Metallic Modification Research Articles

Photocatalytic removal of ammonia nitrogen from water: investigations and challenges for enhanced activity.

Ammonia nitrogen (NH3-N/NH4+-N) serves as a crucial chemical in biochemistry and fertilizer synthesis. However, it is also a toxic compound, posing risks from eutrophication to direct threats to human health. Ammonia nitrogen pollution pervades water sources, presenting a significant challenge. While several water treatment technologies exist, biological treatment, though widely used, has its limitations. Hence, green and efficient photocatalytic technology emerges as a promising solution. However, current monolithic semiconductor photocatalysts prove inadequate in controlling ammonia nitrogen pollution. Therefore, this review focuses on enhancing semiconductor photocatalysts' efficiency through modification, discussing four mechanisms: (1) mono-ionic modification; (2) metallic and non-metallic modification; (3) construct heterojunctions; and (4) enhancement of synergistic effects of multiple technologies. The influencing factors of photocatalytic ammonia nitrogen removal efficiency are also explored. Moreover, the review outlines the limitations of current photocatalytic pollution treatment and discusses future development trends and research challenges. Currently, the main products of ammonia nitrogen removal include NO3-, NO2-, and N2. To mitigate secondary pollution, the green process of converting ammonia nitrogen to N2 using photocatalysis emerges as a fundamental approach for future treatment. Overall, this review aims to deepen understanding of photocatalysis in ammonia nitrogen treatment and guide researchers toward widespread implementation of this endeavor.

Enhanced CO2 Reactive Capture and Conversion Using Aminothiolate Ligand-Metal Interface.

Metallic catalyst modification by organic ligands is an emerging catalyst design in enhancing the activity and selectivity of electrocatalytic carbon dioxide (CO2) reactive capture and reduction to value-added fuels. However, a lack of fundamental science on how these ligand-metal interfaces interact with CO2 and key intermediates under working conditions has resulted in a trial-and-error approach for experimental designs. With the aid of density functional theory calculations, we provided a comprehensive mechanism study of CO2 reduction to multicarbon products over aminothiolate-coated copper (Cu) catalysts. Our results indicate that the CO2 reduction performance was closely related to the alkyl chain length, ligand coverage, ligand configuration, and Cu facet. The aminothiolate ligand-Cu interface significantly promoted initial CO2 activation and lowered the activation barrier of carbon-carbon coupling through the organic (nitrogen (N)) and inorganic (Cu) interfacial active sites. Experimentally, the selectivity and partial current density of the multicarbon products over aminothiolate-coated Cu increased by 1.5-fold and 2-fold, respectively, as compared to the pristine Cu at -1.16 VRHE, consistent with our theoretical findings. This work highlights the promising strategy of designing the ligand-metal interface for CO2 reactive capture and conversion to multicarbon products.

Enhanced holding ability between resin and silanization modified diamonds through sintering Si[sbnd]N bond formation at low temperature

Resin-bonded diamond tools often suffer from poor durability and short lifespan due to the agglomeration of abrasive diamonds and the poor holding ability between diamonds and resin, resulting in diamond detachment during the working process. Modifying the diamond surface is necessary to improve the dispersion of diamonds and the holding ability between diamond and resin. However, common metallic modification methods can cause fine-grained diamonds (FGDs) to agglomerate, and metal plating cannot form a chemical bond with resin at low temperatures for preparing resin-bonded diamond tools. A practical non-metallic method for modifying diamond surfaces was proposed to address these issues, utilizing a silane coupling agent to enhance the binding forces between diamonds and binding agents. A uniform amorphous SiO2 film, with a thickness of 30–40 nm, was developed on FGDs with the hydrolysis and condensation reactions of tetraethylorthosilicate in a water and alcohol mixed solution. The SiO2 layer formed with the CO, CO, and C-O-Si chemical bonds can increase electrostatic repulsion between diamonds, overcoming diamond agglomeration. FGDs modified with SiO2 were combined with phenolic resin and pressed at 170 °C, forming SiN bonds between the resin and SiO2 film and improving the bonding force. Moreover, the SiN bonds can be produced at low temperatures, reducing the risk of diamond detachment during their operation. Hence, the lifespan of modified diamond wheel increase by 22 % than that of pristine diamond wheel. This study provides valuable guidance for developing high-performance, long-lasting, resin-bonded diamond tools.

