Method For Spectral Characterization Research Articles

Synthesis of new polyazomethine-based pyrazole moieties as promising biologically active macromolecules

ABSTRACT Using the polycondensation technique, it was possible to synthesize a new class of biologically active polyazomethine based on pyrazole moiety. The polymerization occurred through the interaction between terephthalaldehyde and various derivatives of diaminopyrazole. The polymers that were made were given the letters PAZm/Py1–4 to reflect the different diaminopyrazole derivatives that were used. The monomer and polymer structures were investigated by common spectral characterization methods. The new PAZm/Py1–4 were examined by gel permeation chromatography (GPC), solubility tests, thermogravimetric analysis (TGA), X-ray diffraction analysis (XRD), and scanning electron microscopy (SEM). The newly synthesized polymers have high thermal stability and normal crystalline behavior. The antibacterial properties of all synthesized polymers were evaluated against the Gram-positive bacteria and the Gram-negative bacteria. Additionally, two types of fungi were used to test how well the prepared polymers worked against fungi. PAZm/Py1 and PAZm/Py4 showed slight antibacterial activity against the representative Gram-positive bacteria, while PAZm/Py2 and PAZm/Py3 had no significant influence. All the tested polymers showed slight to moderate antibacterial activity against the representative Gram-negative bacteria. PAZm/Py1 and PAZm/Py4 had a greater antifungal influence than other polymers.

Online Testing Method for the Fine Spectral Characteristics of Narrow-Band Interference Filters Based on a Narrow-Linewidth Tunable Laser.

The transmission spectrum of a narrow-band interference filter is crucial and highly influenced by factors such as the temperature and angle, thus requiring precise and online measurements. The traditional method of measuring the transmission spectrum of an interference filter involves the use of a spectrometer, but the accuracy of this method is limited. Moreover, placing a narrow-band interference filter inside a spectrometer hinders real-time online measurements. To address this issue, there is demand for high-precision online spectral testing methods. In response to this demand, we propose and experimentally validate a fine spectral characterization method for narrow-band interference filters. This method uses a narrow-linewidth tunable laser, achieving a spectral resolution in the MHz range for online testing. Two types of narrow-band interference filters were tested using the constructed laser spectroscopy experimental system, obtaining a transmission spectrum with a spectral resolution of 318 MHz. In comparison to spectrometer-based methods, our proposed method demonstrates higher spectral accuracy, enables online measurements, and provides more accurate measurements for special spectral interference filters. This approach has significant application value and promising development prospects.

Preparation of Chalcone-Azo reagents and study of their chemical analysis, thermal studies, and biological effects against fungi

Chalcone reagents are used in various fields because of their biological, medical, and medicinal properties. Therefore, this study aimed to prepare a new reagent of Chalcone–Azo and study its chemical and physical properties using different techniques. In this recent work, four reagents were created and tested using thermal behavior in stability curves, solubility in various solvents, and spectral characterization like UV-visible FT-IR. In addition, a biological study was conducted to estimate the effect of these reagents on two types of fungi. Results showed that spectral characterization methods (UV-visible and FT-IR) showed that new groups of compounds were formed, and starter reactants disappeared. This is good proof of forming new reagents. The outcome of thermal behavior in stability curves solubility in various solvents emphasizes these results. The study of using the new reagents as antifungal substances showed that reagent {3} had the highest effect on inhibiting study fungi growth, followed by reagent {4}. Keywords: Reagent, analytical, thermal, fungi, bioassay

Synthesis, covalency parameters, energy calculations and crystal features of acylpyrazolone derived pentavalent Uranyl complex along with DFT and Hirshfeld analysis

