与传统有机荧光材料不同，非典型荧光材料一般由碳碳双键、羰基、氰基等不饱和官能团，以及N、O、S等富电子原子构成的亚荧光团组成。它们的发光可以用“簇聚诱导发光”（Clustering-triggered Emission，CTE）机理解释，即分子中的亚荧光团通过物理/化学相互作用聚集成簇，分子内/间的电子云重叠，构象刚性化，产生有效的空间共轭（Through-space Conjugation，TSC），受激可以发射荧光，甚至磷光。然而，这些非典型荧光聚合物/有机小分子的荧光发射通常局限在蓝光区域，且荧光效率较低，这大大限制了其实际应用。在本论文中，我们通过分子设计及化学反应，实现了丙烯酰胺、蔗糖和抗坏血酸三种有机小分子的荧光发射增强和红移，得到的产物均具有聚集诱导发光（Aggregation-induced Emission，AIE）特性。本论文的主要研究结果如下：

（1）通过酰氯和胺的反应，向丙烯酰胺（AM）分子中引入强吸电子基团，得到了三氟乙基丙烯酰胺小分子（TFAM）。相较于AM，TFMA的荧光发射出现明显的增强和红移，在丙酮溶液（C = 0.05 M）和固体粉末状态下的最大发射波长（λ_em^max）分别为位于蓝绿光区（472 nm）和黄绿光区（560 nm）。TFAM在稀溶液中荧光很弱，浓溶液和固体状态的荧光发射大大增强，具有典型的AIE特性。TFAM的荧光具有激发波长依赖性（Excitation-dependent Fluorescence，EDF）和浓度依赖性（Concentration-dependent Fluorescence，CDF）。在不同激发波长下，TFAM的荧光发射颜色不同。随着浓度的增加，TFAM溶液的荧光发射强度不断增大且λ_em^max明显红移。此外，TFAM的荧光还对温度及金属离子（Fe³⁺和Cu²⁺）具有灵敏的刺激响应。理论计算结果表明，吸电子基的引入限制了TFAM分子中连接C=C和C=O官能团的C-C单键的旋转，促进分子采取更共轭的构象，形成团簇，诱导发光。同时分子间氢键也被认为有利于分子构象僵化，促进荧光发射。

（2）通过对蔗糖分子进行简单的焦糖化处理，得到了一系列焦糖化产物。相比于发射微弱蓝色荧光的蔗糖，在最大激发波长下，焦糖化产物的水溶液（C = 5 mg/mL）和固体粉末分别发射蓝绿色（520 nm）和黄绿色（563 nm）荧光，表现出显著的荧光发射增强和红移。同时，随着焦糖化时间的增加，固体粉末的λ_em^max从黄绿光区（563 nm）逐渐红移至红光区（630 nm）。此外，这些焦糖化产物的荧光还具有EDF和CDF性质。同时，Cd²⁺可以使其荧光明显增强，而Fe³⁺可以使其荧光淬灭。

（3）通过在较低温度（55℃）下对抗坏血酸钠（AANa）水溶液进行热氧处理，得到了荧光发射增强且红移的热氧化产物AANa-h。相比于荧光发射微弱的AANa，AANa-h的浓溶液（C = 5mg/mL）和固体粉末均可发射强的荧光，最大发射波长分别在488 nm和527 nm。AANa-h还表现出浓度增强发光（Concentration Enhanced emission，CEE）和AIE特性，其稀溶液荧光微弱，但随着浓度增加，荧光发射强度不断增加，λ_em^max基本不变。无论是溶液还是固体粉末，AANa-h的荧光都具有EDF性质。此外，在不同溶剂中，AANa-h的荧光发射强度和最大发射波长不同，表现出溶剂依赖性（Solvent-dependent Fluorescence，SDF）。同时，AANa-h的荧光对金属离子也具有刺激响应。

