Cu-based nanomaterials have received considerable attention as promising and cost-effective substrates for surface-enhanced Raman spectroscopy (SERS) applications despite their relatively low enhancement factor (EF) compared to noble metals like gold and silver. In this study, a fast and affordable synthesis route is proposed to obtain a three-dimensional porous copper film (NPC) via an electrodeposition technique based on the dynamic hydrogen bubbling template (DHBT). Two sets of NPC film were synthesized, one without additives and the other with cetyltrimethylammonium bromide (CTAB). The impacts of deposition time on the NPCs' porous morphology, thickness, and SERS performance were systematically investigated. With the optimal deposition time, the nanopore sizes could be tailored from 26.8 to 73 μm without additives and from 12.8 to 24 µm in the presence of CTAB. The optimal additive-free NPC film demonstrated excellent SERS performance at 180 s of deposition, while the CTAB-modified film showed strong enhancement at 120 s towards methylene blue (MB), a highly toxic dye, achieving a detection limit of 10-6 M. Additionally, the samples with CTAB showed better efficiency than those without CTAB. The calculated EF of NPC was found to be 5.9 × 103 without CTAB and 2.5 × 103 with the CTAB, indicating the potential of NPC as a cost-effective candidate for high-performance SERS substrates. This comprehensive study provides insights into optimizing the structural morphology of the NPCs to maximize their SERS enhancement factor and improve their detection sensitivity toward MB, thus overcoming the limitations associated with conventional copper-based SERS substrates.

A low-cost Nanoporous Gold (NPG) has been successfully prepared by chemical dealloying of a Au33Fe67 supersaturated solid solution, whose ribbons were obtained by rapid solidification using melt-spinning technique. The dealloying procedures were carried out in 1M HNO3 at 70 °C for varying durations. As-quenched ribbon and dealloyed samples have been structurally and compositionally investigated using XRD, FESEM and EDS techniques. The obtained NPG is homogeneous with tunable ligament size and shape, easy-to-handle and free-standing. Most notably, a metastable precursor has been favourably obtained from an immiscible Au-Fe system. Furthermore, according to the characterization results, a mechanism of dealloying has been proposed. Pairing Au with cheap and abundant Fe and fabricating an Fe-rich precursor gives an exceedingly cost-effective starting material. No usage of critical raw materials is involved. Then, employing a straight-forward and rapid dealloying procedure to obtain the NPG sample, makes for an overall inexpensive and sustainable production.

This research investigates the nanoscopic features of Advanced High-Strength Steels (AHSS) through a bottom-up approach employing high-speed nanoindentation mapping (HSNM) to elucidate structure-property relationships. The influence of grain boundaries on nanomechanical properties was documented, highlighting the challenge of SEM-EBSD analysis in differentiating phases with identical crystal structures (BCC, FCC, etc.). Integrating SEM-EBSD with HSNM in the same region of interest is essential for detailed insights into phase/microstructure distribution and accurate grain boundary identification.A modular four-step analysis protocol, designed and validated on ferritic-bainitic TRIP steels (TBF), leverages machine learning-enhanced HSNM for significant advancements in AHSS design. The initial phase involves the application of the expectation-maximization algorithm for probability distribution fitting of HSNM data, deriving primary mechanical phase statistics. This exclusively facilitates the correlation of elastic modulus and hardness for each phase/microstructure using nanoindentation data. Further refinement of phase/microstructure to mechanical property correlations was achieved through a supervised machine learning approach, ensuring precise association between EBSD and nanoindentation data. This includes detailed image analysis and clustering of nanoindentation data, enhancing the precision in phase recognition.This methodology addresses the critical challenges in developing 3rd Generation AHSS, aiming to fill the gap in accurately identifying and quantifying phases such as martensite, austenite, bainite, and ferrite, thereby reducing classification and measurement uncertainties. The approach contributes to the fundamental understanding of AHSS microstructures and provides a scalable framework for the comprehensive characterization of structural materials.

