Microstructure–mechanical properties of Ag0/Au0 doped K–Mg–Al–Si–O–F glass-ceramics

In understanding the catalytic efficacy of silver (Ag⁰) and gold (Au⁰) nanoparticles (NPs) on glass-ceramic (GC) crystallization, the microstructure–machinability correlation of a SiO₂–MgO–Al₂O₃–B₂O₃–K₂O–MgF₂ system is studied. The thermal parameters viz., glass transition temperature (T_g) and crystallization temperature (T_c) were extensively changed by varying NPs (in situ or ex situ). Tc was found to be increased (T_c = 870–875 °C) by 90–110 °C when ex situ NPs were present in the glass system. Under controlled heat-treatment at 950 ± 10 °C, the glasses were converted into glass-ceramics with the predominant presence of crystalline phase (XRD) fluorophlogopite mica, [KMg₃(AlSi₃O₁₀)F₂]. Along with the secondary phase enstatite (MgSiO₃), the presence of Ag and Au particles (FCC system) were identified by XRD. A microstructure containing spherical crystallite precipitates (∼50–400 nm) has been observed through FESEM in in situ doped GCs. An ex situ Ag doped GC matrix composed of rock-like and plate-like crystallites mostly of size 1–3 μm ensured its superior machinability. Vicker''s and Knoop microhardness of in situ doped GCs were estimated within the range 4.45–4.61 GPa which is reduced to 4.21–4.34 GPa in the ex situ Ag system. Machinability of GCs was found to be in the order, ex situ Ag > ex situ Au ∼ in situ Ag > in situ Au. Thus, the ex situ Ag/Au doped SiO₂–MgO–Al₂O₃–B₂O₃–K₂O–MgF₂ GC has potential for use as a machinable glass-ceramic.

In understanding the catalytic efficacy of silver (Ag⁰) and gold (Au⁰) nanoparticles (NPs) on glass-ceramic (GC) crystallization, the microstructure–machinability correlation of a SiO₂–MgO–Al₂O₃–B₂O₃–K₂O–MgF₂ system is studied.     

Cu–Ag alloy for engineering properties and applications based on the LSPR of metal nanoparticles

Efficient generation of high-energy hot carriers from the localized surface plasmon resonance (LSPR) of noble metal (Ag, Au and Cu) nanoparticles is fundamental to many applications based on LSPR, such as photovoltaics and photocatalysis. Theoretically, intra- and inter-band electron transitions in metal nanoparticles are two important channels for the non-radiative decay of LSPR, which determine the generation rate and energy of hot carriers. Therefore, on the basis of first-principles calculations and Drude theory, in this work we explore the potential role of alloying Ag with Cu in modulating the generation rate and energy of hot carriers by studying the intra- and inter-band electron transitions in Cu, Ag and Cu–Ag alloys. It is meaningful to find that the d-sp inter-band electron transition rates are notably increased in Cu–Ag alloys. In particular, the inter-band electron transition rates of Cu_0.5Ag_0.5 become larger than that of single Cu and Ag across the whole energy range between 1.5 and 3.2 eV. In contrast, intra-band electron transition rates of Cu–Ag alloys become smaller than that of single Cu and Ag. Because the intra-band electron transitions mainly contribute to the resistive loss in metals, which finally results in a thermal effect rather than high-energy hot carriers, the reduction of intra-band electron transitions in Cu–Ag alloy is beneficial for the transforming the energy absorbed by LSPR into high-energy hot carriers through other non-radiative channels. These results indicate that alloying of Ag and Cu can effectively improve the generation rates of high-energy hot carriers through the inter-band electron transition, but decrease the resistive loss through intra-band transition of electrons, which should be used as a guide in optimizing the non-radiative decay processes of LSPR.

Alloying Ag with Cu can effectively improve the generation rates of high-energy hot carriers.     

