Laser-induced Desorption Research Articles

Molecular Reconfiguration of Disordered Tellurium Oxide Transistors with Biomimetic Spectral Selectivity.

Reconfigurable devices with field-effect transistor features and neuromorphic behaviors are promising for enhancing data processing capability and reducing power consumption in next-generation semiconductor platforms. However, commonly used 2D materials for reconfigurable devices require additional modulation terminals and suffer from complex and stringent operating rules to obtain specific functionalities. Here, a p-type disordered tellurium oxide is introduced that realizes dual-mode reconfigurability as a logic transistor and a neuromorphic device. Due to the disordered film surface, the enhanced adsorption of oxygen molecules and laser-induced desorption concurrently regulate the carrier concentration in the channel. The device exhibits high-performance p-type characteristics with a field-effect hole mobility of 10.02 cm2 V-1 s-1 and an Ion/Ioff ratio exceeding 106 in the transistor mode. As a neuromorphic device, the vision system exhibits biomimetic bee vision, explicitly responding to the blue-to-ultraviolet light. Finally, in-sensor denoising and invisible image recognition in static and dynamic scenarios are achieved.

Laser-Induced Ablation and Desorption of Deuterium-Containing Tungsten Films

The laser-induced desorption (LID) and laser-induced ablation (LIA) methods are compared with each other regarding the possibility of measurements an absolute quantitative analysis of hydrogen isotopes content in first wall materials of fusion reactors. Deuterium containing tungsten films with a thickness of 300–400 nm on a silicon substrate were used as model samples. To implement the LID, the samples were irradiated with laser pulses with a duration of 200 microseconds and an energy density of 50–150 J/cm2, for LIA – 12 ns and 5–15 J/cm2. The registration of residual gases was carried out by quadrupole mass spectrometry. Computer simulation of laser pulse heating was performed for the LID process. The simulation results and experimental data showed that heating at an energy density of 100–150 J/cm2 is sufficient to degas tungsten films of the studied thickness. A comparison of the amount of desorbed deuterium in the LID (150 J/cm2) and LIA (15 J/cm2) modes shows that it is identical within the measurement error and is equal to 4.15±0.15·1014 cm-2.

Dynamic basis of lipopolysaccharide export by LptB2FGC

Lipopolysaccharides (LPS) confer resistance against harsh conditions, including antibiotics, in Gram-negative bacteria. The lipopolysaccharide transport (Lpt) complex, consisting of seven proteins (A-G), exports LPS across the cellular envelope. LptB2FG forms an ATP-binding cassette transporter that transfers LPS to LptC. How LptB2FG couples ATP binding and hydrolysis with LPS transport to LptC remains unclear. We observed the conformational heterogeneity of LptB2FG and LptB2FGC in micelles and/or proteoliposomes using pulsed dipolar electron spin resonance spectroscopy. Additionally, we monitored LPS binding and release using laser-induced liquid bead ion desorption mass spectrometry. The β-jellyroll domain of LptF stably interacts with the LptG and LptC β-jellyrolls in both the apo and vanadate-trapped states. ATP binding at the cytoplasmic side is allosterically coupled to the selective opening of the periplasmic LptF β-jellyroll domain. In LptB2FG, ATP binding closes the nucleotide binding domains, causing a collapse of the first lateral gate as observed in structures. However, the second lateral gate, which forms the putative entry site for LPS, exhibits a heterogeneous conformation. LptC binding limits the flexibility of this gate to two conformations, likely representing the helix of LptC as either released from or inserted into the transmembrane domains. Our results reveal the regulation of the LPS entry gate through the dynamic behavior of the LptC transmembrane helix, while its β-jellyroll domain is anchored in the periplasm. This, combined with long-range ATP-dependent allosteric gating of the LptF β-jellyroll domain, may ensure efficient and unidirectional transport of LPS across the periplasm.

Dynamic basis of lipopolysaccharide export by LptB2FGC.

