Multiple-Sized Amphiphilic Janus Gold Nanoparticles by Ligand Exchange at Toluene/Water Interface

Amphiphilic Janus gold nanoparticles （GNPs） are prospected to encapsulate drug molecules in cancer therapy and to serve as heterogeneous catalysts at oil/water interfaces, where Janus GNPs with differ- ent sizes are required. In this work, multiple-sized precursor GNPs were synthesized by seeded growth method protected with tris（hydroxymethyl）phosphine oxide （THPO） ligand molecule, and a ligand ex- change reaction with triphenylphosphine （PPh3） at the toluene/water interface was employed to prepare amphiphilic Janus GNPs. UV-vis and transmission electron microscopy （TEM） analyses indicate that the as-prepared GNPs are nanocrystals with average diameters of 2.3 nm, 9.5 nm, 16.1 nm and 18.8 nm, re- spectively. Contact angle, Raman and X-ray photonic spectroscopy （XPS） analyses reveal that the self- assembled GNP films exhibit hydrophilic on one side and hydrophobic on another, owing to the adsorption of hydrophilic ligands （THPO and THP） and a similar amount of hydrophobic ligands （PPh3 and PPh30）. Angle-resolved XPS analysis further demonstrates that the individual GNPs actually possess hydro- philic and hydmphobic compartments on the surface, which regularly packed by supramolecular interactions at toluene/water interface to form the self-assembled GNP films.

Engineering Janus gold nanorod–titania heterostructures with enhanced photocatalytic antibacterial activity against multidrugresistant bacterial infection

Photocatalytic antibacterial approach shows great potential in treating multidrug-resistant bacterial infections.However,the bactericidal efficiency heavily depends on the photocatalytic activity of semiconductor materials,which is limited by the fast recombination of photogenerated electron–hole pairs.Janus nano-heterostructures with spatial control growth of TiO_(2)nanoparticles(NPs)at one end of gold nanorods(Au NRs)are designed via surface ligand regulation for photocatalytic sterilization and infected wound healing.The asymmetric nanostructure of Janus gold nanorod-titanium dioxide nanoparticles(Janus AuNR-TiO_(2) NPs)promotes the directional migration of charge carriers and is more conducive to the spatial separation of electron–hole pairs.Moreover,the injection of hot electrons and enhancement of plasmon near-fields from the surface plasmon resonance(SPR)effect further improve the photocatalytic efficiency of Janus AuNR-TiO_(2) NPs.Under simulated sunlight irradiation,large amounts of reactive oxygen species(ROS)are generated for photocatalytic antibacterial activity.Enhanced bactericidal efficiency up to 99.99%against methicillin-resistant Staphylococcus aureus(MRSA)is achieved in vitro.Furthermore,Janus AuNR-TiO_(2) NPs exhibit superior biocompatibility,structural stability,and also remarkably accelerate MRSA-infected wound healing.Taking the above all into consideration,Janus AuNR-TiO_(2) NPs,as an efficient antibacterial photocatalyst,offers a promising strategy for MRSA infectious therapy.