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This study focuses on the optimization of an electric heater design for molten salt pre-heating in a supercritical CO2–molten-salt loop. The scope of the investigation is to analyze typical designs of similar components for identifying possible malfunctions and defining proper modifications in the geometry and operating conditions to address such technical issues and optimize the attained thermal efficiency. By performing computational fluid dynamics simulations for reference designs of such components, two particularities pertinent to the temperature distribution are identified as the most likely ones: the development of hot spots and thermal stratification. As a further step, new designs and operating conditions are proposed and their effects on eliminating the hot spots and stratification development phenomena are evaluated. It is shown that the homogeneous distribution of heat flux density across the heating elements is the most favorable option for avoiding the development of hot spots, while the mitigation of thermal stratification is possible through the development of turbulent flow. The proposed design and operating conditions are expected to facilitate the optimization of molten-salt electric heater operation and promote the development of next-generation molten-salt–supercritical-CO2 concentrating solar power plants. [ABSTRACT FROM AUTHOR]

[Display omitted] A dramatic reduction in man-made CO 2 emissions could be achieved if the cost of electricity generated from concentrated solar power (CSP) plants could become competitive with fossil-fuel-derived electricity. The solar heat-to-electricity conversion efficiency of CSP plants may be significantly increased (and the associated electricity cost decreased) by operating CSP turbines with inlet temperatures ≥750 °C instead of ≤550 °C, and by using thermal energy storage (TES) at ≥750 °C to allow for rapidly dispatchable and/or continuous electricity production. Unfortunately, earth-abundant MgCl 2 –KCl-based liquids currently being considered as low-cost media for large-scale, high-temperature TES are susceptible to oxidation in ambient air, with associated undesired changes in liquid composition and enhanced corrosion of metal alloys in pipes and tanks containing such liquids. In this paper, alternative high-temperature, earth-abundant molten chlorides that are resistant to oxidation in ambient air are identified via thermodynamic calculations. The oxidation resistance, and corrosion-resistant containment, of such molten chlorides at 750 °C are then demonstrated. Such an air-tolerant strategy, involving chemically-robust, low-cost TES media paired with effective containment materials, provides a critical advance towards the higher-temperature operation of, and lower-cost electricity generation from, CSP plants. [ABSTRACT FROM AUTHOR]

Fly ash from two lignite-fed power stations in Greece (Megalopolis and Meliti) has been utilized to synthesize zeolitic materials with upgraded adsorption capacity. Two different siliceous fly ash samples were subjected to hydrothermal treatment at fixed solid/liquid ratio and constant temperature. The zeolitic products have been characterized for their microstructure, chemical, and mineralogical composition by means of SEM, AAS, and XRD, respectively. The primary zeolitic crystals identified were phillipsite and thomsonite, in Megalopolis and Meliti fly ash, respectively. In light of their prospective utilization as liquid-phase sorbents, the specific surface area and porosity of materials were also determined, by means of N 2 -porosimetry. The zeolitic samples were tested for their actual heavy metal-removal capacity by water sampled from active lignite mines in Northern Greece. Artificial aquatic samples with known concentration of heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) were also tested, showing that the synthetic zeolitic materials are good to uptake a wide variety of potential pollutants with up to 100% efficiency. The efficiency of the synthetic zeolitic materials was comparatively assessed, showing that the more intense the presence of phillipsite in the synthetic materials, the greater the uptake rates for certain groups of trace elements. [ABSTRACT FROM AUTHOR]

The photophysics of bulk heterojunctions of a high-performance, low-gap silicon-bridged dithiophene polymer with oleic acid capped PbS quantum dots (QDs) are studied to assess the material potential for light harvesting in the visible- and IR-light ranges. By employing a wide range of nanocrystal sizes, systematic dependences of electron and hole transfer on quantum-dot size are established for the first time on a low-gap polymer-dot system. The studied system exhibits type II band offsets for dot sizes up to ca. 4 nm, whch allow fast hole transfer from the quantum dots to the polymer that competes favorably with the intrinsic QD recombination. Electron transfer from the polymer is also observed although it is less competitive with the fast polymer exciton recombination for most QD sizes studied. The incorporation of a fullerene derivative provides efficient electron-quenching sites that improve interfacial polymer-exciton dissociation in ternary polymer-fullerene-QD blends. The study indicates that programmable band offsets that allow both electron and hole extraction can be produced for efficient light harvesting based on this low-gap polymer-PbS QD composite. [ABSTRACT FROM AUTHOR]

