High-resolution Raman Spectroscopy Research Articles

Lignin valorization: Facile synthesis, characterization and catalytic activity of multiwalled carbon nanotubes/kraft lignin/Pd nanocomposite for environmental remediation

Toxic organic pollutants in wastewaters are becoming a worldwide problem, which threatens life on earth and prevents essential elements to sustain living organisms. Nitro compounds and organic dyes are the most common contaminants, which result in disturbing problems for human health and the environment. The application of heterogeneous nanocatalysts is one of the most efficient methods to overcome this challenge. In view of this, a novel nanocatalyst containing multi-walled carbon nanotubes (MWNTs), Kraft lignin, and Pd nanoparticles (NPs) was synthesized through a straightforward procedure. The synthesis of Pd NPs was performed using laser ablation, generating fine NPs without chemical agents and impurities. The morphology and structure of the prepared nanocomposite were studied by X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron (XPS) and Raman spectroscopy. The efficiency of the as-prepared nanocatalyst in the reduction of methylene blue (MB), 4-nitrophenol (4-NP), and hexavalent chromium [Cr(VI)], was investigated in an aqueous solution using sodium borohydride (NaBH4) or formic acid (HCOOH) as the reducing agents. The progress of the reactions was monitored by UV–Vis spectroscopy. The catalyst can be easily removed from the reaction media by centrifugation and reused five times without any observable decrease in the catalytic activity. Overall, the performance of MWNT/KL reported herein alludes to the prodigious practical significance of this tunable support in real world scenarios such as nanocatalysis and wastewater remediation.

Mapping the Interfacial Electronic Structure of Strain-Engineered Epitaxial Germanium Grown on In x Al1-x As Stressors.

The indirect nature of silicon (Si) emission currently limits the monolithic integration of photonic circuitry with Si electronics. Approaches to circumvent the optical shortcomings of Si include band structure engineering via alloying (e.g., SixGe1–x–ySny) and/or strain engineering of group IV materials (e.g., Ge). Although these methods enhance emission, many are incapable of realizing practical lasing structures because of poor optical and electrical confinement. Here, we report on strong optoelectronic confinement in a highly tensile-strained (ε) Ge/In0.26Al0.74As heterostructure as determined by X-ray photoemission spectroscopy (XPS). To this end, an ultrathin (∼10 nm) ε-Ge epilayer was directly integrated onto the In0.26Al0.74As stressor using an in situ, dual-chamber molecular beam epitaxy approach. Combining high-resolution X-ray diffraction and Raman spectroscopy, a strain state as high as ε ∼ 1.75% was demonstrated. Moreover, high-resolution transmission electron microscopy confirmed the highly ordered, pseudomorphic nature of the as-grown ε-Ge/In0.26Al0.74As heterostructure. The heterointerfacial electronic structure was likewise probed via XPS, revealing conduction- and valence band offsets (ΔEC and ΔEV) of 1.25 ± 0.1 and 0.56 ± 0.1 eV, respectively. Finally, we compare our empirical results with previously published first-principles calculations investigating the impact of heterointerfacial stoichiometry on the ε-Ge/InxAl1–xAs energy band offset, demonstrating excellent agreement between experimental and theoretical results under an As0.5Ge0.5 interface stoichiometry exhibiting up to two monolayers of heterointerfacial As–Ge diffusion. Taken together, these findings reveal a new route toward the realization of on-Si photonics.

Efficient degradation of sulfachloropyridazine by sulfite activation with CuO-Al2O3 composites under neutral pH conditions: Radical and non-radical

In this work, CuO-Al2O3 composites were synthesized at higher temperatures to control the leaching of metal ions, which can activate sulfite (S(IV)) to degrade organic contaminants by generating reactive oxygen species (ROSs). The synthesized catalysts were characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, Brunauer-Emmett-Teller, Raman spectroscopy, and Fourier transform infrared spectrophotometry. Sulfachloropyridazine (SCP) was almost completely removed (＞99%) at pH 6.8, and the leaching amount of Cu accounted for 0.027% of the total amount of Cu after the reaction. Notably, singlet oxygen (1O2) was found for the first time in the activated sulfite system, which removed organic pollutants together with sulfate (SO4•-) and hydroxyl (∙OH) radicals. And Al2O3 plays an important role in the catalyst, including anti-sintering, reducing the leaching of copper ions, and promoting the generation of oxygen vacancies. Based on the types of ROSs and X-ray photoelectron spectroscopy results, a possible ROSs generation mechanism was proposed. In addition, the stability of the catalyst and the effect of different factors on the degradation of SCP, including operating parameters and water quality, were further investigated. The intermediates were detected by using gas chromatography-mass spectrometry and a developmental toxicity assessment of the intermediates was defined based on the Toxicity Estimation Software Tool (TEST). Overall, this paper not only provides a new strategy for sulfite activation but also promotes more attention to non-radical processes in activated sulfite systems.

