Precursor Route Research Articles

Exploiting multiferroicity of TbFeO3 nanoparticles for hydrogen generation through photo/electro/photoelectro-catalytic water splitting

Hydrogen is a potential future energy source that could replace conventional fuel and provide the necessary energy. Multiferroic materials are the most likely choices for water splitting due to their ferroelectric characteristics and ability to function as magnetically recoverable catalysts. Multiferroic terbium orthoferrite nanoparticles were synthesized at low temperature by the polymeric citrate precursor route to study the photocatalytic, electrocatalytic and photoelectrochemical activity towards hydrogen production. Powder X-ray diffraction revealed successful formation of orthorhombic TbFeO3 nanoparticles. A larger aspect ratio of 3.9 and a bandgap of 2.13 eV were seen in the elongated TbFeO3 nanoparticles, which contributes to the photo/electro-catalytic activity. Magnetic and ferroelectric studies revealed weak ferromagnetism and ferroelectric polarization of 0.037 μC cm−2 in TbFeO3 nanoparticles, confirming multiferroicity. Visibly active and multiferroic TbFeO3 nanoparticles showed notable hydrogen evolution of 1.44 mmol h−1 g−1. In electrocatalytic and photoelectrochemical water splitting investigations, TbFeO3 nanoparticles demonstrated current densities of 30 and 60 mA cm−2, respectively. EIS, TRPL, transient photocurrent and Mott-schottky measurements were used to examine charge transfer kinetics. The high H2 evolution and good OER/HER tests were attributed to increased charger separation efficiency due to ferroelectricity induced band bending.

The formation of SnS nanorods orthorhombic phases grown from different molecular precursors

The high theoretical ability of the tin sulfide (SnS) semiconductor makes it a potential material for solar cell applications. However, employing an environmentally friendly and cost-effective framework for the synthesis of SnS sustainable materials is essential. The attraction of the single-source precursor (SSP) route of preparing flexible nanostructured metal sulfide is due to its simplified procedures, high efficiency, fewer reagents and scale-up abilities. In this study, SSP route was used to prepare SnS nanoparticles with tunable sizes and better morphologies from three molecular precursors. XRD shows the structural characteristics of the three samples confirm the presence of orthorhombic phases for SnS1, SnS2 and SnS3. HRTEM images for SnS2 and SnS3 display irregular orthorhombic phases with an average size of 17.11 nm and 3.38–4.19 nm as compared to SnS1, which reveals a spherical structure and a grain size of 2.22–3.33 nm. There have been very few studies that have established nanorods SnS, but none from a single molecular precursor.

Enhancing of Electrical and Dielectric Properties of Barium Zirconate Titanate/Poly (Vinylidene Fluoride) Nano-Composites

The effects of poly (vinylidene fluoride, PVDF) on barium zirconate titanate nanoparticles has been studied. Different concentrations of (BZT-PVDF) nanocomposites using the formula [x (PVDF)/(1 − x) BZT] (where x = zero, 0.2, 0.4, 0.6, 0.8 and 1) were prepared using the hot pressing method. The BZT nanoparticle was prepared using the tartrate precursor route method. The Dc resistivity as a function of reciprocal temperature (1000/T) K−1 for the composite samples has been studied. The dielectric constant (ε) increases with the amount of BZT, which can be described as the increase of interfacial space charge polarization between (PVDF-BZT) nano-composites and the increase in the ionic mobility of the polymer. The ferroelectric hysteresis of prepared nano-composites has been investigated. The increase of BZT content raises the slope of the hysteresis loop and hence the dielectric polarization, which may be attributed to the dominance of smaller grain size and tetragonality. The increasing in dielectric properties for the prepared samples is very useful in industrial applications, such as sensors, actuators and transducers.

