pH-sensitive tunable thermochromic hydrogel with carbon quantum dots for smart windows

Abstract

Thermoresponsive hydrogels have been designed for smart windows to dynamically modulate solar radiation, but their inherent drawbacks of long response time and imperfectly matched phase transition temperature have limited their wide applications. This work reports a novel composite hydrogel consisting of hydroxypropyl cellulose, polyacrylic acid, and carbon quantum dots with intriguing features of tunable transition temperature and enhanced switching speed. The composite hydrogel demonstrated flexible tunability in transition temperature by controlling the hydrogen ion concentration and a fast response speed by dopping with carbon dots for efficient photothermal conversion. The building energy simulation was carried out to investigate the impacts of transition temperature variations and solar regulations on the space cooling/heating loads under different climate conditions, revealing the necessity of tunability of both transition temperature and solar transmittance in thermochromic smart windows. This novel design of thermochromic composite hydrogel provides insight into theoretical and experimental support for future adaptive building envelopes.

Keywords

• thermochromic hydrogel
• transition temperature
• carbon quantum dots
• lower critical solution temperature tunability
• building energy efficiency