Molar Absorptivity Research Articles

Quantification of tungsten in real samples spectrophotometrically using optical sensor

A new methodology was devised to detect tungsten in aqueous samples, employing a sensor membrane crafted by physically incorporating a tungsten-selective compound, 5-(2 -bromophenylazo)-6-hydroxypyrimidine-2,4-dione (BPAHPD), into a plasticized poly(vinyl chloride). The addition of Triton X-114 was observed to be advantageous in augmenting the absorption of HWO4− ions from the liquid phase into the membrane phase, thereby amplifying sensor absorption intensity. The method established a linear dynamic span of 15–350 ng mL−1 for W(VI), exhibiting a notable correlation coefficient of 0.9992. Quantification and detection limits were determined to be 14.85 and 4.45 ng mL−1, correspondingly, under optimized conditions. The Sandell responsiveness and molar absorptivity were calculated at 0.0455 ng cm−2 and 4.04 × 108 L/mol cm−1, respectively. The sensor demonstrated superb selectivity, as demonstrated by the negligible influence of potential interfering species. Statistical analyses, encompassing variance ratio F-tests and Student’s t-tests, indicated no substantial differences. The efficacy of the methodology was authenticated through the scrutiny of genuine samples, with statistical comparison to the ICP-AES method.

BOIMPY Scaffold: Accessing Ultrahigh Molar Extinction Coefficient AIEgen for SWIR Imaging‐Guided Photothermal Cancer Ablation

AbstractDespite the extensive reporting of versatile aggregation‐induced emission luminogens (AIEgens), boosting their molar extinction coefficient (MEC, ε ≈ 103–104 M−1cm−1) remains a formidable challenge, which poses a significant obstacle to achieving the ceiling of their output performance. In this work, an “aggrandizing absorption reservoir” approach is proposed to designing AIEgens with remarkable photons‐harvesting ability, ultimately enlarging its output performance in terms of short‐wave infrared (SWIR, 900–1700 nm) emission and photothermal effect. For the first time, the (bis‐(borondifluoride)‐8‐imidazodipyrromethene) (BOIMPY) unit, which provides sufficient rigidity and strong electron‐withdrawing ability by employing benzimidazole as a bridging ligand binding two BF2 units, is utilized to fabricate novel AIEgen (TPEB) that exhibits an ultrahigh MEC up to 1.29 × 105 M−1 cm−1 at 828 nm. To the best of knowledge, this is the highest MEC reported among AIEgens with near‐infrared absorption. Thanks to its remarkable photon‐harvesting ability, TPEB exhibits strong fluorescence in the SWIR region and a good photothermal effect. The as‐prepared TPEB NPs are successfully applied for SWIR imaging‐guided photothermal antitumor therapy. The proposed “aggrandizing absorption reservoir” approach provides a novel guideline for designing versatile AIEgens for biomedical applications.

Extraction and Physicochemical Characterization of Hydroxyapatites From Horse Humerus Bones of Different Ages (1, 3, 6, and 8 Years old) Calcined at Low Temperature.

The aim of this work is to investigate the changes in the physicochemical properties of hydroxyapatite (HAp) extracted from horse humerus bones of different ages (1, 3, 6, and 8 years) subjected to low temperature calcination (600°C). Thermal analysis revealed significant mass loss due to water, collagen, organic compounds, carbonates, and age-related magnesium out-diffusion. Higher fat content in older bones contributed to increased mass loss. Phosphorus content remained constant across age groups, while calcium and sodium showed age-related fluctuations. Magnesium levels decreased with age, emphasizing its importance for early bone development. The Ca/P ratio deviated from the stoichiometric values due to additional ions from biogenic sources. Infrared spectroscopy identified functional groups in carbonated HAp, with changes observed before and after calcination. The full width at half maximum (FWHM) of the 961 cm-1 band decreased with age, indicating improved crystalline quality. The molar absorption coefficients provided information on the changes in molecular concentration and emphasized the differences between the age groups. X-ray analysis revealed nanocrystalline HAp in all samples, with crystallite size increasing with age. Rietveld analysis showed that the lattice parameters were affected by the presence of organic material, but the lattice constants remained stable, confirming high crystallinity independent of age. TEM analysis confirmed nanocrystalline structures, with crystallite size increasing with age. SEM images showed the characteristic porosity of calcined HAp, with particle size correlating positively with age. Calcination at 600°C preserved the nanoscale properties and microcrystal formation. Raman spectroscopy confirmed the identity of HAp, with FWHM variations indicating age-related changes in crystalline quality. EHAp1 showed increased FWHM, indicating lower crystalline quality and increased trace element content.