Strong coupling of a confined optical field to the excitonic or vibronic transitions of a molecular material results in the formation of new hybrid states called polaritons. Such effects have been extensively studied in Fabry–Pèrot microcavity structures where an organic material is placed between two highly reflective mirrors. Recently, theoretical and experimental evidence has suggested that strong coupling can be used to modify chemical reactivity as well as molecular photophysical functionalities. However, the geometry of conventional microcavity structures limits the ability of molecules "encapsulated" in a cavity to interact with their local environment. Here, we fabricate mirrorless organic membranes that utilize the refractive index contrast between the organic active material and its surrounding medium to confine an optical field with Q-factor values up to 33. Using angle-resolved white light reflectivity measurements, we confirm that our structures operate in the strong coupling regime, with Rabi-splitting energies between 60 and 80 meV in the different structures studied. The experimental results are matched by transfer matrix and coupled oscillator models that simulate the various polariton states of the free standing membranes. Our work demonstrates that mechanically flexible and easy-to-fabricate free standing membranes can support strong light–matter coupling, making such simple and versatile structures highly promising for a range of polariton applications. [ABSTRACT FROM AUTHOR]

Highlights: [•] Selected CO2 sorbents were tested in a batch FB reactor and a TGA apparatus. [•] We assessed the effect of flue gas sulfur on selected sorbent properties. [•] The sulfated FB carbonates were found much less reactive than the TGA ones. [•] A porous Ca–S layer on sorbent particles may mitigate the drawbacks of sulfation. [ABSTRACT FROM AUTHOR]

Eight types of A356 Al-fly ash composites were produced by pressure infiltration of high-Ca lignite fly ash. This type of ash was used for the first time in Al-composites synthesis, and particularly by liquid metal infiltration techniques. After examining mineralogy and chemistry, specific, narrow ash size fractions were used for the synthesis of composites, and properties linked to microstructure and wear strength of the materials. The effect of using ground ash particles on the microstructure and tribological performance of the composites was also investigated. It was concluded that using fine, high-Ca ash particles can improve the properties of composites, and that using ash particles in a ground form can better facilitate the production process of MMCs. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of the study described in this paper was to determine the removal of Cr (total), Cr (VI), Cu, Ni, Pb, Zn and Cd from wastewater using different particle-size-fractions of highly calcareous and highly siliceous fly ashes (FAs). Three different Hellenic FAs (two calcareous and one siliceous) were tested for their capability of precipitating heavy metals from aqueous solutions. Each FA sample was separated into six different size-fractions with a grain diameter range of: [(0–25) (25–40) (40–90) (90–150) (150–400) and (>400)]μm. The different FA grain-fractions were evaluated in terms of their chemical composition, pH, Loss on Ignition (LOI) and CaOf (%). Batch adsorption experiments were then carried out, indicating that the various grain-fractions of the highly siliceous FA were more efficient in precipitating Cr (VI) but less capable of retaining Cd, Cu, Ni, Pb and Zn. On the other hand, the high-Ca fly ashes were proven to be more efficient in uptaking Cd, Cu, Ni, Pb and Zn, but less in hexavalent chromium. This particular tendency was also confirmed in the case of the different particle-size-fractions of same fly ashes. It was actually verified that FAs can be more effective in the field of industrial wastewater-remediation when separated into their size-fractions. [Copyright &y& Elsevier]