In this paper, we have studied the effect on the structure and magnetic properties of partial Pd substitution by Gd in Fe–Pd thin films of nominal composition Fe56Pd44−xGdx (x = 1, 3, 5, and 7), deposited onto Si(100) and Si(100)/SiO2 substrates by thermal evaporation. Several techniques contribute to the characterization of their microstructure and magnetic properties, such as x-ray diffraction (XRD), scanning electron microscopy, alternating gradient field magnetometry, and magnetic force microscopy (MFM). X-ray diffraction shows that the as-deposited films are either amorphous or contain a disordered FePd phase, depending on the film thickness. The transformation of disordered fcc-FePd into ordered fct-FePd has been induced by a heat treatment at 530 °C for 4 h. The addition of gadolinium leads to a reduction in the coercivity as a consequence of the emergence of soft phases and of the progressive reduction of the fct-FePd phase, which is primarily responsible for the observed maze magnetic domains. The exchange coupling between the soft phase and the hard fct-FePd phase is demonstrated by first-order reversal curves (FORCs).

The recognition of phases and microstructures in TRIP-assisted bainitic-ferritic steels is challenging and requires sophisticated techniques to gain insights and reveal mechanical features with nanoscale precision. EBSD and nanoindentation have been employed to assess the surface composition and their properties within a reporting depth of 30 nm. Correlative mechanical microscopy and data science were used to overcome the shortcomings associated with the lack of an inclusive solution that combines the metadata from both techniques. A modular methodology is presented, which involves routines for exploiting structural and mechanical data via reproducible Machine Learning models (code and data are shared). The approach is structured to facilitate reuse by research community for correlating characterization mapping data, not limited to nanoindentation and EBSD. Gaussian mixture models are adopted to extract mechanical phases utilizing the nanomechanical properties. The K-means++ method is used for the first time to mine information from Inverse Polar Figure (IPF) mapping about anisotropy and to extract the knowledge from images for each grain, including grain coordinates and size. Moreover, k-nearest-neighbours regression was used to perform data imputation to fill in the values of descriptors related to missing coordinates relative to those of nanoindentation, grain boundary, EBSD phase, and EBSD anisotropy maps.

Amorphous alloys show potential as implant materials due to their superior mechanical properties and good corrosion resistance. However, the presence of toxic elements in the alloy composition can pose challenges, as they can react with the surrounding tissue, leading to inflammation and cell death. To address this, Ti40Cu40Zr11Fe3Sn3Ag3 at% amorphous alloy is developed. This composition comprises of biocompatible elements (Ti, Zr, and Sn) and antimicrobial elements (Ag, Fe, and Cu), for potential use as implant materials. Chemical pseudo-dealloying using a solution of ammonium hydroxide and hydrogen peroxide is employed to selectively remove copper from the sample surface, which may induce toxicity by prolonged contact, and promote the formation of a patterned passivating Ti/Zr oxide-rich surface to enable possible antimicrobial effects. The surface of the samples was analyzed using atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The modified surfaces show titanium oxide-rich nanostructured topography with depleted amounts of copper from the surface. The kinetics of the selective removal of copper, and the influence of parameters such as electrolyte concentration, immersion time, and stirring velocity on the evolution of morphology were investigated. Our findings elucidate the mechanism of pseudo-dealloying using an ammonia-based solution and demonstrate its efficacy in enhancing the biocompatibility of the alloy. In detail, the pseudo-dealloyed samples exhibited hydrophilic interactions and demonstrated hemocompatibility, making them promising candidates for blood-contacting medical devices. This study underscores the significance of our approach in tailoring the surface properties of amorphous alloys for biomedical applications, paving the way for their utilization in implant materials with improved biocompatibility.

This study focuses on the design of a new Ti based multicomponent amorphous alloy for the development of biocompatible implant materials with enhanced hemocompatibility and cytocompatibility. While this class of amorphous alloys has shown its potential for biomedical implant applications, there are major concerns due to the presence of elements such as copper which can lead to cytotoxicity in the human body during long term implantation. Nevertheless, copper is indispensable in the development of an amorphous alloy. Thus, the objective of this work is to selectively remove copper from the surface of the Ti40Cu40Zr11Fe3Sn3Ag3 (at%) amorphous alloy using the dealloying technique and produce a patterned protective passivated surface rich in Ti and Zr oxides. Nitric acid (HNO3) has been found to be effective in depleting copper from the sample surface. Optimization of treatment parameters such as temperature (70 °C and room temperature) yielded drastic differences in the morphology of the samples studied using Field-Emission Scanning Electron Microscopy. The treated sample surface demonstrated good hemocompatibility and cytocompatibility with primary human osteoblast cells (HOb) and human osteosarcoma cell line (Saos-2). Additionally, the treated samples showed higher ability to produce reactive oxygen species with respect to pristine samples, which could be convenient for preserving the implant from bacterial contamination. These findings contribute to the advancement of producing copper-depleted nanostructured Ti based amorphous alloys for biomedical implant applications.