RNA-Activatable Near-Infrared Photosensitizer for Cancer Therapy.

Photodynamic therapy (PDT) has recently come to the forefront as an exceptionally powerful and promising method for the treatment of cancer. Existing photosensitizers are predominantly engineered to target diverse biomolecules, including proteins, DNA, lipids, and carbohydrates, and have proven to greatly enhance the efficacy or specificity of PDT. However, it is noteworthy that there exists a conspicuous scarcity of photosensitizers specifically designed to target RNAs. Recognizing the crucial and multifaceted roles played by RNAs in various cellular processes and disease states, we have ventured into the development of a novel RNA-targeting photosensitizer, named Se-718, designed specifically for PDT-based cancer therapy. Se-718 has been engineered to exhibit a high molar absorption coefficient in the NIR region, which is crucial for effective PDT. More importantly, Se-718 has demonstrated a distinct RNA-targeting capability, as evidenced through rigorous testing in both circular dichroism and fluorescence experiments. Furthermore, Se-718 has been shown to display both type I and type II photodynamic properties. This unique characteristic enables the efficient killing of cancer cells under a wide range of oxygen conditions, both normoxic (21% O2) and hypoxic (2% O2). The IC50 of Se-718 can be as low as 100 nM, and its light-to-dark toxicity ratio is an impressive 215 times higher, outperforming most photosensitizers currently available. Moreover, in vivo studies conducted with tumor-bearing mice have demonstrated the excellent antitumor effects and high safety profile of Se-718. Considering the outstanding PDT efficacy of Se-718, we are optimistic that the development of RNA-targeting photosensitizers may provide an innovative and highly effective option for cancer therapeutics in the near future.

Steady and transient modeling of dye-sensitive solar cells: The impact of electrode thickness and dye specifications

Investigating the impact of dye compounds on cell performance is crucial for advancing dye-sensitized solar cells (DSSCs). This research focuses on the sensitivity analysis of the effect of critical parameters to enhance DSSC efficiency using a thermo-electric numerical model. These parameters include dye types, trapping parameters, diffusion coefficients, and photoanode thickness. When the type of dye changes, in fact, both physical and chemical properties (molar absorption coefficient, etc.) Change, but to avoid the complexity of solving the equations and only to evaluate the effect of the absorption wavelength range on the cell performance only changes in physical properties are considered. The model calculates steady and transient currents under actual weather conditions and sunlight. It incorporates time/space-dependent relationships for increased accuracy and examines electron, iodide, and triiodide ion interactions under varying environmental conditions. Key concepts include the quasi-Fermi level and the multiple trap model, assuming that trapping processes are faster than electron transport and recombination. The results showed that increasing the trapping parameter can affect the transient current behavior, also increasing the thickness of the photoanode and the wavelength range of the dye increases the efficiency of the cell, so that the N749-BD provides the best performance. The findings provide insights into current–voltage characteristics, electron production, and the effects of photoanode thickness and dye types on cell performance, offering pathways for optimizing DSSC technology.

Greenness appraisal and spectrophotometric estimation of carvedilol in pharmaceutical formulations and study kinetic parameters

