Growth Of Nanostructures Research Articles

Diffusive ex situ galvanic growth of metal nanocrystals on transmission electron microscopy grid

The uniform modification of commercial and standardized objects features considerable potential, as in the case of dip-pen lithography, biosensor kits, and disposable electrodes. In this study, we devised a dense nanoparticle array formation using the metallic mesh of a transmission electron microscopy (TEM) grid, which was formerly solely employed as a sampling stage. Incompletely oxidized cationic species generated from the galvanic replacement reaction of the metallic support mesh at the opposite side of the carbon layer diffused to the exposed top side and led to ex situ nanostar formation. A uniform nanoparticle array was obtained by immersion in an aqueous solution of replacing metal cations without reducing agents or surface energy-controlling compounds. Moreover, the array density was exclusively regulated by the incubation time. The straightforward nanoparticle array formation was successfully extended to various metal mesh TEM grids and different transition metal cations capable of spontaneous redox reactions. Cu mesh TEM grid and Mo grids could be utilized as sacrificial templates, and the growth of Au, Pd, Pt, Ag, and Rh nanostructures was confirmed.

Simulations of tungsten fuzz growth and erosion under He/Ar mixed plasma irradiation on LP-MIES

Extrinsic noble impurities seeding has been commonly used to reduce the heat flux on divertor target. However, the physical sputtering yield on the target could be obviously enhanced due to larger mass of noble impurities. On the other hand, it has been reported that tungsten fuzz can suppress the physical sputtering due to the trapping effect on sputtered particles. Hence, it is interesting to check the erosion behaviors of tungsten fuzz under the irradiation of noble impurities. Recently, experiments of He/Ar mixed plasma irradiation on W target were conducted on LP-MIES device. Dedicated simulations have been performed by SURO-FUZZ code to study the impact of Ar flux on fuzz growth and erosion, which can well reproduce the experimental measurements on LP-MIES. For the case of pure He incidence, the growth of porous nanostructure leads to an obvious reduction in the fraction of the implanted He particles, which stabilizes to 15 % when the fuzz layer thickness exceeds 1500 nm. For He/Ar mixed plasma irradiation, the dependence of the position of the net sputtering on the local porosity has been investigated in detail. It is found that the net physical sputtering mainly occurs in the regions with the local porosity larger than 0.6.

Nanostructured Fe-Doped Ni3S2 Electrocatalyst for the Oxygen Evolution Reaction with High Stability at an Industrially-Relevant Current Density.

A novel oxygen evolution reaction (OER) electrocatalyst was prepared by a synthesis strategy consisting of the solvothermal growth of Ni3S2 nanostructures on Ni foam, followed by hydrothermal incorporation of Fe species (Fe-Ni3S2/Ni foam). This electrocatalyst displayed a low OER overpotential of 230 mV at 100 mA·cm-2, a low Tafel slope of 43 mV·dec-1, and constant performance at an industrially relevant current density (500 mA·cm-2) over 100 h in a 1.0 M KOH electrolyte, despite a minor loss of Fe in the process. Based on a detailed characterization by (in situ) Raman spectroscopy, (quasi-in situ) XPS, SEM, TEM, XRD, ICP-AES, EIS, and Cdl analysis, the high OER activity and stability of Fe-Ni3S2/Ni foam were attributed to the nanostructuring of the surface in the form of stable nanosheets and to the combination of Ni3S2 granting suitable electrical conductivity with newly formed NiFe-based (oxy)hydroxides at the surface of the material providing the active sites for OER.

Seed-Mediated Growth and Advanced Characterization of Chiral Gold Nanorods.

The controlled growth of gold nanostructures with complex shapes and reduced symmetry, exemplified by chiral gold nanorods and nanoparticles, is one of the most dynamic fields of nanochemistry. A timely summary of underlying concepts, including growth mechanisms and redefined chirality measures, would further promote this research area. In this perspective, we aim to establish qualitative connections between the chiral shapes and growth conditions, specifically for the seed-mediated synthesis of chiral gold nanorods as a convenient case of chiral morphogenesis. The crystallographic and morphological features of achiral nanorods used as seeds, the experimental conditions during chiral growth, and the symmetry of the chiral inducers, can all be exploited to obtain nanorods with intricate chiral shapes. Chirality characterization (such as electron tomography techniques) and quantification (including chirality measures) emerge as critical aspects to comprehensively explore and understand such structures, enabling optimization of their geometric and optical features. We conclude by discussing relevant challenges to be addressed toward a better controlled synthesis of chiral plasmonic nanostructures.

