Analysis Of Absorption Spectra Research Articles

Study of morphology, phase composition, optical properties, and thermal stability of hydrothermal zirconium dioxide synthesized at low temperatures.

Oxide nanoparticles exhibit unique features such as high surface area, enhanced catalytic activity, and tunable optical and electrical properties, making them valuable to various industry applications as well as for the development of new research projects. Nowadays, ZrO2 nanoparticles are widely used as catalysts and precursors in ceramic technology. Hydrothermal synthesis with metal salts is one of the most common methods for producing stable tetragonal-phase zirconium dioxide nanoparticles. However, hydrothermal synthesis requires relatively high process temperatures (160-200°C) and the use of advanced heat-resistant autoclaves capable of maintaining high pressure. This paper investigates how different precursors (ZrOCl₂·8H₂O and ZrO(NO₃)₂·2H₂O) and synthesis temperatures (110-160°C) affect the phase composition, optical properties, size, and shape of ZrO₂ nanoparticles produced by hydrothermal synthesis without calcination. In addition, the effect of temperature exposure in the range of 100-1000°C on the phase stability of the synthesized nanoparticles was studied. X-ray diffraction and Raman spectroscopy techniques were used to determine the structure and phase composition, while the optical properties were examined through the analysis of transmission and absorption spectra in the visible and UV ranges. It was found that the obtained particles at synthesis temperatures of 110-130°C have predominantly cubic c-ZrO2 phase, which changes to monoclinic phase when heated above 500°C. Analysis of visible and UV spectroscopy data reveals that the experimental samples have pronounced absorption in the middle UV range (200-260nm) and have an energy band gap Eg varying from 4.8 to 5.1eV. The hydrothermal powders synthesized in this study can be used as absorbers in the mid-UV range and as reinforcing additives in the preparation of technical ceramics.

Electronic Structures and Spectra of Donor-Acceptor Conjugated Oligomers.

Narrow band gap donor-acceptor conjugated polymers present excellent paradigms in photonics and optoelectronics due to their chemical tunability, correlated electronic structures, and tunable open-shell electronic configurations. However, rational design for enhancing the properties of these molecular systems remains challenging. In this study, we employed density functional theory (DFT) calculations to investigate prototypical narrow band gap donor-acceptor conjugated oligomers, consisting of alternating cyclopentadithiophene (CPDT) donors paired with benzothiadiazole (BT), benzoselenadiazole (BSe), benzobisthiadiazole (BBT), and thiadiazoloquinoxaline (TQ) acceptors. Analyses of structures, singlet-triplet gaps, and absorption spectra of oligomers with up to ten repeat units have shown that when incorporating the BT, BSe, and TQ acceptors, the backbone curvature resulted in spiral structures that were energetically favored over their linear counterparts, causing differences in the calculated circular dichroism spectra. Oligomers with BBT-based acceptors preferred, however, a linear geometry, consistent with an open-shell electronic structure. Calculated singlet-triplet splittings demonstrated the importance of long chains and specific structures for consistency with the experiment, while effects of the solvent were also quantified. Based on the predicted low-energy conformations, one-photon absorption spectra for the considered oligomers have shown that using the Tamm-Dancoff approximation within time-dependent DFT for the large systems offers good agreement with the first absorption maxima in measured experimental spectra, thus validating the method for large donor-acceptor oligomers. Natural transition orbital analyses provided insights into the excited-state characteristics. Two-photon absorption maxima were accurately predicted, but the cross-sections were overestimated or underestimated, as dependent on the level of theory employed, to be addressed in future work.

