Geometries and stabilities of transition metals doped perfect and Stone–Wales defective armchair (5,5) boron nitride nanotubes

The binding abilities of transition metals (TMs) (TMs?=?Ni, Pd, and Pt) on perfect and Stone?CWales (SW) defective armchair (5,5) single-walled boron nitride nanotubes (BNNTs) were investigated using density functional theory method at the B3LYP/LanL2DZ level. The geometrical parameters and electronic properties of all BNNTs doped with TM atoms are reported. The strongest binding energy of Ni doped on SW defective BNNT of ?91.87?kcal/mol was found. The binding abilities of the most stable of TMs on the BNNTs are in order: Ni/SW2?CBNNT(Z_N)?>?Pt/SW2?CBNNT(Z_B)?>?Pd/SW2?CBNNT(Z_B). In all case, energy gaps of MTs doped perfect and defective BNNTs are obviously lower than their undoped nanotubes.     

DFT study of chemical mechanism of pre-SERS spectra in Pyrazine–metal complex and metal–Pyrazine–metal junction

The chemical mechanism of Normal Raman Scattering (NRS) and pre-surface enhanced Raman scattering (pre-SERS) spectra for Pyrazine–Ag₂ complex, Ag₂–Pyrazine–Ag₂ junction and Ag₂–Pyrazine–Au₂ junction were investigated with density functional theory (DFT) and charge difference densities (CDDs) for the first time. The NRS intensities of the above three structures enhanced obviously relative to isolated Pyrazine and the enhancement mechanism was confirmed to be static chemical enhancement. The pre-SERS intensities of the above three structures enhanced evidently compared to corresponding NRS intensities, and the enhancement mechanism was confirmed to charge transfer (CT) resonance Raman enhancement. The largest enhanced orders of NRS and pre-SERS intensities among the three structures were up to 10³ and 10⁵, respectively. Compared the intensity of pre-SERS with corresponding intensity of NRS spectra, the enhancement effect of Pyrazine–Ag₂ complex was larger than the others. Intramolecular and intermolecular CT on resonant electronic transition were described by CDDs.     

Preparation and proton conductivity evaluation of a silicate gel composite doped with a metal–Schiff-base–POM-MOF

A silica gel composite (denoted as 1–SG) doped with a proton-conductive metal–Schiff-base–POM-MOF, {[Cu₃(L)₂(H₂O)₄][Cu(DMF)₄(SiW₁₂O₄₀)]·9H₂O} _n (1) (where L is N, N′-bis[1-(2-methoxyphenol-6-yl)-methylidene] hydrazine hydrate, DMF is dimethyl formamide, POM-MOF is polyoxometalates-based metal–organic framework), was prepared by sol–gel method. The structure of as-synthesized 1–SG was confirmed by infrared spectrometry and X-ray powder diffraction, and its proton conductivity was calculated based on electrochemical impedance spectroscopic measurement. It was found that the structural characteristics of complex 1 are retained successfully in the silica gel skeleton of as-prepared 1–SG. Besides, though 1–SG contains just 6.25 wt% complex 1, it exhibits good proton conductivities of as much as 1.51 × 10^?3–1.26 × 10^?2 S cm^?1 in the temperature range of 25–100 °C under a relative humidity of 98 %; and in particular, it shows better proton conductivity than both complex 1 and silica gel at the same conditions, due to the presence of a large number of micropores and mesopores filled with “liquid”.     

Extended investigation of LiOH–LiBr binary system for high-temperature thermal energy storage applications

Journal of Thermal Analysis and Calorimetry - LiOH–LiBr binary system is thoroughly investigated by means of DSC and XRD experimental analysis. Observed discrepancies compared to previous...     