Abstract: The chemical and mineralogical composition of lignite fly ash (FA) varies as a function of the prevalent conditions in both the processes of power production and lignite mining. The differentiation of the qualitative and quantitative composition of the highly-calcareous lignite fly ash, as a function of its particle size distribution, is verified in this paper. According to the results of the conducted research, a fine-grained fraction of considerable amount presents properties that obstruct the sustainable exploitation of calcareous lignite fly ash in cement industry applications. On the other hand, the same grain fraction (because of its hydraulic properties) can be utilized in other sort of applications, based on different criteria, i.e. in road constructions. The coarse-grained fraction (which reflects a low proportion to the total fly ash output) presents the same undesired characteristics as well. Rather, the intermediate grain fraction (75–150μm) presents the highly desirable properties when fly ash is utilized as a pozzolanic additive. In addition, the mechanism of the formation of the intermediate grain fraction strongly prevents the factors that cause the variation of fly ash-quality. It is therefore the optimum part of the whole amount of lignite FA, to be utilized as additive in cement manufacturing. The outcomes of this paper will hopefully contribute towards the crucial goal of the expansion of the utilization of calcareous lignite fly ash by proposing a more effective way of using this material, basically by taking advantage of its fundamental chemical and mineralogical properties. [ABSTRACT FROM AUTHOR]

Abstract: In the present paper, two Class C, lignite fly ashes (FAs) were utilized for the fabrication of Al/fly ash metal matrix composites (MMCs) using the powder metallurgy (PM) technique. Aluminum–fly ash and aluminum/silicon alloy (Al–12% Si)–fly ash mixtures, containing 5, 10 and 15wt.% of – both pozzolanic and hydraulic – FAs were prepared and compacted. The green products were tested for their thermal behavior in order for the sintering temperature to be determined. Then, they were sintered for 2 and 6h. The density of composites was decreasing with the increase of the percentage participation of fly ash particles into them. Apart from that, although FA clusters had been developing in the metal matrix, there was a significant enhancement in the hardness of MMCs when increasing FA content, which is mainly attributed to the intense calcareous nature of the reinforcement material. Volume and mass changes throughout calcination were also estimated as a function of increasing FA weight percent and it seems that CaO (%) of FAs plays a crucial role regarding the post-sintering raise in the mass and volume of composites. Microscopic studies of green and sintered compacts clearly indicated the effectiveness of the sintering process. Additionally, the composites were characterized in terms of their chemical composition and mineralogical structure. The rise of Ca–Si- and Si-mineral phases is intense, particularly for the composites with the highest percentage presence of CaO in FAs (15wt.%) and does not differentiate as a function of the sintering time. [Copyright &y& Elsevier]

Ligand exchange performed during or after the colloidal synthesis of nanocrystals (NCs) provides an efficient way to produce conductive NC solids for optoelectronics. Herein, a post‐synthetic ligand washing process is developed and applied to two different combinations of ligands and perovskite NCs, namely robust green CsPbBr3 NCs capped by didodecyldimethylammonium bromide and near‐infrared FAPbI3 NCs decorated by weakly bound oleic acid ligands. The impact of such processes on the morphological and optoelectronic NC properties is examined while exploring parameters such as the reaction time and the influence of oxygen and humidity. For the FAPbI3 NCs, ligand washing results in extended NC aggregation and substantial photoluminescence loss, with the treatment becoming more aggressive for air‐exposed films. For the CsPbBr3 NCs, the process is insensitive to the environmental conditions and results in partial ligand shell loss and NC close packing rather than bulk‐like aggregation while affecting less the optical properties. Upon ligand removal, the photoconductance increases by up to ≈90% and ≈60% for FAPbI3 NCs and CsPbBr3 NCs, respectively. THz spectroscopy produces qualitatively similar trends of the conductivity with ligand removal time, with THz mobility values as high as 30 and 6 V−1s−1cm2 for glove box prepared FAPbI3 and CsPbBr3 NCs, respectively. [ABSTRACT FROM AUTHOR]

