Crystallite Surface Research Articles

Influence of aluminum zoning toward external surfaces in MFI zeolites on propene oligomerization catalysis.

Brønsted acid zeolites catalyze alkene oligomerization reactions, an important route to produce fuels and chemicals from light hydrocarbon feedstocks. Propene dimerization rates (per H+, 503 K) decrease monotonically with increasing crystallite size in MFI zeolites because heavy oligomer products remain occluded within microporous voids and restrict intrazeolite diffusion of reactants and products. Here, we show that the preferential zoning of framework Al centers and their associated H+ sites toward exterior surfaces of MFI crystallites in an "egg-shell" architecture minimizes the extent of diffusion-enhanced secondary reactions within a given crystallite, which increases both propene dimerization rates (per H+) and selectivity to true oligomer products. These results show that tailoring Al distributions to be spatially zoned toward external surfaces of medium-pore zeolite crystallites is efficacious at minimizing diffusion path lengths to increase alkene oligomerization rates and selectivity to true oligomer products.

Gas sensing properties of hematite nanoparticles synthesized via different techniques.

The synthesis techniques used for metal oxide semiconductors strongly influence their chemical, physical and gas sensing characteristics. In this context, hematite (α-Fe2O3) nanoparticles (NPs) were synthesized using two different techniques, namely, sol-gel (named HSG) and Pechini sol-gel (named HPSG). The average crystallite size and surface area were 15 nm and 76 m2 g-1 and 20 nm and 57 m2 g-1 for HPSG and HSG, respectively. Morphological studies showed that the HSG material was composed of ellipsoid-shaped particles, while the HPSG material had peanut-shaped particles with open pores and channels. The comparison between the sensing performances of HPSG and HSG toward ethanol indicated HPSG to be a better sensing material for ethanol detection. The HPSG sensor exhibited a response of 12 toward 500 ppm ethanol at 250 °C, a fast response time of 5 s and excellent selectivity. The enhanced characteristics were mainly related to the peculiar morphology with a porous nature, which led to more gas adsorption and diffusion. In addition to shape influence, the size of NPs also has an effect on the gas sensing performance. In fact, a decrease in the crystallite size led to an increase in the surface area of the material where the gas molecule-sensing layer interaction took place. The increase in the surface area created more interaction sites, and thus the sensitivity was improved. From these results, the HPSG sensor can be regarded as a promising candidate for ethanol detection.

Structural and Dielectric Studies of Ni1−xAlxFe2O4

The nanoparticles of Ni1−xAlxFe2O4(x = 0,0.5) were synthesized via using sol-gel route and studied the structural and dielectric effect of aluminium content on Nickel site. The X-ray diffraction (XRD) revealed the single-phase cubic spinel structure of the parent compound. The lattice constant, volume, density, bond lengths, specific surface area and crystallite size were determined from the Rietveld refinement. In the Raman analysis, there are five active modes present in the synthesized samples. FTIR spectroscopy confirmed the formation of spinel ferrite and showed the characteristics absorption bands of metal oxygen (Fe-O) observed around 424-450 and 601-620 cm−1 corresponding to the stretching vibration frequency of the metal-oxygen at the octahedral site and tetrahedral site respectively. Dielectric behaviour showed that the value of dielectric constant (ε') and tangent loss (tanδ) decreases with frequency and confirmed the general behaviour of ferrites. The AC Conductivity (σac) was found lower in Ni0.5Al0.5Fe2O4 compared to NiFe2O4.

Crystalline Micro-Sized Carbonated Apatites: Chemical Anisotropy of the Crystallite Surfaces, Biocompatibility, Osteoconductivity, and Osteoinductive Effect Enhanced by Poly(ethylene phosphoric acid).

