Nanoscale Horizons

The near field response of molecules coupled with plasmons at atomistic resolution
He H, Zhen X, Li S, Chen S and Chen X
The interaction between nanoparticles on mirror (NPoM) nanostructures and molecules is of great significance for the development of plasmon-enhanced spectroscopy (PES) techniques. However, the coupling mechanism between resonantly excited molecules and plasmonics has not been fully understood. In this work, we took viologen molecules within an Au plasmonic nanocavity (AuNC) as an example to illustrate how resonant molecules influence the near-field distributions. We found that the near-fields are highly enhanced and the near-field distributions are altered when the monocationic viologen (V˙) is in resonance. In the AuNC, the near-field enhancement of a molecule is significantly enhanced by the adjacent molecules. However, the average near-field enhancements experienced by each molecule decrease with the increasing coverage of the molecular monolayer. Furthermore, the contributions of molecules to the near-field enhancement initially increase and then decrease as coverage increases. The interactions between the molecules and the nanocavity exhibit negative contributions to near-field enhancement. Overall, this work offers valuable insights into the impact of resonantly excited molecules on near-field enhancements in nanocavities and offers guidance for tuning excitation wavelength. We propose that the resonance state and coverage of molecules are critical to improving the sensitivity and specificity of PES techniques.
Electric field-assisted resonance frequency tuning in free standing nanomechanical devices for application in multistate switching using a phase change material
Banswar D, Anand JK, Bukhari SA, Singh S, Prajesh R, Kumar H, Makineni SK and Goswami A
VO possesses a unique property of solid-state phase transition near room temperature wherein it transforms from monoclinic (M1) to tetragonal phase (R) that alters its physical properties, such as resistivity, mechanical modulus, and lattice strain, at an ultrafast time scale known as MIT. Such a phenomenon offers a distinct advantage to use VO in switching applications using heat flux as a stimulus. However, such alteration in properties can also be triggered under an electric field (), which is known as E-MIT. A nanomechanical resonator coated with VO recently received traction where the resonance behavior can be modulated by taking advantage of its phase transition. Herein, we demonstrate that by fabricating a microstring of 400 μm () × 5 μm () × 240 nm () of suspended SiN coated with VO, the frequency () of the resonator can be modulated by applying an electric field. We show that at room temperature, the of the microstring can be either reduced (by 0.5% at 15 V mm) or enhanced (by 2.2% at 25 V mm) or can be varied in a cycle under -field. Using theoretical models, we establish the simulated results and explain the processes behind it, which demonstrate excellent mechanical tuning properties of the VO-based microstring resonator, making it an attractive and alternative option for highly efficient MEMS-based switches and neuromorphic devices.
Concealable physical unclonable function generation and an in-memory encryption machine using vertical self-rectifying memristors
Cho JM, Kim SS, Park TW, Shin DH, Kim YR, Park HJ, Kim DY, Lee SH, Park T and Hwang CS
The importance of hardware security increases significantly to protect the vast amounts of private data stored on edge devices. Physical unclonable functions (PUFs) are gaining prominence as hardware security primitives due to their ability to generate true random digital keys by exploiting the inherent randomness of the physical devices. Traditional approaches, however, require significant data movement between memory units and PUF generation circuits to perform encryption, presenting considerable energy efficiency and security challenges. This study introduces an innovative approach where PUF key generation and encryption are accomplished in the same vertically integrated resistive random access memory (V-RRAM), alleviating the data movement issue. The proposed V-RRAM encryption machine offers concealable PUFs, high area efficiency, and multi-thread data handling using parallel XOR logic operations. The encryption machine is compared with other machines, demonstrating the highest spatiotemporal cost-effectiveness.
