Insight into a pure spinel Co3O4 and boron, nitrogen, sulphur (BNS) tri-doped Co3O4-rGO nanocomposite for the electrocatalytic oxygen reduction reaction

The intricate problems concerning energy require innovative solutions. Herein, we propose a smart composite nano system that can be used in a sustainable and dichotomous manner to resolve energy crises. The current study describes a new way to synthesize a pure spinel cobalt oxide (Co3O4) and boron (B), nitrogen (N), and sulfur (S) tri-doped Co3O4-reduced graphite oxide (rGO) nanocomposite (CBNS). A hydrothermal method has been used for the synthesis of these nanomaterials. The synthesized nanocomposite was characterized by UV-visible spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), X-ray absorption spectroscopy (XAS), and transmission electron microscopy (TEM). The XRD results showed the formation of Co3O4 and B, N, S doped nanocomposite with high purity and crystallinity. XAS analysis elucidates the formation of spinel Co3O4 with tetrahedral and octahedral arrangement of cobalt ions. The peaks at 2.50 Å and 3.07 Å are due to the Co-Co bonding. The electrocatalytic oxygen reduction (ORR) was successfully implemented using these nanocomposites. The electrochemical study exhibits the better activity of the B, N, and S tri-doped Co3O4-rGO nanocomposite due to the mutual effect of B, N and S. The synthesized catalyst has maximum current density of 9.97 mA cm-2 with onset potential (Eonset) of 0.98 V in alkaline medium.

Colloidal Quantum Dots as an Emerging Vast Platform and Versatile Sensitizer for Singlet Molecular Oxygen Generation

Singlet molecular oxygen (1O2) has been reported in wide arrays of applications ranging from optoelectronic to photooxygenation reactions and therapy in biomedical proposals. It is also considered a major determinant of photodynamic therapy (PDT) efficacy. Since the direct excitation from the triplet ground state (3O2) of oxygen to the singlet excited state 1O2 is spin forbidden; therefore, a rational design and development of heterogeneous sensitizers is remarkably important for the efficient production of 1O2. For this purpose, quantum dots (QDs) have emerged as versatile candidates either by acting individually as sensitizers for 1O2 generation or by working in conjunction with other inorganic materials or organic sensitizers by providing them a vast platform. Thus, conjoining the photophysical properties of QDs with other materials, e.g., coupling/combining with other inorganic materials, doping with the transition metal ions or lanthanide ions, and conjugation with a molecular sensitizer provide the opportunity to achieve high-efficiency quantum yields of 1O2 which is not possible with either component separately. Hence, the current review has been focused on the recent advances made in the semiconductor QDs, perovskite QDs, and transition metal dichalcogenide QD-sensitized 1O2 generation in the context of ongoing and previously published research work (over the past eight years, from 2015 to 2023).

Strategy to Probe the Local Atomic Structure of Luminescent Rare Earth Complexes by X-ray Absorption Near-Edge Spectroscopy Simulation Using a Machine Learning-Based PyFitIt Approach

