Revealing synergetic structural activation of a CuAu surface during water-gas shift reaction.

Bimetallic alloy catalysts show strong structural and compositional dependence on their activity, selectivity, and stability. Often referred to as the "synergetic effect" of two metal elements in the alloys, their detailed dynamic information, structurally and chemically, of catalyst surface under reaction conditions remains largely elusive. Here, using aberration-corrected environmental transmission electron microscopy, we visualize the atomic-scale synergetic surface activation of CuAu under a water­gas shift reaction condition. The unique "periodic" structural activation largely determines the dominating reaction pathway, which is related to a possible "carboxyl" reaction route corroborated by density functional theory­based calculation and ab initio molecular dynamics simulation. These results demonstrate how the alloy surface is activated and catalyzes the chemical reaction, which provides insights into catalyst design with atom precision.

One-Step Synthesis of Light Metal Nanoparticle from Metastable Complex.

Metal nanoparticles have attracted considerable scientific and technological interest in recent years, most related explorations and reports are focused on transition and noble metals. However, the synthesis and application of light metal nanoparticles represented by Mg have not been fully exploited, limited by their ultrahigh reactivity in air and preparation in harsh conditions. In this work, a simple and effective one-step organic solvent-assisted ball-milling process is developed to synthesize Mg and Li nanoparticles, which permits the formation of MgH2 in a hydrogen atmosphere in a one-step reaction process at ambient temperature. Further studies suggest that acetone chemisorbs on defects/surfaces of Mg during ball milling leading to the formation of a metastable magnesium complex, which significantly alters the physical and chemical characteristics of Mg grains. The formation of metastable complexes provides an attractive strategy to produce light metal nanoparticles and inspires the authors to study the interaction of organic solvents with light metals.

Building hybrid structure of monolayered S-depleted Mo-S nanocrystals and 3D graphene towards promising aqueous supercapacitor applications.

Two-dimensional (2D) 1H molybdenum disulfide (1H-MoS2) is hard to be directly used in energy storage devices due to its inert basal plane and unfavorable 2D stacking. This work demonstrated how the basal plane of 1H MoS2nanocrystals (NCs) can be activated to offer doubled specific capacitance by simple surface S depletions. Building on the expanded graphene with three-dimensional (3D) structures, as-prepared NCs were chemically grafted on the graphene surface to deliver stable energy storage and high capacitance, which overcame above challenges of 1H-MoS2. Aside from the mostly focused metastable phase, this work confirmed that the stable 1H Mo-S material is also promising in energy storage applications.

Laser-assisted surface activation for fabrication of flexible non-enzymatic Cu-based sensors.

A rapid and effective technique has been develped for the fabrication of sensor-active copper-based materials on the surface of such flexible polymers as terephthalate, polyethylene naphthalate, and polyimide using the method of laser surface modification. For this purpose, we optimized the polymer surface activation parameters using laser sources with a picosecond pulse duration for subsequent selective metallization within the activated region. Furthermore, the fabricated copper structures were modified with gold nanostructures and by electrochemical passivation to produce copper-gold and oxide-containing copper species, respectively. As a result, in comparison with pure copper electrodes, these composite materials exhibit much better electrocatalytic performance concerning the non-enzymatic identification of biologically important disease markers such as glucose, hydrogen peroxide, and dopamine.

Laser Activated and Electroless Metalized Polyurethane Coatings Containing Copper(II) L-Tyrosine and Glass Microspheres.

Polyurethane coatings containing copper(II) L-tyrosine and glass microspheres were laser irradiated and underwent electroless metallization. Various sizes of glass microspheres were incorporated into the polyurethane coating matrix in order to examine their effects on surface activation and electroless metallization. The surface of the coatings was activated by using ArF excimer laser emitting ultraviolet radiation (λ = 193 nm) using different number of laser pulses and their fluence. The effects of surface activation and metallization were evaluated mainly based on optical and scanning electron microcopies (SEM), energy-dispersive X-ray spectroscopy (EDX) and photoelectron spectroscopy (XPS). It was found that the presence of glass microspheres enabled the reduction in copper complex content, intensified the ablation process (higher cone-like structures created) and resulted in higher content of copper metallic seeds. On the other hand, the glass microspheres concentration, which was higher for lower size microspheres, was advantageous for obtaining a fully metallized layer.

Morphological and Structural Properties of Amino-Functionalized Fumed Nanosilica and Its Comparison with Nanoparticles Obtained by Modified Stöber Method.

