High-resolution Transmission Electron Microscopy Images Research Articles

Characterization of Mn5Ge3 Contacts on a Shallow Ge/SiGe Heterostructure.

Mn5Ge3 is a ferromagnetic phase of the Mn-Ge system that is a potential contact material for efficient spin injection and detection. Here, we investigate the creation of Mn5Ge3-based contacts on a Ge/SiGe quantum well heterostructure via solid-state synthesis. X-ray diffraction spectra fitting indicates the formation of Mn5Ge3-based contacts on bulk Ge and Ge/SiGe. High-resolution scanning transmission electron microscopy imaging and energy dispersive X-ray spectroscopy verify the correct Mn5Ge3-based phase formation. Schottky diode measurements, transmission line measurements, and Hall measurements reveal that Mn5Ge3-based contacts serve as good p-type contacts for Ge/SiGe quantum well heterostructures due to having a low Schottky barrier height of 0.10eV (extracted from a Mn5Ge3/n-Ge analogue) and a contact resistance in the order of 1 kΩ. Furthermore, we show that these electrical characteristics have a gate-voltage dependence, thereby providing tunability.

Facile synthesis of lanthanum carbonate octahydrate and lanthanum oxide nanoparticles by sonochemical method: systematic characterizations

Abstract This study could present the size and morphology of two synthesized nanoparticles (NPs) by observing their smallest possible dimensions. Lanthanum carbonate nanoparticles were synthesized by sonochemical method through the interaction of lanthanum acetate hydrate and sodium carbonate in an aqueous medium with a probe sonicator. After rigorous washing followed by drying, the La2(CO3)3·8H2O(S1) NPs were calcined at a temperature of 600 °C to obtain lanthanum oxide nanoparticles (S2). Both NPs were characterised through various instrumental techniques. PXRD study showed orthorhombic with space group of Pccn (56) and hexagonal phases with space group of P 3 ‾ m 1 $P\overline{3}m1$ (164) for S1 and S2 respectively whose morphology and elemental analysis were studied through FESEM and EDX. High resolution TEM image of La2(CO3)3·8H2O and La2O3 showed spherical shapes of the nanoparticles. Further study of XPS and FTIR conveyed detailed information of both nanoparticles whose TGA-DSC showed three step decomposition curves. The size and morphology of the synthesized nanoparticles have been found to have a distinct morphology and are found comparatively smaller in size than those observed in the earlier reported works (Table 1 Table 1: Comparative study of synthesized lanthanum carbonate and lanthanum oxide NPs with various techniques applied by other researchers. Sl. no. Name of NPs Methods Conditions Size of NP Reference 1 La2(CO3)3·8H2O Sonochemical method Time: 25 min XRD: Pccn (56) a = 8.9840 Å b = 9.5800 Å c = 17.0000 Å This work Temperature: 301 K Size: 24.102 nm Starting materials:(a) La(CH3COO)2: 0.050 M(b) Na2CO3:0.050 M TEM: Size: 4–30 nm La2(CO3)3 Reverse micelles Time: 1 h XRD: Size: nanoparticles absent [20] Temperature: 303 K Starting materials:(a) Triton X-100(b) Cyclohexane(c) n-butylalcohol(d) La(NO3)3(aq) e) NaCO3(aq) La2(CO3)3·8H2O Hydrothermal Time: 2–5 days XRD: Pccn a = 8.984 Å b = 9.580 Å c = 17.00 Å [21] Temperature: 773 K Size: nanoparticles absent Prepared by slow hydrolysis of La(CCl3COO)3 La2(CO3)3·1.4H2O Hydrothermal Time: 1 h 30 min Structure unknown [22] Temperature: 368 K Starting material:(a) La2O3 (b) HNO3 (c) Urea La2(CO3)3·1.7H2O Sonochemical Time: 30 min XRD: a = 8.990 Å c = 9.675 Å [23] Temperature: not specified Size: not specified (a) La(OAC)3 (b) Na2CO3 TEM: Size: 25–35 nm Concentration:(a) La(OAC)3: 0.051 M(b) Na2CO3: 0.251 M La2(CO3)3·5H2O Hydrothermal Time: XRD: Pbca a = 9.0167 Å b = 12.842 Å c = 9.6331 Å [24] Temperature: Size: not specified Starting materials:(a) La2O3 (b) HCl(c) Na2CO3 La2(CO3)3·3.4H2O Hydrothermal Time: 3–4 h XRD: P21212 a = 9.57 Å b = 12.65 Å c = 8.94 Å [25] Temperature: 298–308 K Size: not specified Starting materials:(a) LaCl3 (b) NH4HCO3 2 La2O3 Thermal decomposition Time: 2 h P3m1 a = 3.973 Å b = 3.9373 Å c = 6.129 Å [26] Temperature: 1073 K Size: 15 nm Starting material: La(OH)3 nanorods TEM: Size: 23 nm La2O3 Thermal decomposition Time: 2 h XRD: a = 11.347 Å [23] Temperature: 873 K Size: 30 nm Starting material:La2(CO3)3·1.7H2O TEM: Size: 30 nm La2O3 Thermal decomposition Time: not specified Not specified [27] Temperature: 1198 K Starting material:(a) La(NO3)3·9H2O(b) NH4HCO3 La2O3 Thermal decomposition Time: 4 h Not specified [28] Temperature: 1073 K Starting material: La(OH)3 La2O3 Thermal decomposition Time: 2 h P 3 ‾ m 1 $P\overline{3}m1$ a = 3.973 Å b = 3.9373 Å c = 6.129 Å This work Temperature: 873 K XRD: Size: 43.26 nm Starting material: La2(CO3)3·8H2O TEM: Size: 17–34 nm ).