Ti–Mn hydrogen storage alloys: from properties to applications

Efficient and safe storage of hydrogen is an important link in the process of hydrogen energy utilization. Hydrogen storage with hydrogen storage materials as the medium has the characteristics of high volumetric hydrogen storage density and good safety. Among many hydrogen storage materials, only rare earth-based and titanium-based hydrogen storage alloys have been applied thus far. In this work, current state-of-the-art research and applications of Ti–Mn hydrogen storage alloys are reviewed. Firstly, the hydrogen storage properties and regulation methods of binary to multicomponent Ti–Mn alloys are introduced. Then, the applications of Ti–Mn alloys in hydrogen storage, hydrogen compression and catalysis are discussed. Finally, the future research and development of Ti–Mn hydrogen storage alloys is proposed.

The hydrogen storage properties, regulation methods and applications of Ti–Mn hydrogen storage alloys were reviewed.     

Photocurable acrylate epoxy/ZnO–Ag nanocomposite coating: fabrication,mechanical and antibacterial properties

In this study, a UV-curable acrylate epoxy nanocomposite coating has been prepared by incorporation of ZnO–Ag hybrid nanoparticles. For this purpose, firstly ZnO–Ag hybrid nanoparticles were fabricated by a seed-mediated growth method. Then, these ZnO–Ag hybrid nanoparticles (2 wt%) were added into the UV-curable acrylate resin matrices. The photocuring process of nanocomposite was evaluated by various factors, such as the conversion of acrylate double bonds, pendulum hardness and gel fraction. Under the 4.8 s UV-exposure time for full crosslinking, the obtained data indicated that incorporation of ZnO–Ag nanohybrids into the coating matrix changed the crosslinking process of coating significantly. A mechanical teat indicated that the presence of nanohybrids in photocurable coating matrix enhanced its abrasion resistance from 98.7 to 131.6 L per mil (33.3%). The antibacterial test against E. coli over 7 h indicated that E. coli bacteria were killed totally by nanocomposite coating, whereas it was 2.6 × 10⁴ CFU mL⁻¹ for the neat coating without nanoparticles.

ZnO-Ag hybrid nanoparticles were fabricated by seed-mediated growth method and incorporated into the UV-curable acrylate resin matrice to form a composite. This improved the mechanical property of UV-cured coating and exhibited high antibacterial activity against E. coli.     

High-efficiency and durable V–Ti–Nb ternary catalyst prepared by a wet-solid mechanochemical method for sustainably producing acrylic acid via acetic acid–formaldehyde condensation

Based on the precise phase control V species adjustment of vanadium phosphorus oxides (VPOs), a series of metal oxides (Nb₂O₅, MoO₃, WO₃, and Bi₂O₃) were selected as modification agents to further enhance the catalytic activity and retain the excellent durability of VPO–TiO₂-based catalysts for the new procedure of producing acrylic acid via acetic acid–formaldehyde condensation. At an elevated liquid hourly space velocity (LHSV), the (AA + MA) selectivity reached 92.3% with a (MA + AA) formation rate of 63.8 μmol⁻¹ g_cat⁻¹ min⁻¹ over the Nb-decorated catalyst (catalyst VTi–Nb), and it maintained good durability for up to 100 h. The detailed characterization results of XRD, Raman, XPS, NH₃-TPD, CO₂-TPD, and H₂-TPR, demonstrated that the addition of Nb₂O₅ could observably enhance the catalytic efficiency of the VPO–TiO₂ catalyst. It not only improved the catalyst durability by enhancing prereduction of the V⁵⁺ species, but also enhanced the active site density to improve the catalytic activity.

High-efficiency and durable V–Ti–Nb ternary catalyst prepared by a wet-solid mechanochemical method to enhance efficient condensation of HAc/HCHO to AA/MA.     

Recovery of niobium and tantalum by solvent extraction from Sn–Ta–Nb mining tailings

The slag from the extraction processes of metals from their ores may contain valuable components that, if adequately recovered, can be reintroduced in the technological life cycle. This is the case for the material obtained in Penouta mines in the North of Spain. These mineral sites are a main source of tin obtained from cassiterite. The mineral is submitted to a pyrometallurgical process to separate tin, however cassiterite is not the only mineral present in the veins, and large amounts of other minerals are normally discarded, constituting the slag. In the present case, besides cassiterite, one of the most abundant minerals in the ore is columbo tantalite, the source of the strategic coltan. In this work the raw material (slag) has been treated by acid leaching, using HF/H₂SO₄ as the leaching agent. Then liquid–liquid extraction of Nb and Ta was performed, with Cyanex®923 extractant, so that both metals were obtained separately. Then they were precipitated from the corresponding aqeuous solution, and calcined in order to yield Nb₂O₅ of 98.5% purity and tantalum salt, after calcination and purification, of 97.3% purity. The process described in this work opens a possibility to produce high quality materials that are considered critical by the EU from alternative sources exempt of criticality factors.