Lipopolysaccharides (LPS) confer resistance against harsh conditions, including antibiotics, in Gram-negative bacteria. The lipopolysaccharide transport (Lpt) complex, consisting of seven proteins (A-G), exports LPS across the cellular envelope. LptB2FG forms an ATP-binding cassette transporter that transfers LPS to LptC. How LptB2FG couples ATP binding and hydrolysis with LPS transport to LptC remains unclear. We observed the conformational heterogeneity of LptB2FG and LptB2FGC in micelles and/or proteoliposomes using pulsed dipolar electron spin resonance spectroscopy. Additionally, we monitored LPS binding and release using laser-induced liquid bead ion desorption mass spectrometry. The β-jellyroll domain of LptF stably interacts with the LptG and LptC β-jellyrolls in both the apo and vanadate-trapped states. ATP binding at the cytoplasmic side is allosterically coupled to the selective opening of the periplasmic LptF β-jellyroll domain. In LptB2FG, ATP binding closes the nucleotide binding domains, causing a collapse of the first lateral gate as observed in structures. However, the second lateral gate, which forms the putative entry site for LPS, exhibits a heterogeneous conformation. LptC binding limits the flexibility of this gate to two conformations, likely representing the helix of LptC as either released from or inserted into the transmembrane domains. Our results reveal the regulation of the LPS entry gate through the dynamic behavior of the LptC transmembrane helix, while its β-jellyroll domain is anchored in the periplasm. This, combined with long-range ATP-dependent allosteric gating of the LptF β-jellyroll domain, may ensure efficient and unidirectional transport of LPS across the periplasm.

Identification and Antibiogram of Clinically Relevant Non-Diphtheriae Corynebacterium species

Abstract Background and Objectives With the increase in immunosuppressed patients and antimicrobial misuse, Non-diphtheriae Corynebacterium species (NDC spp.) have risen as opportunistic pathogens in hospitalized patients. The present study aimed at comparing Vitek 2C automated identification cards versus MALDI-TOF as the gold standard method for the identification of different NDC spp. and determining the antimicrobial susceptibility of NDC spp. by the disc diffusion method for proper management of patients. Materials and Methods The study included 30 NDC spp. isolates recovered from different samples and were subjected to identification by MALDI-TOF and Vitek 2C. The disc diffusion method was performed to determine the antimicrobial susceptibility of the following antibiotics: pencillin G, tetracycline, gentamicin, ciprofloxacin, vancomycin, and Linezolid. Results Our study showed that Corynebacterium striatum (C. striatum) was the most commonly isolated species (83.3%), followed by C. amycolatum (10%). 36.7% of the isolates were recovered from blood culture while 20 % were recovered from deep wounds. The age of the patients included in the current study ranged from 55 to 85 years with a mean of 46.7 years. 56.7 % of the isolates were collected from female patients and 43.3% from male patients. As Regard isolate identification by Vitek-2C ANC ID CARD compared to MALDI-TOF (matrix-associated laser-induced desorption ionization-time of flight) as the gold standard method, the agreement was 86.7%. Regarding the antimicrobial susceptibility by disc diffusion method, all the isolates showed increased resistance against pencillin (100%), ciprofloxacin (70%), gentamicin (93.3%), tetracycline (76.6%), and clindamycin (70%). On the other hand, vancomycin and linezolid showed promising results where 100 % of the isolates were susceptible. Conclusion We spotlight that NDC spp. should no longer be considered contaminant bacteria in cultures, particularly in immunosuppressed patients. Timely identification, proper clinical correlation, and appropriate therapeutic intervention can lead to favorable outcomes. The high resistance to multiple classes of antibiotics as compounds of the MLSB group, fluoroquinolones, tetracyclines, and β- lactams, thus potentially limiting effective empirical treatment. However, vancomycin and linezolid are still effective against 100 % of the isolates.