Enhance the stability of oxygen vacancies in SrTiO3 via metallic Ag modification for efficient and durable photocatalytic NO abatement

Oxygen vacancy engineering is an appealing strategy in the direction of photocatalytic pollutant purification. Unfortunately, the short lifetime of oxygen vacancies significantly limits photocatalytic efficiencies and their application. Herein, we report that such a scenario can be resolved via plasmonic silver metal modification SrTiO3 containing oxygen vacancies, which can achieve a high NO removal rate of 70.0% and long stability. This outstanding photocatalytic activity can be attributed to the increased optical response range and carrier separation by metallic Ag with the unique character of localized surface plasmonic resonance (LSPR) effect. Moreover, the intrinsic mechanism of how the plasmonic metal could enhance the stability of oxygen vacancies is proposed. The plasmon-driven hot carriers inject SrTiO3 support that promotes the regeneration of oxygen vacancies around the interface, meanwhile, the introduction of Ag nanoparticles prevents the oxygen vacancies from being filled by the reactant. This work elucidates the unique role of plasmonic metal in photocatalysis, providing an innovative idea for improving catalytic stability.

Biodegradable Mg-based implants obtained via anodic oxidation applicable in dentistry: Preparation and characterization

Constant dentistry development causes a need for modern biomaterials with advanced properties. Commonly used titanium-based implants although characterized by satisfying durability, biocompatibility and bioinertness do not meet all the requirements for novel medical devices. Nowadays, the most attractive implants must meet such requirements as biocompatibility, bioactivity and susceptibility to biodegradation which are unobtainable for these Ti-derived ones, thus magnesium biomaterials are considered as the metallic medical devices of latest generation. However, unmodified Mg implants undergo uncontrolled biocorrosion and may mismatch with bone tissue formation. Therefore, development of Mg-based biomaterials of controlled properties is a priority. Anodic modification is a promising technique for metallic materials modification to increase their biological responses and applicability in biomedical areas. In this paper, a successful modification of Mg implants has been carried out via high-voltage anodization process resulting in the preparation of novel biomaterials with interesting properties and high potential in dental applications. Superficial oxidation was confirmed by XRD and XRF analyses. Surface morphology was investigated by SEM microscopy proving suitable for cells adhesion microstructure. In vitro incubation study showed that the biomaterials promote apatites’ formation due to highly porous morphology and locally increased pH enhancing biomineralization via calcium and phosphates ions migration, adsorption and crystallization. Biodegradation tests proved increased resistance to hydrolysis in simulated body fluids due to the surface passivation. Further investigation on biocorrosion revealed improved tolerance to human body conditions. Finally, cell culture study carried out on L929 mouse fibroblasts confirmed superior to native magnesium biocompatibility showing a high potential of newly developed implants in the field of dentistry.

FUNDAMENTAL LIMITS FOR THE LENGTH OF CONDUCTION CHANNEL IN THE FET ON TRANSITION METALS DICHALCOGENIDE SINGLE LAYER BASE

The modeling of the limits of functionality for the FET with conduction channel on transition metals dichalcogenide single layer base and with different source/drain contacts material was performed in this article. The quantum mechanical transparency of the channel barrier was calculated with allowance for the realistic form of the barrier potential. It is demonstrated, that the FET with 4-nm channel of n-MoS2 and MoS2 (metallic modification) source/drain contacts retains high level of functionality for the range of comparatively low gate and drain voltages (the barrier transparency is lower than ½). The similar FET with Pt source/drain contacts, when Schottky barrier is essentially higher and the barrier transparency is essentially lower, keep it’s functionality for the 2 nm channel as well for all the realistic values of gate and drain voltages. The similar result was obtained for the FET with p-WSe2 channel and Pd contacts as well. The obtained estimations confirm the possibility of the complementary inverter on MoS2 n-type FET and WSe2 p-type FET with ultra-short channels in 2–4 nm range.

МЕТОДЫ ХИМИЧЕСКОЙ МОДИФИКАЦИИ ЭПОКСИДНЫХ ОЛИГОМЕРОВ (обзор)

This paper is devoted to one of the most pressing problems of modern non – metallic materials science-chemical modification of thermosetting systems based on epoxy oligomers with active diluents and bismaleimides: polymer binders for reinforced plastics, adhesives, compounds, sealants, and protective paint coatings. Based on the analysis of domestic and foreign scientific literature, as well as patents for inventions, a conclusion was made about the prospects for further research in this direction. The use of these types of modifiers can increase the chemical resistance, crack resistance, strength, impact strength, heat resistance and other valuable properties of polymer composite materials (PCM) based on an epoxy polymer matrix.