The slag from the extraction processes of metals from their ores may contain valuable components that, if adequately recovered, can be reintroduced in the technological life cycle.     

Comparative investigations of in vitro and in vivo bioactivity of titanium vs. Ti–24Nb–4Zr–8Sn alloy before and after sandblasting and acid etching

To avoid the failure of clinical surgery due to “stress shielding” and the loosening of an implant, a new type of alloy, Ti–24Nb–4Zr–8Sn (TNZS), with a low Young''s modulus acted as a new implant material in this work. Meanwhile, the surface characteristics, MC3T3-E1 cell behavior and in vivo osseointegration of the titanium and TNZS before and after sandblasting and acid etching were studied comparatively. TNZS and Ti had the same microstructure based on the transmission electron microscopy results. Meanwhile, the TNZS alloy had a lower Young''s modulus and surface nanohardness compared with pure titanium. However, the corrosion resistance of Ti was better than that of the TNZS sample in simulated body fluid solution. In addition, the TNZS alloy after sandblasting and acid etching (SLATNZS) had excellent cell adhesion, proliferation, differentiation, ALP activity and in vivo osseointegration ability such as there being almost no soft tissue as compared with other implants. Based on the current results, the new type of Ti–24Nb–4Zr–8Sn alloy showed good potential and promising application prospects in its biochemical aspects.

To avoid the failure of clinical surgery due to “stress shielding” and the loosening of an implant, a new type of alloy, Ti–24Nb–4Zr–8Sn (TNZS), with a low Young''s modulus acted as a new implant material in this work.     

A molecular dynamics study on the mechanical properties of Fe–Ni alloy nanowires and their temperature dependence

Fe–Ni alloy nanowires are widely used in high-density magnetic memories and catalysts due to their unique magnetic and electrochemical properties. Understanding the deformation mechanism and mechanical property of Fe–Ni alloy nanowires is of great importance for the development of devices. However, the detailed deformation mechanism of the alloy nanowires at different temperatures is unclear. Herein, the deformation mechanism of Fe–Ni alloy nanowires and their mechanical properties were investigated via the molecular dynamics simulation method. It was found that the local atomic pressure fluctuation of the Fe–Ni alloy nanowire surface became more prominent with an increase in the Ni content. At low temperature conditions (<50 K), the plastic deformation mechanism of the Fe–Ni alloy nanowires switched from the twinning mechanism to the dislocation slip mechanism with the increase in the Ni content from 0.5 at% to 8.0 at%. In the temperature range of 50–800 K, the dislocation slip mechanism dominated the deformation. Simulation results indicated that there was a significant linear relationship between the Ni content, temperature, and ultimate stress in the temperature range of 50–800 K. Our research revealed the association between the deformation mechanism and temperature in Fe–Ni alloy nanowires, which may facilitate new alloy nanowire designs.

Deformation mechanism and mechanical property of Fe–Ni alloy nanowires are investigated through molecular dynamics simulation method.     

Sol–gel-assisted micro-arc oxidation synthesis and characterization of a hierarchically rough structured Ta–Sr coating for biomaterials

Tantalum (Ta) is an element with high chemical stability and ductility that is used in orthopedic biomaterials. When utilized, it can produce a bioactive surface and enhance cell–material interactions, but currently, there exist scarce effective methods to introduce the Ta element onto the surface of implants. This work reported a sol–gel-assisted approach combined with micro-arc oxidation (MAO) to introduce Ta onto the surface of the titanium (TC4) substrate. Specifically, this technique produced a substrate with a hierarchically rough structured topography and introduced strontium ions into the film. The films were uniform and continuous with numerous crater-like micropores. Compared with the TC4 sample (196 ± 35 nm), the roughness of Ta (734 ± 51 nm) and Ta–Sr (728 ± 85 nm) films was significantly higher, and both films (Ta and Ta–Sr) showed increased hydrophilicity when compared with TC4, promoting cell attachment. Additionally, the in vitro experiments indicated that Ta and Ta–Sr films have the potential to enhance the recruitment of cells in the initial culture stages, and improve cell proliferation. Overall, this work demonstrated that the application of Ta and Ta–Sr films to orthopedic implants has the potential to increase the lifetime of the implants. Furthermore, this study also describes an innovative strategy to incorporate Ta into implant films.

