Visualization of Polymer Dynamics in Cellulose Nanocrystal Matrices Using Fluorescence Lifetime Measurements

FLIM-FRAPP: near-simultaneous characterization of multi-scale polymer dynamics via fluorescence microscopy

Characterizing multi-scale dynamics of polymers is crucial to inform property-process relationships, but there is an outstanding gap between accessibility and comprehensive data collection. To this end, we present a new multi-scale characterization method, FLIM-FRAPP, a near-simultaneous, hybrid approach between fluorescence lifetime measurement (FLIM) and fluorescence recovery after patterned photobleaching (FRAPP) to probe the glass transition temperature and self-diffusion coefficient of a model entangled copolymer, poly(methyl acrylate-stat-methyl methacrylate) (P(MA-stat-MMA)). Our investigation reveals opportunities and challenges concerning the nature of fluorescence characterization techniques for the exploration of polymer dynamics.

Bioinspired Composite Materials with Amplified Clusteroluminescence: Chemodosimetric Interaction Targeting Hypochlorite in Aqueous Medium

Owing to the advantages of cellulose such as exceptional biocompatibility and biodegradability, we synthesized cellulose-grafted bisindolyl methane (BIM) (1. Cell) composite. This biobased smart material was used as an effective colorimetric and fluorescent sensor for hypochlorite in the aqueous medium with a detection limit of 0.02 μM. Interestingly, cellulose exhibited inherent clusteroluminescence in solution, which was further intensified by the probe acting as a dopant. Both the boronic acid and bisindole groups in probe 1 are essential for this enhanced fluorescence, as boronic acid enables boronate ester formation with cellulose, while the bisindole groups facilitate additional hydrogen bonding interactions. This unique dual functionality produces a strong, solution-phase clusteroluminescent effect, creating a rigid microenvironment that promotes long-range exciton migration and an amplified fluorescence response. Furthermore, the 1. Cell exhibited ∼2.8-fold quenching, while probe 1 alone exhibited negligible fluorescence change in the presence of hypochlorite. Mechanistic investigation reveals that the probe formed a boronate ester via the interaction with cellulose, which was subsequently cleaved in the presence of hypochlorite. The differences in the response might be attributed to the distinct nature of their self-assemblies; 1. Cell could form long-range highly ordered aggregates, while probe 1 alone in the aqueous medium resulted in spontaneous random aggregates. Additionally, we employed cellulose paper strips to explore the practicability of the probe as a paper-based sensor. The chemically modified paper strips, grafted with probe molecules, were found to be stable for a week and could effectively detect hypochlorite in the presence of interfering analytes via the naked eye and fluorescent color-changing response.

Phasor-FLIM analysis of cellulose paper ageing mechanism with carbotrace 680 dye

Ageing of paper is a complex process of great relevance for application purposes because of its widespread use as support for information storage in books and documents, and as common low-cost and green packaging material, to name a few. A key factor in paper ageing is the oxidation of cellulose, a macromolecule of natural origin that constitutes the main chemical component of paper. Such a complex process results in changes in the cellulose polymeric chains in chemical and structural properties. The scope of this work is to explore the effects of oxidation of cellulose as one of the principal mechanisms of ageing of paper using a fluorescence-based approach. To this aim, fluorescence-lifetime imaging microscopy (FLIM) measurements on pure cellulose samples stained using Carbotrace 680 dye were performed, and data were analyzed by phasor approach. The comparison with results from conventional techniques allowed to map paper microstructure as a function of the sample oxidation degree correlating the fluorescence-lifetime changes to cellulose oxidation. A two-step oxidation kinetics that produced specific modification in paper organization was highlighted indicating that FLIM measurements using Carbotrace 680 dye may provide a simple tool to obtain information on the oxidation process also adding spatial information at sub-micrometric scale.