Single-source Precursor Approach Research Articles

Thin Films of Molybdenum Disulfide Doped with Chromium by Aerosol-Assisted Chemical Vapor Deposition (AACVD)

A combined single-source precursor approach has been developed for the deposition of thin films of Cr-doped molybdenum disulfide (MoS2) by aerosol-assisted chemical vapor deposition (AACVD). Tris(diethyldithiocarbamato)chromium(III) can also be used for the deposition of chromium sulfide (CrS). Films have been analyzed by a range of techniques including scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, Raman spectroscopy, and powder X-ray diffraction (pXRD) to elucidate film morphology, composition, and crystallinity. The presence of Cr in the MoS2 films produces a number of striking morphological, crystallographic, and nanomechanical changes to the deposited films. The chromium dopant appears to be uniform throughout the MoS2 from the scanning transmission electron microscopy (STEM) EDX spectrum imaging of nanosheets produced by liquid-phase exfoliation of the thin films in N-methyl-2-pyrollidone.

Lanthanide-doped CaS and SrS luminescent nanocrystals: a single-source precursor approach for doping.

The incorporation of dopants with optical or magnetic functionalities into colloidal nanocrystals (NCs) has been a longstanding challenge for nanomaterial research. A deeper understanding of the doping kinetics will aid a better control of the doping process. In particular, alkaline-earth sulfides are an important class of host materials for a range of luminescent dopants, including transition-metal and lanthanide ions. Their nanocrystalline analogues have many potential applications. However, the lack of synthetic methodologies hampers their development. Here we introduce a single-source precursor approach that successfully leads to Ce(3+)- and Eu(2+)-doped CaS and SrS luminescent NCs with diameters of ∼10 nm and with luminescent properties similar to those of the bulk analogues. The characteristic absorption and luminescence of Ce(3+) and Eu(2+) depend on the local coordination and are applied to probe dopant ion internalization. We demonstrate that controlling the reactivity of the precursors is crucial for achieving effective doping. By designing the chemical structure of the dopant precursor to vary the reactivity relative to that of the host precursor, the doping efficiency can be controlled. In addition, we have applied a growth doping strategy to further improve internalization of the dopants. Finally, we demonstrate nucleation doping as an alternative method to achieve lanthanide NC doping for dopant and host precursors with strongly different reactivities. The single-source precursor approaches proposed here allow for a flexible design of synthesis strategies and have the potential to be widely applicable to the doping of colloidal chalcogenide NCs with transition-metal and lanthanide dopant ions.

Colorimetric estimation of human glucose level using γ-Fe2O3 nanoparticles: An easily recoverable effective mimic peroxidase

This article reports simple, green and efficient synthesis of γ-Fe2O3 nanoparticles (NPs) (maghemite) through single-source precursor approach for colorimetric estimation of human glucose level. The γ-Fe2O3 NPs, having cubic morphology with an average particle size of 30nm, exhibited effective peroxidase-like activity through the catalytic oxidation of peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2 producing a blue-colored solution. On the basis of this colored-reaction, we have developed a simple, cheap, highly sensitive and selective colorimetric method for estimation of glucose using γ-Fe2O3/TMB/glucose–glucose oxidase (GOx) system in the linear range from 1 to 80μM with detection limit of 0.21μM. The proposed glucose sensor displays faster response, good stability, reproducibility and anti-interference ability. Based on this simple reaction process, human blood and urine glucose level can be monitored conveniently.

Nanostructured manganese oxides as highly active water oxidation catalysts: a boost from manganese precursor chemistry.

