Changes In Surface Composition Research Articles

Surface modification of polyethylene terephthalate films by direct fluoridation for flexible electronic applications

In this study, a comprehensive investigation was carried out to analyse the effects of direct fluorination on the structural, morphological, wettability, thermal and optical properties of polyethylene terephthalate (PET) films. The results show significant changes in surface composition and structure, as well as changes in surface morphology induced by fluorination. In addition, an increase in surface hydrophilicity and surface free energy were observed after fluorination. Although there appeared to be a slight decrease in thermal stability of the fluorinated PET films, they exhibited increased optical transmittance in the UV–visible spectrum compared to the original PET films. These findings demonstrate how fluorinated PET films have better surface qualities, which makes them appropriate for a range of uses including printing, coating, and optoelectronics.

Impact of Surface Composition Changes on the CO2-Reduction Performance of Au-Cu Aerogels.

Over the past decades, the electrochemical CO2-reduction reaction (CO2RR) has emerged as a promising option for facilitating intermittent energy storage while generating industrial raw materials of economic relevance such as CO. Recent studies have reported that Au-Cu bimetallic nanocatalysts feature a superior CO2-to-CO conversion as compared with the monometallic components, thus improving the noble metal utilization. Under this premise and with the added advantage of a suppressed H2-evolution reaction due to absence of a carbon support, herein, we employ bimetallic Au3Cu and AuCu aerogels (with a web thickness ≈7 nm) as CO2-reduction electrocatalysts in 0.5 M KHCO3 and compare their performance with that of a monometallic Au aerogel. We supplement this by investigating how the CO2RR-performance of these materials is affected by their surface composition, which we modified by systematically dissolving a part of their Cu-content using cyclic voltammetry (CV). To this end, the effect of this CV-driven composition change on the electrochemical surface area is quantified via Pb underpotential deposition, and the local structural and compositional changes are visually assessed by employing identical-location transmission electron microscopy and energy-dispersive X-ray analyses. When compared to the pristine aerogels, the CV-treated samples displayed superior CO Faradaic efficiencies (≈68 vs ≈92% for Au3Cu and ≈34 vs ≈87% for AuCu) and CO partial currents, with the AuCu aerogel outperforming the Au3Cu and Au counterparts in terms of Au-mass normalized CO currents among the CV-treated samples.

Anisotropic Cu2O nanostructures: A promising remediation for per- and polyfluoroalkyl substances

Copper oxide (Cu2O) exhibits exceptional optical properties and phase stability at the nanoscale level making it highly desirable in nanotechnology applications. Its unique and distinctive properties make it highly feasible for diverse applications, which include environmental remediation, energy conversion, and catalysis. In this study, we tailor the surface and facet orientation of Cu2O nanoparticles to enhance their efficacy in addressing environmental contaminants such as per- and polyfluorinated substances (PFAS). By adjusting the ratios of the precursor and capping agent, we have synthesized Cu2O nanocubes (NCs) and octahedra (Oh) with average sizes of 450 nm and 650 nm, respectively. The time-dependent UV–Vis interaction studies revealed significant redshifts in absorption spectra upon the addition of Cu2O NCs and Oh to the PFAS solutions, indicative of the changes in the surroundings upon the interaction. FT-IR spectra further confirmed the sorption of PFAS on Cu2O nanostructures with stronger adsorption observed for longer-chain PFAS due to enhanced hydrophobic interactions. XPS analysis further provided insights into the surface composition changes after post-interaction, indicating the presence of PFAS on Cu2O nanostructures. The zeta potential analysis supported the role of electrostatic interactions in PFAS removal. Our results demonstrate that Cu2O Oh exhibits superior PFAS adsorption compared to Cu2O NCs, which is attributed to the exposed facets of a copper atom having a positive surface charge and facilitating electrostatic interactions. Specifically, Cu-terminated (110) or (111) surfaces exhibit enhanced sorption capacity, while the reduced reactivity of Cu-terminated Cu2O (100) surfaces is linked to high energy barrier holes at the surface region. Overall, this study elucidates the interaction mechanisms between Cu2O nanostructures and PFAS which underscores the significance of surface engineering for optimizing their performance in environmental remediation strategies.