Influence of electrosynthesis methods in the electrocatalytical and morphological properties of cobalt and nickel hexacyanoferrate films

Prussian Blue analogues (PBA) based on Cobalt and Nickel thin films were assembled by two distinct methodologies using direct electroprecipitation on the substrate and metallic nanoparticle surface modification. The modified electrodes were characterized by several techniques such as Infrared Reflection-Absorption and Electrochemical Impedance Spectroscopies, Scanning Electron and Atomic Force Microscopies, and Electrochemical methods. The electrocatalytical properties of the films were also evaluated and the rate constants for thiosulfate oxidation were obtained and discussed. The results pointed out that the metallic nanoparticle approach has presented higher electrocatalytic effect, suggesting this methodology towards the construction of high performance electrochemical based devices such as sensors, biosensors, fuel cells and others.

Efficient Oxygen Evolution and Gas Bubble Release Achieved by a Low Gas Bubble Adhesive Iron-Nickel Vanadate Electrocatalyst.

Surface chemistry is a pivotal prerequisite besides catalyst composition toward advanced water electrolysis. Here, an evident enhancement of the oxygen evolution reaction (OER) is demonstrated on a vanadate-modified iron-nickel catalyst synthesized by a successive ionic layer adsorption and reaction method, which demonstrates ultralow overpotentials of 274 and 310mV for delivering large current densities of 100 and 400mAcm-2 , respectively, in 1m KOH, where vigorous gas bubble evolution occurs. Vanadate modification augments the OER activity by i) increasing the electrochemical surface area and intrinsic activity of the active sites, ii) having an electronic interplay with Fe and Ni catalytic centers, and iii) inducing a high surface wettability and a low-gas bubble-adhesion for accelerated mass transport and gas bubble dissipation at large current densities. Ex situ and operando Raman study reveals the structural evolution of β-NiOOH and γ-FeOOH phases during the OER through vanadate-active site synergistic interactions. Operando dynamic specific resistance measurement evidences an accelerated gas bubble dissipation by a significant decrease in the variation of the interfacial resistance during the OER for the vanadate-modified surface. Achievement of a high catalytic turnover of 0.12s-1 suggests metallic oxo-anion modification as a versatile catalyst design strategy for advanced water oxidation.

Poly(acrylic acid) Cross-Linked with Potassium As Gel Polymer Electrolyte in Small Zinc-Air Batteries

Zn-air batteries are considered as a suitable alternative to typical batteries due to the zinc is a highly abundant and environmentally friendly material (exist more than 224 trillions of tons in the first mile of deep). However, zinc anode has several challenges to overcome such as shape changes, dendritic growth, passivation, and corrosion. Two strategies can be followed to decrease/eliminate these issues, one of them consists in the metallic electrode modification, and other in the electrolyte modification. In this work, poly(acrylic acid) cross-linked with potassium (PAAK) was used to develop gel polymer electrolytes (GPEs) in 6 M KOH with and without additives (CTAB), testing their effect on battery performances. PAAK at different weight percentages were evaluated, being 3 wt.% PAAK the most promising concentration displaying a battery performance similar to that displayed by an aqueous 6 M KOH solution (20 mW cm-2). Furthermore, SEM images after a discharge experiment for 4 h at 1.25 mA cm-2 followed by a charge process indicated that the zinc anode maintained its original shape (nanoflakes with thickness of tens of nanometers) in the Zn-air battery operated with the GPE. However, zinc anode suffered shape changes in the 6 M KOH aqueous electrolyte, forming hemispherical particles with sizes between 1 to 4 μm. Also, the battery tests with the GPE displayed a higher durability to that operated with 6 M KOH aqueous electrolyte.

Tunable plasmon resonances of Ag nanoparticles obtained by photoelectric modification under room temperature

Stretched Ag nanoparticles (AgNPs) have been obtained by photoelectric modification with room temperature. Significant elongation occurs on partial AgNPs with diameters ranging from 50 to 120 nm. For AgNPs with diameters larger than 120 nm, protuberances with sizes about 10 nm have been observed after photoelectric modification. Simulations based on finite difference time domain method have been used to reveal the process of the photoelectric modification. Such morphology changes of AgNPs can be attributed to the plasmonic phase transition and electric induced migration of Ag atoms at AgNPs surfaces. Due to the stretching of AgNPs, tunable plasmon resonances in visible spectrum have been obtained. This work could provide a new technology for the metallic nanostructure modification under low temperature.

Potassium doping-induced variations in the structures and photoelectric properties of a MAPbI3 perovskite and a MAPbI3/TiO2 junction.

