Application of surface analysis methods to nanomaterials: summary of ISO/TC 201 technical report: ISO 14187:2011 – surface chemical analysis – characterization of nanomaterials

The ISO technical report 14187 provides an introduction to (and examples of) the information that can be obtained about nanostructured materials by using surface analysis tools. In addition, both general issues and challenges associated with characterizing nanostructured materials and the specific opportunities and challenges associated with individual analytical methods are identified. As the size of objects or components of materials approaches a few nanometers, the distinctions among ‘bulk’, ‘surface’, and ‘particle’ analysis blur. This technical report focuses on issues specifically relevant to surface chemical analysis of nanostructured materials. The report considers a variety of analysis methods but focuses on techniques that are in the domain of ISO/TC 201 including Auger electron spectroscopy, X‐ray photoelectron spectroscopy, secondary ion mass spectrometry, and scanning probe microscopy. Measurements of nanoparticle surface properties such as surface potential that are often made in a solution are not discussed. Copyright © 2012 John Wiley & Sons, Ltd.     

Method for grafting poly(acrylic acid) onto nylon 6,6 using amine end groups on nylon surface

Several methods have been developed for grafting materials to the surface of polymers to alter their surface characteristics. This article reports a procedure for grafting poly(acrylic acid) (PAA) onto nylon 6,6 films via the naturally occurring amine end groups of nylon 6,6 using N‐hydroxy‐succinimide in conjunction with 1‐ethyl‐3‐ (3‐dimethylaminopropyl)carbodiimide hydrochloride (EDC) facilitated amidazation. Reaction conditions were investigated with respect to PAA molecular weight, activator concentrations, reaction temperature, and time. X‐ray photoelectron spectroscopy showed that surface coverage of more than 50% was consistently achieved for 250 kD PAA. The maximum grafting occurred at room temperature with a large excess of EDC with a reaction time of 30 min. The same level of grafting can be achieved using smaller amounts of EDC at 60 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 719–728, 2002; DOI 10.1002/pola.10149     

Characteristics of morphology,structure and composition of titanium surface under its modification by electrochemical polarization in phosphate‐alkaline solutions

The modification of titanium surface under electrochemical polarization (EP) in the phosphate‐alkaline solutions has been studied using the methods of X‐ray diffraction, electron probe microanalysis, atomic force microscopy, X‐ray photoelectron spectroscopy (XPS), cyclic voltammetry and spectroscopic ellipsometry. It is shown that the morphological parameters of the surface, e.g. roughness and stringiness, as well as its structural‐chemical characteristics, e.g. preferred orientation, size and habit of crystallites, titanium chemical forms, thickness and phase composition of oxide film are generally dependent on the polarization potential. The characteristics of titanium surface modified at low anodic potentials 500, 750 and 1000 mV and 10‐min polarization time have been measured. The processes of Ti surface dissolution and etching along grain boundaries are found to be most intensive at 750 mV. Under 500 mV, these processes are poorly developed yet, while at 1000 mV, the surface passivating film formation limits the previous processes. Despite relatively low polarization potentials (1 V), the surficial oxide films have sufficient thickness (up to ~20 nm) and a specific multilayer structure of variable composition and oxidation state of titanium. The data obtained allow to assert that EP represents an effective tool for morphological and a structural chemical modification of a titanium surface. Copyright © 2015 John Wiley & Sons, Ltd.     

Application of the Fe3O4@1,10‐phenanthroline‐5,6‐diol@Mn nano‐catalyst for the green synthesis of tetrazoles and its biological performance

The Fe₃O₄ magnetic particles were modified with 1,10‐phenanthroline‐5,6‐diol (Phen) and the related Mn complex (Fe₃O₄@Phen@Mn) synthesized as a heterogeneous catalyst to be used for the one‐pot three‐component synthesis of various tetrazoles. The catalysts were characterized by several methods, such as the elemental analysis, FT‐IR, X‐ray powder diffraction, dispersive X‐ray spectroscopy, scanning electron microscopy, transmission electron microscopy, dynamic light scattering, thermogravimetric‐differential thermal analysis, vibrating sample magnetometer and X‐ray photoelectron spectroscopy. In addition, the antioxidant and antibacterial activities of the catalyst and its Phen ligand were in vitro screened with 2,2‐diphenyl‐1‐picrylhydrazyl by free radical scavenging methods. Results showed that the synthesized compounds possess strong antioxidant activity (IC50; 0.172  ±  0.005 mg ml^?1) as well as a good antibacterial potential in comparison to standards.     