Vertically aligned Gd2O2SO4:Ln and Gd2O2S:Ln luminescent films with super-hydrophobicity via a novel precursor route (Ln = Pr, Eu, Tb)

Pr3+, Eu3+ and Tb3+ activated Gd2O2S (Gd2O2S:Ln), either in the powder or ceramic form, are well known for their wide applications in photoluminescence (PL), cathodoluminescence (CL) and X-ray excited luminescence (XEL) due to high efficiency. The film form of Gd2O2S:Ln, however, has not been reported up to date to the best of our knowledge. By hydrothermally reacting Gd(NO3)3, (NH4)2SO4 and urea, this work produced a Gd2(OH)2CO3SO4·H2O new compound (GOCSH) that was crystallized in the tetragonal system (space group P-421m) with a layered structure along the [001] crystallographic direction. Furthermore, macroscopically and microscopically uniform GOSCH:Ln films, constructed by vertical self-alignment of platelike crystallites, were successfully fabricated by applying heterogenous nucleation on quartz substrate. Taking the advantage of the exactly the same S/(Gd,Ln) molar ratio, Gd2O2SO4:Ln and Gd2O2S:Ln films of the same microstructures were then derived from the GOSCH:Ln films by annealing in air and hydrogen at 800 °C, respectively, without any additional sulfurization. The mechanism of film formation and the influence of deposition/annealing temperature on film quality were discussed. Aside from luminescence, the films all have microstructure-enabled super-hydrophobicity and are transparent in the visible light region (∼70–93%). The multi-functional films, particularly those of Gd2O2S:Ln, may find potential application in luminescence, display, scintillation and microimaging.

Synthesis and characterization of Ca substituted Ni-Zn nanoferrites- microstructural, magnetic and dielectric analysis

A series of cubic spinel structured, nanocrystalline and monophasic samples of the composition CaxNi0.4Zn0.6−xFe2O4 (x = 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) samples were synthesized via a chemical citrate precursor route, sintered at 700 °C. Raman and X-Ray Diffraction (XRD) investigations confirmed the single-phase cubic spinel configuration of the nanoferrites. A study of linearly fitted Williamson-Hall plots obtained using XRD data revealed the spinel structure of the prepared samples with the minute structural disorder wherein low values were estimated for lattice strain, ε, (0.003 × 10−3 −1.66 ×10−3) and dislocation density, δ, (0.665 × 10−3-1.73 × 10−3) for different Ca concentrations. The nanoferrites of Ca-doped Ni-Zn were found to be highly magnetic when subjected to a maximum applied field of 20 kOe under VSM investigations. Nanoferrite composition with x = 0.4 exhibited the maximum magneto-crystalline anisotropy constant (11452), remanent magnetization (22 emu/g), and coercivity (199.91 Oe) while maximum saturation magnetization (65.27 emu/g) and magnetic moment (2.756 μB) were found for the Ca0.1Ni0.4Zn0.5Fe2O4 composition. The samples were synthesized to explore their utilization in storage devices and high-frequency devices.

Defect‐Decorated NiFe Bimetallic Nanocatalysts for the Enhanced Hydrodeoxygenation of Guaiacol

AbstractSeries of Ni‐based nanocatalysts were fabricated for the HDO of lignin‐derived guaiacol to cyclohexane via a single‐source Ni−Fe−Al layered double hydroxide precursor route and characterized by XRD, BET, TEM, XAS, XPS, H2‐TPR, H2‐TPD, NH3‐TPD, and pyridine absorbed in situ FT‐IR. As‐fabricated bimetallic NiFe nanocatalyst bearing a Fe/Ni molar ratio of 0.5 : 3 attained a higher cyclohexane yield of 70.5 % under mild reaction conditions (i. e., 230 °C and 1.0 MPa of initial hydrogen pressure), compared to monometallic Ni and other NiFe bimetallic nanocatalysts, as well as monometallic Ni and bimetallic NiFe catalysts prepared by the impregnation method. Combination of experimental results and density functional theory calculations manifested that interfacial FeOx species profoundly facilitated the demethoxylation processes of guaiacol and 2‐methoxycyclohexanol intermediate, while both bimetallic NiFe sites and interfacial FeOx species greatly promoted the dehydroxylation of cyclohexanol intermediate.

Optoelectronic Modulation of Silver Antimony Sulfide Thin Films for Photodetection.