In industry, silica nanoparticles (NPs) are obtained by the fuming and the precipitation method. Fumed silica NPs are commonly used in the preparation of nanocomposites because they have an extremely low bulk density (160-190 kg/m3), large surface area (50-600 m2/g), and nonporous surface, which promotes strong physical contact between the NPs and the organic phase. Fumed silica has fewer silanol groups (Si-OH) on its surface than the silica prepared by the Stöber method. However, the number of -OH groups on the fumed silica surface can be increased by pretreating them with sodium hydroxide (NaOH) before further surface modification. In this study, the effectiveness of the NaOH pretreatment was evaluated on commercial fumed silica NPs with a surface area of 200 m2/g. The number of surface -OH groups was estimated by potentiometric titration. The pretreated fumed NPs, and the precipitated NPs (prepared by the Stöber method) were modified with 3-aminopropyltriethoxysilane (APTES) to obtain A200S and nSiO2-APTES, respectively. The NPs were characterized using electron dispersive scanning (EDS), scanning electron microscopy (SEM), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), BET (Brunauer-Emmett-Teller) analysis, and ζ-potential. XRD confirmed the presence of the organo-functional group on the surface of both NPs. After the amino-functionalization, the ζ-potential values of the nSiO2 and A200 changed from -35.5 mV and -14.4 mV to +26.2 mV and +11.76 mV, respectively. Consequently, we have successfully synthesized functionalized NPs with interesting, specific surface area and porosity (pore volume and size), which can be attractive materials for chemical and energy industries.

Electrochemical decolorization of dye wastewater by surface-activated boron-doped nanocrystalline diamond electrode.

Complex organics contained in dye wastewater are difficult to degrade and often require electrochemical advanced oxidation processes (EAOPs) to treat it. Surface activation of the electrode used in such treatment is an important factor determining the success of the process. The performance of boron-doped nanocrystalline diamond (BD-NCD) film electrode for decolorization of Acid Yellow (AY-36) azo dye with respect to the surface activation by electrochemical polarization was studied. Anodic polarization found to be more suitable as electrode pretreatment compared to cathodic one. After anodic polarization, the originally H-terminated surface of BD-NCD was changed into O-terminated, making it more hydrophilic. Due to the oxidation of surface functional groups and some portion of sp(2) carbon in the BD-NCD film during anodic polarization, the electrode was successfully being activated showing lower background current, wider potential window and considerably less surface activity compared to the non-polarized one. Consequently, electrooxidation (EO) capability of the anodically-polarized BD-NCD to degrade AY-36 dye was significantly enhanced, capable of nearly total decolorization and chemical oxygen demand (COD) removal even after several times of re-using. The BD-NCD film electrode favored acidic condition for the dye degradation; and the presence of chloride ion in the solution was found to be more advantageous than sulfate active species.

Surface activation of Pt nanoparticles synthesised by "hot injection" in the presence of oleylamine.

Oleylamine (OA) based "hot injection" colloidal synthesis offers a versatile approach to the synthesis of highly monodisperse metallic and multi-metallic alloyed nanostructures in the absence of potentially toxic and unstable phosphine compounds. For application in heterogeneous catalysis and electrocatalysis, the adsorbed OA species at the metal surfaces should be effectively removed without compromising the structure and composition of the nanostructures. Herein, we investigate the removal of OA from colloidal Pt nanoparticles through 1) "chemical methods" such as washing in acetic acid or ethanol, and ligand exchange with pyridine; and 2) thermal pre-treatment between 185 and 400 °C in air, H2 or Ar atmospheres. The electrochemical reactivity of Pt nanoparticles is acutely affected by the presence of surface organic impurities, making this material ideal for monitoring the effectiveness of OA removal. The results showed that thermal treatment in Ar at temperatures above 400 °C provides highly active particles, with reactivity comparable to the benchmark commercial catalyst, Pt/ETEK. The mechanism involved in thermal desorption of OA was also investigated by thermogravimetric analysis coupled to mass spectrometry (TGA-MS). Oxidation of HCOOH and adsorbed CO in acidic solution were used as test reactions to assess the Pt electrocatalytic activity.

Enhanced surface activation of ground tire rubber via the radiolysis of water for effective rubber recycling.

