Nanoscale Structural Characteristics Research Articles

Nanoscale Structural Characteristics and In Vitro Bioactivity of Borosilicate–Poly(vinyl alcohol) (PVA) Hybrid Aerogels for Bone Regeneration

Nanoscale Structural Characteristics and In Vitro Bioactivity of Borosilicate–Poly(vinyl alcohol) (PVA) Hybrid Aerogels for Bone Regeneration

Tuning the size, concaveness, and aspect ratio of concave cubic gold nanoparticles produced with high reproducibility

Reproducible fabrication of concave cubic gold nanoparticles with precise control over size, concaveness, and aspect ratio is important because the nanoscale structural characteristics can influence their plasmonic and catalytic properties. However, this is particularly challenging because the number of synthetic parameters involved in the fabrication strategy adds complexity to the reaction mechanism. Here, we introduce a simplified seed-mediated method and uncover the unknown conceptual insights on how the different halides and their concentration influence the surface structure and stability of underpotential silver monolayer deposited on the high energy facets of nanoparticles. The results reveal that adding Br− and I− ions to growth solution offers a predominant way to control the reaction kinetics and engineering nanoparticles with a predefined size, morphology, concaveness, aspect ratio, and plasmonic properties. Using spectroscopy and microscopy techniques, we shed new light on the reaction kinetics of concave cubic gold nanoparticles using the combined influence of silver underpotential deposition and halides. The strategy developed here can be expanded to fabricate gold nanoparticles of complex geometries. The results from our electromagnetic calculations suggest that the self-assembled superstructure of concave cubic gold nanoparticles can be more appealing for developing an ultra-sensitive sensing platform than to self-assembled superstructures of truncated cubic gold nanoparticles.

Nanostructural characteristics-mediated plastic behavior of Cu/Ag polycrystalline multilayered materials

For polycrystalline multilayers materials, the typical nanoscale structural characteristics contain grain, twin and hetero interface, which could make collective and remarkable influence on the mechanical property. In this work, taking Cu/Ag polycrystalline multilayers as an example, the coupling effects of grain boundary, twin boundary and hetero interface on the plastic deformation mechanisms are studied using molecular dynamics simulations. The simulation results show that the dominant plastic deformation mechanisms change from dislocation activities for common multilayer material to hetero interfaces sliding when the ratio of material layer thickness to grain size is small enough, leading to a marked decrease of strength. As for the twin boundary, its strengthening effect follows the conventional Hall-Petch relationship when the grain size is larger than the twin thickness. This twin-related strengthening effect becomes weak with the grain size decreases, indicating a competitive relationship between these two characteristic sizes. These findings will shed light on a more comprehensive understanding of size effects on the underlying mechanisms of plastic deformation of polycrystalline multilayers, which provide crucial guidance for the design of novel materials based on polycrystalline multilayers.

Impact of isolation methods on the biophysical heterogeneity of single extracellular vesicles

Extracellular vesicles (EVs) have raised high expectations as a novel class of diagnostics and therapeutics. However, variabilities in EV isolation methods and the unresolved structural complexity of these biological-nanoparticles (sub-100 nm) necessitate rigorous biophysical characterization of single EVs. Here, using atomic force microscopy (AFM) in conjunction with direct stochastic optical reconstruction microscopy (dSTORM), micro-fluidic resistive pore sizing (MRPS), and multi-angle light scattering (MALS) techniques, we compared the size, structure and unique surface properties of breast cancer cell-derived small EVs (sEV) obtained using four different isolation methods. AFM and dSTORM particle size distributions showed coherent unimodal and bimodal particle size populations isolated via centrifugation and immune-affinity methods respectively. More importantly, AFM imaging revealed striking differences in sEV nanoscale morphology, surface nano-roughness, and relative abundance of non-vesicles among different isolation methods. Precipitation-based isolation method exhibited the highest particle counts, yet nanoscale imaging revealed the additional presence of aggregates and polymeric residues. Together, our findings demonstrate the significance of orthogonal label-free surface characteristics of single sEVs, not discernable via conventional particle sizing and counts alone. Quantifying key nanoscale structural characteristics of sEVs, collectively termed ‘EV-nano-metrics’ enhances the understanding of the complexity and heterogeneity of sEV isolates, with broad implications for EV-analyte based research and clinical use.

