In the present work, nanotwin structured TiO2 nanotube (TNT) layers are prepared by the electrochemical anodization technique to form the anatase phase and by surface modification via spin-coating of Ce and V precursors to form Ce-TNT and V-TNT, respectively. The surface and cross-sectional images by SEM revealed that the nanotubes have an average diameter of ∼130 nm and a length of ∼14 μm. In addition, the TEM images revealed the nanotwin structures of the nanotubes, especially the anatase (001) and (112) twin surfaces, that increase the transport of photogenerated charges. The photoinduced degradation of caffeine (CAF) by TNT, Ce-TNT, and V-TNT led to a degradation extent of 16%, 26% and 33%, respectively, whereas it increased to 26%, 38%, and 46% in the presence of H2O2, owing to the involvement of Fenton-based processes (in addition to photocatalysis). The effect of the Fenton-based processes accounts for about 10% of the total degradation extent of CAF. Finally, the mechanism of the photoinduced degradation of CAF was investigated. The main oxidative species were the hydroxyl radicals, and the better efficiency of V-TNT over Ce-TNT and TNT was ascribed to its negative surface, thus improving the interactions with CAF.

In this article, we present a novel approach to produce titania (TiO2) nanofibers with enhanced properties using plasma pre-treatment. Nanofibers were produced from electro-spun polyvinylpyrrolidone (PVP) based nanofibers with titanium(IV) isopropoxide (TTIP) as a precursor. PVP/TTIP fibers were plasma treated using diffuse coplanar surface barrier discharge (DCSBD) followed by thermal calcination at 500 degrees C, 600 degrees C and 700 degrees C. The morphology of nanostructures was characterized using SEM, BET and XRD, the chemical composition was analyzed by XPS, ATR-FTIR, the photocatalytic activity was evaluated by degradation of methylene blue and band gap was determined from diffuse reflectance spectra (DRS) using Tauc plot. Initial plasma treatment caused decomposition of polymer matrix, which led to faster oxidation and crystalline phase transition at lower temperature during the following thermal processing/calcination. The results showed enhanced photocatalytic properties of plasma pre-treated fibers despite the fact they possess higher proportion of rutile and lower specific surface area. UV-vis DRS measurements exhibit lower band gap energy at 700 degrees C, but difference between plasma treated (PT) and non-treated (NT) samples at the same temperature was not observed.

In this work, synthesis of Ag3PO4 and its composite with TiO2 (Ag3PO4/TiO2) toward study of two phenomena naturally occurring in Ag3PO4 is reported, specifically a visible light-driven (i.e., photocorrosion) and chloride ion-driven transformation of Ag3PO4 to AgCl in chloride-free and chloride-present aqueous solution. A deeper insight on this transformation via study of their structural and morphological changes using X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) is performed. Substantial amount of AgCl is detected in both Ag3PO4-based materials after visible light irradiation in chloride-present environment. This led to an increase in optical band gap of Ag3PO4 and Ag3PO4/TiO2 from 2.52 to 2.99 eV and 2.48 to 3.02 eV, respectively. Impact of these structural changes in Ag3PO4 and Ag3PO4/TiO2 on their photocatalytic activity is evaluated from the photoinduced catalytic, antibacterial, and antifungal performance under visible light irradiation. The photocatalytic activity of pristine and photocorroded Ag3PO4 is increased by similar to 10 times compared to that of pristine and photocorroded Ag3PO4/TiO2. Photocorroded Ag3PO4 and Ag3PO4/TiO2 possess minor antibacterial and antifungal activities (cell survival similar to 90%), whereas using pristine Ag3PO4 and Ag3PO4/TiO2 the cell survival is reduced by 100% after 60 and 120 min, respectively.