In this study, we examined the chemical changes occurring in ground tire rubber (GTR) and on its surface as a result of gamma irradiation in water, with low doses of 5, 10, 15, 20, 25, and 30 kGy. To better distinguish the changes the radiation caused in the GTR and the surface activation of the GTR caused by the irradiated water, we also performed radiation treatments in an inert atmosphere. We mixed the treated GTRs with fresh rubber, and after vulcanization, investigated the mechanical properties and conducted dose optimization. The chemical changes occurring in GTR were characterized by Soxhlet-extraction and cross-link density measurements. Changes on the surface were investigated by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). In water irradiation, cross-link density decreased (∼10 %), while in an inert atmosphere, new bonds formed between the chains (∼10 %), with negligible degradation (∼2 %) in both cases. Based on the FTIR spectra, new oxygen-containing groups appeared on the GTR surface in water treatment, while this was not observed in a nitrogen atmosphere. The increase in surface oxygen content was confirmed by XPS, showing a ∼10 % increase as a result of water treatment, while it remained unchanged in the inert atmosphere. We achieved a 30 % increase in tensile strength (5 kGy) without a decrease in elongation properties and a 32 % increase in tear strength (20 kGy) for vulcanizates containing surface-activated GTR. Mechanical properties did not improve with treatments in an inert atmosphere. The oxidizing agents formed during the radiolysis of water activated the surface of the GTR, helping to establish a better connection with the matrix.

Optimization of Starch-Tannin Adhesives for Solid Wood Gluing.

Bio-based solutions for solid timber gluing have always been a very sensitive topic in wood technology. In this work, we optimize the gluing conditions of a starch-tannin formulation, which allows high performance in dry conditions and resistance to water dipping for 3 h, allowing for the D2 classification to be reached according to EN 204. It was observed that the starch-tannin formulations enhanced their performance by increasing the heating temperature, achieving satisfactory results at 140 °C for 13 min. The proportion of polyphenols in the mixture enhances the water resistance but is only tolerated until 20-30%. In particular, the addition of 10% tannin-hexamine enhances the water-resistant properties of starch for both quebracho and chestnut extract. The application of the jet of cold atmospheric plasma allows for good results with more viscous formulations, increasing their penetration in wood. Solid-state 13C-NMR analysis was also performed, and the spectroscopic information suggests establishing a coordination complex between starch and tannin.

Ultrathin Boundary-Less SnO2 Films with Surface-Activated Two-Dimensional Nanograins Enable Fast and Sensitive Hydrogen Gas Sensing.

Fast and reliable semiconductor hydrogen sensors are crucially important for the large-scale utilization of hydrogen energy. One major challenge that hinders their practical application is the elevated temperature required, arising from undesirable surface passivation and grain-boundary-dominated electron transportation in the conventional nanocrystalline sensing layers. To address this long-standing issue, in the present work, we report a class of highly reactive and boundary-less ultrathin SnO2 films, which are fabricated by the topochemical transformation of 2D SnO transferred from liquid Sn-Bi droplets. The ultrathin SnO2 films are purposely made to consist of well-crystallized quasi-2D nanograins with in-plane grain sizes going beyond 30 nm, whereby the hydroxyl adsorption and grain boundary side-effects are effectively suppressed, giving rise to an activated (101)-dominating dangling-bond surface and a surface-controlled electrical transportation with an exceptional electron mobility of 209 cm2 V-1 s-1. Our work provides a new cost-effective strategy to disruptively improve the gas reception and transduction of SnO2. The proposed chemiresistive sensors exhibit fast, sensitive, and selective hydrogen sensing performance at a much-reduced working temperature of 60 °C. The remarkable sensing performance as well as the simple and scalable fabrication process of the ultrathin SnO2 films render the thus-developed sensors attractive for long awaited practical applications in hydrogen-related industries.

Active Cellulose-Based Food Packaging and Its Use on Foodstuff.

The essential role of active packaging is food quality improvement, which results in an extension of shelf life. Active packaging can also further enhance distribution from the origin point, and contributes to food waste reduction, offering greater sustainability. In this study, we introduced a new method for obtaining cellulose-based active packages, combining gamma irradiation as an eco-friendly activation process, and clove essential oil and cold-pressed rosehip seed oil as bioactive agents. Newly obtained bioactive materials were evaluated to assess their structural, hydrophobic, and morphological properties, thermal stability, and antioxidant and antimicrobial properties. The results showed that the plant oils induced their antimicrobial effects on paper, using both in vitro tests, against several bacterial strains (Gram-positive bacteria Listeria monocytogenes and Gram-negative bacteria Salmonella enteritidis and Escherichia coli), and in vivo tests, on fresh cheese curd and beef. Moreover, these oils can help control foodborne pathogens, which leads to extended shelf life.

Surface-Activated Pencil Graphite Electrode for Dopamine Sensor Applications: A Critical Review.