Modification and characterization of tricalcium silicate bio-ceramic powders synthesized by sol-gel process for potential application in dental treatment

Tricalcium silicate powders (Ca3SiO5 or C3S) were fabricated by sol-gel process from the initial materials of Ca(NO3)2·4 H2O and Si(OC2H5)4 (TEOS) in acid medium. Effects of stoichiometry of reagent and catalyst, and temperature on physical-chemical, mechanical, and biological properties of C3S powders were examined systematically. The radiopacity, setting time, compressive strength, and bioactivity were investigated according to ISO recommendations. The radiopacity was compared and evaluated using dopants. The setting time and compressive strength were determined using water solvent. Analysis of bioactivity, antibacterial activity, and biocompatibility of Ca3SiO5 powders was performed and evaluated using simulated body fluid (SBF), and Tetrazolium (WST-1) reagent assay on Escherichia coli bacterium (E. coli), respectively. The milled-C3S powders showed a fine radiopacity with ZrO2 dopant, a shorter setting time, a higher density and a feasible compressive strength. The high purity of the milled-C3S powders with presence of Ca and Si compositions was confirmed by SEM-EDS analysis. Also, hydroxyapatite (HAp) was induced to form on the surface of milled-C3S powders when immersed in SBF. The surface compositional, morphological and chemical structural changes of the milled-C3S powders before and after immersing were analyzed by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results showed that a dense HAp layer was formed after 7 days of immersing. It indicated that C3S powders were bioactive and might be used for preparation of dental biomaterials. The milled-C3S powders also showed a potential antibacterial activity on the E.Coli cells and a high biocompatibility for cell viability. The good physical and excellent mechanical properties, bioactivity, and antibacterial activity confirmed the milled-Ca3SiO5 powders as a promising dental filling material.

Removal mechanism on 4H–SiC single crystal by picosecond laser ablation-assisted chemical mechanical polishing (CMP)

The properties of the single-crystal 4H–SiC are complex and difficult to understand. Consequently, determining the effect of the surface and subsurface structures and composition changes of picosecond laser ablation (PLA) on the material removal mechanism during the CMP stage is challenging. In this study, we used PLA of 4H–SiC surfaces to investigate the mechanism underlying the effect of PLA-assisted CMP, which is considerably larger than the laser ablation threshold, on the removal of 4H–SiC to improve the material removal rate and surface quality of CMP. The TEM and contact angle detection results indicated that the reduction in the fracture strength and increase in the surface energy of high-power PLA contributed to the removal form and chemical action of CMP. Subsequent experimental results showed that the contact angle and hardness of the PLA-treated surfaces in the hydrophilic range were reduced by 45% and 48.6%, respectively. The material removal rate (MRR) of PLA-CMP (alumina slurry) at 45 min was 3.67 μm/h that was a 70% improved CMP removal relative to no picosecond laser ablation (NPLA). The mechanism of PLA-assisted CMP removal was revealed to be related to the plastic cutting of the abrasive and high pressure and temperature, leading to the softening-removal-softening cycle of the material. This study provides a new perspective on the ultraprecise and high-efficiency fabrication of high-quality single-crystal 4H–SiC.

