Step Synthesis Route Research Articles

Recent Advances Towards Practical LiNiO2 Cathode Materials: Optimised Calcination and Modification with W Via a Single Step Synthesis Route

LiNiO2 has been long considered as a promising cathode material owing to its high practical energy density [1,2]. However, structural and surface instabilities, coupled with complexities in the synthesis, have thus far prevented its commercialisation [3]. In this talk I will review our recent work towards the use of LiNiO2 as an actual cathode solution, via carefully controlled calcination conditions [4,5] and stabilization especially in terms of elemental substitution (doping) [6,7], but also of protective surface coating.To address issues with the material’s stability during synthesis and cycling, the use of an ammonium tungstate flux to modify both the LiNiO2 crystal structure and primary particle morphology without introducing additional steps into the synthesis will be discussed here in particular detail. The successful preparation of LiNiO2 modified with an industrially relevant amount of W (< 5 mol %) was confirmed using a combination of electron microscopy and synchrotron-based X-ray diffraction (XRD). Refinement of structural models against the data suggests tungsten dopant ions occupy the Ni site and concurrently induce migration of Ni2+ to the Li sites. Moreover, W enrichment at grain boundaries has been observed under some of the synthesis conditions. Variable temperature XRD was used to highlight the improved stability of the W-doped materials during the calcination at high temperatures. Electrochemical characterisation shows that W-doped LiNiO2 offers improved cycle life at the expense of little specific capacity. The structural consequences of tungsten doping on the behaviour of the material during electrochemical cycling was also investigated using operando XRD, showing reduced mechanical stress upon cycling. In conclusion, we will show that LiNiO2 modified by W with a simple route and no additional processing steps exhibits structural stability at high temperatures, offering a path towards the reliable synthesis of LiNiO2 with controlled morphology, improved chemomechanics and longer cycling life. Reference s : [1] Dahn et al., Structure and Electrochemistry of Li1+-yNiO2 and a New Li2NiO2 Phase with the Ni(OH)2 Structure, Solid State Ionics 1990, 44 (1-2), 87-97.[2] Rougier et al., Optimization of the composition of the Li1-zNi1+zO2 electrode materials: Structural, magnetic, and electrochemical studies, Journal of the Electrochemical Society 1996, 143 (4), 1168-1175[3] Bianchini et al., There and Back Again-The Journey of LiNiO2 as a Cathode Active Material. Angew. Chem., Int. Ed. 2019, 58, 10434−10458.[4] Kurzhals et al., The LiNiO2 Cathode Active Material: A Comprehensive Study of Calcination Conditions and their Correlation with Physicochemical Properties. Part I. Structural Chemistry, Journal of the electrochemical society, 2021, 168 (11) 110518.[5] Riewald et al., The LiNiO2 Cathode Active Material: A Comprehensive Study of Calcination Conditions and their Correlation with Physicochemical Properties. Part II. Morphology, Journal of the electrochemical society, 2022, 10.1149/1945-7111/ac4bf3[6] Goonetilleke et al., Single step synthesis of W-modified LiNiO2 using an ammonium tungstate flux, Journal of Materials Chemistry A 2022, 10.1039.D1TA10568J.[7] Weber et al., Tracing Low Amounts of Mg in the Doped Cathode Active Material LiNiO2, Journal of the electrochemical society, 2022, 10.1149/1945-7111/ac5b38.

Facile single step synthesis of Cu2ZnSnS4 thin films by sputtering from a single target and their electrical characterization

Facile deposition of ternary semiconducting Cu2ZnSnS4 (CZTS) thin films has been a challenge due to a very narrow range of single phase stability in the Cu-Zn-Sn-S system. While sputtering has been a very efficient method of growth of various optoelectronic thin films, the formation of secondary phases should be suppressed during sputter deposition of CZTS films. Differently with the reported studies on deposition of a precursor film followed by a delicately - controlled sulfurization process required for the formation of the kesterite CZTS phase, we demonstrate a single step synthesis route to grow phase pure CZTS thin films using a single elementary target with excess Cu by RF magnetron sputtering at a substrate temperature of 450 °C. The route did not require any post-deposition sulfurization. These films had an optical band gap of ~1.6 eV and white light sensitivity> 200% at a bias potential of 5 V, highly suitable for photovoltaic and photocatalytic activities. Detailed electro-impedance analyses from Nyquist, Bode and Mott-Schottky plots of a Mo/CZTS/Pt/electrolyte device revealed p-type conductivity with a flat band potential of 0.51 V (reversible hydrogen electrode), carrier concentration of 6.2 × 1017 cm−3 and a carrier life time as high as of ~17 μs.