Synthesis and Characterization of Ag/Al2O3 Catalysts for the Hydrogenation of 1-Octyne and the Preferential Hydrogenation of 1-Octyne vs 1-Octene.

Catalysts featuring 2, 5, and 10 wt % silver supported on alumina were prepared by the deposition precipitation method and activated under hydrogen. All catalysts were characterized by Brunauer–Emmett–Teller (BET) measurements, inductively coupled plasma-optical emission spectrometry (ICP-OES), backscattered electron scanning electron microscopy (BSE-SEM), high-resolution transmission electron microscopy (HR-TEM), hydrogen-temperature-programmed reduction (H2-TPR), H2-chemisorption, thermogravimetric analysis (TGA), infrared (IR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, and isopropylamine (IPA) TPD and evaluated in a continuous plug flow fixed-bed reactor. Metal nanoparticles with average sizes of 4.5, 11.5, and 21.1 nm were identified by HR-TEM for the 2, 5, and 10 wt % Ag/Al2O3 catalysts, respectively. A conversion of 99% was observed for 1-octyne over particles between 10 and 15 nm in size, with stable operation up to 24 h (decreasing thereafter) at a temperature of 140 °C and a pressure of 30 bar in the competitive hydrogenation reaction. No conversion of 1-octene was noted in competitive reactions (mixed 1-octyne and 1-octene feed) but rather a gain of 1-octene throughout the 72 h time-on-stream. The performance of all catalysts was influenced by both the metal and support, where the latter impacted the overall acidity of the catalysts, thus affecting their long-term stability.

Improvement of electrical performance using PtSe2/PtTe2 edge contact synthesized by molecular beam epitaxy

One-dimensional (1D) edge contact is considered critical to reducing contact resistance between two-dimensional transition-metal dichalcogenides (TMDs) and contact metal and overcoming surface contact effects, such as surface damage and orbital hybridization. Although several studies have investigated edge contact, some problems such as inevitable etching damage and a limited area persist. Herein, a tellurization method is applied to a specific lateral region to fabricate PtTe2/PtSe2/PtTe2 edge-contact field-effect transistors (FETs) without etching damage. High-resolution X-ray photoelectron spectroscopy and Raman spectroscopy are used to verify tellurization completion, which is evidenced by the complete transformation of PtSe2 to PtTe2 by the substitution of Se atoms with evaporated Te atoms. Furthermore, tellurization is applied to a specific lateral region by utilizing the hexagonal boron nitride to block the interdiffusion of evaporated Te atoms, which is confirmed by Raman spectroscopy and cross-sectional annular dark-field scanning transmission electron microscopy. Finally, the 1D edge-contact FETs fabricated by tellurization demonstrate a higher on–off ratio and carrier mobility than the surface-contact FET. Therefore, this method can be applied to various FETs based on TMDs for improving electrical performance through a reduction in contact resistance.

In Vitro Analysis of Organic Ester Functional Groups in Carious Dentine

Background: With the implementation of minimally invasive selective caries removal protocols to treat cavitated, deep carious dentine lesions, there is a need to investigate specific biochemical moiety distributions to help characterise and distinguish between infected (contaminated) and affected (demineralised) zones within the dentine lesion. The present in vitro investigation aimed to compare the distribution of ester functional groups (1740 cm−1) within carious dentine tissue (infected and affected dentine). The null hypothesis stipulated that there are no differences in ester function intensity/distribution within carious dentine lesions. Materials and Methods: From a total of five extracted human molar teeth with carious dentine lesions, 246 points from 10 sections of carious dentine were examined using high-resolution Raman spectroscopy and characterised into infected, affected and sound dentine. The peak intensity of the characteristic vibration mode of the ester function was calculated from sample scans. Results: Analyses indicated a statistically significant difference in the spectroscopic vibration bands of esters between the infected and affected dentine zones. Conclusion: The ester functional group is higher in intensity in the caries-infected dentine zone compared to the affected tissue. This finding could be used to develop an objective indicator for the selective operative management of carious dentine.

