of samples consisting of ZnO:Al (AZO) oxide films with an intermediate silver nanoparticles layer. Obtaining samples were carried out by the method of sol-gel technology using different types of composition, and the conditions for drying and final annealing of the samples were varied. The study of the samples optical properties consisted of the optical absorption spectra measurements, and their structural properties were determined by X-ray diffraction and small-angle X-ray scattering. Comparison of data obtained from measurements of optical and structural properties of samples confirmed the results obtained from modeling in the Comsol Multiphysics software. X-ray diffraction demonstrated that the AZO films have a polycrystalline structure and are highly textured in the [002] direction. Zinc oxide grains are 10-15 nm. Silver nanoparticles are the comparable with AZO grains and have dimensions of several tens of nanometers. An increase in the annealing temperature of the films leads to a redistribution of silver nanoparticles in the AZO film, the distance between the particles increases. Consequently, the effect of the plasmon eigenmodes of the nanoparticles prevails over the effect of the system of particles oscillations interacting with each other. The analysis of the coatings obtained by the method of small-angle X-ray scattering showed that nanoparticles in the AZO film form an ordered structure.

Characterization of ethanol concentrations at ultraviolet wavelength region

This paper presents the measurement of optical absorption spectrum for differentconcentrations of ethanol at ultraviolet wavelength. Ethanol absorption spectrum wasmeasured using portable spectroscopy setup from Avantes. It consists of Balanced DeuteriumHalogen light source and spectrometer. The light source can deliver a continuous broadspectrum ranging from 0.2 to 2.5 μm and the spectrometer has the detection range ofμm. Several mixtures of ethanol in de-ionized water were prepared with variousconcentrations of 0%, 0.1%, 0.5%, 1.0%, 2.5%, 5%, 10%, 15%, 25%, 50% and 100 vol%.The baseline of the absorption spectrum was being analyzed and corrected using MATLABsoftware. From the results, the spectroscopy setup was successfully detecting ethanolconcentration from 2.5-100vol%. However, only concentration range from 2.5-50vol% hasshown 99% of fulfilment towards the Beer’s Lambert Law.Keywords: ultraviolet wavelength; spectroscopy; optical absorption; ethanol absorption spectrum baseline; Beer's Lambert law

Calibration of GafChromic EBT3 for absorbed dose measurements in 5 MeV proton beam and (60)Co γ-rays.

To study EBT3 GafChromic film in low-energy protons, and for comparison purposes, in a reference (60)Co beam in order to use it as a calibrated dosimetry system in the proton irradiation facility under construction within the framework of the Oncological Therapy with Protons (TOP)-Intensity Modulated Proton Linear Accelerator for RadioTherapy (IMPLART) Project at ENEA-Frascati, Italy. EBT3 film samples were irradiated at the Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali di Legnaro, Italy, with a 5 MeV proton beam generated by a 7 MV Van de Graaff CN accelerator. The nominal dose rates used were 2.1 Gy/min and 40 Gy/min. The delivered dose was determined by measuring the particle fluence and the energy spectrum in air with silicon surface barrier detector monitors. A preliminary study of the EBT3 film beam quality dependence in low-energy protons was conducted by passively degrading the beam energy. EBT3 films were also irradiated at ENEA-National Institute of Ionizing Radiation Metrology with gamma radiation produced by a (60)Co source characterized by an absorbed dose to water rate of 0.26 Gy/min as measured by a calibrated Farmer type ionization chamber. EBT3 film calibration curves were determined by means of a set of 40 film pieces irradiated to various doses ranging from 0.5 Gy to 30 Gy absorbed dose to water. An EPSON Expression 11000XL color scanner in transmission mode was used for film analysis. Scanner response stability, intrafilm uniformity, and interfilm reproducibility were verified. Optical absorption spectra measurements were performed on unirradiated and irradiated EBT3 films to choose the most sensitive color channel to the dose range used. EBT3 GafChromic films show an under response up to about 33% for low-energy protons with respect to (60)Co gamma radiation, which is consistent with the linear energy transfer dependence already observed with higher energy protons, and a negligible dose-rate dependence in the 2-40 Gy/min range. Short- and long-term scanner stabilities were 0.5% and 1.5%, respectively; film uniformity and reproducibility were better than 0.5%. The main purpose of this study was to implement EBT3 dosimetry in the proton low-energy radiobiology line of the TOP-IMPLART accelerator, having a maximum energy of 7 MeV. Low-energy proton and (60)Co calibrated sources were used to investigate the behavior of film response vs to be written in italicum dose. The calibration in 5 MeV protons is currently used for dose assessment in the radiobiological experiments at the TOP-IMPLART accelerator carried out at that energy value.