Modulating surface zinc species via facet engineering for efficient electroreduction of CO2 to CO

Zn-based catalysts have attracted widespread interest in electrocatalytic reduction of CO2 to CO, but they struggle to achieve large current densities and high product selectivity. Herein, we develop two kinds of faceted ZnO nanorods with subtle changes in crystallography and surface composition, simply by adjusting thermal annealing conditions. The ZnO nanorods with high numbers of (101) facets (ZnO (101)) and a reorganized Zn-rich surface exhibit higher catalytic performance compared to conventional ZnO nanorods with more (002) crystal planes and an oxygen-rich surface. The ZnO (101) catalyst shows superior FECO (>90 %) over a broad potential range, and an attractive CO partial current density of − 215.3 mA cm−2 in flow cells. DFT results further reveal that CO2 molecules are more easily activated on the reorganized surface of the ZnO (101), which significantly facilitates the formation of *COOH and inhibits the hydrogen evolution reaction, leading to remarkable activity and selectivity.

Fair surface modification with mixed alkanethiols on gold nanoparticles through minimal unfair ligand exchange.

Surface modification with functional molecules is essential for introducing various surface properties. As gold nanoparticles (AuNPs) have extraordinary chemical, physical, and optical properties, control of their surface, mainly through modification with mixed alkanethiols via Au-S interactions, has attracted much attention. However, surface modification of AuNPs with mixed alkanethiols to provide a strictly regulated composition remains challenging. Further, there are very few methods that can easily establish the nature of ligands and their replacement with similar molecules at nanoparticle surfaces, limiting precise analyses. Herein, we demonstrate an unfair ligand exchange between oligo(ethylene glycol) (OEG)-attached alkanethiols as a source of unfair surface modification utilizing programable thermo-responsive properties of OEG-alkanethiols-modified AuNPs and fair surface modification with mixed OEG-alkanethiols by minimizing this effect. OEG-alkanethiols-modified AuNPs show an assembly/disassembly behavior in response to the solution temperature. Assembly temperature (T A) changes in the presence of other OEG-alkanethiols, confirming the ligand exchange between alkanethiols in an aqueous solution. Kinetic analyses indicate that the competitive exchange reaction of these two alkanethiols results in an unfair ligand exchange, which leads to gradual changes in surface composition. As this ligand exchange between alkanethiols takes a longer time compared to that from citric acid, which initially covered the AuNPs, exact surface modification of AuNPs with OEG-alkanethiols is performed by moderate reaction conditions (25 °C, several to 24 hours). This insight regarding "more prolonged reaction is not always better" could be widely applied for surface modifications with various thiol-ligands.

Self-formation of compositionally complex surface oxides on high entropy alloys observed by accelerated atom probe tomography: a route to sustainable catalysts.

Sustainable catalysts rely on abundant elements which are prone to oxidation. A route to non-noble electrocatalysts is opened by directing the formation of unavoidable surface oxides towards creating a few atomic layers of an active and stable electrocatalyst, which is in direct contact with its metallic, conducting support. This is enabled by combining possibilities of compositionally complex solid solutions with accelerated atomic-scale surface characterization. Surface composition changes from the as-synthesized state to states after exposure to the oxygen evolution reaction (OER) are investigated using a Cantor-alloy-catalyst-coated tip array for atom probe tomography (APT): The film on top of the tip forms a nanoreactor which enables acquisition of intrinsic properties. The as-deposited film has an around 3 nm thick native oxide; short and prolonged OER exposures result in an oxygen-influenced surface layer with lower oxidation depth and altered metal composition. This shows that as-synthesized complex compositions can be used to obtain active and stable surface oxides under electrochemical load, while their surface evolution is observed by accelerated APT.

Use of NIR/NaBH4 combinatorial techniques for simultaneous and high-efficient adsorption of heavy metal ions from contaminated water by Chitosan/Au Janus microdisks