Dimensional effects in analysis of laser-induced-desorption diagnostics data

The accurate assessment of the local tritium concentration in the tokamak first wall by means of the laser-induced desorption (LID) diagnostics is sought as one the key solutions to monitoring the local radioactive tritium content in the first wall of the fusion reactor ITER. Numerical models of gas desorption from solids used for LID simulation are usually closed with the one-dimensional transport models. In this study, the temperature and particle dynamics in the target irradiated by a short laser pulse during LID are analyzed by means of the two-dimensional model to assess the validity of using one-dimensional approximation for recovering the diagnostics signal. The quantitative estimates for the parameters governing the heat and particle transfer are presented. The analytical expressions for the sample spatiotemporal temperature profiles driven by the target irradiation with a Gaussian laser beam with the trapezoid temporal shape are derived. The obtained relations are used to simulate tritium desorption from a tungsten sample driven by pulsed heating. It is shown that depending on the ratio between the laser spot radius and the heat diffusion length, the one-dimensional approach can noticeably overestimate the sample temperature in the limit of small laser spot radius (estimated for tungsten as ∼0.5–1.0 mm), resulting in more than 100% larger amounts of tritium desorbed from the target, compared to the two-dimensional approximation. In the limit of large laser spot radius (≥1.5 mm), both approaches yield comparable amounts of tritium desorbed from the sample.

First results of laser-induced desorption - quadrupole mass spectrometry (LID-QMS) at JET

The paper reports the first demonstration of in situ laser-induced desorption — quadrupole mass spectrometry (LID-QMS) application on a large scale fusion device performed in summer 2023. LID-QMS allows direct measurements of the fuel inventory of plasma facing components without retrieving them from the fusion device. The diagnostic desorbs the retained gases by heating a 3 mm diameter spot on the wall using a 1 ms long laser pulse and detects them by QMS. Thus, it can measure the gas content at any wall position accessible to the laser. The successful LID-QMS application in laboratory scale and on medium size fusion devices has now been demonstrated on the larger scale and it is already foreseen as tritium monitor diagnostic in ITER. This in situ diagnostic gives direct access to retention physics on a short timescale instead of campaign-integrated measurements and can assess the space-resolvedefficacy of detritation methods. LID-QMS can be applied on many materials: on Be deposits like in JET, B deposits like in TEXTOR, C based materials or on bulk-W.

Laboratory characterization of hydrothermally processed oligopeptides in ice grains emitted by Enceladus and Europa.

The Cassini mission provided evidence for a global subsurface ocean and ongoing hydrothermal activity on Enceladus, based on results from Cassini's mass spectrometers. Laboratory simulations of hydrothermal conditions on icy moons are needed to further constrain the composition of ejected ice grains containing hydrothermally altered organic material. Here, we present results from our newly established facility to simulate the processing of ocean material within the temperature range 80-150°C and the pressure range 80-130 bar, representing conditions suggested for the water-rock interface on Enceladus. With this new facility, we investigate the hydrothermal processing of triglycine (GGG) peptide and, for the first time, analyse the extracted samples using laser-induced liquid beam ion desorption (LILBID) mass spectrometry, a laboratory analogue for impact ionization mass spectrometry of ice grains in space. We outline an approach to elucidate hydrothermally processed GGG in ice grains ejected from icy moons based on characteristic differences between GGG anion and cation mass spectra. These differences are linked to hydrothermal processing and thus provide a fingerprint of hydrothermal activity on extraterrestrial bodies. These results will serve as important guidelines for biosignatures potentially obtained by a future Enceladus mission and the SUrface Dust Analyzer (SUDA) instrument onboard Europa Clipper. This article is part of the theme issue 'Dust in the Solar System and beyond'.

Application of Laser-Induced Acoustic Desorption for Molecular Rotational Resonance Spectroscopy.

Molecular Rotational Resonance (MRR) spectroscopy is a uniquely precise tool for the determination of molecular structures of volatile compounds in mixtures, as the characteristic rotational transition frequencies of a molecule are extremely sensitive to its 3D structure through the moments of inertia in a three-dimensional coordinate system. This enables identification of the compounds based on just a few parameters that can be calculated, as opposed to, for example, mass spectrometric data, which often require expert analysis of 10-20 different signals and the use of many standards/model compounds. This paper introduces a new sampling technique for MRR, laser-induced acoustic desorption (LIAD), to allow the vaporization of nonvolatile and thermally labile analytes without the need for excessive heating or derivatization. In this proof-of-concept study, LIAD was successfully coupled to an MRR instrument to conduct measurements on seven compounds with differing polarities, molecular weights, and melting and boiling points. Identification of three isomers in a mixture was also successfully performed using LIAD/MRR. Based on these results, LIAD/MRR is demonstrated to provide a powerful approach for the identification of nonvolatile and/or thermally labile analytes with molecular weights up to 600 Da in simple mixtures, which does not require the use of reference compounds. In the future, applications to more complex mixtures, such as those relevant to pharmaceutical research, and quantitative aspects of LIAD/MRR will be reported.

