Surface Chemical Composition Research Articles

Elucidation of the Interplay between the Features of the Precursor and the Physicochemical Properties of “Core-Shell” Hierarchical Carbon Nitride Electrocatalysts for the Oxygen Reduction Reaction

The oxygen reduction reaction (ORR) is a major bottleneck in the operation of proton-exchange membrane fuel cells (PEMFCs) since it introduces large overpotentials (no less than 250-300 mV), which degrade significantly the energy conversion efficiency of the device. In addition, the electrocatalysts (ECs) yielding the lowest ORR overpotentials in the acidic environment found at the PEMFC cathode are based on Pt, a very scarce critical raw material (CRM). Pt raises concerns as it might trigger serious supply bottlenecks in the event of a practical widespread implementation of PEMFCs in the framework of today’s energy transition. Hence, the development of high-performing and durable ECs for the ORR is a major stepping stone towards the large-scale rollout of PEMFCs.In our research group a new breakthrough approach has been devised for the synthesis of ORR ECs, that is completely different form the preparation routes that are commonly adopted in the state of the art [1, 2]. Briefly, the approach consists in the pyrolysis and subsequent treatment of a precursor obtained by coupling suitable carbon species/sacrificial supports with a zeolitic inorganic-organic polymer electrolyte (Z-IOPE). The latter comprises anionic complexes including the Pt “catalyst” and other “co-catalysts”, which are bridged by organic binders [1,2].On one hand, the proposed approach has already shown its potential to yield ECs exhibiting a performance and durability improved with respect to Pt/C benchmark ECs. On the other hand, the proposed approach is extremely flexible, especially with respect to the synthesis of the initial EC precursor. In principle, it is possible to modulate a number of crucial features of such EC precursor, with a particular reference to: (i) the chemical composition (e.g., in terms of Pt, other “co-catalysts” and N; the latter plays a crucial role to stabilize the active sites into “coordination nests” on the EC surface, raising durability); and (ii) the morphology, that can be “templated” on suitable species (e.g., carbon species, sacrificial supports). The very flexibility of the proposed synthetic process needs to be leveraged appropriately to maximize the performance of the final ORR ECs, at the same time minimizing the efforts wasted on approaches with a low development potential.Herein it is elucidated how the modulation in the parameters involved in the synthesis of the EC precursor (e.g., the binder and the approaches to couple the Z-IOPE with the support) impact the physicochemical and electrochemical properties of the final ECs, with a particular reference to the chemical composition, morphology and distribution of the ORR active sites. An extensive characterization of the final ECs is carried out. Inductively-coupled plasma atomic emission spectroscopy (ICP-AES) and microanalysis are adopted to determine the bulk chemical composition. Near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) is used to elucidate the surface chemical composition and the chemical states of the surface elements. Ultra-high resolution scanning electron microscopy (UHR-SEM) and transmission electron microscopy (TEM) allow for the elucidation of EC morphology. The porosimetric features are probed by automatic gas adsorption instrumentations. Wide-angle X-ray diffraction (WAXD) is crucial to resolve the crystal structure. Cyclic voltammetry with the rotating ring-disk electrode method (CV-TF-RRDE) is used to clarify the “ex-situ” electrochemical performance and ORR reaction mechanism. Finally, the most promising ECs are used in the fabrication of single PEMFCs, that are tested as a function of the operating conditions.It is revealed that, in comparison with the Pt/C benchamark, some ECs are characterized by a much higher intrinsic kinetic performance due to the electronic and bifunctional effects bestowed by the carbon nitride support and the «co-catalysts». Finally, the binder has a marked effect on the stoichiometry, size, and distribution of the PtMx aggregates bearing the active sites.

