Metal Coverage Research Articles

Engineered metal coverage of anode catalyst layer enhancing cell reversal tolerance for proton exchange membrane fuel cells

Anode cell reversal, which is caused by fuel starvation, poses a great threat to the durability of proton exchange membrane fuel cells. Commercially, iridium oxide or iridium is applied to boost oxygen evolution reaction, which alleviates carbon corrosion and protects the catalyst layer structure. However, the key factors that affect the anti-reversal ability and the interaction between Pt, Ir, and carbon support are still unclear. Hence, we systematically studied the performance using three typical carbon supports with three metal contents and different metal deposition orders by experiments and model calculations. A new parameter, “relative metal coverage”, is put forward to evaluate and predict the anti-reversal ability, showing higher relative metal coverage results in a longer reversal time and lower polarization performance degradation rate. Typically, only a 15.5% polarization performance loss after 1700 mins reversal time when the relative metal coverage of high metal content Ir/Pt/Super P anode is one. The results suggest that increasing relative metal coverage is a practical approach to improve reversal tolerance and provide new insights into the reversal tolerant anodes design.

Robust Sandwiched B/TM/B Structures by Metal Intercalating into Bilayer Borophene Leading to Excellent Hydrogen Evolution Reaction

AbstractBilayer borophene, very recently synthesized on Ag and Cu, possesses an extremely flat large surface and excellent conductivity. The van der Waals gap of bilayer borophene can be intercalated by metal atoms, tailoring the properties of bilayer borophene. Herein, sandwiched B/TM/B (transition metal, TM = Co, Ni, Cu, Pd) is proposed as a new 2D formation with both energetic, structural, and thermal stability by TM atoms intercalated into bilayer borophene. In addition, it is a novel platform for the electrocatalytic hydrogen evolution reaction (HER). The intercalation metal atom serves as a single‐atomic catalyst. The TM is protected by outside boron layers from being corroded by acidic/alkaline solutions. B/Cux/B, B/Pdx/B, and B/Alx/B with different metal coverage exhibit defect‐independent extremely low HER free energy in the range of approximately −0.162 to 0.179, −0.134 to 0.183, and −0.082 to 0.086 eV which are comparable to the noble metal Pt. Combining excellent conduction, high structural and thermal stability, low resistance to intercalated behavior, an effortless water splitting process, excellent defect‐independent catalytic performance, cheapness and abundance of raw materials, and corrosion resistance, 2D sandwiched B/TM/B (TM = Co, Ni, Cu, Pd) is believed to be promising for electrocatalysis applications.

First-principles study on the corrosion resistance of oxygen at Fe-Pb/Bi solid-liquid interface

Oxygen control technology is considered to be one of the most effective means to resist the dissolution corrosion of liquid metals. The mechanism for resisting the dissolution corrosion by oxygen is investigated by the interaction between oxygen and liquid metals using First-principles calculations. The energetics results indicate that O atom prevents the adsorption of Pb and Bi atoms and the escape of Fe atoms. The electronics characters of the surfaces indicate there is a trend in bonding O and Pb atoms in a certain distance, and the binding of surrounding Fe atoms is strengthened by the adsorbed O atom. These are predicted to be the initial stages of the formation of protective oxide layers. Besides, the increase in the coverage of liquid metals weakens the bond between Fe and O atoms. In addition, Pb and Bi atoms tend to migrate from the position far away from O atom to the Fe matrix by replacing Fe atoms. The O atoms that cover the surfaces uniformly are beneficial to the corrosion resistance of liquid metals. The results of energetics, electronics and dynamic calculations provide indispensable data to understand the corrosion resistance of the O atom in the environment of liquid metals.

Controlled site coverage of strong metal–support interaction (SMSI) on Pd NP catalysts

The coverage of Pd nanoparticles by SMSI oxides can be controlled with low loadings of TiO(2−x) and by controlling temperature in a reduction, oxidation, and re-reduction process.

