The sensitive identification of molecular markers in complex samples is of foremost importance in several fields. Surface Enhanced Raman Scattering Spectroscopy (SERS) has received increasing interest in recent decades due to its high sensitivity and rapid detection of analytes in low concentration. The project aims at weaving together High-Performance Thin Layer Chromatography (HPTLC) and SERS through a suitable interface in order to expand the applicability of SERS on complex samples. The project breakthrough lies in the development of a substrate, which will take advantage of the chromatographic chemical bridges bonding silica particles with noble metal nanospheres. The interaction of the analyte with the chemical bridges will force the molecules to be in proximity to nanoparticles, providing SERS enhancement. The SERS substrate will also work as HPTLC plate: this is the key to overcome the concept of hyphenation in favor of integration and for the future development of new HPTLC#SERS devices. Main attention will be focused on eliminate the most critical issues of the two techniques - crucial for their actual large scale application. To test the real versatility of the new substrate, comparison with robust techniques will be performed in different fields with fundamental effects on society, as food chemistry, forensics and cultural heritage conservation. In addition, an innovative HPTLC#SERS database will be developed, providing an important deliverable for the characterization of complex matrices; the potential of the new substrates will be tested on several analytes and complex matrices of interest in the three fields. Furthermore, with reference to the great versatility of plasmonic enhancement, the substrate will also be tested for the analysis with Surface-Enhanced InfraRed Absorption (SEIRA), which will represent an alternative detection strategy, amplifying the application potential of the new nano-substrate in the analytical field.
At present some hyphenated chromatographic and spectroscopic systems are starting to show their practical usefulness; however, there has been a lack of cooperation between separation scientists and spectroscopists: FingerSERSing aims at filling this gap by a close cooperation between the Departments of Physics, Chemistry and Environmental Biology.
The synthesis of new stationary chromatographic phases, intrinsically SERS-active, represents a paradigm shift, opening new perspectives to address several analytical issues. Indeed, the nano-functionalization through chemical bridges takes advantages of the fundamental features of separation phases to provide new detection possibilities, overcoming the intrinsic limitations of standard SERS spectroscopy in terms of reproducibility and analyte-specificity.
This new technology represents a real breakthrough, providing high quality analytics to every user and operator, without the need of specialized skills.
This is not science fiction: it has happened in the past, when atmospheric pressure ionization interfaces pioneered the hyphenation of High Performance Liquid Chromatography with Mass Spectrometry giving rise to one of the most powerful analytical technique used today.
The high impact of the proposed research lies on three main issues: the intrinsic features of molecular specificity and low reproducibility of SERS effect; the compatibility with HPTLC separation on an integrated substrate; the effective expendability by non-scientists.
In comparison to standard TLC-SERS approaches, where the MNPs are deposited only on the surface of the plate, in this approach the whole bulk of the stationary phase will be SERS-active since every silica particle will be nano-functionalized all over its surface with noble metals. The variation of different configuration for the Raman measurements (defocusing, hole of the laser, type of objective, etc.) will allow the collection of the SERS signal on the whole layer of analytes adsorbed on the stationary phase, minimizing variations in intensity and increasing the sensitivity and the reproducibility of the technique.
This achievement will represent a turning point for research on SERS, because it corresponds to overcoming the main drawback of the technique.
From the point of view of chromatographic separation, the possibility of interfacing HPTLC to Raman and FTIR spectroscopies through the synthesis on an innovative substrate opens new perspectives for the integration of the two methodologies in an on-line system. The design of these materials represents the starting point for a new technology, which could evolve into compact analytical devices for qualitative and quantitative analysis. The new substrate is the missing piece for the technology transfer of HPTLC and Surface-Enhanced spectroscopies from the research laboratories to industries, institutions, point-of-care diagnostics and more. The combination of the versatility of obtainable stationary phases with the plasmonic enhancement and the complementarity of SERS and SEIRA will result in new applications in analytical chemistry.
Finally, all the steps in the proposed workplan are necessary to make the new technology available to non-specialized operators. All the efforts on critical factors for the interface of chromatography and plasmonic-enhanced spectroscopies are aimed to the development of new devices which could result easy to transfer and to use. The integration feature of the new technology represents an advancement in terms of saving time and money, and it is the key-step for its applicability on a large scale. The project also encompasses a great work of valorization and comparison with existing analytical techniques, in order to show effectively the main advantages of the new platform in terms of applicability in and out of the laboratory and, consequently, to define the fields where the technology transfer is directly possible. The creation of spectral databases is also considered effective from this point of view, creating an immediate link towards the final operators. The HPTLC-SERS and HPTLC-SEIRA databases constitute innovative deliverables of the project, which expand our knowledge about complex matrices in different fields with huge footprint for society, providing also a great analytical tool which combines the potential of separative techniques with the informative power of vibrational spectroscopies.