High-resolution Transmission Electron Microscopy Techniques Research Articles

Field-induced magnetorheological study towards the active magneto-viscoelastic behavior of stable MnFe2O4 magnetic nanofluid

This work presents the fine-tuned synthesis of MnFe2O4 oleic acid-coated magnetic nanoparticles (MNPs) by the chemical co-precipitation method. The X-ray photoelectron spectroscopy (XPS) was utilized to investigate the elemental composition and oxidation state of oleic acid-coated MnFe2O4 MNPs. The Fourier transform infrared spectroscopy (FTIR) spectra were used to confirm the functional groups in the oleic acid-coated MnFe2O4 magnetic nanoparticles. The spherical shape of MnFe2O4 MNPs is confirmed by Field emission scanning electron microscopy (FESEM) and High-resolution transmission electron microscopy (HRTEM) techniques. Zeta potential (ζ) measurements were performed to confirm the stability of MnFe2O4 magnetic nanofluid (MNF). Magnetic measurements (M−vs−H) reveal the saturation magnetization, Ms = 20.3 emu/g and coercivity, HC = 30 Oe, confirming the single domain superparamagnetic nature at 300 K. Field-induced shear thinning behavior of the MnFe2O4 magnetic fluid is confirmed by a power law, η = c γn + n∞ and steady-state behavior measurements. Magneto viscous effect initially increased at a low shear rate of 20 s−1 and then decreased at a higher shear rate of 100 s−1, which confirms the stability of the MnFe2O4 magnetic fluid. Also, the highest deflection angle, θ = 243 m.rad of MnFe2O4 magnetic fluid was observed at a moderate shear rate 100 s−1 and a high magnetic field of 1.2 T, while the lowest value of deflection angle, θ = 65 m.rad was observed in the absence of magnetic field. In contrast, the storage modulus (G') is greater than the loss modulus (G''), in corroboration with the viscoelastic-to-viscous behavior of MnFe2O4 magnetic fluid.

Photocatalytic H2 generation and CO2 reduction by WB5-x cocatalyst of TiO2 catalyst

Catalytic reactions play an important role in modern industry as almost 90 % of the chemical industry is based on catalytic reactions. The development of new, more efficient catalysts will allow significant advances in chemical production, but still remains a rather challenging problem for materials scientists. Here, we have proposed and investigated a new composite photocatalyst based on WB5-x-WB2 and TiO2 for H2 evolution from aqueous ethanol solution and CO2 reduction under visible light irradiation (410 nm). New composite photocatalysts WB5-x-WB2/TiO2 were synthesized and characterized by X-ray diffraction, UV–vis spectroscopy, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. Photocatalytic measurements show that the maximum activity of the composite photocatalyst 4 and 23 times higher than the activity of unmodified TiO2 in CO2 reduction and H2 evolution, respectively. Density functional calculations of the proposed reaction are in agreement with the provided experiments confirming the higher efficiency of the modified catalyst compared to TiO2.

Unveiling the Potential of Pt Nanoparticle-Decorated PEDOT:PSS Membranes for Efficient Gas Separation.

In the dynamic landscape of industrial processes, membrane technology offers a paradigm shift beyond energy-intensive separation techniques, exemplifying a progressive leap toward sustainability. In this regard, highly flexible and uniform poly(3,4-ethylenedioxythiophene)polystyrenesulfonate (PEDOT:PSS)-engineered membranes at a reduced thickness have been fabricated on track-etched poly(ethylene terephthalate) (PET) substrates. The membranes were functionalized and embedded with platinum nanoparticles (Pt NPs) having a higher affinity toward H2 gas. The materials and fabricated membranes were characterized by using high-resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM) techniques for morphological and structural analysis. FTIR and Raman characterizations were performed to study the characteristic bonds. The uniformity and quantification of Pt nanoparticle binding were tested through inductively coupled plasma mass spectrometry (ICP-MS) studies and FESEM with EDS mapping. The gas separation performance was studied using H2, N2, and CO2 gases in pure and mixed (H2/CO2 in 50:50) states. It was observed that the modified membrane showed a 116% increment in H2 permeability and 82 and 107% increment in H2/CO2 and H2/N2 selectivity values with pure gas, while a 121% increment in H2 permeability and 156% increment in H2/CO2 selectivity using mixed gas. The separation performance in pure and mixed gas states with repeated experiments conspicuously highlighted their prospective viability as prime contenders for gas separation applications.