An Optimization Analysis of the Melt-Cutting Diversion Jetting Mechanism for Downhole Drilling Columns

Summary Molten metal jet cutting, based on the transient superexothermic characteristics of aluminum thermal reaction, presents a novel technology for swiftly cutting and disposing of stuck drilling columns in downhole oil and gas wells. The key to achieving efficient cutting in drilling columns lies in the jetting mechanism, which guides the high-speed radial ejection of aluminum thermal reaction products that act upon the metal pipe wall. This study uses computational fluid dynamics (CFD) simulation to establish a fluid domain model for the process of cutting molten drilling columns. The optimization of the jetting mechanism is conducted to improve the circumferential coverage by the molten metal by analyzing the impact of molten metal yield and jetting mechanism parameters (cone angle of the conical conductor, diameter, number and length of nozzles, and shape of the diverter). Finally, an ejection test is carried out to verify the optimized jetting mechanism. Research results show that increasing the cone angle of the conical conductor can increase the flow rate of the molten metal at the upper end of the axial nozzle assembly to smoothly discharge the molten metal. Increasing the number of nozzles with equal diameters can increase the circumferential distribution range of molten metal ejected into the cutting area. However, the molten metal circumferential coverage will be impacted by increasing cutting distance. Increasing the nozzle size can reduce the divergence of the molten metal, thereby improving the coverage of the molten metal in the cutting area. When the nozzle arc length L = 8 mm, the molten metal can cover almost the entire cutting area. Adding a 2-mm horizontal draining table at the end of the diverter can assist the molten metal in changing its flow direction, allowing the molten metal to be ejected in a radial direction. The research results provide a theoretical basis for optimizing fusion cutting tools and formulating cutting processes.

The Angiographic and Clinical Follow-up Outcomes of the Wide-Necked and Complex Intracranial Aneurysms Treated With LVIS EVO-Assisted Coiling.

The Low Profile Visible Intraluminal Support EVO (LVIS EVO) is a self-expandable braided stent, which was recently introduced for the treatment of intracranial aneurysms. Full visibility of the stent and a relatively high metal coverage ratio are the unique features of the LVIS EVO. To assess the safety, efficacy, and midterm durability of LVIS EVO stent-assisted coiling for the treatment of wide-necked intracranial aneurysms. The endovascular databases were reviewed to identify patients treated with LVIS EVO-assisted coiling. The technical success and immediate clinical/angiographic outcomes were assessed. Periprocedural and delayed complications were evaluated. The follow-up angiographic/clinical outcomes were investigated. The preprocedural/follow-up neurological statuses were assessed with the modified Rankin Scale. One hundred three aneurysms in 103 patients (63 females) with a mean age of 54.9 ± 11.3 years were included. The mean maximum sac diameter was 6.2 ± 2.9 mm. The procedural technical success rate was 100%. Immediate postprocedural angiography showed complete occlusion in 77.7%. The mean duration of the angiographic follow-up was 8.8 ± 3.6 months. Follow-up angiography showed complete aneurysm occlusion in 89% of the 82 patients with angiographic follow-up. Recanalization was observed in 7.3% of 82 patients. Two patients (2.4%) required retreatment. In addition, 8.7% of the patients had at least 1 complication, and 2.9% of the patients developed a permanent morbidity. All patients had mRS scores ≤2. The results of this study demonstrate that SAC with LVIS EVO is a relatively safe, efficient, and durable treatment for wide-necked and complex intracranial aneurysms.

Specific chemical adsorption of selected divalent heavy metal ions onto hydrous γ-Fe2O3-biochar from dilute aqueous solutions with pH as a master variable

