**4. Applications**

Nanoporous materials such as carbon nanotubes, nanoporous anodic alumina, nanotubular titania, porous silicon, and NPG have significant potential in the field of biomedicine involving high drug loading capacity and its controlled release. It was seen that a sub-micron-thick sputter-coated NPG thin films have a loading capacity of 1.12 μg/cm2 and molecular release half-lives between 3.6 hours to 12.8 hours [87]. NPG is a promising material for drug delivery applications and for studying the influence of surface modification on the drug release kinetics due to its high effective surface area, well-known surface gold-thiol chemistry, and tunable pore morphology and is depicted in **Figure 7** [88].

Rough and activated noble metals exhibit some unexpected properties in comparison with their smooth counterparts. The electrocatalytic activities of the porous films depend on the roughness factor and the existence of special binding sites on the surface. NPG films possess higher roughness and better electron transport leading to its distinguished performance in the field of catalysis [89]. Studies have shown that NPG is active towards catalyzing low-temperature CO oxidation which is attributed to the peculiar structure of NPG and the prevalence of step and kink sites on the surface of the material [90]. Nanoporous metals have recently attracted considerable attention fueled by their potential use in the filed od catalysis, sensor, and actuator applications by increasing the activity drastically via thick oxide film deposition to stabilize the nanoscale morphology [91]. The potential of nanostructured metallic surfaces has also been seen in optical applications and has been demonstrated for biosensing applications, SERS, guiding and manipulating light, and trapping of micro-sized particles [92]. The electrodeposition approach has been used for depositing a thin layer of AuNPs from 10 mM HAuCl4 for 20 s at −0.2 V (vs. Ag/AgCl) yielding oblate particles of 200 nm average diameter that immobilized an aptamer specific for LPS detection achieving a linear range of 0.1–10.24 ng mL−1 [93]. Thin nanoporous membranes of gold are best suited to the examination of surface plasmons as the analyte can get into the pores of NPG and can modify their dielectric atmosphere are detectable via absorption peaks in SPR

#### **Figure 7.**

*Depiction of surface engineering of NPG film via immobilizing alkanethiols with varying functional groups and chain lengths to enhance the drug delivery performance monitored via fluorescein release signal. Reproduced with permission from reference [88], Copyright 2016, American Chemical Society.*

**155**

**Author details**

Saint Louis, MO, USA

**Conflict of interest**

Palak Sondhi and Keith J. Stine\*

\*Address all correspondence to: kstine@umsl.edu

provided the original work is properly cited.

The authors declare no conflict of interest.

magnetic, and corrosion properties exhibited by metals [99].

Department of Chemistry and Biochemistry, University of Missouri–Saint Louis,

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*Electrodeposition of Nanoporous Gold Thin Films DOI: http://dx.doi.org/10.5772/intechopen.94604*

**5. Conclusion**

are equally detected by SPR measurements [94].

whereas the species that adsorb onto the geometric surface of the pores of the film

The electrodeposition of noble metals on support provides a unique possibility to obtain films of varying thickness and roughness. Many advanced electrodeposition techniques are known so far, and the field is actively developing with specific controllable nanostructural features leading to an increased number of grain boundaries for high catalytic performance [95]. It is interesting to see how the porous gold nanostructures can be electrodeposited on a solid support and the impact of electrodeposition parameters namely, potential and time of deposition, on the morphology and thickness of the film so formed. Detailed investigation on NPG surface pore size and the correlation with electrocatalytic activity has aimed to understand the growth mechanism of NPG [13]. The experimental results from the electrodeposition techniques have highlighted that the formation of a well-organized NPG film requires the appropriate electrochemistry and physics/mechanics interactions between the substrate and the deposits [96]. NPG morphology evolution is highly influenced by the topography of the substrate emphasizing the structure–property relationship and opening doors for such high-throughput combinatorial studies [46]. An exciting new field of research within the domain is the electrodeposition of hybrid thin films which has opened the gate to an unlimited number of new materials [97]. Electrodeposition, therefore, is a promising fabrication technique that has the potential of producing thin NPG films for effective drug delivery systems as precise control of the NPG pore and ligament dimensions can be achieved which in turn control the drug loading and release performance inside the body [98]. Electrodeposition is a distinct form of grain boundary engineering by which a material's property can be enhanced to synthesize advanced materials both in bulk form and as thin films. It is a technologically viable production method for upgrading the mechanical, electrical,

whereas the species that adsorb onto the geometric surface of the pores of the film are equally detected by SPR measurements [94].