We present a facile synthesis of bioinspired manganese oxides for chemical and photocatalytic water oxidation, starting from a reliable and versatile manganese(II) oxalate single-source precursor (SSP) accessible through an inverse micellar molecular approach. Strikingly, thermal decomposition of the latter precursor in various environments (air, nitrogen, and vacuum) led to the three different mineral phases of bixbyite (Mn2 O3 ), hausmannite (Mn3 O4 ), and manganosite (MnO). Initial chemical water oxidation experiments using ceric ammonium nitrate (CAN) gave the maximum catalytic activity for Mn2 O3 and MnO whereas Mn3 O4 had a limited activity. The substantial increase in the catalytic activity of MnO in chemical water oxidation was demonstrated by the fact that a phase transformation occurs at the surface from nanocrystalline MnO into an amorphous MnOx (1<x<2) upon treatment with CAN, which acted as an oxidizing agent. Photocatalytic water oxidation in the presence of [Ru(bpy)3 ](2+) (bpy=2,2'-bipyridine) as a sensitizer and peroxodisulfate as an electron acceptor was carried out for all three manganese oxides including the newly formed amorphous MnOx . Both Mn2 O3 and the amorphous MnOx exhibit tremendous enhancement in oxygen evolution during photocatalysis and are much higher in comparison to so far known bioinspired manganese oxides and calcium-manganese oxides. Also, for the first time, a new approach for the representation of activities of water oxidation catalysts has been proposed by determining the amount of accessible manganese centers.

Single source precursor approach to the synthesis of Bi2S3 nanoparticles: A new amperometric hydrogen peroxide biosensor

Bi2S3 nanoparticles (NPs) are synthesized from a single source precursor complex Bi(ACDA)3 (HACDA=2-aminocyclopentene-1-dithiocarboxylic acid) through a simple solvothermal decomposition process. The precursor complex is characterized by several spectroscopic techniques (FTIR, UV–vis spectroscopy) and finally the structure has been determined by single crystal X-ray diffraction study suggesting an unusual distorted pentagonal pyramidal geometry. The transmission electron microscopic (TEM) study ascertains the NPs to be of rod-like structure with a diameter of approximately 10–40nm and a wide range of edge lengths from 50nm to 300nm. These NPs, immobilized on surface of a glassy carbon electrode (GCE), show high electron transfer ability and good electrochemical behavior and also exhibit electro-catalytic activity toward the reduction of hydrogen peroxide. As a result, this Bi2S3 NPs have been employed as a new H2O2 biosensor for amperometric estimation of H2O2 in a linear range from 10 to 5000μM. In addition to high stability, the present biosensor has good relative standard deviation (RSD=3.2%) and detection limit (DL of 2.5μM at 3σ).

Fast-grown CdS quantum dots: Single-source precursor approach vs microwave route

A cross-disciplinary protocol of characterization by joint techniques enables one to closely compare chemical and physical properties of CdS quantum dots (QDs) grown by single source precursor methodology (SSPM) or by microwave synthetic route (MWSR). The results are discussed in relation with the synthesis protocols. The QD average sizes, reproducible as a function of the temperatures involved in the growth processes, range complementarily in 2.8–4.5 nm and 4.5–5.2 nm for SSPM and MWSR, respectively. Hexagonal and cubic structures after X-ray diffraction on SSPM and MWSR grown CdS QDs, respectively, are tentatively correlated to a better crystalline quality of the latter with respect to the further ones, suggested by (i) a remarkable stability of the MWSR grown QDs after exposure to air during several days and (ii) no evidence of their fragmentation during mass spectrometry (MS) analyses, after a fair agreement between size dispersities obtained by transmission electron microscopy (TEM) and MS, in contrast with the discrepancy found for the SSPM grown QDs. Correlatively, a better optical quality is suggested for the MWSR grown QDs by the resolution of n > 1 excitonic transitions in their absorption spectra. The QD average sizes obtained by TEM and deduced from MS are in overall agreement. This agreement is improved for the MWSR grown QDs, taking into account a prolate shape of the QDs also observed in the TEM images. For both series of samples, the excitonic responses vs the average sizes are consistent with the commonly admitted empirical energy-size correspondence. A low energy PL band is observed in the case of the SSPM grown QDs. Its decrease in intensity with QD size increase suggests a surface origin tentatively attributed to S vacancies. In the case of the MWSR grown QDs, the absence of this PL is tentatively correlated to an absence of S vacancies and therefore to the stable behavior observed when the QDs are exposed to air.

