In addition to the series of articles related to metallic nanoparticles applied to plasmonics, the aim of this review is to discuss the main factors that influence the process of obtaining this type of material. Thus, the article is divided into two main parts: 1) Mechanism, in which a general idea is given regarding the evolution of the concepts involved in the steps of nucleation and growth of metallic nanoparticles, as well as a discussion on the parameters that favor the control of the reaction by kinetics or thermodynamics. Additionally, the main strategies used for composition and shape control, also a brief explanation about the surface of the obtained products are presented. 2) Synthesis, in this section, the main methodologies for obtaining metallic nanoparticles on a laboratory scale are demonstrated, namely those in batch and by electrochemical routes, in addition to the discussion on flow methods, which is believed to be the most effective and viable strategy for obtaining nanoparticles on a large scale.

Em complemento à série de artigos relacionada a nanopartículas metálicas aplicadas em plasmônica, o objetivo desta revisão é transcorrer sobre os principais fatores que influenciam no processo de obtenção desse tipo de material. Dessa forma, o artigo se divide em duas partes principais: 1) Mecanismo, em que é dado uma ideia geral a respeito da evolução dos conceitos envolvidos nas etapas de nucleação e crescimento de nanopartículas metálicas, assim como, uma discussão sobre os parâmetros que favorecem o controle da reação por via cinética ou termodinâmica. Adicionalmente, as principais estratégias utilizadas para controle de composição e forma, além de uma breve explanação sobre a química da superfície dos produtos obtidos também são apresentadas. 2) Síntese, nesta seção são demonstradas as principais metodologias para a obtenção de nanopartículas metálicas em escala laboratorial, sendo elas, as em batelada e por via eletroquímica, além da discussão sobre os métodos em fluxo, que, acredita-se ser a estratégia mais eficiente e viável para a obtenção de nanopartículas em larga escala.

In this second part we will discuss how surface chemistry properties of plasmonic nanomaterials can be tailored by applying coordination chemistry, supramolecular and materials chemistry approaches, in which nanoparticles with well-controlled features conjugated with properly chosen molecules are the basis of functional organized structures that can be applied as high sensitivity sensors and high efficient photocatalysts. To achieve this level of control the interactions between the nanomaterials surface and the chemical environment surrounding it, the metal-ligand interactions on the materials surface and the electrons and energy transfers at the interface should be well understood. Therefore, we will show how the Surface Enhanced Raman Effect (SERS) can be explored to study the nanomaterials interface. Finally, we will discuss the role of plasmonic nanomaterials in sensors, more specifically SERS sensors, and photocatalysis.

We perform an analysis of plasmonic nanomaterials in a two part review, the first of which constitutes the present work. Here, attention is given to the fundamentals of metal nanoparticle optical properties. It is discussed the principles regarding the excitation of localized surface plasmon modes in nanostructures of different sizes, shapes and surrounding media. The discussion is used as basis for the analysis of local properties derived from such excitations, which are used for the introduction of surface-enhanced Raman scattering (SERS). Throughout the review, the fundamentals of plasmonic excitations and their mechanisms of relaxation are used to introduce chemical applications of metal nanoparticles in different areas such as the construction of analytical chemistry sensor devices, enhanced molecular spectroscopy and plasmon-mediated chemical reactions (also referred to as plasmonic photocatalysis).

Abstract: Pentacyanidoferrate(II) complexes of aromatic N-heterocycles, such as 4-cyanopyridine, exhibit characteristic colors and strong metallochromism associated with the donor-acceptor interactions of the metal ions with the cyanide ligands. In the presence of transition metal ions insoluble polymeric complexes are formed, displaying bright yellow, red, brown and green colors with zinc(II), nickel(II), copper(II) and iron(III) ions, respectively. Such metallochromic response is better observed on filter paper, allowing applications in analytical spot tests. The effects can be explored visually and probed by means of modern instrumental facilities, including spectrophotometric and resonance Raman techniques. In this way, by using the cyanopyridinepentacyanidoferrates, the Prussian Blue test for ferric ions can be extended to the entire row of transition metal elements, providing a new and modern insight of such classical Feigl’s spot tests.