Gold Nanorods: Near-Infrared Plasmonic Photothermal Conversion and Surface Coating

In this paper, AuNRs colloids with SPRL located at ~810 nm and ~1100 nm were synthesized using an improved seed method. Based on the NIR lasers available, photothermal conversion of AuNRs were systematically studied compared with that of water. Under low power irradiation, the highest temperature is obtained when the SPRL wavelength of AuNRs is equal to the laser wavelength, and temperature of colloid increases from ~20°C to ~65°C. With increasing laser power (such as 6 W), the AuNRs colloid boils within a few minutes, and nanorods undergo a shape deformation from rod to spherical particle and even fusion, and the SPRL disappears. For further investigation, the obtained AuNRs were coated with SiO2 shell to form a core-shell nanostructure (Au@SiO2). The surface coating can be used not only in keeping the stability of AuNRs for further treatment, but also in increasing plasmonic property and biocompatibility. This work will be useful for designing plasmonic photothermal properties and further applications in nanomedicine.

Yak rumen microbiome elevates fiber degradation ability and alters rumen fermentation pattern to increase feed efficiency

Rumen microbes play an important role in ruminant energy supply and animal performance.Previous studies showed that yak(Bos grunniens)rumen microbiome and fermentation differ from other ruminants.However,little is understood about the features of the rumen microbiome that make yak adapted to their unique environmental and dietary conditions.This study was to investigate the rumen microbiome and metabolome to understand how yak adapt to the coarse forage and harsh environment in the Qinghai-Tibetan plateau.Nine female Qaidam yellow cattle(Bos taurus),9 dzomo(hybrids of cattle and yak)and 9 female plateau yak(B.grunniens),about 5 to 6 years old,were used in this study.Rumen fermentation parameters,fibrolytic enzyme activities,and rumen metataxonomic were determined.Then 18(6 samples per group)were selected for rumen metagenomic and metabolome analysis.Metataxonomic analysis revealed that the rumen microbiota was significantly different among plateau yak,Qaidam yellow cattle,and dzomo(P<0.05).Metagenomic analysis displayed a larger gene pool encoding a richer repertoire of carbohydrate-active enzymes in the rumen microbiome of plateau yak and dzomo than Qaidam yellow cattle(P<0.05).Some of the genes encoding glycoside hydrolases that mediate the digestion of cellulose and hemicellulose were significantly enriched in the rumen of plateau yak than Qaidam yellow cattle,but glycoside hydrolase 57 that primarily includes amylases was abundant in Qaidam yellow cattle(P<0.05).The rumen fermentation profile differed also,Qaidam yellow cattle having a higher molar proportion of acetate but a lower molar proportion of propionate than dzomo and plateau yak(P<0.05).Based on metabolomic analysis,rumen microbial metabolic pathways and metabolites were different.Differential metabolites are mainly amino acids,carboxylic acids,sugars,and bile acids.Changes in rumen microbial composition could explain the above results.The present study showed that the rumen microbiome of plateau yak helps its host to adapt to the Qinghai-Tibetan plateau.In particular,the plateau yak rumen microbiome has more enzymes genes involved in cellulase and hemicellulase than that of cattle,resulting higher fibrolytic enzyme activities inyak,further providing stronger fiber degradation function.

Effective fabrication of porous Au-Ag alloy nanorods for in situ Raman monitoring catalytic oxidation and reduction reactions

Porous metal nanostructures exhibit excellent catalytic properties due to their high surface-to-volume ratios and abundant catalytic active sites. However, it is still challenging to control nanopores density and structural features in a facile route and the preparation of porous alloy nanorods for catalytic application has not been well explored. In this work, we demonstrate a synthetic strategy to fabricate highly porous Au–Ag alloy nanorods(P-Au Ag NRs) by critically dealloying Ag atoms from homogeneous solid Au–Ag alloy nanorods(Au Ag NRs). Combining the merits of the tunable plasmonic properties of noble metal nanorods, excellent stabilities of alloys, and superior catalytic activities of porous structures, we use the P-Au Ag NRs as a Raman probe for the in situ monitoring of the catalytic oxidation of 3,3',5,5' tetramethylbenzidine(TMB) and reduction of 4-nitrothiophenol(4-NTP). We also compare their compositiondependent catalytic activities. The results show that P-Au Ag NRs possess superior chemical stability and higher catalytic activity than those of core-shell structures due to synergistic structural and chemical mechanisms. This strategy provides a predictive design approach for the next-generation alloy catalysts with high-performance.