New nanomaterial could transform how we visualise fingerprints

Researchers created a fluorescent nanoparticle using a combination of materials (MCM-41, chitosan and dansylglycine) to examine latent fingermarks. These nanoparticles have special properties that make them adhere well to fingerprint residues, even old ones. The nanoparticles work on various surfaces, including metal, plastic, glass and complex objects such as polymer banknotes. They have the potential to be used directly at crime scenes without lab facilities, which is a significant advantage over some previous reagents. They produce high-quality fingerprint images, with the vast majority of those tested meeting the UK Home Office standards for a successful identification. This new method captures the finer details of a fingermark, making it easier to identify individuals and is expected greatly to aid in forensic investigations. 

Modification of the MCM-41 NPs with chitosan, followed by surface modification of MCM-41@Ch with DnsGly through interaction between the hydroxyl groups of chitosan and carboxylic acid groups of dansylglycine (see Scheme S1, ESI†).

The research was published in a Royal Society of Chemistry paper, highlighting that the new nanomaterial has proven to be a versatile and effective tool for visualising fingermark evidence. Small angle X-ray scattering (SAXS) techniques at Diamond provided useful data to validate these results. 

The research team includes scientists from the Technical and Scientific Section of Alagoas, Federal Police, Brazil; the National Institute of Criminalistics of the Federal Police, Brazil; the University of Leicester’s School of Chemistry; the Federal University of Alagoas, Brazil; and the UK’s national synchrotron, Diamond Light Source.

Ridge patterns on fingertips remain unchanged during and beyond a person’s life. They provide the primary method of personal identification in criminal investigations. When an object’s surface is touched by a finger, sweat and oily substances are transferred and deposited onto the surface, resulting in the formation of a mark. Most fingermarks are invisible to the naked eye and are referred to as latent fingermarks.  

The international collaboration of researchers developed the new nanostructured hybrid material, MCM-41@chitosan@dansylglycine, to visualise latent fingermarks. This material combines mesoporous silica nanoparticles with a fluorescent dye (dansylglycine) and chitosan, a polysaccharide derived from the exoskeletons of shrimps, crabs and lobsters. 

Images for a fingermark deposited on glass, enhanced with MCM-41@Ch@DnsGly NPs, illuminated at 365 nm and viewed with different filters.

Latent fingermarks require physicochemical development techniques to enhance their visibility and make them interpretable for forensic purposes. Traditional methods for developing fingerprints include optical, physical, and chemical processes that involve interaction between the developing agent (often a coloured or fluorescent reagent) and the fingermark residue. These methods have limitations in recovering high-quality results in certain conditions.  

Recently, new methods using mass spectrometry, spectroscopy, electrochemistry, and nanoparticles have improved the development of latent fingermarks. These techniques offer better contrast, sensitivity, and selectivity, with low toxicity. The ability to adjust nanomaterial properties further enhances the detection of both fresh and aged fingermarks. 

Mesoporous silica nanoparticles (MSNs) have attracted significant interest since the discovery of the M41S family of molecular sieves, which encompasses MCM-41, MCM-48, and SBA-15. These nanoparticles are characterised by their controlled particle size, porosity, high specific surface area, chemical stability, and ease of surface functionalisation.  

Profa. Adriana Ribeiro, Federal University of Alagoas comments:

The team added dansyl fluorophores which exhibit intense absorption bands in the near UV region and emit strong fluorescence in the visible spectrum with high emission quantum yields. 

Professor of Physical Chemistry, Robert Hillman, University of Leicester notes:

Diamond Light Source CEO Prof. Gianluigi Botton adds:

More information about the labSAXS Facility can be found here.