Nanostructured Layer Research Articles

Surface nano-crystallisation and mechanical properties of Ti[sbnd]Ta composite materials after surface mechanical grinding treatment

Surface mechanical milling generates gradient nano-structure surfacial layers that enhance the mechanical properties of titanium (Ti)–tantalum(Ta) composites for medical implants. Herein, the effect of surface mechanical grinding treatment (SMGT) on the surface nano-crystallisation of TiTa laminated composites was investigated in terms of micro-structure and Coherent Scattering Regions (CSRs) size using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. A strengthening effect was verified using a micro-hardness tester and tensile testing machine, and the fracture mechanism was analysed through fracture observation. The experimental results showed that gradient nano-structures were formed on the surface of the TiTa laminated composites after SMGT, with the smallest CSRs size of the outer surface layer of approximately 13.3 ± 0.4 nm. The plastic deformation mechanism of the TiTa laminated composites during SMGT was a dislocation cutting mechanism. The micro-hardness and tensile strength of the TiTa laminated composites increased after SMGT up to 440 HV and 1097.528 MPa, respectively. The fracture mechanism of the TiTa laminated composites after SMGT was a combination of ductile fracture and quasi-cleavage fracture mechanisms. After SMGT, the TiTa laminated composite performed well and exhibited excellent potential for use in biomaterials.

TiO2 nanostructured layer formation on Ti-35Nb and Ti-35Nb-5Ta samples: Impact of Ta addition on polymorphic transformation and oxide composition

Surface bioactivity is a crucial characteristic of Ti-based hard tissue implants as it enables integration with living bone. A nanostructured layer of TiO2 obtained through anodization is believed to enhance bioactivity. This study aimed to investigate the formation and crystallization of a nanostructured oxide layer synthesized on the surface of Ti-35Nb and Ti-35Nb-5Ta samples. The nanostructure was crystalized using heat treatments between 350 °C and 900 °C. In both compositions, anatase was formed between 375 °C and 500 °C, above this temperature anatase was transformed in rutile. Additionally, a doped Nb2O5 phase was also detected between 700 °C and 900 °C. In this same temperature range, the nanostructured oxide layer lost its morphological structure. The presence of Ta in the Ti-Nb-Ta substrate supported the anatase and (Nb)2O5 crystallization at lower temperatures if compared to the Ti-Nb substrate.

Elucidating the modified performance of high nuclearity of Cu nanostructures-PTFE thin film

The aim of this study is to attain an extensive insight on the performance mechanism that is associated with the formation of Cu nanostructures- polytetrafluoroethylene (PTFE) thin film. The work presented Cu nanostructures synthesised via microwave-assisted method at different Cu precursor concentrations to observe the influence of different average particle diameter distribution, {d}_{m} of Cu nanostructures on the fabricated Cu nano thin film. The thin films of Cu nanostructures with a layer of PTFE were fabricated using the Meyer rod coating method. Evaluating the effect of Cu nanostructures at different {d}_{m} with overcoated PTFE layer showed that the resistance of fabricated thin film coated with PTFE is not significantly different from that of the uncoated thin film. The results implicate the influence of the PTFE layer towards the output performance, which can maintain a stable and constant resistance over time without affecting the original properties of pure Cu nanostructures, although some of the Cu nanostructures seep into the layer of PTFE. The novelty of this study lies in the effect of the intrinsic interaction between the layer of Cu nanostructure and PTFE, which modulate the performance, especially in photovoltaic cell application.

A Nanofiber-Based Gas Diffusion Layer for Improved Performance in Air Cathode Microbial Fuel Cells.

