Atomic Layer Deposition of Iron Sulfide and Its Application as a Catalyst in the Hydrogenation of Azobenzenes

The atomic layer deposition (ALD) of iron sulfide (FeS_x ) is reported for the first time. The deposition process employs bis(N ,N′ ‐di‐tert‐butylacetamidinato)iron(II) and H₂S as the reactants and produces fairly pure, smooth, and well‐crystallized FeS_x thin films following an ideal self‐limiting ALD growth behavior. The FeS_x films can be uniformly and conformally deposited into deep narrow trenches with aspect ratios as high as 10:1, which highlights the broad applicability of this ALD process for engineering the surface of complex 3D nanostructures in general. Highly uniform nanoscale FeS_x coatings on porous γ‐Al₂O₃ powder were also prepared. This compound shows excellent catalytic activity and selectivity in the hydrogenation of azo compounds under mild reaction conditions, demonstrating the promise of ALD FeS_x as a catalyst for organic reactions.     

FeS2 Grown Pencil Graphite as an In‐expensive and Non‐enzymatic Sensor for Sensitive Detection of Uric Acid in Non‐invasive Samples

While most electrochemical uric acid (UA) sensors are developed on the conventional electrodes and involve either multiple steps based synthesis routes and/or complicated fabrication processes, this paper is the first demonstration of direct growth of pyrite FeS₂ on pencil‐graphite electrode (PGE) for non‐enzymatic UA sensing. FESEM images of the pyrite FeS₂‐PGE reveal mesoporous microspherical structure of pyrite FeS₂ along with graphite flakes of PGE and EDX, Raman spectroscopic data validate growing of pyrite FeS₂ on PGE. The pyrite FeS₂‐PGE sensor exhibited detection limit of 6.7 μM, excellent linearity, reproducibility, selectivity over glucose, urea, ascorbic acid with the sensitivity of 370 μA mM^?1 cm^?2 in the range of 10–725 μM of UA. These improved analytical performances can be attributed to high conductivity of the pyrite FeS₂, larger electro‐active surface area of the mesoporous microspherical pyrite FeS₂ grown on PGE (than only PGE) and abundance in defect sites originating from both the pyrite FeS₂ as well as functional groups of pencil graphite. Furthermore, the sensor was validated against UA in urine sample and the result supports well with the UA concentration achieved from colorimetric technique. Development of this low cost, non‐enzymatic, sensitive and highly selective pyrite FeS₂‐PGE bases UA sensor is a significant step in the development of practically viable sensors for point‐of‐care applications in clinical and pharmaceutical analyses.     

Synthesis of silk-like FeS2/NiS2 hybrid nanocrystals with improved reversible oxygen catalytic performance in a Zn-air battery

The development of highly active and stable reversible oxygen electrocatalysts is crucial for improving the efficiency of metal-air battery devices. Herein, an efficient liquid exfoliation strategy was designed for producing silk-like FeS₂/NiS₂ hybrid nanocrystals with enhanced reversible oxygen catalytic performance that displayed excellent properties for Zn-air batteries. Because of the unique silk-like morphology and interface nanocrystal structure, they can catalyze the oxygen evolution reaction (OER) efficiently with a low overpotential of 233 mV at j = 10 mA cm^?2. This is an improvement from the recently reported catalysts in 1.0 M KOH. Meanwhile, the oxygen reduction reaction (ORR) activity of the silk-like FeS₂/NiS₂ hybrid nanocrystals showed an onset potential of 911 mV and a half-wave potential of 640 mV. In addition, the reversible oxygen electrode activity of the silk-like FeS₂/NiS₂ hybrid nanocrystals was calculated to be 0.823 V, based on the potential of the OER and ORR. Further, the homemade rechargeable Zn-air batteries using FeS₂/NiS₂ hybrid nanocrystals as the air-cathode displayed a high open-circuit voltage of 1.25 V for more than 17 h and an excellent rechargeable performance for 25 h. The solid Zn-air batteries exhibited an excellent rechargeable performance for 15 h. This study provided a new method for designing interface nanocrystals with a unique morphology for efficient multifunctional electrocatalysts in electrochemical reactions and renewable energy devices.     

