X-ray Photoelectron Spectroscopy Peak Research Articles

Effect of 60Co Irradiation on Boehmite Dissolution in Caustic Solutions.

Here, we examine how radiation impacts the dissolution behavior of boehmite by subjecting dry nanoparticles of different sizes to 60Co γ radiation and subsequently analyzing their dissolution behavior in caustic solutions as a function of temperature. The measured kinetics show that irradiation with an amount 228.24 Mrad significantly slows the dissolution rate, particularly for smaller sizes at lower temperatures. Specifically, the temperature-dependent dissolution rates of irradiated 20 nm boehmite versus pristine material in 3 M NaOH solutions were several times lower (e.g., rate constant of 0.026 vs 0.075 h-1 at 60 °C), with an apparent activation energy 40 kJ mol-1 higher. Although various imaging techniques and X-ray diffraction measurements consistently revealed no obvious differences between pristine and irradiated samples, after irradiation significant binding energy shifts were detected in the X-ray photoelectron Spectroscopy peaks of Al 2p and O 1s, and a change in their relative intensities indicated a lower O/Al ratio. This suggests that γ-irradiation may stabilize boehmite particle surfaces by driving their chemistry and structure toward more stable aluminum oxide forms. This finding may help explain slower dissolution rates of boehmite in nuclear waste and may be useful for the development of more robust predictive models and effective strategies for waste processing.

Following the propagation of erroneous x-ray photoelectron spectroscopy peak fitting through the literature. A genealogical approach

This study considers how poor x-ray photoelectron spectroscopy (XPS) peak fitting in the scientific literature is both affected by previous precedent and affects future published work. It focuses on a highly cited paper (the “Subject” paper) from a respected journal that contains incorrect S 2p peak fits. This paper was studied in a genealogical fashion vis-à-vis the XPS peak fitting in its “child,” “parent,” “grandparent,” and “great-grandparent” papers. Interestingly, precedents were not followed to a high degree between parent and child papers. However, in many cases, even when the authors of a study did not follow the incorrect precedent that they cited, they still incorrectly fit their data. Thus, not necessarily for good reasons, the effects of poor XPS peak fits on future generations of papers may be less than some experts had expected or feared. In many cases, older papers appear to contain better XPS peak fitting than newer ones.

Spectroscopic Differentiation of Structural Transitions from Carbon Nanobelts to Carbon Nanotubes.

In this study, simulated X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were utilized to differentiate the early stage structures as carbon nanobelts (CNBs) evolved into carbon nanotubes (CNTs). The effects of edge type, length, and diameter on the spectroscopic characteristics of armchair and zigzag CNTs were examined. Variations in XPS spectra were found to correspond to changes in the bandgap, while Raman spectra provided distinct bands associated with specific structural features. Notably, in armchair CNTs, the C 1s XPS peak positions exhibited clear differences depending on the structure. Additionally, the Kekulé vibration band and other characteristic bands in Raman spectra varied with length and diameter, enabling differentiation of armchair CNT structures. Although the structural analysis of zigzag CNTs was challenging using XPS, Raman spectroscopy proved to be effective in distinguishing structural differences. This study lays the groundwork for future spectroscopic analyses, contributing to the broader understanding of nanocarbon materials such as CNBs and CNTs and their potential applications in advanced electronic materials.

Green Synthesis of Yttrium Derivatives Nanoparticles Using Pine Needle Leaf Extract: Characterization, Docking, Antibacterial, and Antioxidant Potencies

