Minimizing the emission of industrial effluents and realizing the recovery/extraction of key elements such as the rare earths from low concentration solutions, or during water decontamination processes, are some of the biggest challenges of modern society. Accordingly, the preparation and characterization of a low cost recyclable and reusable superparamagnetic iron oxide nanoparticles (SPION)/zeolite nanocomposite (Zmag) is described, and the possibility of their use for removal of heavy metals and ammonium/ammonia is discussed, generating water whose quality is in compliance with the more strict modern environmental laws. Such materials are suitable for realization of a more efficient dispersion method for adsorption in combination with magnetically aided concentration/separation processes for removal of contaminants. In fact, Zmag was shown to efficiently remove PbII and HgII, as well as NH4+ from water, generating effluents that can be directly disposed in water bodies according to the current environmental law requirements, as stated by EPA (North America Environmental Protection Agency). That nanocomposite material has a competitive production cost and allowed a cutback in the nitrogen (NH3) content from 300 mg L-1 (diluted slurry source) to less than 36 mg L-1. Furthermore, Zmag demonstrated high capacity to concentrate and recover in a cyclic way LaIII.

An electrocatalytic active hybrid material prepared by successive stepwise coordinative deposition of 20 nm diameter gold nanoparticles (AuNP) with 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (TPyP) on fluorine-doped tin oxide (FTO) substrates previously modified with 3-mercaptopropylsilane is described. Their interaction and assembly were studied by UV-Vis spectroscopy and surface enhanced Raman spectroscopy to understand the kinetics as well as the conformation on the porphyrin macrocycle on the electrode surface as a function of its concentration. The hybrid nanomaterial was a build-up in reproducible successive deposition steps as confirmed by the linear rise of the absorption bands assigned to AuNP and TPyP as a function of the number of AuNP/porphyrin hybrid deposition steps, as supported by scanning electron microscopy (SEM) images. Electrodes modified with the hybrid nanomaterials were prepared and characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), as well as their electrocatalytic properties for the oxidation of nitrite and sulfite investigated. FTO electrodes modified with the AuNP/TPyP hybrid showed remarkable electrocatalytic activity as confirmed by reproducible and sensitive amperometric responses for sensing nitrite and sulfite in comparison to the bare electrode while reducing overpotentials respectively to 0.8 and 0.4 V and improving the dynamic range (linear response allowing quantification in the 50 to 500 µmol L-1 range) for detection of analytes.

Nas nanopartículas de ouro, as propriedades químicas e físicas são ditadas principalmente pelos átomos da superfície, os quais podem interagir com espécies doadoras-aceitadoras, ou ligantes, da mesma forma que os complexos metálicos correspondentes. Além disso, os elétrons podem entrar em ressonância com a luz incidente dando origem aos plasmons de superfície, que levam à intensificação do campo elétrico local e ao efeito SERS, proporcionando uma ampla variedade de aplicações na química, biologia e nanotecnologia. Ligantes de ponte, multifuncionais, podem ser usados para intermediar a ligação de íons metálicos aos átomos de ouro da superfície. Essa estratégia permite controlar a estabilização em solução através das cargas dos complexos metálicos, acrescentando, ao mesmo tempo, novas características químicas e maior funcionalidade às nanopartículas modificadas. Dessa forma, uma nova química de coordenação pode ser vislumbrada, combinando nanopartículas metálicas, como as de ouro, e complexos, à luz da química supramolecular e dos efeitos de ressonância plasmônica de superfície.

In gold nanoparticles the surface metal atoms play a major role, determining their chemical and physical properties by interacting with donor-acceptor species or ligands in a similar way as the related metal complexes. In addition, coherent oscillations of the metal electrons in resonance with the frequency of the exciting light give rise to localized surface plasmons responsible for an enhancement of the local electric field and SERS effect, allowing a wide range of applications in chemistry, biology and nanotechnology. Multifunctional bridging ligands can be employed for simultaneously binding metal ions and surface atoms. The attractive point of this approach is the possibility of exploiting the charge controlled stabilization by the metal complexes, while imparting new characteristics and properties to the modified nanoparticles. As a matter of fact, a new, exciting field of coordination chemistry can be envisaged, combining metal nanoparticles and metal complexes, in the light of supramolecular and surface plasmon resonance effects.

Os compostos de inclusão de trans-1,4-bis[(4-piridil)etenil]benzeno (BPEB) e os correspondentes complexos de pentacianoferrato(II) com beta-ciclodextrina foram estudados em solução aquosa por espectroscopia ¹H RMN e UV-Visível. Compostos de inclusão com estequiometria 1:1 foram encontrados para todos os sistemas em solução. Na presença de beta-ciclodextrina, o complexo binuclear de ferro {[Fe(CN)5]2(BPEB)]}6- é convertido espontaneamente em rotaxanos contendo os grupos [Fe(CN)5]3- como grupos terminais volumosos, por um mecanismo de automontagem dissociativa , confirmado por espectroscopia de ¹H RMN.

Inclusion compounds of trans-1,4-bis[(4-pyridyl)ethenyl]benzene (BPEB) and their corresponding pentacyanoferrate(II) complexes with beta-cyclodextrin have been studied in aqueous solution by ¹H NMR and UV-Visible spectroscopy. All the inclusion compounds exhibit 1:1 stoichiometry is aqueous solution. In the presence of beta-cyclodextrin, the binuclear {[Fe(CN)5]2(BPEB)]6- complex is gradually converted into rotaxane species bearing [Fe(CN)5]3-end groups, by a self assembly inclusion mechanism, as confirmed by ¹H NMR spectroscopy.