A. Vázquez-Olmos

Instantaneous Synthesis of Stable Zerovalent Metal Nanoparticles under Standard Reaction Conditions

In this report is discussed a novel, easy, and general synthesis method to prepare zerovalent iron (ZVI) and copper (ZV Cu) nanoparticles (NPs), from colloid dispersions in an environmental friendly organic solvent, ethylene glycol (EG). Conventional metallic salts are used as nanoparticle precursors; sodium borohydride (NaBH4) is the reducing agent, and triethylamine (TEA) is used as the nanoparticle stabilizer. The chemical changes take place instantaneously under normal reaction conditions. Small iron (alpha-Fe0 phase) and copper (fcc phase) NPs with average diameters of 10.2 +/- 3.3 and 9.5 +/- 2.5 nm, respectively, were obtained. In both cases, the experimental evidence reveals the absence of any metal oxide shell coating the particle surfaces, and their powders remain stable, under aerobic conditions at least for 3 weeks. ZVI NPs were characterized by X-RD, Mössbauer, and Raman spectroscopies and by EELS coupled to HR-TEM. Otherwise, copper NPs were characterized by X-RD, Z-contrast, and HR-TEM. This synthesis pathway is particularly suitable for large-scale and high-quality zerovalent metallic nanoparticle (ZV M NP) production due to its simple process and low cost.

Versatile behavior of 2‐guanidinobenzimidazole nitrogen atoms toward protonation, coordination and methylation

The structure, dynamic behavior, protonation, methylation, and coordination sites of 2-guanidinobenzimidazole la were investigated. Structures of compounds [2-guanidinium-1,3,10-trihydrobenzimidazole]sulfate lb, [2-guanidinium-l,3-dihydro-benzimidazole]sulfate lc-ld, [2-guanidinium-l,3-dihydro-benzimidazole]tetrafluoroborate le, [2-guanidinium-l,3-dihydro-benzimidazole]chbride If, [2-guanidinium-1,3dihydro-benzimidazole] perchlorate 1% 2-guanidinoI-methyl-benzimidazole 2a, [2-guanidinium-l,3-dimethyl-benzimidazole]iodide 2b, [2-guanidinium-1methyl-3-hydro-benzimidazole]chloride 2c, [2

Coordination behaviour of 2-guanidinobenzimidazole towards cobalt(II), nickel(II), copper(II) and zinc(II). An experimental and theoretical study

SummaryThe following coordination compounds derived from 2-guanidinobenzimidazole (2GB) (1); [Ni(2GB)2]Cl2· H2O, (2); [Ni(2GB)2]Br2·3H2O, (3); [Ni(2GB)2-(NO3)2, (4); [Ni(2GB)2](OAc)2, (5); [Cu(2GB)Cl2], (6); [Cu(2GB)Br2], (7); [Cu(2GB)2]Br2·2H2O, (8); [Cu(2GB)2](NO3)2·H2O, (9); [Cu(2GB)2](OAc)2· H2O, (10); [Zn(2GB)Cl2]·H2O, (11); [Zn(2GB)Br2]·H2O, (12); [Co(2GB)Cl2(H2O)2]·5H2O, (13); [Co-(2GB)2Cl2]·3H2O, (14); [Co(2GB)2(H2O)2](NO3)2· 4H2O, (15); and [Co(2GB)2(H2O)2](OAc)2, (16) have been synthesized and characterized by i.r. and electronic spectroscopy. In addition (6)–(10) were analysed by e.p.r. The X-ray diffraction structure of compound (4) was obtained. It crystallizes in the monoclinic system, C2/c (a = 22.511(7), b = 6.735(6) and c= 15.345(5)Å, β =115.31(3)°, Z = 4, final R = 0.0360 and Rw = 0.0388 for 1167 observed independent reflections). The nickel(II) atom coordinates two ligands in a square-planar geometry through the imidazolic N(3) and the guanidino N(12).The probable ligand isomers involved in the coordination were determined by theoretical calculations, and the possible structures of the coordination compounds were investigated in order to verify that the experimentally proposed structures were stable. Two different types of coordination compounds were found. One, where the ligand is chelating through the imidazolic N(3) and the guanidino N(12), which is the case for most of the complexes [(2)–(13)]. With only one ligand in the coordination sphere, the structure was either tetrahedral (copper and zinc chloride and bromide complexes) or octahedral (cobalt). With two chelating 2GB units a square-planar geometry was stabilized [(2)–(5) and (8)–(10)]. The second type of coordination behaviour was observed in the cobalt compounds [(14)–(16)]. Here the ligand coordinates monodentate through the imidazolic N(3); the structure is tetrahedral.

Mechanosynthesis of MFe2O4 (M = Co, Ni, and Zn) Magnetic Nanoparticles for Pb Removal from Aqueous Solution

Adsorption of Pb(II) from aqueous solution using MFe2O4 nanoferrites (M = Co, Ni, and Zn) was studied. Nanoferrite samples were prepared via the mechanochemical method and were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), micro-Raman, and vibrating sample magnetometry (VSM). XRD analysis confirms the formation of pure single phases of cubic ferrites with average crystallite sizes of 23.8, 19.4, and 19.2 nm for CoFe2O4, NiFe2O4, and ZnFe2O4, respectively. Only NiFe2O4 and ZnFe2O4 samples show superparamagnetic behavior at room temperature, whereas CoFe2O4 is ferromagnetic. Kinetics and isotherm adsorption studies for adsorption of Pb(II) were carried out. A pseudo-second-order kinetic describes the sorption behavior. The experimental data of the isotherms were well fitted to the Langmuir isotherm model. The maximum adsorption capacity of Pb(II) on the nanoferrites was found to be 20.58, 17.76, and 9.34 mg·g−1 for M = Co, Ni, and Zn, respectively.

CuO nanoparticles with PAMAM dendrimers

Abstract An easy pathway to synthesize a variety of cupric oxide (CuO) nanoshapes by a one-step wet chemical method is reported. CuO nanoparticles and nanorods were obtained from CuCl2 in a mixture of water and DMSO in the absence of a base at room temperature. 1-D CuO nanostructures resembling wires inside tubes, or nanopea pods, were shaped when polyamidoamine (PAMAM) dendrimers of generation 2 (16-NH2 end groups) or 2.5 (32-COO− end groups) were added to the CuO colloids. The evolution in time of the different nanostructures was followed by UV–visible spectroscopy. The XRD patterns, Raman spectroscopy and high-resolution transmission electron microscopy show clear evidence that all nanoshapes obtained in this work are composed by CuO. This method is a simple, versatile, and economical alternative for the fabrication of CuO nanostructures and might provide a practical reference for the controlled synthesis of other nanoarchitectures.

Moles quantification in liquid samples by Raman spectroscopy

The mole is a unit of measurement that expresses amounts of a chemical substance. Its importance lies in that the mass and the number of molecules of a substance can be determined with this value. In this work, we suggest a mathematical expression that relates the number of moles of the sample studied with the Raman signal and the experimental parameters used. In other words, with this mathematical expression it is possible to obtain quantitative information in a simple manner from Raman spectra. We have applied this method to different samples and we have observed an excellent correlation between the experimental and expected data.