Single-source Precursor Research Articles

High temperature stable amorphous SiBCN microwave absorption ceramics derived from one-pot synthesis of single-source precursors

Silicoboron carbonitride (SiBCN) ceramics are developed as microwave absorption material for high-temperature environments under multicomponent doping and in-situ crystallization. In this study, amorphous SiBCN microwave absorption ceramics was derived from single-source hyperbranched polyborosilazanes containing benzene rings synthesized by the one-pot method. The carbon element and ordered carbon ratio of the pyrolyzed SiBCN ceramics enhanced with an increase in the proportion of dichlorodiphenylsilane. By adjusting the monomer ratio and pyrolysis temperature of ceramic precursor, the polymer derived ceramics (PDCs) could achieve good microwave absorption properties while remaining amorphous, with minimum reflection coefficient (RCmin) up to -30.79 dB and maximum effective absorption bandwidth (EABmax) up to 4.07 GHz. Meanwhile, the PDC-SiBCN ceramics exbibited outstanding high temperature stability with essentially no mass loss in argon (Ar) and air atmospheres until 1400 °C. This novel, convenient PDC-SiBCN preparation with potential for scaled-up production provides new ideas for microwave absorption materials for applications in extreme environments.

Polymer‐Derived Ceramic Coatings with Excellent Thermal Cycling Stability

In the present work, transition metal‐containing preceramic silicon polymers were synthesized via chemical modification of a commercially available organopolysilazane with Hf and Ta amido complexes as well as with borane dimethyl sulfide complex. The incorporation of transition metals into the polymer structure, their influence on ceramization and processability were thoroughly investigated. Moreover, the prepared preceramics were coated onto silicon wafers via spin coating and converted into crack‐free, amorphous SiHfTa(B)CN‐based ceramic coatings with excellent adhesion to the substrate. The composition of the ceramic coatings was investigated via X‐ray photoelectron spectroscopy (XPS) and their high‐temperature behavior was studied via oxidation tests performed at 1100 °C. Moreover, a thermal cycling procedure to temperatures above 1250 °C with rapid heating and cooling rates (i.e., in the range of 100–120 K s−1) was applied to the ceramic coating, which showed no damage even after ten thermal cycles, indicating their outstanding performance and their potential for use as environmental barrier coatings at high temperatures.

Development of Molybdenum trioxide (MoO3) by spin coating method for photovoltaic application

Molybdenum trioxide, MoO3 , thin films have been deposited on glass substrates by Spin-coating method using ammonium heptamolybdate tetrahydrate ((NH4 )6Mo7O244H2O ) as a single source precursor of Mo and O and. They were subjected to atmospheric heat treatment at different temperatures (200°C, 400°C and 500°C). MoO3 thin films obtained, were characterized using X-ray diffraction techniques (XRD), Scanning Electron Microscopy (SEM), Energy Dispersed Spectroscopy (EDS) and integrating sphere. The XRD patterns of annealed films show the formation of ΜοΟ3 in a polycrystalline phase, formation of MoO3 was also confirmed by EDS. The SEM photographs show that the thin films obtained are in layer-type structure and their grains size increases with increasing of annealing temperatures. The measurement results of integrating sphere show that the MoO3 thin film prepared at 500°C transmit about 72% and reflect about 12% of the visible spectrum.

Ag-Fe2O3 nanocomposites for synergistically enhanced antibacterial activity

Doping of metal or metal ions in the host lattice with good dopant distribution or forming a local contact boosts materials properties for specific applications. This work used the solution combustion approach (SCA) to synthesize Ag-Fe2O3 nanocomposites (SICs) following the single-source precursor doping strategy with good final material stoichiometry. The elemental distribution and composition, crystallinity, and morphology of SCA-based synthesized materials were analyzed using common techniques such as TEM, FESEM-EDS, and XRD. Even though the Lewis hard and soft acids and bases (HSAB) idea was precise for inclusion of Ag dopant in the Fe2O3 lattice, the formation of Schottky junctions between Ag and Fe2O3 is dominance as a result of dopant-host radii size differences. The independent peak for both Ag and Fe2O3 crystals on the XRD pattern analysis without peak shift confirms the dominance of Schottky junction formation. The presence of local contact between Ag and Fe2O3 was also confirmed by the HRTEM analysis, with d-spacing values of 0.22 and 0.36 nm, respectively. Compared to the bare Fe2O3, the antibacterial potential of the SIC is much greater, with a 23-mm zone of inhibition on Pseudomonas aeruginosa gram-negative bacteria, which confirms the presence of a synergistic effect.