The well-defined three-dimensional matrix of a micro-sized silicon/carbon composite promoting lithium-ion transportation
Wang D, Ma M, Xu W, Ma Y, Li L and Li X
Micro-sized silicon is a promising anode material due to its high theoretical capacity and low cost. However, its bulk particle size poses a challenge during electrochemical cycling, and the long ion/electron transport paths within it limit the rate capability. Herein, we propose a structural engineering approach for establishing a well-defined three-dimensional (3D) micro-sized silicon/carbon matrix to achieve efficient omnidirectional ionic and electronic conductivity within micro-sized silicon and effectively mitigate the volume changes. The prepared materials, comprising ordered two-dimensional porous silicon nanosheets, offer direct two-dimensional electrolyte transport channels aligned parallel to the layer plane and porous channels oriented perpendicular to the layer plane. These well-defined omnidirectional pathways enable more efficient electrolyte mass transport than the disordered paths within the traditional 3D porous silicon anodes. A robust carbon shell, securely bonded to silicon through dual covalent bonding, effectively shields these pathways, buffering the volume changes and offering an electronically conductive 3D carbon network.
Prediction methods for phonon transport properties of inorganic crystals: from traditional approaches to artificial intelligence
Wei Y, Liu Z and Qin G
In inorganic crystals, phonons are the elementary excitations describing the collective atomic motions. The study of phonons plays an important role in terms of understanding thermal transport behavior and acoustic properties, as well as exploring the interactions between phonons and other energy carriers in materials. Thus, efficient and accurate prediction of phonon transport properties such as thermal conductivity is crucial for revealing, designing, and regulating material properties to meet practical requirements. In this paper, typical strategies used to predict phonon transport properties in modern science and technologies are introduced, and relevant achievements are emphasized. Moreover, insights into the remaining challenges as well as future directions of phonon transport-related exploration are proposed. The viewpoints of this paper are expected to provide a valuable reference to the community and inspire relevant research studies on predicting phonon transport properties in the near future.
Unraveling energetics and states of adsorbing oxygen species with MoS for modulated work function
Yan H, Chen H, Cui X, Guan Q, Wang B and Cai Y
MoS and related transition metal dichalcogenides (TMDs) have recently been reported as having extensive applications in nanoelectronics and catalysis because of their unique physical and chemical properties. However, one practical challenge for MoS-based applications arises from the easiness of oxygen contamination, which is likely to degrade performance. To this end, understanding the states and related energetics of adsorbed oxygen is critical. Herein, we identify various states of oxygen species adsorbed on the MoS surface with first-principles calculations. We reveal a "dissociative" mechanism through which a physisorbed oxygen molecule trapped at a sulfur vacancy can split into two chemisorbed oxygen atoms, namely a top-anchoring oxygen and a substituting oxygen, both of which show no adsorbate induced states in the bandgap. The electron and hole masses show an asymmetric effect in response to oxygen species with the hole mass being more sensitive to oxygen content due to a strong hybridization of oxygen states in the valence band edge of MoS. Alteration of oxygen content allows modulation of the work function up to 0.5 eV, enabling reduced Schottky barriers in MoS/metal contact. These results show that oxygen doping on MoS is a promising method for sulfur vacancy healing, carrier mass controlling, contact resistance reduction, and anchoring of surface electron dopants. Our study suggests that tuning the chemical composition of oxygen is viable for modulating the electronic properties of MoS and likely other chalcogen-incorporated TMDs, which offers promise for new optoelectronic applications.
Edge-doped substituents as an emerging atomic-level strategy for enhancing M-N-C single-atom catalysts in electrocatalysis of the ORR, OER, and HER
Xie L, Zhou W, Qu Z, Huang Y, Li L, Yang C, Li J, Meng X, Sun F, Gao J and Zhao G
M-N-C single-atom catalysts (MN) have gained attention for their efficient use at the atomic level and adjustable properties in electrocatalytic reactions like the ORR, OER, and HER. Yet, understanding MN's activity origin and enhancing its performance remains challenging. Edge-doped substituents profoundly affect MN's activity, explored in this study by investigating their interaction with MN metal centers in ORR/OER/HER catalysis (Sub@MN, Sub = B, N, O, S, CH, NO, NH, OCH, SO; M = Fe, Co, Ni, Cu). The results show overpotential variations (0 V to 1.82 V) based on Sub and metal centers. S and SO groups optimize FeN for peak ORR activity (overpotential at 0.48 V) and reduce OER overpotentials for NiN (0.48 V and 0.44 V). N significantly reduces FeN's HER overpotential (0.09 V). Correlation analysis highlights the metal center's key role, with Δ and Δ showing mutual predictability ( = 0.92). proves a reliable predictor for Sub@CoN (Δ/Δ, = 0.96 and 0.72). Machine learning with the KNN model aids catalyst performance prediction ( = 0.955 and 0.943 for Δ/Δ), emphasizing M-O/M-H and the d band center as crucial factors. This study elucidates edge-doped substituents' pivotal role in MN activity modulation, offering insights for electrocatalyst design and optimization.
