NIR‐II Responsive Upconversion Nanoprobe with Simultaneously Enhanced Single‐Band Red Luminescence and Phase/Size Control for Bioimaging and Photodynamic Therapy

Abstract

Lanthanide based upconversion (UC) nanoprobes have emerged as promising agents for biological applications. Extending the excitation light to the second near‐infrared (NIR‐II), instead of the traditional 980/808 nm light, and realizing NIR‐II responsive single‐band red UC emission is highly demanded for bioimaging application, which has not yet been explored. Here, a new type of NIR‐II (1532 nm) light responsive UC nanoparticles (UCNPs) with enhanced single‐band red UC emission and controllable phase and size is designed by introducing Er3+ as sensitizer and utilizing Mn2+ as energy manipulator. Through tuning the content of Mn2+ in NaLnF4:Er/Mn, the crystal phase, size, and emitting color are readily controlled, and the red‐to‐green (R/G) ratio is significantly increased from ≈20 to ≈300, leading to NIR‐II responsive single band red emission via efficient energy transfer between Er3+ and Mn2+. In addition, the single band red emitting intensity can be further improved by coating shell to avoid the surface quenching effect. More importantly, NIR‐II light activated red UC bioimaging and photodynamic therapy through loading photosensitizer of zinc phthalocyanine are successfully achieved for the first time. These findings provide a new strategy of designing NIR‐II light responsive single‐band red emissive UCNPs for biomedical applications.

Erythrocyte membrane-camouflaged DNA-functionalized upconversion nanoparticles for tumor-targeted chemotherapy and immunotherapy

“…20 In recent years, lanthanide-based upconversion nanoparticles (UCNPs) have come into focus due to their distinctive chemical and optical properties. 21 According to research, UCNPs that carry and protect single-stranded DNA have been employed in cancer treatment and bioimaging. 22 On the one hand, the fast coordination of the phosphate groups on the DNA backbone with Ln 3+ exposed on the UCNPs causes DNA absorption onto the UCNP surface.…”

Utilizing Energy Transfer in Mn2+/Ho3+/Yb3+ Tri-doped ZnAl2O4 Nanophosphors for Tunable Luminescence and Highly Sensitive Visual Cryogenic Thermometry

“…Among lanthanides, Er 3+ , Tm 3+ , and Ho 3+ ions are typically utilized as activator ions in UC phosphors and generally exhibit UC visible emissions consisting of both green and red emission bands along with weak blue emissions. − The green emission has lower escaping tendency from tissues and may generate autofluorescence that lowers the spatial resolution and thus is undesirable. , The singular red UC emission is essential for high bioimaging sensitivity owing to the large penetration depth, high escape tendency in tissues, and less light scattering. − Many efforts have been made to achieve the ideal single-component red UC emission of the Er 3+ –Yb 3+ and Ho 3+ –Yb 3+ sensitizer–activator pair by tailoring the luminescence properties using strategies such as optimization of synthetic methods, tuning sensitizer doping concentrations, and NIR pump power modulation and inducing specific pathways for energy transfer (ET) via codoping of other ions. Fortunately, the relaxation dynamics of activator lanthanide ions could be influenced by inclusion of other dopant ions such as Cr 3+ , Mn 2+ , Mn 4+ , Zr 4+ , Mg 2+ , Ce 3+ , or Gd 3+ in the host lattice. − For example, Giordano et al reported enhanced red-UCL with incorporation of Ce 3+ ions in the NaBiF 4 /Yb 3+ /Ho 3+ phosphor, Rai et al . utilized codoping of Gd 3+ to enhance red UC in the Er 3+ /Yb 3+ system, Srivastava et al reported a single red emission facilitated by Er 3+ → Cr 3+ ET, and Tian et al showcased the manipulation of red and green UC emissions via codoping of Mn 2+ ions in the NaYF 4 : Er 3+ /Yb 3+ system.…”

Multifunctional Laser-Induced Bubble Microresonator for Upconversion Emission Enhancement

“…The importance and versatility of upconversion nanoparticles (UCNPs) have been proven in various applications ranging from displays, bioimaging, sensing, optoelectronics, , photovoltaics, photocatalysis, , therapeutics, , and diagnostics . UCNPs can exhibit antistokes emissions under near-infrared (NIR) excitation. − They are capable of emitting ultraviolet and visible photons by absorbing multiple NIR photons due to their multiple energy levels or ladder-like energy level systems. , However, the quantum yield of the upconversion emission is generally low due to the multiphoton processes and low absorption cross-section, which hinders the applications of UCNPs.…”