Evaluation of electrodeposition synthesis of gold nanodendrite on screen-printed carbon electrode for nonenzymatic ascorbic acid sensor

Gold nanodendrite (AuND) is a type of gold nanoparticles with dendritic or branching structures that offers advantages such as large surface area and high conductivity to improve electrocatalytic performance of electrochemical sensors. AuND structures can be synthesized using electrodeposition method utilizing cysteine as growth directing agent. This method can simultaneously synthesize and integrate the gold nanostructures on the surface of the electrode. We conducted a comprehensive study on the synthesis of AuND on screen-printed carbon electrode (SPCE)-based working electrode, focusing on the optimization of electrodeposition parameters, such as applied potential, precursor solution concentration, and deposition time. The measured surface oxide reduction peak current and electrochemical surface area from cyclic voltammogram were used as the optimization indicators. We confirmed the growth of dendritic gold nanostructures across the carbon electrode surface based on FESEM, EDS, and XRD characterizations. We applied the SPCE/AuND electrode as a nonenzymatic sensor on ascorbic acid (AA) and obtained detection limit of 16.8 μM, quantification limit of 51.0 μM, sensitivity of 0.0629 μA μM−1, and linear range of 180–2700 μM (R2 value = 0.9909). Selectivity test of this electrode against several interferences, such as uric acid, dopamine, glucose, and urea, also shows good response in AA detection.

Controlled growth of ruthenium dioxide nanostructures in borosilicate glass melts

Ruthenium, a fission product generated during the fission of uranium oxide fuel in a reactor, interacts with alkali metals such as sodium in the upper layer of the cold cap, forming a sodium ruthenate intermediate (NaxRuyOz), which promotes the crystallization of acicular RuO2 within the glass melt. During vitrification, RuO2 predominantly settles at the bottom of the melt owing to its high density and low solubility, significantly increasing both the conductivity and viscosity of the glass melt. Herein, the formation of NaxRuyOz, along with the chemical reactions promoting the crystallization of RuO2 in the waste glass, was comprehensively investigated. The results of X-ray diffraction and X-ray spectroscopy indicate that lamellar and granular Na3RuO4 do not form directly through the reaction between NaNO3 and RuO2 but rather through an intermediate stage from Na2RuO4. This reaction critically affects the morphology of RuO2 within the waste glass. The uncalcined mixture of NaNO3 and RuO2 was found to interact with the glass melt, forming granular RuO2 crystals, whereas the reaction of Na3RuO4 with the glass melt was found to lead to the formation of acicular RuO2 crystals. The results of X-ray absorption fine structure analysis indicate that the valence state of Ru in NaRu-BSG is slightly higher than that in reference RuO2, which was attributed to the presence of trace amounts of Na3RuO4 in the glass.

High-Efficiency Condensation Heat Transfer Interfaces Based on Superwetting Copper Microgroove/Nanocone Structure.

Utilizing superhydrophobic micro/nanostructures to enhance condensation heat transfer (CHT) of copper surfaces has attracted intensive interest in recent years due to its significance in multiple industrial fields including nuclear power generation, thermal management, water harvesting, and desalination. However, superhydrophobic surfaces have instability risk caused by microcavity defect-induced vapor penetration and/or hydrophobic chemistry destruction. Here, we report a superwetting copper hierarchical microgroove/nanocone (MGNC) structure strategy that can realize high-efficiency CHT over a whole range of surface subcooling. By regulating groove width, fin width, groove depth, and nanostructure growth time, we obtain the optimal MGNC structure, where the CHT coefficient is 121% and 107% higher than that of hydrophilic flat surfaces at surface subcooling of 2 and 15 K, respectively. Such remarkable enhancement can be ascribed to the synergy of three interface effects: more nucleation sites for phase-change energy exchanging, thinner condensate films for reducing thermal resistance, and parallel microchannels for timely drainage. Compared with superhydrophobic strategies, our strategy not only can be mass-producible but also has other inherent advantages: no microcavity-induced performance failure risk as well as being free of chemistry modification, which makes the fabrication process simpler and more economic. Hierarchical micropillar/nanocone structure is also fabricated as the contrast sample for highlighting the superiority of the superwetting MGNC structure in enhancing CHT. This work not only enriches research systems of superwettability surfaces but also helps develop high-performance chips' cooling devices and explore more potential applications.

