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Nanoparticle (NP) analysis performed by laser ablation–single particle-inductively coupled plasma mass spectrometry (LA-sp-ICPMS) has recently allowed for multimodal insights to be gained about NPs in biological tissues. In our previous work, NP localizing, sizing and counting, as well as differentiating between the metal NP signal and its ionic form were achieved. In all of these, a low laser fluence (<1 J cm−2) was used, as it was observed that higher laser fluences can induce NP degradation, thus invalidating the results. This work is an in-depth study of gold NP (AuNP) degradation upon laser ablation, and provides guidelines for selection of the optimal laser fluence associated with NP analysis in gelatine as a matrix which mimics biological tissues. AuNPs of known size and with a narrow size distribution (CV < 5%) were used to keep track of the measured NP size with changing laser fluence. In addition, optical profilometry was utilized to measure the amount of material ablated as a function of the laser fluence, and provide a more accurate estimation of the NP degradation. [ABSTRACT FROM AUTHOR]

Background: One of the most critical issues concerning in situ mass spectrometry lies in accounting for elements and molecules that overlap target isotopes of analytical interest in a sample. This study traced the instrumental mass fractionation of Rb and Sr isotopes during laser ablation-multicollector-inductively coupled plasma mass spectrometry (LA-MC-ICPMS) to obtain reliable 87Sr/86Sr ratios for high-Rb/Sr samples. Findings: In the LA-MC-ICPMS analysis, Kr interferences were corrected using Ar and He gas blanks measured without ablating material. Contributions from doubly charged Er and Yb ions were corrected using the intensities of half masses and isotopic compositions reported in the literature. After Kr correction, the calculated 166Er2+ intensity of NIST SRM 610 approached the measured intensity at mass 83, and the 173Yb2+/171Yb2+ ratio agreed with the recommended value within error ranges. Kr- and REE2+-stripped peak intensities were further corrected for Rb interference. Use of the Sr mass bias factor for the calculation of measured 87Rb/85Rb yielded 87Sr/86Sr ratios consistent with the recommended and expected values for low-Rb/Sr materials, such as NIST SRM 616, modern shark teeth, and plagioclase collected from Jeju Island, but failed to account for the 87Rb interference from high-Rb/Sr materials including NIST SRM 610 and SRM 612. We calculated in situ mass bias factor of Rb from the known 87Sr/86Sr ratios of the standards and observed a correlation between Rb and Sr mass fractionation, which allowed inference of the Rb bias from the standard run. Reliable 87Sr/86Sr and 85Rb/86Sr ratios were obtained for SRM 610 and SRM 612 using the inferred mass bias factor of Rb calculated by the standard bracketing method. Conclusions: This study revealed that Rb and Sr isotopes behave differently during LA-MC-ICPMS and suggests the potential usefulness of the standard bracketing method for measuring the Rb–Sr isotopic compositions of high-Rb/Sr materials. [ABSTRACT FROM AUTHOR]

In allusion to difficult machining problems of new 2. 5-dimensional carbon fiber reinforced ceramic-based (Cf/SiC) composite materials by conventional machining, the 2. 5-dimensoonal Cf/SiC composite materials were ablated by nanosecond laser. After ablating, the morphology of ablation hole characteristics were observed by scanning electron microscope and the ablation removal mechanism was analyzed. The influences of laser parameters on the ablation hole were discussed. The results show that the ablation phenomena of Cf/SiC composites occur m the laser ablation area, such as ablation holes, resolidification, fiber fracture, end swelling, and elliptical material performance change area with long axis along fiber direction. Oxidation reaction may be found during laser ablation processes of Cf/SiC composites materials. The ablation hole diameter increases with the increasing ablation power and ablation time. When the ablation time and ablation power are large enough, there may be a case where the ablation hole is blocked or partially blocked by the solidification materials. The beam waist radius of nanosecond laser was calculated to be as 223 µm, and the ablation threshold of Cf/SiC composite materials is 0.32 J/cm² by nanosecond laser. [ABSTRACT FROM AUTHOR]

• Thermal damage reduction at the laser input energy densities E L−Input < 40 J/mm2. • Thermal ablation with nanosecond laser in contrast with the picosecond laser. • No effect of heat affected zone at E L−Input < 6.25 J/mm2. • Efficiency of laser ablation for both applied lasers was almost in a same range. Silicon nitride (Si 3 N 4) has exceptional mechanical, thermal and chemical properties and is therefore, advantageous for many applications. However, the employment of Si 3 N 4 is impeded by the high finishing cost. Short and ultrashort pulse laser ablation are considered as a non-contact machining processes and are utilised in recent years to overcome constrains of conventional machining of Si 3 N 4. However, there is still a lack of research on the effects of different laser parameters such as pulse duration on the mechanism of laser ablation. In this study, laser-material interaction of two different types of solid-state lasers with 10 ps and 100 ns pulse durations was investigated at the constant power of 50 W on a Si 3 N 4 workpiece. The width of thermal damages and heat-affected zone (HAZ) is extremely reduced within laser input energy density (E L−Input) less than 40 J/mm2 for both types of laser. It is found that in case of the nanosecond laser ablation, molten droplets inside the laser cut prevent diffusion of the laser beam at E L−Input higher than 62.5 J/mm2. This effect could not be observed in ablation with the picosecond laser. Compared to the nanosecond laser, the picosecond laser is more efficient for ablating the workpiece material at laser input energy densities higher than 120 J/mm2. [ABSTRACT FROM AUTHOR]

This letter reports observation of ablated holes as small as 0.7 μm fabricated by single 25 ns pulses of KrF (λ=248 nm) laser focused onto a 5.6 μm spot. Samples with high thermal conductivity films with respect to that of the substrate (Si/silica, Al/glass) repeatedly showed considerable reduction in the size of the ablated spot (0.7- and 1.2-μm-diam holes, respectively). This letter also presents a likely mechanism of the observed super-resolution and the criteria necessary to achieve super-resolution. Due to the nonoptical origin of this effect it is expected that a tightly focused (<0.5 μm) laser beam can be used to ablate with nanoscale (<100 nm) resolution. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]