Properties Of Nanoscale Materials Research Articles

Atomic layer annealing for spatial tailoring in sub-4 nm AlN RRAM devices with low-voltage operation

This article investigates the spatial tailoring of nitrogen vacancies by atomic layer annealing (ALA) on resistive random access memory (RRAM) devices with an AlN resistive switching layer. The ALA technique involves the in-situ layer-by-layer He/Ar plasma treatment in the cycle of atomic layer deposition for AlN. The AlN RRAM devices prepared with the ALA treatment near the TiN electrode have significantly superior uniformity of the operation voltages and the switching resistances, along with a lower cycle-to-cycle variation in endurance. This enhancement could be attributed to the relatively stable location of rupture and formation of conductive filaments, as a result of the film densification and the suppression of nitrogen vacancies in the AlN region treated with the ALA process. The AlN RRAM devices also demonstrate excellent retention of more than 106 seconds at 125°C. In addition, the ultra-thin 3.3 nm AlN switching layer contributes to low operation voltages of AlN RRAM. The outcomes manifest that the ALA technique could effectively improve the properties of nanoscale materials through precise spatial tailoring, with an accuracy up to atomic scale.

Terahertz nanoscopy: Advances, challenges, and the road ahead

Exploring nanoscale material properties through light-matter interactions is essential to unveil new phenomena and manipulate materials at the atomic level, paving the way for ground-breaking advancements in nanotechnology and materials science. Various elementary excitations and low-energy modes of materials reside in the terahertz (THz) range of the electromagnetic spectrum (0.1–10 THz) and occur over various spatial and temporal scales. However, due to the diffraction limit, a slew of THz studies are restricted to drawing conclusions from the spatially varying THz responses around half of the probing wavelengths, i.e., from tens to a couple of hundred micrometers. To address this fundamental challenge, scanning near-field optical microscopy (SNOM), notably scattering-type SNOM (s-SNOM), combined with THz sources has been employed and is fueling growing interest in this technique across multiple disciplines. This review (1) provides an overview of the system developments of SNOM, (2) evaluates current approaches to understand and quantify light-matter interactions, (3) explores advances in THz SNOM applications, especially studies with THz nano-scale spatial responses employing an s-SNOM, and (4) envisions future challenges and potential development avenues for the practical use of THz s-SNOM.

Review On Silver Nano Particles

The aspect of human life, making nanotechnology an exciting field for biomedical applications. Over the years, metal nanoparticles, such as silver, have attracted a lot of attention because of their extraordinary optical, electrical, and antibacterial qualities. Unfortunately, those nanoparticles' aggregation and toxicity have restricted their employment in more advantageous applications. Choosing therapeutically active bimolecular judiciously to functionalize the surface of these particles would undoubtedly improve their biological applicability and biocompatibility. In addition to providing an overview of the current approaches being used to biofunctionalize silver nanoparticles for certain purposes, the current review the distinct size-dependent properties of nanoscale materials have had a significant impact on every aims to highlight the application areas of these particles. Nanotechnology is a promising subject for biomedical applications because of the distinctive size-dependent features of materials at the nanoscale that have greatly touched all aspects of human life. Because of their exceptional optical, electrical, and antibacterial qualities, metal nanoparticles—like silver—have attracted a lot of attention over time. However, their employment in highly optimized applications has been limited due to their poisonous nature and tendency to aggregate. The biocompatibility and biological applicability of these particles are certain to be improved by the logical selection of therapeutically active bimolecular to functionalize their surface. The present review endeavors to emphasize the various application areas of silver nanoparticles while providing an overview of the current approaches entailed in biofunctionalizing these particles for particular uses. Key Word: silver nanoparticles, synthesis, characterization, applications, mechanisms

A Comprehensive Review of Electron Microscopy in Materials Science: Technological Advances and Applications

In nanomaterials and microstructural evolution, electron microscopy has had an important effect on materials investigation. Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), Electron Diffraction, Operando Electron Microscopy, and Aberration-Corrected Electron Microscopy offer the investigation on understanding of nanoscale material properties and structure. The present research covers the basics, advantages and disadvantages, and material-related applications of various electron microscopy techniques. TEM is useful for investigating atomic arrangements and imperfections in materials, while SEM offers micro- to nanoscale topographical, morphological, & compositional information. EDS, frequently employed with SEM or TEM, analyzes elements and compounds to determine material compositions. Opando Electron Microscopy allows researchers to observe and assess materials during catalytic reactions and battery charge/discharge cycles. This approach is vital for knowing how dynamic processes influence nanoscale material characteristics and behaviour. Another advanced technique, Aberration-Corrected Electron Microscopy, corrects lens aberrations that interfered with electron microscope resolution. This adjustment enables imaging at sample-limited resolutions, allowing further studies of atomic structures & flaws. These electron microscopy methods significantly improve nanomaterial microstructural evolution understanding. These have enabled extensive study of flaws, transitions between phases, and formation mechanisms, which are essential to producing optimal materials.

