­Improved Luminescence and Photocatalytic Proprieties of Sm3+-doped ZnO Nanoparticles Via Modified Sol-Gel Route: An Unified Experimental and DFT+U Approach

In the current study, a modified sol-gel route was followed to produce undoped and Sm3+ doped (1, 3 and 5 mol %) nanoparticles. The study of opto-structural properties of Sm3+ doped NPs was carried out both experimentally and theoretically. Complete dissolution of Sm3+ ions into the ZnO lattice was obvious from XRD analysis. Morphological evolution with doping was studied using FESEM and TEM. XPS was carried out to confirm the presence of Sm3+ on the surface of the doped NPs. Increasing dopant quantity resulted in a red shift of the NPs along with a reduction in band gap with increasing absorption in the visible range, and a minimum of 3.18 eV of optical band gap for Zn0.97Sm0.03O was found. Photoluminescence spectroscopy revealed a drop in the recombination rate of electron-hole with increasing doping till 3 mole %, followed by an increase for Zn0.95Sm0.05O. Photogenerated electron-hole pair recombination was revealed by the orange band in the luminescence spectra. Theoretical analysis was also carried out with density function theory (DFT). This work also unfolds the fundamental understanding of the structural properties of the synthesized NPs to enhance photocatalytic activity successfully. Later, photocatalytic activity for the optimum composition i.e., 3 mole percent, was assessed experimentally.

Small Alcohols as Surfactants and Hydrate Promotors

Many methods to produce hydrate reservoirs have been proposed in the last three decades. Thermal stimulation and injection of thermodynamic hydrate inhibitors are just two examples of methods which have seen reduced attention due to their high cost. However, different methods for producing hydrates are not evaluated thermodynamically prior to planning expensive experiments or pilot tests. This can be due to lack of a thermodynamic toolbox for the purpose. Another challenge is the lack of focus on the limitations of the hydrate phase transition itself. The interface between hydrate and liquid water is a kinetic bottle neck. Reducing pressure does not address this problem. An injection of CO2 will lead to the formation of a new CO2 hydrate. This hydrate formation is an efficient heat source for dissociating hydrate since heating breaks the hydrogen bonds, directly addressing the problem of nano scale kinetic limitation. Adding limited amounts of N2 increases the permeability of the injection gas. The addition of surfactant increases gas/water interface dynamics and promotes heterogeneous hydrate formation. In this work we demonstrate a residual thermodynamic scheme that allows thermodynamic analysis of different routes for hydrate formation and dissociation. We demonstrate that 20 moles per N2 added to the CO2 is thermodynamically feasible for generating a new hydrate into the pores. When N2 is added, the available hydrate formation enthalpy is reduced as compared to pure CO2, but is still considered sufficient. Up to 3 mole percent ethanol in the free pore water is also thermodynamically feasible. The addition of alcohol will not greatly disturb the ability to form new hydrate from the injection gas. Homogeneous hydrate formation from dissolved CH4 and/or CO2 is limited in amount and not important. However, the hydrate stability limits related to concentration of hydrate former in surrounding water are important. Mineral surfaces can act as hydrate promotors through direct adsorption, or adsorption in water that is structured by mineral surface charges. These aspects will be quantified in a follow-up paper, along with kinetic modelling based on thermodynamic modelling in this work.

Reduction of In Vivo Placental Amino Acid Transport Precedes the Development of Intrauterine Growth Restriction in the Non-Human Primate

Intrauterine growth restriction (IUGR) is associated with reduced placental amino acid transport (AAT). However, it remains to be established if changes in AAT contribute to restricted fetal growth. We hypothesized that reduced in vivo placental AAT precedes the development of IUGR in baboons with maternal nutrient restriction (MNR). Baboons were fed either a control (ad libitum) or MNR diet (70% of control diet) from gestational day (GD) 30. At GD 140, in vivo transplacental AA transport was measured by infusing nine (13)C- or (2)H-labeled essential amino acids (EAAs) as a bolus into the maternal circulation at cesarean section. A fetal vein-to-maternal artery mole percent excess ratio for each EAA was measured. Microvillous plasma membrane (MVM) system A and system L transport activity were determined. Fetal and placental weights were not significantly different between MNR and control. In vivo, the fetal vein-to-maternal artery mole percent excess ratio was significantly decreased for tryptophan in MNR. MVM system A and system L activity was markedly reduced in MNR. Reduction of in vivo placental amino acid transport precedes fetal growth restriction in the non-human primate, suggesting that reduced placental amino acid transfer may contribute to IUGR.