Enhanced Oxygen Evolution Reaction Activity of Fe-Doped Lithium Nickel-Based Metal Oxide through Modification of Nickel Oxidation State

The oxygen evolution reaction (OER) involves the four-electron transfer process of water oxidation to produce oxygen gas and protons. However, this reaction is kinetically sluggish and requires high overpotential compared to hydrogen evolution reaction (HER). Herein, we have fabricated Fe-doped LiNiO2 using electrospray deposition (ESD) technique. With this technique, we can modify the electronic structure of LiNiO2 by controlling amounts of Fe, and the morphology can be controlled with various parameters such as applied voltage, spray rate, and substrate temperature. The synergistic effect of iron doping can modify the electronic structure of the surface Ni ions and increase oxidation state of Ni2+ to Ni3+. Through this oxidation state change, Ni becomes more electrophilic and then adsorbed oxygen in the M – O step, which is considered as rate-determining step in OER, easily reacts with OH ions. In electrochemical analysis, the optimized Fe-doped LiNiO2 showed improved OER performance compared to LiNiO2. The surface chemical compositions of the Fe-doped LiNiO2 electrode were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). From our result, we can improve OER performance and stability with simple control of ESD technique parameters and electronic structure modification by Fe doping.

Lysosome‐Inspired Enclosed and Deep Surface Decontamination Strategy for Management of Peri‐Implant Infections

AbstractSurface decontamination is a crucial step in the treatment of peri‐implant infections, yet deep and mild cleansing techniques are lacking. Drawing inspiration from lysosomes, which enclose hydrolytic enzymes within their membranes to safely and effectively degrade organics within cells, the use of a near‐infrared (NIR)/H2O2‐activated TiO2‐x‐Alginate system for enclosed and deep surface decontamination is proposed. It leverages synergistically generated reactive oxygen species (ROS) to eliminate bacterial contaminants, mimicking the process of lysosomal digestion. By employing Ca2+ spray‐induced surface gelation, the TiO2‐x and H2O2 around implant surface are enclosed, creating a membrane‐like isolation. This system robustly degrades extracellular polymeric substances (EPS)‐mimic biomacromolecules, removes organic residues (OR) from both mono‐species (Staphylococcus aureus and Porphyromonas gingivalis) biofilm and polymicrobial ex vivo biofilm of peri‐implantitis, while avoiding healthy tissue irritation. Encouragingly, this system has also demonstrated powerful decontamination capabilities when applied to clinic‐retrieved infected dental implants. Notably, this technique restores the pristine implant surface topography and chemical composition, which are further revealed by the minimal inflammation response observed in macrophage culture and subcutaneous implantation. Consequently, osteoblast functionalities are effectively restored, and re‐osseointegration in vivo is also greatly enhanced. Thus, this deep decontamination strategy holds great promise for clinical applications in managing peri‐implant infections.

Synthesis and characterisation of lead-magnesium-boron nanocomposite for radiation shielding application.

There is a need for the replacement of toxic lead with nontoxic materials in radiation shielding applications. Instead of pure lead, lead mixed compounds/mixtures/alloys are considered to be less toxic and hence preferred for radiation shielding purposes. The compounds with magnesium are said to be having good magnetic and mechanical properties. Meanwhile, the boron element avoids secondary radiation and absorbs neutrons. The compound which is a mixture of lead, magnesium and boron is expected to be a good shielding material for radiation for X-rays/gamma rays. Hence in the present study, we have synthesised the lead-magnesium-boron (LMB) nanocomposites (NCs) using the green synthesis approach for the first time. LMB is synthesised by solution combustion method using Aloe vera as a reducing agent. The synthesised NCs are characterised using well-known characterisation techniques. Powder X-ray diffraction confirmed the formation of multi-phase LMB NCs, and average crystal size is found to be 13-15nm. Surface morphology and chemical composition are affirmed by SEM and EDX. The optical energy gap is found to be 1.87eV. FTIR confirmed the functional groups. X-rays/gamma rays, neutrons and bremsstrahlung radiation shielding efficiency are measured by experimental and theoretical, compared with conventional shielding materials. LMB NCs have proved to be efficient. Hence, LMB NCs proved to be potential in X-rays/gamma rays, neutrons and bremsstrahlung radiation shielding.