Synthesis,structure and reactivity of complexes containing a transition metal–bismuth bond

The transition metal chemistry of bismuth has attracted significant interest since the 1970s. The low cost and high abundance of bismuth(III) reagents, such as the trihalides, makes them ideal starting materials and the size of the bismuth centre allows three- and higher-coordinate complexes to be synthesised, in which the bismuth atom is linked to one or more transition metal fragments. The ability to vary these metal fragments gives access to a plethora of available structures, with cyclopentadienylcarbonyl, metal carbonyl and sandwich compounds of bismuth in existence. Significant recent study has focused on applications in catalysis, where bismuth species can act as cross-coupling agents in carbon–carbon, carbon–nitrogen and carbon–oxygen bond forming reactions. Another striking feature is the variation in bonding situations that can be observed when studying the organometallic chemistry of bismuth. For example, dative and covalent interactions have been reported, in addition to cases of dibismuth acting as a two-, four- or six-electron donating ligand. This review aims to demonstrate the multi-faceted nature of the transition metal chemistry of bismuth and provide a detailed coverage of this topic.     

“Aggregation-induced emission” of transition metal compounds: Design,mechanistic insights,and applications

In the last decades, compounds with ‘Aggregation-Induced Emission’ (AIE), which are weakly or non-emissive at all in solution but exhibit a strong luminescence in aggregated states, have emerged as an extraordinary breakthrough in the field of luminescent materials, allowing to circumvent ‘Aggregation Caused Quenching’ (ACQ), which in many cases prevents the development of efficient solid-state materials for optoelectronic applications.Since the discovery of AIE, many AIE-active materials have been developed, most of them composed of organic molecules, and thus fluorescent in nature. Although a wide range of applications such as bioimaging, sensing, multi-stimuli responsive materials, and optoelectronic devices have been proposed for this new class of materials, triplet harvesting phosphorescent materials have much longer lifetimes as compared to their singlet harvesting analogues, and for this particular reason, the development of AIE-active phosphorescent materials seems to be a promising strategy from the applications point of view. In this respect, the synthesis of new AIE-active systems including heavy metals that would facilitate the population of low-lying excited triplet states via spin-orbit coupling (SOC), for which the strength increases as the fourth power of atomic number, i.e. Z⁴, is highly desirable. This review covers the design and synthetic strategies used to obtain the AIEgens reported in the literature that contain either d-block metals such as Cu(I), Zn(II), Re(I), Ru(II), Pd(II), Ir(III), Pt(II), Au(I), and Os(IV), describing the mechanisms proposed to explain their AIE. New emerging high-tech applications such as OLEDs, chemical sensors or bioimaging probes proposed for these materials are also discussed in a separate section.     

SERS of 7-azaindole adsorbed on Ag doped sol–gel film and Ag sol: a comparative investigation

Surface enhanced Raman scattering (SERS) studies have been undertaken on Ag doped sol–gel derived film with 7-azaindole (7-AI) used as the reference compound. The enhancement factor in the film is comparable with the result of the chloride aggregated silver citrate sol. Along with the spectral observation and assignments of the frequencies, the significance of colloidal sol–gel film in which the size of the metal is in the dimensions of nanometers have been discussed.     

Thermo-physical properties of pure ethylene glycol and water–ethylene glycol mixture-based boron nitride nanofluids

Journal of Thermal Analysis and Calorimetry - Nanofluids are suspensions of solid nanoparticles in conventional heat transfer fluids, and they often exhibit improved heat transfer characteristics....     

The possibility of semiconductor–metal transition in a spherical quantum dot

We observe an abrupt change in diamagnetic susceptibility at critical donor concentration for an $\text{ Al }_\mathrm{x}\text{ Ga }_\mathrm{1-x}\text{ As/GaAs }$ Al x Ga 1 ? x As/GaAs quantum dot system in the effective mass approximation indicating a possible semiconductor metal transition. The effect of confining potential and the laser intensity on the abrupt change in diamagnetic susceptibility has also been studied. The effect of nonparabolicity of the conduction band has been included in our calculations. Results are presented and discussed.     

