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Due to their structural features, macrocyclic compounds such as calixarenes, conjugated with a variety of fluorophores have led to the development of fluorescent probes for numerous applications. This review covers the recent advances (from 2009 to date) made in calixarene-based fluorescent sensors and their biological applications. In addition to the fluorescence mechanisms used to signal the analyte binding, this article focuses mainly on the detection of biological relevant ions, on the selective sensing of biomolecules, such as amino acids, enzymes, drugs and other organic compounds, and on intracellular imaging. Calixarene-containing fluorescent nanoparticles and nanoaggregates for imaging and drug delivery are also described. Finally, this review presents some conclusions and future perspectives in this field. [ABSTRACT FROM AUTHOR]

A model for the morphology (size, shape, and crystallinity) of carbon dots (CDs) in the solid state consistent with the observed photoluminescence in solution is proposed herein. Overwhelming evidence has been collected that links the data coming from solid‐state analysis (high‐resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), and matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry (MS)) to that of solution (pulsed‐field gradient (PFG)‐NMR spectroscopy, time‐resolved fluorescence anisotropy (TRFA), and steady‐state/time‐resolved fluorescence), allowing the establishment of an overall structural model for CDs. According to this model, the so‐called carbon dots, observed under HRTEM imaging, are in fact supramolecular organized structures dynamically assembled from small to medium‐sized molecular species when the solvent is removed to give the solid form. In this way, the imaged nanoparticles (TEM/AFM) are not covalently bound entities formed during the synthetic process, but instead supramolecular entities formed by noncovalent interactions. These particles, if at all present in solution, have the form of loose associations of relatively small molecules. This study was conducted on CDs obtained from the hydrothermal carbonization (HTC) of a biomass waste (olive wet pomace). [ABSTRACT FROM AUTHOR]

A β-cyclodextrin labeled with seven naphthoyloxy chromophores was studied by steady-state and time-resolved fluorescence spectroscopy in order to get information on the dynamics of energy hopping between chromophores. The steady-state fluorescence anisotropy was recorded as a function of excitation wavelength in a mixture of methanol and ethanol at 110 K (rigid glass). The fluorescence anisotropy decay was obtained under the same conditions by the multifrequency phase-modulation technique upon excitation at 290 nm. The data were analyzed and interpreted on the basis of a theoretical model involving a unique rate constant for energy hopping between nearest neighbors. In particular, this model predicts a long-time leveling-off of the emission anisotropy at 1/7th of the fundamental anisotropy, which is confirmed by both steady-state and time-resolved data and thus indicates that there is no preferred mutual orientation between the chromophores. As regards the rate of energy hopping, an average value of 2 × 109 s-1 can be deduced from the comparison between the theoretical and experimental decays. This value is shown to be consistent with a dipole-dipole mechanism of energy transfer. © 1996 American Chemical Society.

This document is a correction notice for an article titled "Anion Binding by Fluorescent Ureido-Hexahomotrioxacalix[3]arene Receptors: An NMR, Absorption and Emission Spectroscopic Study" published in the journal Molecules. The correction addresses an error in Figure 7 of the original publication, where the same plot was mistakenly placed twice. The corrected version of Figure 7a,b is provided in the correction notice. The authors assure that this correction does not affect the scientific conclusions of the study. [Extracted from the article]

In this work, the oxygen transport and hydrodynamic flow of the PBS Vertical-Wheel MINI™ 0.1 bioreactor were characterized using experimental data and computational fluid dynamics simulations. Data acquired from spectroscopy-based oxygenation measurements was compared with data obtained from 3D simulations with a rigid-lid approximation and LES-WALE turbulence modeling, using the open-source software OpenFOAM-8. The mass transfer coefficients were determined for a range of stirring speeds between 10 and 100 rpm and for working volumes between 60 and 100 mL. Additionally, boundary condition, mesh refinement, and temperature variation studies were performed. Lastly, cell size, energy dissipation rate, and shear stress fields were calculated to determine optimal hydrodynamic conditions for culture. The experimental results demonstrate that the k L can be predicted using S h = 1.68 R e 0.551 S c 1 3 G 1.18 , with a mean absolute error of 2.08%. Using the simulations and a correction factor of 0.473, the expression can be correlated to provide equally valid results. To directly obtain them from simulations, a partial slip boundary condition can be tuned, ensuring better near-surface velocity profiles or, alternatively, by deeply refining the mesh. Temperature variation studies support the use of this correlation for temperatures up to 37 °C by using a Schmidt exponent of 1/3. Finally, the flow was characterized as transitional with diverse mixing mechanisms that ensure homogeneity and suspension quality, and the results obtained are in agreement with previous studies that employed RANS models. Overall, this work provides new data regarding oxygen mass transfer and hydrodynamics in the Vertical-Wheel bioreactor, as well as new insights for air-water mass transfer modeling in systems with low interface deformation, and a computational model that can be used for further studies. [ABSTRACT FROM AUTHOR]