Spectroscopic properties of Eu-doped oxynitride glass–ceramics for white light LEDs

Novel oxynitride glass–ceramics with tremendously improved quantum yield and adjustable color coordinates were prepared with the conventional melt-and-quench method and subsequent annealing heat treatment. X-ray diffraction (XRD) and transmission electron microscopy (TEM) images revealed CaAl2Si2O8 and Y20N4Si12O48 crystalline phases were homogenously precipitated in the glass matrix. The optical absorption and photoluminescence (PL) spectrum measurements showed that a large portion of Eu3+ ions were reduced into Eu2+ which were crystallized into CaAl2Si2O8 phase during the heat treatment by substituting Ca2+ ions in them. Emission spectra evidently show that Eu2+ and Eu3+ ions were preferentially incorporated in CaAl2Si2O8 and Y20N4Si12O48 crystalline phases, respectively. This assignment was further supported by cation ionic radii and local charge balances, as well as defect chemistry considerations. The total emission intensity including both Eu2+ and Eu3+ ions was enhanced with increasing the annealing temperature, due to the conversion of Eu3+ to Eu2+ and the enhanced quantum efficiency of Eu3+ in the crystalline phase as compared to the glass matrix. As a result, the quantum yields (QYs) of the glass–ceramics were also enhanced significantly from 2.07% (the precursor glass) up to 43.33% (the maximum of the glass–ceramics). The emission ratio of Eu2+/Eu3+ changed from <1.0 to >4.0, which led this novel glass–ceramics with adjustable color coordinates ranging from red to blue controlled by varying the annealing temperature.

Observation of ferroelectricity induced by defect dipoles in the strain-free epitaxial CaTiO3 thin film

CaTiO3 is a well-known incipient ferroelectric material that does not undergo a ferroelectric phase transition in spite of the intriguing dielectric constant behavior. Especially, unlike a prototypical incipient ferroelectric SrTiO3, the paraelectric state of CaTiO3 cannot be easily destroyed by small perturbations, including cation doping and epitaxial strain. We present that a nearly strain-free epitaxial CaTiO3 film grown at a low oxygen partial pressure exhibits polarization–voltage hysteresis loops and the distinct difference of piezoresponse force microscopy phase signals, implying that a ferroelectric phase is induced. Such results are shown even at room temperature. We suggest that the observed ferroelectric behavior in CaTiO3 film comes from the defect dipoles composed of vacancies inside the film. Using electron-probe microanalysis and optical absorption spectra measurements, we found that CaTiO3 film has considerable Ca and O vacancies, forming the localized defect state in electronic structure. This work highlights the importance of vacancies and their clusters, such as defect dipoles, in understanding the electronic properties of perovskite oxide thin films, including ferroelectricity.

Electronic structure and lattice dynamics of CaxMg1−xS in the rock-salt phase

Electronic band structure and lattice dynamical properties of CaxMg1−xS alloys in the rock-salt phase have been investigated. The calculations are performed in the framework of ab initio pseudo-potential approach within the generalized gradient approximation. Reasonable agreement is generally obtained between our results and the available experimental observations and previous calculations. The deviation of the alloy lattice constant and bulk modulus from linearity has been examined and discussed. Fundamental band gaps and Г–X and Г–L separations in higher-lying conduction bands are predicted. In agreement with reflectivity spectrum and recent optical absorption spectrum measurements, CaS in the rock-salt phase is found to be an indirect band-gap (Г–X). Similarly to CaS, the electronic band structure calculations showed that MgS is also an indirect band-gap (Г–X) semiconductor. However, a system transition between indirect and direct structures has been predicted in the Ca concentration range 0.12–0.83. Upon alloying the phonon modes are significantly changed showing that the longitudinal optical–transverse optical (LO–TO) splitting becomes narrower as one proceeds from pure rock-salt MgS to pure rock-salt CaS.