Enhancing dye-sensitized solar cells efficiency through organic dyes-sensitized holmium-doped TiO2/SnO2 nanocomposites blended with P3HT

The pursuit of sustainable energy solutions has spurred innovation in photovoltaic technology, with dye-sensitized solar cells (DSSCs) emerging as promising contenders. This study presents a novel approach leveraging holmium-doped TiO2/SnO2 nanocomposites sensitized with organic dyes, Arsenazo-III, carminic acid, and dithizone, blended with poly (3-hexylthiophene) (P3HT). Through meticulous characterization and analysis, key parameters including short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), and overall percent efficiency (%) were scrutinized to evaluate photovoltaic performance comprehensively. Absorption spectra analysis facilitated the calculation of band gaps, revealing a significant reduction from 3.10 eV in pure Titania (TiO2) nanoparticles to 2.72 eV upon doping with Holmium and coupling with SnO2. Notably, Arsenazo-III dye-sensitized holmium-doped TiO2/SnO2 nanocomposites exhibited highest power conversion efficiency, achieving a promising efficiency of 2.10 %, which marked a significant improvement over the reference device (0.82 %). This improvement is attributed to the synergistic effects of holmium dopant incorporation and SnO2 interaction, enhancing light responsiveness. The findings not only validate the efficacy of nanohybrid assemblies but also contribute valuable insights to solar cell technology advancement.

X-ray spectromicroscopy of single NiO antiferromagnetic nanoparticles

The chemical and magnetic properties of NiO nanoparticles (NP) have been studied with single-particle sensitivity by means of synchrotron-based, polarization-dependent X-ray absorption spectroscopy using photoemission electron microscopy around the Ni L3,2 edges. Three samples of NP in a size range of 40-120 nm were synthesized by thermal decomposition and subsequent calcination processes. The analysis of the local X-ray absorption spectra of tens of individual NP indicates a strong dependence of their Ni oxidation state with the calcination protocol of each sample. Additional electron-microscopy-based images and spectra of a few individual NP as well as other standard macroscopic data are in very good agreement with these experimental findings. These results showcase the relevance of combining standard and advanced single-particle studies to gain further insight into the understanding and control of electronic and magnetic phenomena at the nanoscale.

Studies on Electronic Structure and Optical Properties of MoS2/X (X = WSe2, MoSe2, AlN, and ZnO) Heterojunction by First Principles

The single-layer MoS2 is a highly sought-after semiconductor material in the field of photoelectric performance due to its exceptional electron mobility and narrow bandgap. However, its photocatalytic efficiency is hindered by the rapid recombination rate of internal photogenerated electron–hole pairs. Currently, the construction of heterojunctions has been demonstrated to effectively mitigate the recombination rate of photogenerated electron–hole pairs. Therefore, this paper employs the first principles method to calculate and analyze the four heterojunctions formed by MoS2/WSe2, MoS2/MoSe2, MoS2/AlN, and MoS2/ZnO. The study demonstrates that the four heterojunctions exhibit structural stability. The construction of heterojunctions, as compared to a monolayer MoS2, leads to a reduction in the band gap, thereby lowering the electron transition barrier and enhancing the light absorption capacity of the materials. The four systems exhibit II-type heterojunction. Therefore, the construction of heterojunctions can effectively enhance the optical properties of these systems. By forming heterojunctions MoS2/WSe2 and MoS2/MoSe2, the absorption coefficient in the visible light region is significantly increased, resulting in a greater ability to respond to light compared to that of MoS2/ZnO and MoS2/AlN. Consequently, MoS2-based heterojunctions incorporating chalcogenide components WSe2 and MoSe2, respectively, exhibit superior catalytic activity compared to MoS2 heterojunctions incorporating non-chalcogenide components ZnO and AlN, respectively. The absorption spectrum analysis reveals that MoS2/MoSe2 exhibits the highest light responsivity among all investigated systems, indicating its superior photoelectric performance.

Nucleic acid binding affinity and antioxidant activity of N-m-Tolyl-4-Chlorophenoxyacetohydroxamicacid

