IR Laser Ablation Research Articles

Association constants of guanine oligomers with alkali-metal ions studied using atmospheric pressure droplet IR-laser ablation mass spectrometry

Abstract Guanine (G) molecules form a stable tetramer with a metal ion called a G-quartet. We observed G-quartets by using atmospheric pressure droplet Infrared-laser ablation mass spectrometry, which enables us to analyze the abundance of chemical species in solutions. We estimated the association constants of Gn and M+ (M+ = Li+, Na+, and K+) from the intensities of G1–5H+ and G1–4M+ in the obtained mass spectra. The larger association constants of G4 than those of Gn (n ≠ 4) indicate the stability of G-quartets.

Study of the Recoil Impulse of Gaseous Products of IR Laser Ablation of Polystyrene and Polystyrene/Carbon Nanotubes Composite Obtained by Radiation Polymerization of Styrene

Study of the Recoil Impulse of Gaseous Products of IR Laser Ablation of Polystyrene and Polystyrene/Carbon Nanotubes Composite Obtained by Radiation Polymerization of Styrene

Study of the Recoil Impulse of Gaseous Products of IR Laser Ablation of Polytetrafluoroethylene

Study of the Recoil Impulse of Gaseous Products of IR Laser Ablation of Polytetrafluoroethylene

Gas-phase heme structure of the singly charged cytochrome c anion produced by IR-laser ablation of a droplet beam

Photoelectron detachment yield (PDY) spectroscopy is an effective tool for elucidating gas phase protein structures compared with other spectroscopies in aqueous solutions. In general, investigations of low-charged ions are necessary to elucidate the intrinsic properties of protein because excess charge perturbs the electronic state of the protein. In this study, we measured PDY spectrum of the most low-charged cytochrome c (cyt c) anion, [cyt c]- by IR-laser ablation of a droplet beam. This result shows a spectral blueshift from the absorption peak of aqueous cyt c and the PDY peak of the [cyt c]6- ion reported in the previous study.

IR laser ablation of high boiling elements (C, Mo, Ta, W and Re)

ABSTRACT Pulsed IR lasers were employed to irradiate high boiling elements, such as C, Mo, Ta, W and Re, in high vacuum. The ablation yield, given in terms of removed mass per pulse, was investigated using a ns laser at intensities of the order of 1010 W/cm2 and a sub-ns laser operating at about 1015 W/cm2. The produced plasma in high vacuum was studied by the time-of-flight measurements of emitted ions. The plasma-accelerated particles can be deposited and implanted on a near substrate to form a very adherent thin film useful for applications involving high temperatures and hard materials.

Gas-Phase Resonance Raman Spectroscopy Combined with IR-Laser Ablation of a Droplet Beam: Local Structural Analysis of Myoglobin.

Gas phase spectroscopy is a powerful tool for examining fundamental chemical structures and properties free from solvent molecules. We developed a gas-phase resonance Raman spectroscopy combined with IR-laser ablation of a droplet beam, which allowed us to elucidate local structures around chromophores in gas-phase proteins and DNAs. To demonstrate the potential of this approach, we applied this method to myoglobin, one of the heme proteins, and elucidated its structures in the gas phase and in aqueous solution. The experimental spectra are compared with calculated spectra of stable heme structures for the structural determination. These results show the oxidation/spin states of the Fe atom in myoglobin in the gas phase and were compared with the aqueous solution from the obtained resonant Raman spectra. The present method gives an important tool to investigate the gas-phase structure of large biomolecules.

Conformation of protonated guanine nucleotides via infrared multiphoton dissociation spectroscopy: Observation of rotamers in the anti-conformation

Guanosine 5′-monophosphate (GMP) is a component in RNA, which functions as a messenger in biological systems. Infrared multiphoton dissociation (IRMPD) spectroscopy, combined with IR-laser ablation of a droplet beam, reveals that the most stable conformer of gas-phase protonated GMP has a keto form and an anti-conformation. This includes two types of rotamers with different orientations of OH groups in the sugar ring. This suggests that our own laser ablation of droplet beam method promotes conformation-selective IRMPD spectroscopy with an effective cooling system in the gas phase.

RNA sampling from tissue sections using infrared laser ablation

RNA was obtained from discrete locations of frozen rat brain tissue sections through infrared (IR) laser ablation using a 3-μm wavelength in transmission geometry. The ablated plume was captured in a microcentrifuge tube containing RNAse-free buffer and processed using a commercial RNA purification kit. RNA transfer efficiency and integrity were evaluated based on automated electrophoresis in microfluidic chips. Reproducible IR-laser ablation of intact RNA was demonstrated with purified RNA at laser fluences of 3–5 kJ/m2 (72 ± 12% transfer efficiency) and with tissue sections at a laser fluence of 13 kJ/m2 (79 ± 14% transfer efficiency); laser energies were attenuated ∼20% by the soda-lime glass slides used to support the samples. RNA integrity from tissue ablation was >90% of its original RIN value (∼7) and the purified RNA was sufficiently intact for conversion to cDNA and subsequent qPCR assay.

