INORGANIC RINGS AND CLUSTERS AS SINGLE-SOURCE PRECURSORS TOWARD STOICHIOMETRY CONTROLLED SYNTHESIS OF MATERIALS: GAS PHASE CHEMISTRY IN COMMAND

Potential of the inorganic rings and clusters as single-source precursors to 13–15 binary materials and composites is examined employing quantum-chemical methods. Importance of the gas phase association reactions during MOCVD processes from organometallic and hydride precursors is emphasized. Generation of the gas phase [HMYH]_n clusters (M = Al,Ga,In; Y = N,P,As) with large oligomerization degree (n ≥ 30) is thermodynamically favorable even at high temperature conditions (1000 K) for all M,Y pairs. High stability of the N-containing clusters makes mixed metal oligomer imidometallanes excellent single-source precursors for the stoichiometry-controlled MOCVD of 13–15 composites.     

The single molecular precursor approach to metal telluride thin films: imino-bis(diisopropylphosphine tellurides) as examples

Interest in metal telluride thin films as components in electronic devices has grown recently. This tutorial review describes the use of single-source precursors for the preparation of metal telluride materials by aerosol-assisted chemical vapour deposition (AACVD) and acquaints the reader with the basic techniques of materials characterization. The challenges in the design and synthesis of suitable precursors are discussed, focusing on metal complexes of the recently-developed imino-bis(diisopropylphosphine telluride) ligand. The generation of thin films and nanoplates of CdTe, Sb(2)Te(3) and In(2)Te(3) from these precursors are used as illustrative examples.     

热解单源前驱体方法可控制备纳米金属硫化物

本文简要综述了本研究组近年来在利用热解单源前驱体合成方法制备纳米金属硫化物方面的相关工作．通过采用不同的反应前驱体,改变反应时间、反应温度,选择不同的表面配体分子及反应溶剂等手段实现了对纳米金属硫化物形貌、尺寸、组成和晶相的精确调控．除了对合成方法和过程进行介绍外,本文还简要讨论了具有特定形貌的金属硫化物的形成机理,并对几类典型硫化物的应用研究进行了总结．     

Organometallics meet colloid chemistry: a case study in three phases based on molecular carbonyl precursors containing zinc and manganese

Two organometallic compounds containing zinc and manganese in different ratios are used as single-source precursors for the preparation of various new, bimetallic oxide materials with nanoscaled dimensions. It is shown that the materials synthesis can be performed in the solid-state, the liquid-phase, and even in the gas-phase. The molecular composition of the precursors determines the composition of the resulting materials. In addition, two novel methods for the preparation of highly crystalline metal oxide colloids are presented: The coupling between a gas-phase process and a colloidal approach, and the application of ozone as an oxidant for the transformation of metal carbonyls into oxides in the liquid phase.     

Single-source precursors to gallium and indium oxide thin films

Gallium and indium oxide thin films have received much attention in recent years for their wide range of applications. This review summarises the literature concerning single-source precursors and the methods employed to deposit gallium and indium oxide thin films using these compounds. An update of the literature outlining compounds which are potential single-source precursors to these materials is also included.     

Structure and morphology of spinel MFe2O4 (M=Fe, Co, Ni) nanoparticles chemically synthesized from heterometallic complexes

We synthesized magnetic spinel ferrites from trimetallic single-source precursors. Fe(II), Co(II), and Ni(II) ferrite nanoparticles in the range of 9-25 nm were synthesized by solvothermal decomposition of trimetallic acetate complex precursors in benzyl ether in the presence of oleic acid and oleylamine, using 1,2-dodecanediol as the reducing agent. For comparison, spinel ferrite nanoparticles were synthesized by stoichiometric mixtures of metal acetate or acetylacetonate salts. The nanoparticles (NP) were characterized by TEM, DLS, powder XRD, and Raman spectroscopy; and their magnetic properties were characterized by ZFC-FC and M(H) measurements. The ferrite-NP were more homogeneous and had a narrower size distribution when trimetallic complexes were used as precursors. As a consequence, the magnetic properties of these ferrite-NP are closer to the aimed room temperature superparamagnetic behavior, than are those of other ferrites obtained by a mixture of salts.     

Chalcogen-containing metal chelates as single-source precursors of nanostructured materials: recent advances and future development

Abstract

The analysis of the use of chalcogenide metal chelates as single-source precursors of nanostructured materials has been carried out. The influence of the nature of the ligand, temperature, capping agents, thermolysis time, and solvent on the kinetic laws of thermolysis and the properties of the resulting nanomaterials is considered. Particular attention is paid to thermolysis of polynuclear chalcogenide metal chelates. The basic data on the synthesis of metal-polymer nanocomposites by thermolysis of chalcogenide metal chelates in the presence of polymers are summarized. The problems and future prospects of obtaining nanostructured materials by thermolysis of chalcogenide metal chelates are outlined. The bibliography includes articles published during the last 5 years.     