In this paper we have studied the effect on the structure and magnetic properties of partial Pd substitution by Gd in Fe-Pd thin films of nominal composition Fe56Pd44-xGdx (x = 1, 3, 5 and 7), deposited onto Si(100) and Si(100)/SiO2 substrates by thermal evaporation. Several techniques contribute to the characterisation of their microstructure and magnetic properties, such as, X-ray diffraction (XRD), scanning electron microscopy (SEM), alternating gradient field magnetometry (AGFM), magnetic force microscopy (MFM). The X-ray diffraction shows that the as-deposited films are either amorphous or contain a disordered FePd phase, depending on film thickness. The transformation of disordered fcc-FePd into ordered fct-FePd has been induced by a heat treatment at 530 °C for 4 hours. The addition of gadolinium leads to a reduction of the coercivity as a consequence of emergence of soft phases and of the progressive reduction of the fct-FePd phase which is primarily responsible for the observed maze magnetic domains. The exchange coupling between the soft phase and the hard fct-FePd phase is demonstrated by first-order reversal curves (FORC).

The ultramafic body of Monte Avic (Aosta Valley, Western Alps, Italy) consists of antigorite serpentinite and Ti-clinohumite metadunite. They host late metamorphic veins, up to a couple of centimeters thick, compact, and homogeneous, with a "porcelain" appearance. Vein colors range from yellowish to light greenish, light yellowish fading to white, or rare orange. The veins consist of 15-sector PS-15 polygonal serpentine, with chemical composition Mg-2.85 Fe-0.08 Si-2.05 O(7.0)5 [OH](3.95). Recognition of this unusual phase is supported by diagnostic satellite reflections in the X-ray powder diffraction pattern (e.g., at d(obs) of 2.502, 2.336, 2.151, and 1.966 angstrom) TEM images (showing 15-sector polygonal fibers, mostly 200 nm in diameter and a few mu m in length, forming a randomly oriented felt) and a mu-Raman wavenumber, matching previous data. This different evidence affords the successful distinction of PS-15 and PS-30, alternatively using TEM images, X-ray powder diffraction, or the low- and high-wavenumber mu-Raman spectra. At Monte Avic, the vein emplacement was accompanied by significant fluid pressure, as suggested by deformation and dismembering of the host rock, with PS-15 grown within isotropic stress microenvironments characterized by fluid-filled voids. Random growth of the mass-fiber polygonal serpentine was favored by low-strain conditions. PS-15 veins formed at the end of the long polyphase Alpine orogenic evolution, with hydrous fluids possibly deriving from serpentinite dehydration in the depth.

In this work, melt-spun ribbons of AlSi10Mg added with modifiers (Er, Sr, or nano-TiB 2 ) were produced to investigate the combined effect of modification and rapid solidification on eutectic Si. The resulting eutectic microstructures are more isotropic in comparison to that of the base alloy affecting the mechanical properties of the alloys. The modification of Si morphology and supersaturation caused by the modifiers were investigated by microscopy, X-ray diffraction, and differential scanning calorimetry. Compared to melt-spun AlSi10Mg, the eutectic Si network is finer and less continuous when Er or Sr is added, and disrupted with rounded crystals dispersed in the matrix when adding nano-TiB 2 . The level of supersaturation decreases in the order Er–nano-TiB 2 –Sr. A transition from columnar Al grains at the wheel side to finer equiaxed grains at the air side was found in the unmodified ribbon and in the one containing nano-TiB 2 by means of electron backscattered diffraction. The Er- and Sr-modified ribbons display equiaxed Al grains of constant size throughout their thickness. The average hardness obtained by nano-indentation tests was lower than that of AlSi10Mg. The less continuous Si network causes the hardness drop but provides more isotropic mechanical properties.

