Dual-Mode Colorimetric/Fluorimetric pH-Sensing and In Situ Visualization of Latent Fingerprints by Haloflourochromic Nanoprobes Prepared from Self-Assembled Multi-Responsive Star-Shaped Block-Copolymers with Anisotropic Janus Morphology
Abstract
Haloflourochromism is a new phenomenon related to fluorimetric and colorimetric responses created by a smart haloflourochromic molecule when exposed to acidic or alkaline media, or aqueous solutions with different pHs, which have potential applications for designing intelligent nanoprobes. To develop haloflourochromic nanoparticles, the symmetric 4-arm star-shaped blockcopolymers based on methyl methacrylate (MMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) were synthesized by a core-first strategy and sequential atom transfer radical polymerization (ATRP). Investigation of the chemical structure and quality of symmetric starshaped block-copolymers confirmed successful synthesis with a degree of polymerization (DP) of 24 for PMMA block and 29 for PDMAEMA block, along with a narrow polydispersity index (PDI ≈ 1.25), indicating a well-controlled polymerization process and uniform molecular architecture.Self-assembly of 4-arm star-shaped macromolecules resulted in the formation of anisotropic Janus nanoparticles with different shapes, such as mushroom or acorn seed shapes, snowman, dumbbelllike, multi-lobed, vesicle, and hollow sphere with a particle size in the range of 0.5-2 μm with a narrow particle size distribution. Because of observed unique morphologies, the star-shaped nanoparticles were used as a nanocarrier for encapsulating haloflourochromic oxazolidine molecules (OXOH and OXNM) to develop haloflourochromic nanoparticles for probing pH in the range of 1-14 and In Situ real-time visualization of individual latent fingerprints by aggregationinduced emission and fluorescence imaging. In addition to visual detection by the naked eye, the obtained results displayed successful fluorimetric and colorimetric sensing of the pH (1-14) by UV-Vis and fluorescence spectroscopy. The In Situ real-time visualization of latent fingerprints exhibited high intensity bright red emission, high spatial resolution, and negligible background fluorescence, successfully revealing all three levels of fingerprint details.