Laser-Induced Desorption Spectroscopy with an Inductively Coupled Plasma Source—Examination of Technique Applicability for Detection of Retained Hydrogen

Laser-Induced Desorption Spectroscopy with an Inductively Coupled Plasma Source—Examination of Technique Applicability for Detection of Retained Hydrogen

Multicoverage Study of Femtosecond Laser-Induced Desorption of CO from Pd(111).

We study the strong coverage dependence of the femtosecond laser-induced desorption of CO from Pd(111) using molecular dynamics simulations that consistently include the effect of the laser-induced hot electrons on both the adsorbates and surface atoms. Adiabatic forces are obtained from a multicoverage neural network potential energy surface that we construct using data from density functional theory calculations for 0.33 and 0.75 monolayer (ML). Our molecular dynamics simulations performed for these two trained coverages and an additional intermediate coverage of 0.60 ML reproduce well the peculiarities of the experimental findings. The performed simulations also permit us to disentangle the relative role played by the excited electrons and phonons on the desorption process and discover interesting properties of the reaction dynamics as the relevance that the precursor physisorption well acquires during the dynamics as coverage increases.

Design and characterization of an optical-fiber-coupled laser-induced desorption source for gas-phase dynamics experiments.

Preparation of neutral non-volatile molecules intact in the gas phase for mass spectrometry or chemical dynamics experiments remains a challenge for many classes of molecules. Here, we report the design and characterization of a fiber-coupled laser-based thermal desorption source capable of preparing intact neutral molecules at high molecular densities in the gas phase for use in velocity-map imaging experiments. Within this source, the sample is deposited onto a thin tantalum foil. Irradiation of the foil from the reverse side by a focused laser beam leads to highly localized heating of the sample, resulting in desorption of a plume of molecules into the gas phase. The fiber-coupled design simplifies the alignment of the desorption laser beam, and the ability to rotate the foil relative to the fixed laser beam allows the sample to be continually refreshed under vacuum. We use 118nm photoionization of three test molecules-uracil, adenine, and phenylalanine-to characterize the source and to demonstrate various aspects of its performance. These include the dependence of the velocity-map imaging performance on the size of the interaction region and the dependence of the laser-induced desorption source emission on desorption laser power and heating time. Signal levels recorded in these measurements are comparable to those we typically obtain in similar experiments using a pulsed supersonic molecular beam, and we, therefore, believe that the source has considerable potential for use in a wide range of chemical dynamics and other experiments.

Possibility of using machine learning methods to reconstruct solid body parameters during laser-induced desorption analysis

The possibility of using machine learning methods for solving the inverse problem of the laser-induced desorption quadrupole mass-spectrometry (LID-QMS) diagnostic is studied. The formulation of the problem is given, and a general scheme of its solution is proposed. A test model of gas transport in a solid body is considered, which is used to construct a database of gas transport parameters in the sample. The application of the synthetic data and machine learning methods, viz. the interpolation technique, the method of K nearest neighbors, and the neural networks, for solving the LID-QMS inverse problem is investigated. The advantages and disadvantages of each approach are discussed.