Heterogeneous atoms mediated formation MnCo2S4/PNG heterostructures for high-performance supercapacitors

Transition metal sulfides are considered as potential electrode materials for high performance energy storage devices. However, structural instability during electrochemical reactions has seriously hindered their wide applications. In this study, we demonstrate that MnCo2S4/PNG (N- and P-doped graphene) composite constructed with hetero-atomic induction exhibits excellent morphological stability. Heterogeneous atoms doping on graphene can change its surface charge distribution. Under the induced effect of surface charge, the crystal growth and assembly process of MnCo2S4 nanostructure are changed as well, which leads to MnCo2S4 nanoparticles (NPs) uniformly anchored on the curled and folded PNG layer. In this case, it avoids the agglomeration of MnCo2S4 NPs, and thus increasing the specific surface area and pore volume of the composite, which is conducive to the full contact between the electrode and the electrolyte and therefore the rapid diffusion rate of the electrolyte ions at the interfaces. The obtained 1.4MnCo2S4/PNG material has a specific capacitance of 2465 F g−1 at 1 A g−1. In addition, the electrode possesses high conductivity, excellent rate performance and cyclic stability. The assembled 1.4MnCo2S4/PNG//PNG asymmetric supercapacitor yields an energy density of up to 65.1 Wh kg−1 under the power density of 800 W kg−1, showing excellent energy storage characteristics.

A novel hydrothermal approach to preparing ZnO flower-like using CQDs as growth seeds

This study presents a new synthesis route to prepare ZnO flower-like particles. Firstly, carbon quantum dots (CQDs) were prepared hydrothermally, using the Malva sylvestris flower as the sole carbon source. Subsequently, flower-like particles of ZnO/CQDs were synthesized using CQDs seeds and the same hydrothermal process. The efficiency of the redox process of solar excitation was measured by reducing the dye methylene blue (MB). The SEM and TEM characterization shows ZnO flower-like particles of around 1.5 µm whose petals are formed by crystallites of around 10 nm. ZnO nanocrystals appear embedded in an amorphous carbon matrix. TEM images show carbon quantum dots on the surface of ZnO flowers. Without using Malva sylvestris, ZnO morphologies are not formed; instead, 2D nanolaminates appear. The ZnO/CQDs nanocomposite achieved 98 % MB degradation in 80 min. The small size of CQDs can be a good scenario for the growth of crystalline nanostructures using the nanocarbon seed.

Anisotropic growth of Ag nanonails induced by plasmon-mediated chemical reactions in cross-shaped nanocavity array

The Ag nanonail rooted in Au cross-channel nanocavity is fabricated by plasmon-mediated chemical reactions (PMCRs). The Au cross-channel nanocavity is prepared based on two-dimensional polystyrene (PS) nanosphere template through wet etching, and the shape of Au cross-channel nanocavity changes from trapezoidal to triangular, depending on the wet etching time. The growth of Ag nanostructures in Au channels by PMCRs indicates the morphology of Ag nanostructures has changed from Ag nanoparticles to nanonails, which is regulated by the shape of Au nanocavities and the exciting light polarization. The hotspots distributions results in the anisotropic growth of Ag nanostructures induced by PMCRs, which leading to the different Ag nanostructures depending on the shape of Au nanocavity and light polarization, as confirmed by FDTD simulations. In comparison with others reports, our nanocavity provide more parameters to control the shapes of Ag nanostructures, the nanocavity shape, the light polarization and the growth time. Our work provides a profound insight into the construction of periodic nanostructures and reconstruction of hotspots.