A Single Source Precursor Route to Group 13 Homo‐ and Heterometallic Oxides as Highly Active Supports for Gold‐Catalyzed Aerobic Epoxidation of trans‐Stilbene

AbstractA new Mitsubishi‐type of star‐shaped homoleptic derivative of indium(III), In4(mdea)6 (2, mdeaH2 = N‐methyldiethanolamine), was synthesized by the chloro–aminoalkoxo exchange reaction of a heteroleptic complex In6Cl6(mdea)6 (1) and used as a facile single source molecular precursor for the sol–gel preparation of high surface area indium oxide. Successful deposition of gold nanoparticles (1 wt.‐%) of average size 3.3 nm on the above metal oxide by using HAuCl4·3H2O afforded a highly efficient Au/In2O3 catalyst for the aerobic epoxidation of trans‐stilbene at low temperature. The above single source precursor approach was further extended to obtain other group 13 homo‐ and heterometallic oxides, namely, α‐Ga2O3, β‐Ga2O3 and Al4Ga2O9, as highly active supports for gold catalysts. The obtained Au/M2O3 (M = Ga, In) and Au/Al4Ga2O9 catalysts were thoroughly characterized by using several physicochemical techniques such as XRD, high resolution transmission electron microscopy (HR‐TEM), energy‐dispersive X‐ray (EDX) spectroscopy, and X‐ray photoelectron spectroscopy (XPS). A comparative study of the above catalysts for the model aerobic oxidation of stilbene in methylcyclohexane was undertaken.

Single-source precursor approach for the preparation of CdS nanoparticles and their photocatalytic and intrinsic peroxidase like activity

CdS nanoparticles (NPs) with different shapes and sizes (rods and spheres) have been synthesized through decomposition of a newly synthesized precursor complex [Cd(SOCPh)2Lut2] using structure-directing solvents such as ethylenediamine (EN), dimethylsulfoxide (DMSO) and ammonia (NH3). In addition, CdS NPs is also prepared by thermal decomposition of the precursor complex under N2 atmosphere. The precursor complex is characterized by elemental analyses, TGA, FTIR, UV–vis spectroscopy and single crystal X-ray diffraction. The distorted tetrahedron geometry of the precursor complex has been determined by X-ray diffraction, which crystallizes in monoclinic crystal system of P2(1)/n space group with a=11.0487(17)Å, b=16.396(3), c=15.413(2)Å, α=90.00°, β=109.708(4)°, γ=90.00° and Z=4. The CdS NPs are characterized using powder X-ray diffraction, transmission electron microscopy, BET analyses, UV–vis absorption and photoluminescence spectroscopy. The photo-catalytic activity of CdS NPs is studied by the degradation of Rose Bengal (RB) dye, indicating an excellent photocatalytic activity compared to that of commercial TiO2. The mechanism behind photocatalytic degradation of RB in presence of CdS NPs is elucidated using terephthalic acid photoluminescence probing technique and evidence have shown that the photogenerated holes to be the predominant active species. This paper also demonstrates the intrinsic peroxidase like activity of CdS NPs toward peroxidase substrates 3,3′,5,5′-tetramethyl benzidine (TMB) and hydrogen peroxide. Kinetic analysis indicates that the catalysis by CdS NPs show typical Michaelis–Menten kinetics. Moreover, our synthesized CdS NPs show higher catalytic performances with a higher binding affinity for the substrate TMB than horseradish peroxidase (HRP) and other recently reported nano-mimitics.

Solution‐Based Synthesis and Design of Late Transition Metal Chalcogenide Materials for Oxygen Reduction Reaction (ORR)

Late transition metal chalcogenide (LTMC) nanomaterials have been introduced as a promising Pt-free oxygen reduction reaction (ORR) electrocatalysts because of their low cost, good ORR activity, high methanol tolerance, and facile synthesis. Herein, an overview on the design and synthesis of LTMC nanomaterials by solution-based strategies is presented along with their ORR performances. Current solution-based synthetic approaches towards LTMC nanomaterials include a hydrothermal/solvothermal approach, single-source precursor approach, hot-injection approach, template-directed soft synthesis, and Kirkendall-effect-induced soft synthesis. Although the ORR activity and stability of LTMC nanomaterials are still far from what is needed for practical fuel-cell applications, much enhanced electrocatalytic performance can be expected. Recent advances have emphasized that decorating the surface of the LTMC nanostructures with other functional nanoparticles can lead to much better ORR catalytic activity. It is believed that new synthesis approaches to LTMCs, modification techniques of LTMCs, and LTMCs with desirable morphology, size, composition, and structures are expected to be developed in the future to satisfy the requirements of commercial fuel cells.