A low-cost Nanoporous Gold (NPG) has been successfully produced by utilizing the simple method of chemical dealloying. Ribbons of a supersaturated solid solution Au33Fe67 were obtained by rapid solidification using melt -spinning technique. Chemical dealloying of the ribbons was achieved in 1 M HNO3 at 70 degrees C for varying lengths of time. The as-quenched ribbon and as-dealloyed samples have been structurally and compositionally investigated using XRD, FESEM and EDS techniques. The obtained NPG is homogeneous with tunable ligament size and shape, easy-to-handle and free-standing. NPG has been successfully applied as substrate for Surface-Enhanced Raman Scattering (SERS) using 4,4 '-bi-pyridine probe molecule. An impressive enhancement in the SERS effect has been observed. The detection limit is recorded to be as low as 10-15 M. The NPG sample shows great potential as an economical and highly sensitive SERS-active substrate for life science applications and ultrasensitive instru-mentation. Catalytic properties have been explored demonstrating a high activity of the material. Most notably, a metastable precursor has been favourably obtained from an immiscible Au-Fe system. Usage of critical raw materials has been avoided. A cost-effective starting material has been used in the form of an Fe-rich precursor by pairing abundant and cheap Fe with Au. Then, an elegant and rapid dealloying procedure makes the overall production of NPG an inexpensive and sustainable process.

Abstract Crystalline silica (CS) is a well-known human carcinogen and freshly fractured CS is strongly held to be more toxic than aged dust. Mechanical fracturing indeed generates on CS surface a specific family of Nearly-Free Silanols (NFS), a moiety that was proved to destabilize cell membranes and initiate inflammation in vivo. During milling, silica nanoparticles are also generated, however their contribution to the overall toxicity of quartz is still largely unexplored. Nanoquartz can be synthetized via bottom-up methods, but the surface chemistry of those crystals strongly differs from nanoparticles resulting from fracturing. We report here a top-down milling procedure to obtain a nanometric quartz that shares with fractured quartz the key surface properties relevant to toxicity. Fracturing procedure was optimized by coupling dry and wet milling steps, using water as a dispersing agent, and varying milling times and rotational speeds. We obtained a set of samples that would be classified as nanomaterials under EU CLP regulation (>50% of particles in number are < 100 nm) and exhibited a strong tendency to form submicrometric agglomerates. Deagglomeration with surfactants or simulated body fluids was negligible. Partial lattice amorphization and bimodal crystallite domain size were observed, as confirmed by the presence of two distinct domains of scattering with nanometric (< 50 nm) and submicrometric (0.8-1 µm) crystallite size. A moderate membranolytic activity, which nicely correlated with the amount of surface NFS, signalled that our nanoquartz may induce inflammation in vivo. Overall, a membranolytic nanoquartz for investigating the toxic activity of nanometric silica was obtained.

Occupational exposure to quartz dust is associated with fatal diseases. Quartz dusts generated by mechanical fracturing are characterized by a broad range of micrometric to nanometric particles. The contribution of this nanometric fraction to the overall toxicity of quartz is still largely unexplored, primarily because of the strong electrostatic adhesion forces that prevent isolation of the nanofraction. Furthermore, fractured silica dust exhibits special surface features, namely nearly free silanols (NFS), which impart a membranolytic activity to quartz. Nanoquartz can be synthetized via bottom-up methods, but the surface chemistry of such crystals strongly differs from that of nanoparticles resulting from fracturing. Here, we report a top-down milling procedure to obtain a nanometric quartz that shares the key surface properties relevant to toxicity with fractured quartz. The ball milling was optimized by coupling the dry and wet milling steps, using water as a dispersing agent, and varying the milling times and rotational speeds. Nanoquartz with a strong tendency to form submicrometric agglomerates was obtained. The deagglomeration with surfactants or simulated body fluids was negligible. Partial lattice amorphization and a bimodal crystallite domain size were observed. A moderate membranolytic activity, which correlated with the number of NFS, signaled coherence with the previous toxicological data. A membranolytic nanoquartz for toxicological investigations was obtained.