Atomic Layer Deposition of Cobalt Phosphide for Efficient Water Splitting

Transition‐metal phosphides (TMP) prepared by atomic layer deposition (ALD) are reported for the first time. Ultrathin Co‐P films were deposited by using PH₃ plasma as the phosphorus source and an extra H₂ plasma step to remove excess P in the growing films. The optimized ALD process proceeded by self‐limited layer‐by‐layer growth, and the deposited Co‐P films were highly pure and smooth. The Co‐P films deposited via ALD exhibited better electrochemical and photoelectrochemical hydrogen evolution reaction (HER) activities than similar Co‐P films prepared by the traditional post‐phosphorization method. Moreover, the deposition of ultrathin Co‐P films on periodic trenches was demonstrated, which highlights the broad and promising potential application of this ALD process for a conformal coating of TMP films on complex three‐dimensional (3D) architectures.     

金属氧化物与现代微电子学:过渡金属前体化合物及转化为材料的化学过程

金属氧化物薄膜如HfO₂（被称为高k电介质）是现代微电子器件的关键组件,广泛用于计算机（平板电脑,笔记本电脑和台式机）、智能电话、智能电视、汽车和医疗设备中。具有大介电常数（k）的金属氧化物已经取代了介电常数小的SiO₂（k=3.9）,从而使得微电子元件进一步小型化。过渡金属化合物在化学气相沉积（CVD）和原子层沉积（ALD）中被广泛用作前体,通过与O₂、H₂O或O₃的反应生成金属氧化物薄膜。微电子金属氧化物膜是纳米材料最广泛应用的一个领域。本文概观该领域的最新进展,包括我们对d⁰过渡金属配合物与O₂反应的研究。     

金属氧化物与现代微电子学——过渡金属前体化合物及转化为材料的化学过程

金属氧化物薄膜如HfO₂（被称为高k电介质）是现代微电子器件的关键组件,广泛用于计算机（平板电脑,笔记本电脑和台式机）、智能电话、智能电视、汽车和医疗设备中。具有大介电常数（k）的金属氧化物已经取代了介电常数小的SiO₂（k=3.9）,从而使得微电子元件进一步小型化。过渡金属化合物在化学气相沉积（CVD）和原子层沉积（ALD）中被广泛用作前体,通过与O₂、H₂O或O₃的反应生成金属氧化物薄膜。微电子金属氧化物膜是纳米材料最广泛应用的一个领域。本文概观该领域的最新进展,包括我们对d⁰过渡金属配合物与O₂反应的研究。     

Low‐Temperature Atomic Layer Deposition of MoS2 Films

Wet chemical screening reveals the very high reactivity of Mo(NMe₂)₄ with H₂S for the low‐temperature synthesis of MoS₂. This observation motivated an investigation of Mo(NMe₂)₄ as a volatile precursor for the atomic layer deposition (ALD) of MoS₂ thin films. Herein we report that Mo(NMe₂)₄ enables MoS₂ film growth at record low temperatures—as low as 60 °C. The as‐deposited films are amorphous but can be readily crystallized by annealing. Importantly, the low ALD growth temperature is compatible with photolithographic and lift‐off patterning for the straightforward fabrication of diverse device structures.     

Molecular Precursors for the Phase‐Change Material Germanium‐Antimony‐Telluride,Ge2Sb2Te5 (GST)

This review provides an overview of the precursor chemistry that has been developed around the phase‐change material germanium‐antimony‐telluride, Ge₂Sb₂Te₅ (GST). Thin films of GST can be deposited by employing either chemical vapor deposition (CVD) or atomic layer deposition (ALD) techniques. In both cases, the success of the layer deposition crucially depends on the proper choice of suitable molecular precursors. Previously reported processes mainly relied on simple alkoxides, alkyls, amides and halides of germanium, antimony, and tellurium. More sophisticated precursor design provided a number of promising new aziridinides and guanidinates.     

Formation of Hierarchical FeCoS2–CoS2 Double‐Shelled Nanotubes with Enhanced Performance for Photocatalytic Reduction of CO2

Hierarchical FeCoS₂–CoS₂ double‐shelled nanotubes have been rationally designed and constructed for efficient photocatalytic CO₂ reduction under visible light. The synthetic strategy, engaging the two‐step cation‐exchange reactions, precisely integrates two metal sulfides into a double‐shelled tubular heterostructure with both of the shells assembled from ultrathin two‐dimensional (2D) nanosheets. Benefiting from the distinctive structure and composition, the FeCoS₂–CoS₂ hybrid can reduce bulk‐to‐surface diffusion length of photoexcited charge carriers to facilitate their separation. Furthermore, this hybrid structure can expose abundant active sites for enhancing CO₂ adsorption and surface‐dependent redox reactions, and harvest incident solar irradiation more efficiently by light scattering in the complex interior. As a result, these hierarchical FeCoS₂–CoS₂ double‐shelled nanotubes exhibit superior activity and high stability for photosensitized deoxygenative CO₂ reduction, affording a high CO‐generating rate of 28.1 μmol h^?1 (per 0.5 mg of catalyst).     

