Changes In Absorption Spectra Research Articles

Solvatochromism, electric dipole moments, optical properties and electronic structure of biphenylcarbonitrile liquid crystals

The UV–Vis. absorbance and fluorescence spectra of 4HC (4′-heptyl-4-biphenyl carbonitrile) and 4OB (4′-Octyl-4-biphenylcarbonitrile) liquid crystals were measured in 23 solvents with different polarities. As dependent on changing of solvents, while the change in absorbance spectrum of liquid crystals have less, change in fluorescence spectrum have more. Molecular interactions were quantitavely investigated by using Linear solvation energy relationships. Optical forbidden energy gap has been determined with using Tauc plot. The refractive index has been calculated with semi-empirical methods. The relationships between refractive index and Eg has been commented in n-hexane, acetic acid, water and 1,4-dioxane. The electric dipole moment has been calculated by using the Bilot-Kawski, Lippert-Mataga, Bakshiev, Kawski-Chamma-Viallet and Reichardt methods. Solvatochromic shifts showed to having large dipole moments of 4OB and 4HC LCs. Their molecular orbital energies, electric dipole moments, MEP, SAS, and reactivity properties of 4HC and 4OB LCs has been found by quantum chemical calculations. It was observed that the dipole moment of 4HC was higher than 4OB.

Intramolecular hydrogen bonding steered optical recognition of fluoride ion and consequent opto-chemical logic responses: Spectroscopic and computational studies

This work demonstrates the synthesis and characterization of a thiosemicarbazide core containing Schiff base molecule (MNHC) and its use as a chemosensor for the selective, ratiometric, and colorimetric detection of fluoride ions. The study reveals that in the presence of F− ions, MNHC displays a ratiometric change of absorption maxima at two different wavelengths (432 and 330 nm). MNHC involves an intramolecular hydrogen bonding initiating the possibility of keto-enol tautomerism which is thoroughly investigated by DFT study. Interestingly, the intramolecular hydrogen bonding enhances the acidity of the –NH proton and consequently the –NH center becomes more labile for F− ions binding over the other –NH proton. This fact is confirmed by 1H NMR study. Remarkably, F− ion forms intermolecular hydrogen bonding with the –NH moiety disrupting the intramolecular hydrogen bonding. The changes in absorption spectra in the presence of F− ions occur due to the intermolecular hydrogen bonding-assisted abstraction of the –NH proton. On the other hand, when H2O is added to the MNHC-F− composite, the spectroscopic signature of free MNHC is completely regenerated due to the transfer of proton from H2O to the nitrogen center of MNHC. In addition, 1:1 binding stoichiometry and 53.7 μM detection limit for fluoride ion are also confirmed. Moreover, utilizing these spectroscopic responses, different kinds of important opto-chemical logic gates like YES, NOT, PASS 0, PASS 1, INHIBIT, TRANSFER, and IMPLICATION are developed. Moreover, the F− ion-assisted competitive nature between the intramolecular vs intermolecular hydrogen bonding is thoroughly explored by substantial DFT study.

Determination of singlet oxygen quantum yield based on the behavior of solvent dimethyl sulfoxide oxidation by singlet oxygen

BackgroundPhotodynamic therapy (PDT) is emerging as a promising cancer treatment. The PDT efficacy is primarily attributed to the generation of singlet oxygen (1O2), stemming from the integrated effects of the photosensitizer, oxygen, and light. The singlet oxygen quantum yield (ΦΔ) serves as a bridge that links these parameters to the overall efficacy of PDT. The near-infrared luminescence of 1O2 provides a direct way for determining ΦΔ, but suffers from a poor signal-to-noise ratio. While the chemical trap probe method is detection-friendly, but it has a strict requirement for the excitation wavelength. Therefore, the existing methods for ΦΔ measurement are insufficient. ResultsIn this work, we developed an approach to determine ΦΔ of a broader range of photosensitizers using only the commonly used solvent dimethyl sulfoxide (DMSO), which can be oxidized by 1O2 to dimethyl sulfone. This method establishes the relationship between 1O2 production and changes in DMSO absorption spectra, eliminating the need for additional chemical probes. This method was validated by measuring the ΦΔ of rose bengal (RB) through systematic changes in absorption spectrum of DMSO under various RB concentrations and different excitation light power densities. Moreover, the ΦΔ of hematoporphyrin monomethyl ether (HMME), as determined by this method, is consistent with measurements obtained using the 1,3-diphenylisobenzofuran (DPBF) trapping probe. This consistency further validates the reliability of this method. Significance and noveltyThis work presents a direct, probe-free method to determine ΦΔ, reducing potential interference and expanding the range of useable excitation wavelengths. Its ability to measure ΦΔ using only DMSO enhances the accuracy of photosensitizer measurement, and broadens the applicability of the method to a wide range of samples, thereby advancing research on the properties of photosensitizers and further promoting the development of PDT.