A σ-donating acylpyrazolone DMBPMP (4-(3,5-dimethyl benzoyl) 1-phenyl 3-methyl 5-pyrazolone) ligand and its Uranyl acylpyrazolone complex [UO2(DMBPMP)2(EtOH)] were synthesized to analyze the nature of covalency, reactivity, and redox properties. The structure, pentavalent bipyramidal geometry, and complex composition are mainly scrutinized through their single-crystal x-ray crystal data, molar conductivity, gravimetric estimation, FTIR significant vibrations, δ-values of 1H NMR, 13C NMR and TG-DTA plots. The covalency of the Uranyl complex mainly depends on average bond length values on the pentagonal equatorial plane, Uranyl axial bond lengths, stretching frequency values, coordinated solvent on the fifth coordination site, and different aryl group substitution on the first position of the pyrazolone ring; and it can be confirmed through FTIR, single-crystal, and electronic UV–Vis spectral characterization methods. The UV–Vis data was also valuable for identifying n → π*, π → π*, and LMCT transitions and calculating Sinha’s covalency parameters, which shows that the complex can show maximum covalent character in DMSO solvent and covalency decreases in DMSO > DMF > Ethyl acetate > Ethanol > CHCl3 order. DFT calculations were performed to get an excellent correlation and comparison with all experimental values. This correlation and comparision is helpful to identify global index parameters to get an idea of the physical as well as chemical properties of such systems and to confirm the characteristics theoretically by HOMO-LUMO energy gap, theoretical vibrations, natural electronic configuration, and NBO charges. The Hirshfeld surface analysis was also carried out to identify the crystal strength through interaction energies and energy frameworks in the ligand and intermolecular non-covalent surface interactions with fingerprint plot details in both ligand and complex. Electro-chemical analysis in CV-DPV plots provides information on the redox properties of uranyl moiety.

Exploration of Role of Concentration on Sensing Activities using Novel unsymmetrical Schiff bases

Simultaneous condensation reaction of thiocarbohydrazide with simple aromatic aldehyde and highly reactive ferrocenecarboxaldehyde resulted with unusual unsymmentric Schiff bases associated with multi metal ion sensing property. Spectral characterization methods indicate the formation of the new materials. Guest- host relationship established between various metal ions and receptors changes the electronic spectra drastically and for the addition of Cu2+ ions, formation of MLCT charge transfer band responsible for the coordination of metal ion with receptor has been noticed. Data calculated from the results of responses recorded for the applied potential to the metal added and metal free receptor solution exposes the concentration of metal ions required for the effective sensing process.

Demonstration of a New Characterization Method for Weak Measurement.

In this work, the difference between the weak measurement method and the weak value amplification process and the classical measurement process is thoroughly discussed, and the transition conditions of the weak value enhancement are obtained. A transition mode of the weak measurement and the classical measurement is proposed for the first time, and a better fitting model of the measurement results is found by performing a systematic analysis. On top of that, the importance of the new fitting method for the application of the weak measurement system is verified during the industrial production of organic molecular -nucleic acid, protein, polysaccharide-hydrolysis or synthesis. At the same time, a variety of spectral characterization methods are proposed and the advantages and disadvantages of the different characterization methods are analyzed through carrying out experiments. Consequently, the wide implementation of weak measurement-based detection technology is attained.

Retrieving the refractive index of a sphere from the phase spectrum of its light-scattering profile

We studied the Fourier spectrum of the light-scattering profiles of single particles in the Rayleigh-Gans-Debye (RGD) and Wentzel–Kramers–Brillouin (WKB) approximations. In the case of a homogeneous sphere, we found the relationship between the key parameters of the spectrum (including its phase) and the sphere characteristics – both analytically and numerically in the framework of the approximations and the rigorous Lorentz–Mie theory, respectively. Based on these results, we have improved the existing spectral characterization method for spheres extending the applicability range to particles with a higher refractive index.

Nitrogen vacancy type defect luminescence of AlN nanopowder

Abstract Native luminescent defects were investigated in AlN nanopowder (NP) using spectral characterization methods. Photoluminescence and its excitation spectra were studied within a wide temperature range from 8K up to room temperature. It was found that in AlN NP a broad luminescence band appears within a blue spectral region consisting of at least two sub-bands at 415 nm and 390 nm, which can be related to presence of two different but in the same time similar defect types. These luminescent defects are located either inside the bulk material or on the material surface. Interaction of the surface defects with environmental oxygen was found resulting in quenching of the blue luminescence (BL). Three BL mechanisms were revealed, depending on spectral region of the exciting light, resulting in intra-center luminescence, recombination luminescence and exciton caused luminescence. Variations of the F-centers are proposed to be responsible for the BL in AlN NP.