Correlated excitonic signatures of individual van der Waals NiPS antiferromagnet nanoflakes
Chandrasekaran V, DeLaney CR, Trinh CT, Parobek D, Lane CA, Zhu JX, Li X, Zhao H, Campbell MA, Martin L, Wyckoff EF, Jones AC, Schneider MM, Watt J, Pettes MT, Ivanov SA, Piryatinski A, Dunlap DH and Htoon H
Composite quasi-particles with emergent functionalities in spintronic and quantum information science can be realized in correlated materials due to entangled charge, spin, orbital, and lattice degrees of freedom. Here we show that by reducing the lateral dimension of correlated antiferromagnet NiPS flakes to tens of nanometers and thickness to less than ten nanometers, we can switch-off the bulk spin-orbit entangled exciton in the near-infrared (1.47 eV) and activate visible-range (1.8-2.2 eV) transitions. These ultra-sharp lines (<120 μeV at 4.2 K) share the spin-correlated nature of the bulk exciton by displaying a strong linear polarization below Néel temperature. Furthermore, exciton photoluminescence lineshape analysis indicates a polaronic character coupling with at-least 3 phonon modes and a comb-like Stark effect through discretization of charges in each layer. These findings augment the knowledge on the many-body nature of excitonic quasi-particles in correlated antiferromagnets and also establish the nanoscale correlated antiferromagnets as a promising platform for integrated magneto-optic devices.
Emerging Investigator Series: Dr Mohammad Malakooti, University of Washington, USA
Our Emerging Investigator Series features exceptional work by early-career nanoscience and nanotechnology researchers. Read Mohammad Malakooti's Emerging Investigator Series article 'Green synthesis of iron-doped graphene quantum dots: an efficient nanozyme for glucose sensing' (https://doi.org/10.1039/D4NH00024B) and read more about him in the interview below.
Emerging 2D materials hardware for in-sensor computing
Shi Y, Duong NT and Ang KW
The advent of the novel in-sensor/near-sensor computing paradigm significantly eliminates the need for frequent data transfer between sensory terminals and processing units by integrating sensing and computing functions into a single device. This approach surpasses the traditional configuration of separate sensing and processing units, thereby greatly simplifying system complexity. Two-dimensional materials (2DMs) show immense promise for implementing in-sensor computing systems owing to their exceptional material properties and the flexibility they offer in designing innovative device architectures with heterostructures. This review highlights recent progress and advancements in 2DM-based in-sensor computing research, summarizing the unique physical mechanisms that can be leveraged in 2DM-based devices to achieve sensory responses and the essential biomimetic synaptic characteristics for computing functions. Additionally, the potential applications of 2DM-based in-sensor computing systems are discussed and categorized. This review concludes with a perspective on future development directions for 2DM-based in-sensor computing.