Facile Synthesis of Three‐Dimensional Pt‐TiO2 Nano‐networks: A Highly Active Catalyst for the Hydrolytic Dehydrogenation of Ammonia–Borane

Three‐dimensional (3D) porous metal and metal oxide nanostructures have received considerable interest because organization of inorganic materials into 3D nanomaterials holds extraordinary properties such as low density, high porosity, and high surface area. Supramolecular self‐assembled peptide nanostructures were exploited as an organic template for catalytic 3D Pt‐TiO₂ nano‐network fabrication. A 3D peptide nanofiber aerogel was conformally coated with TiO₂ by atomic layer deposition (ALD) with angstrom‐level thickness precision. The 3D peptide‐TiO₂ nano‐network was further decorated with highly monodisperse Pt nanoparticles by using ozone‐assisted ALD. The 3D TiO₂ nano‐network decorated with Pt nanoparticles shows superior catalytic activity in hydrolysis of ammonia–borane, generating three equivalents of H₂.     

X‐Ray Photoelectron Spectral Studies on Planar NiS4 and NiS2P2 Chromophores. Single Crystal X‐Ray Structural Study on [1, 4‐Bis(diphenylphosphino‐k,P, P')butane](piperidinecarbodithioato‐S,S')‐Nickel(II) Perchlorate

X‐ray photoelectron spectral study was made on the complexes Ni(nmedtc)₂( 1 ), [Ni(nmedtc)(PPh₃)₂]ClO₄( 2 ), [Ni‐(nmedtc)(dppe)]BPh₄( 3 ) (where nmedtc = N‐methyl, N‐ethanoldithiocarbamate, dppe = 1, 2‐bis(diphenylphosphino)ethane). The nickel 2p_3/2 binding energy values for chelated and free phosphine complexes are 854.0 and 854.1 eV which are significantly different from Ni2p_3/2 BE value of NiS₄ chromophore, indicating the relative dearth of electron density on Ni in NiS₂P₂ chromophores. The presence of two phosphine groups in NiS₂P₂ chromophore alleviates the electron density on the metal atom. More electron density is being pulled away from the metal atom in chelates than in the PPh₃ analogue. This observation is in line with solution studies by cyclic voltammetry. A one‐electron reduction potential was observed to be the minimum for NiS₂P₂ chromophores compared to the others. Also the crystal structure of the complex [Ni(pipdtc)(1, 4‐dppb)]ClO₄ (pipdtc^‐ = piperidinecarbodithioato anion, 1, 4‐dppb = bis(diphenylphosphino)butane) prepared by the reaction between Ni(pipdtc)₂, NiCl₂�6₂2O, and 1, 4‐dppb in CH₃CN‐CH₃OH is reported.     

Studies on the compounds in the BaFeS system. I. Linear chain antiferromagnetism of Ba2FeS3 and related compounds Ba2CoS3 and Ba2MnS3

Magnetic susceptibilities of Ba₂FeS₃, Ba₂CoS₃, and Ba₂MnS₃ show rounded maxima at 130, 125, and 100 K, respectively, which are due to quasi-one-dimensional antiferromagnetic short-range ordering. Intrachain interactions, $\text{J}\text{k}$, are estimated to be ?20, ?15, and ?12 K, respectively. ⁵⁷Fe Mössbauer spectra of Ba₂FeS₃ and ⁵⁷Fe-doped Ba₂CoS₃ and Ba₂MnS₃ at 4.2 K show long-range antiferromagnetic ordering, due to the interchain interaction. The profile of Mössbauer spectra at 4.2 K is analyzed based on the coexistence of magnetic hyperfine and quadrupole interactions, and magnetic hyperfine fields at 4.2 K are estimated to be 36, 29, and 59 kOe, respectively.     

