标题： 通过自敏化钬掺杂纳米颗粒实现高效的短波红外上转换 显示英文标题

标题： Efficient short-wave infrared upconversion by self-sensitized holmium-doped nanoparticles

摘要： 光子上转换，将多个低能光子结合以产生一个高能光子，在生物医学、催化和光子应用中具有广泛兴趣。 掺杂镧系元素的纳米颗粒（LnNP）是一种独特的上转换纳米转换器，可以实现超大的反斯托克斯位移（>1000 nm）和高光稳定性，不会发生光漂白和光闪烁。 LnNPs的激发波长已被限制在第二近红外窗口（1000-1700 nm），主要由铒离子敏化，其吸收中心位于1.5$\mu$m附近。在这里，我们展示了新型自敏化的钬（Ho）掺杂纳米转换器，进一步将敏化范围扩展到2$\mu$m的短波红外，并实现高效的上转换到640 nm。 我们表明，这种上转换是一个四光子转换过程，其背后的能量转移上转换机制。 通过仔细控制掺杂浓度和外壳，我们实现了高达15.2%的上转换与下转换效率，超过理论最大值的一半。 将钬掺杂的LnNPs放置在一个等离子体纳米腔器件中，由于钬的发射寿命从29$\mu$s显著缩短至<1 ns，从而实现了发射强度的大幅增强（最多32倍），表明具有高达3x10$^4$的高Purcell增强因子。 这些结果在短波红外上转换和LnNP发射的纳米等离子体增强领域开辟了新的可能性，具有在检测、诊疗、光子学和光电学方面的潜在应用。 显示英文摘要

摘要： Photon upconversion, combining several low-energy photons to generate one high-energy photon is of wide interest for biomedical, catalytic and photonic applications. Lanthanide-doped nanoparticles (LnNP) are a unique type of upconversion nanoconverter, which can realize ultralarge anti-Stokes shift (>1000 nm) and high photostability, without photo-bleaching and photo-blinking. The excitation wavelength of LnNPs has been limited to the second near-infrared window (1000-1700 nm), mainly sensitized by erbium ions with absorption centered around 1.5 $\mu$m. Here, we demonstrate novel self-sensitized holmium (Ho)-doped nanoconverters to further expand the sensitization range to the short-wave infrared at 2 $\mu$m and achieve efficient upconversion to 640 nm. We show that this upconversion is a 4-photon conversion process with an underlying energy transfer upconversion mechanism. Via careful control of dopant concentration and shelling we achieve a relative upconversion-to-downconversion efficiency up to 15.2%, more than half the theoretical maximum. The placement of the Ho doped LnNPs into a plasmonic nanocavity device enables large gains in emission intensity (up to 32-fold), due to the dramatic shortening of the emission lifetime of Ho from 29 $\mu$s to <1 ns, indicating a high Purcell-enhancement factor of 3x10$^4$. These results open new possibilities at the frontier of short-wave infrared upconversion and the nanoplasmonic enhancement of LnNP emission, with potential applications in detection, theranostics, photonics and optoelectronics.