Numerous studies have established that carvedilol acts as a vasodilator and is effective in managing hypertension. Consequently, this research focuses on the development and validation of analytical methods for the quantification of carvedilol. Various techniques, including UV/Vis spectrophotometric methods, have been investigated alongside innovative, straightforward, accurate, and sensitive approaches. In this study, we established a method based on the interaction between carvedilol and alizarin yellow dye in an aqueous medium, allowing for a reaction time of 20 min for completion. Upon conclusion of the reaction, a purple-colored product is formed, which exhibits maximum absorption at a wavelength of 536 nm. This method adheres to Beer's law within the concentration range of 10–50 µg/mL, with a molar absorptivity of 2.560×103 L·mol−1·cm−1, a Sandel index of 0.158 µg. cm−2, the detection limit of 0.4190 µg/mL, and the quantitative limit is 1.2698 µg/mL. The recovery rate was determined to be 100.7010 %, and the relative standard deviation did not exceed 1.3094 %. The method was applied to estimate the concentration of carvedilol in its pharmaceutical formulation in tablet form CARVEDISAM. Additionally, the kinetics of the resulting complex were studied, revealing that the kinetics are of first order. To assess the environmental impact of contemporary UV spectrophotometric methods, the Green Analytical Greenness Metric (AGREE) software and the Green Analytical System Index (GAPI) were utilized to evaluate the greenness profile. The developed UV method is more sustainable and environmentally friendly.

Structural, optical spectroscopic, and density functional theory calculations of squaraine dye for organic electronic applications

The structural, optical spectroscopic, and density functional theory calculations of 2,4-Bis[4-(N,N-diisobutylamino)−2,6-dihydroxyphenyl] squaraine dye (SQ) are promising investigations that can be useful in photochemical mechanisms explanation and in designing promising chemosensors. The nature of the bonds, the chemical composition of SQ, crystallographic structure, morphology, and quality characteristics were explored by FTIR, XRD, and SEM investigations. The crystallite size, the dislocation density, and the lattice strain were found to be 57.3 nm, 3.045 × 10−4 nm−2, and 3.065 × 10−3, respectively. The spectrum behavior of the absorbance and molar absorption coefficient spectra of SQ in DCM with three concentrations were analyzed to get some important optical properties of SQ dye. The determined optical gap transition equals Egapopt=1.81eV. Quantum chemical computations and optimized molecular geometries identified where electrophilic attacks are likely and analyzed the molecule’s electrostatic potential. Using DFT calculations at the B3LYP/6-31+G(d,p) level, the electronic structure of the squaraine molecule was confirmed, showing a HOMO–LUMO gap of 1.73 eV. MEP analysis indicated that the oxygen atoms are electron-rich, suggesting potential for hydrogen bonding and electrophilic interactions.

Kinetic modelling of UVC and UVC/H2O2 oxidation of an aqueous mixture of antibiotics in a completely mixed batch photoreactor

The removal kinetics of an aqueous mixture of thirteen antibiotics (i.e., ampicillin, cefuroxime, ciprofloxacin, flumequine, metronidazole, ofloxacin, oxytetracycline, sulfadimethoxine, sulfamethoxazole, sulfamethazine, tetracycline, trimethoprim and tylosin) by batch UVC and UVC/H2O2 processes has been modeled in this work. First, molar absorption coefficients (ε), direct quantum yields (Φ) and the rate constants of the reaction of antibiotics with hydroxyl radical (kHO•) (model inputs) were determined for each antibiotic and compared with literature data. The values of these parameters range from 0.3 to 21.8 mM−1 cm−1 for ε, < 0.01 to 67.8 mmol·E−1 for Φ and 3.8 × 109 to 1.7 × 1010 M−1 s−1 for kHO•. Second, a regression model was developed to compute the rate constants of the reactions of the antibiotics with singlet oxygen (k1O₂) from experimental data obtained in batch UVC experiments treating a mixture of the antibiotics. k1O₂ values in the 1–50 × 106 M−1 s−1 range were obtained for the antibiotics studied. Finally, a semi-empirical kinetic model comprising a set of ordinary differential equations was solved to simulate the evolution of the residual concentration of antibiotics and hydrogen peroxide (model outputs) in a completely mixed batch photoreactor. Model predictions were reasonably consistent with the experimental data. The kinetic model developed might be combined with computational fluid dynamics to predict process performance and energy consumption in UVC and UVC/H2O2 applications at full scale.