This work investigates a new nanostructured gas diffusion layer (nano-GDL) to improve the performance of air cathode single-chamber microbial fuel cells (a-SCMFCs). The new nano-GDLs improve the direct oxygen reduction reaction by exploiting the best qualities of nanofibers from electrospinning in terms of high surface-area-to-volume ratio, high porosity, and laser-based processing to promote adhesion. By electrospinning, nano-GDLs were fabricated directly by collecting two nanofiber mats on the same carbon-based electrode, acting as the substrate. Each layer was designed with a specific function: water-resistant, oxygen-permeable polyvinylidene-difluoride (PVDF) nanofibers served as a barrier to prevent water-based electrolyte leakage, while an inner layer of cellulose nanofibers was added to promote oxygen diffusion towards the catalytic sites. The maximum current density obtained for a-SCMFCs with the new nano-GDLs is 132.2 ± 10.8 mA m-2, and it doubles the current density obtained with standard PTFE-based GDL (58.5 ± 2.4 mA m-2) used as reference material. The energy recovery (EF) factor, i.e., the ratio of the power output to the inner volume of the device, was then used to evaluate the overall performance of a-SCMFCs. a-SCMFCs with nano-GDL provided an EF value of 60.83 mJ m-3, one order of magnitude higher than the value of 3.92 mJ m-3 obtained with standard GDL.

Arc erosion characteristics of W-fuzz samples with different thicknesses of the nanostructured layer

An analysis of the results of measuring the erosion rates of W-fuzz samples with different fuzz thicknesses subject to arcing has been performed. Based on the examination of the structure of arc tracks, it has been concluded that a sharp increase in the erosion rate was accompanied by melting of the nanostructured layer. At the same time, numerous frozen droplets were observed at the boundary of the cathode spot track on the samples with a large fuzz thickness. Individual droplets were also found at some distance from the boundary. The experimental results have been interpreted theoretically using the explosive emission (ecton) model and the results of the analysis of thermal processes occurring in the cathode spot.

Layered Architectural Fabrication of a Novel Sulfite Nanobiosensor by Encapsulation of Sulfite Oxidase on a Polypyrrole-Multiwalled Carbon Nanotubes Composite Decorated with Platinum Nanoparticles.

The fabrication of a highly selective and ultrasensitive sulfite nanobiosensor based on a layered architectural fabrication aided by the encapsulation of sulfite oxidase (SOx) in Nafion (Naf) matrix on a multiwalled carbon nanotubes-polypyrrole (MWCNTs-PPy) composite decorated with platinum nanoparticles (PtNPs) is described. The MWCNTs are deposited in the inner layer on a Pt electrode during electropolymerization of pyrrole (Py), followed by decoration with a PtNPs layer and subsequent encapsulation of SOx with Naf in the third layer capped with a fourth thin PtNPs layer. Images obtained by field emission scanning electron microscopy (FESEM) reveal that high-density PtNPs are deposited onto the 3D nanostructured inner MWCNTs-PPy layer and the electrochemical behavior is investigated. A large surface area provided by the incorporation of MWCNTs in the composite and decoration with PtNPs enables increased SOx loading, SOx retention, and substantial improvement in sensing performance. The resulting layered PtNPs/SOx-Naf/PtNPs/MWCNTs-PPy nanobiosensor exhibits a fast response time (within 3 s), a linear calibration range of 20nmm - 6m with an excellent sensitivity of 71µA mm-1cm-2 and a detection limit of 5.4nm. The nanobiosensor was effective in discriminating against common interferants and was successfully applied to sulfite determination in real samples.

Application of concanavalin A as a new diagnostic strategy for SARS-COV-2 spike protein

The coronavirus disease 2019 (COVID-19) pandemic was the first modern global public health crisis recognized for overwhelming the health public system. In the viral envelope, there are glycoproteins that can be identified, making them useful in diagnosing infections such as the one caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this work, we developed a sensor platform applicable to the identification of carbohydrates present in the spike protein of SARS-CoV-2. The nanostructured platform was composed of a thin film of poly (thiophene-3-acetic acid) (PTAA) and nano gold urchins (AuNUs), enhancing the electrical signal at the interface of the gold electrode. Coupled to this nanostructured layer, the lectin Concanavalin A (ConA) was immobilized, which has binding affinity to mannose and N-acetylglucosamine residues. In this context, ConA was used as a biorecognition element against Spike protein carbohydrates. Gradual assembly of the sensor platform and recombinant viral target recognition were evaluated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and atomic force microscopy (AFM). The proposed biosensor showed high sensitivity, with a limit of detection (LOD) of Spike isolated 0.20 ng/µL and Spike serum 0.14 ng/µL, along with high selectivity against interfering molecules. Our results stand out as an innovative alternative for detecting viral glycoproteins, with promising applications in detecting SARS-CoV-2 in clinical samples.

