Neutron detectors are vital in many applications, from medical science to aerospace engineering. Surface-Enhanced Raman Spectroscopy (SERS) has emerged as a promising technique for such highly sensitive applications. In SERS, the bringing together of a light source together with nanomaterials, which are typically metallic nanoparticles, can enhance the Raman signals of analyte molecules. Analyte is often used to refer to a chemical compound being used in a laboratory, such as glucose, lactate or cholesterol.
The unique capability of this enhancement, along with the development of increasingly sensitive, compact and portable Raman spectrometers, has led to the development of ultrasensitive sensors, which have a wide range of potential applications in various fields, including biomedicine, environmental monitoring, food safety, and homeland security. One of the key advantages of SERS is its versatility and compatibility with a wide range of analytes. It is this versatility that makes SERS applicable to all these numerous fields, where the identification and quantification of specific compounds are essential.
Crucially, the sensitivity and selectivity of SERS can be further enhanced by tailoring the surface properties of the nanostructures through chemical modification, which makes SERS an appealing technique for rapid and accurate detection in real-world scenarios. Therefore, SERS is now the focus of new research and has recently been found to not only be able to recognize molecular species but also to detect changes caused by external factors to species absorbed on the surface.
Detection of slow neutrons, in the thermal and epithermal energy range, has strong interest in a similarly wide range of applications. In this study, the team chose to characterize SERS substrates, that were made by a nanostructured gold film grown at room temperature by Pulsed Laser Deposition (PLD) technique.This gold film has been found to exhibit unique SERS activity. In this technique, a portion of the material is vaporized by a high-energy laser pulse which then expands in a controlled ambient atmosphere that favous the agglomeration of gold nanoparticles that finally deposit on the substrate.
The team then immersed a set of substrates in small beakers containing different concentrations of liquids, all containing 4-mercaptophenyboronic acid (4-MPBA), which were able to form a monolayer covalently bonded to the gold surface. Finally, prototype devices were tested at our VESUVIO instrument to assess the sensitivity of the materials, as well as their accuracy, precision and working range.
To evaluate the neutron flux, the devices were exposed to varying neutron irradiation times, followed by SERS measurements. Analysis revealed that the 4-MPBA molecules were transformed into the compound thiophenol after neutron absorption. The ratio was found to be proportional to the irradiation times, indicating the number of absorption reactions resulting from both thermal and epithermal contributions. The gold film grown by PLD therefore demonstrated its stability and high reliability as a SERS neutron detector, which makes it a promising candidate for future neutron detection and dosimetry applications.
The team is composed by R.C. Ponterio and S. Trusso (CNR-IPCF), G. Festa and C. Scatigno (Enrico Fermi Research Center), G. Romanelli (University of Tor Vergata), A. Piperno (University of Messina).
The full paper is available at DOI: 10.1016/j.apsusc.2023.159186
