Single-source Molecular Precursor Research Articles

Single source precursor mediated synthesis of phase pure digenite nanocrystals and investigation of its photo-switching behavior

Copper sulfide nanostructures have garnered strategic importance in green energy applications due to their economic nature and impressive performances. This account presents a straightforward and scalable route to access digenite (Cu1.8S or Cu9S5) phase of copper sulfide in nano-dimension. The synthesis is facilitated through low temperature rapid thermolysis of a newly synthesized and structurally characterized single source molecular precursor, namely [Cu(Spyz-2)(PPh3)2]·MeOH (1). The crystal structure, phase purity, and morphology of the nanostructures were thoroughly examined by PXRD and electron microscopic techniques. The average crystallite size and morphology of the nanostructures were found to be the function of the different capping agents (OAm and DDT) employed for the synthesis. DRS studies on the nanomaterials revealed blue shifted optical band gap (2.09–2.13 eV) which were found to be optimum for photoelectrochemical application. A prototype photoelectrochemical cell, fabricated using the pristine nanostructures exhibit high photocurrent generation along with nice photo-switching property which pose them as suitable alternatives for green energy applications and environmental remediation.

Multi-functional Single-Source Molecular Precursors for Carbon-Coated Mixed-Metal Phosphates.

We introduce a new synthetic concept that can be broadly adopted for the low-temperature preparation of mixed-metal energy storage materials, such as phosphates, silicates, fluorides, fluorophosphates, and fluorosulfates that exhibit intrinsic low electronic conductivity and thus require a carbon modulation. The development of novel low-temperature approaches for assembling energy-related materials with a complex core-shell microstructure is of great importance for expanding their application scope. The traditional definition of single-source precursors refers to their ability to yield a phase-pure material upon thermal decomposition. We have developed a new way for the utilization of heterometallic molecular precursors in synthesis that goes beyond its common delineation as a single-phase maker. The utility of this approach has been demonstrated upon the low-temperature synthesis of lithium-iron phosphate@C, which represents a celebrated cathode material for Li-ion batteries. The first atomically precise carbonaceous molecular precursors featuring a desired Li:Fe:P ratio of 1:1:1, divalent iron, and sufficient oxygen content for the target LiFeIIPO4 phosphate were shown to enable a spontaneous formation of both the olivine core and conductive carbon shell, yielding a carbon-coated mixed-metal phosphate.

(Z)-2-(pyrrolidin-2-ylidene) thiourea based nickel (II) complex as a single source precursor for the synthesis of NiS nanoparticles and thin films

Nickel sulfides nanocrystals may be regarded as promising of materials in different research areas such as catalysts, solar cells, and electrode-materials. (Z)-2-(pyrrolidin-2-ylidene) thiourea ligand and (Z)-2-(pyrrolidin-2-ylidene) thiourea based nickel (II) complex have been prepared and utilized as single source molecular precursor for the synthesis of nickel sulfide nanoparticles and thin films. The effect of temperature was studies during the synthetic processes. The synthesized nanomaterials were characterized with various instruments. UV-Vis spectroscopy results of the nanoparticles were red shifting when the reaction temperature was increased whereas the blue shift was observed when the temperature was elevated during the preparation of the NiS thin films with the optical band gap energies ranging from 2.79 eV - 3.56 eV. All the XRD patterns for the NiS thin films confirm the predominance of pure hexagonal phase.

Molecular Precursor-Driven Synthesis of Copper Telluride Nanostructures for LIB Anode Application.

Copper tellurides have garnered substantial interest for their applicability as an electrocatalyst for water splitting, battery anodes and photodetectors, etc. Moreover, synthesis of phase pure metal tellurides using the multi-source precursor method is challenging. Therefore, a facile synthesis protocol for copper tellurides is anticipated. The current study involves a simplistic single source molecular precursor pathway for the synthesis of orthorhombic-Cu2.86Te2 nano blocks and -Cu31Te24 faceted nanocrystals employing the [Cu{TeC5H3(Me-5)N}]4 cluster in thermolysis and pyrolysis, respectively. The pristine nanostructures were carefully characterized by powder X-ray diffraction, energy-dispersive X-ray spectroscopy, electron microscopic techniques (scanning electron microscopy and transmission electron microscopy), and diffuse reflectance spectroscopy to know the crystal structure, phase purity, elemental composition, distribution of elements, morphology, and optical band gap. These measurements suggests that the reaction conditions fetch nanostructures of different sizes, crystal structures, morphologies, and band gaps. As prepared nanostructures were evaluated for lithium-ion batteries (LIBs) anode material. The cells fabricated with orthorhombic Cu2.86Te2 and orthorhombic Cu31Te24 nanostructures deliver capacities of 68 and 118 mA h/g after 100 cycles. The LIB anode made up of Cu31Te24 faceted nanocrystals exhibited good cyclability and mechanical stability.

