Alexander Pyatenko

Single-Crystalline Rutile TiO2 Hollow Spheres: Room-Temperature Synthesis, Tailored Visible-Light-Extinction, and Effective Scattering Layer for Quantum Dot-Sensitized Solar Cells

A general synthesis of inorganic single-crystalline hollow spheres has been achieved through a mechanism analogous to the Kirkendall effect, based on a simple one-step laser process performed at room temperature. Taking TiO(2) as an example, we describe the laser process by investigating the influence of experimental parameters, for example, laser wavelength, laser fluence/irradiation time, liquid medium, and concentration of starting materials, on the formation of hollow spheres. It was found that the size-tailored TiO(2) hollow spheres demonstrate tunable light scattering over a wide visible-light range. Inspired by the effect of light scattering, we introduced the TiO(2) hollow spheres scattering layer in quantum dot-sensitized solar cells and achieved a current notable 10% improvement of solar-to-electric conversion efficiency, indicating that TiO(2) hollow spheres are potential candidates in optical and optoelectronic devices.

Selective pulsed heating for the synthesis of semiconductor and metal submicrometer spheres.

Spherical particles are of great interest because they are athermodynamicallyfavorablestatein terms ofsurfaceenergy.Recent work has fully demonstrated their potential to obtaininteresting and useful functionalities in many fields ofapplication, such as photonic crystals, biomedicine, sensing,catalysis, environmental remedies, and solar cells.

Size‐Tailored ZnO Submicrometer Spheres: Bottom‐Up Construction, Size‐Related Optical Extinction, and Selective Aniline Trapping

Fabrication of size-tailored semiconductor/metal submicrometer spherical particles has recently attracted signifi cant interest due to their unique physicochemical properties and emerging applications in many strategically important fi elds such as photonic crystals, pharmaceuticals, electronics, catalysis, energy, and environmental protection. [ 1 ] ZnO, with a wide bandgap of 3.37 eV and a large exciton binding energy of 60 meV, is one of the key semiconductors, widely utilized in piezoelectric transducers, varistors, phosphors, sensors, solar cells, and transparent conducting fi lms. [ 2 ] Due to the intrinsic nature of polar hexagonal-phase ZnO with an a : c axial ratio of 1:1.6, diverse well-defi ned 1D nanostructures have been synthesized [ 3 ] and utilized in a variety of functional device applications, such as light-emitting diodes, nanolasers, photodetectors, fi eld-effect transistors, photovoltaic devices, nanogenerators, and chemical sensors. [ 4 ] Comparatively, the creation of spherical crystals of ZnO, which are thought to be an attractive material for photonic crystals, sensors, solar cells, and photocatalysts, has seldom been reported. [ 5 ] Furthermore, even within those few existing reports, the resultant submicrometer ZnO spherical particles have usually been built up by secondary structures, such as nanoparticles and nanoplates, [ 5 ] where the lack of close contact between nanostructures will inevitably infl uence and possibly reduce the performance of ZnO submicrometer spheres in electric, magnetic, optoelectric, and thermoelectric applications. Consequently, it remains a challenge to acquire ZnO submicrometer spheres constructed without subunits. However, the synthesis of such spherical semiconductor/metal particles has been rarely reported. One effective approach has

Fabrication of Crystalline Silicon Spheres by Selective Laser Heating in Liquid Medium

Micrometer and submicrometer crystalline silicon spheres were fabricated by selective laser heating of irregular silicon particles in liquid medium. TEM, SEM, XRD, and XPS characterized the structure and morphology of the prepared silicon spheres. The results suggested that they were spherical with a single crystalline structure. In this study, the formation mechanism of the spheres is analyzed, and the process parameters are optimized to obtain high-quality silicon spheres. A theoretical deduction regarding the relationship between critical laser energy density and particle size is also discussed, by which we can predict that larger spheres can be obtained at higher laser energy densities.