Thiazole-derived pyrazin-2-carbohydrazide chemosensors: Colorimetric & photoluminescent detection of silver ions for theoretical, environmental, and cell imaging

In this work, a simple and versatile chemosensor receptor TZPYZ was synthesized through the combination of thiazole with pyrazine-2-carbohydrazide, resulting in a confirmed chemical structure via various analytical techniques including FT-IR, 1H, and 13C Nuclear Magnetic Resonance Spectroscopy, as well as High-Resolution Mass Spectroscopy analysis. TZPYZ exhibits specific colorimetric and photoluminescent responses to Ag+ ions in a solvent solution consisting of DMSO and H2O (7:3, v/v). Upon addition of Ag+ ions, noticeable changes in absorption spectra occur, resulting in a visible color change from pale yellow to blue. Additionally, an enhanced emission intensity with wavelength at 523 nm, when excited at 410 nm. Notably, TZPYZ demonstrated exceptional selectivity for Ag+ ions over other metal cations, achieving a detection limit (LOD) of 10.6 × 10−9 M and 6.74 × 10−9 M and using the UV–visible & photoluminescent titration method. Interference studies indicated minimal disruption from other metal ions on emission at 523 nm, highlighting TZPYZ discerning capability for Ag+ ions. With a binding affinity of 3.622 × 10−11 M−1, TZPYZ proved effective in detecting Ag+ ions across various water samples, showcasing its practical utility. The mechanism of interaction between TZPYZ and Ag+ ions was investigated using various experimental techniques, including Job’s plot, Benesi-Hildebrand investigations, 1H NMR, and HRMS analysis. Test strips coated with TZPYZ showed selective detection of Ag+ ions, indicating its potential for on-site applications. Furthermore, DFT computations provided insights into the structural and electronic properties of TZPYZ and its complex with Ag+ ions, further elucidating the binding mechanism and stability of the complex. In addition, TZPYZ demonstrated compatibility with biological systems, as fluorescence imaging tests on MCF-7 breast cancer cells confirmed both its non-cytotoxic nature and its proficiency in detecting intracellular silver ions. Based on these findings, TZPYZ is highlighted as a highly sensitive and selective chemosensor for Ag+ ions, with promising applications in environmental analysis and bioimaging.

Development of a gold nanoparticle-based novel diagnostic prototype for in vivo detection of Indian red scorpion (Mesobuthus tamulus) venom

Indian red scorpion Mesobuthus tamulus is responsible for substantial mortality in India and Sri Lanka; however, no specific diagnostic method is available to detect the venom of this scorpion in envenomed plasma or body fluid. Therefore, we have proposed a novel, simple, and rapid method for detecting M. tamulus venom (MTV) in the plasma of envenomed animals using polyclonal antibodies (PAb) raised against three modified custom peptides representing the antigenic epitopes of K+ (Tamapin) and Na+ (α-neurotoxin) channel toxins, the two major MTV toxins identified by proteomic analysis. The optimum PAb formulation containing PAb 1, 2, and 3 in proportion (1:1:1, w/w/w) acted synergistically, demonstrating significantly higher immunological recognition of MTV than anti-scorpion antivenom (developed against native toxins) and individual antibodies against peptide immunogens. The PAb formulation could detect MTV optimally in envenomed rat plasma (intravenous and subcutaneous routes) at 30–60 min post-injection. The acetonitrile precipitation method developed in this study to augment the MTV detection sensitivity enriched the low molecular mass peptide toxins in envenomed rat plasma, which was ascertained by mass spectrometry analysis. The gold nanoparticles conjugated PAb formulation, characterised by biophysical techniques such as Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM), demonstrated their interaction with low molecular mass MTV peptide toxins in envenomed rat plasma. This interaction results in the accumulation of the gold nanoparticles, thus leading to signal change in absorbance spectra that can be discerned within 10 min. From a standard curve of MTV spiked plasma, the quantity of MTV in envenomed rat plasma could be determined by gold nanoparticle-PAb formulation conjugate.