Carbonated hydroxyapatites (CAp) are very close to natural bone apatite in chemical composition and are regarded as a prospective bone mineral substitute for bone surgery and orthopedics. However, until now, the studies and applications of CAp were limited because of the amorphous nature of the synthetic CAp. In the present work, microsized highly crystalline carbonated apatites with uniform hexagonal (hCAp) or platelike (pCAp) morphology have been studied for the first time in vitro and in vivo, comparing against commercial hydroxyapatite (HAp) and β-tricalcuim phosphate (βTCP). In vitro experiments on dissolution of those calcium phosphate ceramics (CPCs) in acetate (pH 5.5) and Tris (pH 7.3) buffer solutions showed the following rank order of the dissolution rates: βTCP > hCAp > pCAp > HAp. The higher dissolution rate of hCAp in comparison with pCAp is explained by chemical anisotropy of the crystallite surfaces, which was proven by SEM studies of the changes in the morphology of hCAp and pCAp crystallites during hydrolysis. A 5-week experiment on subcutaneous implantation of CPC species showed the following rank order of bioresorption rates: βTCP > pCAp > hCAp > HAp. pCAp matrixes exhibited the highest biocompatibility, confirmed by histomorphological analysis. Three-month bone regeneration experiments involving a rat tibial defect model were conducted with 250-500 μm granules of pCAp and pCAp-PEPA [pCAp, pretreated with 2 wt % poly(ethylene phosphoric acid)]. Notably, pCAp-PEPA implants were resorbed at higher rates and induced the formation of more mature osseous tissue, a compact bone with Haversian systems.

Partial hydrogenation of 1,3-butadiene over nickel with alumina and niobium supported catalysts

The hydrogenation of 1,3 butadiene (BD) is an important industrial process that is generally used to generate butenes and aromatics, which are important petrochemicals and constituents of transportation fuels. Ni-based catalysts have gained increasing interest in the academic community and industry because of their superior hydrogenation activity, ability to exist in multiple oxidation states and most importantly, affordability compared to the less-abundant precious metal catalysts. In this work, we explore the ability of alumina (Al2O3) and niobia (Nb2O5) as catalytic supports for Ni as the active metal since they have shown excellent potential for hydrogenation of alkenes. Specifically, we compare the metal-support interactions, which disperse Ni effectively throughout the catalyst surface, textural and pore parameters, Ni crystallite size, surface morphology, elemental composition, coke formation and tendencies of both catalysts through extensive characterization techniques such as H2-temperature programmed reduction (H2-TPR), N2-adsorption–desorption, X-ray diffraction (XRD), scanning electron microscopy combined with electron-dispersive spectra (SEM-EDS), and thermal analysis of the spent catalysts. Limited reports on the use of niobium oxides and alumina as supports for Ni in the partial hydrogenation of BD prompted us to explore this literature gap. The catalytic reactions were conducted using a quartz tube reactor between a temperature range of 50 and 400 °C at regular intervals of 50 °C under operating pressures of 1 atm. A comprehensive analysis of the products from the reaction was carried out using gas-chromatography with mass spectrometry (GC–MS) detector and corroborated these results with those from infrared spectroscopy (FTIR). Reaction mechanisms of aliphatic and aromatic product formation were proposed and verified with literature and our own characterization results. The tests on the spent catalysts also helped to reveal the extent of deactivation of the catalysts due to carbon deposition. Mechanisms of catalyst deactivation and nature of carbonaceous deposits were explored and elaborate scientific reasoning was provided as to why Ni/alumina showed better performance in terms of product yields and BD conversion. Ways to mitigate the harmful effects of coke formation and its deposition are also discussed. The novelty of our work is that a comprehensive comparison of the performance of Ni/alumina and Ni/niobia for hydrogenation of BD along with extensive discussions on coke formation, its chemical nature and proposed reaction chemistry based on obtained characterization results of the catalysts and the products of BD hydrogenation has not been done before for this system. In this way, we show the low-temperature conversion of BD represents an economically efficient and relatively simple method to convert toxic, carcinogenic and environmentally hazardous BD into high-value products using low-cost and chemically efficient catalysts.