Structural, Electrical and Optical Properties of Zn-Doped SrVO3 Thin Films Grown By Co-Sputtering

Due to its optical and electrical characteristics, SrVO3 is a strongly correlated metal that has received extensive research in recent years. This makes it a promising transparent conducting oxide (TCO) for a variety of optoelectronic applications. The most widely used TCO at the moment, indium tin oxide, suffers from resource depletion. By analyzing and improving these interesting properties, SrVO3 might be able to take its place [1]. Unfortunately, in order to obtain SrVO3 as a crystallized phase, non-compatible with microelectronic industry thin film growth techniques must be used. Moreover, they require specific substrates for achieving the crystalline state, such as SrTiO3, LaAlO3, and (LaAlO3)0,3(Sr2TaAlO6)0,7 (LSAT) [2]. Nevertheless, recent studies made by our groups have demonstrated that crystalline SrVO3 layers may be produced on less expensive substrates such as glass or silicon substrates, with the simple use of a TiO2 buffer layer. This recent finding is covered by a global patent [3].In the present work, we report experimental investigations on the reactively co-sputtering of SrVO3 and ZnO targets in a H-rich plasma, on Si substrates, with and without a TiO2 buffer layer, to grow transparent and conductive films. TiO2 buffer layer has been deposited on Si Substrate by Atomic Layer Deposition as reported elsewhere [4]. We looked at the effects of growth temperatures (TG) and the hydrogen rate rH (the ratio of H2 to Ar) on the thin films’ structural, electrical, and optical characteristics. XRD, high-resolution TEM, and AFM techniques were used to examine the films’ structural characteristics. The 4 probes approach, Van der Pauw measurements using a PPMS, and Hall effect measurements were used to examine the electrical properties. Finally, spectroscopic ellipsometry was used to conduct optical characterizations.The structural analysis showed that it is possible to favor the growth of crystalline SrVO3 layers on top of the TiO2 buffer layer by optimizing TG and rH (Figure 1a). In some specific conditions, a partially crystallized layer of SrVO3 was also directly deposited on a Si substrate without the use of such a buffer layer, which has never been reported in the literature and thus is encouraging for the future growth of such material on-low-cost substrate (Figure 1b). The Zn concentration in the film is only 0.15 at% because the radio-frequency (RF) power density applied to the ZnO target is much lower than the one applied to the SrVO3 target. The presence of dopants during the development process may favor the crystallization of SrVO3, which may help to explain this partial crystallization. This finding might pave the way for buffer-free complete crystallization of SrVO3 on Si substrates.When the films are grown on a TiO2 buffer layer, measurements of the physical properties have evidenced that it is possible to form thin films with optical transparency ranging from 70 to 75%, between 475 and 800 nm (Figure 1c). The thin films’ electrical resistivities at ambient temperature reach values of 1.2 × 10−3 Ohm.cm, according to electrical characterizations performed on them using the 4 probes method. Moreover, the PPMS data reveal a decrease in resistivity as a function of temperature (Figure 1d) which is the signature of semiconductor behavior. Such a feature has never been reported elsewhere and is probably due to an excess of oxygen in the layer induced 2 by the reactive growth approach. The vanadate films detailed in this paper present a sufficiently low resistivity to be used for microelectronics applications since the films produced with optimal values of rH and TG are more conductive than the undoped semiconductor films typically used as TCOs, such as ZnO and SnO2. In addition, these films feature an optical band gap, and therefore offer the opportunity to create materials with photoluminescence properties by doping them with rare earth ions for example. This is extremely promising for the design of light-emitting diodes or sensors.[1] L. Zhang et al, “Correlated metals as transparent conductors,” Nature materials, vol. 15,12 2015.[2] A. Boileau et al, “Tuning of the optical properties of the transparent conducting oxide SrVO3 by electronic correlations,” Advanced Optical Materials, vol. 7, p. 1801516, 01 2019.[3] Patent FR3113185[4] A. Jolivet et al, “Structural, optical, and electrical properties of TiO2 thin films deposited by ALD: Impact of the substrate, the deposited thickness and the deposition temperature,” Applied Surface Science, vol. 608, p. 155214, 2023. Figure 1

