Surface-enhanced Raman scattering from molecules adsorbed on TiO 2 nanoparticles has been observed. This is attributed to the dominant contribution of the TiO 2 -to-molecule charge-transfer mechanism. The chargetransfer process is largely dependent on the intrinsic nature of the adsorbed molecules and the surface properties of the semiconductor. Both the stronger electron attracting ability of groups para-to the mercapto group bonded with TiO 2 surface and the plentiful surface states of TiO 2 nanoparticles are favorable to TiO 2 -tomolecule charge-transfer and SERS for molecules adsorbed on TiO 2 .

In this paper, a series of silver-deposited TiO2 (Ag−TiO2) nanoparticles (NPs) with a varying content of Ag were prepared by a photoreduction method and were attempted to serve as SERS-active substrates for the first time. SERS signals of 4-MBA molecules adsorbed on Ag−TiO2 NPs were further enhanced considerably relative to those enhancements on pure TiO2 NPs. The surface-deposited Ag on TiO2 can inject additional electrons into molecules adsorbed on the TiO2 surface through the conduction band of TiO2 NPs because of plasmon resonance absorption of Ag under incident visible laser, besides the intrinsic TiO2-to-molecule charge-transfer (CT) contribution. The two contributions mentioned are responsible for the whole SERS intensity of the molecules adsorbed on Ag−TiO2 NPs. This work is valuable in developing nanosized TiO2 used as a promising, nontoxic and biologically compatible SERS-active substrate as well as in studying the CT mechanism between Ag and TiO2 for potential photoelectrochemical applications.

Melamine, a nitrogen-rich chemical, was implicated in pet and human food recalls in 2007, which caused enormous economic losses to the food industry. In this study, melamine concentration in wheat gluten, chicken feed, and processed foods (that is, cake and noodle) was measured by surface enhanced Raman spectroscopy (SERS) in combination with SERS-active substrates. SERS was able to rapidly detect 0.1% melamine in wheat gluten, 0.05% in chicken feed, 0.05% in cakes, and 0.07% in noodle, respectively. A partial least squares (PLS) model was established for the quantification of melamine in foods by SERS: R= 0.90, RMSEP = 0.33. In addition, SERS results were verified by HPLC analysis based on a simplified FDA method. Compared with HPLC, the SERS method is much faster and simpler, requires minimum sample preparation, but still yields satisfactory qualitative and quantitative results. These results demonstrate that it is an applicable approach to use SERS to screen foods, eliminate presumptive negative samples of melamine contamination from the sample population, and then verify presumptive positive samples using HPLC protocols. Combining these 2 methods could provide a more rapid and cost-effective way for monitoring melamine contamination in increasingly large numbers of imported foods and feed products.

Enhancement mechanism of the hydrogen evolution reaction (HER) attributed to the synergistic effect of electron-traps and surface plasmon resonance (SPR).

Lineage persistence and explosive radiation were important processes for establishing high species diversity of Lilieae in the QTP region. Both long-distance dispersal and migration across Beringia probably contributed to the modern distribution range of Lilieae. Our study shows that biotic interchanges between the QTP region and Irano-Turanian region and the Mediterranean Basin were bi-directional, suggesting the latter was a secondary centre of diversity.

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As a durable catalyst electrode, a cobalt-borate nanosheet array on a Ti mesh shows high activity for water oxidation in 0.1 M K-Bi (pH: 9.2), achieving a geometrical catalytic current density of 10 mA cm−2 at an overpotential of 469 mV.

A general south-north genetic divergence has been observed among Han Chinese in previous studies. However, these studies, especially those on mitochondrial DNA (mtDNA), are based either on partial mtDNA sequences or on limited samples. Given that Han Chinese comprise the world’s largest population and reside around the whole China, whether the north-south divergence can be observed after all regional populations are considered remains unknown. Moreover, factors involved in shaping the genetic landscape of Han Chinese need further investigation. In this study, we dissected the matrilineal landscape of Han Chinese by studying 4,004 mtDNA haplogroup-defining variants in 21,668 Han samples from virtually all provinces in China. Our results confirmed the genetic divergence between southern and northern Han populations. However, we found a significant genetic divergence among populations from the three main river systems, that is, the Yangtze, the Yellow, and the Zhujiang (Pearl) rivers, which largely attributed to the prevalent distribution of haplogroups D4, B4, and M7 in these river valleys. Further analyses based on 4,986 mitogenomes, including 218 newly generated sequences, indicated that this divergence was already established during the early Holocene and may have resulted from population expansion facilitated by ancient agricultures along these rivers. These results imply that the maternal gene pools of the contemporary Han populations have retained the genetic imprint of early Neolithic farmers from different river basins, or that river valleys represented relative migration barriers that facilitated genetic differentiation, thus highlighting the importance of the three ancient agricultures in shaping the genetic landscape of the Han Chinese.