Structural magnetic and electrochemical properties of tetragonal α1-LiVOPO4 synthesis by sol-gel method as a cathode material for Li-ions batteries

In this particular investigation, the tetragonal α1-LiVOPO4 cathode material was successfully synthesized employing a sol-gel technique for the first time. The X-ray diffraction studies have confirmed the tetragonal structure with the space group P4/nmm. A range of characterizations, such as Fourier-transformed infrared spectroscopy and magnetic measurements, have been executed. The Scanning Electron Microscopy (SEM) coupled with Energy-Dispersive X-ray Spectroscopy (EDS) has been employed to assess the surface morphology and chemical composition of the sample produced. Additionally, electrochemical measurements, including galvanostatic charge-discharge, cyclic voltammetry, and Electrochemical Impedance Spectroscopy (EIS), have been conducted. The material has demonstrated an outstanding electrochemical performance, which can be attributed to the facile diffusion of Li+ ions along a two-dimensional pathway and the efficient charge transfer process.

Timeliness of Cold Plasma Treatment on Surface Modification of Polylactic Acid Fibers

Polylactic acid (PLA) fiber is a promising material due to its biodegradability, excellent mechanical properties, and good biocompatibility. However, its surface is chemically inert and has poor interfacial compatibility with gases due to a low number of polar groups. To address this issue, this study utilized cold plasma and solution wet pretreatment with varying pH levels to modify the surface of PLA fibers. The use of solution wet pretreatment helped mitigate the negative effects of plasma treatment on the timeliness, which improved the long-term stability of the PLA fibers surface properties. These modifications increased the suitability of the material for various applications. The surface of PLA fibers was modified using cold plasma and wet pretreatment with pH solutions of varying degrees. The surface chemical composition and hydrophilicity of modified fibers remained relatively stable for up to 120 days. Conversely, unpretreated fibers reverted to their original chemically inert state after 14 days.

Comparative study of anodizing and chromate conversion coatings in enhancing the wear and corrosion properties of 6063 Al alloy

ABSTRACT The present study compares the corrosion and tribological performance of anodic oxide (AO) and chromate conversion (CC) coatings deposited on 6063-T6 aluminum alloy. The goal is to determine how these treatments benefit the performance of the underneath substrate. The corrosion protection properties of the coatings were evaluated by potentiodynamic polarization measurement in 3.5 wt. % NaCl solution. The friction and sliding wear behavior of coatings were studied by pin-on-disk test and their erosion behavior was examined by air jet solid particle erosion test. The surface structure, chemical composition, roughness, wettability, and hardness of specimens were also characterized. The results showed that the AO coating with porous surface morphology was found to be thicker, rougher, and harder along with greater wettability, when compared to CC coating. Furthermore, the AO coating with polarization resistance of 6.64 × 103 Ω.cm2 enhanced the corrosion resistance of the substrate more than 8 times. In addition, the AO coating under dry and wet sliding conditions reduced the aluminum alloy substrate wear rate by about 80% and 52%, respectively. However, due to being more brittle, the AO coating lost more weight than the CC coating during the solid particle erosion test.

Advancing biomedical substrate engineering: An eco-friendly route for synthesizing micro- and nanotextures on 3D printed Ti–6Al–4V

This study investigates the impact of a combined approach involving sandblasting and electrochemical surface treatment using a deep eutectic solvent Ethaline, a eutectic mixture of choline chloride and ethylene glycol, on the surface characteristics of Ti–6Al–4V biomedical substrates fabricated through direct selective laser melting (DSLM). Research has focused on surface morphology, topography, chemical composition, and cell adhesion. The novel approach demonstrated the ability to create a hierarchical surface structure with both micro and nanopatterns. The rough edges resulting from the sandblasting process were effectively smoothed through subsequent electrochemical processing. Additionally, the issue of residual sand particles, which commonly arise in sandblasting procedures, was successfully addressed with the new method. The results indicated that Ti alloy samples subjected to sandblasting and electrochemical treatment in Ethaline exhibited improved surface hydrophilicity. In-vitro cell adhesion tests confirmed the potential for bio-inspired properties of DSLM-printed Ti–6Al–4V biomedical substrates achieved through the combination of sandblasting and electrochemical processing in Ethaline.

