Dark-field Transmission Electron Microscopy Research Articles

Quantitative revealing the solute segregation behavior at melt pool boundary in additively manufactured stainless steel using a novel processing method for precise positioning by HAADF-STEM

Laser-powder bed fusion (LPBF) enables the fabrication of complex metallic components by manipulating various laser scan strategies to control microstructure and texture. Multiple thermal cycling and rapid solidification lead to non-equilibrium, non-uniform microstructure, and micro-segregation at the melt pool boundary (MPB), whose accurate location is still invisible by transmission electron microscopy (TEM), and quantitative concentration remains imprecise. In this study, we proposed a novel method to make it clear by controlling the crystallographic texture of 316 L stainless steel through unique LPBF processing parameters to obtain a single-crystal-like microstructure of the cellular structures along the laser scanning direction. The accurate location of the track-track MPB is distinguishable by means of the transverse and longitudinal cellular dislocation structures on both sides. The edge-on state of the track-track MPB makes the quantitative concentration analysis precisely using high-angle annular dark-field scanning TEM with energy-dispersive X-ray spectroscopy, which is in good agreement with the Scheil-Gulliver solidification simulations.

Correlative Lorentz and Dark Field TEM for Studying Skyrmion-Defect Interactions in van der Waals Ferromagnet Co-doped Fe5GeTe2

Correlative Lorentz and Dark Field TEM for Studying Skyrmion-Defect Interactions in van der Waals Ferromagnet Co-doped Fe5GeTe2

Complex-Color Darkfield TEM Interfaces for Crystal, Defect, & Strain Analysis

Complex-Color Darkfield TEM Interfaces for Crystal, Defect, & Strain Analysis

Unveiling microstructural damage for leakage current degradation in SiC Schottky diode after heavy ions irradiation under 200 V

Single-event burnout and single-event leakage current (SELC) in silicon carbide (SiC) power devices induced by heavy ions severely limit their space application, and the underlying mechanism is still unclear. One fundamental problem is lack of high-resolution characterization of radiation damage in the irradiated SiC power devices, which is a crucial indicator of the related mechanism. In this Letter, high-resolution transmission electron microscopy (TEM) was used to characterize the radiation damage in the 1437.6 MeV 181Ta-irradiated SiC junction barrier Schottky diode under 200 V. The amorphous radiation damage with about 52 nm in diameter and 121 nm in length at the Schottky metal (Ti)–semiconductor (SiC) interface was observed. More importantly, in the damage site the atomic mixing of Ti, Si, and C was identified by electron energy loss spectroscopy and high-angle annular dark-field scanning TEM. It indicates that the melting of the Ti–SiC interface induced by localized Joule's heating is responsible for the amorphization and the possible formation of titanium silicide, titanium carbide, or ternary phases. The mushroom-like hillock in the Ti layer can be attributed to Rayleigh–Taylor instability, as another evidence for ever-happened localized melting near the Schottky interface. These modifications at nanoscale in turn cause localized degradation of the Schottky contact, resulting in permanent increase in leakage current. This experimental study provides very valuable clues for a thorough understanding of the SELC mechanism in SiC diodes.

Bridge-oxygen bonding modulates Ru single atoms for peroxymonosulfate activation: Importance of high-valent Ru species and 1O2

The application of single-atom catalysts (SACs) to advanced oxidation processes (AOPs) based on peroxymonosulfate (PMS) has attracted considerable attention. However, the catalytic pathways and mechanisms underlying these processes remain unclear. In this study, NiFe-LDH was synthesized and single Ru atoms were stably loaded onto it by forming Ru–O–M (M=Ni or Fe) bonds (Ru@NiFe-LDH). This was demonstrated using high-angle annular dark-field scanning TEM (HAADF-STEM) and X-ray absorption fine structure spectra (XANES). The Ru@NiFe-LDH/PMS system showed a high catalytic reactivity (100 % sulfamethoxazole degradation in only 30 min), high stability (97 % reactivity was maintained after continuous operation for 400 min), and wide pH suitability (working pH range 3–11) for AOPs. The crucial roles of the high-valent species (Ru(V) = O) and 1O2 in this reaction were verified. Density functional theory (DFT) calculations revealed that electron transfer produced a positively charged Ru. This enhances the adsorption of negatively charged PMS anions onto the Ru monoatomic sites, thereby, causing the formation of Ru-PMS* complexes. This study implies that the structure–function relationship between organic compounds and SACs plays a significant role in PMS-based AOPs, and provides a comprehensive mechanism for the role of high-valent species in heterogeneous Fenton-like systems.

