Colloidally Stable Monolayer Nanosheets with Colorimetric Responses

Area of Science:

• Materials Science
• Nanotechnology
• Organic Chemistry

Background:

• Chromogenic layered materials have been known for decades.
• Fabricating colloidally stable monolayer organic 2D nanosheets in aqueous media with colorimetric responses remains a significant challenge.

Purpose of the Study:

• To report the first solution synthesis of chromic monolayer nanosheets using topochemical polymerization.
• To investigate the properties and potential applications of these novel polydiacetylene (PDA) nanosheets.

Main Methods:

• Solution synthesis of chromic monolayer nanosheets via topochemical polymerization of self-assembled amphiphilic diacetylenes in aqueous media.
• Characterization of nanosheet thickness, lateral size, and colloidal stability.
• Assembly of nanosheets into films via vacuum filtration and inkjet printing.
• Evaluation of thermochromic and near-infrared (NIR) light-induced colorimetric responses.

Main Results:

• Successfully synthesized stable, monolayer polydiacetylene (PDA) nanosheets in aqueous media.
• PDA nanosheets exhibit tunable thickness (3-4 nm in solution, 1.9 nm dried) and micrometer-scale lateral dimensions.
• Aqueous stability enables excellent processability for film formation and inkjet printing.
• Films and printed patterns show reversible blue-to-red thermochromism.
• Films demonstrate reversible colorimetric transitions upon exposure to near-infrared light, a novel property for PDA-only systems.

Conclusions:

• The developed colloidal PDA nanosheets represent a new class of chromic organic 2D nanomaterials.
• These nanosheets offer potential as building blocks for intelligent hybrid materials.
• Potential applications include sensing, display technologies, and anticounterfeiting solutions.