Researchers from the Georgia Institute of Technology have developed a new one-shot precursor injection method to synthesize uniform 35 nm gold nanospheres. This method removes the need for the traditional step-by-step addition of precursors.
Gold nanospheres are important in point-of-care diagnostics. However, producing them at scale with consistent size and shape has been a longstanding challenge.
The study outlines a simplified manufacturing process that converts gold nanocubes into 35 nm nanospheres. This is done using heat-induced surface reactions. Instead of slow, dropwise precursor addition, the new method uses high-temperature incubation. This triggers bromide ion desorption, oxidative etching, and atomic movement.
The result is a more consistent and scalable way to produce nanospheres. These are well-suited for biomedical uses, including rapid pathogen detection.
Lateral flow immunoassays (LFIAs), such as those used in home COVID-19 tests, rely on the optical properties of gold nanoparticles to produce fast, visible results. However, traditional synthesis methods often lead to particles with inconsistent shapes, which can reduce test accuracy.
Uniform gold nanospheres larger than 30 nm are valuable because their strong optical signals and large surface areas improve sensitivity and binding in diagnostic applications. However, producing such uniform particles often requires slow, dropwise chemical dosing. This makes scaling up the process difficult. As a result, there is a need for a more efficient and controlled method to produce diagnostic-grade nanospheres at an industrial scale.
The new synthesis process has three steps. First, 10 nm gold spheres are produced using a fast one-shot precursor injection. These small particles serve as seeds. In the second step, the seeds grow into 30 nm nanocubes through a one-step process that uses potassium bromide. The bromide selectively caps certain crystal facets to control how the cubes form.
In the final step, the nanocubes are heated in a CTAC solution at 97 °C. This heat causes bromide ions to detach from the surface. The process then undergoes oxidative etching and surface atom movement, which reshapes the cubes into uniform spheres.
Spectroscopic data showed a gradual blue shift and a narrowing of the plasmon resonance peak. This confirmed that the nanocubes had successfully transformed into spheres. When compared to dropwise synthesis methods, these spheres showed better uniformity, clearer optical signals, and greater colloidal stability. The method is also compatible with continuous-flow systems, suggesting it could be scaled up for commercial use without reducing quality or consistency.
This study focused on simplifying the process of making gold nanospheres while maintaining high quality. By understanding the role of bromide in shaping the particles, the researchers developed a method that is both scientifically sound and practical for large-scale use. The one-shot strategy combines basic nanochemistry with scalable engineering to produce nanoparticles that meet real-world diagnostic needs.
Being able to produce uniform gold nanospheres at scale has many uses, especially in medical diagnostics. In these settings, speed, accuracy, and scalability are essential. These particles can be coated with biomolecules to detect specific diseases with high precision. This makes them useful in outbreak situations or in remote healthcare environments.
This research aimed to simplify gold nanosphere synthesis while maintaining high quality. By identifying the key role of bromide in shaping the particles, the team developed a method that is both scientifically sound and commercially practical. The one-shot approach connects basic nanochemistry with scalable engineering, making it possible to produce nanoparticles suitable for real-world diagnostic use.
Producing uniform gold nanospheres at scale has important applications in medical diagnostics, where speed, accuracy, and scalability are critical. These particles can be coated with biomolecules to detect specific pathogens, making them useful in outbreak situations or remote healthcare settings.
Beyond diagnostics, this method may also be useful in drug delivery, biosensing, and photothermal cancer therapy—areas where particle uniformity directly impacts performance. As demand for precise nanomaterials increases, this approach offers a scalable and reliable way to meet the needs of emerging biomedical technologies.
The study was supported in part by a project sponsored by Gemina Laboratories for synthesis, a National Science Foundation research award (CHE-2002653) for SERS measurements, and start-up funding from the Georgia Institute of Technology.
Journal Reference:
Li, K. K., et al. (2025) Rational Synthesis of Uniform Au Nanospheres under One-Shot Injection: From Mechanistic Understanding to Experimental Control. Precision Chemistry. doi.org/10.1021/prechem.4c00105