Cu-based nano-multilayer film produced by HiPIMS for antimicrobial properties and its application in photodetector

This paper reports on the use of high-power impulse magnetron sputtering to deposit Cu-based nano-multilayer films (CuZrTiAl) on Si wafers and AISI 304 stainless steel. Co-sputtering can be performed using multiple simultaneous targets to decrease the cost of manufacturing alloy targets at industrial scales. Co-sputtering mode allows variations in the power supplied to the various targets to control the intensity of the plasma jets and thereby tailor the composition of the deposited films. Our primary aim in this study was to elucidate the effects of Al target power (from 0.3 to 1.3 kW) on the structure and antibacterial properties of the resulting coatings. Varying the Al target power was shown to alter the chemical composition, layer thickness, and structure. EPMA results revealed that increasing the power from 0.3 to 1.3 kW caused a monotonic increase in Al content from 6.1 to 18.3 at%. Dark-field TEM images revealed that decreasing the period thickness from 8.6 to 4.6 nm caused the ultra-thin film Cu to transform into a single isolated nano-crystal, which facilitated the release of Cu ions to improve antibacterial effects (from 84 % to 99 % for Escherichia coli). This study also demonstrated the recycling of the proposed Cu-based nanoscale multilayer films to fabricate metal-doped ZnO nanowires for use in photodetectors. The photodetector achieved a photocurrent-to-dark-current ratio of 150 when using an LED light source with a wavelength of 365 nm.

Hot deformation behaviour of Swaged Zircaloy-4 at varying strain rate and its microstructural evolution

Zirconium alloy demonstrates a favourable combination of strength, ductility, low neutron absorption cross-section, as well as excellent corrosion and oxidation resistance. In the context of its application as a reactor component, the critical hot deformation behaviour of isothermally swaged Zr-4 alloy has been extensively studied. Different combinations of elevated temperatures (873 K to 1023 K) and strain rates (0.01 s−1 to 10/s) have shown enhancement in flow stress. Analysis of stress flow, microstructural changes, and activation energy behaviour was performed using a state-of-the-art thermomechanical simulator with 50% reduction in sample thickness. The modified Arrhenius equation was employed to correlate theoretical and experimental flow stress behaviour. EBSD was utilized to understand texture evolution in hot deformed samples, revealing a transformation from pure basal to basal plus pyramidal poles concerning the compression direction. Texture evolution played a significant role in microstructural development, further characterized through TEM, which showed influential characteristics like subgrain boundaries, dislocations, and precipitate behaviour. Dynamic recrystallization mechanisms in swaged Zr-4 hot deformed samples were analysed using bright and dark field TEM modes, which were subsequently correlated with other microstructural characteristics such as grain morphology and structural defects.

Dual-scale clusters enabling exceptional mechanical properties of a CoNiCr-based MP159 superalloy at 650 °C

Prior or early-stage precipitation products, e.g., GP zones and chemical short-range ordering, attract tons of interests recently due to their extremely small size and notable hardening effects. In this work in a commercial CoNiCr-based MP159 superalloy, we, for the first time, simultaneously introduced two kinds of these products, i.e., the atomic-scale L11 cluster, and the nano L12 cluster with 2.7 nm in size, by simply removing the standard annealing process and directly conducting the intermediate 650 °C tension. The ultra-dense co-existence of these dual-scale clusters generates over 200 MPa hardening effect at the specific 650 °C when compared to the standardly-annealed MP159 alloy that contains only larger (∼6.0 nm) L12 precipitates. High-angle annular dark field-transmission electron microscopy associated with atom probe tomography evidence that firstly, the atomic-scale cluster is of the L11 type, similar to the one observed in the NiCoV medium entropy alloy. And secondly, the composition of the nano L12 cluster is abnormally close to (Ni,Co)3Ti, whose equilibrium crystalline structure is otherwise D024. This likely leads to a high anti-phase boundary energy hence high shearing resistance for dislocations.

