Synthesis,Structure, Properties,and Applications of Bimetallic Nanoparticles of Noble Metals

Bimetallic nanoparticles of noble metals are of high interest in imaging, biomedical devices, including nanomedicine, and heterogeneous catalysis. Synthesis, properties, characterization, biological properties, and practical applicability of nanoparticles on the basis of platinum group metals and the coin metals Ag and Au are discussed, also in comparison with the corresponding monometallic nanoparticles. In addition to the parameters that are required to characterize monometallic nanoparticles (mainly size, size distribution, shape, crystallographic nature, surface functionalization, charge), further information is required for a full characterization of bimetallic nanoparticles. This concerns the overall elemental composition of a bimetallic nanoparticle population (ratio of the two metals) and the internal distribution of the elements in individual nanoparticles (e.g., the presence of homogeneous alloys, core–shell systems, and possible intermediate stages). It is also important to ensure that all particles are identical in terms of elemental composition, that is, that the homogeneity of the particle population is given. Macroscopic properties like light absorption, antibacterial effects, and catalytic activity depend on these properties. The currently available methods for a full characterization of bimetallic nanoparticles are discussed, and future developments in this field are outlined.     

Tailoring terpenoid plasma polymer properties by controlling the substrate temperature during PECVD

Polymers derived from natural, minimally‐processed materials have recently emerged as a more sustainable alternative to synthetic polymers, with promising applications in biocompatible and biodegradable devices. Plasma‐enhanced deposition is well‐suited to one‐step, fast, and efficient synthesis of highly crosslinked inert polymers directly from natural resources, however, fabrication of biologically active polymers remains a challenge. Plasma processing parameters influence the properties such as surface energy, roughness, morphology, and chemical composition of deposited polymers and thus their final applications. This article reports on the important role of substrate temperature (T_S) in the chemical composition, wettability, refractive index, and crosslinking density of plasma polymers derived from terpenoids. Experiments are conducted as a function of deposition power P_d, and substrate temperature, T_S. T_S varied from 40 to 280 °C and is externally controlled. Atomic force microscopy analysis reveals the change in deposition mechanism attributed to shadowing effect at higher T_S and P_d. Increase in band gap (E_g) with high T_s deposition for terpenoid based plasma polymers is observed. Swelling behavior analyzed by in situ ellipsometry affirms the enhanced crosslink density with increasing deposition rate. Fourier transform infrared analysis exhibits the formation of additional chemical moieties with increasing T_S. Increase in deposition rate with increasing T_S at higher P_d supports the theory of direct incorporation of depositing particles as dominant mechanism of plasma polymerization in this study. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45771.     

Deliberate Individual Change Framework for Understanding Programming Practices in four Oceanography Groups

Computing affects how scientific knowledge is constructed, verified, and validated. Rapid changes in hardware capability, and software flexibility, are coupled with a volatile tool and skill set, particularly in the interdisciplinary scientific contexts of oceanography. Existing research considers the role of scientists as both users and producers of code. We focus on how an intentional, individually-initiated but socially-situated, process of uptake influences code written by scientists. We present an 18-month interview and observation study of four oceanography teams, with a focus on ethnographic shadowing of individuals undertaking code work. Through qualitative analysis, we developed a framework of deliberate individual change, which builds upon prior work on programming practices in science through the lens of sociotechnical infrastructures. We use qualitative vignettes to illustrate how our theoretical framework helps to understand changing programming practices. Our findings suggest that scientists use and produce software in a way that deliberately mitigates the potential pitfalls of their programming practice. In particular, the object and method of visualization is subject to restraint intended to prevent accidental misuse.     

Reduction Extraction Method for Determining the Enthalpies of Decomposition Reactions of Different Boron Nitride Modifications

Pulsed (7–10 sec) reduction extraction in a helium gas carrier stream has been used for the first time to determine the standard enthalpies and the internal energies of thermal dissociation reactions for various modifications of boron nitride (BN) with and without carbon. The temperature dependences of the weight content of nitrogen extracted from nanosized (4–10 nm) and microsized (<1; 4–5 μm) BN powders in the range 2100–4000 K with a step of ~200 ± 25 K have been established. Nitrogen extraction from layered BN modifications (graphene and graphite structures) begins at 2400–2500 K and reaches 100% at 3500 K. The thermal decomposition curve for nanoand micropowders of dense BN modifications (wurtzite and sphalerite structures) is similar to that for the layered modifications and is shifted toward the high-temperature region by 900 K. The standard enthalpies of decomposition reactions for different BN modifications have been determined: 231 kJ/mole for graphene-like, 249 kJ/mole for graphite-like, 296 kJ/mole forwurtzite-like, and 391 kJ/mole for sphalerite-like modifications.     

Latent structure of the alexithymia construct: A taxometric investigation.