Silver antimony sulfide, as a ternary chalcogenide, has attracted great attention in the field of optoelectronics in recent years. In particular, it has appealing properties, such as excellent stability, solution processability, and versatile composition tunability. Benefiting from the recent development of processing techniques, AgSbS2 has emerged as a promising candidate for next-generation, thin-film photovoltaics. On the contrary, AgSbS2-based photodetectors have been barely reported. In this work, we systematically investigated the composition engineering of silver antimony sulfide compounds with a precursor route. Their optoelectronic properties were fully characterized, and the composition was optimized for photodetection. High-performance phototransistors were first reported based on field-effect thin film transistors with interfacial modification. The obtained AgSbS2 phototransistors exhibited relatively high photosensitivity, low dark current and noise, superior device stability, and excellent detectivity covering the whole range from ultraviolet to near-infrared, highlighting the great potential for next-generation photodetection.

Realizing load bearing-heat insulation integration of lightweight porosity-controlled SiC(rGO) bulk ceramics via precursor route for hypersonic vehicles

Realizing integration of admirable load bearing and outstanding heat insulation characteristics of porosity-controlled ceramics for hypersonic vehicles is a great challenge. Herein, an ingenious strategy based on re-pyrolysis process of ball-milling-induced fillers/precursors(pore-forming agents) blends is proposed to prepare porous SiC(rGO) bulk polymer-derived ceramics (PDCs) for thermal protection. During re-pyrolysis, dense integrated β-SiC/SiOxCy/Cfree(rGO) framework, belonging to SiC(rGO)p tightly tied by SiC(rGO) from polycarbosilane-vinyltriethoxysilane-graphene oxide (PCS-VTES-GO, PVG), can be formed to maintain brilliant mechanical properties of products. Meanwhile, good interfacial compatibility of nanocomposite structure within the framework also contributes to load capacity. A uniquely uniform distribution of dentinal tubules-like pores, originated from polystyrene (PS) in SiC(rGO) region, could relax stress at crack tips and ensure good thermal insulation. Particularly, lightweight porous SiC(rGO) bulk PDCs with 10 wt% PS content possess low thermal conductivity (0.25 W·m−1·K−1), excellent fracture toughness (1.96 MPa·m1/2), outstanding hardness (3.58 GPa), optimal compressive strength (51.80 MPa) and good flexural strength (33.86 MPa). Their large-sized molding ability and good high-temperature oxidation resistance were significantly demonstrated by further exploration. Such well-balanced high load bearing and good heat insulation integration nature can be used to make thermal insulators with complex shapes in a facile and economical manner.

An Aqueous-Based BiVO4 Precursor for Controlled and Enhanced Properties Towards Water Splitting

Electrochemical deposition of Bi is often obtained from non-aqueous solutions due to its natural instability in water-based solutions. In this work, we report an easy and highly reproducible method for Bi deposition on optical conductive supports as a precursor for BiVO4 synthesis. After obtaining BiVO4 from the Bi layers through hydrothermal reaction with a vanadyl precursor, the material is further modified via potentiodynamic polarization as previously demonstrated for TiO2-based materials [1]. Such a modification was used to prepare the BiVO4 electrodes for further Ni-based (NiOOH) electrocatalyst decorations [2]. The formed interfaces are studied using (photo)electrochemical and physicochemical methods to evaluate its activity towards oxygen evolution reaction. The results suggest, after tailored layer control, a comparable efficiency for the BiVO4 based on electrochemical deposition from aqueous solutions and methods based on organic solvents. Finally, electrochemical modification seemed to have a positive effect on the BiVO4 performance towards oxygen evolution. Thus, this work demonstrates a cheaper and simpler synthesis route for BiVO4 precursors and a simple method for activity modification without adding extra synthesis steps resulting in highly efficient BiVO4 photocatalysts.Figure 1. (upper left) Electrochemical setup for Bi deposition. (lower left) Cyclic voltammograms for Bi deposition. (Right) Photographs of several BiVO4 synthesis stages. Figure 1

Dual functionalized Fe2O3 nanosheets and Co9S8 nanoflowers with phosphate and nitrogen-doped carbon dots for advanced hybrid supercapacitors

