Absorption Mapping Research Articles

Identifying the location and micellization of PEG-b-PCL multiblock copolymers in PLA/PCL blends via AFM nanoscale IR spectroscopy

The IR absorption mapping of two multiblock copolymers based on poly(ethylene glycol) and poly(ε-caprolactone) segments (PEG-b-PCL) in poly(acid lactic) and poly(ε-caprolactone) blends (PLA/PCL) was performed via AFM nanoscale IR spectroscopy. These copolymers, having the same number average molar masses (Mn‾) but varying block sizes, were added into the blend in different amounts (1 and 5 wt%) using a co-rotating twin-screw extrusion. The results revealed that copolymers with smaller blocks are preferentially located near the interface when incorporated in small quantities. Increasing the copolymer content led to preferential diffusion into the PLA matrix. Compatibilization with the longer block-size copolymers also led to preferential diffusion in the PLA matrix, albeit with a tendency to form micelles. This hampers the overall mechanical properties of the blend, making the compatibilized blend more brittle than neat PLA. Compatibilization with the short block-size copolymers showed no micellization and improved the mechanical behavior of PLA/PCL.

Correlation between birefringence and absorption mapping in large-size Sapphire substrates for gravitational-wave interferometry

In high-sensitive laser interferometers, such as the gravitational-wave detector KAGRA, ultra-high-quality mirrors are essential. In the case of KAGRA, where cavity mirrors are cooled down to 20 K, large-size Sapphire crystals are used as the substrate for the main mirrors to achieve both a good optical quality (i.e., low absorption and uniform refractive index) and optimized thermal behavior under cryogenic temperatures. To implement the very tight optical specifications required by this demanding application, it is mandatory to test the optical homogeneity of different substrates. In order to characterize refractive-index inhomogeneities of large-size uniaxial samples such as the KAGRA Sapphire test masses, we developed a dedicated setup, allowing to resolve birefringence changes with a sensitivity in the order of Δn≈2×10-10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta n\\approx 2 \ imes 10^{-10}$$\\end{document} and a spatial resolution of 1mm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$1\\,{{{\\hbox {mm}}}}^{2}$$\\end{document}. Moreover, the same setup allows us to simultaneously record residual absorption maps, thus allowing for a comparison between birefringence and absorption features. In this paper, we will present for the first time measurements on a KAGRA-sized Sapphire substrate which has been characterized in terms of absorption already in an earlier work. Both birefringence inhomogeneities and absorption distributions will be compared and correlations discussed.

Micro-tomographic and infrared spectral data mining for breast cancer diagnosis

This study aimed to introduce a multidimensional data mining method of breast cancer (BC) diagnosis using the X-ray phase-sensitive microtomography (XPCT) and Fourier transform infrared spectroscopy (FTIR), which is a comparable approach to clinical histopathologic examination (H&E) and blood biochemical tests for achieving a simple in-situ quantitative diagnosis. Based on the high brilliance synchrotron radiation, nondestructive three-dimensional (3D) micro-tomograms of tissues and infrared absorption spectra and mapping of representative biomacromolecules of tissue and blood samples were obtained with higher signal to noise ratios (SNRs). The comparative analysis had been made between in-situ digital sections and stained histological sections. The XPCT images accurately visualized the micromorphology of tumor lesions, including fat granule degenerations, ductal proliferations, microcalcifications, collagen strands of dimensions less than 20 µm. The FTIR mapping and spectra effectively revealed the biological component distributions and tumor-related variations of lipids, proteins and nucleic acids between breast tumors and normal tissues, integrated with XPCT data into formation of complementary data. It enables to identify the complex biomolecular tumor markers, especially, the specific fine-structures of second derivative spectrum were found in 1400–1750 cm−1. Moreover, the attenuated total reflection FTIR (ATR-FTIR) data of fresh blood samples were collected to demonstrate spectral specificity and feasibility of machine learning (ML) classification for BC diagnosis compared to clinic blood biochemical tests. The random forest (RF) model was found to be the best model for differentiating BC with 100% accuracy. Therefore, the proposed methodology was proved to be a powerful tool to nondestructively visualize and classify soft tissue tumors.

