Theivanayagam C. Deivaraj

Preparation of PtNi nanoparticles for the electrocatalytic oxidation of methanolElectronic supplementary information (ESI) available: TEM images of Pt nanoparticle seeds prepared from the methanol reduction of Pt salts. See http://www.rsc.org/suppdata/jm/b3/b307040a/

Carbon supported PtNi nanoparticles were prepared by hydrazine reduction of Pt and Ni precursor salts under different conditions, namely by conventional heating (PtNi-1), by prolonged reaction at room temperature (PtNi-2) and by microwave assisted reduction (PtNi-3). The nanocomposites were characterized by XRD, EDX, XPS and TEM and used as electrocatalysts in direct methanol fuel cell (DMFC) reactions. Investigations into the mechanism of PtNi nanoparticle formation revealed that platinum nanoparticle seeding was essential for the formation of the bimetallic nanoparticles. The average particle size of PtNi prepared by microwave irradiation was the lowest, in the range of 2.9–5.8 nm. The relative rates of electrooxidation of methanol at room temperature as measured by cyclic voltammetry showed an inverse relationship between catalytic activity and particle size in the following order PtNi-1 < PtNi-2 < PtNi-3.

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 NaBH 4 reduction of (phen)SnCl 4 (phen = 1, 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 Li + host, could also effectively buffer the specific volume changes in Sn-based Li storage compounds during charging (Li + insertion) and discharging (Li + extraction) reactions.

Stability and hybridization-driven aggregation of silver nanoparticle–oligonucleotide conjugates

Gold nanoparticles are well known to form stable oligonucleotide conjugates, via thiol–metal interaction, which are capable of specific DNA-hybridization induced aggregation. Preparation of an analogous conjugate with Ag particles, except when coated with a layer of Au, has been reported to yield conjugates that are unstable in the hybridization environment. We report herein the hybridization-induced aggregation of such “bare” Ag-particle conjugates prepared via a similar facile procedure to Au with slight modification. We found that the pH during functionalization is the critical factor determining the success of preparing conjugates that remain stable throughout the functionalization process and during hybridization. We reasoned that this is a consequence of the pH-dependent charge of the oligonucleotide, and demonstrated that pH strongly affects the amount of oligonucleotides adsorbed on the particle surface, thereby imparting stability to the particles. This finding has the potential to be generalized to other metal particle–oligonucleotide systems with borderline stability, helping to expand the repertoire of visible-range plasmon signatures useful for diagnostic application.

Self assembly of heptanuclear zinc(II) clusters linked by angular spacer ligands

Abstract Two one-dimensional coordination polymeric chains namely, [Zn7(μ4-O)2(CH3CO2)10(bpe)] (1) and ([Zn7(μ4-O)2(CH3CO2)10(dpds)] (2) (bpe=1,2-bis(4-pyridyl)ethane and dpds=4,4′-dipyridyldisulfide) have been obtained by self assembly method from Zn(O2CCH3)2 and spacer ligands dpe and dpds in the ratio 7:1, and characterized by X-ray crystallography. Compound 1 is a quasi-linear one-dimensional coordination polymer whereas 2 has the zigzag polymeric chain structure. The conformations of the backbone of these flexible angular ligands appear to influence the way in which the heptanuclear metal aggregates are bonded in the solid state. In 1, the py–C–C–py fragment has an anti conformation with the torsion angle, 180°. The S–C–C–S torsion angle for dpds in 2 is 61.8(5)° with the interplanar angle between the pyridine rings of 89.4(4)°.

A microemulsion-based preparation of tin/tin oxide core/shell nanoparticles with particle size control

Nearly monodispersed tin/tin oxide core/shell nanoparticles were prepared by a reverse microemulsion technique. A phenanthroline–tin chloride complex was used in an optimized microemulsion system to obtain small particle size and good size control (mean = 3.2 nm, standard deviation = 0.5 nm). Preparation in the absence of phenathroline in an otherwise identical microemulsion composition would result in larger particles and a broader size distribution (mean = 7.4 nm, standard deviation = 1.8 nm). The nanoparticles were extensively characterized and the sequence of events leading to the nanoparticle formation is postulated.

