Fluorescence Behavior Research Articles

Drug-Assisted White Light Generation Via Self-Assembly.

White-light (WL) generation using small organic molecules has gained significant attention from researchers working on the interface of supramolecular chemistry and organic materials. Self-assembled multi-chromophoric materials utilizing a drug molecule and microenvironment-sensitive intramolecular charge transfer dye as an emitter offer the possibility of tunable emission. In this investigation, we focused on WL generation via the combination of a polarity-sensitive red-emitting styryl chromone (SC) and a blue-emitting anticancer and psychotherapeutic drug Norharmane (NHM) in a self-assembled micellar system. A detailed spectroscopic investigation allows us to understand the premicellar aggregation process of different types of surfactants with varying charges using the SC dye. Encapsulation of SC and NHM emitters inside the micellar system offers an improved fluorescent behavior, resulting in WL emission due to complementary wavelength overlap. The generated WL is highly photostable and thermally reversible in the self-assembled system. This investigation highlights the significance of the co-assembly of SC dye and NHM drug for the generation of a highly stable WL.

Fluorescence Behavior of Cyanine Fluorophore Cy3 Confined in Anodic Porous Alumina: Advanced Surface Analysis

In this study, an advanced analysis of the three-dimensional (3-D) surface microtexture of anodic porous alumina (APA) arrays was conducted to investigate their efficacy in confining cyanine fluorophore Cy3. The microstructural characterization of APA plays a pivotal role in enhancing the understanding of the material's surface properties, especially when applied to biological arrays and fluorescent dye confinement. To achieve this, Atomic Force Microscopy (AFM) was employed to obtain precise 3-D surface microtexture data. These measurements were complemented by stereometric analyses, adhering to ISO 25178-2: 2012 standards, ensuring a robust quantitative and qualitative evaluation of the surface micromorphology. The analysis revealed a clear correlation between surface roughness parameters and micromorphological changes as a function of varied processing conditions. Notably, the increase in certain fabrication parameters led to significant alterations in the superficial texture, with observable changes in the fractal dimension of the surface structure. The APA arrays, fabricated using a specialized anodization technique followed by a tailored annealing procedure, exhibited extraordinarily large pore sizes, ranging from 1 to 2 μm, which are well-suited for accommodating the Cy3 dye molecules. These pore dimensions offer an enhanced capacity for dye confinement, providing a stable environment for the cyanine fluorophore while promoting optimal fluorescence behavior.

Low-cost Production Method for Fluorescent Particles for Liquid Flow Velocimetry Applications

Abstract In this Technical Note, we present a simple and low-cost production method for fluorescent particle perfectly suitable for velocimetry applications. We leverage the unique ability of Nile Red (NR) fluorophores to adsorb on the polymer surface and/or embed itself in between polymeric chains. The laboratory procedure to dye polyamide particles with the NR and the monetary advantages over commercially available fluorescent particles are outlined. Subsequently, the fluorescence behavior of the dyed particles is tested under a laser illumination source in polar and non-polar liquids. The distinct advantage of the emission spectrum of the NR-dyed particles is demonstrated with sample test results.

Organic Luminescent Cocrystals Based on Benzotriazole Derivatives: Synthesis, Characterization, Crystal Structure and Fluorescence Behavior.

Organic cocrystals have garnered significant research attention owing to their distinctive properties and promising applications. However, challenges in molecular structure design and control of intermolecular interactions continue to impede further advancements. In this study, two novel cocrystals were successfully formed from a series of synthesized benzotriazole derivatives. The resulting cocrystals exhibit bright green and yellow fluorescence under 365 nm light. To elucidate the microstructure of the obtained cocrystals, systematic characterization techniques such as solid-state fluorescence emission spectroscopy, Single-crystal X-ray diffraction (SCXRD), Power X-ray diffraction (PXRD) and density functional theory (DFT) were performed. These benzotriazole-based cocrystals demonstrate distinct fluorescent responses to alkaline and acidic environments, respectively. Additionally, preliminary tests for fingerprint recognition yielded satisfactory results. These findings suggest that the two cocrystals hold potential applications in acid-alkali sensing, anti-counterfeiting labels, and smart material development, while also providing valuable insights for the design and optimization of solid-state luminescent materials.

Unraveling the structure-property relationships in fluorescent phenylhydrazones: the role of substituents and molecular interactions.

