Impact of polymorphism shape of titania nanocrystals on the hydrogen evolution reaction.

Herein, we investigated the impact of polymorphism dimension control of titania nanocrystals towards hydrogen generation. Two different forms of titania nanoparticles have been synthesized following the solvothermal method, leading to the formation of two distinct physicochemical features. Detailed structural, morphological, and optical studies revealed that the formation of titania nanorods correspond to rutile while granular particles correspond to the anatase phase.

Observing the Migration of Hydrogen Species in Hybrid Perovskite Materials through D/H Isotope Exchange.

Unlike heavier elements, the migration of hydrogen species in perovskite materials cannot be directly tracked using imaging or mass spectrocopy techniques. Our results show that quantitative analysis of D/H exchange in PbCHNDI allows indirect monitoring of H migration by following the N-D vibration using polarization-modulated infrared reflection-absorption spectroscopy. Kinetic analysis shows that the isotope exchange process is pseudo-first order and particularly sensitive to the intensity of light and relative humidity, and, to a lesser degree, sample thickness.

Electronic Properties of Free-Standing Surfactant-Capped Lead Halide Perovskite Nanocrystals Isolated in Vacuo.

We report an investigation of lead halide perovskite CHNHPbBr nanocrystals and associated ligand molecules by combining several different state-of-the-art experimental techniques, including synchrotron radiation-based XPS and VUV PES of free-standing nanocrystals isolated in vacuum. By using this novel approach for perovskite materials, we could directly obtain complete band alignment to vacuum of both CHNHPbBr nanocrystals and the ligands widely used in their preparation. We discuss the possible influence of the ligand molecules to apparent perovskite properties, and we compare the electronic properties of nanocrystals to those of bulk material.

In situ identification of cation-exchange-induced reversible transformations of 3D and 2D perovskites.

The optical and structural properties of hybrid perovskites can be tuned by the post-synthetic introduction of new cations. To advance the development of this approach, knowledge of the reaction mechanism is essential, but has not yet been elucidated. Here, the effect of n-octylamine on three-dimensional (3D) methylammonium lead bromide (MAPbBr3) was investigated by in situ X-ray photoelectron spectroscopy.

Physical Mechanism Behind Enhanced Photoelectrochemical and Photocatalytic Properties of Superhydrophilic Assemblies of 3D-TiO Microspheres with Arrays of Oriented, Single-Crystalline TiO Nanowires as Building Blocks Deposited on Fluorine-Doped Tin Oxide.

In comparison to the one-dimensional (1D) semiconductor nanostructures, the hierarchical, three-dimensional (3D) microstructures, composed of the arrays of 1D nanostructures as building blocks, show quite unique physicochemical properties due to efficient photon capture and enhanced surface to volume ratio, which aid in advancing the performance of various optoelectronic devices. In this contribution, we report the fabrication of surfactant-free, radially assembled, 3D titania (rutile-phase) microsphere arrays (3D-TMSAs) composed of bundles of single-crystalline titania nanowires (NWs) directly on fluorine-doped conducting oxide (FTO) substrates with tunable architecture. The effects of growth parameters on the morphology of the 3D-TMSAs have been studied thoroughly.

Direct Observation of Reversible Transformation of CHNHPbI and NHPbI Induced by Polar Gaseous Molecules.

Despite its competitive photovoltaic efficiency, the structural transformations of the prototypical hybrid perovskite, methylammonium lead iodide, are facilitated by interactions with polar molecules. Changes in optical and electronic properties upon exposure to ammonia potentially can enable the use of hybrid perovskites in gas-sensing applications. We investigated the effects of ammonia on CHNHPbI by exposing perovskite films to a wide range of vapor pressures.

Low-Energy Electron-Induced Transformations in Organolead Halide Perovskite.

Methylammonium lead iodide perovskite (MAPbI3 ), a prototype material for potentially high-efficient and low-cost organic-inorganic hybrid perovskite solar cells, has been investigated intensively in recent years. A study of low-energy electron-induced transformations in MAPbI3 is presented, performed by combining controlled electron-impact irradiation with X-ray photoelectron spectroscopy and scanning electron microscopy. Changes were observed in both the elemental composition and the morphology of irradiated MAPbI3 thin films as a function of the electron fluence for incident energies from 4.

Study of the nucleation and growth of antibiotic labeled Au NPs and blue luminescent Au8 quantum clusters for Hg(2+) ion sensing, cellular imaging and antibacterial applications.

Herein, we report a detailed experimental study supported by DFT calculations to understand the mechanism behind the synthesis of cefradine (CFD--an antibiotic) labeled gold nanoparticles (Au NPs) by employing CFD as both a mild reducing and capping agent. The analysis of the effect of growth conditions reveals that a higher concentration of HAuCl4 results in the formation of an increasing fraction of anisotropic structures, higher temperature leads to the formation of quasi-spherical particles instead of anisotropic ones, and larger pH leads to the formation of much smaller particles. The cyclic voltammetry (CV) results show that when the pH of the reaction medium increases from 4 to 6, the reduction potential of CFD increases which leads to the synthesis of nanoparticles (in a pH 4 reaction) to quantum clusters (in a pH 6 reaction).

Modulation of Reaction Kinetics for the Tuneable Synthesis of Gold Nanoparticles and Quantum Clusters: Application of Gold Quantum Clusters as "Turn-Off" Sensing Probe for Sn Ions.

The syntheses of gold nanoparticles (Au NPs) and gold quantum clusters (Au QCs) that employ cefadroxil (CFX; an antibiotic) as both reducing and capping agents are reported. The HAuCl /CFX concentration, temperature, and pH are crucial factors in the modulation of the nucleation and growth kinetics of the reaction, and consequently, in guiding the size and morphology of as-synthesized Au NPs. Interesting results are observed if the reaction is performed under different pH conditions.