Extracellular vesicles of different cellular origin feature distinct biomolecular corona dynamics
Musicò A, Zendrini A, Reyes SG, Mangolini V, Paolini L, Romano M, Papait A, Silini AR, Di Gianvincenzo P, Neva A, Cretich M, Parolini O, Almici C, Moya SE, Radeghieri A and Bergese P
Initially observed on synthetic nanoparticles, the existence of biomolecular corona and its role in determining nanoparticle identity and function are now beginning to be acknowledged in biogenic nanoparticles, particularly in extracellular vesicles - membrane-enclosed nanoparticle shuttling proteins, nucleic acids, and metabolites which are released by cells for physiological and pathological communication - we developed a methodology based on fluorescence correlation spectroscopy to track biomolecular corona formation on extracellular vesicles derived from human red blood cells and amniotic membrane mesenchymal stromal cells when these vesicles are dispersed in human plasma. The methodology allows for tracking corona dynamics under physiological conditions. Results evidence that the two extracellular vesicle populations feature distinct corona dynamics. These findings indicate that the dynamics of the biomolecular corona may ultimately be linked to the cellular origin of the extracellular vesicles, revealing an additional level of heterogeneity, and possibly of bionanoscale identity, that characterizes circulating extracellular vesicles.
Rhodium nanospheres for ultraviolet and visible plasmonics
Muñeton Arboleda D, Coviello V, Palumbo A, Pilot R and Amendola V
The development and understanding of alternative plasmonic materials are crucial steps for leveraging new plasmonic technologies. Although gold and silver nanostructures have been intensively studied, the promising plasmonic, chemical and physical attributes of rhodium remain poorly investigated. Here, we report the synthesis and plasmonic response of spherical Rh nanoparticles (NPs) with sizes in the 20-40 nm range. Due to the high cohesive energy of this metal, synthesis and experimental investigations of Rh nanospheres in this size range have not been reported; yet, it becomes possible here using a green and one-step laser ablation in liquid method. The localized surface plasmon (LSP) of Rh NPs falls in the ultraviolet spectral range (195-255 nm), but the absorption tail in the visible region increases significantly upon clustering of the nanospheres. The surface binding ability of Rh NPs towards thiolated molecules is equivalent to that of Au and Ag NPs, while their chemical and physical stability at high temperatures and in the presence of strong acids such as aqua regia is superior to those of Au and Ag NPs. The plasmonic features are well described by classical electrodynamics, and the results are comparable to Au and Ag NPs in terms of extinction cross-section and local field enhancement, although blue shifted. This allowed, for instance, their use as an optical nanosensor for the detection of ions of toxic metals in aqueous solution and for the surface enhanced Raman scattering of various compounds under blue light excitation. This study explores the prospects of Rh NPs in the realms of UV and visible plasmonics, while also envisaging a multitude of opportunities for other underexplored applications related to plasmon-enhanced catalysis and chiroplasmonics.
"Sweet MOFs": exploring the potential and restraints of integrating carbohydrates with metal-organic frameworks for biomedical applications
Zuliani A, Ramos V, Escudero A and Khiar N
The unique features of metal-organic frameworks (MOFs) such as biodegradability, reduced toxicity and high surface area offer the possibility of developing smart nanosystems for biomedical applications through the simultaneous functionalization of their structure with biologically relevant ligands and the loading of biologically active cargos, ranging from small drugs to large biomacromolecules, into their pores. Aiming to develop efficient, naturally inspired biocompatible systems, recent research has combined organic and materials chemistry to design innovative composites that exploit carbohydrate chemistry for the functionalization and structural modification of MOFs. Scientific investigation in the field has seen a significant rise in the past five years, and it is becoming crucial to acknowledge both the limits and benefits of this approach for future investigation. In this review, the latest research results merging carbohydrates and MOFs are discussed, with a particular emphasis on the advances in the field and the remaining challenges, including addressing sustainability and real-case applicability.
On the design of cell membrane-coated nanoparticles to treat inflammatory conditions
Marinho A, Reis S and Nunes C
Biomimetic-based drug delivery systems (DDS) attempt to recreate the complex interactions that occur naturally between cells. Cell membrane-coated nanoparticles (CMCNPs) have been one of the main strategies in this area to prevent opsonization and clearance. Moreover, coating nanoparticles with cell membranes allows them to acquire functions and properties inherent to the mother cells. In particular, cells from bloodstream show to have specific advantages depending on the cell type to be used for that application, specifically in cases of chronic inflammation. Thus, this review focuses on the biomimetic strategies that use membranes from blood cells to target and treat inflammatory conditions.