Effect of concentration and wavelength of excitation on the photophysics of salicylate anion in acetonitrile and water

Sodium salicylate (NaSA) molecule exists as salicylate anion in acetonitrile (ACN) and water solvents, and exhibits large Stokes shifted fluorescence due to excited state intramolecular proton transfer (ESIPT), with decay times of ∼5 ns in ACN and ∼3.9 ns in water by 300 nm (absorption maxima) excitation. Previous studies report both ground and excited state enol-keto tautomerization in ACN, but only excited state tautomerization in water at 10−4 M. However, the current work explores the effect of concentration and excitation wavelengths on the photoinduced dynamics of ESIPT in the salicylate anion. On increasing the concentration of NaSA, no change in absorption spectra appears in both the solvents, and emission spectra of NaSA in water remain unaffected by changes in concentration or excitation wavelength, whereas, a slight red shift and decrease in FWHM appears in ACN. Time-domain fluorescence measurements show predominantly single-exponential decay throughout the emission profile by 300 nm excitation above the 10−5 M concentration in both the solvents, while by 375 nm excitation, multi-exponential fluorescence decay is observed at low concentrations, and as the concentration of NaSA increases, this decay behaviour tends to converge towards a single exponential decay. These results suggest that solute–solvent interactions stabilize the ground-state intermolecular hydrogen-bonded species at low concentrations, while higher concentrations weaken these interactions, leading to emission solely from the salicylate anion. Peak fit analysis of excitation spectra confirms enol-keto tautomerization in both the solvents, with the keto form being more stabilized in ACN. These findings underscore that in ACN, behaviour of NaSA is influenced by both concentration and excitation wavelength and contrary to previous reports, the keto form of the molecule is also present in water, though at a very low concentration and an increase in non-radiative transitions in water cause fluorescence quenching.

A methodological approach to age estimation of the intra-puparial period of the forensically relevant blow fly Calliphora vicina via Fourier transform infrared spectroscopy.

Estimating the age of immature blow flies is of great importance for forensic entomology. However, no gold-standard technique for an accurate determination of the intra-puparial age has yet been established. Fourier transform infrared (FTIR) spectroscopy is a method to (bio-)chemically characterise material based on the absorbance of electromagnetic energy by functional groups of molecules. In recent years, it also has become a powerful tool in forensic and life sciences, as it is a fast and cost-effective way to characterise all kinds of material and biological traces. This study is the first to collect developmental reference data on the changes in absorption spectra during the intra-puparial period of the forensically important blow fly Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae). Calliphora vicina was reared at constant 20°C and 25°C and specimens were killed every other day throughout their intra-puparial development. In order to investigate which part yields the highest detectable differences in absorption spectra throughout the intra-puparial development, each specimen was divided into two different subsamples: the pupal body and the former cuticle of the third instar, that is, the puparium. Absorption spectra were collected with a FTIR spectrometer coupled to an attenuated total reflection (ATR) unit. Classification accuracies of different wavenumber regions with two machine learning models, i.e., random forests (RF) and support vector machines (SVMs), were tested. The best age predictions for both temperature settings and machine learning models were obtained by using the full spectral range from 3700 to 600 cm-1. While SVMs resulted in better accuracies for C. vicina reared at 20°C, RFs performed almost as good as SVMs for data obtained from 25°C. In terms of sample type, the pupal body gave smoother spectra and usually better classification accuracies than the puparia. This study shows that FTIR spectroscopy is a promising technique in forensic entomology to support the estimation of the minimum post-mortem interval (PMImin), by estimating the age of a given insect specimen.