A hierarchically rough structured Ta–Sr coating for biomaterials fabricated by a sol–gel-assisted micro-arc oxidation technique.     

Improving the dynamics of a Nd–Mg–Ni-based alloy by combining Ni element and mechanical milling

To improve the reversible kinetics and electrochemical performance of a Nd–Mg–Ni-based alloy, NdMg₁₁Ni + x wt% Ni (x = 100 or 200) samples were prepared through combining the addition of Ni element and ball-milling technology. Meanwhile, the effects of the addition of Ni element and the duration of milling on the NdMg₁₁Ni samples were researched. The results indicate that the addition of Ni element has a beneficial effect on the dynamics of the samples. Meanwhile, the milling duration also has a beneficial effect on the high-rate discharging capabilities, the gaseous hydrogenation rate, and the dehydrogenation dynamics. When the ball-milling time is increased from 5 h to 60 h, the value of R^d₂₀ (the ratio of the dehydrogenation capabilities within 20 min to the saturated hydrogenation capabilities) is raised from 62.20% to 71.59% for the x = 200 sample, and from 58.03% to 64.81% for the x = 100 sample; this is believed to be due to a decline in the activation energy resulting from an increase in the Ni content and ball-milling time. In addition, the E_a value of NdMg₁₁Ni + 200 wt% Ni with a ball-milling time of 60 h is 55.7 kJ mol⁻¹.

Both ball grinding and increasing the nickel content can effectively reduce the dehydrogenation activation energy of a RE–Mg-based alloy.     

Preparation and properties of capric acid–stearic acid-based ternary phase change materials

Two kinds of CA–SA-based ternary phase change materials (PCMs), namely, capric acid–stearic acid–palmitic acid (CA–SA–PA) and capric acid–stearic acid–octadecanol (CA–SA–OD), were prepared by the melting–blending method. By the step cooling curve method, the optimum mass ratio of the two PCMs were determined to be CA : SA : PA = 77.4 : 8.6 : 14.0 and CA : SA : OD = 81.9 : 9.1 : 9.0, and the crystallization temperatures were 19.20 °C and 23.90 °C, respectively. The phase transition temperatures as measured by DSC were 18.60 °C and 24.82 °C, and the latent heat of phase transition were 129.15 J g⁻¹ and 161.74 J g⁻¹, respectively. The results are in good agreement with those measured by the step cooling curve method. The chemical and crystalline properties of the two PCMs were analyzed by FT-IR and XRD. It was found that CA–SA is combined with PA or OD by physical action, and the components have good compatibility and form a good eutectic structure. In addition, the results of heat storage and heat release experiments and the 500 times of accelerated melting–solidification cycling test showed that the two kinds of PCMs have good heat resistance and thermal reliability. Therefore, the prepared CA–SA–PA and CA–SA–OD have good performance and great application potential in building energy saving and solar energy utilization.

Two kinds of CA–SA-based ternary phase change materials (PCMs), namely, capric acid–stearic acid–palmitic acid (CA–SA–PA) and capric acid–stearic acid–octadecanol (CA–SA–OD), were prepared by the melting–blending method.     