In Situ Nanomechanics: Opportunities Based on Superplastic Nanomolding.

In situ nanomechanics, referring to the real-time monitoring of nanomechanical deformation during quantitative mechanical testing, is a key technology for understanding the physical and mechanical properties of nanoscale materials. This perspective reviews the progress of in situ nanomechanics from the aspects of preparation and testing of nanosamples, with a major focus on one-dimensional (1D) nanostructures and discussions of their challenges. We highlight the opportunities provided by in situ nanomechanics combined with the superplastic nanomolding technique, especially in the aspects of regulating physical and chemical properties which are highly exploitable for mechanoelectronics, mechanoluminescence, piezoelectronics, piezomagnetism, piezothermography, and mechanochemistry.

Diabetology and Nanotechnology: A Compelling Combination

Abstract:: The convergence of diabetology and nanotechnology has emerged as a promising synergy with the potential to revolutionize the management and treatment of diabetes mellitus. Diabetes, a complex metabolic disorder affecting millions worldwide, necessitates innovative approaches to enhance monitoring, diagnosis, and therapeutic interventions. Nanotechnology, a burgeoning field that manipulates materials at the nanoscale, offers unprecedented opportunities to address the challenges posed by diabetes. This abstract explores the multifaceted interface between diabetology and nanotechnology, highlighting key areas of integration. Nanotechnology has paved the way for the development of advanced glucose monitoring systems with enhanced accuracy, sensitivity, and patient convenience. Miniaturized biosensors and implantable devices equipped with nanoscale materials enable continuous and real-time glucose monitoring, empowering individuals with diabetes to make timely and informed decisions about their dietary and insulin management. Furthermore, nanotechnology has facilitated breakthroughs in targeted drug delivery, addressing the limitations of conventional therapies in diabetes treatment. Nano-sized drug carriers can improve bioavailability, enable controlled release, and enhance the selectivity of therapeutic agents, minimizing side effects and optimizing treatment outcomes. Moreover, nanoengineered materials have opened avenues for tissue engineering and regenerative medicine, offering the potential to restore damaged pancreatic islets and insulin-producing cells. The amalgamation of diabetology and nanotechnology also holds promise for early disease detection and prevention. Nanoscale diagnostic tools, such as biomarker-based nanoprobes and lab-onchip devices, offer rapid and accurate detection of diabetes-related biomolecules, enabling timely interventions and reducing the risk of complications. However, this compelling combination also presents challenges that warrant careful consideration. Safety, biocompatibility, regulatory approval, and ethical implications are crucial factors that demand meticulous evaluation during the translation of nanotechnology-based solutions into clinical practice. In conclusion, the integration of diabetology and nanotechnology represents a transformative paradigm that has the potential to reshape the landscape of diabetes management. By harnessing the unique properties of nanoscale materials, researchers and clinicians are poised to usher in an era of personalized and precise diagnostics, therapeutics, and preventive strategies for diabetes mellitus. As advancements in nanotechnology continue to unfold, the journey towards realizing the full potential of this compelling combination remains an exciting frontier in medical science.

Photocontrolled self-assembly based on photoresponsive ruthenium complexes

Abstract Self-assembly, which occurs through noncovalent interactions among molecules, is a ubiquitous phenomenon in the natural world. Light is a particularly attractive stimulus for manipulating self-assembled structures due to its precise and noninvasive nature. Photoresponsive ruthenium (Ru) complexes are emerging as promising candidates for controlling self-assembly due to their unique coordination chemistry and reversible light-triggered behavior. Specifically, Ru complexes can undergo photodissociation of their ligands in aqueous solutions, leading to the formation of Ru-H2O species, and this process can be used to control the disassembly of assembled structures upon illumination. Conversely, upon cessation of the light stimulus, some Ru–ligand coordination bonds can be restored, resulting in reassembly of the structures. Herein, we mainly introduce our recent progress in the use of Ru(Ⅱ) complexes to create photocontrolled self-assemblies with applications ranging from cancer therapy to the manipulation of the morphology and properties of nanoscale materials. Finally, we discuss the challenges and future directions of photocontrolled assemblies with Ru complexes.