(Digital Presentation) Modifying LiNiO2 with W Via a Single Step Synthesis Route

LiNiO2 has been long considered as a promising cathode material owing to its high practical energy density. However, structural and surface instabilities, coupled with complexities in the LiNiO2 synthesis, have thus far prevented its commercialisation. To address issues with the material’s stability during synthesis and cycling, the use of an ammonium tungstate flux is demonstrated here to modify both the LiNiO2 crystal structure and primary particle morphology without introducing additional steps into the synthesis. The successful preparation of LiNiO2 modified with an industrially relevant amount of W (< 5 mol %) was confirmed using a combination of electron microscopy and synchrotron-based X-ray diffraction (XRD). Refinement of structural models against the data suggests tungsten dopant ions occupy the Ni site and concurrently induce migration of Ni2+ to the Li sites. Moreover, W enrichment at grain boundaries has been observed under some of the synthesis conditions. Variable temperature XRD was used to highlight the improved stability of the W-doped materials during the calcination at high temperatures. Electrochemical characterisation shows that W-doped LiNiO2 offers improved cycle life at the expense of little specific capacity. The structural consequences of tungsten doping on the behaviour of the material during electrochemical cycling was also investigated using operando XRD, showing reduced mechanical stress upon cycling. In conclusion, we will show that LiNiO2 modified by W with a simple route and no additional processing steps exhibits structural stability at high temperatures, offering a path towards the reliable synthesis of LiNiO2 with controlled morphology, improved chemomechanics and longer cycling life.

The enhanced light harvesting performance of dye-sensitized solar cells based on ZnO nanorod-TiO2 nanotube hybrid photoanodes

In this study, TiO2/ZnO hybrid nanocomposites (TZ) were fabricated by two step synthesis route for potential applications as photoanode in dye sensitized solar cells (DSSC). Titania nanotubes were grown on titanium sheets by electrochemical oxidation. ZnO nanorods were decorated with hydrothermal method by equimolar (0.1 M) precursors on TiO2 nanotubes. Hydrothermal temperatures values were changed to find the optimal ZnO decoration density to increase photo conversion efficiency. The characterization of the photoanodes was made using FE-SEM, XRD and XPS techniques. The results show that hydrothermal reaction temperature can dramatically enhance the light harvesting performance of TZ photoanodes. The photo conversation efficiency of DSSC by TZ photoanode was reached 1.67 % for hydrothermal temperature of 130 °C which is twofold higher than that of DSSC by TiO2 nanotubes (0.81 %). The improvement in photo conversation conversion efficiency can be assigned to synergetic effect in TZ photoanode, lower recombination rate and charge transfer resistance.

Lubricious ionic polymer brush functionalised silicone elastomer surfaces

Infection, erosion of mucosal and uro-epithelial layers, tissue trauma and encrustation associated with catheterisation is still an issue faced by health-care professionals and patients – effecting patients subject to spinal cord injuries, chemotherapy and incontinence to name a few. Over the past decade efforts have been made to optimise catheter surfaces in an attempt to reduce the occurrence of trauma related complications during insertion. Organic and inorganic materials have been mooted as potential methods of reducing bio-film formation and increasing lubricity. The use of charged species has been further hypothesised as a potential method to reduce the occurrence of bio-film formation, reducing the need for therapeutic intervention. This study investigates the feasibility of functionalising silicone surfaces with charged ionic polymer brush technologies with the view to reduce urethral trauma and infection for indwelling and self-catheterisation devices. A simple three step synthesis route has been proposed, complimented by surface analysis and tribological assessment of the surfaces. The effects of initial monomer content on the functional outcomes of the surfaces has been investigated. Functionalisation of surfaces was seen to significantly reduce the hydrophobicity of the surfaces. A significant reduction in the coefficient of friction from μ = 0.4 to 0.005 for un-functionalised and functionalised surfaces, respectively, was seen. The speed dependence and effects of lubricant chemistry on the coefficient of friction have also been investigated.