The development of novel electrode materials with admirable electrochemical behaviors is a new opportunity to meet the current demand for the high energy density of supercapacitors. Herein, a facile molecular precursor route is used to synthesize dual functionalized Fe2O3 two-dimensional nanosheets with phosphate and nitrogen-doped carbon dots (P-Fe2O3/NCDs) modifications. Taking full use of the excellent characteristics of each component, the optimized P-Fe2O3/NCDs anode material achieves superior electrochemical features with an outstanding specific capacitance of 453 F g−1 at 1 A g−1. The cycling stability of P-Fe2O3/NCDs nanosheets is as high as 91.0 % after 10,000 cycles at 15 A g−1. Subsequently, phosphate and NCDs modified Co9S8 (P-Co9S8/NCDs) nanoflowers with convenient ion transport properties are fabricated, which possess a satisfied electrochemical capacity of 569 C g−1 at 1 A g−1 with desirable cycling stability at 15 A g−1. Impressively, the designed P-Co9S8/NCDs//P-Fe2O3/NCDs hybrid supercapacitor can achieve an excellent energy density of 85.1 Wh kg−1 at 937.5 W kg−1 and can retain 93.9 % capacitance efficiency after 20,000 cycles at 10 A g−1. The superior properties of the dual functionalized electrode materials provide a new choice for constructing advanced hybrid supercapacitors.

Stereolithography-based additive manufacturing of polymer-derived SiOC/SiC ceramic composites

In order to overcome challenges typically encountered during additive manufacturing of ceramics via the polymer precursor route, a novel polymer-derived SiOC/SiC composite system suitable for advanced geometric designs achievable by lithography-based ceramic manufacturing was established. The photoreactive resin system filled with 20 wt% SiC exhibits suitable viscosity characteristics, adequate stability against sedimentation, and a fast photocuring behavior. After printing and pyrolytic conversion, SiC particulates were well-dispersed within the polymer-derived SiOC matrix. A direct comparison with the unfilled polysiloxane-based resin system showed that the addition of particulate SiC increases handleability, reduces shrinkage, and significantly increases critical wall thicknesses up to 5 mm. The biaxial Ball-on-Three-Balls testing methodology yielded a characteristic strength of 325 MPa for SiOC/SiC composites. The results highlight the high potential of particle-filled preceramic polymer systems toward the fabrication of high-performance SiC-based materials by lithography-based additive manufacturing.

Microstrain and Urbach Energy Relaxation in FAPbI3-Based Solar Cells through Powder Engineering and Perfluoroalkyl Phosphate Ionic Liquid Additives.

Structural and electronic imperfections are the origin of defects and lead to nonradiative recombination that is detrimental to fabricating efficient perovskite solar cells. Here, we propose a powder engineering methodology for α-FAPbI3 as a precursor material. Our developed methodology of α-FAPbI3 synthesis mitigates the notorious structural and electronic imperfections evidenced by a significant decline in the microstrain and Urbach energy as compared to reported δ-FAPbI3 powder and conventional precursor routes. In addition to the performance enhancement in photovoltaics, our engineered powder showed remarkable thermal and moisture stability along with cost-effectiveness through the employment of low-grade PbI2. Further, through additive engineering, with the use of ultrahydrophobic perfluoroalkyl phosphate anion-based ionic liquids, the microstrain and Urbach energy achieved the lowest values of 1.67 × 10-4 and 12.47 meV, respectively, as a result of defect passivation and a semi-ionic F-Pb interaction that stabilizes the surface.

Investigation of cationic transformations involving 5-ethynyl-4-arylpyrimidines

An innovative synthetic approach towards 5-ethynyl-4-arylpyrimidines was developed involving acid-catalyzed electrophilic alkylation of phenols with 5-bromopyrimidine, followed by oxidation and palladium-catalyzed Sonogashira cross-coupling reaction. Reactions of these compounds in the presence of trifluoromethanesulfonic acid were investigated. It was discovered these reactions take a different route for precursors with a different position of phenol group in an arene substituent.