A γ-Fe2O3-biochar was synthesized using ferrate as precursor. Results showed that ferrate treatment of biochar increased surface acidity and magnetism strength, which enhanced metal ion adsorption and enabled easy magnetic separation of spent biochar after use. The adsorption characteristics of selected metal ions including Cu(II), Pb(II), Zn(II), Ni(II), Cd(II) and Co(II) onto hydrous γ-Fe2O3-biochar were studied. The adsorption isotherms were well fitted by the Langmuir adsorption model. The γ-Fe2O3-biochar exhibited significantly high monolayer metal coverage capacity. For example, the maximum Cu(II) adsorption density was 55.45 × 10-5 mol/g, which was 4.0 times that of plain biochar (13.75 × 10-5 mol/g) at pH 6. Metal ion adsorption reactions could be described by surface complex formation, involving all M(II) hydroxy species and surface hydroxy species, i.e., ≡FeOH and ≡COH. Both experimental and calculation results suggested the formation of inner- and outer-sphere complexes. Coulombic and specific chemical forces contributed to the total adsorption energy, with specific chemical energy being the dominating component for the adsorption of hydrolyzable metal ions onto γ-Fe2O3-biochar surface. Under the context of surface complex formation, it is visualized that metal ion hydrolysis reactions occurred on γ-Fe2O3-biochar surface, in parallel to that in the bulk phase.

Avoiding Shading Losses in Concentrator Photovoltaics Using a Soft-Imprinted Cloaking Geometry

Shading losses are a longstanding obstacle in photovoltaic devices, particularly in concentrator photovoltaics, where the tradeoff between shading and resistive losses limits the concentration at which the highest power conversion efficiency is achieved to values far below the capabilities of concentrator optics. Here, we demonstrate a simple and scalable fabrication method that enables large front metal coverage while keeping shading losses to a minimum. Soft-imprint lithography is used to create trenches in a transparent polymer above the metal contacts, enabling cloaking via refraction at a range of angles near normal incidence. Using optical characterization techniques, we first confirm that the metal contacts are indeed optically cloaked. We then demonstrate an increase in short-circuit current density from 29.95 to 39.12 mA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> for a Si solar cell with 25% front metal coverage before and after patterning, respectively. We investigate the angular performance of the trench pattern and further demonstrate how such a cloaking strategy could be implemented in concentrator photovoltaics to enable efficiency peaks at concentrations beyond 1000 suns.

The difference of physical and chemical properties of surface components and gasification characteristics between coke and tuyere coke

The physicochemical properties and gasification characteristics of the surface components of two batches of coke entering the furnace and coke at the tuyere were studied by various detection methods and kinetic methods. The results show that: Tuyere coke has better gasification reactivity, the fitting degree of VM model and RPM model for incoming coke is higher than URCM model, but RPM model is more suitable for tuyere coke, so RPM model is more suitable to describe the gasification reaction of the two kinds of coke. The average activation energy of two batches of tuyere coke calculated by RPM model is reduced by 33.72kJ/mol and 35.05kJ/mol respectively, and there is a linear relationship between the activation energy and the coverage of alkali metals in coke. Arrhenius formula calculates that the gasification reaction rate of two batches of coke at 900 °C increases by 50.67 times and 102.80 times respectively.

Mid-Infrared Response from Cr/n-Si Schottky Junction with an Ultra-Thin Cr Metal.

Infrared detection technology has been widely applied in many areas. Unlike internal photoemission and the photoelectric mechanism, which are limited by the interface barrier height and material bandgap, the research of the hot carrier effect from nanometer thickness of metal could surpass the capability of silicon-based Schottky devices to detect mid-infrared and even far-infrared. In this work, we investigate the effects of physical characteristics of Cr nanometal surfaces and metal/silicon interfaces on hot carrier optical detection. Based on the results of scanning electron microscopy, atomic force microscopy, and X-ray diffraction analysis, the hot carrier effect and the variation of optical response intensity are found to depend highly on the physical properties of metal surfaces, such as surface coverage, metal thickness, and internal stress. Since the contact layer formed by Cr and Si is the main role of infrared light detection in the experiment, the higher the metal coverage, the higher the optical response. Additionally, a thicker metal surface makes the hot carriers take a longer time to convert into current signals after generation, leading to signal degradation due to the short lifetime of the hot carriers. Furthermore, the film with the best hot carrier effect induced in the Cr/Si structure is able to detect an infrared signal up to 4.2 μm. Additionally, it has a 229 times improvement in the signal-to-noise ratio (SNR) for a single band compared with ones with less favorable conditions.