We studied the influence of etching time in hydrofluoric acid and methanol solution on the structure and morphology of n-type porous silicon (PSi). Dissolution of Si in the solution of hydrofluoric acid with methanol with surface oxidation occurs. All investigated samples reveal pores with increasing average size proportional to the etching time. Areic density and RMS roughness observed by scanning electron and atomic force microscopies have maximum for 10 min etching time. Additional etching time leads to slight increase in the pore size diameter and decreasing the RMS roughness of layers. All amorphous PSi samples are covered with the SiO2 layer containing probably HySiOx and SiFxHy complexes. The presence of SiH complexes leads probably to the growth of PSi layers with pores. The thickness of this layer depends on etching time and probably contains HySiOx and SiFxOy complexes.

In this work, synthesis of Ag 3 PO 4 and its composite with TiO 2 (Ag 3 PO 4 /TiO 2 ) toward study of two phenomena naturally occurring in Ag 3 PO 4 is reported, specifically a visible light-driven (i.e., photocorrosion) and chloride ion-driven transformation of Ag 3 PO 4 to AgCl in chloride-free and chloride-present aqueous solution. A deeper insight on this transformation via study of their structural and morphological changes using X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) is performed. Substantial amount of AgCl is detected in both Ag 3 PO 4 -based materials after visible light irradiation in chloride-present environment. This led to an increase in optical band gap of Ag 3 PO 4 and Ag 3 PO 4 /TiO 2 from 2.52 to 2.99 eV and 2.48 to 3.02 eV, respectively. Impact of these structural changes in Ag 3 PO 4 and Ag 3 PO 4 /TiO 2 on their photocatalytic activity is evaluated from the photoinduced catalytic, antibacterial, and antifungal performance under visible light irradiation. The photocatalytic activity of pristine and photocorroded Ag 3 PO 4 is increased by ~ 10 times compared to that of pristine and photocorroded Ag 3 PO 4 /TiO 2 . Photocorroded Ag 3 PO 4 and Ag 3 PO 4 /TiO 2 possess minor antibacterial and antifungal activities (cell survival ~ 90%), whereas using pristine Ag 3 PO 4 and Ag 3 PO 4 /TiO 2 the cell survival is reduced by 100% after 60 and 120 min, respectively. Graphic abstract

This paper proposes the method for diagnosing the administration systems as a prerequisite for an enterprise's business processes reengineering. The method is based on identifying these systems' capacity to facilitate the achievement of the established purposes of the company ("target-means" principle) in the context of transposed projections of the Balance Scorecard (internal processes within administration systems; personnel learning and growth in them; "customers" satisfaction with administration systems; financial aspects of these systems).

The paper presents the results of Deep Level Transient Fourier Spectroscopy (DLTFS) analysis of MOS structures based on a porous p-Si substrate prepared by metal assisted anodic etching. Only three types from five types of samples were appropriate for DLTFS study by their electrical parameters. DLTFS measurements show that metallic contamination occurred in the sample preparation process. The reference, non-etched sample was also subjected to high temperature annealing to form thermal oxide. Au and Zn were confirmed in all DLTFS investigated samples. The impact of anodic etching parameters on defect distribution in the investigated samples is discussed.

Article presents the model and principles of the «smart» home system development using the modular structure and architectural pattern of the data stream Redux. Combination of these principles allow to develop «smart» house system rapidly, taking into account the variety of usage specifics and their scaling, thanks to the combination of pre-designed software and hardware modules.

The article proposes the model of the influence of the environment instability on organizational flexibility and performance of the enterprise. The empirical testing of the model is based upon three main assumptions. The interconnection among uncertainty, dynamics and complexity of external economic environment and enterprise’s flexibility is proved. The influence of organizational flexibility on the performance of the enterprise is stated. The basis for resource parameters of flexibility is determined.

We have investigated the effect of the etching time on the Raman spectra of porous silicon prepared by anodic etching. Electrochemical destruction of the substrate increasing with the etching time and the correlation between the microstructure of the silicon wafer and the shape and position of their Raman spectra have been observed. Raman analysis has shown that the intensity of the Raman dominant silicon band decreases and the bandwidth is shifted to lower frequencies, depending on the morphology of the sample. Therefore we believe that the electrochemical destruction of the surface of Si substrates leads to surface amorphization.