Green nanoparticles are synthesized using environmentally friendly methods, and natural materials hold significant importance. This makes the process environmentally sustainable and reduces the production of harmful waste by-products. Green nanoparticles exhibit reduced toxicity which is crucial for biomedical applications. The current study suggested that yttrium nanoparticles (YNPs) should be synthesized, characterized, and evaluated for their diverse biological applications due to the rise in antibacterial resistance. The YNPs were prepared using a pine needle leaf extract (PNLE). The structural and morphological features have been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–vis), and vibrating sample magnetometry (VSM). The XRD pattern demonstrated the presence of yttrium oxide and yttrium nitrate phases. The crystallite size and particle size of the synthesized YNPs measured 1.696 nm and 24.55 nm, respectively. The XPS peaks showed two components with binding energies at 530.940 eV and 532.18 eV due to the bond between O–Y and OH–Y, respectively. Additionally, the ferromagnetic nature of the YNPs was confirmed by VSM analysis. The YNPs were tested for antibacterial activity on six uropathogenic bacteria (S. aureus, S. haemolyticus, E. faecalis, E. coli, K. pneumonia, and P. aeruginosa) using the microdilution assays, to find the minimum inhibitory concentration (MIC) as well as the minimum bactericidal concentration (MBC), the agar well diffusion assay, and antibiofilm screening assays, where they showed bacteriostatic action against all isolates (0.5–1 mg/mL MIC) and significant inhibition of biofilm formation (80% inhibition rate). The antioxidant capacity assessed by 1,1, diphenyl-2-picrylhydrazyl (DPPH) radical scavenging revealed 50% DPPH scavenging. Moreover, docking studies exhibited that YNPs inhibit crucial bacterial enzymes, including DNA gyrase, penicillin-binding proteins, carbapenemase, LasR-binding protein, and dihydropteroate synthase. These findings may explain the mechanisms responsible for the observed antibacterial effects of YNPs. Overall, these findings underscore YNPs as promising candidates for antioxidant and antibacterial applications.

XPS guide for insulators: Electron flood gun operation and optimization, surface charging, controlled charging, differential charging, useful FWHMs, problems and solutions, and advice

Current day x-ray photoelectron spectroscopy (XPS) instrument makers have made significant advances in charge compensation systems over the last 20 years, which makes it easier to analyze insulators, but samples still have many differences in chemistry, dielectric properties, sizes, surface roughness, etc. that force instrument operators to tweak flood gun settings if they want or need to obtain high quality chemical state spectra that provide the most information. This guide teaches which flood gun variables to check, and how to optimize electron flood gun settings by presenting high energy resolution, chemical state spectra that show the result of using a poorly aligned flood gun on modern XPS instruments equipped with a monochromatic aluminum Kalpha x-ray source. This guide is focused on the XPS measurement of insulators—nonconductive metal oxides and polymers. This guide shows that by measuring commonly available polymers (polypropylene and polyethylene terephthalate) or ceramic materials (SiO2 and Al2O3), the operator can easily characterize the good and bad effects of XY position settings and other settings provided by modern electron flood gun systems. This guide includes many original, never-before-published XPS peak full width at half maximum (FWHM) that will greatly assist peak-fitting efforts. This guide reveals a direct correlation between electron count-rate and best charge-control settings. This guide discusses sample and instrument issues that affect surface charging and explains how to check the quality of charge control by measuring the FWHM and binding energy of C (1s) or O (1s) spectra produced from the sample currently being analyzed. A list of other charge-control methods is provided, along with advice and a best-known method. The availability of large extensive databases of actual spectra is extremely beneficial to users who need real-world examples of high quality chemical state spectra to guide their in-house efforts to collect high quality spectra and to interpret valuable information from the peak-fits of those spectra.

Oxidation state of cobalt oxide in thermal-cyclic atomic layer etching of cobalt by plasma oxidation and organometallization

Thermal-cyclic atomic layer etching of Co blanket film and a fine pattern by plasma oxidation and organometallization were investigated. To obtain a smoothly etched surface and self-limiting etching, a two-step temperature-etching process was used. Co was first oxidized using O2 plasma at a low temperature of 25 °C. Then, the Co oxide formed in the first step was organometallized with acetylacetone (acacH) and sublimed at a high temperature of 210 °C, which is appropriate for organometallization and sublimation. The etched amount per cycle was 0.6 nm. This value is the same as the saturated oxidation amount. The root-mean-square roughness after 20-cycle etching was 0.53 nm, and an atomically smooth etched surface was obtained. From the x-ray photoelectron spectroscopy (XPS) analysis, the oxidation state of Co oxide with a 530-eV O1s peak was dominant for organometallization with acacH. As the temperature increased, the O1s XPS peak of the Co oxide shifted lower to 529 eV and formed a columnar-shaped oxide. However, with acacH, oxide was organometallized when the O1s peak was at 530 eV.