Dimethyl Ether Carbonylation on H-MOR Zeolite, Modified Cu, Co, Mg

Mordenite and ferrierite (Zeolyst International, H-form, SiO2/Al2O3 ≈ 20) were used to study the adsorption, thermally programmed desorption, and carbonylation of dimethyl ether (DME). The behavior of mordenite with Cu, Co, and Mg cations introduced by ion exchange has also been studied. DME carbonylation was carried out at 200°C, pressure 3 MPa, space velocity 8000 ml g–1 h–1 in a mixture, vol. %: ⁓2.2 DME, 92.8–95.5 CO, rest. N2. After the induction period, the methyl acetate content is about 4–5 times higher for mordenite compared to ferrierite. The formation of water, methanol and hydrocarbons was observed in small quantities. The introduction of Cu, Co, Mg cations into mordenite by ion exchange (single ion exchange, cation/Al ratio no more than 35%) not only increased the stability, but also increased the activity in the DME carbonylation reaction. It was found that an increase in the content of copper (from 1.19 to 2.23 wt %) and Mg (from 0.62 to 1.8 wt %) differently affects the activity. In the case of copper, an increase in activity was observed, while in the case of magnesium, the activity decreased. Preliminary reduction of copper-exchange mordenite leads to a decrease in activity and the appearance of metallic copper particles on the surface of mordenite crystallites. According to in situ diffuse reflectance infrared spectroscopy, the introduction of magnesium cations by triple ion exchange leads to a noticeable decrease in the number of Brønsted acid sites (BACs) in both the 12-MR and 8-MR channels of mordenite. The catalytic characteristics of ferrierite practically do not change when copper and magnesium are introduced by ion exchange.

Synthesis of N-doped TiO2 nanoparticles with enhanced photocatalytic activity for 2,4-dichlorophenol degradation and H2 production

Nitrogen-doped titanium dioxide (N-TiO2) nanoparticles were prepared using a modified sol-gel method. The as-prepared nanoparticles were characterized by state-of-the-art techniques for their optical, structural and morphological properties. The crystallite size, surface area and bandgap energy of reference TiO2 and N-TiO2 nanoparticles were found to be 16.1 and 10.9 nm, 83.6 and 131.8 m2 g−1 and 3.23 and 2.89 eV, respectively. The photocatalytic activities, in terms of 2,4-dichlorophenol (2,4-DCP) degradation, of reference TiO2 and N-TiO2 were found to be 46.9% and 65.4% at 120 min of treatments under UV light irradiation and 21.5% and 77.6% at 240 min of treatment under visible light irradiation, employing 153.4 µM 2,4-DCP, 1 g/L photocatalyst dosage, and pH 5.6. Interestingly, considerable H2 production rate (i.e., 386 μmol h−1 g−1) was observed for visible/N-TiO2 system in presence of 0.2 wt% Pt. The study revealed that visible/N-TiO2 photocatalytic system can be used as an economically viable technology for environmental sustainability.

Alkylammonium lead chloride perovskites: Synthesis, characterization and catalytic activity for conversion of lignin into value added products

Lignin is the utmost abundant source of renewable aromatics hence its depolymerization into functionalized aromatics is attractive but challenging as well. A lot of interest is diverting to photocatalysis as a promising sustainable approach to depolymerizing lignin. In the present studies, photocatalytic lignin depolymerization has been investigated under UV-light irradiation using i-propylamine lead chloride perovskites (AS1-AS3) as catalysts. These catalysts were characterized by Powder X-ray Diffraction, Scanning Electron Microscopy, Ultraviolet–Visible, Photoluminescence, and Fourier Transform Infra-Red Spectroscopic techniques to evaluate crystallite size, surface morphology, band gaps, and quantum yields. Depolymerization of lignin was monitored by taking UV spectra and catalytic pathways were studied through various kinetic models. The depolymerization extent was monitored for different catalyst doses (0.05g–0.1 g), lignin concentration (50ppm–200 ppm), and temperatures (25–100 °C). More than 50% depolymerization rate was obtained for each catalyst using 100 ppm lignin concentration. AS3 has shown maximum efficiency in depolymerizing lignin. Pseudo-first order and modified Freundlich were found to be best-fitted kinetic models for experimental data of lignin depolymerization. The activation energy (Ea) for the depolymerization reaction was calculated to be 6.8 kJ/mol which is extraordinarily less than conventional depolymerization of lignin exhibiting significant catalytic competencies of synthesized catalysts. One of the products (L-AS3) of lignin depolymerization activity carried out at room temperature was characterized through GCMS analysis which indicated the breakdown of the polymeric structure of lignin into small monomeric functionalities. 2-methoxy-4-methylphenol (9%), benzene (4%), cyclohexene (16%), phenol (6%), catechol (12%) and 2-methoxy-5-propenyl phenol (10%) were detected by GCMS analysis of lignin depolymerization product.

