Glasses based on fluorides of metals of the I–IV groups: Synthesis,properties, and application

A review of the current studies on the synthesis, glass formation, structure, and optical properties of fluoride glasses in various glass-forming systems is presented. With a view to form and select active optical media for broad spectrum lasers, extensive studies are conducted to clarify the fluorescence mechanisms in fluoride glasses of various compositions doped with REE activators. Studies on obtainment of REE-activated fluoride transparent glass ceramics are discussed. Promising directions of practical application of such materials in optics and laser technology are shown.     

Structural and optical properties of inorganic–organic hybrid material of acetanilide tetrachloromercurate(II)

The crystal growth of acetanilide tetrachloromercurate(II), an inorganic–organic hybrid derivative has been achieved by solution growth through slow cooling method. The X-ray diffraction structural analysis of the hybrid material results that the compound exist in orthorhombic space group P2₁2₁2₁ with lattice parameters; a?=?13.111(2) ?, b?=?11.311(2) ?, c?=?8.355(6) ?, α?=?β?=?γ?=?90° and unit cell volume?=?1436.24 ?³. The fourier transform infrared spectroscopy profile shows that the C–C and C–N stretching modes of acetanilide ring and the observed spectra falls in mid-infrared range υ(526–2850) cm^?1. The field emission scanning electron microscope image confirms that the hybrid material has a prismatic shape with an average granular size of ~25 nm. The energy dispersive X-ray spectroscopy analyzes the elemental proportions of the hybrid materials. Transmission electron microscopy image shows the narrow distribution of nano-spatial agglomeration of secondary interactions in inorganic–organic particles. The optical band gap (Eg?=?3.75 eV) as calculated by linear fit profile of Tauc plot for allowed transition predicts that the hybrid material has potential applications in solar cells, electronic and opto-electronic devices.     

Relation between structure and mechanical properties (elastoplastic and fracture behavior) of hybrid organic–inorganic coating

The mechanical properties of various inorganic organic films were studied and compared in order to investigate the relation between structural modifications and the mechanical behavior. Films were prepared by a sol–gel process and spin-coated on silicon substrate. The organic–inorganic hybrid is composed of a mixture of colloidal silica and organosiloxane precursors. The functionality of the organosiloxane and the nature of its organic part have been modified to obtain a structural change. Mechanical properties were studied using nanoindentation. Analysis of the strength evolution as a function of depth of indentation shows the layer hardness and elastic modulus. Moreover, coating and interface toughness and residual stresses were determined by a time resolved study of energy dissipation during indentation. The structural changes were determined using liquid and solid ²⁹Si NMR spectroscopy. Quantity of partially and fully condensed species in the deposited sol and final solid are discussed in relation to the mechanical properties.     

Enhanced visible-light-driven photocatalytic and dielectric properties of inorganic–organic hybrid (NiO-g-C3N4) nanocomposite for degradation of rhodamine blue

In this work, NiO NP’s was synthesized by the hydrothermal method and g-C₃N₄ nanosheets prepared via thermal treatment method, then NiO/g-C₃N₄ (80:20 wt%) was successfully achieved by a simple mixing method. The optimized NiO/g-C₃N₄ hybrid nanocomposite was acting as an efficient photocatalyst for degradation of rhodamine blue (RhB) under visible light irradiation. As prepared pristine (NiO and g-C₃N₄) and inorganic–organic hybrid nanocomposite (NiO/g-C₃N₄) materials were characterized by various spectral techniques. From XRD and TEM results, the NiO nanoparticles before and after loading on g-C₃N₄ surface retained the crystalline phase(fcc) and spherical structure, indicating the synthesis strategy is promising which does not alter its composition and morphology. The adsorption edge of NiO/g-C₃N₄ was shifted towards lower energy region when compared with pure NiO and g-C₃N₄ alone reflects that the resulting nanocomposite has larger adsorption efficiency under visible light and thus increases the charge separation efficiency during degradation process. The percentage of degration of RhB for NiO, g-C₃N₄ and NiO/g-C₃N₄ hybrid is calculated to be 81, 89 and 94% indicates the effective degradation illuminated under visible light. The enhanced photocatalytic activity of NiO/g-C₃N₄ photocatalyst probably recognized for the successful interfacial charge separation between NiO and g-C₃N₄ thus avoids recombination of photoexcited electron–hole pair.

