A multifunctional photo-thermal therapeutic nano-platform Y2O3:Nd^3+/Yb^3+/Er^3+@SiO2@Cu2S(YR-Si-Cu2S)was designed through a core-shell structure,expressing the function of bio-tissue imaging,real-time temperature detection,a{3} photo-thermal therapy u{3}er 808 nm light excitation.In this system,the core Y2O3:Nd^3+/Yb^3+/Er^3+(YR)takes the responsibility of emitting optical information a{3} monitoring temperature,while the shell Cu2S nano-particles carry most of the photo-thermal conversion function.The temperature sensing characteristic was achieved by the fluorescence intensity ratio using the thermally coupled energy levels(TCLs)4S3/2/2H11/2 of Er^3+,a{3} its higher accuracy for real-time temperature measurement in the bio-tissue than that of an infrared thermal camera was also proved by sub-tissue experiments.Furthermore,the photo-thermal effect of the present nano-system Y2O3:Nd^3+/Yb^3+/Er^3+@SiO2@Cu2S was confirmed by Escherichia coli(E.coli)a{3} Staphylococcus aureus(S.aureus)ablation.Results i{3}icate that YR-Si-Cu2S has application prospect in temperature-controlled photo-thermal treatment a{3} imaging in bio-tissues.
Nd3+-doped fiber lasers at around 900 nm based on the 4F3/2→4I9/2 transition have obtained much research attention since they can be used as the laser sources for generating pure blue fiber lasers through the frequency doubling.Here,an all-fiber laser at 915 nm was realized by polarization-maintaining Nd3+-doped silica fiber.A net gain per unit length of up to 1.0 dB/cm at 915 nm was obtained from a 4.5 cm fiber,which to our best knowledge is the highest gain coefficient reported in this kind of silica fiber.The optical-to-optical conversion efficiency varies with the active fiber length and the reflectivity of the output fiber Bragg grating(FBG),presenting an optimal value of 5.3%at 5.1 cm fiber length and 70%reflectivity of the low reflection FBG.Additionally,the linear distributed Bragg reflector short cavity was constructed to explore its potential in realizing single-frequency 915 nm fiber laser.The measurement result of longitudinal-mode properties shows it is still multi-longitudinal mode laser operation with 40 mm laser cavity.These results indicate that the Nd3+-doped silica fiber could be used to realize all-fiber laser at 915 nm,which presents potential to be the seed source of high-power fiber laser.
The past few years witnessed extensive emergence of short-wavelength upconversion（UC） emission stimulated photoactivation studies. However, low efficiency of multi-photon process greatly limits further applications. Here, ultraviolet（UV） upconversion emissions originated from multi-photon process of Tm^3＋ were studied with Nd^3＋-sensitized NaGdF4：Yb,Tm@NaYF4：Nd,Yb core/shell nanoparticles. Crucial factors, including the contents of sensitizers Nd^3＋, Yb^3＋ and activator Tm^3＋, as well as the excitation power density were investigated based on the UV emission. Spectral results showed that high contents of Nd^3＋ in shell region up to 50%（molar fraction hereafter） and Yb^3＋ of 10% were essential to mediate the energy transfer via the core/shell interface and facilitate multi-photon UV emissions. Compared with segregated activator and sensitizer, a core/shell strategy with isolated Nd^3＋ in the shell was important for higher UV emission. Although the upconverting process was initiated with Nd^3＋→Yb^3＋, the short-wavelength emissions were intrinsically coming from four- and five-photon process. The optimized nanoparticles were found to be able to manipulate the configuration transition of azobenzene molecules, and it could be promising for near infrared（NIR） triggered optical switches applications.
Significant attenuation and overheating, caused by the absorption of the excitation band （980 nm） in water, are the major obstacles in the in vivo application of lanthanide-doped upconversion nanoparticles （UCNPs）. Therefore, appropriately- structured Nd3^＋-doped UCNPs with 808 nm excitation could be a promising alternative. Herein, we developed core-shell-shell structured Nd3^＋-sensitized UCNPs as imaging agents, and decorated them onto the surface of polydopamine （PDA） to construct a novel multifunctional core/satellite nanotheranostic （PDA@UCNPs） for in vivo imaging guidance photothermal therapy using single 808 nm laser irradiation. The core-shell-shell structured design enabled outstanding upconversion luminescence properties and strong X-ray attenuation, thereby making the nanocomposites potential candidates for excellent upconversion luminescence/computed tomography dual modal imaging. In addition, the PDA core not only provides high photothermal conversion efficiency and outstanding antitumor effect, but also endows the platform with robust biocompatibility owing to its natural features. Therefore, this multifunctional nanocomposite could be a promising theranostic in future oncotherapy, with high therapeutic effectiveness but low side effects. This study would stimulate interest in designing bio- application-compatible multifunctional nanocomposites, especially for cancer diagnosis and treatment in vivo.