One-Step Synthesis and Operando Electrochemical Impedance Spectroscopic Characterization of Heterostructured MoP-Mo2N Electrocatalysts for Stable Hydrogen Evolution Reaction.

This study presents a novel synthesis of self-standing MoP and Mo2N heterostructured electrocatalysts with enhanced stability and catalytic performance. Facilitated by the controlled phase and interfacial microstructure, the seamless structures of these catalysts minimize internal resistivity and prevent local corrosion, contributing to increased stability. The chemical synthesis proceeds with an etching step to activate the surface, followed by phosphor-nitriding in a chemical vapor deposition chamber to produce MoP-Mo2N@Mo heterostructured electrocatalysts. X-ray diffraction analyses confirmed the presence of MoP, Mo2N, and Mo phases in the electrocatalyst. Morphology studies using scanning electron microscopy characterize the hierarchical growth of structures, indicating successful formation of the heterostructure. X-ray photoelectron spectroscopy (XPS) analyses of the as-synthesized and postcatalytic activity samples reveal the chemical shift in terms of the binding energy (BE) of the Mo 3d XPS peak, especially after catalytic activity. The XPS BE shifts are attributed to changes in the oxidation state, electron transfer, and surface reconstruction during catalysis. Electrochemical evaluation of the catalysts indicates the superior performance of the MoP-Mo2N@Mo heterostructured catalyst in hydrogen evolution reactions (HER), with lower overpotentials and enhanced Tafel slopes. The stability tests reveal changes in double layer capacitance over time, suggesting surface reconstruction and an increased active surface area during catalysis. Operando electrochemical impedance spectroscopy (EIS) further elucidates the dynamic changes in resistance and charge transfer during HER. Overall, a comprehensive understanding of the synthesis, characterization, and electrochemical behavior of the developed MoP-Mo2N@Mo heterostructured electrocatalyst, as presented in this work, highlights its potential utilization in sustainable energy applications.

Optimization of Electrode Materials Using Nanocarboxylic Polystyrene Promotes Accumulation for Chromium in Zea mays from Water and Soil Contamination.

Chromium is a multivalent metal with great development in the energy storage field because it can effectively improve the electrochemical performance of the material. However, chromium(VI) is soluble in water and toxic, which causes serious metal pollution in the environment. In addition, nanoplastics are difficult to degrade and easy to accumulate, which is an urgent environmental problem to be solved. Therefore, we choose Zea mays to absorb chromium ions, nanopolystyrene, nanocarboxylic polystyrene, and their complexes, which can coordinate and decompose with various polymers in Z. mays, and produce coordination, conjugation, mixed valence, and adjacent group effects. Due to the above effects, the UV-vis spectrum of the material is blueshifted; the X-ray photoelectron spectroscopy peaks of Cr 2p have a chemical shift; the pore structure is optimized; the graphitization degree is improved; the content of N, O, and Cr in the material increases; and the elements are evenly distributed. The series of optimization processes makes the electrodes exhibit excellent electrochemical performance in both supercapacitors and lithium-ion batteries. At 0.5 A·g-1, the specific capacitance of the electrode reaches 490 F·g-1. After 10,000 cycles, its specific capacitance remains at 429.3 F·g-1, and the Coulombic efficiency is 89.9%. In lithium-ion batteries, the initial discharging capacity of the electrode is 1071.7 mAh·g-1 at 0.05 A·g-1. After 5000 cycles, its specific capacity can still reach 242 mAh·g-1 at 0.2 A·g-1, and the Coulombic efficiency is above 95%.