Synthesis of monometallic macrostructured catalysts for bromate reduction in a continuous catalytic system

The last few years have seen great leaps in the use of mechano-chemically modified carbon nanotubes in catalysis. While high improvements in catalytic performance have been achieved, the nature of the technique is not compatible with typical strategies for CNT coating of macro-structured catalysts by chemical vapor deposition. Developing macro-structured catalysts is a key step towards the sustainability of multi-phase catalysis and requires a methodology for coating with mechano-chemical modified CNT metallic catalysts. Preparing water-based slurries is not straightforward due to the CNT’s hydrophobicity, and the use of organic solvents is unsustainable. A novel methodology for the washcoating of macro-structures with pre-modified monometallic CNT catalysts was assessed. A compromise between surfactant use, post-coating treatment, and the catalyst activity/integrity, was achieved by solubilisation of the surfactant in a isopropanol:acetone mixture. The activity of the prepared catalysts was affected by the metallic dispersion, surfactant coverage, and distribution of the palladium throughout the catalytic layer. Palladium centers in the bottommost layers were found to be unavailable for liquid phase reaction. The activity of the catalysts prepared with pre-formed carbon monometallic powders was improved by adopting a coating strategy to maximize the availability of the metallic particles near the surface of the catalytic layer.

Investigation of surface endothelialization on nitinol: Effects of composite hydrogel coatings

BackgroundDue to high metal coverage and high mesh density，flow diverters (FD) are widely used for endovascular reconstruction of cerebrovascular disease. However, incomplete endothelialization, restenosis, and thrombosis hamper the long term clinical success. Thus, an effective coating to accelerate the endothelialization of the cerebrovascular FD raw materials and reduce the incidence of thrombosis and restenosis is needed. MethodsA novel composite hydrogel composed of matrigel and sodium alginate (SA) with different blending ratios, which was cross-linked with calcium chloride, was successfully prepared. The hydrophilicity of the coating surface was detected by measurement of the contact angle, and the surface morphology of the nitinol (NiTi) before and after modification was characterized by scanning electron microscopy (SEM). The elastic modulus was utilized to verify the mechanical properties and plasticity of the coating, and the release experiment was conducted to characterize the composite hydraulic coagulation. Additionally, biocompatibility was tested by in vitro cellular experiments. ResultsThe SEM observations showed that when the concentrations of matrigel and SA were 5 and 3 mg/ml, respectively, cross-linking with 40 mg/ml calcium chloride solution was resulted in formation of the uniform M/SA composite hydrogel coating. The contact angle of M/SA-NiTi was only (32.28 ± 1.55°) (P < 0.0001), indicating a strong hydrophilicity of M/SA-NiTi. The 48 h coating release rate is 61.5%. In addition, M/SA-NiTi exhibited to have better biocompatibility and plasticity than B-NiTi and M-NiTi. ConclusionsMatrigel/sodium alginate composite hydrogel coating has good biocompatibility and low thrombosis characteristics, and strong drug-carrying capacity, which is expected to accelerate the endothelialization after FD implantation. It has also a great potential application value in the surface modification of biological materials.

Use of 1000fps High Speed X-ray Angiography (HSAngio) to quantify differences in flow diversion effects of three stents with different coverage densities in a cerebral aneurysm invitro model.

High temporal resolution images acquired using 1000fps HSAngio can be used to visualize blood flow patterns and derive flow velocities during neurointerventional procedures. In this work we use this technology to quantify the changes in the blood flow velocities inside a cerebral aneurysm after treatment with three different stents with varying degrees of metal coverage density; stent A : <2%, stent B: 23% and stent C: 40%. A 3D printed in-vitro model of internal carotid artery aneurysm was connected to a flow loop (60% water, 40% glycerol solution used as circulation fluid, circulation flow rate 8 L/s). An automatic programmable injector (KD Scientific Legato 110) was used to inject iodine contrast agent at a rate of 88 mL/min in 3secs. 1000 fps HSAngio sequences of the contrast injection were acquired using an Aries single photon counting detector (Direct Conversion Inc., Stockholm). From these images blood flow velocities were calculated using an optical flow algorithm. As expected the biggest reduction in blood flow velocity inside the aneurysm was 32.4% after deployment of stent C. However, the velocity profile distribution indicated there was still a significant inflow jet into the aneurysm which could be caused by a endoluminal leak between the stent and the vessel wall. The average reduction was only 14% after placement of stent B and 3% after placement of stent A. Blood velocity distribution maps derived using 1000fps HSAngiography technology can be used to evaluate the quality of flow diversion within the aneurysm after placement of stent. Critical information such as endo luminal leakage which can cause treatment failure can also be detected.

