Additive Manufacturing of Gold Nanostructures Using Nonlinear Photoreduction under Controlled Ionic Diffusion.

Wera Di Cianni,Michele Giocondo,Francisco J Delgado,Alberto S De León,Sergio I Molina,María De La Mata,Giovanni Desiderio

doi:10.3390/ijms22147465

Abstract

Multiphoton photoreduction of photosensitive metallic precursors via direct laser writing (DLW) is a promising technique for the synthesis of metallic structures onto solid substrates at the sub-micron scale. DLW triggered by a two photon absorption process is done using a femtosecond NIR laser (λ = 780 nm), tetrachloroauric acid (HAuCl4) as a gold precursor, and isinglass as a natural hydrogel matrix. The presence of a polymeric, transparent matrix avoids unwanted diffusive processes acting as a network for the metallic nanoparticles. After the writing process, a bath in deionized water removes the gold precursor ions and eliminates the polymer matrix. Different aspects underlying the growth of the gold nanostructures (AuNSs) are here investigated to achieve full control on the size and density of the AuNSs. Writing parameters (laser power, exposure time, and scanning speed) are optimized to control the patterns and the AuNSs size. The influence of a second bath containing Au3+ to further control the size and density of the AuNSs is also investigated, observing that these AuNSs are composed of individual gold nanoparticles (AuNPs) that grow individually. A fine-tuning of these parameters leads to an important improvement of the created structures’ quality, with a fine control on size and density of AuNSs.

Highlights

Published: 12 July 2021Recent progress in the field of additive manufacturing (AM) in conjunction with the development of nanotechnology allowed the implementation of new nanomaterials in the industrial production fully aligned with the industry 4.0 paradigm
Gold nanostructures (AuNSs) were synthesized through the two-photon absorption (TPA)–direct laser writing (DLW) process, taking advantage of the photoreduction with a fine-tuning of shape and size acting on the ionic concentration of the salt, using a solid opaque substrate, a natural polymeric matrix, and an aqueous solution of a gold precursor, HAuCl4
Natural protein that forms a hydrogel when dissolved in water at room temperature

Summary

Introduction

Published: 12 July 2021Recent progress in the field of additive manufacturing (AM) in conjunction with the development of nanotechnology allowed the implementation of new nanomaterials in the industrial production fully aligned with the industry 4.0 paradigm. The improvement fine tuning in the properties could lead to the production of new industrial targets and different types of devices and sensors, with potential applications from medicine to aeronautics [1,2,3,4]. At this scale, the size and the spatial configuration of produced single features start to influence the characteristics of the whole object, enabling an array of new, exotic, and otherwise unachievable properties [5]. The industrial production is registering a significant demand for the fabrication of Au-containing nanomaterials because of their numerous applications in photonics, biomedicine, electronics, and optics [6,7,8,9,10,11]

Methods

Results

Conclusion