A comprehensive picture of the nanosecond-laser generation of colloidal nanoparticles in liquids is nowadays the demand of their high-throughput industrial fabrication for diverse perspective biomedical, material science, and optoelectronic applications. In this study, using silicon as an example, we present a self-consistent experimental visualization and theoretical description of key transient stages during nanosecond-laser generation of colloidal nanoparticles in liquids: plasma-mediated injection of ablated mass into the liquid and driving the vapor bubble, finalized by the colloid appearance in the liquid. The explored fundamental transient stages envision the basic temporal and spatial scales, as well as laser parameter windows, for the demanded high-throughput nanosecond-laser generation of colloidal nanoparticles in liquids.

In this paper, we report the study of the low-voltage locally enhanced electric field treatment (LEEFT) of E. coli bacteria via TEM analysis and FT-IR and Raman spectrometry. The formation of pores was confirmed by TEM, which revealed the membrane rupture along with the formation of precipitates in the membrane and the cell volume, and by photoluminescence spectra of propidium iodide dye. LEEFT results in the alternation of DNA and RNA structure, indicated by the change in its α-helical and β-helical forms, decrease and narrowing of the nucleic acids-related IR and Raman peaks. Membrane damage is illustrated by the ambiguous character after low-voltage exposure: several membrane fatty acids’ peaks are broadening, while the others narrow, which indicates the overall change of the molecular bonds in their moiety, and may result from the rigidification during the shrinkage of the inner membrane and the increase in fluidity of the outer membrane. The corresponding fingerprints of cytochrome c and bo, located in the membrane or in the periplasm, on Raman spectra, reflect the arising changes in their structure and moiety. The observed changes were partially confirmed by TEM images, which indicate the dense precipitates’ formation in the cell volume and membrane, as well as the cytoplasmic membrane shrinkage away from the outer membrane.

Raman microspectroscopy has become an effective method for analyzing the molecular appearance of biomarkers in skin tissue. For the first time, we acquired in vitro Raman spectra of healthy and malignant skin tissues, including basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), at 532 and 785 nm laser excitation wavelengths in the wavenumber ranges of 900–1800 cm⁻¹ and 2800–3100 cm⁻¹ and analyzed them to find spectral features for differentiation between the three classes of the samples. The intensity ratios of the bands at 1268, 1336, and 1445 cm⁻¹ appeared to be the most reliable criteria for the three-class differentiation at 532 nm excitation, whereas the bands from the higher wavenumber region (2850, 2880, and 2930 cm⁻¹) were a robust measure of the increased protein/lipid ratio in the tumors at both excitation wavelengths. Selecting ratios of the three bands from the merged (532 + 785) dataset made it possible to increase the accuracy to 87% for the three classes and reach the specificities for BCC + SCC equal to 87% and 81% for the sensitivities of 95% and 99%, respectively. Development of multi-wavelength excitation Raman spectroscopic techniques provides a versatile non-invasive tool for research of the processes in malignant skin tumors, as well as other forms of cancer.

Ablative multi-shot preparation of gold nanoparticle hydrosols was carried out by raster-scanning a gold plate in deionized water using focused 1030 nm laser pulses of variable pulse width (0.3–6 ps). The relative nanoparticle yield, correlated with the extinction coefficient of colloidal solutions, exhibited an extraordinary non-monotonic variation versus the laser pulse width, which is explained by the electronic dynamics in gold in the lower limit, and either film water boiling or sub-critical peak laser powers in the upper limit.

We report the successful inactivation of P. aeruginosa strain by femtosecond infrared (IR) laser radiation at the resonant wavelengths of 3.15 μm and 6.04 μm, chosen due to the presence of characteristic molecular vibrations in the main structural elements of the bacterial cells in these spectral ranges: vibrations of amide groups in proteins (1500–1700 cm⁻¹), and C-H vibrations in membrane proteins and lipids (2800–3000 cm⁻¹). The underlying bactericidal structural molecular changes were revealed by the stationary Fourier-transform IR spectroscopy, with the spectral peaks parameters being obtained by Lorentzian fitting with the hidden peaks revealed by the second derivative calculations, while no visible damage to the cell membranes was identified by scanning and transmission electron microscopy.

We report the bactericidal effect of Ag and Cu NPs with different concentrations on methicillin-resistant S. aureus strain in comparison to the effect of AgNO₃ and CuCl₂ solutions, characterized by microbiological tests, TEM and Fourier-transform infrared spectroscopy. NPs were produced by nanosecond laser ablation in distilled water and characterized by scanning electron microscopy, UV-vis, energy dispersive X-ray, FT-IR spectroscopy, as well as X-ray diffraction, dynamic light scattering size and zeta-potential measurements. Microbiological tests showed antibacterial activity of NPs and metal ion-containing salts. Comparative FT-IR spectroscopy of bacteria, treated with metal NPs and salts, showed the broadening of amide I and II bands, a CH₂-related peak and its frequency decrease, indicating the increase of membrane fluidity. The main mechanisms of the antibacterial effect were proposed: Ag and Cu NPs release ions and ROS, which result in lipid peroxidation; AgNO₃ forms precipitates on the cell surface, which lead to the mechanical rupture of the membrane and subsequent possible penetration of the precipitates in the emerged damaged spots, complete destruction of the membrane and bacterial death; Cu ions from the CuCl₂ solution cause damage to phosphorus- and sulfur-containing biomolecules, which leads to disruption of intracellular biochemical processes. The theories were confirmed by FT-IR spectroscopy and TEM.