It has been experimentally demonstrated that mixed metallic cation modification could be an effective strategy to enhance the performance and stability of perovskite-based solar cells (PSCs). However, there is limited microscopic understanding at the atomic/molecular level of the behavior of small radius alkali metal cation doping in both perovskite materials and perovskite/TiO2 junctions. Here, we perform a first-principles density functional theory study on the doping-induced variation of the geometric and electronic structures of MAPbI3 (MA = methylammonium) and the MAPbI3/TiO2 junction. The impacts of different doping methods, and different charge states and locations of the given dopants have been investigated. At first, we theoretically confirm that the structures doped by K+ are the most thermally stable compared to the structures doped by the other charge states of K, and that K+ dopants prefer to modify the perovskite lattice interstitially and stay near the MAPbI3/TiO2 interface. Meanwhile, we find that a severe geometric deformation occurs if two doped lattices come into contact directly, indicating that the lattice may rapidly collapse from the interior if the doping concentration is too high. Additionally, we observe that K+ doped interstitially near the MAPbI3/TiO2 interface causes the intensive distortion of the surface Ti-O bonds and severe bond-length fluctuations. Consequently, this results in distorted TiO2 bands of the interfacial layer and a slight decrease of the band offset of conduction bands between two phases. This work complements experiments and provides a better microscopic understanding of the doping modification of the properties of perovskite materials and PSCs.

Testing of diffractive optical element as part of specific CO2 laser equipment for metallic materials modification

Testing of a reflective diffractive optical element (DOE) as part of specific CO2 laser equipment Oerlikon OPL 2000 for metallic materials modification was performed. The power density distribution in a plane located behind the DOE focal plane has been measured. It was found that DOEs make it possible to form a predetermined beam power density profile and to perform the transformation of laser energy, chosen by calculation previously. The use of these optical elements in the laser material treatment reveals new possibilities for controlling properties and operational characteristics of processed components. Additional redistribution of the beam power to edges of the laser spot is achieved by increasing the proportion of energy reflected by DOE peripheral zones, for example, by increasing the aperture of the focusable beam. It is proposed using a telescopic system of two lenses to change the aperture of the laser beam focusable by the DOE.

High-pressure triggered quantum tunneling tuning through classical percolation in a single nanowire of a binary composite

In the era of miniaturization, the one-dimensional nanostructures presented numerous possibilities to realize operational nanosensors and devices by tuning their electrical transport properties. Upon size reduction, the physical properties of materials become extremely challenging to characterize and understand due to the complex interplay among structures, surface properties, strain effects, distribution of grains, and their internal coupling mechanism. In this report, we demonstrate the fabrication of a single metal-carbon composite nanowire inside a diamond-anvil-cell and examine the in situ pressure-driven electrical transport properties. The nanowire manifests a rapid and reversible pressure dependence of the strong nonlinear electrical conductivity with significant zero-bias differential conduction revealing a quantum tunneling dominant carrier transport mechanism. We fully rationalize our observations on the basis of a metal-carbon framework in a highly compressed nanowire corroborating a quantum-tunneling boundary, in addition to a classical percolation boundary that exists beyond the percolation threshold. The structural phase progressions were monitored to evidence the pressure-induced shape reconstruction of the metallic grains and modification of their intergrain interactions for successful explanation of the electrical transport behavior. The pronounced sensitivity of electrical conductivity to an external pressure stimulus provides a rationale to design low-dimensional advanced pressure sensing devices.

Carbon Fiber Supported Pt-Co Electrocatalyst for Coal Electrolysis for Hydrogen Production

Carbon fibers (CFs) supported platinum-cobalt (Pt-Co) electrocatalysts are prepared with H2 heat-treatment and used for hydrogen production by coal electrooxidation. Pt-Co alloy was formed and characterized by X-ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The results show that the electrocatalystic activity and long-time stability of Pt-Co/CFs for coal electrolysis are enhanced with the introduction of cobalt. The PtCo/CFs (1:1) catalyst exhibits better catalytic activity than PtCo/CFs (7:3) and PtCo/CFs (3:7). The strong catalytic activities of the catalysts are attributed to synergistic effect between metallic alloying and modification of surface electrons of the bimetallic Pt-Co electrocatalysts.

