Changes In Absorption Spectra Research Articles

Взаимодействие метиленового синего с одноцепочечными полинуклеотидами poly(rA) и poly(rU) и с двухцепочечным полинуклеотидом poly(rA)-poly(rU)

Interaction of dye-intercalator methylene blue (MB) with single-stranded (ss-) polynucleotides poly(rA), poly(rU) and double-stranded poly(rA)-poly(rU) has been studied by the method of absorption spectroscopy at various concentration ratios ligand/phosphate (concentration of ss-polynucleotides by phosphate residue). It was revealed that in the absorption layer of methylene blue, in the wavelength change interval 500≤λ≤750 nm, the absorption spectra of the complexes MB-ss-poly(rA) decrease more sharply, as compared to MB spectrum, along with polynucleotide concentration enhancement in the solution. It was also revealed that the absorption spectra of the complexes MB-ss-poly(rU) decrease moderately at the increase of this polynucleotide concentration in the solution. In the spectra of the complexes MB-ss-poly(rU) a pseudo-isosbestic point is formed, while in the spectra of the complexes MB-ss-poly(rA) there is no such point. The pseudo-isosbestic point is formed also in the spectra of the complexes MB-poly(rA)-poly(rU). It was also revealed that the absorption spectra of the complexes of MB with ss-poly(rA) and poly(rA)-poly(rU) are shifted to the longer wavelengths by ~5-7 nm, while the shift in the absorption spectra of the complexes MB-ss-poly(rU) composes almost ~2 nm. The absorption spectra changes of the complexes of MB with the mentioned polynucleotides indicate that MB shows higher specificity to poly(rA), as compared to poly(rU) and poly(rA)-poly(rU). The obtained data also indicate that MB binds to poly(rA) and poly(rA)-poly(rU) by intercalation and electrostatic modes, and with ss-poly(rU) – mainly by electrostatic mechanism.

Enhancing the Terahertz Absorption Spectrum Based on the Low Refractive Index All-Dielectric Metasurface

We presented an angle-multiplexing low refractive index dielectric metasurface for terahertz absorption spectrum enhancement of lactose with high Q resonance properties. The unit cell structure of the acrylonitrile butadiene styrene (ABS) square structure is designed and optimized. The resonant peak shifts of the dielectric metasurface are analyzed by changing the incident angle of the terahertz wave. Then the α-lactose films with different thicknesses are added to investigate the enhancement effect. The resonant peak amplitude of the angle-multiplexing low refractive index dielectric metasurface absorption spectrum changes greatly with the absorption spectrum of the samples. The results illustrate that the enhanced absorption spectrum formed by the linked envelope can be up to 45 times stronger than that without the unit cell structures and also exhibits a high-quality factor. The proposed dielectric metasurface provides great potential in enhancing the terahertz absorption spectrum.

Selective Recognition and Reversible “Turn-Off” Fluorescence Sensing of Acetate (CH3COO−) Anion at Ppb Level Using a Simple Quinizarin Fluorescent Dye

A simple and cost-effective optical sensing system based on quinizarin fluorescent dye (QZ) for the selective and reversible sensing of CH3COO− anions is reported. The anion binding affinity of QZ towards different anions was monitored using electronic absorption and fluorescence emission titration studies in DMSO. The UV-visible absorption spectrum of QZ showed a decrease in the intensity of the characteristic absorption peaks at λ = 280, 323, and 475 nm, while a new peak appeared at λ = 586 nm after the addition of CH3COO− anions. Similarly, the initial strong emission intensity of QZ was attenuated following titration with CH3COO− anions. Notably, similar titration using other anions, such as F−, Cl−, I−, NO3−, NO2−, and H2PO4-, caused no observable changes in both absorption and emission spectra. The selective sensing of CH3COO− anions was also reflected by a sharp visual color change from bright green to faint green under room light. Further, the binding was found to be reversible, and this makes QZ a potential optical and colorimetric sensor for selective, reversible, and ppb-level detection of CH3COO− anions in a DMSO medium.