Molecular architectonics of DNA for functional nanoarchitectures.

DNA is the key biomolecule central to almost all processes in living organisms. The eccentric idea of utilizing DNA as a material building block in molecular and structural engineering led to the creation of numerous molecular-assembly systems and materials at the nanoscale. The molecular structure of DNA is believed to have evolved over billions of years, with structure and stability optimizations that allow life forms to sustain through the storage and transmission of genetic information with fidelity. The nanoscale structural characteristics of DNA (2 nm thickness and ca. 40–50 nm persistence length) have inspired the creation of numerous functional patterns and architectures through noncovalent conventional and unconventional base pairings as well as through mutual templating-interactions with small organic molecules and metal ions. The recent advancements in structural DNA nanotechnology allowed researchers to design new DNA-based functional materials with chemical and biological properties distinct from their parent components. The modulation of structural and functional properties of hybrid DNA ensembles of small functional molecules (SFMs) and short oligonucleotides by adapting the principles of molecular architectonics enabled the creation of novel DNA nanoarchitectures with potential applications, which has been termed as templated DNA nanotechnology or functional DNA nanoarchitectonics. This review highlights the molecular architectonics-guided design principles and applications of the derived DNA nanoarchitectures. The advantages and ability of functional DNA nanoarchitectonics to overcome the trivial drawbacks of classical DNA nanotechnology to fulfill realistic and practical applications are highlighted, and an outlook on future developments is presented.

Block Polymer Membranes Functionalized with Nanoconfined Polyelectrolyte Brushes Achieve Sub-Nanometer Selectivity.

The well-defined nanostructure of membranes manufactured from self-assembled block polymers enables highly selective separations; however, recent efforts to push the pore size of block polymer-based membranes to the lower end of the size spectrum have only been moderately successful for a variety of reasons. For instance, the conformational changes of the stimuli-responsive functional groups lining the pore walls of some block polymer membranes result in varied pore sizes that limit their operational range. Here, we overcome this challenge through the directed design of the third moiety of an A-B-C triblock polymer. The use of this macromolecular design paradigm allows for the preparation of a 500 nm thick polyisoprene-b-polystyrene-b-poly(2-acrylamido-ethane-1,1-disfulonic acid) (PI-PS-PADSA) coating atop a hollow fiber membrane support. This nanoporous test bed, which exhibits an average pore radius of 1 nm, demonstrates an extremely high solute selectivity by fully gating solutes that have only an 8 Å size difference, a separation that is based solely on a sieving mechanism. Furthermore, the nanoscale structural characteristics of the solvated PADSA pore walls are elucidated by quantifying the rejection of neutral solutes and calculating the hydraulic permeability values in solutions of high ionic strength (1 mM ≤ I ≤ 3 M) and over a broad range of solution pH (1 ≤ pH ≤ 13). These key results provide a solid foundation for defining structure-property-performance relationships in the emerging area of nanoporous triblock polymer thin films. Moreover, the successful demonstration of the test bed separation device offers a tangible means by which to manufacture next-generation nanofiltration membranes that require a robust performance profile over a dynamic range of conditions.

Investigation of nanoscale structural alterations of cell nucleus as an early sign of cancer

