## 1 Introduction  
Molecular imprinting techniques have attracted research interest globally in recent years [1; 2; 3; 4]. Molecularly imprinted polymers (MIPs) have many advantages over other recognition systems, e.g., low cost and easy synthesis, high stability under harsh chemical and physical conditions, and excellent reusability [5]. Consequently, MIPs have been used in many fields, including solid-phase extraction [6; 7; 8], drug delivery [9; 10], catalysis [11], and sensing [12; 13]. However, the traditional methods of MIP preparation have a number of drawbacks, e.g., incomplete template removal,low rebinding capacity, poor template accessibility, slow mass transfer, and difficult solid-liquid separation [14; 15]. Surface molecular imprinting on various surfaces, including SiO\({}_{2}\) nanoparticles [16], carbon materials [17], polymeric supports [18], metal oxide particles [19], and magnetic materials [20], has been used to overcome these problems. Magnetic nanoparticles have been widely used in the preparation of magnetic molecularly imprinted polymers (MMIPs) because of their properties such as small size, high magnetic susceptibility, and high surface-to-volume ratio. MMIPs can be easily separated from a complex matrix using an external magnet, enabling convenient and efficient preconcentration to avoid using time-consuming solid-phase extraction and column packing [21; 22]. Potential interference from leakage of residual template molecules embedded in MIPs can be prevented by using a dummy molecular imprinting technique, in which a structural analog of the target compound is used as a template for MIP preparation [23]. Melamine, which is a triamine and contains a nitrogen heterocyclic ring, is an important organic chemical; it is used in the production of melamine resins, which are widely used in wood processing, plastics, paints, papermaking, textiles, leather, electrical goods, and medicines [24]. Melamine detection became a hot topic after cases of infant kidney stones caused by melamine-poisoned infant formula powders in China, and pet deaths from melamine-poisoned feeds in USA [25; 26]. Melamine had been illegally added to infant formula powders, dairy products and pet feeds to enhance the protein content measured by the Kjeldahl method. Since 2008, the Chinese government has forbidden the artificial addition of melamine to any food, and the temporary limitation of the volume of melamine in liquid milk is 0.05 mg/Kg. Analytical methods such as high-performance liquid chromatography (HPLC) [27], gas chromatography-mass spectrometry (GC-MS) [28], HPLC-MS/MS [29], surface-enhanced Raman scattering [30], electrochemical immunosensing [31], and enzyme-linked immunoassays (ELISA) [32] have been used for melamine determination. Although these analytical methods are highly sensitive, selective, and efficient, they are time consuming, expensive, and need sophisticated instruments and highly skilled personnel. Fluorescent sensors provide a promising method for the detection of trace pollutants because such methods are simple, rapid, and have high sensitivity and selectivity [33; 34]. The use of combinations of MIPs and fluorescence assays to detect melamine in milk and infant formula milk powder has been reported [35; 36; 37]. Fluorescent MIP sensors can be divided into two categories based on their preparation method. In the first method, fluorescent materials such as a fluorescent functional monomers or quantum dots are used for molecular imprinting. The interactions between template molecules and the fluorescent functional monomers or quantum dots in the MIPs cause changes in the fluorescence signals, which can be monitored to detect target molecules quantitatively [38; 39]. However, the synthesis and modification of fluorescent functional monomers are complicated and quantum dots cannot be uniformly embedded into MIPs. These problems prevent the widespread use of this type of fluorescent MIP sensor.