Development of a novel PPTA/cellulose composite insulation paper with low dielectric constant and improved mechanical properties by BTCA crosslinking

AbstractThis study investigates the effect of 1,2,3,4‐butane tetracarboxylic acid (BTCA) crosslinking treatment on the electrical properties of poly‐p‐phenylene terephthalate (PPTA)/cellulose insulation paper to prepare a novel composite insulation paper with low dielectric constant and good electrical performance. Three‐layer PPTA/cellulose composite paper crosslinked by BTCA under various conditions, composite paper without crosslinking, directly mixed composite paper, and conventional Kraft paper are prepared. The morphology and surface chemical composition of the paper samples are characterized. Dielectric, mechanical, and thermal properties are investigated. Results show that the BTCA concentration of 0.2 mol L−1 with a 180°C curing temperature is the relatively superior crosslinking condition to prepare a novel composite with low dielectric constant and good comprehensive performance. The dielectric constant and loss of the novel composite paper decrease to 3.21 and 0.392 at 50 Hz. The tensile strength of the BTCA crosslinked three‐layer PPTA/cellulose composite paper (thickness: 130 μm) has reached 10.01 kN m−1, increased by 41.6% than the directly mixed composite paper. The novel BTCA crosslinked composite paper also shows improved thermal stability. The BTCA crosslinking proves to be a promising method to improve the dielectric properties and electrical performance of the PPTA/cellulose composite paper.

One-step synthesis of Pt-Nd co-doped Ti/SnO2-Sb nanosphere electrodes used to degrade nitrobenzene.

Ti/SnO2-Sb electrodes possess high catalytic activity and efficiently degrade nitrobenzene (NB); however, their low service life limits their wide application. In this study, we used one-step hydrothermal synthesis to successfully prepare Pt-Nd co-doped Ti/SnO2-Sb nanosphere electrodes. Scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were applied to characterize the surface morphology, microstructure, and chemical composition of the electrodes, respectively. The electrochemical activity and stability of the electrodes were characterized via linear sweep and cyclic voltammetry, electrochemical impedance spectroscopy, and an accelerated service life test; their performance for NB degradation was also studied. An appropriate amount of Pt-Nd co-doping refined the average grain size of SnO2 and formed a uniform and compact coating on the electrode surface. The oxygen evolution potential, total voltammetric charge, and electron transfer resistance of the Ti/SnO2-Sb-Nd-Pt electrodes were 1.88 V, 3.77 mC/cm2, and 11.50 Ω, respectively. Hydroxy radical was the main active radical species during the electrolytic degradation of nitrobenzene with Ti/SnO2-Sb-Nd-Pt. After Pt-Nd co-doping, the accelerated service life of the electrodes was extended from 8.0 min to 78.2 h (500 mA/cm2); although the NB degradation rate decreased from 94.1 to 80.6%, the total amount of theoretical catalytic degradation of NB in the effective working time increased from 17.4 to 8754.1 mg/cm2. These findings reveal good application potential for the electrodes and provide a reference for developing efficient and stable electrode materials.

Effect of sodium hypochlorite and ethylenediaminotetraacetic acid activated by laser and ultrasonic energy on surface morphology and chemical composition of intracanal dentin.