Novel Nanocomposites for Luminescent Thermometry with Two Different Modalities.

In this work, we successfully integrated fluorescent nanodiamonds (FNDs) and lanthanide ion-doped upconversion nanoparticles (UCNPs) in a nanocomposite structure for simultaneous optical temperature sensing. The effective integration of FND and UCNP shells was confirmed by employing high-resolution TEM imaging, X-ray diffraction, and dual-excitation optical spectroscopy. Furthermore, the synthesized ND@UCNP nanocomposites were tested by making simultaneous optical temperature measurements, and the detected temperatures showed excellent agreement within their sensitivity limit. The simultaneous measurement of temperature using two different modalities having different sensing physics but with the same composite nanoparticles inside is expected to greatly improve the confidence of nanoscale temperature measurements. This should resolve some of the controversy surrounding nanoscale temperature measurements in biological applications.

Photocatalytic degradation of textile dye with titanium (IV) doped tungsten oxide nanoparticles

Water pollution from textile industries is a major concern with respect to the availability of clean drinking water. The removal of textile (organic) dyes through photocatalytic degradation with pure WO3 and titanium (IV) doped tungsten oxide [Ti (IV)-WO3] nanospheres were studied under visible light. The WO3 and Ti (IV)-WO3 nanospheres were synthesized via microwave-assisted method at microwave power of 160 W for the duration of 20 mins. The as synthesised WO3 and Ti (IV)-WO3 nanospheres were characterized for their structural, microstructural, and spectroscopic properties by using powder X-ray diffraction (XRD), UV–Visible (UV-Vis) spectroscopy, Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and High-resolution transmission electron microscopy (HR-TEM). The X-ray diffractograms confirmed the formation of highly pure WO3 and Ti (IV)-WO3 nanospheres. The average crystallite size of WO3 and Ti (IV)-WO3 nanospheres were calculated as 53.37 nm and 35.24 nm respectively using Debye Scherrer equation. The bandgap of Ti (IV)-WO3 was found to be decreased to 2.5 eV from 3.2 eV (WO3) respectively. It can be deduced that Ti (IV)-WO3 can be utilized as efficient visible light (λ>420 nm) driven photocatalyst as the bandgap was < 3 eV. The agglomerated spherical nanoparticles were seen for WO3 and Ti (IV)-WO3 in the HR-TEM images. The photocatalytic activity of textile dye was analyzed by UV-Vis spectrophotometer under visible light. The photocatalytic organic dye degradation was investigated. The enhanced photocatalytic activity of titanium (IV) doped tungsten oxide (10 wt%) was observed to be ~100% in 100 mins. This makes titanium (IV) doped tungsten oxide nanospheres, a potential nanomaterial for water purification.