Structural and optical properties of 60B2O3–(20−x)Na2O–10PbO–10Al2O3:xTiO2:yNd2O3 glasses

In this work we investigate the effect of replacing Na2O by TiO2 on the structural and spectroscopic characteristics of the Nd2O3-doped 60B2O3–(20−x)Na2O–10PbO–10Al2O3:xTiO2:yNd2O3 borate glass matrix. Measurements of X-ray patterns, glass temperatures (Tg), vibrational (Raman and infrared (IR)) and optical (absorption and emission) spectra were carried out. The trend of Tg, the Judd–Ofelt parameters and Nephelauxetic ratio as the TiO2 and Nd2O3 concentration increases was interpreted quantitatively and qualitatively in terms of the network bonds and coordination numbers. Measurements of Tg across the Nd-doped glass series for different levels of Ti suggests changes in the rigidity of the matrix due to change of coordination of boron oxide resulting from the BO4–BO3 back conversion effect. The changes observed in the Raman and IR spectra are related to the BO3→BO4 conversion effect. The variation of the Judd–Ofelt parameters Ω(2) and Ω(6) indicates that the average rare earth-ligand radius decreases establishing an electronic density distribution when Nd3+ concentration increases. This effect is interpreted in terms of Judd–Ofelt parameters and by the bonding parameter b1/2 due to Nephelauxetic effect.

Design length scales for carbon nanotube photoabsorber based photovoltaic materials and devices

Semiconducting carbon nanotubes are attractive materials for harvesting light in photovoltaic solar cells and photodetectors. A crucial aspect of designing efficient photovoltaic devices using nanotubes is minimizing the length scale for the absorption of light (LA) and maximizing the length scale across which excitons diffuse (LD) in fibers and films of these materials. In order to facilitate the optimization of these parameters, here we model how LA and LD are affected by nanotube bandgap polydispersity, inter-nanotube coupling, film disorder, orientation, and defects. Our models are guided by previous experimental measurements of optical absorption spectra and exciton inter-nanotube transfer rates made on isolated and bundled nanotubes in conjunction with kinetic Monte Carlo simulations. Our results provide criteria for materials selection and the design of efficient carbon nanotube-based light harvesting devices, in various architectures.

Structural and electronic evolution of Cr 2O 3 on compression to 55 GPa

Synchrotron single-crystal x-ray diffraction experiments have been performed on corundum-type Cr 2O 3 up to a pressure of 55 GPa in Ne and He pressure transmitting media. Diffraction experiments were complemented by measurements of optical absorption spectra with single crystal samples up to 60 GPa. Results of the diffraction data analysis rule out the earlier reported monoclinic distortion at 15–30 GPa, but indicate evidence of two discontinuous transitions of electronic or magnetic nature, most likely associated with a change in magnetic ordering and charge transfer. The compression mechanism established from single crystal refinements indicates much smaller distortion of the Cr 3+ coordination environment than was previously assumed.

Optical Absorption Spectrum Measurements of Silicon Based Semiconductor Thin Films by Using a Spectroscopic Photocurrent Method

Optical Absorption Spectrum Measurements of Silicon Based Semiconductor Thin Films by Using a Spectroscopic Photocurrent Method

Small-sized silver nanoparticles for studies of biological effects

The influence of the hydration extent, AOT and silver ion concentration on average particle size and size distribution in micellar solution of silver nanoparticles obtained by biochemical synthesis was investigated. Formation and stability of nanoparticles were controlled by measurements of optical absorption spectra. Particle sizes were determined by transmission electron microscopy. Combinations of varied parameters have been found, making it possible to prepare three micellar solutions of spherical silver nanoparticles with a different average size in the range 4.6–10.5 nm and narrow size distribution (the standard deviation does not exceed 2.5 nm). For the water dispersions prepared from such solutions by the specially developed procedure, possible applications for studies of size effects in the biological action of nanoparticles are also discussed.

Enhanced photoacoustic stability of gold nanorods by silica matrix confinement

Photoacoustic tomography (PAT) has garnered much attention for its high contrast and excellent spatial resolution of perfused tissues. Gold nanorods (GNRs) have been employed to further enhance the imaging contrast of PAT. However, the photon fluences typically needed for PA wave induction often also result in GNR shape changes that significantly reduce the efficiency of acoustic wave generation. In this work, we propose, synthesize, and evaluate amorphous silica-coated gold nanorods (GNR-Si) in an effort to improve contrast agent stability and ameliorate efficiency loss during photoacoustic (PA) wave induction. TEM and optical absorption spectra measurements of GNR and GNR-Si show that encasing GNRs within amorphous silica provides substantial protection of nanorod conformation from thermal deformation. PA signals generated by GNR-Si demonstrate considerably greater resistance to degradation of signal intensity with repetitive pulsing than do uncoated GNRs, thereby enabling much longer, high-contrast imaging sessions than previously possible. The prolongation of high-contrast imaging, and biocompatibility and easy surface functionalization for targeting ligands afforded by amorphous silica, suggest GNR-Si to be potentially significant for the clinical translation of PAT.