The aim of the study was to evaluate the structural and chemical changes in intracanal dentin after root canal irrigation with sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) using additional activation with a novel Er:YAG Shock Wave-Enhanced Emission Photoacoustic Streaming (SWEEPS), ultrasonic irrigation (UI), and Nd:YAG irradiation. Root canals of extracted human premolars were instrumented with distilled water and distributed into groups according to the irrigation protocol used: Group 1: conventional needle irrigation (CI) with 3% NaOCl; group 2: CI with 15% EDTA; and group 3: CI with NaOCl+EDTA. In group 4, root canals were irrigated with NaOCl+EDTA+NaOCl using the following techniques: CI (group 4A), SWEEPS (group 4B), UI (group 4C). In group 4D, root canals were finally irradiated with Nd:YAG laser. After the irrigation, the intracanal dentin sample was collected and analyzed using spectroscope with a Fourier transformation of infrared spectrum in Attenuated total reflection technique (FTIR-ATR) to calculate apatite/collagen ratio. Scanning electron microscopy (SEM) and energy dispersive x-ray spectrometry (EDS) were used to determine its chemical composition. FTIR-ATR showed no significant difference in the phosphate/amid I ratio between the control and the experimental groups (p > 0.05). SWEEPS and UI of NaOCl+EDTA+NaOCl caused the most pronounced decrease of Ca and P (p < 0.05) value compared to CI and control group, and canal wall erosion. SWEEPS and UI of NaOCl+EDTA+NaOCl caused the most pronounced decrease of Ca and P value and significant canal wall erosion. However, no difference in phosphate/amide ratio was reported among groups. RESEARCH HIGHLIGHTS: SWEEPS and UI of NaOCl+EDTA+NaOCl caused the most pronounced decrease of Ca and P values and significant canal wall erosion. There was no difference in phosphate/amide ratio among the irrigation protocols.

Investigating the contribution of grown new particles to cloud condensation nuclei with largely varying preexisting particles – Part 1: Observational data analysis

Abstract. This study employed multiple techniques to investigate the contribution of grown new particles to the number concentration of cloud condensation nuclei (CCN) at various supersaturation (SS) levels at a rural mountain site in the North China Plain from 29 June to 14 July 2019. On 8 new particle formation (NPF) days, the total particle number concentrations (Ncn) were 8.4 ± 6.1×103 cm−3, which was substantially higher compared to 4.7 ± 2.6×103 cm−3 on non-NPF days. However, the CCN concentration (Nccn) at 0.2 % SS and 0.4 % SS on the NPF days was significantly lower than those observed on non-NPF days (p&lt;0.05). This was due to the lower cloud activation efficiency of preexisting particles resulting from organic vapor condensation and smaller number concentrations of preexisting particles on NPF days. A case-by-case examination showed that the grown new particles only yielded a detectable contribution to Nccn at 0.4 % SS and 1.0 % SS during the NPF event on 1 July 2019, accounting for 12 % ± 11 % and 23 % ± 12 % of Nccn, respectively. The increased Nccn during two other NPF events and at 0.2 % SS on 1 July 2019 were detectable but determined mainly by varying preexisting particles rather than grown new particles. In addition, the hygroscopicity parameter values, concentrations of inorganic and organic particulate components, and surface chemical composition of different sized particles were analyzed in terms of chemical drivers to grow new particles. The results showed that the grown new particles via organic vapor condensation generally had no detectable contribution to Nccn but incidentally did. However, this conclusion was drawn from a small size of observational data, leaving more observations, particularly long-term observations and the growth of preexisting particles to the CCN required size, needed for further investigation.

2D Ti3C2Tx modified with nano-AgPNPs antioxidant constructed hierarchical interface for high-throughput oily wastewater separation

Over-exploitation of fossil energy has led to the formation of enormous amounts of oily wastewater, which is increasingly polluting the environment of water bodies. The Ti3C2Tx-modified separation material is limited by surface roughness and surface chemical composition, and the permeation flux decreases significantly during continuous testing. In this study, silver-loaded polydopamine nanospheres (nano-AgPNPs) as antioxidants were prepared by in-situ reduction from Ag+ ions and polydopamine nanospheres, and then they self-assembled with Ti3C2Tx nanosheets to obtain hierarchical micro-nano structural nano-AgPNPs modified Ti3C2Tx [(AgPNPs)xT (x = 0.25, 0.5, 0.75, and 1)]. Because of their strong reduction properties, nano-AgPNPs antioxidants can effectively protect the active edges of Ti3C2Tx from dissolved oxygen, and greatly improve the oxidation resistance of Ti3C2Tx nanosheets, with no significant changes in morphology and physical phase after long-term placement. (AgPNPs)xT formed underwater oleophobic interfaces with the hierarchical structure on polyurethane (PU) sponge to prepare (AgPNPs)xT@PU separation sponges. Among them, (AgPNPs)0.5T@PU sponge showed the highest comprehensive performance with separation efficiency higher than 99.6% for various oil-water mixtures, especially high-throughput and permeation flux up to 247,787 L m–2 h–1 for cyclohexane-water mixtures. In addition, nano-AgPNPs greatly broadened the layer spacing of Ti3C2Tx and can form a functionalized interface of modified Ti3C2Tx on polyamide (PA) membrane and provide additional permeation channels, which enabled the (AgPNPs)0.5T@PA membrane to have excellent toluene-water emulsion separation efficiency up to 99.6%.