     

Non-cytotoxic organic–inorganic hybrid bioscaffolds: An efficient bedding for rapid growth of bone-like apatite and cell proliferation

Synthesis and characterization of organic–inorganic macroporous hybrid scaffolds were investigated. The materials were prepared by combining 2-hydroxyethylmethacrylate (HEMA) and triethoxyvinylsilane (TEVS) chemically modified by Ca^2 + and PO₄^3 ? ions via sol–gel route. In this study we have constructed a sugar-based cracks-free three-dimensional (3D) network with interconnected porous architecture within the range of 150–300 μm and rough topography. The obtained results revealed that both topography and composition of prepared materials allow rapid growth of the bone-like apatite (HAp) layer on their surface after soaking in biological medium. Preliminary studies have shown that hybrids covered by HAp are non-cytotoxic and allow cell proliferation that make them a promising scaffolds in the field of bone regenerative medicine. The materials were mainly characterized by powder X-ray diffraction analysis (PXRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy–energy-dispersive spectroscopy (SEM–EDS) and transmission electron microscopy–energy-dispersive spectroscopy (TEM–EDS).     

Study on the structural formation of new useful multiporous material ‘nano–meso ZSM-5’ and its application in producing biofuel

New ‘nano–meso ZSM-5’ (NM-ZSM-5) material was successfully synthesised by hydrothermal treatment using silica derived from rice husk. The synthesis of the material involves two steps of crystallisation, including the formation of ZSM-5 zeolite seed and mesoporous structure. The effect of crystallisation time on the formation of mesoporous structure was studied in the range 0–40?h. Samples were characterised by X-ray diffraction, infrared spectroscopy, transmission electron microscopy, Brunauer–Emmett–Teller and ²⁷Al-NMR methods. The results show that the best time for crystallisation is 14?h. The synthesised material has a multiporous structure, including micropore system of ZSM-5 zeolite, mesopore system of MCM-41 and another pore system which has a diameter in the range 10–50?nm (mesoporous system) due to the burning of organic compounds that remain in the material during the calcination process. In addition, the synthesised NM-ZSM-5 achieves crystallinity of approximately 100%. The catalytic performance of NM-ZSM-5 material was evaluated by the catalytic cracking reaction to produce biofuel from vegetable oil sludge. The research proved that NM-ZSM-5 is one of the most suitable catalysts for this process. The catalytic cracking reaction over NM-ZSM-5 yields products that are similar to those of the petroleum cracking process, such as dry gases, liquefied petroleum gas, gasoline, light cycle oil and heavy cycle oil.     

Thermal stability and crystallization behaviour of amorphous Zr-M-Si (M=IV–VIII group transition metals) alloys

By rapidly quenching with a melt-spinning apparatus, it has been possible to produce ductile amorphous single-phase ternary Zr_85–x M _x Si₁₅ (M=IV–VIII group transition metals) alloys in wide composition ranges. The crystallization temperature, activation energy for crystallization and hardness increase significantly only with the addition of group V and VI elements (V, Nb, Ta, Cr, Mo and W). Such a solute element effect could be interpreted on the basis that the chemical bonding between the solute elements and silicon is stronger for the group V and VI elements than for the other group elements. Crystallization studies of the amorphous Zr₈₅Si₁₅ and Zr₆₅Nb₂₀Si₁₅ alloys have been carried out through transmission electron microscopy and differential scanning calorimetry techniques. The binary alloy crystallizes by the uniform precipitation of b c c-Zr over the entire area of the amorphous matrix followed by the appearance of the metastable b c tetragonal Zr₃Si compound from the remaining amorphous phase. On the other hand, the ternary alloy transforms by the simultaneous precipitation of-Zr(Nb) and b c tetragonal Nb₃Si. The-Zr and Zr₃Si phases were found to be in metastable states, the equilibrium structure being a mixture of-Zr and Zr₄Si compound in the binary alloy.     