X‐ray induced degradation of surface bound azido groups during XPS analysis

Mesoporous silica SBA‐15 was synthesized and silanized with azidopropyl triethoxysilane in order to design a clickable material. Fourier transform infrared analysis permitted to prove the attachment of the azidopropylene groups to SBA‐15 resulting in the reactive and functional material N₃‐SBA‐15. X‐ray photoelectron spectroscopy was used to determine the surface composition of SBA‐15. However, we unexpectedly found that the surface bound azido groups undergo X‐ray induced decomposition during the X‐ray photoelectron spectroscopy analysis resulting in the formation of nitrenes. These are very reactive groups able to intercalate C―C and C―H bonds of the propylene chains as judged from the N1s peak shape. Possible mechanisms of intercalation are suggested. C1s and N1s peaks were recorded at different exposure time. N/C, N⁺/N and N⁺/C undergo exponential decay. N⁺/N reaches the value of zero in less than 80 min of exposure to the X‐ray source. The N⁺/C decay plot was fitted with first‐order kinetics, and the decomposition kinetic constant (k_dec) was found to equal to 516.4 s^?1. This is a fast X‐ray induced degradation which must be considered with care when examining clickable materials with surface bound alkyl azido groups. Copyright © 2016 John Wiley & Sons, Ltd.     

Observation of surface contamination layer by X‐ray reflectometry (XRR) analyses

Ultra‐thin HfO₂ films of 3.5, 5.0, and 8.0 nm nominal thicknesses were prepared, respectively, on silicon substrates by using atomic layer deposition method. Through the analyses of X‐ray reflectometry (XRR), X‐ray photoelectron spectroscopy, and transmission electron microscopy for HfO₂ films with and without sample cleaning, the effects of surface contamination on XRR curve and film thickness were investigated, and contamination layer was observed and the thickness of the layer was determined. X‐ray photoelectron spectroscopy results indicated that the amount of surface contamination varied considerably because of the surface cleaning. XRR curve shapes and the positions of thickness fringes changed and the thickness from Fourier analyses of the curves were different for the same sample due to the different surface contamination. Contamination layer of about 1 nm thickness was observed by Fourier analysis of XRR curve. Simulation for XRR curve showed the best fit to data when contamination layer of about 1 nm thickness was considered, and the result was consistent with that of the Fourier analysis. Copyright © 2016 John Wiley & Sons, Ltd.     

Preparation and characterization of nanostructured thin films of Au and Ag nanoparticles synthesized by ascorbic acid on modified glass surface

Immobilization of Ag and Au nanoparticles (NPs) synthesized by ascorbic acid on chemically modified glass surface has been studied. 3‐[2‐(2‐Aminoethylamino)ethylamino]propyl‐trimethoxysilane (AMPTS), N‐(2‐aminoethyl)‐3‐aminopropyltrimethoxysilan, and 3‐trimethoxysilyl‐1‐propanethiol (MSPT) were used as surface modifying agents. To improve immobilization efficiency, the ammonia solution has been used along with the silane reagents, which assisted to adsorb the metal NPs on glass surface. It was found that AMPTS and MSPT have considerable effect on deposition of Ag and AuNPs on glass substrate. The fabricated thin films were characterized by using UV‐Vis spectroscopy, atomic force microscopy, energy‐dispersive X‐ray spectroscopy and subjected to antimicrobial resistance test. The UV–Vis spectra show a distinctive plasmon resonance absorbance peak for thin films of Au and AgNPs prepared with MSPT and AMPTS, respectively. Atomic force microscopy images indicate that formation of Au and AgNPs with spherical morphology after immobilization on the glass substrate and also the dimensions of NPs on the surface appear larger than those observed in the parent colloidal solution. Energy‐dispersive X‐ray spectroscopy measurements confirmed the presence of silver and gold on the modified glass surface, and elemental composition was measured. The Au and AgNPs thin films show antibacterial activity against gram negative (Escherichia coli) and gram positive (Staphylococcus aureus) bacteria in comparison with a blank sample. Copyright © 2015 John Wiley & Sons, Ltd.     