Identification and control of crystalline nuclei facets imparting to the breaking of symmetry selection rules of optical phonon modes in GaP/Si (001)

The complex interfacial structural issues associated with hetero-polar epitaxial integration of GaP on Si(001) are resolved by improving the kinetics of gallium and phosphorous adatoms during the initial nucleation process. This is achieved through the use of Raman spectroscopy as a feedback mechanism. The peak intensity ratio of forbidden (transverse optical)-to-allowed (longitudinal optical) phonons of GaP under unpolarized Raman scattering is contemplated as an initial guide to ascertain the relative density of defect-mediated non-(001) GaP facets. The azimuthal-angle dependent polarized Raman spectroscopy is then applied to identify and quantify the nucleation of higher-index non-(001) ({111} and {112}) faceted islands in the nucleation layer and their propagation in the overgrown structures. The nucleation of GaP adatoms on the Silicon surface at ∼525 °C leads to a smooth surface and substantially suppresses the defect-mediated facets. The optimal mobility and controlled adsorption of adatoms of Ga and P on the substrate surface under intermediate nucleation kinetics foster the charge-neutral interface, and hence the defect-suppressed two-dimensional layer growth of GaP. The proposed Raman spectroscopy methodology emerges as a rapid and economical alternative to existing in situ reflection anisotropy spectroscopy and high-resolution transmission electron microscopy techniques for structural identification. This method of growth optimization can also be applied to other III-V polar semiconductors to achieve high-quality and efficient monolithic integration of devices on existing Si technology.

Facile synthesis and photophysical properties of combustion derived Dy3+doped Ca9La(PO4)7 nanophosphors for advanced solid-state lighting applications

Globally, the energy consumption has accelerated, which has driven the research to increase sustainable energy sources. In this context, this is the first report on the exploration of the structural and photometric aspects of Dy3+ doped Ca9La(PO4)7 i.e., CLP: Dy3+ nanophosphors for designing WLEDs economically. Herein, the solution combustion method was utilized for fabricating the desired nanophosphor, thereafter their morphological behavior, and crystallite size were studied in detail via X-ray diffraction, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) techniques which confirmed the rhombohedral crystal architecture with R3c space group affirming the potential of the fabricated nanomaterials in optoelectronics. CLP: Dy3+nanophosphors depicted reproducible emission spectra with peaks at 4F9/2 → 6H13/2, 15/2 attributed to intra-configurational transitions of Dy3+ ions. The increasing dopant concentration beyond 20 mol % reduced the intensity of emission peaks which could be ascribed to the dipole–dipole interactions of the neighboring ions. The optical band gap of 5.38 eV derived via Kubelka-Munk relations established their role in semiconductors. Moreover, their Commission international de I’eclairge (CIE) chromaticity coordinates were studied in detail to reveal the emission color with color purity and Correlated Color Temperature (CCT) values. All the results favored and exemplified the incredible role of CLP: Dy3+ nanophosphors for emerging future prospects in advanced optoelectronic technology.

Bamboo stem biomass waste-derived excitation-dependent carbon dots for nanomolar detection of fungicide dodine in real samples and their pH-sensitive bacterial interaction studies

The present work investigates the mitigation of dodine (DD) fungicide residue, which is recognized for its adverse environmental consequences, by the use of carbon dots (CDs) prepared from bamboo stem biomass (BS-CDs). This work focuses on the synthesis of BS-CDs using the one-step hydrothermal method, which has been shown the remarkable sensing efficiency even at low concentrations. The synthesized BS-CDs were analyzed through X-ray diffraction (XRD), X-ray photoelectron (XPS), Fourier transform infrared (FTIR), Raman spectroscopy, and high-resolution transmission electron microscopic techniques (HRTEM). The BS-CDs were spherical and mono-dispersed, with an average size of 3.71 nm. By utilizing the fluorescence quenching property of BS-CDs, a detection limit of 4.3 nM for DD was successfully achieved. The non-toxic profile of BS-CDs has been confirmed by cytotoxicity studies using MTT assay. Application research mostly focuses on exploring the interaction between CDs and bacteria, hence elucidating their pH-sensitive characteristics. Real sample (fruits and vegetables) analysis was carried out to assess the viability of the detection approach, and the results showed respectable recovery rates (105 to 115 %) with a relative standard deviation (∼2 %). The findings provide a positive outlook for addressing the presence of DD residue in ecologically vulnerable regions, emphasizing the viability of using BS-CDs as an environmentally friendly remedy.