Sensitive detection and estimation of particle non-sphericity from the complex Fourier spectrum of its light-scattering profile

We develop a fast method to estimate the non-sphericity of arbitrary-shaped particles from the complex Fourier spectrum of its light-scattering profile (LSP), measured with the scanning flow cytometer (SFC). We show that previously used amplitude spectrum is not sufficiently sensitive to the non-sphericity and extensively study the phase of the spectral peak for spheroids in the framework of the Rayleigh–Gans–Debye (RGD) approximation. Based on this analysis we construct a new spectral parameter P – the weighted deviation of the complex spectrum around the peak from that for an equivalent sphere determined by the previously published spectral characterization method for spheres (SCMS). We also propose a geometric indicator of non-sphericity η as the relative volume difference from that of the best-fit sphere. These two new parameters apply to particles of arbitrary shape and strongly correlate with each other for rigorously simulated LSPs for spheroids and biconcave disks in a wide range of sizes, refractive indices, and orientations. This correlation is the core of the new method, allowing one to provide both the estimate and the confidence range of η from the experimental value of P. The method is both sensitive and specific to small non-sphericity. For instance, the median error of estimated aspect ratio for simulated LSPs of spheroids is 0.024. We test the resulting algorithm on the real experimental measurements of milk fat globules and red blood cells (RBCs) during the spherization process. These results raise a question about the actual shape of a spherized RBC in the flow inside the SFC. The applicability domain of the method is determined mainly by that of the SCMS and includes biological objects with sizes larger than 7 wavelengths in the liquid host medium. Moreover, we briefly discuss the potential extension of the method to larger refractive indices.

High-resolution multi-scan compact Fourier transform-infrared spectrometer.

The Fourier transform-infrared (FT-IR) spectrometer is a widely used high-resolution spectral characterization method in materials, chemicals, and more. However, the inverse relation between the spectral resolution and the interferometer's arm length yields a tradeoff between spectral resolution and spectrometer footprint. Here, we introduce a novel method to overcome this traditional FT-IR resolution limit. The enhanced high-resolution multi-scan compact FT-IR spectrometer we present achieves an effectively long interferogram by combining multiple short FT-IR scans. Simulation and experimental results demonstrate a significant increase in the spectral resolution of a FT-IR spectrometer by employing our interferogram stitching algorithm.

Spectral analysis for broadband fluorescence: temperature sensing with the YAG:Ce phosphor as an example

Temperature-dependent fluorescence of YAG:Ce was studied as an example of a spectral characterization method. According to the steady-state emission at various temperatures, four types of temperature sensing functions were retrieved using behaviors of 1) wavenumber at emission band maximum magnitude, 2) wavenumber of emission band barycenter, 3) emission bandwidth, and 4) the ratio of intensities at different wavelengths in the emission band. All four types of functions demonstrate a near linear relationship with temperature in the measured temperature range. Function No. 2 shows finer precision than function No. 1, while they have the same meaning in physics. Mechanisms of the temperature dependence are discussed after a brief review of emission peak shifts of Ce3+-doped garnets. Function No. 3 shows an abnormal narrowing of the band with increasing temperature which can be related to the narrowing ground levels’ splitting gap. In the experiment, the two novel spectral characterization methods showed their advantages: the barycenter technique contains the smallest uncertainty, and the self-referenced intensity ratio technique provides flexible ratiometric sensing functions for various measurement needs.

Binary pseudo-random patterned structures for modulation transfer function calibration and resolution characterization of a full-field transmission soft x-ray microscope.

We present a modulation transfer function (MTF) calibration method based on binary pseudo-random (BPR) one-dimensional sequences and two-dimensional arrays as an effective method for spectral characterization in the spatial frequency domain of a broad variety of metrology instrumentation, including interferometric microscopes, scatterometers, phase shifting Fizeau interferometers, scanning and transmission electron microscopes, and at this time, x-ray microscopes. The inherent power spectral density of BPR gratings and arrays, which has a deterministic white-noise-like character, allows a direct determination of the MTF with a uniform sensitivity over the entire spatial frequency range and field of view of an instrument. We demonstrate the MTF calibration and resolution characterization over the full field of a transmission soft x-ray microscope using a BPR multilayer (ML) test sample with 2.8 nm fundamental layer thickness. We show that beyond providing a direct measurement of the microscope's MTF, tests with the BPRML sample can be used to fine tune the instrument's focal distance. Our results confirm the universality of the method that makes it applicable to a large variety of metrology instrumentation with spatial wavelength bandwidths from a few nanometers to hundreds of millimeters.

