Adsorption of a PEO–PPO–PEO triblock copolymer on metal oxide surfaces with a view to reducing protein adsorption and further biofouling

Biomolecule adsorption is the first stage of biofouling. The aim of this work was to reduce the adsorption of proteins on stainless steel (SS) and titanium surfaces by modifying them with a poly(ethylene oxide) (PEO)–poly(propylene oxide) (PPO)–PEO triblock copolymer. Anchoring of the central PPO block of the copolymer is known to be favoured by hydrophobic interaction with the substratum. Therefore, the surfaces of metal oxides were first modified by self-assembly of octadecylphosphonic acid. PEO–PPO–PEO preadsorbed on the hydrophobized surfaces of titanium or SS was shown to prevent the adsorption of bovine serum albumin (BSA), fibrinogen and cytochrome C, as monitored by quartz crystal microbalance (QCM). Moreover, X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry were used to characterize the surfaces of the SS and titanium after competitive adsorption of PEO–PPO–PEO and BSA. The results show that the adsorption of BSA is well prevented on hydrophobized surfaces, in contrast to the surfaces of native metal oxides

Very low effective Schottky barrier height for erbium disilicide contacts on n-Si through arsenic segregation

The segregation of As+ ions implanted into thin Er films deposited on n-Si substrates is studied after ErSi2-x formation. The same lowering of the effective Schottky barrier height (SBH) below 0.12 eV is obtained at moderate annealing temperatures, regardless of the redistribution of As dopants at the ErSi2-x/Si interface. On the other hand, if the implanted dose is slightly enhanced, the annealing temperature required to reach sub-0.12-eV effective SBH can be further reduced. This process enables the formation of very low effective SBH ErSi2-x/n-Si contacts with a low thermal budget

Thickness characterization toolbox for transparent protective coatings on polymer substrates

The thickness characterization of transparent protective coatings on functional, transparent materials is often problematic. In this paper, a toolbox to determine the thicknesses of a transparent coating on functional window films is presented. The toolbox consists of a combination of secondary ion mass spectrometry and profilometry and can be transferred to other transparent polymeric materials. A coating was deposited on designed model samples, which were characterized with cross-sectional views in transmission and in scanning/transmission electron microscopy and ellipsometry. The toolbox was then used to assess the thicknesses of the protective coatings on the pilot-scale window films. This coating was synthesized using straightforward sol-gel alkoxide chemistry. The kinetics of the condensation are studied in order to obtain a precursor that allows fast drying and complete condensation after simple heat treatment. The shelf life of this precursor solution was investigated in order to verify its accordance to industrial requirements. Deposition was performed successfully at low temperatures below 100 °C, which makes deposition on polymeric foils possible. By using roll-to-roll coating, the findings of this paper are easily transferrable to industrial scale. The coating was tested for scratch resistance and adhesion. Values for the emissivity (ε) of the films were recorded to justify the use of the films obtained as infrared reflective window films. In this work, it is shown that the toolbox measures similar thicknesses to those measured by electron microscopy and can be used to set a required thickness for protective coatings

Propylene metathesis over molybdenum silicate microspheres with dispersed active sites

In this work, we demonstrate that amorphous and porous molybdenum silicate microspheres are highly active catalysts for heterogeneous propylene metathesis. Homogeneous molybdenum silicate microspheres and aluminum-doped molybdenum silicate microspheres were synthesized via a nonaqueous condensation of a hybrid molybdenum biphenyldicarboxylate-based precursor solution with (3-aminopropyl)triethoxysilane. The as-prepared hybrid metallosilicate products were calcined at 500 °C to obtain amorphous and porous molybdenum silicate and aluminum-doped molybdenum silicate microspheres with highly dispersed molybdate species inserted into the silicate matrix. These catalysts contain mainly highly dispersed MoOx species, which possess high catalytic activity in heterogeneous propylene metathesis to ethylene and butene. Compared to conventional silica-supported MoOx catalysts prepared via incipient wetness impregnation (MoIWI), the microspheres with low Mo content (1.5-3.6 wt %) exhibited nearly 2 orders of magnitude higher steady-state propylene metathesis rates at 200 °C, approaching site time yields of 0.11 s-1CF CryoE; European Regional Development Fund-Project “UP CIISB, (CZ.02.1.01/0.0/0.0/18_046/0015974, LM2018110); Francqui Foundation; Grant Agency of Masaryk University, (MUNI/A/1298/2022, MUNI/J/0007/2021); U.S. Department of Energy, USDOE; Basic Energy Sciences, BES, (DE-SC0016214); Massachusetts Institute of Technology, MIT; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT, (LM2023042, RP/CPS/2022/007); Grantová Agentura České Republiky, GA ČR, (GJ20-03636Y); Central European Institute of Technology, CEITECMinistry of Education, Youth, and Sports of the Czech Republic within the INTER-EXCELLENCE II program; Ministry of Education, Youth, and Sports of the Czech Republic [RP/CPS/2022/007]; U.S. Department of Energy, Office of Basic Energy Sciences [DE-SC0016214]; European Regional Development Fund-Project "UP CIISB" [CZ.02.1.01/0.0/0.0/18_046/0015974, LM2018110]; MEYS CR [GJ20-03636Y, LM2023042]; Czech Science Foundation; Grant Agency of Masaryk University [MUNI/J/0007/2021, MUNI/A/1298/2022]; Francqui Foundation for the Francqui Research Professor chai

Mechanistic Insight into Gas Cluster-Induced Sputtering of Kilodalton Molecules Using Kinetic Energy Distribution Measurements