Synthesis of Iron Oxide Nanoparticles Using Potassium Trioxalatoferrate[III] as a Single Source Precursor and its Application for Degradation of Organic Dyes

Synthesis of Iron Oxide Nanoparticles Using Potassium Trioxalatoferrate[III] as a Single Source Precursor and its Application for Degradation of Organic Dyes

A sustainable CVD approach for ZrN as a potential catalyst for nitrogen reduction reaction.

In pursuit of developing alternatives for the highly polluting Haber-Bosch process for ammonia synthesis, the electrocatalytic nitrogen reduction reaction (NRR) using transition metal nitrides such as zirconium mononitride (ZrN) has been identified as a potential pathway for ammonia synthesis. In particular, specific facets of ZrN have been theoretically described as potentially active and selective for NRR. Major obstacles that need to be addressed include the synthesis of tailored catalyst materials that can activate the inert dinitrogen bond while suppressing hydrogen evolution reaction (HER) and not degrading during electrocatalysis. To tackle these challenges, a comprehensive understanding of the influence of the catalyst's structure, composition, and morphology on the NRR activity is required. This motivates the use of metal-organic chemical vapor deposition (MOCVD) as the material synthesis route as it enables catalyst nanoengineering by tailoring the process parameters. Herein, we report the fabrication of oriented and facetted crystalline ZrN thin films employing a single source precursor (SSP) MOCVD approach on silicon and glassy carbon (GC) substrates. First principles density functional theory (DFT) simulations elucidated the preferred decomposition pathway of SSP, whereas ab initio molecular dynamics simulations show that ZrN at room temperature undergoes surface oxidation with ambient O2, yielding a Zr-O-N film, which is consistent with compositional analysis using Rutherford backscattering spectrometry (RBS) in combination with nuclear reaction analysis (NRA) and X-ray photoelectron spectroscopy (XPS) depth profiling. Proof-of-principle electrochemical experiments demonstrated the applicability of the developed ZrN films on GC for NRR and qualitatively hint towards a possible activity for the electrochemical NRR in the sulfuric acid electrolyte.

The Novel Simple Path for Preparation of Fe3O4, ZnO, NiO and Co3O4 Nano-Crystallites Using Curcumin Transition Metal Complexes as Single-Source Precursors (SSP) and their Antimicrobial Activity

The Novel Simple Path for Preparation of Fe3O4, ZnO, NiO and Co3O4 Nano-Crystallites Using Curcumin Transition Metal Complexes as Single-Source Precursors (SSP) and their Antimicrobial Activity

A chemically induced, room temperature, single source precursor to CuS (covellite) nanomaterials: synthesis and reactivity of [Cu(S2CNHBz)]n.

Addition of two equivalents of NaS2CNHBz to CuSO4 affords the yellow diamagnetic coordination polymer [Cu(S2CNHBz)]n (1), resulting from intramolecular electron-transfer and concomitant formation of the thiourea, (BzNH)2CS. 1 reacts with PPh3 and 1,1'-bis(diphenylphosphino)ferrocene (dppf) in CH2Cl2 to give monomeric [Cu(κ2-S2CNHBz)(PPh3)2] (2) and [Cu(κ2-S2CNHBz)(κ2-dppf)] (3), respectively, both of which have been crystallographically characterised. While 1 is thermally stable in dimethylsulfoxide (DMSO) up to ca. 70 °C, addition of nBuNH2 to 1 leads to its rapid decomposition to afford CuS (covellite) nanomaterials; indeed in neat nBuNH2, covellite formation is rapid at room temperature. Thus, 1 serves as an effective low-temperature base-induced single source precursor to covellite nanomaterials.

(Ph3P)2Ag(μ-SeCH2Ph)2In(SeCH2Ph)2]: a new heterobimetallic single source precursor as a springboard to bulk, nano and thin film ternary AgInSe2 materials

A new heterobimetallic complex [(Ph3P)2Ag(μ-SeCH2Ph)2In(SeCH2Ph)2] was structurally characterized and utilized as an air and moisture stable versatile single source precursor for AgInSe2 materials.

1,2-Bis-(diphenylphosphino)ethane (dppe) appended cobalt(iii)-dithiocarbamates as single source precursors of cobalt sulfide/cobalt phosphide composites: apt electrocatalytic materials for water splitting reactions

Three new heteroleptic Co(iii)dppe dithiocarbamates were synthesized and employed as single source precursors of cobalt sulfide/cobalt phosphide nanocomposites that were used as electrocatalysts for the OER and HER.