Growth optimization, optical, and dielectric properties of heteroepitaxially grown ultrawide-bandgap ZnGa2O4 (111) thin film

Ultrawide bandgap ZnGa2O4 (ZGO) thin films were grown on sapphire (0001) substrates at various growth temperatures with a perspective to investigate the electrical and optical characteristics required for high-power electronic applications. Due to the variation in the vapor pressure of Zn and Ga, severe loss of Zn was observed during pulsed laser deposition, which was solved by using a zinc-rich Zn0.98Ga0.02O target. A pure phase single-crystalline ZGO thin film was obtained at a deposition temperature of 750 °C and an oxygen pressure of 1 × 10−2 Torr. The out-of-plane epitaxial relationship between the sapphire and ZGO thin film was obtained from φ-scan. The x-ray rocking curve of the ZGO thin film grown at 750 °C exhibits a full width at half maximum of ∼0.098°, which indicates a good crystalline phase and quality of the thin film. Core-level x-ray photoelectron spectroscopy of ZGO grown at 750 °C indicated that Zn and Ga were in the 2+ and 3+ oxidation states, respectively, and the atomic ratio of Zn/Ga was estimated to be ∼0.48 from the fitted values of Zn-2p3/2 and Ga-2p3/2. The high-resolution transmission electron microscopy images revealed a sharp interface with the thickness of the ZGO film of ∼265 nm, and the signature of minor secondary phases was observed. The bandgap of the ZGO film at different growth temperatures was calculated from the ultraviolet-diffuse reflectance spectroscopy spectra, and its value was obtained to be ∼5.08 eV for the 750 °C grown sample. The refractive index (n) and the extinction coefficient (k) were determined to be ∼1.94 and 0.023 from the ellipsometric data, respectively, and the real dielectric function (ɛr) was estimated to be ∼6.8 at energy 5 eV. The ultrawide bandgap and dielectric function of ZGO recommend its possible potential applications in deep-ultraviolet optoelectronic devices and high-power electronics.

In-Situ Flame-Synthesized Carbon Nanomaterials via an Impinging Swirl Flow with an N-Butanol Pool

ABSTRACT This study aims to investigate the impact of flow rotation and oxygen concentration on the synthesis of carbon nanomaterials using n-butanol diffusion flames in a rotating stagnation flow with a liquid pool and a catalytic Ni substrate. With increasing angular velocity (ω), the diffusion flame shifts slightly toward the upper oxidizer nozzle, experiences a lower strain rate, and becomes stronger with a higher maximum flame temperature at a fixed oxygen concentration (ΩO). Meanwhile, the soot layer thickens and gradually turns yellowish. Field Emission Scanning Electron Microscopy (FESEM) analyses confirm that carbon nanotubes (CNTs) can only be fabricated at ω = 2 or 3 rps when ΩO = 21%, highlighting the critical role of flow rotation. Interestingly, the optimal positions for CNT synthesis consistently occur at the same sampling position (1.5 mm below the upper edge of the blue flame) for all values of oxygen concentration (ΩO). The corresponding temperature ranges for ΩO = 19%, 18%, and 17% are approximately 950°C, 820–920°C, and 800–850°C, respectively, which align with existing literature. High-resolution transmission electron microscopy (HRTEM) images reveal both typical straight tubular and bamboo-like CNT structures. Raman spectra indicate superior graphitization at high angular velocities (ω). Notably, at ω = 0 rps, the intensity ratio of the D- and G-bands is greater than 1 (ID/IG >1); however, as ω increases, the opposite holds (ID/IG <1), with its value gradually decreasing. This suggests that the swirl effect enhances graphite layer crystallization. Importantly, the strain rate controlled by flow rotation significantly influences CNT fabrication, considering both residence time and carbon source. The key finding of this study is that swirl flow enhances both the quality and quantity of CNTs synthesized via n-butanol diffusion flames.