Photo-induced synthesis of star poly(DL-Lactide)-templated Au and Ag nanoparticles and evaluation of their catalytic performance

In this report, photochemical synthesis of monodispersed gold (Au) and silver (Ag) nanoparticles (NPs) was reported using cholic acid functionalized star poly(DL-lactide) (CA-(PDLLA)) as a capping and reducing agent. CA-(PDLLA) was synthesized by ring-opening polymerization (ROP) of DL-lactide with a feed ratio of 1:120 (cholic acid: DL-lactide). The molecular weight of CA-(PDLLA) was measured by using the gel permeation chromatography (GPC) technique. The thermal properties of the polymer and its nanocomposite materials were studied by thermogravimetric analysis (TGA). The optical properties of Ag and Au NPs were studied by UV–visible absorption spectroscopy. Morphological studies and size of the polymer-nanocomposites were assessed by using field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) techniques. The percentage composition of Au and Ag present in the polymer-nanocomposites was calculated using energy-dispersive X-ray spectroscopic (EDX) analysis. Finally, the synthesized polymer-metal nanocomposites were used as heterogeneous catalysts for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) as a model reaction and the apparent rate constant (kapp) values of CA-(PDLLA)-AuNPs and CA-(PDLLA)-AgNPs were found to be 5.76 × 10−4 s−1 and 19.7 × 10−4 s−1, respectively.

Graphitic carbon nitride (g–C3N4)-based electrochemical sensors for the determination of antiviral drug acyclovir

Acyclovir (ACR) is an antiviral drug used to treat chickenpox, shingles, and herpes infections in various parts of the body, including infants. It shortens illness duration and reduces symptoms, but may cause kidney damage and allergic reactions in some individuals. It may also be beneficial for those with compromised immune systems. ACR, despite its positive attributes, can cause kidney damage and allergic reactions in some individuals, requiring careful observation and monitoring. ACR was detected electrochemically in this work using graphitic carbon nitride (g-C3N4), which was effectively synthesized. Energy dispersive X-ray (EDX), X-ray diffraction (XRD), Raman, Fourier-transform infrared (FT-IR), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HR-TEM) techniques were used to characterize the synthesized g-C3N4. To monitor ACR, g-C3N4 combined with pure carbon paste (g-C3N4/CPE) was used in voltammetric techniques. The sensor's ability to detect the ACR via g-C3N4 was investigated utilizing the amperometric i-t curve method. Electrochemical impedance spectroscopy (EIS) was used to examine the electrochemical characteristics of various electrodes. The Rct of the bare glassy carbon electrode (GCE), the bare CPE, and the g-C3N4/CPE were, respectively, 12770Ω, 3794Ω, and 3114Ω. From 10 μM to 80 μM ACR concentration, the current response rose linearly. The constructed sensor had an exceptional detection limit of 3.52 nM. By introducing 100 μM concentrations of a variety of common interferents to the ACR solution during the measurement, it was possible to evaluate the impact of several foreign interferents on the outcomes at the g-C3N4. The electrochemical behavior of ACR was investigated in respect to several electrokinetic variables. The mechanism of potential electrochemical oxidation was demonstrated. The developed g-C3N4/CPE effectively identified ACR quantitatively in samples of human blood serum and urine.

Plasmon-Enhanced Perovskite Solar Cells Based on Inkjet-Printed Au Nanoparticles Embedded into TiO2 Microdot Arrays.