Advances in ultrafast plasmonics

In the past 20 years, we have reached a broad understanding of many light-driven phenomena in nanoscale systems. The temporal dynamics of the excited states are instead quite challenging to explore, and, at the same time, crucial to study for understanding the origin of fundamental physical and chemical processes. In this review, we examine the current state and prospects of ultrafast phenomena driven by plasmons both from a fundamental and applied point of view. This research area is referred to as ultrafast plasmonics and represents an outstanding playground to tailor and control fast optical and electronic processes at the nanoscale, such as ultrafast optical switching, single photon emission, and strong coupling interactions to tailor photochemical reactions. Here, we provide an overview of the field and describe the methodologies to monitor and control nanoscale phenomena with plasmons at ultrafast timescales in terms of both modeling and experimental characterization. Various directions are showcased, among others recent advances in ultrafast plasmon-driven chemistry and multi-functional plasmonics, in which charge, spin, and lattice degrees of freedom are exploited to provide active control of the optical and electronic properties of nanoscale materials. As the focus shifts to the development of practical devices, such as all-optical transistors, we also emphasize new materials and applications in ultrafast plasmonics and highlight recent development in the relativistic realm. The latter is a promising research field with potential applications in fusion research or particle and light sources providing properties such as attosecond duration.

Scanning tunneling microscopy and spectroscopy characterization of Nb films for quantum applications

Niobium thin films are key components of superconducting microwave resonators. Interest in these devices has increased dramatically because of their application in quantum systems. Despite tremendous effort to improve their performance, loss mechanisms are still not well understood. Nb/substrate and Nb/air interfaces are likely culprits in contributing to decoherence and ultimately limiting the performance of superconducting devices. Here, we investigate the Nb/substrate interface by studying the effect of hydrogen-passivated H:Si(111) substrates on the local superconducting properties of ∼40 nm thick Nb films compared to Nb films grown on typical Si(001) substrates. Specifically, low-temperature scanning tunneling microscopy and spectroscopy are employed to compare nanoscale material properties. The atomically flat monohydride H:Si(111) substrates are found to yield a smoother and less defective interface with the Nb film. Correspondingly, the Nb films grown on H:Si(111) substrates present more uniform superconducting properties and exhibit less quasiparticle broadening.

Low-Molecular-Weight Organogelators Based on N-dodecanoyl-L-amino Acids-Energy Frameworks and Supramolecular Synthons.

Lauric acid was used to synthesize the low-molecular-weight organogelators (LMOGs), derivatives of two endogenous (L)-alanine, (L)-leucine, and three exogenous (L)-valine, (L)-phenylalanine, and (L)-proline amino acids. The nature of processes responsible for the gel formation both in polar and in apolar solvents of such compounds is still under investigation. Knowing that the organization of surfactant molecules affects the properties of nano scale materials and gels, we decided to elucidate this problem using crystallographic diffraction and energy frameworks analysis. The single crystals of the mentioned compounds were produced successfully from heptane/tBuOMe mixture. The compounds form lamellar self-assemblies in crystals. The energetic landscapes of single crystals of a series of studied amphiphilic gelators have been analyzed to explore the gelling properties. The presented results may be used as model systems to understand which supramolecular interactions observed in the solid state and what energy contributions are desired in the designing of new low-molecular-weight organic gelators.

Restructuring of emergent grain boundaries at free surfaces – An interplay between core stabilization and elastic stress generation

Emergent grain boundaries at free surface impact a wide range of material properties but little is known about their atomic-scale behavior. Using scanning tunneling microscopy and calculations, we studied the structure of emergent grain boundaries at the surfaces of planar nanocrystalline copper (111) films and bicrystals. We show that for a wide range of misorientation angles there exists a strong energetic preference for boundary cores to lie along close-packed planes that leads to the restructuring of emergent grain boundaries at free surfaces and involves the rotation of adjoining grains and the generation of elastic stresses in the triple junction region. The interplay of the stress field and the core stabilization determines the length scale of the restructuring, which can extend to depths of 15 nm for low angle boundaries. These results point to a new universal mechanism of boundary relaxation at metal surfaces that is expected to be important in grain coalescence, film stress evolution and in controlling properties of nanoscale materials.

The Promise of Emergent Nanobiotechnologies for In Vivo Applications and Implications for Safety and Security.

