Redox State Dynamics at the Surface of MoVTe(Sb)NbO M1 Phase in Selective Oxidation of Light Alkanes

The influence of Te or Sb on the catalytic properties of the M1 phase of MoVTe(Sb)NbO catalysts in the oxidation of propane or oxidative dehydrogenation of ethane has been investigated. The results show that Te and Sb affect the intrinsic activity of the catalyst for ethane and propane oxidation in the same way and that the Te-containing M1 phase was significantly more active than the Sb-containing phase, even when they contained the same amount of vanadium, which is known to be the active species for the reactions. This feature has been explained by a strong modification of the relative number of available V⁵⁺ sites, which is related to the fact that Sb tend to stabilize vanadium in active site, in a reduced state. Sb and Te were also shown to affect the selectivity in the case of propane oxidation but not in the case of ethane oxidative dehydrogenation. This demonstrated that they should be involved directly in the further transformation of the alkene molecules that are formed as an intermediate and presumably play a role in the α-hydrogen abstraction from these molecules, as proposed earlier. Blocking problems related to the substitution of Te by Sb in view of industrialization are also discussed.     

NS3 Protease from Hepatitis C Virus: Biophysical Studies on an Intrinsically Disordered Protein Domain

The nonstructural protein 3 (NS3) from the hepatitis C virus (HCV) is responsible for processing the non-structural region of the viral precursor polyprotein in infected hepatic cells. NS3 protease activity, located at the N-terminal domain, is a zinc-dependent serine protease. A zinc ion, required for the hydrolytic activity, has been considered as a structural metal ion essential for the structural integrity of the protein. In addition, NS3 interacts with another cofactor, NS4A, an accessory viral protein that induces a conformational change enhancing the hydrolytic activity. Biophysical studies on the isolated protease domain, whose behavior is similar to that of the full-length protein (e.g., catalytic activity, allosteric mechanism and susceptibility to inhibitors), suggest that a considerable global conformational change in the protein is coupled to zinc binding. Zinc binding to NS3 protease can be considered as a folding event, an extreme case of induced-fit binding. Therefore, NS3 protease is an intrinsically (partially) disordered protein with a complex conformational landscape due to its inherent plasticity and to the interaction with its different effectors. Here we summarize the results from a detailed biophysical characterization of this enzyme and present new experimental data.     

Plasmonic sensors in multi-analyte environment: Rate constants and transient analysis

This paper investigates multicomponent gas adsorption at the active surface of plasmonic chemical sensors and shows that there are situations where transients in a single sensor element can be used for simultaneous detection of different gases in multicomponent mixtures. A general master equation set is provided, describing multicomponent adsorption. Analytical expressions for sorption rates are derived and high-accuracy simplified models are proposed. Expressions for adsorption rate constants and rates and for number of binding sites are proposed. The derived analytical model takes into account the adsorbate molecule size, distribution of binding sites as determined by the crystallographic structure of the sensor surface and multi-site adsorption. The model allows for the calculation and optimization of deterministic behavior of the system. It is shown that trace amounts of target gas species can be made detectable by adding controlled amounts of known carrier gas. Besides being applicable in plasmonic sensor design and optimization, the obtained results may be of importance in situations where fast and low-cost detection of trace amounts of gases is needed, including natural gas leakage in residential heating, radon outgassing in dwellings, environmental protection, homeland defense and hazardous materials management, greenhouse footprint investigations, etc.     

Towards Effective Photothermal/Photodynamic Treatment Using Plasmonic Gold Nanoparticles

Gold nanoparticles (AuNPs) of different size and shape are widely used as photosensitizers for cancer diagnostics and plasmonic photothermal (PPT)/photodynamic (PDT) therapy, as nanocarriers for drug delivery and laser-mediated pathogen killing, even the underlying mechanisms of treatment effects remain poorly understood. There is a need in analyzing and improving the ways to increase accumulation of AuNP in tumors and other crucial steps in interaction of AuNPs with laser light and tissues. In this review, we summarize our recent theoretical, experimental, and pre-clinical results on light activated interaction of AuNPs with tissues and cells. Specifically, we discuss a combined PPT/PDT treatment of tumors and killing of pathogen bacteria with gold-based nanocomposites and atomic clusters, cell optoporation, and theoretical simulations of nanoparticle-mediated laser heating of tissues and cells.     