BackgroundThe cell and tissue structural properties assessed with a conventional bright-field light microscope play a key role in cancer diagnosis, but they sometimes have limited accuracy in detecting early-stage cancers or predicting future risk of cancer progression for individual patients (i.e., prognosis) if no frank cancer is found. The recent development in optical microscopy techniques now permit the nanoscale structural imaging and quantitative structural analysis of tissue and cells, which offers a new opportunity to investigate the structural properties of cell and tissue below 200 – 250 nm as an early sign of carcinogenesis, prior to the presence of microscale morphological abnormalities. Identification of nanoscale structural signatures is significant for earlier and more accurate cancer detection and prognosis.ResultsOur group has recently developed two simple spectral-domain optical microscopy techniques for assessing 3D nanoscale structural alterations – spectral-encoding of spatial frequency microscopy and spatial-domain low-coherence quantitative phase microscopy. These two techniques use the scattered light from biological cells and tissue and share a common experimental approach of assessing the Fourier space by various wavelengths to quantify the 3D structural information of the scattering object at the nanoscale sensitivity with a simple reflectance-mode light microscopy setup without the need for high-NA optics. This review paper discusses the physical principles and validation of these two techniques to interrogate nanoscale structural properties, as well as the use of these methods to probe nanoscale nuclear architectural alterations during carcinogenesis in cancer cell lines and well-annotated human tissue during carcinogenesis.ConclusionsThe analysis of nanoscale structural characteristics has shown promise in detecting cancer before the microscopically visible changes become evident and proof-of-concept studies have shown its feasibility as an earlier or more sensitive marker for cancer detection or diagnosis. Further biophysical investigation of specific 3D nanoscale structural characteristics in carcinogenesis, especially with well-annotated human cells and tissue, is much needed in cancer research.

Nanoscale alloying effect of gold–platinum nanoparticles as cathode catalysts on the performance of a rechargeable lithium–oxygen battery

The understanding of nanoscale alloying or the phase segregation effect of alloy nanoparticles on the catalytic properties is important for a rational design of the desired catalysts for a specific reaction. This paper describes findings of an investigation into this type of structural effect for carbon-supported bimetallic gold–platinum nanoparticles as cathode catalysts in a rechargeable lithium–oxygen battery. The nanoscale structural characteristics in terms of size, alloying and phase segregation were shown to affect the catalytic properties of the catalysts in the Li–O2 battery. In addition to the composition effect, the catalysts with a fully alloyed phase structure were found to exhibit a smaller discharge–charge voltage difference and a higher discharge capacity than those with a partial phase segregation structure. This finding is significant for the design of alloy nanoparticles as air cathode catalysts in rechargeable lithium–air batteries, demonstrating the importance of the control of the nanoscale composition and phase properties.

Nuclear nano-morphology markers of histologically normal cells detect the “field effect” of breast cancer

Accurate detection of breast malignancy from histologically normal cells ("field effect") has significant clinical implications in a broad base of breast cancer management, such as high-risk lesion management, personalized risk assessment, breast tumor recurrence, and tumor margin management. More accurate and clinically applicable tools to detect markers characteristic of breast cancer "field effect" that are able to guide the clinical management are urgently needed. We have recently developed a novel optical microscope, spatial-domain low-coherence quantitative phase microscopy, which extracts the nanoscale structural characteristics of cell nuclei (i.e., nuclear nano-morphology markers), using standard histology slides. In this proof-of-concept study, we present the use of these highly sensitive nuclear nano-morphology markers to identify breast malignancy from histologically normal cells. We investigated the nano-morphology markers from 154 patients with a broad spectrum of breast pathology entities, including normal breast tissue, non-proliferative benign lesions, proliferative lesions (without and with atypia), "malignant-adjacent" normal tissue, and invasive carcinoma. Our results show that the nuclear nano-morphology markers of "malignant-adjacent" normal tissue can detect the presence of invasive breast carcinoma with high accuracy and do not reflect normal aging. Further, we found that a progressive change in nuclear nano-morphology markers that parallel breast cancer risk, suggesting its potential use for risk stratification. These novel nano-morphology markers that detect breast cancerous changes from nanoscale structural characteristics of histologically normal cells could potentially benefit the diagnosis, risk assessment, prognosis, prevention, and treatment of breast cancer.

By what means should nanoscaled materials be constructed: molecule, medium, or human?

There is great potential in nanoscale science and technology, and construction of macrosized materials and systems possessing nanoscale structural features is a crucial factor in the everyday application of nanoscience and nanotechnology. Because nanoscale substances are often constructed through self-assembly of unit molecules and nanomaterials, control of the self-assembly process is required. In order to establish general guidelines for the fabrication of materials with nanoscale structural characteristics, i.e., nanoscaled materials, we introduce here examples of recent research in related fields categorised as: (i) self-assembled structures with forms generally determined by intrinsic interactions between molecules and/or unit nanomaterials, (ii) self-assemblies influenced by their surrounding media, especially interfacial environments, (iii) modulation of self-assembly by artificial operation or external stimuli. Examples are not limited to organic molecules, which are often regarded as the archetypal species in self-assembly chemistry, and many examples of inorganic assemblies and hybrid structures are included in this review.

