金属纳米簇（metal nanoclusters, M NCs）作为一种新型的纳米材料，由于具有光致发光、量子尺寸效应、合成简便和优异的生物相容性等独特的性质，在化学传感和生物成像领域有广泛的应用。以多肽或蛋白质为配体的金属纳米簇具有毒性低、荧光性质稳定等优点而受到广泛关注。但是目前金属纳米簇的应用也受到荧光量子产率较低、选择性响应较差等问题的限制。

利用双金属和混合配体可能带来的独特优势，我们合成了金/银双金属纳米簇和混合配体的银纳米簇，对环境及生命相关的分子进行了识别检测，并对响应机理进行了深入研究。本论文的具体研究内容如下：

（1）发展了多肽保护的金/银双金属纳米簇（多肽@Au/Ag NCs），用于溶酶体中的次氯酸根（ClO^—）荧光成像检测。多肽@Au/Ag NCs通过一步法合成，其中多肽既作为配体又作为还原剂，制备的双金属纳米簇的量子产率高于相同条件下合成的金纳米簇和银纳米簇。由于ClO^—诱导多肽配体的氧化及金属中心Ag含量的降低，导致多肽@Au/Ag NCs荧光猝灭并伴有最大发射波长轻微红移。多肽@Au/Ag NCs的荧光猝灭程度（F₀/F）与ClO^—浓度在0.1~100 μmol/L范围内呈良好的线性关系，检出限（LOD）为80 nmol/L，该探针可用于活细胞溶酶体中ClO^—的荧光成像检测。

（2）合成了谷胱甘肽（GSH）为配体的近红外发光金/银双金属纳米簇（GSH@Au/Ag NCs），在Cd²⁺存在下该纳米簇发光会显著增强，且表现出对Cd²⁺较高的响应选择性和敏感性。Cd²⁺和GSH配体间的静电相互作用和配位作用使得纳米簇彼此间距离变近，复合物间的Au(I)···Au(I)相互作用增强，并且抑制纳米簇内或纳米簇间的分子内振动，导致非辐射弛豫概率降低，GSH@Au/Ag NCs的发光增强。GSH@Au/Ag NCs可作为检测Cd²⁺的荧光增强型探针，并实现了水样中Cd²⁺的加标检测和活细胞中Cd²⁺的荧光成像。

（3）合成了天然混合蛋白—鸡蛋清（Chicken Egg White，CEW）为配体的银纳米簇（CEW@Ag NCs），可用于碘离子（I^—）的高选择性识别。CEW@Ag NCs具有红色荧光，最大发射波长为~630 nm（λex= 400 nm），其荧光可被I^—有效猝灭，而不受硫离子（S^2—）的干扰。X射线光电子能谱（XPS）和透射电镜（TEM）结果表明，I^—可能参与Ag NCs的氧化蚀刻，从而导致纳米簇的分解和荧光猝灭。作为简化模型，卵清蛋白和溶菌酶为配体合成的Ag NCs对I^—的响应选择性也有所提高，证实了混合蛋白作为配体可以改善纳米簇识别响应的选择性。这可能是由于混合配体保护的Ag NCs具有更高的表面覆盖率和更稳定的结构，不易被破坏，基于I^—和银原子间的独特反应，混合配体保护的Ag NCs能够识别I^—而不受S^2—干扰。

Metal nanoclusters (M NCs), an emerging nanomaterial, have been widely used for chemical sensing and biological imaging owing to their unique physical and chemical properties, such as photoluminescence, quantum size effect, easy synthesis and excellent biocompatibility. In addition, metal nanoclusters stablized by proteins or peptides have attracted much attention due to their low toxicity and stable fluorescent properties. However, the application of metal nanoclusters was limited by the disadvantages of low fluorescence quantum yield and poor response selectivity.

Taking the unique advantages of the bimetal or mixed ligands, gold/silver bimetal nanoclusters and mixed ligands capped silver nanoclusters were synthesized, and were used for sensing of environmentally or biologically relavent molecules. The contents of this thesis are as follows:

(1) Peptide-capped gold/silver nanoclusters (peptide@Au/Ag NCs) for lysosome-targeted imaging of hypochlorite (ClO^—) were developed. The peptide@Au/Ag NCs were synthesized via a one-pot method using peptide as both a ligand and a reducing agent. The ?uorescence quantum yield of peptide@Au/Ag NCs were much higher than those of peptide-capped gold nanoclusters or silver nanoclusters. In the presence of ClO^—, the ?uorescence of peptide@Au/Ag NCs was quenched, accompanied by a redshift due to ClO^—-induced oxidation of the peptide ligand and decreased Ag content in Au/Ag NCs. The relative ?uorescence intensity F₀/F had favourable linearity for ClO^— concentrations in the range of 0.1–100 μmol/L (R² = 0.9954), with a detection limit (LOD) of 80 nmol/L. The lysosome-targeted peptide@Au/Ag NCs were applied to detect ClO^— in lysosomes in living cells via ?uorescence imaging.

(2) A near-infrared fluorescence gold/silver bimetal nanoclusters (Au/Ag NCs) probe with glutathione (GSH) as ligand was successfully synthesized. The luminescence of GSH@Au/Ag NCs could be significantly enhanced in the presence of Cd²⁺, and the probe had highly selectivity and sensitivity to Cd²⁺. It was speculated that the electrostatic interaction and coordination between Cd²⁺ and GSH caused the accumulation of nanoclusters, thereby the Au(I)···Au(I) interaction among the complexes was enhanced, and the vibrations within or among the nanoclusters were suppressed, leading to the reduction of non-radiative relaxation probability and enhanced luminescence of GSH@Au/Ag NCs. GSH@Au/Ag NCs could be used as a “turn-on” probe for detecting Cd²⁺, and the spiked Cd²⁺ detection in real water samples and fluorescence imaging in living cells were realized.

(3) Silver nanoclusters (Ag NCs) employing natural mixed protein-chicken egg white (CEW) as ligand were synthesized. Red fluorescent CEW@Ag NCs with maximum emission wavelength at ~630 nm (λex=400 nm) were obtained. The fluorescence could be effectively quenched by iodide (I^?), which was not interfered by sulfur ions (S^2?) unlike many other Ag NCs. It was speculated that the mixed protein protected-nanoclusters were more stable, thus the responding selectivity was better than that of single protein ligand such as lysozyme capped nanoclusters. According to the X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) results, I^? could participate oxidative etching of silver nanoclusters, resulting in decomposition of nanoclusters and fluorescence quenching. Silver nanoclusters synthesized by the mixture of lysozyme and ovalbumin as ligands also have improved responding selectivity to I^?, confirming that mixed proteins as ligand could improve selectivity.