Design, synthesis, and spectroscopic profiling of novel coumarin dyes: Investigating solvent sensitivity and photophysical properties.

Coumarin dyes are highly versatile and widely employed as fluorescent chemosensors in a variety of fields, including molecular imaging, bioorganic chemistry, analytical chemistry, materials chemistry, biology, and medical science. Thanks to their outstanding photostability and high quantum yield, they represent an ideal choice for developing sensitive and selective sensing platforms. In this study, we successfully designed and synthesized four new dyes based on the coumarin dye molecular skeleton, investigating their solvent sensitivity and spectroscopic properties. Our novel coumarin dyes were synthesized by a straightforward approach, reacting coumarin-3-carboxylic acid succinimidyl ester derivatives with corresponding amines in 1,4-dioxane as a solvent. We carefully monitored the completion of the reactions using thin-layer chromatography (TLC) and characterized these dyes using spectral and elemental analyses. We further investigated the UV, fluorescence, time-correlated single photon counting (TCSPC) technique and time-resolved spectroscopy (TRES) of these dyes in different solvents and on polymer film poly(methyl methacrylate) (PMMA). The quantum yield of the synthesized dyes was determined, with values observed to range between 0.55 and 0.94. Most of the dye-solvent and dye-polymer combinations exhibited single exponential decay, with lifetimes ranging from 2.3 to 3 ns. Minor deviations from single exponential behavior were observed for most of the dyes in toluene, while significant deviations were observed for coumarin dyes with piperazine moiety. We have provided a rationalization of these results in terms of the chemical functionalities of the various dyes. Furthermore, we investigated the effect of interactions between 7-methoxy-2-oxo-N-(2-(piperazin-1-yl)ethyl)-2H-chromene-3-carboxamide and silica nanoparticles (Ludox) on the spectroscopic properties of these dyes, with charge transfer being one possible mechanism contributing to the behavior of the dyes. Additionally, we explored the effect of trifluoroacetic acid (TFA) on the dyes' emission intensity and fluorescence decay. Based on our UV and fluorescence measurements of the dyes in different solvents, we have concluded that these dyes can create excellent donor-acceptor pairs for our upcoming fluorescence resonance energy transfer (FRET) experiments.

Investigations on the interactions of DiAmsar with serum albumins: Insights from spectroscopic and molecular docking techniques.

Diamine-sarcophagine (DiAmsar) binding to human serum albumin (HSA) and bovine serum albumin (BSA) was investigated under simulative physiological conditions. Fluorescence spectra in combination with Fourier transform infrared (FT-IR), UV-visible (UV-vis) spectroscopy, cyclic voltammetry (CV), and molecular docking method were used in the present work. Experimental results revealed that DiAmsar had an ability to quench the HSA and BSA intrinsic fluorescence through a static quenching mechanism. The Stern-Volmer quenching rate constant (Ksv ) was calculated as 0.372 × 10(3) M(-1) and 0.640 × 10(3) M(-1) for HSA and BSA, respectively. Moreover, binding constants (Ka ), number of binding sites (n) at different temperatures, binding distance (r), and thermodynamic parameters (∆H°, ∆S°, and ∆G°) between DiAmsar and HSA (or BSA) were calculated. DiAmsar exhibited good binding propensity to HSA and BSA with relatively high binding constant values. The positive ∆H° and ∆S° values indicated that the hydrophobic interaction is main force in the binding of the DiAmsar to HSA (or BSA). Furthermore, molecular docking results revealed the possible binding site and the microenvironment around the bond.

Optical properties of water-soluble CdTe quantum dots passivated by a biopolymer based on poly((2-dimethylaminoethyl) methacrylate) grafted onto κ-carrageenan.

Poly ((2-dimethylaminoethyl) methacrylate) grafted onto κ-carrageenan (κC-g-PDMA) as a biopolymer was synthesized and applied for surface modification of water-soluble CdTe quantum dots (QDs). The effects of DMA concentration, molar ratio of κC-g-PDMA/CdTe, reaction temperature and time on optical properties of CdTe QDs were investigated via fluorescent (FL) and UV- visible spectra. The results showed that the κC-g-PDMA significantly affects the optical properties of CdTe QDs. The obtained samples were characterized by Fourier transform infrared spectrum (FT-IR), thermogravimetric (TG) analysis, and transmission electron microscopy (TEM). The antibacterial activity, antifungal assays, and cytotoxicity of modified QDs were examined, and a good biocompatibility was observed.