This article discusses the creation of a disk-shaped microsorbent with Janus morphology made with chitosan and coated with gold on one side using the sputtering technique. The aim of the research is to explore how sodium borohydride and near-infrared (NIR) light can enhance the adsorption of heavy metal ions by our synthesized adsorbent. The changes in surface morphology and composition of the chitosan part of Janus microdisks, after acid treatment and crosslinking reaction, before and after adsorption process were investigated through scanning electron microscopy (SEM). The chitosan/Au Janus microdisks were utilized in auto-catalyzed adsorption of heavy metals including, Pb, Cu, Cd, Zn, and Ni, in the presence of sodium borohydride. The isotherm, kinetic, and thermodynamic curves of adsorbance in the presence of metals were investigated. In addition, the performance of Janus microsorbents in the co-existing ions solution was studied under different conditions. The synthesized microsorbents can remove Cu ions selectively from contaminated water (>99 %) with the help of sodium borohydride. In addition, the NIR light irradiation exhibited a synergistic effect on the adsorption of Cd, Ni, and Pb ions in the presence of sodium borohydride. The borohydride ions can change the surface charge of microdisks after adsorption on their surface and increase the adsorption rate of metal cations. In addition, NIR light irradiation can accelerate the reaction of sodium borohydride with metal ions.

Surface Characterization and Bulk Property Analysis of Aluminum Powders Treated with Hydrophobic Coatings: Stearic Acid and Phenyl-Phosphonic Acid

Stearic and phenyl-phosphonic acids were applied to fine aluminum particles to understand their effect on the surface chemical composition and bulk properties of the surface-treated powders. During the solution phase deposition process, the surface composition changes chemically through a condensation reaction between the acid and particle surface hydroxyl groups, forming covalent chemical bonds. The retention of both types of acids was verified through characterization using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The presence of stearic acid on the particle surface was observed through signature absorbance peaks, including interfacial C-O bonding modes, carboxylate, and carbonyl moieties, all present on both the treated powder. Spectra using XPS showed an increase in -CH relative intensity signal on the particle surface when compared to the raw material when considering the the carbon 2p photoelectron peak. Similar findings confirmed the presence of the phenyl-phosphonic acid when comparing to the raw material. The IR spectrum confirmed the presence of P-O-Al, P-O, and phosponates as a result of the surface bonding between the reagent and particles. XPS always provided evidence through the presence of phosphorous 2p and 2s photoelecton peaks at 191.3 and 133.4 eV, respectively. The bulk properties of both surface treated powders improved, as shown through improved apparent/tap density and a decreased Hausner Ratio (Group C to Group A behavior). Rheological characterization provided additional evidence by showing a reduced specific energy, flow rate index, and cohesion. The particle packing was improved as evidenced through reduced compressibility as a function of applied normal stress.

Tracking Oxygen Evolution Activities of Perovskite Oxide Catalysts By 3D Electrochemical Impedance Spectroscopy