Effect of ultrasonic surface rolling process on the microstructure and corrosion behavior of zirconium alloy in high-temperature water condition

Ultrasonic surface rolling processing (USRP) was carried out at zirconium (Zr) alloy with different rolling speeds to prepare gradient nanostructured layers, and the corrosion behavior of USRP treated Zr alloy was studied under 360 °C/18.6 MPa water condition. The surface morphology, microstructure, phase composition, and element distribution of USRP treated Zr alloy after corrosion was investigated. Results show that the oxide layer on Zr alloy comprises of t-ZrO2, m-ZrO2, and metal Zr. The thickness of oxide layer Zr alloy is reduced after USRP treatment, indicating that the gradient nanostructure can effectively improve corrosion resistance. This process is attributed to that the gradient nanostructure layer is helpful for the nucleation of equiaxed t-ZrO2 at the oxide/metal (O/M) interface with small grain size. The high compressive stress induced by USRP treatment is beneficial for the maintenance of t-ZrO2 phase and inhabiting the phase transformation from t-ZrO2 to m-ZrO2, which reduces the micro-cracks and defects due to volume expansion. The oxide layer on USRP treated Zr alloy with high content of t-ZrO2 phase presents a dense structure and prevents oxygen anions from diffusing to Zr alloy.

Role of nanostructured Ni surface layer in enhanced Hastelloy alloy diffusion bonding at temperatures far beyond recrystallization

Enhanced Hastelloy alloy diffusion bonding was investigated via introducing nanostructured Ni surface layer. Because the bonding temperature was significantly higher than the nanostructured Ni destabilization temperature, rapidly complete recrystallization and dramatic grain growth occurred. The beneficial effect of high-density short-circuit defects provided by nanocrystalline on enhanced diffusion ought to be limited. However, significantly accelerated diffusion was still observed in the joint. The unique contribution of the nanostructured layer in evolving microstructure is to promote the formation of diffusion-induced recrystallization at the interface, where solute elements could diffuse rapidly along the moving boundaries at a rate several orders of magnitude larger than static grain boundaries. The retained ultrafast atomic diffusion paths result in a bonding temperature of 250 °C–350 °C lower than the conventional diffusion bonding approach. The tensile strength of the achieved joint reached 833 MPa, which was nearly equal to that of the as-delivered substrate.

Morphology and Phase-Controlled Synthesis of Defect-Rich Layered Cobalt Hydroxide Nanostructures for the Oxygen Evolution Reaction

Morphology and Phase-Controlled Synthesis of Defect-Rich Layered Cobalt Hydroxide Nanostructures for the Oxygen Evolution Reaction

Highly Enantioselective Synthesis of Pharmaceuticals at Chiral-Encoded Metal Surfaces.

Enantioselective catalysis is of crucial importance in modern chemistry and pharmaceutical science. Although various concepts have been used for the development of enantioselective catalysts to obtain highly pure chiral compounds, most of them are based on homogeneous catalytic systems. Recently, we successfully developed nanostructured metal layers imprinted with chiral information, which were applied as electrocatalysts for the enantioselective synthesis of chiral model compounds. However, so far such materials have not been employed as heterogeneous catalysts for the enantioselective synthesis of real pharmaceutical products. In this contribution, we report the asymmetric synthesis of chiral pharmaceuticals (CPs) with chiral imprinted Pt-Ir surfaces as a simple hydrogenation catalyst. By fine-tuning the experimental parameters, a very high enantioselectivity (up to 95 % enantiomeric excess) with good catalyst stability can be achieved. The designed materials were also successfully used as catalytically active stationary phases for the continuous asymmetric flow synthesis of pharmaceutical compounds. This illustrates the possibility of producing real chiral pharmaceuticals at such nanostructured metal surfaces for the first time.