Tunability properties in the paraelectric state of the Pb(Mg1/3Nb2/3)O3 ceramics

Pb(Mg_1/3Nb_2/3)O₃ ceramics prepared via columbite method exhibit high crystallinity and high density after sintering at 1200 °C. Typical relaxor behavior are demonstrated by the dielectric data. Although showing a diffuse phase transition, at room temperature the system is in its paraelectric state, i.e. the PMN structure is fully cubic. The dc-tunability was investigated above the room temperature, when other field-induced contributions than ferroelectric polarization might cause non-linearity. A random non-interacting dipolar unit in a double well potential was employed to describe the ?(E) non-linearity. The temperature-dependence of the average polarization corresponding to the polar nanoregions in the paraelectric state of the PMN relaxor was calculated from the ?(E) data at various temperatures above T_m. A similar trend of decreasing as increasing temperature shows the spin-glass local order parameter determined from the dielectric constant data in the paraelectric state. The local order parameter in the paraelectric state is determined by the nanopolar domains size and correlations.     

Contaminants abatement by ozone in secondary effluents. Evaluation of second‐order rate constants

BACKGROUND: The ozonation of a mixture of contaminants commonly found in secondary effluents has been carried out in an artificially contaminated secondary effluent. Competitive ozonation experiments in heterogeneous and homogeneous mode have also been carried out to determine the second‐order direct ozonation rate constants. RESULTS: Inlet ozone concentration, alkaline conditions and addition of 10^?3 mol L^?1 of H₂O₂ positively affected the degree of mineralization and the disappearance of chemical oxygen demand of the mixture. Reaction rates depend on pH; at pH 7 the following direct ozone rate constants were obtained: 2.7 × 10⁵, 2.5 × 10³, 2.5 × 10⁴, 6.2 × 10⁵, 3.2 × 10⁵, 3.4 × 10⁵, 8.0 × 10⁵ and 4.6 × 10⁵ mol^?1 L¹ s^?1 for acetaminophen, metoprolol, caffeine, antipyrine, norfloxacin, ketorolac, doxycycline, hydroxybiphenyl, and diclofenac, respectively. CONCLUSIONS: The positive effect on TOC and COD removal that ozone dosage exerts is not applicable to individual contaminants. An optimum ozone concentration can be found with no further improvement of the depletion rate of organics as the ozone inlet concentration is increased. Carbonates affect the oxidation of recalcitrant compounds like atrazine. Carbonate concentration must be considered when dealing with real effluents. Addition of hydrogen peroxide can increase the mineralization level obtained, however the increase in complexity and costs does not justify its addition. Copyright © 2011 Society of Chemical Industry     

Self-Cleaning Surfaces for Heat Recovery During Industrial Hydrocarbon-Rich Gas Cooling: An Experimental and Numerical Study

The cooling of hydrocarbon-rich gases in industrial processes often leads to severe fouling, which impedes heat recovery, restricts operative conditions, and increases maintenance costs. The present work investigates whether self-cleaning surfaces represent a possible solution to overcome this technological bottleneck. Hydrophilic and hydrophobic treatments of compact heat exchanger plates are experimentally and numerically investigated during cooling of syngas produced from biomass gasification. The experimental evidences related to the operation of heat exchanger plates are assessed first, and a deeper insight into the relevant phenomena is thereafter obtained by performing numerical simulations. Our analysis identifies the hydrophobic treatment as the most promising solution and unveils the induced self-cleaning mechanism: the formation of small-sized and movable condensed droplets that enhance the collection and removal of gas impurities. These findings open up new routes toward the development of cheaper, more efficient, and sustainable gas cooling systems. © 2018 American Institute of Chemical Engineers AIChE J, 65: 317–325, 2019