Hydrophobic and Sticky Silver-Decorated Nanoimprinted ZnO Nanograss Substrates for Enhanced SERS Performance

Kuan-Ting Kuo; Wen-Huei Chang; Hsiang Chen; Jyun-Jie Chen; Chun-Hung Lin

doi:10.1021/acsami.5c07665

Hydrophobic and Sticky Silver-Decorated Nanoimprinted ZnO Nanograss Substrates for Enhanced SERS Performance

ACS Appl Mater Interfaces. 2025 Jun 26. doi: 10.1021/acsami.5c07665. Online ahead of print.

Authors

Kuan-Ting Kuo¹, Wen-Huei Chang², Hsiang Chen³, Jyun-Jie Chen¹, Chun-Hung Lin^{1

4

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Affiliations

¹ Department of Photonics, National Cheng Kung University, Tainan 70101, Taiwan.
² Department of Applied Chemistry, National Pingtung University, Pingtung 90003, Taiwan.
³ Department of Applied Materials and Optoelectronic Engineering, National Chi Nan University, Nantou 54561, Taiwan.
⁴ Program on Key Materials, Academy of Innovative Semiconductor and Sustainable Manufacturing, National Cheng Kung University, Tainan 70101, Taiwan.
⁵ Meta-nanoPhotonics Center, National Cheng Kung University, Tainan 70101, Taiwan.

PMID: 40571560
DOI: 10.1021/acsami.5c07665

Abstract

This study successfully fabricated silver-decorated, submicrometer patterned zinc oxide (ZnO) nanograss substrates using nanoimprint lithography (NIL) and hydrothermal synthesis to achieve enhanced surface-enhanced Raman scattering (SERS) sensitivity. The ZnO nanograss structures were precisely patterned via NIL, allowing for controlled spatial arrangement and selective growth, with grating periods ranging from 1000 to 2000 nm and defined area widths between 500 and 1000 nm. Silver nanoparticles were deposited on the substrates through electron beam evaporation. The patterned design of the ZnO nanograss substrates significantly enhanced grating-mediated resonant excitation of localized surface plasmon resonance (LSPR), optimizing the interaction between incident light and the substrate. This resulted in more concentrated and focused light fields, which further amplified the LSPR effects. The impact of substrate hydrophobic characteristics, induced by dark storage for up to 3 months, on SERS performance was thoroughly investigated, with contact angles increasing from 93.5 to 144° during storage. These sticky properties facilitated the concentration of analyte molecules, significantly enhancing Raman signal intensity. Various periodic patterns, including one-dimensional (1D) gratings and two-dimensional (2D) arrays, were optimized to determine the ideal grating period for maximum Raman signal enhancement, achieving an analytical enhancement factor of 6.31 × 10¹⁰. Comprehensive characterization techniques, such as scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), were used to analyze the substrates' morphology, elemental composition, and structural properties. SERS sensitivity was evaluated using malachite green (MG) molecules, revealing an impressive limit of detection (LOD) of 1.85 × 10^-15. Furthermore, the substrates exhibited excellent long-term stability and signal reproducibility, maintaining consistent SERS performance after extended storage. This research establishes a cost-effective and highly sensitive SERS platform, offering significant potential for applications in chemical, environmental, and biochemical analysis.

Keywords: ZnO nanograss; hydrothermal method; malachite green; nanoimprint lithography; selective growth; silver nanoparticles; sticky hydrophobic surface; surface-enhanced Raman spectroscopy.