Band gap engineering of niobate composites through incorporation of Ni2+ metal ions and its property evaluation

A simple low cost, two step synthesis route, based on hydrothermal and wet chemical synthesis techniques, has been successfully adopted to prepare pure and Ni2+ doped potassium niobate-sodium niobate (KNi x Nb1-x O3-NaNbO3, x = 0, 0.02, 0.1, 0.25, 0.50) composites (by equal weight percentage). The synthesized materials have been thoroughly analyzed through XRD, FTIR, and HRTEM techniques. Further, morphological analyses through FESEM have revealed existence of mixed morphology, comprising of rod-shaped and irregular spherical structures, in the system. Diffuse Reflectance (DR) UV-Vis spectroscopy has been used to analyze the band gap values of the synthesized materials, and it has been observed that Ni2+ doping has significantly reduced the band gap values of the composites. Methylene Blue (MB) photodegradation analyses under UV irradiation have revealed absence of significant variation in the photodegradation efficiency values of the materials (photocatalysts) on doping. Dielectric studies have revealed low dielectric constant (ɛr) and loss tangent (tan δ) values, indicating an alteration to the perovskite structure of the composite materials, which in effect leads to a possible intensification of the cento-symmetric nature of the individual constituent niobate materials and thus, weakens the dielectric response of the composites in the process.

One-step synthesis and microstructure of CuO-SDC composites

Abstract An in situ one step synthesis route based on the polymeric precursor method was used to produce dual phase CuO-samaria doped ceria (SDC) nanocomposite powders. This chemical route allowed to obtain composite powders with reduced particle size and uniform distribution of Cu, Ce and Sm elements. The particulate material was characterized by powder X-ray diffraction (XRD) combined with Rietveld refinement. CuO-SDC sintered in air between 950 to 1050 °C and subsequently reduced to Cu-SDC cermets were further characterized by XRD and scanning electron microscopy. The open porosity was measured using the Archimedes’ principle. Suitable microstructures for both charge transfer and mass transport processes (30 to 45% porosity) were attained in Cu-SDC cermets previously fired at 1000 to 1050 °C. Overall results indicated that CuO-SDC composites and Cu-SDC cermets with potential application as anodes for solid oxide fuel cells (SOFCs) can be obtained by microstructural design. An anode supported half-cell was prepared by co-pressing and co-firing gadolinia doped ceria (CGO) and the herein synthesized CuO-SDC nanocomposite powder.

Effect of Zn(NO3)2 concentration in hydrothermal–electrochemical deposition on morphology and photoelectrochemical properties of ZnO nanorods

Zn(NO3)2 concentration had been reported to be significantly influential on electrodeposition of ZnO structures. In this work, this issue is revisited using hydrothermal–electrochemical deposition (HED). Seedless, cathodic electrochemical deposition of ZnO films is carried out on ITO electrode at 130°C in a closed glass reactor with varying Zn(NO3)2 concentration. Regardless of the concentration of Zn2+ precursor (0.001–0.1M) in the deposition solution, vertically aligned 1-D ZnO nanorods are obtained as opposed to electrodepositions at lower temperatures (70–80°C). We also report the effects of high bath temperature and pressure on the photoelectrochemical properties of the ZnO films. Manipulation of precursor concentration in the deposition solution allows adjustment of the aspect ratio of the nanorods and the degree of texturation along the c-axis; hence photoinduced current density. HED is shown to provide a single step synthesis route to prepare ZnO rods with desired aspect ratio specific for the desired application just by controlling the precursor concentration.

Selected Nitrocarbamates of Glycerine &amp; Co. and the First Acetylene Derivative

Abstract A simple two step synthesis route for the preparation of several energetic multivalent nitrocarbamates of easily available alcohols is presented. The carbamates were obtained by the reaction of the alcohols and the reactive reagent chlorosulfonyl isocyanate (CSI) with subsequent aqueous work‐up. The nitration of the carbamates was performed with mixed acid (nitric and sulfuric acid). The thermal stabilities were explored by using differential scanning calorimetry and the energies of formation were calculated on the CBS‐4M level of theory, as well as several detonation and propulsion parameters for the application as energetic materials. All compounds were fully characterized and discussed in addition with single X‐ray diffraction.

