Abstract: The free energy surface (FES) for carbon segregation from nickel nanoparticles is obtained from advanced molecular dynamics simulations. A suitable reaction coordinate is developed that can distinguish dissolved carbon atoms from segregated dimers, chains and junctions on the nanoparticle surface. Because of the typically long segregation time scale (up to ms), metadynamics simulations along the developed reaction coordinate are used to construct FES over a wide range of temperatures and carbon concentrations. The FES revealed the relative stability of different stages in the segregation process, and free energy barriers and rates of the individual steps could then be calculated and decomposed into enthalpic and entropic contributions. As the carbon concentration in the nickel nanoparticle increases, segregated carbon becomes more stable in terms of both enthalpy and entropy. The activation free energy of the reaction also decreases with the increase of carbon concentration, which can be mainly attributed to entropic effects. These insights and the methodology developed to obtain them improve our understanding of carbon segregation process across materials science in general, and the nucleation and growth of carbon nanotube in particular.

Abstract: The flexoelectric and electronic properties of zig-zag graphene nanoribbons are explored under mechanical bending using state of the art first principles calculations. A linear dependence of the bending induced out of plane polarization on the applied strain gradient is found. The inferior flexoelectric properties of graphene nanoribbons can be improved by more than two orders of magnitude by hydrogen and fluorine functionalization (CH and CF nanoribbons). A large out of plane flexoelectric effect is predicted for CF nanoribbons. The origin of this enhancement lies in the electro-negativity difference between carbon and fluorine atoms, which breaks the out of plane charge symmetry even for a small strain gradient. The flexoelectric effect can be further improved by co-functionalization with hydrogen and fluorine (CHF Janus-type nanoribbon), where a spontaneous out of plane dipole moment is formed even for flat nanoribbons. We also find that bending can control the charge localization of valence band maxima and therefore enables the tuning of the hole effective masses and band gaps. These results present an important advance towards the understanding of flexoelectric and electronic properties of hydrogen and fluorine functionalized graphene nanoribbons, which can have important implications for flexible electronic applications. (C) 2020 Elsevier Ltd. All rights reserved.

Abstract: Hyperbolic polaritons in ultra thin materials such as few layers of van derWaals heterostructures provide a unique control over light-matter interaction at the nanoscale and with various applications in flat optics. Natural hyperbolic surface plasmons have been observed on thin films of WTe2 in the light wavelength range of 16-23 mu m (similar or equal to 13-18 THz) [Nat. Commun. 11, 1158 (2020)]. Using time-dependent density functional theory, it is found that carbon doped monolayer phosphorene (beta-allotrope of carbon phosphide monolayer) exhibits natural hyperbolic plasmons at frequencies above similar or equal to 5 THz which is not observed in its parent materials, i.e. monolayer of black phosphorous and graphene. Furthermore, we found that by electrostatic doping the plasmonic frequency range can be extended to the mid-infrared. (C) 2021 Elsevier Ltd. All rights reserved.

Abstract: The electrochemical detection of cephalosporins is a promising approach for the monitoring of cephalosporin levels in process waters. However, this class of antibiotics, like penicillins, is composed of chemically active molecules and susceptible to hydrolysis and aminolysis of the four membered β-lactam ring present. In order to develop a smart monitoring strategy for cephalosporins, the influence of degradation (hydrolysis and aminolysis) on the electrochemical fingerprint has to be taken into account. Therefore, an investigation was carried out to understand the changes of the voltammetric fingerprints upon acidic and alkaline degradation. Changes in fingerprints were correlated to the degradation pathways through the combination of square wave voltammetry and liquid chromatography quadrupole time-of-flight analysis. The characteristic electrochemical signals of the β-lactam ring disappeared upon hydrolysis. Additional oxidation signals that appeared after degradation were elucidated and linked to different degradation products, and therefore, enrich the voltammetric fingerprints with information of the state of the cephalosporins. The applicability of the electrochemical monitoring system was explored by the analysis of the intact and degraded industrial process waters containing the key intermediate 7-aminodeacetoxycephalosporanic acid (7-ADCA). Clearly, the intact process samples exhibited the expected core signals of 7-ADCA and could be quantified, while the degraded samples only showed the newly formed degradation products.