Nanotechnology, the multidisciplinary field based on the exploitation of the unique physicochemical properties of nanoparticles (NPs) and nanoscale materials, has opened a new realm of possibilities for biological research and biomedical applications. The development and deployment of mRNA-NP vaccines for COVID-19, for example, may revolutionize vaccines and therapeutics. However, regulatory and ethical frameworks that protect the health and safety of the global community and environment are lagging, particularly for nanotechnology geared toward biological applications (ie, bionanotechnology). In this article, while not comprehensive, we attempt to illustrate the breadth and promise of bionanotechnology developments, and how they may present future safety and security challenges. Specifically, we address current advancements to streamline the development of engineered NPs for in vivo applications and provide discussion on nano–bio interactions, NP in vivo delivery, nanoenhancement of human performance, nanomedicine, and the impacts of NPs on human health and the environment.

Performance of different traditional and machine learning-based atomistic potential functions in the simulation of mechanical behavior of Fe nanowires

Characterization of nanoscale material properties using experimental methods is difficult due to their high costs and complexities. Hence, many researchers apply alternative techniques, such as atomic/molecular simulations, to overcome the limitations of experimental methods. A well-established method to study material behavior at nanoscales is molecular dynamics simulation. However, the accuracy of its results is highly dependent on the selection of appropriate potential functions/force fields modeling atomic interactions. This work investigates the effects of considering different potential functions on the mechanical characteristics of BCC Fe nanostructures using molecular dynamics simulations. Laboratory data are used to verify the calculated elastic properties of bulk structures. Furthermore, systematic simulations are performed to determine the elastic properties of nanowires under tensile loading, various potential functions, and different temperatures. According to the results, Ackland's potential function and experimental data are in excellent agreement. On the contrary, Asadi's potential function shows an opposite trend comparing other functions and experimental mechanical data. In addition, the potential function formulated based on artificial neural networks is capable to capture tension-induced necking phenomena in Fe nanowires.

Field induced electron emission from graphene nanostructures

Electric fields play a crucial role in modulating the electronic properties of nanoscale materials. Electron emission, induced by an electric field, is a representative phenomenon. Experimental and theoretical aspects of such electron emission from graphene are briefly reviewed. The emission occurs at the edge of graphene flakes, not at the surface, because the edge highly concentrates the electric field. Emission currents are sensitive to the edge shapes and edge functionalization. This review provides guiding principles for designing high-efficiency field-emission devices by using graphene nanostructures.

Correlative piezoresponse and micro-Raman imaging of CuInP2S6–In4/3P2S6 flakes unravels phase-specific phononic fingerprint via unsupervised learning

Characterizing the novel properties of layered van der Waals materials is key for their application in functional devices. A better understanding of this type of material requires correlative imaging of diverse nanoscale material properties. Within this class of materials, CuInP2S6 (CIPS) has received a significant degree of interest due to its ionically mediated room temperature ferroelectricity. Moreover, it is possible to form stable self-assembled heterostructures of ferroelectric CuInP2S6 (CIPS) and non-ferroelectric (i.e., lacking Cu) In4/3P2S6 (IPS) phases, by controlling the targeted composition and kinetics of synthesis. In this work, we present a correlative nanometric imaging study of the phononic modes and piezoelectricity of the phase-separated thin heteroepitaxial CIPS/IPS flakes. We show that it is possible to isolate the different phononic modes of the two phases by spatially correlating them with their distinct ferroelectric behavior. The coupling of our experimental data with unsupervised learning statistical methods enables unraveling specific Raman peaks that are characteristic of each chemical phase (CIPS and IPS) present in the composite sample, discarding the less significant ones.

Towards kilohertz synchrotron coherent diffractive imaging

X-ray coherent diffractive imaging (CDI) techniques have been applied with widespread impact to study nanoscale material properties. New fast framing detectors may reveal dynamics that occur at millisecond timescales. This work demonstrates by simulation that kilohertz synchrotron CDI is possible, by making use of redundant information from static parts of the image field. Reconstruction ambiguities are strongly suppressed by applying a spatio-temporal constraint, obviating the need for slower methods of introducing diversity such as ptychography. The relationship between image fidelity and time resolution is investigated and shows that dynamics an order of magnitude faster can be reconstructed, compared with conventional CDI.

Biocompatible Probes Based on Rare-Earth Doped Strontium Aluminates with Long-Lasting Phosphorescent Properties for In Vitro Optical IMAGING.