IntroductionPromoting the oxygen evolution reaction (OER) is important for more efficient electrochemical water splitting because its sluggish reaction kinetics degenerate the overall efficiency. Perovskite oxides (ABO3) are known as promising electrocatalysts for the OER, which have a flexibility of composition and structure. Among these electrocatalysts, Ba0.5Sr0.5Co0.8Fe0.2O3–δ (BSCF) exhibits good OER activities in an alkaline solution1. One of its specific properties is the change of the surface structure and composition during the OER in alkaline solutions, leading the improvement of the OER activity2. In general, the OER activities of metal oxides significantly depend on electrochemical surface area (ECSA) and activity per surface area (specific activity). However, it is not easy to decouple these two factors when the surface structure and composition change continuously during the OER.Electrochemical impedance spectroscopy (EIS) has been used as a useful tool, which provides information related to electrode/electrolyte interface3. Here, in order to reveal the origin of the OER activities behavior, we used 3D EIS including time axis and tracked the ECSA and specific activity of perovskite oxides during the OER in alkaline solutions.Experimental methodsPerovskite oxides used in this study (BSCF, La0.5Sr0.5Co0.8Fe0.2O3–δ (LSCF) and LaCoO3–δ (LCO)) were synthesized by the sol–gel method.The OER activities of obtained perovskite oxides were evaluated using a three-electrode electrochemical cell with a rotating disk electrode (RDE) in 1.0 mol dm–3 KOH solution. A working electrode was prepared by drop-casting an ink suspension with perovskite oxides (0.25 mg cm–2), acetylene black (0.05 mg cm–2), and Nafion (0.05 mg cm–2) on glassy carbon. Pt wire and a reversible hydrogen electrode (RHE) were used as the counter and reference electrodes, respectively. 3D EIS was obtained in the following steps: First, cyclic voltammetry (CV) was performed at certain cycles (1, 5, 10 ,30, and 50 cycles). Second, the electrode was left at open circuit potential for 5 min. Finally, potentiostatic EIS (PEIS) was recorded 5 times (approximately 10 min), and then Nyquist plots at 5 min from the beginning of the first PEIS were compared.Results and discussionFrom CV measurements of perovskite oxides, while the OER activities of BSCF increased, those of LSCF and LCO slightly decreased with increasing CV cycles. Figure shows Nyquist plots of perovskite oxides after certain CV cycles. The impedance spectra show a semicircle in the high- and mid-frequency regions, respectively. While a semicircle in the high-frequency region was independent on the direct current (DC) potential, the mid-frequency region semicircle was dependent on DC potential. The contrasting behavior indicated that the semicircle in the mid-frequency region corresponds to the charge transfer resistance, which contains the information of double-layer capacitance for the OER. Therefore, we tracked the semicircle in the mid-frequency region during the OER.A semicircle in the mid-frequency region of BSCF gradually decreased with CV cycles, indicating that the BSCF surface changed to a preferred structure during the OER cycles. As a result of the equivalent circuit fitting, the charge transfer resistance decreased and the double-layer capacitance increased with CV cycles. On the other hand, a semicircle in the mid-frequency region of LSCF and LCO remained unchanged or slightly increased.More detailed evaluation of their ECSA and specific activities during OER will be discussed at the conference.Reference[1] J. Suntivich, K. J. May, H. A. Gasteiger, J. B. Goodenough and Y. Shao−Horn, Science, 334, 1383 (2011).[2] K. J. May, C. E. Carlton, K. A. Stoerzinger, M. Risch, J. Suntivich, Y.-L. Lee, A. Grimaud and Y. Shao-Horn, J. Phys. Chem. Lett., 3, 3264 (2012)[3] V. A. Alves, L. A. da Silva, and J. F. C. Boodts, Electrochim. Acta, 44, 1525 (1998). Figure 1

Expediting High‐Yield Mxene Carbides and Nitrides Synthesis for Next‐Generation 2D Materials

AbstractThis research aims to enhance MXene (Ti3C2Tx) synthesis from MAX phases (Ti3AlC2) through a hydro‐solvothermal exfoliation process, with a focus on reducing time and temperature requirements. Prior hydrothermal studies have encountered challenges due to high reaction temperatures. In comparison to previous research, this work achieves superior results at lower temperatures. Two optimized MXene preparation routes are investigated and the etchant's impact on MXene surface chemistry is analyzed. Comprehensive X‐ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X‐ray Spectroscopy (EDS), X‐ray Photoelectron Spectroscopy (XPS), Fourier transform infrared (FTIR), Raman spectroscopy, and Atomic Force Microscopy (AFM) analyses provide insights into hydrosolvothermal synthesis (H‐Ti3C2Tx ) multilayers(ML), confirming/challenging recent spectroscopic assignments. Remarkably, hydro‐solvothermal treatment induces significant changes in surface composition, increasing hydroxyl (─OH) groups without oxidation and reducing fluorine (─F) groups on the H‐ Ti3C2Tx surface. These study's results hold promise for applications in energy storage and electromagnetic wave shielding. This research accomplishes three main objectives: i) secures hydrothermal synthesis of two‐ dimensional (2D) MXenes, ii) efficiently utilizes lithium fluroide‐ hydrochloric acid (LiF−HCl) etching for high‐quality MXene flakes with minimal defects, and iii) understands hydro‐solvothermal kinetics. This approach advances MXene synthesis with enhanced material quality and production efficiency (>98%), in a more eco‐friendly and safer manner. This eco‐conscious synthesis underscores MXene's versatility and eco‐friendly methods' significance, reshaping MXene exploration and sustainable material synthesis, with potential implications for future electrochemical applications.

