Centre for Forensic Science, University of Technology Sydney, Broadway, NSW 2007, Australia.
Centre for Forensic Science, University of Technology Sydney, Broadway, NSW 2007, Australia.
Forensic Sci Int. 2024 May;358:112019. doi: 10.1016/j.forsciint.2024.112019. Epub 2024 Apr 4.
Iron oxide powder suspension (FePS) is a fingermark development technique that can be used on adhesive and non-porous surfaces, the efficacy of which is known to be influenced by the surfactant used in the formulation. Despite previous work optimising surfactants for use in FePS, there is limited understanding of the interactions between surfactants, powders and fingermark residue which aid the successful development of fingermarks. To better understand the effect of surfactant on development quality produced by FePS, this research assessed a wide range of surfactants of different ionic natures and evaluated their ability to develop fingermarks based on the quality of ridge detail, contrast and background development produced. It was found that surfactants play a critical role in the selective deposition of powder on fingermark residue, as formulations made with only water (no surfactant) produced heavy background deposition. The efficacy of each surfactant depended on the quality parameter considered, and the addition of some surfactants hindered fingermark development. Effective surfactants such as T20, KP and TX100 prevented background development and produced well contrasted developed marks. Poor contrast was produced by LN, SP80/T80 and T80 due to indiscriminate powder deposition either across the entire sample or preventing any powder to deposit on the surface, demonstrating the role surfactants play in allowing powder deposition in this technique. The effectiveness of a surfactant in PS was not directly dependent on its ionic nature, and most surfactants were more effective when diluted from stock concentrations. This research has provided a robust base for future work improving fundamental understanding of FePS, which will greatly aid the efficacy of future optimisation efforts.
氧化铁粉末悬浮液（FePS）是一种指纹显现技术，可用于粘性和非多孔表面，其功效已知受配方中使用的表面活性剂的影响。尽管之前已经针对 FePS 优化了表面活性剂的使用，但对于表面活性剂、粉末和指纹残留物之间的相互作用的理解有限，这些相互作用有助于成功显现指纹。为了更好地了解表面活性剂对 FePS 产生的显影质量的影响，本研究评估了不同离子特性的广泛范围的表面活性剂，并根据产生的脊纹细节、对比度和背景显影的质量来评估它们显现指纹的能力。结果发现，表面活性剂在粉末对指纹残留物的选择性沉积中起着关键作用，因为只用水（无表面活性剂）制成的制剂会产生严重的背景沉积。每种表面活性剂的功效取决于所考虑的质量参数，并且一些表面活性剂的添加会阻碍指纹的显现。有效的表面活性剂，如 T20、KP 和 TX100，可防止背景沉积并产生对比度良好的显影指纹。LN、SP80/T80 和 T80 产生的对比度差，原因是粉末不分青红皂白地沉积在整个样品上或阻止任何粉末沉积在表面上，这表明表面活性剂在该技术中允许粉末沉积的作用。表面活性剂在 PS 中的有效性并不直接取决于其离子特性，大多数表面活性剂在从储备浓度稀释时更有效。这项研究为未来改进对 FePS 的基本理解提供了坚实的基础，这将极大地有助于提高未来优化工作的效果。