Plasma enhanced inkjet printing of particle-free silver ink on polyester fabric for electronic devices

Most formulations of metal inks comprise of a suspension of nanoparticles however, these suffer when printed by the formation of unwanted agglomeration. The exploration and optimisation of particle-free silver-complex ink is causing a strong demand for inkjet printing of these formulations over nanoparticle-based suspension inks. This is due to the enhanced printability and rapid conversion via thermal reduction into a conductive material, which can be utilised in electronics manufacture. We developed a silver-complex ink for ‘smart-clothing’ through inkjet printing. The high-quality printing - characterised by no satellite droplet formation and fast speed - is demonstrated upon polyester fabric by the formation of electrical circuitry using a thermal reduction process. Fabric printing is limited by good metal coverage and adhesion, which we demonstrate and improve on in the work by the application of a low temperature, atmospheric air plasma pre-treatment to the polyester surface, which improves printed silver density and coverage using a plasma device which is easy to operate and economic. Printed silver layer reduction and film crystallinity is characterised from high resolution scanning electron microscopy, and spectroscopy (Ultraviolet-visible and Raman) detailing growth mechanisms for high track feature conductivity, producing a low sheet resistivity of 1.378 ± 0.001 Ω/□ and by the lighting of a 1.9 V, 250 mA Light Emitting Device, highlighting its application for conductive features processing. • Conductive films on PET fabric. • Ink jet printing particle-free silver-complex ink. • Conductive thin Ag films, 1.378 ± 0.001 Ω/□. • Enhancement of printed density and coverage by atmospheric plasma pre-treatment.

Networks derived from poly(methylhydrosiloxane) of various average molecular weights – characterization and incorporation of Pt particles

In the work, polysiloxane networks were prepared by hydrosilylative cross-linking of two poly(methylhydrosiloxane)s (PMHS) differing in the average molecular weight: PMHS1 of Mn = 3 800 g/mol and PMHS2 of Mn = 13 800 g/mol using linear divinyldisiloxane (ViMMVi) and cyclic tetravinyltetrasiloxane (D4Vi) as cross-linkers. It was found that PMHS2-based materials were characterized by higher cross-link densities than the PMHS1-derived ones, the effect being more pronounced in the case of D4Vi than ViMMVi. This was explained by the presence of entangled chains in PMHS2 and high functionality of D4Vi. Higher cross-link density resulted in lower rate of platinum incorporation into PMHS2-based networks, conducted in PtCl4 solutions in tetrahydrofuran. The reaction of Pt4+ ions from the solutions with Si-H groups remaining in the networks led to the formation of metallic Pt nanoparticles (2–5 nm in size) in all the materials. Due to higher cross-link density, however, which inhibited Pt penetration into the bulk, surface metal coverage in the PMHS2-originated networks was higher as compared to the ones obtained from PMHS1. Presence of Pt resulted in most cases in the increase in residual mass after treatment at 1000 °C in Ar atmosphere (the so-called ceramic yield) with respect to the initial samples. Results of the studies point to the significant influence of the average molecular weight on properties of PMHS-based networks and may be helpful when planning the use of such materials as ceramic precursors or as carriers for metal particles for various, e.g. catalytic applications.