Synthetic Tailoring of Ionic Conductivity in Multicationic Substituted, High-Entropy Lithium Argyrodite Solid Electrolytes.

Superionic conductors are key components of solid-state batteries (SSBs). Multicomponent or high-entropy materials, offering a vast compositional space for tailoring properties, have recently attracted attention as novel solid electrolytes (SEs). However, the influence of synthetic parameters on ionic conductivity in compositionally complex SEs has not yet been investigated. Herein, the effect of cooling rate after high-temperature annealing on charge transport in the multicationic substituted lithium argyrodite Li6.5[P0.25Si0.25Ge0.25Sb0.25]S5I is reported. It is demonstrated that a room-temperature ionic conductivity of ∼12 mS cm-1 can be achieved upon cooling at a moderate rate, superior to that of fast- and slow-cooled samples. To rationalize the findings, the material is probed using powder diffraction, nuclear magnetic resonance and X-ray photoelectron spectroscopy combined with electrochemical methods. In the case of moderate cooling rate, favorable structural (bulk) and compositional (surface) characteristics for lithium diffusion evolve. Li6.5[P0.25Si0.25Ge0.25Sb0.25]S5I is also electrochemically tested in pellet-type SSBs with a layered Ni-rich oxide cathode. Although delivering larger specific capacities than Li6PS5Cl-based cells at high current rates, the lower (electro)chemical stability of the high-entropy Li-ion conductor led to pronounced capacity fading. The research data indicate that subtle changes in bulk structure and surface composition strongly affect the electrical conductivity of high-entropy lithium argyrodites.

Effect of Electrocautery and Laser Treatment on the Composition and Morphology of Surface-Modified Titanium Implants.

The purpose of this study was to investigate the effects of different peri-implantitis treatment methods (Er,Cr:YSGG laser, diode laser, and electrocautery) on various titanium implant surfaces: machined; sandblasted, large-grit, and acid-etched; and femtosecond laser-treated surfaces. Grade 4 titanium (Ti) disks, with a diameter of 10 mm and a thickness of 1 mm, were fabricated and treated using the aforementioned techniques. Subsequently, each treated group of disks underwent different peri-implantitis treatment methods: Er,Cr:YSGG laser (Biolase, Inc., Foothill Ranch, CA, USA), diode laser (Biolase, Inc., Foothill Ranch, CA, USA), and electrocautery (Ellman, Hicksville, NY, USA). Scanning electron microscopy, energy-dispersive X-ray spectroscopy, and wettability were used to characterize the chemical compositions and surfaces of the treated titanium surfaces. Significant changes in surface roughness were observed in both the electrocautery (Sa value of machined surface = 0.469, SLA surface = 1.569, femtosecond laser surface = 1.741, and p = 0.025) and Er,Cr:YSGG laser (Ra value of machined surface = 1.034, SLA surface = 1.380, femtosecond laser surface = 1.437, and p = 0.025) groups. On femtosecond laser-treated titanium implant surfaces, all three treatment methods significantly reduced the surface contact angle (control = 82.2°, diode laser = 74.3°, Er,Cr:YSGG laser = 73.8°, electrocautery = 76.2°, and p = 0.039). Overall, Er,Cr:YSGG laser and electrocautery treatments significantly altered the surface roughness of titanium implant surfaces. As a result of surface composition after different peri-implantitis treatment methods, relative to the diode laser and electrocautery, the Er,Cr:YSGG laser increased oxygen concentration. The most dramatic change was observed after Er:Cr;YSGG laser treatment, urging caution for clinical applications. Changes in surface composition and wettability were observed but were not statistically significant. Further research is needed to understand the biological implications of these peri-implantitis treatment methods.