Stereoselective synthesis of a natural product inspired tetrahydroindolo[2,3-a]-quinolizine compound library

A natural product-inspired synthesis of a compound collection embodying the tetrahydroindolo[2,3-a]quinolizine scaffold was established with a five step synthesis route. An imino-Diels–Alder reaction between Danishefsky’s diene and the iminoesters derived from tryptamines was used as a key reaction. Reductive amination of the ketone function and amide synthesis with the carboxylic acid derived from the ethyl ester, were used to decorate the core scaffold. Thus a compound library of 530 tetrahydroindolo[2,3-a]quinolizines was generated and submitted to European lead factory consortium for various biological screenings.

Tannic acid assisted one step synthesis route for stable colloidal dispersion of nickel nanostructures

We report here a one step synthesis route for highly stable colloidal dispersion of nickel (Ni) nanostructures in ethylene glycol (EG). tannic acid (TA), a naturally occurring molecule was used as reducing as well as capping agent. Different instrumental techniques were used to characterize the end product. It has been found that the particles are pure crystalline nickel with a face-centred-cubic (fcc) structure which are uniformly distributed throughout the surface of Ni–TA complex hybrid nanostructures resulting flower-like morphology. The synthesized nanoparticles are remarkably stable for several months. It is supposed that the TA-capped Ni nanoparticles with significantly increased stability and dispersibility could be used as a novel nanoscale material in various technological applications.

Physical property characterization of single step synthesized NdFeAsO0.80F0.20 bulk 50 K superconductor

We report an easy single step synthesis route of title compound NdFeAsO0.80F0.20 superconductor having bulk superconductivity below 50 K. The title compound is synthesized via solid-state reaction route by encapsulation in an evacuated (10-3 Torr) quartz tube. Rietveld analysis of powder X-ray diffraction data shows that compound crystallized in tetragonal structure with space group P4/nmm. R(T)H measurements showed superconductivity with T c (R = 0) at 48 K and a very high upper critical field (H c2) of up to 345 T. Magnetic measurements exhibited bulk superconductivity in terms of diamagnetic onset below 50 K. The lower critical field (H c1) is around 1000 Oe at 5 K. In normal state i.e., above 60 K, the compound exhibited purely paramagnetic behavior and thus ruling out the presence of any ordered FeO x impurity in the matrix. In specific heat measurements a jump is observed in the vicinity of superconducting transition (T c ) along with an upturn at below T = 4 K due to the AFM ordering of Nd+3 ions in the system. The Thermo-electric power (TEP) is negative down to T c , thus indicating dominant carriers to be of n-type in NdFeAsO0.80F0.20 superconductor. The granularity of the bulk superconducting NdFeAsO0.8F0.2 sample is investigated and the intra and inter grain contributions have been individuated by looking at various amplitude and frequencies of the applied AC drive magnetic field.

A Two Step Synthesis Route of WC Nanopowders

Here, a novel molten salt route to synthesize ceramic WC nanopowders was presented. Compared to the traditional synthesis procedures, this method is relatively low cost involving two-step synthesis route. In the argon atmosphere at 650 oC, the powders were the mixed WC and W2C phases. These synthesized powders were transferred to a small crucible (30 mL) containing molten salt, which were put into a 500 mL crucible with some carbon powder in it as reducing atmosphere, followed by maintaining the reaction temperature at 1100 °C for 1 h. The phase purity and composition were characterized by the powder X-ray diffractometer (XRD). It was found that W2C was transformed thoroughly into WC, which indicated the successful synthesis of WC powders using this method. The mechanism of the reaction process in molten salt has been discussed finally. The thermogravimetric analysis indicated that the as-prepared samples showed good thermal stability and oxidation resistance in high temperature. The methodology reported in this work was fundamentally important, which may find potential industrial applications.

Synthesis of phthalocyanine stabilized rhodium nanoparticles and their application in biosensing of cytochrome c

A single step synthesis route is described for the preparation of rhodium nanoparticles using a cobalt aminophthalocyanine macrocyclic complex as a stabilizer. The results of nanoparticles characterization using electronic absorption, Raman and X-ray spectroscopes as well as transmission electron microscopy are reported. Rhodium nanoparticle modified electrode behavior as examined by cyclic and differential pulse voltammetry is also provided. The nanoparticles were found to be well dispersed and stabilized throughout the macromolecular matrix. TEM studies showed that they have an average diameter of 3 to 5 nm with spherical shape. The colloidal rhodium was then used for electrochemical sensing of cytochrome c using glassy carbon electrode. The results showed that the colloidal rhodium nanoparticles enhanced the electron transfer process between cytochrome c and the electrode. Differential pulse voltammetric measurements of cytochrome c at the colloidal rhodium nanoparticles modified glassy carbon electrode showed a linear relationship with the oxidation peak currents in the concentration range of 100 nM to 3 μM of cytochrome c.