This study investigates the structure-property relationships of a series of phenylhydrazones bearing various electron-donating and electron-withdrawing substituents, such as methoxy, dimethylamino, morpholinyl, hydroxyl, chloro, bromo, and nitro groups. The compounds were synthesized, and their structures were characterized using single-crystal X-ray diffraction, powder X-ray diffraction, FTIR spectroscopy, NMR spectroscopy, and DSC. Three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy and UV-Vis spectroscopy were employed to elucidate the complex interplay between the molecular skeleton, substituents, and the resulting photophysical properties. Quantum mechanical calculations provided further insights into the electronic structure and excited-state dynamics of the investigated compounds. The phenylhydrazones exhibited emission wavelengths ranging from 438 to 482 nm, with the molecular backbone playing a crucial role in determining the emission wavelength. The incorporation of electron-donating substituents, such as methoxy and dimethylamino groups, led to enhanced fluorescence intensity, while the presence of nitro groups, resulted in complete fluorescence quenching. This comprehensive study establishes rational design principles for the development of highly emissive phenylhydrazones with tuned photophysical properties and highlights the significance of the molecular skeleton in dictating the fluorescence behavior of this class of compounds.

Solvent-Responsive Fluorescence Behaviors of Aggregation-Induced Emission Poly(acrylic acid) Composites

Solvent-Responsive Fluorescence Behaviors of Aggregation-Induced Emission Poly(acrylic acid) Composites

Pyridinium‐Based Schiff‐Base Fluorescent Chemosensor for Sequential Detection of Al3+ Ions and TNP: Applications in Cell Imaging and Latent Fingerprint Visualization

AbstractA fluorescent pyridinium‐based chemosensor (E)‐1‐(2‐(3‐hydroxy‐4‐((pyridin‐2‐ylimino) methyl) phenoxy) ethyl) pyridin‐1‐ium bromide (BzPySB) was synthesized and characterized using various spectroscopic techniques. The chemosensing potential of BzPySB was explored using UV‐vis and fluorescence spectroscopy in the aqueous medium. The turn‐on fluorescence behavior was observed for BzPySB in the presence of Al3+, while other metal ions were non‐responsive. The B−H and Job′s plot confirmed the 1 : 1 stoichiometric ratio of the BzPySB and Al3+. The in situ generated complex BzPySB‐Al3+ offered selectivity toward TNP via fluorescence turn‐off phenomena with high Ksv and LOD values. The “off‐on‐off” sensing mechanism was elucidated through 1H NMR, mass spectrometry, and DFT calculations. The probe also detected Al3+ in plant and MCF‐7 cells, highlighting its potential in biological systems. Moreover, BzPySB exhibited solid‐state luminescent properties credited to weak π‐π interaction, leading to its successful application in the visualization of latent fingerprints.

Mitochondrial membrane potential-independent near-infrared fluorescent probes for viscosity-exclusive imaging.

Elucidating the intrinsic relationship between disease and mitochondrial viscosity is crucial for early diagnosis. However, current mitochondrial viscosity fluorescent probes are highly dependent on mitochondrial membrane potential (MMP) and are sensitive to other mitochondrial microenvironment parameters. To address these issues, a mitochondria-targeting MMP-independent and viscosity exclusive near-infrared (NIR) fluorescent probe, ACR-DMA, was developed. ACR-DMA consists of thiophene acetonitrile as the skeleton and viscosity-sensitive unit, a pyridinium cation for the mitochondria-targeting group, and a benzyl bromide subunit for mitochondrial immobilization. It is very sensitive to viscosity and shows significant "turn-on" fluorescence behavior at 710 nm with a more than 150-fold fluorescence intensity increase. Furthermore, ACR-DMA can be firmly immobilized in mitochondria and can monitor viscosity changes induced by nystain, monensin, and lipopolysaccharide. Additionally, it was successfully used to visualize mitochondrial viscosity changes resulting from tumors, inflammation, and drug-induced acute kidney injury, revealing the relationship between viscosity and disease both in vitro and in vivo. ACR-DMA is expected to be a promising candidate for diagnosing mitochondrial viscosity-related diseases.

Electronic and photophysical properties of copper (II) Complexes: Insights into solvatochromic Effects, Photoreduction, and fluorescence behavior

Electronic and photophysical properties of copper (II) Complexes: Insights into solvatochromic Effects, Photoreduction, and fluorescence behavior

Debut of enzyme-responsive anionic cyanine for overlap-free NIR-II-to-I dual-channel tumour imaging

The work offers an elegant paradigm for designing a ratiometric NIR-II probe by modulating the fluorescence behaviour of anionic cyanine scaffolds, which was successfully used for in vivo fluorescence angiography and precise tumours localization.