Structural, DFT calculations and photophysical and photochemical characteristics of 1-((E)-2-phenylethenyl)-2-(4-(2-((E)-2-phenylethenyl) phenoxy) butoxy) benzene (PPPBB)

X-ray single crystal structure and spectroscopic and photophysical parameters of the titled compound were studied. The titled compound shows thermal stability prior to melting at 126.17 °C with Δ H value of 109.991 J g−1. Photophysical parameters include singlet electronic absorption, molar absorption coefficient, oscillator strength, and dipole moment of electronic transition, fluorescence spectra, excited state lifetime, and fluorescence quantum yield for 1-((E)-2-phenylethenyl)-2-(4-(2-((E)-2-phenylethenyl) phenoxy) butoxy) (PPPBB) in different solvents. PPPBB displays a little change in maximum absorption and emission spectra with solvent polarity, indicating a slight change in dipole moment of dye molecules upon excitation. The dipole moments' (Δ μ) difference between the excited and ground states was obtained from the Lippert–Mataga method. Ground and electronic excited states' geometric optimization was performed using density functional theory (DFT) and time-dependent density functional theory (time dependent-DFT), complemented with spectral findings. A good agreement between theoretical data and experimental observations was found. The net photochemical quantum yield (φc) of PPPBB dye was calculated in various solvents.

Detection of tomato leaf curl New Delhi virus DNA using U-bent optical fiber-based LSPR probes

The detection of Tomato leaf curl New Delhi virus (ToLCNDV) DNA has been presented using U-bent fiber optic sensor (FOS) by an evanescent wave absorption method in the visible region. The localized surface plasmon resonance (LSPR) based FOS was developed by immobilizing gold nanoparticles on the amine-functionalized surface and the receptor probe was prepared by attaching a short segment of the complementary DNA (cDNA) on this surface. Further, the cDNA attachment was confirmed by monitoring the real-time change in LSPR absorption spectra. The conjugation protocol of single-strand DNA (ssDNA) from the viral genome of ToLCNDV was established like antibody-antigen-based assays by observing the real-time change in absorption kinetics. Consequently, a linear correlation between ssDNA concentration and the conjugation-dependent change in refractive index (RI) has been observed. The limit of detection (LOD) using two different cDNA immobilized FOS probes was determined to be 50±10 ng/μL and the change in RI was found 12.5±1.3×10−4 RIU/Abs. From this systematic binding study, a straightforward target-specific sensor has been constructed using a digital electronic logic gate analogy. This device has significant commercial potential for the development of a portable LSPR sensor for real-time detection of plant pathogens in addition to the possibility of multi-target environments.

Synthesis and characterization of novel Al(III)‐metallopolymer and its application as a non‐volatile resistive memristive material

AbstractIn this study, Al(III)‐metallopolymer is synthesized with our previously reported ligand to understand the difference in the interaction of the reported ligand with transition metal ions (Fe(II) and Cr(II) ions) and smaller cationic radius main group metal ion. Al(III)‐metallopolymer is thoroughly characterized by different analytical techniques to understand the structure–property relationship. Surface morphological analyses reveal the formation of long nano‐fiber strands on the respective substrates. This polymer has shown reversible redox behavior, which is ligand centric as no d‐orbitals are available on the central metal ion for the electron push‐pull mechanism. Al(III)‐metallopolymer is fluorescent active, and it is shown a reversible change in absorption spectrum on the application of the appropriate potential. This ligand‐based redox‐switching also generates a bistable state when a metal–insulator(thin film of polymer)‐metal sandwich device is probed in between ±1 V, and it is stable in the ambient condition to sustain several flip‐flop cycles without any degradation for 103 s as observed from the experimental data. This work enlightens a new metallopolymer with a low value of SET‐RESET voltage and a long retention time for the future memristive device, which can operate at very low voltage compared to conventional Si‐based memory chips.