Characterization of nanostructure of naturally occurring disordered sp2 carbon by impedance spectroscopy

We analyzed main structural models of sp2 carbon with a structure similar to glassy carbon from the point of view of impedance spectroscopy in the range from hertz frequencies to 15 MHz. We used samples of natural carbon (shungites, anthraxolites) with a structure and properties close to synthetic glassy carbon. The impedance spectroscopy results were compared to high-resolution transmission electron microscopy (HRTEM) images, which revealed a complex nanoscale structure including stacks of misoriented graphene layers, multilayer ribbons, and closed fullerene-like structures. The high locality of the HRTEM method often does not allow identifying the predominant nano-sized structure if two or more types of structural elements are observed in one sample. Using impedance spectroscopy, we found samples with an inductive type of resistance indicating predominant extended and tortuous elements (ribbons, fibrils), as well as samples with a capacitive type of resistance with a significant predominance of nano-sized stacks of graphene layers with impurities/dielectric gaps and micropores.

A facile, environmentally-benign, green and a novel synthesis of tert-butyl-quinolines by using Fe3O4-MWCNT@CeO2 as recyclable catalyst

The aim of the present work is to examine the catalytic activity of ceria (CeO2) supported on a nano-composite of iron oxide and multi-walled carbon nanotubes (Fe3O4-MWCNT). A simple impregnation protocol was used to synthesize Fe3O4-MWCNT@CeO2 nano-composite, and a diversity of analytical techniques (including XRD, BET, TGA, SEM, TEM, and EDS) were used to thoroughly describe the catalyst material. The CeO2 supported on Fe3O4-MWCNT were found to be uniformly distributed throughout the nano-composite, irregular spherical in shape, and ranged in size from 5 to 15 nm, according to high-resolution TEM image. Afterwards, the synthesis of novel tert-butyl-quinoline analogues via a multi-component condensation comprising substituted aldehydes, dimedone, 3°-butylacetoacetate, and NH4OAc was used to evaluate the catalytic performance of the Fe3O4-MWCNT@CeO2 nano-composite. Their large specific surface area, porosity, unique exposed surfaces, and stability all contribute to their effectiveness. The catalyst's extremely active surfaces are highlighted by the notably high turn-over frequency. Thus, using ethanol as the green solvent, we suggest an effective and reusable catalytic approach that works at mild reaction condition with excellent product yields (90–97 %). This makes that nano-composite inexpensive, safe for the environment, and very atom-efficient. When compared to existing commercial approaches, our protocol is found to be more sustainable and efficient.

Orientation-dependent oxidation behavior of Cu under In-situ E-Beam irradiation

Herein, we present an atomic in-situ investigation of Cu oxidation along different orientations stimulated by high-energy electron beams (E-Beam) in transmission electron microscopy (TEM). By following the microstructural evolution of the Cu substrate in real time, high-resolution TEM (HRTEM) images reveal an orientation-dependent oxidation mechanism, whereby Cu along [110] zone axis migrates onto the surface and be oxidized while Cu along [100] zone axis is oxidized completely both in bulk and at the surface. The different oxidation mechanisms can be attributed to the differing diffusion rates of oxygen in Cu structures along directions. Moreover, the growth of Cu oxides is found to follow a layer-by-layer mechanism, where Cu mostly migrates onto nanocrystal {110} planes. This behavior would lead to the oxides wider in geometric shape and therefore promote the aggregation of adjacent oxides. These findings have important implications for the practical use of copper-based materials in oxidizing environments.

