Temperature-dependent colloidal behavior of polymer-stabilized gold nanoparticles.

Temperature-dependent colloidal behavior of polymer-stabilized gold nanoparticles.

The present work takes an overarching look on how particles can alter the functional and structural properties of shape memory alloys (SMAs). We consider precipitates which form in binary and ternary NiTi-based alloys, including the high-temperature SMAs NiTiHf and NiTiZr. We also take a look at precipitates which form in Cu–Al–Zn, Cu–Al–Ni, and Co–Ni–Ga–SMAs. We take these alloy systems as examples to review different effects of particles on local alloy chemistry and local stress and strain states at particle/matrix interfaces. Their influence on the nucleation and growth of martensite and on the propagation of a martensitic transformation front is discussed, and the consequences for macroscopic functional and structural properties like phase transformation temperatures and widths of thermal hysteresis are highlighted. Emphasis is also placed on particles which form because elements like C and O are picked up during alloy production and affect functional and structural properties. Finally, it is suggested to take a look at additive manufactured SMAs with added inert nano/micro-particles, which would facilitate the investigation of the mechanical constraints, and which may lead to SMAs with improved structural and functional properties.

Starch is the main integral components of the millets and it is widely used in the food processing sectors for development of functional foods. The extraction and isolation methods of starch from millet grains are greatly affected their functional and structural properties. Therefore, in current study, the effects of different wet milling extraction methods such as water, acidic, and alkaline are investigated on the physical, structural, thermal, and functional properties of barnyard millet starch. The results show that the starch extracted from barnyard millets using alkaline method shows higher yield of starch (64.76%) with good amylose content (34.52%). In addition, the functional properties such as water binding capacity (211.39%), oil binding capacity (223.84%), higher color attributes (whiteness), thermal stability (91.62 °C), textural properties (74.70 g), and lower particle size (19.44 µm) are recorded in barnyard millet starch extracted using alkaline steeping method. The results of the field emission scanning electron microscopes (FESEM) are showed polygonal, spherical, and rounded shapes of all types of extracted starch granules. Whereas, the acidic method is more fused structures of starch granules as compared to water and alkaline methods. The results of the current study reveal that the application of alkaline method is the most potential to extract starch from barnyard millet with good quality and functional properties for further food applications.

Since the discovery of ferroelectricity (FE) in HfO2-based thin films, they are gaining increasing attention as a viable alternative to conventional FE in the next generation of non-volatile memory devices. In order to further increase the density of elements in the integrated circuits, it is essential to adopt a three-dimensional design. Since atomic layer deposition (ALD) processes are extremely conformal, ALD is the favored approach in the production of 3D ferroelectric random access memory. Here, we report the fabrication of fully ALD-grown capacitors comprising a 10-nm-thick FE Hf0.5Zr0.5O2 layer sandwiched between TiN electrodes, which are subjected to a detailed investigation of the structural and functional properties. The robust FE properties of Hf0.5Zr0.5O2 films in capacitors are established by several alternative techniques. We demonstrate a good scalability of TiN/Hf0.5Zr0.5O2/TiN FE capacitors down to 100-nm size and the polarization retention in the test “one transistor-one capacitor” (1T-1C) cells after 1010 writing cycles. The presence of a non-centrosymmetric orthorhombic phase responsible for FE properties in the alloyed polycrystalline Hf0.5Zr0.5O2 films is established by transmission electron microscopy. Given the ability of the ALD technique to grow highly conformal films and multilayered structures, the obtained results indicate the route for the design of FE non-volatile memory devices in 3D integrated circuits.