Optical and Photocatalytic Properties of Heavily F–-Doped SnO2 Nanocrystals by a Novel Single-Source Precursor Approach

Heavily F-doped SnO(2) nanocrystals were successfully prepared by a novel synthetic approach involving low-temperature oxidation of a Sn(2+)-containing fluoride complex KSnF(3) as the single-source precursor with H(2)O(2). The F-doped SnO(2) powder was characterized by powder X-ray diffraction, TG-MS, BET surface area, diffuse reflectance spectroscopy, XPS, PL, FTIR spectroscopy, Raman spectroscopy, EPR spectroscopy, SEM, and TEM. Broadening of the diffracted peaks, signifying the low crystallite size of the products, was quite evident in the powder X-ray diffraction pattern of SnO(2) obtained from KSnF(3). It was indexed in a tetragonal unit cell with lattice constants a = 4.7106 (1) Å and c = 3.1970 (1) Å. Agglomeration of particles, with an average diameter of 5-7 nm, was observed in the TEM images whose spotwise EDX analysis indicated the presence of fluoride ions. In the core level high-resolution F 1s spectrum, the peak observed at 685.08 eV was fitted by the Gaussian profile yielding the fluoride ion concentration to be 21.23% in the SnO(2) lattice. Such a high fluoride ion concentration is reported for the first time in powders. SnO(2):F nanocrystals showed greater thermal stability up to 300 °C when heated in a thermobalance under flowing helium, after which generation of small quantities of HF was observed in the TG coupled mass spectrometry analysis. The band gap value, estimated from the Kubelka-Munk function, showed a large shift from 3.52 to 3.87 eV on fluoride ion doping, as observed in the diffuse reflectance spectrum. Such a large shift was corroborated to the overdoped situation due to the Moss-Burstein effect with an increase in the carrier concentration. In the photoluminescence (PL) spectrum, SnO(2):F nanocrystals exhibited a broad green emission arising from the singly ionized oxygen vacancies created due to higher dopant concentration. The evidence for singly ionized vacancies was arrived from the presence of a signal with a g value of 1.98 in the ESR spectrum of SnO(2):F at room temperature. The disordered nature of the rutile lattice and the enormous oxygen vacancies created due to fluoride ion doping were evident from the broad bands observed at 455, 588, and 874 cm(-1) in the room-temperature Raman spectrum of SnO(2):F. As the consequence of the oxygen vacancies, F-doped SnO(2) was examined for the function as a photocatalyst in the degradation of aqueous RhB dye solution under UV irradiation. A very high photocatalytic efficiency was observed for the F-doped SnO(2) nanocrystals as compared to pure SnO(2). The BET surface area of pure SnO(2) was quite high (207.81 m(2)/g) as compared to the F-doped SnO(2) nanocrystals (45.16 m(2)/g). Pore size analysis showed a mean pore diameter of 1.97 and 13.97 nm for the pure and doped samples. The increased photocatalytic efficiency was related to the very high concentration of oxygen vacancies in SnO(2) induced by F doping.

Controlling precursor stability and evaporation through molecular design. Pseudo single source precursor approach to MOCVD SrTiO 3 thin films

Strontium titanate SrTiO 3 thin films have attracted interest as a possible gate dielectric material. Preparation of its high quality coatings is hindered by difference in volatility of the homometallic precursors – strontium beta-diketonates and titanium alkoxides. The only earlier known single-source precursor, a sec-alkoxide derivative Sr 2Ti 2(thd) 4(OiPr) 8, has limited volatility. Bimetallic primary alkyl chain complexes, Sr 4Ti 2O(thd) 4(OR) 10(ROH) 2, R = Et, nPr, are stable and volatile, but possess a wrong composition. Highly volatile precursor Sr 2Ti 2(thd) 4(O iBu) 8 has been prepared using an iso-alkoxide, combining proper ligand size with the sterical requirements, and characterized by multivariate evaporation analysis. Its evaporation is associated with complete decomposition into homometallic species, which, however, are evaporated in a single step. This permits to successfully use this novel precursor for SrTiO 3 thin film deposition by DLI-MOCVD technique in a sufficiently broad established temperature range. Using optimized experimental conditions, 100 nm thick strontium titanate films with high permittivity have been successfully obtained on (1 0 0) Si.