Brain temperature monitoring in newborn infants: Current methodologies and prospects.

Brain tissue temperature is a dynamic balance between heat generation from metabolism, passive loss of energy to the environment, and thermoregulatory processes such as perfusion. Perinatal brain injuries, particularly neonatal encephalopathy, and seizures, have a significant impact on the metabolic and haemodynamic state of the developing brain, and thereby likely induce changes in brain temperature. In healthy newborn brains, brain temperature is higher than the core temperature. Magnetic resonance spectroscopy (MRS) has been used as a viable, non-invasive tool to measure temperature in the newborn brain with a reported accuracy of up to 0.2 degrees Celcius and a precision of 0.3 degrees Celcius. This measurement is based on the separation of chemical shifts between the temperature-sensitive water peaks and temperature-insensitive singlet metabolite peaks. MRS thermometry requires transport to an MRI scanner and a lengthy single-point measurement. Optical monitoring, using near infrared spectroscopy (NIRS), offers an alternative which overcomes this limitation in its ability to monitor newborn brain tissue temperature continuously at the cot side in real-time. Near infrared spectroscopy uses linear temperature-dependent changes in water absorption spectra in the near infrared range to estimate the tissue temperature. This review focuses on the currently available methodologies and their viability for accurate measurement, the potential benefits of monitoring newborn brain temperature in the neonatal intensive care unit, and the important challenges that still need to be addressed.

Uniaxial Strain Engineering via Core Position Control in CdSe/CdS Core/Shell Nanorods and Their Optical Response.

Anisotropic strain engineering has emerged as a powerful strategy for enhancing the optoelectronic performance of semiconductor nanocrystals. Here, we show that CdSe/CdS dot-in-rod structures offer a platform for fine-tuning the optical response of CdSe quantum dots through anisotropic strain. By controlling the spatial position of the CdSe core within a growing CdS nanorod shell, varying degrees of uniaxial strain can be introduced. Placing CdSe cores at the end of the CdS nanorod induces strong asymmetric compression along the c-axis of the wurtzite CdSe core, dramatically altering its absorption and emission characteristics, whereas CdSe cores located near the middle of the nanorod experience a comparatively weak uniaxial strain field. The change in absorption and emission spectra and dynamics for highly strained end-position CdSe/CdS nanorods is explained by (1) relative shifting of the valence band light hole and heavy hole levels and (2) introduction of a strong piezoelectric potential, which spatially separates the electron and hole wave functions. The ability to tune the degree of uniaxial strain through core position control in a nanorod structure creates opportunities for precisely modulating the electronic properties of CdSe nanocrystals while simultaneously taking advantage of dielectric and optical anisotropies intrinsic to 1D nanostructures.

New stilbene-biscarbothioamide based colorimetric chemosensor and turn on fluorescent probe for recognition of Hg2+ cation

A new symmetrical biscarbothioamide based stilbene 2,2′-(4,4′-(ethene-1,2-diyl)bis(benzoyl))bis(N-phenylhydrazine-1-carbothioamide) (TUS) as turn on fluorescent probe and colorimetric chemosensor for detection of mercury cation was synthesized and characterized by NMR spectra, Mass spectra, IR spectra, and elemental analyses. The selectivity towards various metal cations was investigated at pH 5, TUS exhibited good colorimetric selectivity to Hg2+ ion that could be directly observed by naked-eye color change from colorless to faint yellow with short response time. Moreover, the stoichiometric ratio and the interaction of TUS fluorescent probe with Hg2+ was determined to be 1:2 complex formation, which confirmed by Job's plot, mass spectra and 1H NMR titration. The detection limit of TUS towards Hg2+ was calculated to be 0.15 µM. The effect of the pH change in absorption and emission spectra with the absence and presence of Hg2+ cations were studied. The TUS was used for bio-imaging of HepG-2 cells and intracellular detection of Hg2+ by confocal microscope.