Comprehensive characterization of Ba1−xSrxTiO3: Correlation between structural and multifunctional properties

A large amount of one‐dimensional (1D) Ce‐doped ZnO nanostructures with different morphologies has been successfully synthesized by annealing a polymeric precursor at various temperatures. The evolution of the morphologies and microstructures was investigated by field‐emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), and high‐resolution TEM (HRTEM). The results show that the morphologies vary drastically with increasing synthesis temperature and the photoluminescence (PL) of the products depends on both the synthesis and measurement temperatures. The CeO layer forms first and becomes a catalytic center for the ZnO growth. At a synthesis temperature lower than the boiling point of Zn, Zn and O atoms can stack epitaxially along the CeO catalytic layer and form a bicrystal nanobelt‐like structure with a trapezoid‐like end and a concave growth fault center. At a synthesis temperature higher than the boiling point of Zn, however, nanowires with an incommensurately modulated superstructure are obtained due to the high reaction rate and the formation of a periodic separation of the CeO layer. As for the room‐temperature PL of ZnO, the incorporation of donor Ce leads to the disappearance of the green band and the appearance of a purplish‐blue emission peak, whose position shifts towards the red and whose intensity decreases with increasing synthesis temperature. Analysis of this temperature‐dependent luminescence indicates that the purplish‐blue emission of nanobelts prepared at 850 °C originates from a donor‐bound exciton emission, and, contrary to the nanowires, it undergoes a change from an emission of the electron–hole plasma (EHP) to an emission of the donor‐bound exciton with decreasing measurement temperature.

FeCoCu ternary nanoparticles distributed and stabilized in the carbon matrix of FeCoCu/C metal-carbon nanocomposites have been synthesized using controlled IR pyrolysis of precursors consisting of the “polymer / iron acetylacetate / cobalt and copper acetates” type system obtained by joint dissolution of components followed by solvent removal. The effect of the synthesis temperature on the structure, composition and electromagnetic properties of the nanocomposites has been studied. By XRD was shown that the formation of the FeCoCu ternary nanoparticles occurs due to the interaction of Fe3С with the nanoparticles of the CoCu solid solution. An increase in the synthesis temperature leads to an increase in the size of the metal nanoparticles due to their agglomeration and coalescence as a result of matrix reconstruction. Furthermore, ternary alloy nanoparticles having a variable composition may form depending on the synthesis temperature and the content ratio of the metals. Raman spectroscopy has shown that the crystallinity of the carbon matrix of the nanocomposites increases with the synthesis temperature. The frequency responses of the relative permittivity and permeability of the nanocomposites have been studied at 3–13 GHz. It has been shown that a change in the content ratio of the metals noticeably increases both the dielectric and the magnetic losses. The former loss is caused by the formation of a complex nanostructure of the nanocomposite carbon matrix while the latter one originates from an increase in the size of the nanoparticles and a shift of the natural ferromagnetic resonance frequency to the low-frequency region. The reflection loss has been calculated using a standard method from the experimental data on the frequency responses of the relative permittivity and permeability. It has been shown that the frequency range and the absorption of electromagnetic waves (from –20 to –52 dB) can be controlled by varying the content ratio of the metals in the precursor. The nanocomposites obtained as a result of the experiment deliver better results in comparison with FeCo/C nanocomposites synthesized under similar conditions.

The diversity of biotechnological applications of algae can be attributed to their abundant production of bioactive metabolites. Polysaccharides are one of the most common and significant groups of (bio) organic molecules. Marine algae are a rich source of natural polysaccharides, such as mucopolysaccharides, cell wall–structure polysaccharides, and storage polysaccharides. Their structure, function, and bio-active properties are unique to each species. The microalgal and cyanobacterial extracellular polysaccharides aid a wide range of biological activities. The polysaccharides derived from algae are emerging as potential biomolecules for innovative therapeutic applications, such as wound dressing, drug delivery, etc. Further, algal polysaccharides are widely utilized for commercial applications in cosmeceuticals, nutraceuticals, pharmaceuticals, functional foods, food packaging, bio-plastics, and plant bio-stimulants. The polysaccharide-rich algal biomass can also serve as a potential feedstock for bioenergy production under a sustainable and renewable bio-economy framework. This chapter provides insight into the recent developments in research on algal polysaccharides, their source, structural properties, bioactive potential, and applications.

