The “laser ablation split stream” (LASS) technique is a powerful tool for mineral‐scale isotope analyses and in particular, for concurrent determination of age and Hf isotope composition of zircon. ...Because LASS utilizes two independent mass spectrometers, a large range of masses can be measured during a single ablation, and thus, the same sample volume can be analyzed for multiple geochemical systems. This paper describes a simple analytical setup using a laser ablation system coupled to a single‐collector (for U‐Pb age determination) and a multicollector (for Hf isotope analyses) inductively coupled plasma mass spectrometer (MC‐ICPMS). The ability of the LASS for concurrent Hf + age technique to extract meaningful Hf isotope compositions in isotopically zoned zircon is demonstrated using zircons from two Proterozoic gneisses from northern Idaho, USA. These samples illustrate the potential problems associated with inadvertently sampling multiple age and Hf components in zircons, as well as the potential of LASS to recover meaningful Hf isotope compositions. We suggest that such inadvertent sampling of differing age and Hf components can be a significant cause of excess scatter in Hf isotope analyses and demonstrate that the LASS approach offers a robust solution to these issues. The veracity of the approach is demonstrated by accurate analyses of 10 reference zircons with well‐characterized age and Hf isotopic composition, using laser spot diameters of 30 and 40 µm. In order to expand the database of high‐precision Lu‐Hf isotope analyses of reference zircons, we present 27 new isotope dilution‐MC‐ICPMS Lu‐Hf isotope measurements of five U‐Pb zircon standards: FC1, Temora, R33, QGNG, and 91500.
Key Points
Separate analyses of age+Hf isotopes leads to spurious results in zoned zircons
The LASS method is ideal for in situ analysis of complex zircons
Twenty-seven new Lu‐Hf isotope dilution analyses of reference zircons are given
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Laser ablation in liquids is actively used for generation of clean colloidal nanoparticles with unique shapes and functionalities. The fundamental mechanisms of the laser ablation in ...liquids and the key processes that control the nanoparticle structure, composition, and size distribution, however, are not yet fully understood. In this paper, we report the results of first atomistic simulations of laser ablation of metal targets in liquid environment. A model combining a coarse-grained representation of the liquid environment (parameterized for water), a fully atomistic description of laser interactions with metal targets, and acoustic impedance matching boundary conditions is developed and applied for simulation of laser ablation of a thin silver film deposited on a silica substrate. The simulations, performed at two laser fluences in the regime of phase explosion, predict a rapid deceleration of the ejected ablation plume and the formation of a dense superheated molten layer at the water-plume interface. The water in contact with the hot metal layer is brought to the supercritical state and transforms into an expanding low density metal-water mixing region that serves as a precursor for the formation of a cavitation bubble. Two distinct mechanisms of the nanoparticle formation are predicted in the simulations: (1) the nucleation and growth of small (mostly ⩽10nm) nanoparticles in the metal-water mixing region and (2) the formation of larger (tens of nm) nanoparticles through the breakup of the superheated molten metal layer triggered by the emergence of complex morphological features attributed to the Rayleigh-Taylor instability of the interface between at the superheated metal layer and the supercritical water. The first mechanism is facilitated by the rapid cooling of the growing nanoparticles in the supercritical water environment, resulting in solidification of the nanoparticles located in the upper part of the mixing region on the timescale of nanoseconds. The computational prediction of the two mechanisms of nanoparticle formation yielding nanoparticles with different characteristic sizes is consistent with experimental observations of two distinct nanoparticle populations appearing at different stages of the ablation process.
The contribution deals with growth of ZnO nanowires on metal catalysts by using of pulsed laser deposition and with the influence of growth temperature. The process of nanowires preparation comprised ...two technological steps—both were based on pulsed laser ablation processes: (1) production of metal nanoparticles by laser ablation in liquids and (2) pulsed laser deposition of ZnO nanowires by ablation of ZnO target on substrate with metal nanoparticles. Nanoparticles from various metals (Au, Ag, Ni, Cu, Al, Mg, Zn, Sn and BiSn alloy) were prepared by pulsed laser ablation at 1064 nm in deionised water. Colloids contained metal nanoparticles were applied on Si (100) substrates, and after drying, nanoparticles served as catalysts of VLS crystallisation. Temperatures in interval 600—200 °C were experimentally compared for the nanowires growth with applied ablation laser working at 248 nm. The lowest achieved temperature value for growth of ZnO nanowires was 425–450 °C. However, among applied metals Cu and Al nanoparticles only successfully catalysed ZnO nanowires at this temperature. Properties of prepared samples were investigated by scanning electron microscopy and photoluminescence. Experimental results revealed that along with the growth temperature, selection of proper metal catalyst is also important factor for nanowires crystallisation.