Rare earth(III) β-diketonates are highly remarkable luminophores in the visible spectral region among the rare earth compounds, owing to the efficient contribution from the 4f-4f intraconfigurational transitions. To get detailed structural insight into the RE³⁺ sites (RE = Eu, Gd, and Sm), X-ray absorption near-edge spectroscopy (XANES) can be very potent in probing the local chemical environment around the RE³⁺ ion. In this work, a PyFitIt machine learning approach was employed as a new strategy to simulate the Eu, Gd, and Sm L₃-edge XANES and thereby determine the local atomic structure of the luminescence RE³⁺ β-diketonate complexes, [Eu(tta)₃(H₂O)₂], [C₄mim][Eu(dbm)₄], [Gd(tta)₃(H₂O)₂], and [Sm(dbm)₃(phen)] (tta, 3-thenoyltrifluoroacetonate; dbm, dibenzoylmethane; phen, phenanthroline; and C₄mim, 1-butyl-3-methylimidazolium bromide). Continuous Cauchy wavelet transform validated the PyFitIt calculated XANES by visualizing very efficiently the coordination geometries, composed of O and O/N backscatterers around the RE³⁺ (RE = Eu and Gd) and Sm³⁺ ions, respectively, as a pinkish-red color map in the two-dimensional images of the corresponding complexes. Extended X-ray absorption fine structure fit in Artemis also corroborated the three-dimensional structures generated by PyFitIt XANES simulation for all the compounds. Though, relatively slightly higher bond distance values for the Sm³⁺ complex are due to the higher atomic radius of the Sm³⁺ ion when compared to the Eu³⁺ and Gd³⁺ complexes. Meanwhile, higher Debye-Waller factor (σ²) values for the [C₄mim][Eu(dbm)₄] when compared to the [Eu(tta)₃(H₂O)₂] indicated the structure disorder, owing to the distortion in the local geometry. It is noteworthy that the optical properties, described mainly by the Ω_λ (λ = 2 and 4) 4f-4f intensity parameters, are very sensitive to the local coordination environment around the Eu³⁺ ion. Thus, a close agreement between the experimental and theoretically calculated Ω_λ parameter values confirmed that the PyFitIt calculated square antiprismatic structures are precisely similar to the real structures of the Eu³⁺ complexes.

Emergence of the first XAFS/XRF beamline in the Middle East: providing studies of elements and their atomic/electronic structure in pluridisciplinary research fields

XAFS/XRF is a general-purpose absorption spectroscopy beamline at the Synchrotron-light for Experimental Science and Applications in the Middle East (SESAME), Jordan. Herein, its optical layout is presented along with its powerful capabilities in collecting absorption and fluorescence spectra within a wide energy range (4.7-30 keV). The beamline is equipped with a conventional fixed-exit double-crystal monochromator that allows the collection of an X-ray absorption spectrum within a few minutes in step-by-step mode. An on-the-fly scanning mode will be implemented shortly where the acquisition time will be reduced to less than a minute per scan. The full automation of the beamline allows performing successive measurements under different conditions. The different experimental setups and special features available to users are reported. Examples of XRF and XAFS measurements are presented, showing the performance of the beamline under different standard conditions.

Hydrothermal synthesis and characterization of transition metal (Mn/Fe/Cu) co-doped cerium oxide-based nano-additives for potential use in the reduction of exhaust emission from spark ignition engines

The goal of this work was to synthesize new cerium oxide-based nano-additives to minimise emissions from spark ignition (SI) engines fueled with gasoline blends, such as carbon monoxide (CO), unburned hydrocarbons (HC) and oxides of nitrogen (NO_x). To investigate the effect of transition metal dopants on their respective catalytic oxidation activity, nano-sized CeO₂ catalysts co-doped with Mn, Fe, Cu and Ag ions were successfully produced by a simple hydrothermal technique. The synthesis of nano-catalysts with cubic fluorite geometry was confirmed by XRD data. The addition of transition metal ions to the CeO₂ lattice increased the concentration of structural defects like oxygen vacancies and Ce³⁺ ions, which are advantageous for the catalytic oxidation reaction, as also supported by XAFS and RAMAN analysis. Further, nano-gasoline fuel emission parameters are measured and compared to straight gasoline fuel. The results demonstrated that harmful exhaust pollutants such as CO, HC and NO_x were significantly reduced. The high surface area, better redox characteristics and presence of additional oxygen vacancy sites or Ce³⁺ ions have been linked to the improved catalytic performance of the synthesized catalyst.

Illustrating the synthesis of doped and undoped CeO₂ nanomaterial and its potential application as a promising catalyst for additives to minimize emissions from spark ignition (SI) engines fueled with gasoline blends.

