This study introduces a Janus colloid surfactant catalyst platform exhibiting remarkable catalytic activity and magnetic responsiveness in Pickering emulsion microreactors. The patching of catalytic nanoparticles (NPs) such as Pd NPs and Ag NPs on amphiphilic Janus microparticles (JMPs) permits the control of catalytic activity for the organic reactions occurring in emulsion droplets. Through model organic reactions including oxidation, amination, and reduction, we show that the JMP catalysts assemble at the reactant–water interface of Pickering emulsions and play an essential role in enhancing the reaction kinetics and product yields. Moreover, when Fe₂O₃ NPs were co-patched site specifically, the Pickering emulsion droplets showed magnetic responsiveness, thus leading to facile recovery of products and effective recycling of JMP catalysts. The colloid surfactant catalysts developed in our study are expected to advance the environment-friendly catalyst system for green chemistry.

Although volatile organic compounds (VOCs) are becoming increasingly recognized as harmful agents and potential biomarkers, selective detection of the organic targets remains a tremendous challenge. Among the materials being investigated for target recognition, peptides are attractive candidates because of their chemical robustness, divergence and their homology to natural olfactory receptors. Using a combinatorial peptide library and either a graphitic surface or phenyl-terminated self-assembled monolayer as relevant target surfaces, we successfully selected three interesting peptides that differentiate a single carbon deviation among benzene and its analogues. The heterogeneity of the designed target surfaces provided peptides with varying affinity toward targeted molecules and generated a set of selective peptides that complemented each other. Microcantilever sensors conjugated with each peptide quantitated benzene, toluene and xylene to sub-ppm levels in real time. The selection of specific receptors for a group of volatile molecules will provide a strong foundation for general approach to individually monitoring VOCs.