Naked-Eye-Detectable Supramolecular Sensing System for Glutaric Acid and Isophthalic Acid

Abstract We report a molecular sensor, comprising a porphyrin core and four 2-aminoquinolyl groups at meso positions, for the naked-eye detection of glutaric acid and isophthalic acid, both featuring a C3 spacer between two CO2H groups. In the presence of the C3 dicarboxylic acids, solutions of the porphyrin sensor underwent significant changes in color and absorption spectra. NMR spectroscopy and X-ray crystallography revealed that the porphyrin derivative bound to two molecules of the C3 dicarboxylic acids selectively to form 1:2 complexes, which dimerized through strong π-stacking interactions. Magnetic circular dichroism (MCD) spectroscopy and density functional theory (DFT) calculations suggested that the red-shifting of the Q-bands in the absorption spectra of the porphyrin derivative arose from tilted quinolyl rings in the dimeric complexes. In addition, we found that a test strip containing the porphyrin sensor could also be used to efficiently detect glutaric acid and isophthalic acid.

A New Way to Predict the Efficiency of Optical Limiters without Providing an Experiment: Processing of TDDFT Calculations for the Case of Pure Two-Photon Absorption.

Laser-power-limiting devices play a predominant role in photonics because of their potential for protecting human eyes and optical devices that are sensitive to intense laser beams. This paper describes a new methodology for predicting the efficiency of optical limiting based on electric-field-induced changes in absorption spectra calculated with the TDDFT quantum-chemical method. Analytical equations are derived to evaluate the optical thresholds and speed of switching on, the dynamic range, and the degree of nonlinear attenuation of the radiation fluxes for the case of two-photon absorption. Thus, the researcher does not need to conduct costly experiments to evaluate the suitability of nonlinear absorbers for the creation of optical limiters. The possibility of developing a forecasting model is demonstrated by an example of a series of stable slipped-cofacial phthalocyanine J-type dimers, which were synthesized and investigated previously.

Scrutinzing the interaction of bovine serum albumin and human hemoglobin with isatin-triazole functionalized rhodamine through spectroscopic and In-silico approaches

• Spectral methods have been used to investigate the interaction of R1 with HHb and BSA. • Thermodynamic parameters suggested exothermic spontaneous binding processes involving hydrogen bonding and van der Waal interaction. • Molecular docking and molecular dynamics have been utilized to discuss the principle binding sites of proteins for R1 . • R1 proposes preferentially binding to the hydrophobic cavity in site III of proteins. A Rhodamine-based fluorescent probe R1 has been successfully utilized to detect BSA and HHb proteins via non-covalent bonding. The protein binding nature with R1 has been unravelled by the characteristic changes in absorption, emission and circular dichroism spectra that indicated their noticeable interaction. The experimental results have also shown the moderate strength between proteins and R1 from the quenching of proteins through the static quenching mechanism. The hyperchromism in the absorption band of proteins with R1 has given vital information and binding affinity values have been calculated from Stern-Volmer plots. The calculated values of the thermodynamic parameters revealed a spontaneous binding processes occurring primarily via hydrogen bonding and van der Waal interactions. Furthermore, in-silico approaches have been utilized to make a comparison and conclusion with spectroscopic results. The outcome of these studies could be useful to examine the drug-protein binding for further exploitation.

Carbon nanotube resonator enhancement of Majorana fermions induced slow light in a hybrid semiconductor/superconductor device

We theoretically investigate the Rabi-like splitting in the absorption spectrum of a single electron spin mediated by Majorana fermions in a hybrid semiconducting nanowire/superconductor system. The absorption spectra can display the symmetrical splitting phenomenon, and their related optical propagation such as fast light and slow light are investigated in different parametric regimes. When we consider implanting a spin into the carbon nanotube (CNT) resonator, the Rabi-like splitting in the absorption spectrum changes into asymmetric Fano resonance, which is accompanied by the rapid steep dispersion promising the slow- or fast-light effect, and even reaching tunable fast-to-slow light propagation (or vice versa) with controlling different parameter regimes. Moreover, we also investigate the role of the CNT resonator, which behaves as a phonon cavity enhancing the fast and slow light effect.