Growth of WO3 nanostructure deposited on TiO2 nanotube arrays for electrochemical enzyme-free glucose sensor

In this study, a novel WO3-TiO2 hybrid nanostructure-based electrochemical non-enzymatic glucose biosensor has been developed. The anodization method was utilized to successfully produce TiO2 nanotubes on Ti6Al4V alloy functioning as substrates and WO3 nanomaterial decorate on the surface of TiO2 nanotubes (TNTs) deposited through electrochemical technique. The incorporation of WO3 on TNTs has resulted in a high electroactive surface and more degradation resistance in comparison to pure TNTs, resulting in enhanced electron transfer rate and electrode stability. High-resolution transmission electron microscopy (HR-TEM), field emission scanning electron microscopy (FE-SEM), and X-ray diffraction were used to investigate the crystalline structure and morphology of the WO3-TiO2 nanostructure. The electrochemical properties of the hybrid electrodes were investigated employing amperometry, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The hybrid electrode had a promising sensitivity (1228.12 μA/mM/cm2), low detection limit (0.19 mM), wide linear range (1.0–6.5 mM), and short response time (2-s). The sensors also demonstrated superior levels of reproducibility, repeatability, and stability.

Nucleation-Limited Kinetics of GaAs Nanostructures Grown by Selective Area Epitaxy: Implications for Shape Engineering in Optoelectronics Devices.

The growth kinetics of vertical III-V nanowires (NWs) were clarified long ago. The increasing aspect ratio of NWs results in an increase in the surface area, which, in turn, enhances the material collection. The group III adatom diffusion from the NW sidewalls to the top sustains a superlinear growth regime. In this work, we report on the growth of different GaAs nanostructures by selective area MOVPE on GaAs (111)B substrates. We show that the opening dimensions and geometry qualitatively alter the morphology and height evolution of the structures. We compare the time evolution of vertical GaAs NWs stemming from circular holes and horizontal GaAs nanomembranes (NMs) growing from one-dimensional (1D) rectangular slits on the same substrate. While NW heights grow exponentially with time, NMs surprisingly exhibit sublinear kinetics. The absence of visible atomic steps on the top facets of both NWs and NMs suggests layer-by-layer growth in the mononuclear mode. We interpret these observations within a self-consistent growth model, which links the diffusion flux of Ga adatoms to the position- and shape-dependent nucleation rate on top of NWs and NMs. Specifically, the island nucleation rate is lower on top of the NMs than that on the NWs, resulting in the total diffusion flux being directed from the top facet to the sidewalls. This gives a sublinear height evolution for the NMs. These results open innovative perspectives for shape engineering of III-V nanostructures and new avenues for the design of optoelectronics and photonic devices.

Chemical precursor-dependent dual effect of doping on the gas-sensing performance of metal oxide semiconducting materials

In this study, we report a chemical precursor-dependent dual effect of doping on the gas-sensing performance of metal oxide semiconducting materials. Our findings challenge the conventional notion that optimal doping consistently enhances gas-sensing properties. Acetate and nitrate salts were used as chemical precursors, lanthanum (La) was used as a dopant, and ZnO was used as a semiconducting material. All materials were synthesized under identical conditions by a two-step process involving dip coating and hydrothermal methods. Gas-sensing results demonstrated an improvement in the performance of the acetate-based doped film and a decline in that of the nitrate-based doped film compared to their respective pure counterparts. Among the produced sensors, 1 wt% La-doped ZnO sensor produced by the acetate precursor proved to be convenient for usages in real markets. It showed superior performance with a high response (62) at a relatively low operating temperature (150℃) towards 50 ppm of NH3 gas. The sensor also demonstrated exceptional baseline stability, high short-term and long-term consistency, good selectivity, and strong tolerance to humidity (up to 70 RH%) with slightly slow adsorption-desorption rates. The dual effect was discussed with respect to dopant- and precursor-induced variations in structural and surficial characteristics, revealed by XRD, Raman, FESEM, AFM, and XPS. The discussion delved deeper into the role of chemical precursors on nanostructure growth and, for the first time, illuminated a temperature-dependent complex gas-sensing principle governed by the detected p-n shift of the semiconductor type of the sensing elements, confirmed by Hall effect.