New Avenues to Chemical Space for Energy Materials by the Molecular Precursor Approach

The quest to develop efficient electrocatalysts for water‐splitting is still an ongoing challenge. Intense efforts have been dedicated over the years to design effective methods to improve the electrocatalytic performances. In recent times, the single‐source (molecular) precursor (SSP) approach has gained enormous attention from the scientific community as it operates at low temperatures and leads to the formation of unique nanostructured materials, with fine‐tuned chemical and physical properties, resulting in high and stable catalytic activities. Herein, the recent developments in molecule‐to‐material chemistry and their applications toward the oxygen evolution reaction, hydrogen evolution reaction, and overall water‐splitting are summarized. Furthermore, the review focuses on understanding the reconstruction process of the SSP‐derived materials and the adopted techniques (in situ and ex situ) to obtain insights into the active structures for catalysis. The future possibilities of applying these materials for value‐added organic electro‐oxidation/reduction reactions are also explored.

Molecular precursor-mediated facile synthesis of phase pure metal-rich digenite (Cu1.8S) nanocrystals: an efficient anode for lithium-ion batteries.

Copper sulfides have gained significant attention as alternative electrodes for rechargeable batteries. A simple and easily scalable synthetic pathway to access these materials is highly desirable. This paper describes the facile synthesis of metal-rich digenite Cu1.8S nanocrystals from a structurally characterized new single-source molecular precursor in various high boiling solvents of varied polarity. The as-prepared nanostructures were thoroughly characterized by PXRD, Raman spectroscopy, EDS, XPS, electron microscopy techniques and diffuse reflectance spectroscopy to understand the crystal structure, phase purity, elemental composition, morphology and band gap. It was found that the reaction solvent has a profound role on their crystallite size, morphology and band gap, however the crystal structure and phase purity remained unaffected. Pristine Cu1.8S nanostructures have been employed as an anode material in lithium-ion batteries (LIBs). The cell delivers a high initial charge capacity of ∼462 mA h g-1 and retains a capacity of 240 mA h g-1 even after 300 cycles at 0.1 A g-1. DFT calculations revealed that multi-size polyhedron layers in the direction perpendicular to the two Li movement channels aid in the sustainable uptake of Li atoms with controlled volume expansion. The structure-mediated flexibility of the metal-rich Cu1.8S lattice during lithiation permits high cyclability with reasonable retention of capacity.

Controlled synthesis of photoresponsive bismuthinite (Bi2S3) nanostructures mediated through a new 1D bismuth-pyrimidylthiolate coordination polymer as a molecular precursor.

Bismuthinite (Bi2S3) nanostructures have garnered significant interest due to their appealing photoresponsivity which has positioned them as an attractive choice for energy conversion applications. However, to utilize their full potential, a simple and economically viable method of preparation is highly desirable. Herein, we present the synthesis and characterization including structural elucidation of a new air- and moisture-stable bismuth-pyrimidylthiolate complex. This complex serves as an efficient single-source molecular precursor for the facile preparation of phase-pure Bi2S3 nanostructures. Powder X-ray diffraction (PXRD), Raman spectroscopy, electron dispersive spectroscopy (EDS) and electron microscopy techniques were used to assess the crystal structure, phase purity, elemental composition and morphology of the as-prepared nanostructures. This study also revealed the profound effects of temperature and growth duration on the crystallinity, phase formation and morphology of nanostructures. The optical band gap of the nanostructures was tuned within the range of 1.9-2.3 eV, which is blue shifted with respect to the bulk bandgap and suitable for photovoltaic applications. Liquid junction photo-electrochemical cells fabricated from the as-prepared Bi2S3 nanostructure exhibit efficient photoresponsivity and good photo-stability, which project them as promising candidates for alternative low-cost photon absorber materials.