Preparation of hollow carbon nanospheres from oxidation of spent tyre oil‐derived carbon black in air

AbstractHollow carbon nanospheres (HCNS) were prepared from carbon black (CB) derived from spent tyre pyrolysis oil. The pristine CB produced by partial oxidation of the pyrolysis oil in a drop tube furnace was subsequently oxidised in air in a fixed bed reactor to yield HCNS. The effect of oxidation temperature (300 to 700°C) and time (1 to 8 h) on the burn‐off (Bt) of the sample over the duration (t) of oxidation and average reaction rate (Rt) was assessed. The BET surface area and pore volume and the nanostructure of the HCNS samples obtained were characterised using N2 adsorption–desorption and high‐resolution transmission electron microscope (HRTEM) techniques, respectively. Higher temperature and longer oxidation time led to higher Bt. As Bt increased, the BET surface area and pore volume initially increased linearly due to the removal of the amorphous core and then decreased because of the collapse of the shell of the carbon nanostructure. At Bt of ~56%, the maximum BET surface area and pore volume of the HCNS were 383.2 m2 g−1 and 0.39 cm3 g−1, respectively, compared to ~19.5 m2 g−1 and 0.033 cm3 g−1 of the pristine CB. The HRTEM images indicate that the change in BET surface area corresponds to the formation of the HCNS, as the core of the CB particle was preferentially consumed to create a hollow structure. The formation of HCNS follows an internal oxidation model, which is characterised by rapid core consumption and relatively slow shell consumption.

Enhanced photocatalytic, photoluminescence and fingerprint properties of Dy3+ ions doped BaZrO3 nanopowders for multifunctional applications

In the present investigation photoluminescent, photocatalytic and advanced forensic applications of hydrothermally prepared BaZrO3:Dy3+ (1–9 mol%) nanopowders were studied in detail. Fresh green Aloe Vera (AV) gel was used as capping agent for the preparation of NPs. The pure cubic phase was observed by powder X-ray diffraction (PXRD) profiles. Fourier transform infrared (FTIR) was utilized to investigate the functional groups present in the prepared NPs. The modification in surface morphology was investigated by using Field emission scanning electron microscope (FESEM) images. The grain size was evaluated by utilizing transmission electron microscope (TEM) images and found to be around 48 nm. Further, with the help of high-resolution TEM (HR-TEM) images the interplanar distance was calculated and found to be 0.32 nm. Photoluminescence (PL) studies were carried out in detail using excitation and emission spectra. The maximum intensity was detected for peak 388 nm ascribed to 6H15/2 → 4I13/2 + 4F7/2 of Dy3+ transition under 574 nm emanation wavelength. The obtained emanation spectra consist of 3 characteristics peaks of Dy3+ ions at 480, 574 and 666 nm attributed to 4F9/2→ 6H15/2, 4F9/2→ 6H13/2 and 4F9/2→ 6H11/2 respectively. The PL intensity increases up to 7 mol% dopant ion weight and afterwards it decreases due to concentration quenching phenomena. The dipole–dipole interaction was responsible for this quenching. The color coordinates results in white emission witnessed from the Commission International de I'Eclairage (CIE) and correlated color temperature (CCT) diagrams. The average CCT value was observed around 4836 K. Further, the color purity (CP) and external quantum efficiency (QE) was estimated and found to be 86 % and 64 % respectively. The photocatalytic degradation activity was also studied for the prepared powders and found that, the optimum degradation was observed till 180 min. The kinetics studies revealed that, the present powders were in agreement with the 0th order with estimated ko = 0.015 with R2 value of 0.98 respectively. The powders were also explored for their latent fingerprint (LFP) visualization on various porous and non-porous surfaces and found that, the powders exhibited all types of fingerprint ridge details including the 3rd type such as sweat pores and scar. The observed all outcomes specify that, the prepared powders can be used as a potential candidate for the fabrication of white LEDs (wLEDs), excellent photocatalyst and fingerprint visualization.

Understanding the Electron Beam Resilience of Two-Dimensional Conjugated Metal-Organic Frameworks.