Patterned Mg2Si structures can be attractive for use in optoelectronic, thermoelectric, and other devices. Such structures can be fabricated as conformal Mg2Si films on patterned Si substrates via direct reaction of these substrates with Mg vapor at modest temperatures and ambient pressure. Here, we report the kinetic mechanism (rate-limiting step and associated rate law) that controls such vapor/solid reactive formation of conformal Mg2Si films. To avoid oxidation during silicide formation, experiments were conducted within metal ampoules that were sealed in an argon atmosphere. Upon heating each sealed ampoule to 600 °C, Mg vapor (generated from solid Mg sealed within the ampoule) underwent reaction with a Si single-crystal plate (located a fixed distance from the solid Mg within the ampoule). Kinetic data were obtained by evaluating the change in thickness of the product Mg2Si film, and the specimen mass change per area, with reaction time at 600 °C. The changes in mass and in film thickness were both found to follow parabolic kinetics, with the rate constants obtained from both types of measurements in good agreement. Changes in the diffusion distance of the Mg vapor to the reacting Si single-crystal plate, and in the crystal orientation of the plate, were found to have negligible influences on the reaction kinetics. Such data were consistent with solid-state diffusion through the Mg2Si product layer as the rate-limiting step. An inert marker experiment was used to determine the predominant interface at which Mg2Si formed, and to evaluate the rate-limiting species controlling such formation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Threshold value of laser fluence for obtaining stoichiometric films is 0.8 J/cm2. • Threshold value of background pressure for stoichiometric films is 0.01 mbar. • The electrical properties of the films are mostly affected by the Cu 2−x Se phase. • High absorption coefficient of ∼2–3 ∗ 104 cm−1 for CuIn 0.7 Ga 0.3 Se 2 films. • Long photoluminescence lifetime of ∼50 ns for the film grown at 500 °C. Abstract This work reports on the influence of pulsed laser deposition growth parameters on the properties of CuIn 0.7 Ga 0.3 Se 2 thin films. Polycrystalline CuIn 0.7 Ga 0.3 Se 2 thin films were grown on soda-lime glass substrates under various growth conditions. Morphological, compositional, structural, electrical and optical properties of CuIn 0.7 Ga 0.3 Se 2 thin films were investigated as a function of laser fluence, background gas and substrate temperature. A threshold of laser fluence, 0.8 J/cm2, and background pressure, 0.01 mbar, determined through a systematic parametric investigation, for obtaining stoichiometric films. A minor secondary phase of Cu 2−x Se was observed by X-ray diffraction, and found to gradually diminish with increasing deposition temperature. The film grown at 500 °C shows the purest CuIn 0.7 Ga 0.3 Se 2 chalcopyrite phase. The electrical properties of the films, i.e., dark resistivity, carrier concentration and mobility, are shown to be mostly affected by the Cu 2−x Se phase and the crystal quality of the films. All films exhibit high absorption coefficients of ∼2–3 ∗ 104 cm−1 in the vicinity of the band-edge; a blue shift of the energy gap with deposition temperature is attributed to the relaxation of the lattice strain, as corroborated by the respective shift of (1 1 2) peak of the XRD patterns. The monotonic increase of the photoluminescence intensity accompanied by the concomitant decrease of the emission linewidth and Stokes shift indicate an improvement in the material quality and uniformity as deposition temperature increases in accordance with the structural and electrical measurement findings. Long PL lifetime of ∼50 ns is measured in the band-edge region for the film grown at 500 °C, suggestive of a single phase material with low defect density. Our results overall indicate that high-quality, stoichiometric CuIn 0.7 Ga 0.3 Se 2 thin films can be obtained using pulsed laser deposition, a rapid single-step growth method that eliminates the need for post-selenization. [ABSTRACT FROM AUTHOR]

In this study, 3H‐phenothiazin‐3‐one is identified as a photocatalyst for the photochemical oxidation of sulfides to sulfoxides. This photocatalytic method uses a low catalyst loading (0.05 mol%), molecular oxygen as the sole oxidant, and a blue LED lamp as the irradiation source. It can be applied to the oxidation of both alkyl‐aryl and alkyl‐alkyl sulfides. Moreover, the method is also applicable in the synthesis of the known pharmaceutically active compounds Modafinil and Sulforaphane. [ABSTRACT FROM AUTHOR]