Hydrogen-driven dramatically improved mechanical properties of amorphized ITO–Ag–ITO thin films

An oxide/metal/oxide (OMO) multi-structure, which has good electrical, optical, and mechanical stability, was studied as a potential replacement of polycrystalline In–Sn–O (ITO). However, the degradation of mechanical properties caused by the polycrystalline structure of the top layer forming on the polycrystalline metal layer needs to be improved. To address this issue, we introduced hydrogen in the oxide layers to form a stabilized amorphous oxide structure despite it being deposited on the polycrystalline layer. An ITO/Ag/ITO (IAI) structure was used in this work, and we confirmed that the correct amount of hydrogen introduction can improve mechanical stability without any deterioration in optical and electrical properties. The hydrogen presence in the IAI as intended was confirmed, and the assumption was that the hydrogen suppressed the formation of microcracks on the ITO surface due to low residual stress that came from decreased subgap level defects. This assumption was clearly confirmed with the electrical properties before and after dynamic bending testing. The results imply that we can adjust not only IAI structures with high mechanical stability due to the right amount of hydrogen introduction to make stabilized amorphous oxide but also almost all oxide/metal/oxide structures that contain unintended polycrystalline structures.

An oxide/metal/oxide (OMO) multi-structure, which has good electrical, optical, and mechanical stability, was studied as a potential replacement of polycrystalline In–Sn–O (ITO).     

n–n ZnO–Ag2CrO4 heterojunction photoelectrodes with enhanced visible-light photoelectrochemical properties

In this study, ZnO nanorods (NRs) were hydrothermally grown on an Au-coated glass substrate at a relatively low temperature (90 °C), followed by the deposition of Ag₂CrO₄ particles via a successive ionic layer adsorption and reaction (SILAR) route. The content of the Ag₂CrO₄ particles on ZnO NRs was controlled by changing the number of SILAR cycles. The fabricated ZnO–Ag₂CrO₄ heterojunction photoelectrodes were subjected to morphological, structural, compositional, and optical property analyses; their photoelectrochemical (PEC) properties were investigated under simulated solar light illumination. The photocurrent responses confirmed that the ability of the ZnO–Ag₂CrO₄ heterojunction photoelectrodes to separate the photo-generated electron–hole pairs is stronger than that of bare ZnO NRs. Impressively, the maximum photocurrent density of about 2.51 mA cm⁻² at 1.23 V (vs. Ag/AgCl) was measured for the prepared ZnO–Ag₂CrO₄ photoelectrode with 8 SILAR cycles (denoted as ZnO–Ag₂CrO₄-8), which exhibited about 3-fold photo-enhancement in the current density as compared to bare ZnO NRs (0.87 mA cm⁻²) under similar conditions. The improvement in photoactivity was attributed to the ideal band gap and high absorption coefficient of the Ag₂CrO₄ particles, which resulted in improved solar light absorption properties. Furthermore, an appropriate annealing treatment was proven to be an efficient process to increase the crystallinity of Ag₂CrO₄ particles deposited on ZnO NRs, which improved the charge transport characteristics of the ZnO–Ag₂CrO₄-8 photoelectrode annealed at 200 °C and increased the performance of the photoelectrode. The results achieved in the present work present new insights for designing n–n heterojunction photoelectrodes for efficient and cost-effective PEC applications and solar-to-fuel energy conversions.

ZnO NRs hydrothermally grown on Au coated glass substrate, followed by deposition of Ag₂CrO₄ particles via SILAR route. The content of the Ag₂CrO₄ particles on the ZnO NRs were controlled by changing the number of SILAR cycles.     

Enhanced antibacterial properties of biocompatible titanium via electrochemically deposited Ag/TiO2 nanotubes and chitosan–gelatin–Ag–ZnO complex coating

A novel double-layered antibacterial coating was fabricated on pure titanium (Ti) via a simple three-step electrodeposition process. Scanning electronic microscopy (SEM) images show that the coating was constructed with the inner layer of TiO₂ nanotubes doped with silver nanoparticles (TNTs/Ag) and the outer layer of chitosan–gelatin mixture with zinc oxide and silver nanoparticles (CS–Gel–Ag–ZnO). In comparison, we also investigated the composition, structure and antibacterial properties of pure Ti coated with TNTs, TNTs/Ag or TNTs/Ag + CS–Gel–Ag–ZnO, respectively. The TNTs was about 100 nm wide and 240 nm to 370 nm tall, and most Ag nanoparticles (Ag NPs) with diameter smaller than 20 nm were successfully deposited inside the tubes. The CS–Gel–Ag–ZnO layer was continuous and uniform. Antibacterial activity against planktonic and adherent bacteria were both investigated. Agar diffusion test against Staphylococcus aureus (S. aureus) shows improved antibacterial capacity of the TNTs/Ag + CS–Gel–Ag–ZnO coating, with a clear zone of inhibition (ZOI) up to 14.5 mm wide. Dead adherent bacteria were found on the surface by SEM. The antibacterial rate against planktonic S. aureus was as high as 99.2% over the 24 h incubation period.