Salicylidene-based dual-responsive 'turn on' fluorometric chemosensors for the selective detection of Zn2+, Al3+ and F- ions: theoretical investigation and applications in the live cell imaging of zebrafish larvae and molecular logic gate operation.

Four salicylidene-based dual-responsive chemosensors 1,5-bis(5-bromosalicylaldehyde)carbohydrazone (R1), 1,5-bis(5-bromosalicylaldehyde)thiocarbohydrazone (R2), 1,5-bis(3-ethoxysalicylaldehyde)carbohydrazone (R3) and 1,5-bis(3-ethoxysalicylaldehyde)thiocarbohydrazone (R4) were synthesized and characterized. The molecular structures of R1 and R3 were confirmed by single crystal X-ray diffraction technique, which crystallized in the orthorhombic Pbcn and monoclinic P21/n space groups, respectively. The chemosensor molecules were investigated for their recognition properties against the selected cations (K+, Ca2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Fe3+ and Al3+) and anions (F-, Cl-, Br-, I-, HSO4-, H2PO4-, ClO4-, N3- and NO3-) by colorimetry, absorption spectroscopy, fluorescence spectroscopy, 1H NMR spectroscopy and theoretical studies. The sensor molecules showed colorimetric responses for the Co2+, Ni2+, Cu2+ and Fe3+ cations and the F- anion. Interestingly, the Zn2+ and Al3+ cations showed only the 'turn on' fluorometric response, whereas the F- anion showed both colorimetric and fluorometric responses. The binding constants were determined using the Benesi-Hildebrand (B-H) equation from the fluorescence titrations and found to be higher for R3 towards the Al3+ cation (2.03 × 106 M-1) with a low limit of detection (1.79 μM) and for R4 towards the F- anion (5.13 × 105 M-1) with a low limit of detection (5.23 μM). The chemosensors established 1 : 2 and 1 : 1 binding stoichiometries with the sensed cations and anion, respectively, as confirmed by Job's plots. The computational studies show a lower band gap of HOMO-LUMO when the chemosensors bind with the sensed inorganic ions compared to the free chemosensors. Furthermore, the observed fluorescent behaviour of the Zn2+ and Al3+ cations have motivated us to investigate the practical applications in the live cell-imaging of zebrafish larvae as well as in the development of a molecular logic gate.

Synthesis of multi-peak emitting carbon dots using phenylenediamine isomers

Revealing the relationship between structure and optical properties of multi-peak emissive carbon dots (CDs) is important. Three types of multi-peak emission CDs were synthesized by one-step hydrothermal method with phenylenediamine (PD) isomers (o/m/p) and maleic anhydride serving as precursors. During the synthesis process, three PDs exhibited different microstructural and chemical states, resulting in various fluorescence emission centers. The multi-peak emission behavior of o-CDs and m-CDs is composed of molecular fluorophores and carbon core states, while that of p-CDs consists of surface states and carbon core states. These different fluorescence centers lead to diverse fluorescence behaviors of the CDs in different solvents and environments. This work inspires the clarification of the relationship between the structural and optical properties of multi-peak emissive CDs.

Preparation of cellulose-based fluorescent aggregations with various morphologies and their microstructure-correlated fluorescence behavior.

We provided an efficient method for preparing fluorescent materials with high specificity. Firstly, the cellulose-based aggregations with adjustable morphologies and sizes were obtained by cross-linking copolymerization and self-assembly. Then, after encapsulating the fluorescein isothiocyanate (FITC) into the hydrophobic microregions of the cellulose-based aggregations by ultrasound/dialysis method, a series of cellulose-based fluorescent aggregations with different morphologies was obtained. The flower-like, tentacle-like, microsphere, hollow sphere, coral-like and solid sphere fluorescent aggregations could be obtained by changing the mass ratio of cellulose to gelatin, the degree of alkylation and the length of the alkyl chain. Scanning electron microscope (SEM), Dynamic light scattering (DLS), UV-vis and Zeta potential confirmed the formation of the cellulose-based aggregations with different morphologies and sizes, which provided basis for the successful encapsulation of FITC. The flower-like fluorescent aggregation showed the maximum fluorescence intensity. This was due to the rigid structure of cellulose, electrostatic repulsion, hydrogen bonding, and the larger surface area in flower-like aggregation, which was conducive to inhibiting π-π stacking and hydrogen bonding interaction of FITC, thus promoting the electron radiative transition. Also, cellulose-based fluorescent aggregation could be processed into fluorescent fiber, coating and printing pattern, and had potential applications in information storage, scene warning, and special fiber.