Influence of punch geometry (head-flat diameter) and tooling type (‘B’ or ‘D’) on the physical–mechanical properties of formulation tablets

The presented study assessed the influence of punch geometry (head-flat [HF] diameter) and tooling type (‘B’ or ‘D’) on the physical–mechanical properties of tablets prepared by direct-compression of two guaifenesin (25% or 40% w/w) formulations. Tablets of both formulations were prepared on instrumented, single-layer, rotary tablet press using 10?mm, flat-faced, ‘B’ or ‘D’-type tooling with different HF diameters, and compression forces (CF) ranging from 5 to 25?kN with 5?kN increments. The tablets were evaluated for dimensions, weight variation, tensile strength (TS), friability, and capping index. In general, tablets prepared using ‘D’ tooling showed a significantly (p?<?0.05) higher TS compared to those prepared using ‘B’ tooling, likely due to higher dwell-times associated with ‘D’ tooling. Formulations containing 25% w/w guaifenesin showed a significantly (p?<?0.05) higher TS compared to those containing 40% w/w guaifenesin, at given compression CF, punch geometry, or tooling type. This could be due to the higher ratio of Prosolv^® SMCC contributing to the compressibility. For both formulations compressed using ‘B’ tooling, differences in TS profiles were observed between different HF tooling. The TS of these tablets increased significantly with increasing HF diameter. For formulations compressed using ‘D’ tooling, this trend was observed only up to a CF of 15?kN, beyond which the TS plateaued, possibly due to work-hardening of the formulation at higher CF. These formulations also exhibited capping at CF above 15?kN and with higher HF diameters. The study showed a significant influence of punch geometry and tooling type on the physical properties of tablets.     

Influence of the international collaboration in the field of metric studies of science and technology: the case of Mexico (1971–2018)

Scientometrics - We perform a bibliometric analysis of the research production and impact of Mexican scholars involved in the area of metric studies of science and technology in the period...     

Environmental impact of toxic metals and metalloids from the Muñón Cimero mercury-mining area (Asturias, Spain)

This paper presents the results of the sampling surveys carried out in order to evaluate the environmental problems associated to La Soterraña, an abandoned Hg mine in Asturias, north of Spain. In particular, this paper overviews the impact of mining and metallurgical activities on terrestrial and aquatic environments. The wastes generated during the mining activity (ore extraction and processing) and later accumulated on the ground, contain great amount of sulphides, becoming potentially acid-generating. Consequently, the mobility of heavy metals and other ecotoxic elements is enhanced. Wastes are generally located close to watercourses and on very steep hillsides, where they are exposed to oxidative weathering, posing a significant risk due to the release of ecotoxic elements to the environment. Background levels were determined at sites, which had not been directly affected by mercury mining. A multielemental geochemical study of mining wastes, soils, stream sediments, water and air samples collected in the area of influence of the old mining and metallurgical works was carried out. Total Hg and As concentrations in soils reach values up to 502 and 19,940 mg kg⁻¹, respectively, 500 and 2000 times higher than the local background levels. The effects of mining seem to be intense both in waters and stream sediments, as well as in the local atmosphere, whose Hg content is 10 times higher than the background level in the area. Therefore, the target carcinogenic risk was exceeded for As and Hg in La Soterraña site.     