Copper nanoparticles seeded functionalized‐PVC plastic surface for electroless nickel deposition

A novel and facile activation process for electroless nickel deposition was developed. The semi‐interpenetrating polymer network hydrogel biofilm was used to functionalize the inert poly(vinyl chloride) (PVC) surface, and then Cu nanoparticles, which can initial the subsequent electroless nickel deposition successfully seeded on the functionalized‐PVC surface. The samples were characterized by scanning electron microscopy, X‐ray photoelectron spectroscopy, X‐ray diffraction, and transmission electron microscopy. The results show that the hydrogel film provided the PVC surface with amino groups and Cu nanoparticles of 20–50 nm in size could be functioned as the catalytic nuclei for the subsequent electroless metal deposition on PVC plastic. It can be concluded that the novel Cu activation was effective for the nickel deposition on PVC surface, because of more chemisorption sites for Cu nanoparticles generated on PVC surface. Copyright © 2013 John Wiley & Sons, Ltd.     

Facile Chan‐Lam coupling using ferrocene tethered N‐heterocyclic carbene‐copper complex anchored on graphene

Ferrocene tethered N‐heterocyclic carbene‐copper complex anchored on graphene ([GrFemImi]NHC@Cu complex) has been synthesized by covalent grafting of ferrocenyl ionic liquid in the matrix of graphene followed by metallation with copper (I) iodide. The [GrFemImi]NHC@Cu complex has been characterized by fourier transform infrared (FT‐IR), fourier transform Raman (FT‐Raman), CP‐MAS ¹³C NMR spectroscopy, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), energy dispersive X‐ray (EDX) analysis, X‐ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) surface area analysis and X‐ray diffractometer (XRD) analysis. This novel complex served as a robust heterogeneous catalyst for the synthesis of bioactive N‐aryl sulfonamides from variety of aryl boronic acids and sulfonyl azides in ethanol by Chan‐Lam coupling. Recyclability experiments were executed successfully for six consecutive runs.     

The first montmorillonite‐supported surface single‐structure titanium complex: synthesis,characterization and catalytic activity in alkene epoxidation

A well‐defined single‐site titanium‐modified montmorillonite (MMT) with only one geometric construction ((?SiO)₃–Ti–NMe₂) was obtained in moderate conditions. Reaction of tetrakis(dimethylamido)titanium with hydroxylated MMT was conducted by surface organometallic chemistry technique, and the surface structure was characterized by in situ Fourier transform infrared spectroscopy, ¹³C cross polarization magic angle spinning nuclear magnetic resonance, X‐ray photoelectron spectroscopy, extended X‐ray absorption fine structure, and elemental analysis. The catalytic activity in alkene epoxidation was evaluated, and the results revealed that the steric hindrance of the substances is responsible for the catalytic activity of the MMT‐supported titanium complex but to the characteristic restricted layer‐like structure of the MMT. Copyright © 2014 John Wiley & Sons, Ltd.     

Study on surface structure of plasma‐treated polydimethylsiloxane (PDMS) elastomer by slow positron beam

In this paper, the variations in surface structure of polydimethylsiloxane elastomers before and after argon plasma treatments have been investigated by X‐ray photoelectron spectroscopy, slow positron beam, and scanning electron microscope. An inorganic silica‐like layer was probed by X‐ray photoelectron spectroscopy after 3 minutes or longer time of treatments, and the sample surface turned into totally hydrophilic. Short time (1 and 2 min) plasma exposure mainly removed preexisting low molecular weighted (LMW) siloxanes on sample surface. By using slow positron beam, the thicknesses of silica‐like layer for 3‐, 5‐, and 10‐minute–treated samples were estimated to be around 30, 66, and 91 nm, respectively. Beneath the silica‐like layer, a loose polymeric structure was also detected, which was ascribed to the accumulation of LMW siloxanes. Scanning electron microscope images showed that the silica‐like layer cracked after 10 minutes of plasma treatment, which provided direct diffusion pathways for LMW siloxanes. Hence, 10‐minute–treated sample showed rather low organic composition near surface. Slow positron beam provides valuable depth profile information for evaluating the surface aging condition of polydimethylsiloxane composite.     