Effects of surface anisotropy on the surface morphological response of plasma-facing tungsten

Surface free energy has been hypothesized as the cause behind the experimental evidence (Parish et al., 2014) of a strong correlation between crystallographic orientation and surface morphology changes in helium ion-irradiated tungsten at the early stages of ‘fuzz’ growth in fusion plasma-facing tungsten. Here, this hypothesis is tested through self-consistent dynamical simulation based on an atomistically informed model of surface evolution in plasma-irradiated tungsten. Low-energy helium plasma irradiation of a tungsten surface, even when the ion energy is below the sputtering threshold, generates surface vacancy-adatom pairs in addition to adatoms from the flux of self-interstitial atoms to the surface resulting from the growth of high-pressure helium bubbles. Along with the stress-driven surface morphological instability as the primary driving force, preferential diffusion of these surface adatoms modulated by the associated Ehrlich–Schwoebel (ES) barriers, combined with the surface free energy anisotropy drive the anisotropic surface nanostructure growth. Simulation results for helium irradiation on W(100) show growth of pyramidal surface features, akin to experimental observations. This work confirms the hypothesis on the effect of tungsten surface crystallographic orientation on helium-ion-induced surface morphology changes, where surface mound formation is the outcome of a stress-driven surface morphological instability, while the anisotropic growth of the mounds is controlled by the ES-barrier-modulated anisotropic surface adatom diffusion and faceting of the mounds is controlled by the surface free energy anisotropy.

Plasma-enabled growth of vertically oriented carbon nanostructures for AC line filtering capacitors

Self-standing vertically oriented carbon nanostructures (VCNs) were synthesized using a large-scale microwave plasma under low-pressure conditions, employing methane as a carbon precursor. The influence of plasma operational and substrate conditions on nanostructure growth and morphology were systematically studied. Furthermore, post-synthesis N-doping of VCNs with nitrogen content of 2.4 at% N was achieved using an Ar-N2 microwave plasma. Plasma-enabled direct deposition of VCNs, both doped and un-doped, onto nickel foils has been accomplished. The assessment of the developed nanostructures as electrodes in high-frequency AC filtering capacitors, has demonstrated an overall capacitance of approximately 480 µF at 100 Hz, with a cut-off frequency of 4 kHz for a phase angle of −45°. The excellent electrochemical performance can be attributed to the appropriate structural and morphological properties peculiar for the directly deposited on nickel foil VCNs providing binder-free electrode fabrication, thus enhancing the electrode’s conductivity and charge transfer kinetics. This plasma-enabled approach for electrode design on a large scale, coupled with excellent filtering performance, paves the way for many applications in high-frequency scenarios, offering an environmentally friendly alternative to conventional electrolytic capacitors.

Single-crystalline HfO2 nanostructures with novel ferromagnetic properties

Hafnium oxide (HfO2) has special technological significance due to its superior properties such as high dielectric constant (κ∼25), wide bandgap (∼5.7 eV), and superb thermal and chemical stabilities. Its room-temperature ferromagnetism and excellent CMOS technology compatibility make it a promising candidate for seamless CMOS-spintronics integration. Low-dimensional single-crystalline HfO2 nanostructures, particularly one dimensional (1D) nanostructures, are expected to exhibit enhanced ferromagnetic properties due to large specific surface areas and potentially more surface defects. To date, the synthesis of single-crystalline HfO2 1D nanostructures has, however, remained elusive. Here, single-crystalline dopant-free HfO2 nanostructures with notable morphologies, including HfO2 1D nanostructures, are grown using catalyst-assisted pulsed laser deposition. It is shown that Sn plays a crucial role in producing these 1D nanostructures by increasing both the VLS nucleation and growth rates. Magnetization measurements reveal room-temperature ferromagnetism in HfO2 nanowires, contrasting with weak paramagnetic responses in HfO2 nanostructured films. We also provide the first direct evidence of oxygen vacancies as the source of room-temperature ferromagnetism in HfO2. To account for the observed magnetic property, we employ a modified bound magnetic polaron-band ferromagnetism hybrid model, which is also generally applicable to dopant-free nanostructures of other metal oxides. This work provides new insights into the growth of novel metal oxide 1D nanostructures and the design of new dilute magnetic semiconducting oxides for potential integrated CMOS-spintronics applications.

