It is shown that the luminescence of Sm3+ ions, which were doped into anatase nanopowder, is highly sensitive to the presence of oxygen gas. The luminescence was effectively excited through TiO2 band-to band absorption and exhibited oxygen sensitivity in a wide concentration range from pure O-2 gas down to 100 ppm of O-2 in a nitrogen atmosphere. An increase in oxygen concentration led to a stronger intensity and longer lifetime of Sm3+ luminescence, an exactly opposite behavior to luminescence-based sensors described by Stern-Volmer law. An original physical model is developed for describing such luminescent enhancement mechanism: it is proposed, that the adsorbed oxygen suppresses the inherent luminescence quenching of Sm ions taking place via a resonant energy transfer to acceptor defects in the material. Electron transfer between the adsorbed oxygen and these defects changes the structure of electronic energy levels and hence the energy accepting ability of the latter. The model allows describing the oxygen dependent non-exponential luminescence decays in a quantitative manner and relates the luminescence characteristics to the material parameters such as the surface-to-volume ratio of nanocrystallites and the density of acceptor defects and gas adsorption sites. (C) 2018 Elsevier B.V. All rights reserved.

We report using simple dip-coating method to cover the surface of graphene with nanodiamonds for future optical detection of defects on graphene. Most important part of the immobilization process is the pre-functionalization of both, nanodiamond and graphene surfaces to obtain the selectiveness of the method. This work focuses on an example of using electrostatic attraction to confine nanodiamonds to graphene. Raman spectroscopy, microluminescence imaging and scanning electron microscopy were applied to characterize obtained samples.

The ZnS layers morphology, structure, composition, and optical properties were investigated with respect to the precursors (zinc chloride and thiocarbamide, Zn:S) molar ratio in spray solution (1:1, 1:2, and 1:3) and growth temperatures in the range of 400–600 °C. Scanning electron microscopy (SEM), X‐ray diffraction (XRD), energy dispersive X‐ray analysis (EDX), UV–VIS, and PL spectroscopy were applied to characterize the ZnS layers. Layers obtained at temperatures up to 450 °C are not well crystallized and contain residues originated from undecomposed precursors. ZnS films become crystalline at Ts = 500 °C. Layers grown from 1:1 solution at 550 °C are mixture of ZnS and ZnO phases, whereas at 600 °C layers of ZnO were obtained. Films produced from 1:2 solution at 500–600 °C are of ZnS with a wurtzite structure and Eg of 3.66 eV, but contain traces of ZnO phase when grown at 550 or 600 °C. Appearance of ZnO phase in the films grown from 1:1 and 1:2 solutions is explained by the results of the studies on the formation and decomposition of dichlorobis(thiocarbamide)zinc(II) complex as an intermediate compound formed in the solution of zinc chloride and thiocarbamide. Spraying the solutions with Zn:S = 1:3, which contain more thiocarbamide than required for the complex formation, results in single‐phase ZnS layers with wurtzite structure at growth temperatures up to 600 °C. Moreover, ZnS layers obtained from 1:3 solution at 550 °C and higher are composed of highly c‐axis oriented ZnS nanorod‐like crystals with diameter of ca. 80 nm and length of ca. 300 nm.

While the popularity of the usage of room temperature microfluidic systems is booming in different technologies such as bio-technology, micro-scale chemistry, micro-printing and many others, systems applicable under high temperature and pressure are still remarkably under-developed. The main drawback of the existing systems is the inadequate quality of the available construction materials. In this work, extrusion of metal-oxo-alkoxide sol-gel precursors through the nozzle is utilized to produce the liquid thread that is allowed to self-transform into ceramic microtubes by a chemical curing process. The focus is on YSZ (8% Y2O3 stabilized ZrO2), which exhibits a stable 100% tetragonal phase nanocrystalline structure up to 1000 degrees C. These tubes have excellent mechanical characteristics and can withstand 1000 atm pressure inside the tubes. Owing to these and other physical, chemical and mechanical properties, there are many potential applications for these tubes, one example being that the high optical quality of the YSZ tubes could be useful for guiding of light. Ionic conductivity with no electronic component makes these tubes suitable for ionic membrane applications like solid oxide fuel cells (SOFCs) or corresponding gas sensors. Finally, we demonstrate a single-tube-based miniature plasma jet device potentially applicable as an ion source for local surface treatment or possibly as a micro plasma propulsion device for space applications.

Hereby we report a new microstructured luminescent material – Eu-doped yttria-stabilized zirconia (YSZ) microtube – prepared by a special sol–gel route. Transparent, crack-free and brightly luminescent microtubes were obtained after thermal treatment at temperatures as high as 1100°C. The implications of time-resolved and site-selective studies of Eu3+ luminescence are discussed. The decay kinetics of Eu3+ luminescence is modeled following the Judd–Ofelt theory and matched to the experimental data.

In the frame of the current work novel set of Sm-doped zirconia (ZrO2) microrolls were composed by using specially modified sol–gel technique followed by annealing cycle from 500°C to 800°C. Via Raman and XRD scattering of zirconia as well as the photoluminescence (PL) spectra of the samarium ions the crystal phase formation was monitored and characterised qualitatively. The microrolls are shown first to form tetragonal phase which is stabilised by Sm ions, residual organic dopants and shear forces acting on the bent surface. The microrolls go through phase transformation to monoclinic as the annealing temperature is increased leading to partial breakup of the macroscopic structure.