目的：随着工业化进程的加速，重金属污染问题日益严峻，严重威胁着生态环境和人类健康。近年来，介孔二氧化硅纳米微球（Mesoporous Silica Nanoparticles, MSN）因其形貌可控和光稳定性高等优势，在重金属离子检测与传感领域展现出广泛应用前景。本文设计并合成了三种具有不同荧光响应机制的荧光MSN复合微球（双响应型、比率型以及“开-关-开”型），并系统研究了其结构特性、光学性能及荧光传感行为，为重金属离子检测的应用提供了新的思路。

方法：（1）本文采用水热法和酸蚀刻法分别制备了硫、氮掺杂的碳点（SN-CDs）与MSN，利用湿浸渍法合成了一种具有双响应型的荧光MSN（SN-CDs@MSN）。通过pH、盐浓度和紫外照射实验验证其选择性和光稳定性，并分别对Cu²⁺和Hg²⁺进行测试确定其检出限与回收率；（2）本文利用改良的Stöber法将蓝色碳点（CDs）嵌入的MSN中，并将其表面进行氨基功能化来结合金纳米簇（AuNCs），构建了一种比率型荧光MSN复合微球（CDs@MSN@AuNCs）。通过光稳定性和选择性实验评估其光学性能，并对Cu²⁺进行比率荧光检测确定其检测限；（3）本文采用水热法合成了一种氮掺杂碳点（NCDs），将其负载于MSN的通道中，构建了一种“开-关-开”响应型的荧光MSN复合微球（NCDs@MSN）。通过pH、NaCl浓度和紫外光照实验验证其选择性和光稳定性，并基于“开-关-开”型荧光响应机制，对Hg²⁺和L-半胱氨酸的检测限及回收率进行测定。

结果：（1）制备的SN-CDs@MSN表现出高稳定性的特征，对Cu²⁺和Hg²⁺分别表现出荧光增强和荧光猝灭效应，实现了高灵敏度检测，其检测限分别为24.92 μM和6.04 μM。在实际样品测定中，对不同样品的Cu²⁺和Hg²⁺的回收率分别在99.3%～101.6%和98.0%～103.7%之间，展现出良好的准确性和回收率；（2）合成的CDs@MSN@AuNCs具有良好的光稳定性，以CDs作为稳定的参比信号，而AuNCs则作为特异性识别元件，实现对Cu²⁺的比率荧光检测，检测限低至5.46 μM，并可实现直观视觉识别。在实际水样检测中，CDs@MSN@AuNCs表现出高回收率（98.8%～103.2%）和良好的重复性（RSD≤2.84%）；（3）NCDs@MSN表现出卓越的化学稳定性，作为荧光“关闭”探针可实现对Hg²⁺的高选择性检测，检测限为1.88 μM。同时，NCDs@MSN-Hg²⁺体系可作为荧光“开启”传感器，实现对L-半胱氨酸的高灵敏检测，检测限为2.62 nM。在实际检测中，对Hg²⁺的回收率为98.4%～105.2%，证实了其在复杂环境中的可靠性和适用性。

结论：本研究成功制备了三种具有优异结构特性和光学性能的荧光MSN，均表现出良好的光稳定性和抗干扰能力，可在复杂环境中实现对重金属离子的高效、灵敏检测。同时，这种基于不同荧光响应机制（双响应型、比率型及“开-关-开”型）的荧光探针，突破了传统荧光探针功能单一的局限，显著扩展了荧光传感材料的应用范围，为荧光检测技术的创新与发展提供了新的思路。

Objective: With the acceleration of industrialization, the problem of heavy metal pollution is becoming more and more serious, which seriously threatens the ecological environment and human health. In recent years, composite microspheres based on mesoporous silica nanoparticles (MSN) have demonstrated a wide range of applications in the field of heavy metal ion detection and sensing due to the advantages of controllable morphology and high photostability. In this study, three types of fluorescent MSN composite microspheres with different fluorescence response mechanisms (dual-responsive, ratiometric, and “on-off-on”) were designed and synthesized, and their structural properties, optical properties, and fluorescence sensing behaviors were systematically investigated, which provided new ideas for the application of heavy metal ion detection.

Methods: (1) In this study, sulfur and nitrogen doped carbon dots (SN-CDs) and MSN microspheres were prepared by hydrothermal and acid etching methods, respectively. A fluorescent MSN composite microsphere (SN-CDs@MSN) with dual-responsive type was synthesized by using wet impregnation method. The selectivity and photostability were verified by pH, salt concentration and UV irradiation experiments, and the detection limit and recovery were determined by tests on Cu²⁺ and Hg²⁺ ions, respectively; (2) In this thesis, a ratiometric fluorescent MSN composite microsphere (CDs@MSN@AuNCs) was constructed by embedding blue carbon dots (CDs) into MSN by modified Stöber method and amino functionalization of its surface to bind gold nanoclusters (AuNCs). The optical properties were evaluated by light stability and selectivity experiments, and the detection limit of Cu²⁺ was determined by ratiometric fluorescence detection; (3) In this study, a nitrogen-doped carbon dots (NCDs) was synthesized by hydrothermal method, and it was loaded into the channel of MSN to construct an “on-off-on”responsive fluorescent MSN composite microsphere (NCDs@MSN). The selectivity and photostability were verified by pH, NaCl concentration and UV irradiation experiments. Based on the “on-off-on” fluorescence response mechanism, the detection limit and recovery rate of Hg²⁺ and L-cysteine were determined.

Results: (1) The synthesized SN-CDs@MSN exhibited high stability and demonstrated distinct fluorescence responses towards Cu²⁺ and Hg²⁺, with fluorescence enhancement for Cu²⁺ and fluorescence quenching for Hg²⁺, enabling highly sensitive detection. The detection limits were determined to be 24.92 μM for Cu²⁺ and 6.04 μM for Hg²⁺. In real sample analysis, the recovery rates for Cu²⁺ and Hg²⁺ ranged from 99.3% to 101.6% and from 98.0% to 103.7%, respectively, indicating excellent accuracy and recovery performance; (2) The prepared CDs@MSN@AuNCs exhibited excellent photostability, utilizing CDs as a stable reference signal while AuNCs served as a specific recognition element for ratiometric fluorescence detection of Cu²⁺. The detection limit is as low as 5.46 μM, and intuitive visual recognition can be achieved. In the actual water sample detection, CDs@ MSN@AuNCs showed high recovery (98.8%~103.2%) and good repeatability (RSD≤2.84%); (3) The NCDs@MSN exhibited excellent chemical stability and high selectivity for Hg²⁺ detection as a fluorescent “off” probe with a detection limit of 1.88 μM. At the same time, the NCDs@MSN-Hg²⁺ system can be used as a fluorescent “on” sensor to achieve highly sensitive detection of L-cysteine with a detection limit of 2.62 nM. In the actual detection, the recovery rate for Hg²⁺ ranged from 98.4% to 105.2%, confirming its reliability and applicability in complex environments.

Conclusion: In this study, three types of fluorescent MSN composite microspheres with excellent structural and optical properties were successfully prepared. All of them demonstrated excellent photostability and anti-interference ability and could achieve efficient and sensitive detection of heavy metal ions in complex environments. Fluorescent probes based on different fluorescence response mechanisms (dual-response, ratiometric and “on-off-on”) break through the limitations of traditional fluorescent probes with single function, significantly expand the application range of fluorescent sensing materials, and provide new ideas for the innovation and development of fluorescence detection technology.

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