A series of six new free base porphyrins were synthesized for use as photosensitizers in TiO 2 dye-sensitized photo-electrochemical cells. The porphyrin sensitizers are attached to the TiO 2 photoelectrode by phosphonic or carboxylic acid anchoring groups. These anchoring groups were placed on different substitution positions on the porphyrin moiety. The new dyes were fully characterized by absorption and emission spectroscopies, electrochemistry and photo-electrochemical spectroscopy. The photo-electrochemical performances of the sensitizers are discussed and compared to the known 5,10,15,20-tetra(4-carboxyphenyl)porphyrin sensitizer. In this study, we show that the nature of the anchoring group (phosphonic or carboxylic acids) has little impact on the photo-electrochemical performance of the cell. However, the substitution position of the anchoring group on the porphyrin strongly influences the monochromatic photon-to-electron conversion efficiency of the resulting cell. The results indicate that the electronic coupling of this type of dye with the d-band of the semiconductor is one of the key parameters in the design of efficient sensitizers.

Modulating the assembly of the ruminal microbiota might have practical implications in production. We tested how an early-life dietary intervention in lambs influences the diversity and function of the ruminal microbiota during and after the intervention. Microbiota resilience during a repeated dietary intervention was also tested. The treatment, aiming to mitigate enteric methane emissions, combined garlic essential oil and linseed oil. Fifty-six lambs and their dams were allocated to two groups and treatment (T1) or placebo (C1) was drenched from birth until 10 weeks of life. Lambs were weaned at 8 weeks. From 16 to 20 weeks, lambs in each group were divided in two subgroups that received (T1–T2 and C1–T2) or not (T1–C2 and C1–C2) the same treatment. Measurements were done at 8, 14, and 20 weeks. Average daily gain was similar between groups. Methane production was reduced by treatment at 8 and 20 weeks but at 14 weeks it was similar between C1 and T1. Interestingly, early-life treated lambs displayed a numerical increase (P = 0.12) in methane emissions at 20 weeks compared with non-treated lambs. Concentration of VFA was not affected by the intervention at 8 or 14 weeks but a lower concentration was observed in T2 lambs compared with C2 at week 20. Metataxonomics (rRNA gene) revealed differences in archaeal communities between groups of lambs when treatment was applied (weeks 8 and 20); whereas, in accord with methane emissions, these differences disappeared when treatment was discontinued (week 14). Protozoal community structure was not affected by treatment. In contrast, bacterial community structure differed between treated and non-treated lambs during and after the intervention. Rumen and urine LC-MS and NMR metabolomics at week 20 separated C2 from T2 lambs and correlation analysis highlighted interactions between microbes and metabolites, notably that of methylated compounds and Methanomassiliicocceae methanogens. This study demonstrates that a long-term early-life intervention induced modifications in the composition of the rumen bacterial community that persisted after the intervention ceased with little or no effect on archaeal and protozoal communities. However, there was no persistency of the early-life intervention on methanogenesis indicating resilience for this function.