Influence of the sintering atmosphere on the physico-chemical properties and the osteoclastic resorption of β-tricalcium phosphate cylinders.

One of the most widely used materials for bone graft substitution is β-Tricalcium phosphate (β-TCP; β-Ca3(PO4)2). β-TCP is typically produced by sintering in air or vacuum. During this process, evaporation of phosphorus (P) species occurs, leading to the formation of a calcium-rich alkaline layer. It was recently shown that the evaporation of P species could be prevented by co-sintering β-TCP with dicalcium phosphate (DCPA; CaHPO4; mineral name: monetite). The aim of this study was to see how a change of sintering atmosphere could affect the physico-chemical and biological properties of β-TCP. For this purpose, three experimental groups were considered: β-TCP cylinders sintered in air and subsequently polished to remove the surface layer (control group); the same polished cylinders after subsequent annealing at 500°C in air to generate a calcium-rich alkaline layer (annealed group); and finally, β-TCP cylinders sintered in a monetite-rich atmosphere and subsequently polished (monetite group). XPS analysis confirmed that cylinders from the annealed group had a significantly higher Ca/P molar ratio at their surface than that of the control group while this ratio was significantly lower for the cylinders from the monetite group. Sintering β-TCP in the monetite-rich atmosphere significantly reduced the grain size and increased the density. Changes of surface composition affected the activity of osteoclasts seeded onto the surfaces, since annealed β-TCP cylinders were significantly less resorbed than β-TCP cylinders sintered in the monetite-rich atmosphere. This suggests that an increase of the surface Ca/P molar ratio leads to a decrease of osteoclastic resorption. STATEMENT OF SIGNIFICANCE: Minimal changes of surface and bulk (< 1%) composition have major effects on the ability of osteoclasts to resorb β-tricalcium phosphate (β-TCP), one of the most widely used ceramics for bone substitution. The results presented in this study are thus important for the calcium phosphate community because (i) β-TCP may have up to 5% impurities according to ISO and ASTM standards and still be considered to be "pure β-TCP", (ii) β-TCP surface properties are generally not considered during biocompatibility assessment and (iii) a rationale can be proposed to explain the various inconsistencies reported in the literature on the biological properties of β-TCP.

Mass spectrometry and in situ x-ray photoelectron spectroscopy investigations of organometallic species induced by the etching of germanium, antimony and selenium in a methane-based plasma

Organometallic positive ions were identified in inductively coupled plasmas by means of mass spectrometry during the etching of Ge, Sb, Se materials. A preliminary study was focused on identifying M x H y + (M = Ge, Sb, Se) positive ion clusters during a H2/Ar etching process. The methane addition to the H2/Ar mixture generates CH x reactive neutral species. The latter react with the metalloids within gas phase to form M x C y H z + organometallic ions. In addition, the etching of Sb2Se3 and Ge19.5Sb17.8Se62.7 bulk targets forms mixed products via ion-molecule reactions as evidenced by the presence of SeSbC x H y + ion clusters. Changes in surface composition induced by the newly formed organometallic structures were investigated using in situ x-ray photoelectron spectroscopy. In the case of the Ge and Sb surfaces, (M)–M–C x environments broadened the Ge 2p3/2, Ge 3d, Sb 3d and Sb 4d spectra to higher values of binding energy. For the Se surface, only the hydrogen and methyl bonding could explain the important broadening of the Se 3d core level. It was found that the Ge39Se61 thin film presents an induced (Ge)–Ge–Se entity on the Ge 2p3/2 and Ge 3d core levels.