The exceptional property of plasmonic materials to localize light into sub-wavelength regimes has significant importance in various applications, especially in photovoltaics. In this study, we report the localized surface plasmon-enhanced perovskite solar cell (PSC) performance of plasmonic gold nanoparticles (AuNPs) embedded into a titanium oxide (TiO2) microdot array (MDA), which was deposited using the inkjet printing technique. The X-ray (XRD) analysis of MAPI (methyl ammonium lead iodide) perovskite films deposited on glass substrates with and without MDA revealed no destructive effect of MDA on the perovskite structure. Moreover, a 12% increase in the crystallite size of perovskite with MDA was registered. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) techniques revealed the morphology of the TiO2_MDA and TiO2-AuNPs_MDA. The finite-difference time-domain (FDTD) simulation was employed to evaluate the absorption cross-sections and local field enhancement of AuNPs in the TiO2 and TiO2/MAPI surrounding media. Reflectance UV-Vis spectra of the samples comprising glass/TiO2 ETL/TiO2_MDA (ETL-an electron transport layer) with and without AuNPs in TiO2_MDA were studied, and the band gap (Eg) values of MAPI have been calculated using the Kubelka-Munk equation. The MDA introduction did not influence the band gap value, which remained at ~1.6 eV for all the samples. The photovoltaic performance of the fabricated PSC with and without MDA and the corresponding key parameters of the solar cells have also been studied and discussed in detail. The findings indicated a significant power conversion efficiency improvement of over 47% in the PSCs with the introduction of the TiO2-AuNPs_MDA on the ETL/MAPI interface compared to the reference device. Our study demonstrates the significant enhancement achieved in halide PSC by utilizing AuNPs within a TiO2_MDA. This approach holds great promise for advancing the efficiency and performance of photovoltaic devices.

Effect of Nano Quaternary Ni1-xZnxFe2-2xMn2xO4 on the Structural, Optical and Dielectric Characteristics of Poly(Methyl Methacrylate)/Polyethylene Oxide Blends

Poly(methyl methacrylate)/polyethylene oxide (PMMA/PEO)/Ni1-xZnxFe2-2xMn2xO4 blends of various composition were formed using coprecipitation and casting techniques. X-ray diffraction (XRD) analysis was performed on the blends and fillers. High-resolution transmission electron microscopy technique revealed that the fillers had a crystallite size of 15–25 nm. The impact of Ni1-xZnxFe2-2xMn2xO4 loading on the light absorbance, transmission, reflectance, refractive index and extinction coefficient and the dielectric constant, energy loss functions, and optical conductivity of PMMA/PEO blend was examined. The absorbance of the PMMA/PEO blend increased irregularly as it was loaded with the nanocomposite samples, and it peaked at x = 0.25. The transmittance reduced to a minimum value (28–58%) as the blend was doped with x=0.25. The PMMA/PEO blended polymer’s direct and indirect band gaps were 5.02 and 4.74 eV, respectively. As the blend was loaded with NiFe2O4 alone, they reached their minimum values (direct/indirect: 4.94/4.66 eV). Depending on the amounts of Zn and Mn ions in the NiFe2O4 doped PMMA/PEO blends, the various blends displayed a blue-violet color on their chromaticity diagram. The electrical dielectric constant, electric modulus, ac conductivity and energy density of the different blends depended on the amount of Zn and Mn ions added in the NiFe2O4 matrix.

The atomic structure and mechanisms of formation of some geometrically incompatible interfaces within cubic B2 austenite – monoclinic B19′ martensite shape memory alloy microstructures

Microstructures of aged nickel‑titanium‑hafnium shape memory alloys (SMAs) Ni50.3Ti41.2Hf8.5 and Ni50.3Ti43.7Hf6 (at.%) are examined using high-resolution transmission electron microscopy (HRTEM) techniques. Characterizations of the structures of austenite-martensite, martensite-martensite, and martensite-precipitate interfaces provide new insights into cubic B2 austenite–monoclinic B19′ martensite phase transformation and martensite reorientation mechanisms. Specifically, in the absence of external load, theoretically unfavorable (001) compound martensite twins nucleate at H-phase precipitate interfaces. At the interface of these twins and the austenite matrix, a zig-zag-rise structure follows an extension of superdislocation theory previously developed to explain analogous zig-zag structured interfaces in non-shape-memory martensitic alloys. Additionally, 〈011〉 type II martensite twins that are theoretically favorable to form were also observed within the austenite matrices. However, instead of forming defect-free habit planes accommodated by elastic strains as predicted by theory, misfit dislocations worked in cooperation with elastic strain fields to accommodate atomic misfits between the austenite and martensite phases, and the elastic strain fields were smaller at the interfaces. Finally, the atomic scale thermoelastic mechanism of <011> type II twins reorienting to form (001) compound twins within the martensite is proposed in a manner consistent with direct observations of such interfaces. In total, connections with previous work on other binary and ternary NiTi base alloys show that these new mechanistic understandings generalize to other B2 - B19′ SMAs that should not perform well according to the elasticity-based Phenomenological Theory of Martensite Crystallography, yet still exhibit robust cyclic thermomechanical performances due to transformation-plasticity interactions.

