Adsorption of nucleic acid bases on metal surface of nanoparticles has received much attention recently in bio- and nanotechnology, while it still remains a controversial problem in how adenine is adsorbed onto the metal surface. As the nitrogen in adenine plays an important role in the molecular recognition and interaction, the spectral feature related to the nitrogen is the key to analysis of the adsorption configurations. For this purpose, we employed density functional theory (DFT) calculations at B3LYP/6-311+G­(d,p) level for the simulation of adsorption configurations, and in the meantime we checked the corresponding surface enhanced Raman spectroscopy (SERS) of 15N fully labeled adenine adsorbed on the surfaces of silver and gold nanoparticles both experimentally and theoretically. The agreement of spectral positions, intensities, and isotopic shifts of the SERS bands, suggests that adenine adsorbed on either silver or gold surface takes the same adsorption configuration in which N7H adenine interacts with Ag4 +/Au4 + cluster through both N3 and N9 sites. This study therefore may not only provide new insight into the interaction of adenine with noble metals but also have demonstrated the effective approach based on the combination of DFT and SERS tools applied in isotopic molecules to the issue of adsorption of nucleic acid bases onto metal surfaces in general.

Carbon nitride semiconductors are competitive candidates for visible-light-responsive photocatalysts, but encounter weakened exciton dissociation arising from the elevated Coulomb force of singlet Frenkel excitons with narrowing bandgaps. We overcome this contradiction by co-infusing π-electron-rich domains and polarizable hydroxyl units into mesoporous carbon nitride, realized by solution thermal shock. The embedded delocalized πconjugated aromatic domains derived from nonconjugated macromolecules downshift the conduction band edge and contribute to spatial separation of photogenerated electrons in the lowest unoccupied molecular orbital and holes in the highest occupied molecular orbital. Meanwhile, polarizable hydroxyls induce distinct electron flow from heptazine-based skeletons to periphery sites and enhance water adsorption as well as proton reduction capacity. Consequently, the polymeric carbon nitride delivers an enhanced hydrogen evolution rate that is 17.5 times larger than thermally treated counterparts derived from urea fabricated via conventional strategies. These results show that our strategy can infuse different functional motifs into carbon nitride and thus improve photocatalytic activity.

This paper reports on the synthesis and application of biocompatible and sensitive SERS nanoparticles for the study of uptake of nanoparticles into living cells in a microfluidic chip through surface-enhanced Raman spectroscopy (SERS). The nanoparticles were fabricated as beta-cyclodextrin-coated silver nanoparticles (Ag@CD NPs) modified with para-aminothiophenol (p-ATP) and folic acid (FA) on the surface. The p-ATP molecules act as the Raman reporter while the FA tags have high affinity for folate receptors (FR) that are over-expressed on the surface cancerous cells, so that the nanoparticles can enter the cells and be monitored by the Raman reporter. Therefore, the nanoparticles could be utilized not only as cell invaders due to endocytosis but also as a SERS sensitive probe to monitor the effect of FR-targeted drugs such as dihydroartemisinin (DHA) that induce the population change of FR on the membrane of living cells. As a result, we have successfully demonstrated that we are able to employ the Ag@CD@p-ATP@FA NPs to evaluate the number of NPs entering living cells quantitatively and correspondingly the drug effect on cancer cells in a well-controlled way.