Ascertaining the microstructural evolution and strengthening mechanisms of the gradient nanostructured pure titanium fabricated by ultrasonic surface rolling process

This work utilized the ultrasonic surface rolling process (USRP) to construct a gradient nanostructured (GNS) layer in pure titanium. The microstructural characterization at different depths was conducted using a transmission electron microscope (TEM) and electron backscatter diffraction (EBSD) to elucidate the grain refinement mechanisms. Results showed that the {10−12} extension twins (ETs) and {11−22} compression twins (CTs) and their intersections accommodate the strain at the early deformation stage. As the strain increased, the dense dislocation walls (DDWs) and dislocation cells (DCs) gradually evolved into laminated structures with low-angle grain boundaries (LAGBs). Compared to conventional severe plastic deformation (SPD) technology, the LAGB-dominated grain refinement mechanism delays the onset of the transformation process from LAGBs to high-angle grain boundaries (HAGBs). With the coaction of discontinuous dynamic recrystallization (dDRX) and amorphization, the grains are extremely refined to 11.7 nm. Tensile test results suggested that a considerable strength-ductility synergy is achieved. The enhanced strength was attributed to grain size, dislocation, and synergetic strengthening mechanisms, accounting for 55.5 %, 20.7 %, and 23.8 %, respectively. This work deepens the current understanding of the formation mechanism of the GNS layer in pure titanium processed by USRP and the relationship between microstructure and mechanical properties.

Biomimetic surface functionalization of Ti metal incorporated with Ca-Zn and evaluation of in-vitro biological properties

This study aims at incorporating Ca2+ and Zn2+ions into the nano-structured titania layer over Ti metal by a simple chemical and thermal treatment approach. The incorporation of these ions was controlled by varying the volumetric ratios of calcium nitrate and zinc nitrate solution on the alkali pre-treated Ti metal followed by heat treatment at 600 °C. The elemental incorporation of Ca predominantly forms calcium titanate and rutile TiO2, while the simultaneous incorporation of Ca-Zn developed anatase TiO2. Subsequently, the optimized Ca-Zn ratio with predominant anatase TiO2 over the surface (Ti-Na-2.5Ca:7.5Zn) of Ti metal was subjected to further detailed evaluation of surface properties and in-vitro characteristics. This dual-element incorporated nanonetwork structure has shown significant improvement in surface roughness and wettability which influence the rate of protein adsorption. Further detailed evaluation displayed the existence of incorporated Zn2+ as ZnO, which supported the Zn/ZnO mediated antibacterial activity against Staphylococcus aureus and Escherichia coli. In-vitro studies also showed the biocompatible efficiency of Ca and Zn ions through their cell adhesion ability, mitochondrial potential, cell viability, and nuclear integrity with minimum effect on single-cell DNA damage towards MG-63 cells. The mRNA expression levels of osteogenic genes such as OSX, RUNX2, OPN, and OCN were analysed using RT-PCR in the MG-63 cells that are cultured over surface-modified Ti metal which further explained the effect of incorporated Ca and Zn ions in regulating their expression. A similar supporting analysis was found during the mineralization process as well, thus this particular surface modification is expected to fasten osteointegration in in-vivo. These promising results suggest our Ca-Zn-incorporated Ti metal as a potential candidate for bone implant applications.