Characterization of Bismuth Trioxide Nanoparticles and Evaluating Binding Affinity with Proteins

AbstractProtein‐nanoparticle conjugation, or protein‐corona, is important for nanomedicine, nano diagnostic, and nano therapy applications. α‐Bismuth oxide nanoparticles (α‐Bi2O3 NPs) were prepared from bismuth nitrate powder using the sol‐gel method and characterized using various techniques, including Energy Dispersive X‐Ray Spectroscopy (EDS), X‐ray Diffraction (XRD), Raman spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), UV‐VIS‐NIR Spectroscopy, and Brunauer‐Emmett‐Teller (BET). X‐ray diffraction studies revealed that NPs are in the alpha phase with a monoclinic structure. The energy band gap, average surface area and crystallite size are 2.81 eV, 2.42 m2, and 15–106 nm, respectively. Transmission electron microscopy revealed particle size is 32.21 nm, with a d‐spacing of 2.529 Å. The surface‐to‐volume ratio is calculated and found to be 2.553×106 m−1. For the first time, a direct protein interaction with NPs was examined with standard proteins such as bovine serum albumin (BSA), carbonic anhydrase, phosphorylase b, and total human serum proteins and analyzed using mass spectroscopy. Proteomic analysis showed that proteins such as BSA, phosphorylase b, and carbonic anhydrase exhibited a strong affinity with Bi2O3 NPs. However, it was found that there was less or no association between Annexin A6, human serum albumin, Zinc finger protein, and Bestrophin‐2 with Bi2O3 NPs.

Nickel layers properties produced by electroplating were influenced by spinning permanent magnet

A spinning magnet is an alternative engineering approach to produce the Ni layer. In the present research, the Ni layer was plated on Cu alloy substrates influenced by a spinning magnet. Various rotating speeds (0, 500, and 800 rpm) were used to influence the Ni layer’s properties were formed. A digital scale was used to measure the deposition rate and cathodic current efficiency. XRD, SEM-EDS, potentiostat, and hardness tests were performed to determine the properties of the Ni layers. A rotating magnetic field can reduce the deposition rate and cathodic current efficiency by reducing the ionic movement from the anode to the cathode. The XRD and SEM results revealed a distinct crystallite size and surface morphology. Exhibiting a spinning could result in a decrease in oxygen in the Ni layer and a slight change in the corrosion rates. Different hardness is also seen in the various sample due to crystallite size.

Understanding remarkable promotional effects of Zn on alumina in catalytic hydrolysis of perfluorocarbon

Perfluorocarbons (PFCs) such as CF4 are extensively used as etchants and cleaning agents in semiconductor manufacturing. Because of their significant global warming potential, it is important to develop efficient technologies to decompose PFCs. In this study, we synthesized a series of Zn-promoted γ-Al2O3 catalysts with varying Zn contents for CF4 hydrolysis. Physical characterizations and kinetic studies indicated that the Lewis acid sites of unpromoted γ-Al2O3 predominantly adsorb H2O compared to CF4 under the reaction conditions, resulting in limited catalytic activity (H2O poisoning). As the Zn/Al molar ratio increased up to 0.1, nanocrystalline ZnAl2O4 was selectively formed on the surface of γ-Al2O3 crystallites, generating a core-shell-like structure. The Lewis acid sites on the ZnAl2O4 surfaces exhibited enhanced CF4 adsorption and weakened H2O adsorption compared to those on γ-Al2O3, thereby alleviating the detrimental effect of H2O poisoning. Consequently, despite the reduction in the total number of Lewis acid sites upon Zn addition, Zn-promoted γ-Al2O3 catalysts exhibited significantly enhanced catalytic activity. Furthermore, the ZnAl2O4 covering the γ-Al2O3 crystallites inhibited their phase transition to α-Al2O3, improving catalytic stability. When the Zn content was increased excessively (Zn/Al > 0.1), bulk ZnAl2O4 crystallites with low Lewis acidity were formed, resulting in a substantial loss of catalytic activity.