Photo‐induced surface transformations of silica nanocomposites

The photo‐induced, physicochemical surface transformations to silica nanoparticle (SiNP) ‐ epoxy composites have been investigated. The silica nanocomposites (SiNCs) were prepared using a two‐part epoxy system with a 10% mass fraction of SiNPs and exposed to varying doses of high intensity, ultraviolet (UV) radiation at wavelengths representative of the solar spectrum at sea level (290 nm to 400 nm) under constant temperature and humidity. Visibly apparent physical modifications to the SiNC surface were imaged with scanning electron microscopy. Surface pitting and cracking became more apparent with increased UV exposure. Elemental and surface chemical characterization of the SiNCs was accomplished through X‐ray energy dispersive spectroscopy and X‐ray photoelectron spectroscopy, while attenuated total reflectance Fourier transform infrared spectroscopy revealed changes to the epoxy's structure. During short UV exposures, there was an increase in the epoxy's overall oxidation, which was accompanied by a slight rise in the silicon and oxygen components and a decrease in overall carbon content. The initial carbon components (e.g. aliphatic, aromatic and alcohol/ether functionalities) decreased and more highly oxidized functional groups increased until sufficiently long exposures at which point the surface composition became nearly constant. At long exposure times, the SiNC's silicon concentration increased to form a surface layer composed of approximately 75% silica (by mass). Published 2012. This article is a U.S. Government work and is in the public domain in the USA.     

Dye degradation studies of Mo‐doped TiO2 thin films developed by reactive sputtering

TiO₂ thin films with various Mo concentrations have been deposited on glass and n‐type silicon (100) substrates by this radio‐frequency (RF) reactive magnetron sputtering at 400°C substrate temperature. The crystal structure, surface morphology, composition, and elemental oxidation states of the films have been analyzed by using X‐ray diffraction, field emission scanning electron microscopy, atomic force microscopy, and X‐ray photoelectron spectroscopy, respectively. Ultraviolet‐visible spectroscopy has been used to investigate the degradation, transmittance, and absorption properties of doped and undoped TiO₂ films. The photocatalytic degradation activity of the films was evaluated by using methylene blue under a light intensity of 100 mW cm⁻². The X‐ray diffraction patterns show the presence of anatase phase of TiO₂ in the developed films. X‐ray photoelectron spectroscopy studies have confirmed that Mo is present only as Mo⁶⁺ ions in all films. The Mo/TiO₂ band gap decreases from ~3.3 to 3.1 eV with increasing Mo dopant concentrations. Dye degradation of ~60% is observed in Mo/TiO₂ samples, which is much higher than that of pure TiO₂.     

Differentiating calcium carbonate polymorphs by surface analysis techniques—an XPS and TOF‐SIMS study

Calcium carbonate has evoked interest owing to its use as a biomaterial, and for its potential in biomineralization. Three polymorphs of calcium carbonate, i.e. calcite, aragonite, and vaterite were synthesized. Three conventional bulk analysis techniques, Fourier transform infrared (FTIR), X‐ray diffraction (XRD), and SEM, were used to confirm the crystal phase of each polymorphic calcium carbonate. Two surface analysis techniques, X‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectroscopy (TOF‐SIMS), were used to differentiate the surfaces of these three polymorphs of calcium carbonate. XPS results clearly demonstrate that the surfaces of these three polymorphs are different as seen in the Ca(2p) and O(1s) core‐level spectra. The different atomic arrangement in the crystal lattice, which provides for a different chemical environment, can explain this surface difference. Principal component analysis (PCA) was used to analyze the TOF‐SIMS data. Three polymorphs of calcium carbonate cluster into three different groups by PCA scores. This suggests that surface analysis techniques are as powerful as conventional bulk analysis to discriminate calcium carbonate polymorphs. Copyright © 2008 John Wiley & Sons, Ltd.     

Studies of Cu‐doped ZnS thin films prepared by sputtering technique

Radio frequency magnetron sputtering technique has been used to deposit Cu‐doped ZnS thin films on glass and n‐type Si(100) substrates at room temperature. Crystalline structure, surface morphology, and elemental oxidation states have been studied by X‐ray diffraction, field emission scanning electron microscopy, atomic force microscopy, and X‐ray photoelectron spectroscopy. Ultraviolet–visible spectroscopy has been employed to measure the transmittance, reflectance, and absorbance properties of coated films. The deposited thin films crystallize in zinc blende or sphalerite phases as proved by X‐ray diffraction analysis. The intensity of diffraction peaks decreases with increasing the dopant concentrations. The predominant diffraction peak related to (111) plane of ZnS is observed at 28.52° along with other peaks. The peak positions are shifted to higher angles with an increase of Cu concentrations. X‐ray photoelectron spectroscopy studies show that Cu is present in +1 oxidation state. Transmittance, reflectance, and absorbance properties of the deposited films have a slight variation with dopant concentrations. Copyright © 2016 John Wiley & Sons, Ltd.     