A glutathione responsive photosensitizer based on hypocrellin B for photodynamic therapy

As a typical natural photosensitizer, hypocrellin B (HB) offers the advantages of high molar extinction coefficient, high phototoxicity, low dark toxicity, and fast metabolism in vivo. However, the lack of tumor specificity hinders its clinical applications. Herein, we designed and synthesized a glutathione (GSH) responsive photosensitizer based on HB. The 7 − nitro − 2,1,3 − benzoxadiazole (NBD) covalently connected to HB not only served as a fluorescence quenching group but also as a GSH activating group. The photosensitizer HB−NBD showed almost no fluorescence and singlet oxygen generation as a result of the photoinduced electron transfer between HB and NBD. The designed photosensitizer HB−NBD can be activated by GSH in solutions and cancer cells, and then obtain recuperative fluorescence and photosensitive activity.

Effect of electron-donating and -withdrawing substitutions in naphthoquinone sensitizers: The structure engineering of dyes for DSSCs in Quantum Chemical Study

Dye-sensitized solar cells (DSSCs) are cost-effective photovoltaic devices that convert solar energy into electricity using a dye sensitizer, TiO2 photoanode, electrolyte, and counter electrode. This study investigates the impact of substituents on the performance of naphthoquinone-based dye sensitizers in DSSCs. We analyzed various naphthoquinone derivatives’ electronic structures and light absorption properties using DFT and TD-DFT. Our results demonstrate that electron-donating groups enhance DSSC performance by improving light absorption and electron injection. Specifically, naphthoquinone derivatives with methoxy (Dye-2) and methyl (Dye-3) groups showed superior properties. TD-DFT analysis revealed high molar extinction coefficients over a broad spectrum, making these dyes efficient at capturing sunlight. Additionally, these dyes effectively interact with TiO2, which is crucial for photostability and photovoltaic performance. In conclusion, naphthoquinone derivatives with electron-donating groups significantly improve DSSC performance, with Dye-2 and Dye-3 being strong candidates for high-performance applications.

Gold Nanoparticles Modulate Excimer and Exciplex Dynamics of PDDCP-Conjugated Polymers.

How plasmonic nanostructures modulate the behavior of exciplexes and excimers within materials remains unclear. Thus, advanced knowledge is essential to bridge this gap for the development of optoelectronic devices that leverage the interplay between plasmonic and conjugated polymer hybrid materials. Herein, this work aims to explore the role of gold nanoparticles (AuNPs) in modulating exciplex and excimer states within the conjugated polymer poly(2,5-di(3,7-dimethyloctyloxy) cyanoterephthalylidene) (PDDCP), known for its photoluminescent and semi-conductive properties, aiming to create innovative composite materials with tailored optical features. The spectral analysis was conducted to investigate the effects of AuNPs on the PDDCP, varying AuNP volume percentages to measure changes in the absorption profile, molar extinction coefficient (ε), absorption cross-section (σa), and optical bandgap (Eg). Fluorescence spectra of the mixture at different volume ratios were also examined to assess exciplex formation, while amplified spontaneous emission (ASE) profiles were analyzed to study the behavior and photochemical stability of the polymer-NP hybrid material. Increasing AuNP volume induced both blue and red shifts in the absorption profile of the PDDCP. Higher AuNPs concentrations correlated with decreased ε and σa, inversely impacting Eg. The emission spectra obtained at varied AuNP volume ratios indicated significantly enhanced exciplex and excimer formations. The ASE profiles remained consistent but showed reduced intensity with increasing AuNPs concentrations, indicating their influence on hybrid material behavior and stability. The findings suggest that AuNPs affect PDDCP's optical characteristics, altering the absorption profile, bandgap, and fluorescence spectra. Furthermore, the observed reduction in ASE intensity highlights their influence on the behavior and photochemical stability of the hybrid material. These results contribute to a better understanding of the versatile applications of plasmonic-conjugated hybrid polymers.

Narrow Range of Coagulation of Ion Associates of Poly(styrene sulfonate) with Alcian Blue Dye.