Mitigation of graphene oxide toxicity in C. elegans after chemical degradation with sodium hypochlorite

Graphene oxide (GO) is a promising and strategic carbon-based nanomaterial for innovative and disruptive technologies. It is therefore essential to address its environmental health and safety aspects. In this work, we evaluated the chemical degradation of graphene oxide by sodium hypochlorite (NaClO, bleach water) and its consequences over toxicity, on the nematode Caenorhabditis elegans. The morphological, chemical, and structural properties of GO and its degraded product, termed NaClO-GO, were characterized, exploring an integrated approach. After the chemical degradation of GO at room temperature, its flake size was reduced from 156 to 29 nm, while NaClO-GO showed changes in UV-vis absorption, and an increase in the amount of oxygenated surface groups, which dramatically improved its colloidal stability in moderately hard reconstituted water (EPA medium). Acute and chronic exposure endpoints (survival, growth, fertility, and reproduction) were monitored to evaluate material toxicities. NaClO-GO presented lower toxicity at all endpoints. For example, an increase of over 100% in nematode survival was verified for the degraded material when compared to GO at 10 mg L^-1. Additionally, enhanced dark-field hyperspectral microscopy confirmed the oral uptake of both materials by C. elegans. Finally, this work represents a new contribution toward a better understanding of the links between the transformation of graphene-based materials and nanotoxicity effects (mitigation), which is mandatory for the safety improvements that are required to maximize nanotechnological benefits to society.

Graphene oxide-silver nanoparticle hybrid material: an integrated nanosafety study in zebrafish embryos

This work reports an integrated nanosafety study including the synthesis and characterization of the graphene oxide-silver nanoparticle hybrid material (GO-AgNPs) and its nano-ecotoxicity evaluation in the zebrafish embryo model. The influences of natural organic matter (NOM) and a chorion embryo membrane were considered in this study, looking towards more environmentally realistic scenarios and standardized nanotoxicity testing. The nanohybrid was successfully synthesized using the NaBH₄ aqueous method, and AgNPs (~ 5.8 nm) were evenly distributed over the GO surface. GO-AgNPs showed a dose-response acute toxicity: the LC₅₀ was 1.5 mg L^-1 for chorionated embryos. The removal of chorion, however, increased this toxic effect by 50%. Furthermore, the presence of NOM mitigated mortality, and LC₅₀ for GO-AgNPs changed respectively from 2.3 to 1.2 mg L^-1 for chorionated and de-chorionated embryos. Raman spectroscopy confirmed the ingestion of GO by embryos; but without displaying acute toxicity up to 100 mg L^-1, indicating that the silver drove toxicity down. Additionally, it was observed that silver nanoparticle dissolution has a minimal effect on these observed toxicity results. Finally, understanding the influence of chorion membranes and NOM is a critical step towards the standardization of testing for zebrafish embryo toxicity in safety assessments and regulatory issues.

Effect of the Albumin Corona on the Toxicity of Combined Graphene Oxide and Cadmium to Daphnia magna and Integration of the Datasets into the NanoCommons Knowledge Base

In this work, we evaluated the effect of protein corona formation on graphene oxide (GO) mixture toxicity testing (i.e., co-exposure) using the Daphnia magna model and assessing acute toxicity determined as immobilisation. Cadmium (Cd2+) and bovine serum albumin (BSA) were selected as co-pollutant and protein model system, respectively. Albumin corona formation on GO dramatically increased its colloidal stability (ca. 60%) and Cd2+ adsorption capacity (ca. 4.5 times) in reconstituted water (Daphnia medium). The acute toxicity values (48 h-EC50) observed were 0.18 mg L-1 for Cd2+-only and 0.29 and 0.61 mg L-1 following co-exposure of Cd2+ with GO and BSA@GO materials, respectively, at a fixed non-toxic concentration of 1.0 mg L-1. After coronation of GO with BSA, a reduction in cadmium toxicity of 110 % and 238% was achieved when compared to bare GO and Cd2+-only, respectively. Integration of datasets associated with graphene-based materials, heavy metals and mixture toxicity is essential to enable re-use of the data and facilitate nanoinformatics approaches for design of safer nanomaterials for water quality monitoring and remediation technologies. Hence, all data from this work were annotated and integrated into the NanoCommons Knowledge Base, connecting the experimental data to nanoinformatics platforms under the FAIR data principles and making them interoperable with similar datasets.

