ABSTRACT
Herein, we have successfully constructed a solid-state Z-scheme photosystem with enhanced light absorption capacity by combining the optoelectrical properties of AgNPs with those of the MoS2/RGO/NiWO4 (Ag-MRGON) heterostructure. The Ag-MRGON Z-scheme system demonstrates improved photo-electrochemical (PEC) water-splitting performance in terms of applied bias photon-to-current conversion efficiency (ABPE), which is 0.52%, and 17.3- and 4.3-times better than those of pristine MoS2 and MoS2/NiWO4 photoanodes, respectively. The application of AgNPs as an optical property enhancer and RGO as an electron mediator improved the photocurrent density of Ag-MRGON to 3.5 mA/cm2 and suppressed the charge recombination to attain the photostability of â¼2 h. Moreover, the photocurrent onset potential of the Ag-MRGON heterojunction (i.e., 0.61 VRHE) is cathodically shifted compared to those of NiWO4 (0.83 VRHE), MoS2 (0.80 VRHE), and MoS2/NiWO4 heterojunction (0.73 VRHE). The improved PEC water-splitting performance in terms of ABPE, photocurrent density, and onset potential is attributed to the facilitated charge transfer through the RGO mediator, the plasmonic effect of AgNPs, and the proper energy band alignments with the thermodynamic potentials of hydrogen and oxygen evolution.
ABSTRACT
Electric current responsive magnetic composite particles are prepared in three steps. In the first step, spherical and mesoporous submicrometer-sized magnetic iron oxide (Fe3O4) core particles are prepared by solvothermal method. Then magnetic Fe3O4 particles are functionalized with amine groups using glycine, where the COO- group of glycine formed a bridging bidentate interaction with the hydroxyl groups on Fe3O4 particle surface. Finally polyaniline (PAni) is grafted onto the functional Fe3O4 surface via in situ seeded chemical oxidative polymerization of aniline. The average size of Fe3O4/PAni composite particles is 418.82 nm with mesoporous surface structure. Electron microscopic images confirmed that PAni pockets are localized on the surface of Fe3O4 core particles. The surface composition is further confirmed by Fourier transform IR (FTIR), X-ray photoelectron spectroscopy (XPS) and thermogravimety (TG) analyses. Fe3O4/PAni composite particles possessed strong paramagnetic property (47.77 emu g-1). The electrical conductivity of Fe3O4/PAni composite particles (1.46 × 10-4 S cm-1) remained in the same order of magnitude as that of reference PAni particles (3.42 × 10-4 S cm-1). The release behavior of biologically active molecules such as trypsin (TR), albumin (AL) and p-acetamido phenol (pAP) is studied using low intensity electric current as stimuli to prevent degradation. Depending on the nature, up to Ë 33-88% of adsorbed biomolecules/drug are released from the electromagnetic Fe3O4/PAni composite particles. Compared to Fe3O4 particles, Fe3O4/PAni composite particles exhibited moderate antibacterial property.
Subject(s)
Aniline Compounds/pharmacology , Anti-Bacterial Agents/pharmacology , Bacteria/drug effects , Ferric Compounds/pharmacology , Magnetite Nanoparticles/chemistry , Adsorption , Aniline Compounds/chemistry , Anti-Bacterial Agents/chemistry , Electric Conductivity , Electromagnetic Phenomena , Ferric Compounds/chemistry , Microbial Sensitivity Tests , Particle Size , Porosity , Surface PropertiesABSTRACT
We demonstrate visualization of localized intense electromagnetic fields in real space in well-tailored dimeric and trimeric gold nanospheres by using near-field optical techniques. With two-photon induced luminescence and Raman measurements, we show that the electric field is confined at an interstitial site in the aggregate. We also demonstrate optical switching operations for the electric-field localized sites in the trimer structure.