Protein corona potentiates the recovery of nanoparticle-induced disrupted tight junctions in endothelial cells
Ghouri MD, Tariq A, Saleem J, Muhaymin A, Cai R and Chen C
Nanoparticle interactions with biological systems are intricate processes influenced by various factors, among which the formation of protein corona plays a pivotal role. This research investigates a novel aspect of nanoprotein corona-cell interactions, focusing on the impact of the protein corona on the recovery of disrupted tight junctions in endothelial cells. We demonstrate that the protein corona formed on the surface of star-shaped nanoparticles induces the aggregates of ZO-1, which is quite important for the barriers' integrity. Our research emphasizes that the APOA1 pre-coating on the nanoparticles reduces the ZO-1 expression of endothelial cells offering a promising strategy for overcoming the bio barriers. These findings contribute to our understanding of the interplay between nanoparticles, protein corona, and endothelial cell junctions, offering insights for developing innovative therapeutic approaches targeting the blood-brain barrier integrity. Our study holds promise for the future of nanomedicine, nano drug delivery systems and development of strategies to mitigate potential adverse effects.
Full-color peptide-based fluorescent nanomaterials assembled under the control of amino acid doping
Shen Y, Sun Y, Liang Y, Xu X, Su R, Wang Y and Qi W
Peptide-based biofluorescents are of great interest due to their controllability and biocompatibility, as well as their potential applications in biomedical imaging and biosensing. Here, we present a simple approach to synthesizing full-color fluorescent nanomaterials with broad-spectrum fluorescence emissions, high optical stability, and long fluorescence lifetimes. By doping amino acids during the enzyme-catalyzed oxidative self-assembly of tyrosine-based peptides, we can precisely control the intermolecular interactions to obtain nanoparticles with fluorescence emission at different wavelengths. The synthesized peptide-based fluorescent nanomaterials with excellent biocompatibility and stable near-infrared fluorescence emission were shown to have potential for bioimaging applications. This research provides new ideas for the development of new bioluminescent materials that are cost-effective, environmentally friendly, and safe for biomedical use.
Theoretical insights and design of MXene for aqueous batteries and supercapacitors: status, challenges, and perspectives
Zhao J, Ma N, Wang T, Wang Y, Liang B, Zhang Y, Luo S, Xiong Y, Wang Q and Fan J
Aqueous batteries and supercapacitors are promising electrochemical energy storage systems (EESSs) due to their low cost, environmental friendliness, and high safety. However, aqueous EESS development faces challenges like narrow electrochemical windows, irreversible dendrite growth, corrosion, and low energy density. Recently, two-dimensional (2D) transition metal carbide and nitride (MXene) have attracted more attention due to their excellent physicochemical properties and potential applications in aqueous EESSs. Understanding the atomic-level working mechanism of MXene in energy storage through theoretical calculations is necessary to advance aqueous EESS development. This review comprehensively summarizes the theoretical insights into MXene in aqueous batteries and supercapacitors. First, the basic properties of MXene, including structural composition, experimental and theoretical synthesis, and advantages in EESSs are introduced. Then, the energy storage mechanism of MXene in aqueous batteries and supercapacitors is summarized from a theoretical calculation perspective. Additionally, the theoretical insights into the side reactions and stability issues of MXene in aqueous EESSs are emphasized. Finally, the prospects of designing MXene for aqueous EESSs through computational methods are given.