Self-reducing precursors for aluminium metal thin films: evaluation of stable aluminium hydrides for vapor phase aluminium deposition.

Thin films of Al as interconnect materials and those of AlN as wide bandgap semiconductor and piezoelectric material are of great interest for microelectronic applications. For the fabrication of these thin films via chemical vapor deposition (CVD) based routes, the available precursor library is rather limited, mostly comprising aluminium alkyls, chlorides, and few small amine-stabilized aluminium hydrides. Herein, we focused on rational precursor development for Al, their characterization and comparison to existing precursors comprising stabilized aluminium hydrides. We present and compare a series of potentially new and reported aluminium hydride precursors divided into three main groups with respect to their stabilization motive, and their systematic structural variation to evaluate the physicochemical properties. All compounds were comprehensively characterized by means of nuclear magnetic resonance spectroscopy (NMR), Fourier-transform infrared spectroscopy (FTIR), elemental analysis (EA), electron-impact ionization mass spectrometry (EI-MS) and thermogravimetric analysis (TGA). Promising representatives were further evaluated as potential single source precursors for aluminium metal formation in proof-of-concept experiments. Structure and reaction enthalpies with NH3 or H2 as co-reactants were calculated via first principles density functional theory simulations and show the great potential as atomic layer deposition (ALD) precursors for Al and AlN thin films.

Insights into the nucleation and growth of BiOCl nanoparticles by in situ X-ray pair distribution function analysis and in situ liquid cell TEM.

The synthesis of bismuth oxyhalides as defined nanostructures is hindered by their fast nucleation and growth in aqueous solutions. Using our recently developed single-source precursor, the formation of bismuth oxychloride in such solutions can be slowed significantly. As reported herein, this advance enables BiOCl formation to be investigated by in situ X-ray total scattering and in situ liquid cell transmission electron microscopy. In situ pair distribution function analysis of X-ray total scattering data reveals the local order of atomic structures throughout the synthesis, while in situ liquid cell transmission electron microscopy allows for tracking the growth of individual nanoparticles. Through this work, the precursor complex is shown to give rise to BiOCl upon heating in solution without the observation of structurally distinct intermediates. The emerging nanoparticles have a widened interlayer spacing, which moderately decreases as the particles grow. Mechanistic insights into the formation of bismuth oxyhalide nanoparticles, including the absence of distinct intermediates within the available time resolution, will help facilitate future design of controlled BiOX nanostructures.

Zinc and cadmium thioamidate complexes: rational design of single-source precursors for the AACVD of ZnS.

A series of zinc(II) thioamidate complexes [Zn{SC(iPr)NR}2]n for R = iPr (n = 2) (2), tBu (3) (n = 1), Ph (4) (n = 2) and Cy (5) (n = 2) and one cadmium(II) thioamidate complex [Cd{SC(iPr)NtBu}2]3, (6), were designed and synthesised as single-source precursors for AACVD ZnS and CdS. Solid-state structures of all four zinc(II) compounds revealed distorted tetrahedral or trigonal bipyramidal geometries, with varying tendencies for dimeric association, mediated by {Zn-S} bridging bonds. The thermogravimetric analysis identified the {tBu} derivertive, 3, as the most promising precursor based on its low decomposition onset (118 °C) and clean conversion to ZnS. This was attributed to the greater availability of β-hydrogen atoms promoting the pyrolysis mechanism. The corresponding cadmium thioamide 6 was found to crystallise as a trimetallic molecule which lacked the thermal stability to be considered viable for AACVD. Hence, 3 was used to deposit ZnS thin films by AACVD at 200-300 °C. Powder X-ray diffraction confirmed phase-pure growth of hexagonal wurtzite ZnS, with approximate crystallite sizes of 15-20 nm. Scanning electron microscopy revealed densely packed spherical nanoclusters. The morphology and crystallinity were most consistent for depositions between 250-300 °C. Energy dispersive X-ray spectroscopy indicated slightly sulfur-deficient stoichiometries.

Formation of uranium disulfide from a uranium thioamidate single-source precursor.