Diverse-shaped iron sulfide nanostructures synthesized from a single source precursor approach

Iron sulfide nanostructures with diverse shapes (nanoparticles, nanoribbons and nanoplates) have been synthesized via a single-source precursor of Fe(Ddtc)3 or Fe(Ddtc)2(Phen) (Phen = 1,10-phenanthroline; Ddtc = diethyldithiocarbamate) in the mixture solvents of oleic acid (OA)/oleylamine (OM)/1-octadecene (ODE). The chemical compositions of the as-formed iron sulfide nanostructures are found to be determined by the valencies of iron in the precursors. For phase-pure Fe3S4 and Fe7S8 nanostructures, their shape-selective syntheses could be realized mainly by modifying the ratio of reaction solvent compositions and the chemical composition of precursors. The growth of nanoparticles and nanoplates of iron sulfide is likely due to the selective adsorption of the capping ligands on specific crystal planes of the nanocrystals. Meanwhile, for FeSx nanoribbons, the growth of nanoribbons may come from the template-direction of micellar structures formed by self-assembly of capping ligands. Furthermore, the Fe3S4 and Fe7S8 nanostructures display strong ferromagnetic properties at room temperature.

One-Pot Synthesis of Single-Source Precursors for Nanocrystalline LED Phosphors M2Si5N8:Eu2+ (M = Sr, Ba)

Highly efficient red-emitting nitridosilicate phosphors Sr2Si5N8:Eu2+ and Ba1.5Sr0.5Si5N8:Eu2+ (doping level 1 %) applicable to phosphor converted pc-LEDs were synthesized in nanocrystalline form at low temperatures employing a novel single-source precursor approach. Synthesis starts from nanocrystalline silicon and uses mixed metal amides M(NH2)2 with M = Sr, Ba, Eu as reactive intermediates. In a second approach, a single-source precursor mixture obtained from a one-pot reaction of the corresponding elements (Sr/Ba, Eu, Si) was obtained in supercritical ammonia. Thermoanalytical in situ investigations gain a deeper insight into the degradation mechanism of the mixed metal amide precursors and revealed the onset for the formation of the 2-5-8 phosphor materials at temperatures slightly above 900 °C. Formation of the products is complete below 1400 °C. Under these conditions, the nitridosilicate phosphors form spherically shaped particles with crystallites of 200 nm in size. Spherical particles are desira...

Atomically Efficient Synthesis of Self-assembled Monodisperse and Ultrathin Lanthanide Oxychloride Nanoplates

Monodisperse and ultrathin LaOCl nanoplates were synthesized via the thermolysis of La(CCl(3)COO)(3) in long chain amine and 1-octadecene. This single source precursor approach is simple but atomically efficient. The uniform amine-capped LaOCl nanoplates can be aligned into nanowire-like and nanorod-like superstructures, as a result of the different strengths of the interchain molecular interactions of the capping molecules during the self-assembly process of the nanoplates.