Semantic integration of diverse data in materials science: Assessing Orowan strengthening

This study applies Semantic Web technologies to advance Materials Science and Engineering (MSE) through the integration of diverse datasets. Focusing on a 2000 series age-hardenable aluminum alloy, we correlate mechanical and microstructural properties derived from tensile tests and dark-field transmission electron microscopy across varied aging times. An expandable knowledge graph, constructed using the Tensile Test and Precipitate Geometry Ontologies aligned with the PMD Core Ontology, facilitates this integration. This approach adheres to FAIR principles and enables sophisticated analysis via SPARQL queries, revealing correlations consistent with the Orowan mechanism. The study highlights the potential of semantic data integration in MSE, offering a new approach for data-centric research and enhanced analytical capabilities.

Detection of BiGa hetero-antisites at Ga(As,Bi)/(Al,Ga)As interfaces

In this work, we show how diffraction-based chemically sensitive dark-field transmission electron microscopy (DFTEM) reveals the presence of Bi hetero-antisites (BiGa) at the interface of Ga(As,Bi)/(Al,Ga)As quantum well (QW) structures grown by molecular beam epitaxy on GaAs(001). The presence of BiGa is demonstrated by the striking appearance of “dark-lines” at the interfaces under two-beam DFTEM imaging conditions using the (002) diffraction spot. Additional analytical scanning (S)TEM procedures reveal Ga depletion and Bi accumulation at the exact position of the dark-lines, consistent with BiGa at this location. The precise location of the dark-lines agrees with the position of growth interruptions made to adjust substrate temperature and the As/Ga flux ratio and, most importantly, the realization of a Bi pre-treatment before QW growth. We believe the Bi pre-treatment may have favored formation of BiGa hetero-antisites. We validate the use of g002 DFTEM for further investigations of the intricate bismuth incorporation into the lattice and its dependence on the growth conditions. Finally, g002 DFTEM imaging is positioned as a very powerful technique for the detection of point defects in general in materials with the zinc-blende crystal structure, beyond dilute bismide alloys.

A P2/P3 Biphasic Layered Oxide Composite as a High-Energy and Long-Cycle-Life Cathode for Potassium-Ion Batteries.

Layered transition metal oxides are extensively considered as appealing cathode candidates for potassium-ion batteries (PIBs) due to their abundant raw materials and low cost, but their further implementations are limited by slow dynamics and impoverished structural stability. Herein, a layered composite having a P2 and P3 symbiotic structure is designed and synthesized to realize PIBs with large energy density and long-term cycling stability. The unique intergrowth of P2 and P3 phases in the obtained layered oxide is plainly characterized by X-ray diffraction refinement, high-angle annular dark field and annular bright field-scanning transmission electron microscopy at atomic resolution, and Fourier transformation images. The synergistic effect of the two phases of this layered P2/P3 composite is well demonstrated in K+ intercalation/extraction process. The as-prepared layered composite can present a large discharge capacity with the remarkable energy density of 321 Wh kg-1 and also manifest excellent capacity preservation after 600 cycles of K+ uptake/removal.

Electrocatalysis of ammonia on NiCu nanoclusters with higher activity and stability synthesized by a simplified polyol technique

This work focuses on a simplified polyol process by which to synthesize five different NiCu/C nanoclusters (NCs) electrocatalysts with the variation of mass and atomic ratio. NCs are characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy, transmission electron spectroscopy (TEM), and scanning electron microscopy with energy-dispersive spectroscopy (EDS) for their crystallite and electronic structures, morphological studies, and elemental composition. The high-angle annular dark-field scanning TEM coupled with EDS elemental mapping has confirmed that nanoparticles (NPs) are formed with Ni and Cu, and NPs are subsequently noted to conform into NCs in such a fashion that NiCu NPs are interconnected to each other rather than overlapping considered a unique distribution of NiCu NCs on the carbon support observed in STEM. NPs arrangement in the conformation of NCs has largely increased in the coverage of NiCu-oxyhydroxides working as active sites for ammonia electrocatalysis evidenced in cyclic voltammograms and XPS investigation. NCs were employed for the oxidation of NH4OH, NH4Cl, NH4NO3, and (NH4)2SO4 of which NiCu/C-2 has shown the highest performance over other NiCu/C samples and their individuals. NiCu/C-2 is also found to have higher stability than other mono/bi-metallic electrocatalysts on the stability test preformed in an electrochemical environment. In addition, the sharp drops of the current in the chronoamperometric curves have been investigated during the stability test.