ZnIn2S4 nanostructure grown on electronegative h-BN for highly efficient photocatalytic hydrogen evolution

The photo-corrosion issue inherent in metal sulfide semiconductors is quite pronounced, making the enhancement of electron-hole pair separation efficiency in these photocatalysts a pivotal strategy for boosting photocatalytic hydrogen production. This study introduces a novel approach where hexagonal boron nitride (h-BN) acts as a substrate for the in situ growth of ZnIn2S4 nanostructures, resulting in the formation of h-BN@ZnIn2S4 (BN@ZIS) nanocomposites. The electronegativity of h-BN nanosheets is harnessed to facilitate the recombination or electrostatic attraction of photogenerated holes in the ZnIn2S4 photocatalyst. This strategy effectively promotes the separation of photogenerated electron-hole pairs, which is crucial for enhancing photocatalytic performance. The microstructure, morphology and optical properties of BN@ZIS nanocomposites were meticulously investigated. The findings reveal that the incorporation of h-BN nanosheets loads to a more uniform dispersion of the ZnIn2S4 nanostructure, which not only increases the specific surface area but also fosters a tight heterojunction interface between h-BN and ZnIn2S4. In conclusion, the photocatalytic hydrogen production capabilities of the BN@ZIS nanocomposites were rigorously evaluated. Pure h-BN lacks photocatalytic hydrogen production activity. Conversely, the optimized BN@ZIS composite demonstrated a remarkable enhancement, exhibiting a photocatalytic efficiency that is 9.65 times greater than that of pristine ZnIn2S4. Furthermore, a plausible mechanism by which BN@ZIS augments photocatalytic hydrogen production has been proposed. This strategy, leveraging the synergistic interaction between h-BN and ZnIn2S4, is anticipated to be applicable to other semiconductor systems, opening avenues for the advancement of photocatalytic technologies.

(Invited) Shape Engineering of Nanostructured III-V Semiconductor Lasers

Group III-V semiconductors have revolutionised electronics and optoelectronics due to their superior physical and optoelectronic properties including high carrier mobility, direct bandgap and band structure engineering capability. Reducing the device size to nanoscale brings many unique properties, such as large surface-area-to-volume ratio, high aspect ratio, carriers and photons confinement effect. These nanostructures have already been demonstrated for potential applications in light emitters, photodetectors, solar cells and for photoelectrochemical water splitting. However, to date most efforts on the growth of these nanostructures have been limited to nanowires.In this talk, we demonstrate selective area growth of III-V nanostructures, showing the possibility of obtaining other functional nanostructures, beyond the limitation of rod-like geometry. We demonstrate that by changing the pattern design on the mask and growth conditions, we are able to grow and control the shapes to form nanostructures such as membranes, flowers, rings, spirals, stars, ellipses etc. These shape-engineered nanostructures open up possibilities of new applications based on devices with novel geometries.In particular, we will show the results of our InP micro-ring lasers which have excellent cavity due to the atomically flat facets. Micro-disk and micro-ring lasers are light emitting devices that operate in the whispering gallery mode. They are important components for integrated photonics applications as light from can these devices can be efficiently coupled to on-chip waveguides. By coupling the micro-ring laser to a nanowire antenna, we further demonstrate that we can tune the emission directionality to the device.