A novel complex antibacterial coating fabricated via a simple three-step electrodeposition process shows high antibacterial rate of 99.2%.     

Photocatalysed direct amination of benzene and ammonia over Ti–V-MCM-41

Aniline is one of the important organic chemical raw materials and is widely used in the chemical production industry, including dyes, pharmaceuticals, pesticides, explosives, spices, etc. At present, the yield and selectivity of aniline synthesis by direct amination are relatively low, and how to improve the catalytic efficiency has become an urgent problem to be solved. A series of Ti–V-MCM-41 catalysts with different silicon–titanium ratios was prepared by the hydrothermal synthesis method. According to the analysis of XRD, FT-IR, UV-vis DRS, BET, and SEM characterization of Ti–V-MCM-41, it was found that V–O–Si and Ti–O–Si were distributed on Ti–V-MCM-41. The direct photocatalysis amination of benzene and ammonia to aniline can be realized under mild conditions with this catalyst. The yield and selectivity of aniline were improved to 6.11% and 90.7%, respectively, by optimizing the synthesis and reaction conditions.

A series of Ti–V-MCM-41 catalysts with different silicon–titanium ratios was prepared by the hydrothermal synthesis method. The yield and selectivity of aniline were improved to 6.11% and 90.7% by optimizing the synthesis and reaction conditions.     

Tensile mechanical performance of Ni–Co alloy nanowires by molecular dynamics simulation

In this present contribution, tensile mechanical properties of Ni–Co alloy nanowires with Co content from 0 to 20% were studied by molecular dynamics. The simulation results show the alloy nanowire with the Co content of 5% has the highest yield value of 9.72 GPa. In addition, more Frank dislocations were generated during the loading process to improve the performance of the alloy nanowire. The Young''s modulus increases little by little from 105.68 to 179.78 GPa with the increase of Co content. Secondly, with the increase of temperature, the yield strength gradually decreases to 2.13 GPa. Young''s modulus tends to decrease linearly from 170.7 GPa to 48.21 GPa. At the temperatures of 500 K and 700 K, it is easier to form Frank dislocation and Hirth dislocation, respectively, in the loading process. The peak value of the radial distribution function decreases and the number of peaks decreases, indicating the disappearance of the ordered structure. Finally, after the introduction of the surface and inner void, the yield strength of the nanowire drops about to 8.97 and 6.6 GPa, respectively, and the yield strains drop to 0.056 and 0.043. In the case of the existence of internal void, perfect dislocation and Hirth dislocation can be observed in the structure.

The addition of a little Co can promote the formation of Frank and other fixed dislocations, making the alloy system have high yield strength. The defects in nanowires accelerated the occurrence of yield behavior.     

The effects of Sn content on the corrosion behavior and mechanical properties of Mg–5Gd–3Y–xSn–0.5Zr alloys

The effects of Sn content on the corrosion behavior and mechanical properties of Mg–5Gd–3Y–0.5Zr alloy were studied by SEM, EDS, XRD and electrochemical testing. Results show that Sn can refine the grain size and promote the precipitation of Mg₅(Gd,Y) phase. When the Sn content is 1.5–2 wt%, a needle-like Mg₂Sn phase will be precipitated in the alloy. Mg–5Gd–3Y–1Sn–0.5Zr alloy had the lowest corrosion rate, which is attributed to the barrier effect of the grain boundary and dispersed Mg₅(Gd,Y) phase on corrosion. However, the Mg₂Sn phase formed by excessive Sn addition will accelerate galvanic corrosion. At the same time, Mg–5Gd–3Y–1Sn–0.5Zr alloy had best mechanical properties. In 1.5Sn and 2Sn alloys, the cleavage effect of the needle-like Mg₂Sn phase on the matrix reduced mechanical properties.