Influence of AlN spacer and GaN cap layer in GaN heterostructure for RF HEMT applications

The influence of GaN cap layer and AlN spacer layer on mobility, carrier concentration, bandgap, crystal structure, inherent strain and stress is investigated for three widely used GaN heterostructure viz. Al0.3Ga0.7N/GaN, Al0.3Ga0.7N/AlN/GaN and GaN/Al0.3Ga0.7N/AlN/GaN on 6H-SiC substrate. The growth process is kept identical with less than 1% standard deviation for all three samples in order to investigate the true effect of GaN cap and AlN spacer layers on heterostructure properties. The GaN heterostructure properties have been extensively studied by Hall measurement, high-resolution x-ray diffraction, Raman and photoluminescence spectroscopy. The interdependency among structural, mechanical, electrical and optical properties of GaN heterostructure due to incorporation of AlN space and GaN cap layer is established. Furthermore, presented characterization results for all three heterostructures are identical with semiconductor device physics-based simulation. The carrier mobility and concentration were found least in conventional AlGaN/GaN heterostructure. It has been observed a pronounced increase of inherent tensile stress and carrier concentration by introducing AlN spacer layer between AlGaN and GaN, whereas carrier mobility increased by employing GaN cap layer on the top of the heterostructure.

Size-Dependent Order-Disorder Crossover in Hydrophobic Hydration: Comparison between Spherical Solutes and Linear Alcohols.

Theory and computer simulation studies have predicted that water molecules around hydrophobic molecules should undergo an order–disorder transition with increasing solute size around a 1 nm length scale. Some theories predict the formation of a clathrate-like ordered structure around smaller hydrophobic solutes (<1 nm) and the formation of disordered vapor–liquid interfaces around larger solutes (>1 nm) and surfaces. Experimental validation of these predictions has often been elusive and contradictory. High-resolution Raman spectroscopy has detected that water around small hydrophobic solutes shows a signature similar to that of bulk water at lower temperature (increased ordering and a stronger hydrogen-bonded network). Similarly, water around larger solutes shows an increasing population of dangling OH bonds very similar to higher temperature bulk water. Thus, the solute size dependence of the structure and dynamics of water around hydrophobic molecules seems to have an analogy with the temperature dependence in bulk water. In this work, using atomistic classical molecular dynamics (MD) simulations, we have systematically investigated this aspect and characterized this interesting analogy. Structural order parameters including the tetrahedral order parameter (Q), hydrogen bond distribution, and vibrational power spectrum highlight this similarity. However, in contrast to the experimental observations, we do not observe any length-dependent crossover for linear hydrophobic alcohols (n-alkanols) using classical MD simulations. This is in agreement with earlier findings that linear alkane chains do not demonstrate the length-dependent order–disorder transition due to the presence of a sub-nanometer length scale along the cross section of the chain. Moreover, the collapsed state of linear hydrocarbon chains is not significantly populated for smaller chains (number of carbons below 20). In the context of our computational results, we raise several pertinent questions related to the sensitivity of various structural and dynamical parameters toward capturing these complex phenomena of hydrophobic hydration.

Growth and analysis of the tetragonal (ST12) germanium nanowires.

New semiconducting materials, such as state-of-the-art alloys, engineered composites and allotropes of well-established materials can demonstrate unique physical properties and generate wide possibilities for a vast range of applications. Here we demonstrate, for the first time, the fabrication of a metastable allotrope of Ge, tetragonal germanium (ST12-Ge), in nanowire form. Nanowires were grown in a solvothermal-like single-pot method using supercritical toluene as a solvent, at moderate temperatures (290-330 °C) and a pressure of ∼48 bar. One-dimensional (1D) nanostructures of ST12-Ge were achieved via a self-seeded vapour-liquid-solid (VLS)-like paradigm, with the aid of an in situ formed amorphous carbonaceous layer. The ST12 phase of Ge nanowires is governed by the formation of this carbonaceous structure on the surface of the nanowires and the creation of Ge-C bonds. The crystalline phase and structure of the ST12-Ge nanowires were confirmed by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. The nanowires produced displayed a high aspect ratio, with a very narrow mean diameter of 9.0 ± 1.4 nm, and lengths beyond 4 μm. The ST12-Ge nanowire allotrope was found to have a profound effect on the intensity of the light emission and the directness of the bandgap, as confirmed by a temperature-dependent photoluminescence study.