Investigation of light-matter interaction in single vertical nanowires in ordered nanowire arrays.

Quasi one-dimensional semiconductor nanowires (NWs) in either arrays or single free-standing forms have shown unique optical properties (i.e., light absorption and emission) differently from their thin film or bulk counterparts, presenting new opportunities for achieving enhanced performance and/or functionalities for optoelectronic device applications. However, there is still a lack of understanding of the absorption properties of vertically standing single NWs within an array environment with light coupling from neighboring NWs within certain distances, due to the challenges in fabrication of such devices. In this article, we present a new approach to fabricate single vertically standing NW photodetectors from ordered InP NW arrays using the focused ion beam technique, to allow direct measurements of optical and electrical properties of single NWs standing in an array. The light-matter interaction and photodetector performance are investigated using both experimental and theoretical methods. The consistent photocurrent and simulated absorption mapping results reveal that the light absorption and thus photoresponse of single NWs are strongly affected by the NW array geometry and related light coupling from their surrounding dielectric environment, due to the large absorption cross section and/or strong light interaction. While the highest light concentration factor (∼19.64) was obtained from the NW in an array with a pitch of 1.5 μm, the higher responsivity per unit cell (equivalent to NW array responsivity) of a single vertical NW photodetector was achieved in an array with a pitch of 0.8 μm, highlighting the importance of array design for practical applications. The insight from our study can provide important guidance to evaluate and optimize the device design of NW arrays for a wide range of optoelectronic device applications.

Synthesis and Formulation of Powerful ZnO Q-Dots/CNTs@Fe3O4 Nanopackage as a Predominant Anti-HIV-1 Infection

Usage of fine and uniform Fe3O4 nanoparticles (NPs) including super-paramagnetic unique properties developed state of the nanobio-formulations in recent years. We have shown a new formulated nanocomposition of super-paramagnetic iron oxide (Fe3O4) NPs (as substrate) with carbon nanotubes (CNTs) (as activator). Besides, ZnO@CNTs was synthesized as a magic assistant/hybrid for ZnO quantum dots nanoparticles (Q-Dots NPs) in this nanopackage. This novel formulated water-based nanofluid product consists of strong stabilizer, suitable dispersant-wetting agent complex and desirable water in oil emulsifier (w/o) package to damage HIV infection (AIDS) type 1. The achieved results demonstrated that smart nanofluid formulation had excellent functions as inhibitor, controller and treatment (Antiretroviral therapy (ART)) for HIV-1 integrase and could act as strong oxidizing agent. The nanofluid product was completely characterized with SEM morphology, TEM images, FTIR spectroscopy, XRD pattern, UV–Vis absorption spectroscopy, EDS and mapping of internal layers for one of the SEM surface morphology. Moreover, HIV-1 replication Assay, RT (reverse transcriptase) Assay, integrase assay, and cytotoxicity tests were performed and compared with Zidovudine (ZDV) and Raltegravir (RAL) as control antiretroviral medications. The specific interaction of this nanopackage with the target RNA and DNA proteins has been very interesting through main redox reactions.

Degradable Fluorene- and Carbazole-Based Copolymers for Selective Extraction of Semiconducting Single-Walled Carbon Nanotubes

Among the solution-based purification methods of as-produced single-walled carbon nanotubes (SWCNTs), conjugated polymer sorting is one of the most promising approaches to obtain semiconducting SWCNTs (s-SWCNTs) with high purity. In order to meet the demand for pure polymer-free s-SWCNTs after polymer wrapping, we synthesized several degradable fluorene- and carbazole-based copolymers for selective extraction of s-SWCNTs. The copolymers are interlinked by imine bonds, and thus, the cleavage can be easily accomplished by acid treatment. The polymer/SWCNT complex dispersions were prepared with as-produced HiPco SWCNTs in toluene and characterized with absorption, photoluminescence excitation and emission mapping, and Raman spectroscopy. Among the synthesized polyimines, fluorene-carbazole copolymers show extremely high separation yield toward s-SWCNTs and high separation purity, while the fluorene–fluorene and fluorene-p-phenylene copolymers show lower yield but higher selectivity to s-SWCNT with specific pairs of (n,m) indices. Quantitative removal of the polymer after acid-triggered degradation was confirmed by X-ray photoelectron spectroscopy. Moreover, the released dispersant-free s-SWCNTs can be further rewrapped by different polymers. Our results pave the way toward the use of dispersant-free semiconducting carbon nanotubes (CNTs) to develop the next generation of CNT devices.

