To date, the increase in reactive oxygen species (ROS) production for effectual photodynamic therapy (PDT) treatment still remains challenging. In this study, a facile and effective approach is utilized to coat mesoporous silica (mSiO2) shell on the ligand-free upconversion nanoparticles (UCNPs) based on the LiYF4 host material. Two kinds of mesoporous silica-coated UCNPs (UCNP@mSiO2) that display green emission (doped with Ho3+) and red emission (doped with Er3+), respectively, were successfully synthesized and well characterized. Three photosensitizers (PSs), merocyanine 540 (MC 540), rose bengal (RB), and chlorin e6 (Ce6), with the function of absorption of green or red emission, were selected and loaded into the mSiO2 shell of both UCNP@mSiO2 nanomaterials. A comprehensive study for the three UCNP@mSiO2/PS donor/acceptor pairs was performed to investigate the efficacy of fluorescence resonance energy transfer (FRET), ROS generation, and in vitro PDT using a MCF-7 cell line. ROS generation detection showed that as compared to the oleate-capped and ligand-free UCNP/PS pairs, the UCNP@mSiO2/PS nanocarrier system demonstrated more pronounced ROS generation due to the UCNP@mSiO2 nanoparticles in close vicinity to PS molecules and a higher loading capacity of the photosensitizer. As a result, the three LiYF4 UCNP@mSiO2/PS nanoplatforms displayed more prominent therapeutic efficacies in PDT by using in vitro cytotoxicity tests.

Upconversion nanoparticles (UCNPs) and polymerizable molecules of aggregation-induced emission (AIE) were combined to produce white light emission. Blue and ultraviolet light-emitting doped lanthanide UCNPs (LiYF4:Yb3+/Tm3+@LiYF4:Yb3+), polymerizable red light-emitting 1,4-bis(piperidinyl-1-propenyl bromide)anthracene (1,4-BPPA), and green light-emitting 9,10-BPPA AIE molecules were mixed with photopolymerizable acrylate oligomers for photopolymerization to form a luminescent film. The fluorescence spectrum, obtained by exciting the LiYF4:Yb3+/Tm3+@LiYF4:Yb3+ UCNPs with 980 nm near-infrared light, exhibited visible light emission, and high-energy emission included ultraviolet light at 365 nm and blue light at 450 and 475 nm. The high-energy light produced through the transfer of energy from the UCNPs excited 1,4-BPPA and 9,10-BPPA molecules to emit red and green light, thus producing a hybrid of red, blue, and green light emission that resulted in white light. X-ray diffractometry, scanning electron microscopy, ultraviolet–visible spectrometry, and fluorescence spectrometry were used to analyze the materials. The CIE coordinates of the white light-emitting film were (0.3358, 0.3536), corresponding to a correlated color temperature of 5370 K. The results demonstrate that upconversion particles and polymerizable AIE molecules can be combined to fabricate a white light-emitting diode film.