Chinese researchers have introduced an innovative approach to developing a 3D Surface-Enhanced Raman Scattering (SERS) substrate, achieving excellent focus tolerance and adhesion robustness. This advancement enhances the practicality of SERS technology for real-world applications.

Published in Advanced Functional Materials, the study was conducted by the researchers from the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences (CAS), the City University of Hong Kong and other institutions.

SERS is a powerful analytical technique that significantly amplifies Raman scattering signals of low-concentration molecules by enhancing the local electromagnetic field intensity on material surfaces. It is widely used in fields such as biochemical sensing, biomedical imaging, food safety, and public security. However, broader applications have been limited by the insufficient laser focus tolerance and structural adhesion stability of traditional substrates.

To address these limitations, the researchers investigated the optical properties of 3D nanowire-networks, building on their previous development of a nano-lattice mechanical metamaterial that surpasses size limitations and possesses exceptionally high energy absorption capabilities (Nat. Commun. 14, 1243 (2023); Adv. Energy Mater. 13, 2300129 (2023)).

The researchers designed a novel SERS substrate made of highly interconnected 3D gold nanowire-networks. Experimental results show that the gold nanowire-network demonstrates significant focus tolerance. The substrate can detect non-resonant probe molecules like 4-mercaptopyridine at concentrations as low as 1×10^-12 mol/L, with high signal uniformity.

Owing to the solid interconnection of nanowires in 3D space, the substrate is extremely robust, capable of withstanding ultrasonic treatment, water flow, and even direct sampling in the Yellow River, while maintaining stable performance.

Moreover, in terms of optical mechanism, the researchers established an effective medium model. This revealed that the substrate’s excellent focus tolerance results from the synergistic effects of enhanced light scattering rate, increased local optical state density, and broadened electromagnetic eigenmodes. These features enable the structure to have efficient light capture capability and significant 3D near-field enhancement effects.

According to the study, by solving the focal precision challenge while maintaining robustness, researchers have not only proposed a highly sensitive SERS substrate, but also established a viable platform to advance SERS from controlled laboratory environments toward challenging real-world scenarios.

This research was supported by the National Natural Science Foundation of China, the Science and Technique Program of Gansu Province of China, and the Research Grants Council of Hong Kong.

DOI: https://doi.org/10.1002/adfm.202525115

Figure. The 3D gold nanowire-network SERS substrate with focus tolerance and structural stability: a-b. Model of the 3D gold nanowire-networks prepared using ion track technology; c. Scanning electron microscope image of the actual substrate, with nanowire diameter of 35 nm; d. The 3D substrate maintains 50% SERS signal within a defocusing range of 192.8±19.6 μm under a 20× objective lens; e. SERS stability test in an ultrasonic water stress environment, which shows stable signal even after 30 minutes of ultrasonic treatment; f. The effective medium model reflects the high local state density of the nanowire-network structure near the excitation light. (Image from IMP)