Simple Summary: Gold nanoparticles have gained significant attention in the field of cancer research and treatment due to their unique properties and potential applications to medical imaging, targeted drug delivery, and combined use for cancer diagnosis and therapy. In this study, we developed novel gold nanoparticles with a bipyramidal shape, which have been functionalized to improve fluorescence imaging in the near-infrared biological window and facilitate the targeted delivery of chemotherapy to triple-negative breast tumors. We successfully tested these nanoparticle formulations in both in vitro and preclinical tumor models. Their ability to be combined with a wide range of fluorophores, therapeutics, and targeting agents demonstrates their clinical potential against various cancer types. There is an imminent need for novel strategies for the diagnosis and treatment of aggressive triple-negative breast cancer (TNBC). Cell-targeted multifunctional nanomaterials hold great potential, as they can combine precise early-stage diagnosis with local therapeutic delivery to specific cell types. In this study, we used mesoporous silica (MS)-coated gold nanobipyramids (MS-AuNBPs) for fluorescence imaging in the near-infrared (NIR) biological window, along with targeted TNBC treatment. Our MS-AuNBPs, acting partly as light amplification components, allow considerable metal-enhanced fluorescence for a NIR dye conjugated to their surfaces compared to the free dye. Fluorescence analysis confirms a significant increase in the dye's modified quantum yield, indicating that MS-AuNBPs can considerably increase the brightness of low-quantum-yield NIR dyes. Meanwhile, we tested the chemotherapeutic efficacy of MS-AuNBPs in TNBC following the loading of doxorubicin within the MS pores and functionalization to target folate receptor alpha (FRα)-positive cells. We show that functionalized particles target FRα-positive cells with significant specificity and have a higher potency than free doxorubicin. Finally, we demonstrate that FRα-targeted particles induce stronger antitumor effects and prolong overall survival compared to the clinically applied non-targeted nanotherapy, Doxil. Together with their excellent biocompatibility measured in vitro, this study shows that MS-AuNBPs are promising tools to detect and treat TNBCs. [ABSTRACT FROM AUTHOR]

We report on excitation dynamics in pristine and bulk heterojunction films of the low bandgap silicon-bridged dithiophene copolymer poly[(4,4′-bis(2-ethylhexyl)dithieno[3,2-b:2′, 3′-d]silole)-2,6-diyl-alt-(4,7-bis(2-thienyl)-2,1,3-benzothiadiazole)-5,5′-diyl] with methanofullerene derivatives. The combination of ultrafast transient transmission and photoluminescence allows us to probe the relaxation of both exciton and polaron states in a relatively wide spectral and temporal range. Measurements reveal that the majority of excitations undergo ultrashort non-radiative relaxation while a small fraction of the photoexcited species decays slowly within hundreds of ps. In the blend films, significantly longer decays are observed suggesting the presence of long lived holes and/or charged-transfer type of excitons. [ABSTRACT FROM AUTHOR]

Wood fly ash is an industrial by-product of the combustion of different wood materials and is mostly disposed of as waste on landfills. In our preliminary experiments, wood ash exhibited antibacterial activity against urban wastewater bacteria and we focused on wood fly ash as a potential substrate for wastewater disinfection. The addition of ash at a concentration of 10 g L-1 (1 %) caused an instant increase of pH in urban wastewater and landfill leachate. High pH (10.1-12.7) inactivated bacterial populations in the wastewater and the removal of faecal coliforms and intestinal enterococci after 6 h of contact was 100 % (below the detection limit; <1 CFU per mL) with the most efficient ash sample (ash from combustion of beech) both in urban wastewater and landfill leachate. Properly chosen wood fly ash, i.e. one that tends to increase the pH to the greatest extent, proved to be a very effective disinfection substrate. Considering that water treated with wood ash has a high pH and needs to be neutralised before discharge, ash would be suitable for disinfection of leachates when smaller volumes are treated [ABSTRACT FROM AUTHOR]