Pulsed laser irradiation of colloidal nanoparticles: a new synthesis route for the production of non-equilibrium bimetallic alloy submicrometer spheres

A new one-step approach was developed to synthesize bimetallic alloy submicrometer spheres, which are immiscible under equilibrium, using AuCo as a model system. Uniform, single-phase AuCo alloy submicrometer particles (∼230 nm) with a well-defined spherical morphology were successfully formed via pulsed laser irradiation of Au and Co-oxides nanoparticles dispersed in ethanol and characterized with a combination of electron microscopy, diffraction and magnetization measurements.

General Bottom‐Up Construction of Spherical Particles by Pulsed Laser Irradiation of Colloidal Nanoparticles: A Case Study on CuO

The development of a general method to fabricate spherical semiconductor and metal particles advances their promising electrical, optical, magnetic, plasmonic, thermoelectric, and optoelectric applications. Herein, by using CuO as an example, we systematically demonstrate a general bottom-up laser processing technique for the synthesis of submicrometer semiconductor and metal colloidal spheres, in which the unique selective pulsed heating assures the formation of spherical particles. Importantly, we can easily control the size and phase of resultant colloidal spheres by simply tuning the input laser fluence. The heating-melting-fusion mechanism is proposed to be responsible for the size evolution of the spherical particles. We have systematically investigated the influence of experimental parameters, including laser fluence, laser wavelength, laser irradiation time, dispersing liquid, and starting material concentration on the formation of colloidal spheres. We believe that this facile laser irradiation approach represents a major step not only for the fabrication of colloidal spheres but also in the practical application of laser processing for micro- and nanomaterial synthesis.

Synthesis of new metastable nanoalloys of immiscible metals with a pulse laser technique

The generation of nanoalloys of immiscible metals is still a challenge using conventional methods. However, because these materials are currently attracting much attention, alternative methods are needed. In this article, we demonstrate a simple but powerful strategy for the generation of a new metastable alloy of immiscible metals. Au1−xNix 3D structures with 56 at% of nickel in gold were successfully manufactured by the pulsed laser irradiation of colloidal nanoparticles. This technology can be used for preparing different metastable alloys of immiscible metals. We hypothesise that this technique leads to the formation of alloy particles through the agglomerations of nanoparticles, very fast heating, and fast cooling/solidification. Thus, we expect that our approach will be applicable to a wide range of inorganic solids, yielding even new metastable solids that fail to be stable in the bulk systems, and therefore do not exist in Nature.

Tetragonal zirconia spheres fabricated by carbon-assisted selective laser heating in a liquid medium

Submicrometer-sized tetragonal zirconia spheres are synthesized by carbon-assisted selective pulsed laser heating in a liquid medium at room temperature. Sphere formation and phase transformation from the monoclinic to the tetragonal phase are only observed by laser irradiation of a colloidal solution containing raw zirconia mechanically milled with nanocarbon. This result indicates that nanocarbon, having close contact with zirconia particles, plays a very important role in forming submicrometer-sized tetragonal zirconia spheres.

Synthesis of Au-Based Porous Magnetic Spheres by Selective Laser Heating in Liquid

We report the synthesis of Au-based submicrometer-sized spherical particles with uniform morphology/size and integrated porosity-magnetic property in a single particles. The particles are synthesized by a two-step process: (a) selective pulsed laser heating of colloidal nanoparticles to form particles with Au-rich core and Fe-rich shell and (b) acid treatment which leads to formation of porous architecture on particle surface. The simple, fast, inexpensive technique that is proposed demonstrates very promising perspectives for synthesis of composite particles.

Preparation of silver spheres by selective laser heating in silver-containing precursor solution

Dispersed uniform submicron-sized silver spheres were prepared by selective laser heating in the silver-containing precursor solution, which was produced by dissolving the irregular Ag2O in aliphatic amine. By optimizing the process conditions, silver spheres in the range of 578 ± 109 nm were obtained. The smooth surface morphology and solid structure were studied by SEM and TEM. The silver content was characterized by XRD and EDS. Finally, the mechanism of the silver spheres formation was also discussed in detail.