Structural properties, bandgap, and complex dielectric function in Bi2Te3 thermoelectric by Valence Electron Energy Loss Spectroscopy (VEELS) analysis

This article describes the results and discussion performed to analyze the bandgap, optoelectronic properties, and complex dielectric function of Bi2Te3 thermoelectric material, using Valence Electron Energy Loss Spectroscopy. A key aspect of the report presented in this article is that the properties described above have not been analyzed and reported using the Valence Electron Energy Loss Spectroscopy technique. The material’s structure was analyzed using Rietveld and High-Resolution Transmission Electron Microscopy techniques. The band gap obtained value is 0.91 eV by Valence Electron Energy Loss Spectroscopy. Whereas, values obtained by other techniques are between 0.26 and 0.92 eV for Bi2Te3. The real part (ε1) and imaginary part (ε2) of the complex dielectric function (ε * ) were measured. For ε1, the principal peak at 1.03 eV and a second peak at 1.4 eV were observed. Furthermore, the optical dielectric constant is 8.6 for (ε0 = 0 eV), which is related to electronic contributions and is given by the refractive index squared (n2).

High-temperature graphitization characteristics of vitrinite and inertinite

In order to explore the graphitization characteristic differences between vitrinite and inertinite in coal, this study conducted high-temperature thermal simulation experiments (at five temperature points: 1800°C, 2100°C, 2400°C, 2700°C, and 3000°C) using inertinite-rich and vitrinite-rich samples as graphitization precursors. The quantitative comparison for the evolution characteristics of their graphite lattice was carried out using high-resolution transmission electron microscopy (HRTEM), X-ray diffractometer (XRD), and Raman spectroscopy (Raman) techniques. HRTEM revealed that an evident increase in carbon layer numbers and degree of extension was observed with increasing treatment temperature, XRD showed the variation of lattice parameters (d002/La/Lc) with temperature, Raman data revealed the variation of lattice defects (R2/R3) with temperature. It was discussed about the differences of graphite lattice construction processes between inertinite and vitrinite, throughout the entire temperature range of the experiment, the d002 spacing of inertinite was always smaller than that of vitrinite, indicating a higher degree of graphitization. vitrinite exhibited a uniform and smooth evolution state throughout the entire heating process, while inertinite exhibited an “inert” state between 1800°C and 2100°C (d002 values stagnated near at 0.3440 nm). With increasing simulated temperature, the defect level (R2 and R3) of vitrinite rapidly decreased below that of inertinite, throughout the entire temperature range, vitrinite demonstrated superior defect healing ability in terms of both rate and capability compared to inertinite. Under high-temperature thermal simulation, the three-dimensional lattice construction and defect elimination of vitrinite exhibited synchronous evolution characteristics. On the other hand, the formation of the graphite lattice in inertinite showed an evolutionary trend of “first three-dimensional lattice construction, followed by gradual defect elimination”.

A novel approach for the biosynthesis of silver nanoparticles using the defensive gland extracts of the beetle, Luprops tristis Fabricius

