Herein, we prepared a dual-emitting cellulose film with pH response, which offers high transparency, good flexibility, and intense thermal stability. The color of the fluorescent film that changes from green to blue-green to cyan was achieved by covalently attaching organic dye fluorescein isothiocyanate (FITC), inorganic pigment NH₂-CaAl₂O₄:Eu²⁺,Dy³⁺ (NH₂-CAO), and organic–inorganic fluorescence species onto hydroxypropyl methylcellulose (HMPC) chains, respectively. Benefiting from the “anchoring” and “dilution” effects of the HMPC skeleton, HPMC-FITC and HPMC@NH₂-CAO fluorescent solutions and solid-state films emit green and blue-green fluorescence at 535 and 480 nm, respectively. The obtained pH-responsive cellulose-based dual-emitting film can continuously emit cyan light at the two emission peaks of 480 and 535 nm for a long time and exhibits strong fluorescence intensity under exceedingly alkaline conditions. Moreover, the HPMC-based fluorescent solution coated on glass and fabric substrate shows strong fluorescence under 365 nm UV light stimulation. Compared with the existing cellulose-based fluorescent films, this work expands the emission wavelength range of cellulose-based fluorescent films and prolongs the luminescent time of environment-responsive fluorescent films. This provides a new way to prepare intelligent color-changing fabric-coating materials and sensitive pH sensors based on biomass.

中文翻译：

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含有异硫氰酸荧光素和 CaAl2O4:Eu2+,Dy3+ 磷光体的 pH 响应双发射羟丙基甲基纤维素基材料

在此，我们制备了一种具有 pH 响应的双发光纤维素薄膜，该薄膜具有高透明度、良好​​的柔韧性和强烈的热稳定性。荧光膜的颜色从绿色变为蓝绿色再到青色是通过共价连接有机染料异硫氰酸荧光素（FITC）、无机颜料NH ₂ -CaAl ₂ O ₄ :Eu ²⁺ ,Dy ³⁺ (NH ₂ - CAO) 和有机-无机荧光物质分别连接到羟丙基甲基纤维素 (HMPC) 链上。受益于 HMPC 骨架、HPMC-FITC 和 HPMC@NH ₂的“锚定”和“稀释”效应-CAO 荧光溶液和固态薄膜分别在 535 和 480 nm 处发出绿色和蓝绿色荧光。所获得的pH响应性纤维素基双发光薄膜可以在480和535 nm两个发射峰长时间连续发射青色光，并在极碱性条件下表现出很强的荧光强度。此外，涂覆在玻璃和织物基材上的基于 HPMC 的荧光溶液在 365 nm 紫外光刺激下显示出强烈的荧光。与现有的纤维素基荧光膜相比，这项工作扩大了纤维素基荧光膜的发射波长范围，延长了环境响应荧光膜的发光时间。这为制备基于生物质的智能变色织物涂层材料和灵敏的 pH 传感器提供了一种新方法。