Catalyst engineering is a key point for selective growth of single-walled carbon nanotubes (SWCNT) with chemical vapor deposition (CVD). Here, we develop a new general synthesis method able to produce a wide range of homogenous bimetallic catalyst nanoparticles with controlled stoichiometry and sizes. The basics of this catalyst synthesis is to use preformed stoichiometric bimetallic Prussian blue analog (PBA) nanoparticles. Catalyst nanoparticles are then prepared in-situ in a hot filament CVD reactor with subsequent high temperature treatment in reducing atmosphere prior to SWCNT growth. The capabilities of the synthesis route are demonstrated by testing five PBA systems involving various transition metals. Transmission electron microscopy (TEM), scanning TEM and energy dispersive X-ray spectroscopy (STEM-EDX), and in-situ X-ray photoelectron spectroscopy (XPS) measurements are used to finely follow the size and composition of the catalyst at each step of the process. Each system yields small size catalysts with a narrow distribution, which act as efficient catalysts for SWCNT growth with a good yield and small diameter distribution. The versatility of the PBA family paves a new way for a fine tuning of the catalyst properties monitored by the metal involved in the PBA, and for opening routes to more selective SWCNT synthesis.

Laboratoire de Génie Electrique de Paris, CNRS UMR8507; SUPELEC; UPMC Univ Paris 06; Univ Paris-Sud, 11 rue Joliot Curie, F-91192, Gif-sur-Yvette, France CEA, IRAMIS, SPCSI Chemistry of Surfaces and Interfaces Group, F-91191 Gif-sur-Yvette, France CEA, IRAMIS, LLB, Laboratory for Molecular Electronics, F-91191 Gif-sur-Yvette, France Univ. Paris-Sud, ICMMO, UMR CNRS 8182, 15 rue Georges Clemenceau, F-91440 Orsay, France ∗Corresponding author: laurent.baraton@lgep.supelec.fr

We have used an atomic force microscope (AFM) to manipulate and study ligand-capped cadmium selenide nanorods deposited on highly oriented pyrolitic graphite (HOPG). The AFM tip was used to manipulate (i.e., translate and rotate) the nanorods by applying a force perpendicular to the nanorod axis. The manipulation result was shown to depend on the point of impact of the AFM tip with the nanorod and whether the nanorod had been manipulated previously. Forces applied parallel to the nanorod axis, however, did not give rise to manipulation. These results are interpreted by considering the atomic-scale interactions of the HOPG substrate with the organic ligands surrounding the nanorods. The vertical deflection of the cantilever was recorded during manipulation and was combined with a model in order to estimate the value of the horizontal force between the tip and nanorod during manipulation. This horizontal force is estimated to be on the order of a few tens of nN.

The functionalisation of a Si(100) silicon wafer allows for the oriented grafting of a monolayer of Mn12 nanomagnets using a two-step procedure.

An uncommon synergism in the concerted action of OH- and PR3 toward the simple Ru(II) complex Ru(CO)3Cl2(thf) allows a highly efficient reduction of the metal in ethanol or acetonitrile solution at 0 degrees C, with selective production of the corresponding Roper's-type Ru(0) complexes Ru(CO)2(PR3)3 in high yields within 10 min.

Imaging and spectroscopy of individual CdSe nanocrystals have been performed with the scanning tunneling microscope (STM) on atomically resolved hydrogenated Si(100) surfaces. The CdSe nanocrystals have been deposited under vacuum onto the surface by using the pulse valve method. Two different types of CdSe nanocrystals, capped either with trioctylphosphine oxide ligands or with cadmium stearate ligands, have been studied to optimize their anchoring to the surface. The I(V) spectroscopy shows a characteristic resonant excitation spectrum through the unoccupied levels of the nanocrystals with no significant charging effect. This suggests that the nanocrystals are weakly coupled to the surface, thus requiring a stronger coupling with the STM tip to achieve a measurable tunnel current. These results demonstrate the importance of depositing nanocrystals on clean and atomically well-defined surfaces for reliable measurement of their properties.