Abstract: Detection of antigenic biomarkers present in trace amounts is of crucial importance for medical diagnosis. A parasitic disease, human toxocariasis, lacks an adequate diagnostic method despite its worldwide occurrence. The currently used serology tests may stay positive even years after a possibly unnoticed infection, whereas the direct detection of a re-infection or a still active infection remains a diagnostic challenge due to the low concentration of circulating parasitic antigens. We report a time-efficient sandwich immunosensor using small recombinant single-domain antibodies (nanobodies) derived from camelid heavy-chain antibodies specific to Toxocara canis antigens. An enhanced sensitivity to pg/mL levels is achieved by using a redox cycle consisting of a photocatalytic oxidation and electrochemical reduction steps. The photocatalytic oxidation is achieved by a photosensitizer generating singlet oxygen (1O2) that, in turn, readily reacts with p-nitrophenol enzymatically produced under alkaline conditions. The photooxidation produces benzoquinone that is electrochemically reduced to hydroquinone, generating an amperometric response. The light-driven process could be easily separated from the background, thus making amperometric detection more reliable. The proposed method for detection of the toxocariasis antigen marker shows superior performances compared to other detection schemes with the same nanobodies and outperforms by at least two orders of magnitude the assays based on regular antibodies, thus suggesting new opportunities for electrochemical immunoassays of challenging low levels of antigens.

Abstract: Stable emissive carbon nanodots were generated in zeolite crystals using near infrared photon irradiation gradually converting the occluded organic template, originally used to synthesize the zeolite crystals, into discrete luminescent species consisting of nano-sized carbogenic fluorophores, as ascertained using Raman microscopy, and steady-state and time-resolved spectroscopic techniques. Photoactivation in a confocal laser fluorescence microscope allows 3D resolved writing of luminescent carbon nanodot patterns inside zeolites providing a cost-effective and non-toxic alternative to previously reported metal-based nanoclusters confined in zeolites, and opens up opportunities in bio-labelling and sensing applications.

Abstract: Plasma reactors are interesting for gas-based chemical conversion but the fundamental relation between the plasma chemistry and selected conditions remains poorly understood. Apparent kinetic parameters for the loss and formation processes of individual components of gas conversion processes, can however be extracted by performing experiments in an extended residence time range (2–75 s) and fitting the gas composition to a firstorder kinetic model of the evolution towards partial chemical equilibrium (PCE). We specifically investigated the differences in kinetic characteristics and PCE state of the CO2 dissociation and CH4 reforming reactions in a dielectric barrier discharge reactor (DBD), how these are mutually affected when combining both gases in the dry reforming of methane (DRM) reaction, and how they change when a packing material (non-porous SiO2) is added to the reactor. We find that CO2 dissociation is characterized by a comparatively high reaction rate of 0.120 s−1 compared to CH4 reforming at 0.041 s−1; whereas CH4 reforming reaches higher equilibrium conversions, 82% compared to 53.6% for CO2 dissociation. Combining both feed gases makes the DRM reaction to proceed at a relatively high rate (0.088 s−1), and high conversion (75.4%) compared to CO2 dissociation, through accessing new chemical pathways between the products of CO2 and CH4. The addition of the packing material can also distinctly influence the conversion rate and position of the equilibrium, but its precise effect depends strongly on the gas composition. Comparing different CO2:CH4 ratios reveals the delicate balance of the combined chemistry. CO2 drives the loss reactions in DRM, whereas CH4 in the mixture suppresses back reactions. As a result, our methodology provides some of the insight necessary to systematically tune the conversion process.

Abstract: A novel type of activated carbon fiber filter was developed for indoor air purification. The filter is equipped with electrodes for thermo-electrical regeneration at the point of saturation. The electrodes are arranged in such a way that the filter forms a pleated structure with an electrode in the tip of each pleat. This allows for a uniform temperature distribution on the filter surface during the regeneration process and the pleated structure reduces the overall pressure drop across the filter. The latter was validated by Computational Fluid Dynamics, using Darcy-Forchheimer parameters derived in previous work. The CFD model was further used to perform a virtual sensitivity study in search for the optimal ACF filter design by varying the pleat length, pleat height and filter thickness. Finally, adsorption and desorption properties were investigated with acetaldehyde and toluene as model compounds. Freundlich and Langmuir adsorption parameters, derived in previous work were successfully validated with a Multiphysics model.