Optical properties of periodically and aperiodically nanostructured p-n junctions

Recently, semiconductor nanograting layers have been introduced and their optical properties have been studied. Spectroscopic ellipsometry has shown that nanograting significantly modifies the dielectric function of c-Si layers. Photoluminescence spectroscopy reveals the emergence of an emission band with a remarkable peak structure. It has been observed that nanograting also alters the electronic and magnetic properties. In this study, we investigate the quantum efficiency and spectral response of Si p-n junctions fabricated using subwavelength grating layers and aperiodically nanostructured layers. Our findings indicate that the quantum efficiency and spectral response are enhanced in the case of nanograting p-n junctions compared to plain reference junctions. Aperiodically nanostructured junctions exhibit similar results to nanograting junctions. However, aperiodic nanostructuring is a more straightforward fabrication method and, consequently, more appealing for the solar cell industry.

Enhancing the photoelectrochemical activity and stability of plate-like WO3 photoanode in neutral electrolyte solution using optimum loading of BiVO4 layer and NiFe–LDH electrodeposition

Tungsten trioxide (WO3) is an attractive candidate that can be used as a photoanode in the photoelectrochemical (PEC) water splitting device. However, WO3 photoanode is known for its high thermodynamic and chemical stability only in strong acidic (low pH) electrolyte solution and its relatively wide bandgap energy (2.8 eV) leads to insufficient absorption of visible light. The current study explored a WO3/BiVO4 heterojunction photoanode, consisting of plate-like WO3 covered with a uniform and highly porous BiVO4 thin layer, with electrodeposition of NiFe–LDH as a co-catalyst for oxygen evolution reaction. This top layer of BiVO4 nanostructure not only exhibited an enhancement in absorption of visible light but also protected the underneath plate-like WO3 from being attacked by the neutral environment of electrolyte solution (pH=∼7), resulting in significant improvement in its stability. The electrodeposition of NiFe–LDH using an acidic aqueous electrolyte solution (pH=3.7) was employed to overcome the sluggish kinetics of water oxidation on the surface of BiVO4. To overcome the weakness of the chemical dissolution of BiVO4 nanostructure in strong acidic solution, the electrodeposition time was carefully optimized for 50 s, leading to a uniform distribution of co-catalyst on the surface of WO3/BiVO4 heterostructure without the dissolving of BiVO4 in the acidic media. The WO3/BVO5/NiFe50 photoanode with the highest PEC performance (photocurrent density of around 1.78 mA/cm2 at 1.23 V vs. RHE) could maintain around 75% of its initial photocurrent after 24 h.

Mathematical model of the formation of barite-lead mineralization of the Ushkatyn III deposit (Central Kazakhstan)

The genesis of stratiform deposits of lead and barite in sedimentary rocks is of great interest from the point of view of replenishing reserves of polymetallic ores. The aim of the work is to establish the regularity of the hydrogenic formation of ores in limestones, taking into account the influence of the nanosurface of pores and cracks based on a mathematical model of the movement and characteristics of ore-bearing solutions in the pores. The thicknesses of the surface layer of limestones and minerals included in the ore-containing strata and sulfide minerals are calculated. The results indicate that they are nanostructures with special physical properties different from the rest of the substance, which is confirmed by the regularity of the formation of a heavy sulfur isotope in ores of various textural types. The influence of hydrotherms with different densities, kinematic viscosity, and velocity on the intensity of mineralization formation in cracks and pores of limestone, as well as the occurrence of new feathering cracks around the fractures of dismemberment, is estimated. The dependence of the hydrothermal flow density on the diffusion of the liquid is established. The equation of kinematic viscosity is derived from the pressure in the solution flow, the velocity of its movement, the mass of particles of ore-forming elements, and sulfur isotopes under thermodynamic conditions of determined Gibbs energies. The relationship of the viscosity of the solution with the surface tension of the nanolayer of limestone particles in cracks and pores is shown, indicating that the greater this energy, the greater the velocity of movement of ore-forming solutions, the fewer branches of newly formed cracks around the dissection crack. The mathematical model is applicable for the numerical analysis of the regularity of mineralization in cracks, taking into account the influence of the nanostructural layer of cracks and pores of limestone in the thermodynamic conditions of the occurrence of an ore-bearing formation.

