The increasing interest in various nanoparticles (NPs) with well-defined properties requires their convenient and efficient production. Here, we exploit a new proposed scheme for pulsed laser ablation in liquid (PLAL), where nanosecond laser pulses process a 45 degrees tilted, rotating copper (Cu) disc, partially submerged into ethanol. This disc rotation spreads a thin ethanol layer on its surface. The generated plasma, formed following the laser impact, led to film splashing and caused NP accumulation in the ethanol pool. Analysis of fast camera frames and measured acoustic-wave (AW) amplitudes suggest mechanistic insight and allow optimizing the parameters. The laser fluence, ablation time, and particularly the rotating target speed, controlling the layer thickness, are varied to determine their effect on the ablation products. The observed dependence of the measured AW amplitudes, surface plasmon resonance intensities, and power-specific productivities on laser fluence match the calculation results, accounting for the effective laser energies generating the plasma. This promising technique enables the continuous synthesis of crystalline Cu NPs with high efficiency and concentration, providing a basis for further optimization of solid target ablation toward the achievement of specific particles for various applications.

Temperature programmed desorption - mass spectrometry was utilized to study the non isothermal hydrogen desorption from as-received and pre-oxidized TiH2 powder samples. Above the temperature of 750 degrees C, hydrogen desorption from the thermally decomposed as received powder is kinetically delayed compared to that from the pre-oxidized samples. The scanning electron microscopy observations suggest that the delay stems from simultaneous surface coarsening and particles sintering that occur predominantly in the as-received powder at lower temperatures. It is also suggested that the difference in morphology evolution of the as-received and pre-oxidized powders originates from the dependence of Ti diffusion on the concentration of oxygen dissolved in Ti, since the oxide layer itself was found to dissociate at lower temperatures (similar to 500 degrees C). (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

The literature view regarding the composition of deposited fingermarks has long been that the average water content is in the range of 98-99wt.%. This value has recently been challenged by Kent, claiming that it should be 20wt.% at most. Herein we have measured the weight percentage of water content in freshly-deposited fingermarks, with and without hand pre-washing. Two complementary techniques were utilized for the measurements, namely quartz crystal microbalance (QCM) for determining the relative mass-loss and its rate at ca. 37°C, and temperature-programmed desorption-mass spectrometry (TPD-MS) for establishing that the mass loss arises solely from the complete evaporation of all the water content in the fingermarks (done with hand pre-washing only). Unlike the traditional narrow-range values of 98-99% and the limiting value of 20wt.% suggested by Kent, our measurements indicate the occurrence of a broad 20-70% water content. Higher contents of water in fingermarks were found post hand pre-washing, most probably due to removal of the sebum from the fingertips, but none of the results exceeded 90%.

PH13-8Mo is a precipitation hardened martensitic stainless steel, known for its high strength but also for its high sensitivity to hydrogen embrittlement. Small punch test, SPT (also referred to as the ball punch test, BPT), is a relatively simple and new technique to assess the mechanical properties of samples under biaxial loading conditions. The current study utilizes the unique loading conditions of SPT to investigate the mechanical behavior and fracture prior to and after the hydrogen charging of PH13-8Mo steel. The mechanical characteristics were investigated at different metallurgical conditions: solution and quenched (SQ); fully-aged (550 °C for 4 h) and over-aged (600 °C for 4 h). Samples were cathodically hydrogen charged in a 1 M H2SO4 solution containing NaAsO2 (0.125 mg/L) at 50 mA/cm2 for different durations of 0.5 h, 2 h, and 19 h, and compared to the as-heat-treated condition. A fractographic examination was performed following the SPT measurements by scanning electron microscopy (SEM). Transmission electron microscopy (TEM) and x-ray diffraction (XRD) analyses were used as complementary characterization tools. It is shown that upon hydrogen charging, the SPT fracture mode changes from ductile to completely brittle with a transition of mixed mode cracking also affecting the SPT load-displacement curve.

RATIONALE:Cold EI is defined as electron ionization of cold molecules in supersonic molecular beams (SMB). Gas chromatography/mass spectrometry (GC/MS) with Cold EI provides informative mass spectra, which combine the usual library-searchable EI fragment ions with enhanced molecular ions for improved library-based identification probabilities. However, in some cases, such as in the analysis of complex petrochemical matrices, a soft ionization method that provides only molecular ions is desirable.METHODS:GC/MS with Cold EI was used with a fly-through ion source at selected electron energies, including at low electron energies, in an attempt to observe molecular ions alone.RESULTS:We explored low electron energy Cold EI and found that once the sample compound is cooled by the supersonic expansion it can be reheated via reflected scattered helium atoms near the skimmer. Furthermore, once a labile molecular ion is formed it can undergo undesirable collision-induced dissociation (CID) in the same way as in tandem mass spectrometry (MS/MS), and the magnitude of such CID can be significant for labile molecular ions such as those of hydrocarbons. In order to reduce these adverse effects we reduced the helium pressure at the ion source and MS vacuum chamber by increasing the nozzle-skimmer distance. Cold EI at low electron energies was explored with a squalane isomer (C30 H62 ) and with n-C24 H50 .CONCLUSIONS:It was found that an increased nozzle-skimmer distance resulted in a noticeable increase in the abundance ratio of molecular ions to low mass fragment ions. Consequently, Cold EI at low electron energies and a large nozzle-skimmer distance converts EI into Soft Cold EI while further approaching the ideal of a molecular ion only ionization method.

