Changes In Absorption Spectra Research Articles

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.

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

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.

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.

Exploiting Hydrogen Interaction of Drugs and Biodegradable Scaffolds Using Nanoparticles Loaded Nanofibers

AbstractThis study presents a detailed investigation of the structural and surface modifications of Fe3O4 nanoparticles (NPs). Fourier Transform Infrared (FTIR) spectroscopy was utilized to analyze the distinct characteristic peaks of Fe3O4 NPs and their subsequent modifications with stearic acid (ST) layers. The FTIR analysis revealed characteristic peaks at 580 cm−1, and 441 cm−1, corresponding to the Fe‐O stretching vibrations of the bulk Fe3O4 NPs. The successful loading of stearic acid onto the Fe3O4 NPs was confirmed by the appearance of new peaks at 1413 cm−1 and 2908 cm−1, indicative of the asymmetric CH2 stretch and CH3 umbrella vibration modes of stearic acid. UV‐Vis spectroscopy further corroborated the efficient loading of tetracycline and ibuprofen onto Fe3O4/DST nanoparticles, as evidenced by changes in absorption spectra. N2 adsorption‐desorption isotherms illustrated the presence of micro and meso pores on the surface of Fe3O4 NPs, with alterations in pore volume and diameter post‐surface modification and drug loading. Evaluation of magnetic properties indicated a reduction in saturation magnetization after surface modification and drug loading, attributed to changes in homogeneity and surface moments. Differential Reflectance Spectroscopy (DRS) and Raman spectroscopy elucidated distinctive peaks and shifts in spectra, confirming the composition and structural changes in drug‐loaded nanofibers.

Spectroscopic behavior of bufotenine and bufotenine N-oxide: Solvent and pH effects and interaction with biomembrane models

Bufotenine is a fluorescent analog of Dimethyltryptamine (DMT) that has been widely studied due to its psychedelic properties and biological activity. However, little is known about its spectroscopic properties in different media. Thus, we present in this work, for the first time, the spectroscopic behavior of bufotenine and bufotenine N-oxide by means of their fluorescence properties. Both molecules exhibit changes in optical absorption and emission spectra with variations in pH of the medium and in different solvents. Assays in the presence of biomembranes models, like micelles and liposomes, were also performed. In surfactants titration experiments, the spectral shift observed in fluorescence shows the interaction of both molecules with pre-micellar structures and with micelles. Steady state anisotropy measurements show that both bufotenine and bufotenine N-oxide, in the studied concentration range, interact with liposomes without causing changes in the fluidity of the lipid bilayer. These results can be useful in studies that aim at searching for new compounds, inspired by bufotenine and bufotenine N-oxide, with relevant pharmacological activities and also in studies that use these molecules as markers of psychiatric disorders.

An Introduction to Processing, Fitting, and Interpreting Transient Absorption Data.

Transient absorption (TA) spectroscopy is a powerful time-resolved spectroscopic method used to track the evolution of excited-state processes through changes in the system's absorption spectrum. Early implementations of TA were confined to specialized laboratories, but the evolution of commercial turn-key systems has made the technique increasingly available to research groups across the world. Modern TA systems are capable of producing large datasets with high energetic and temporal resolution that are rich in photophysical information. However, processing, fitting, and interpreting TA spectra can be challenging due to the large number of excited-state features and instrumental artifacts. Many factors must be carefully considered when collecting, processing, and fitting TA data in order to reduce uncertainty over which model or set of fitting parameters best describes the data. The goal of data preparation and fitting is to reduce as many of these extraneous factors while preserving the data for analysis. In this method, beginners are provided with a protocol for processing and preparing TA data as well as a brief introduction to selected fitting procedures and models, specifically single wavelength fitting and global lifetime analysis. Commentary on a number of commonly encountered data preparation challenges and methods of addressing them is provided, followed by a discussion of the challenges and limitations of these simple fitting methods.

A sensor array based on a nanozyme with polyphenol oxidase activity for the identification of tea polyphenols and Chinese green tea

Green tea is popular among consumers because of its high nutritional value and unique flavor. There is often a strong correlation among the type of tea, its quality level and the price. Therefore, the rapid identification of tea types and the judgment of tea quality grades are particularly important. In this work, a novel sensor array based on nanozyme with polyphenol oxidase (PPO) activity is proposed for the identification of tea polyphenols (TPs) and Chinese green tea. The absorption spectra changes of the nanozyme and its substrate in the presence of different TPs were first investigated. The feature spectra were scientifically selected using genetic algorithm (GA), and then a sensor array with 15 sensing units (5 wavelengths × 3 time) was constructed. Combined with the support vector machine (SVM) discriminative model, the discriminative rate of this sensor array was 100% for different concentrations of typical TPs in Chinese green tea with a detection limit of 5 μM. In addition, the identification of different concentrations of the same tea polyphenols and mixed tea polyphenols have also been achieved. Based on the above study, we further developed a facile and efficient new method for the category differentiation and adulteration identification of green tea, and the accuracy of this array was 96.88% and 100% for eight types of green teas and different adulteration ratios of Biluochun, respectively. This work has significance for the rapid discrimination of green tea brands and adulteration.