A single-source-precursor approach was developed to synthesize uranium-based materials outside of the typically-studied oxides. This approach allows for shorter reaction times, milder reaction conditions, and control over the chemicals present in synthesis. To this end, the first homoleptic uranium thioamidate complex was synthesized as a precursor for US2 materials. Pyrolysis of the thioamidate results in decomposition via an alkene elimination pathway and formation of γ-US2, which has historically been hard to access without the need for a secondary sulfur source. Despite the oxophilicity of uranium, the method successfully forms US2 without the inclusion of oxygen in the bulk final product. These findings are supported by simultaneous thermal analysis, elemental analysis, powder X-ray diffraction, and uranium L3-edge X-ray absorption fine-structure spectroscopy. This work represents the first example of a single-source precursor approach to target and synthesize actinide materials other than the oxides.

Aerosol-Assisted Chemical Vapor Deposition of 2H-WS2 From Single-Source Tungsten Dithiolene Precursors.

The tungsten carbonyl dimethyldithiolene (dmdt) complexes W(CO)4(dmdt), W(CO)2(dmdt)2, and W(dmdt)3 were evaluated as potential single-source precursors for the chemical vapor deposition of WS2. The results of TGA-MS, DIP-MS, and pyrolysis with NMR analysis were consistent with a thermal decomposition pathway in which loss of 2-butyne through a retro[3+2]cycloaddition of the dithiolene ligand generated terminal sulfido ligands. Aerosol-assisted chemical vapor deposition onto silicon substrates was performed using all three complexes, yielding 2H-WS2 thin films as characterized by Raman spectroscopy and GI-XRD. Film morphology and elemental composition of the films were determined using SEM, EDS, and XPS. Four-point probe measurements afforded a film resistivity of 8.37 Ωcm for a sample deposited from W(dmdt)3 in toluene at 600 °C.

A soft molecular single-source precursor approach to synthesize a nanostructured Co9S8 (pre)catalyst for efficient water oxidation and biomass valorization

A nanocrystalline Co9S8 (pre)catalyst derived from a novel {CoIIS4} complex is reported for the oxygen evolution reaction (OER) and selective biomass valorization. During OER, Co9S8 reconstructs completely into a CoOOH active phase via S-leaching.

Ultralow-content Pt nanodots/Ni3Fe nanoparticles: interlayer nanoconfinement synthesis and overall water splitting.

Minimizing precious metal loading into electrocatalysts for water splitting is vital to promoting hydrogen energy technology toward practical applications. Low-content loading of precious-metal electrocatalysts is achieved by decorating precious metal nanostructures on co-electrocatalysts typically via surface confinement. Here, an electrocatalyst of ultralow-content Pt nanodots (0.71 wt%)/Ni3Fe nanoparticles on reduced oxidation graphene (Pt/Ni3Fe/rGO) is constructed for overall water splitting by pyrolyzing a single-source precursor PtCl63- guest-intercalated MgNiFe-layered double hydroxide (MgNiFe-LDH) host via a distinctive interlayer confinement. Consequently, Pt/Ni3Fe/rGO demonstrates attractive overpotentials of 240 and 76 mV at 10 mA cm-2 for the oxygen and hydrogen evolution reactions (OER and HER), respectively, outperforming those of its /Ni3Fe/rGO counterpart. Moreover, the Pt/Ni3Fe/rGO∥Pt/Ni3Fe/rGO electrolyzer generates a current density of 10 mA cm-2 at 1.55 V, with a retention of 92.4% after 50 h. Furthermore, the measured specific activity and low transfer resistance, as well as the density functional theory (DFT) calculations, indicate that the active Pt/Ni3Fe in Pt/Ni3Fe/rGO can optimize the adsorption/desorption of reaction intermediates and thus boost OER/HER kinetics, all of which lead to enhanced performance. The results demonstrate that such an interlayer confinement-based synthesis strategy can allow for the design of cost-effective precious nanodots as potential electrocatalysts.

Electrodeposition of Transition Metal Dichalcogenide Thin- Films from Non-Aqueous Solvents