Hydroxamic acids represent a group of weak organic acids, both naturally occurring and synthetically derived, characterized by the general formula RC(= O)N(R’OH). In this study, we investigated the binding behavior of N-m-tolyl-4-chlorophenoxyaceto hydroxamic acid with calf thymus DNA (ct-DNA) and torula yeast RNA (t-RNA) through a combination of techniques including UV–visible spectroscopy, fluorescence emission analysis, viscometry, and computational simulations using AutoDock4 software. Our findings reveal that the mode of binding between the compound and the nucleic acids is consistent with intercalation. Competitive binding experiments demonstrated that the complex competes effectively with ethidium bromide (EB) for binding to ct-DNA/t-RNA, displacing EB from its binding sites. Additionally, the introduction of the compound into the DNA-EB system resulted in a quenching of fluorescence emission peaks. Analysis of absorption spectra indicated a red shift and hypochromic shift when the compound interacted with DNA, further supporting the intercalative binding mode. The calculated binding constant (Kb) value for the compound is 6.62 × 104 M−1 and 5.40 × 103 M−1 indicating a strong interaction with ct-DNA and t-RNA respectively. We determined the Stern–Volmer constants for ct-DNA and t-RNA as 9.96 × 104 M−1 and 8.13 × 105 M−1, respectively. The binding free energy values for ct-DNA/t-RNA were calculated to be − 3.741 × 107 and − 5.425 × 108 kcal/mol, respectively. Viscometric studies corroborated the UV results, showing a continuous increase in relative viscosity of ct-DNA/t-RNA solutions with the addition of the optimal hydroxamic acid concentration. Furthermore, we assessed the antioxidant activity of the compound using DPPH-radical scavenging and β-carotene linoleic acid assays. Gel electrophoresis results demonstrated the compound's remarkable efficacy in preventing DNA damage. Collectively, all experimental evidence supports the conclusion that N-m-tolyl-4-chlorophenoxyaceto hydroxamic acid binds to ct-DNA/t-RNA through an intercalative mechanism, which is consistent with our molecular docking simulations.

Synthesis and characterizations of a novel trans-Pd(O,N)2 complex with an AZO-dye ligand: Crystal structure, theoretical studies and DNA binding interactions

The transition metal-azo dye complexes have attracted attention in both fundamental and applied research due to their electronic and structural properties, particularly due to their potential to yield new compounds with diverse biological activities and anticancer agents. A novel square planar-trans-Pd(O,N)2 was synthesized with a high yield utilizing a one-pot approach employing (E)-methyl 2-((2-hydroxynaphthalen-1-yl)diazenyl)benzoate as the AZO-dye ligand. In order to analyze their structure and understand their properties. The desired complex was characterized using FT-IR, UV–Vis, NMR, and CHN-EA techniques. Subsequently, theoretical modeling of the complex was performed using MEP/MAC/NPA methodologies. Two methodologies were employed to monitor the coordination process of AZO-ligand with Pd(II): UV–Vis absorption and FT-IR spectrum analysis. The TD-DFT and DFT/IR behaviors were simultaneously assessed to compare the experimental results with theoretical predictions. Furthermore, both SC-XRD and DFT analysis demonstrated that the deprotonated phenolic diazene form of the AZO-ligand attached to the Pd(II) center by utilizing one nitrogen atom of the AZO-ligand and the ionic oxygen of the phenol. The SC-XRD analysis verified the presence of a slightly distorted square-planar geometry around the PdII center in the neutral trans-Pd(O,N)2 complex. All of the oxygen atoms in the complex participated in non-classical C-H….O hydrogen bonding, leading to the formation of novel edge-fused rings R22(24) and R22(12) synthons. These synthons create a 3D-network with a linked parallel matrix. Interestingly, Hirshfeld surface analysis (HSA) stimulation revealed many hot sites on the complex surface, confirming the formation of strong non-classical [C-H....O] interactions. From the observed docking behavior with the DNA, it can be concluded that the trans-Pd(O,N)2 showed superior binding compared to the free AZO-ligand. The results of this work are a contribution to the study of this class of metal complexes and their physicochemical properties and offer promising perspectives for the realization of new works.

Analyzing structural changes and variable range hopping conduction in [formula omitted] perovskite: Effect of Sr2+ doping at Bi-site

In this present investigation, we explored the impact of Sr2+ doping at the Bi-site on the structural, electrical, and optical characteristics of Na0.5Bi0.5TiO3 (NBT) nanomaterial. By employing the citrate auto-combustion method, we synthesized pure Na0.5Bi0.5TiO3 nano-perovskites, as well as various Sr-doped counterparts. Analysis of the observed X-ray diffraction patterns through Rietveld refinement revealed a rhombohedral phase with space group R3c, although the composition doped with 10 % Sr exhibited impurity phases. The introduction of Sr2+ ions had a discernible influence on diverse microstructural parameters, including lattice parameters (a and c), microstrain, X-ray density, and particle size. Detailed morphological and elemental assessments were conducted utilizing TEM, FE-SEM, and EDX spectroscopy. The analysis of UV–Vis absorption spectra yielded a reduction in the optical band gap with increasing Sr addition up to 8 % doping, followed by an increase. Random Free-Energy Barrier Model (RBM) was employed to analyze complex AC conductivity. The three-dimensional Godet's Variable Range Hopping (3D G-VRH) model was also applied to elucidate the electrical transport properties.