Controlled fabrication of novel zirconia nanoparticles with tailored size, morphology, crystal phases, surface properties, and acidity via Indonesian Boehmeria virgata-mediated eco-friendly synthesis

Green synthesis of ZrO2 NPs from plant sources has gained significant attention due to its advantages, such as eco-friendly and low-cost production compared to chemical synthesis methods. The objectives of this work were to study the characteristics of green synthesized ZrO2 NPs using three types of Boehmeria virgata leaf extracts in n-hexane (ZrO2–H), methanol (ZrO2-M), and water (ZrO2–W) at various calcination temperatures (500, 700, and 900 °C). ZrO2 NPs with different structures, morphologies, surface properties, and acidity were fabricated through an eco-friendly synthesis method using three types of Indonesian B. virgata leaf extract at various calcination temperatures. The resulting ZrO2 NPs exhibited monoclinic and tetragonal phases, while a tetragonal-dominated structure was detected on ZrO2–H 700, ZrO2-M 700, and ZrO2-M 900 NPs. SEM images showed that ZrO2–H and ZrO2-M NPs possessed homogenous nanospheres shape, whereas the combination of nanoflakes and nanospheres was observed in ZrO2–W NPs. Based on the analysis of TEM micrographs, the average nanoparticle sizes of ZrO2–H, ZrO2-M, and ZrO2–W at calcination temperatures of 900 °C were determined to be 16.02 nm, 34.63 nm, and 17.63 nm respectively. The formed ZrO2 NPs prepared using BVLEs, exhibited a specific surface area ranging from 11.32 to 58.86 m2/g, a pore volume ranging from 0.058 to 0.183 cm³/g, and a pore diameter ranging from 9.85 to 58.65 nm. The acidity of ZrO2 NPs ranged from 0.0397 mmol/g up to 1.6045 mmol/g. The calcination temperature influenced the XRD crystallite size, surface texture (specific area and porosity), and acidity of ZrO2 NPs mediated by BVLEs. This green and simple synthesis method offers an alternative technique for forming highly valuable ZrO2 NPs compared to chemical synthesis methods.

Ultra-fine microstructure and exceptional low coercivity developed in a high-Bs Fe-Si-B-P alloy by co-alloying Ni, Mo, and Cu

Designing soft magnetic alloys with high saturation magnetic induction (Bs) is of great importance for improving the power density of electric and electronic devices. For high-Bs nanocrystalline alloys, the main problem is the grain coarsening effect induced by high Fe content (>80 at.%), which deteriorates the soft magnetic properties. In present work, we designed new Fe-based nanocrystalline alloys by microalloying a Fe-Si-B-P alloy. The co-alloying of Ni, Mo, and Cu effectively refines the microstructure of nanocrystalline alloys from 28.5 nm to 13.1 nm and increased the stability of soft magnetic properties. Even though there are 28-nm-large surface crystallites in the amorphous precursors, an exceptional low coercivity of 1–2 A/m with a high Bs of 1.81 T was developed after nanocrystallization. These excellent magnetic properties could be maintained within a wide annealing temperature window of 50 K and an annealing time window up to 600 s for high heating rate annealing.