Improving Na+ transport kinetics and Na+ storage of hierarchical rhenium-nickel sulfide (ReS2@NiS2) hollow architecture by assembling layered 2D-3D heterostructures

Mixed metal sulfides have been widely used as anode material of sodium-ion batteries (SIBs) because of their excellent conductivity and sodium ion storage performance. Herein, ReS₂@NiS₂ heterostructures have been triumphantly designed and prepared through anchoring ReS₂ nanosheet arrays on the surface of NiS₂ hollow nanosphere. Specifically, the carbon nanospheres was used as hard template to synthesize NiS₂ hollow spheres as the substrate and then the ultrathin two-dimensional ReS₂ nanosheet arrays were uniformly grown on the surface of NiS₂. The internal hollow property provides sufficient space to relieve the volume expansion, and the outer two-dimensional nanosheet realizes the rapid electron transport and insertion/extraction of Na⁺. Owing to the great improvement of the transport kinetics of Na⁺, NiS₂@ReS₂ heterostructure electrode can achieve a high specific capacity of 400 mAh/g at the high current density of 1 A/g and still maintain a stable cycle stability even after 220 cycles. This hard template method not only paves a new way for the design and construct binary metal sulfide heterostructure electrode materials with outstanding electrochemical performance for Na⁺ batteries but also open up the potential applications of anode materials of SIBs.     

Coated/Sandwiched rGO/CoSx Composites Derived from Metal–Organic Frameworks/GO as Advanced Anode Materials for Lithium‐Ion Batteries

Rational composite materials made from transition metal sulfides and reduced graphene oxide (rGO) are highly desirable for designing high‐performance lithium‐ion batteries (LIBs). Here, rGO‐coated or sandwiched CoS_x composites are fabricated through facile thermal sulfurization of metal–organic framework/GO precursors. By scrupulously changing the proportion of Co²⁺ and organic ligands and the solvent of the reaction system, we can tune the forms of GO as either a coating or a supporting layer. Upon testing as anode materials for LIBs, the as‐prepared CoS_x‐rGO‐CoS_x and rGO@CoS_x composites demonstrate brilliant electrochemical performances such as high initial specific capacities of 1248 and 1320 mA h g^?1, respectively, at a current density of 100 mA g^?1, and stable cycling abilities of 670 and 613 mA h g^?1, respectively, after 100 charge/discharge cycles, as well as superior rate capabilities. The excellent electrical conductivity and porous structure of the CoS_x/rGO composites can promote Li⁺ transfer and mitigate internal stress during the charge/discharge process, thus significantly improving the electrochemical performance of electrode materials.     

Optimizing the Atomic Layer Deposition of Alumina on Perovskite Nanocrystal Films by Using O2 As a Molecular Probe

Encapsulation methods have shown to be effective in imparting improved stability to metal-halide perovskite nanocrystals (NCs). Atomic layer deposition (ALD) of metal oxides is one of the promising approaches for such encapsulation, yet better control on the process parameters are required to achieve viable lifetimes for several optoelectronic and photocatalytic applications. Herein, we optimize the ALD process of amorphous aluminum oxide (AlO_x) as an encapsulating layer for CsPbBr₃ NC thin films by using oxygen (O₂) as a molecular diffusion probe to assess the uniformity of the deposited AlO_x layer. When O₂ reaches the NC surface, it extracts the photogenerated electrons, thus quenching the PL of the CsPbBr₃ NCs. As the quality of the ALD layer improves, less quenching is expected. We compare three different ALD deposition modes. We find that the low temperature/high temperature and the exposure modes improve the quality of the alumina as a gas barrier when compared with the low temperature mode. We attribute this result to a better diffusion of the ALD precursor throughout the NC film. We propose the low temperature/high temperature as the most suitable mode for future implementation of multilayered coatings.     

CoS2 Nanoparticles Embedded in Covalent Organic Polymers as Efficient Electrocatalyst for Oxygen Evolution Reaction with Ultralow Overpotential

Cobalt disulfide (CoS₂) has been explored as attractive electrocatalyst for oxygen evolution reaction (OER). However, bulk CoS₂ sheets have limited catalytic activity due to low exposure of active sites. Herein, through an in-situ vulcanization approach, CoS₂ nanoparticles are embedded into bipyridine-containing covalent organic polymer (BP-COP). The as-prepared nanocomposite CoS₂@BP-COP exhibits high catalytic activity toward OER with an ultra-low overpotential of 270 mV (vs. RHE) at a current density of 10 mA cm⁻², a small Tafel slope of 36 mV dec⁻¹, and an excellent durability for 24 h without decay. The surface of CoS₂ is partially converted into CoOOH to form CoS₂/CoOOH as active sites under OER conditions. CoS₂@BP-COP displays superior OER catalytic activity to CoS₂ nanosheets and commercially available RuO₂ under the same conditions. The outstanding OER performance activity of CoS₂@BP-COP could be attributed to the uniform and small particle sizes of CoS₂/CoOOH distributed in BP-COP.     