B_{1g}-Phonon Anomaly Driven by Fermi Surface Instability at Intermediate Temperature in YBa_{2}Cu_{3}O_{7-δ}.

We performed temperature- and doping-dependent high-resolution Raman spectroscopy experiments on YBa_{2}Cu_{3}O_{7-δ} to study B_{1g} phonons. The temperature dependence of the real part of the phonon self-energy shows a distinct kink at T=T_{B1g} above T_{c} due to softening, in addition to the one due to the onset of the superconductivity. T_{B1g} is clearly different from the pseudogap temperature with a maximum in the underdoped region and resembles charge density wave onset temperature, T_{CDW}. We attribute the B_{1g}-phonon softening to an energy gap on the Fermi surface induced by a charge density wave order, which is consistent with the results of a recent electronic Raman scattering study. Our work demonstrates a way to investigate Fermi surface instabilities above T_{c} via phonon Raman studies.

Nickel-Decorated Mesoporous Iron–Cerium Mixed Oxides: Microstructure and Catalytic Activity in Methanol Decomposition

Nickel-decorated mesoporous cerium-iron oxide composites were synthesized by a combination of incipient wetness impregnation and template-assisted hydrothermal techniques. The effects of the Fe/Ce ratio and the calcination temperature of cerium-iron oxides on the phase composition, texture, structure, and redox properties of the composites were studied by a combination of N2 physisorption, XRD, high-resolution transmission electron microscopy, SEM, Mössbauer, Raman, XPS, ultraviolet-visible and FTIR spectroscopies, H2-temperature-programmed reduction, and total oxidation of ethyl acetate as a catalytic test. The combined physicochemical characterization and in situ FTIR investigation of methanol decomposition was used for a proper understanding of the microstructure of the Ni/FeCe oxide composites and the mechanism of the reaction occurring on them. The complex role of the FeCe support in the stabilization of highly dispersed Ni particles, the generation of surface intermediates, and the impact of the support phase transformation under the reaction medium are discussed.

Enhanced Photocurrent of the Ag Interfaced Topological Insulator Bi2Se3 under UV- and Visible-Light Radiations.

Bi2Se3 is a topological quantum material that is used in photodetectors, owing to its narrow bandgap, conductive surface, and insulating bulk. In this work, Ag@Bi2Se3 nanoplatelets were synthesized on Al2O3(100) substrates in a two-step process of thermal evaporation and magnetron sputtering. X-ray diffractometer (XRD), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS) revealed that all samples had the typical rhombohedral Bi2Se3. Field-emission scanning electron microscopy (FESEM)-energy dispersive x-ray spectroscopy (EDS), XPS, and HRTEM confirmed the presence of the precipitated Ag. The optical absorptance of Bi2Se3 nanoplatelets in UV-visible range decreased with the Ag contents. Results of photocurrent measurements under zero-bias conditions revealed that the deposited Ag affected photosensitivity. A total of 7.1 at.% Ag was associated with approximately 4.25 and 4.57 times higher photocurrents under UV and visible light, respectively, than 0 at.% Ag. The photocurrent in Bi2Se3 at 7.1 at.% Ag under visible light was 1.72-folds of that under UV light. This enhanced photocurrent is attributable to the narrow bandgap (~0.35 eV) of Bi2Se3 nanoplatelets, the Schottky field at the interface between Ag and Bi2Se3, the surface plasmon resonance that is caused by Ag, and the highly conductive surface that is formed from Ag and Bi2Se3. This work suggests that the appropriate Ag deposition enhances the photocurrent in, and increases the photosensitivity of, Bi2Se3 nanoplatelets under UV and visible light.