Knowledge of the atomic structure of layer-stacked two-dimensional conjugated metal-organic frameworks (2D c-MOFs) is an essential prerequisite for establishing their structure-property correlation. For this, atomic resolution imaging is often the method of choice. In this paper, we gain a better understanding of the main properties contributing to the electron beam resilience and the achievable resolution in the high-resolution TEM images of 2D c-MOFs, which include chemical composition, density, and conductivity of the c-MOF structures. As a result, sub-angstrom resolution of 0.95 Å has been achieved for the most stable 2D c-MOF of the considered structures, Cu3(BHT) (BHT = benzenehexathiol), at an accelerating voltage of 80 kV in a spherical and chromatic aberration-corrected TEM. Complex damage mechanisms induced in Cu3(BHT) by the elastic interactions with the e-beam have been explained using detailed ab initio molecular dynamics calculations. Experimental and calculated knock-on damage thresholds are in good agreement.

Electrospun Cu-Co ferrite nanofibers: synthesis, structure, optical and magnetic properties, and anti-cancer activity.

In this study, we investigated Cu-Co ferrite nanofibers (NFs) that were synthesized for the first time employing the electrospinning technique. The structure, phase purity and crystallite size of all the prepared NFs were revealed by powder X-ray diffraction (PXRD) analysis. The NFs crystallized in the Fd3̄m (no. 227) space group and the cation distribution arrangement over distinct sites in their structure was analyzed. Scanning electron microscopy (SEM) together with energy-dispersive X-ray (EDX) spectroscopy analysis showed the microstructure of the NFs and verified their expected chemical compositions. High-resolution transmission electron microscopy (TEM) images confirmed the fibrous nature and the construction of the NFs. The band gap energies derived from the UV-vis reflectance spectra showed a blue shift with an increase in the amount of Cu in the sample from 1.42 eV to 1.86 eV. Magnetization (M) as a function of magnetic field (H) measurements performed at ambient and low temperatures showed the ferrimagnetic behavior of all the NFs. The magnetic parameters including coercivity (Hc), saturation magnetization (Ms), remanent magnetization (Mr), and squareness ratio were determined from the recorded magnetization curves. At 300 K, Ms was reduced from 78.8 to 42.4 emu g-1, Mr reduced from 22.8 to 7.6 emu g-1 and the Bohr magneton reduced from 3.3 to 1.8μB with an increase in the content of Cu in the samples. The same trend was observed at 10 K, where Ms was reduced from 93.7 to 50.9 emu g-1, Mr reduced from 60.9 to 35.9 emu g-1 and the Bohr magneton reduced from 3.94 to 2.16μB. Alternatively, Hc has the highest values for x = 0 (850 Oe at 300 K and 5220 Oe at 10 K) and x = 0.6 (800 Oe at 300 K and 5400 Oe at 10 K). The anti-cancer activity of the NFs was evaluated using the MTT cell viability assay, showing a reduction in the viability of both HCT-116 and HeLa cancer cells compared to non-cancerous HEK-293 cells after treatment with the NFs. Apoptotic activity was examined by DAPI staining, where treatment with the NFs induced chromatin condensation and nuclear disintegration in HCT-116 cells.

The synthesis of CoAl0.3Fe1.7O4/SmFeO3 nanocomposites with enhanced properties for technological applications

The main challenge of the current study is to produce nanocomposites (NCs) of (1-x) CoAl0.3Fe1.7O4 /(x)SmFeO3 with improved structural and magnetic properties using the citrate auto-combustion technique. High-resolution transmission electron microscopy images showed nanostructures with average particle sizes of 32.5 and 52.5 nm for SmFO3 and CoAl0.3Fe1.7O4, respectively. The anisotropy constant values for x = 0.3 are nearly 11 times greater than SmFeO3. The ratio of SmFeO3 incorporated into NCs adjusts their switching field distribution (SFD), making NCs with a low SFD recommended for recording applications. NCs offer the combined advantages of the two constituent phases and can be used to create new and more advanced applications. Based on the estimated data, the prepared NCs can operate at a frequency between 0.1 and 11.9 GHz, making them suitable for developing nanotechnology devices from radio waves traveling through the S-band to the Ku band.Graphical abstract