Redox Mechanism in Na-Ion Battery Cathodes Probed by Advanced Soft X-Ray Spectroscopy.

A Na-ion battery (NIB) device is a promising solution for mid-/large-scale energy storage, with the advantages of material abundance, low cost, and environmental benignity. To improve the NIB capacity and retainability, extensive efforts have been put into the developments of NIB electrode materials. The redox activities of the transition metal (TM)-based NIB electrodes are critical in defining the capacity and stability. Here, we provide a comprehensive review on recent studies of the redox mechanisms of NIB cathodes through synchrotron-based soft X-ray absorption spectroscopy (sXAS) and mapping of resonant inelastic X-ray scattering (mRIXS). These soft X-ray techniques are direct and effective tools to fingerprint the TM-3d and O-p states with both bulk and surface sensitivities. Particularly, 3d TM L-edge sXAS has been used to quantify the cationic redox contributions to the electrochemical property; however, it suffers from lineshape distortion for the bulk sensitive signals in some scenarios. With the new dimension of information along the emitted photon energy, mRIXS can address the distortion issue of in TM-L sXAS; moreover, it also breaks through the limitation of conventional sXAS on detecting unconventional TM and O states, e.g., Mn(I) in NIB anode and oxidized oxygen in NIB cathodes. The mRIXS fingerprint of the oxidized oxygen state enables the detection of the reversibility of the oxygen redox reaction through the evolution of feature intensity upon electrochemical cycling and thus clarifies various misunderstandings in our conventional wisdom. We conclude that, with mRIXS established as a powerful tool, its potential and power will continue to be explored for characterizing novel chemical states in NIB electrodes.

Spatial distribution of defects in natural type IIb diamond after irradiation and annealing

Natural blue diamonds are among the rarest and most valuable of gemstones; however, they are occasionally treated by a variety of methods to improve the color or in attempts to obscure the evidence of treatment. In this study, two sections were cut from a rough naturally sourced type IIb diamond. One was subjected to electron irradiation along one edge. Subsequently, both were isochronally annealed from 300 °C to 1200 °C and the optical defects were documented by changes in infrared (IR) absorption and photoluminescence spectroscopic mapping. The thermal behavior of these centers (TR12, 3H, NV0, GR1, 648.2 and 776.4 nm centers among others) along with their spatial distribution in the irradiated and non-irradiated diamond provided additional insights into their configuration.After irradiation, the uncompensated boron concentration as determined by IR spectroscopy for this sample showed a pronounced decrease particularly at positions close to the irradiation edge. This uncompensated boron decreased further with low temperature annealing (300–600 °C) principally due to interstitial migration. At temperatures >600 °C, the uncompensated boron concentration rebounded due to vacancy migration that likely depletes or annihilates compensating defects. Among the photoluminescence (PL) defects, the 3H center (ZPL = 503.5 nm) showed a much greater thermal stability in the irradiated sample compared to its non-irradiated counterpart.

Quantitative Nanoscale Absorption Mapping: A Novel Technique To Probe Optical Absorption of Two-Dimensional Materials.

Two-dimensional semiconductors, in particular transition metal dichalcogenides and related heterostructures, have gained increasing interest as they constitute potential new building blocks for the next generation of electronic and optoelectronic applications. In this work, we develop a novel nondestructive and noncontact technique for mapping the absorption properties of 2D materials, by taking advantage of the underlying substrate cathodoluminescence emission. We map the quantitative absorption of MoS2 and MoSe2 monolayers, obtained on sapphire and oxidized silicon, with nanoscale resolution. We extend our technique to the characterization of the absorption properties of MoS2/MoSe2 van der Waals heterostructures. We demonstrate that interlayer excitonic phenomena enhance the absorption in the UV range. Our technique also highlights the presence of defects such as grain boundaries and ad-layers. We provide measurements on the absorption of grain boundaries in monolayer MoS2 at different merging angles. We observe a higher absorption yield of randomly oriented monolayers with respect to 60° rotated monolayers. This work opens up a new possibility for characterizing the functional properties two-dimensional semiconductors at the nanoscale.

