Phosphates Induced H-Type or J-Type Aggregation of Cationic Porphyrins with Varied Side Chains.

Non-covalent interactions have been extensively used to fabricate nanoscale architectures in supramolecular chemistry. However, the biomimetic self-assembly of diverse nanostructures in aqueous solution with reversibility induced by different important biomolecules remains a challenge. Here, we report the synthesis and aqueous self-assembly of two chiral cationic porphyrins substituted with different types of side chains (branched or linear). Helical H-aggregates are induced by pyrophosphate (PPi) as indicated by circular dichroism (CD) measurement, while J-aggregates are formed with adenosine triphosphate (ATP) for the two porphyrins. By modifying the peripheral side chains from linear to a branched structure, more pronounced H- or J-type aggregation was promoted through the interactions between cationic porphyrins and the biological phosphate ions. Moreover, the phosphate-induced self-assembly of the cationic porphyrins is reversible in the presence of the enzyme alkaline phosphatase (ALP) and repeated addition of phosphates.

Enhanced Photoluminescence of Curcuma longa Extracts via Chitosan-Mediated Energy Transfer for Textile Authentication Applications.

Dyes for security markings play a pivotal role in safeguarding the integrity of products across various fields, such as textiles, pharmaceuticals, food, and manufacturing among others. However, most commercial dyes used as security markings are costly and may contain toxic and harmful substances that pose a risk to human health. Curcumin, a natural phenolic compound found in turmeric, possesses distinct photoluminescent properties alongside its vibrant yellow color, making it a potential candidate material for authentication applications. This study demonstrates a cost-effective and eco-friendly approach to develop enhanced photoluminescent emissions from curcumin dyes for textile authentication. Curcumin was extracted from C. longa using sonication-assisted-solvent extraction method. The extract was dip-coated and dyed into the textile substrates. Chitosan was introduced as a post-mordanting agent to stabilize the curcumin and as a co-sensitizer. Co-sensitization of curcumin with chitosan triggers energy transfer to enhance its luminescent intensity. The UV-visible absorption peak at 424 nm is associated with the characteristic absorption of curcumin. The photoluminescence measurements showed a broad emission peaking at 545 nm with significant enhancement attributed to the energy transfer induced by chitosan, thus showing great potential as a naturally derived photoluminescent dye for authentication applications.

Adenosine Triphosphate Templated Self-Assembly of Cationic Porphyrin into Chiral Double Superhelices and Enzyme-Mediated Disassembly.

Self-assembly of small molecules through noncovalent interactions into nanoscale architectures has been extensively studied in supramolecular chemistry. However, it is still challenging to develop a biologically inspired self-assembly system that functions in water with complex structure and dynamics by analogy with those found in nature. Here, we report a new water-soluble cationic porphyrin that undergoes adenosine triphosphate (ATP)-templated self-assembly into right-handed double-helical supramolecular structures. Direct observation of the porphyrin-ATP assembly by transmission electron microscopy has been accomplished. The assemblies consist of superhelical fibers with length greater than 1 µm and width ∼46 nm. The chiral superhelical fibers show reversible disassembly to monomers upon hydrolysis of ATP catalyzed by alkaline phosphatase (ALP), and the nanofibers can be re-formed with subsequent addition of ATP. Moreover, transient self-assembly of a chiral double helix is formed when ALP is present to consume ATP.