Galactic cosmic rays (GCR) are among the main deterrents to manned space exploration. Currently, the most realistic way to reduce the dangers caused by GCR to acceptable levels is passive shielding. Light materials guarantee the strongest dose attenuation per unit mass. High-density polyethylene is considered the gold standard for radiation protection in space. Nevertheless, accelerator-based experimental campaigns already showed the advantages of more hydrogen-rich innovative shielding materials such as lithium hydride. The experimental campaigns of this work focused on the absorbed dose attenuation properties of lithium-based hydrides chemically stabilized with a paraffin matrix. Such materials were compared to pure lithium-based hydrides, polyethylene, structural materials such as spacecraft aluminum alloys and lithium batteries, and in situ shielding materials such as Moon regolith and its main components silicon and silicon dioxide. The experimental results were compared to simulations performed with PHITS, FLUKA, and Geant4, which are among the most used Monte Carlo codes for radiation protection in space. The simulations showed systematic differences and highlighted the pressing need for reliable nuclear cross-section models.

In this study, we report nanoporous gold (NPG) as an economic, efficient, and stable alternative electrocatalyst for methanol electro-oxidation. The said sample was successfully prepared from an Fe-rich metastable Au33Fe67 supersaturated solid solution acting as the precursor, which was formed into ribbons by the phenomenon of rapid solidification using melt-spinning technique. The as-quenched ribbon was then chemically dealloyed in 1 M HCl at 70 °C for different durations of time. A homogeneous, free-standing, and mechanically stable NPG sample was obtained with tunable ligament shape and size. The morphology and composition were characterized by using SEM with EDS, while the structure by XRD. The sample was examined as an electrocatalyst for methanol electro-oxidation profiting off its large surface area; cyclic voltammetry (CV) was the technique employed for electrochemical studies. In a basic solution of methanol and KOH, the sample displays a low peak potential of 0.47 V vs. Ag/AgCl for methanol electro-oxidation with a high peak current density of 0.43 mA/cm2. In addition, it demonstrates outstanding stability and high poisoning tolerance. It is noteworthy that the fabrication process of the NPG sample from start to end was intentionally opted to be sustainable, cost-effective, rapid, and feasible. The usage of critical raw materials was avoided. As a whole, the properties and results put forth by the NPG sample make it an inexpensive, sustainable, and excellent alternative as an electrocatalyst for methanol electro-oxidation.

Crystalline silica (CS) is a well-known human toxicant and inhalation of the airborne particles with size lower than 4 µm is associated to severe occupational diseases, such as silicosis and lung cancer.1 The International Agency for the Research on Cancer (IARC) classified CS as carcinogenic to humans and freshly fractured CS is held to be more toxic than aged dust.1,2 Fracturing generates on CS a specific family Nearly-Free Silanols (NFS), which are able to destabilize cell membranes,3 and some nanometric particles. We aim here to create and assess the possible toxicological impact and the chemical characteristics of the nanometric fraction (nano-CS) formed when CS is fractured. A highly pure CS of synthetic origin4 (α-quartz, micrometric in size) was ball-milled to obtain ultrafine particles. We coupled a dry milling step and a wet milling step, using water as dispersing agent, and we generated particles with specific surface area (SSA) ranging from 37 to 60 m2/g. These SSA values signaled the generation of a relevant nanometric fraction. The increase in SSA paralleled the energy delivered to quartz during the milling, that exceeded by far the energies commonly used in industrial processing. Morphology, crystallinity, size, surface silanols, including quantification of NFS, and membranolytic activity toward red blood cells were assessed. The nano-CS samples exhibited: i) a partial lattice amorphization that increased with the increase of the milling energy; ii) the presence of two distinct domains of scattering that indicated the occurrence of crystallite with nanometric (< 50 nm) and submicrometric (0.8-1 µm) size; iii) a strong tendency to form micrometric agglomerates , which could be partially dispersed with ultrasounds and surfactants in water suspensions; and iv) a moderate membranolytic activity that correlated with the presence of NFS. We selected a nano-CS sample that would be classified as a nanomaterial under EU CLP regulation (>50% of particles in number are < 100 nm).5 The nano-CS sample will be used in the next future as a reference material to quantify the nanometric fraction of silica powders and assess the potential exposure to nano-CS in industrial hygiene context. In conclusion, the preparation and characterization of nano-CS was achieved and the physico-chemical characteristics that could be relevant for silica toxicity were assessed. The nano-CS reference material will be used to quantify nano-CS in industrial scenario, and to clarify the toxic activity of nanometric silica obtained by mechanical fracturing. [1] IARC, Monograph Vol. 100C, 2012 [2] Turci et al, Part Fibre Toxicol, 2016, 13, 32. [3] Pavan et al, Proc. Natl. Amer. Soc. USA, 2020, 117 (45), 27836 [4] Pastero et al., 2016, Cryst. Growth Des. 16, 4, 2394–2403. [5] SCoEaNIHR, E. S., 2010, 'Scientific Basis for the Definition of the Term “nanomaterial”', European Commission.

