采用水热法和共沉淀法分别合成了纳米La2(MoO4)3∶Eu荧光材料和纳米Fe3O4磁性材料, 并利用透射电子显微镜、 X射线衍射仪、 荧光光谱仪表征纳米材料的形貌尺寸、 晶体结构、 荧光性能。 经表征, 纳米La2(MoO4)3∶Eu荧光材料的微观形貌为片状结构, 晶体结构为四方晶型, 其发射光谱中出现了Eu3+的特征发射峰; 纳米Fe3O4磁性材料的微观形貌为球形颗粒, 晶体结构为立方晶型, 并具有超顺磁性。 然后, 将以上两种纳米材料以一定比例混合均匀, 制备了具有超顺磁性的La2(MoO4)3∶Eu/Fe3O4纳米荧光粉末。 经表征, 该磁性纳米荧光粉末的微观形貌为片状结构与球形颗粒的混合, 其发射峰位置未发生变化, 而发光强度有所降低, 但仍能够满足指纹显现的需要。 最后, 将制备的纳米磁性荧光粉末用于显现不同类型客体表面的潜在指纹。 显现效果表明, 对于光滑客体表面的指纹, 使用磁性纳米荧光粉末与纳米荧光粉末的显现效果无明显差异; 对于粗糙客体表面的指纹, 使用磁性纳米荧光粉末能够清晰显现出指纹的细节特征, 其显现效果明显优于普通纳米荧光粉末, 并能够有效避免粉末扬尘现象。 本研究制备的纳米磁性荧光粉末是一种理想的指纹显现材料, 其指纹显现具有背景干扰低、 显现效果好、 适用范围广、 无粉末扬尘等优点, 在刑事案件现场具有广阔的应用前景。

In this study, fluorescent La2(MoO4)3∶Eu and magnetic Fe3O4 nanomaterials were synthesized by hydrothermal and coprecipitation, respectively. The size, morphology, crystal structure, and fluorescent property of as-synthesized nanomaterials were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) spectroscopy, and fluorescence spectroscopy (FS). The La2(MoO4)3∶Eu fluorescent nanomaterials were flaky in shape, and the crystal structure was tetragonal La2(MoO4)3 phase. The La2(MoO4)3∶Eu fluorescent nanomaterials could emit strong red fluorescence under 254 nm ultraviolet(UV) excitation.While the magnetic Fe3O4 nanomaterials were spherical in shape with an average diameter of about 60 nm, and the crystal structure was cubic Fe3O4 phase. Subsequently, the above two nanomaterials were mixed together in a certain ratio to form the La2(MoO4)3∶Eu/Fe3O4 superparamagnetic fluorescent nanomaterials. The as-prepared La2(MoO4)3∶Eu/Fe3O4 nanomaterials were of sheet structure mixed with spherical particles in shape, which could emit red fluorescence weaker than pureLa2(MoO4)3∶Eu fluorescent nanomaterials under 254 nm ultraviolet excitation.　However,　the red fluorescence from La2(MoO4)3∶Eu/Fe3O4 nanomaterials could still meet the needs of the fingerprint development. Although the as-prepared nanomaterials and La2(MoO4)3∶Eu fluorescent nanomaterials have same effect in developing fingerprint on smooth object,　the as-prepared nanomaterials could form a suitable fringe by using a magnetic applicator to prevent dust pollution and develop the detail features of fingerprint with bright red fluorescence stimulated by the excitation of 254 nm ultraviolet light. Finally, the as-prepared nanomaterials were applied to develop the fresh latent fingerprints on various smooth and rough substrates. The results showed that the latent fingerprints developed by our nanomaterials could appear the detailed features of friction ridges with a high contrast. In addition, the nanomaterials-based fingerprint development also possessed some other advantages, such as low background interference, high developing contrast, wide application range of substrates, and no powder dusting. The as-prepared fluorescent nanomaterials are superparamagnetic fluorescent nanomaterials.　The performance of this powder is obviously better than non-magnetic fluorescent nanomaterials. Therefore, the as prepared superparamagnetic fluorescent nanomaterials have been proved to be an ideal material for latent fingerprint development, which have great potential in forensic applications.