Impact of Tb3+ ion concentration on the morphology, structure and photoluminescence of Gd2 O2 SO4 :Tb3+ phosphor obtained using thermal decomposition of sulfate hydrate

Gadolinium oxysulfate doped with terbium (Gd₂ O₂ SO₄ :Tb³⁺ ; 0.1, 1.0, and 10.0 mol%) materials were obtained using thermal decomposition from sulfate hydrate under a dynamic air atmosphere and between 1320-1400 K. The materials were characterized using Fourier transform infrared spectroscopy, thermogravimetric/derivative thermogravimetric investigations and X-ray powder diffraction patterns. The Tb₂ O₂ SO₄ compound was obtained at 1300 K and was used to compare thermal stability and photoluminescence behaviour with that of Gd₂ O₂ SO₄ :Tb³⁺ (0.1, 1.0, and 10.0 mol%). Magnetic susceptibility measurements indicated the presence of 15% Tb⁴⁺ phases within Tb₂ O₂ SO₄ . The materials were excited at 377 nm and displayed green narrow lines with the strongest emission peak at 545.5 nm due to the ⁵ D₄ →⁷ F₅ transition of Tb³⁺ ions. Brightness of terbium-activated gadolinium oxysulfate phosphors was enhanced with increase in the concentration of Tb³⁺ . Detailed analysis of spectroscopic properties of materials under investigations revealed efficient Gd₂ O₂ SO₄ to Tb³⁺ and Tb³⁺ to Tb³⁺ energy transfers. Increase in dopant concentration led to the enhancement of ⁵ D₄ →⁷ F_J emission intensity and reduction of ⁵ D₃ →⁷ F_J emission intensity via cross-relaxation mechanisms. Distribution of particle size was increased by controlling dopant concentration in the host lattice. Obtained results confirmed that these materials could be applied potentially in field emission display devices and light-emitting diodes.

Toxicity assessment of TiO2-MWCNT nanohybrid material with enhanced photocatalytic activity on Danio rerio (Zebrafish) embryos

The increasing production and use of nanomaterials is causing serious concerns about their safety to human and environmental health. However, the applications of titanium dioxide nanoparticles (TiO₂NP) and multiwalled carbon nanotubes (MWCNT) hybrids has grown considerably, due to their enhanced photocatalytic efficiency. To our knowledge, there are no reports available to the scientific community about their toxicity. In this work, we perform a toxicity assessment of TiO₂NP and TiO₂-MWCNT nanohybrid materials using Zebrafish embryos standardized 96 h early life stage assay, under different exposure conditions (with and without UV light exposure). After exposure the parameters assessed were acute toxicity, hatching rate, growth, yolk sac size, and sarcomere length. In addition, μ-probe X-ray fluorescence spectroscopy (µ-XRF) was employed to observe if nanoparticles were uptaken by zebrafish embryos and consequently accumulated in their organisms. Neither TiO₂NP nor TiO₂-MWCNT nanohybrids presented acute toxicity to the zebrafish embryos. Moreover, TiO₂NP presents sublethal effects for total length (with and without UV light exposure) on the embryos. This work contributes to the understanding of the potential adverse effects of the emerging nanohybrid materials towards safe innovation approaches in nanotechnology.

