The Surface-enhanced Raman spectroscopy is the essential tool for various levels of the molecular studies. In order to become widely used as a fast analytical tool, the enhancing structures such as the nanoparticles have to be simple, inexpensive, and offer good flexibility in enhancing properties and the spectral range. In this paper, we investigated the plasmonic properties of the metal nanoparticles, to which the molecules of interest can be adsorbed, forming the bionanocomplexes. Here, for the first time, we provided the collection of the results gathered in one article, which can serve as the basis or guidance for designing the SERS studies on different bionanocomplexes, various nanoparticle structures, sizes, and excitation wavelengths. The presented plasmonic properties describe the spectral position of the plasmonic resonances as results of their size and structure. The electric field enhancement as a key contributor to the SERS effect is given as well. We considered silver and gold nanoparticles and their variations. Gold is one of the best choice, due to its relevant surface properties, however, suffers from the plasmonic activity and rather static spectral position of the plasmonic resonances. Therefore, one of the main purposes was to show the effective resonance tuning using simple and less expensive geometries. We showed the possibility to adjust the plasmonic resonances with the excitation wavelengths from the blue region to the near infrared region of lasers most commonly used for Raman spectroscopy. The presented studies indicated the high potential of the core-shell structures for this kind of applications.

The bionanocomplexes of proteins and nanoparticles are promising bionanomaterials for medical purposes like the sensitive and the selective diagnostic devices, as well as, the modern therapeutic agents. The presence of the noble metals allows for obtaining the plasmonic effect and for generating the surface-enhanced Raman scattering phenomenon (SERS). The knowledge of the nanoparticle interaction with the protein molecule is extremely necessary for the development of the suitable product. The interaction of the bionanocomplex components can cause the conformational changes in the protein structure and the modification of surface properties of the nanoparticles. In the case of the binding of the gold nanoparticles with the enzymes, it is critical to preserve the catalytic activity, which is connected with maintaining the proper molecule structure. In the presented study, the Fourier transform infrared spectroscopy was used for the investigation of the interaction and the structural properties of the cholesterol oxidase (ChOX)—the gold nanoparticles bionanocomplex. The ChOX is one of the most important enzymes for the medical diagnostics and the promising antibacterial agent. The infrared spectra of the AuNP-ChOX bionanocomplex and the ChOX in different forms (the solid and the suspended in the buffer) are presented and discussed. The obtained spectra include the considerable number of the absorption lines identified and attributed to the corresponding chemical bonds and the functional groups of the protein. The analysis of the obtained infrared spectra revealed the important information about the changes of the protein structure after the immobilization on the gold nanoparticles. Moreover, it allows to recognize the differences in the structure of the protein in a different environment, which is of great importance in the context of bionanotechnology.

In the HgCdTe (MCT) alloys, a zero-gap state $E_g={\Gamma }_6-{\Gamma }_8=0$ may occur as the composition varies from HgTe to CdTe. This singular mechanism of the $E_g$ variation may be triggered by an external pressure or by a temperature. In this Letter, we present experimental data of the optical reflectivity in the far-infrared (FIR) domain in a wide interval of temperature (from 10 to 290 K) of the ${\mathrm{Hg}}_{1-x}{\mathrm{Cd}}_x\mathrm{Te}$ ($x=0.115$) samples. Since the intensity of classical IR sources drops abruptly in this spectral region, a brilliant synchrotron radiation FIR source has been used. The results clearly show that frequencies of the optical phonon modes exhibit discontinuity in their temperature dependence when a zero-gap state occurs.

The clustering model proposed by Verleur and Barker [Phys. Rev. 149, 715 (1966)] to interpret far infrared data for face-centered-cubic ternary compounds is critically analyzed. It is shown that their approach, satisfactory for fitting some ternary compound spectral curves, is too restricted by its one-parameter β model to be able to describe preferences (with respect to a random distribution case) for the five tetrahedron configurations.

This work presents far-infrared reflectivity spectra collected with synchrotron radiation on specially prepared CdTe monocrystals in the temperature region of $30–300\mathrm{K}$ . The investigated samples were of three different types characterized by the three different levels of hydrogenation—strong, middle, and low ones. In order to interpret the experimental data, the imaginary part of the dielectric function was evaluated by means of Kramers-Kronig transformation. To determine quantitatively the influence of hydrogen atoms on the phonon and vibrational spectra of hydrogenated CdTe crystals we used the special statistical model proposed in this paper. This model takes into account the tetrahedron as the basic structural unit and distinguishes the contribution of the hydrogen-bearing tetrahedra from the contribution of the hydrogen-free ones to the crystal phonon spectra.