N,N‐Dimethylformamide as a Reaction Medium for Metal Nanoparticle Synthesis

Abstract

The versatility of wet chemical methods has rendered them extremely popular for the preparation of metal nanoparticles with tailored size and shape. This Feature Article reviews the use of N,N‐dimethylformamide (DMF) for the reduction of metal salts, mainly Au and Ag, while also acting as a solvent. Apart from describing the ability of DMF to reduce metal salts, the effect of different parameters, such as the concentration of capping agent and metal precursors, the presence of preformed seeds acting as catalysts or their crystalline structure, on particle morphology are analyzed. Published reports on the use of different capping agents are summarized, with particular emphasis on the role of poly(vinylpyrrolidone) to determine the morphology of the particles. Finally, a brief overview is provided on the modulation of the optical response in DMF‐based metal nanoparticle colloids with tunable size and shape.

Preparação de nanopartículas de prata e ouro: um método simples para a introdução da nanociência em laboratório de ensino

“…A oscilação longitudinal é bastante sensível às razões entre as dimensões das partículas; desta maneira, pequenas variações da geometria esférica podem produzir mudanças expressivas nas cores. 13,31,32 Foi possível estimar o diâmetro médio das nanopartículas de prata em cada caso. Trabalhos anteriores relatam as relações existentes entre os tamanhos das nanopartículas e os dados de largura a meia altura e comprimento de onda máximo das bandas de absorção exibidos pelos espectros eletrônicos.…”

“…Nesse caso, a banda de absorção dos plasmons de superfície é deslocada para 528 nm, juntamente com o surgimento de uma nova banda mais larga, centrada em 758 nm, também devido ao aumento de anisotropia das nanopartículas. 15,32 Essa mudança no perfil do espectro eletrônico é condizente com a agregação das nanopartícu-las de ouro, como evidenciado por imagens de TEM. A Figura 5b mostra a imagem obtida após a adição de cistamina, onde é possível observar que não houve o crescimento significativo das partículas, com diâmetro médio de 22 nm, no entanto, observou-se uma forte agregação das mesmas.…”

Surfactant-free solution-based synthesis of metallic nanoparticles toward efficient use of the nanoparticles’ surfaces and their application in catalysis and chemo-/biosensing

“…The point to note is that DMF can work as both a solvent and a reducing agent in the preparation of metal colloids. The ability to reduce metal ions (i.e., their reduction rate) increases significantly at a temperature > 100 ° C. The ability of DMF to reduce AuCl 4 -ions to Au 0 has been reported to be lower than that for Ag + ions [26] . It has been suggested that catalysis by either polyvinylpyrrolidone (PVP) or by the seeds of the metal, itself, is required for the reduction of gold ions, although the formation of Au nanoparticles both in the absence and in the presence of the metal seeds has been reported [27,28] .…”

“…Finally, it is an excellent solvent for both organic and inorganic compounds. Liz-Marz á n and coworkers have pioneered the use of DMF for reducing metal ions such as those of silver and gold at high temperatures [26] . The point to note is that DMF can work as both a solvent and a reducing agent in the preparation of metal colloids.…”

“…It has been suggested that catalysis by either polyvinylpyrrolidone (PVP) or by the seeds of the metal, itself, is required for the reduction of gold ions, although the formation of Au nanoparticles both in the absence and in the presence of the metal seeds has been reported [27,28] . Therefore, it has been proposed that the use of AuCl 3 in place of HAuCl 4 may be preferable for the synthesis of Au nanoparticles via the DMF-based reduction method [26,29] . This is because AuCl 3 can be more readily reduced than HAuCl 4 , owing to the difference in the reduction potentials of Au …”