The characterisation of dental enamel using transmission Kikuchi diffraction in the scanning electron microscope combined with dynamic template matching

The remarkable physical properties of dental enamel can be largely attributed to the structure of the hydroxyapatite (HAp) crystallites on the sub-micrometre scale. Characterising the HAp microstructure is challenging, due to the nanoscale of individual crystallites and practical challenges associated with HAp examination using electron microscopy techniques. Conventional methods for enamel characterisation include imaging using transmission electron microscopy (TEM) or specialised beamline techniques, such as polarisation-dependent imaging contrast (PIC). These provide useful information at the necessary spatial resolution but are not able to measure the full crystallographic orientation of the HAp crystallites. Here we demonstrate the effectiveness of enamel analyses using transmission Kikuchi diffraction (TKD) in the scanning electron microscope, coupled with newly-developed pattern matching methods. The pattern matching approach, using dynamic template matching coupled with subsequent orientation refinement, enables robust indexing of even poor-quality TKD patterns, resulting in significantly improved data quality compared to conventional diffraction pattern indexing methods. The potential of this method for the analysis of nanocrystalline enamel structures is demonstrated by the characterisation of a human enamel TEM sample and the subsequent comparison of the results to high resolution TEM imaging. The TKD – pattern matching approach measures the full HAp crystallographic orientation enabling a quantitative measurement of not just the c-axis orientations, but also the extent of any rotation of the crystal lattice about the c-axis, between and within grains. Results presented here show how this additional information highlights potentially significant aspects of the HAp crystallite structure, including intra-crystallite distortion and the presence of multiple high angle boundaries between adjacent crystallites with rotations about the c-axis. These and other observations enable a more rigorous understanding of the relationship between HAp structures and the physical properties of dental enamel.

Ellipsoidal shaped Co3O4 quantum dots synthesis by atmospheric microplasma discharge: An electrochemical study

Spinel Co3O4 quantum dots (QDs) were synthesized for supercapacitor application using a customized plasma discharge reactor that generates stable non-equilibrium, high-density microplasma at ambient conditions. Microplasma, generated above the cobalt nitrate hexahydrate [Co(NO3)2·6H2O] solution using argon gas at 35 W discharge power, induced particle nucleation via high-energy electron collisions. High-resolution transmission electron microscopy (HR-TEM) images demonstrated that Co3O4 particles had an ellipsoidal morphology with an average size of 4 nm. Electrochemical investigation exhibited pseudocapacitive behavior, yielding a significant specific capacitance of 348.5 Fg−1 at 1 Ag−1 current density with a notable retention capacity in 1 M KOH electrolyte. These findings confirm Co3O4 QDs suitability as electrode material for supercapacitor applications.

Preparation of poly(methyl methacrylate)-zinc oxide hybrid nanoparticles via miniemulsion polymerization

The encapsulation of zinc oxide (ZnO) nanoparticles with poly(methyl methacrylate) in the presence of triethylene glycol dimethacrylate (TEGDMA) as a crosslinking agent was synthesized by the miniemulsion polymerization technique. The ZnO as a catalyze was varied from 1 wt% - 7 wt%. Several techniques were used to analyze the PMMA/TEGDMA/ZnO hybrid. The morphology and particle size distribution of the PMMA hybrid was observed using a field emission scanning electron microscope (FE-SEM). The diameter of the PMMA/TEGDMA/ZnO hybrid was in the range of 57 nm to 115 nm. The morphology of the PMMA/ZnO hybrids was sphere-shaped with a narrow particle size distribution and no agglomeration of the hybrids occurred. The encapsulation and crystalline structure of the PMMA ZnO hybrid were determined using a high-resolution transmission electron microscope (HR-TEM). The HR-TEM image demonstrated that the ZnO was encapsulated in the PMMA hybrid. In addition, the high magnification of the TEM image demonstrated the lattice spacing of ZnO and the diffraction mode image presented the crystalline structure of ZnO. Therefore, the photocatalytic properties of the PMMA/ZnO hybrid were examined via the degradation of methylene blue (MB) solution under dark and UV-A irradiation. It was found that the photocatalytic activities of the PMMA/ZnO hybrid increased when the ZnO content increased up to 7 wt%. The maximum MB degradation for PMMA/TEGDMA/ZnO 7 wt% and PMMA/ZnO 7 wt% were 80.1 % and 77.6 %, respectively. Thus, the photocatalytic efficiency of the PMMA/ZnO increased in the presence of TEGDMA as a crosslinking agent.