Synthesis of Cu2+ doped ZnO@ZnCdS thin film: Optical and electrochemical characterization

Doping strategies modify the optical and electrochemical characteristics of materials. In this research, we investigated the impact of Cu2⁺ doping in ZnO@ZnCdS nanocomposites synthesized via the co-precipitation approach. A comprehensive analysis was conducted on the structural, morphological, optical, and electrochemical features of the samples using various techniques, including scanning electron microscopy (SEM), atomic force microscopy (AFM), Energy Dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), UV–Visible absorption, and photoluminescence (PL). Notably, Cu2⁺ doping induces changes in morphology, crystal size, absorption spectra, and band gap energy. Surface investigations reveal a flower-like structure, while XRD analysis indicates an increase in crystal size from 25.5 to 35.2 in thin films with copper content. The absorption spectra of UV–visible-doped ZnO@ZnCdS thin films exhibit reduced peak intensity upon Cu2⁺ addition. Also, optical absorption analysis shows a shift towards longer wavelengths in the emission of ZnO@ZnCdS due to Cu2⁺ inclusion during doping. Likewise, the band gap energy ranges from 1.37 eV to 2.22 eV for ZnO@ZnCdS and Cu2⁺ doped ZnO@ZnCdS, respectively, as determined using Tauc plots. PL spectrum of the Cu2⁺ doped ZnO@CdS nanocomposite indicates emissions in the blue and green regions. Specifically, under 325 nm excitation, the copper-doped material displays a prominent blue and a less intense red emission at 420 nm at 685 nm, respectively. Furthermore, the electrochemical analysis revealed that doping caused a reduction in Rct and an elevation in CSP. These results offer important considerations for the development of cutting-edge functional optoelectronic materials.

Optimizing Molecular Packing via Steric Hindrance for Reducing Non-Radiative Recombination in Organic Solar Cells.

Innovative molecule design strategy holds promise for the development of next-generation acceptor materials for efficient organic solar cells with low non-radiative energy loss (ΔEnr). In this study, we designed and prepared three novel acceptors, namely BTP-Biso, BTP-Bme and BTP-B, with sterically structured triisopropylbenzene, trimethylbenzene and benzene as side chains inserted into the shoulder of the central core. The progressively enlarged steric hindrance from BTP-B to BTP-Bme and BTP-Biso induces suppressed intramolecular rotation and altered the molecule packing mode in their aggregation states, leading to significant changes in absorption spectra and energy levels. By regulating the intermolecular π-π interactions, BTP-Bme possesses relatively reduced non-radiative recombination rate and extended exciton diffusion lengths. The binary device based on PB2 : BTP-Bme exhibits an impressive power conversion efficiency (PCE) of 18.5 % with a low ΔEnr of 0.19 eV. Furthermore, the ternary device comprising PB2 : PBDB-TF : BTP-Bme achieves an outstanding PCE of 19.3 %. The molecule design strategy in this study proposed new perspectives for developing high-performance acceptors with low ΔEnr in OSCs.

Optimizing Molecular Packing via Steric Hindrance for Reducing Non‐Radiative Recombination in Organic Solar Cells

AbstractInnovative molecule design strategy holds promise for the development of next‐generation acceptor materials for efficient organic solar cells with low non‐radiative energy loss (ΔEnr). In this study, we designed and prepared three novel acceptors, namely BTP‐Biso, BTP‐Bme and BTP‐B, with sterically structured triisopropylbenzene, trimethylbenzene and benzene as side chains inserted into the shoulder of the central core. The progressively enlarged steric hindrance from BTP‐B to BTP‐Bme and BTP‐Biso induces suppressed intramolecular rotation and altered the molecule packing mode in their aggregation states, leading to significant changes in absorption spectra and energy levels. By regulating the intermolecular π–π interactions, BTP‐Bme possesses relatively reduced non‐radiative recombination rate and extended exciton diffusion lengths. The binary device based on PB2 : BTP‐Bme exhibits an impressive power conversion efficiency (PCE) of 18.5 % with a low ΔEnr of 0.19 eV. Furthermore, the ternary device comprising PB2 : PBDB‐TF : BTP‐Bme achieves an outstanding PCE of 19.3 %. The molecule design strategy in this study proposed new perspectives for developing high‐performance acceptors with low ΔEnr in OSCs.