The ionic association of Alcian Blue dye with poly(styrene sulfonate) in aqueous solutions was studied for analytical purposes. The quadruple-charged cationic dye, Alcian Blue, was found to form colloidal ionic associates with poly(styrene sulfonate) anions. When the amounts of opposite charges are nearly equal, the resulting ionic associates lose solubility and coagulate rapidly. This effect occurs within a narrow range of the ratio of poly(styrene sulfonate) to Alcian Blue. At the point of charge equivalence, the zeta potential of the resulting particles is zero, which facilitates flocculation. The resulting flocs enlarge to approximately 0.05-0.5 mm and precipitate rapidly. FTIR spectroscopy confirms that the precipitate contains both poly(styrene sulfonate) and Alcian Blue dye. Sedimentation kinetics was studied in detail using scanning turbidimetry. Due to the high molar absorbance of the Alcian Blue dye at 600 nm, the point of equimolar charge ratio was precisely determined by spectrophotometry. The complete precipitation of ionic associates occurs when the amount of poly(styrene sulfonate) ranges from 1.4 to 1.55 mmol per 1 g of Alcian Blue dye. Such a narrow coagulation range allows for the use of the studied effect for quantitative analysis. Both Alcian Blue dye and poly(styrene sulfonate) can be quantified if one of their concentrations is known.

Spectrophotometric determination of Meloxicam in Pure Form and its Pharmaceutical Formulation following azo dye formation with 4-nitroaniline

A fast, cheap, and straightforward spectrophotometric method has been proposed to determine meloxicam (MEL) in its pure form and pharmaceutical formulation. The technique involves diazotizing the (NH2) group in 4-nitroaniline with NaNO2 followed by a reaction with meloxicam to produce a stable and colored complex in a basic medium. This complex demonstrates maximum absorbance at 514 nm. The developed method's linearity ranges from 2.0 - 25 μg mL-1, and the molar absorptivity is 1.5989×104 L mol-1 cm-1. The RSD% is lower than 1.55%. Additionally, the limit of detection (LOD) is 0.2019 μg mL-1. The method successfully determines the pharmaceutical preparation containing meloxicam (Loxim tablets) with a recovery rate of no less than 97.9%.

Palladium catalyzed carbon-carbon bond formation on tunable quinolines with DFT study

The synthesis of new quinoline fluorophores was accomplished through a meticulous four-step molecular assembly utilizing Suzuki and acid-amine cross-coupling reactions. The integrity of each fluorophore was rigorously confirmed via comprehensive spectroscopic analyses, including 1H and 13C NMR, DEPT-135, H-H COSY, HSQC NMR and HRMS techniques. Subsequently, the absorbance and emission spectra of the newly synthesized fluorophores were thoroughly investigated. Notably, these fluorophores displayed impressive characteristics, with high intensity and significant molar extinction coefficients, along with Stokes shifts ranging from 0.5052 × 104 to 0.6234 × 104 in acetonitrile (ACN) solvent. Absorbance spectra were found to confine within the 320–360 nm range, while emission spectra were consistently observed within the 380–450 nm range upon excitation at 350 nm. The electronic structure of the molecules was elucidated using techniques such as Density Functional Theory (DFT) and Molecular Electrostatic Potential (MEP) mapping. Additionally, the calculated global reactivity parameters provided valuable insights. In particular, compound 8b exhibited a distinctly larger energy gap compared to other fluorophores, demonstrating its exceptional properties. The comparison between experimental and theoretical UV-Vis spectra also showcased the remarkable consistency and quality of the synthesized fluorophores, highlighting the significant potential of this work in the field of fluorophore development.

Control of Aromatic Disinfection Byproducts in Potable Reuse Water by the UV222/H2O2 vs UV254/H2O2 Advanced Oxidation Processes.

Research has demonstrated the difficulty associated with degrading the conventional 1-2 carbon aliphatic halogenated byproducts of disinfectant reactions with organic matter [disinfection byproducts (DBPs)] within advanced oxidation process (AOP) units in potable reuse trains, but the efficacy of AOP units for treating the emerging classes of halogenated aromatic DBPs is unclear. We herein demonstrate more effective removal of 28 halogenated aromatic DBPs in the UV/H2O2 AOP at 222 nm (UV222) than in the conventional UV/H2O2 AOP at 254 nm. Direct photolysis of 28 halogenated aromatic DBPs was greatly enhanced at 222 nm with fluence-based photodecay rate constants of 4.31 × 10-4-1.53 × 10-2 cm2 mJ-1, which was mainly attributed to the higher molar absorption coefficients of halogenated aromatic DBPs at 222 nm than 254 nm. Generally, quantum yields of halogenated aromatic DBPs at both 222 and 254 nm followed the order of halophenols > halohydroxybenzaldehydes > halonitrophenols. All 28 halogenated aromatic DBPs exhibit high reactivity toward HO• with second-order rate constants ranging from 2.18 × 109 to 1.15 × 1010 M-1 s-1 determined by X-ray radiolysis. The UV fluence required to achieve 90% loss of halogenated aromatic DBPs in the UV222/H2O2 AOP was 75-95% lower than that in the UV254/H2O2 AOP, and 90% removal of most tested halogenated aromatic DBPs can be achieved in the UV222/H2O2 AOP within the UV fluence levels commonly applied in potable reuse (700-1000 mJ cm-2).