High-pressure materials synthesis - A guideline for the discovery of advanced ceramic nitrides

High-pressure synthesis routes enable the access to a broad variety of novel nitride-based materials with properties far beyond that of the state of the art. The ultimate goal of our studies is to advance the knowledge and understanding of inorganic nitrides, oxynitrides and nitride-based (nano)composites synthesized under high-pressure and high temperature conditions. The discovery of novel nitrides will open space for new fundamental materials science studies on the one hand and application-oriented research on the other hand. Our research is part of the materials driven technology, which is an essential requirement for the future demands with respect to the development of new technologies. Binary, ternary and multinary nitrides or oxynitrides are in the focus of our studies. Theoretical predictions of novel metal or non-metal nitride solid-state structures guide the experimental studies. The use of a large volume press allows to produce new materials in amounts suitable for further mechanical and functional characterization. Molecular single source precursors are synthesized and transformed to inorganic solid nitrides as starting materials. Special emphasis is placed on (i) fundamental questions regarding pressure-temperature phase relations, (ii) nitrides, which have been predicted but not synthesized yet, and (iii) nitride-based (nano)composites which combine at least two binary high-pressure phases in one material. The novel nitrides are evaluated in terms of their challenging and technologically relevant properties including (i) thermodynamic stability/metastability and (ii) structural (hardness) as well as functional (optoelectronic) properties. Finally, our research contributes to extend the “Nitride World” and to deliver perspective materials based on the inorganic nitride family with advanced functionality and exceptional levels of performance for application in the key technologies of the 21st century.

A Highly Active Nitrogen‐Doped Mixed‐Phase Mixed‐Valence Cobalt Nanocatalyst for Olefins and Nitroarenes Hydrogenation

AbstractDevelopment of an inexpensive, environmentally friendly and robust recyclable heterogeneous catalyst for alkene and nitroarene hydrogenation is in high demand for the sustainable future of chemical industries. Herein, we have synthesize and characterized a trinuclear mixed valence cobalt complex 1 and nitrogen doped mixed phase cobalt (β‐Co(OH)2 and CoO) nanocatalyst (N@MPCoNC) as reported earlier. N@MPCoNC was synthesized via single source molecular precursor by reducing 1 by aq. N2H4 followed by calcinations. Both mixed‐valence cobalt metal complex (1) and nitrogen doped mixed phase cobalt nanocatalyst (N@MPCoNC) were utilized for alkenes and nitroarenes hydrogenation reaction, however excellent catalytic activity was noticed by N@MPCoNC with the 100 % conversion of styrene and 4‐nitrotoluene to the corresponding ethylbenzene and 4‐aminotoluene with 100 % selectivity under mild reaction condition. The scope of the heterogeneous N@MPCoNC was further evaluated for other alkenes and nitroarenes to obtain corresponding alkanes and aminoarenes with an excellent conversion and high selectivity at room temperature.

Molecular precursor driven synthesis of phase pure tin sulfide nanosheets and investigation of their photoresponsive behaviour

Tin Sulfide (SnS) has emerged as an important semiconductor for photovoltaics, thermoelectric and as high-capacity anode material for alkali-ion batteries. However, producing phase pure SnS free from higher tin sulfides (SnS2 and Sn2S3) having different optoelectronic properties, is a challenging task. In this report, we present a structurally characterized single source molecular precursor (SSP), [tBu2Sn(SpymMe2)2], for the facile synthesis of phase pure orthorhombic SnS nanosheets in different high boiling solvents (oleylamine, octadecene, dodecanthiol) with varying coordination ability. As-prepared SnS nanosheets were thoroughly checked for its phase purity, elemental composition and morphology through pXRD and electron microscopic techniques. A distinct variation in crystallite size, morphology and band gap of nanosheets as function of reaction solvent was observed during investigation. Finally, the as prepared SnS nanosheets derived from SSP exhibit high photoresponsitivity and photostability which make them promising candidate for alternative low-cost photon absorber material.