Porous silicon (PSi) is a semiconductor produced by a dissolution p-type silicon wafers in hydrofluoric acid (HF) solution by applying a positive potential to a silicon electrode. We investigate the effect of etching time on morphology, structure and photoluminescence of PSi produced by a solution of hydrofluoric acid (HF) and methanol without UV irradiation. We found that surface structure depends strongly on etching time. From Fourier transform infrared spectroscopy and grazing incidence X-ray diffraction we suggest formation towards less-ordered amorphous phase of PSi. All samples reveal red-band photoluminescence. Although we observe different morphology of samples (channel-like morphology versus nanometer-sized hillocks morphology) slight effect on PL active structures (small red shift) was observed. We suggest that source of luminescence in our experiment is hydrogenated amorphous silicon structures and various HySiOx complexes. We cannot rule out the effect of SixFyO complexes. Surface morphology has small effect on photoluminescence. (C) 2018 Elsevier B.V. All rights reserved.

The paper presents the results of current and capacitance measurements completed by Deep Level Transient Spectroscopy (DLTS) analysis of MOS structures based on a porous p-Si substrate. On structures prepared by metal assisted anodic etching, parameters were evaluated that represent the degree of the conversion effect of the photovoltaic phenomenon. Under optimal conditions of anodic preparation of the structure, after thermal oxidation and formation of a 14 nm of SiO2 thick layer a photovoltaic response with an open circuit voltage of 0.45 V was recorded.

TiO2 nanotube (TiNT) arrays were grown on silicon substrate via electrochemical anodization of titanium films sputtered by magnetron. To improve the photocatalytic activity of arrays annealed in air (o-TiNT), doping of o-TiNT with vanadium was performed (o-V/TiNT). These non-doped and doped TiNT arrays were also hydrogenated in H-2/Ar atmosphere to r-TiNT and r-V/TiNT samples, respectively. Investigation of composition and morphology by X-ray diffraction (XRD), electron microscopy (SEM and TEM) and Xray photoelectron spectroscopy (XPS) showed the presence of well-ordered arrays of anatase nanotubes with average diameter and length of 100 nm and 1.3 mu m, respectively. In both oxidized and reduced V-doped samples, vanadium is partly dissolved in the structure of anatase and partly deposited in form of oxide on the nanotube surface. Vanadium-doped and reduced samples exhibited higher rates in the photodegradation of organic dyes (compared to non-modified o-TiNT sample) and this is caused by limitation of electron-hole recombination rates and by shift of the energy gap into visible region. The photocatalytic activity was measured under UV, sunlight and visible irradiation, and the corresponding efficiency increased in the order (o-TiNT) < (r-TiNT) < (o-V/TiNT) < (r-V/TiNT). Under visible light, only r-TiNT and r-V/TiNT showed significant photocatalytic activity. (C) 2017 Elsevier B.V. All rights reserved.

Evaluation of photoluminescence spectra of porous silicon (PS) samples prepared by electrochemical etching is presented. The samples were measured at temperatures 30, 70 and 150 K. Peak parameters (energy, intensity and width) were calculated. The PL spectrum was approximated by a set of Gaussian peaks. Their parameters were fixed using fitting a procedure in which the optimal number of peeks included into the model was estimated using the residuum of the approximation. The weak thermal dependence of the spectra indicates the strong influence of active defects.

The morphology and chemical bods of p-type and n-type porous Si was compared. The surface of n-type sample is smooth, homogenous without any features. The surface of p-type sample reveals micrometer-sized islands. FTIR investigation reveals various distribution of SiOxHy complexes in both p-and n-type samples. From the conditions leading to porous silicon layer formation (the presence of holes) we suggest both SiOxHy and SiFxHy complexes in the layer.

