Deep Oxidative Desulfurization of Planar Compounds Over Functionalized Metal-Organic Framework UiO-66(Zr): An Optimization Study.

This study aims to determine the catalytic activity and stability of ligand-modified UiO-66 with different functional groups (-NO2, -OH) in deep oxidative desulfurization from a model fuel (MF). The planar sulfur compounds included dibenzothiophene (DBT), 2-methylbenzothiazole (2-MB), and 4,6-dimethyldibenzothiophene (4,6-DMDBT) in n-dodecane as the fuel phase. The synthesized functionalized metal-organic framework (MOF) samples were characterized by X-ray powder diffraction (XRD), Fourier transform infrared (FTIR), proton nuclear magnetic resonance (1H NMR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), nitrogen adsorption-desorption analysis, and microwave plasma-atomic emission spectrometer (MP-AES). The experiment assessment and desulfurization reaction optimization were carried out by the central composite design methodology. Response surface methodology and analysis of variance were employed to evaluate the individual process factors, their interactions, and sulfur removal responses. The responses showed that the oxidation of the planar compounds declined following the sequence DBT > 2-MB ≫ 4,6-DMDBT for all the MOFs. The findings revealed that at 66.7 °C, 3.0 equiv of oxidative agent over sulfur and 9.7 of MOF over sulfur by weight achieved the highest removal efficiency of 98.68% DBT, 93.23% 2-MB, and 69.32% 4,6-DMDBT for UiO-66-NO2 as a catalyst from the model fuel. It was also observed that UiO-66-NO2 had a higher efficiency in deep oxidative desulfurization when compared to other UiO-66-based catalysts used in the current study. Under optimal conditions, all the MOFs showed acceptable catalytic activity and reusability after four runs, although gradual loss of activity was observed.

Iron Triad-Based Bimetallic M-N-C Nanomaterials as Highly Active Bifunctional Oxygen Electrocatalysts.

The use of precious metal electrocatalysts in clean electrochemical energy conversion and storage applications is widespread, but the sustainability of these materials, in terms of their availability and cost, is constrained. In this research, iron triad-based bimetallic nitrogen-doped carbon (M-N-C) materials were investigated as potential bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The synthesis of bimetallic FeCo-N-C, CoNi-N-C, and FeNi-N-C catalysts involved a precisely optimized carbonization process of their respective metal-organic precursors. Comprehensive structural analysis was undertaken to elucidate the morphology of the prepared M-N-C materials, while their electrocatalytic performance was assessed through cyclic voltammetry and rotating disk electrode measurements in a 0.1 M KOH solution. All bimetallic catalyst materials demonstrated impressive bifunctional electrocatalytic performance in both the ORR and the OER. However, the FeNi-N-C catalyst proved notably more stable, particularly in the OER conditions. Employed as a bifunctional catalyst for ORR/OER within a customized zinc-air battery, FeNi-N-C exhibited a remarkable discharge-charge voltage gap of only 0.86 V, alongside a peak power density of 60 mW cm-2. The outstanding stability of FeNi-N-C, operational for about 55 h at 2 mA cm-2, highlights its robustness for prolonged application.

Cu2ZnSnS4 monograin layer solar cells for flexible photovoltaic applications.

Monograin powder technology is one possible path to developing sustainable, lightweight, flexible, and semi-transparent solar cells, which might be ideal for integration with various building and product elements. In recent years, the main research focus of monograin technology has centered around understanding the synthesis and optoelectronic properties of kesterite-type absorber materials. Among these, Cu2ZnSnS4 (CZTS) stands out as a promising solar cell absorber due to its favorable optical and electrical characteristics. CZTS is particularly appealing as its constituent elements are abundant and non-toxic, and it currently holds the record for highest power conversion efficiency (PCE) among emerging inorganic thin-film PV candidates. Despite its advantages, kesterite solar cells' PCE still falls significantly behind the theoretical maximum efficiency due to the large VOC deficit. This review explores various strategies aimed at improving VOC losses to enhance the overall performance of CZTS monograin layer solar cells. It was found that low-temperature post-annealing of CZTS powders reduced Cu-Zn disordering, increasing Eg by ∼100 meV and VOC values; however, achieving the optimal balance between ordered and disordered regions in kesterite materials is crucial for enhancing photovoltaic device performance due to the coexistence of ordered and disordered phases. CZTS alloying with Ag and Cd suppressed non-radiative recombination and increased short-circuit current density. Optimizing Ag content at 1% reduced CuZn antisite defects, but higher Ag levels compensated for acceptor defects, leading to reduced carrier density and decreased solar cell performance. Co-doping with Li and K resulted in an increased bandgap (1.57 eV) and improved VOC, but further optimization is required due to a relatively large difference between measured and theoretical VOC. Heterojunction modifications led to the most effective PCE improvement in CZTS-based solar cells, achieving an overall efficiency of 12.06%.