Visible‐Blind ZnMgO Colloidal Quantum Dot Downconverters Expand Silicon CMOS Sensors Spectral Coverage into Ultraviolet and Enable UV‐Band Discrimination

Selective spectral detection of ultraviolet (UV) radiation is highly important across numerous fields from health and safety to industrial and environmental monitoring applications. Herein, a nontoxic, visible-blind, quantum dot (QD)-based sensing scheme that expands the spectral coverage of silicon complementary metal-oxide-semiconductor (CMOS) sensors into the UV, enabling efficient UV detection without affecting the sensor performance in the visible and UV-band discrimination, is reported. This scheme uses zinc magnesium oxide (ZnMgO) QDs with compositionally tunable absorption across UV and high photoluminescence quantum yield in the visible. The efficient luminescence and large Stokes shift of these QDs are exploited herein to act as an efficient downconverting material that enhances the UV sensitivity of Si-photodetectors (Si-PDs). A Si-PD integrated with the QDs results in a ninefold improvement in photoresponsivity from 0.83 to 7.5mA W-1 at 260nm. Leveraging the tunability of these QDs, a simple UV-band identification scheme is further reported, which uses two distinct-bandgap ZnMgO QDs stacked in a tandem architecture whose spectral emission color depends on the UV-band excitation light. The downconverting stack enables facile discrimination of UV light using a standard CMOS image sensor (camera) or by the naked eye and avoids the use of complex optics.

Low-profile visualized intraluminal support stent for the endovascular treatment of traumatic intracranial internal carotid artery pseudoaneurysms.

Optimal treatment strategies for traumatic intracranial internal carotid artery (ICA) pseudoaneurysms are controversial. The low-profile visualized intraluminal support (LVIS) device is a braided stent with a metal coverage rate between traditional laser cut stents and flow diversion devices. We report here our therapy strategy using the LVIS stent-assisted coiling for treatment of traumatic intracranial ICA pseudoaneurysms. Patients with traumatic intracranial ICA pseudoaneurysms treated by the LVIS stent-assisted coiling in our center between January 2015 and June 2021 were reviewed. The complications, radiographic, and clinical outcomes of these patients were analyzed. A total of 12 patients with 12 pseudoaneurysms were included. The mean maximum aneurysm diameter was 6.2 ± 3.1mm. Nine patients had a subarachnoid hemorrhage; five patients with Hunt-Hess grade III and four patients with grade IV. All procedures were successfully performed without intraoperative complications. Immediate postoperative angiogram showed that six (50%) aneurysms were Raymond grade 1, four (33.3%) were grade 2, and two (16.7%) were grade 3. Postoperative multiple cerebral infarction occurred in two patients because of vasospasm. Of the ten patients with angiographic follow-up (mean, 29.9months), two received additional coiling because of recanalization of the pseudoaneurysm, and all aneurysms were completely obliterated at the last examination of the patients. During the clinical follow-up period (mean, 26.8months), the overall mortality and morbidity were 25% (3/12) and 8.3% (1/12), respectively. LVIS stent-assisted coiling was a feasible approach for the treatment of traumatic ICA pseudoaneurysms.

Hemodynamic analysis and implantation strategies of delayed intracranial aneurysm rupture after flow diverter treatment.

BackgroundDelayed aneurysm rupture after flow diverters (FDs) is a serious complication which mechanism remains unclear. The hemodynamics of FDs with proximal or distal densification implantation strategies have rarely been reported. In this study, we investigated not only the hemodynamic factors involved in postoperative rupture, but also the hemodynamic effects of different FDs implantation strategies on avoiding this complication.MethodsWe selected 2 internal carotid artery (ICA) aneurysms with similar morphological characteristics, both of which were treated with FDs but had opposite therapeutic outcomes (Case 1, ruptured after FD treatment; Case 2, recovered). The FDs strategies we designed were strategy A [with homogeneous 30% metal coverage ratio (MCR)], strategy B (with distal densification of 40% and proximal 30% MCR) and strategy C (with proximal densification of 40% and distal 30% MCR). Virtually FDs deployment and computational fluid dynamics (CFD) method were performed to simulate FDs implantation strategies and analyze the hemodynamics associated with postoperative rupture.ResultsAfter FDs implantation, the velocity of blood entering the aneurysm decreased (Case 1, 25.4%; Case 2, 30.6%), but the inflow jet impingement still existed in Case 1. The overall WSS decreased similarly in both cases, but the high WSS region hardly diminished in Case 1. For overall wall pressure, Case 2 decreased slightly but increased in Case 1. Of the three FDs implantation strategies, strategy C had the best hemodynamic effects, including the maximum blood velocity reduction and a tendency to form a more stable flow pattern, the maximum reduction rate of overall WSS and the effective diminish of high WSS area as well as the overall decrease of wall pressure.ConclusionsNot significant decrease of blood flow velocity entering the aneurysm adding persistent impact of inflow jet impingement, high WSS area that did not diminish and abnormal increase of pressure on the aneurysm wall may be causative of postoperative rupture and bleeding of ICA aneurysms. In addition, the hemodynamic effects were favorable when the FD was improved to proximal densification, which may reduce the risk of delayed aneurysm rupture following FDs treatment.KeywordsDelayed rupture; flow diverter (FD); computational fluid dynamics (CFD); intracranial aneurysm (IAs); internal carotid artery (ICA)