Synthesis,crystal structure,photoluminescence and dielectric properties of a new organic–inorganic compound: tetrachlorocadmate (II) 2.2′-bipyridinium

Single crystals of a new organic–inorganic compound (C₁₀H₁₀N₂) CdCl₄ were grown by the slow evaporation technique and characterized by X-ray diffraction, Hirshfeld surface, Infrared absorption, Solid state ¹³C NMR, photoluminescence (PL) properties, differential scanning calorimetry (DSC) and dielectric measurements. The title compound belongs to the monoclinic space group P2₁/c with the following unit cell parameters: a?=?7.29420(1), b?=?13.9206(3), c?=?14.3880(3) Å, β?=?100.247(2)° and Z?=?4. The structure can be described by the alternation of two different cationic-anionic layers. It consists of isolated [CdCl₄]^2? tetrahedral anions and 2.2′ bipyridinium (C₁₀H₁₀N₂)²⁺ cations, which are connected via N–H?Cl hydrogen bonds. The Hirshfeld surface analysis was conducted to investigate intermolecular interactions and associated 2D fingerprint plots, revealing the relative contribution of these interactions in the crystal structure quantitatively. Furthermore, the room temperature infrared (IR) spectrum of the title compound was recorded and analyzed on the basis of detailed vibrational studies found in the literature; the detailed assignment confirms the presence of the organic groups. Solid state ¹³C NMR spectrum shows four signals, confirming the solid state structure determined by X-ray diffraction. Besides, photoluminescence measurements showed a strong emission line at 2.95 eV associated with radiative recombinations of excitons confined within the [CdCl₄]^2? which were investigated at room temperature. Finally, the thermal analysis studies were performed, and phase transition was found in the temperature range between 300 and 550 K, while the electrical measurements were performed to discuss the phase-transition mechanism.     

Keggin type inorganic–organic hybrid material containing Mn(II) monosubstituted phosphotungstate and S-(+)-sec-butyl amine: Synthesis and characterization

A new inorganic–organic POM-based hybrid material comprising Keggin type mono manganese substituted phosphotungstate and enantiopure S-(+)-sec-butyl amine was synthesized in an aqueous media by simple ligand substitution method. The synthesized hybrid material was systematically characterized in solid as well as solution by various physicochemical techniques such as elemental analysis, TGA, UV–vis, FT-IR, ESR and multinuclear solution NMR (³¹P, ¹H, ¹³C). The presence of chirality in the synthesized material was confirmed by CD spectroscopy and polarimeter. The above study reveals the attachment of S-(+)-sec-butyl amine to Keggin type mono manganese substituted phosphotungstate through N → Mn bond. It also indicates the retainment of Keggin unit and presence of chirality in the synthesized material. An attempt was made to use the synthesized material as a heterogeneous catalyst for carrying out aerobic asymmetric oxidation of styrene using molecular oxygen. The catalyst shows the potential of being used as a stable recyclable catalytic material after simple regeneration without significant loss in conversion.     

An analytical model for number of fibre–fibre contacts in paper and expressions for relative bonded area (RBA)

This paper proposes an analytical model for calculating the number of fibre–fibre contacts per unit fibre length from the cross-sectional dimensions of the fibres in a sheet and sheet density. This model has been verified with data of the number of fibre–fibre contacts measured directly in handsheets. The measured fibre–fibre contacts in the handsheets were classified into full and partial contacts. The model best fits this data when 1.5 partial contacts are equated to one full contact. A plot of measured versus predicted equivalent full contacts produced a linear correlation with a slope of 0.99 and correlation coefficient of R ²  = 0.93. The model was used to derive expressions for the fraction of the available fibre surface, which is bonded to other fibres, a quantity called the Relative Bonded Area (RBA). The validity of the model was checked using experimental data for RBA. RBA was determined both by nitrogen adsorption ( ) and by scattering coefficient (RBA_sc). The extrapolation method of Ingmanson and Thode to determine S ₀, the scattering coefficient of an unbonded sheet, proved to be inaccurate. We estimated S ₀ for some samples from their linear relationship between scattering coefficient and nitrogen adsorption. The new model accurately predicted both and RBA_sc.     