A ratiometric fluorescent probe for cysteine and glutathione differentiation and its application for cysteine detection in foods

Cysteine (Cys) and glutathione (GSH) are crucial biothiols implicated in cellular redox balance, necessitating accurate detection methods. Herein, we developed a novel fluorescent probe based on the fluorescent dye pyronin (PYR), capable of monitoring both Cys-and GSH using ratiometric fluorescence signals. The probe, named PYR-CG, where "C" stands for Cys-and "G" stands for GSH, demonstrates selective detection capabilities for Cys-and GSH. UV absorption and fluorescence emission spectra changes revealed distinct shifts upon interaction with Cys-and GSH. Theoretical and experimental studies validated PYR-CG's responsiveness to Cys-and GSH, elucidating its mechanism as a ratiometric probe. Notably, PYR-CG exhibited rapid response kinetics for Cys-and GSH, with low detection limits of 88 nM and 164 nM, respectively. Importantly, PYR-CG demonstrated exceptional selectivity for Cys-and GSH over interfering analytes. Screening of molecules with similar structures to Cys-further affirmed PYR-CG's specificity, particularly towards N-terminal Cys-in peptides. Furthermore, recovery experiments underscored PYR-CG's reliability for quantitative Cys-detection in complex food samples. Our findings highlight the innovative design and practical applicability of PYR-CG, offering a valuable tool for sensitive and selective detection of Cys-in diverse biological and food samples.

Bioinspired Hg2+-sensing fluorogenic probe based on amino acid–functionalized rhodamine

Inspired by the suitability of rhodamine spirolactam switching for superresolution imaging and fluorescent probe development, we herein synthesized rhodamine-based probes with sulfur-bearing amine and amino acid moieties and screened their abilities to respond to Hg2+ in the presence of other metal ions. The probe based on S-methylcysteine methyl ester–substituted rhodamine 6G (Rho6G-6) was identified as optimal because of its straightforward synthesis and rapid, selective, and sensitive (detection limit = 8 × 10–9 M) response to Hg2+ manifested by absorption spectrum and emission color changes. The complexation of Hg2+ by Rho6G-6 was examined by absorbance and fluorescence analyses, electrospray ionization–mass spectrometry, and 1H nuclear magnetic resonance (NMR) titration experiments. Furthermore, the practical applicability of the above probe was demonstrated by naked-eye colorimetric Hg2+ detection using paper test strips and the fluorescence-based qualitative mapping of the Hg2+ distribution in living HeLa cells and the organs of live mice. Thus, unlike other probe design strategies, the use of flexible S-methyl amino acids for Hg2+ binding provides new opportunities and strategies for photopromoting the ring switching of the rhodamine spirothiolactam.

Beverage Deterioration Monitoring Based on Surface Tension Dynamics and Absorption Spectrum Analysis

Biochemical information sensing has always been one of the challenges in ubiquitous sensing research for mobile computing. Microorganisms will cause undetectable deterioration in drink production, such as wine and beverage, and microbial contamination is highly susceptible during storage like some liquors can be bottled for sometimes over ten years. Microbial culture methods are common for quality monitoring but unsuitable for real-time beverage quality monitoring. As far as we know, we are the first to use ubiquitous sensing for real-time microbial contamination detection. We designed a lightweight monitoring system called Microbe-Radar, which uses light signals to monitor real-time beverage quality. Microbe-Radar uses eight LEDs and a photodiode to detect fine-grained surface tension and absorption spectrum changes caused by microbial metabolites and growth during deterioration. Characteristic offset degree measurement and absorption spectrum dimension expansion are two critical technologies. Moreover, we implemented countermeasures against ambient light noise and sloshing interference. Microbe-Radar's surface tension and absorption spectrum measurement errors are only 0.89 mN/m and 2.4%, respectively, making identifying the contamination duration, microorganism content, and microorganism composition worthwhile. Experiments showed Microbe-Radar could determine potential issues with liquor quality when the liquid becomes health-threatening or even just contaminated, with an accuracy of 97.5%. Microbe-Radar can also be extended to beverage deterioration warning, with deterioration prediction accuracy of more than 90.6% for five beverages (milk, apple juice, etc.).