Physical, optical and spectral properties of Sm3+ and Eu3+ ions doped zinc boro-phosphate glass

This study focuses on the synthesis of Sm³⁺ and Eu³⁺ rare earth ions doped zinc boro-phosphate glasses and their physical, optical and spectral characterization. Photoluminescence was carried out through both steady-state and time-domain luminescence measurements. The glasses were prepared via the melt quenching technique, and they exhibit impressive mechanical strength and transparency. Judd-Ofelt analysis of the near-infrared absorption spectra revealed parameters Ω₂, Ω₄, and Ω₆, indicating low covalency and reduced site asymmetry for the rare earth ions compared to those in silicate-based glasses. When excited with violet light, the Sm³⁺-doped samples emitted bright orange luminescence, resulting from radiative relaxation from the ⁴G₅/₂ state to lower energy levels. The calculated branching ratios correspond well with the observed emission peak ratios. However, increasing the Sm³⁺ ion concentration resulted in reduced luminescence intensity and shorter fluorescence lifetimes, due to cross-relaxation effects. In the Sm³⁺/Eu³⁺ co-doped glasses, energy transfer from Sm³⁺ to Eu³⁺ ions was detected upon selective excitation of Sm³⁺ ions. This energy transfer efficiency was found to increase with higher concentrations of Eu³⁺ ions.

Role of graphene substrate in the formation of MoS2-based nanoparticles with improved sensitivity to NO2 gas

MoS2 coatings were formed on surface-oxidized silicon, chemical vapor deposition (CVD)-grown graphene, and reduced fluorinated graphene (rFG) from ammonium tetrathiomolybdate. The samples were annealed under ultra-high vacuum conditions at a temperature of 1000 °C. Analysis of X-ray photoelectron and X-ray absorption spectra revealed a bonding between MoS2 and the supporting material that was particularly strong for CVD-graphene. Uniform covering of the flat CVD-graphene surface with MoS2 nanoparticles and numerous contacts between them promoted the removal of sulfur and the formation of exposed molybdenum edges. A cracked MoS2 coating consisting of dense domains was formed on the wrinkled rFG surface. The study of samples as NO2 gas sensors revealed the best performance of MoS2/CVD-graphene. The sensor detected NO2 in air below 50 ppb at room temperature, had good response and recovery, operated in humid air, and demonstrated excellent NO2 selectivity. The other two sensors gave signals at elevated temperatures. The advantage of MoS2/CVD-graphene is due to improved electron transport in the hybrid, accessibility of small MoS2 nanoparticles to the analyte, and passivation of high-energy molybdenum sites by oxygen, which improves NO2 desorption.

LiNbO3:Ho3+ Crystal as a Material for Radiation-Balanced Lasing in the 640–670 nm Region

Holmium-doped congruent-composition lithium niobate (LiNbO3:Ho, LN:Ho) crystals were grown by the Czochralski method. The absorption of the LN:1at% Ho3+ crystal was recorded at room temperature. On the basis of the analysis of emission and absorption spectra of the LN:1at% Ho3+ crystal, the possibilities of obtaining, at room temperature, radiation-balanced (RB) lasing in the region of 640–670 nm wavelengths corresponding to the inter-Stark transitions of manifolds 5F5 and 5I8 was theoretically investigated. The RB lasing parameters were calculated and the optimal pump and laser wavelengths were determined: λOP=652.1 nm, λOL=653.6 nm. The values for the RB lasing efficiency and radiation amplification in the considered wavelength region were obtained: Feff=3.23×10−22cm2, Fgain=6.08×10−22 cm2.