Electrolyte Based Modeling of Corrosion Processes in Sulfuric Acid Mixtures – Part 1: Non-Oxidizing Conditions

The corrosion behavior of stainless steels and Ni-base alloys in non-oxidizing sulfuric acid mixtures at concentrations below approximately 30 moles/Kg H2O is modeled. The redox potential in sulfuric acid across a broad concentration range, from 0 to 80 mole percent (0 to 95.6 weight percent), is determined by the proton reduction reaction. Thus, in the absence of other oxidizing species, sulfuric acid behaves as a non-oxidizing (reducing) acid. The calculated corrosion rate, using an electrochemical model up to about 30 moles/Kg H2O (about 75 weight percent) is in agreement with experimental values. The predicted polarization curves of anodic and cathodic processes showed that the alloys in these environments are in active dissolution regime, consistent with experimental data. The model predictions of corrosion rates in H2SO4+HCl, H2SO4+HF, and H2SO4+HCl+HF mixtures are in agreement with weight-loss corrosion data. The corrosion rate of alloys in the non-oxidizing sulfuric acid mixtures correlated to an equivalent alloy composition given by (Ni0.7-Cr0.1+Mo+0.5W). The effect of alloying elements under these conditions may be related to their beneficial effect on active dissolution and proton reduction reaction rates.

Engendering persistent organic room temperature phosphorescence by trace ingredient incorporation

Pure organic persistent room temperature phosphorescence (RTP) has shown great potential in information encryption, optoelectronic devices, and bio-applications. However, trace impurities are generated in synthesis, causing unpredictable effects on the luminescence properties. Here, an impurity is isolated from a pure organic RTP system and structurally characterized that caused an unusual ultralong RTP in matrix even at 0.01 mole percent content. Inspired by this effect, a series of compounds are screened out to form the bicomponent RTP system by the trace ingredient incorporation method. The RTP quantum yields reach as high as 74.2%, and the lifetimes reach up to 430 ms. Flexible application of trace ingredients to construct RTP materials has become an eye-catching strategy with high efficiency, economy, and potential for applications as well as easy preparation.

Studying the Effect of High Substrate Temperature on the Microstructure of Vacuum Evaporated TAPC: C60 Organic Solar Thin Films

Organic solar cells (OSCs), also known as organic photovoltaics (OPVs), are an emerging solar cell technology composed of carbon-based, organic molecules, which convert energy from the sun into electricity. Key for their performance is the microstructure of the light-absorbing organic bulk heterojunction. To study this, organic solar films composed of both fullerene C60 as electron acceptor and different mole percentages of di-[4-(N,N-di-p-tolyl-amino)-phenyl]-cyclohexane (TAPC) as electron donor were evaporated in vacuum in different mixing ratios (5, 50 and 95 mol%) on an ITO-coated glass substrate held at room temperature and at 110 °C. The microstructure of the C60: TAPC heterojunction was studied by grazing incidence wide angle X-ray scattering to understand the effect of substrate heating. By increasing the substrate temperature from ambient to 110 °C, it was found that no significant change was observed in the crystal size for the C60: TAPC concentrations investigated in this study. In addition to the variation done in the substrate temperature, the variation of the mole percent of the donor (TAPC) was studied to conclude the effect of both the substrate temperature and the donor concentration on the microstructure of the OSC films. Bragg peaks were attributed to C60 in the pure C60 sample and in the blend with low donor mole percentage (5%), but the C60 peaks became nondiscernible when the donor mole percentage was increased to 50% and above, showing that TAPC interrupted the formation of C60 crystals.