Combined IR and XPS analysis of the native (1 0 0) surface of single‐crystalline silicon after HFaq etching

A combined analysis, based on angle‐resolved X‐ray photoelectron spectroscopy and multiple‐internal‐reflection infrared spectroscopy, of the (1 0 0) silicon surface after etching in dilute aqueous solution of HF is presented. The analysis shows that the surface is mainly formed by a heterogeneous distribution of SiH, SiH₂ and SiH₃ terminations, but contains (in addition to sub‐stoichiometric oxidized silicon) a form of reduced silicon, not consistent with the currently accepted picture of the native HF_aq‐etched surface. Copyright © 2007 John Wiley & Sons, Ltd.     

Formation of PdNiZn thin film at oil‐water interface: XPS study and application as Suzuki‐Miyaura catalyst

Nanosheet of PdNiZn and nanosphere of PdNiZn/reduced‐graphene oxide (RGO) with sub‐3 nm spheres have been successfully synthesized through a facile oil‐water interfacial strategy. The morphology and composition of the films were determined by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive analysis of X‐ray (EDAX) and elemental mapping. In the present study, we have developed a method to minimize the usage of precious Pd element. Due to the special structure and intermetallic synergies, the PdNiZn and PdNiZn/RGO nanoalloys exhibited enhanced catalytic activity and durability relative to Pd nanoparticles in Suzuki‐Miyaura C‐C cross‐coupling reaction. Compared to classical cross‐coupling reactions, this method has the advantages of a green solvent, short reaction times, low catalyst loading, high yields and reusability of the catalysts.     

Improved interfacial properties of carbon fiber/UHMWPE composites through surface coating on carbon fiber surface

Carbon fibers were coated in an attempt to improve the interfacial properties between carbon fibers and ultra‐high molecular weight polyethylene resin matrix. Atomic force microscopy, scanning electron microscopy, and X‐ray photoelectron spectroscopy were performed to characterize the changes of carbon fiber surface. Atomic force microscopy results show that the coating of carbon fiber significantly increased the carbon fiber surface roughness. X‐ray photoelectron spectroscopy indicates that silicon containing functional groups obviously increased after modification. Interlaminar shear strength was used to characterize the interfacial properties of the composites.     

Core level studies of calcite and dolomite

Conventional X‐ray photoelectron spectroscopy (XPS) and synchrotron‐based X‐ray photoelectron spectroscopy (HRXPS) have been used to study Iceland spar calcite (CaCO₃) and dolomite (CaMg(CO₃)₂). The obtained full widths at half maximum (FWHMs) are mostly narrower than in the previous results, which together with the symmetry of the fitted peaks indicate effective neutralisation of surface charging. Some previously unidentified features observed in the Ca 2p, C 1s and O 1s spectra of calcite have been suggested to be bulk plasmons. Also, surface core level shifts in Ca 2p (in calcite) and Mg 2p (in dolomite) spectra have been obtained and found to be consistent between XPS and HRXPS measurements. A peak attributed to carbide (CaC₂) has been suggested to indicate beam‐assisted interaction with hydrocarbons found on the surface. Copyright © 2014 John Wiley & Sons, Ltd.     

Surface and Interface Chemistry in Colloidal Quantum Dots for Solar Applications Studied by X‐Ray Photoelectron Spectroscopy

Control of the surface and interface chemistry of colloidal quantum dots (CQDs) is critical to achieving a product with good air stability and high performing optoelectronic devices. Through various surface passivation treatments, vast improvements have been made in fields such as CQD photovoltaics; however devices have not currently reached commercial standards. We show how X‐ray photoelectron spectroscopy (XPS) can provide a better understanding of exactly how surface treatments act on CQD surfaces, and the effect of surface composition on air stability and device performance.. We illustrate this with PbS‐based CQDs, using XPS to measure oxidation processes, and to quantify the composition of the topmost surface layer after different surface treatments. We also demonstrate the use of synchrotron radiation‐excited depth‐profiling XPS, a powerful technique for determining the surface composition, chemistry and structure of CQDs. This review describes our recent progress in characterization of CQD surfaces using SR‐excited depth profiling XPS and other photoemission techniques.