Cations chelation and cytotoxicity of 8-hydroxyquinolone derivatives in water solutions

8-hydroxyquinolines (8HQ) derivatives have a wide range of activities, including antibacterial, antiviral, anticancer, antiparasitic and antifungal. They form complexes with divalent and trivalent metal cations. Low solubility of 8HQ in water limits their use. Absorbance spectra of aqueous solutions of 8HQ derivatives in the presence of Mg2+, Ca2+ and Zn2+, their stability over time, cytotoxicity and fluorescence in prostate and breast cancer cell lines were investigated. The 8HQ derivatives 2-(2-phenylethenyl)quinolin-8-ol (STQ-H) and 2-[2-(4-cyanophenyl)ethenyl]quinolin-8-ol (STQ-CN) were used. The cytotoxicity and fluorescence investigation was carried out on prostate DU-145 and breast MDA-MB-231 cancer cell lines. Changes of absorbance spectra of aqueous solutions of STQ-H and STQ-CN were revealed, which indicates the importance of the molar ratio of Mg2+, Ca2+, Zn2+ and chelator about 1:1. Absorbance of STQ-CN solution in a cations mixture was radically increased at equal molar proportions of each. Aqueous solutions of STQ-H were more stable than STQ-CN in the presence of Mg2+, Ca2+ and Zn2+ for 60 min. A high sensitivity of cells to STQ-CN was revealed. IC50 were 17.55 × 10−6 M for DU-145 and 1.96 × 10−6 M for MDA-MB-231. No cytotoxicity of STQ-H to DU-145 was detected, but it inhibited MDA-MB-231 (IC50 5.4 × 10−6 M). Fluorescence investigations were indicated a similar rate of both STQ-H and STQ-CN accumulation in the cytoplasm

Selective and Effective Sensing of Cyanide Ion with no Interference in Water by Phenothiazine-indolium Fused Optical Sensor.

The sensor with electron donor phenothiazine-2-carbaldehyde and electron acceptor indolium carboxylic acid, is developed with an intramolecular charge transfer transition between them. The synthesized molecule senses cyanide ion in water. The cyanide ion reacts with the molecule via nucleophilic addition in the indolium ring with a noticeable purple to colorless change in the solution observed. Also with the cyanide ion interaction, the sensor exhibits change in UV-visible absorption and fluorescence spectra. While the other ion does not show spectral and visual changes when interacts with the sensor molecule. Also the interference study reveals that the molecule is highly selective towards cyanide ion. Different source of water samples confirms the CN- ion sensing efficiency of the molecule. 1:1 interaction between the molecule PTI and cyanide ion is confirmed from the results of Jobs plot, 1H NMR and HRMS. Paper strips were prepared and this can act as a simple tool to sense cyanide ion in various water samples.

In English

Changes in the light absorption spectrum when mixing colloids of Ag nanoparticles with a diameter of 7 nm in a quercetin shell with a nutrient medium were studied in the present article. Colloids of silver nanoparticles were prepared by chemical reduction of AgNO3 silver salt with sodium tetrahydroborate (NaBH4) in an aqueous solution. Quercetin is a flavonoid of plant origin. It was chosen to stabilize nanoparticles due to its capability to form complexes with metals. The quercetin shell is capable to preserve the bactericidal effect of silver NPs on bacteria and weaken their toxic effect on healthy cells of the human body. The absorption spectra of solutions from which nanoparticle colloids were synthesized were used to control the synthesis result. The Luria-Bertani nutrient medium was studied in the work. Absorption spectra of the nutrient medium and nanoparticle colloids were again obtained immediately before mixing. Then, the nutrient medium and the nanoparticle colloid were mixed in volume proportion 1:1, and the absorption spectrum of the mixture was mesured. The absorption spectrum of the mixture did not reproduce a simple overlay of the nanoparticle colloid spectrum on the absorption spectrum of the nutrient medium. To describe the experimental spectra, a colloid of stabilized silver nanoparticles, a nutrient medium, and a mixture of a colloid and a nutrient medium were considered by nanocomposites of various organic and inorganic nanoparticles in a liquid. As a result, experimental absorption spectra were theoretically approximated by related to these nanoparticles elementary oscillators. The error of the discrepancy between experimental and simulated spectra did not exceed 3%. Analysis of the complex spectra of the mixture of the nanoparticle colloid and the nutrient medium has shown that the frequency of the localized plasmon resonance in the nanoparticles most likely does not change. It means that for studying the effect of nanoparticles on biological objects (microbes or viruses), the wavelength of external irradiation must be chosen equal to the wavelength of LPR in the colloid.

Benzazole-Based ESIPT Fluorophores: Proton Transfer from the Chalcogen Perspective. A Combined Theoretical and Experimental Study.