Avoiding common errors in X-ray photoelectron spectroscopy data collection and analysis, and properly reporting instrument parameters

Despite numerous tutorials and standards written to the technical community on X-ray photoelectron spectroscopy (XPS), difficulties with data acquisition, analysis, and reporting persist. This work focuses on common errors in XPS that are frequently observed in the scientific literature and their sources. Indeed, this work covers: (i) XPS data collection, initial data analysis, and data presentation, (ii) Handling XPS backgrounds, (iii) Common errors in XPS peak fitting, and (iv) XPS data presentation and reporting. Graphical examples of errors and appropriate ways of handling data and correcting errors are provided. Additional readings are listed for greater in-depth exploration of the subjects discussed.

Effects of different compositional ratios on physical structure and optical properties of thin films during alloying of Zn<sup>2+</sup> and TiO<sub>2</sub>

A batch of TiO<sub>2</sub> films with different Zn<sup>2+</sup> compositions are prepared on a single crystal silicon substrate by using sol-gel method to observe the changes in optical and photocatalytic properties in the alloying process of Zn<sup>2+</sup> and TiO<sub>2</sub>. X-ray diffractometer (XRD) is used to observe the changes in the crystal structures of the films in the alloying process and to track the formation of ZnTiO<sub>3</sub> compounds. Scanning electron microscope (SEM) and atomic force microscope (AFM) are used to observe the phenomena of a large number of holes on the surfaces of the films due to the limited solubility of the crystal lattice for Zn<sup>2+</sup> in the alloying process. X-ray photoelectron spectroscopy (XPS) and optical bandgap are used to observe the changes at a level of the electronic structure of the films in the alloying process of Zn<sup>2+</sup> with TiO<sub>2</sub>. Finally, by degrading the methylene blue solution, it is shown that a small amount of Zn<sup>2+</sup> doping is completely dissolved in TiO<sub>2</sub>, destroying the TiO<sub>2</sub> crystalline quality. As the compositional share of Zn<sup>2+</sup> continues to increase to 15%, the limited solubility of TiO<sub>2</sub> for Zn<sup>2+</sup> is verified in the XPS peak fitting, resulting in a large number of hole structures in the film, and the active specific surface area of the film is enhanced, while Zn<sup>2+</sup> effectively traps the photogenerated e<sup>–</sup>/h<sup>+</sup>. In order to continue to observe the effect of Zn<sup>2+</sup> concentration on TiO<sub>2</sub>, we increase the concentration of Zn<sup>2+</sup> to 40% and observe the phenomenon in the alloying process of Zn<sup>2+</sup> with TiO<sub>2</sub>. It is shown that the appearance of the compound ZnTiO<sub>3</sub> can act as a complex center for e<sup>–</sup>/h<sup>+</sup> and a significant decrease in the percentage of TiO<sub>2</sub> leads to a gradual decrease in the photocatalytic efficiency of the films after alloying.

Metal-Impregnated Petroleum Coke-Derived Activated Carbon for the Adsorption of Arsenic in Acidic Waters.

The efficacy of metal-impregnated petroleum coke (PC) activated carbon for the adsorption of arsenite and arsenate in acidic waters is investigated in this study. Unmodified PC activated carbon, FeCl3-loaded activated carbon, KMnO4-loaded activated carbon, and a mixed FeCl3-KMnO4-loaded activated carbon were used for evaluation. The surface characteristics of the activated carbons before and after arsenic adsorption were analyzed by X-ray photoelectron spectroscopy (XPS). Arsenate adsorption was significantly improved by the addition of an iron-manganese-loaded activated carbon, increasing adsorption from 8.12 to 50.93%. Oxidation-reduction reactions are proposed based on the observed arsenic 2p3/2, iron 2p3/2, and manganese 2p3/2 XPS peaks. While iron in the iron-loaded activated carbon is not acting as the reducing agent, it is acting as a conductor for the flow of electrons from the activated carbon to the arsenic for reduction to take place prior to the physisorption of the arsenic. In the manganese-loaded activated carbon, manganese acts as the reducing agent for arsenic prior to arsenic adsorption to the surface through physisorption. XPS of the post-arsenic(V) exposure samples showed that the Fe2O3 species were reduced from 32.18 to 1.66% in the FeMn-loaded sample, while the FeOOH species were increased from 53.16 to 81.71%. Similarly, MnO in the FeMn-loaded activated carbon dropped from 26.82 to 15.40%, while MnOOH and MnO2 increased from 39.98 and 33.20 to 43.96 and 40.64%, respectively. This is consistent with the proposed mechanism. The adsorption of arsenite was also evaluated to show that the modification of the activated carbon adsorbed not only the arsenic(V) species but also the more toxic arsenic(III) species without the need for oxidation of the arsenic prior to adsorption.

