A series of TiO
2
photocatalysts loaded with various metals (Pt, Pd, Ni, and Cu) were prepared by using the wet impregnation method. Their physicochemical properties were studied by using XRD, BET, ...TPR-H
2
, FTIR and TPD-NH
3
/CO
2
techniques. The photocatalytic activity of samples was investigated in the gas-phase reduction of carbon dioxide under continuous flow operation mode. Among all investigated catalysts, the Pt and Ni were the most active in terms of the formation rate of methanol. In general, the photocatalytic activity of modified TiO
2
decreased with increasing metal loading and reaction time. The reversible deactivation of photocatalysts was associated with the covering of TiO
2
surface by the reaction products.
We propose an approach to identify points on a timeline of Ag wet electroless deposition on macroporous silicon (macro-PS) that correspond to formation of Ag particles possessing prominent ...surface-enhanced Raman scattering (SERS) activity. This approach is measuring a surface potential of macro-PS, which sharply decreases at the moment of nearly complete saturating the Si skeleton surface with Ag particles of diameter below 60 nm favorable for an intensive surface plasmon resonance. The most intensive SERS-spectra of 5,5′-dithio-bis-2-nitrobenzoic acid (DTNB) were collected on macro-PS covered with Ag particles for 20 min. Considering breaking S–S bonds of DTNB in presence of Ag, which leads to chemisorption of monomolecular TNB layer on the surface of Ag structures, we claim 2 × 10−9 M TNB detection limit. Lower concentration at 10−10 M resulted in absence of SERS-spectra in some spots showing that the analyte was adsorbed unevenly. The analytical enhancement factor was calculated as ∼0.7 × 107.
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•Ag particle diameter is below 60 nm during wet deposition on macropore walls in Si.•Ag wet growth on Si terraces between macropores leads to bimodal Ag particles size.•SERS-spectra of analyte/Ag on Si terraces are not as reproducible as in macropores.•Surface potential at wet deposition of Ag is an indirect marker of SERS-activity.•Laser focus in Ag/macropore or on Ag/Si terrace defines quality of SERS-analysis.
The NQ21 peptide has relatively recently attracted attention in the biomedical sphere due to its prospects for facilitating the engineering of the HIV1 vaccine and ELISA test. Today, there is still a ...need for a reliable and fast methodology that reveals the secondary structure of this analyte at the low concentrations conventionally used in vaccines and immunological assays. The present research determined the differences between the surface-enhanced Raman scattering (SERS) spectra of NQ21 peptide molecules adsorbed on solid SERS-active substrates depending on their geometry and composition. The ultimate goal of our research was to propose an algorithm and SERS-active material for structural analysis of peptides. Phosphate buffer solutions of the 30 µg/mL NQ21 peptide at different pH levels were used for the SERS measurements, with silver particles on mesoporous silicon and gold-coated “nanovoids” in macroporous silicon. The SERS analysis of the NQ21 peptide was carried out by collecting the SERS spectra maps. The map assessment with an originally developed algorithm resulted in defining the effect of the substrate on the secondary structure of the analyte molecules. Silver particles are recommended for peptide detection if it is not urgent to precisely reveal all the characteristic bands, because they provide greater enhancement but are accompanied by analyte destruction. If the goal is to carefully study the secondary structure and composition of the peptide, it is better to use SERS-active gold-coated “nanovoids”. Objective results can be obtained by collecting at least three 15 × 15 maps of the SERS spectra of a given peptide on substrates from different batches.
This work investigates the process of elimination of carbon deposits formed during the mixed reforming of methane mixture. The mixed reforming of methane to synthesis gas was studied over Ni/Al
2
O
3
...catalyst in the 650–750°C. The amount of carbon deposit on the surface of catalyst varied from 2.8 to 5.9%, depending on the reaction temperature. The reactivity of carbon species was evaluated in the oxygen, hydrogen, carbon dioxide, and water mixtures. The obtained results revealed the presence of highly active carbon form (etched at a temperature below 200 °C) and inactive form (gasification at a temperature above 500 °C). The SEM and Raman analyses confirmed the presence of carbon in the form of filaments. Among all investigated gasification agents, water vapor was found to be the most efficient in removing the carbon deposit due to better adsorption of water on the surface of aluminum oxide. The overall mechanism of mixed methane reforming along with carbon gasification was shown.
In this work, the photocatalytic activity of the Cu-Rh/TiO2 system in the ultraviolet and visible regions was studied. A rough TiO2 layer was formed on a metal grid by electrophoretic deposition. The ...Cu-Rh nanoalloy on the surface of the TiO2 layer was obtained by the method of sequential vacuum-thermal evaporation of components followed by heat treatment of the condensate. This approach makes it possible to form Cu-Rh nanostructures of a given composition in a wide concentration range. According to the phase equilibrium diagram of the Cu-Rh system for temperatures below 1150 °C, separation two solid solutions should be observed: rich in Cu and rich in Rh. However, a detailed study of the structure by high-resolution transmission electron microscopy analysis characterizes the obtained nanoislands as a single-phase solid solution, the lattice parameter of which changes linearly in accordance with Vegard's law.
The resulting photocatalytic system, which is an array of Cu-Rh nanoislands with a ratio of 25/75, 50/50, 75/25 at% on a TiO2 layer, was used for CO2 photoreduction. It has been demonstrated that TiO2 modified with Cu-Rh nanoislands has a higher photocatalytic activity in the ultraviolet region as compared to pure TiO2. At the same time, it retains it to a much greater extent in the visible range, in contrast to pure TiO2.