Abstract: The present study investigates the heavy metal content of coal fly ash (FA) samples coming from three different sampling points (secondary cyclone, cooler and filter) of a pilot plant combustion facility. The combustion experiments were carried out in a 0.1MW Circulated Fluidized Bed (CFB) boiler using South African coal, with the addition of limestone for sulfur capture. FA was tested for the presence of selected heavy metals using inductively coupled plasma optical emission spectrometry (ICP-OES); batch leaching tests were conducted as well. The samples were also characterized in terms of their microstructure, chemical and mineralogical composition, total surface area and particle size distribution. Most of the studied metals (Cd, Cr, Cu, Ni, Mn, Zn) showed enrichment in the fine, filter FA particles, while Pb was mostly concentrated in the cooler sample. Regarding leaching characteristics of the examined samples, Cr was found to occur in considerable amounts. Although the use of CFB technology for the combustion of solid fuels steadily gets bigger worldwide, only a very limited number of studies have environmentally assessed CFB-coal FAs to date. Thus, the current study aims to contribute toward building a more integrated knowledge on the environmental impact of this abundant power production by-product. [ABSTRACT FROM AUTHOR]

Abstract: Polish bituminous (PB) and South African (SA) coal fly ash (FA) samples, derived from pilot-scale circulated fluidized bed (CFB) combustion facilities, were utilized as raw materials for the synthesis of zeolitic products. The two FAs underwent a hydrothermal activation with 1M NaOH solution. Two different FA/NaOH solution/ratios (50, 100g/L) were applied for each sample and several zeolitic materials were formed. The experimental products were characterized by means of X-ray diffraction (XRD) and energy dispersive X-ray coupled–scanning electron microscope (EDX/SEM), while X-ray fluorescence (XRF) was applied for the determination of their chemical composition. The zeolitic products were also evaluated in terms of their cation exchange capacity (CEC), specific surface area (SSA), specific gravity (SG), particle size distribution (PSD), pH and the range of their micro- and macroporosity. Afterwards the hybrid materials were tested for their ability of adsorbing Cr, Pb, Ni, Cu, Cd and Zn from contaminated liquids. Main parameters for the precipitation of the heavy metals, as it was concluded from the experimental results, are the mineralogical composition of the initial fly ashes, as well as the type and the amount of the produced zeolite and specifically the mechanism by which the metals ions are hold on the substrate. [Copyright &y& Elsevier]

An analytical, numerical and experimental study is presented on the deagglomeration and dispersion of fine coal fly ash (CFA) reinforcing particles in an A380 aluminium matrix using a piston-actuated oscillating micro-grid mixing method with a specially designed grid geometry. Based on real-time measurement of the piston force, the apparent viscosity of the melt and the effectiveness of the deagglomeration are measured indirectly. The oscillating micro-grid mixing process is shown to be considerably more time-efficient that comparative stir-casting processes currently employed, leading to a two-fold or three-fold reduction in processing time for the same or better mixing quality, or alternatively a nearly two-fold reduction in the standard deviation of the micro-hardness throughout the material. [ABSTRACT FROM AUTHOR]

We investigate the employment of carefully selected solvent additives in the processing of a commercial perovskite precursor ink and analyze their impact on the performance of organometal trihalide perovskite (CH3NH3PbI3-xClx) photovoltaic devices. We provide evidence that the use of benzaldehyde can be used as an effective method to preserve the stoichiometry of the perovskite precursors in solution. Benzaldehyde based additive engineering shows to improve perovskite solid state film morphology and device performance of CH3NH3PbI3-xClx based solar cells. [ABSTRACT FROM AUTHOR]

1,3-Diaryl-1,4-dihydro-1,2,4-benzotriazin-4-yls are air stable organic radicals which have been exploited for their interesting magnetic properties. Herein, we present the optical properties of the “parent” radical namely 1,3-diphenyl-1,4-dihydro-1,2,4-benzotriazin-4-yl (aka “the Blatter radical”), which possesses absorption bands that span the UV and visible spectrum that lead to broadband emission across the same spectral region. As shown in our experiments, the emission originates from excited electronic states of the radical, with, however, low quantum yield. Emission across the visible is also observed from thin films of the radical when inserted into PMMA matrices. As radical concentration within the polymer matrix is increased, systematic modifications in the spectral and temporal characteristics of the fluorescence indicate the formation of radical ground state aggregates. [ABSTRACT FROM AUTHOR]