Analysis of surface properties of Mg doped ZnS and ZnSe thin films through x-ray photoelectron spectroscopy

The surface properties of the spray-deposited Mg-doped ZnS and ZnSe films were investigated using X-ray photoelectron spectroscopy (XPS). The energy levels of the core electrons in ZnMgS and ZnMgSe, their peak positions, area ratios, and full width at half maximum were determined. Chemical shifts in Auger peaks, which are highly sensitive to changes in the chemical environment were used in the analysis. Compositional analysis indicated selenium deficiency in the ZnMgSe films. XPS peak of magnesium 2p showed a shift from 50.46 eV for ZnMgSe film to 50.63 eV for ZnMgS film and Mg 2s peak shift from 86.56 eV for ZnMgSe to 87.64 eV for ZnMgS films. A careful justification for the formation of oxides in the ZnMgSe films is also given. Ionicity for both films is about 0.51. Peak shifts in the Auger and core-level peaks are used to analyze the material's bonding strength, oxidation states, and bonding types.

Insufficient reporting of x-ray photoelectron spectroscopy instrumental and peak fitting parameters (metadata) in the scientific literature

This study was motivated by earlier observations. It is a systematic examination of the adequacy of reporting of information (metadata) necessary to understand x-ray photoelectron spectroscopy (XPS) data collection and data analysis in the scientific literature. The information for this study was obtained from papers published in three high-quality journals over a six-month period in 2019 and throughout 2021. Each paper was evaluated to determine whether the authors had reported (percentages of the papers properly providing the information are given in parentheses) the spectrometer (66%), fitting software (15%), x-ray source (40%), pass energy (10%), spot size (5%), synthetic peak shapes in fits (10%), backgrounds in fits (10%), whether the XPS data are shown in the main body of the paper or in the supporting information (or both), and whether fitted or unfitted spectra were shown (80% of published spectra are fit). The Shirley background is the most widely used background in XPS peak fitting. The Al Kα source is the most widely used x-ray source for XPS data collection. casaxps is the most widely used fitting program for XPS data analysis. There is good agreement between the results gathered during the two years of our survey. There are some hints the situation may be improving. This study also provides a list of the information/parameters that should be reported when XPS is performed.

Europium doped titanium dioxide nanocrystalline: synthesis, structure and optical properties

Abstract
 Uniform, spherical-shaped TiO2: Eu nanoparticles with different doping concentrations were synthesized using the sol-gel method. The structural, morphology, optical, luminescent, and surface properties of the samples were investigated at different Eu3+ concentration. The morphology, crystalline structure, and chemical composition of the samples were characterized by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The X-ray diffraction results reveal that the obtained powder nanoparticles consist of a single phase tetragonal structure. The crystallite sizes calculated by utilizing Scherrer’s equation were found in the range of 18.94 – 7.77 nm for TiO2:Eu samples annealed at 550οC. The SEM images reveal an irregular agglomerated morphology indicating a decrease in particle size with an increase in Eu3+ concentration. X-ray photoelectron spectroscopy (XPS) high resolution spectra of the Ti-2p peak confirmed that Ti atoms were in a doubly ionized state, and the deconvolution of the O1s XPS peak show the presence of oxygen related defects in the sample. EDS results confirm a systematic increase of Eu content in the as-prepared samples with the increase of europium concentration. Incorporation of europium in the titania particles induces a structural deformation and a blueshift of their absorption edge. The luminescence intensity increases with Eu3+ concentration up to 3 mol% and then quenched. While the PL emission of the as-grown samples is dominated by the 5D0 - 7Fj transition of Eu3+ ions, the emission intensity reduces drastically after thermal annealing due to outwards segregation of dopant ions.
 Keywords: Titanium dioxide; Photoluminescence Spectroscopy; XPS; Nanocrystalline; Anatase; Rutile. 