α-Fe2O3 derived from metal-organic frameworks as high performance sensing materials for acetone detection

High-performance gas sensors are critical for monitoring the environment, detecting health problems and ensuring safety. Metal-organic frameworks (MOFs) are considered promising gas-sensitive materials due to their elevated porosity, large specific surface area, and various morphologies. The conversion of MOFs into metal oxides can be achieved by oxidation and roasting processes, where the structure and surface chemical composition are significantly affected by the temperature at which the roasting is performed. The structures of α-Fe2O3 have been controlled by optimizing the heat treatment temperatures (350 °C, 400 °C, 450 °C and 500 °C) using MIL-100(Fe) as template which was synthesized using a hydrothermal method with reduced iron powder and 1,3,5-BTC as precursors. The gas sensitivity tests revealed that the α-Fe2O3 material obtained through annealing at 400 °C exhibited excellent sensitivity to acetone，which can be attributed to the combination of its porous structure and oxygen vacancy defects. Gas-sensitive materials, synthesized using MOFs as a template with meticulous tuning of the calcination temperature, exhibit exceptional properties. These materials hold great potential for advancing sensor materials in the field of gas sensor technology.

Comparative study of corrosion inhibition effect on steel rebars in carbonated concrete-pore-solutions: Tolyltriazole vs. sodium phosphate

Concrete structures exposed to carbonated environments are susceptible to steel reinforcement corrosion, leading to structural deterioration and reduced service life. In this research, the effectiveness of two commonly used corrosion inhibitors, tolyltriazole (TTA) and trisodium phosphate (TSP), in carbonated concrete pore (CCP) solutions was compared to enhance the corrosion resistance of steel rebar. The study involved the preparation of simulated carbonated concrete pore solutions to mimic the environment of concrete structures exposed to carbonation. The concrete-pore solutions were simulated by immersing the specimens in a carbonation chamber. Electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP) tests were performed to evaluate the corrosion resistance of the steel rebars. The corrosion potential, polarization resistance, and corrosion current density were measured and compared among the different groups. Additionally, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) analyses were conducted to examine the surface morphology, chemical composition and corrosion products formed on the steel rebars. The CCP solution with equal concentrations of TTA and TSP demonstrated the highest corrosion resistance and corrosion inhibition efficiency. TTA and TSP effectively inhibit pitting corrosion of steel in CCP solution, according to SEM, EDS, and XPS analyses. The findings suggested that there is a competitive interaction between phosphate ions and TTA on the steel surface, leading to an antagonistic impact on corrosion inhibition. It was suggested that the [Fen(TTA)p]m complex would produce a protective coating on the surface of steel, which would act as a synergistic inhibitor.

The influence of reconstructive transformation from micro-/nanostructured copper(II) hydroxide to copper oxides as electrodes for high-performance supercapacitors

