On the role of post-CCVD synthetic impurities, functional groups and functionalization-based oxidation debris on carbon nanotubes

A new method has been developed to separately study the effects of (i) impurities resulting from the catalytic chemical vapor deposition synthesis itself, (ii) the attached functional groups and (iii) the oxidation debris on the properties of carboxyl-functionalized multiwall carbon nanotubes (CNTs) by incorporating a Soxhlet-extractor enhanced acetone washing process into the synthesis method. Palladium nanoparticles supported on the carbon nanotubes were investigated in the hydrogenation of cyclohexene to cyclohexane. Despite the fact that the specific surface area and the Pd dispersion were both low, the Pd/CNT catalyst with post-synthetic impurities showed ~20 times higher catalytic activity compared to functional group free, acetone-washed samples. While oxidation debris originating from the functionalization was found to affect both the specific surface area and the G/D ratio obtained from Raman spectra, it had little effect on the size of the supported Pd nanoparticles or catalytic activity. On the other hand, functional groups have significant effect on the catalytic activity without influencing the specific surface area, the G/D ratio or the Pd nanoparticle dispersion

Sápi András - Bolyai János Ösztöndíj Jelentés – (2014.09.01 – 2015.08.31.)

A Bolyai János Ösztödíj első évében végzett kutatások összefoglaló jelentése

Complexity of a Co3O4 System under Ambient-Pressure CO2 Methanation: Influence of Bulk and Surface Properties on the Catalytic Performance

Although using supported noble-metal catalysts for CO2 hydrogenation is an effective solution due to their excellent catalytic properties, metal oxide supports themselves can exhibit good activity being more economically feasible. This work focuses on investigating the complexity of the Co3O4 system during the CO2 methanation reaction, which is usually accompanied by the formation of unstable dispersions of cobalt oxide and metallic Co. Herein, we have tested different types of Co3O4: synthetically prepared mesoporous m-Co3O4 (BET surface area, 95 m2/g) and commercial c-Co3O4 (BET surface area, 15 m2/g; purchased from Merck) in the CO2 methanation reaction under different reduction temperatures (273−673 K). The reduction temperature was adjusted to 573 K for both the catalysts to reach the optimal Co/cobalt oxide ratio and consequently the best catalytic performance. m-Co3O4 is more active (CO2 conversion 95%) and stable at higher temperatures compared to c-Co3O4 (CO2 conversion 63%) due to its morphology-induced ∼66 times higher surface basicity. DRIFTS results showed differences in the detected surface species: formate was observed on m-Co3O4 and was proven to contribute to the total methane formation. It was revealed that in CO2 methanation reaction, both bulk and surface properties such as morphology, cobalt oxidation states, acid−base properties, and presence of defect sites directly affect the catalytic performance and reaction mechanism. Furthermore, 1% 5 nm Pt nanoparticles were loaded onto the Co3O4s to check the competitiveness of the catalysts. This study evidences on a cheap noblemetal- free catalyst for CO2 methanation consisting of m-Co3O4 with competitive activity and ∼100% CH4 selectivity

Controlled Photocatalytic Synthesis of Core–Shell SiC/Polyaniline Hybrid Nanostructures

Hybrid materials of electrically conducting polymers and inorganic semiconductors form an exciting class of functional materials. To fully exploit the potential synergies of the hybrid formation, however, sophisticated synthetic methods are required that allow for the fine-tuning of the nanoscale structure of the organic/inorganic interface. Here we present the photocatalytic deposition of a conducting polymer (polyaniline) on the surface of silicon carbide (SiC) nanoparticles. The polymerization is facilitated on the SiC surface, via the oxidation of the monomer molecules by ultraviolet-visible (UV-vis) light irradiation through the photogenerated holes. The synthesized core–shell nanostructures were characterized by UV-vis, Raman, and Fourier Transformed Infrared (FT-IR) Spectroscopy, thermogravimetric analysis, transmission and scanning electron microscopy, and electrochemical methods. It was found that the composition of the hybrids can be varied by simply changing the irradiation time. In addition, we proved the crucial importance of the irradiation wavelength in forming conductive polyaniline, instead of its overoxidized, insulating counterpart. Overall, we conclude that photocatalytic deposition is a promising and versatile approach for the synthesis of conducting polymers with controlled properties on semiconductor surfaces. The presented findings may trigger further studies using photocatalysis as a synthetic strategy to obtain nanoscale hybrid architectures of different semiconductors

Potential Benefits of Discrete-Time Controllerbased Treatments over Protocol-based Cancer Therapies

In medical practice, the effectiveness of fighting cancer is not only determined by the composition of the used drug, but determ ined by the administration method as well. As a result, having drugs with a suitable action profile is just a promising beginning, but without appropriate delivery method s , the therapy still can be ineffective. Finding the optimal biologic dose is an empir ical process in medical practice; however, using controllers, an automated optimal administration can be determined . In this paper , we evaluate the effectiveness of different drug delivery protocols; using in silico simulations (like bolus dose s, low - dose metron omic regimen and continuous infusion therapy ). In addition, we compare these results with discrete - time controller - based treatments containing state feedback, setpoint control, actual state observer and load estimation

Consequences of subacute intratracheal exposure of rats to cadmium oxide nanoparticles: Electrophysiological and toxicological effects

Cadmium is a metal used in various industrial applications, whereby exposure to Cd-containing fumes is likely. The submicron sized particles in the fumes represent an extra risk due to their high mobility within the organism and high surface area. Toxicity of Cd on the liver, kidney and bones is well known, but there are less data on its neurotoxicity. Here, male Wistar rats were treated for 3 and 6 weeks by intratracheal instillation of CdO2 nanosuspension. The treated rats’ body weight gain was significantly decreased, and in the high dose rats (0.4 mg/kg Cd daily) the weight of lungs and thymus was significantly increased. In this group, the spectrum of spontaneous cortical electrical activity was shifted to higher frequencies, the latency of sensory evoked potentials was lengthened, and the frequency following ability of the somatosensory evoked potential was impaired – even without detectable Cd deposition in the brain. The data support the role of the nano-sized Cd in the causation of nervous system damage and show the possibility of modeling human neurotoxic damage in rats

Model-based Angiogenic Inhibition of Tumor Growth using Modern Robust Control Method

Cancer is one of the most destructive and lethal illnesses of the modern civilization. In the last decades, clinical cancer research shifted towards molecular targeted therapies which have limited side e�ects in comparison to conventional chemotherapy and radiation therapy. Anti-angiogenic therapy is one of the most promising cancer treatment methods. The dynamical model for tumor growth under angiogenic stimulator/inhibitor control was posed by Hahnfeldt et al. (1999), and it was investigated and partly modi�ed many times. In this paper, a modi�ed version of the originally published model is used in order to describe a continuous infusion therapy. To generalize individualized therapies a robust control method is proposed using H 1 methodology. Uncertainty weighting functions are determined based on the real pathophysiological case and simulations are performed on di�erent tumor volumes to demonstrate the robustness of the proposed method

Parameter optimization of H∞ controller designed for tumor growth in the light of physiological aspects

According to the fact that cancer diseases are leading causes of death all around the world, development of cancer fighting therapies is necessary. Beside the medical knowledge, there is an extra need for engineering approach to solve this complex problem. The aim of this paper is to design controller for tumor growth under angiogenic inhibition, which on the one hand minimizes the input signal as far as possible (in order to have less side effects and greater cost-effectiveness) and on the other hand results in appropriately low tumor volume. Since the model contains uncertainties and measurement noise, the controller was designed using modern robust control methodology. Choosing of the ideal system and the weighting functions were done in the light of physiological aspects