Oxygen isotope exchange during thermal dehydration of copper selenate pentahydrate was studied using the temperature-programmed decomposition mass spectrometry technique. The oxygen exchanges between the water of crystallization and the selenate in the solid phase. The results fairly indicate the preferable exchange between the oxygen atom of the most strongly bound water molecule and, at most, one specific oxygen atom in the selenate ion. The oxygen exchange probability was found to amount to 41.6%. Noteworthy is the fact that a small degree of oxygen exchange was also found to occur between selenate anion and liquid water. In addition, relating to previous studies on copper sulfate, the present study shows that both compounds possess identical oxygen exchange mechanisms in the solid state during their dehydration.

Temperature programmed desorption mass spectrometry (TPD-MS) and thermal gravimetry (TG) were utilized for the study of the thermal dehydration and decomposition of copper selenate pentahydrate (CuSeO4·5H2O). From the two techniques we suggest that the dehydration is a 3-step process reaching completion at 300 °C. The decomposition process however, is far more complicated consisting of several successive steps occurring between 480 and 900 °C. Initiated with the emission of oxygen, the decomposition of the anhydrous salt continues with SeO2 emission via several unstable intermediates up to the conversion of the remaining copper monoxide into dicopper monoxide accompanied by oxygen emission.

High-resolution temperature-programmed desorption mass spectrometry (TPD-MS) with a supersonic molecular beams (SMB) inlet system enables us to analyse quantitatively CO, CO2 and water from various sites on carbon molecular sieve fibres (CMSF). Three water sites up to 350 degrees C are observed. The first main water site is from desorption of physically adsorbed water molecules on the surface oxides and inside the micropores. The other two sites result from dehydration and decomposition of surface oxides. The effects of relative humidity, oxide concentration and pore structure on adsorption of water on CMSF are studied. Gradual oxide group decomposition at low temperature, up to 250 degrees C, is monitored and the kinetics of surface oxide formation in air at room temperature is studied.

Organic molecules acquired with hyperthermal (1–20 eV) kinetic energy undergo efficient surface ionization. This hyperthermal surface ionization (HSI) may produce both positive and negative ions. The dissociative ionization of alkyl halides results in the production of negative ions of the functional group having high electron affinity, and positive ions of the alkyl radical, which can further dissociate into smaller fragments. The effect of the alkyl chain lenght and the bromine isotope effect on the obtained HSI mass spectra were studied in several alkyl halide molecules. While the negative ion formation yield is found to be independent of the size of the alkyl radical, the positive ion formation yield strongly increases with the size of the CnH2n + i radical for n = 1–4 and then a quasi saturation is observed. The observed radical fragmentation increases with the incident molecular kinetic energy and was affected by the molecular structure and the surface temperature and cleanliness. A considerable (up to 24%) heavy brominem isotope increased ionization is observed at intermediate molecular kinetic energies. Piperidine HSI on a rhenium filament exhibits a single (M - 1) ion while its HSI from an oxidized rhenium filament having a much higher work function is characterized by a much richer fragmentation pattern. The dissociative ionization mechanism is rationalized in terms of a surface—molecule electron transfer followed by an immediate dissociation into a negative halogen ion and an alkyl radical. This radical, which usually has a low ionization potential, can transfer an electron to the surface and scatter as a positive ion. At high kinetic energies, the radicals or positive ions can further dissociate near the surface, and then scatter away as lower mass ions with ion yield which depends on their surface reneutralization probabilities. Thus, the observed fragmentation pattern is governed by surface chemicl and electron transfer processe and not by gas phase unimolecular ion dissociation, as found with large polyatomic molecules.

Cholesterol in a hydrogen-seeded supersonic molecular beam was scattered from a continuously oxidized rhenium foil. The hyperthermal surface scattering exhibited efficient molecular ionization with a controlled amount of molecular ion dissociation. At 5.3 eV incident molecular kinetic energy the hyperthermal surface ionization mass spectrum was dominated by the parent molecular ion. Upon the increase of the molecular kinetic energy, a gradual increase in the degree of ion dissociation was observed. At 22eV incident kinetic energy the parent ion was completely dissociated and the mass spectrum was dominated by an extensive consecutive fragmentation. An efficient kinetic-vibrational energy transfer was observed, and it is extimated to be over 18% of the available incident kinetic energy. The implication for surface collisionally-activated dissociation of polyatomic ions is discussed. Rhenium oxide is suggested as an optimal surface for this purpose, as well as for the hyperthermal surface ionization of neutral species.