Metal anion-alkyl ammonium complexes as direct write precursors to produce nanopatterns of metals, nitrides, oxides, sulfides, and alloys

The study explores the possibility of using metal anions complexed with tetraoctylammonium bromide (ToABr) as single-source direct write precursors in e-beam and soft lithography processes to obtain micro- and nanoscale patterns of various metals, i.e., Au, Pd, Pt, Ag, Pb and Cu, as well as of their alloys (AuCu), oxides (Co(3)O(4), ZnO), nitrides (CoN, InN, GaN), and sulfides (Ag(2)S). The extraction efficiency of ToABr for different metal anions is found to be varied (40-90%), but the obtained precursors are easily processable as they have reasonable solubility in common solvents and are obtainable as smooth films, both being important for high-resolution patterning. The e-resist action of the precursors originates from the extreme e-beam sensitivity of the hydrocarbon chain present in ToABr, while direct micromolding has been possible due to easy flow of the precursor solutions in capillaries. The interaction of the anion and ToABr being mainly electrostatic enables easy removal of the hydrocarbon from patterned regions by thermolysis on a hot plate in the ambient or in controlled atmosphere to form the desired product. This method can be easily generalized.     

Solvent-free MALDI investigation of the cationization of linear polyethers with alkali metals

The MALDI technique with solvent-free sample preparation has been applied to evaluate relative gas-phase affinities of polyether chain polymers with alkali metal cations. The study is performed on poly(ethylene glycol) and poly(propylene glycol) polymers of different lengths (PEG600, PEG1000, PPG425, PPG750) and the alkali metal cations Li(+), Na(+), K(+), and Cs(+). The experiments show that the lattice energy of the alkali metal salts employed as cation precursors can have a strong influence on the outcome of conventional MALDI measurements. With the solvent-free method, these crystal binding effects can be made negligible by combining in the same sample alkali metal salts with different counterions. The recorded MALDI spectra show that the polyether-cation aggregation efficiencies decrease systematically with growing cation size. This cation size selectivity is considerably enhanced for the polymers with the shorter chains, which can be attributed to the reduced ability of the polymer to build a coordination shell around the larger cations. The steric effects introduced by the side CH3 group of propylene glycol with respect to ethylene glycol also enhance the preference for cationization of the polymer by the smaller cations. These observations correct some qualitative trends derived from previous studies, which did not account for lattice energy effects of the cation precursors.     

Synthesis and properties of Zn-Mg heterobimetallic carbamates. Crystal structures of the first reported single source precursors for Zn(x)mg(1-x)O thin films

The first mixed-metal Zn-Mg carbamates have been synthesised using a novel strategy of co-reaction between zinc and magnesium alkylamido intermediates. The complexes were structurally characterised by single-crystal X-ray diffraction; the nuclearity of these carbamato core subunits was found to vary from tetrameric to octameric with respect to the level of magnesium incorporated. The presence of magnesium in the predominantly zinc carbamato lattice was confirmed by refinement of the site occupancies of the metal atoms during the crystal data analysis, and it was found that displacement of up to 7.8% of zinc sites by magnesium atoms could be achieved before breakdown of the structure. Characterisation of the complexes' physicochemical properties revealed that they were suitable for use as single-source chemical vapour deposition (SSCVD) precursors in the deposition of Zn(x)Mg(1-x)O thin films, an emerging material with promising band-gap engineering prospects.     

From "parasitic" association reactions toward the stoichiometry controlled gas phase synthesis of nanoparticles: a theoretically driven challenge for experimentalists

In the present record a model for the gas-phase reactions during the chemical vapor deposition (CVD) processes of group 13-15 materials is presented, based on the results of extensive quantum-chemical modeling. Thermodynamic criteria have been introduced to evaluate the importance of a range of association reactions. For the organometallic and hydride derivatives, association processes are found to be favorable both thermodynamically and kinetically. Formation of high mass association products takes place under CVD conditions, including laser-assisted CVD. Structural and thermodynamic properties of the most important ring and cluster intermediates have been predicted. The stoichiometry-controlled synthesis of the 13-15 ternary alloys and nanoparticles using cluster compounds as single-source precursors is predicted to be viable. The association pathway described may be generalized to the CVD reactions of many binary materials (12-16, 13-16, 13-15, 14-15, 14-16).     

A novel soft hydrothermal (SHY) route to crystalline PbS and CdS nanoparticles exhibiting diverse morphologies

We report a simple and rapid aqueous route to crystalline nanoparticles of PbS and CdS using single-source precursors and a conventional household pressure cooker.     

Heterometallic Carboxylate Complexes as Precursors for Mixed Oxides: II. d–d Carboxylates

Russian Journal of General Chemistry - The current status of research into the thermal behavior of heterometallic d–d carboxylates that are suitable candidates for single-source precursors of...     