The knowledge domain of the academy of international business studies (AIB) conferences: a longitudinal scientometric perspective for the years 2006–2011

Conferences play a major role for the development of scientific domains. While journal and article contributions in the field of international business (IB) are a general and well researched area of scientometric studies, conferences are not. The absence of a systematic assessment of international business conferences as a reference to the collective status of the Academy of International Business (AIB) community is astonishing. Whatever reasons are accountable for that fact, this paper starts to fill that gap. It establishes a knowledge network composed of the last six years AIB conferences. We collected all the contributions in full text with their abstracts and keywords from 2006 to 2011. All the data have been organized in a data system and we used the information-theoretic clustering method which allows different analytical views through the entire knowledge corpus. The results indicate significant statistical differences between topic modules and keyword threads of the yearly conferences. There are three keywords which dominate as a leitmotif between 2006 and 2011, but the detailed structure changes from conference to conference significantly.     

High carrier mobility and remarkable photovoltaic performance of two-dimensional Ruddlesden–Popper organic–inorganic metal halides (PA)2(MA)2M3I10 for perovskite solar cell applications

Two-dimensional Ruddlesden–Popper (2DRP) metal halides have attracted extensive attention in photovoltaic applications due to their high stability, low self-doping levels and long-lived free carriers. Among them, (PA)₂(MA)₂Pb₃I₁₀ presents itself as a superior candidate, demonstrating greater moisture resistance and improved heat and light stability over many other 2DRP metal halides. This study takes on the opportunity to search for lead-free alternatives by investigating the optoelectronic and carrier transport properties, as well as the photovoltaic performance of such (PA)₂(MA)₂M₃I₁₀ type metal halides as the photovoltaic absorber, where M = Pb, Cd, Cr, Cu, Ge, Mn, Ni, Sn, Yb, Zn. Our results indicate that the bandgap of (PA)₂(MA)₂M₃I₁₀ can be tuned to the optimum photovoltaic application range of 0.9–1.6 eV, along with improved optical and enhanced photo-response capacity, when Sn, Cd, Mn, Ge, and Zn are used to replace Pb. In particular, (PA)₂(MA)₂Zn₃I₁₀ possesses the largest Stokes shift and Huang-Rhys factor, while showing the best photoluminescence tendency and broadest emission nature. (PA)₂(MA)₂Ge₃I₁₀ displays the most excellent of carrier transport capacities with high mobilities of 73 cm² V⁻¹ s⁻¹ and 43 cm² V⁻¹ s⁻¹ for electron and hole carriers, respectively, which are even comparable to that of 3D counterparts. Furthermore, (PA)₂(MA)₂Zn₃I₁₀ is predicted to have the highest power conversion efficiency of 23.36% based on an empirical energy loss (0.5 eV), which is quite close to the Shockley–Queisser limit, thereby featuring it as a suitable absorber for photovoltaic applications. These findings shed light on new strategies for designing and developing lead-free 2DRP metal halides targeted at future applications in photovoltaic solar cell devices.     

How meaningful are risk determinations in the absence of a complete dataset? Making the case for publishing standardized test guideline and ‘no effect’ studies for evaluating the safety of nanoparticulates versus spurious ‘high effect’ results from single investigative studies