Cu2O nanoparticles were synthesized by pulsed laser ablation (Nd:YAG laser, 7 ns, and 1064 nm) of Cu plate immersed in liquid media from ultra-pure water, and its particle sizes were varied by ...changing the repetition rates between pulses to be useful for optoelectronic applications. The prepared colloidal suspension nanoparticles were characterized based on different physical process as the diffraction of X-ray laser beam, the electronic transition of UV–visible light source, or plasma emission from laser-matter interaction by the techniques of X-ray diffraction, UV–visible spectroscopy, and laser-induced breakdown spectroscopy, respectively. These techniques showed decreasing in the average particle sizes as increasing in the repetition rate of a pulsed laser. After that, the optical nonlinearity of the prepared samples was investigated by the Z-scan technique to inform the nonlinear parameters as 2nd order nonlinear absorption coefficient (β), 3rd order nonlinear susceptibility (X3), and the nonlinear reflective index (n2), optical limiting property and its proposed mechanism. The prepared nanostructured materials of Cu2O materials have a good optical limiter material with a limiting threshold value around 0.7 GW/cm2 and a damage threshold around 1.4 GW/cm2. These results confirmed that the saturable absorption process was carried by two-photon absorption, especially when the repetition rate of the used pulsed laser during the laser ablation process.
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Laser ablation molecular isotopic spectrometry (LAMIS) was recently reported for rapid isotopic analysis by measuring molecular emission from laser-induced plasmas at atmospheric pressure. With ...13C-labeled benzoic acid as a model sample, this research utilized the LAMIS approach to clarify the formation mechanisms of C2 and CN molecules during laser ablation of organic materials. Because the isotopic ratios in the molecular bands could deviate from statistical distribution depending on their formation pathways, the dominant mechanism can be identified through a comparison of the experimental observed isotopic patterns in the molecular emission with the theoretical statistical pattern. For C2 formation, the experimental 12C12C/13C12C ratios not only support a recombination mechanism through atomic carbon at early delay time but also indicate the presence of other operating mechanisms as the plasma evolves; it is proposed that some of the C2 molecules are released directly from the aromatic ring of the sample as molecular fragments. In contrast, the temporal profiles in the 12C/13C ratios derived from CN emission exhibited opposite behavior with those derived from C2 emission, which unambiguously refutes mechanisms that require C2 as a precursor for CN formation; CN formation likely involves atomic carbon or species with a single carbon atom.
•C2 and CN formation mechanisms during laser ablation of organic material studied•Some C2 molecules are directly desorbed from the organic compound.•C2 molecules are not important precursor for CN-radical formation.
Homogeneity, mass fractions of about forty trace elements and Sr isotope composition of Ca carbonate reference materials (RMs) between original and nano‐powdered pellets are compared. Our results ...using nanosecond and femtosecond LA‐(MC)‐ICP‐MS show that the nano‐pellets of the RMs MACS‐3NP, JCp‐1NP and JCt‐1NP are about a factor of 2–3 more homogeneous than the original samples MACS‐3, JCp‐1 and JCt‐1, and are therefore much more suitable for microanalytical purposes. With the exception of Si, the mass fractions of the synthetic RM MACS‐3 agree with its fine‐grained analogue MACS‐3NP. Very small, but significant, differences between original and nano‐pellets are observed in the RMs JCp‐1 and JCt‐1 for some trace elements with very low contents, indicating the need for re‐certification. Strontium mass fractions in the analysed RMs are high (1500–7000 mg kg−1), and their isotope compositions determined by LA‐MC‐ICP‐MS in the original and the nano‐pellets agree within uncertainty limits.
key points
Investigations of carbonate reference materials using fs‐ and ns‐ LA‐ICP‐MS.
Nanopowdered pellets are a factor 2 –3 more homogenous than original samples.
New reference values for MACS‐3 are provided.
Background
Microaggregates are suspected to protect soil organic carbon (SOC) from microbial decay, but its residence time is not well understood.
Aims
We aimed at unraveling the relevance of ...microaggregates for C storage and testing the hypothesis that C in the interior of aggregates is older, compared to the exterior.