Surface-Oxidized Polymer-Stabilized Silver Nanoparticles as a Covering Component of Suture Materials.

In this work, we obtained silver nanoparticles stabilized with polyvinylpyrrolidone, ranging in size from 70 to 110 nm, which exhibits good crystallinity and anisotropic structure. For the first time, we studied the influence of the molar ratio of silver between silver and peroxide on the oxidation process of the nanoparticles and determined the regularities of this process by analyzing changes in absorption spectra. Our results showed that at molar ratios of Ag:H2O2 = 1:1 and 1:5, dependences of changes in the intensity, position and half-width of the absorption band of the plasmon resonance are rectilinear. In vivo studies of silver nanoparticles have shown that silver nanoparticles belong to the toxicity class III (moderately hazardous substance) and to the third group according to the degree of accumulation. We established that silver nanoparticles and oxidized silver nanoparticles form a uniform layer on the surface of the suture material. We found that the use of the suture material with silver nanoparticles and oxidized silver nanoparticles does not cause allergic reactions in the organisms of laboratory animals.

Copper (I)-catalyzed ‘Quick Click’ generated 1,2,3-triazole anthraquinone linkers for selective detection of Fe (II) ions

The current report describes a fast and high yielding synthesis of 1,4-dihydroxyanthraquinone based 1,2,3-triazole linkers T1 and T2 through a stereoselective Copper (I) – catalyzed alkyne azide cycloaddition (CuAAC) reaction and their sensing behavior for the selective detection of Fe(II) ions by UV–Visible spectroscopy. UV–Visible absorption studies were performed using 0.5 mM solution of testing probes in 4:1 acetonitrile/water (v/v) solvent with a set of metal ions such as Mn (II), Cd (II) Hg (II), Ni (II), Pb (II), Zn (II), Fe (II), Fe (III), Ce (III), Cr (III), Co (II), Ba (II), K (I) and Na (I). The significant change in absorption spectrum was observed for both the probes with the addition of Fe (II) ions. The spectrograms recorded with the successive increase in concentration of Fe (II) ions from 0.013 mM to 0.14 mM shows isosbestic points at two particular wavelengths along with an observable blue shift of 4 nm and 7 nm in between the isosbestic points for probes T1 and T2 respectively and the limit of detection of 10 µM for triazole derivative T1, where as it is 9.3 µM for T2.

Вплив опромінення фізіологічного розчину високоенергетичними електронами на фізико-хімічні властивості та цитотоксичну активність доксорубіцину

The effect of preliminary irradiation of an aqueous solution of sodium chloride (saline) with 1 MeV high-energy electron beams on optical and cytotoxic/cytostatic properties of the dissolved Doxorubicin cancer drug is studied. With the use of Lewis lung carcinoma cell culture, it has been shown that the said treatment results in an increased cytotoxic/cytostatic action of the Doxorubicin, being the most pronounced in the range of low concentrations of the drug. The delivered dose of ionizing radiation on the saline ranged from 4 to 80 kGy. The maximum changes in the IR absorption spectra of Doxorubicin have been observed for the solutions irradiated with 10 kGy. The possible causes of the observed effects are discussed.

