Core(Au)-shell(Ag)structure nitrogen dots for the recognition of nitroaniline isomers by surface-enhanced Raman scattering

In this work, we report a facile synthesis method for NDs-Au@AgNPs surface-enhanced Raman scattering(SERS) substrate using Au seeds prepared by nitrogen-rich quantum dots(NDs). As a new member of quantum-dots family, NDs are rich in nitrogen and oxygen-containing functional groups and therefore can be used as an efficient reducing and stabilizing agent for the synthesis of AuNPs. The NDs-Au@AgNPs with core-shell structures was synthesized by seed-mediated growth method in presence of NDs-AuNPs seeds and exhibited high SERS activity with a high SERS enhancement factor of 10~7. The NDs-Au@AgNPs SERS substrate was effectively used for the recognition and detection of isomers of meta, ortho and para nitroanilines, while commercial SERS substrate cannot. In addition, the possible adsorption behavior was further studied, which is of great significance for the related work about differentiation of isomers and the mechanism of SERS enhancement.

Synthesis of Nitroanilines Catalyzed by Horseradish Peroxidase in the Presence of NaNO2 and H2O2

The synthesis of nitroanilines catalyzed by horseradish peroxidase（HRP） in the presence of sodium nitrite and hydrogen peroxide was investigated, o-Nitroaniline and p-nitroaniline were found in the nitrated products. 2-Aminotoluene and 4-aminotoluene could also be nitrated to give corresponding nitrated products. This protocol has great potentials to open new avenues useful for the synthesis of nitroaniline and its derivatives.

Elucidating the Chemisorption Phenomena in SERS Studies via Computational Modeling

Colloidal gold solutions with nanostars and nanospheres as well as KlariteTM gold and gold-copper bimetallic substrates were used for SERS analysis of aniline and nitroaniline isomers to investigate their chemisorption phenomena. Computational modeling based on Density Functional Theory (DFT) was used in conjunction with the SERS analysis to study the adsorption behaviors of the analytes on metal surfaces. Gold nanospheres and KlariteTM samples produced about a 10-fold increase in signal enhancement compared to gold nanostars for the SERS analysis of aniline, nitroaniline isomers, and nitrobenzene. Signal enhancement is significantly greater for aniline compared to nitrobenzene and it is dependent on the proximity of the NH2 to the NO2 group for the nitroaniline isomers. Charge-transfer in chemisorbed analytes is an important contributing factor for SERS signal. The relative strengths of enhancement can be predicted by the DFT calculation of the HOMO-LUMO energy gaps of the analyte-metal cluster. Aniline and the three nitroaniline isomers showed stronger preference for the copper substrates if both the gold and copper substrates are present. The NO2 group in 2-nitroaniline has a very strong preference and affinity for the copper in the Au-Cu bimetallic cluster.

Photochemical Nitration of Protected Anilines by 5-Methyl-1,4-dinitroimidazole

Nitroanilines are important building blocks in pharmaceuticals,materials and dyes.Nitration methods for anilines under mild conditions are highly desired.Herein,we report a photochemical method for the nitration of anilines bearing various protecting groups by 5-methyl-1,4-dinitroimidazole as a new type of nitro source.This method is light-controlled and proceeds under mild reaction conditions with high efficiency.Fmoc-,Ts-and alkyl-protected anilines are all well nitrated with good functional group tolerance.