Structure of Amyloid Peptide Ribbons Characterized by Electron Microscopy, Atomic Force Microscopy, and Solid-State Nuclear Magnetic Resonance.

Polypeptides often self-assemble to form amyloid fibrils, which contain cross-β structural motifs and are typically 5-15 nm in width and micrometers in length. In many cases, short segments of longer amyloid-forming protein or peptide sequences also form cross-β assemblies but with distinctive ribbon-like morphologies that are characterized by a well-defined thickness (on the order of 5 nm) in one lateral dimension and a variable width (typically 10-100 nm) in the other. Here, we use a novel combination of data from solid-state nuclear magnetic resonance (ssNMR), dark-field transmission electron microscopy (TEM), atomic force microscopy (AFM), and cryogenic electron microscopy (cryoEM) to investigate the structures within amyloid ribbons formed by residues 14-23 and residues 11-25 of the Alzheimer's disease-associated amyloid-β peptide (Aβ14-23 and Aβ11-25). The ssNMR data indicate antiparallel β-sheets with specific registries of intermolecular hydrogen bonds. Mass-per-area values are derived from dark-field TEM data. The ribbon thickness is determined from AFM images. For Aβ14-23 ribbons, averaged cryoEM images show a periodic spacing of β-sheets. The combined data support structures in which the amyloid ribbon growth direction is the direction of intermolecular hydrogen bonds between β-strands, the ribbon thickness corresponds to the width of one β-sheet (i.e., approximately the length of one molecule), and the variable ribbon width is a variable multiple of the thickness of one β-sheet (i.e., a multiple of the repeat distance in a stack of β-sheets). This architecture for a cross-β assembly may generally exist within amyloid ribbons.

Enhancing Reproducibility in Precipitate Analysis: A FAIR Approach with Automated Dark-Field Transmission Electron Microscope Image Processing

High-strength aluminum alloys used in aerospace and automotive applications obtain their strength through precipitation hardening. Achieving the desired mechanical properties requires precise control over the nanometer-sized precipitates. However, the microstructure of these alloys changes over time due to aging, leading to a deterioration in strength. Typically, the size, number, and distribution of precipitates for a quantitative assessment of microstructural changes are determined by manual analysis, which is subjective and time-consuming. In our work, we introduce a progressive and automatable approach that enables a more efficient, objective, and reproducible analysis of precipitates. The method involves several sequential steps using an image repository containing dark-field transmission electron microscopy (DF-TEM) images depicting various aging states of an aluminum alloy. During the process, precipitation contours are generated and quantitatively evaluated, and the results are comprehensibly transferred into semantic data structures. The use and deployment of Jupyter Notebooks, along with the beneficial implementation of Semantic Web technologies, significantly enhances the reproducibility and comparability of the findings. This work serves as an exemplar of FAIR image and research data management.

Structural, thermal and optical characteristics of Fe 1−X Zr X alloy by using mechanical milling approach: influence of Zr4+ ion

By changing Zr concentrations, Fe1-x-Zrx(x = 0.25 & 1 at%) alloys were successfully produced in an argon atmosphere using the mechanical alloying method. The produced Fe1-x-Zrxalloys were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersion x-ray analysis (EDAX), fourier transform infrared spectroscopy (FTIR), thermogravimetry analyzer (TG-DTA), ultraviolet-visible spectroscopy (UV–vis) absorption, and photoluminescence (PL) spectroscopy. According to XRD pattern analysis, the prepared alloys had a cubic crystalline structure and complete solid solution formation. The prepared alloy samples the average crystallite size was calculated using the Scherrer formula. The average crystallite size for the 0.25 at% Zr concentration is found to be 7.79 nm and 11.8 nm for the 1 at% Zr concentration. Lattice parameter changes are a very important tool for confirming the complete dissolution of the Zr atom in the Fe matrix.The TEM-dark field image confirms that the grain size is in the nanometric range (<100 nm). TEM-SAED spotty continuous ring pattern confirmed the complete solution formation is well correlated with the XRD results. The elemental composition of materials can be determined quantitatively through energy dispersive x-ray analysis in the Fe1-x-Zrxalloy. The elemental distribution of the mechanically alloyed samples shows that Zr elements are homogeneously distributed in the Fe matrix. Bands at 3428 cm−1 in the FTIR spectrum have been linked to O–H stretching vibrations. CH2 and CH stretching vibrations were associated with peaks of about 2920 cm−1 and 2850 cm−1. The weight loss and gain changes were observed and represented in the TG-DST graph; we found that overall weight changes are + 10.7% (gain) at 1023 °C for Fe 1-x-Zr x (x = 0.25 at%) alloy. However, when compared to 0.25 at% of Zr alloy, Fe-Zr (x = 1 at%) exhibits a low weight gain (+ 6.54%). The UV–visible absorbance edge revealed a blue shift when Zr was added, indicating alloy production. The energy band gap of materials was calculated using UV–vis, and it has been observed that the band gap reduces as Zr concentration increases. Zr was added to Fe1-x-Zrxalloy nanoparticles, resulting in 514 nm and 775 nm emission wavelengths. The greatest emission wavelengths and strong flawless sharp emission peaks were discovered to be between 450 nm and 550 nm. The higher PL emission peak was 514 nm at 0.25 at% of Zr.

