Optical Spectroscopic Techniques in Nanomaterial Science: Raman, Infrared, Photoluminescence

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Nanophotonics Materials and Devices".

Deadline for manuscript submissions: closed (15 January 2022) | Viewed by 4672

Special Issue Editor

Faculty of Physics, Sofia University, 5 James Bourchier Boulevard, 1164 Sofia, Bulgaria
Interests: Raman spectroscopy; Infrared spectroscopy; Lattice dynamics Calculations; Encapsulated nanowires; Magnetically ordered materials; Multiferroic materials

Special Issue Information

Dear Colleagues,

Optical spectroscopic techniques are indispensable tools in modern nanomaterial science, as the light–matter interactions provide a wealth of complementary information over the traditional diffraction and electron microscopy techniques. Quantum confinement effects substantially modify the electronic structure and the optical excitation spectrum in nanoscopic volumes of materials. These changes are readily observable in photoluminescence (PL) spectra and are on the basis of several modern optoelectronic applications.  Low-dimensional objects, like layered materials and nanowires, often display local atomic coordination and symmetry not existing in the corresponding bulk substances. The breakdown of local atomic symmetry in low dimensional materials as a rule leads to the activation of phonons, which are otherwise Raman and infrared inactive in the bulk. This fact makes the Raman and infrared spectroscopy sensitive probes for the atomic bonding and arrangement in a wide range of nanomaterials. For example, in recent decades, Raman spectroscopy has become a major characterization technique for most of the carbon allotropes.

Another actively growing field of research in nanomaterial science concerns surface enhanced spectroscopic techniques based on the resonant coupling between the optical wave and the surface plasmon on properly designed plasmonic nanostructures. For example, surface-enhanced Raman spectroscopy (SERS) is among the fewer analytic techniques capable of sensing individual molecules.

The aim of this Special Issue of Nanomaterials is to cover recent advances in optical spectroscopic techniques – photoluminescence, Raman and infrared, in the most general scope of modern nanoscience. Papers describing the development of new nanomaterial characterization protocols, as well as more fundamental research giving insight into the structural, electronic, and optical properties of nanomaterials, are welcome.

Dr. Victor Genchev Ivanov
Guest Editor

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Keywords

  • Characterization
  • Quantum confinement
  • Quantum dots
  • Nanowires
  • 2D materials
  • Surface-enhanced optical spectroscopies
  • Plasmonic nanostructures
  • Functional nanomaterials

Published Papers (3 papers)

