Acridinium Benzoates for Ratiometric Fluorescence Imaging

Enhancing the photocatalytic upcycling of polystyrene to benzoic acid: a combined computational-experimental approach for acridinium catalyst design

Converting polystyrene into value-added oxygenated aromatic compounds is an attractive end-of-life upcycling strategy. However, identification of appropriate catalysts often involves laborious and time-consuming empirical screening. Herein, after demonstrating the feasibility of using acridinium salts for upcycling polystyrene into benzoic acid by photoredox catalysis for the first time, we applied low-cost descriptor-based combinatorial in silico screening to predict the photocatalytic performance of a family of potential candidates. Through this approach, we identified a non-intuitive fluorinated acridinium catalyst that outperforms other candidates for converting polystyrene to benzoic acid in useful yields at low catalyst loadings (≤5 mol%). In addition, this catalyst also proved effective with real-life polystyrene waste containing dyes and additives. Our study underscores the potential of computer-aided catalyst design for valorizing polymeric waste into essential chemical feedstock for a more sustainable future.

Enhanced Fluorescence by Inter/Intramolecular Hydrogen Bonding in Si-Substituted Coumarins

Introducing heteroatoms in organic fluorophores offers a unique strategy to tune their photophysical properties without dangling structural decorations. Silicon-substituted coumarins (Si-coumarins) are the analogues of coumarin with the substitution of ester oxygen atoms by silicon atoms. In Si-coumarins, significant fluorescence enhancement in protic solvents through the formation of inter/intramolecular hydrogen bonds (H-bonds) offered great potential in various aspects with many unique photophysical properties. The energies of nπ* and ππ* states in Si-coumarins are elaborately tuned by inter/intramolecular H-bonds and solvents after incorporating silicon atoms. For example, the inter/intramolecular H-bonds elevate the energy of the nπ* state in protic solvents, leading to an enlarged energy gap between the nπ* and ππ* states. Thus, fluorescence is enhanced by reducing the nonradiative transition through the nπ* state in coumarins, resulting in many unique photophysical properties. The understanding of H-bonds in Si-coumarins offers more potential strategies for the design of novel fluorophores.

Ratiometric fluorescence sensing with logical operation: Theory, design and applications

The construction of ratiometric fluorescence sensing logic systems has gradually become a hot topic in fluorescence analysis, due to the multi-target analysis potential of logic operations and the high specificity and selectivity of ratiometric fluorescence sensing. In this paper, the basic principles of various logic functions implemented in ratiometric fluorescence detection are discussed in the context of sensing mechanisms, and the strategies for constructing logic systems in different ratiometric fluorescence sensing application areas are summarized. Although there are limitations such as cumbersome operations and complicated experiments, ratiometric fluorescence sensing logic circuits that combine the visualization of logic operations and the accuracy of ratiometric fluorescence are still worthy of in-depth study. This review may be useful for researchers interested in the construction of logic operations based on ratiometric fluorescence sensing applications.

Acridinium benzoates for ratiometric fluorescence imaging of cellular viscosity

A series of fluorescent molecular rotors, acridinium benzoates (Acr-A,B,C,D), were designed for ratiometrically monitoring cellular viscosity. High sensitivity to viscosity was observed in probe Acr-A with an insignificant steric effect in the acridinium nitrogen. Acr-A was employed to distinguish cancer cells from normal cells and track the dynamics of viscosity during cellular apoptosis.