No abstract

β-NaYF4 : Yb,Er upconversion nanoparticles (UCNPs) can emit bright green fluorescence under near-infrared (NIR) light excitation which is safe to the body and can penetrate deeply into tissues. The application of UCNPs in biolabeling and imaging has received great attention recently. In this work, β-NaYF4 : Yb,Er UCNPs with an average size of 35 nm, uniformly spherical shape, and surface modified with amino groups were synthesized by a one-step green solvothermal approach through the use of room-temperature ionic liquids as the reactant, co-solvent and template. The as-prepared UCNPs were introduced into Caenorhabditis elegans (C. elegans) to achieve successful in vivo imaging. We found that longer incubation time, higher UCNP concentration and smaller UCNP size can make the in vivo fluorescence of C. elegans much brighter and more continuous along their body. The worms have no apparent selectivity on ingestion of the UCNPs capped with different capping ligands while having similar size and shape. The next generation of worms did not show fluorescence under excitation. In addition, low toxicity of the nanoparticles was demonstrated by investigating the survival rates of the worms in the presence of the UCNPs. Our work demonstrates the potential application of the UCNPs in studying the biological behavior of organisms, and lays the foundation for further development of the UCNPs in the detection and diagnosis of diseases.

No abstract

Periodic broccoli-shaped Au and Ag surface-enhanced Raman spectroscopy (SERS) arrays were fabricated by combining ordered SiO 2 colloidal crystal templates with the physical deposition technique. The SiO 2 colloidal crystal-assisted Au and Ag SERS substrates have a long-range, adjustable periodic structure and a clean surface without incorporating any reductants or surfactant chemicals. Different from depositing directly on the flat substrates, the colloidal crystal-assisted nanostructure array has a larger effective surface area under the same projected area of laser irradiation, which exposes more "hot spots". An increased roughness and a larger surface area have also been created as the highly bumpy surface feature of the broccoli-shaped SERS morphologies, resulting in a greater Raman amplification than the conventional metal film over nanosphere (MFON). SERS performances by Au and Ag SERS arrays reveal that the long-range broccoli-like morphology is a promising SERS platform as it is highly sensitive, reproducible and stable. The colloidal crystal-assisted Ag SERS array has a slightly higher enhancement factor (EF) than the Au SERS array, and they both are of the order of 10 7 enhancement. Compared to our previous work, which directly deposited noble metal nanoparticles onto flat substrates, the EF of the colloidal crystal-assisted SERS array is improved by one to two orders of magnitude. Finite-difference time-domain (FDTD) simulation was performed to estimate the electromagnetic field distribution. Finally, two endocrine disrupting chemicals (EDCs) (dioctyl phthalate (DOP) and dibutyl phthalate (DBP), homologous series) at different concentrations were successfully identified by Au and Ag SERS arrays with the detection limits of 0.24 Â 10 À9 M and 0.22 Â 10 À9 M, respectively. This study suggests that the broccoli-like Au and Ag SERS arrays are promising candidates for chemical sensing and this SERS substrate fabrication technique can be accessible to the standard industrial processes. † Electronic supplementary information (ESI) available: FE-SEM images of SiO 2 colloidal crystal-assisted Ag SERS substrates at different deposition time (90 s, 180 s, and 300 s). EFs calculation of the broccoli-shaped Au and Ag SERS substrates. See