Disentangling the phase sequence and correlated critical properties in Bi0.7La0.3FeO3 by structural studies

This work addresses the study of the high-temperature phase sequence of ${\mathrm{Bi}}_{0.7}{\mathrm{La}}_{0.3}{\mathrm{FeO}}_{3}$ by undertaking temperature-dependent high-resolution neutron powder diffraction (NPD) and Raman spectroscopy measurements. A determination of lattice parameters, phase fractions, and modulation wave vector was performed by Pawley refinement of the NPD data. The analysis revealed that ${\mathrm{Bi}}_{0.7}{\mathrm{La}}_{0.3}{\mathrm{FeO}}_{3}$ exhibits an incommensurate modulated orthorhombic $Pn{2}_{1}a(00\ensuremath{\gamma})000$ structure at room temperature, with a weak ferromagnetic behavior, likely arising from a canted antiferromagnetic ordering. Above ${T}_{1}=543\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, the low-temperature modulated $Pn{2}_{1}a(00\ensuremath{\gamma})000$ evolves monotonically into a fractionally growing Pnma structure up to ${T}_{\mathrm{N}}=663\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. At 663 K, the low-temperature canted antiferromagnetic phase is suppressed concurrently with the switching of the former into a nonmodulated $Pn{2}_{1}a$ structure that continues to coexist with the Pnma one, until the latter is expected to reach the 100% fraction of the sample volume at high temperatures above 733 K. The $Pn{2}_{1}a$ space group is obtained from the Pnma one through the ${\mathrm{\ensuremath{\Gamma}}}_{4}^{\ensuremath{-}}$ polar distortion. Neutron diffraction and Raman spectroscopy results provide evidence for the emergence of noteworthy linear spin-phonon coupling. In this regard, magnetostructural coupling is observed below ${T}_{\mathrm{N}}$, revealed by the relation between the weak ferromagnetism of the canted iron spins and the ${\mathrm{FeO}}_{6}$ octahedra symmetric stretching mode. The correlation between magnetization and structural results from NPD provides definite evidence for the magnetic origin of the structural modulation. The analysis of the temperature-dependent magnetization and the magnetic peak intensity as well yields a critical exponent (\ensuremath{\beta}) value of 0.38. The lower limit of the phase coexistence temperature ${T}_{1}=543\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, marking the emergence of the Pnma phase, is also associated with the temperature whereupon the modulation magnitude starts to decrease.

Measurement of shock velocity and temperature in laser-shocked carbon disulphide using time-resolved Raman spectroscopy

High-resolution time-resolved Raman spectroscopy of laser-shocked liquid carbon disulfide (CS2) is reported. The symmetric stretching mode (ν1) and first overtone of the bending mode (2 ν2) of CS2 at 656 cm−1 and 802 cm−1 wavenumbers respectively are analyzed to monitor the possible phase transitions occurring in the sample during shock wave propagation in the pressure range 0.4 – 4.4 GPa by varying the laser intensity on target from 0.2 GW/cm2 (40 mJ) to 6.4 GW / cm2 (1300 mJ). A liquid to solid phase transition is observed at 1.5 GPa, as compared to 0.8 GPa in static compression. The difference in these measurements is thought to be due to the high temperatures involved in the dynamic compression experiments described. The shock wave velocities in CS2 at 1.5 GPa and 2.6 GPa are calculated by measuring the intensity ratio of Raman modes emerging from the shocked region to that of the whole sample. 1D radiation-hydrodynamic simulations are performed to corroborate the experimental data. Enhancement of the Raman cross-section of carbon disulfide is observed from 2.5 GPa, which is much lower than the previously reported threshold of 8 GPa as reported by Yoo et al., [24]. This discrepancy in results is thought to be due to the significant contribution of temperature along with the pressure in laser-driven nanosecond single shock experiment.

Methane storage in clathrate hydrates containing water‐miscible oxirane promoters