Nanoscale structural characteristics and electron field emission properties of transition metal–fullerene compound TiC 60 films

Transition-metal compound TiC 60 thin films were grown by co-deposition from two separated sources of fullerene C 60 powder and titanium. Study of structural properties of the films, by Raman spectroscopy, atomic force microscopy, and scanning tunneling spectroscopy reveals that the films have a deformed C 60 structure with certain amount of sp 3 bonds and a rough surface with a large number of nanoclusters. z– V tunnelling spectroscopic measurements suggest that several charge transport mechanisms are involved in as the tip penetrates into the thin film. Conventional field electron emission (FEE) measurements show a high emission current density of 10 mA/cm 2 and a low turn-on field less than 8 V/μm, with the field enhancement factors being 659 and 1947 for low-field region and high-field region, respectively. By exploiting STM tunneling spectroscopy, local FEE on nanometer scale has also been characterized in comparison with the conventional FEE. The respective field enhancement factors are estimated to be 99–355 for a gap varying from 36 to 6 nm. The enhanced FEE of TiC 60 thin films can be ascribed to structural variation of C 60 in the films and the electrical conducting paths formed by titanium nanocrystallites embedded in C 60 matrix.

Polarization leakage and asymmetric Raman line broadening in microwave dielectric ZrTiO 4

Nano-scale structural characteristics and broken symmetry associated with the formation of incommensurately ordered phase from the high-temperature disordered phase of ZrTiO 4 were studied using Raman scattering method. For this purpose, the Raman peak at 815 cm −1 caused by the A g -symmetry normal mode was employed as a nano-structural probe. A polarization leakage was observed in the polarized Raman spectra of single-crystal ZrTiO 4. The observed leakage was attributed to the random orientation of the short-range ordered domains in the beginning stage of the normal-to-incommensurate transformation. The computational result based on the phonon-confinement model indicated that the asymmetric Raman line broadening in the incommensurately ordered ZrTiO 4 single-crystal was directly related to the existence of the faulted boundary having the average periodicity of 3.9 nm along the a-axis.

Deformation mechanism at large strains in a high-Nb-containing TiAL at room temperature

This paper investigates the deformation behavior and nano-scale structural characteristics after large deformation (29%) at room temperature of a Ti–45Al–9Nb–2.5Mn (at.%) alloy with duplex microstructure. Dislocation glide is the main deformation mode at low strains (such as 2%). The interaction of moving dislocations reduces the mobility of dislocations by pinning, and when deformation strain reachs 5%, both dislocation glide and mechanical twining are active. With further increase in strain, deformation twining becomes the dominant deformation mode, dividing the original γ grains and lamellar structure into nano-scale. The characteristic feature of the deformation twin in γ grains after large deformation at room temperature is the bent deformation twin (DT or DT′). There are many sub-structures in the DT, which makes the (111) T not exactly straight. High resolution TEM observations showed that (111) DL plane of the DT twins exhibits a large misorientation angle with the (111) M plane of the γ matrix. The orientation relationship between the matrix and the DT or DT′ is actually not the expected true twin relationship. The existence of numerous 1/3[111] Frank partial dislocations was regarded as accommodating the bending of the boundaries of DT. Local zigzag bending of the barrier twin boundaries can be observed due to twin intersections. Intersection induced lattice distortion in the intersection area for type I twin intersection is more severe than that for type II intersection. As results of the relaxation of the heavy lattice distortion, nano-scale subgrains boundaries may form together with a rectangular region near the intersection area. Nanotwins could be observed in the rectangular region for type I intersection. The nanotwins are formed with a homogeneous 1/6[11 2 ̄ ] twinning dislocation glide mechanism. For type II twin intersection, the intersection induces the formation of secondary twinning ST in the barrier twin. No region with nanotwins can be observed near the intersection area. The local stress concentration in type II twin intersection may be relaxed by the emission of dislocations from the intersection area.