Copper(II) hydroxides, particularly Cu(OH)2 micro/nanostructures, are metastable under normal conditions. Notably, Cu(OH)2 micro-/nanostructures undergo structural restructuring and phase transitions during electrochemical reactions. In this study, the effects of electrolyte concentration, current, and duration of the electrochemical reaction on the crystal morphology, structure, and chemical composition of Cu(OH)2 micro-/nanostructured composite electrodes were investigated by anodic oxidation. The results showed that a Cu(OH)2 nanorod-like structure was formed on the electrode surface in the KOH electrolyte at a concentration of 3 M, while Cu2O crystals were synthesized at electrolyte concentrations of 1 M and 6 M. The growth current of the Cu(OH)2 nanorod-like structures ranged from 30 mA to 70 mA. At a reaction time of 10–80 min, the micro-/nanostructure of the electrode surface changed from an unstable Cu2O to a stable CuO phase through metastable Cu(OH)2. The synthesized Cu(OH)2 composite electrode exhibited an area-specific capacitance of 2777 mF cm–2 at a scanning rate of 10 mV s–1. In particular, the relationships between the surface morphology, structure, and chemical composition of the Cu(OH)2 composite electrode and the electrolyte concentration during cyclic voltammetry were studied. The results showed that in the KOH electrolyte at 1 M concentration, the Cu(OH)2 micro-/nanostructure transformed into Cu2O under electrochemical action, Cu(OH)2 transformed into both the Cu2O and CuO phases at 3 M electrolyte concentration, and Cu(OH)2 transformed into the CuO phase when the electrolyte concentration was increased to 6 M, indicating that the concentration of the alkaline electrolyte had a significant effect on the reconstruction and phase transformation of the Cu(OH)2 micro-/nanostructures. These results are expected to address the pressing issues in the application of metastable Cu(OH)2 micro/nanostructured composite electrodes in high-performance supercapacitors, such as insufficient energy, mass transfer, and structural instability.

Impact of the Sc3+/In3+ co-substitution on the structural, magnetic, and microwave characteristics of Co0.5Ni0.5Fe2O4 nanospinel ferrites

In this article, In3+ and Sc3+ ions dual-substituted NiCo nanospinel ferrites (ScIn→CoNiFe2O4 NSFs) have been synthesized through citrate-gel auto combustion method to investigate the effect of In3+ and Sc3+ ions on magnetic, and microwave characteristics. The following techniques TEM, SEM, EDX, and XRD were applied to characterize surface morphology, chemical composition, phase identification, and crystallinity of products, respectively. The XRD verified a phase formation of spinel structure with a minor amount of Sc2O3 was observed for products having x ≥ 0.04. The average crystal size (DXRD) of the products was estimated within the 33–68 nm range using the Scherrer equation. SEM and HR-TEM analyses exhibited accumulating sphere-shaped particles. By fitting the room-temperature spectra obtained from Mössbauer spectroscopy (Moss), Hyperfine interactions were determined. The cation distribution shows that there is a migration of In3+ ions in the lattice in an A→B direction with increasing concentrations while the B site is preferred by the larger Sc+3. M−H plots for 300 and 10 K illustrated all products carried out with a ferrimagnetic character. An enhancement in saturation magnetization (Ms) was remarked with Sc–In doping ratio up to 0.04 and thereafter a drop as the Sc–In concentration increased. The tendency in Ms values might be described by correlating it to the cation distribution amongst Oh and Td (octahedral and tetrahedral, respectively) sublattices. Temperature-dependent magnetization measurements were also investigated, which further confirmed the maintenance of the ferrimagnetic character throughout the temperature range 10–300 K. The peculiarities of the microwave properties have been analyzed by the measured S-parameters in the range of 6–18 GHz. It was assumed that the energy losses due to reflection are a combination of electrical and magnetic losses due to polarization processes and magnetization reversal processes in the region of inter-resonant processes. The average value of the reflection coefficient is −14.48 … −14.24 dB. A significant attenuation of the reflected wave energy opens up broad prospects for practical applications as coatings for providing electromagnetic compatibility.

Microbial colonization patterns and biodegradation of petrochemical and biodegradable plastics in lake waters: insights from a field experiment.