Methods
We sampled soil under C3 vegetation and at a site where cropping shifted to C4 vegetation 36 years ago. We isolated free and macroaggregate‐occluded size fractions (250–53 µm) by wet sieving and ultrasound, manually isolated aggregates therefrom, and analyzed whether vegetation‐related differences in δ13C could be traced at the interior and exterior of microaggregate cross‐sections using elemental and laser ablation‐isotope ratio mass spectrometry.
Results
Size fraction weights comprised <5% of microaggregates. Based on a source partitioning approach including C3‐ and C4‐derived C, we found mean residence times of SOC in occluded and free microaggregates of 62 and 105 years, respectively. Thus, C storage was longer than that in size fractions (35 years) and bulk soil (58 years). The small‐scale variability of δ13C within aggregate cross‐sections was considerable, both in C3 and C4 soil, yet without significant (p = 0.46) differences between interior and exterior locations.
Conclusions
We conclude that microaggregates do not persist in an intact form in such a long‐term that systematic differences in δ13C patterns between exterior and interior parts can develop.
The focused ion beam technique has become a standard tool for micro-mechanical sample preparation in the last decade due to its high precision and general applicability in material removal. Besides ...disadvantages such as possible ion damage and high operation costs especially the characteristically small removal rates represent a bottleneck for this application. In contrast, femtosecond lasers provide material removal rates orders of magnitude higher, with small or ideally without thermal impact on the surrounding material. Hence, a combination of these two methods offers an ideal tool for time-efficient, micrometer-sized sample preparation. A prototype implementing this idea is presented here in combination with a case study. Cantilevers with a length of several hundred micrometers were machined into 25 μm, 50 μm and 100 μm thick, cold rolled tungsten foils. Scanning electron microscopy analyses reveal the influence of laser parameters and different scanning routines on the resulting sample quality and the effect of the laser pulse length (femtoseconds versus nanoseconds) on the ultra-fine grained microstructure. Finally, the performance for unprecedented rapid sample preparation is demonstrated with a sample array consisting of 100 cantilevers with a dimension of 420×60×25 μm3 processed in only half an hour, opening completely new testing possibilities.
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•A prototype device combining a focused ion beam and a femtosecond laser is presented.•A case study of fabricating cantilevers for micro-mechanical tests into cold rolled tungsten foils was performed.•No coarsening of the ultra-fine grained microstructure was found after femtosecond laser ablation.•A sample array consisting of 100 cantilevers with a dimension of 420×60×25 μm3 was processed in only half an hour.
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•rGO/ZnO nanosheets sensitized by Au have been successfully synthesized by pulsed laser ablation and sputtering method.•Au/rGO/ZnO sensor has a high response, long-term stability, and ...selectivity under UV illumination at room temperature.•The enhanced mechanism could be attributed to the high conductivity of rGO, spill-over of Au, and high surface area of ZnO.
Extended surface area in addition to higher conductivity and abundant free electrons/holes generation has been key players for any efficient sensor design. Therefore, contribution from graphene as highest conductive material and plasmonics from gold (Au) were expected to facilitate efficient zinc oxides (ZnO) nanostructures-based Hydrogen gas detection. We have presented herewith a facile route to synthesize ZnO nanosheets from elongated nanoblocks of the same in presence of reduced graphene oxide (rGO) under laser ablation environment. Au decorated such rGO/ZnO heterostructured nanosheets were found to be highly selective and sensitive to H2 detection under ultraviolet radiation at room temperature (RT). A detailed investigation was carried out to confirm topographic evolution through high resolution scanning electron microscopy. Optical band gap and infrared absorption of as-synthesized specimens at different stages were investigated further in addition to structural confirmation using X-ray diffraction analysis. Raman spectroscopy, a complementary technique was utilized to investigate the specimens at different stages too. SEM-aided elemental analysis inferred that gold nanoparticles were homogeneously distributed over the rGO/ZnO heterostructure. A custom-made setup designed at our disposal were utilized to understand the selectivity and sensitivity of as-fabricated heterostructure for H2 detection. The H2 gas sensing properties of Au nanoparticles decorated rGO/ZnO heterostructure were investigated at RT under UV irradiation and compared with those observed using pristine ZnO nanostructure at high working temperature. A plausible mechanism was illustrated with reference to well-known ‘spell-over’ scenario usually observed in plasmonic sensors.
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