An Optical Au³⁺ Sensor Based on layer-by-layer PEI/PAA-Rho thin Films on ITO

Area of Science:

• Materials Science
• Analytical Chemistry
• Nanotechnology

Background:

• Developing selective and sensitive sensors for metal ions is crucial for environmental and biological monitoring.
• Polymeric thin films offer versatile platforms for sensor development due to their tunable properties.

Purpose of the Study:

• To develop a sensitive and selective sensor for detecting gold ions (Au³⁺).
• To utilize layer-by-layer (LbL) assembly with functionalized polymers for enhanced sensing capabilities.

Main Methods:

• Fabrication of LbL thin films using polyethylenimine (PEI) and poly (acrylic acid) (PAA) conjugated with rhodamine (Rho).
• Investigated colorimetric and fluorescence responses of the PAA-Rho polymeric sensors to Au³⁺.
• Characterized the sensor's film deposition, surface morphology (SEM), and structure (ATR-FTIR, XRD).

Main Results:

• The PAA-Rho polymeric sensors exhibited high selectivity and sensitivity towards Au³⁺ compared to other metal ions.
• Non-fluorescent spirolactam form transformed into fluorescent ring-opened amide upon Au³⁺ interaction, causing fluorescence enhancement and color change.
• Negligible interference from common co-existing metal ions was observed; linear absorbance increase confirmed successful film deposition.

Conclusions:

• The developed LbL sensor effectively detects Au³⁺ ions within the concentration range of 1 × 10^-6 to 1 × 10^-3 M.
• This approach provides an easily understandable and intrinsically sensitive method for Au³⁺ detection in environmental and biological samples.