In recent decades, the demand for biomedical imaging tools has grown very rapidly as a key feature for biomedical research and diagnostic applications. Particularly, fluorescence imaging has gained increased attention as a non-invasive, inexpensive technique that allows real-time imaging. However, tissue auto-fluorescence under external illumination, together with a weak tissue penetration of low wavelength excitation light, largely restricts the application of the technique. Accordingly, new types of fluorescent labels are currently being investigated and, in this search, phosphorescent nanoparticles promise great potential, as they combine the interesting size-dependent properties of nanoscale materials with a long-lasting phosphorescence-type emission that allows optical imaging well after excitation (so avoiding autofluorescence). In this work, core-shell structures consisting of SrAlO:Eu,Dy luminescent cores encapsulated within a biocompatible silica shell were prepared, showing a green persistent phosphorescence with an afterglow time of more than 1000 s. A high-energy ball milling procedure was used to reduce the size of the starting phosphors to a size suitable for cellular uptake, while the silica coating was produced by a reverse micelle methodology that eventually allows the excitation and emission light to pass efficiently through the shell. Confocal fluorescence microscopy using HeLa cancer cells confirmed the potential of the all-ceramic composites produced as feasible labels for in vitro optical imaging.

Vibrational Property of α-Borophene Determined by Tip-Enhanced Raman Spectroscopy.

We report a Raman characterization of the α borophene polymorph by scanning tunneling microscopy combined with tip-enhanced Raman spectroscopy. A series of Raman peaks were discovered, which can be well related with the phonon modes calculated based on an asymmetric buckled α structure. The unusual enhancement of high-frequency Raman peaks in TERS spectra of α borophene is found and associated with its unique buckling when landed on the Ag(111) surface. Our paper demonstrates the advantages of TERS, namely high spatial resolution and selective enhancement rule, in studying the local vibrational properties of materials in nanoscale.

Semiconductor Nanowire Arrays for High‐Performance Miniaturized Chemical Sensing

AbstractChemiresistive sensing is one of the most promising technologies for portable and miniaturized chemical sensing, with applications ranging from air quality monitoring to explosive detection and medical diagnostics. Recently, there have been growing efforts in developing microchip based chemical sensors operating at room temperature with high sensitivity, selectivity, spatial and temporal resolution, long‐term stability, and cost‐effectiveness. Here, the engineering of highly performing miniaturized gas sensors consisting of chemiresistive vertical indium phosphide nanowire (NW) arrays is reported for the first time, and their potential for the selective detection of nitrogen dioxide (NO2), a major air pollutant, is demonstrated. By carefully engineering the NW geometry (i.e., diameter and pitch), a superior sensing performance than those previously reported semiconductor‐based NO2 sensors is achieved, obtaining a limit of detection of 3.1 ppb at room temperature, with outstanding selectivity, and long‐term stability. Kinetic analysis and electrical simulation further reveal the array geometry correlated sensing mechanism, providing insights for the design of future NW array‐based devices. These findings indicate that, owing to their unique nanoscale structures, material properties, and CMOS compatible manufacture processes, III‐V compound semiconductor NW arrays present a new and promising chemical sensing platform for development of future high performance, miniaturized on‐chip sensing system.

Effect of time and spatial domains on monolayer 2D material interface thermal conductance measurement using ns ET-Raman

Raman-based approaches to characterizing thermal properties of nanoscale and microscale materials have proven to be powerful experimental methods. This work explores the potential of energy-transport state-resolved Raman (ET-Raman) for the precise determination of interfacial thermal conductance (G) between monolayer 2D materials and their substrates. ET-Raman employs a continuous wave laser and nanosecond (ns) pulsed laser to induce both steady state and transient heating while simultaneously collecting 2D material temperature information from the Raman signal. A 3D numerical model built using the finite volume method simulates the two differentiated thermal transport processes. The simulated temperature rises are compared with experimental Raman temperature information to extract G. In this study, we investigate the temporal effects of the pulse frequency and pulse width of the ns laser on precise characterization of G. By running multiple simulations for a range of pulsed laser frequencies and pulse widths, we determine that ET-Raman is most sensitive to precise interfacial thermal conductance measurements with short pulse widths (~below 20 ns) and with pulsing frequencies that ensure sufficient cooling time between consecutive pulses (~below 500 kHz). We also conclude that substrate thickness and laser spot size play critical roles in heat distribution and subsequent sensitivity to meaningful G measurements. As both laser spot size and SiO2 substrate thickness decrease, detection of interfacial thermal transport becomes more difficult. These results offer essential guidance in the design of future Raman-based approaches to thermal measurements using pulsed lasers.