A Terpyridine Based 1,2,3-Triazol-1,4-diyl-Fluoroionophore-A Fluorometric Study Towards 3d Metal Ions in Acetonitrile.

In this paper, we report on the sensing role of the 1,2,3-triazol unit in a 1,4-diyl arrangement in a fully π-conjugated fluorescent probe 1 (cf. Scheme 1) towards the fluorometric detection of 3d metal ions. The 1,2,3-triazol-1,4-diyl-fluoroionophore 1 was designed in a donor(D)-acceptor(A) arrangement with a 1,2,3-triazol unit as a π-linker between a terpyridine (A) ionophore and a diethylaminocoumarin (D) fluorophore to study the fluorescence behavior towards the divalent 3d metal ions Mn2+, Fe2+, Co2+, Ni2+, Cu2+ and Zn2+. This fluoroionophore 1 is based on an intramolecular charge transfer (ICT) and shows a moderate quantum yield (φf) of 0.508 in acetonitrile. A modulation of the ICT process in 1 through Fe2+, Co2+, Cu2+, Ni2+ and Zn2+ leads to a small red shift of the lowest energetically lying absorption UV/Vis absorption band and to a very strong 3d metal ion induced fluorescence quenching. It should be considered, that the installation of a 1,2,3-triazole unit as a fully π-linker in ICT probes originates no ratiometric fluorescence response towards Fe2+, Co2+, Cu2+, Ni2+ and Zn2+.

Multiphoton Excited Fluorescence Imaging over Metal-Organic Frameworks.

Multiphoton excited fluorescence (MPEF) imaging has emerged as a powerful tool for visualizing biological processes with high spatial and temporal resolution. Metal-organic frameworks (MOFs), a class of porous materials composed of metal ions or clusters coordinated with organic ligands, have recently gained attention for their unique optical properties and potential applications in MPEF imaging. This review provides a comprehensive overview of the design, synthesis, and applications of multiphoton excited fluorescence imaging using MOFs. We discuss the principles behind the fluorescence behavior of MOFs, explore strategies to enhance their photophysical properties, and showcase their applications in bioimaging. Additionally, we address the current challenges and future prospects in this rapidly evolving field, highlighting the potential of multiphoton excited fluorescence imaging by MOFs for advancing our understanding of complex biological processes.

Synthesis and Characterization of Multifunctional Fluorescent-Magnetic Platinum Nanoclusters.

There is great interest in the development of new multifunctional fluorescent-magnetic nanomaterials for use as multimodal diagnostic imaging probes and site-specific drug delivery tools. Metal nanoclusters (NCs) have been reported to possess either fluorescent or magnetic properties, but not both. In this paper, we report the synthesis and characterization of multifunctional fluorescent-magnetic Pt NCs. Our synthesized NCs (0.8 ± 0.2 nm in diameter) exhibit both bright red fluorescence (excitation: 535 nm, emission: 620 nm) and ferromagnetic behavior with hysteresis, which represents a noteworthy and significant advance in the development of Pt NCs. Our findings suggest the potential of our NCs to be applied in multimodal fluorescent-magnetic nanomaterials for biomedical applications.

Aggregation‐Driven Fluorescence Behavior of EuMOF for Aldehydes Detection

ABSTRACTThis research leverages the fluorescence properties of a europium metal–organic framework (EuMOF) to assess the presence of aldehydes in food. The EuMOF demonstrates three distinct excitation peaks, with an unusual change in fluorescence intensity attributed to the excessive aggregation observed in the initial two peaks. Aldehydes, specifically monoaldehyde compounds (MACs) and dialdehyde compounds (DACs), can engage with the amine groups on the surface of the EuMOF through a Schiff reaction. This interaction disrupts the accumulation process during dilution and allows for the quantification and differentiation of aldehyde compounds based on their unique fluorescence behaviors. By conducting a series of sample dilutions, the ratio between the first two fluorescence excitation peaks can be determined, leading to the creation of a data matrix. The quantitative evaluation of aldehyde‐derived compounds is enabled by deconstructing the original sample matrix using reference matrices of EuMOF and a reaction mixture containing the aldehyde standard. This innovative technique for monitoring aldehydes eliminates the need for sample pretreatment, aldehyde derivatization, and the use of hazardous chemicals in the detection process, offering significant economic and public health benefits.