Gold nanoparticles (AuNPs) have been proved to be ideal scaffolds to build nanodevices whose performance can be tuned by changing their coating. In particular, the interaction of AuNPs with proteins was revealed to be highly dependent on the physico-chemical properties of the gold cluster protecting monolayer. In this work we studied the behavior of three different alkanethiolate-coated AuNPs (AT-AuNPs) when they are incubated with a model amyloidogenic protein, β2-microglobulin (β2m), whose clinical relevance in dialysis-related amyloidosis (DRA) and structural properties are well known. To the aim we synthesized 6-mercaptohexanoic acid-coated AuNPs (MHA-AuNPs) and (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide-coated AuNPs (MUTAB-AuNPs) of 7.5 nm diameter and 3-mercaptopropionic acid-coated AuNPs (MPA-AuNPs) of 3.6 nm diameter. To study the effects of the incubation with β2m of these NPs that differ in charge and dimension, we employed NMR, UV-vis and fluorescence spectroscopy, along with transmission electron microscopy (TEM). The three tested AuNP systems gave different results. We found that MHA-AuNPs precipitate with the protein into large agglomerates inducing β2m unfolding, MUTAB-AuNP precipitation is triggered by the protein that remains unchanged in solution, at least at the higher considered protein/NP ratio, and MPA-AuNPs interact preferentially with a localized region of the protein that stays essentially stably dissolved. These results stress the complexity of the bio-nano interface and the relevance and viability of the fine control of NP properties to master protein-NP interactions.

Structural and optical properties of highly (110)-oriented non-polar ZnO evaporated films on Si substrates

We report on the structural and vibrational properties of Co nanoparticles formed by ion implantation and thermal annealing in amorphous silica. The evolution of the nanoparticle size, phase, and structural parameters were determined as a function of the formation conditions using transmission electron microscopy, small-angle x-ray scattering, and x-ray absorption spectroscopy. The implantation fluence and annealing temperature governed the spherical nanoparticle size and phase. To determine the latter, x-ray absorption near-edge structure analysis was used to quantify the hexagonal close packed, face-centered cubic and oxide fractions. The structural properties were characterized by extended x-ray absorption fine structure spectroscopy (EXAFS) and finite-size effects were readily apparent. With a decrease in nanoparticle size, an increase in structural disorder and a decrease in both coordination number and bondlength were observed as consistent with the non-negligible surface-area-to-volume ratio characteristic of nanoparticles. The surface tension of Co nanoparticles calculated using a liquid drop model was more than twice that of bulk material. The size-dependent vibrational properties were probed with temperature-dependent EXAFS measurements. Using a correlated anharmonic Einstein model and thermodynamic perturbation theory, Einstein temperatures for both nanoparticles and bulk material were determined. Compared to bulk Co, the mean vibrational frequency of the smallest nanoparticles was reduced as attributed to a greater influence of loosely bonded, undercoordinated surface atoms relative to the effect of capillary pressure generated by surface curvature.

Summary form only given. Electrodeposition of cobalt is a complex and rich problem. Several reports have shown that the wire diameter, deposition conditions, additives and temperature can give rise to very different structural and magnetic properties. We have studied the structural and magnetic properties of Co nanowires as a function of the electrolytic bath acidity. The structural properties have been studied by transmission electron microscopy (TEM) and the magnetic properties have been characterized by hysteresis loops and ferromagnetic resonance (FMR).