Silver Nanoparticle-Decorated Silica Nanospheres and Arrays as Potential Substrates for Surface-Enhanced Raman Scattering.

Poly(vinylpyrrolidone) (PVP) was used as both a modifier and reductant to in situ deposit silver nanoparticles (denoted Ag NPs) on the surface of silica nanospheres (nanosilica or nano-SiO2), affording Ag-decorated nanosilica (denoted SiO2@Ag). The as-obtained SiO2@Ag composite can form silver nanoparticle-decorated silica nanosphere arrays (denoted SiO2@Ag arrays) via evaporation-induced self-assembly. The as-prepared SiO2@Ag composite and SiO2@Ag array were used as the SERS substrates to measure the Raman signals of the dilute solutions of rhodamine 6G (denoted R6G), an organic dye that is a potential pollutant to the environment. The findings indicate that the as-prepared SiO2@Ag composite and SiO2@Ag array as potential SERS substrates simultaneously exhibit a high degree of metal coverage and small size of Ag NPs as well as good stability and abundant “hot spots”, which contributes to their desired Raman enhancement capacities. For the detection of trace R6G, they provide a limit of detection of as low as 10–9–10–11 M as well as good reproducibility, showing promising potential for monitoring chemical and biological molecules.

Graphene/Phosphorene nano-heterostructure as a potential anode material for (K/Na)-ion batteries: Insights from DFT and AIMD

Rechargeable Potassium and Sodium-ion batteries started to receive a vast amount of attention in recent years against their Lithium-ion counterparts. However, the development of a high-performing anode material for these ion batteries is still to be explored. In this work, we conduct a first-principles study on the adsorption and diffusion behaviors of Potassium (K) and Sodium (Na) in a Graphene/Phosphorene (G/P) van der Waals nano-heterostructure, in order to assess its suitability as an anode for both K-ion and Na-ion batteries. We investigate the electrochemical properties of the system, including binding energies, band structure, ion diffusivity out-side and in-side the G/P system, as well as the heterostructure’s stability at a high metallic coverage. The calculated binding energies for K and Na are −2.69 eV and −2.42 eV, respectively, which are strong enough to prevent metallic clustering during the cycling. The diffusion of K/Na within G/P’s regions shows strong directional anisotropy with a low diffusion barrier of 0.04 eV for K and 0.05 eV for Na along the zigzag direction. We also observe that the addition of K/Na atoms into the G/P system turns its semi-metallic nature into a metallic one. Moreover, we demonstrate that the intercalation of K/Na atoms within the G/P structure give low operating potentials of approximately 0.29 V for K and 0.58 V for Na. Thus, the nano-heterostructure can provide a theoretical storage capacity of 433 mAh/g and 580 mAh/g respectively for K and Na. Finally, the thermal stability of a fully potassiated/sodiated G/P system at room temperature is revealed by the ab-initio Molecular-Dynamics (AIMD) calculations. Considering all these properties, we conclude that the G/P nano-heterostructure can be considered as a good candidate for negative-electrode-materials for both K- and Na-ion batteries.