As the share of natural gas in the global demand for energy continues to increase, there is a growing need for sustainable, energy-efficient, and cost-effective natural gas storage and transportation technologies. This study investigates methane hydrates (MHs) containing two oxirane compounds, namely, propylene oxide (PO) and epoxyisobutane (EIB), for their potential use in hydrate-based methane storage (HBMS) applications. The microstructures of the MHs containing both PO and EIB were identified as the sII type by high-resolution powder diffraction (HRPD), 13C NMR, and Raman spectroscopy. Moreover, the addition of PO/EIB significantly improved the thermodynamic stability of simple MH. In particular, as EIB increased the equilibrium temperature by 15 K, the EIB + CH4 hydrate remained stable up to ambient temperature (19°C) even under a mild pressure (30 bar). It was also clearly demonstrated that PO and EIB act as simple hydrate formers (SHFs) with good water miscibility. The EIB + CH4 hydrate also showed a remarkable CH4 capacity of 0.117 mol CH4/mol H2O or 117 m3 CH4 (at STP)/m3 hydrate, nearly identical to the theoretical maximum. It is believed that both PO and EIB could potentially be employed to facilitate sustainable and energy-efficient HBMS technologies owing to the combined excellence of their high promotion capability and energy density, and good water miscibility. Novelty statements Both PO and EIB act as powerful promoters with good water miscibility. Both PO and EIB act as simple sII hydrate formers. Approximately 120 m3 of methane gas can be stored in 1 m3 of EIB hydrate.

Surface Morphology and Microstructure Evolution of Single Crystal Diamond during Different Homoepitaxial Growth Stages.

Homoepitaxial growth of step-flow single crystal diamond was performed by microwave plasma chemical vapor deposition system on high-pressure high-temperature diamond substrate. A coarse surface morphology with isolated particles was firstly deposited on diamond substrate as an interlayer under hillock growth model. Then, the growth model was changed to step-flow growth model for growing step-flow single crystal diamond layer on this hillock interlayer. Furthermore, the surface morphology evolution, cross-section and surface microstructure, and crystal quality of grown diamond were evaluated by scanning electron microscopy, high-resolution transmission electron microcopy, and Raman and photoluminescence spectroscopy. It was found that the surface morphology varied with deposition time under step-flow growth parameters. The cross-section topography exhibited obvious inhomogeneity in crystal structure. Additionally, the diamond growth mechanism from the microscopic point of view was revealed to illustrate the morphological and structural evolution.

Investigating the oxidative reactivity and nanostructural characteristics of diffusion flame generated soot using methyl crotonate and methyl butyrate blended diesel fuels

Combustion-generated particulate matter has a consequential fallout on climate, environment, and human health. Thus, comprehension of soot formation and mitigation processes using biodiesel additives is a focal point of modern combustion research. This study presents an intricate investigation of enhanced oxidative reactivity and its dependence on the soot nanostructural properties induced by distinctive blending of a saturated and an unsaturated biodiesel surrogates namely, methyl butyrate (MB) and methyl crotonate (MC) respectively with pure diesel. 25% MB-75% diesel fuel resulted in the lowest sooting propensity and lowest activation energy (155.4 ± 2 kJ/mol) for soot oxidation in comparison to pure diesel fuel and diesel soot (175.1 ± 2 kJ/mol). The soot was collected using a smoke point apparatus involving a wick-fed laminar diffusion flame at atmospheric pressure after meticulous observation of the smoke points. The detailed nanostructural characterization of the flame generated soots were performed using high-resolution transmission electron microscopy, X-ray diffraction, elemental analysis and Raman spectroscopy. BET surface area analysis, and thermogravimetric analysis were carried out for surface area distinction and activation energy calculations respectively. It revealed that, addition of MB to diesel resulted in improved fuel combustion with reduction in primary soot particle diameter, greater inter-planar separation, increased fringe tortuosity and greater crystal structure disorder resulting in its enhanced reactivity with O2. The 25% MC-75% diesel blend resulted in relatively greater sooting propensity while its soot exhibited lower crystal structure disorder and greater activation energy (165.0 ± 2 kJ/mol) for O2 induced oxidation compared to 25% MB-75% diesel, possibly due to the resonance stabilized radical (RSRs) formation that altered the fuel combustion chemistry. Therefore, this study successfully depicts that the structural differences in the surrogate fuels do influence the soot formation and oxidation kinetics. These structural effects therefore need to be considered when formulating the global multiphase kinetic models for biodiesel-diesel fuel combustion.11Dedicated to Prof. Purnakala Samant on the occasion of her 50th birthday celebration.

