Recent advancements in nanotechnology have introduced gold nanorods (GNRs) as valuable materials for various applications, especially within the biomedical field. These tiny structures are prized for their tunable surface plasmon resonance (SPR) and unique optical properties, which could potentially revolutionize imaging, therapy, and drug delivery. Yet, achieving precise control over GNRs' size and shape has remained challenging due to conventional synthesis methods often yielding polydisperse samples and requiring high concentrations of cytotoxic surfactants. A study recently published introduces an innovative approach—an electrochemical synthesis method—that could address these challenges by leveraging open circuit potential (OCP) data derived from colloidal synthesis.
The researchers, led by Mehrsa Khalilipour from Tarbiat Modares University, propose utilizing the electrochemical growth of gold nano-seeds immobilized on fluorine-doped tin oxide (FTO) substrates. This method utilizes physical vapor deposition (PVD) followed by thermal annealing to create the Au seeds directly on the substrate, offering advantages such as eliminating the need for seed solutions and significantly reducing toxicity associated with traditional surfactants. "This method provides control over the synthesis process, allowing us to produce GNRs of higher uniformity and larger sizes than typical methods would allow," the authors wrote.
The electrochemical approach allows for the growth of GNRs up to 700 nm long, surpassing the typical 100 nm limitations faced by traditional synthesis methods. This innovation associates the GNRs' increased size with enhanced optical and thermal properties, making them ideal candidates for applications like biomedical imaging, photothermal therapy, and deep tissue penetration.
The methodology revolves around the optimization of various electrochemical parameters, which is pivotal for achieving GNRs with desired attributes. The initial stages involve electrode fabrication using the FTO substrate, followed by the controlled deposition of gold onto the surface. Unlike traditional methods, this electrochemical synthesis minimizes cytotoxic surfactant use, addressing growing concerns over biocompatibility.
The results indicate significant improvements across various metrics. Notably, the uniformity and tunability of GNR sizes mean increased stability, heightened sensitivity for biosensing applications, and extended circulation times beneficial for drug delivery systems. The findings reinforce the versatility of GNRs across diverse scientific and medical applications.
"By systematically adjusting parameters such as electrode potential and CTAB concentration, we achieved well-defined nanostructures. The electrochemical method stands out for its scalability and cleanliness, making it environmentally friendly," stated the authors, underscoring the method's relevance for sustainable nanotechnology.
This novel technique not only improves our comprehension of GNR growth mechanisms but also serves as a framework for fabrications of other nanostructured materials. Consequently, this work could pave the way for new biomedical tools and solutions, significantly impacting how we address current challenges related to nanomedicine and targeted therapies.
Future research will focus on refining electrochemical parameters and exploring applications specific to varied nanostructures. The technique's unique ability to provide real-time monitoring of the synthesis process positions it as a favorable option for the scalable production of high-quality GNRs for numerous applications.