Abstract: Purple non-sulfur bacteria (PNSB) show potential for microbial protein production on wastewater as animal feed. They offer good selectivity (i.e., low microbial diversity and high abundance of one species) when grown anaerobically in the light. However, the cost of closed anaerobic photobioreactors is prohibitive for protein production. Although open raceway reactors are cheaper, their feasibility to selectively grow PNSB is thus far unexplored. This study developed operational strategies to boost PNSB abundance in the biomass of a raceway reactor fed with volatile fatty acids. For a flask reactor run at a 2 day sludge retention time (SRT), matching the chemical oxygen demand (COD) loading rate to the removal rate in the light period prevented substrate availability during the dark period and increased the PNSB abundance from 50-67 to 88-94%. A raceway reactor run at a 2 day SRT showed an increased PNSB abundance from 14 to 56% when oxygen supply was reduced (no stirring at night). The best performance was achieved at the highest surface-to-volume ratio (10 m(2) m(-3) increased light availability) showing productivities up to 0.2 g protein L-1 day(-1) and a PNSB abundance of 78%. This study pioneered in PNSB-based microbial protein production in raceway reactors, yielding high selectivity while avoiding the combined availability of oxygen, COD, and darkness.

Abstract: Landfill mining (LFM) refers to the excavation and processing of formerly buried waste streams. It offers significant environmental and societal benefits through the mitigation of greenhouse gas emissions or the reduction of long-term waste management costs. LFM’s profitability, however, is still in question and public investment support might be necessary to fully exploit its potential. To enable decision-makers to identify the best solutions for a landfill site, societal impacts of LFM still have to be investigated. Throughout relevant literature, societal impacts of LFM projects have only selectively been studied and it remains unclear if and which benefits justify policy interventions. This paper firstly provides a comprehensive conceptualization of the societal impact of an LFM project and dives into the underlying societal context of this emerging industry. It disentangles formerly identified burdens and benefits by applying a system dynamics approach to LFM research. Based on this approach, four causal loop diagrams are presented showing how LFM is embedded into its societal context, analyzing the composition of the net societal impact of an LFM project, the mechanisms influencing LFM’s public acceptance, and the dynamics of the market acceptance of LFM products. Key variables and leverage points have been identified, such as (i) technology choices influencing avoided impacts from the mitigations of primary resource consumption, since many societal impacts are closely related to environmental impacts, (ii) a timely and broad stakeholder involvement to prevent project opposition, and (iii) the after-use of the mined landfill, generating a major part of the local and regional societal benefits but also creating potential conflicts between stakeholder interests. Key intradimensional trade-offs and potential conflicts were identified in (i) spatial and (ii) temporal risk distribution, (iii) conflicting societal goals of the after-use such as job creations and recreation, as well as (iv) material and energy recuperation. These findings provide important insights for LFM decision-makers and can help to implement this emerging industry in a sustainable way.

Abstract: Climate-Smart Agriculture (CSA) is seeking to overcome the food security problem and develop rural livelihoods while minimizing negative impacts on the environment. However, when such synergies exist, the situation of small-scale farmers is often overlooked, and they are unable to implement new practices and technologies. Therefore, the main aim of this study is to improve CSA by adding the neglected but very important element “small-scale farmer”, and introduce Vulnerable-Smart Agriculture (VSA) as a complete version of CSA. VSA indicates, based on the results of this study, that none of the decisions made by policymakers can be realistic and functional as long as the voice of the farmers influenced by their decisions is not heard. Therefore, to identify different levels for possible interventions and develop VSA monitoring indicators, a new conceptual framework needs to be developed. This study proposed such a framework consisting of five elements: prediction of critical incidents by farmers, measuring the consequences of incidents, identifying farmers' coping strategies, assessing farmers' livelihood capital when facing an incident, and adapting to climate incidents. The primary focus of this study is on farmers' learning and operational preparation to deal with tension and disasters at farm level. Understanding the implications of threats from climate change and the recognizing of coping mechanisms will contribute to an increase in understanding sustainable management.

Abstract: Aerobic heterotrophic bacteria (AHB) and purple non-sulfur bacteria (PNSB) are typically explored as two separate types of microbial protein, yet their properties as respectively a bulk and added-value feed ingredient make them appealing for combined use. The feasibility of cocultivation in a sequential photo- and chemotrophic approach was investigated. First, mapping the chemotrophic growth kinetics for four Rhodobacter, Rhodopseudomonas and Rhodospirillum species on different carbon sources showed a preference for fructose (µmax 2.4–3.9 d−1 28 °C; protein 36–59%DW). Secondly, a continuous photobioreactor inoculated with Rhodobacter capsulatus (VFA as C-source) delivered the starter culture for an aerobic batch reactor (fructose as C-source). This two-stage system showed an improved nutritional quality compared to AHB production: higher protein content (45–71%DW), more attractive amino/fatty acid profile and contained up to 10% PNSB. The findings strengthen protein production with cocultures and might enable the implementation of the technology for resource recovery on streams such as wastewater.