In this study, we present a comprehensive photophysical investigation of ESIPT-reactive benzazole derivatives in both solution and the solid state. These derivatives incorporate different chalcogen atoms (O, S, and Se) into their structures, and we explore how these variations impact their electronic properties in both ground and excited states. Changes in the UV-Vis absorption and fluorescence emission spectra were analyzed and correlated with the chalcogen atom and solvent polarity. In general, the spectral band of the benzazole derivative containing selenium was redshifted in both the ground and excited states compared to that of its oxygen and sulfur counterparts. Furthermore, we observed that the solvent played a distinctive role in influencing the ESIPT process within these compounds, underscoring once again the significant influence of the chalcogen atom on their photophysical behavior. Theoretical calculations provided a deeper understanding of the molecular dynamics, electronic structures, and photophysical properties of these compounds. These calculations highlighted the effect of chalcogen atoms on the molecular geometry, absorption and emission characteristics, and intramolecular hydrogen bonding, revealing intricate details of the ESIPT mechanism. The integration of experimental and computational data offers a detailed view of the structural and electronic factors governing the photophysical behavior of benzazole derivatives.

Combined Effect of Mn(II) and Resorcinol on Duckweed

This study explores the combined toxic effect of Mn(II) and resorcinol (0.01 n and 0.2 n) on duckweed (Lemna minor). During the acute experiments, the plants released electrolytes into the aquatic environment after 30 min of exposure to the toxicants, indicating a disruption of tissue permeability as a test response. The experiments showed that the toxicity of the equinormal mixtures of resorcinol and Mn(II) (0.2 n each) increased relative to their single solutions. This was observed both in the freshly prepared solutions and in the solutions stored for 20 h prior to the experiments. The change in the UV absorption spectra indicates that there was complexation or other interaction between resorcinol and Mn(II) at equinormal concentrations (0.01 n). At the Mn(II) : resorcinol ratio of 1:20 (0.01 n Mn(II) and 0.2 n resorcinol), the toxicity of the system to duckweed decreased compared to the separate effects of these substances. The results obtained highlight the importance of considering the interactions between heavy metals and phenolic compounds when assessing the quality of aquatic environments.

Optical absorption tensors based on C70 trimers and polymers

The optical absorption spectra of C60-dimers and polymers were investigated by Kikuo et al. in 1996 (Harigaya, 1996). As a complement to these earlier studies, the optical absorption spectrum of the C70 fullerene has been investigated in the present study. The main purpose was then to compare the absorption spectra of the C70 dimers and trimers and, more specifically, to clarify the effect of these molecular structures on their absorption spectra. What was most important and decisive was the importance of the conjugation parameter of these C70-based molecules. A tight-binding model was used in calculating the optical absorption spectra of both C70 dimers and polymers, as well as of the C70 trimers and polymers. The change in conjugation parameter for each of these species was found to cause variations in the corresponding optical absorption spectrum. It was found that the absorption tensors of the C70 trimer and polymer depended on the value of the conjugation parameters (b=0.5 and b=0.8). However, the optical absorption spectrum was almost the same for the conjugation parameters b=0.1 and b=0.2. In addition, the value of the band gap was also different depending on the different conjugation parameters, with a reduced value for larger values of this parameter. As a conclusion, smaller values of the conjugation parameter were not found to have a large effect on the absorption spectra of the C70 dimers and trimers, or in other words, the effect was hardly visible. On the contrary, the larger values caused drastic changes in the optical absorption spectra of the C70 dimers and trimers.

A Chromogenic Probe for Detection of Biologically Important Anions and its Implications for Designing Molecular Logic Gates.

Detection of fluoride (F-), acetate (AcO-), and cyanide (CN-) anions is vital from the biological and environmental aspects. In the present contributions, we have introduced a simple Salen-type chromogenic sensor, BEN, to detect these biologically important anions. Changes in UV-visible absorption spectra and color of BEN solution from very pale yellow to pink color are similar for each of these anions and found to be reversible only in the case of F- ions in attendance of HSO4- ions. The estimated limit of detection of BEN solution for detecting F-, AcO-, and CN- anions is found to be below the micromolar (μM) concentration level. Our fabricated handy paper test kit is suitable for qualitatively naked-eye detection of the anions. An immediate quantitative estimation of these important anions is possible using our BEN employing a smartphone, avoiding any costly experimental setup.