Hyperthermal DABCO is scattered from H-covered Pt(111). The ionization by electron and proton transfer is measured as a function of the incident molecular kinetic energy and the angle of incidence. The positive ions produced are energy analyzed showing hyperthermal distributions which are dependent on the incident energy. This means that no equilibration occurs at the surface and therefore protonation at hyperthermal energy is an Eley-Rideal reaction. The protonation yield depends linearly on the incident DABCO flux and the H-coverage on the Pt(111) surface. The ionization yield for both electron and proton transfer depends on the incident energy as k(Ei−Etr)n with a similar threshold energy of 1.5 eV. From this we learn that direct protonation occurs by electron transfer and a subsequent binding of an H-atom. Within the error bars we found no difference between H-atom and D-atom transfer. Protonation of other molecules with a high proton affinity such as dimethylaniline at H-covered Pt(111) was measured as well. Analytical applications for both surface analysis and molecular detection are discussed.

Hyperthermal molecular DABCO [N(C2H4)3N] is scattered from hydrogen-covered Pt(111). Some of the scattered molecules are protonated at the surface and leave with a kinetic energy which is strongly dependent in the incident energy. This means that proton abstraction is occurring immediately on collision and it serves as a clear demonstration of an Eley-Rideal mechanism. No isotope effect was observed, excluding a tunneling mechanism. The proton transfer shows a threshold energy equal to the difference between the surface work function and the molecular ionization potential. The reaction therefore proceeds via a molecule-surface electron transfer and a subsequent H-atom abstraction.

Hyperthermal beams of cyclohexane and carbon tetrachloride were scatte from a 2% W−Th filament. Chlorine negative ions generated by chemically induced hyperthermal surface ionization were monitored by quadrupole mass spectrometer. The surface temperature of the filament was 2400K. (AIP)

We have found that a wide range of organic molecules with hyperthermal kinetic energy (1–20 eV) can undergo an efficient molecular ionization or dissociative ionization upon scattering from a surface. The molecular kinetic energy is obtained in a simple supersonic expansion of the organic heavy molecule seeded in hydrogen (or helium) carrier gas through a pinhole nozzle.

The Pt(111)-surface ionization of hyperthermal mercury atoms (4--10 eV) was studied in helium- and hydrogen-seeded supersonic molecular beams. In spite of the large energy difference of 4.7 eV between the atomic ionization potential and the surface work function, an efficient ionization was observed. The ionization mechanism is discussed in terms of an extensive energy transfer to the surface and the creation of a transient local hot spot. Analytical applications are mentioned.

Electrospray LC–MS, LC–MS with Cold EI and GC–MS with Cold EI (Electron Ionization (EI) of vibrationally cold molecules in supersonic molecular beams (SMB)) are compared in their sample identification capabilities. Two test mixtures were used: (a) acetaminophen, caffeine, sulfadimethoxine, terfenadine and reserpine; and (b) octafluoronaphthalene (OFN), pyrene, cholesterol and agidol 40. The major strength of EI in both LC–MS with Cold EI and GC–MS with Cold EI is its compatibility with library based sample identification that provides samples names and structures at the isomer level. GC–MS with Cold EI alleviates two major downsides of GC–MS with standard EI as it provides enhanced molecular ions that are often weak or missing in standard EI and, it significantly extends the range of compounds that are amenable for analysis. Consequently, reserpine and agidol 40 that are incompatible with standard GC–MS analyses are analyzed by GC–MS with Cold EI and yield effective library based identification. In cases involving sample compounds that are not in the library, ESI–LC–MS provides elemental formula information (when combined with high resolution MS) while GC–MS with Cold EI also provides elemental formula when TAMI software is used for the quadrupole mass accuracy improvement combined with isotope abundance analysis. We found that both LC–MS with Cold EI and GC–MS with Cold EI have broader range of small molecules amenable for analysis than ESI–LC–MS that fails to analyze relatively non-polar compounds and exhibits highly non-uniform and compound dependent ionization yields that span over four orders of magnitude. The total ion mass chromatograms S/N of ESI–LC–MS and LC–MS with Cold EI are comparable while it is better (>100 times per on-column amount) for GC–MS with Cold EI.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMolecular ionization and dissociative ionization at hyperthermal surface scatteringAlbert Danon and Aviv AmiravCite this: J. Phys. Chem. 1989, 93, 14, 5549–5562Publication Date (Print):July 1, 1989Publication History Published online1 May 2002Published inissue 1 July 1989https://pubs.acs.org/doi/10.1021/j100351a045https://doi.org/10.1021/j100351a045research-articleACS PublicationsRequest reuse permissionsArticle Views198Altmetric-Citations77LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTInternal energy effects on mass spectrometric fragmentationA. Danon, A. Amirav, J. Silberstein, I. Salman, and R. D. LevineCite this: J. Phys. Chem. 1989, 93, 1, 49–55Publication Date (Print):January 1, 1989Publication History Published online1 May 2002Published inissue 1 January 1989https://pubs.acs.org/doi/10.1021/j100338a015https://doi.org/10.1021/j100338a015research-articleACS PublicationsRequest reuse permissionsArticle Views196Altmetric-Citations29LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts