Application Of X-ray Photoelectron Spectroscopy Research Articles

In2S3 nanoparticles modify the porous Fe2V4O13 nanostructure photoanode to enhance charge separation efficiency and photoelectrochemical water splitting performance

In this study, we demonstrate for the first time a promising photoanode of Fe2V4O13/In2S3 (FVO/IS) nanoparticles (NPs) for photoelectrochemical (PEC) water splitting. Most importantly, this work presents the first application of X-ray photoelectron spectroscopy in tracking electron flow direction within FVO/IS to reveal the formation of heterojunction having the electron flow from IS to FVO. Mott-Schottky measurement confirms that the modification of IS NPs establishes the type II heterojunction between FVO and IS, favorable for the transport and separation of carriers. Spectral measurements of electrochemical impedance spectroscopy, photoluminescence and Bode diagram confirm the effective separation of carriers and the prolongation of the charge lifetime in the FVO/IS heterojunction photoanode. Moreover, the electrochemical measurements evidently demonstrate the substantial enhancement in the charge separation efficiency (ηseparation) and charge transfer efficiency (ηtransfer) of the photoanode, leading to significantly enhanced PEC water splitting capability. As a result, in contrast with the pure FVO NPs photoanode, the photocurrent density of the constructed FVO/IS NPs photoanode is increased by 27 times without bias. This study paves a new approach for boosting the PEC water splitting activity of FVO photoanodes by constructing heterostructures through modification with other semiconductors.

Applications of X-Ray Photoelectron Spectroscopy to Catalytic Studies: From Routine Analysis to Cutting Edge Surface Characterization

Applications of X-Ray Photoelectron Spectroscopy to Catalytic Studies: From Routine Analysis to Cutting Edge Surface Characterization

Antibacterial Properties of Silver Nanoclusters with Carbon Support on Flexible Polymer.

Here, we aimed at the preparation of an antibacterial surface on a flexible polydimethylsiloxane substrate. The polydimethylsiloxane surface was sputtered with silver, deposited with carbon, heat treated and exposed to excimer laser, and the combinations of these steps were studied. Our main aim was to find the combination of techniques applicable both against Gram-positive and Gram-negative bacteria. The surface morphology of the structures was determined by atomic force microscopy and scanning electron microscopy. Changes in surface chemistry were conducted by application of X-ray photoelectron spectroscopy and energy dispersive spectroscopy. The changes in surface wettability were characterized by surface free energy determination. The heat treatment was also applied to selected samples to study the influence of the process on layer stability and formation of PDMS-Ag or PDMS-C-Ag composite layer. Plasmon resonance effect was determined for as-sputtered and heat-treated Ag on polydimethylsiloxane. The heating of such structures may induce formation of a pattern with a surface plasmon resonance effect, which may also significantly affect the antibacterial activity. We have implemented sputtering of the carbon base layer in combination with excimer laser exposure of PDMS/C/Ag to modify its properties. We have confirmed that deposition of primary carbon layer on PDMS, followed by sputtering of silver combined with subsequent heat treatment and activation of such surface with excimer laser, led to the formation of a surface with strong antibacterial properties against two bacterial strains of S. epidermidis and E. coli.

A complementary characterisation technique for spin crossover materials; the application of X-ray photoelectron spectroscopy for future device applications.

Spin crossover (SCO) materials have long been studied for their inherent electronic switchability, which has been well investigated for potential application in electronic and switching devices. As the technologies for the fabrication of thin films and monolayers continue to develop at an exceedingly rapid pace, an emerging challenge for the SCO community has become the characterisation of spin transitions in the surface layers of a material, as well as understanding the origins of discrepancies observed between SCO in thin films and that of the bulk material. For the manufacture of such devices to become a reality, it is crucial to understand how spin crossover is affected by interactions with the substrate material and within thin films. As such, detailed analysis of the surface layers without interference from the substrate material emerged as a critical area of characterisation for future developments in SCO devices. In this regard, X-ray Photoelectron Spectroscopy (XPS) has emerged as a complementary technique for the analysis of SCO in the surface layers of a material, becoming an essential part of a multi-technique protocol that is driving advances in the field. Here we describe the complementary application of XPS to a variety of SCO materials, review major developments and provide illustrative examples of innovations made through surface analysis with XPS.

Application of X-ray photoelectron spectroscopy (XPS) and a functional near infrared spectroscopy (fNIRS) in medicine

The development of modern clinical medicine and the truthful medical diagnosis require hard physicochemical data. Furthermore, the social demands for more accurate and collected data, which refer to human health in real conditions and in real time, force the quest for techniques which would be possible to be applied in a broadly understood clinical field. In this article two techniques are described. A high vacuum technique which is an X-ray photoelectron spectroscopy (XPS), and a functional near infrared spectroscopy (fNIRS), which might be applied in vivo condition. For the both techniques, the results pointing their applicability in the clinical and modern biochemical research are described.

Application of X-ray photoelectron spectroscopy to study interfaces for solid-state lithium ion battery

<sec>Solid-state lithium-ion batteries have attracted much attention due to their high safety, high energy densities and other advantages. However, solid-state lithium-ion batteries cannot realize large-scale commercial use. There are key scientific and technical issues that have not been resolved, especially interface issues, such as high resistance and instability of the interface. The X-ray photoelectron spectroscopy (XPS), as an important surface analysis method, can perform qualitative and semi-quantitative chemical analysis of the interface, which makes XPS can be widely used to study the solid-state lithium-ion battery interfaces. In this paper, we review the recent research progress of solid-state lithium-ion battery interfaces by using XPS, and summarize and review the XPS experimental principle, experimental method, experimental results and their effects on interface performance. The XPS analysis methods for solid-state lithium-ion batteries include <i>ex-situ</i> XPS, <i>in-situ</i> XPS reflecting the real-time changes of the battery interface, and operando XPS based on the actual working conditions of the battery. </sec><sec>The <i>ex-situ </i>XPS can study oxide solid electrolyte interfaces, sulfide solid electrolyte interfaces and artificial solid electrolyte interface (SEI) layers to access information about the chemical composition of the interface, predict the performance of the interface, obtain the chemical distribution in space, and evaluate the chemical structure and irregularity of the interface. With ultraviolet photoemission spectroscopy (UPS) the interface work function, energy band bending and energy structure of the full battery can be obtained. <i>In-situ</i> XPS can effectively study the process of chemical reactions between the electrolyte and the electrode. The key prerequisite is the controllable <i>in-situ</i> construction of the electrolyte/electrode interface. <i>In-situ</i> XPS research can directly study the electrochemical changes of the interface. <i>In-situ</i> XPS/UPS can study the energy level alignment of solid-state lithium-ion batteries, indicating that a space charge layer is formed at the solid electrolyte interface, and the energy band bending occurs. The degree of energy band bending is reflected in the binding energy shifts of the related elements at the interface. The change of the energy structure in the deposition process can be determined by the binding energy shifts of the related elements at the interface and the change of the interface work function. Operando XPS performs XPS characterization at the same time under the working condition of the battery. Operando XPS can be combined with electrochemical characterization to observe the effects of interface reaction and solid electrolyte decomposition products on electrochemical performance, thereby determining the main components that affect electrochemical performance. It can also be combined with the <i>ex-situ</i> XPS to study the interface reaction mechanism and influencing factors. The information obtained includes the chemical states of elements after the interface reaction has occurred, the evolution of interface elements in the process of real-time interface reaction, the energy structure change and interface component overpotential, thus having a better understanding of interface composition, interfacial structure change, kinetics of interface reaction, and interfacial ion migration of the solid-state lithium ion batteries.</sec>

Effective attenuation lengths for different X-ray photoelectron spectroscopy applications

Researchers provide a review of how effective attenuation lengths (EAL) can be used in XPS and give guidance on how EAL values can be obtained for specific applications.

