Gold wire morphing into a high-resolution microscope tip.

Unlock Nanoscale Secrets: How to Build Your Own Super-Resolution Microscope Tips on a Budget

Reese Marlowe in Science & Nature August 2025 • 4 min read.

"Revolutionize your research with affordable, homemade TERS tips that rival expensive alternatives – dive into our step-by-step guide!"

Tip-enhanced Raman spectroscopy (TERS) has become an indispensable tool in nanospectroscopy, enabling researchers to achieve single-molecule sensitivity and sub-nanometer spatial resolution. This technique combines the chemical and structural information of Raman spectroscopy with the signal amplification provided by plasmonic resonances in metal tips.

However, the demand for efficient, reproducible, and cost-effective probes for TERS is constantly growing. Traditional methods for producing TERS tips often involve expensive equipment, skilled operators, and complex fabrication processes. This presents a barrier for many researchers seeking to utilize the power of TERS in their work.

Electrochemical etching offers a promising alternative. This technique is easy to implement, accessible to most labs, and requires only low-cost equipment and minimal training. While electrochemical etching can sometimes suffer from surface roughness and reproducibility issues (particularly with silver), gold tips produced through this method exhibit good surface quality, small radii of curvature, and can be stored safely for extended periods.

The Two-Step Etching Protocol: A Step-by-Step Guide

Gold wire morphing into a high-resolution microscope tip.

This article outlines a new protocol for fabricating TERS tips from 125 µm diameter gold wires using a two-step electrochemical etching process. This method builds upon existing techniques, optimizing for speed, reliability, and cost-effectiveness. The result? High-performance TERS tips created in your own lab.

The setup includes an adjustable DC voltage generator connected to the gold wire (anode) and a platinum wire formed into a ring (cathode). A micrometric translator manipulates the gold wire during immersion and extraction from the solution. The etching process is visually monitored under a stereo microscope.

Here’s a summary of the key steps:

Pre-Etching (High Voltage): Immerse the gold wire and apply 5 VDC for 15-20 seconds to quickly reduce the wire's diameter. Expect bubbling during this phase.
Etching (Low Voltage): Reduce the voltage to 2.1-2.3 VDC to form the tip slowly and smoothly without bubbling.
Rinsing: To eliminate residual impurities from the surface, wash the tips by shaking in the etching solution and, subsequently, by pouring a few drops of HCl and rinsing in ethanol and water.
Drying: Finally, the tips are dried under a nitrogen flux.

The magic behind tip formation lies in the interplay of electrochemical corrosion and meniscus dynamics. The gold electrochemical corrosion is driven by a redox process in an acidic environment. Superficial gold atoms are oxidized, transforming into Au(I) or Au(III), which then combine with chlorine ions. At the platinum wire, H+ ions are reduced, forming H2 gas. The ethanol helps to suppress bubbling during the critical second stage.

A New Era of Accessible Nanospectroscopy

This new two-step etching protocol opens the door to more accessible nanospectroscopy. By significantly reducing the cost and complexity of TERS tip fabrication, researchers can now explore the nanoscale world with greater ease and affordability. This method encourages innovation, empowering labs to develop and customize their own high-performance probes. It will also make tip-enhanced Raman spectroscopy more accessible to wider audience.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.3762/bjnano.9.254, Alternate LINK

Title: Low Cost Tips For Tip-Enhanced Raman Spectroscopy Fabricated By Two-Step Electrochemical Etching Of 125 Μm Diameter Gold Wires

Subject: Electrical and Electronic Engineering

Journal: Beilstein Journal of Nanotechnology

Publisher: Beilstein Institut

Authors: Antonino Foti, Francesco Barreca, Enza Fazio, Cristiano D’Andrea, Paolo Matteini, Onofrio Maria Maragò, Pietro Giuseppe Gucciardi

Published: 2018-10-22

Everything You Need To Know

What is tip-enhanced Raman spectroscopy (TERS), and why is there a growing demand for it?

Tip-enhanced Raman spectroscopy (TERS) combines the chemical and structural information obtained from Raman spectroscopy with the signal amplification resulting from plasmonic resonances in metal tips. This allows researchers to achieve single-molecule sensitivity and sub-nanometer spatial resolution, making it an invaluable tool for nanospectroscopy. Its growing demand stems from its ability to provide detailed insights at the nanoscale.

Can you walk me through the key steps of the two-step electrochemical etching protocol for creating TERS tips?

The two-step electrochemical etching protocol involves a pre-etching phase at 5 VDC to quickly reduce the gold wire's diameter, followed by an etching phase at 2.1-2.3 VDC to form the tip slowly and smoothly. Rinsing eliminates impurities using the etching solution, HCl, ethanol and water and drying under a nitrogen flux ensures a clean, high-quality TERS tip.

What chemical processes are involved in tip formation during the electrochemical etching of TERS tips, and what role does ethanol play?

The electrochemical etching method creates TERS tips through a redox process in an acidic environment. Gold atoms on the surface are oxidized into Au(I) or Au(III) which then combine with chlorine ions. Simultaneously, hydrogen ions are reduced to form H2 gas at the platinum wire. Ethanol suppresses bubbling during the etching phase, ensuring precise tip formation.

What are the limitations of electrochemical etching, and how do the resulting silver tips compare to gold tips?

While electrochemical etching offers a cost-effective way to produce gold TERS tips, silver tips may face surface roughness and reproducibility issues. Gold tips, on the other hand, exhibit good surface quality, small radii of curvature, and can be stored safely for extended periods, making them more reliable for TERS applications.

What are the broader implications of this new two-step etching protocol for the field of nanospectroscopy and scientific research?

By offering a cost-effective and accessible method for creating TERS tips, the two-step etching protocol expands the accessibility of tip-enhanced Raman spectroscopy, and nanospectroscopy more generally. This empowers researchers to explore the nanoscale world, develop custom high-performance probes, and make advances without the barrier of needing expensive and complex equipment.