Discovering novel natural resources for the biological synthesis of metal nanoparticles is one of the two key challenges facing by the field of nanoparticle synthesis. The second challenge is a lack of information on the chemical components needed for the biological synthesis and the chemical mechanism involved in the metal nanoparticles synthesis. In the current study, microwave-assisted silver nanoparticle (AgNP) synthesis employing the defensive gland extract of Mupli beetle, Luprops tristis Fabricius (Order: Coleoptera; Family: Tenebrionidae), addresses these two challenges. This study was conducted without killing the experimental insect. Earlier studies in our laboratory showed the presence of the phenolic compounds, 2,3-dimethyl-1,4-benzoquinone, 1,3-dihydroxy-2-methylbenzene, and 2,5-dimethylhydroquinone in the defensive gland extract of L. tristis. The results of the current study show that the phenolic compounds in the defensive gland extract of the beetle has the ability to reduce silver ions into AgNPs and also acts as a good capping and stabilizing agent. A possible mechanism for the reduction of silver nitrate (AgNO3) into AgNPs is suggested. The synthesized AgNPs were characterized by Ultraviolet–Visible (UV–Vis) spectroscopy, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy energy-dispersive X-ray (SEM–EDX) analysis and high-resolution transmission electron microscopic (HR-TEM) techniques. The stability of biologically synthesized nanoparticles was studied by zeta potential analysis. The TEM analysis confirmed that AgNPs are well dispersed and almost round shaped. The average size of nanoparticle ranges from 10 to 20 nm. EDX analysis showed that silver is the prominent metal present in the nanomaterial solution. The AgNPs synthesized have antibacterial property against both Staphylococcus aureus and Escherichia coli. Radical scavenging (DPPH) assay was used to determine the antioxidant activity of the AgNPs. AgNPs exhibited anticancer activity in a cytotoxicity experiment against Dalton’s lymphoma ascites (DLA) cell line.

Evaluation of synthesis time in the growth of vertical-aligned MWCNTs by spray pyrolysis

Multi-Wall Carbon Nanotubes (MWCNTs) were analyzed on crystalline silicon substrates (type P) under optimal temperature conditions, using different synthesis times (2, 3, 4, 5, 10, 20, 30, 60, 120, and 180 min) in order to examine the effect on the structural quality and length of the CNTs produced by ultrasonic spray pyrolysis, using pure toluene and ferrocene as precursor solutions under argon flow. Structural, optical, and morphological differences of the MWCNTs grown were analyzed. Raman spectroscopy evidenced the MWCNTs' high quality, noted by the ID/IG (from 0.41 to 0.68) and I2D/IG intensity ratios around 0.75. Morphological differences of the MWCNTs grow evaluated by Field Emission Scanning Electron Microscopy (FE-SEM); the micrographs examined the thickness of CNTs' layers. High-Resolution Transmission Electron Microscopy (HRTEM) technique was used to determine the diameters of CNTs, which were found from 15 to 140 nm. X-Ray Diffraction (XRD) showed two characteristic peaks around 26° and 44°, which corroborated that the MWCNTs were well-graphitized. The influence of the time in these CNTs demonstrated that the final length of these nanotubes could easily reach micrometers. The alienation was better as time increased, and the graphitization extent is good in most cases compared to other more expensive synthesis methods.

Nano-refinement of the face-centered cubic Zr(Fe,Cr)2 secondary phase particles in Zircaloy-4 alloy via localized-shearing/bending-driven fracture under high-temperature compression

Nanoparticles are extensively introduced to improve the mechanical, physical, and chemical properties of alloys. In the present study, the underlying nano-refinement mechanisms of face-centered cubic Zr(Fe, Cr)2 secondary phase particles (SPPs) that precipitated in Zircaloy-4 alloy under high-temperature compression were investigated in detail by utilizing high-resolution transmission electron microscopy (HRTEM) and conventional TEM techniques. The frequently observed Zr(Fe, Cr)2 SPPs were incoherent with the matrix and exhibited brittle fracture behaviors without measurable plasticity. HRTEM observations revealed two mechanisms underlying the nano-refinement of incoherent micro-sized SPPs via localized shear fracture on {112¯}SPP and nanoprecipitate-assisted bending fracture, respectively. The latter was, for the first time, found to occur when the movements of large SPPs were blocked by nanometer-sized SPP during alloy deformation. Accordingly, two force models were proposed to visualize their potential nano-refinement processes. The knowledge attained from this study sheds new light on the deformation behaviors of Zr(Fe, Cr)2 SPPs and their associated size refinement mechanisms under high-temperature compression, and is expected to greatly benefit the process optimization of zirconium alloys to achieve precipitate nano-refinement.

