A novel organometallic synthetic method has been developed for the preparation of crystalline ZnO nanoparticles of controlled size and shape. Isotropic nanoparticles with a mean size between 3 and 6 nm and nanorods with a mean diameter of 3–4 nm and length up to 120 nm have been obtained in this way. This synthetic method takes advantage of the exothermic reaction of the precursor Zn(c‐C6H11)2 (1) toward moisture and air and involves the presence of long‐alkyl‐chain amines as stabilizing ligands. The influence of the different experimental parameters (concentration, solvent, nature of the ligand, time, and temperature) on the size and shape of the ZnO nanoparticles has been studied, together with the mechanism of their formation, by NMR spectroscopy, transmission electron microscopy, and X‐ray diffraction techniques. The nanoparticles prepared in this way can be dissolved in most of the common organic solvents, forming colloidal solutions. The surface state of the nanoparticles as well as the possibility of forming luminescent solutions from which regular monolayers can be deposited are also reported.

The emission properties of nanocrystalline ZnO particles prepared following an organometallic synthetic method are investigated. Spherical particles and nanorods are studied. The shape of the particles and the ligands used are shown to influence the luminescence properties in the visible domain. Two different emissions are observed at 440 nm (approximately 2.82 eV) and at 580 nm (approximately 2.14 eV) that are associated with the presence of surface defects on the particles. The first emission corresponds to the well-known yellow emission located at 580 nm (approximately 2.14 eV) with a lifetime of 1850 ns for 4.0 nm size ZnO nanoparticles. The second emission at 440 nm (approximately 2.82 eV) is observed when amine functions are present. This strong blue emission is associated with an excitation energy less than that associated with the yellow emission displaying a lifetime of nine nanoseconds. A possible hole trapping effect by the amine groups on the surface of the ZnO particles is discussed as the origin of this emission. The modification of the intensities between the two visible emissions for different particle shapes is proposed to be related to a specific location of the amine ligands on the surface of the particles.

The X-ray structure of (Tl[Au(C(6)Cl(5))(2)])(n), 1, consists of 1-D linear polymer chains parallel to the crystallographic z axis. The crystal structure of 1 has channels that run parallel to these chains with interatom distances in the range 3.231-4.076 A. There are holes in these channels with diameters as large as 10.471 A, which can accommodate a variety of solvents. Complex 1 displays reversible vapochromic emission and absorption spectral behavior when the solid is exposed to a variety of organic vapors such as acetone, acetonitrile, triethylamine, acetylacetone, tetrahydrothiophene, 2-fluoropyridine, tetrahydrofuran, and pyridine. Complex 1 is luminescent at room temperature and at 77 K in the solid state. UV excitation at 495 nm leads to an emission at 531 nm.

Nanomaterials made easy! The facile oxidation of [Zn(c‐C6H11)2] at room temperature in an organic solvent containing long‐chain amine ligands leads to the formation of size‐ and shape‐controlled crystalline ZnO nanoparticles (see picture). These particles, in the form of nanodisks and nanorods of low size dispersity in the 3–10 nm size range, are fully soluble in organic solvents (e.g., THF) and photoluminescent.

The optical properties of [Au 2 Ag 2 (C 6 F 5 ) 4 (OCMe 2 ) 2 ] n (1) have been studied in the solid state at room temperature and at 77 K and in acetone solution (5 × 10 -4 M). The crystal structure of 1, analyzed by X-ray diffraction, consists of polymeric chains formed by repetition of Au 2 Ag 2 moieties linked through short gold-gold interactions. The emission profile observed for 1 in dilute acetone solution (5 × 10 -4 M) is assignable to pentafluorophenyl localized ππ* excited states or from π-MMCT transitions, and in the solid-state arises from metal-centered (dσ*) 1 (pσ) 1 or (dδ*) 1 (pσ) 1 excited states. When the absorption and emission spectra of compound 1 in acetone are registered at different concentrations, they display a band that does not obey the Lambert-Beer law. This deviation is consistent with molecular aggregation in solution through gold-gold interactions, and a clear correlation between the emission wavelength and the structure of 1 in the solid state and in solution is shown. DFT calculations accord with the observed experimental behavior and show the nature of the orbitals involved in each transition.

Abstract:© Versita Sp. z o.o. Chemical methods provide an easy way to synthesize silver nanoparticles (Ag NPs) in solution. These metal nanoparticles have a great potential for biomedical applications as an antibacterial, antifungal, and antiviral agent or in wound healing. The adjustment of the parameters involved in these reactions permits a precise control over the size, shape, monodispersity, and the surfaces of the nanoparticles. These nanoparticles are being used in the design of new hybrid organic-inorganic or inorganic nanomaterials for biomedical applications.

The luminescence in a series of new bimetallic gold-silver vapochromic structures can be efficiently switched among different colors simply by exposure to solvent vapors. The emission color in these systems is controlled by both aurophilic interactions and halogen bonding, which affect the emission energy through different orbitals.

Addition of two equivalents of diphenylthiomethylphosphine (PPh2-CH2SPh) to the starting materials [Au(tht)2]A (tht = tetrahydrothiophene), AgCF3SO3, or [Cu(CH3CN)4]CF3SO3 produces the mononuclear derivatives [M(PPh2CH2SPh)2]A (M = Au, A = CF3SO3 (1a); M = Au, A = ClO4 (1b); M = Ag, A = CF3SO3 (4); M = Cu, A = CF3SO3 (5)) which are able to form the heterodinuclear complexes [AuM'(PPh2CH2SPh)2](CF3SO3)2 (M' = Ag (2), Cu (3)) with a P-Au-P environment. If the starting gold complex is [Au(C6F5)(tht)], reaction with the phosphine produces [Au(C6F5)-(PPh2CH2SPh)] (6) from which, by reaction with AgCF3SO3 or [Cu(CH3CN)4]CF3SO3, the "snake"-type linear complexes [Au2M(C6F5)2-(PPh2CH2SPh)2]CF3SO3 (M = Ag (7), Cu (8)) are obtained. If the silver starting complex is AgCF3CO2, reaction in a 1:1 ratio gives the tetranuclear complex [Au2Ag2(C6F5)2(PPh2CH2SPh)2-(CF3CO2)2] (9). When the molar ratio is 1:2 the trinuclear complex [AuAg2(C6F5) (CF3CO2)2(PPh2CH2SPh)] (10) is obtained. According to ab initio calculations, the presence of only one gold atom is enough to induce metallophilic attractions in the group congeners, and this effect can be modulated depending on the gold ligand.