Despite a wealth of research on the validity of alexithymia and its association with a number of common medical and psychiatric disorders, the fundamental question of whether alexithymia is best conceptualized as a dimensional or categorical construct remains unresolved. In the current investigation, taxometric analysis is used to examine the nature of the latent structure of alexithymia. Several nonredundant taxometric procedures were performed with item sets from the 20-item Toronto Alexithymia Scale (R. M. Bagby, J. D. A. Parker, & G. J. Taylor, 1994) as indicators. These procedures were applied separately in large community (n = 1,933) and undergraduate (n = 1,948) samples and in a smaller sample of psychiatric outpatients (n = 302). The results across various taxometric procedures and the different samples provide strong support that alexithymia is a dimensional construct. Some theoretical implications of these findings for research on the alexithymia construct are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Arginine of Chlamydomonas reinhardtii [Fe–Fe] hydrogenase HydA1 plays a crucial role in electron transfer to its catalytic center

[Fe–Fe] hydrogenases, with hydrogen evolution activities outperforming [Ni–Fe] hydrogenases by 3–4 orders of magnitude, are still the most promising enzyme class for hydrogen production purposes. For Chlamydomonas reinhardtii [Fe–Fe] hydrogenase HydA1 the question of catalytic activity and electron transport is of main importance. Here we report the characterization of two mutant forms of C. reinhardtii HydA1. An aspartic acid in place of arginine¹⁷¹ leads to a six-fold increase of the catalytic activity in comparison to the wild type protein during methyl viologen-dependent hydrogen production. Tryptophan in position 171 does not result in any change in methyl viologen-induced activity. At the same time these mutations lead to a strong decrease in ferredoxin-dependent hydrogen production while the catalytic center of mutant forms stays intact. The localization of this amino acid (arginine¹⁷¹) in the environment of CrHydA1 H-cluster indicates that the limitation of the catalytic activity of this hydrogenase is due to the electron transfer step to the catalytic center where the reduction of protons takes place.     

Investigation of the effect of a protective layer on parameters of quartz low-pressure gas-discharge lamps with oxide electrodes

Low pressure amalgam lamps are widely used for disinfection of air and water surfaces. The application of amalgam instead of pure mercury makes it possible to design a high-efficiency powerful ultraviolet lamp and to improve the ecological impact of disinfection equipment. This paper describes the effect of oxide electrodes and a quartz inner surface on the lifetime of a lamp and on the ultraviolet-intensity reduction in low pressure lamps. We show that the burning time of the noble-gas arc discharge at a low pressure depends on the interaction between the discharge plasma and the inner quartz surface. Use of a rare-earth-metal-oxide protective layer on the inner quartz surface increases the lifetime of the lamp and prevents ultraviolet-intensity reduction in low-pressure amalgam lamps.     

Antimicrobial properties and thermal stability of polycarbonate modified with 1‐alkyl‐3‐methylimidazolium tetrafluoroborate ionic liquids

Four water immiscible ionic liquids (ILs): 1‐hexyl‐3‐methylimidazolium tetrafluoroborate, 1‐heptyl‐3‐methylimidazolium tetrafluoroborate, 1‐octyl‐3‐methylimidazolium tetrafluoroborate and 1‐dodecyl‐3‐methylimidazolium tetrafluoroborate have been synthesized. Polycarbonate (PC) films containing ILs were prepared by solvent casting from methylene chloride solutions. Scanning electron microscopy measurements showed the high homogeneity of PC/IL films with the IL content up to 4 wt %. The tendency to IL aggregation was observed for polymeric films with higher IL content (5%). PC/IL composites were found to have the reduced thermal decomposition temperature under both an air and a nitrogen atmosphere in comparison with the neat PC. The effect of IL content on the antimicrobial activity of PC films against Escherichia coli bacteria was studied. Pronounced antimicrobial efficacy was revealed for PC/IL films for all studied ILs starting from 3 wt % of IL. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40050.     

Nanoscale graphite-supported Pt catalysts for oxygen reduction reactions in fuel cells

The nanoscale graphite particles were prepared and the Pt catalysts supported on such graphites were developed for oxygen reduction in the polymer electrolyte membrane fuel cells. Catalytic activity and carbon corrosion of the developed catalysts were evaluated using rotating disc electrode techniques and results were compared with those of a state-of-the-art commercial E-TEK Pt catalyst supported on carbon black Vulcan XC72. The results showed that the particle distribution and the structure of the developed Pt nanoparticles supported on the nanoscale graphite were similar to those of the commercial catalyst. The accelerated degradation testing results showed that the electrochemical active surface area losses after 1500 cycles were 46.92% and 62.2% for the developed catalyst and the commercial catalyst, respectively, while mass activity losses were 45.3% and 84.2%, respectively. The temperature-programmed oxidation results suggest that the developed catalysts had better corrosion resistance than the commercial catalyst. The developed Pt catalysts had similar catalytic performance to the commercial catalyst; however, the developed catalysts had much better corrosion resistance than the commercial catalyst. Overall, nanoscale graphite can be a promising electrocatalyst support to replace the currently used Vulcan XC72 carbon black.