Photocatalytic Activities of FeNbO4/NH2-MIL-125(Ti) Composites toward the Cycloaddition of CO2 to Propylene Oxide

Photocatalytic utilization of CO2 in the production of value-added chemicals has presented a recent green alternative for CO2 fixation. In this regard, three FeNbO4/NH2-MIL-125(Ti) composites of different mole ratios were synthesized, characterized using Powder X-ray diffraction (PXRD), UV–vis diffuse reflectance spectroscopy (UV-Vis DRS), Brunauer–Emmett–Teller (BET), Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray (EDX). PXRD patterns confirm the co-existence of the parent components in the prepared composites. Moreover, the surface area increased as the mole percent of NH2-MIL-125(Ti) in the composites increased due to the large surface area of NH2-MIL-125(Ti). Prepared composites were investigated for the photocatalytic insertion of CO2 into propylene oxide. FeNbO4(75%)/NH2-MIL-125(Ti)(25%) showed the highest percent yield of 52% compared to the other two composites. Results demonstrate the cooperative mechanism between FeNbO4 and NH2-MIL-125(Ti) and that the reaction proceeded photocatalytically.

Engineering fluorinated-cation containing inverted perovskite solar cells with an efficiency of >21% and improved stability towards humidity

Efficient and stable perovskite solar cells with a simple active layer are desirable for manufacturing. Three-dimensional perovskite solar cells are most efficient but need to have improved environmental stability. Inclusion of larger ammonium salts has led to a trade-off between improved stability and efficiency, which is attributed to the perovskite films containing a two-dimensional component. Here, we show that addition of 0.3 mole percent of a fluorinated lead salt into the three-dimensional methylammonium lead iodide perovskite enables low temperature fabrication of simple inverted solar cells with a maximum power conversion efficiency of 21.1%. The perovskite layer has no detectable two-dimensional component at salt concentrations of up to 5 mole percent. The high concentration of fluorinated material found at the film-air interface provides greater hydrophobicity, increased size and orientation of the surface perovskite crystals, and unencapsulated devices with increased stability to high humidity.

Nanocarriers of Eu3+ doped silica nanoparticles modified by APTES for luminescent monitoring of cloxacillin

<abstract> <p>Drug nanocarriers have been continuously improved to promote satisfactory release control. In this sense, luminescent materials have become an alternative option in clinical trials due to their ability to monitor drug delivery. Among the nanocarriers, silica stands out for structural stability, dispersibility, and surface reactivity. When using ceramic nanocarriers, one of the challenges is their interaction and selectivity capability for organic molecules, such as drugs. In order to overcome such adversity, superficial modifications can be carried out to enable a higher affinity for the desired drug. Thus, the present study aimed to obtain silica nanoparticles (NPs) doped with low concentrations of europium (III) superficially modified by (3-aminopropyl)triethoxysilane (APTES) to assess their interaction with the model drug cloxacillin benzathine. This drug was chosen because it is part of the ampicillin family and is commonly used in several treatments. Near-spherical and homogeneous silica NPs were obtained via sol-gel synthesis, with particle sizes of approximately 21 nm. It was possible to verify the fluorescence capacity of the silica NPs when doped with europium (III) in a mole percent that varied from 0.5 to 3.0%. A 10% volume percent of APTES caused the silica nanoparticles to increase the degree of hydrophobicity, with a shift in the contact angle from 8° to 51°. After surface modification by APTES, the silica nanocarrier (10 g·L^-1) achieved a satisfactory degree of CLOX incorporation (25 g·L^-1), increasing the adsorptive capacity to values above 50%. Therefore, silica NPs doped with europium (III) in a low percent of 0.5% (mole) modified by APTES showed promising results as an alternative option for trials and clinical studies of drug incorporation.</p> </abstract>

Au–Ag alloy nanoparticle-incorporated AgBr plasmonic photocatalyst

A solid-phase photochemical method produces Au–Ag alloy nanoparticles (NPs) with a sharp size distribution and varying composition in AgBr crystals (Au–Ag@AgBr). These features render Au–Ag@AgBr promising as a material for the plasmonic photocatalyst further to provide a possibility of elucidating the action mechanism due to the optical tunability. This study shows that the visible-light activity of Au–Ag@AgBr for degradation of model water pollutant is very sensitive to the alloy composition with a maximum at the mole percent of Au to all Ag in AgBr (y) = 0.012 mol%. Clear positive correlation is observed between the photocatalytic activity and the quality factor defined as the ratio of the peak energy to the full width at half maximum of the localized surface plasmon resonance band. This finding indicates that Au–Ag@AgBr works as a local electromagnetic field enhancement-type plasmonic photocatalyst in which the Au–Ag NPs mainly promotes the charge separation. This conclusion was further supported by the kinetic analysis of the light intensity-dependence of external quantum yield.