Localized surface plasmon resonance shift of biosynthesized and functionalized quasi-spherical gold nanoparticle systems.

Rapid and more environment-friendly means of gold nanoparticle synthesis is necessary in many applications, as in ion detection. Leaf extracts have become effective and economical reducing agents for gold nanoparticle formation, however, effects of extract combinations have not been thoroughly investigated. With the exploitation of combined extract effects, gold nanoparticles were synthesized then functionalized and investigated to produce selected nanoparticle systems which are capable of detecting aqueous lead(ii) ions with minimum detection limits of 10-11 ppm.

Photovoltaic and photocatalytic properties of bismuth oxyiodide-graphene nanocomposites.

In this study, we evaluate the photovoltaic and photocatalytic properties of chemical vapor deposited bismuth oxyiodide (BiOI) and bismuth oxyiodide-graphene (BiOI-GR) nanocomposite thin films. The BiOI thin film has an average thickness of 574 nm and a bandgap of around 2 eV. The BiOI and BiOI-GR thin films exhibited nanoflake morphology.

Electrochemical impedance analysis of perovskite-electrolyte interfaces.

The flat band potentials and carrier densities of spin coated and sprayed MAPbI, FACsPbI, and MAPbBr perovskite films were determined using the Mott-Schottky relation. The films developed a space charge layer and exhibited p-type conduction with a carrier concentration of ∼10 cm for spin coated films. Electrochemical impedance spectra showed typical space charge impedance at frequencies >1 kHz, and an exceptional high capacitance at frequency <1 kHz owing to an ion diffusion component.

Site-Selective Passivation of Defects in NiO Solar Photocathodes by Targeted Atomic Deposition.

For nanomaterials, surface chemistry can dictate fundamental material properties, including charge-carrier lifetimes, doping levels, and electrical mobilities. In devices, surface defects are usually the key limiting factor for performance, particularly in solar-energy applications. Here, we develop a strategy to uniformly and selectively passivate defect sites in semiconductor nanomaterials using a vapor-phase process termed targeted atomic deposition (TAD).

Substrate-controlled band positions in CH₃NH₃PbI₃ perovskite films.

Using X-ray and ultraviolet photoelectron spectroscopy, the surface band positions of solution-processed CH3NH3PbI3 perovskite thin films deposited on an insulating substrate (Al2O3), various n-type (TiO2, ZrO2, ZnO, and F:SnO2 (FTO)) substrates, and various p-type (PEDOT:PSS, NiO, and Cu2O) substrates are studied. Many-body GW calculations of the valence band density of states, with spin-orbit interactions included, show a clear correspondence with our experimental spectra and are used to confirm our assignment of the valence band maximum. These surface-sensitive photoelectron spectroscopy measurements result in shifting of the CH3NH3PbI3 valence band position relative to the Fermi energy as a function of substrate type, where the valence band to Fermi energy difference reflects the substrate type (insulating-, n-, or p-type).

Observation of charge transport in single titanium dioxide nanotubes by micro-photoluminescence imaging and spectroscopy.

We present the first report of photoluminescence spectra and images of single TiO(2) (anatase) nanotubes. In previous work using ensembles of conventional TiO(2) nanoparticles, we interpreted the broad photoluminescence (PL) spectrum to be a superposition of hole trap emission, peaking in the green, and broad red PL arising from electron traps. PL spectra of individual nanotubes in inert environment show a similar broad emission, with peaks at around 560-610 nm.