Annealing Temperature Dependence of Various Properties of ZnO Nanoparticles Investigated with Soft XAS

In this paper, structural, optical and electronic properties of ZnO nanoparticles were investigated with the variation in the annealing temperature. X-ray diffraction, High-Resolution Transmission Electron Spectroscopy, Absorption spectroscopy, Raman Spectroscopy and Soft X-ray spectroscopy techniques were invoked to investigate and gauge the effect of annealing temperature on these properties. Intact Hexagonal Wurtzite phase of the nanoparticles with increasing crystallinity and spherical shape with particle size between 20[Formula: see text]nm and 23[Formula: see text]nm [using both X-ray Diffractometer (XRD) and High-resolution Transmission of electron microscopy (HRTEM)], blue shift of absorption peak from 372[Formula: see text]nm to 366[Formula: see text]nm and Optical Band Gap from 3.24[Formula: see text]eV to 3.17[Formula: see text]eV (UV-Vis-NIR), narrowing of [Formula: see text] mode in Raman Spectra; all indicated enhanced crystallinity with increased annealing temperature. Effects produced by the sole variable such as annealing temperature on the indicative parameters in a definite order catapult the annealing conditions as a significant candidate for customized properties. To have a deeper insight at the electronic levels, Synchrotron-based X-ray absorption spectroscopic studies of ZnO nanoparticles were undertaken. The analysis of Soft XAS spectra showed the change in number of O 2[Formula: see text] and Zn 4[Formula: see text] unoccupied states with increasing particle size and crystallinity of ZnO nanoparticles for varying annealing temperature.

Structural and electrical characterisation of PtS from H2S-converted Pt

A manufacturing-compatible 300 mm chamber reactor for atomic layer deposition or chemical vapour deposition, and pre-fitted with H2/H2S gases that can be uniformly delivered to the wafer surface, is employed to thermally convert Pt to PtS in a H2/H2S gaseous atmosphere for 7 hours at a chamber temperature of 550 °C. Prior to conversion, platinum layers 5 nm thick are uniformly deposited by electron beam evaporation onto ∼30 nm of amorphous aluminium sesquioxide deposited by atomic layer deposition on, (a) p-type silicon, and (b) c-plane sapphire. Structural characterisation is performed by high-resolution cross-sectional transmission-electron microscopy, scanning-electron microscopy and Raman spectroscopy, confirming the formation of continuous films of polycrystalline platinum monosulfide (PtS) with a ∼15 nm thickness. Electrical characterisation is performed by 4-point resistivity and Hall-effect transport measurements on van der Pauw structures of PtS on aluminium sesquioxide on c-plane sapphire, and by back-gate junctionless MOSFET device measurements for PtS on aluminium sesquioxide on p-type silicon, showing that PtS behaves as a semiconductor with a mobility of ∼16 cm2/V.s and with an n-type carrier concentration of ∼1.2 × 1015 cm−3. Advanced commercial-grade Sentaurus simulations, alongside density-functional theory calculations, agree well with the experimental observations and suggest a large bandgap of ∼1.58 eV may be possible that could lead to a low off-current and a high Ion/Ioff ratio, suggesting that PtS may be an advanced material candidate for future device integration with CMOS and for 3D integration applications in Beyond-CMOS and More-than-Moore technologies.

Defect-Rich Amorphous Iron-Based Oxide/Graphene Hybrid-Modified Separator toward the Efficient Capture and Catalysis of Polysulfides.

The sluggish sulfur reduction reaction, severe shuttle effect, and poor conductivity of sulfur species are three main problems in lithium-sulfur (Li-S) batteries. Functional materials with a strong affinity and catalytic effect toward polysulfides play a key role in addressing these issues. Herein, we report a defect-rich amorphous a-Fe3O4-x/GO material with a nanocube-interlocked structure as an adsorber as well as an electrocatalyst for the Li-S battery. The composition and defect structure of the material are determined by X-ray diffraction, high-resolution transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy measurements. The distinctive open framework architecture of the as-engineered composite inherited from the metal-organic framework precursor ensures the stability and activity of the catalyst during extended cycles. The oxygen defects in the amorphous structure are capable of absorbing polysulfides and similarly work as catalytic centers to boost polysulfide conversion. Taking advantage of a-Fe3O4-x/GO on the separator surface, the Li-S battery shows a capacity over 610 mA h g-1 at 1 C and a low decay rate of 0.12% per cycle over 500 cycles and superior rate capability. The functional material made via the low-cost synthesis process provides a potential solution for advanced Li-S batteries.