International Journal of

---

In this work, potential of the nanosecond laser processing technique on manipulating the surface wettability of 316L bio grade stainless steel is investigated. Results show that the steel wettability toward water, improves significantly after the laser treatment. Different analyses are assessed in correlation with wettability using Scanning Electron Microscope (SEM), Scanning Tunneling Microscope (STM) and Energy Dispersive X-ray spectroscopy (EDX). It is found that the improvement in the wettability relates to the combined effects of the increase in the surface roughness, oxygen content and the form of the created surface morphologies. Laser fluence is found as the most dominant processing parameter and the higher the incident fluence results in the higher surface roughness and improvement of the wettability. However, measurements indicate that all the treated surfaces become hydrophobic after air exposure for a few days. It is shown that the time dependency of the surface wettability relates to the chemical activity and the reduction of the Oxygen/Carbon (O/C) ratio on the treated surfaces. The behaviors are further studied with investigating the effects of the keeping environment. The long-term wettability alteration differs for the samples that are kept in different mediums. Results indicate that the nanosecond pulsed laser treatment is a versatile approach to create either hydrophobic or hydrophilic steel surfaces for industrial and medical applications.

---

In this paper, the scattering of a plane monochromatic electromagnetic wave from a nanowire with circular cross-section in the transverse electric (TE) mode is simulated using the well-known Stratton-Chu surface integral equations. For an ordinary dielectric nanowire the refraction phenomenon is nicely simulated. In the case of a plasmonic nanowire no sign of surface plasmon excitation and propagation is seen. Transition from electrostatic regime to the geometrical shadow through diffraction regime by decreasing the light wavelength is also observable.

---

In this article, the effect of plasmonic properties of metal nanoparticles with different shapes, and moreover, their plasmonic-photonic interaction, on solar cell performance were investigated and simulated. Because of low conversion efficiency and then high cost of solar cells, it is difficult to commercialize and replace them with conventional energy resources. But in recent years, the plasmonic solar cell has been very popular. In this study, it is shown that the enhancement of near-field electromagnetic waves severely affects the generation rate, which handles the carrier’s generation in the solar cell equations and causes alteration of the photocurrent. This means that by manipulating the plasmonic properties of nanoparticles (shape and density) and their interaction with photons in solar cell structure, distribution of electromagnetic fields will be altered. Hence, the optical power related to the poynting vector is changed. So, with the aim of improving the solar cell some important parameters such as alteration of nanoparticle shape and their inter-distance were investigated. Finally, a comparison between traditional solar cells and our improved structure was undertaken.

---

Photobiomodulation therapy (PBMT) or Low level light Therapy (LLLT), is the stimulatory effect of light on the cell behavior. It has been considered as a potential therapeutic intervention. Glioblastoma is a malignant primary brain tumor without any effective treatment. This in vitro study investigated the effect of PBMT on proliferation rate and vital activity of human glioblastoma U87 cell line. Three different wavelengths were considered: 632 nm (red light, 2.1 mW/cm²), 534 nm (green light, 1.2 mW/cm²), and 457 nm (blue light, 6.5 mW/cm²). The cell behavior was studied during a period of four hours up to 60 hours after irradiation. The irradiated cells were inspected by different assays for cell count, cell viability, cell death, and free radical production rate and were compared with the control non-irradiated ones. The results show a reduction in cell viability for all the three wavelengths. However, the effect is more pronounced for blue light. Cell death assessments, staining and flow cytometry, and NBT assay shows that blue light is not lethal, but that it reduces the free radical production rate. Temporal analysis shows that the maximum effect on cell proliferation will be observed around 48 hours after irradiation. It could be concluded that light, particularly shorter wavelengths, has an inhibitory effect on the in vitro proliferation rate of U87 cell line by affecting the energetics of the cell. The effect is stimulatory and persistent for periods comparable to cell doubling time.

---

Xanthene and its derivatives are important in medical diagnosis and laser technology. In this work, spectral features of fluorescein disodium were investigated in different environments with different polarity characteristics. Hence, the absorption and fluorescence spectra of this molecule were studied in different environments. Our results show that spectral features of fluorescein disodium depend strongly on substituents in its structure and molecular interactions. To investigate the contribution of various molecular interactions on the spectral behavior of the used sample, the linear solvation energy relationship concept is used. Moreover, the dipole moment variations from ground to excited states were estimated using molecular spectral features in different solvent media. According to the results, the dipole moment value in the excited state is higher than that in the ground state.

---

Laser pulse overlapping (LPO) is an important factor affect the behavior of the laser treated surfaces. For laser surface treatment especially at high fluences, the laser beam must be focused to reach the desired fluence. Then laser beam or sample scanning in 2 directions is done to treat a surface area. In this paper, effect of the distance between laser treated lines (scanned in x direction) on the surface properties including morphological changes and wettability modifications of 304 stainless steel is investigated. The results show that the morphology and chemistry of the surface are influenced effectively by changing the overlap between laser treated line on the surface. Then, it should be considered as an important parameter in laser modification of a large surface with focused laser beam.