Optical Properties of Cationic Perylenediimide Nanowires in Aqueous Medium: Experimental and Computational Studies

Cationic perylenediimide derivative, namely N,N’-di(2-(trimethylammoniumiodide)ethylene) perylenediimide (TAIPDI), has been synthesized and characterized in an aqueous medium by using dynamic light scattering (DLS), X-ray diffraction (XRD), fourier-transform infrared (FTIR), scanning electron microscope (SEM), and high-resolution transmission electron microscopy (HRTEM) techniques. The optical absorption and fluorescence spectra of TAIPDI revealed the formation of aggregated TAIPDI nanowires in water, but not in organic solvents. In order to control the aggregation behavior, the optical properties of TAIPDI have been examined in different aqueous media, namely cetyltrimethylammonium bromide (CTAB), and sodium dodecyl sulfate (SDS). Furthermore, the utilization of the examined TAIPDI for constructing supramolecular donor–acceptor dyad has been achieved by combining the electron accepting TAIPDI with the electron donating 4,4’–bis (2-sulfostyryl)-biphenyl disodium salt (BSSBP). The formed supramolecular dyad TAIPDI-BSSBP through the ionic and electrostatic π-π interactions have been well examined by various spectroscopic techniques, e.g., steady-state absorption and fluorescence, cyclic voltammetry, and time-correlated single-photon counting (TCSPC), and first principle computational chemistry methods. Experimental results suggested the occurring of intra-supramolecular electron transfer from BSSBP to TAIPDI with rate constant and efficiency of 4.76 × 109 s−1 and 0.95, respectively. The ease of construction, absorption in the UV–Visible region, and fast electron transfer process render the supramolecular TAIPDI-BSSBP complex as a donor–acceptor material for optoelectronic devices.

Quenching effect in luminescent and magnetic properties of Fe3O4/α-Fe2O3/Y2O3:Eu3+ nanocomposites

In this paper, Fe3O4/α-Fe2O3/Y2O3:Eu3+ multifunctional nanocomposites were synthesized using a hydrothermal method. Fe3O4/α-Fe2O3/Y2O3:Eu3+ nanocomposites are core-shell nanostructures consisting of a superparamagnetic nanomagnetite core, which is converted to hematite during the synthesis. As a theranostic material, hematite could be used in drug-release processes, while nanomagnetite generates heat in a hyperthermia cancer treatment. An outer shell of Y2O3:Eu3+ nanophosphor is added to give nanocomposites photoluminescent properties and to render them visible in bioimaging. Structural, optical, and magnetic features of nanocompositesare studied using X-ray diffraction (XRD), fourier-transform infrared spectroscopy (FTIR), Raman, photoluminescence (PL), vibrating-sample magnetometer (VSM), and high-resolution transmission electron microscope (HRTEM) techniques. Photoluminescence properties of nanocomposites show a quenching effect related to the proportion of magnetite and Y2O3:Eu3+. A luminescence quenching mechanism is proposed based on the optical effects of a core-shell structure. Magnetic saturation grows proportionally with the amount of magnetite present, which indicates that Fe3O4 magnetic structure is not altered, even by the hematite that forms around it. The synthesized nanocomposites possess a core-shell morphology modified by the different proportions of their components. The optical, structural, and magnetic nanocomposite properties found will be of interest in theranostic materials research in the biomedical field.

Synthesis of Boron-Doped Carbon Nanomaterial

A new method for the synthesis of boron-doped carbon nanomaterial (B-carbon nanomaterial) has been developed. First, graphene was synthesized using the template method. Magnesium oxide was used as the template that was dissolved with hydrochloric acid after the graphene deposition on its surface. The specific surface area of the synthesized graphene was equal to 1300 m2/g. The suggested method includes the graphene synthesis via the template method, followed by the deposition of an additional graphene layer doped with boron in an autoclave at 650 °C, using a mixture of phenylboronic acid, acetone, and ethanol. After this carbonization procedure, the mass of the graphene sample increased by 70%. The properties of B-carbon nanomaterial were studied using X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and adsorption-desorption techniques. The deposition of an additional graphene layer doped with boron led to an increase of the graphene layer thickness from 2-4 to 3-8 monolayers, and a decrease of the specific surface area from 1300 to 800 m2/g. The boron concentration in B-carbon nanomaterial determined by different physical methods was about 4 wt.%.