Facile fabrication of aluminium alloys with gradient nanostructures incorporating α-Al2O3 particles for enhanced tribological properties

Aluminium alloys are crucial in lightweighting equipment. However, their limited wear resistance hinders their further utilization. Herein, a gradient nanostructure layer incorporating α-Al2O3 particles is successfully fabricated on aluminium alloy 2024 using a novel method called strengthening grinding treatment (SGT). The tribological properties were investigated by a ball-on-disc tribometer. The results show that SGT effectively enhances the anti-wear performance. Compared to the untreated sample, the average friction coefficient and the wear rate of the SGT-treated sample decreased by 34.7 % and 90.1 %, respectively. The wear surface analysis demonstrates that the presence of α-Al2O3 in the gradient nanostructure effectively restricts shear deformation and crack generation. Additionally, the formation of a wear-resistant tribofilm composed of 'glaze' during friction contributes to further wear reduction.

Spontaneous plasma formation via electrical explosion of nanostructured metal surface layers in plasma–surface interactions

The article is aimed at studying the issue of spontaneous, i.e., triggerless ignition of arcing plasma splashes due to explosive-electron-emission pulses at fiber-form nanostructured (W-fuzz) surface during plasma–surface interaction. There has been proposed an equivalent sputtering yield for arcing Yeff = 4.8 γ C/mg, where γ is the rate of plasma production (mass per charge) from a cathode by vacuum arc discharge. The ratio of the released-to-incident atoms Yeff can reach the value of about 10 for the plasma production rate of 2 mg/C. The increase in the plasma production rate γ has been estimated as (i) an increase in mass due to mechanical destruction of neighboring nanofragments and (ii) a decrease in ions average charge. The resulting twentyfold increase in γ at few-μm layers agrees with the experimental observations. The critical temperature Tcr (and corresponding cohesive energy Ecoh = 5 Tcr) for the W-fuzz nanostructure has been estimated as Tcr = 2 n/n0 eV, where n/n0 is the relative density of the W-fuzz nanostructure. It falls below 1 eV for typical fuzz layer thickness larger than few tenths of μm. This results in the experimentally observed reduction of the average W-ions charge in vacuum arc plasma.

Vertical Halide Segregation and Stability of Two-Dimensional Layered Perovskite Nanostructures: Implications for Optoelectronic Devices

Vertical Halide Segregation and Stability of Two-Dimensional Layered Perovskite Nanostructures: Implications for Optoelectronic Devices

In Situ Synthesis of Co-WO3 Anodic Layers for Enhanced Photoelectrochemical Water Splitting

Photoelectrochemical water splitting under solar radiation is one of the most studied areas of science. However, there are still many problems connected with this topic such as the low efficiency of systems or their usability only in the region of ultraviolet radiation. Anodic metal oxides are used as working electrodes in PEC cells due to their unique geometry, relatively high surface area, simple preparation, and their unique properties. Nanostructured tungsten oxide is characterized by strong photocorrosion stability in aqueous solutions and stable physicochemical properties. The main advantage of this material is its bang gap energy (2.6 eV), which is much lower than that of the commonly used titanium dioxide (3.2 eV). In consequence, absorption in the visible light region is significantly increased (up to 12% of the solar spectrum). The main objective of this project is to develop and optimize the single-step fabrication method of cobalt-doped nanostructured anodic tungsten oxide with enhanced photoelectrochemical properties under solar radiation. Particular attention will be paid to finding the correlation between the concentration of Co2+ ions in the electrolyte and their amount embedded in the anodic layer. A complex characterization (SEM/EDS, XRD, XPS, UV-Vis DRS) of nanostructured Co-WO3 layers will be performed to establish correlations between material morphology, composition, structure, and its optical, semiconducting, spectro-, photo- and electrochemical properties.AcknowledgementsThis research was partially funded within the budget of the "Excellence Initiative - Research University" program at the Jagiellonian University in Krakow.