Institute for Preservation and Conservation of Chinese Ancient Books, Fudan University, Library, Fudan University, 220 Handan Road, Shanghai 200433, China.
Shanghai Institute of Quality Inspection and Technical Research, 900 Jiang Yue Road, Shanghai 201114, China.
ACS Appl Mater Interfaces. 2024 Nov 6;16(44):60902-60911. doi: 10.1021/acsami.4c09598. Epub 2024 Sep 10.
Paper-based cultural relics often undergo acidification and deterioration during long-term preservation. Accurate detection of paper acidity is of great significance to assess aging status and extend the preservation lifetime of paper-based cultural relics. Rapid identification of the acidification degree and acid distribution across multiple regions of paper is essential. Inspired by fluorescent sensing technology, pH-sensitive cadmium telluride (CdTe) quantum dots (QDs) and rhodamine B (RB) fluorescent probes are synthesized and incorporated onto the nanofibers of a bacterial cellulose (BC) membrane to enable visual acidity detection of paper. Due to the complementary pH detection range of CdTe QDs and RB probes, the composite BC membrane exhibits a clear pH response across an acidic to neutral range (pH 3.0-7.5). Notably, the contrasting fluorescent colors of the two probes within the BC membrane allow for easy visualization of paper pH and acidity distribution with the naked eyes. A distinct color transition from red to green was observed on the fluorescent BC membrane when it is applied to a model paper with a gradient pH distribution. The feasibility of this method was verified by using the flat-headed pH electrode method. Additionally, common metal ions in most paper fillers, inks, pigments, as well as some sugars and amino acids showed minimal interference with the pH response of the composite BC membrane, highlighting its potential and broad applicability for visual acidity detection in paper-based cultural relics.
纸质文物在长期保存过程中常常会发生酸化和劣化。准确检测纸张的酸度对于评估老化状态和延长纸质文物的保存寿命具有重要意义。快速识别纸张不同区域的酸化程度和酸分布至关重要。受荧光传感技术的启发，合成了 pH 敏感的碲化镉（CdTe）量子点（QDs）和罗丹明 B（RB）荧光探针，并将其掺入细菌纤维素（BC）膜的纳米纤维中，以实现对纸张酸度的可视化检测。由于 CdTe QDs 和 RB 探针的互补 pH 检测范围，复合 BC 膜在酸性到中性范围（pH 3.0-7.5）内表现出清晰的 pH 响应。值得注意的是，BC 膜内两种探针的对比荧光颜色使得可以用肉眼轻松观察纸张的 pH 值和酸度分布。当将其应用于具有梯度 pH 分布的模型纸张时，在荧光 BC 膜上观察到从红色到绿色的明显颜色转变。平头 pH 电极法验证了该方法的可行性。此外，大多数纸张填料、油墨、颜料中的常见金属离子以及一些糖和氨基酸对复合 BC 膜的 pH 响应几乎没有干扰，这突出了其在纸质文物可视化酸度检测中的潜在和广泛适用性。
