Nanomaterial-based optical indicators: Promise, opportunities, and challenges in the development of colorimetric systems for intelligent packaging

The market and the future trends of smart packaging show a tendency towards a continuous increase. Several reports have revealed about the increase of consumer concern for food quality and safety, which gives rise to the demand of intelligent packaging. Nano-enabled food packaging has attracted considerable interest and driven a variety of potential applications in the intelligent packaging. The presence of nanomaterials as nanodevices or nanosensors has been recognized as a part of the modern intelligent packaging for monitoring the condition of packaged food or the environment surrounding the product. Among of nanosensors, optical indicator has been widely applied in the market due to the convenient and easy to use. The utilization of nanomaterial such as metal nanoparticles or photonic nanocrystals shows superior performance in novel communicative functions than the traditional colorimetric indicator because of their unique optical properties and high surface reactivity. This review focuses exclusively on ongoing scientific research and recent technological breakthroughs related to nanotechnology-derived colorimetric indicators. The challenges of their application are highlighted and discussed to provide adequate information for future development.