Primary amines as heterogeneous catalysts in an enantioselective [2,3]-Wittig rearrangement reaction.

A series of heterogeneous catalysts anchored to different polystyrene-based supports has been prepared and applied in an asymmetric [2,3]-Wittig rearrangement reaction of cyclohexanone derivatives. Among them, primary amino acid-derived (aminomethylated)polystyrene-supported catalysts showed excellent reactivity leading to the formation of rearranged products in good enantioselectivities of both diastereomers. Reusability issues connected to the deactivation of the catalyst were proved to be dependent on the end-capping strategy chosen for the blocking of the unreacted active sites of the resin. This issue of end-capping has not previously been in focus. Using bulkier pivaloyl end-capping moiety, we were able to recycle the catalyst in six consecutive cycles with only marginal deceleration of the reaction. Moreover, the epimerization of the product that occurred while conducting a rearrangement reaction in the presence of a homogeneous catalyst was almost fully eliminated by switching the catalytic system to heterogeneous.

Influence of Protic Ionic Liquid-Based Flame Retardant on the Flammability and Water Sorption of Alkalized Hemp Fiber-Reinforced PLA Composites.

This article investigates the effects of combining a novel protic ionic liquid-based fire retardant (FR) with alkalized hemp fiber. A pivotal importance of this study refers to the hydrophilic properties and limits regarding poor thermal resistance of green composites where standard guidelines for fire risks are crucial. Although it is well-studied that alkalization is essential for green composite's moisture and mechanical durability, research on the flammability of such a combined treatment for natural fiber-reinforced biopolymer composites is lacking. The alkaline treatment used in the current study follows a process already studied as optimal, particularly for the selected hemp fiber. The fire performance was examined using a bench scale approach based on self and piloted ignition from cone calorimeter tests. The result from the Fourier-transform infrared analysis of the hemp fiber confirms phosphorylation following the fire-retardant treatment, which was visible from the morphological examination with scanning electron microscope. The presence of FR in the composites led to impactful moisture sorption. However, the FR composites demonstrated an enhanced response to fire, indicating potential use as a Class B standard for building construction, and hazard level 3 (HL3) classification as an interior material in vehicles, provided the problem of high emission of smoke is mitigated.

Process Optimization for Catalytic Oxidation of Dibenzothiophene over UiO-66-NH2 by Using a Response Surface Methodology.

This research investigates the catalytic performance of a metal-organic framework (MOF) with a functionalized ligand-UiO-66-NH2-in the oxidative desulfurization of dibenzothiophene (DBT) in n-dodecane as a model fuel mixture (MFM). The solvothermally prepared catalyst was characterized by XRD, FTIR, 1H NMR, SEM, TGA, and MP-AES analyses. A response surface methodology was employed for the experiment design and variable optimization using central composite design (CCD). The effects of reaction conditions on DBT removal efficiency, including temperature (X 1), oxidant agent over sulfur (O/S) mass ratio (X 2), and catalyst over sulfur (C/S) mass ratio (X 3), were assessed. Optimal process conditions for sulfur removal were obtained when the temperature, O/S mass ratio, and C/S mass ratio were 72.6 °C, 1.62 mg/mg, and 12.1 mg/mg, respectively. Under these conditions, 89.7% of DBT was removed from the reaction mixture with a composite desirability score of 0.938. From the results, the temperature has the most significant effect on the oxidative desulfurization reaction. The model F values gave evidence that the quadratic model was well-fitted. The reusability of the MOF catalyst in the ODS reaction was tested and demonstrated a gradual loss of activity over four runs.

Development of Functional Composite Cu(II)-Polyoxometalate/PLA with Antimicrobial Properties.