Passive localization of surface vessels in shallow water using broadband, unintentionally radiated noise

The waveguide invariant relates ocean waveguide propagation conditions to the spectral interference patterns (or striations) in range-frequency plots. The striations are the result of interaction between propagating modes. A method of source localization, using a horizontal line array (HLA), that exploits this relationship will be presented. Source azimuth is estimated using conventional Bartlett beamforming, after which source range is estimated from spectral interference observed along the HLA as well as knowledge of the waveguide invariant. Automation of this process makes use of a spectral characterization method for striation slope estimation, which works well in some but not all cases. The use of a physics-based, range-dependent waveguide invariant model to improve the range estimates will also be discussed. This method has been applied to acoustical data recorded in 2007 at the Acoustical Observatory off the coast of Port of the Everglades, Florida. Localization results compare favorably with radar-based Automatic Identification System (AIS) records. [Work supported by ONR Undersea Signal Processing.]

Spectral Characterization of Near-Infrared Acousto-optic Tunable Filter (AOTF) Hyperspectral Imaging Systems Using Standard Calibration Materials

In this study, we propose and evaluate a method for spectral characterization of acousto-optic tunable filter (AOTF) hyperspectral imaging systems in the near-infrared (NIR) spectral region from 900 nm to 1700 nm. The proposed spectral characterization method is based on the SRM-2035 standard reference material, exhibiting distinct spectral features, which enables robust non-rigid matching of the acquired and reference spectra. The matching is performed by simultaneously optimizing the parameters of the AOTF tuning curve, spectral resolution, baseline, and multiplicative effects. In this way, the tuning curve (frequency-wavelength characteristics) and the corresponding spectral resolution of the AOTF hyperspectral imaging system can be characterized simultaneously. Also, the method enables simple spectral characterization of the entire imaging plane of hyperspectral imaging systems. The results indicate that the method is accurate and efficient and can easily be integrated with systems operating in diffuse reflection or transmission modes. Therefore, the proposed method is suitable for characterization, calibration, or validation of AOTF hyperspectral imaging systems.

Novel spectral characterization method for color printer based on the cellular Neugebauer model

The cellular Yule-Nielson spectral Neugebauer (CYNSN) model to characterize a typical CMYK (i.e., cyan, magenta, yellow, and black) 4-ink color printer is presented. By reconstructing spectral reflectance, models with high accuracy of spectral and colorimetric predictions are built. A novel cell-searching algorithm is proposed and used together with the iteration method to invert the cellular Neugebauer model efficiently. Large numbers of high quality hardcopy samples are produced to evaluate model performance and prove the feasibility of the algorithm. The spectral-based model performs better compared with the usual model based on CIE1931 XYZ tristimulus values.

Spectral characterization and calibration of AOTF spectrometers and hyper-spectral imaging systems

The goal of this article is to present a novel method for spectral characterization and calibration of spectrometers and hyper-spectral imaging systems based on non-collinear acousto-optical tunable filters. The method characterizes the spectral tuning curve (frequency–wavelength characteristic) of the AOTF (Acousto-Optic Tunable Filter) filter by matching the acquired and modeled spectra of the HgAr calibration lamp, which emits line spectrum that can be well modeled via AOTF transfer function. In this way, not only tuning curve characterization and corresponding spectral calibration but also spectral resolution assessment is performed simultaneously over the whole imaging plane. The obtained results indicated that the proposed method is efficient, accurate and feasible for routine calibration of AOTF spectrometers and hyper-spectral imaging systems and thereby a highly competitive alternative to the existing calibration methods.

Estimation of spectral reflectance of object surfaces with the consideration of perceptual color space

Due to the nonlinear transform from spectral reflectance to CIELAB values, the solution obtained by minimizing reflectance error in traditional spectral characterization methods will not be optimal when evaluated by colorimetric error. We propose a reflectance estimation method with consideration of perceptual color space. It combines two approaches, i.e., colorimetric-based spectral calculation and weighted spectral calculation. The experimental results show that the proposed method performs better than previous methods in terms of color difference with very slight degradation in spectral accuracy.