Exploring synthesis and annealing influence on WS2 (tungsten disulfide): Structural, morphological, optical, and magnetic profiles

The resurgence of interest in Transition Metal Dichalcogenides (TMDCs) stems from their remarkable magnetic and optical properties, reminiscent of graphene. TMDCs like MoS2, MoSe2, WS2, and WSe2 exhibit substantial bandgaps that shift from indirect to direct in single layers. This characteristic enables diverse applications such as solar cells, transistors, photodetectors, and electroluminescent devices, without the direct use of graphene. In this study, polycrystalline WS2 powder was synthesized via the solid-state reaction method. We systematically investigated the structural, morphological, optical, and magnetic properties concerning the synthesized WS2 and its variants annealed at different temperatures. Through X-ray powder diffraction (XRD) analysis, we confirmed the hexagonal structure of the as-synthesized compound, with a space group of P 63/mmc. Interestingly, no structural transitions were observed in the annealed samples. Morphological examination revealed a plate-like structure across all samples. The determination of the optical bandgap was facilitated by UV-DRS absorption spectrum analysis. Our findings showcased the ferromagnetic behavior of the synthesized WS2, corroborated by magnetic measurements and electron paramagnetic resonance (EPR) analysis. These insights contribute to a deeper understanding of TMDCs and pave the way for their tailored utilization in advanced technological applications.

Insights about the effect of metal–organic framework hybridization with graphene-like materials

Abstract Hybrids based on the copper-based metal–organic framework HKUST-1 and graphene-like materials (GL) have been synthesized at different concentrations of GL, and investigated by means of solid state nuclear magnetic resonance (ssNMR) and x-ray absorption techniques (NEXAFS and XANES) with the aim of elucidating the effect of the hybridization on the structural properties of HKUST-1. The comparative analysis of ssNMR and x-ray absorption spectra recorded on parent materials (GL and pure HKUST-1) and on the hybrids indicates that the overall structural features of HKUST-1 are preserved in the presence of increasing GL amounts (up to 30 wt.%) and confirms that the framework development is not massively altered by the presence of graphene-related materials (GRMs) in the synthetic medium.

Excited-State Dynamics of a Bright Fluorescent Dye with Precise Control of Emission Color Using Acid-Base Equilibrium, Intramolecular Charge Transfer, and Host-Guest Chemistry.

A fluorescent dye, a dithiophene-conjugated benzothiazole derivative (DTBz), was prepared to have high fluorescence emission quantum yields (ΦF) across various organic solvents. Its emission color modulation, from bright blue to deep red, was achieved through intramolecular charge transfer (ICT), acid-base equilibrium, and host-guest chemistry. Although it exhibits a weak solvatochromic effect, DTBz exhibited a bright fluorescence emission around 480 nm upon excitation at 390 nm in most solvents. In polar solvents, such as MeOH (methanol), EtOH (ethanol), DMF (N,N-dimethylforamide), and DMSO (dimethyl sulfoxide), an additional ICT emission band emerged around 640 nm, notably intense in DMSO, resulting in a bright greenish-white emission (ΦF = 0.67). The addition of 1,8-diazabicyclo[5,4.0]undec-7-ene (DBU) altered emission characteristics, reducing emission from the local excited (LE) state and enhancing ICT state emission. The degree of emission spectral change saturation with DBU addition varied with the solvent nature. Polar solvents with high dielectric constants, like DMSO and DMF, saw a complete disappearance of LE state emission with 5 equiv of DBU, resulting in a deep red emission (ΦFs of 0.53 and 0.48, respectively). Femtosecond transient absorption spectroscopy and time-resolved photoluminescence measurements elucidated the excited-state dynamics, revealing a long-lived excited state (τ-H = 10.3 ns) at a lower energy emission (640 nm), identified as DTBz-*, supported by transient absorption spectra analysis. Further analysis, including time-resolved fluorescence decay measurements and time-dependent density-functional theory (TD-DFT) calculations, underscored the role of deprotonation of DTBz's hydroxyl group in promoting the ICT process. The CIE coordination plot demonstrated wide linear emission color changes upon successive DBU additions in all solvents, while emission color precision was achieved through host-guest chemistry. Emission changes induced by DBU were reverted to the original state upon beta-cyclodextrin (β-CD) addition, with the 1H NMR study revealing the competition between acid-base equilibrium and host-guest complex formation as the cause of emission color change.