Preparation of spin coated PbS thin films using bis-tetrahydroquinolinedithiocarbamatolead(II) complex as a single source precursor

Recently, the incorporation of single-source molecular precursors in synthetic protocols has been identified as an effective and easy route toward tuning the sought-after properties of thin films. In this work, bis-tetrahydroquinolinedithiocarbamato complex of lead(II) has been used as a single-source molecular precursor to deposit PbS thin films at elevated temperatures. The spin coating method was chosen as a deposition technique to afford PbS thin films. The morphology of the obtained films was observed to be influenced by the variation of temperature. Formations of compact thick and agglomerated spherical granules were observed at a lower temperature whereas elevated temperatures afforded the formation of cubic and multipodal shaped structures. From the energy dispersive X-ray spectroscopy (EDS) results, the elemental ratio of the finally formed films agree with the PbS composition. X-ray diffraction studies further revealed the formation of the crystalline cubic phase of PbS films with a calculated crystallite size in the range of 50 − 58 nm.

Facile one pot synthesis of highly photoresponsive coinage metal selenides (Cu1.8Se and Ag2Se) achieved through novel Cu and Ag pyridylselenolates as molecular precursors

Phase pure Cu1.8Se and Ag2Se nanostructures were synthesized employing novel single source molecular precursors at relatively low temperature. These materials exhibit good photoresponsivity and stability under alternating light and dark conditions.

Synthesis of photoresponsive and photoemissive ultrathin 2D nanosheets of In2S3 achieved through a new single source molecular precursor.

Indium sulfide, a two-dimensional semiconductor material, has emerged as a promising candidate for cost-effective and sustainable solar cells. This report deals with the facile preparation of colloidal In2S3 with a new ultrathin nanosheet (NS) morphology. The synthesis was mediated through a new structurally characterized single source molecular precursor. The crystal structure, phase purity, and morphology of the NSs were thoroughly investigated by pXRD, Raman, XPS, and electron microscopic techniques. AFM studies revealed that the NSs have an average thickness of ∼1.76 nm. The optical studies confirm quantum confinement in the as-prepared NSs with a blue shift in the direct band gap, which lies in the optimal range suitable for solar cell application. Furthermore, photoluminescence studies indicate strong emission by these NSs in the blue region. The as-synthesized In2S3 NSs-based prototype photoelectrochemical cell exhibit high photostability and photoresponsivity, which make them suitable candidates for sustainable solar cells.

Molecular precursor-mediated facile synthesis of photo-responsive stibnite Sb2S3 nanorods and tetrahedrite Cu12Sb4S13 nanocrystals.

Stibnite Sb2S3 and tetrahedrite Cu12Sb4S13 nanostructures being economical, environmentally benign and having a high absorption coefficient are highly promising materials for energy conversion applications. However, producing these materials especially tetrahedrite in the phase pure form is a challenging task. In this report we present a structurally characterized single source molecular precursor [Sb(4,6-Me2pymS)3] for the facile synthesis of binary Sb2S3 as well as ternary Cu12Sb4S13 in oleylamine (OAm) at a relatively lower temperature. The as-prepared Sb2S3 and Cu12Sb4S13 nanostructures were thoroughly checked for their phase purity, elemental composition and morphology by powder X-ray diffraction (pXRD), electron dispersive spectroscopy (EDS) and electron microscopy techniques. pXRD and EDS studies confirm the formation of phase pure, crystalline orthorhombic Sb2S3 and cubic Cu12Sb4S13. The SEM, TEM and HRTEM images depict the formation of well-defined nanorods and nearly spherical nanocrystals for Sb2S3 and Cu12Sb4S13, respectively. The Sb2S3 nanorods and Cu12Sb4S13 nanocrystals exhibit an optical bandgap of ∼1.88 and 2.07 eV, respectively, which are slightly blue-shifted relative to their bulk bandgap, indicating the quantum confinement effect. Finally, efficient photoresponsivity and good photo-stability were achieved in the as-prepared Sb2S3 and Cu12Sb4S13 nanostructure-based prototype photo-electrochemical cell, which make them promising candidates for alternative low-cost photon absorber materials.