Efficient multicolor tunability of ultrasmall ternary-doped LaF3 nanoparticles: energy conversion and magnetic behavior

Luminescence-tunable multicolored LaF₃:xCe³⁺,xGd³⁺,yEu³⁺ (x = 5; y = 1, 5, 10, and 15 mol%) nanoparticles have been synthesized via a low cost polyol method. Powder X-ray diffraction and high-resolution transmission electron microscopy studies confirm the hexagonal phase of the LaF₃:xCe³⁺,xGd³⁺,yEu³⁺ nanophosphors with average sizes (oval shape) ranging from 5 to 7 nm. Energy-dispersive X-ray spectroscopy analyses show the uniform distribution of Ce³⁺, Gd³⁺, and Eu³⁺ dopants in the LaF₃ host matrix. The photoluminescence spectra and electron paramagnetic resonance measurements guarantee the presence of Eu²⁺, corroborated through DC susceptibility measurements of the samples displaying paramagnetic behavior at 300 K, whereas weak ferromagnetic ordering is shown at 2 K. The non-radiative energy transfer processes from the 4f(²F_5/2) → 5d state (Ce³⁺) to the intraconfigurational 4f excited levels of rare earth ions and simultaneous emissions in the visible region from the 4f⁶5d¹ (Eu²⁺) and ⁵D₀ (Eu³⁺) emitting levels, leading to overlapped broad and narrow emission bands, have been proclaimed. The energy transfer mechanism proposes involvement of the Gd³⁺ ion sub-lattice as the bridge and finally trapping by Eu^2+/3+, upon excitation of the Ce³⁺ ion. The calculation of experimental intensity parameters (Ω_2,4) has been discussed and the highest emission quantum efficiency (η = 85%) of the Eu³⁺ ion for the y = 10 mol% sample is reported. The advantageous existence of the Eu²⁺/Eu³⁺ ratio along with variously doped nanomaterials described in this work, results in tunable emission color in the blue-white-red regions, highlighting the potential application of the samples in solid-state lighting devices, scintillation devices, and multiplex detection.

Dissociated spatial patterning of gap junctions and cell adhesion junctions during postnatal differentiation of ventricular myocardium

Nonuniformity in the spatial patterning of gap junctions between heart muscle cells is now recognized as an important determinant of electromechanical function in working myocardium. Breakdown of the normal geometry of electrical intercellular connectivity in diseased myocardium correlates with reentry, arrhythmia, and conduction disturbance. The developmental mechanism(s) that determines this precise spatial order in gap junction organization in normal myocardium is at present unknown. To examine this question, we have used immunoelectron and immunoconfocal microscopy to analyze the spatial distributions of gap junctional (connexin43), desmosomal (desmoplakin), and adherens junctional (N-cadherin) components during maturation of rodent and canine left ventricular myocardium. In rats, a striking divergence in the distribution of gap junctions and cell adhesion junctions emerged within the first 20 days of postnatal life. It was found that although gap junctions initially demonstrated dispersed distributions across myocyte cell membranes, desmosomes and adherens junctions showed more rapid polarization toward cell termini (ie, nascent intercalated disks) after birth. Over subsequent postnatal development (20 to 90 postnatal days), gap junctions became progressively concentrated in these cell adhesion junction-rich zones of membrane. Quantitative analyses of this process in a series of rats aged 15 embryonic and 1, 5, 10, 20, 40, 70, and 90 postnatal days indicated that significantly higher levels (P < .01) of N-cadherin and desmoplakin than of connexin43 were immunolocalized to cell termini by as early as postnatal day 5. Although all three junctions types showed increasing polarization to myocyte termini with development, variation between junctions remained significant (P < .05) at all times points between 5 and 70 postnatal days. Only at 90 postnatal days, when the animals were nearly full grown, did the proportions of gap junction, desmosome, and adherens junction at intercalated disks become statistically similar (P > .05). Examination of myocardium from 1- and 3-month-old canines revealed that related differential changes to the spatiotemporal distribution of intercellular junctions occurred during postnatal maturation of the dog heart, suggesting that the process was not rodent specific. It is concluded that this progressive change in the organization and pattern of association between gap junctions and cell adhesion junctions is likely to be an important factor in maturation of electromechanical function within the mammalian heart.