Pencil graphite electrode (PGE) is an alternative, commercially available, ready-to-use, screen-printed electrode for a wide range of electroanalytical applications. Due to the complex-matrix composition and unpredictable electro-inactive nature of PGE in its native form, a surface pre-treatment/activation procedure is highly preferred for using it as an electroactive working electrode for electroanalytical applications. In this article, we review various surface pre-treatment and modification procedures adopted in the literature with respect to the sensitive and selective detection of dopamine as a model system. Specific generation of the carbon-oxygen functional group, along with partial surface exfoliation of PGE, has been referred to as a key step for the activation. Based on the Scopus® index, the literature collection was searched with the keywords "pencil and dopamine". The obtained data were segregated into three main headings as: (i) electrochemically pre-treated PGE; (ii) polymer-modified PGEs; and (iii) metal and metal nanocomposite-modified PGE. This critical review covers various surface activation procedures adopted for the activation for PGE suitable for dopamine electroanalytical application.

A Comparative Study of Three Approaches to Fibre's Surface Functionalization.

Polyester-based scaffolds are of research interest for the regeneration of a wide spectrum of tissues. However, there is a need to improve scaffold wettability and introduce bioactivity. Surface modification is a widely studied approach for improving scaffold performance and maintaining appropriate bulk properties. In this study, three methods to functionalize the surface of the poly(lactide-co-ε-caprolactone) PLCL fibres using gelatin immobilisation were compared. Hydrolysis, oxygen plasma treatment, and aminolysis were chosen as activation methods to introduce carboxyl (-COOH) and amino (-NH2) functional groups on the surface before gelatin immobilisation. To covalently attach the gelatin, carbodiimide coupling was chosen for hydrolysed and plasma-treated materials, and glutaraldehyde crosslinking was used in the case of the aminolysed samples. Materials after physical entrapment of gelatin and immobilisation using carbodiimide coupling without previous activation were prepared as controls. The difference in gelatin amount on the surface, impact on the fibres morphology, molecular weight, and mechanical properties were observed depending on the type of modification and applied parameters of activation. It was shown that hydrolysis influences the surface of the material the most, whereas plasma treatment and aminolysis have an effect on the whole volume of the material. Despite this difference, bulk mechanical properties were affected for all the approaches. All materials were completely hydrophilic after functionalization. Cytotoxicity was not recognized for any of the samples. Gelatin immobilisation resulted in improved L929 cell morphology with the best effect for samples activated with hydrolysis and plasma treatment. Our study indicates that the use of any surface activation method should be limited to the lowest concentration/reaction time that enables subsequent satisfactory functionalization and the decision should be based on a specific function that the final scaffold material has to perform.

Effect of Adding Pyrolysis Carbon Black (CBp) on Soft Friction and Metal Wear during Mixing.

In the cracking process of waste tires, pyrolysis carbon black (CBp), as a solid product, accounts for about 35% of the total tire rubber content. Here, the treated CBp has been gradually applied to the tire formula to improve the recycling efficiency of waste tires. This study elucidated the influence of adding CBp during the tire mixing process on soft friction and metal wear. Compared with industrial carbon black (I-CB), the friction coefficient of CBp was smaller at different mixing stages, and the ripple caused by adhesion friction was not evident. After the modified CBp (M-CBp) was obtained by implementing the surface activation of common CBp (C-CBp), the friction coefficient between M-CBp and metal increased by 10%, while the filler dispersion and comprehensive mechanical properties showed an upward trend. The wear rate of metal was higher than that observed after adding I-CB during the same mixing mode; thus, it was necessary to strengthen the wear resistance of the inner-wall surface of the mixing chamber. The -OH group on the M-CBp surface can also participate in the silane coupling reaction and aggravate the metal wear of the mixer chamber wall. Through a comparison of results, the mixing friction coefficient can reflect the strength of filler-rubber interaction, which in turn can preliminarily represent the dispersion effect and comprehensive properties, reveal the reason behind the poor performance of CBp, and highlight the need for modification from the perspective of tribology.

The Effect of Antimony (III) Oxide on the Necessary Amount of Precursors Used in Laser-Activated Coatings Intended for Electroless Metallization.

The article presents research on the potential use of organometallic compounds with the addition of antimony (III) oxide Sb2O3 as a coating additive that will make coatings susceptible to electroless metallization after prior surface irradiation with 193 nm wavelength laser radiation and a different number of laser pulses. The surface modification and activation effects were assessed by optical-imagining as well as by scanning electron microscopy (SEM) with energy dispersive analysis (EDX). It was found that the presence of Sb2O3 in the coating made it possible to reduce the content of the copper complex, causing an intensive surface ablation, resulting in the formation of a conical structure with a higher content of metallic copper nuclei.

Effect of Various Surface Treatments on Wettability and Morphological Properties of Titanium Oxide Thin Films.