Preparation of Carbon-Supported PtNi Nanoparticles via the Single Source Molecular Precursor Approach

Carbon-supported PtNi nanoparticles have been prepared from the thermolysis of a single source precursor [(bipy) 3 Ni](PtCl 6 ). The single source precursor is highly stable under ambient conditions, allowing easy materials handling and storage. The carbon-supported PtNi nanoparticles had a mean diameter of 8.3 nm and were obtained by a two-stage process involving (i) the ballmilling of carbon and the precursor and (ii) the thermal degradation of the homogenized mixture at 550°C in a flowing H 2 /Ar gas mixture. The carbon-supported bimetallic nanoparticles were characterized by powder X-ray diffraction scanning electron microscopy-energy-dispersive X-ray, and transmission electron microscopy. The electro-oxidation of methanol over this catalyst was investigated and benchmarked against a commercial E-TEK Pt/C catalyst. The catalytic activity was higher for this homemade catalyst, which also displayed improved resistance to catalyst deactivation.

Single-source precursors to ternary silver indium sulfide materials.

Compounds of type [(Ph3P)2AgIn(SC(O)R)4] (R = Me (1), Ph (2)) are excellent single-source precursors for AgInS2 bulk materials by pyrolysis and AgIn5S8 films by aerosol assisted chemical vapour deposition (AACVD).

Group 11 and 13 metal thiocarboxylate compounds as single source molecular precursor for bulk metal sulfide materials and thin films

Abstract A number of new Cu(I), Ag(I), Ga(III) and In(III) metal thiocarboxylate compounds have been synthesized and characterized using various methods including X-ray crystallography. Thermal degradation of these compounds resulted in the formation of the corresponding metal sulfide materials. The metal sulfides thus obtained were characterized using XRD and SEM techniques. Solid solutions of the type (Et3NH)[In1xGax(SC{O}Ph)4] have been used as single source precursors to the corresponding In2xGaxS3 materials. In addition, compounds of the type [(Ph3P)CuM(SC{O}Ph)4], and [(Ph3P)2AgM(SC{O}R)4] (M = Ga3+ and In3+; R = Me and Ph) have been found to be useful as single source precursors for CuMS2, AgGaS2, AgInS2 and MIn5S8 materials and thin films.

Trialkylammonium salts of [M(SC{O}R)4]−(M = Ga3+ and In3+) as precursors for metal sulfide thin films

A series of trialkylammonium salts of indium and gallium thiocarboxylates, [Et3NH][M(SC{O}Ph)4]·H2O (M = In3+ (1), Ga3+ (2)) and [n-Bu3NH][In(SC{O}Ph)4] (3), [R3NH][In(SC{O}Me)4] (R = Et (4) and n-Bu (5)) have been synthesized and characterized. The structure of 2 has been determined by single crystal X-ray diffraction and was found to be isomorphous and isostructural with [Et3NH][In(SC{O}Ph)4]·H2O (1) reported earlier. Thermal properties of 1–5 were studied. Compound 4 exhibits a phase transition which was characterized by DSC. Thermogravimetric and pyrolysis experiments of 1, 3, 4 and 5 showed the formation of tetragonal β-In2S3 while 2 yielded poorly crystalline monoclinic Ga2S3. Thin films of tetragonal In2S3 were obtained on a Ni coated Si substrate by MOCVD experiments using 1. Under similar conditions, 2 resulted in a film containing both cubic γ-Ga2S3 and hexagonal Ni0.96S. When a Cu coated Si substrate was used 1 deposited thin films of tetragonal CuInS2, while 2 furnished a mixture of tetragonal Cu1.96S and tetragonal CuGaS2 films. The composition of the thin films also depends on the temperature employed during the growth process. The composition, stoichiometry, phase analysis and surface morphology of the thin films obtained have been unequivocally characterized using XRD, SEM, TEM, RBS, Selective Area Electron Diffraction and XPS. It appears that the decomposed product(s) of 1 and 2 react with the substrate to form the metal sulfide thin films.

Syntheses and structures of Group 12 metal thioacetate anions, [M(SC{O}Me)nCl4-n]2- (n = 3 and 4) and [Cd2Cl2(SC{O}Me)4]2-

Abstract We have utilized the possibility of altering the ratio of reactants to result in tetrahedral anions, [M(SC{O}Me)nCl4−n]2− (n=3, 4) and [Cd2Cl2(SC{O}Me)4]2−. Complexes of the formula [Ph4P]2[M(SC{O}Me)4] (M=Zn(II) (1), Cd(II) (2) or Hg(II) (3)) were synthesized by the reaction of thioacetate ligand with the metal salts and Ph4PCl in 4:1:2 molar ratio in suitable solvents. The geometry of Zn(II) in 1 is nearly tetrahedral and the distortion in tetrahedron increases in the order of 1