Raman spectra and force constants of planar square molecules of the type AB4

Stammreich, H.; Forneris, Roberto

doi:10.1016/0371-1951(60)80097-5

Cited by 79 publications

(16 citation statements)

References 5 publications

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“…The AuBr 4 is identified by two peaks located at 197 cm -1 and 212 cm -1 . [40][41][42][43] In the reactive solution, the AuBr 4 peaks are not present, as expected from UV-Vis spectroscopic analysis, but a peak at 210 cm -1 is observed which is associated to the presence of AuBr 2 -. 43,44 The formation of Au(I) and the absence of Au(0) species for high bromide ions concentrations indicates that while reaction 1 takes place, the nucleation of AuNPs by reactions 2 and/or 3 is somehow inhibited under this conditions.…”

Section: Halide Ions Effectsupporting

confidence: 63%

Gold nucleation inhibition by halide ions: a basis for a seed-mediated approach

et al. 2015

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In the present work we examine the effect on gold nucleation of halide ions, a typical synthetic variable in the wet-chemical production of gold nanostructures. It was found that the gold homogeneous nucleation by chemical reduction of aqueous gold ions is kinetically quenched by the rise in the halide ions concentration and this effect is stronger as the Au-halide complex stability increases. The nucleation quenching is not exclusively related to a specific reducing agent but appears to be a more general behavior and is affected by the pH of the media. While no nucleation is observed, Au(I) metastable species coexist together with the reducer constituting metastable solutions. It is demonstrated that the nucleation inhibition by halide ions can be employed as a basis for a seed-mediated approach to produce gold nanostructures. The metastable solutions are proved to function as growth baths where Au(I) reduction is triggered on the surface of previously synthesized gold nanoparticles driving their growth in absence of secondary nucleation. It is also shown how, with this approach, the synthesis conditions can be rationally designed in order to obtain gold nanoparticles with the desired properties in a controlled and reproducible fashion. ion concentration grows, the Au(0) nucleation is quenched leading to the formation of larger AuNPs for intermediate concentrations and to the formation of Au(I) for high concentrations.Halide ions kinetically quench the gold homogeneous nucleation by chemical reduction of aqueous gold salts. Under suitable conditions, gold nucleation is inhibited and Au(I) metastable species coexist with the reducer. Hence, this metastable solutions constitute a basis for a seed-mediated approach since the Au(I) reduction can be activated on the surface of seed AuNPs driving their growth.

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Section: Halide Ions Effectsupporting

confidence: 63%

Gold nucleation inhibition by halide ions: a basis for a seed-mediated approach

et al. 2015

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“…A consistent analysis of spectroscopic results shows that chloroformic liquors containing AuBr 4 − , [Ag(SCN) 2 ] − , and BH 4 − as counter anions of trimetyl-hexadecyl-ammonium are effectively produced from aqueous | chloroform and solid | chloroform extraction processes. The extracted liquor containing AuBr 4 − is easily identified by its characteristic orange color (UV-Visible range, peaks at 260 nm and 394 nm) 29 as well as by Raman spectroscopy (109 cm −1 , 197 cm −1 and 212 cm −1 ) 30,31 . No colored Ag(SCN) 2 − and BH 4 − were both identified by Raman and FTIR spectroscopy.…”

Section: Methodsmentioning

confidence: 99%

Morphological evolution of noble metal nanoparticles in chloroform: mechanism of switching on/off by protic species

et al. 2015

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The morphological stability/morphological reshaping of noble metal nanoparticles are studied experimentally in order to unravel the chemical mechanisms lying beneath. Gold and silver nanoparticles (AuNPs and AgNPs, respectively) formed in chloroformic environment are used, as model synthetic systems, to study phenomena of morphological change. The morphological evolution of NPs that follows their formation, is characterized by spectroscopy (UV-Visible, Raman and FTIR) and TEM (Transmission Electron Microscopy). The change of NP morphology involves the increase of the average NP size and the broadening of size distribution, in a close resemblance with the effect characteristically obtained from the Ostwald ripening. The effect of the poor solvating properties of chloroform in stabilizing small charged species (H+, Ag+, Au+) as well as the principle of electroneutrality of matter are analyzed in order to formulate a feasible reaction scheme consisting of a three-step processes: the generation of soluble intermediary species by corrosion of nanoparticles, the diffusion of intermediary species from one nanoparticle to another, and the re-deposition process involving the reduction of intermediary species. This basic reaction scheme is used as hypothesis to plan and perform experiments, which reveal that molecular oxygen dissolved in the dispersive medium can drive NP corrosion, however, protic species are also required as co-reactant. The polarity of the hydrogen bond and the ligand properties of the anions produced by deprotonation are feature of the protic species that enable/disable the corrosion and, in turn, the NP morphological evolution.

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“…Os espectros Raman dos quatro complexos apresentaram, de fato, as três frequências ativas no Raman esperadas pela simetria D 4h : estiramento simétrico (A 1g ), estiramento anti-simétrico (B 2g ) e dobramento de ângulo no plano (B 1g ). 40 No caso do íon poli-halogênio (ICl 4 ) -, Stammreich 42,43 Isto motiva a análise de coordenadas normais realizada por Stammreich et al: 44 obter indícios sobre a natureza da ligação química a partir das constantes de força dos íons poli-halogênios. As frequências vibracionais dos modos de estiramento simétrico ν 1 e antissimétrico ν 3 observadas, respectivamente, nos espectros Raman e infravermelho dos íons triatômicos (ICl 2 ) -, (BrCl 2 )e (Br 3 )prontamente permitem obter as constantes de força do estiramento X-Y, f r , e a constante de interação entre as ligações adjacentes, f rr , de um campo de força de valência.…”

Section: Halogênios E Inter-halogêniosunclassified

Uma Releitura Dos Artigos Científicos Do Prof. Hans Stammreich

Ribeiro

2019

Quím. Nova

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Recebido em em 03/05/2019; aceito em 12/07/2019 publicado em 21/10/2019 REREADING THE WORKS OF PROF. HANS STAMMREICH. In this work we provide a revision of the studies by Raman spectroscopy carried out by Prof. Hans Stammreich in the São Paulo University. The works of Prof. Stammreich are discussed focusing on the most important conclusion of each paper and the scientific issue at the time of publication. Approximately twentyfive papers are discussed, which were separated into four groups according to the investigated systems: metal carbonyls, halogens and inter-halogens, halogen compounds, and oxoanions.

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Raman spectra and force constants of planar square molecules of the type AB4

Cited by 79 publications

References 5 publications

Gold nucleation inhibition by halide ions: a basis for a seed-mediated approach

Gold nucleation inhibition by halide ions: a basis for a seed-mediated approach

Morphological evolution of noble metal nanoparticles in chloroform: mechanism of switching on/off by protic species

Uma Releitura Dos Artigos Científicos Do Prof. Hans Stammreich

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