Designable Synthesis of Layered Silicates and Tunable Interlayer Expanded to Zeolites.

Layered zeolitic silicates and corresponding interlayer-expanded porous materials exhibit attractive application potential in wide fields. Nonetheless, designable synthesis and structure analysis of layered silicates remain challenging. Herein, two kinds of layered silicates are synthesized using different di-quaternary ammonium-type organic structure-directing agents (OSDAs). Their crystal structures are analyzed and verified by 3D electron diffraction (3D ED) and high-resolution TEM imaging. The suitable configurations of OSDA can lead to desirable interlayer states. Additionally, two new zeolite structures both with 12-membered ring (MR) channels intersected by 8 MR channels and larger interlayer spaces are constructed from layered silicate precursors by interlayer silylation. The new zeolitic material exhibits potential application in adsorption of organic pollution and catalytic reaction. This study is expected to develop versatile ways for the design and synthesis of layered silicates even zeolites and provide references in characterizing layered materials and zeolites as well.

In Situ Modulation of Oxygen Vacancies on 2D Metal Hydroxide Organic Frameworks for High-Efficiency Oxygen Evolution Reaction.

The discovery of non-precious catalysts for replacing the precious metal of ruthenium in the oxygen evolution reaction (OER) represents a key step in reducing the cost of green hydrogen production. The 2D d-MHOFs, a new 2D materials with controllable oxygen vacancies formed by controlling the degree of coordination bridging between metal hydroxyl oxide and BDC ligands are synthesized at room temperature, exhibit excellent OER properties with low overpotentials of 207 mV at 10mA cm-2. High-resolution transmission electron microscopy images and density functional theory calculations demonstrate that the introduction of oxygen vacancy sites leads to a lattice distortion and charge redistribution in the catalysts, enhancing the OER activity of 2D d-MHOFs comprehensively. Synchrotron radiation and in situ Raman/Fourier transform infrared spectroscopy indicate that part of oxygen defect sites on the surface of 2D d-MHOFs are prone to transition to highly active metal hydroxyl oxides during the OER process. This work provides a mild strategy for scalable preparation of 2D d-MHOFs nanosheets with controllable oxygen defects, reveals the relationship between oxygen vacancies and OER performance, and offers a profound insight into the basic process of structural transformation in the OER process.

Gold Nanoparticles Bioproduced in Cyanobacteria in the Initial Phase Opened an Avenue for the Discovery of Corresponding Cerium Nanoparticles.

The production of isolated metallic nanoparticles with multifunctionalized properties, such as size and shape, is crucial for biomedical, photocatalytic, and energy storage or remediation applications. This study investigates the initial particle formations of gold nanoparticles (AuNPs) bioproduced in the cyanobacteria Anabaena sp. using high-resolution transmission electron microscopy images for digital image analysis. The developed method enabled the discovery of cerium nanoparticles (CeNPs), which were biosynthesized in the cyanobacteria Calothrix desertica. The particle size distributions for AuNPs and CeNPs were analyzed. After 10 h, the average equivalent circular diameter for AuNPs was 4.8 nm, while for CeNPs, it was approximately 5.2 nm after 25 h. The initial shape of AuNPs was sub-round to round, while the shape of CeNPs was more roundish due to their amorphous structure and formation restricted to heterocysts. The local PSDs indicate that the maturation of AuNPs begins in the middle of vegetative cells and near the cell membrane, compared to the other regions of the cell.