Versatile Technique to Produce a Hierarchical Design in Nanoporous Gold

Palak Sondhi; Dharmendra Neupane; Jay K. Bhattarai; Hafsah Ali; Alexei V. Demchenko; Keith J. Stine

doi:10.3791/65065

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Method Article

Versatile Technique to Produce a Hierarchical Design in Nanoporous Gold

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DOI:

10.3791/65065

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February 10th, 2023

Palak Sondhi¹ , Dharmendra Neupane¹ , Jay K. Bhattarai² , Hafsah Ali¹ , Alexei V. Demchenko³ , Keith J. Stine¹

¹Department of Chemistry and Biochemistry, University of Missouri-Saint Louis, ²Mallinckrodt Pharmaceuticals Company, ³Department of Chemistry, Saint Louis University

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Summary

Nanoporous gold with a hierarchical and bimodal pore size distribution can be produced by combining electrochemical and chemical dealloying. The composition of the alloy can be monitored via EDS-SEM examination as the dealloying process advances. The material's loading capacity can be determined by studying protein adsorption onto the material.

Abstract

The potential to generate variable pore sizes, simplistic surface modification, and a breadth of commercial uses in the fields of biosensors, actuators, drug loading and release, and the development of catalysts have unquestionably accelerated the usage of nanoporous gold (NPG)-based nanomaterials in research and development. This article describes the process of the generation of hierarchical bimodal nanoporous gold (hb-NPG) by employing a step-wise procedure involving electrochemical alloying, chemical dealloying techniques, and annealing to create both macro- and mesopores. This is done to improve the utility of NPG by creating a bicontinuous solid/void morphology. The area available for surface modification is enhanced by smaller pores, while molecular transport benefits from the network of larger pores. The bimodal architecture, which is the result of a series of fabrication steps, is visualized using scanning electron microscopy (SEM) as a network of pores that are less than 100 nm in size and connected by ligaments to larger pores that are several hundred nanometers in size. The electrochemically active surface area of the hb-NPG is assessed using cyclic voltammetry (CV), with a focus on the critical roles that both dealloying and annealing play in creating the necessary structure. The adsorption of different proteins is measured by solution depletion technique, revealing the better performance of hb-NPG in terms of protein loading. By changing the surface area to volume ratio, the created hb-NPG electrode offers tremendous potential for biosensor development. The manuscript discusses a scalable method to create hb-NPG surface structures, as they offer a large surface area for the immobilization of small molecules and improved transport pathways for faster reactions.

Introduction

Often seen in nature, hierarchical porous architectures have been imitated at the nanoscale to alter the physical characteristics of materials for improved performance¹. Interconnected structural elements of various scales of length are a characteristic of the hierarchical architecture of porous materials². Dealloyed nanoporous metals typically have unimodal pore size distributions; hence, multiple techniques have been devised to produce hierarchically bimodal porous structures with two separate pore size ranges³. The two fundamental objectives of the material design approach, namely the large spe....