Photodissociation spectroscopy of protonated guanosine monophosphate based on IR-laser ablation of droplet beam and quadrupole ion trap mass spectrometry

Photodissociation (PD) spectroscopy of protonated guanosine monophosphate (GMPH+) ions was performed using IR-laser ablation of droplet beam and quadruple ion trap techniques. Photofragmentation of GMPH+ gave a protonated guanine ion (GH+) as the main product. A wide-range PD spectrum (3.9–5.4 eV) monitored by the GH+ ion intensity showed four characteristic electronic transitions related to their three different anti glycosyl-bond conformers of GMPH+, which were identified by their π-π* transitions based on time dependent density functional theory calculation. Furthermore, the narrow-bandwidth PD spectrum (4.28–4.33 eV) shows the existence of syn glycosyl-bond conformation with keto form.

Photodissociation Spectroscopy of Hydrated Myoglobin Ions Isolated by IR-laser Ablation of a Droplet Beam: Recovery from pH-denatured Structure by Gas-phase Isolation

Photodissociation spectra near the Soret region were acquired for hydrated myoglobin (Mb) ions isolated in the gas phase. The spectra had a large red shift relative to that from an acidic aqueous s...

Large-Scale Laser Fabrication of Antifouling Silicon-Surface Nanosheet Arrays via Nanoplasmonic Ablative Self-Organization in Liquid CS2 Tracked by a Sulfur Dopant

Large-scale surface nanopatterning of a commercial silicon (Si) wafer in the form of regular 1D arrays of high-aspect-ratio vertical nanosheets (NSs) for antifouling and other potential promising optoelectronic, nanophotonic, and sensing applications was performed via multishot picosecond IR-laser ablation under a 5-mm-thick carbon disulfide liquid layer. Specifically, the nanopatterned surface layer demonstrates the broad ultralow mid-IR transmittance and the high content of sulfur, carbon, and even oxygen in the modified submicron-thick top layer, preventing the appearance of a Staphylococcus aureus bacterial biofilm. High-resolution transmission electron microscopy studies exhibit the anticorrelating inner versus outer surface abundance of donor sulfur versus adverse carbon and oxygen components and the amorphous structure of the sulfur-hyperdoped NSs atop their crystalline basements. These NSs indicate their appearance via the interfacial vapor/plume bubble-mediated codeposition of Si ablation nanoplu...

Plasma-mediated Nanosecond-Laser Generation of Si Nanoparticles in Water

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Thermal effects on 3D crater shape during IR laser ablation of monocrystalline silicon: From femtoseconds to microseconds

Analyzing the thermal effects (e.g., heat affected zone and debris analysis) on a laser-ablated crater using electron or atomic force microscopy is a time-consuming process while optical microscopy is limited to providing 2D information. The current work details an alternative method to identify and quantify the thermal effects based on an analysis of the 3D shape of craters. Starting from a thermal diffusion model, an iso-thermal function was developed and an iso-energetic function was defined based on the energy beam distribution. A systematic study of the 3D craters ablated on silicon was carried out at the four temporal regimes that are applicable in the industry: the femtosecond regime at 330 fs, the picosecond regime at 10 ps, the nanosecond regime in the range of 25–220 ns, and the microsecond regime in the range of 2–20 μs. It was shown that the defined Percentage Difference (PD) between the residual sum of squares (RSS) of the ellipsoid function and the RSS of the paraboloid function against the experimental crater, respectively, can be used to evaluate the presence of thermal effects. This corresponded with the results obtained using scanning electron microscope analysis. The analysis of the PD indicated how the crater shape was affected by the pulse duration while the non-thermal/thermal cutoff starting from the ps regime was studied. In addition, the crater shape was found to be affected by the laser beam fluence: for time regimes below the microsecond level, the thermal effects were seen to increase with higher laser beam fluence.

Infrared laser ablation sample transfer of tissue DNA for genomic analysis.

Infrared (IR) laser ablation was used to remove material from tissue sections mounted on microscope slides, with subsequent capture in a solvent-containing microcentrifuge tube. Experiments conducted with a 3200-bp double-stranded plasmid DNA template demonstrated IR-laser ablation transfer of intact DNA. The transfer efficiency and the molecular integrity of the captured DNA were evaluated using Sanger sequencing, gel electrophoresis, and fluorimetric analysis. The plasmid DNA was reproducibly transferred with an efficiency of 59±3% at laser fluences of between 10 and 20kJ/m2 at a wavelength of 3μm. IR laser ablation sample transfer was then used to ablate and capture DNA from 50-μm-thick rat brain and kidney tissue sections. DNA was extracted from the captured material using five commercial DNA extraction kits that employed significantly divergent methodologies, with all kits recovering sufficient DNA for successful amplification by polymerase chain reaction (PCR). Four sets of primers were employed, targeting one region of the CYP 11b2 gene (376bp) and three different regions of the Snn1g gene (298, 168, and 281bp). The PCR results were not consistently reliable when using unpurified ablation samples; however, after extraction, all samples produced PCR products of the expected size. This work expands the sampling capabilities of IR laser ablation, demonstrating that DNA can be isolated from tissue samples for genomic assays. Due to the small size of the ablation regions (1mm2), this technique will be useful for sampling discrete cell populations from tissue sections. Graphical abstract Infrared laser ablation transfer of intact DNA from a tissue section.