Nitrogen flow rate dependent atomic coordination, phonon vibration and surface analysis of DC magnetron sputtered nitrogen rich-AlN thin films

In this work, the effect on crystallite orientation, surface morphology, fractal geometry, structural coordination and electronic environment of DC magnetron sputtered AlN films were investigated. X-ray diffraction results disclosed that the c-axis orientation of AlN films increased with the preferred wurtzite hexagonal structure above 17% N2 flow. X-ray reflectivity data confirmed AlN film density increased with increasing N2 flow and was found to be 3.18 g/cm3 for 40% N2. The transition of electrons from N 1s to 2p states hybridized with Al 3p states because of π* resonance was obtained from X-ray absorption spectroscopy of the N K-edge. The semi-empirical coordination geometry of nitrogen atoms has been studied by deconvolution of N K-edge. The surface composition of AlN films at 40% N2 consists of 32.08, 51.94 and 15.97 at.% Al, N and O respectively. Blue-shifting of A1(LO) and E1(LO) modes in the Raman spectra at phonon energies 800 and 1051 cm−1 respectively was most likely due to the presence of oxygen bonds in the AlN films.

Properties of Mn3O4 thin film electrodes prepared using spray pyrolysis for supercapacitor application

Film electrodes are made by depositing a thin layer of an electroactive material onto a conductive substrate. The performance of thin film electrodes in energy storage devices is significantly governed by their preparative conditions, particularly the molar concentration of the initial precursor. In the current study, the preparation of Mn3O4 thin film electrodes utilizing the chemical spray pyrolysis technique is discussed. The effect of molar concentration on the structural, morphological, and electrochemical properties of the thin film electrodes was thoroughly investigated using techniques including X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) studies. Additionally, X-ray photoelectron spectroscopy (XPS) was employed to gain more insight into the oxidation states of the sample with the best electrochemical performance. Findings suggested that the molar concentration considerably affects the crystallite size, surface area, surface roughness, and wettability, which would directly impact the functionality of the electrode. It was concluded that the electrode deposited using the molar concentration of 0.06 M showed significantly improved performance according to the electrochemical measurements. The areal capacitance of up to 105.3 mF/cm2 in the aqueous electrolyte was recorded from CV measurements at a scan rate of 5 mVs−1. These electrodes could be an option for low-cost, environmentally friendly electrochemical capacitors if prepared under optimal deposition conditions.

Surface-disorder and cationic-site defect-induced ferromagnetism and correlated Raman vibrational modes in Sn0.9 In0.1O2 nanocrystalline thin-films

Exploration of magnetism in otherwise nonmagnetic wide-band oxides through defect-engineering has been become a new challenge to achieve the goal of room-temperature ferromagnetic semiconductor for potential applications in spintronics. In this backdrop, we report surface-disorder and cationic-site defect-induced FM in series of Sn0.9In0.1O2 nanocrystalline thin films prepared using pulsed laser deposition different Argon (Ar) pressure. With the increase of deposition pressure, surface morphology of Sn0.9In0.1O2 nanocrystalline thin-films changes as nanoclusters, nanofibres, nanoflakes and nanowires respectively, crystallite size decreases and surface disorder increases gradually. Raman, X-ray photoelectron and Photoluminescence spectroscopic analysis confirm the formation tin-vacancy (VSn) and associated combinational defects that significantly increase the ferromagnetic signal in In-doped SnO2 thin-films. The substitution of trivalent In3+ in Sn site also cause serious lattice distortion which transform the Raman inactive modes A2g and Eu modes into Raman active modes and thus appeared at 574 cm−1 and 354 cm−1 respectively. The nanowires of Sn0.9In0.1O2 are found to possess highest concentration of VSn defects and therefore it exhibits strongest ferromagnetic moment (MS) ∼ 11.1 emu/cm3 and highest Curie temperature (TC) ∼ 572 K. The gradual decrease in carrier concentration with the increasing deposition pressure suggests stabilization of hole-mediated VSn-induced room temperature FM in series of In-doped SnO2 nanocrystalline thin-films.

