Nanostructured Assemblies of Gold and Silver Nanoparticles for Plasmon Enhanced Spectroscopy Using Living Biotemplates

Abstract

Abstract:The ability to control the assembly of nanoparticles on substrates used in plasmon-enhanced spectroscopy continues to drive research in the field of nanofabrication. Here we describe the use of fungi as soft biotemplates to fabricate nanostructured microtubules with gold and gold-silver nanoparticles with potential applications as sensors and biosensors. In the first step, spores of the filamentous fungus Cladosporium sphaerospermum were inoculated in a suspension of gold nanoparticles, forming stable microtubules of gold nanoparticles during fungus growth. These materials were exposed to a second suspension of silver nanoparticles, resulting in complexes multilayers structures of gold and silver nanoparticles, which were evaluated as substrates for surface-enhanced Raman scattering (SERS) using small amounts of thiophenol as probe molecules directly on the microtubules. Both gold and the gold-silver substrates provide the SERS effect.

High-Density Plasmonic Nanoparticle Arrays Deposited on Nanoporous Anodic Alumina Templates for Optical Sensor Applications

“…In comparison to other scalable and cost-competitive noble metal colloid deposition techniques for optical sensor applications [29,30,31,32], our method is truly lithography-free and produces isolated 2D particle arrays with small and controllable gaps (20–60 nm range).…”

Heterogeneous Microtubules of Self-assembled Silver and Gold Nanoparticles Using Alive Biotemplates

“…22 However, these successive layers cannot be simply explained in terms of chemical bonds between nanoparticles and the fungus. Therefore, some attractive interaction should occur between these nanoparticles mediated by molecules secreted by the fungus [23][24][25] . Gold or silver nanoparticles keep their colloidal stability indefinitely, but small changes in ionic strength, temperature or dielectric constant can destabilize the colloidal suspension owing to their influence on the diffuse electric double layer around each nanoparticle.…”

“…25 In our studies, we observed that the formation of subsequent multilayers could be associated to the influence of the secondary metabolites produced by living fungus due the stress caused by the presence of metal nanoparticles, since we did not observe nanoparticles deposited on the surface of dead fungus. 23,24 The interaction of these hydrophobic molecules with colloidal nanoparticles seems to be responsible by the deposition of successive layers of nanoparticles on the fungus surface.…”

“…Reproducibility and uniformity are fundamental aspects of any technology related to nanomaterials. 23,24,27 Although the synthesis of colloidal nanocrystals appears to be simple, supra-nanoparticles assemblies is still a challenge. 28 For this reason, the use of biological templates to control the assembly of nanoparticles allows the fabrication of functional materials through the exploration of cooperative and synergetic effects.…”

“…In fact, filamentous fungi exhibit variable responses to fungal strain and growth media, which include the amount and the composition of nutrients, pH, temperature and humidity. [23][24][25] In fixed condition, fungi will reproduce the morphological and physico-chemical behaviour, which will guarantee the production of materials of identical performance. On the other hand, growing fungi biotemplates in different volumes can introduce problems in scale-up that will interfere with the material quality.…”