Performance enhancement of dye solar cell using mixed synthetic organic dyes

The potential of dyes derived from Bromophenol and Rhodamine, both as single and mixed dyes, in dye-sensitized solar cells (DSSCs) to achieve panchromatic light harvesting and enhance cell performance is assessed in this study. The study finds that a high molar extinction coefficient caused by the combined properties of the dyes matched with the spectrum area where the novel sensitizers deficit light-harvesting, indicating effective co-sensitization. To ascertain the dyes' characteristics and appropriateness as sensitizers, a variety of methods, including cyclic voltammetry, UV–Vis spectroscopy, and Fourier-transform infrared spectroscopy (FTIR), are used. Cyclic voltammetry results indicate that the dyes under study exhibit excellent redox stability and sufficient thermodynamic dynamic force for efficient electron introduction. According to the photovoltaic performance statistics, the mixed dye of Rhodamine and Bromophenol based cell had the maximum efficiency (η) and power (Jsc) are 4.06 mA and 1.29 %, respectively. This is made feasible by photosensitive light-harvesting, remarkable visual activity, and sufficient energy levels. Acidified mixed dyes were more able to load on the TiO2 surface due to their homogenous dispersion, reduced steric barriers, and multi-anchor group connected to the semiconductor surface. With such novel mixed dye, it is expected that the mixed dye with not only high efficiency but higher Jsc value will be an alternative to single dyed based DSSCs.

Design of an Acidic pH-Activated NIR Fluorescent Convertible Rhodamine-Hemicyanine Probe-Peptide Conjugate for Living Cancer Cell Active Targeted Selective Tracking of Lysosomes.

We have synthesized an acidic pH-activatable dual targeting ratiometric fluorescent probe-peptide conjugate using the SPPS protocol on Rink amide AM resin. Living carcinoma cell specific active targeting, successive cell penetration, and selective staining of lysosomes are accomplished. Real-time monitoring of lysosomes, 3D, and multicolor cancer cell imaging are also attained. The de novo design consists of the integration of multifunctionality into a single molecular scaffold, e. g., RGDS peptide residue to target cancer cell surface overexpressed receptor αVβ3 integrin, live-cell penetrating organic unsymmetrical rhodamine-hemicyanine chromophore comprising a lysosome targeting morpholine group, and an acidic pH openable spiro-lactam ring for a visible-to-NIR switchable ratiometric response. Water-soluble fluorescent probe-peptide conjugate exhibits intramolecular spirolactamization at basic pH through Arg amide N. The visible spirolactam state predominantly exists at physiological and basic pH and can be switched to the highly conjugated NIR open amide state (λem=735 nm) through spiro-lactam ring opening triggered by acidic pH with a huge bathochromic shift (Δλabs=336 nm, ΔλFL=265 nm). Moreover, pH-sensitive ratiometric optical switching is achieved. This in situ acidic cancer cell lysosome activatable multifunctional fluorophore-peptide conjugate shows augmented molar absorptivity, enhanced quantum yield, and improved fluorescence lifetime at acidic lysosomal pH; negligible cytotoxicity; and dual targeted ratiometric imaging capability of living cancer cell selective lysosomes with a pKa value of 5.1.