Optimization for hydrogen gas quantitative measurement using tunable diode laser absorption spectroscopy

Gas sensors are vital for safety, quality control, and environmental preservation across diverse industries. Tunable diode laser absorption spectroscopy (TDLAS) is widely employed for gas analysis due to its high sensitivity and selectivity. However, quantifying low concentrations of hydrogen gas using TDLAS in the infrared region proves challenging due to its lower absorption compared to other gases in the NIR region. This study introduces an innovative method for precise hydrogen gas measurement through the analysis of absorption spectra at different pressures and the employment of a high-pressure gas cell. By applying these methodologies to a calibration-free technique, we can realize the optimal measurement conditions for increasing the gas detection limit and stabilizing the wavelength lock for the laser diode. As a result, a linear relationship between hydrogen gas concentration and sensor response is achieved in the wide detection range of 0.01% to 100%. Under the optimal measurement conditions, our TDLAS system’s stability is demonstrated with minimum detection limits of 0.2866% and 0.0055% at integration times of 1 s and 30 s, respectively.

Tunable Ag Nanocavity Enhanced Green Electroluminescence from SiNx:O Light-Emitting Diode.

As the driving source, highly efficient silicon-based light emission is urgently needed for the realization of optoelectronic integrated chips. Here, we report that enhanced green electroluminescence (EL) can be obtained from oxygen-doped silicon nitride (SiNx:O) films based on an ordered and tunable Ag nanocavity array with a high density by nanosphere lithography and laser irradiation. Compared with that of a pure SiNxO device, the green electroluminescence (EL) from the SiNx:O/Ag nanocavity array device can be increased by 7.1-fold. Moreover, the external quantum efficiency of the green electroluminescence (EL) is enhanced 3-fold for SiNx:O/Ag nanocavity arrays with diameters of 300 nm. The analysis of absorption spectra and the FDTD calculation reveal that the localized surface plasmon (LSP) resonance of size-controllable Ag nanocavity arrays and SiNx:O films play a key role in the strong green EL. Our discovery demonstrates that SiNx:O films coupled with tunable Ag nanocavity arrays are promising for silicon-based light-emitting diode devices of the AI period in the future.

Exploring the structural and optical properties of lithium-chromium phosphate Li3Cr2(PO3)4

The Lithium-chromium phosphate Li3Cr2(PO3)4 sample was synthesized via the solid-state reaction method. The morphological integrity and chemical homogeneity were verified by energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM). Infrared and Raman patterns were also analyzed. Optical absorption spectrum analysis, conducted within the range of 10000 cm−1 to 30000 cm−1 at room temperature, yielded some optical parameters (Eg, Eu, δ, k, n). The Neuhauser model is used to interpret the interference dip which was on the absorption spectrum of Li3Cr2(PO3)4. The Fourier transform of the autocorrelation function leads to the Zero Phonon Lines of the observed absorption energies. The electronic structure of Cr3+ (3d (Huang et al., 2009) 33) ions in Li3Cr2(PO3)4 was calculated using Racah method, which allowed for precise calculations of Racah and crystal-field parameters. The results showed good agreement between the theoretical and experimental energy levels.

Non-destructive diagnosis of Inflammatory Bowel Disease by near-infrared spectroscopy and aquaphotomics