Spectroscopic setup for submicrometer-resolution mapping of low-signal absorption and luminescence using photothermal heterodyne imaging and photon-counting techniques.

A spectroscopic setup that enables the mapping of absorption and photoluminescence with submicrometer spatial resolution and high sensitivity is described. A photothermal heterodyne imaging pump/probe technique is employed for absorption mapping, and low-signal, spatially resolved photoluminescence is recorded using photon counting. High-spatial-resolution mapping is accomplished by using high-numerical-aperture microscope objective focusing laser beams (pump and probe) into a submicrometer spot and raster-scanning sample mounted on the nanopositioning translation stage. Performance of the setup is illustrated by mapping absorption and luminescence of the hafnium oxide film with embedded hafnium nanoparticles and multilayer dielectric grating. In both cases, submicrometer spatial resolution is demonstrated, and possible physical mechanisms leading to image contrast on a submicrometer scale are discussed.

Antimicrobial and physicomechanical natures of silver nanoparticles incorporated into silicone-hydrogel films

PurposeThe effects of silver nanoparticles (AgNPs) incorporated in silicone-hydrogel films on their physicochemical properties and microbial activity were investigated. MethodsSilicone-hydrogel composite films (SiHCFs) were prepared by in-situ chemical reduction of silver ions added in different concentrations (0, 10, 20, 30, 40, 60, and 80 ppm) followed by ultraviolet (UV) casting. The reduction of silver ions into AgNPs was confirmed by transmission electron microscopy (TEM) and absorption spectroscopy over ultraviolet and visible (UV–vis) wavelengths. Incorporation of AgNPs into SiHCFs was confirmed by UV–vis absorption spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopic mapping. The physico- mechanical properties of the SiHCFs were evaluated. Antimicrobial activity and biofilm formation of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus were assessed. ResultsTEM, UV–vis absorption, SEM, and EDX mapping showed that silver ions were reduced in the mixture of co-polymerizing monomers and incorporation of AgNPs into SiHCFs was achieved. Mechanical properties of the SiHCFs were enhanced with increasing AgNPs concentration without affecting their chemical and thermal properties. SiHCFs exhibited transmittance greater than 90% at a wavelength 600 nm. Bacterial growths in the solutions bathing the SiHCFs with increasing silver concentration were 95, 78, 4, 2, 0, 0, 0% respectively, for Escherichia coli; 95, 82, 4, 0.6, 0, 0, 0% for Pseudomonas aeruginosa; and 93, 79, 4, 0.5, 0, 0, 0% for Staphylococcus aureus. ConclusionsIncorporation of AgNPs into SiHCFs demonstrated sufficient release of AgNPs to inhibit bacterial growth and reduce biofilm formation, with collateral enhancement of some mechanical properties of SiHCFs.

Imaging Plasmon Hybridization of Fano Resonances via Hot-Electron-Mediated Absorption Mapping

The inhibition of radiative losses in dark plasmon modes allows storing electromagnetic energy more efficiently than in far-field excitable bright-plasmon modes. As such, processes benefiting from the enhanced absorption of light in plasmonic materials could also take profit of dark plasmon modes to boost and control nanoscale energy collection, storage, and transfer. We experimentally probe this process by imaging with nanoscale precision the hot-electron driven desorption of thiolated molecules from the surface of gold Fano nanostructures, investigating the effect of wavelength and polarization of the incident light. Spatially resolved absorption maps allow us to show the contribution of each element of the nanoantenna in the hot-electron driven process and their interplay in exciting a dark plasmon mode. Plasmon-mode engineering allows control of nanoscale reactivity and offers a route to further enhance and manipulate hot-electron driven chemical reactions and energy-conversion and transfer at the nanoscale.

