Capaccio, Angela (2021) Development of novel nano-structured materials for Enhanced Raman Spectroscopies: an insight in SERS and TERS applications. [Tesi di dottorato]


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Item Type: Tesi di dottorato
Resource language: English
Title: Development of novel nano-structured materials for Enhanced Raman Spectroscopies: an insight in SERS and TERS applications
Date: 5 May 2021
Number of Pages: 177
Institution: Università degli Studi di Napoli Federico II
Department: Fisica
Dottorato: Fisica
Ciclo di dottorato: 33
Coordinatore del Corso di dottorato:
Rusciano, GiuliaUNSPECIFIED
Date: 5 May 2021
Number of Pages: 177
Keywords: Raman spectroscopy; SERS; TERS; nano-fabrication; plasmonics
Settori scientifico-disciplinari del MIUR: Area 02 - Scienze fisiche > FIS/03 - Fisica della materia
Date Deposited: 21 May 2021 06:57
Last Modified: 07 Jun 2023 11:06

Collection description

Owing to their ultrahigh selectivity and sensitivity, the plasmon-enhanced Raman spectroscopies (PERS) methods have emerged as diverse and exciting cutting-edge techniques for the investigation of biosystems at nanometric scales in air or water environments. By exploiting the plasmonic properties of noble metal nanoparticles, the PERS methods enable to remove the main obstacle of the Raman spectroscopy represented by the small Raman cross- section. Among them, the Surface Enhanced Raman Spectroscopy (SERS) is certainly the most important in terms of the number of applications in many fields of science (physics, chemistry, and biomedicine). One of the interesting features of the SERS is that the huge amplification of inelastic Raman photons can reach up to 12 orders of magnitude allowing even the detection at single-molecule level. In addition, the strong distance dependence of the plasmonic near-field effect (∼ 10-20 nm) makes effective the SERS only for molecules in proximity to metal-nanostructured surfaces and, thus, suitable not only for the bio-analysis of membranes but also for the surface characterization in science materials. Anyway, beyond the high sensitivity, the limitation of the SERS is represented by the diffracted-limited spatial resolution. A significant improvement is given by the modern tip-enhanced Raman spectroscopy (TERS) technique. By combining the high resolution of scanning-probe microscope (SPM) technology and the sensitivity of SERS, TERS is capable to correlate topographical and chemical information of a sample at nanoscale level. In fact, the Raman signal coming from the probed molecules is strongly enhanced via SERS effect when they are in proximity of the apex of a metalized or metallic SPM tips. Moreover, the scattering efficiency of TERS signal is greatly increased when the metal surface of the probe is nano-structured. The spatial resolution of TERS signals is mainly ruled by the tip-radius, which is typically of few tens of nanometers, therefore allowing to reach a lateral resolution in the range of 10-50 nm, far beyond the diffraction limit. Anyway, the development of reliable and effective plasmonic devices for SERS and TERS applications represents the major obstacle towards a wider diffusion of TERS/SERS as powerful analytical tools in material science and life science. In the case of TERS, the main technological challenge is based on the fabrication of metal nano-structures on the tip. Compared to SERS substrates that are produced on large-area surfaces, the sub-micron dimensions of the tip apex make the nano-structuring task more tricky. In this frame, the current thesis work aims to present a novel and versatile method for the preparation of appropriate AFM-TERS tips and SERS substrates. The innovative approach is based on the application of a radio-frequency discharge produced by an inductively coupled plasma (ICP) on commercial Ag-covered AFM probes. The plasma treatment produces an intriguing metallic porous nanotexture resembling a coral-like structure. The so-produced probes have been characterized by showing an amplification up to six orders of magnitude and a spatial resolution down to 10 nm, which render these devices particularly attractive for nanometer chemical characterization. In addition, this method has been successfully implemented for the fabrication of broad-band SERS-active platforms. This protocol has shown to be effective to produce substrates that can amplify the Raman signal up to seven orders of magnitude. Finally, another method for the fabrication of SERS substrates, based on the self-assembly of block copolymer (BCP) loaded with Ag-NPs, is proposed. The sensitivity of the so-prepared substrates has been tested by revealing the over-expression of target proteins in membranes of cancer cells.


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