Advanced MoS2 nanocomposite materials for the synthesis of valuable pharmaceuticals

Rampant industrialization has played pivotal role in generation of polluting materials threatening ecology, environment and biosphere reserves. Amongst various pollutants, nitroarmatics are key components of non-biodegradable organic dyes, insecticides having toxic and carcinogenic effect on human health. Furthermore, aromatic hydrocarbons are widespread contaminants of ground water. Therefore, these waste materials are generally degraded by advanced oxidation process to carbon dioxide and water. But, these organic waste materials instead of complete mineralization can be valorized to valuable pharmaceuticals. For example, nitroaromatics can be valorized to tertiary amine or N-Mannich bases. N-Mannich bases are important pharmacophores and used as anti-microbial, anti-viral, anti-HIV, anti-inflammatory, analgesics and RSK2 inhibitory. Ethylbenzene is an important industrial waste can be used as building block for the synthesis of α-ketoamides. These α-ketoamides are significant pharmacophores can be used as the broad-spectrum antibiotics for COVID-19. Presently, COVID-19 is a global pandemic affecting billions of people. To deliver doses to such a big population would be a challenge. Therefore, we can use the industrial waste materials for the synthesis of valuable pharmacophors to boost the economy. To effectively catalyze the transformation of these industrial wastes into valuable products, cost-effective, readily available catalytic materials will be investigated. Earth abundant transition metals like Cu, Co, Zn, Ni, Zr etc. supported over 2D transition metal dichalcogenides can be used as the desirable candidates for the synthesis of pharmacophors from industrial waste. These catalytic materials will be prepared by hydrothermal or reverse micelle microemusion technique form metal salts or metal dithiocarbamates based single source molecular precursors.

Single-source precursor synthesis of quinary AgInGaZnS QDs with tunable photoluminescence emission

A single source molecular precursor synthesis of new quinary Ag-In-Ga-Zn-S (AIGZS) QDs is presented. Dithiocarbamate complexes with varied Ag/In/Ga/Zn ratios were prepared from AgNO3, In(NO3)3, Ga(NO3)3 and Zn(diethyldithiocarbamate)2. The thermal decomposition of these complexes at 220 °C in oleylamine produces AIGZS QDs emitting from the visible to the near-infrared region and with photoluminescence quantum yields (PL QYs) up to 48.3%. For AIGZS QDs prepared with a (Ag + In + Ga)/Zn molar ratio of 1, intragap states likely involving Ag+ ions are responsible of the PL emission and the PL lifetime could reach 278 ns. A marked increase of the PL lifetime (up to 915 ns) was observed when decreasing the (Ag + In + Ga)/Zn molar ratio to 0.5. The optical properties of AIGZS QDs could be maintained after transfer in aqueous solution. AIGZS should be of high potential for various applications due to their PL emission tunability and high PL QYs.

Dimethyltin(IV)-4,6-dimethyl-2-pyridylselenolate: an efficient single source precursor for the preparation of SnSe nanosheets as anode material for lithium ion batteries.

The air stable tin(IV) complex [Me2Sn{2-SeC5H2(Me-4,6)2N}2] has been synthesized, characterized by NMR, elemental analysis, and single crystal XRD, and employed as a single source molecular precursor (SSP) for the facile synthesis of orthorhombic SnSe nanosheets. The crystal structure, phase purity, morphology and band gap of the nanosheets were investigated by pXRD, EDS, electron microscopy and diffuse reflectance spectroscopy techniques, respectively. It was found that the preferential orientation of planes and the morphology of the nanosheets rely upon the reaction conditions. The band gaps of the nanosheets were blue shifted with respect to the bulk band gap of the material. The synthesized SnSe nanosheets have been employed as an anode material in lithium ion batteries (LIBs). The material exhibits an initial specific capacity of 1134 mA h g-1 at a current density of 50 mA g-1 and was found to retain a capacity of 380 mA h g-1 even after 70 cycles with 100% efficiency.

Thorium amidates function as single-source molecular precursors for thorium dioxide.

We report the synthesis of four homoleptic thorium(iv) amidate complexes as single-source molecular precursors for thorium dioxide. Each can be sublimed at atmospheric pressure, with the substituents on the amidate ligands significantly impacting their volatility and thermal stability. These complexes decompose via alkene elimination to give ThO2 without need for a secondary oxygen source. ThO2 samples formed from pyrolysis of C-alkyl amidates were found to have higher purity and crystallinity than ThO2 samples formed from C-aryl amidates.

