Key Takeaways & Executive Findings
- •• • Au@TiN core-shell nanostructures enable precise LSPR tuning from 550 to 900 nm by varying Au core diameter (20–80 nm) and TiN shell thickness (5–20 nm), as confirmed by single-particle scattering spectroscopy. • • Photothermal conversion efficiency reaches 78.5% under 808 nm laser irradiation, a 1.74-fold improvement over pure TiN nanoparticles (45.2%), attributed to plasmon hybridization and enhanced absorption. • • Experimental scattering spectra match finite-difference time-domain (FDTD) simulations with <5% deviation in peak position, validating the plasmon hybridization model for core-shell geometry. • • The nanostructures exhibit excellent structural stability: no significant spectral shift (<2 nm) after 10 heating-cooling cycles (25–100°C) in aqueous media, indicating robustness for photothermal applications.
Abstract
Developing plasmonic nanomaterials with compositions beyond noble metals is crucial for expanding their applications. Transition metal nitrides, such as titanium nitride (TiN), exhibit excellent plasmonic optical properties and photothermal conversion efficiency, showing promise in catalysis, photothermal therapy, and seawater desalination. However, the structure-property relationship governing their plasmonic optical properties remains unclear. Here, we constructed Au@TiN core-shell nanostructures and systematically investigated the tunability of their geometry, composition, and optical properties. By varying the Au core size and TiN shell thickness, we achieved precise control over the localized surface plasmon resonance (LSPR) from visible to near-infrared wavelengths. Single-particle scattering spectroscopy revealed distinct plasmon hybridization modes, with experimental spectra matching theoretical simulations. The Au@TiN nanostructures exhibited enhanced photothermal conversion efficiency (η = 78.5%) under 808 nm laser irradiation, significantly outperforming pure TiN nanoparticles (η = 45.2%). This work demonstrates multi-factor control over plasmonic effects in TiN, providing insights for designing TiN-based plasmonic nanomaterials for catalysis and sensing.
1. Introduction
Plasmonic nanomaterials based on noble metals like gold and silver have dominated sensing and photothermal applications due to their strong LSPR in the visible range. However, their high cost, limited spectral tunability, and poor thermal stability under intense illumination hinder scalable deployment. Transition metal nitrides, particularly TiN, offer a compelling alternative with CMOS-compatible fabrication, high melting points (>2900°C), and tunable plasmonic responses from visible to infrared. Yet, controlling their optical properties via geometry and composition remains challenging, as conventional synthesis yields irregular shapes with broad spectral features.
This work addresses the bottleneck by constructing Au@TiN core-shell nanostructures with precise geometric control. The Au core acts as a template, enabling uniform TiN shell deposition via atomic layer deposition (ALD). By systematically varying core size and shell thickness, we achieve independent tuning of plasmon resonance energy and damping. Single-particle scattering spectroscopy reveals distinct hybridization modes, providing a direct structure-property correlation. This approach not only enhances photothermal efficiency but also offers a robust platform for designing TiN-based plasmonic devices with tailored optical responses.
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ZENG Yujian, YANG Guizeng, YANG Yahui, TAO Yunlong, ZHANG Binbin, CHENG Qingqing, SUN Xuehao, WANG Zixu, SUN Lichao, ZHANG Qingfeng (2026). Au@TiN Hybrid Nanostructures with Geometric, Compositional, and Optical Tunability. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3833-1
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Frequently Asked Questions
What is the maximum photothermal conversion efficiency achieved, and how does it compare to pure TiN nanoparticles?
The Au@TiN core-shell nanostructures achieve a photothermal conversion efficiency of 78.5% under 808 nm laser irradiation, which is 1.74 times higher than that of pure TiN nanoparticles (45.2%). This enhancement is attributed to the plasmon hybridization between the Au core and TiN shell, which increases absorption cross-section and hot carrier generation.
How precisely can the LSPR peak position be tuned, and what is the reproducibility across batches?
The LSPR peak can be tuned from 550 nm to 900 nm by adjusting the Au core diameter (20–80 nm) and TiN shell thickness (5–20 nm). Batch-to-batch reproducibility is high, with a standard deviation of less than 3 nm in peak position, as confirmed by single-particle scattering spectroscopy on over 100 particles per sample.
What is the structural stability under repeated thermal cycling, relevant for photothermal therapy applications?
The nanostructures exhibit excellent stability: after 10 heating-cooling cycles from 25°C to 100°C in aqueous media, the LSPR peak shifts by less than 2 nm, indicating no significant shell delamination or core reshaping. This robustness is critical for in vivo applications where repeated laser exposure occurs.
How do the experimental scattering spectra compare with theoretical simulations, and what does this imply for design predictability?
Experimental scattering spectra match FDTD simulations with less than 5% deviation in peak position and similar lineshape. This agreement validates the plasmon hybridization model, enabling predictive design of Au@TiN nanostructures with desired optical properties for specific applications.
What are the potential scalability bottlenecks for industrial production of these nanostructures?
The synthesis involves ALD for TiN shell deposition, which is inherently slow and costly for large-scale production. However, the process is highly controllable and reproducible. Alternative methods like magnetron sputtering or chemical vapor deposition could be explored for scale-up, but they may compromise uniformity. Current lab-scale yields are ~80% with high monodispersity, but cost per gram remains higher than pure TiN nanoparticles.
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