Cracking study of pentakis(dimethylamino)tantalum vapors by Knudsen cell mass spectrometry

Organometallic molecules are commonly used as gaseous precursors in Atomic Layer Deposition/Chemical Vapor Deposition (ALD/CVD) processes. However, the use of these molecules, which are generally thermally unstable at temperatures close to the deposition temperature, requires an understanding of their gas‐phase chemical behavior. The thermal cracking of the gaseous precursor, pentakis(dimethylamino) tantalum (PDMAT), generally adopted in the ALD/CVD TaN deposition processes, has been studied in the temperature range from 343 to 723K using a specific reactor coupled with a high‐temperature mass spectrometer. This reactor – built as tandem Knudsen cells – consists of two superimposed cells. The first stage reactor – an evaporation cell – provides an input saturated vapor flow operating from room temperature to 333K. The second stage cell, named the cracking cell, operated from 333 to 723K in the present study. Experiments showed the appearance of many gaseous species when the cracking temperature increased and, in particular, dimethylamine, corresponding to the saturated organic branches of PDMAT. Decomposition products of the HNC₂H₆ branch were observed at relatively high temperature, namely above 633K. This gas‐phase study – as for the preceding saturated one – shows the presence of oxygen‐containing molecules in PDMAT cracked vapor. Thus, it explains the systematic presence of oxygen contamination in the deposited TaN films observed in ALD/CVD industrial processes. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis of Copper‐Substituted CoS2@CuxS Double‐Shelled Nanoboxes by Sequential Ion Exchange for Efficient Sodium Storage

The construction of hybrid architectures for electrode materials has been demonstrated as an efficient strategy to boost sodium‐storage properties because of the synergetic effect of each component. However, the fabrication of hybrid nanostructures with a rational structure and desired composition for effective sodium storage is still challenging. In this study, an integrated nanostructure composed of copper‐substituted CoS₂@Cu_xS double‐shelled nanoboxes (denoted as Cu‐CoS₂@Cu_xS DSNBs) was synthesized through a rational metal–organic framework (MOF)‐based templating strategy. The unique shell configuration and complex composition endow the Cu‐CoS₂@Cu_xS DSNBs with enhanced electrochemical performance in terms of superior rate capability and stable cyclability.     

Synthesis,Spectral, Cyclic Voltammetric Studies,and Single Crystal X‐Ray Structure Determination of the Planar NiS2P2, NiS2PN,and NiS2PC Chromophores

Synthesis, spectral and cyclic voltammetric characterization of [Ni(dedtc)(4‐MP)₂](ClO₄) ( 1 ), [Ni(dedtc)(4‐MP)(NCS)]( 2 ), [Ni(dedtc)(PPh₃)(NCS)] ( 3 ) and [Ni(dedtc)(PPh₃)(CN)] ( 4 ) (dedtc = diethyldithiocarbamate, 4‐MP = tri(4‐methylphenyl)phosphine, PPh₃ = triphenylphophine) are reported. IR spectra of complexes 1‐4 show the characteristic thioureide (C‐N) bands at higher wave numbers compared to that of the parent dithiocarbamate complex [Ni(dedtc)₂]. The d‐d transitions are observed in the region 452—482 nm. The CV studies clearly show the presence of reduced electron density on the nickel ions in mixed ligand complexes 1‐4 compared to the parent dithiocarbamate. Single crystal X‐ray structure studies show all the complexes to containplanar NiS₂P₂, NiS₂PN, and NiS₂PC chromophores in keeping with the observed diamagnetism. In all the complexes the Ni‐S distances are asymmetric. The thioureide C‐N distance of the complexes 1‐4 are less thanthe C‐N distance observed in the parent [Ni(dedtc)₂].     

Rapid microwave-assisted preparation of binary and ternary transition metal sulfide compounds

Transition metal chalcogenides are of interest for energy applications, including energy generation in photoelectrochemical cells and as electrodes for next-generation electrochemical energy storage. Synthetic routes for such chalcogenides typically involve extended heating at elevated temperatures for multiple weeks. We demonstrate here the feasibility of rapidly preparing select sulfide compounds in a matter of minutes, rather than weeks, using microwave-assisted heating in domestic microwaves. We report the preparations of phase pure FeS₂, CoS₂, and solid solutions thereof from the elements with only 40 min of heating. Conventional furnace and rapid microwave preparations of CuTi₂S₄ both result in a majority of the targeted phase, even with the significantly shorter heating time of 40 min for microwave methods relative to 12 days using a conventional furnace. The preparations we describe for these compounds can be extended to related structures and chemistries and thus enable rapid screening of the properties and performance of various compositions of interest for electronic, optical, and electrochemical applications.