Effective Attenuation Lengths for Different Quantitative Applications of X-ray Photoelectron Spectroscopy

The effective attenuation length (EAL) is a useful parameter in quantitative applications of x-ray photoelectron spectroscopy (XPS). This parameter is used in place of the inelastic mean free path (IMFP) in expressions for different XPS applications to correct those expressions for elastic scattering of the photoelectrons. We consider expressions used to determine (i) the thickness of an overlayer film on a planar substrate, (ii) the surface composition, (iii) the depth of a thin marker or delta layer, and (iv) the shell thickness of a core–shell nanoparticle. An EAL can be used for each of these applications. In general, the EAL depends on the particular defining equation as well as on the XPS configuration. Many attempts were made in the 1970s and 1980s to measure EALs for the determination of overlayer-film thicknesses, but there were often wide scatters in the reported results due to the difficulty in preparing uniform films with known thicknesses. We have therefore been motivated to calculate EALs for each application. The SRD 82 database from the National Institute of Standards and Technology (NIST) provides EALs for the measurement of overlayer-film thicknesses and of marker-layer depths. These EALs can be determined for photoelectron energies between 50 eV and 2 keV and for user-specified XPS configurations. We review EAL predictive equations for the determination of overlayer-film thicknesses on a planar substrate for XPS with unpolarized x rays and with linearly polarized x rays as well as an EAL predictive equation for quantitative analysis by XPS. These equations are simple analytical expressions that are valid for well-defined ranges of experimental conditions and for useful ranges of electron energies. We also point out that EALs for the determination of overlayer-film thicknesses can be derived from the simulated photoelectron intensities obtained from the NIST Database for the Simulation of Electron Spectra for Surface Analysis (SRD 100). Where possible, we make comparisons of the calculated EALs with illustrative experimental results. A key parameter in the EAL predictive equations is the so-called albedo, a useful measure of the strength of elastic-scattering effects in a material. The albedo is a simple function of the IMFP and the transport mean free path (TRMFP). We provide a tabulation of albedo and TRMFP values in the supplementary material for 41 elemental solids and 42 inorganic compounds for photoelectron energies between 50 eV and 30 keV. For other materials, albedo values can be determined from IMFP and TRMFP data available in the NIST SRD 82 and SRD 100 databases.

Practical Guides for X-Ray Photoelectron Spectroscopy (XPS): First Steps in planning, conducting and reporting XPS measurements.

Over the past three decades, the widespread utility and applicability of X-ray photoelectron spectroscopy (XPS) in research and applications has made it the most popular and widely used method of surface analysis. Associated with this increased use has been an increase in the number of new or inexperienced users which has led to erroneous uses and misapplications of the method. This article is the first in a series of guides assembled by a committee of experienced XPS practitioners that are intended to assist inexperienced users by providing information about good practices in the use of XPS. This first guide outlines steps appropriate for determining whether XPS is capable of obtaining the desired information, identifies issues relevant to planning, conducting and reporting an XPS measurement, and identifies sources of practical information for conducting XPS measurements. Many of the topics and questions addressed in this article also apply to other surface-analysis techniques.

Application of X-ray photoelectron spectroscopy to examine surface chemistry of cancellous bone and medullary contents to refine bone sample selection for nuclear DNA analysis

X-ray photoelectron spectroscopy was used to evaluate differences in elemental composition of human bone tissue types and identify soil infiltration.

Direct Observation of Structural Evolution of Metal Chalcogenide in Electrocatalytic Water Oxidation.

As one of the most remarkable oxygen evolution reaction (OER) electrocatalysts, metal chalcogenides have been intensively reported during the past few decades because of their high OER activities. It has been reported that electron-chemical conversion of metal chalcogenides into oxides/hydroxides would take place after the OER. However, the transition mechanism of such unstable structures, as well as the real active sites and catalytic activity during the OER for these electrocatalysts, has not been understood yet; therefore a direct observation for the electrocatalytic water oxidation process, especially at nano or even angstrom scale, is urgently needed. In this research, by employing advanced Cs-corrected transmission electron microscopy (TEM), a step by step oxidational evolution of amorphous electrocatalyst CoS x into crystallized CoOOH in the OER has been in situ captured: irreversible conversion of CoS x to crystallized CoOOH is initiated on the surface of the electrocatalysts with a morphology change via Co(OH)2 intermediate during the OER measurement, where CoOOH is confirmed as the real active species. Besides, this transition process has also been confirmed by multiple applications of X-ray photoelectron spectroscopy (XPS), in situ Fourier-transform infrared spectroscopy (FTIR), and other ex situ technologies. Moreover, on the basis of this discovery, a high-efficiency electrocatalyst of a nitrogen-doped graphene foam (NGF) coated by CoS x has been explored through a thorough structure transformation of CoOOH. We believe this in situ and in-depth observation of structural evolution in the OER measurement can provide insights into the fundamental understanding of the mechanism for the OER catalysts, thus enabling the more rational design of low-cost and high-efficient electrocatalysts for water splitting.

