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Researchers from the Indian Institute of Science Education and Research (IISER) Pune and the Indian Institute of Technology-Bombay have developed an innovative, cost-effective method to produce high-quality metal nanoparticles, as detailed in a study in the journal Small Methods.

This pioneering technique, known as confined dewetting, could have wide applications in biomedical diagnostics and chemical detection by enabling highly sensitive and reliable sensors.

The study, led by Dr. Ayesha Rahman (Research Scientist at I-Hub Quantum Technology Foundation hosted by IISER Pune), Prof. Anirban Sain (faculty member at the Department of Â鶹ÒùÔºics, IIT Bombay), and Dr. Atikur Rahman (faculty member at the Department of Â鶹ÒùÔºics, IISER Pune), introduces a simple yet powerful approach to create uniform, high-density metal nanoparticles on various surfaces, including flat, curved, and microtextured substrates.

Imagine a super-thin (about 10,000 times thinner than a human hair) layer of metal, like a gold film spread on a piece of glass. When you heat it, the metal starts to bunch into tiny droplets, similar to how water beads up on a non-sticky pan.

This happens because the metal tries to minimize its surface energy. Now, if we squeeze the metal film between two surfaces, like making a sandwich, and apply heat, it breaks up into tiny, uniform droplets that are packed closely together. This process is called confined dewetting, and it can be used to make highly sensitive sensors for biomedical and chemical applications.

By sandwiching a thin metal film between a substrate and a layer of PDMS (a flexible, silicone-based material) during heating, the researchers achieved precise control over the size and spacing of nanoparticles, resulting in particles with minimal size variation and gaps as small as a few nanometers.

This level of precision is critical for applications requiring consistent and enhanced performance, such as detecting trace amounts of biological or chemical substances.

Traditional methods of nanoparticle production are based on expensive and complex processes and often do not produce uniform nanoparticles.

In contrast, the 'confined dewetting' technique, applied on metal films for the first time in the present paper, is versatile and can be implemented on a large scale. Metals such as silver, gold, copper and their alloys can be used in this technique. Moreover, the technique can be applied to a variety of substrates, from glass slides to optical fibers.

The PDMS layer shapes the nanoparticles and protects them from oxidation. This results in pure and stable nanoparticles. These properties are very important when using the sensing technology in practice.

The nanoparticles produced using this method exhibit exceptional optical properties, making them ideal for advanced sensors based on localized surface plasmon resonance (LSPR) and surface-enhanced Raman scattering (SERS).

In tests using a probe molecule, the researchers demonstrated that their nanoparticles detected concentrations as low as one picomolar (a trillionth of a mole per liter), far surpassing the sensitivity of conventional methods. The authors of this study anticipate that this capability could enable earlier detection of diseases through biomarkers or identify minute traces of chemicals in environmental or industrial settings.

Speaking on the potential applications of this new method, one of the principal investigators on the paper, Dr. Atikur Rahman said, "The study also provides a theoretical framework explaining how the elasticity and low surface tension of PDMS reduce particle size and enhance uniformity, offering a blueprint for further advancements using similar materials.

"With applications ranging from medical diagnostics to chemical analysis and beyond, this breakthrough positions confined dewetting as a game-changer in nanotechnology."