The fabrication of thin films of colloidal semiconductor nanocrystals is attracting much attention due to their exceptional optoelectronic properties. This requires the development of new methods for depositing nanocrystals under well-controlled conditions. Here, we report the use of the pulse injection method to deposit CdSe nanocrystals under ultrahigh vacuum (UHV) on clean and well-ordered surfaces. The deposition of nanocrystals has been tested by x-ray photoelectron spectroscopy (XPS) and near edge x-ray absorption fine structure spectroscopy. Special attention has been paid to the preparation of very pure solutions of CdSe nanocrystals using cadmium stearate, trioctylphosphine oxide (TOPO) and the TOP/Se adduct for the nanocrystals synthesis followed by dissolution in pentane. It has been found that CdSe nanocrystals adsorb with similar sticking coefficients on graphite, hydrogenated silicon (100) and hydrogenated diamond (100) surfaces. Furthermore, the XPS analysis has revealed that the surface of the CdSe nanocrystal is Cd rich, which has important consequences for the optical and chemical properties. This ability to deposit semiconductor nanocrystals under UHV conditions on clean and well-ordered surfaces opens up new perspectives for studying in a reliable manner all their chemical, electronic and optical properties.

A “user-friendly” catalyst system generated in situ in the absence of alkyne from Mo(CO)6, p-chlorophenol and a polyether over a bed of molecular sieves, is seen to achieve the metathesis of phenylpropyne at 50°C with a significant rate enhancement depending on the nature of the ether, with 1,2-diphenoxyethane exhibiting the highest efficiency.

Ruthenium phthalocyanine (RuPc) monolayers were obtained by self-assembly on pyridino-functionalized metal oxide substrates, by coordination between the ruthenium ions and the pyridino groups. The substrates were functionalized by silanization with a bifunctional silane. Soluble ruthenium phthalocyanines, axially coordinated by labile benzonitrile groups, were used. A ligand exchange reaction was involved, one benzonitrile group being replaced by pyridine. These RuPc monolayers were characterized by transmission W-vis spectroscopy, atomic force microscopy, polarization modulation infrared reflection-absorption spectroscopy, and time-of-flight secondary ion mass spectrometry. A second ligand exchange reaction allowed us to build RuPc bilayers by two different strategies. A mixed RuPc/cobalt porphyrin;bilayer was also obtained.

Axial metal complexation was used in the organization of the cobalt(II) meso-tetra(trimethylsilylethynyl)porphyrin, CoPTMS, by the Langmuir−Blodgett (LB) technique or by self-assembly (SA). The axial ligand is a para-substituted pyridine that carries a long aliphatic chain, C18NHPy, in the case of the LB technique or a triethoxysilane group, SiPy, in the case of SA. In both cases, monomolecular films of nonaggregated porphyrins have been obtained and characterized by IR and UV spectroscopies, linear dichroism, and X-ray diffraction. A 1/1/5 mixture of CoPTMS, C18NHPy, and methyl eicosanoate spread on a silver nitrate subphase led to the formation of a silver acetylide polychelate of porphyrins. After transfer onto a solid substrate, the macrocycles displayed a flat-on orientation. The polychelate monolayers are robust enough to allow easy dissolution of the methyl eicosanoate filling molecule without disturbing the macrocycle orientation inside the LB film.

The synthesis of several functionalized mono-, di-, tri-, and tetraphosphines is described. These compounds are used for the attempted preparation of hyperbranched polymers and dendrimers possessing free phosphino groups at each branching point within the structure. Theses attempts were not fully successful, but several phosphaacetylenic derivatives have been isolated.

Ruthenium phthalocyanines bearing pyridine-4-carboxaldehyde as an axial ligand were synthesized. The carboxaldehyde group of the apical ligand pointing out from the phthalocyanine ring was used to link the complex to chemically modified surfaces. The resulting monolayer was characterized by ellipsometry, IRRAS, XPS, X-ray reflectivity, and SPM. The grafting of RuPc to the surface is stable.

C92H120O20. triclinic, P (1) over bar (No. 2), a=16.162(3)Angstrom, b = 16.234(3) Angstrom, c = 18.301(4) Angstrom, alpha = 75.82(3)degrees beta = 79.79(3)degrees, gamma = 71.16(3)degrees, V = 4380.6 Angstrom(3) Z= 2, R-gt(F)= 0.079, wR(ref)(F-2)= 0.229, T= 100 K.

Self-assembled monolayers of 1,4-diisocyanobenzene on gold were used to bind ruthenium phthalocyanines to the surface by axial ligation of the macrocycle with isocyanide groups pointing out from the SAM. The 1,4-diisocyanobenzene SAM and the RuPc-1,4-diisocyanobenzene bilayer were characterized by ellipsometry, IRRAS, XPS, and SPM. The grafting of RuPc to the SAM is stable. The thickness of the film increases from 10 to 15 Angstrom upon RuPc ligation. IRRAS reveals that both ends of the 1,4-diisocyanobenzene are affected by the N=C to metal interaction occurring at the other end. XPS indicates that each RuPc macrocycle covers similar to 12 1,4-diisocyanobenzene molecules in the bilayer.