Photoacoustic imaging and its preclinical application in ophthalmology

SummaryPhotoacoustic imaging is an emerging optical imaging technique featuring optical illumination and acoustic detection. Short laser pulses deposit their energy in optical absorbers where light energy is converted to acoustic energy. Therefore photoacoustic imaging is a direct way of absorption mapping in 3D. Since absorbers, or chromophores, have unique absorption spectra, spectrascopic photoacoustic imaging can distinguish different absorbers by wavelength unmixing. In preclinical and clinical settings, photoacoustic microscopy, one major modality in photoacoustic imaging, can be used for ophthalmic imaging. Without the use of contrast agents, two absorbers can be distinguished: melanin and hemoglobin. Even though the application of photoacoustic microscopy in ophthalmic imaging is relatively new and still in its primitive phase, here we can see how photoacoustic microscopy can reveal the details of blood vessels and melanin in the eye. We will also discuss the potentials of photoacoustic imaging for ophthalmology.

Dependence of Raman and absorption spectra of stacked bilayer MoS2 on the stacking orientation.

Stacked bilayer molybdenum disulfide (MoS2) exhibits interesting physical properties depending on the stacking orientation and interlayer coupling strength. Although optical properties, such as photoluminescence, Raman, and absorption properties, are largely dependent on the interlayer coupling of stacked bilayer MoS2, the origin of variations in these properties is not clearly understood. We performed comprehensive confocal Raman and absorption mapping measurements to determine the dependence of these spectra on the stacking orientation of bilayer MoS2. The results indicated that with 532-nm laser excitation, the Raman scattering intensity gradually increased upon increasing the stacking angle from 0° to 60°, whereas 458-nm laser excitation resulted in the opposite trend of decreasing Raman intensity with increasing stacking angle. This opposite behavior of the Raman intensity dependence was explained by the varying resonance condition between the Raman excitation wavelength and C exciton absorption energy of bilayer MoS2. Our work sheds light on the intriguing effect of the subtle interlayer interaction in stacked MoS2 bilayers on the resulting optical properties.

Seismic scattering and absorption mapping of debris flows, feeding paths, and tectonic units at Mount St. Helens volcano

Abstract Frequency-dependent peak-delay times and coda quality factors have been used jointly to separate seismic absorption from scattering quantitatively in Earth media at regional and continental scale; to this end, we measure and map these two quantities at Mount St. Helens volcano. The results show that we can locate and characterize volcanic and geological structures using their unique contribution to seismic attenuation. At 3 Hz a single high-scattering and high-absorption anomaly outlines the debris flows that followed the 1980 explosive eruption, as deduced by comparison with remote sensing imagery. The flows overlay a NNW–SSE interface, separating rocks of significant varying properties down to 2–4 km, and coinciding with the St. Helens Seismic Zone. High-scattering and high-absorption anomalies corresponding to known locations of magma emplacement follow this signature under the volcano, showing the important interconnections between its feeding systems and the regional tectonic boundaries. With frequency increasing from 6 to 18 Hz the NNW–SSE tectonic/feeding trends rotate around an axis centered on the volcano in the direction of the regional-scale magmatic arc (SW–NE). While the aseismic high-scattering region WSW of the volcano shows no evidence of high absorption, the regions of highest-scattering and absorption are consistently located at all frequencies under either the eastern or the south-eastern flank of the volcanic edifice. From the comparison with the available geological and geophysical information we infer that these anomalies mark both the location and the trend of the main feeding systems at depths greater than 4 km.

QUANTIFYING DARK GAS

A growing body of evidence has been supporting the existence of so-called “dark molecular gas” (DMG), which is invisible in the most common tracer of molecular gas, i.e., CO rotational emission. DMG is be-lieved to be the main gas component of the intermediate extinction region from Av~0.05-2, roughly corresponding to the self-shielding threshold of H2 and 13 CO. To quantify DMG relative to HI and CO, we are pursuing three observational techniques; HI self-absorption, OH absorption, and THz C + emission. In this paper, we focus on preliminary results from a CO and OH absorption survey of DMG candidates. Our analysis shows that the OH excitation temperature is close to that of the Galactic continuum back-ground and that OH is a good DMG tracer co-existing with molecular hydrogen in regions without CO. Through systematic “absorption mapping” by the Square Kilometer Array (SKA) and ALMA, we will have unprecedented, comprehensive knowledge of the ISM components including DMG in terms of their temperature and density, which will impact our understanding of galaxy evolution and star formation profoundly.