The paper deals with the complex refractive index and photoluminescence in the IR-VIS light region of two sample types (i) black p-type silicon (BSi) produced by the surface structure chemical transfer method using Pt catalytic mesh, and (ii) porous p-type silicon prepared by standard electrochemical etching.We present, compare, and discuss the values of the IR-VIS complex refractive index obtained by calculation using the Kramers-Kronig transformation and the photoluminescence properties thereof.The results indicate that differences between the optical properties of the BSi and the porous Si are given by (a) the oxidation procedure of BSi, (b) the thickness of the formed black and porous Si layer, and by (c) the porosity of both layer types.We assume that the photoluminescence signal generated by oxidized BSi structures can be mainly related to the quantum confinement effect, while the photoluminescence of the porous p-type Si is caused by the optical activity of the SiO x H y compounds covering its surface region.

This contribution deals with the black silicon (BS) nanocrystalline specimens produced using the surface structure chemical transfer method (SSCT).This method can produce a nanocrystalline Si black color layer on c-Si with a thickness range of ~50 nm to ~300 nm via the contact of c-Si immersed in the chemical solution HF + H 2 O 2 with a catalytic mesh.The photoluminescence properties are related to the formation of nanocrystals, the structural properties of which are similar to those formed on the back of a sawn Si wafer and the resulting splitting of large Si crystals.X-ray diffraction of the Si front and back sides confirms the dominant reflection of the 311 Si crystalline planes.We suppose that the formation of the black silicon over-layer is pre-determined by the crystalline defects induced by the applied sawing procedure, even though saw damage (defects introduced by the applied sawing procedure) is not necessary for the SSCT method.The formation of the pn type Si solar cell is presented, including black silicon over-layer and without antireflection coating, with efficiency of ~19.1%.

The present paper deals with the photoluminescence (PL) of the multicolor silicon (MC-Si) – a nanocrystalline layer produced by the surface structure chemical transfer (SSCT) method on the p-type Si. The PL behaviours recorded at room temperature are compared with ∼500-nm-thick porous Si prepared electrochemically in the HF + methanol solution on the same Si substrate. The PL spectra of porous Si are shifted to higher energy in comparison with MC-Si. The PL records were fitted by Gaussian curves. We attribute the PL band of porous Si with maximum 2.3 eV to the own luminescence of ∼2.5-nm-thick nanocrystalline Si grains observed due to quantum confinement. This PL band is missing in the PL spectra of MC-Si structures due to the absence of Si nanocrystals of similar size. The PL bands of both MC-Si and porous Si between 1.89 and 2.05 eV are connected with SiO(x) compounds covering the surfaces of Si nanocrystals. Additional two PL bands of all MC-Si structures at 1.69–1.70 eV and 1.80–1.84 eV we relate with defects created at the interface SiO(x)/Si of nanocrystallines because defects (including dangling bonds, residing H and OH) can be successfully passivated by the thermal oxidation at ∼850 °C.

Plasma generated by DCSBD was investigated for cleaning and removing of organic contaminants from semiconductor materials. ITO glass used in photovoltaics and three types of most often used silicon surfaces in semiconductor industry - precleaned silicon, thermally oxidized silicon and H-terminated silicon was studied. The changes in chemical bonds on silicon surfaces were investigated by FTIR. Removing of IPA from silicon substrates was observed by XPS measurements. Effectivity of DCSBD as cleaning agent in comparison with iso-propylacohol was investigated on ITO glass samples by XPS measurement.

Thin films of titanium dioxide with thickness of about 150nm were deposited by spin coating method on a sapphire substrate from a sol–gel and annealed at various temperatures (from 600°C to 1000°C). Structural, optical and hydrogen gas sensing properties of the films were investigated. The annealing temperatures from 600 to 800°C led to anatase phase with grain size in the range of 14–28nm. Further increase of the annealing temperature resulted in transformation to rutile phase with larger grain size of about 100–120nm. The optical band gap tended to decrease with increasing annealing temperature. The estimated values of activation energy for charge transport were in the range of 0.6–1.0eV for films annealed at temperatures from 600°C to 800°C and 0.37–0.38eV for films annealed at 900°C and 1000°C. The films annealed at 900°C and 1000°C showed better hydrogen sensitivity, what can be at least partially caused by their higher surface roughness.