Deuteration as a General Strategy to Enhance Azobenzene‐Based Photopharmacology

AbstractChemical photoswitches have become a widely used approach for the remote control of biological functions with spatiotemporal precision. Several molecular scaffolds have been implemented to improve photoswitch characteristics, ranging from the nature of the photoswitch itself (e.g. azobenzenes, dithienylethenes, hemithioindigo) to fine‐tuning of aromatic units and substituents. Herein, we present deuterated azobenzene photoswitches as a general means of enhancing the performance of photopharmacological molecules. Deuteration can improve azobenzene performance in terms of light sensitivity (higher molar extinction coefficient), photoswitch efficiency (higher photoisomerization quantum yield), and photoswitch kinetics (faster macroscopic rate of photoisomerization) with minimal alteration to the underlying structure of the photopharmacological ligand. We report synthesized deuterated azobenzene‐based ligands for the optimized optical control of ion channel and G protein‐coupled receptor (GPCR) function in live cells, setting the stage for the straightforward, widespread adoption of this approach.

Spectrophotometric analysis and mechanistic insights investigation of a developed CT complex as colorimetric real-time sensing performance towards Fe2+ in aqueous medium

A newly developed charge transfer complex (CTC) is explored for colorimetric real-time sensing behavior towards the Fe2+ ion, as a highly selective real-time colorimetric chemosensor material. The synthesized and characterized CTC / P1, [(2HP)+(SA)−] is cheap, remarkably distinctive, and simple to manufacture. Beyond the exposure limitations, iron is also the most common cofactor in enzyme reactions, which is, therefore a crucial part of life. However, too much or not enough iron leads to anemia, liver damage, cancer, Alzheimer's disease, and Parkinson's disease. In this report, unusual sensing capacity has been reported with a relatively low detection limit of 1.247 ppb for Fe2+ ions in aqueous medium, which was lowest at 1.267 ppb in previous reports of CTC sensors. By using a static quenching process, the incredible sensing behavior of this material as a chemosensor was determined. Colorimetric sensing behavior in real-time has also been observed. The complex has been described using a variety of methods, including UV-visible and FTIR spectroscopy. In FTIR spectra, the CTC (P1) showed a change in wavenumber when compared to its reactants. Furthermore, the complex's stoichiometry was measured using UV-visible spectroscopy by taking mixture with an equimolar ratio using the straight-line approach known as the Benesi-Hildebrand equation, which was found to be 1:1. Oscillator strength (f), transition dipole moment (μEN), molar extinction coefficient (εCT), energy of interaction (ECT), and stability constant (KCT) were among the thermodynamic and physical characteristics studied. Van't Hoff's equation was used to compute other parameters such as Gibbs free energy (G°), absorptivity coefficient (ε), Resonance energy (RN), etc. [O+—H……O−] hydrogen bonding was used to depict the interaction between reactants (salicylic acid and 2-hydroxypyridine). The stability of the P1 as a function of temperature is demonstrated through TG/DTA analysis.

Synthesis of a dual-response signal sensor and naked-eye recognition of hypochlorite in real water samples

An innovative dual-modal colorimetric and fluorometric probe MDXM is synthesized based on the dihydro-1H-xanthene motif via Knoevenagel reaction. The incorporation of a malononitrile group into the dihydro-1H-xanthene motif via a double bond results in an extensive macroconjugated π-system, which endows MDXM with a pronounced molar absorptivity and effectively quenches the intramolecular charge transfer (ICT) effect. Upon exposure to hypochlorite, the C = C bond in MDXM undergoes cleavage, resulting in the formation of an aldehyde group. This process restores the ICT effect and manifests as a clear fluorescent ''turn-on'' signal at 530 nm, with a remarkably linear response across the ClO− concentration range of 0–60 μM. The probe achieves a notably low detection limit of 7.14 nM, reflecting its exceptional sensitivity. In the presence of 15 common metal ions and oxidizing agents, MDXM can specifically identify hypochlorite with excellent anti-interference ability. The response mechanism of MDXM to hypochlorite was confirmed through Nuclear Magnetic Resonance (NMR) spectroscopy and computational Density Functional Theory (DFT) calculations. The practical applicability of MDXM is underscored by its successful implementation in analyzing hypochlorite in 5 varied real water samples. This showcases MDXM's promise for environmental and analytical chemistry, providing a robust tool for hypochlorite detection in diverse settings.