Upconversion luminescence (UCL) has great potential for highly sensitive biosensing due to its unique wavelength shift properties. The main limitation of UCL is its low quantum efficiency, which is typically compensated using low-noise detectors and high-intensity excitation. In this work, we demonstrate surface plasmon polariton (SPP)-enhanced UCL for biosensing applications. SPPs are excited by using a gold grating. The gold grating is optimized to match the SPP resonance with the absorption wavelength of upconverting nanoparticles (UCNPs). Functionalized UCNPs conjugated with antibodies are immobilized on the surface of the fabricated gold grating. We achieve an UCL enhancement up to 65 times at low excitation power density. This enhancement results from the increase in the absorption cross section of UCNPs caused by the SPP coupling on the grating surface. Computationally, we investigated a slight quenching effect in the emission process with UCNPs near gold surfaces. The experimental observations were in good agreement with the simulation results. The work enables UCL-based assays with reduced excitation intensity that are needed, for example, in scanning-free imaging.

中文翻译：

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用于生物传感应用的表面等离子体激元增强上转换发光


上转换发光（UCL）由于其独特的波长位移特性，在高灵敏度生物传感方面具有巨大的潜力。 UCL 的主要限制是其低量子效率，通常使用低噪声探测器和高强度激发来补偿。在这项工作中，我们展示了用于生物传感应用的表面等离子激元 (SPP) 增强 UCL。 SPP 通过使用金光栅来激发。金光栅经过优化，可将 SPP 共振与上转换纳米颗粒 (UCNP) 的吸收波长相匹配。与抗体缀合的功能化 UCNP 被固定在制造的金光栅的表面上。我们在低激发功率密度下实现了高达 65 倍的 UCL 增强。这种增强是由于光栅表面上的 SPP 耦合导致 UCNP 吸收截面的增加所致。通过计算，我们研究了金表面附近的 UCNP 在发射过程中的轻微猝灭效应。实验观察结果与模拟结果非常吻合。这项工作使得基于 UCL 的检测能够降低激发强度，例如免扫描成像所需的激发强度。