The photovoltaic performance of blends of a series of 4,4′-Difluoro-4-bora-3a,4a-diaza-s-indacenes)-based (BODIPY) conjugated polymers donors with fullerene electron acceptors is investigated. Despite the high Voc values observed, solar cell device yields relatively low power conversion efficiencies. Our study takes into account the materials’ structure-property relationship, light harvesting capabilities, charge transport, collection properties and morphological characteristics to elucidate factors affecting the photovoltaic performance in this class of polymers. We show that elimination of low molecular weight species and suitable electrodes for hole collection can be used to overcome some of the observed limitations on photovoltaic performance. [ABSTRACT FROM AUTHOR]

Lead halide perovskites (CH3NH3PbX3, where X = I, Br) and other metal halide complexes (MXn, where M = Pb, Cd, In, Zn, Fe, Bi, Sb) have been studied as inorganic capping ligands for colloidal nanocrystals. We present the methodology for the surface functionalization via ligand-exchange reactions and the effect on the optical properties of IV-VI, II-VI, and III-V semiconductor nanocrystals. In particular, we show that the Lewis acid-base properties of the solvents, in addition to the solvent dielectric constant, must be properly adjusted for successful ligand exchange and colloidal stability. High luminescence quantum efficiencies of 20-30% for near-infrared emitting CH3NH3PbI3-functionalized PbS nanocrystals and 50-65% for red-emitting CH3NH3CdBr3- and (NH4)2ZnCl4-capped CdSe/CdS nanocrystals point to highly efficient electronic passivation of the nanocrystal surface. [ABSTRACT FROM AUTHOR]

PbS quantum dots (QDs) of different sizes capped with short (NH4)3AsS3 inorganic ligands are produced via ligand exchange processes from oleate-capped PbS QDs. The solid-state photophysical properties of the control organic-capped and the inorganic-ligand-capped QDs are investigated to determine their potential for optoelectronic applications. Ultrafast transient transmission shows that in the oleate-capped QDs, carrier recombination at sub-nanosecond scales occurs via Auger recombination, traps, and surface states. At longer times, intense signals associated with radiative recombination are obtained. After ligand exchange, the QDs become decorated with (NH4)3AsS3 complexes and relaxation is dominated by efficient carrier transfer to the ligand states on timescales as fast as ≈2 ps, which competes with carrier thermalization to the QD band edge states. Recombination channels present in the oleate-capped QDs, such as radiative and Auger recombination, appear quenched in the inorganic-capped QDs. Evidence of efficient carrier trapping at shallow ligand states, which appears more intense under excitation above the (NH4)3AsS3 gap, is provided. A detailed band diagram of the various relaxation and recombination processes is proposed that comprehensively describes the photophysics of the QD systems studied. [ABSTRACT FROM AUTHOR]

Highlights: [•] We proved that MHEM can be effectively used for heat exchanger simulations. [•] A surface profile from the combustion simulation was the inlet boundary condition. [•] A decoupled furnace and heat exchanger simulation can be effectively applied. [Copyright &y& Elsevier]

Abstract: The mobility of inorganic pollutants is of key concern for a range of industrial and engineering applications of fly ash produced during the combustion of lignite in power generation. This paper investigates the role that the geochemical features of lignite, the ash composition and the partitioning of elements during combustion play in determining leaching properties of lignite fired by-products. The work is based on surveys on three lignite-fired power plants in Greece. Calcium-rich ashes show a high abatement potential for SO2 and other gaseous pollutants. For most elements, the concentrations in the parent lignite and the ashes follow the same trend. Relative enrichments in Cd, Co, Cr, Cu, Mo, Ni, Pb, U, V, W, Zn fingerprint the regional and local geological settings of the lignite basins. The total and leachable concentrations of highly volatile elements are strongly influenced by the interaction with ubiquitous free lime. A broad array of elements is highly insoluble in alkaline ash, while a few oxyanionic-forming elements display substantial mobility. Their mode of occurrence in the parent lignite plays a primary role in the leaching of combustion ashes. The outcomes of this study may assist in addressing the impact of co-firing high ash or high Ca alternative fuels on the leaching properties of combustion by-products. [Copyright &y& Elsevier]