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Research

11 pages, 2416 KiB  
Article
Pinning and Anharmonic Phonon Effect of Quasi-Free-Standing Bilayer Epitaxial Graphene on SiC
by Li Sun, Peng Wang, Xuejian Xie, Xiufang Chen, Fapeng Yu, Yanlu Li, Xiangang Xu and Xian Zhao
Nanomaterials 2022, 12(3), 346; https://doi.org/10.3390/nano12030346 - 21 Jan 2022
Viewed by 1373
Abstract
Epitaxial graphene on SiC without substrate interaction is viewed as one of the most promising two-dimensional (2D) materials in the microelectronics field. In this study, quasi-free-standing bilayer epitaxial graphene (QFSBEG) on SiC was fabricated by H2 intercalation under different time periods, and [...] Read more.
Epitaxial graphene on SiC without substrate interaction is viewed as one of the most promising two-dimensional (2D) materials in the microelectronics field. In this study, quasi-free-standing bilayer epitaxial graphene (QFSBEG) on SiC was fabricated by H2 intercalation under different time periods, and the temperature-dependent Raman spectra were recorded to evaluate the intrinsic structural difference generated by H2 time duration. The G peak thermal lineshift rates dω/dT showed that the H2 intercalation significantly weakened the pinning effect in epitaxial graphene. Furthermore, the G peak dω/dT value showed a perspicuous pinning effect disparity of QFSBEG samples. Additionally, the anharmonic phonon effect was investigated from the Raman lineshift of peaks. The physical mechanism responsible for dominating the G-mode temperature-dependent behavior among samples with different substrate coupling effects was elucidated. The phonon decay process of different samples was compared as the temperature increased. The evolution from in situ grown graphene to QFSBEG was determined. This study will expand the understanding of QFSBEG and pave a new way for its fabrication. Full article
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15 pages, 3420 KiB  
Article
Silver Flowerlike Structures for Surface-Enhanced Raman Spectroscopy
by Gitchka G. Tsutsumanova, Neno D. Todorov, Stoyan C. Russev, Miroslav V. Abrashev, Victor G. Ivanov and Alexey V. Lukoyanov
Nanomaterials 2021, 11(12), 3184; https://doi.org/10.3390/nano11123184 - 24 Nov 2021
Cited by 2 | Viewed by 1648
Abstract
Micro- and nanoflowers are a class of materials composed of particles with high surface-to-volume ratio. They have been extensively studied in the last decade due to simple preparation protocols and promising applications in biosensing, as drug delivery agents, for water purification, and so [...] Read more.
Micro- and nanoflowers are a class of materials composed of particles with high surface-to-volume ratio. They have been extensively studied in the last decade due to simple preparation protocols and promising applications in biosensing, as drug delivery agents, for water purification, and so on. Flowerlike objects, due to their highly irregular surface, may act also as plasmonic materials, providing resonant coupling between optical waves and surface plasmon excitations. This fact allows us to infer the possibility to use micro- and nanoflowers as effective surface-enhanced Raman scattering (SERS) substrate materials. Here, we report on the design and Raman enhancement properties of silver flowerlike structures, deposited on aluminum surface. A simple and cost-effective fabrication method is described, which leads to SERS substrates of high developed surface area. The morphology of the silver flowers on a nanoscale is characterized by self-organized quasiperiodic stacks of nanosheets, which act as plasmonic cavity resonators. The substrates were tested against rhodamine-6G (R6G) water solutions of concentration varying between 10−3 M and 10−7 M. Optimal SERS enhancement factors of up to 105 were established at R6G concentrations in the 10−6–10−7 M range. Full article
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13 pages, 2524 KiB  
Article
Pressure-Dependent Clustering in Ionic-Liquid-Poly (Vinylidene Fluoride) Mixtures: An Infrared Spectroscopic Study
by Teng-Hui Wang, Wei-Xiang Wang and Hai-Chou Chang
Nanomaterials 2021, 11(8), 2099; https://doi.org/10.3390/nano11082099 - 18 Aug 2021
Cited by 4 | Viewed by 1764
Abstract
The nanostructures of ionic liquids (ILs) have been the focus of considerable research attention in recent years. Nevertheless, the nanoscale structures of ILs in the presence of polymers have not been described in detail at present. In this study, nanostructures of ILs disturbed [...] Read more.
The nanostructures of ionic liquids (ILs) have been the focus of considerable research attention in recent years. Nevertheless, the nanoscale structures of ILs in the presence of polymers have not been described in detail at present. In this study, nanostructures of ILs disturbed by poly(vinylidene fluoride) (PVdF) were investigated via high-pressure infrared spectra. For 1-(2-hydroxyethyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([HEMIm][TFSI])-PVdF mixtures, non-monotonic frequency shifts of the C4,5-H vibrations upon dilution were observed under ambient pressure. The experimental results suggest the presence of microheterogeneity in the [HEMIm][TFSI] systems. Upon compression, PVdF further influenced the local structure of C4,5–H via pressure-enhanced IL–PVdF interactions; however, the local structures of C2–H and hydrogen-bonded O–H were not affected by PVdF under high pressures. For choline [TFSI]–PVdF mixtures, PVdF may disturb the local structures of hydrogen-bonded O–H. In the absence of the C4,5–H⋯anion and C2–H⋯anion in choline [TFSI]–PVdF mixtures, the O–H group becomes a favorable moiety for pressure-enhanced IL–PVdF interactions. Our results indicate the potential of high-pressure application for designing pressure-dependent electronic switches based on the possible changes in the microheterogeneity and electrical conductivity in IL-PVdF systems under various pressures. Full article
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