A Facile and Efficient Synthesis of BODIPY-Based Fluorescent Probes for Selective Detection of Hydrazine.

A facile and ratiometric BODIPY-based fluorescent probe 4 was developed for the selective detection of hydrazine in solution phase. The BODIPY-based fluorophores 3 and 4 were easily prepared in high yields from the L-proline catalyzed reaction between α/β-formyl BODIPY 1 a/1 b and 3-cyanoacetylindole 2. Use of easily accessible substrates, benign solvent, catalytic amount of L-proline and high product yields are the advantageous features of the developed protocol. Prepared BODIPYs 3 (536 nm) and 4 (567 nm) showed bathochromic shifts (36-67 nm) in UV-Visible absorption maxima when compared to parent BODIPY (500 nm) in dichloromethane (DCM). The stable and economical BODIPY-based probe 4 exhibited rapid response and remarkable selectivity towards hydrazine when compared to other commonly occurring analytes. At low concentration, the BODIPY probe 4 (10 μΜ) is non-fluorescent, however, a significant enhancement in fluorescent (turn-on) was observed with the increasing concentration of hydrazine (0-100 μΜ). This change in fluorescent behaviour may be ascribed to intramolecular charge transfer (ICT) effect as supported by density functional theory (DFT) calculations. With a 4.3 μM detection limit, the BODIPY probe 4 was also found to be useful in detecting hydrazine in real environmental samples.

Thermodynamic Fluorescence Behavior of a Fluorenone Derivative through Solvent‐ and Temperature‐Controlled Hydrogen Bonding

AbstractA fluorenone derivative with an extended conjugated structure emitting visible light was examined as a functional fluorescent dye that responds to solvent and heat stimuli in a precisely controlled manner. Intermolecular hydrogen bonds between the fluorenone dye and solvent, which cause fluorescence (FL) quenching due to vibronic coupling, were broken and regenerated by adjusting the hydrogen bond acidity and basicity of solvent mixtures in various combinations or by varying the temperature. The fluorenone dye exhibited a unique heat‐induced FL emission enhancement during heating and returned to the quenched state during cooling. Thus, this FL change was highly reversible and repeatable. Moreover, through thermodynamic consideration based on the spectroscopic analysis, the Gibbs energy change was calculated for each solvent mixture composition to predict the thermodynamic preference for FL enhancement.

Antenna effect on Zn(II) porphyrin-based molecular ensembles for the detection of 2,4-dinitrophenol through energy and electron transfer process.

Twomodular systems were synthesizedcomposed of triphenylamine (ZnTPAP) and pyrene (ZnPyP) covalently linked at meso position of the Zn(II) porphyrins. Both compounds behaved as energy transfer antenna and orthogonal units to enhance the electron donating ability of Zn(II) porphyrins. Detailed photophysical and aggregation studies reveal that an appreciable electronic interaction exists between peripheral units to the porphyrin π-system so that they behave like strong donor materials. The electrochemical and computational studies demonstrate delocalization of the frontier highest occupied molecular orbital (-5.08eV) over the triphenylamine entities (ZnTPAP) in addition to the porphyrin macrocycle. Fluorescence experiments withZnTPAP and ZnPyP in the presence ofdifferent nitro analytes at various concentrations show turn-off fluorescence behaviour and exhibit superior selectivity towards 2,4-dinitrophenol (DNP) with limit of detection (LOD) of ~ 2.3 and 9.2ppm for ZnTPAP and ZnPyP. Photoinduced electron transfer process is involvedin the static and dynamicfluorescence quenching process. A Stern-Volmer quenching association constant (Ksv) determination revealed that ZnTPAP is more sensitive than the ZnPyP. This is attributed to thestrong donating behaviour of TPA unitscaused by intermolecular interaction through metal center and strong π-π interactions with nitro analytes. The present study provides new insights into the ability to tune the affinity and selectivity of porphyrin-based sensors utilising electronic factors associated with the central Zn(II) ion. Furthermore, a smartphone-interfaced portable fluorimetric method by recognising colour variations in RGB and the luminance (L) values facilitate sensitive and real-time sensing at low concentration levels will have a significant impact on development of a new class of chemosensors.