The effects of Sn content on the corrosion behavior and mechanical properties of Mg–5Gd–3Y–0.5Zr alloy were studied by SEM, EDS, XRD and electrochemical testing. Results show that Sn can refine the grain size and promote the precipitation.     

Synthesis of antimicrobial AlOOH–Ag composite nanostructures by water oxidation of bimetallic Al–Ag nanoparticles

The facile one-step synthesis of AlOOH–Ag nanocomposite has been performed. Bimetallic Al–Ag nanoparticles prepared by electrical explosion of Al and Ag wires were used as a precursor. AlAg nanoparticles consisted of a supersaturated Al–6 at% Ag solid solution and Ag-rich Guinier–Preston zone several nanometer in diameter that were not detected by XRD due to their extremely small size and peculiarities of their crystal structure. An environmentally friendly process of water oxidation at 60 C was used to convert Al–Ag nanoparticles into AlOOH–Ag nanocomposites. In the course of oxidation, chemical dealloying of Al–Ag solid solution took place yielding porous agglomerates with inclusions of very fine 5–30 nm Ag nanoparticles. The agglomerates consisted of 2–5 nm thick crumpled nanosheets of boehmite 200 nm in size. The synthesized AlOOH–Ag nanocomposites possessed high antibacterial activity against both Gram-negative and Gram-positive microorganisms as indicated by the time-kill assay. The presented results open up new processing possibilities of metal-oxide composite nanostructures with attractive properties that can be used in catalysis, water purification and biomedical applications.

The facile one-step synthesis of AlOOH–Ag nanocomposite has been performed.     

Electrical and mechanical properties of self-supported hydroxypropyl methylcellulose–polyaniline conducting films

The purpose of this work was to develop a simple method to produce self-supported films composed of hydroxypropyl methylcellulose (HPMC) and polyaniline (PANI) by the direct mixture of aqueous dispersions of both polymers with subsequent drying. The addition of HPMC, a cellulose derivative with an excellent film-forming capacity, was fundamental to overcoming the poor processability of PANI, which impairs its use in many technological applications. All films showed conductivity in the order of 10⁻² to 10⁻³ S cm⁻¹, which is in the range for metals or semiconductors. The typical electroactivity of PANI was also maintained in the hybrid films. The thermal stability and the mechanical properties of the pristine PANI were also improved with the addition of HPMC. Cellulose-containing conducting polymers can be considered a material of the future, with possible applications in several areas, such as smart wallpapers, e-papers, and sensors.

The purpose of this work was to develop a simple method to produce self-supported films composed of hydroxypropyl methylcellulose (HPMC) and polyaniline (PANI) by the direct mixture of aqueous dispersions of both polymers with subsequent drying.     

Au–Ag and Pt–Ag bimetallic nanoparticles@halloysite nanotubes: morphological modulation,improvement of thermal stability and catalytic performance

In this study, Au–Ag and Pt–Ag bimetallic nanocages were loaded on natural halloysite nanotubes (HNTs) via galvanic exchange based on Ag@HNT. By changing the ratio of Au to Ag or Pt to Ag in exchange processes, Au–Ag@HNT and Pt–Ag@HNT with different nanostructures were generated. Both Au–Ag@HNT and Pt–Ag@HNT systems showed significantly improved efficiency as peroxidase-like catalysts in the oxidation of o-phenylenediamine compared with monometallic Au@HNT and Pt@HNT, although inert Ag is dominant in the composition of both Au–Ag and Pt–Ag nanocages. On the other hand, loading on HNTs enhanced the thermal stability for every system, whether monometallic Ag nanoparticles, bimetallic Au–Ag or Pt–Ag nanocages. Ag@HNT sustained thermal treatment at 400 °C in nitrogen with improved catalytic performance, while Au–Ag@HNT and Pt–Ag@HNT maintained or even had slightly enhanced catalytic efficiency after thermal treatment at 200 °C in nitrogen. This study demonstrated that natural halloysite nanotubes are a good support for various metallic nanoparticles, improving their catalytic efficiency and thermal stability.

Bimetallic Au–Ag@HNT and Pt–Ag@HNT nanocages showed significantly improved efficiency in the oxidation of o-phenylenediamine as peroxidase-like catalyst compared with corresponding monometallic nanoparticles.