Absorption spectroscopy and imaging from the visible through mid-infrared with 20 nm resolution.

Absorption spectroscopy and mapping from visible through mid-IR wavelengths has been achieved with spatial resolution exceeding the limit imposed by diffraction via the photothermal induced resonance technique. Correlated vibrational (chemical), and electronic properties are obtained simultaneously with topography with a wavelength-independent resolution of ≈20 nm using a single laboratory-scale instrument. This marks the highest resolution reported for PTIR, as determined by comparing height and PTIR images, and its first extension to near-IR and visible wavelengths.

Focus on spectroscopy and spectrometry

Focus on spectroscopy and spectrometry

High pressure does not counterbalance the advantages of open techniques over closed techniques during heated intraperitoneal chemotherapy with oxaliplatin

Heated intraperitoneal chemotherapy (HIPEC) treats residual microscopic disease after cytoreductive surgery. In experimental models, the open HIPEC technique has shown a higher and more homogenous concentration of platinum in the peritoneum than achieved using the closed technique. A 25-cm H2O pressure enhances the penetration of oxaliplatin. Because pressure is easier to set up with the closed technique, high pressure may counterbalance the drawbacks of this technique versus open HIPEC, and a higher pressure may induce a higher penetration. Because higher concentration does not mean deeper penetration, a study of tissues beneath the peritoneum is required. Finally, achieving a deeper penetration (and a higher concentration) raises the question of the passage of drugs through the surgical glove and the surgeon's safety. Four groups of pigs underwent HIPEC with oxaliplatin (150 mg/L) for 30 minutes in open isobaric pressure and pressure at 25 cm H2O, and closed pressure at 25 and 40 cm H2O. Systemic absorption and peritoneal mapping of the concentration of platinum were analyzed, as well as in the retroperitoneal tissue and the surgical gloves. Blood concentrations were higher in open groups. In the parietal surfaces, the concentrations were not different between the isobaric and the closed groups (47.08, 56.39, and 48.57 mg/kg, respectively), but were higher in the open high-pressure group (85.93 mg/kg). In the visceral surfaces, they were lower in the closed groups (3.2 and 3.05 mg/kg) than in the open groups (7.03 and 9.56 mg/kg). Platinum concentrations were similar in the deep retroperitoneal tissue when compared between isobaric and high-pressure procedures. No platin was detected in the internal aspect of the gloves. The use of high pressure during HIPEC does not counterbalance the drawbacks of closed techniques. The tissue concentration of oxaliplatin achieved with the open techniques is higher, even if high pressure is applied during a closed technique. Open 25 cm H2O HIPEC achieved the highest tissue penetration of oxaliplatin, but did not enhance the depth of oxaliplatin penetration. High pressure did not enhance the risk of HIPEC.

High resolution imaging with differential infrared absorption micro-spectroscopy

Although confocal infrared (IR) absorption micro-spectroscopy is well established for far-field chemical imaging, its scope remains restricted since diffraction limits the spatial resolution to values a little above half the radiation wavelength. Yet, the successful implementations of below-the-diffraction limit far-field fluorescence microscopies using saturated irradiation patterns for example for stimulated-emission depletion and saturated structured-illumination suggest the possibility of using a similar optical patterning strategy for infrared absorption mapping at high resolution. Simulations are used to show that the simple mapping of the difference in transmitted/reflected IR energy between a saturated vortex-shaped beam and a Gaussian reference with a confocal microscope affords the generation of high-resolution vibrational absorption images. On the basis of experimentally relevant parameters, the simulations of the differential absorption scheme reveal a spatial resolution better than a tenth of the wavelength for incident energies about a decade above the saturation threshold. The saturated structured illumination concepts are thus expected to be compatible with the establishment of point-like point-spread functions for measuring the absorbance of samples with a scanning confocal microscope recording the differential transmission/reflection.