Novel composite self-disinfecting films of polylactic acid (PLA) filled with nanosized particles of double sodium-copper(II) paratungstate B Na2Cu3(CuOH)2[W12O40(OH)2]·32H2O (POM) were developed. The solvent casting (POM/PLA film) and solvent-free melt extrusion methods (Extr. POM/PLA film) were applied for film preparation. The copper (II) ion release to water from both types of the films after 10 days at different temperatures demonstrated that the PLA matrix acts as a diffusion barrier, and the resulting concentration of released copper in water at room temperature remained low, at 0.79% for POM/PLA film and 0.51% for Extr. POM/PLA film. The POM-containing films reveals a significant inhibitory effect against E. coli ATCC 25922 in the agar diffusion test. The numbers of CFUs in washes of the films after incubation for 24 h were found to be 3.6 log CFU mL-1 (POM/PLA film) and 4.1 log CFU mL-1 (Extr. POM/PLA film). The films combine the antibacterial properties of POM and a bio-based polymer matrix, which makes them a prospective coating material for applications in hospital indoor environments. Excellent thermal stability of POM gives a technological advantage for industrial manufacturing to allow the processing of novel composite material in the solvent free (molten) state.

Spent Li-Ion Battery Graphite Turned Into Valuable and Active Catalyst for Electrochemical Oxygen Reduction.

Employing Li-ion batteries (LIBs) in portable electronics has become a necessity in the modern world but, due to the short application time for any given battery (1-3 years), the quantity of spent LIBs (SLIBs) waste is becoming substantial. Herein, a novel strategy for recycling SLIB graphite and reforming it as a valuable catalyst material for electrochemical oxygen reduction reaction was proposed. SLIB graphite has been used as a precursor material for graphite oxide, which was thereafter doped with nitrogen to prepare nitrogen-doped graphene (NG-Bat). The prepared NG-Bat was characterized by various physical characterization methods and the electrochemical properties of the resulting catalyst material were investigated in alkaline media. It was found that NG-Bat prepared from SLIB had superior physical and electrochemical properties in comparison to commercial nitrogen-doped graphene. The findings clearly demonstrate the importance of the recycling of SLIB graphite and its great potential to be re-applied for various applications.

Investigation of mechanical and physicochemical properties of clinically retrieved titanium-niobium orthodontic archwires.

PURPOSE: Most of the orthodontic archwires used in the clinical practice nowadays contain nickel (Ni), however, many patients, especially kids, are allergic to Ni. One possible Ni-free alternative is the Titanium-Niobium (Ti-Nb) archwire. Unfortunately, there is not enough information about its mechanical properties in the literature, especially after clinical usage. Therefore, the aim of this work was to investigate and compare the mechanical properties, chemical composition, structure and morphology of as received and used in clinical practice Ti-Nb orthodontic archwires. MATERIALS AND METHODS: We investigated and compared as received and clinically retrieved after 4 and 6 weeks respectively Ti-Nb archwires with dimensions 0.43 × 0.64 mm (0.017 in. × 0.025 in.). The following methods were used: instrumented indentation testing (nanoindentation), X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. RESULTS: The nanoindentation investigations of as received and used Ti-Nb archwires revealed a decreasing in their indentation hardness with increased periods of use in the patient's mouth. Moreover, an increasing of the concentration of Ti in the content of the TiNb alloy was associated with an increased period of use in the oral cavity. The SEM analysis showed changes in surface morphology with increasing the period of use of the archwires. CONCLUSIONS: The results showed that there are slight changes in the mechanical and physicochemical properties of the investigated wires after their use in the patient's mouth. That is why we do not recommend them for recycling.

Aqueous photocatalytic degradation of selected micropollutants by Pd-modified titanium dioxide in three photoreactor types.

The goals of the present study were to synthesise highly efficient Pd-TiO2 photocatalyst, to characterise its performance in slurry in smaller scale and to investigate its performance in the aqueous photocatalytic oxidation of three antibiotics: doxycycline, sulphamethizole and amoxicillin. The performance of the photocatalyst was evaluated in an open batch slurry reactor equipped with a fluorescent long-wavelength ultraviolet (UVA) lamp (0.2 L). With the fastest degrading doxycycline, experimental research was continued in a fixed-bed continuous flow photoreactor (0.13 L), with the Pd-TiO2 photocatalyst attached to a glass plate, and a medium laboratory-scale three-phase fluidised-bed reactor (2 L) equipped with four fluorescent UVA lamps, with the photocatalyst attached to the surface of expanded clay granules employed as the bed material. While showing very high activity in the batch slurry reactor, far surpassing P25 Aeroxide, the performance of Pd-TiO2 with doxycycline was comparable to P25 in the semi-continuous reactors.