Ionic‐Liquid‐Assisted Precursor Route Syntheses of Highly Dispersed Supertetrahedral T3 In‐S/Se Clusters for Photocatalytic Hydrogen Production

AbstractHerein, two pure inorganic isostructural supertetrahedral T3 cluster based compounds with different ratio of S : Se, namely [Bmmim]6[In10QCl4](MIm)2 (Q=S9.5Se6.5 (In‐S/Se‐1), S2Se14 (In‐S/Se‐2), Bmmim=1‐butyl‐2,3‐dimethylimidazolium, MIm=1‐methylimidazole), have been obtained via an ionic‐liquid‐auxiliary precursor approach. Single‐crystal X‐ray diffraction (SCXRD) characterization showed that their structures are comprised of a discrete supertetrahedral T3 [In10QCl4]6− cluster charge‐balanced via six [Bmmim]+ cations. Importantly, the T3 clusters of In‐S/Se‐1 and In‐S/Se‐2 can be highly dispersed in dimethyl sulfoxide (DMSO). As a result, the T3 clusters uncovered more active sites after being dispersed, thereby exhibiting∼6 times of hydrogen generation rate of that in the solid state. Furthermore, benefitting from higher visible‐light absorption, larger driving force from conduction band (CB) and rapider photogenerated carrier migration, the photocatalytic H2 evolution activity was monotonically improved with increasing of the Se concentration in the T3 clusters. This work provides an alternative strategy for obtaining novel hybrid metal chalcogenide crystalline compounds for efficient energy conversion.

High aspect-ratio of MoS2 nanoribbons via a single-source precursor route for photocatalytic degradation

Ultra-thin MoS2 nanoribbons are becoming a promising candidate for photocatalysis due to their unique properties, such as nanoribbons-width-dependent bandgaps, high electronic density of states, and carrier transport in a certain direction. It is still a challenge to synthesize MoS2 nanoribbons in a facile, energy-saving and controllable way. Herein, MoS2 nanoribbons with an aspect ratio over 100 were synthesized by a single-source precursor solution route. Selective adsorption of 1-dodecanethiol on the 101¯0 of MoS2 causes the preferentially growth along the [0 0 0 1] direction, resulting in the formation of MoS2 nanoribbons. The MoS2 nanoribbons exhibit a high photocatalytic degradation activity and more than 92.0 % methyl orange can be degraded within 50 min.

Preparation of high pore volume γ-Al2O3 nanorods via “gibbsite-AACH” precursor route in a membrane dispersion microreactor

In this work, several mesoporous γ-Al2O3 nanorods with high pore volume and narrow pore size distribution were controllable prepared via “gibbsite-AACH (ammonium aluminum carbonate hydroxide)” precursor route in a membrane dispersion microreactor. The effects of reaction temperature, (NH4)2CO3 concentration and calcination temperature on the samples were intensively studied. The highly uniformed morphology was assured due to the high mixing intensify in the membrane dispersion microreactor and the successful conversion of the precursor in the slurry. Under optimal conditions, these as-prepared γ-Al2O3 nanorods behaved high pore volume of 1.65 mL/g and narrow pore size distribution of 3–20 nm with a length and width of 150–200 nm and 30–60 nm, respectively. Furthermore, the adsorption experiment of the prepared samples were carried out under natural pH value, and the as-prepared sample of AACH-500 exhibited favorable adsorption performance for Congo red (CR) solution. The maximal adsorption capacity was up to 2006.7 mg/g, thus indicating that the as-prepared mesoporous γ-Al2O3 nanorods are in adsorption and other application potential of the field.

Single source precursor route for the first graphene oxide-Pd6P nanocomposite: application in electrochemical hydrogen evolution reaction.

For the first time, Pd6P has been synthesised using a simple, straightforward and one-pot method i.e., thermolysis of a Pd(II) complex of a bidentate (P, N) organophosphorus ligand (anthracene-9-yl-CHN-CH2CH2-PPh2). The electrocatalyst (obtained after grafting nanospheres of Pd6P over layers of graphene oxide) shows high activity in electrochemical hydrogen evolution reactions (HER) with an overpotential of 133 mV to drive 10 mA cm-2 of cathodic current density. The GO-Pd6P nanocomposite is robust and effective for a continuous HER run for up to 16 hours.