Different from traditional organic fluorescent materials, nonconventional fluorescent materials are always composed of electron-rich heteroatomic subfluorophores, including unsaturated functional groups (carbon-carbon double bond, carbonyl group, cyan group, etc.) and electron-rich atoms (N, O, S, etc.). Their luminescence can be explained by “clustering-triggered emission” (CTE) mechanism, that is, the subfluorophores in the molecules gather into clusters through physical/chemical interactions, leading to the overlap of the intramolecular/intermolecular electron clouds, the rigidification of the molecular conformations, and hence the extension of the effective through-space conjugation (TSC), which results in fluorescence or even phosphorescence emissions. However, the luminescence of nonconventional fluorescent materials is usually confined in the blue region, and the luminescence efficiency is low, which greatly limits their practical application. In this work, we achieved fluorescence enhancement and red-shift of three kinds of organic small molecules (acrylamide, sucrose and sodium ascorbate) through molecular design and chemical reactions. All the products show AIE characteristics. The main research results are as follows:

(1) Trifluoroethylacrylamide (TFAM) was obtained by introducing strong electron-withdrawing groups into the acrylamide (AM) molecule through the reaction of acyl chloride and amine. Compared with AM, the fluorescence emissions of TFAM is significantly enhanced and red-shifted, and the maximum excitation wavelengths (λ_em^max) of the TFAM acetone solution (C = 0.05 M) and solid powder are in the blue-green (472 nm) and orange-red (560 nm) regions, respectively. The photoluminescence (PL) intensity of TFAM is weak in dilute solutions, but it greatly increases in concentrated solutions and solid powder, showing an obvious AIE characteristic. TFAM exhibits excitation-dependent fluorescence (EDF) and concentration-dependent fluorescence (CDF). TFAM emits fluorescence of different colors under different excitation wavelengths. The PL intensity of TFAM solutions increases with increasing concentrations, and the λ_em^max red-shifts as well. In addition, the fluorescence of TFAM is sensitive to temperature and metal ions (Fe³⁺ and Cu²⁺). The theoretical calculation results show that the introduction of electron-withdrawing groups limits the rotation of C-C bonds connecting C=C and C=O groups in TFAM molecules, which promotes the molecules to adopt more conjugated conformations to form clusters and induces luminescence. At the same time, intermolecular hydrogen bonds are also believed to facilitate the rigidification of molecular conformations and promote fluorescence emission.

(2) A series of caramelized products were obtained by simple caramelization of sucrose. Compared with the sucrose emitting faint blue fluorescence, the caramelized products in aqueous solutions (C = 5 mg/mL) and solid state emits blue-green (520 nm) and yellow-green (563 nm) fluorescence, respectively, showing apparent fluorescence enhancement and red-shift. The λ_em^max of the solid powder of caramelization products gradually shifts from yellow-green (563 nm) to red (630nm) region with the increase of caramelization time. Moreover, the fluorescence of the caramelized products also shows EDF and CDF properties. And Cd²⁺ ions can obviously enhance the emissions, while Fe³⁺ ions quench them.

(3) A thermal oxidation product AANa-h with enhanced and red-shifted fluorescence emission was obtained by thermal oxidation treatment of sodium ascorbate (AANa) in aqueous solutions at a low temperature (55℃). In comparison with non-emissive AANa, both concentrated solutions and solid powder of AANa-h can emit strong fluorescence, and the λ_em^max of the AANa-h solution (C = 5 mg/mL) and solid powder is 488 nm and 527 nm, respectively. AANa-h also exhibits concentration enhanced emission (CEE) and AIE characteristics. The PL intensity in diluted solutions is weak. With the increase of the concentration, the PL intensity increases continuously, while λ_em^max remains. In both solutions or solid powders, the fluorescence of AANa-h shows EDF properties. Moreover, both the PL intensity and λ_em^max of AANa-h vary with solvents, showing solvent-dependent fluorescence (SDF). The fluorescence of AANa-h also is also responsive to metal ions.