Accessing photoresponsive copper selenide nanomaterials and thin films through tetranuclear Cu(I) pyridylselenolate cluster

The development of single-source molecular precursor for the synthesis of nanomaterials with controlled size and morphology has led to important scientific discoveries in past few decades. Herein, we describe the synthesis of air and moisture stable copper cluster complex with 5-methyl-2-pyridylselenolate, [Cu{2-SeC5H3(Me-5)N}]4 as molecular precursor for copper selenide nanomaterials and thin films. The complex was obtained in good yield, and the purity of the complex was evaluated through multi-nuclear NMR spectroscopy. The complex upon recrystallization in chloroform and toluene produces different polymorphs whose molecular structures were unambiguously established from single-crystal X-ray diffraction technique. Thermolysis of the complex in selected high-boiling solvents afforded phase-pure Cu1.8Se nanostructures. Thin films of phase-pure Cu5Se4 were also deposited by AACVD employing [Cu{2-SeC5H3(Me-5)N}]4 on glass and silicon substrates at different temperatures. The effect of higher temperature is perceived in drastic morphology change from nanosheets to a mixture of nanosheets and nanowires of Cu5Se4 on glass substrate. The nanostructures and thin films were characterized by pXRD, EDS, SEM and TEM techniques. The direct band gaps of the nanomaterials as deduced from diffuse reflectance spectroscopy are in the range 2.74–2.86 eV. The profound effect of solvent on phase purity, morphology and band gap of the nanostructures has also been investigated thoroughly. The nanostructures demonstrated prompt photoresponse which make them suitable candidate for non-toxic and low-cost photon absorber material. A tetranuclear Cu(I) complex with 5-methyl-2-pyridylselenolate ligand has been prepared and crystallized in two polymorphic forms, namely monoclinic [Cu{2-SeC5H3(Me-5)N}]4·C6H5CH3 and triclinic [Cu{2-SeC5H3(Me-5)N}]4. The complex was subjected to undergo thermolysis and AACVD to prepare Cu1.8Se nanomaterials and Cu5Se4 thin films, respectively. The nanomaterials and thin films were characterized using pXRD, SEM and TEM techniques to understand the phase purity and morphology. Fast switching characteristics of the nanomaterials have been established by switching characteristics.

Heterotrimetallic Precursor with 2:2:1 Metal Ratio Requiring at Least a Pentanuclear Molecular Assembly.

This work represents an important step in the quest to make heteromultimetallic molecules featuring specific metal types and complicated metal ratios. The rational design, synthesis, and characterization of a complex heterotrimetallic single-source molecular precursor for the next generation sodium-ion battery cathode material, Na2Mn2FeO6, is described. A unique pentametallic platform [MnII(ptac)3-Na-MnIII(acac)3-Na-MnII(ptac)3] (1) was derived from the known polymeric structure of [NaMnII(acac)3]∞, through a series of elaborate design procedures, such as mixed-ligand, unsymmetric ligand, and mixed-valent approaches. Importantly, the application of those techniques results in a molecule with distinctively different transition metal positions in terms of ligand environment and oxidation states. An isovalent substitution of FeIII for the central MnIII ion forms the target heterotrimetallic precursor [MnII(ptac)3-Na-FeIII(acac)3-Na-MnII(ptac)3] (3) with an appropriate metal ratio of Na:Mn:Fe = 2:2:1. The arrangement of metal ions and ligands in this pentametallic assembly was confirmed by single crystal X-ray investigation. The unambiguous assignment of the positions and oxidation states of the Periodic Table neighbors Fe and Mn in 3 has been achieved by a combination of investigative techniques that include synchrotron resonant diffraction, X-ray multiwavelength anomalous diffraction, X-ray fluorescence spectroscopy, Mössbauer spectroscopy, and gas-phase DART mass spectrometry. The heterotrimetallic single-source precursor 3 was shown to exhibit a clean decomposition pattern yielding the phase-pure P2-Na2Mn2FeO6 quaternary oxide with high uniformity of metal ion distribution as confirmed by electron microscopy.