Synthesis of The gold Nanoparticles with Novel Shape via Chemical Process and Evaluating The structural, Morphological and Optical Properties

Silver and gold nanoparticles are promising agents that can enhance the antibacterial activity of conjugated/capped extract of plant compounds. The aim of our study is to synthesize silver nanoparticles from Gymnema sylvestre plant extract. In this study, the antimicrobial activity of conjugated silver which was green synthesized and gold nanoparticle that was obtained from a commercial source was evaluated using disk-diffusion method against Escherichia coli and Aspergillus niger. Transmission electron microscopy, scanning electron microscopy, ultraviolet-visible spectroscopy, and Fourier transform infrared spectroscopy analyses were also carried out to characterize the conjugated silver and gold nanoparticles. The conjugation of silver and gold nanoparticles was performed chemically using 16-mercaptodecanoic acid. Our results revealed that conjugated silver and gold nanoparticle both showing larger inhibition zones against E. coli and A. niger. The minimum inhibitory concentration (MIC) of the above metallic conjugation was found to be stable with MIC was reported to be 1 mM. When comparing the sample analysis on conjugation of gold and silver nanoparticles against E. coli and A. niger, the antimicrobial activity recorded was 2.0 ± 0.01 and 2.32 ± 0.04 cm, respectively, with no significance difference was found (P = 0.85). In conclusion, the combination of two different nanoparticles is efficient for microbial inhibition and can be useful for studying antimicrobial activities with the combination of different nanomaterials in future.

PurposeThe purpose of the study was to determine the relative effects of deamidation and/or truncation on the structural and functional properties of αB-crystallin.MethodsUsing wild-type (WT) αB-crystallin and the αB deamidated mutant (i.e., αB N146D), we generated NH2-terminal domain deleted (residues no. 1–66; αB-NT), deamidated plus NH2-terminal domain deleted (αB N146D-NT), COOH-terminal extension deleted (residues no. 151–175; αB-CT), and deamidated plus COOH-terminal extension deleted (αB N146D-CT) mutants. All of the proteins were purified and their structural and functional (chaperone activity with insulin as target protein) properties were determined and compared to WT αB-crystallin.ResultsThe desired deletions in the αB-crystallin mutants were confirmed by DNA sequencing and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometric analysis. The homomers of αB-CT and its deamidated form (αB N146D-CT) became water insoluble, whereas the αB N146D, αB-NT, and αB N146D-NT species remained water-soluble. CD spectroscopic studies revealed that the mutants with deletion of NH2- or COOH-termini or deamidation showed increased β-sheet and decreased α-helical contents with the exception of αB N146D-CT, which showed a substantial increase in α-helix and decrease in β-sheet content. Results of intrinsic Trp fluorescence suggested little change in Trp microenvironment of αB N146D relative to WT αB, but substantial alterations on deletion of COOH-terminal extension or a combination of this deletion plus deamidation. Hydrophobic binding studies using the hydrophobic probe 8-anilino-1-naphthalene sulfonate (ANS) showed that, relative to WT αB structure, the N146 deamidation, COOH-terminal extension deletion or a combination of this deamidation and deletion resulted in a relatively compact structure whereas the NH2-terminal domain deletion and a combination of this deletion plus deamidation resulted in a relaxed structure. All the αB mutants showed higher molecular mass ranging between 1.2×106 to 5.4×106 Da, relative to WT αB which had a molecular mass of 5.8×105 Da. Chaperone activity across all αB species decreased in the following order: WTαB > αB N146D-CT > αB N146D-NT > αB-NT > αB-CT > αB N146D. Specifically, substantial losses in chaperone activity (only 10% to 20% protection) were seen in αB N146D, αB-NT, and αB-CT. However, in the species with the combination of deamidation plus NH2- or COOH-terminal deletion, the percent protection was about 24% in αB N146D-NT and about 40% in αB N146D-CT.ConclusionsAlthough all mutants formed oligomers even after deamidation, on deletion of either NH2-terminal domain or COOH-terminal extension or a combination of these deletions and deamidation, their structural properties were substantially altered. The results suggested that the NH2-terminal domain is relatively more important than the COOH-terminal extension for the chaperone function of αB. The non-deamidated N146 residue, NH2-terminal domain and COOH-terminal extension are also of critical importance to the maintenance of αB-crystallin chaperone activity.