Microfluidic synthesis of robust carbon dots-functionalized photonic crystals

Robust hybrid microbeads with multiple optical signals have garnered widespread interests for various applications. However, the inefficient physical combination and the potential toxicity of raw materials (heavy metal-based quantum dots) have limited their sustainable development. Herein, we report a microfluidic strategy to achieve the continuous production of environmentally friendly carbon dots (CDs)-functionalized photonic crystal (PC) microbeads. The efficient mass and heat transfer on microscales and the covalent bonding crosslink between CDs and poly (methyl methacrylate-butyl acrylate-methacrylic acid) (P(MMA-BA-MAA)) colloid particles ensure effective assembly of CDs-P(MMA-BA-MAA) PC microbeads in the microchannel. Benefiting from this, the CDs-P(MMA-BA-MAA) hybrid microbeads behave stable fluorescence properties, together with highly saturated and angle-independent structural color, which can overcome the optical information confusion and distortion. Meanwhile, the obtained CDs-P(MMA-BA-MAA) hybrid microbeads show dual optical signal responsiveness through the variation of fluorescence and structural color under different ionic environment. Based on this, we realize the dual ionic sensing by constructing CDs-P(MMA-BA-MAA) hybrid microbeads arrays, which broadens the application of optical hybrid microbeads. In addition, we also prepare robust hybrid film and flexible lamp belt. The obtained robust CDs-functionalized PC hybrid microbeads with various attractive optical properties have a broad prospect in optical display, sensors, biological coding and antireflection coatings.