•Nanoislands of the Cu-Rh alloy were obtained by sequential thermal evaporation of Cu and Rh.•Nanoislands of the Cu-Rh alloy are a single-phase solid solution in contrast to the bulk Cu-Rh alloy.•TiO2 modified with Cu-Rh nanoalloys converts CO2 into methanol and acetaldehyde and is photoactive in the visible range.
A novel biologically active organic ligand L (N'-benzylidenepyrazine-2-carbohydrazonamide) and its three coordination compounds have been synthesized and structurally described. Their physicochemical ...and biological properties have been thoroughly studied. Cu(II), Zn(II), and Cd(II) complexes have been analyzed by F-AAS spectrometry and elemental analysis. The way of metal-ligand coordination was discussed based on FTIR spectroscopy and UV-VIS-NIR spectrophotometry. The thermal behavior of investigated compounds was studied in the temperature range 25-800 °C. All compounds are stable at room temperature. The complexes decompose in several stages. Magnetic studies revealed strong antiferromagnetic interaction. Their cytotoxic activity against A549 lung cancer cells have been studied with promising results. We have also investigated the biological effect of coating studied complexes with silver nanoparticles. The morphology of the surface was studied using SEM imaging.
This paper presents the results of facile fabrication of a non-enzymatic glucose sensor by forming a sensing element based on TiO2 nanofilaments using direct ink writing (DIW). The glucose ...concentration in the solution was determined by changing the resistance of the TiO2 layer. Nanowires (NW) were obtained by hydrothermal synthesis in 10 M sodium alkali solution followed by heat treatment. The surface morphology of obtained samples was studied using scanning electron microscopy. The formation of a sensitive layer was carried out on a 3D printer with a specially designed print head from a suspension based on an aqueous solution of polyvinyl alcohol (PVA) followed by heat treatment in air. The suspension was analyzed for viscosity and contact angle. The sensitive layers were formed on a silicon substrate with a SiO2 surface oxide layer and gold contacts. Layers of TiO2 NW were formed between the contacts. The sensitivity of the sensor to glucose solutions of various concentrations was studied. As a result of the studies, the studied structures showed sensitivity to a glucose solution in the range from 1 to 100 mmol.
In this study, we developed a filtering material for facial masks, which is capable of trapping and subsequent inactivation of bacteria under white light emitting diodes (LED) or sunlight ...irradiation. Such a functionality is achieved via the modification of the composite membrane based on porous polymer with photocatalytic (TiO
) and plasmonic (Ag) nanoparticles. The porous polymer is produced by means of a computer numerical control machine, which rolls a photoresist/thermoplastic mixture into a ~20-µm-thick membrane followed by its thermal/ultraviolet (UV) hardening and porosification. TiO
nanoparticles are prepared by hydrothermal and sol-gel techniques. Colloidal synthesis is utilized to fabricate Ag nanoparticles. The TiO
photocatalytic activity under UV excitation as well as a photothermal effect generated by plasmonic Ag nanoparticles subjected to LED irradiation are studied by the assessment of methylene blue (MB) decomposition. We demonstrate that, in contrast to the filter of the standard facial medical mask, the polymer membrane modified with spray-coated TiO
and Ag nanoparticles prevents the penetration of
from its top to bottom side and significantly inhibits bacterial growth when exposed to LED or sunlight.
The study of individual cell processes that occur both on their surface and inside is highly interesting for the development of new medical drugs, cytology and cell technologies. This work presents ...an original technique for fabricating the silver-coated pipette and its use for the cell analysis by combination with surface-enhanced Raman spectroscopy (SERS) and scanning ion-conducting microscopy (SICM). Unlike the majority of other designs, the pipette opening in our case remains uncovered, which is important for SICM. SERS-active Ag nanoparticles on the pipette surface are formed by vacuum-thermal evaporation followed by annealing. An array of nanoparticles had a diameter on the order of 36 nm and spacing of 12 nm. A two-particle model based on Laplace equations is used to calculate a theoretical enhancement factor (EF). The surface morphology of the samples is investigated by scanning electron microscopy while SICM is used to reveal the surface topography, to evaluate Young's modulus of living cells and to control an injection of the SERS-active pipettes into them. A Raman microscope-spectrometer was used to collect characteristic SERS spectra of cells and cell components. Local Raman spectra were obtained from the cytoplasm and nucleus of the same HEK-293 cancer cell. The EF of the SERS-active pipette was 7 × 10
. As a result, we demonstrate utilizing the silver-coated pipette for both the SICM study and the molecular composition analysis of cytoplasm and the nucleus of living cells by SERS. The probe localization in cells is successfully achieved.
Copper and gold doped copper catalysts supported on multi-walled carbon nanotubes were prepared by wet impregnation and deposition-precipitation methods, respectively. The catalysts were tested in ...the oxy-steam reforming of methanol (OSRM) and characterized by XRD, SEM-EDS, TOF-SIMS, thermo-gravimetric analysis and temperature-programmed desorption of ammonia. The reactivity results showed the promotion effect of gold on the activity and selectivity of the copper catalysts in the OSRM. The formed Cu-Au alloy as an active phase was responsible for the activity and selectivity improvement of the bimetallic catalysts in the oxy-steam reforming of methanol. The formation of an Au-Cu alloy was confirmed by the XRD, TOF-SIMS and SEM-EDS techniques. The reducibility and acidity of the tested catalysts are important factors, which influence the activity of the copper and gold-copper catalysts.
Copper and gold doped copper catalysts supported on multi-walled carbon nanotubes were prepared by wet impregnation and deposition-precipitation methods, respectively.
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