Measurement of G-phase volume fraction and number density in duplex stainless steels using transmission electron microscopy

Duplex stainless steels (DSS) have a high toughness and strength due the presence of both austenitic and ferritic phases. These alloys have had limited use in power production applications due to thermal embrittlement caused by spinodal decomposition and development of G-phase precipitates in the ferrite. Lean grade DSS alloys (e.g., 2101, 2003) may offer improved thermal stability due to the reduction of Cr- and Ni-equivalent elements when compared to standard grade compositions (e.g., 2205, 2209). The abundance of the G-phase was measured in five duplex stainless steels, three wrought alloys (2101, 2003, 2205) and their matching filler metals (2101-w, 2209-w), after aging at 427 °C for 1000 h and 10,000 h. The G-phase volume fraction, number density, size, and precipitate spacing were found using quantitative analysis of transmission electron microscopy dark field images and the composition of G-phase precipitates on other clusters were characterized with atom probe tomography (APT). In the welded alloys, the G-phase was found to develop rapidly, relative to the wrought material. A positive correlation was found between the nickel equivalent composition of the alloy and the G-phase volume fraction. The alloys 2205, 2209, and 2101-w, which are higher in Cr and Ni, all showed significant G-phase precipitation, further strengthening the hypothesis that lean grade DSS alloys are more thermally stable against precipitation in the ferrite. Electron diffraction showed a secondary phase present in the 2101 wrought alloy at 10,000 h, but it was not crystallographically consistent with the G-phase; APT showed the presence of nanoclusters rich in both nickel and copper for this alloy. No secondary phases or clusters were found in 2003 after 10,000 h of aging, so it may be a candidate alloy for applications that require long-life times at high operating temperatures.

Cross-sectional transmission electron microscopy studies of Si coated heat-treated stainless steel with improved optical absorption for solar thermal applications

Heat-treatment of stainless steel substrate is reported to improve absorptance due to an increase in roughness along with the formation of surface oxides. Depositing a thin Si layer on stainless steel prior to the heat-treatment results in the formation of islands of nano-micrometer sizes with gaps between them which helps in improving absorptance. Cross-sectional Transmission Electron Microscopy studies are required to understand the development of the surface structures and improved optical properties. The cross-sectional bright- and dark-field Transmission Electron Microscopy images showed the presence of a bright Si-rich region where small nanocrystalline islands were embedded. On top of this layer, larger nanocrystalline protrusions were observed. Energy Dispersive X-ray analysis and Selected Area Diffraction data showed that the substrate elements diffuse out through the Si layer forming smaller islands of various Fe-Cr-Mn-based silicides in the Si layer and islands of Fe, Cr, and Mn-based silicides and oxides at the surface. The High-Resolution Transmission Electron Microscopy images showed that the islands are nanocrystalline in nature and are embedded in a Si-rich amorphous region. The absence of O in the Si-rich layer in SAD data was observed. Also, from the top layer EDX data, Fe peak intensity was found to be higher than Cr peak intensity. These observations indicate that the presence of the Si layer helps in reducing the inward diffusion of O into the substrate, thus preventing internal oxidation. Also, this Si layer prevents the Cr from forming a continuous Cr oxide layer and instead forms mixed oxide/silicide islands which enhance optical properties. Similar studies in the heat-treated substrate without a Si layer showed the presence of sharp-angled nanocrystalline structures of Fe-Cr-based oxides and smooth-angled nanocrystalline structures of Fe-Mn-based oxides on the surface.