4-(1H-Imidazo[4,5-f][1,10]phenanthrolin-2-yl)benzaldehyde as a probe in pure solvents: Solvatochromism, electric dipole moment and pH influence

The spectral properties of 4-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)benzaldehyde (1) in eleven organic solvents of different polarity have been studied. In order to determine the contributions of specific and non-specific interactions between the considered compound and the solvents, the solvatochromic Lippert-Mataga, McRae, Bakhshiev methods have been applied. The compound demonstrates positive solvatochromism. The dipole moment of the excited state of 1 obtained using the Reichardt method is equal to 10.56/7.08 D for trans- and cis-conformers, respectively, and agrees well with the theoretically calculated value. The influence of the polarizability of 1 on changes in the dipole moments has been analyzed using the Bilot-Kawski method. The multiple linear regression analysis in the framework of the Kamlet-Abboud-Taft and Catalán models has highlighted that the main properties which determine the Stokes shift of 1 are the acidity and dipolarity of the solvent. The variation of pH by additions of acid or base to solution 1 leads to significant changes in absorption and fluorescence spectra, therefore, 1 can be of interest as a solvatochromic probe, being sensitive to acidic/base properties of the environment. It has also been found out that the anion form of 1 is present in the DMSO solution. An addition of N,N-dimethylcyclohexylamine intensifies the dissociation of the considered compound in the DMSO solution and suppresses the fluorescence at a large amine excess.

Constructing ultra-stable photothermal plastics assisted by carbon dots with photocaged reactivity

Constructing ultra-stable photothermal plastics assisted by carbon dots with photocaged reactivity

Synthesis, characterization and applications of schiff base chemosensor for determination of Cu2+ ions

A novel thiazole-based Schiffbase chemosensor SB1 with N- and O- donor atoms was synthesized and characterized by different techniques (UV–vis, 13C NMR, 1H NMR, and FT-IR analysis). The chemosensor SB1 was used for the determination of Cu2+ ions in various samples. The significant spectral changes in absorption spectra of chemosensor SB1 at 220 and 416 nm and the color change from light yellow to yellowish-brown indicate high selectivity and sensitivity towards Cu2+ ions as compared to other cations (Na+, K+, Ag+, Zn2+, Ni2+, Pb2+, Mn2+, Mg2+, Co2+, Cd2+, Sn2+, Hg2+, Cr3+, Fe3+, and Al3+). The sensing mechanism of SB1 was investigated through various techniques such as FT-IR, UV–vis and 1H NMR titration experiment and further confirmed by DFT computational studies. The 2:1 binding mode between SB1 and Cu2+ ions was confirmed by Job‘s plot using UV–vis spectrophotometry. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.015 and 0.0471 µg mL−1, respectively. The percent recovery of Cu2+ from various environmental samples was found to be 95.00–103.33% at various levels. These obtained results demonstrate that chemosensor SB1 is a cost-effective, facile, selective, sensitive, and colorimetric sensing platform to detect trace amounts of Cu2+ ions in variousenvironmental and agricultural samples.

Quantitative exploration of the absorber behavior of metal–insulator–metal metamaterials within terahertz via an asymmetric peak model

Terahertz (THz) metamaterials have been developed for THz sensing, detection, imaging, and many other functions due to their unusual absorbers. However, the unusual absorption spectra change with different incident angles. Thus, we designed and fabricated a focal plane array with metal-insulator-metal (MIM) structure metamaterial absorbers for further research. The absorption spectrum with incident angles from 20 to 60 was measured using THz time-domain spectroscopy (THz-TDS), and the experimental results reveal that the absorption spectrum changes with incident angle variations. A basic analytical asymmetric peak model for extracting absorption-frequency characteristics was developed in this study to quantitatively explore this variation in the absorber behavior with incident angles. The best result was that the frequency corresponding to the highest absorption can be easily found using this peak model. The experimental data was coherent with the validation of the asymmetric peak model. Moreover, a second model to quantitatively relate parameters to the incident angle was discovered, allowing for the prediction of absorption spectrum shifts and changes. The absorption spectrum was predicted to have a valley-like absorption curve at particular incident angles based on the secondary models deduction. The proposed extraction method's essential feature is that it can be applied to any physics-based MIM metamaterial system. Such a model will guide the design and optimization of THz metamaterial absorbers, sensors, imagers, and many others.