Effect of material properties on the laser-induced desorption of hydrogen from tungsten

One of the priority tasks for sustainable operations of future fusion devices is the systematic control of hydrogen isotope content in plasma-facing components. A remote non-damaging analysis of the gas content can be realised by applying laser-induced desorption (LID). LID is based on local heating of the studied surface, followed by the detection of desorbed particles. Interpretation of the LID measurements relies on the definition of effective desorption region from which particles are being released. This region strongly depends on the properties of a laser pulse, an analysed material, and defect centres containing hydrogen isotopes. To investigate the role of these properties on LID, a series of numerical simulation was conducted for the case of hydrogen release from a 10 μm tungsten layer, initiated under nanosecond, microsecond, and millisecond heat loads. The simulations were performed using a common reaction-diffusion model with sequentially varied tungsten thermal conductivity, detrapping energy of hydrogen from traps, concentration of hydrogen traps, and their initial filling ratio. Additionally, the Soret effect was considered in order to estimate its impact on the LID efficiency. Findings reveal that the peak surface temperature reached during heating can characterise the LID efficiency under a particular heat pulse. The LID efficiency dependence on the peak surface temperature weakly varies with material thermal properties, but can alter with the change of trap parameters. The detrapping energy of hydrogen from traps considerably influences the desorption efficiency, while concentration and the initial filling ratio of traps have a moderate effect. The Soret effect is shown to noticeably affect the LID efficiency per a laser pulse only at near-melting temperatures of tungsten. Finally, results demonstrate that the highest desorption efficiency from thick layers can be reached using laser pulses with millisecond duration regardless of surface effects, when the release under short-term pulses can be limited by them.

Femtosecond Laser-Induced Desorption of Hydrogen Molecules from Ru(0001): A Systematic Study Based on Machine-Learned Potentials

Femtosecond Laser-Induced Desorption of Hydrogen Molecules from Ru(0001): A Systematic Study Based on Machine-Learned Potentials

Investigation on the Edge Doping Process of Nitrogen-Doped Carbon Materials by In Situ Pyrolysis Mass Spectrometry and Laser-Induced Acoustic Desorption Mass Spectrometry

Nitrogen-doped carbon materials demonstrate high performance as electrodes in fuel cells and higher oxygen reduction reactivity than traditional Pt-based electrodes. However, the formation process of nitrogen-doped carbon materials has long been a mystery. In this study, the formation mechanism of nitrogen-doped carbon materials from polyaniline (PANI) pyrolysis was studied by the combination of in situ pyrolysis vacuum ultraviolet photoionization time-of-flight mass spectrometry (Py-VUVPI-TOF MS) and substrate-enhanced, laser-induced acoustic desorption source time-of-flight mass spectrometry (SE-LIAD-TOF MS). The initial pyrolysis species, including free radicals and intermediates, were investigated via in situ Py-VUVPI-TOF MS during the temperature-programmed desorption process (within tens of microseconds). The pyrolysis residues were collected and further investigated via SE-LIAD-TOF MS, revealing the product information of the initial pyrolysis products. The results show that the edge doping of carbon materials depends on free radical reactions rather than the direct substitution of carbon atoms by nitrogen atoms. Meanwhile, pyrrole nitrogen and pyridine nitrogen are formed by the free radical cyclization reaction and the amino aromatization reaction at the initial stage of pyrolysis, while the formation of graphitic nitrogen depends on the further polymerization reaction of pyrrole nitrogen and pyridine nitrogen.

Direct Determination of the Gas-Solid Interface Reaction Products of Melatonin with Ozone by Laser-Induced Acoustic Desorption – Mass Spectrometry (LIAD-MS)

Melatonin is a potent defensive molecule against oxidative damage. The knowledge of the interaction between melatonin and reactive oxygen species (ROS) is important for understanding antioxidant mechanisms. However, direct observation of reaction products of melatonin with ozone (a reactive oxygen species) in vitro is absent. In this paper, a simple and rapid method using a laser-induced acoustic desorption time-of-flight mass spectrometer (LIAD-TOFMS) is reported to characterize the reaction products of melatonin with ozone at the gas-solid interface. The advantage of this approach is the direct analysis of the products without secondary treatment. A series of oxidation products were observed, including primary hydroxymelatonin (HO-MLT), N1-acetyl-N2-formyl-5-methoxykynurenin (AFMK), and secondary (N1-acetyl-5-methoxykynurenin, AMK). Another significant finding is two pathways for the reaction of melatonin with ozone in vitro. These results demonstrate a novel strategy for the direct determination of reaction products at the gas-solid interface.

