The synthesis of carbon dots (CDs) from green precursors has received considerable attention recently. However, most of the natural biomass-derived products without further surface treatment usually have quite low quantum yield (QY) varying in the range of 2–30%. Herein, we report the sustainable fabrication of highly fluorescent CDs from food waste, turtle shells, and demonstrate their applications in the fields of multisignal coding and anti-counterfeiting with a combination of colloidal photonic crystals (CPCs). We utilized turtle shells as precursors to synthesize fluorescent CDs via a simple pyrolysis method. The resultant CDs without further surface treatment have an absolute photoluminescence (PL) QY of 45% and high dispersibility in various solvents. Then, we realized collective optical properties with a combination of CDs and CPCs, including diffractive light abilities and fluorescence. CPC/CD bead codes with a structural color and fluorescence were prepared via a microfluidic device. CPC/CD patterned films with PL and angular dependence of structural colors were also constructed via a 3D microfluidic printing technique, which are useful for multisignal anti-counterfeiting and various optoelectronic applications.

All‐inorganic halide perovskite nanocrystals (PNCs) have drawn increasing attention owing to their splendid optical properties. However, such nanomaterials suffer from intrinsic instability, greatly limiting their practical application. Meanwhile, environmental regulation has restricted the emissions of volatile organic compounds (VOCs), initiating a search for alternative approaches to PNC synthesis and film forming. Herein, fiber‐spinning chemistry (FSC) is proposed for easy‐to‐perform synthesis of highly stable PNC fibrous films. The FSC process utilizes spinning fibers as reactors, reducing the generation of VOCs. This method enables the fabrication of CsPbX3 (X = Cl, Br, I) PNCs/poly(methyl methacrylate)/thermoplastic polyurethanes fibrous films at room temperature in one step, exhibiting tunable emission between 450 and 660 nm. Significantly, the in situ generation of PNCs in hydrophobic core–shell nanofibers results in highly improved fluorescence stability. PNCs/polymer fibrous films keep constant in photoluminescence (PL) after storage at atmosphere for 90 d and retain 82% PL after water immersion for 120 h (vs fluorescence quenching in 10 d in air or 5 h in water for pristine PNCs). The PNCs/polymer fibrous films endowed with superior optical stability and great flexibility show promising potentials in flexible optoelectronic applications. This work paves a facile way toward high‐performance nanoparticles/polymer fibrous films.

Carbon dots synthesized by the hydrothermal treatment of dicyandiamide and o-phenylenediamine in dilute H2SO4 exhibit efficient excitation-independent red dual-emission useful for ratiometric fluorescence sensing and cellular imaging.

Quantum dot (QD)‐based liquid crystal displays (LCDs) are emerging as a new generation of LCDs due to their good performance. However, the QD fluorescent materials in LCDs are vulnerable to water and high temperatures, severely limiting their practical and long‐term use. Here, flexible and ultrastable QD‐based color‐converting films for LCD backlights are fabricated using robust poly(styrene‐methyl‐methacrylate‐acrylic acid) (poly(St‐MMA‐AA)) nanoparticle/polyamide 66 nanofiber (NPs@PA66) film with unique fiber–particle–fiber microstructure as protective substrate. Through an emerging strategy called electro‐microfluidic spinning technology (EMST), the nanofiber film not only exhibits excellent flexibility but also remarkably improves the mechanical property via the in situ particle‐mediated enhancement mechanism. An LCD backlight using the NPs@PA66 nanofiber film as QD loading substrate shows a wide color gamut of 116% and long‐term fluorescence stability under high temperature of 200 °C. More importantly, the fluorescence lifetime of NPs@PA66/QDs backlight reaches up to ≈64500 h, ≈22 times higher than that using encapsulated sandwiched polyethylene terephthalate (PET) QD film. These findings offer a promising method toward high‐strength nanofiber manufacturing, high‐stability flexible electronics and optoelectronic display devices.