The purpose of this paper is to provide an in-depth review of plasmonic metal nanoparticles made from rhodium, platinum, gold, or silver. We describe fundamental concepts, synthesis methods, and optical sensing applications of these nanoparticles. Plasmonic metal nanoparticles have received a lot of interest due to various applications, such as optical sensors, single-molecule detection, single-cell detection, pathogen detection, environmental contaminant monitoring, cancer diagnostics, biomedicine, and food and health safety monitoring. They provide a promising platform for highly sensitive detection of various analytes. Due to strongly localized optical fields in the hot-spot region near metal nanoparticles, they have the potential for plasmon-enhanced optical sensing applications, including metal-enhanced fluorescence (MEF), surface-enhanced Raman scattering (SERS), and biomedical imaging. We explain the plasmonic enhancement through electromagnetic theory and confirm it with finite-difference time-domain numerical simulations. Moreover, we examine how the localized surface plasmon resonance effects of gold and silver nanoparticles have been utilized for the detection and biosensing of various analytes. Specifically, we discuss the syntheses and applications of rhodium and platinum nanoparticles for the UV plasmonics such as UV-MEF and UV-SERS. Finally, we provide an overview of chemical, physical, and green methods for synthesizing these nanoparticles. We hope that this paper will promote further interest in the optical sensing applications of plasmonic metal nanoparticles in the UV and visible ranges.

Biologically active substances from microalgae can exhibit antioxidant, immunostimulating, antibacterial, antiviral, antitumor, antihypertensive, regenerative, and neuroprotective effects. Lipid complexes of microalgae Chlorella vulgaris and Arthrospira platensis exhibit antibacterial activity and inhibit the growth of the Gram-positive strain Bacillus subtilis; the maximum zone of inhibition is 0.7 ± 0.03 cm at all concentrations. The carbohydrate-containing complex of C. vulgaris exhibits antibacterial activity, inhibits the growth of the Gram-positive strain B. subtilis, Bacillus pumilus; the maximum zone of inhibition is 3.5 ± 0.17 cm at all concentrations considered. The carbohydrate complex of A. platensis has antimicrobial activity against the Gram-negative strain of Escherichia coli at all concentrations, and the zone of inhibition is 2.0–3.0 cm. The presence of mythelenic, carbonyl groups, ester bonds between fatty acids and glycerol in lipid molecules, the stretching vibration of the phosphate group PO₂, neutral lipids, glyco- and phospholipids, and unsaturated fatty acids, such as γ-linolenic, was revealed using FTIR spectra. Spectral peaks characteristic of saccharides were found, and there were cellulose and starch absorption bands, pyranose rings, and phenolic compounds. Both algae in this study had phenolic and alcohol components, which had high antibacterial activity. Microalgae can be used as biologically active food additives and/or as an alternative to antibiotic feed in animal husbandry due to their antibacterial properties.

Platelet activation plays a key role in the pathogenesis of cardiovascular complications in patients with coronary and cerebrovascular ischemic disease. The most important task in the treatment and prevention such complications is the complete suppression of platelet activity. Inhibition of platelet aggregation is currently a key therapeutic approach in the treatment and prevention of cardiovascular atherosclerotic origin. The development of new and more effective methods for prediction of the response of patients to antiplatelet therapy and its subsequent correction appears to be the most important task of modern physics, biophysics, and medicine. Platelets obtained from patient specimens have been investigated by Surface-enhanced Raman spectroscopy (SERS) with the diode-pumped solid-state laser ( λ = 532 nm) on Au/Ti rough surfaces. As a result, a set of optimal experimental parameters for platelets discrimination have been determined. Platelet spectral data for healthy volunteers, healthy volunteers on antiplatelet therapy and individuals with cardiovascular pathology on antiplatelet therapy have been analyzed. We suggest that the obtained results allow the usage of the SERS as a diagnostic tool for determination of both inhibition of platelet aggregation and its structure conformation.

This review presents the state of the art in using density functional theory (DFT) to investigate the mechanism of chemical enhancement in surface enhanced Raman scattering (SERS). Computational DFT models have been shown to align well with experimental data and to be useful in their interpretation. In this context, the combined use of theoretical data and experimental SERS results can help explore the mechanisms contributing to chemical amplification. This review examines the application of DFT to estimate chemical enhancement of SERS under the following conditions: the presence of silver ions on the surface, the size and stability of metal clusters, the energy characteristics of the investigated molecule in the system from the cluster size in molecule-nanoparticle models, changes in the spatial orientation of the molecule on the nanoparticle surface depending on the concentration of molecules. Additionally, the review analyses the influence of the metal cluster shape and size in DFT calculations in simplified cluster systems. This information will be useful for researchers working with experimental SERS aspects.

This work presents the dependences of the absorption intensity of the acid-soluble chitosan biopolymer films in the infrared (IR) region of the spectrum on the concentrations of silver and gold nanoparticles (NPs) of different morphologies. The interaction mechanisms in the vibrational spectra overlapping area of the silver NPs and chitosan molecules (2500–3500 cm⁻¹) were observed. The influence of the metal NPs on the dipole moments of the OH-, NH₃ ⁺- and CH-chitosan molecule group oscillations was established. This interaction leads to a linear increase of the IR absorption intensity with an increase of the silver nanoparticle concentration, synthesized by the citrate and borohydride methods. The presence of silver and gold ablative NPs in the chitosan films demonstrates the IR absorption intensity exponential decrease with the metal NPs’ concentrations.