Transmission Electron Microscopy Peeled Surface Defect of Perovskite Quantum Dots to Improve Crystal Structure.

Transmission electron microscopy (TEM) is an excellent characterization method to analyze the size, morphology, crystalline state, and microstructure of perovskite quantum dots (PeQDs). Nevertheless, the electron beam of TEM as an illumination source provides high energy, which causes morphological variation (fusion and melting) and recession of the crystalline structure in low radiolysis tolerance specimens. Hence, a novel and facile strategy is proposed: electron beam peel [PbBr6]4- octahedron defects from the surface of QDs to optimize the crystal structure. TEM and high-angle annular dark-field scanning TEM (HAADF) tests indicate that the [PbBr6]4- octahedron would be peeled from the surface of QDs when QDs samples were irradiated under high-power irradiation, and then a clear image would be obtained. To avoid interference from a protective film of "carbon deposits" on the surface of the sample when using high resolution TEM, amorphous carbon film (15-20 nm) was deposited on the surface of QDs film and then characterized by TEM and HAADF. The detection consequences showed that the defection of PbBr2 on the surface of QDs will gradually disappear with the extension of radiation time, which further verifies the conjecture.

Pd sub-nanolayer on Au core for enhanced catalytic hydrogenation reduction of oxyanions pollutants: Synergistic effect of Pd and Au

Oxyanion pollutants in industrial wasterwater, such as (Cr(VI)), BrO3− (Br(V)) and SeO32− (Se(IV)) have detrimental or toxic effects on individual health when their concentrations accumulated to a certain level. The conversion of these oxyanions into harmless/industrial-valuable products or removal from wastewater is of significance. Herein, we designed Pd sub-nanolayer on Au core catalysts supported on Al2O3 (sub-Pd-Au/Al2O3) for highly effective catalytic hydrogenation reduction of oxyanions under ambient conditions. The sub-Pd(0.049)-Au(0.927)/Al2O3 catalyst exhibited the highest catalytic activity and TOF value for Cr(VI), Br(V) and Se(IV) reduction, respectively, by optimizing the Pd loading amount. The synergistic effect between Pd sub-nanolayer and Au core enhanced catalytic activity by regulating the Pd dispersion and site property, according to thorough characterizations that included high-angle annular dark-field transmission electron microscopy (HAADF-TEM) image, in-situ CO-IR adsorption, CO chemisorption, and X-ray photoelectron spectroscopy (XPS). This work might provide some new lights on design of highly efficient catalysts for the elimination of oxyanion pollutants.

Exploiting the interaction between halloysite and charged PNAs for their controlled release.

The design and development of nanomaterials that could be used in nanomedicine are of fundamental importance to obtain smart nanosystems for the treatment of several diseases. Halloysite, because of its interesting features, represents a suitable nanomaterial for the delivery of different biologically active species. Among them, peptide nucleic acids (PNAs) have attracted considerable attention in recent decades for their potential applications in both molecular antisense diagnosis and as therapeutic agents, although up to now, the actual clinical applications have been very limited. Herein we report a systematic study on the supramolecular interaction of three differently charged PNAs with halloysite. Understanding the interaction mode of charged molecules with the clay surfaces represents a key factor for the future design and development of halloysite based materials which could be used for the delivery and subsequent intracellular release of PNA molecules. Thus, three different PNA tetramers, chosen as models, were synthesized and loaded onto the clay. The obtained nanomaterials were characterized using spectroscopic studies and thermogravimetric analysis, and their morphologies were studied using high angle annular dark field transmission electron microscopy (HAADF/STEM) coupled with Energy Dispersive X-ray spectroscopy (EDX). The aqueous mobility of the three different nanomaterials was investigated by dynamic light scattering (DLS) and ζ-potential measurements. The release of PNA tetramers from the nanomaterials was investigated at two different pH values, mimicking physiological conditions. Finally, to better understand the stability of the synthesized PNAs and their interactions with HNTs, molecular modelling calculations were also performed. The obtained results showed that PNA tetramers interact in different ways with HNT surfaces according to their charge which influences their kinetic release in media mimicking physiological conditions.