AbstractOccupational exposure to quartz dust is associated with fatal diseases. Quartz dusts generated by mechanical fracturing are characterized by a broad range of micrometric to nanometric particles. The contribution of this nanometric fraction to the overall toxicity of quartz is still largely unexplored, primarily because of the strong electrostatic adhesion forces that prevent isolation of the nano-fraction. Furthermore, fractured silica dust exhibits special surface features, namely Nearly Free Silanols (NFS), which impart membranolytic activity to quartz. Nanoquartz can be synthetized via bottom-up methods, but the surface chemistry of those crystals strongly differs from nanoparticles resulting from fracturing. We report here a top-down milling procedure to obtain a nanometric quartz that shares with fractured quartz the key surface properties relevant to toxicity. Ball milling was optimized by coupling dry and wet milling steps, using water as a dispersing agent, and varying milling times and rotational speeds. Nanoquartz with a strong tendency to form submicrometric agglomerates was obtained. Deagglomeration with surfactants or simulated body fluids was negligible. Partial lattice amorphization and bimodal crystallite domain size were observed. A moderate membranolytic activity, which correlated with the amount of NFS, signaled coherence with previous toxicological data. Membranolytic nanoquartz for toxicological investigations was obtained.

An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The two most common polymorphs of MnO2, ramsdellite and pyrolusite, are often found in natural association. Our starting sample is from the Mistake mine (Arizona) containing macroscopic crystals of both ramsdellite (a = 4.5131(6), b = 9.2689(13), c = 2.8610(4) Å, V = 119.69(3) Å3; S.G. Pbmn) and pyrolusite (a = 4.4030(2), c = 2.87392(16) Å, V = 55.715(5) Å3; S.G. P42/mnm), along with a smaller amount of “groutellite”. A mixed powder was used to study the ramsdellite→pyrolusite transformation by in situ high-temperature X-ray powder diffraction. Our results reveal that this transformation is not a direct transition, but it occurs in two steps, as a function of temperature; ramsdellite transforms into an amorphous phase, which then recrystallizes into pyrolusite. Amorphization of ramsdellite and crystallization of pyrolusite kinetics were studied by the universal equation for solid–solid reactions. The two activation energies are comparable, but the pre-exponential factor of the ramsdellite amorphization is two orders of magnitude larger than pyrolusite crystallization’s. As a consequence, ramsdellite→pyrolusite transformation implies the formation of an amorphous transition, due to a mismatch between the conversion rates, that reaches its maximum at around 630 K and then decreases at higher T, when pyrolusite crystallization is strongly promoted.

Characterized by a large surface area to volume ratio, nanostructured metal oxides possess unique chemical and physical properties with applications in electronics, catalysis, sensors, etc. In this study, Mo3Al8, an intermetallic compound, has been used as a precursor to obtain nanostructured molybdenum oxides. It was prepared into ribbons by arc-melting and melt-spinning techniques. Single and double-step free corrosion of the as-quenched material have been studied in 1 M KOH, 1 M HF and 1.25 M FeCl3 at room temperature. In both cases, nanostructured molybdenum oxides were obtained on a surface layer a few microns thick. Two of the as-prepared samples were tested for their electrocatalytic capability for hydrogen evolution reaction (HER) in 0.5 M H2SO4 giving low onset potential (−50 mV, −45 mV), small Tafel slopes (92 mV dec−1, 9 mV dec−1) and high exchange current densities (0.08 mA cm−2, 0.35 mA cm−2 respectively). The proposed nanostructured molybdenum oxides are cost-effective and sustainable due to the cheap and abundant starting material used and the simple synthetic route, paving the way for their possible application as HER electrocatalysts.