Determination of the Thickness of Nanofilms Using X-Ray Photoelectron Spectroscopy

Determination of coating thicknesses whose dimensions lie in the nanometer range is an important analytical application of X-ray photoelectron spectroscopy (XPS). The coating thickness is determined as a result of comparing peak intensities measured using lines corresponding to the coating with those of characteristic substrate lines. It is shown that the error in determining thicknesses using a procedure that completely disregards processes of elastic electron scattering reaches 50%. At present, the influence of elastic scattering processes is taken into account by replacing the inelastic mean free path with the fitting parameter called the effective attenuation length. Physical phenomena occurring in the case of the inclusion of an elastic photoelectron scattering channel are analyzed in this paper. Two approaches to the description of XPS spectra are considered: the first one is implemented using invariant embedding methods, and the second one used the method of discrete ordinates with the matrix exponent. On the basis of the first method, the influence of multiple elastic-scattering events on the XPS energy spectra is studied. The second one shows a high effectiveness when calculating no loss peaks of photoelectrons emitted by multilayer samples.

The impact of the scanning XPS microprobe on industrial applications of X-ray photoelectron spectroscopy

We will review the evolution of x-ray photoelectron spectroscopy (XPS / ESCA) instrumentation and applications that led to the development of the scanning XPS microprobe, describe its unique capabilities, and how they have impacted the use of XPS for industrial applications.

Passivity of Metals Studied by Surface Analytical Methods, a Review

Anodic oxide and hydroxide films on metals are very important for corrosion protection and they determine the electrochemical properties of electrode surfaces. For a better understanding of the leading corrosion mechanisms the chemical composition as well as the structure and electronic properties of passive layers are of decisive importance. They have been investigated with numerous ex situ and in situ methods. In this review special attention is given in a first part to the application of X-ray Photoelectron Spectroscopy (XPS), Ion Scattering Spectroscopy (ISS) and Rutherford Backscattering (RBS) as ex situ methods, which provide detailed information on the chemical composition and the multilayer structure of these films. The second part concentrates on the application of Scanning Tunneling Microscopy (STM) to obtain information on the atomic structure of these layers and their changes with environmental parameters. Passive layers are usually complicated multilayer structures. Their protecting properties are determined by the chemical characteristics of the metals and their anodic oxides as well as the environmental factors as the potential and the composition of the contacting electrolyte. The investigation of some metals and alloys like Cu, Fe, Co, Al/Cu and Fe/Cr are presented in detail to give insight to the application of electrochemical and surface analytical methods. It is the aim of this review to show, that one has to apply many methods in combination to understand the mechanisms of the leading corrosion processes and the nature of the passive behavior. References to more detailed reviews and original papers are given.

X-ray Photoelectron Spectroscopy: A Unique Tool To Determine the Internal Heterostructure of Nanoparticles

We review the existing literature on the application of X-ray photoelectron spectroscopy in the study of nanocrystals. The unique ability of this technique to provide quantitative and reliable descriptions of highly complex internal structures of a variety of nanocrystals has been discussed in detail. We show that an accurate description of the nanocrystal internal structure is crucial and a prerequisite to understand many different properties, particularly optical properties, of such nanocrystal systems. We also discuss limitations and future outlook of this technique.

Probing iron redox state in multicomponent glasses by XPS

Knowing the redox state of polyvalent elements in glass is important for understanding and controlling the glass properties. In this work we demonstrate the applicability of X-ray photoelectron spectroscopy (XPS) in the determination of the iron redox state in a multicomponent glass having a basalt-like composition. The XPS measurements reveal an entropy-driven reduction of ferric iron to ferrous iron upon increasing melt temperature. Furthermore, the local ferric iron enriched domains, i.e., a kind of inhomogeneity in the glass, is identified by means of XPS. It is proved that XPS is a useful and reliable tool for probing both the average redox state and inhomogeneities in glassy materials.