Heterometallic Carboxylate Complexes as Precursors for Mixed Oxides: III. 3d–4f Carboxylates

Russian Journal of General Chemistry - The current status of research into the thermal behavior of heterometallic 3d–4f carboxylates that are suitable candidates for single-source precursors...     

α‐Carbonyl Cations in Sulfoxide‐Driven Oxidative Cyclizations

The selective, metal‐free generation of α‐carbonyl cations from simple internal alkynes was accomplished by the addition of a sulfoxide to a densely substituted vinyl cation. The high reactivity of the α‐carbonyl cations was found to efficiently induce hydrogen and even carbon shift reactions with unusual selecivities. Complex compounds with highly congested tertiary and all‐carbon‐substituted quartenary carbon centers can thus be accessed in a single step from simple precursors. Mechanistic analysis strongly supports the intermediacy of the title compounds and provides a simple predictive scheme for the migratory aptitude of different substituents.     

Single source molecular precursor routes to lead chalcogenides

The use of single-source molecular precursors for lead chalcogenide thin films by CVD or as nanoparticles by solution methods is reviewed. The potential applications of these materials in solar energy are discussed along with the relative advantages of the various methods.     

Syntheses of semiconductor nanoparticles using single-molecular precursors

Methods for the preparation of II-VI, III-V, and II-V as well as other compound semiconductor nanoparticles using main group single-molecular precursors have been developed. The work involves the design and synthesis of compounds containing all the elements required within the desired nanoparticulate material. Precursors are tailored to give reproducible, clean decomposition at moderate temperatures, leading to high quality, defect free, mono-dispersed nanoparticles. In this article we cover key aspects of precursor and nanoparticle synthesis. One of the more successful and reproducible series of single-source precursors used, and the one on which we have concentrated our research efforts, is the bis(dialkyldithio-/diseleno-carbamato)cadmium(II)/zinc(II) compounds, M(E(2)CNR(2))(2) (M = Zn or Cd, E = S or Se, and R = alkyl) for the preparation of chalcogenide nanoparticulate materials. Preliminary mechanistic studies suggest that the precursor to nanoparticle deposition route is strongly influenced by the alkyl substituent groups present, and may well determine the phase and quality of the final metal chalcogenide nanoparticles produced. Herein we discuss the synthesis of semiconductor nanoparticles using such single-molecular precursors.     

Synthesis and characterization of metal substituted AlxCr1−x(acetylacetonate)3 single-source precursors for their application to MOCVD of thin films

A detailed study, involving the synthesis of a single-source precursor containing two metal ions sharing the same crystallographic site, has been undertaken to elucidate the use of such a single-source precursor in a CVD process for growing thin films of oxides comprising these two metals, ensuring a uniform composition and distribution of metal ions. The substituted complexes Cr_1−xAl_x(acac)₃, where acac = acetylacetonate, have been prepared by a co-synthesis method, and characterized using UV–Vis spectroscopy, TGA/DTA measurements, and single crystal X-ray diffraction at low temperature. All the studied compositions crystallize in the monoclinic space group P2₁/c with Z = 4 in the unit cell. It was observed that the ratio (Al:Cr) of the site occupancy for the metal ions, obtained from single crystal refinement, is in agreement with the results obtained from complexometric titrations. All the solid state structures have the metal in an octahedral environment forming six-membered chelate rings. M–O acac bond lengths and disorder in the terminal carbon have been studied in detail for these substituted metal–organic complexes. One composition among these was chosen to evaluate their suitability as a single-source precursor in a LPMOCVD process (low-pressure metal–organic chemical vapour deposition) for the deposition of a substituted binary metal oxide thin film. The resulting thin films were characterized by X-ray diffraction, scanning electron microscopy, and infrared spectroscopy.     

Heterometallic Carboxylate Complexes as Precursors for Mixed Oxides: I. s–d Carboxylates

The current status of research into the thermal behavior of heterometallic s–d carboxylates that are suitable candidates for single-source precursors of mixed oxides was considered. Emphasis was placed on the thermal stability and conditions of conversion of complexes to mixed oxides The influence of the composition and nature of the precursor on the composition and properties of the resulting mixed oxides was demonstrated.

     

A new facile route for the preparation of single-source precursors for bulk, thin-film, and nanocrystallite I-III-VI semiconductors

We report a new simplified synthetic procedure for commercial manufacture of ternary single-source precursors (SSPs). This new synthetic process has been successfully implemented to fabricate known SSPs on bulk scale and the first liquid SSPs to the semiconductors CuInSe(2) and AgIn(x)S(y). Single crystal X-ray determination reveals the first unsolvated ternary AgInS SSP. SSPs prepared via this new route have successfully been used in a spray assisted chemical vapor deposition (CVD) process to deposit polycrystalline thin films, and for preparing ternary nanocrystallites.