One-pot polycondensation and characterization of melamine-based polymer for mercury and sodium hypochlorite sensing

A porous, low-cost, organic, amorphous and carbon-nitride functionalized polymer was synthesized using melamine and 5-bromo-2-thiophenecarboxaldehyde. One-pot polycondensation method was opted, to yield hyper-crosslinked polyaminal network which was used for the detection of NaOCl and Hg2+. Reaction proceeds in single step without addition of any catalyst and gives promising yield. The authenticity of the synthesized polymer MB was established using X-Ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR) and Energy-dispersive spectroscopy (EDS). However, the morphology and thermal stability of MB was studied using X-Ray diffraction (XRD) & Scanning electron microscopy (SEM) and Thermogravimetric analysis (TGA) & Differential thermal analysis (DTA) respectively. BET studies were carried out to analyze the porous structure of MB. The pore diameter is centred at 6.2851 nm with specific surface area of 24.348 m2 g–1 and pore volume of 0.038258 cm3 g–1. The TGA curve showed that it has a good thermal stability (250°C). The synthesized compound was checked for its sensing behaviour with different analytes (metal ions: Cu2+, Cr2+, Mg2+, Cd2+, Mn2+, Zn2+, Pb2+, Hg2+; acids: HCl, H2SO4, HNO3 and ROS: t-BuOOH, KO2, NaOCl) in deionized water and was found to show significant change in intensity with NaOCl and Hg2+. The change in absorption spectra was observed at varied concentrations of NaOCl and Hg2+ solutions in deionized water using UV-Vis. Spectrophotometer.

Unveiling structural and energetic characterization of the emissive RNA alphabet anchored in the methylthieno[3,4-d]pyrimidine heterocycle core.

This study presents a comprehensive theoretical exploration of the fluorescent non-natural emissive nucleobases- mthA, mthG, mthC, and mthU derived from the methylthieno[3,4-d]pyrimidine heterocycle. Our calculations, aligning with experimental findings, reveal that these non-natural bases exert minimal influence on the geometry of classical Watson-Crick base pairs within an RNA duplex, maintaining H-bonding akin to natural bases. In terms of energy, the impact of the modified bases, but for mthG, is also found to be little significant. We delved into an in-depth analysis of the photophysical properties of these non-natural bases. This investigation unveiled a correlation between their absorption/emission peaks and the substantial impact of the modification on the energy levels of the highest unoccupied molecular orbitals (HOMO) and the lowest unoccupied molecular orbital (LUMO). Notably, this alteration in energy levels resulted in a significant reduction of the HOMO-LUMO gap, from approximately 5.4-5.5 eV in the natural bases, to roughly 3.9-4.7 eV in the modified bases. This shift led to a consequential change in absorption and emission spectra towards longer wavelengths, elucidating their bathochromic shift.

Self-indicating polymers: a pathway to intelligent materials.

Self-indicating polymers have emerged as a promising class of smart materials that possess the unique ability to undergo detectable variations in their physical or chemical properties in response to various stimuli. This article presents an overview of the most important mechanisms through which these materials exhibit self-indication, including aggregation, phase transition, covalent and non-covalent bond cleavage, isomerization, charge transfer, and energy transfer. Aggregation is a prevalent mechanism observed in self-indicating polymers, where changes in the degree of molecular organization result in variations in optical or electrical properties. Phase transition-induced self-indication relies on the transformation between different phases, such as liquid-to-solid or crystalline-to-amorphous transitions, leading to observable changes in color or conductivity. Covalent bond cleavage-based self-indicating polymers undergo controlled degradation or fragmentation upon exposure to specific triggers, resulting in noticeable variations in their structural or mechanical properties. Isomerization is another crucial mechanism exploited in self-indicating polymers, where the reversible transformation between the different isomeric forms induces detectable changes in fluorescence or absorption spectra. Charge transfer-based self-indicating polymers rely on the modulation of electron or hole transfer within the polymer backbone, manifesting as changes in electrical conductivity or redox properties. Energy transfer is an essential mechanism utilized by certain self-indicating polymers, where energy transfer between chromophores or fluorophores leads to variations in the emission characteristics. Furthermore, this review article highlights the diverse range of applications for self-indicating polymers. These materials find particular use in sensing and monitoring applications, where their responsive nature enables them to act as sensors for specific analytes, environmental parameters, or mechanical stress. Self-indicating polymers have also been used in the development of smart materials, including stimuli-responsive coatings, drug delivery systems, food sensors, wearable devices, and molecular switches. The unique combination of tunable properties and responsiveness makes self-indicating polymers highly promising for future advancements in the fields of biotechnology, materials science, and electronics.

Ultrafast spectroscopy of the hydrophilic carotenoid crocin at various pH.

This study delves into the pH-dependent effects on the excited-state behavior of crocin, a hydrophilic carotenoid with diverse functions in biological systems. Steady-state spectroscopy demonstrates notable changes in absorption and fluorescence spectra, characterized by a pH-dependent blue shift and altered resolution of vibrational bands. Transient absorption spectra further elucidate these effects, highlighting a significant blue shift in the S1-Sn peak with increasing pH. Detailed kinetic analysis shows the pH-dependent dynamics of crocin's excited states. At pH 11, a shortening of effective conjugation is observed, resulting in a prolonged S1/ICT lifetime. Conversely, at pH 9, our data suggest a more complex scenario, suggesting the presence of two distinct crocin species with different relaxation patterns. This implies structural alterations within the crocin molecule, potentially linked to the deprotonation of hydroxyl groups in crocin and/or saponification at high pH.