Layered Metal Oxide Nanosheets with Enhanced Interlayer Space for Electrochemical Deionization.

Electrochemical deionization is regarded as one of the promising water treatment technologies. Here, CoAl-layered metal oxide nanosheets intercalated by sodium dodecyl sulfate (SDS) with an enhanced interlayer spacing from 0.76 to 1.33nm are synthesized and used as an anode. The enlarged interlayer spacing provides an enhanced ion-diffusion channel and improves the utilization of the interlayer electroactive sites, while heat treatment, transferring layered double hydroxides to layered metal oxides (LMOs), offers additional active oxidation reaction sites to facilitate the electro-sorption rate, contributing to the high salt adsorption capacity (31.78mgg-1 ) and average salt adsorption rate (3.75mgg-1 min-1 ) at 1.2V in 500mgL-1 NaCl solution. In addition, the excellent long-term cycling stability (92.9%) after 40 cycles proves the strong electronic interaction between SDS and the host layer, which is validated by density functional theory calculations later on. Moreover, the electro-sorption mechanism of LMOs that originated from the reconstruction of the layered structure based on the "memory effect" is revealed according to the X-ray photoelectron spectroscopy peak shifts of Co element. This strategy of expanding the interlayer spacing combined with heat treatment makes LMOs a competitive candidate for electrochemical water deionization.

Synthesis and study of the quantum-confinement effect of gold-nanoclusters via optical properties protected by 2-phenylethanethiol ligand

Herein, gold-nanoclusters Au6(SR)6 are synthesized in the argon atmosphere, using 2-phenylethanethiol and tetraoctylammonium bromide, as ligands and surfactants, respectively. Au6(SR)6 possesses ca. 1.95 eV HOMO-LUMO gap, which is comparatively high and is also a dominant factor for quantum confinement effect. Moreover, the X-ray Photoelectron Spectroscopy (XPS) study shows the peak of Au 4f7/2 appears at 86.89 eV, which describes the consistency regarding the size of clusters with XPS peak shift for Au 4f7/2 value. In addition, the full width half maximum (FWHM) increases accordingly by decreasing the size of clusters.

Guide to XPS data analysis: Applying appropriate constraints to synthetic peaks in XPS peak fitting

Peak fitting of x-ray photoelectron spectroscopy (XPS) data is the primary method for identifying and quantifying the chemical states of the atoms near the surface of a sample. Peak fitting is typically based on the minimization of a figure-of-merit, such as the residual standard deviation (RSD). Here, we show that optimal XPS peak fitting is obtained when the peak shape (the synthetic mathematical function that represents the chemical states of the material) best matches the physics and chemistry of the underlying data. However, because this ideal peak shape is often unknown, constraints on the components of a fit are usually necessary to obtain good fits to data. These constraints may include fixing the relative full width at half maxima (peak widths), area ratios, and/or the relative positions of fit components. As shown in multiple examples, while unconstrained, less-than-optimal peak shapes may produce lower RSDs, they often lead to incorrect results. Thus, the “suboptimal” results (somewhat higher RSDs) that are obtained when constraints are applied to less-than-perfect peak shapes are often preferable because they prevent a fit from yielding unphysical or unchemical results. XPS peak fitting is best performed when all the information available about a sample is used, including its expected chemical and physical composition, information from other XPS narrow and survey scans from the same material, and information from other analytical techniques.