Abstract: Mainstream nitrogen removal by partial nitritation/anammox (PN/A) can realize energy and cost savings for sewage treatment. Selective suppression of nitrite oxidizing bacteria (NOB) remains a key bottleneck for PN/A implementation. A rotating biological contactor was studied with an overhead cover and controlled air/N2 inflow to regulate oxygen availability at 20 °C. Biofilm exposure to dissolved oxygen concentrations < 0.51 ± 0.04 mg O2 L-1 when submerged in the water and < 1.41 ± 0.31 mg O2 L-1 when emerged in the headspace (estimated), resulted in complete and long-term NOB suppression with a low relative nitrate production ratio of 10 ± 4%. Additionally, weekly biofilm stressor treatments with free ammonia (FA) (29 ± 1 mg NH3-N L-1 for 3 h) could improve the NOB suppression while free nitrous acid treatments had insufficient effect. This study demonstrated the potential of managing NOB suppression in biofilm-based systems by oxygen control and recurrent FA exposure, opening opportunities for resource efficient nitrogen removal.

Abstract: The development of sensor materials of which gas sensitivity activates under light illumination is of great importance for the design of portable gas analyzers with low power consumption. In the present work a ZnO/CsPbBr3 nanocomposite based on nanocrystalline ZnO and colloidal cubic-shaped perovskite CsPbBr3 nanocrystals (NCs) capped by oleic acide and oleylamine was synthesized. The individual materials and obtained nanocomposite are characterized by x-ray diffraction, low-temperature nitrogen adsorption, x-ray photoelectron spectroscopy, high angle annular dark field scanning transmission electron microscopy with energy-dispersive Xray spectroscopy mapping and UV-vis absorption spectroscopy. The spectral dependence of the photoconductivity of the ZnO/CsPbBr3 nanocomposite reveals a well-defined peak that strongly correlates with the its optical absorption spectrum. The nanocomposite ZnO/CsPbBr3 shows enhanced photoresponse under visible light illumination (lambda(max) = 470 nm, 8 mW/cm(2)) in air, oxygen and argone, compared with pure nanocrystalline ZnO. Under periodic illumination in the temperature range of 25-100 degrees C, the ZnO/CsPbBr3 nanocomposite shows a sensor response to 0.5-3.0 ppm NO2, unlike pure nanocrystalline ZnO matrix, which demonstrates sensor sensitivity to NO2 under the same conditions above 100 degrees C. The effects of humidity on the sensor signal and photoresponse are also discussed.

Abstract: Illicit drug consumption is a worldwide worrying phenomenon that troubles modern society. For this reason, law enforcement agencies (LEAs) are placing tremendous efforts into tackling the spreading of such substances among our community. New sensing technologies can facilitate the LEAs duties by providing portable and affordable analytical devices. Herein, we present for the first time a sensitive and low-cost electrochemical method, i.e. square-wave adsorptive stripping voltammetry on carbon screen-printed electrodes (SPE), for the detection of five illicit drugs (i.e. cocaine, heroin, 3,4-methylenedioxymethamphetamine, 4-chloro-alpha-pyrrolidinovalerophenone, and ketamine) in oral fluid by the aid of a surfactant. Particularly, the surfactant is adsorbed at the carbon electrode’s surface and yields the adsorption of illicit drug molecules, allowing for an enhanced electrochemical signal in comparison to surfactant-free media. First, the surfactant-mediated behavior is deeply explored at the SPE by cyclic voltammetry, electrochemical impedance spectroscopy, and Fourier-transform infrared spectroscopy. Subsequently, the electrochemical behavior of the five illicit drugs is studied and optimized to render optimal analytical performance. Accordingly, the analytical system exhibited a wide linear concentration range from 1 to 30 µM with sub-micromolar limits of detection and high sensitivity. This performance is similar to other reported electrochemical sensors, but with the advantage of using an unmodified SPE, thus avoiding costly and complex functionalization of the SPE. Finally, the methodology was evaluated in diluted oral fluid samples spiked with illicit drugs. Overall, this work describes a simple, rapid, portable, and sensitive method for the detection of illicit drugs aiming to provide oral fluid testing opportunities to LEAs.