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Femtosecond laser irradiation of titanium oxide thin films: accumulation effect under IR beam
摘要： This paper discusses the mechanisms of laser-induced periodic surface structures (LIPSS) formation using a high repetition rate femtosecond laser beam irradiation of magnetron-sputtered titanium oxide thin films (TiO1.8) grown onto SiO2/Si substrates. An Yb:YKW 500 fs linearly polarized laser emitting at a wavelength, λ, of 1030 nm, was used to irradiate the films (300 nm thickness) at a repetition rate of 100 kHz under both static and dynamic (scanning) conditions. Under static beam conditions, an incubation behavior related to materials in thin film form was established with a damage threshold of 72 mJ/cm2. Close to this fluence value and increasing the number of laser shots from 1 to 1000, micro-cracking occurred and propagated inside the beam waist diameter zone estimated close to 60 μm. In addition, using a higher fluence value of 280 mJ/cm2, i.e., well above the damage threshold, a melting occurred in an intermediate zone within the irradiated area, with a surprising ‘cure effect’ that contributes to the micro-cracks stabilization. Simultaneously, at the center of the Gaussian laser beam spot, the entire film ablation was observed. Furthermore, irradiation under dynamic mode with a scanning speed of 4 mm/s and a repetition rate of 100 kHz were achieved for the large-scale processing of the TiO1.8 films up to surface area of 25 × 25 mm2. For these irradiation conditions case that correspond to a fluence of 110 mJ/cm2 and a cumulative number of shots of 3000, 2D-LIPSS nano-cracks (200 nm length and λ/8 to λ/9 period) are obtained over the whole irradiated surface, a phenomenon that is mainly attributed to a thermo-mechanical ablation mechanism.
关键词： Femtosecond laser beam,Titanium oxide film,Micro/nano-cracks,High repetition rate,Incubation,LIPSS
更新于2025-09-23 15:21:01
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[American Society of Agricultural and Biological Engineers 2018 Detroit, Michigan July 29 - August 1, 2018 - ()] 2018 Detroit, Michigan July 29 - August 1, 2018 - <i>The dose-effect relationships between green light and metabolism rate in chick embryos</i>
摘要： Green light during artificial incubation can affect the development of chick embryos. However, there has been relatively little work systematically assessing dose-effect relationships between green light and metabolism rate in chick embryos. Eggs (n=800) were incubated under photoperiods of either 0 h of light and 24 h of darkness (0L:24D), 6 h of light and 18 h of darkness (6L:18D), 12 h of light and 12 h of darkness (12L:12D), or 18 h of light and 6 h of darkness (18L:6D). In accordance with dose-effect on embryonic development, the response of carbon dioxide production rate to variations in illuminance was consistent with lipid reserve in yolk residue and hepatic glycogen in chick embryos. This sensitivity to green light indicates that the variation in illuminance within certain range of green light can have a significant impact on embryonic development and metabolic rate in chick embryos during artificial incubation. The results of this study indicate that providing 18 h of green light during incubation can have significantly improved the development and metabolism of the chick embryos.
关键词： chick embryos,metabolism rate,artificial incubation,green light
更新于2025-09-23 15:21:01
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Study of the physicochemical surface alterations and incubation phenomena induced on iron targets by nanosecond pulsed laser ablation in liquids: Effect on productivity and characteristics of the synthesized nanoscale zero-valent iron (nZVI) particles
摘要： This work presents a systematic study of the significant role of the surface physicochemical alterations produced during the laser ablation of massive iron disks submerged in different solvents on the generation of colloidal iron nanoparticles. For that purpose, the laser ablation thresholds and the incubation coefficients for various pulse numbers per site and pulse energies have been measured under distilled water (DW) and ethanol (EtOH). After that, a complete physicochemical characterization of these targets indicated higher threshold fluence values for the ablation experiments conducted in EtOH than those performed in DW. The threshold fluence values decreased also with the decrease of the pulse overlap for both solvents, being it much more pronounced in EtOH. In addition, the related incubation coefficient showed that the incubation effect is lower for experiments conducted in DW. The characteristics of the synthesized nZVI particles were also a function of the solvent nature and the pulse overlap: laser ablation in DW leaded to iron oxide nanoparticles, whereas core-shell iron nanoparticles were obtained in EtOH. Moreover, high pulse overlap values lead to chemical alterations, resulting in a decrease of the composition homogeneity and a strong increase of the nanoparticle polydispersity.