The effect of three popular surface activation methods for a titanium oxide (titania) surface was thoroughly investigated to identify the most effective protocol for the enhancement of hydrophilicity. All the methods, namely H2O2 activation, UV irradiation and oxygen plasma treatment resulted in an enhanced hydrophilic titania surface, which was evidenced by the reduced contact angle values. To study in detail the chemical and morphological features responsible for the increased hydrophilicity, the treated surfaces were submitted to inspection with atomic force microscopy and X-ray photoelectron spectroscopy. The correlation between the treatment and titania surface hydroxylation as well as hydrophilic behavior have been discussed.

Modification of Polymeric Surfaces with Ultrashort Laser Pulses for the Selective Deposition of Homogeneous Metallic Conductive Layers.

In recent years, the demand for highly integrated and lightweight components has been rising sharply, especially in plastics processing. One strategy for weight-saving solutions is the development of conductive tracks and layouts directly on the polymer housing parts in order to be able to dispense with the system integration of additional printed circuit boards (PCB). This can be conducted very advantageously and flexibly with laser-based processes for functionalizing polymer surfaces. In this work, a three-step laser-based process for subsequent selective metallization is presented. Conventional injection molded components without special additives serve as the initial substrate. The Laser-Based Selective Activation (LSA) uses picosecond laser pulses to activate the plastic surface to subsequently deposit palladium. The focus is on determining the amount of deposited palladium in correlation to the laser and scan parameters. For the first time, the dependence of the metallization result on the accumulated laser fluence (Facc) is described. The treated polymer parts are characterized using optical and scanning electron microscopy as well as a contact-type profilometer.

The Impact of Isocyanate Index and Filler Functionalities on the Performance of Flexible Foamed Polyurethane/Ground Tire Rubber Composites.

The structure and performance of polyurethane (PU) foams are strongly driven by the stoichiometry of the polyaddition reaction, quantitatively described by the isocyanate index. It determines the balance between isocyanate and hydroxyl groups in the reacting system and is affected by the introduction of additional functionalities originated, e.g., from applied fillers. Nevertheless, this issue is hardly taken into account in research works. Herein, the structure and performance of PU/ground tire rubber (GTR) composites differing in their isocyanate index (from 0.8 to 1.2) and prepared with and without considering the GTR functionalities in formulation development were investigated. Incorporating GTR into the PU matrix led to a reduction in average cell diameter (from 2 to 30% depending on the isocyanate index) compared to unfilled foams. However, formulation adjustments did not show a significant impact on cellular structure. The only decrease in open cell content was noted, from 10% for the 0.9 index to 40% for 1.2. Such changes were related to the increasing strength of the PU cellular structure able to maintain inside the increasing amount of carbon dioxide. On the other hand, considering hydroxyl values of GTR noticeably affected the thermomechanical performance of composites. The shift of glass transition temperature (Tg), even by 10 °C for 1.2 isocyanate index, enhanced the performance of materials, which was expressed in an 8-62% drop in the composite performance factor, pointing to the enhanced reinforcing effect resulting from filler incorporation. The stiffening of foams, related to the variations in PU segmental structure, also caused minor changes in the course of thermal degradation of PU/GTR composites due to the inferior thermal stability of hard segments. The obtained results provide important insights into the development of formulations of PU composites filled with materials containing reactive functional groups able to disrupt the stoichiometric balance of the polyaddition reaction.

Comparative Evaluation of Cu(acac)2 and {[Cu(µ-O,O'-NO3) (L-arg) (2,2'-bpy)]·NO3}n as Potential Precursors of Electroless Metallization of Laser-Activated Polymer Materials.

This paper presents a comparative assessment of Cu(acac)2 and {[Cu(µ-O,O'-NO3) (L-arg)(2,2'-bpy)]·NO3}n as potential precursors for the electroless metallization of laser activated polymer materials. Coatings consisting of polyurethane resin, one of the two mentioned precursor compounds, and antimony oxide (Sb2O3), as a compound strongly absorbing infrared radiation, were applied on the polycarbonate substrate. The coatings were activated with infrared Nd: YAG laser radiation (λ = 1064 nm) and electroless metallized. It was found that after laser irradiation, a micro-rough surface structure of the coatings was formed, on which copper was present in various oxidation states, as well as in its metallic form. For selected parameters of laser irradiation, it was possible to deposit a copper layer on the coating containing Cu(acac)2 and Sb2O3, which is characterized by high adhesion strength. It was also found that the {[Cu(µ-O,O'-NO3) (L-arg)(2,2'-bpy)]·NO3}n complex was not an effective precursor for the electroless metallization of Nd:YAG laser activated coatings. An attempt was made to determine the influence of the precursor chemical structure on the obtained metallization effects.