Pulsed laser reshaping and fragmentation of upconversion nanoparticles — from hexagonal prisms to 1D nanorods through “Medusa”-like structures

One dimensional (1D) nanostructures attract considerable attention, enabling a broad application owing to their unique properties. However, the precise mechanism of 1D morphology attainment remains a matter of debate. In this study, ultrafast picosecond (ps) laser-induced treatment on upconversion nanoparticles (UCNPs) is offered as a tool for 1D-nanostructures formation. Fragmentation, reshaping through recrystallization process and bioadaptation of initially hydrophobic (β-Na_1.5Y_1.5F₆: Yb³⁺, Tm³⁺/β-Na_1.5Y_1.5F₆) core/shell nanoparticles by means of one-step laser treatment in water are demonstrated. “True” 1D nanostructures through “Medusa”-like structures can be obtained, maintaining anti-Stokes luminescence functionalities. A matter of the one-dimensional UCNPs based on direction of energy migration processes is debated. The proposed laser treatment approach is suitable for fast UCNP surface modification and nano-to-nano transformation, that open unique opportunities to expand UCNP applications in industry and biomedicine.

     

Salient features of deactivation of an iron oxide catalyst for dehydrogenation of methylbutenes to isoprene in industrial adiabatic reactors

The problems of deactivation of iron oxide catalysts in the process of industrial dehydrogenation of methylbutenes to isoprene have been considered. The dependence of deactivation of the catalyst fixed bed on the time on-stream of different sections of the catalyst along the reactor height has been examined. The cause of poor performance of a part of the catalyst bed has been revealed and substantiated. Based of the results of the study, the authors propose an approach to predicting the catalyst performance during a long time on-stream.     

Features of producing an ohmic contact to frontal surfaces of photoconversion structures

This paper describes a technique for producing mechanically strong and high-temperature ohmic multilayer metal contacts to silicon photoconverters.     

Characterization of vanadyl phthalocyanine based surface-type capacitive humidity sensors

This study presents the fabrication and characterization of novel surface-type capacitive humidity sensors using vanadyl phthalocyanine (VOPc) as the active material. The devices, which comprise three different thicknesses,have been fabricated using the thermal evaporation technique. A thin film of VOPc is deposited on thoroughly cleaned glass substrates with pre-pattemed Ag electrodes. The capacitive effect of the samples under humidity has been in-vestigated. Comparison of the samples with different thicknesses shows that the thinnest device seems more sensitive towards humidity. The humidity dependent capacitance properties of the sensor make it beneficial for use in commercial hygrometers.     

Stabilized treatment of recycled water in byproduct capture shop

Problems in the cooling-water cycle are addressed. Data are presented regarding the treatment of the recycled cooling water and the coking byproducts by Nalco reagents.     

Methods to decrease losses of energy generated by solar electrical modules

It is shown that the energy loss of blocking diodes decreases if some part of a solar module surface is shadowed. A powerful blocking diode for solar modules based on the silicon n ⁺ n-pp ⁺ structure is suggested.     

Kinetics of leaching of lead sulfate in sodium chloride solutions

A powder dissolution method is used to study the kinetics of leaching of lead sulfate from a lead cake in the temperature range 298–353 K and the concentration range 50–270 g/l of a sodium chloride solution. The results obtained are used to calculate the apparent activation energy (E _a = 12.41 kJ/mol); its value indicates that the process of leaching of lead sulfate from a lead cake occurs in a diffusion zone. This process is shown to be described by a first-order kinetic equation.