Influence of direct fluorination treatment on surface and optical properties of colorless and transparent polyimides

Due to excellent comprehensive performance, colorless and transparent polyimide (CPI) films are the greatest potential substrates for flexible displays, lighting, and solar cells. In this work, CPI films were modified by direct fluorination to increase the wettability and transmittance. The effects of fluorination duration on the chemical structure and surface physical morphology of CPI films were investigated in detail by attenuated total reflection infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results show that, depending on the fluorination duration, direct fluorination causes significant changes in surface composition and structure. The F/C and O/C ratios of the samples were enhanced as the fluorination time increased. Surface microcrack increased at initially, then decreased as fluorination time increased. The fluorinated surfaces exhibit a high hydrophily and lipophobicity, and consequently a very high surface energy, according to contact angle measurements. In comparison to original CPI film, the fluorinated CPI films exhibited higher optical transmittance in the ultraviolet–visible light region compared with original CPI film. In addition, the fluorinated CPI films showed good thermal stability up to 500 °C and higher glass transition temperatures (Tg) compared with original CPI film.

‘Newton’ fast shutter system for neutron scattering instruments at the ESS and ISIS neutron sources

Interfacial processes are involved in many areas of chemistry, physics and biochemistry, but following the structural changes of surfaces and thin films at relevant timescales remains challenging. Time-of flight neutron reflectometry can determine changes in surface composition and film thickness, but the speed of these measurements is typically limited by the neutron flux over the range of wavelengths available at existing instrumentation. This necessarily means that, even using the time-of-flight method, measurements over several angles of incidence are required to cover the full Q-range important for structural determination. The very high intensity of the ESS pulsed source makes such configuration changes very inefficient, as the measurements can potentially be recorded in seconds or even milliseconds. Here, we present a conceptual design and some preliminary results from a new type of fast beam shutter system that will allow efficient measurement of broad angular ranges at sub-second timescales. The shutter system is conceptually also potentially useful for a fast aperture application on the ZOOM instrument at the ISIS Target station 2. By using two perpendicular shutters with slits cut into them, it is possible to create a square aperture within the beam as the neutron pulse passes. We believe that the flexibility demonstrated will mean that this system has the potential to be generally useful in many neutron instrumentation applications.

In-situ coating wear condition monitoring based on solid-liquid triboelectric nanogenerator and its mechanism study

Various more or less wear-resistant coatings have been developed and used to protect metal substrates. However, the damage caused by wear is still a problem for most coatings. It is of great importance to monitor the wear of coatings in real-time during the applications. Recently reported wear monitoring methods (image processing, luminescent layers and the use of a sensing underlayer) require complex external equipment or additional coating preparation process steps, which limit their applications. As an emerging technology, a triboelectric nanogenerator (TENG) can convert mechanical energy into electricity, and it has been applied as a self-powered sensor. In this study, a new coating wear monitoring method is developed based on a solid-liquid TENG. The developed TENG generates electric signals corresponding to different wear states, which facilitates easy monitoring of the coating’s wear conditions. The results show that the surface composition change caused by wear is the main reason affecting the TENG signal output. The coating-liquid contact-separation motion generates real-time output signals that directly reflect the coating wear states without the need of any additional equipment. This study provides a promising new technology for in-situ coating wear monitoring.

Effect of Atmospheric Conditions on Ultraviolet Photoconductivity of Zinc Oxide Nanoparticles

ZnO nanoparticles have gained considerable interest lately due to their remarkable optical and electrical properties, which enable them to have the potential to be the next generation of transparent semiconductors. However, interactions with atmospheric water and surface carbonates limited and seriously threatened device stability and dependability. The UV photoconductivity of the ZnO NP films is heavily influenced by oxygen adsorption and organic species in the ambient air. The stability of the ZnO photodetector prepared, annealed, and tested in a nitrogen atmosphere was improved in terms of current magnitude and sustaining photocurrent cycles. ZnO NPs films processed in the air show considerable change in surface composition compared to nitrogen indicated by surface organic complexes. In an oxidized manufacturing environment, the compounds above were effectively eliminated while partly degraded in nitrogen. We find that the ZnO NPs surface is highly reactive with ambient CO2, generating surface carbonates groups that promote electrically active surface states.