A Simple Method for Improving the Spatial Resolution in Infrared Laser Ablation Mass Spectrometry Imaging.

In mass spectrometry imaging of tissues, the size of structures that can be distinguished is determined by the spatial resolution of the imaging technique. Here, the spatial resolution of IR laser ablation is markedly improved by increasing the distance between the laser and the focusing lens. As the distance between the laser and the lens is increased from 1 to 18 m, the ablation spot size decreases from 440 to 44 μm. This way, only the collimated center of the divergent laser beam is directed on the focusing lens, which results in better focusing of the beam. Part of the laser energy is lost at longer distance, but this is compensated by focusing of the radiation to a smaller area on the sample surface. The long distance can also be achieved by a set of mirrors, between which the radiation travels before it is directed to the focusing lens and the sample. This method for improving the spatial resolution can be utilized in mass spectrometry imaging of tissues by techniques that utilize IR laser ablation, such as laser ablation electrospray ionization, laser ablation atmospheric pressure photoionization, and matrix-assisted laser desorption electrospray ionization. Graphical Abstract ᅟ.

Mechanism of Protein Molecule Isolation by IR Laser Ablation of Droplet Beam.

Gas-phase isolation of bovine serum albumin (BSA) from aqueous solutions is performed by IR laser ablation of a droplet beam. Multiply charged BSA ions (positive and negative) were produced by the IR laser irradiation onto a droplet beam of aqueous BSA solutions with various pH values prepared by addition of hydrochloric acid or sodium hydroxide to the solution. The isolation mechanism was discussed based on the charge state of the isolated BSA ions. A nanodroplet model explains the gas-phase charge distribution of the BSA ions. This study provides a fundamental basis for further studies of a wide variety of biomolecules in the gas phase isolated directly from solution.

Polyfluorides and Neat Fluorine as Host Material in Matrix-Isolation Experiments.

The use of neat fluorine in matrix isolation is reported, as well as the formation of polyfluoride monoanions under cryogenic conditions. Purification procedures and spectroscopic data of fluorine are described, and matrix shifts of selected molecules and impurities in solid fluorine are compared to those of common matrix gases (Ar, Kr, N2 , Ne). The reaction of neat fluorine and IR-laser ablated metal atoms to yield fluorides of chromium (CrF5 ), palladium (PdF2 ), gold (AuF5 ), and praseodymium (PrF4 ) has been investigated. The fluorides have been characterized in solid fluorine by IR spectroscopy at 5 K. Also the fluorination of Kr and the photo-dismutation of XeO4 have been studied by using IR spectroscopy in neat fluorine. Formation of the [F5 ](-) ion was obtained by IR-laser ablation of platinum in the presence of fluorine and proven in a Ne matrix at 5 K by two characteristic vibrational bands of [F5 ](-) at $\tilde \nu $=850.7 and 1805.0 cm(-1) and its photo-behavior.

Laser plasma interaction during visible and IR laser ablation of chromite mineral target

In this work, we present optical emission studies of the laser induced Chromite mineral plasma produced by the fundamental (1064 nm) and second (532 nm) harmonics of a Q-switched pulsed Nd:YAG laser. The spectra predominantly reveal the spectral lines of neutral Cr as well as dominant spectral lines of constituent elements. The experimentally observed line profiles of neutral chromium have been used to extract the electron temperature (Te) using Boltzmann plot method. Whereas, the electron number density (Ne) has been determined from the Stark broadened line profiles. We have also studied the variation of electron temperature and electron number density as a function of laser irradiance at atmospheric pressure. We have also studied the variation of these plasma parameters (Te and Ne) as a function of the laser irradiance as well as distance along the direction of plasma plume. The validity of the assumption of local thermodynamic equilibrium (LTE) is also discussed in the light of the experimental data and analysis.

Serial removal of caries lesions from tooth occlusal surfaces using near-IR image-guided IR laser ablation.

Previous studies have established that caries lesions can be imaged with high contrast without the interference of stains at near-IR wavelengths greater than 1300-nm. It has been demonstrated that computer controlled laser scanning systems utilizing IR lasers operating at high pulse repetition rates can be used for serial imaging and selective removal of caries lesions. In this study, we report our progress towards the development of algorithms for generating rasterized ablation maps from near-IR reflectance images for the removal of natural lesions from tooth occlusal surfaces. An InGaAs camera and a filtered tungsten-halogen lamp producing near-IR light in the range of 1500-1700-nm were used to collect crosspolarization reflectance images of tooth occlusal surfaces. A CO2 laser operating at a wavelength of 9.3- μm with a pulse duration of 10-15-μs was used for image-guided ablation.

Investigation of alkali metal polyfluorides by matrix-isolation spectroscopy

From CsF crystals to molecular polyfluorides.