Chemical Synthesis and Magnetotransport of Magnetic Semiconducting Fe1−xCoxSi Alloy Nanowires

We report single-crystal nanowires of magnetic semiconducting Fe1-xCoxSi alloys synthesized using a two-component single source precursor approach. Extending our previous syntheses of FeSi and CoSi nanowires from Fe(SiCl3)2(CO)4 and Co(SiCl3)(CO)4 precursors, we found that a homogeneous solution formed upon mixing these two precursors due to melting point suppression. This liquid constitutes the single-source precursor suitable for delivery through chemical vapor deposition, which enables the chemical synthesis of Fe1-xCoxSi alloy nanowires on silicon substrates covered with a thin (1-2 nm) SiO2 layer. Using scanning and transmission electron microscopy and energy dispersive X-ray spectroscopy and mapping, we demonstrate two homogenously mixed alloy nanowire samples with very different Co substitution concentrations (x): 6+/-5%, the ferromagnetic semiconductor regime, and 44+/-5%, the helical magnetic regime. The magnetotransport properties of these alloy nanowires are pronouncedly different from that of the host structures FeSi and CoSi, as well as from one another, and consistent with the physical properties as expected for their corresponding compositions. These novel magnetic semiconducting silicide nanowires will be important building blocks for silicon-based spintronic nanodevices.

Semiconductor/porous silica glass nanocomposites via the single-source precursor approach

The utilization of single-source molecular precursor approach to obtain II–VI and IV–VI semiconductors encapsulated in porous Vycor glass (PVG) is described. The procedure is based on the impregnation of cadmium and lead(II) diethyl-dithiocarbamate complexes, Cd(S 2CNEt 2) 2 and Pb(S 2CNEt 2) 2, inside the porous environment of PVG followed by a thermal treatment of the glass. The pyrolysis of the impregnated precursor gives rise to binary semiconductors CdS and PbS, respectively. The impregnation step is driven by interactions between the precursors and active sites located at glass pore surfaces. After completing the impregnation–decomposition cycle, it was found that the active glass sites were regenerated, making new cycles possible. The amount of encapsulated semiconductor increases linearly as a function of the number of cycles. Nanocomposites obtained after 1–10 cycles were prepared and characterized by optical spectroscopy, X-ray diffraction powder and transmission electron microscopy.

Tin Nanoparticle Loaded Graphite Anodes for Li‐Ion Battery Applications.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Single-Crystalline and Monodisperse LaF3 Triangular Nanoplates from a Single-Source Precursor

Single-crystalline and monodisperse LaF3 triangular nanoplates (2.0 x 16.0 nm) in trigonal tysonite structure were synthesized by the thermolysis of a single-source precursor (SSP), La(CF3COO)3, in a hot oleic acid/octadecene solution. The combined use of SSP and coordinating and noncoordinating solvents was demonstrated to have played key roles in the formation of such high-quality nanoplates, which could spontaneously organize into two types of superlattices (edge-to-edge and face-to-face) on a large area. This SSP approach has advantages of one-step, mass production, and easy operation, and may represent a rather general route toward metal fluoride nanocrystals.

Geometrical Molecular Structure Design Concept in Approach to Homo- and Heterometallic Precursors of Advanced Materials in Sol?Gel Technology

The article describes the principles of the Single Source Precursor approach to inorganic materials and introduces the Geometrical Molecular Structure Design Concept (MSDC) based on the choice of a proper molecular structure type for the desired precursor and completing it with ligands providing both the necessary number of donor atoms and the sterical protection of the chosen core. Application of MSDC is illustrated with examples taken from development of new approaches in the synthesis of oxide and sulfide catalysts and ferroelectric oxide materials.

Tin Nanoparticle Loaded Graphite Anodes for Li-Ion Battery Applications

Nearly monosized Sn nanoparticles were produced by an in situ prepared single-source molecular precursor approach. The experimental conditions in the reduction of 10 phenanthroline) in water were carefully controlled to produce two different particle size ranges, 2-5 nm (mean: 3.5 nm, standard deviation: 0.8 nm) and 7-13 nm (mean: 10.0 nm, standard deviation: 1.7 nm). The Sn nanoparticles were subsequently dispersed in graphite (KS6) and the application of the resulting nanocomposites as an active anode material for Li-ion batteries was explored. The graphite-Sn nanocomposites showed significant improvement in the cyclability of Sn over previously reported results. The cyclability improvement is believed to be due to the smallness of the Sn particles and their uniform distribution in a soft matrix (graphite) which, in addition to being a capable host, could also effectively buffer the specific volume changes in Sn-based Li storage compounds during charging insertion) and discharging extraction) reactions. © 2004 The Electrochemical Society. All rights reserved.