High Surface and High Nanoporosity Boron Nitride Adapted to Hydrogen Sequestration

High surface area nanoporous powders of hexagonal boron nitride (h-BN) have been prepared from molecular precursors to be used for hydrogen sequestration. The more promising samples were obtained using a precursor derived from trichloroborazine (TCB). The precursor was first reacted with ammonia at room temperature leading to the molecular complex Cl3B3N3H3, 6 NH3 which was heated up to 650 °C under ammonia and then up to 1000 °C under nitrogen, giving rise to a high reactive h-BN powder. This crude powder was stabilised by an annealing up to 1800 °C under nitrogen atmosphere leading to a very stable compound exhibiting a specific area of more than 300 m2·g-1 and presenting a very specific nanometric spherical texture. Some samples were doped with platinum (about 1 wt.%) to enhance the activity of pure h-BN using an original one step synthesis route starting from a mixture of BN and Pt precursors. Attempts to sequester hydrogen into these powders were made successfully at -196 °C under 10 MPa, but the stored amount was only about 0.3 wt.% and the platinum added BN powders did not lead to an enhancement of the storage capacity.

Synthesis of amino-functionalized mesoporous silica–zirconia mixed oxide using sodium silicate and zirconium carbonate complex

Amino-functionalized mesostructured silica–zirconia mixed oxide has been synthesized through a very convenient one step synthesis route using water soluble sodium silicate, zirconium(IV) carbonate complex and 3-aminopropyltriethoxysilane in the presence of anionic surfactant sodium dodecyl sulphate under basic condition, exhibiting excellent adsorption properties towards arsenate ions. Moderately high surface area has been achieved using Si/Zr ratio 2.06 and 10 mol% 3-aminopropyltriethoxysilane with respect to the amount of silica. The presence of mixed oxide framework is clearly visible from the peak shift of Si–O–Si stretching frequency in FTIR spectra. The S BET and pore volume of the composite was found to be 420 m 2 g −1 and 0.4396 ml g −1 respectively with uniform and narrow pore size distribution centered at 42.8 Å. The mesoporous composite showed good absorption properties towards arsenate anion and anionic dye molecules.

Highly enantioselective synthesis of a fluorescent amino acid

A high enantiomeric excess (>99.5%) synthesis of l-2-amino-3-(7-methoxy-4-coumaryl) propionic acid (l-Amp) is described. The two step synthesis route of this non-proteinogenic amino acid includes an oxazinone derivative as glycine enolate, which is alkylated with the fluorogenic group.

Synthesis of N‐tert‐butyl‐α‐(4‐[18F]fluorophenyl)‐nitrone ([18F]FPBN) for in vivo detection of free radicals

AbstractWe have synthesized the fluorine‐18 labeled derivative of N‐tert‐butyl‐α‐phenylnitrone (PBN), a free radical spin trapping agent widely used with electron spin resonance (ESR). N‐tert‐Butyl‐α‐(4‐[18F]fluorophenyl)‐nitrone ([18F]FPBN) could be prepared with low radiochemical yield (3% decay corrected) by the direct aromatic nucleophilic substitution of N‐tert‐butyl‐α‐(4‐nitrophenyl)nitrone with [18F]fluoride. An alternate two step synthesis route consisted of the nucleophilic [18F]fluoride substitution of 4‐N, N, N‐trimethylammoniumbenzaldehyde triflate to yield 4‐[18F]fluorobenzaldehyde, which was distilled into a vial containing N‐tert‐butyl‐hydroxylamine in 2N NaOH. 4‐[18F]Fluorobenzaldehyde readily reacted with the hydroxylamine to form [18F]FPBN. [18F]FPBN was obtained in overall decay corrected yields of 24% in a total synthesis time &lt; 45 min. and was suitable for further applications in in vivo studies of free radicals.