(Invited) Eu- Oxide and Oxyhydroxide Nanofilms for Luminescent Photonic Components

Optically-doped rare-earth (RE) nanostructures find application in a diverse range of fields, including lighting (e.g. LEDs), displays, quantum memories, and biosensors such as luminescent nano-thermometers [1-5]. This is possible thanks to the ability of RE ions to provide robust and reliable light emission when incorporated in a solid. Since their performance depends critically on the composition and structure of the host material in order to successfully implement these RE-doped solids in technological applications it is desirable to achieve the controlled growth of low dimensional nanostructures that show efficient emission. This will enable on-chip component fabrication and their integration in photonic devices. The starting point of such technological development is the preparation of light emitting nanometer-thick films.In this contribution, we present an alternative approach for the development of europium-based nanofilms, departing from conventional doping methods that rely on host matrices, typically oxides and oxinitrides of diverse elements, to encapsulate the Eu2+ or Eu3+ emitter ions [4-6]. We highlight the efficacy of employing direct Eu compounds, maximizing the number of active emitters in the nanofilms and resulting in the observation of intense emission from these nanostructures. Our search started with original studies on Eu oxides (EuOx 1/3<x<1), and demonstrated a broad tuning of their emission by controlling their stoichiometry [1]. In this context, we present the progress achieved through the successful fabrication of europium oxyhydroxide (EuOOH) nanofilms [7]. It is noteworthy that the conventional method for producing hydroxides and oxyhydroxides involves chemical hydrothermal procedures with multiple steps, including dehydration, ultimately yielding powders and micro-crystals unsuitable for integration. In contrast, our methodology employs a clean physical evaporation technique under vacuum conditions, yielding thin films ready for integration. Crystalline monoclinic EuOOH nanofilms were successfully grown on silicon substrates by using pulsed laser deposition (PLD) and a subsequent annealing at a low temperature (250ºC). We will provide evidence of the physical mechanisms governing OH incorporation and discuss the influence of oxygen (O) and hydroxyl (OH) content on the resulting red emission of the Eu3+ ions related to the 5D0→2FJ transition, and on the optical properties of the films through the visible and infrared spectrum.[1] A. Mariscal-Jiménez et al, J. Phys. Chem. C 2020, 124, 15434.[2] P. Gomez-Rodriguez, et al, Nanophotonics 2021, 16, 3995-4007.[3] T. Zhong and P. Goldner, Nanophotonics 2019, 8, 2015.[4] D. Jaque and F. Vetrone, Nanoscale 2012, 4, 4301.[5] I. Camps, A. Mariscal-Jiménez, and R. Serna, Appl. Surf. Sci. 2023, 613, 1.[6] C. W. Bond et al. Opt. Mater. 2021, 122, 111796.[7] A. Caño, B. Galiana, G. B. Perea, J. Gonzalo and R. Serna, Appl. Surf. Sci. 2023, 640, 158236.

(Invited) Boosting Oxygen Evolution Reaction by Stabilization of Ultrasmall Ruthenium Nanoclusters on Thiol-Functionalized Metal-Organic Framework

Rational designing of efficient nanocatalysts plays a crucial role in catalyzing kinetically sluggish reactions like Oxygen Evolution Reaction (OER). However, the uncontrolled nucleation and growth of nanostructures poses major effectiveness and economic challenges in the implementation and commercialization of noble metal-based electrocatalysts. Functionalized Metal-Organic Frameworks (MOFs) have the properties to stabilize such unstable nanoclusters in extremely small sizes by compensating for their high surface energy and Ostwald’s ripening effect. Here, we have reported the synthesis of ultrasmall Ruthenium nanoclusters stabilized through thiol-functionalized Ni-MOF (Ru@Ni-M-SH). The stabilization of ruthenium under reduced conditions on the MOF surface was facilitated by the lower electronegativity and increased orbital overlapping effect of sulfur, resulting in an average size of 1.5 nm. A perturbed electronic structure confirmed from XPS as well as XAS studies revealed the fundamental understanding behind electronic redistribution. Backed with such a favorable electronic structure, the catalytic OER activity for Ru@Ni-M-SH outperformed the state-of-the-art RuO2 with three times higher current density (242 mA/cm2) and 143 mV reduced overpotential. With 95% Faradaic efficiency, the Turnover Frequency (TOF) and Mass activity of Ru@Ni-M-SH were found to be several orders higher as compared to RuO2. Unlike other Ru-based catalysts, Ru@Ni-M-SH showed extremely high stability with over 24 h of chronoamperometry study. With thorough in-situ analysis providing information regarding catalytically active sites and intermediates, Ru@Ni-M-SH established itself as an economically sustainable OER electrocatalyst.