Electron density mapping and bonding in Mn doped CoFe2O4 using XRD, and its correlation with room temperature optical and magnetic properties

Single-phase Mn-doped Cobalt spinel ferrite prepared via the self-combustion method shows mixed spinel structure. Cation occupancy in tetrahedral A and octahedral B sites was observed through XPS, XRD, and VSM analysis. Crystallite size, porosity, surface area, and energy band gap results pave a path to optical absorption related applications. The energy band gap of MnxCo1-xFe2O4 nanoparticles were estimated using the Tauc plot and the values ranging from 1.123 eV to 1.247 eV. XPS-based energy level splitting of Mn 2p3/2 and Mn 2p1/2 confirms the occupation of Mn2+ and Mn3+ in octahedral and tetrahedral sites, respectively. The magnetic hysteresis from VSM depicts the formation of semi-hard ferrite with a maximum saturation magnetization of 79.612 emu/g and a coercivity of 1056 Oe, and the magnetic parameters decrease with the increase in manganese doping concentration. The Maximum Entropy Method (MEM)-based electron density mapping shows the electronic structure and bonding nature. Using MEM, a novel and favourable maximal coercivity condition is correlated with the high and moderate numerical bond critical density of 1.123 e/Å3 for A-O and 0.413 e/Å3 for B-O interactions, respectively. Strong A-O covalent bonds and feeble B-O covalent bonds are characteristics of spinel ferrites with high magnetization. The oxygen positional parameter values for all the samples not exceed 0.377 which is very close to the ideal value of 0.375.

Surfactant-assisted hydrothermal synthesis of large surface area nickel nanoparticles for electrochemical applications

A large surface area is an imperative parameter for electrocatalytic materials applied in electrochemical devices. In the present work, Ni nanoparticles were synthesized by hydrothermal method using three surfactants: sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and polyvinyl pyrrolidone (PVP) and two base media, i.e., sodium hydroxide (NaOH) and ammonium hydroxide (NH4OH). We investigated the effects of different surfactants and base mediums on Ni nanoparticles' crystallite size, particle size, and surface area. Experimental results revealed that Ni nanoparticles with smaller particle sizes (50–90 nm) and large surface area (28.4–64 m2/g) were obtained when NaOH was used as the base medium with all surfactants. Further, a high specific capacitance of 417 F/g, minimum charge transfer resistance of 490 Ω, and 91 % capacitance retention demonstrated that Ni nanoparticles obtained using PVP in NaOH could be applied as potential working electrode material in enhancing the performance of supercapacitor devices.

Effect of Manganese Distribution on Sensor Properties of SnO2/MnOx Nanocomposites.

Nanocomposites SnO2/MnOx with various manganese content (up to [Mn]/[Sn] = 10 mol. %) and different manganese distribution were prepared by wet chemical technique and characterized by X-ray diffraction, scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis and mapping, IR and Raman spectroscopy, total reflection X-ray fluorescence, mass-spectrometry with inductive-coupled plasma (ICP-MS), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR) spectroscopy. A different distribution of manganese between the volume and the surface of the SnO2 crystallites was revealed depending on the total Mn concentration. Furthermore, the identification of surface MnO2 segregation was performed via Raman spectroscopy. There is a strong dependence of the sensor signal toward CO and, especially, NO) on the presence of MnO2 surface segregation. However, manganese ions intruding the SnO2 crystal structure were shown to not almost effect on sensor properties of the material.

Study of the Properties of CdS:Al (R = [Al3+]/[Cd2+] = 0.30, 0.40, 0.50) Thin Films Grown by the CBD Method in an Ammonia-Free System.

CdS:Al thin films were fabricated on a glass substrate using the CBD method. The effect of aluminum incorporation on the structural, morphological, vibrational, and optical properties of CdS thin layers was investigated by X-ray diffraction (XRD), Raman spectroscopy (RS), atomic force microscopy (AFM), scanning electron microscopy (SEM), and UV-visible (UV-vis) and photoluminescence (PL) spectroscopies. XRD analysis of deposited thin films confirmed a hexagonal structure with a preferred (002) orientation in all samples. The crystallite size and surface morphology of the films are modified with aluminum content. Raman spectra exhibit fundamental longitudinal optical (LO) vibrational modes and their overtones. Optical properties were studied for each thin film. Here, it was observed that the optical properties of thin films are affected by the incorporation of aluminum into the CdS structure.