Potential use of LIAD time-of-flight mass spectrometry for the detection of biomolecules: An example of detecting nucleobases in DNA

Deoxyribonucleic acid (DNA) carries the genetic information necessary for the synthesis of RNA and proteins; it is a biological macromolecule essential for the development and proper functioning of living organisms and is composed of nucleobases, deoxyribose, and phosphate. The four nucleobases in DNA are adenine (AD), guanine (GU), thymine (TY), and cytosine (CY). Abnormal concentrations of these four nucleobases in an organism have a significant impact on disease diagnosis. Therefore, the qualitative and quantitative detection of these DNA nucleobases in organisms is helpful to diagnose certain diseases. In this work, we report the simultaneous determination of purine (AD, GU) and pyrimidine (TY, CY) nucleobases in DNA using laser-induced acoustic desorption (LIAD) with electron ionization (EI)/time-of-flight mass spectrometry (TOFMS). The purine (MW 120 Da) samples were used as model compounds to assess the sensitivity and quantitative performance of the instrument. Its limits of detection assessed using the LIAD/EI/MS method were ∼0.5–1.2 pg under optimal conditions, and their calibration curves exhibited good linearity (R2 = 0.98). The LIAD/TOFMS was successfully applied in the simultaneous detection of AD, GU, TY, and CY in real DNA samples. The advantage of this technique is simple, fast, and without complex pre-treatment processes. In addition, a quartz-enhanced LIAD (QE-LIAD) source was used to improve the signal strength. The desorption for complex biomolecules shows that the QE-LIAD is still a “gentle” desorption source.

OLYMPIA-LILBID: A New Laboratory Setup to Calibrate Spaceborne Hypervelocity Ice Grain Detectors Using High-Resolution Mass Spectrometry

The coupling of an Orbitrap-based mass analyzer to the laser-induced liquid beam ion desorption (LILBID) technique has been investigated, with the aim to reproduce the mass spectra recorded by Cassini's Cosmic Dust Analyzer (CDA) in the vicinity of Saturn's icy moon Enceladus. LILBID setups are usually coupled with time-of-flight (TOF) mass analyzers, with a limited mass resolution (∼800 m/Δm). Thanks to the Orbitrap technology, we developed a unique analytical setup that is able to simulate hypervelocity ice grains' impact in the laboratory (at speeds in the range of 15-18 km/s) with an unprecedented high mass resolution of up to 150 000 m/Δm (at m/z 19 for a 500 ms signal duration). The results will be implemented in the LILBID database and will be useful for the calibration and future data interpretation of the Europa Clipper's SUrface Dust Analyzer (SUDA), which will characterize the habitability of Jupiter's icy moon Europa.

Infrared photodesorption of CO from astrophysically relevant ices studied with a free-electron laser.

The infrared excitation and photodesorption of carbon monoxide (CO) and water-containing ices have been investigated using the FEL-2 free-electron laser light source at the FELIX laboratory, Radboud University, The Netherlands. CO-water mixed ices grown on a gold-coated copper substrate at 18 K were investigated. No CO photodesorption was observed, within our detection limits, following irradiation with light resonant with the C-O vibration (4.67 μm). CO photodesorption was seen as a result of irradiation with infrared light resonant with water vibrational modes at 2.9 μm and 12 μm. Changes to the structure of the water ice, which modifies the environment of the CO in the mixed ice, were also seen subsequent to irradiation at these wavelengths. No water desorption was observed at any wavelength of irradiation. Photodesorption at both wavelengths is due to a single-photon process. Photodesorption arises due to a combination of fast and slow processes of indirect resonant photodesorption (fast), and photon-induced desorption resulting from energy accumulation in the librational heat bath of the solid water (slow) and metal-substrate-mediated laser-induced thermal desorption (slow). Estimated cross-sections for the slow processes at 2.9 μm and 12 μm were found to be ∼7.5 × 10-18 cm2 and ∼4.5 × 10-19 cm2, respectively.