Smart surface coatings of silicon (Si) nanoparticles are shown to be good examples for dramatically improving the cyclability of lithium-ion batteries. Most coating materials, however, face significant challenges, including a low initial Coulombic efficiency, tedious processing, and safety assessment. In this study, a facile sol-gel strategy is demonstrated to synthesize commercial Si nanoparticles encapsulated by amorphous titanium oxide (TiO ), with core-shell structures, which show greatly superior electrochemical performance and high-safety lithium storage. The amorphous TiO shell (≈3 nm) shows elastic behavior during lithium discharging and charging processes, maintaining high structural integrity. Interestingly, it is found that the amorphous TiO shells offer superior buffering properties compared to crystalline TiO layers for unprecedented cycling stability. Moreover, accelerating rate calorimetry testing reveals that the TiO -encapsulated Si nanoparticles are safer than conventional carbon-coated Si-based anodes.

In this paper, we present a study on learning visual recognition models from large scale noisy web data. We build a new database called WebVision, which contains more than 2.4 million web images crawled from the Internet by using queries generated from the 1, 000 semantic concepts of the ILSVRC 2012 benchmark. Meta information along with those web images (e.g., title, description, tags, etc.) are also crawled. A validation set and test set containing human annotated images are also provided to facilitate algorithmic development. Based on our new database, we obtain a few interesting observations: 1) the noisy web images are sufficient for training a good deep CNN model for visual recognition; 2) the model learnt from our WebVision database exhibits comparable or even better generalization ability than the one trained from the ILSVRC 2012 dataset when being transferred to new datasets and tasks; 3) a domain adaptation issue (a.k.a., dataset bias) is observed, which means the dataset can be used as the largest benchmark dataset for visual domain adaptation. Our new WebVision database and relevant studies in this work would benefit the advance of learning state-of-the-art visual models with minimum supervision based on web data.

Integrating chromophores into chiral photonic crystals to fabricate materials that exhibit circularly polarized luminescence (CPL) is promising as this method allows efficient manipulation of the spontaneous emission within photonic bandgaps (PBGs). However, tuning the wavelength of CPL and the dissymmetry factor (g lum) in a convenient and accurate manner remains a significant challenge. Here, right-handed, tunable upconverted CPL (UC-CPL) emission was achieved by integrating multiple emissive, upconverting nanoparticles into cellulose nanocrystal based chiral photonic films that had tunable PBGs. Glycerol was used to tune the PBGs of the chiral photonic films, which yielded tunable UC-CPL emission at 450 and 620 nm with a tailored g lum. Moreover, humidity responsive UC-CPL at blue wavelength was obtained from glycerol-composite photonic film, with a g lum that ranged from −0.156 to −0.033. It was possible because the PBG and chirality of photonic composite was responded to the relative humidity. This work gives valuable insight into tunable and stimuli-responsive CPL photonic systems.

Hydrogenated silicon (Si : H) thin films were obtained by plasma-enhanced chemical vapor deposition (PECVD). Raman spectroscopy was used to investigate the structural evolution in phosphor-doped n-type amorphous hydrogenated silicon thin films, which were prepared under different substrate temperatures and gas pressures. Meanwhile, the effect of nitrogen doping on the structure of P-doped thin films was also investigated by Raman spectroscopy. Moreover, the transition from the amorphous state to the nanocrystalline state of undoped Si : H films deposited through low argon dilution was studied by Raman spectroscopy, X-ray diffraction, and transmission electron microscopy. The results show that Raman spectroscopy can sensitively detect the structural evolution in hydrogenated silicon thin films deposited under different conditions in a PECVD system.

Here, we report the enhanced luminescence and optical gain by appropriate P-doping in Si nanocrystals (NCs)/SiO multilayers with ultra-small size of ∼1.9 nm. The luminescence intensity is enhanced by 19.4% compared to that of an un-doped NC and the optical gain is as high as 171.8 cm, which can be attributed to the reduction of surface defect states by the passivation of P impurities as revealed by electron spin resonance spectra. Further increasing the P-doping ratios results in the increase of conduction electrons due to the substitutional doping of phosphorus in the Si NCs, which favors the Auger recombination process. Consequently, both the luminescence intensity and the optical gain decrease rapidly. It is demonstrated that introduction of the suitable impurities can effectively modulate the surface chemical environment of Si NCs, which provides a new way to control the physical properties of Si NCs.