• Hot-pressed Al 2 O 3 /Cr and Ti 2 O 3 /Cr composites were exposed to air and CO 2 at 750 °C. • Exclusive external Cr 2 O 3 scale growth occurred on Al 2 O 3 /Cr for up to 700 h at 750 °C. • Finer-grained Cr 2 O 3 formed in CO 2 on Al 2 O 3 /Cr, and thickened faster, than in air. • Nitrides or carbides were not detected below Cr 2 O 3 scales formed in air or CO 2. • Thick external TiO 2 scales and Cr 2 O 3 -bearing internal oxide zones formed on Ti 2 O 3 /Cr. Hot-pressed Al 2 O 3 /Cr and Ti 2 O 3 /Cr composites were exposed to synthetic air or CO 2 at 750 °C. The Al 2 O 3 /Cr composites formed external Cr 2 O 3 scales, and exhibited slow parabolic oxidation kinetics, in both gases. The Cr 2 O 3 scales formed in CO 2 possessed finer grains, and thickened at a faster rate, than Cr 2 O 3 scales formed in air. The Ti 2 O 3 /Cr composites formed thick external TiO 2 scales with internal oxidation zones that also contained Cr 2 O 3 scales on subsurface Cr grains. After 20 h at 750 °C, the Ti 2 O 3 /Cr composites exhibited parabolic oxidation kinetics in both gases, although the oxidation rates were significantly higher than for the Al 2 O 3 /Cr composites. [ABSTRACT FROM AUTHOR]

• CdS/CIGS heterojunction structures were deposited using PLD in a single step process. • The process eliminated the need for selenization and use of other growth techniques. • Low series and high shunt resistances were obtained for CdS grown at 200 and 300 °C. • Lowest ideality factor and leakage current were achieved for CdS grown at 300 °C. This work reports on the utilization of pulsed laser deposition (PLD) for the preparation of CdS thin films and CdS/Cu(In,Ga)Se 2 heterojunction structures on soda-lime glass (SLG) and Mo-coated SLG substrates, respectively, under various process conditions. Single phase, stoichiometric and high optical quality CdS films are obtained at a fluence of 1.1 J/cm2 and at deposition temperatures of 200–400 °C. The results of this investigation were used to grow CdS on Cu(In,Ga)Se 2 /Mo/SLG. Both Cu(In,Ga)Se 2 and CdS layers have been deposited sequentially using PLD without interrupting the deposition process. The influence of CdS deposition temperature on the properties of CdS/Cu(In,Ga)Se 2 heterojunction has been extensively studied and is reported herein for the first time. Low series and high shunt resistances are obtained for the samples where CdS was grown at 200 and 300 °C. The CdS/Cu(In,Ga)Se 2 diode grown at CdS deposition temperature of 300 °C exhibits the lowest ideality factor and leakage current, indicating the better quality of the diode. The results of this work demonstrate that high-quality CdS/Cu(In,Ga)Se 2 diodes are obtained using pulsed laser deposition in a single-step growth process, eliminating the need for selenization of Cu(In,Ga)Se 2 and the use of other growth techniques such as chemical bath deposition for CdS. [ABSTRACT FROM AUTHOR]

In this study, we report the luminescence color tuning in the lanthanide metal-organic framework (LnMOF) ([La(bpdc)Cl(DMF)] (1); bpdc2− = [1,1′-biphenyl]-4,4′-dicarboxylate, DMF = N,N-dimethylformamide) by introducing dual emission properties in a La3+ MOF scaffold through doping with the blue fluorescent 2,2′-diamino-[1,1′-biphenyl]-4,4′-dicarboxylate (dabpdc2−) and the red emissive Eu3+. With a careful adjustment of the relative doping levels of the lanthanide ions and bridging ligands, the color of the luminescence was modulated, while at the same time the photophysical characteristics of the two chromophores were retained. In addition, the photophysical properties of the parent MOF (1) and its doped counterparts with various dabpdc2−/bpdc2− and Eu3+/La3+ ratios and the photoinduced energy transfer pathways that are possible within these materials are discussed. Finally, the temperature dependence study on the emission profile of a doped analogue containing 10% dabpdc2− and 2.5% Eu3+ (7) is presented, highlighting the potential of this family of materials to behave as temperature sensors. [ABSTRACT FROM AUTHOR]