Once dispersed in water, plastic materials become promptly colonized by biofilm-forming microorganisms, commonly known as plastisphere. By combining DNA sequencing and Confocal Laser Scanning Microscopy (CLSM), we investigated the plastisphere colonization patterns following exposure to natural lake waters (up to 77 days) of either petrochemical or biodegradable plastic materials (low density polyethylene - LDPE, polyethylene terephthalate - PET, polylactic acid - PLA, and the starch-based MaterBi® - Mb) in comparison to planktonic community composition. Chemical composition, water wettability, and morphology of plastic surfaces were evaluated, through Transform Infrared Spectroscopy (ATR-FTIR), Scanning Electron Microscopy (SEM), and static contact angle analysis, to assess the possible effects of microbial colonization and biodegradation activity. The phylogenetic composition of plastisphere and planktonic communities was notably different. Pioneering microbial colonisers, likely selected from lake waters, were found associated with all plastic materials, along with a core of more than 30 abundant bacterial families associated with all polymers. The different plastic materials, either derived from petrochemical hydrocarbons (i.e., LDPE and PET) or biodegradable (PLA and Mb), were used by opportunistic aquatic microorganisms as adhesion surfaces rather than carbon sources. The Mb-associated microorganisms (i.e. mostly members of the family Burkholderiaceae) were likely able to degrade the starch residues on the polymer surfaces, although the Mb matrix maintained its original chemical structure and morphology. Overall, our findings provide insights into the complex interactions between aquatic microorganisms and plastic materials found in lake waters, highlighting the importance of understanding the plastisphere dynamics to better manage the fate of plastic debris in the environment.

Hydrofluoric acid-free etched MAX on 3D-printed nanocarbon electrode for photoelectrochemical hydrogen production

MXenes have emerged as a promising material for a disparate range of photo-electrochemical conversion and energy storage devices. However, most reported synthesis process involves hydrofluoric acid (HF) and fluoride-based compounds. HF severe toxicity persists impediment to the scalable production and fabrication of MXenes. Thus, fluoride-free protocols are currently being explored. Here, we demonstrate a novel fluoride-free protocol for the etching of the MAX phase (Ti3AlC2) utilizing an acidic mixture of nitric acid, phosphoric acid, and acetic acid. Such acidic etching modulated the electronic structure and chemical composition of the MAX surface converting it into MAX-derived flower-like titanium phosphate and titanium oxide which boosts its photo-electrochemical properties. The photo-electrochemical hydrogen evolution reaction is evaluated using 3D-printed and screen-printed carbon electrodes exposing under visible light illumination with 365 and 460 nm wavelengths. Such HF-free etched Ti3AlC2 MAX and the MAX-derived flower-like titanium phosphate and titanium oxide coated 3D-printed nanocarbon and screen-printed carbon electrodes demonstrate a novel process to be applied for an energy conversion application. This work will pave the way to etch other MAX phases through an environment-friendly and easy-handling technique that is to be used beyond photo-electrochemical applications.

Plasma Immersion Ion Implantation of a Fe-Mn-C Based Steel for Biomedical Applications: Effect of Gases and Treatment Times on the Surface Properties

Current research on biodegradable iron-based alloys mainly focuses at regulating the material degradation rate, as well as its biological behavior, especially from the point of view of the hemocompatibility and cytocompatibility. In fact, fine-tuning of the surface roughness, morphology and chemical composition can improve the functional response of the material. For that purpose, a surface modification strategy, namely plasma immersion ion implantation (PIII), is proposed to perform the selective modification of surface properties without affecting the bulk ones. In this work, the influence of treatment time (timp = 15, 60 and 120 min.) and implanted species (O, N or C) on the surface properties of a Fe-13Mn-1.2C resorbable alloy was investigated. The findings demonstrated that varying the process gas and the exposition time led to a variety of topographies, surface energies and chemical compositions. XPS analyses and depth profiles clearly showed the impact of the process parameters on the surface features and element distribution, due to implanted species penetration into the alloy. The implanted samples showed a delayed clotting time, thus a better hemocompatibility. In contrast, nitrogen-treated surfaces displayed a more pronounced hemolytic behavior, whereas oxygen and methane did not. PIII implantation appears to be a versatile solution for fine-tuning surface topography, composition and biological properties, making the process promising for the improvement of metallic biodegradable vascular implants.