Inflammatory Bowel Disease includes Crohn's Disease and Ulcerative Colitis. Currently, diagnosing involves a series of current diagnostic methods that are invasive, time-consuming, and expensive. Near-infrared spectroscopy and aquaphotomics can detect changes in biofluids and thus have the potential to diagnose disease. This study aimed to investigate the diagnostic ability of near infrared spectroscopy and aquaphotomics for Inflammatory Bowel Disease and its types. This method used blood plasma and saliva samples absorbance spectrum and multivariate analysis with the Principal Component Analysis and, Linear Discriminant Analysis, Quadratic Discriminant Analysis, and Support Vector Machine in the range 1300–1600 nm and 12 water absorbance bands in this range, separately. In the near-infrared range, total accuracy of 100% led to the separation of the healthy group and Inflammatory Bowel Disease and then the separation of the healthy group and patients with Ulcerative Colitis and Crohn's Disease. The aquaphotomics approach was used to investigate the changes in the 12 water absorbance bands and their impact on the accuracy of the diagnostic method. Aquaphotomics also detected 100% of the mentioned samples. We achieved a fast, accurate, non-invasive method based on near-infrared spectroscopy and aquaphotomics to diagnose Inflammatory Bowel Disease and its types using blood plasma or saliva samples. The current study found that monitoring blood plasma or saliva using near-infrared spectra offers an opportunity to thoroughly investigate biofluids and changes in their water spectral patterns caused by complex physiological changes due to Inflammatory Bowel Disease and its types, and to visualize these changes using aquagram.

Impact of the spatial structure of alkyl chains on properties of thiophene-substituted diketopyrrolopyrroles: Part II – Spectroscopic study

The study concerns the impact of a difference in geometry of the side alkyl chains of oligothiophene derivatives of diketopyrrolopyrrole (DPP) on their spectroscopic properties and aggregation in solutions, in Langmuir layers, and thin films. Using a combination of theoretical and experimental approaches, this study aims to explain the aggregating behaviour of thiophene-substituted DPP derivatives. Various methods were used to characterise the dyes, including absorption spectroscopy also with polarized light, fluorescence spectroscopy, Langmuir techniques, and time-dependent density functional theory (TD-DFT) calculations. The presented results emphasise a significant impact of side alkyl chains on DPP's molecular behaviour, notably evident in thin-layer structures. Interestingly, the deconvolution of the absorption spectra revealed three bands in the red region. Insightful analysis of temperature-dependent absorption, excitation, and emission fluorescence spectra indicates the co-existence of monomer, dimer, and a higher aggregate forms, most likely a tetrameric structures. Moreover, such a complexity of molecular organisation of dyes appears already in the solution. Differences in spectral properties of the dyes studied are robustly visible in changes in the spectra of the air–water interface, where the dye with the branched side group changes the mutual orientation in dimeric structures, leading to the formation of H-type aggregates, which was observed as an almost 20-nm spectral blue shift during Langmuir layer compression. The results presented highlight the need for care in interpretation of the intensity ratio of DPP spectra and spectral shift as the sole determinants of the aggregation state.

Synthesis, optical properties, DNA, β-cyclodextrin interactions, and antioxidant evaluation of novel isoxazolidine derivative (ISoXD2): A multispectral and computational analysis

ISoXD2 are well explored among versatile and outstanding class of pharmacophores for the preparation and discovery of drugs. Herein, the electronic absorption and emission spectra of ISoXD2 were investigated in three different solvents. The observed transition was attributed to π-π* with charge transfer character. Changes in the excited state and shift of the absorption and emission peaks to longer wavelengths are observed as a result of increasing solvent polarity, due to the interactions between the ISoXD2 molecule and the solvent molecules surrounding it. Changing the solvent confirms its solvatochromic effect. UV–vis and fluorescence analysis revealed that ISoXD2 binds to deoxyribonucleic acid (DNA) by intercalation mode, with a stoichiometric ratio of 1:1.5. Moreover, the fluorescence intensity of DNA bound to ethidium bromide (EB) in the presence of ISoXD2 was investigated. From this analysis, the Stern-Volmer quenching constant (Ksv), quenching rate constant (kq), binding constant (Kb) and binding sites number (n) were found to be 5.654 × 103 M−1, 2.827 × 1011 M−1 s−1, 3.81 × 104 M−1 and 1.225, respectively. The interaction between ISoXD2 and β-CD was investigated through absorption spectra analysis. Kb for this interaction was determined to be 4.9 × 104 M−1. The free radical-scavenging ability of the prepared ISoXD2, examined by DPPH and ABTS assays have shown a good antioxidant activity. Furthermore, modeling study was conducted to explore their plausible binding mechanism with ISoXD2 and to support the experimental results.