Sb2S3 grown by ultrasonic spray pyrolysis and its application in a hybrid solar cell.

Chemical spray pyrolysis (CSP) is a fast wet-chemical deposition method in which an aerosol is guided by carrier gas onto a hot substrate where the decomposition of the precursor chemicals occurs. The aerosol is produced using an ultrasonic oscillator in a bath of precursor solution and guided by compressed air. The use of the ultrasonic CSP resulted in the growth of homogeneous and well-adhered layers that consist of submicron crystals of single-phase Sb2S3 with a bandgap of 1.6 eV if an abundance of sulfur source is present in the precursor solution (SbCl3/SC(NH2)2 = 1:6) sprayed onto the substrate at 250 °C in air. Solar cells with glass-ITO-TiO2-Sb2S3-P3HT-Au structure and an active area of 1 cm2 had an open circuit voltage of 630 mV, short circuit current density of 5 mA/cm2, a fill factor of 42% and a conversion efficiency of 1.3%. Conversion efficiencies up to 1.9% were obtained from solar cells with smaller areas.

Low-cost plasmonic solar cells prepared by chemical spray pyrolysis.

Solar cells consisting of an extremely thin In2S3/CuInS2 buffer/absorber layer uniformly covering planar ZnO were prepared entirely by chemical spray pyrolysis. Au nanoparticles (Au-NPs) were formed via thermal decomposition of a gold(III) chloride trihydrate (HAuCl4·3H2O) precursor by spraying 2 mmol/L of the aqueous precursor solution onto a substrate held at 260 °C. Current-voltage scans and external quantum efficiency spectra were used to evaluate the solar cell performance. This work investigates the effect of the location of the Au-NP layer deposition (front side vs rear side) in the solar cell and the effect of varying the volume (2.5-10 mL) of the sprayed Au precursor solution. A 63% increase (from 4.6 to 7.5 mA/cm(2)) of the short-circuit current density was observed when 2.5 mL of the precursor solution was deposited onto the rear side of the solar cell.

Modification of light absorption in thin CuInS2 films by sprayed Au nanoparticles.

The chemical spray pyrolysis method was used to deposit CuInS2 (CIS) thin films and Au nanoparticles (NPs) in two configurations: glass/Au-NP layer covered with CuInS2 film (Au-NP/CIS) and glass/CuInS2 films covered with Au-NP layer (CIS/Au-NP). According to X-ray diffraction (XRD), the spray of 2 mM HAuCl4 aqueous solution with a volume of 2.5 to 15 ml onto a glass substrate at 340°C results in metallic Au nanoparticles with a similar mean crystallite size in the range of 30 - 38 nm. The mean crystallite sizes remain in the range of 15 - 20 nm when grown onto a CIS film. The prepared films show plasmonic light absorption with increasing intensity in the spectral range of 500- 800 nm when increasing the volume of HAuCl4 solution sprayed. When compared to bare CIS on glass, the absorptance was increased ca. 4.5 times in the case of glass/Au-NP/CIS and ca. 3 times in the case of glass/CIS/Au-NP configuration. The glass/Au-NP/CIS configuration had an advantage since Au-NP could be embedded without chemically damaging the CIS.

Photoluminescence of spray pyrolysis deposited ZnO nanorods.

Photoluminescence of highly structured ZnO layers comprising well-shaped hexagonal rods is presented. The ZnO rods (length 500-1,000 nm, diameter 100-300 nm) were grown in air onto a preheated soda-lime glass (SGL) or ITO/SGL substrate by low-cost chemical spray pyrolysis method using zinc chloride precursor solutions and growth temperatures in the range of 450-550°C. We report the effect of the variation in deposition parameters (substrate type, growth temperature, spray rate, solvent type) on the photoluminescence properties of the spray-deposited ZnO nanorods. A dominant near band edge (NBE) emission is observed at 300 K and at 10 K. High-resolution photoluminescence measurements at 10 K reveal fine structure of the NBE band with the dominant peaks related to the bound exciton transitions. It is found that all studied technological parameters affect the excitonic photoluminescence in ZnO nanorods.PACS: 78.55.Et, 81.15.Rs, 61.46.Km.