Abstract

A recent review article critically assessed the effectiveness of published research articles in nanotoxicology to meaningfully address health and safety issues for workers and consumers. The main conclusions were that, based on a number of flaws in study designs, the potential risk from exposures to nanomaterials is highly exaggerated, and that no ‘nano-specific’ adverse effects, different from exposures to bulk particles, have been convincingly demonstrated. In this brief editorial we focus on a related tangential issue which potentially compromises the integrity of basic risk science. We note that some single investigation studies report specious toxicity findings, which make the conclusions more alarming and attractive and publication worthy. In contrast, the standardized, carefully conducted, ‘guideline study results’ are often ignored because they can frequently report no adverse effects; and as a consequence are not considered as novel findings for publication purposes, and therefore they are never considered as newsworthy in the popular press. Yet it is the Organization for Economic Cooperation and Development (OECD) type test guideline studies that are the most reliable for conducting risk assessments. To contrast these styles and approaches, we present the results of a single study which reports high toxicological effects in rats following low-dose, short-term oral exposures to nanoscale titanium dioxide particles concomitant with selective investigative analyses. Alternatively, the findings of OECD test guideline 408, standardized guideline oral toxicity studies conducted for 90 days at much higher doses (1000 mg kg^?1) in male and female rats demonstrated no adverse effects following a very thorough and complete clinical chemical, as well as histopathological evaluation of all of the relevant organs in the body. This discrepancy in study findings is not reconciled by the fact that several biokinetic studies in rats and humans demonstrate little or no uptake of nanoscale or pigment-grade TiO₂ particles following oral exposures. We conclude that to develop a competent risk assessment profile, results derived from standardized, guideline-type studies, and even ‘no effect’ study findings provide critically useful input for assessing safe levels of exposure; and should, in principle, be readily acceptable for publication in peer-reviewed toxicology journals. This is a necessary prerequisite for developing a complete dataset for risk assessment determinations.     

How meaningful are risk determinations in the absence of a complete dataset? Making the case for publishing standardized test guideline and ‘no effect’ studies for evaluating the safety of nanoparticulates versus spurious ‘high effect’ results from single investigative studies

A recent review article critically assessed the effectiveness of published research articles in nanotoxicology to meaningfully address health and safety issues for workers and consumers. The main conclusions were that, based on a number of flaws in study designs, the potential risk from exposures to nanomaterials is highly exaggerated, and that no ‘nano-specific’ adverse effects, different from exposures to bulk particles, have been convincingly demonstrated. In this brief editorial we focus on a related tangential issue which potentially compromises the integrity of basic risk science. We note that some single investigation studies report specious toxicity findings, which make the conclusions more alarming and attractive and publication worthy. In contrast, the standardized, carefully conducted, ‘guideline study results’ are often ignored because they can frequently report no adverse effects; and as a consequence are not considered as novel findings for publication purposes, and therefore they are never considered as newsworthy in the popular press. Yet it is the Organization for Economic Cooperation and Development (OECD) type test guideline studies that are the most reliable for conducting risk assessments. To contrast these styles and approaches, we present the results of a single study which reports high toxicological effects in rats following low-dose, short-term oral exposures to nanoscale titanium dioxide particles concomitant with selective investigative analyses. Alternatively, the findings of OECD test guideline 408, standardized guideline oral toxicity studies conducted for 90 days at much higher doses (1000 mg kg⁻¹) in male and female rats demonstrated no adverse effects following a very thorough and complete clinical chemical, as well as histopathological evaluation of all of the relevant organs in the body. This discrepancy in study findings is not reconciled by the fact that several biokinetic studies in rats and humans demonstrate little or no uptake of nanoscale or pigment-grade TiO₂ particles following oral exposures. We conclude that to develop a competent risk assessment profile, results derived from standardized, guideline-type studies, and even ‘no effect’ study findings provide critically useful input for assessing safe levels of exposure; and should, in principle, be readily acceptable for publication in peer-reviewed toxicology journals. This is a necessary prerequisite for developing a complete dataset for risk assessment determinations.     

Effect of ‘Zn’ substitution on structural,morphological, magnetic and optical properties of Co–Zn ferrite nanoparticles for ferrofluid application

Journal of Materials Science: Materials in Electronics - The Co1?xZnxFe2O4 (Co–Zn) ferrite nanoparticles with x varying from 0.0 to 0.4 have been manufactured by facile chemical...