Over the past decade, high-quality lanthanide doped upconverting nanoparticles (UCNPs) have been successfully synthesized with the rapid development of nanotechnology. Due to the unique electron configuration of lanthanide ions, there are rich energy level structures in the near-infrared, visible and ultraviolet spectral range. However, for UCNPs, only a limited number of efficient upconversion excitation and emission have been generated due to the limited number of sensitizer (Yb(3+)) and activator (Tm(3+), Er(3+), and Ho(3+)) ions, and the application is mainly focused on the bio-imaging by using the upconversion luminescence of UCNPs. Recently, more and more researchers have started to focus on tuning of upconversion optical properties and developing of multi-functional UCNPs by using the combination of sub-lattice mediated energy migration, core@shell structural engineering and UCNPs based nanocomposites which greatly expands the range of applications for lanthanide-doped UCNPs. Therefore, a "nanolab" can be created on UCNPs, where the property modulation can be realized via the designed host-dopants combinations, core@shell nanostructure, energy exchange with "alien species" (organic dyes, quantum dots, etc.), and so on. In this paper, we provide a comprehensive survey of the latest advances made in developing lanthanide-doped UCNPs, which include excitation and emission energy levels guided designing of the UCNP nanostructure, the synthesis techniques to fabricate the nanostructure with optimum energy level structure and optical properties, the fabrication of UCNPs-based nanocomposites to extend the applications by introducing the additional functional components, or integrating the functional moiety into one nanocomposite.

Multifunctional dual-compartment Janus mesoporous silica nanocomposites of UCNP@SiO2@mSiO2&PMO (UCNP = upconversion nanoparticle, PMO = periodic mesoporous organosilica) containing core@shell@shell structured UCNP@SiO2@mSiO2 nanospheres and PMO single-crystal nanocubes have been successfully synthesized via a novel anisotropic island nucleation and growth approach with the ordered mesostructure. The asymmetric Janus nanocomposites show a very uniform size of ~300 nm and high surface area of ~1290 m(2)/g. Most importantly, the Janus nanocomposites possess the unique dual independent mesopores with different pore sizes (2.1 nm and 3.5-5.5 nm) and hydrophobicity/hydrophilicity for loading of multiple guests. The distinct chemical properties of the silica sources and the different mesostructures of the dual-compartments are the necessary prerequisites for the formation of the Janus nanostructure. With the assistance of the near-infrared (NIR) to ultraviolet/visible (UV-vis) optical properties of UCNPs and heat-sensitive phase change materials, the dual-compartment Janus mesoporous silica nanocomposites can be further applied into nanobiomedicine for heat and NIR light bimodal-triggered dual-drugs controllable release. It realizes significantly higher efficiency for cancer cell killing (more than 50%) compared to that of the single-triggered drugs delivery system (~25%).

Supporting Information:I. Detailed process for the synthesis of the core NPs. Synthesis of hexagonal phase (β) NaGdF 4 :Yb,Er core NPs:The synthesis of the core NPs with a size of ~ 4.5 nm in this work were similar to previously report by van Veggel et al. 1 In a typical procedure, GdCl 3 (0.8 mmol), YbCl 3 (0.18 mmol), ErCl 3 (0.02 mmol), OA (4 mL) and ODE (15 mL) were mixed together and heated to 140 °C under vacuum until a clear solution formed, after that, the solution was cooled to room temperature. A solution of NaOH (2.5 mmol) and NH 4 F (4 mmol) in methanol (10 mL) was added and the mixture was stirred for a few hours. The reaction mixture was then heated at 70 °C to remove the methanol. Afterward, the solution was heated to 270 °C and maintained for 45 min under a gentle argon flow. Subsequently, the solution was cooled to room temperature and the NPs precipitated, centrifuged and washed twice with ethanol. The NPs were finally dispersed in 10 mL of cyclohexane for further use. Synthesis of cubic phase (α) small core NPs with (NaYbF 4 :Er) and without (NaYF 4 ) dopants:The trifluoroacetates (TFA) of Y, Yb, Tm, and Er were prepared by the procedure reported by Roberts et al. 2 The syntheses of the core NPs in this work were similar to that reported previously by Chen et al. 3 In a typical procedure (NaYbF 4 :Er, ~ 9 nm), 1.00 mmol of Na-TFA, 0.90 mmol of Yb-TFA, and 0.10 mmol of Er-TFA were dispersed in 16.0 mL of OA and 8.0 mL of OAM. The result solution was then heated at 120 °C under vacuum with magnetic stirring for 30 min to remove water and oxygen. Finally, the solution was heated to 275 °C at a rate of about 15 °C/min under Ar gas protection and kept at this temperature under vigorous stirring for about 30 min. Finally, the mixture was cooled to room temperature precipitated,

The low-efficiency cellular uptake property of current nanoparticles greatly restricts their application in the biomedical field. Herein, we demonstrate that novel virus-like mesoporous silica nanoparticles can easily be synthesized, showing greatly superior cellular uptake property. The unique virus-like mesoporous silica nanoparticles with a spiky tubular rough surface have been successfully synthesized via a novel single-micelle epitaxial growth approach in a low-concentration-surfactant oil/water biphase system. The virus-like nanoparticles’ rough surface morphology results mainly from the mesoporous silica nanotubes spontaneously grown via an epitaxial growth process. The obtained nanoparticles show uniform particle size and excellent monodispersity. The structural parameters of the nanoparticles can be well tuned with controllable core diameter (∼60–160 nm), tubular length (∼6–70 nm), and outer diameter (∼6–10 nm). Thanks to the biomimetic morphology, the virus-like nanoparticles show greatly superior cellular uptake property (invading living cells in large quantities within few minutes, <5 min), unique internalization pathways, and extended blood circulation duration (t1/2 = 2.16 h), which is much longer than that of conventional mesoporous silica nanoparticles (0.45 h). Furthermore, our epitaxial growth strategy can be applied to fabricate various virus-like mesoporous core–shell structures, paving the way toward designed synthesis of virus-like nanocomposites for biomedicine applications.