Application of X-ray photoelectron spectroscopy for studying the molecular structure of corrosion inhibitor — Zinc complex of 1-hydroxyethylidene diphosphonic acid

The molecular structure of zinc complex of 1-hydroxyethylidene diphosphonic acid was studied by X-ray photoelectron spectroscopy. The obtained data were compared with IR absorption spectrum of the same substance to acquire new information on the molecular structure. It was shown that coordination of the phosphonate group by zinc atom retains the localization of P-O π bond, the phosphonate group does not have a third-order axis of symmetry, and Zn atom can occupy positions with different coordination. Thermal destruction of the complex is accompanied by decomposition of hetero-organic ligand with detachment of the hydrocarbon fragment along C-P bonds and formation of inorganic zinc salts.

Application of X-ray Photoelectron Spectroscopy (XPS) for the Surface Characterization of Gunshot Residue (GSR)

Gunshot residue (GSR) is typically found on the hands or clothing of persons who have been in the environment of a discharging firearm, but it may also be found on objects in the vicinity of the discharge. Computer-controlled scanning electron microscopy (CCSEM) is the method preferred by the forensic community for the automated analysis of GSR. GSR samples are therefore typically collected from a crime suspect's hands and/or clothing using SEM sample stubs coated with a conductive adhesive. The three major components in modern firearm cartridge primers are lead styphanate (initiator), antimony sulfide (fuel), and barium nitrate (oxidizer). GSR consists of the products of combustion of these primer materials. Large populations of particles in the size range of ~1–10 μm are rapidly screened by energy-dispersive X-ray spectroscopy (EDS) for the presence of combinations of Pb, Sb, and Ba. When combinations of these three elements are detected, the particles are flagged as potential GSR particulate. Flagged particles with significant Pb/Sb/Ba compositions are subsequently relocated for a live identification and a positive confirmation of GSR. Positive particles are classified as being either “characteristic of GSR” (that is, all three key elements are present) or “consistent with GSR” (that is, any two of the key elements are present) based on the particle composition and morphology. Classification is based on the presence of the constituent elements and is not dependant on the element amounts. If a particle does not meet the proper compositional or morphological criteria, it is rejected as GSR. However, CCSEM generally does not provide information regarding the population of particles much less than 1 μm or the surface chemistry of the GSR particles. This article examines the fine fraction of GSR particles with high-resolution electron microscopy and complements the microscopy data with surface chemistry information from X-ray photoelectron spectroscopy (XPS).

The Application of X-Ray Photoelectron Spectroscopy in Understanding Corrosion Mechanisms of Magnesium and Mg-Al Alloys

The authors present a review of their research work on the application of X-ray photoelectron spectroscopy (XPS) to characterise thin (~ 3 nm) natural oxide films that spontaneously form on the surface of magnesium and its alloys in contact with the oxygen in air, and thick (> 1 μm) corrosion films rich in carbonates and other species that form during exposure to a humid atmosphere. The results obtained can provide much useful information about the protection mechanisms of these materials. Emphasis is placed on the relationship between the alloy's Al content and the characteristics of the natural oxide film and the relationship between segregation of calcium impurities from the bulk to the outer surface of the metal and repercussions on electrochemical behaviour. The natural oxide film may alone be sufficiently protective in less aggressive environments, making it of interest to know its characteristics. A detailed study will also be made of the changes in chemical composition that may occur in this passivating film with increasing exposure time to a humid atmosphere, deteriorating or reinforcing its anticorrosive properties. In particular, an attempt will be made to research the effect on corrosion behaviour of: (a) the time the different specimens are exposed to the aggressive agent (humid atmosphere); (b) the possible formation during corrosive attack of layers that are rich in carbonates and other species; and (c) the presence of aluminium (alloying element) on the protective properties of the corrosion layers.

Application of X-ray photoelectron spectroscopy to characterization of Au nanoparticles formed by ion implantation into SiO 2

In X-ray photoelectron spectroscopy (XPS) of Au nanoparticles, the width of 5 d valence band changes with Au particle size. This enables us to estimate the size of Au nanoparticles by using XPS. In this work, the 5 d-band width has been measured for Au nanoparticles formed by ion implantation into SiO 2. The 5 d-band width is found to be correlated strongly with the Au concentration. As the Au concentration increases, the 5 d-band width becomes larger, indicating that the Au nanoparticles with the larger size tend to be formed in the vicinity of the projected range of Au ions. This correlation agrees very well with the results from transmission electron microscopy.