Recent progress in organic secondary ion mass spectrometry (SIMS) relied essentially on the development of new cluster beams, especially large atomic and molecular clusters formed via the adiabatic expansion of a gas in vacuum (Arn+, [CH4]n+, [CO2]n+, [H2O]n+). Although computer simulations and a few experimental investigations have shed light on certain fundamental aspects of large cluster-induced molecular desorption, the analytical application of these new beams usually preceded the detailed understanding of their interaction with surfaces. Here, to gain insight into the molecular emission process, the axial kinetic energy distributions (KEDs) of secondary ions emitted from organic films bombarded with Ar330–5000+ and Bi5+ clusters were measured using a reflectron time-of-flight secondary ion mass spectrometer. Irganox 1010 was chosen as a model kilodalton molecule because a large body of SIMS data involving this molecule already exists in the literature. Our results show that the axial KED of Irganox molecular and fragment ions varies as a function of the scaled kinetic energy E/n of the Ar cluster projectile and so does the fraction of ions produced above the surface via unimolecular dissociation, which exhibit an energy deficit with respect to the full acceleration provided at the entrance of the spectrometer. Below a few tens of eV/atom, the KEDs of ions such as (M – H)− (m/z 1175) become gradually narrower and their formation via metastable decay in the gas phase above the surface intensifies. Interestingly, the molecular ion M•+ (m/z 1176) is essentially produced in the gas phase with both Arn+ and Bi5+ cluster beams. Specifics of the observed KEDs of negative and positive molecular ions are discussed in comparison with results of other experiments recently reported in the literature and of molecular dynamics (MD) computer simulations using a coarse-grained representation of kilodalton organic molecules. The measurement of the axial kinetic energy of molecular and fragment ions sputtered from Irganox 1010 under argon and bismuth cluster bombardment, complemented with MD simulations, offers a clearer microscopic view of the emission process

Temperature Dependence of Arn+ Cluster Backscattering from Polymer Surfaces: a New Method to Determine the Surface Glass Transition Temperature

In this work, time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to study the intensity variations of the backscattered Arn+ clusters as a function of temperature for several amorphous polymer surfaces (polyolefins, polystyrene, and polymethyl methacrylate). For all these investigated polymers, our results show a transition of the ratio Ar2+/(Ar2+ + Ar3+) when the temperature is scanned from -120°C to +125°C (the exact limits depend on the studied polymer). This transition generally spans over a few tens of degrees and the temperature of the inflection point of each curve is always lower than the bulk glass transition temperature (Tg) reported for the considered polymer. Due to the surface sensitivity of the cluster backscattering process (several nanometers), the presented analysis could provide a new method to specifically evaluate a surface transition temperature of polymers, with the same lateral resolution as the gas cluster beam

Capabilities of static TOF-SIMS in the differentiation of first-row transition metal oxides.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) analyses were performed on the first-row transition metal oxides from scandium to zinc in positive and negative detection modes. The nature of the numerous M(x)O(y)(+/-) ionic species generated by 15 keV Ga(+) primary ion bombardment allows the identification of a given metal-oxygen system. To identify the metal valence in the oxide under investigation, several procedures were investigated: the detection of specific and characteristic ions, the use of ion abundance ratios and the use of a valence model. Owing to their importance in many fields of materials science, each of these speciation methodologies was evaluated for the differentiation of vanadium, titanium, chromium, manganese, iron, cobalt and copper oxides. Trivalent-hexavalent chromium distinction was first intensely investigated because it really corresponds to a model system for inorganic speciation. For each series of metal oxides, the more pertinent speciation criteria were then systematically tested. The limitations of the proposed methodologies are discussed. Their use is made complicated when pollutants or a superficial oxide layer, with a stoichiometry different from that of the bulk, are present. Finally, thermodynamic considerations relative to the stability of the M(x)O(y)(+/-) ions may also modify the relationship between the analyzed oxide and the observed positive and negative secondary ion mass spectra

Time-of-flight secondary ion mass spectrometry: characterisation of stainless steel surfaces immersed in natural seawater.

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been employed to study the biofouling of stainless steel samples immersed in seawater. The aim of these characterisations was to understand the initial mechanisms of biomolecule adsorption for relatively short immersion times (from 0 to 24 h).The results show that: (i) there were unavoidable sample "precontaminations" on the surfaces, despite precaution during their preparation and manipulation (washing, drying and storing); (ii) the major peaks detected were the substrate ones whatever the immersion time [However, some organic (nitrogen and oxygen containing) and inorganic secondary ions appeared and grew with the immersion time.]; (iii) the surface contaminations, the nonuniformity of the adsorbed material so as and bacteria have been clearly observed by high-lateral resolution molecular ToF-SIMS mapping

Effect of nanoconfinement on the sputter yield in ultrathin polymeric films: Experiments and model

This fundamental contribution on secondary ion mass spectrometry (SIMS) polymer depth-profiling by large argon clusters investigates the dependence of the sputter yield volume (Y) on the thickness (d) of ultrathin films as a function of the substrate nature, i.e. hard vs soft. For this purpose, thin films of polystyrene (PS) oligomers (∼4,000 amu) are spin-coated, respectively, onto silicon and poly (methyl methacrylate) supports and, then, bombarded by 10 keV Ar3000+ ions. The investigated thickness ranges from 15 to 230 nm. Additionally, the influence of the polymer molecular weight on Y(d) for PS thin films on Si is explored. The sputtering efficiency is found to be strongly dependent on the overlayer thickness, only in the case of the silicon substrate. A simple phenomenological model is proposed for the description of the thickness influence on the sputtering yield. Molecular dynamics (MD) simulations conducted on amorphous films of polyethylene-like oligomers of increasing thickness (from 2 to 20 nm), under comparable cluster bombardment conditions, predict a significant increase of the sputtering yield for ultrathin layers on hard substrates, induced by energy confinement in the polymer, and support our phenomenological model