A new two-dimensional, spiropyran-based polymer fluorescent nanoprobe with quantitative-fluorescent and photochromic properties for multi-substance detection.

One challenge of the structural design of a fluorescent probe is how to improve the detection performance on trace target analytes in complex samples. Herein a new polymer fluorescent nanoprobe (2DSP-C28) has been synthesized, by adopting a two-dimensional (2D), spiropyran (SP)-based nanosheet structure with hydrophobic long-chain alkanes (C28). Unlike a traditional SP-based small molecule probe, the 2DSP-C28probe can exhibit quantitative-fluorescent and photochromic properties. Under the detection of metal-ions, the nanoprobe in dimethyl sulfoxide aqueous solution is selectively fluorescent-quenched-responsive for Fe-ions (∼100µM), with a characteristic stoichiometric ratio of <10, a high sensitivity (limit of detection: ∼0.2µM). When the nanoprobe is incorporated into electrospun polyethylene oxide, it can be used for gas detection, and display a color-change with acid-base gas and identify the HF gas. It is expected that this new polymer fluorescent nanoprobe can be promisingly applied for rapidly environmental monitoring on the ion or gas pollution.

Thiol-ene chemistry incorporates a new spiropyran-containing polyurethane ionogel with photochromic, photomechanical and photoconductive properties.

The photocuring technology based on thiol-ene click reaction can be easily applied for copolymerizing or crosslinking the acrylate monomers for ionogels. However, there is still a problem: when the acrylate monomers contain the popular spiropyran as the stimuli-responsive group, it should be concerned about the participation of the active CC bond from the ring-opened spiropyran during a thiol-ene reaction, which may in turn affect the stimuli-responsiveness of the spiropyran. Up to now, the structure and properties of spiropyran-containing ionogels in this case have still not been well investigated. Therefore, in this work we carefully study a new spiropyran-containing polyurethane ionogel by crosslinking an acrylate-terminated, spiropyran-containing polyurethane prepolymer and a polythiol in ionic liquid through thiol-ene chemistry. It is found for the first time that, during constructing an ionogel, the coexistence of a reversible thiol-ene reaction between the CC bond from the ring-opened spiropyran and the thiol group can bring about a different reverse photochromic behavior. The proposed mechanism of the abnormal photochromism is analyzed. In addition, it is also observed that the thiol-ene chemistry can incorporate photomechanical and photoconductive properties into the new spiropyran-containing ionogel.