Shape controllable MoS2 nanocrystals prepared by the single precursor route for electrocatalytic hydrogen evolution

MoS2 has attracted great attention as a prospective electrocatalyst for generating hydrogen via water electrolysis due to its abundant and inexpensive sources. However, bulk MoS2 has weak electrocatalytic activity because of its low electrical conductivity and few edge-active sites. Controllable synthesis of MoS2 with ultrasmall size or complex morphology may be an available strategy to boost its conductivity and edge-active sites. Herein, a facile single-precursor strategy was developed to prepare nanoscale MoS2 with various morphologies, including quantum dots, nanorods, nanoribbons, and nanosheets. In-depth studies show that the formation of MoS2 with various shapes is determined by both kinetic and thermodynamic factors such as reaction time and temperature. Electrocatalytic tests reveal that MoS2 quantum dots have high electrocatalytic performance with a low overpotential of 255 mV and a small Tafel slope of 66 mV dec−1 due to the abundant exposed active edges and excellent intrinsic conductivity.

3D printing of metals using biodegradable cellulose hydrogel inks

Additive manufacturing (AM) is a fabrication technique that digitally deposits materials in layers to form a desired 3D structure or shape. It is not as wasteful in materials compared to digital subtractive manufacturing (SM). In 3D printing, complex and unique metallic structures, more energy intensive and expensive techniques such as selective laser melting (SLM) or electron beam melting (EBM) are often used. As metals are an important class of materials used in AM, there is a need for safer and relatively less expensive 3D printing alternatives for widespread adoption. Material extrusion AM methods include fused deposition modeling (FDM) and direct ink writing (DIW), where thermal and viscosity parameters are used to optimize printing. This study presents a materials extrusion precursor route on 3D printing metallic structures with a biodegradable cellulose hydrogel and safer water-based composite ink containing irregularly shaped metallic powders and carboxymethyl cellulose (CMC-Na). Montmorillonite clay and guar gum additives were used to modify the ink viscosity during extrusion and provide post 3D printing structural integrity and stability. By using this composite ink, a part can be made with 75–80% metal composition for sintering. The sintering process at 1050 and 985 °C for 316L stainless steel (316LSS) and copper (Cu), respectively, removes the cellulose hydrogel, leaving a 100% metal. Large interconnected open and closed pores were formed for both approaches: 316LSS and Cu each had a total of about 31.92% and 32.07% porosity, respectively. Total closure of pores was not achieved and a small shrinkage was observed in both samples. The elastic modulus of the 3D-printed 316LSS structure was measured 0.053 GPa. A number of potential uses for optimized porous metallic structures, particularly in biomedical and energy applications are also discussed.

Molecular precursor route for the phase selective synthesis of α-MnS or metastable γ-MnS nanomaterials for magnetic studies and deposition of thin films by AACVD

Heterocyclic dithiocarbamate complex of manganese and the adducts of the complex with 1,10-phenanthroline and 2,2-bipyridyl respectively were synthesized and characterized. The complexes were used as single-source precursors for the preparation of MnS nanoparticles via thermolysis in oleylamine (OLA) and dodecanethiol (DT). The optimized reaction parameters have resulted in the formation of α-MnS and γ-MnS nanoparticles depending on the dispersion medium and the nature of the precursor. The same precursors were also used for the deposition of MnS thin films by the aerosol-assisted chemical vapour deposition (AACVD) method in varying solvents and temperatures. The morphology and phase of the synthesized nanoparticles were shown to be affected by the precursor type and the nature of the surfactants. TEM images show the formation of nanoparticles of various morphologies ranging from spherical monodispersed to large elongated pointed rods, depending on the precursor type. SEM images showed that the morphology of the deposited thin films is affected by precursor type and the deposition temperature. Worm-like to rod-like films were observed on TEM images at 350 °C, which changes to spherical or cubic films at 450 °C. Magnetic measurements at room temperature showed the α-MnS and γ-MnS nanoparticles in paramagnetic states due to Mn2+ moments. The susceptibility for the γ-phase is at least double that of the α-phase. Finite and small hysteretic effects in low fields are indicative of small ordered antiferromagnetic phases due to negative exchange interaction between Mn2+ ions.