Facile Assembly Enhanced Spontaneous Fluorescent Response of Ag⁺ Ion Containing Polyelectrolyte Multilayer Films

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Conjugated small molecules typically show "turn-on" fluorescence, while polymers often exhibit "turn-off" responses with metal ions.
• Developing "turn-on" fluorescent polymers for sensing applications is an ongoing challenge.

Purpose of the Study:

• To present a novel branched poly(ethylene imine)-poly(acrylic acid)-Ag+ ion complex exhibiting "turn-on" fluorescence in a thin film.
• To demonstrate the material's potential for sensing applications, such as formaldehyde vapor and halide ions.

Main Methods:

• Layer-by-layer fabrication of polymer-ion complex thin films.
• Characterization using UV-vis, spectrofluorometry, X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma mass spectrometry (ICP-MS).

Main Results:

• The poly(ethylene imine)-poly(acrylic acid)-Ag+ complex displayed a "turn-on" fluorescence response exclusively when all three components were present.
• The optically active complex involves amine and carboxylic acid groups, confirmed by characterization.
• The material functions in the solid state, facilitating device integration.
• Successful demonstration of formaldehyde vapor and halide ion sensing via fluorescence quenching.

Conclusions:

• A novel "turn-on" fluorescent material based on a polymer-metal ion complex has been developed.
• The material's solid-state functionality and sensing capabilities highlight its potential for practical applications.
• Simple fabrication using commercially available polymers and layer-by-layer assembly makes this approach highly accessible.