关键词： Incubation effect,Nanosecond pulsed laser ablation in liquids,Raman spectroscopy,Colloidal nanoscale zero-valent iron particles,Laser ablation threshold,Laser induced-chemical surface alteration
更新于2025-09-19 17:13:59
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Study on the interactions between graphene quantum dots and Hg(II): Unraveling the origin of photoluminescence quenching of graphene quantum dots by Hg(II)
摘要： The present investigation reveals that when Hg(II) interacts with the colloidal solution of graphene quantum dots (GQDs), initially it forms complex with GQDs and then reduces to Hg(0) and Hg(I) resulting the complete quenching of GQDs blue luminescence. This is in contradiction with the earlier reports in which the quenching of GQDs by Hg(II) is attributed to complexation alone. In order to understand the reasons for the quenching of GQDs by Hg(II), a detailed study was undertaken by varying the pH of GQDs solution, incubation time and concentration of Hg(II). The emission studies indicate that formation of Hg(0) is less favorable at pH 7 whereas its formation is more favorable at pH 13. It is assumed that the formation of Hg(OH)2 in alkaline pH facilitates Hg(II) reduction easier than at neutral pH. The SEM and TEM images confirm the presence of spherical Hg(0) particles with different sizes depending upon Hg(II) concentration, pH and incubation time. The results obtained from emission, XPS and differential pulse voltammetry (DPV) studies reveal that Hg(II) was reduced to Hg(0) via Hg(I) on GQDs surface. The differential pulse voltammogram of 40 min incubated Hg(II)-GQDs coated GC electrode shows three oxidation peaks at 0.34, 0.48 and 0.65 V, corresponding to Hg(I) to Hg(II) and Hg(0) to Hg(II), respectively.
关键词： metallic Hg,incubation time,mechanism for quenching,effect of pH,Interaction of GQDs with Hg(II)
更新于2025-09-19 17:13:59
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Selective rear-side ablation of aluminum thin layers with ultrashort-pulsed laser radiation
摘要： In recent years, several applications for laser ablation of thin metal layers from the fused silica substrate side have been studied. The rear-side ablation is a highly effective ablation method for thin layer structuring and reveals a high structuring quality. Therefore, the present work dealt with the selective rear-side ablation of thin aluminum layers (10–50 nm) on fused silica with ultrashort-pulsed laser radiation (λ = 1028 nm, ??H = 0.2–10 ps and w0,86 = 15.2 μm). The influences of pulse duration and layer thickness on the ablation thresholds as well as the incubation coefficients were determined. For layer thicknesses of 30 and 50 nm, a decrease of the ablation threshold with increasing pulse duration was determined. Whereas, the ablation threshold remained constant for layer thicknesses of 10 and 20 nm. Different morphologies were observed depending on the process parameters. The rear-side ablation of aluminum proceeded over the melting phase and no lift-off process had taken place. In addition to experimental investigations, calculations were carried out to determine the theoretical threshold fluences. The theoretical values were compared to experimental data. With the help of these investigations, the quality of the structuring of aluminum layers can be improved.
关键词： ultrashort-pulsed laser radiation,incubation coefficients,aluminum thin layers,laser ablation,rear-side ablation
更新于2025-09-16 10:30:52
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Laser-assisted MAL-PDT associated with acoustic pressure wave ultrasound with short incubation time for field cancerization treatment: a left-right comparison
摘要： Background: Laser-assisted MAL-PDT has been reported to increase the effectiveness of conventional PDT. Nonetheless, clinical effects of this association when reducing MAL is poorly discussed. Furthermore, the association of acoustic pressure wave ultrasound with laser-assisted MAL-PDT with short incubation time for field cancerization had not been reported before. Objectives: To compare clinical effects of ablative fractional laser-assisted MAL-PDT associated with acoustic pressure wave ultrasound (IMPACT US) with 1-hour field cancerization on the forearms, as well as the impact on safety and tolerability. Methods: Fifteen patients with 638 AK (grade I-III) with field cancerized-skin on the forearms were enrolled in this left-right trial. Two protocols were randomly chosen. One side was treated with conventional MAL-PDT, whereas the other with laser-assisted MAL-PDT associated with acoustic pressure wave ultrasound with 1-hour incubation time. Actinic keratoses were quantitively measured, and the other signs of sun-damaged skin, like pigmentation and texture, in field cancerized skin were qualitatively evaluated before and after six months. Side effects were assessed subjectively during the procedure and one week after. Results: All patients completed the study. At six months after treatment, both protocols reduced the number of AK (72%; CO2 + PDT, and 65%; MAL-PDT). The difference between these two protocols was not statistically significant (p = 0.77). The improvement of pigmentation and texture of field cancerized skin was more significant on the side treated with laser-assisted MAL-PDT associated with acoustic pressure wave ultrasound. Both protocols were well tolerated and without significant difference in adverse events. Conclusion: Laser-assisted MAL-PDT using CO2 laser and acoustic pressure wave ultrasound with short incubation time of 1 hour was as effective as conventional MAL-PDT for field-cancerized skin with actinic keratosis in forearms with better cosmetic outcome.
关键词： Incubation time,Skin field cancerization,Actinic keratosis,Ablative fractional laser assisted photodynamic therapy,laser-assisted drug delivery
更新于2025-09-12 10:27:22