Enhancement of Aromatic Products from Catalytic Fast Pyrolysis of Lignite over Hierarchical HZSM-5 by Piperidine-Assisted Desilication

HZSM-5 was post-treated by piperidine-assisted desilication (PAD) and metallic Co and/or Zr modification to introduce the meso-/microporous system and metal active sites to enhance the activity for catalytic fast pyrolysis (CFP) of lignite for aromatic products. CFP was conducted over parent and hierarchical HZSM-5 in a drop tube reactor at 600 °C and a gas residence time of 1.5 s. The results showed that assisted desilication with piperidine (PI) concentration of 0.3 mol/L (AT0.2–PI0.3), retained the morphology of HZSM-5, and avoided severe alkaline corrosion. This was due to the shield of the zeolite crystals from extensive dissolving of NaOH by organic amines. It not only decreased the deactivation rate of the catalyst, but also enhanced the mass transfer in the catalyst. The selectivity of light aromatics (LAs) such as benzene, toluene, ethylbenzene, xylene, and naphthalene remarkably increased to 24.9% over AT0.2–PI0.3 in comparison to the HZSM-5. In addition, introducing bimetallic Zr–Co facilitated...

Biomimetic PDMS-hydroxyurethane terminated with catecholic moieties for chemical grafting on transition metal oxide-based surfaces

The aim of this work was to synthesize a non-isocyanate poly(dimethylsiloxane) hydroxyurethane with biomimetic terminal catechol moieties, as a candidate for inorganic and metallic surface modification. Such surface modifier is capable to strongly attach onto metallic and inorganic substrates forming layers and, in addition, providing water-repellent surfaces. The non-isocyanate route is based on carbon dioxide cycloaddition into bis-epoxide, resulting in a precursor bis(cyclic carbonate)-polydimethylsiloxane (CCPDMS), thus fully replacing isocyanate in the manufacture process. A biomimetic approach was chosen with the molecular composition being inspired by terminal peptides present in adhesive proteins of mussels, like Mefp (Mytilus edulis foot protein), which bear catechol moieties and are strong adhesives even under natural and saline water. The catechol terminal groups were grafted by aminolysis reaction into a polydimethylsiloxane backbone. The product, PDMSUr-Dopamine, presented high affinity towards inhomogeneous alloy surfaces terminated by native oxide layers as demonstrated by quartz crystal microbalance (QCM-D), as well as stability against desorption by rinsing with ethanol. As revealed by QCM-D, X-ray photoelectron spectroscopy (XPS) and computational studies, the thickness and composition of the resulting nanolayers indicated an attachment of PDMSUr-Dopamine molecules to the substrate through both terminal catechol groups, with the adsorbate exposing the hydrophobic PDMS backbone. This hypothesis was investigated by classical molecular dynamic simulation (MD) of pure PDMSUr-Dopamine molecules on SiO2 surfaces. The computationally obtained PDMSUr-Dopamine assembly is in agreement with the conclusions from the experiments regarding the conformation of PDMSUr-Dopamine towards the surface. The tendency of the terminal catechol groups to approach the surface is in agreement with proposed model for the attachment PDMSUr-Dopamine. Remarkably, the versatile PDMSUr-Dopamine modifier facilitates such functionalization for various substrates such as titanium alloy, steel and ceramic surfaces.

Metallic modification of molybdenum disulfide monolayer via doping charge carriers: A DFT investigation

Density-functional theory has been applied to investigate the effect of doping charge carriers on the electronic structure of single-layer MoS2. The charge of the super cell changes from zero to n=±3e with e the absolute value of the elementary electric charge. Results firmly support the view that such an effect is manifested in the form of semiconductor-metal transition in addition to shift in the Fermi level. Examining the total number of allowed states at the Fermi level also reveals that the more positive/negative the charge of the super cell, the higher the electrical conductivity of the monolayer.

Silver-coated megaprostheses: review of the literature.

Periprosthetic infection remains one of the most serious complications following megaendoprostheses. Despite a large number of preventive measures that have been introduced in recent years, it has not been possible to further reduce the rate of periprosthetic infection. With regard to metallic modification of implants, silver in particular has been regarded as highly promising, since silver particles combine a high degree of antimicrobial activity with a low level of human toxicity. This review provides an overview of the history of the use of silver as an antimicrobial agent, its mechanism of action, and its clinical application in the field of megaendoprosthetics. The benefits of silver-coated prostheses could not be confirmed until now. However, a large number of retrospective studies suggest that the rate of periprosthetic infections could be reduced by using silver-coated megaprostheses.

Enhanced stability and metallic modification of polymeric and carbonaceous nanospheres through precursor engineering via a one-pot aqueous strategy assisted by iron ions

Solidified polymer nanospheres and the corresponding mesoporous carbon nanospheres incorporated with ultra-fine Fe3O4nanocrystals were fabricated by a one-pot aqueous route assisted by iron ions.