XeF gas assisted focused electron beam induced etching of niobium thin films: towards direct write editing of niobium superconducting devices
Gellerup S, Emery R, Retterer ST, Randolph SJ and Rack PD
In this work, we explore focused electron beam induced etching (FEBIE) of niobium thin films with the XeF precursor as a route to edit, on-the-fly, superconducting devices. We report the effect of XeF pressure, electron beam current, beam energy, and dwell time on the Nb etch rate. To understand the mass transport and reaction rate limiting mechanisms, we compare the relative electron and XeF gas flux and reveal the process is reaction rate limited at low current/short dwell times, but shifts to mass transport limited regimes as both are increased. The electron stimulated etching yield is surprisingly high, up to 3 Nb atoms/electron, and for the range studied has a maximum at 1 keV. It was revealed that spontaneous etching accompanies the electron stimulated process, which was confirmed by varying the etched box size. An optimized etch resolution of 17 nm was achieved. Given that the Nb superconducting coherence length is 38 nm and scales with thickness, this work opens the possibility to direct write Nb superconducting devices low-damage FEBIE.
Polymer-confined synthesis of gram-scale high-entropy perovskite fluoride nanocubes for improved electrocatalytic reduction of nitrate to ammonia
Xue G, Wang T, Guo H, Zhang N, Carmalt CJ, Hofkens J, Lai F and Liu T
High-entropy perovskite fluoride (HEPF) has gradually attracted attention in the field of electrocatalysis due to its unique properties. Although traditional co-precipitation methods can efficiently produce HEPF, the resulting catalysts often lack regular morphology and tend to aggregate extensively. Here, nanocubic K(CuMgCoZnNi)F HEPF (HEPF-2) was successfully prepared on a gram-scale by a polyvinylpyrrolidone (PVP)-confined nucleation strategy. Benefiting from its large electrochemically active surface area and well-exposed active sites, the HEPF-2 demonstrates dramatically enhanced electrocatalytic activity in electrocatalytic nitrate reduction to ammonia, leading to an improved ammonia yield rate (7.031 mg h mg), a high faradaic efficiency (92.8%), and excellent long-term stability, outperforming the irregular HEPF nanoparticles (HEPF-0) prepared without the assistance of PVP. Our work presents an efficient and facile method to synthesize perovskite fluorides with a well-defined structure, showing great promise in the field of high-performance electrocatalysis.
Semiconductor nanowire heterodimensional structures toward advanced optoelectronic devices
Yan X, Li Y and Zhang X
Semiconductor nanowires are considered as one of the most promising candidates for next-generation devices due to their unique quasi-one-dimensional structures and novel physical properties. In recent years, advanced heterostructures have been developed by combining nanowires with low-dimensional structures such as quantum wells, quantum dots, and two-dimensional materials. Those heterodimensional structures overcome the limitations of homogeneous nanowires and show great potential in high-performance nano-optoelectronic devices. In this review, we summarize and discuss recent advances in fabrication, properties and applications of nanowire heterodimensional structures. Major heterodimensional structures including nanowire/quantum well, nanowire/quantum dot, and nanowire/2D-material are studied. Representative optoelectronic devices including lasers, single photon sources, light emitting diodes, photodetectors, and solar cells are introduced in detail. Related prospects and challenges are also discussed.
Lasing in an assembled array of silver nanocubes
Juodėnas M, Khinevich N, Klyvis G, Henzie J, Tamulevičius T and Tamulevičius S
We demonstrate a surface lattice resonance (SLR)-based plasmonic nanolaser that leverages bulk production of colloidal nanoparticles and assembly on templates with single particle resolution. SLRs emerge from the hybridization of the plasmonic and photonic modes when nanoparticles are arranged into periodic arrays and this can provide feedback for stimulated emission. It has been shown that perfect arrays are not a strict prerequisite for producing lasing. Here, we propose using high-quality colloids instead. Silver colloidal nanocubes feature excellent plasmonic properties due to their single-crystal nature and low facet roughness. We use capillarity-assisted nanoparticle assembly to produce substrates featuring SLR and comprising single nanocubes. Combined with the laser dye pyrromethene-597, the nanocube array lases at 574 nm with <1.2 nm linewidth, <100 μJ cm lasing threshold, and produces a beam with <1 mrad divergence, despite less-than-perfect arrangement. Such plasmonic nanolasers can be produced on a large-scale and integrated in point-of-care diagnostics, photonic integrated circuits, and optical communications applications.