Production, characterization, and photocatalytic properties of Eu:Y2O3 nanopowders

AbstractEu:Y2O3 nanophosphors (NPs) with different Eu concentrations (3, 5, and 7 at%) were successfully synthesized via the sol–gel method. All synthesized powders had a cubic bixbyite‐type crystal structure with space group Ia‐3. It was observed they had agglomerated sphere‐like morphologies. In addition, a neck formation between the particles, which was the result of the sintering effect at the increasing calcination temperature, was also observed by scanning electron microscopy analysis. Raman and X‐ray photoelectron spectroscopy (XPS) analyses confirmed that the Eu dopant entered into the Y2O3 host. The XPS peak positions shifted to relatively higher binding energy values with increasing dopant concentration and calcination temperature. Increasing Eu dopant concentration in the host structure also increased the 3+ valence ions. The band gap values of the NPs varied between 4.30 and 4.54 eV. The powders doped with 5 at% Eu was active as photocatalysts and the powders that were synthesized at 800°C exhibited highly photocatalytic activity.

Solution deposition conditions influence the surface properties of 3-mercaptopropyl(trimethoxysilane) (MPTS) films

The deposition of organosilanes onto semiconducting and metal oxide surfaces is a versatile approach to impart corrosion resistance or provide a site for the subsequent immobilization of a range of molecules. Organosilane deposition is however, quite a complex process, with many factors influencing the film properties. Here, we investigated the deposition of 3-mercaptopropyl(trimethoxysilane) (MPTS) in organic solvents on Si substrates with various post-deposition treatments and subsequently characterize film properties using surface analytical techniques including ellipsometry, X-ray photoelectron spectroscopy (XPS), static water contact angles, and attenuated total reflection Fourier transform infra-red (ATR-FTIR) spectroscopy. Condensation of MPTS onto Si surfaces was most efficient in more anhydrous and hydrophobic solvents such as toluene, with monolayer thickness values (≈0.77 nm) being observed at MPTS concentrations of 0.08–1% (v/v), whereas all thickness values were seen to be below monolayer coverage when deposition was carried out in ethanol, regardless of the concentration used. It was found that the shortcomings of ethanol deposition can be overcome by applying a pre-hydrolysis period at low pH to achieve similar film thicknesses and properties compared to toluene at shorter deposition times - which is important when functionalization needs to be carried out in plastic consumables. Moreover, with minimal post-deposition treatments it was found that controllable film thicknesses can also be achieved with a high-retention of thiol functional groups which is evidenced by a clear S 2p XPS peak at a binding energy of 164.0 eV. However, these films will only be loosely bound to the surface and be lost upon further treatments. Overall, the procedures developed are important for many applications such as biomolecule immobilization, and the functionalization of planar substrates and nanoparticles, where the organosilane thickness, degree of order, reactivity and surface concentration of thiols influence film functionality.

A rapid classification method of tea products utilizing X-ray photoelectron spectroscopy: Relationship derived from correlation analysis, modeling, and quantum chemical calculation

The classification of tea products is nowadays mainly determined by sensory assessment and chemical analysis methods. These methods are subjective, time-consuming, and laborious. In this work, a rapid analytical method for tea classification was proposed on the basis of X-ray photoelectron spectroscopy (XPS) and quantum chemical calculation. A total of 56 kinds of tea products were studied. By utilizing the data fusion strategy, the correlation between XPS peak parameters and tea characteristics was established. The quantum chemical calculations of the core-level ionization potentials deepen the understanding of the XPS features. The binding energy of the main fitted peak for O 1s, BE1O1s, was found to have a good correlation with tea polyphenols contents, which can be used to classify tea products into six tea types (black, dark, green, oolong, white, and yellow tea) with an accuracy greater than 90 %. The results suggest that the proposed XPS method is suitable for the rapid discrimination of tea classification, which contributes to the efficient application of tea.