Transition metal dichalcogenides (TMDCs) are an interesting group of 2D materials characterised with a layered structure analogous to graphene and they possess unique electronic and optical properties, especially when in the few- and mono-layer form. Developing scalable techniques for depositing TMDCs is a major challenge which needs to be overcome to fabricate functional devices with these materials. Electrodeposition is an industrially relevant technique that has some key advantages over other conventional deposition methods. It is a low cost and easily scalable technique and could be used for obtaining complex nanoscale features and for depositing over topologically demanding surfaces. Even though the electrodeposition of MoS2 has been achieved both in aqueous and non-aqueous electrolytes, not much progress has been made in the deposition of other TMDC materials. Tungsten based TMDCs such as WS2 and WSe2 are shown to be very promising materials in different applications, however electrodepositing them remains extremely challenging. One of the major obstacles here is developing electrochemically active precursors which are compatible with the electrolyte system and able to deliver both the tungsten and chalcogens to the electrolyte. Controlling and optimizing the deposition process to obtain few- and mono-layer TMDCs is another challenge. In addition, the choice of substrates for deposition is very important, especially for direct growth of ultra-thin TMDCs. Electrodeposition, being a bottom-up deposition method, would benefit from an atomically thin and smooth substrate such as graphene for depositing few- and mono-layer TMDCs.Here we present non-aqueous electroplating as a scalable alternative technique for tungsten-based TMDC deposition, with WS2 and WSe2 as examples. Tailored single source precursors were developed to use in non-aqueous electrolytes. WS2 was electrodeposited from dichloromethane (CH2Cl2) using the [NEt4]2[WS2Cl4] precursor. WSe2 was then electrodeposited from acetonitrile (CH3CN) electrolyte using [WSeCl4] as the precursor. Electrochemical quartz crystal microbalance (EQCM) studies were performed to optimize the deposition process and to probe the mechanism of precursor electrochemistry. Electrochemical deposition parameters were then carefully adjusted to obtain few- and mono-layer TMDCs. Patterned graphene electrodes were used as an atomically thin and smooth platform for the deposition of few- and mono-layer WS2. Few-layer TMDC films obtained on graphene were found to be much smoother than films deposited on other standard substrates such as titanium nitride (TiN) or Pt. These TMDC/graphene structures gave interesting 2D heterostructures which are technologically important for different applications.This work was funded by EPSRC grant references EP/V062689/1, EP/V062387/1 and EP/P025137/1

Unconventional Synthesis of Metal (Ni, Co, Ag) Antimony Alloy Particles.

Bimetallic alloy materials attract interest owing to their properties and stability compared to pure metals, especially alloys with nanoscale dimensions. Metal antimony (MSb) alloys, specifically NiSb, are widely used for charge storage applications due to their high stability. Most synthetic approaches to form these materials require drastic conditions (e.g., high temperatures, potent reducing agents, and extended reaction times), limiting control over the final morphology. The other viable approach is a galvanic replacement that uses unstable materials as precursors. In this work, we present a new and facile method to prepare several MSb (M = Ni, Co, Ag) alloys with shape control by reacting Sb2S3 particles with a metal(M)-sulfide single source precursor in trioctylphosphine (TOP) under mild conditions. Furthermore, we explore the role of TOP as a reducing agent and demonstrate how both alloy constituents are crucial for mutual stabilization. Electrochemical studies are also performed on these NiSb particles, showing their ambipolar nature and allowing their utilization as the active ingredient in the demonstrated high-energy-density symmetric supercapacitor.

Green synthesis and structural and cytotoxic properties of a new silver(I) complex: Solid-state, single-source precursor of Ag and Ag2O NPs

A new silver complex, [Ag(2-pymc)(NO3)] (Ag-1) [2-pymc = methyl-2-(pyridine-2yl-methylene) hydrazinecarboxylate], was prepared and subjected to elemental analysis including Fourier transform infrared (FT-IR) and ultraviolet–visible (UV–vis) spectroscopic methods. Single-crystal X-ray diffraction (SC-XRD) study demonstrated [Ag(2-pymc)(NO3)] monomers in the crystal structure. The silver ion is triple coordinated by an N, N-chelating 2-pymc and one oxygen atom of a monodendate nitrate anion. Interestingly, Ag-1 acted as a single-source, solid-state molecular precursor (SSMP) for synthesizing both Ag and Ag2O nanoparticles (NPs) at different reaction conditions. The crystallinity and purity of the as-synthesized Ag and Ag2O NPs were investigated by powder XRD, whereas the size and surface morphology were determined by TEM analysis. The results showed that the formed Ag NPs were well dispersed and spherically shaped with an average diameter of 30–32 nm. The Ag2O NPs were not homogeneous but showed irregular shapes with an average diameter of 40–42 nm. Ag-1 showed antibacterial activity against selected Gram-positive (Bacillus megaterium) and Gram-negative (Pseudomonas Stutzeri) bacteria. The cytotoxicity of Ag-1 against MCF-7 cancer cells was also tested.