Metallophosphoranes: The hidden face of transition metal–phosphine complexes

Reactions in which metallophosphoranes, of general formula L_nMPR₄, have been implicated as intermediates or possible transition states are reviewed. Such species can be accessed via nucleophilic attack on metal–phosphine complexes, with the source of nucleophile being either external or internal in the form of an anionic co-ligand. The reverse process, transfer of a group from a {PR₄} ligand to a metal, has also been observed with the formation of a metal phosphine. Thus metallophosphoranes have been postulated to play a role in isomerization processes and novel M–X/P–R exchange reactions. Metallophosphoranes have also been implicated in unusual ‘phosphine-assisted C–F bond activation’ reactions. Recent computational studies on these processes are discussed.     

DFT Calculations of Vibrational Frequencies of Carbon–Nitrogen Clusters: Raman Spectra of Carbon Nitrides

We have performed the calculation of structures of clusters containing carbon and nitrogen atoms. We determine the bond lengths in each case. We also calculate the vibrational frequencies of all of the clusters. We compare the calculated values of the vibrational frequencies with those measured by the Raman spectra of amorphous carbon nitrides. Some of the calculated frequencies are in agreement with those measured. We identity that linear structures and hence “back bones” are present in the glassy state.     

Structural,spectroscopic, luminescence sensing and TD–DFT theoretical studies of a CuP2N-type complex

Luminescent cuprous complexes are an important class of coordination compounds due to their relative abundance, low cost and ability to display excellent luminescence. The title heteroleptic cuprous complex, [2,2′-bis(diphenylphosphanyl)-1,1′-binaphthyl-κ²P,P′](2-phenylpyridine-κN)copper(I) hexafluoridophosphate, rac-[Cu(C₄₄H₃₂P₂)(C₁₁H₉N)]PF₆, conventionally abbreviated rac-[Cu(BINAP)(2-PhPy)]PF₆ ( I ), where BINAP and 2-PhPy represent 2,2′-bis(diphenylphosphanyl)-1,1′-binaphthyl and 2-phenylpyridine, respectively, is described. In this complex, the asymmetric unit consists of a hexafluoridophosphate anion and a heteroleptic cuprous complex cation, in which the cuprous centre in a CuP₂N coordination triangle is coordinated by two P atoms from the BINAP ligand and by one N atom from the 2-PhPy ligand. Time-dependent density functional theory (TD–DFT) calculations show that the UV–Vis absorption of I should be attributed to ligand-to-ligand charge transfer (LLCT) characteristic excited states. It was also found that the paper-based film of this complex exhibited obvious luminescence light-up sensing for pyridine.     

Relativistic DFT calculations of the NMR properties and reactivity of transition metal methane σ-complexes: insights on C-H bond activation

Relativistic ZORA DFT methods have been employed to predict the NMR properties of methane and methyl hydride complexes of rhodium and iridium. Two of these compounds, the rhodium methane and the iridium methyl hydride complexes, have been recently characterized by NMR spectroscopy. Calculations reveal that relativistic effects are largely responsible of the high shielding observed for the proton and carbon resonances of the methane moiety. The key steps for the reaction mechanism of C-H cleavage catalyzed by both compounds have been investigated at the relativistic level. Although the structure of the intermediates and TSs for the Rh and Ir complexes is rather similar, subtle differences in the energetics are responsible of the different catalytic activity of the two complexes.     

Hybrid sol–gel coatings doped with transition metal ions for the protection of AA 2024-T3

The protective capabilities of sol–gel coatings are determined by their physical barrier properties. For an effective protection, a homogenous crack-free material is required, which prevents from attacks of corrosive species. When the coating is damaged, active corrosion protection is usually achieved by the use of inhibitors. Among the different inhibitors rare earth ions and especially cerium have shown effective inhibiting properties. Due to the complexity of the corrosion processes, a combination of inhibitors is expected to be superior to a monocomponent inhibiting. The aim of this study was to prove which other ions, used in combination with cerium, can improve the corrosion protection abilities of hybrid silica based inorganic–organic sol–gel coatings applied on aluminium alloy 2024 substrates. Mixtures of cerium nitrate with two other potential inhibitor substances were incorporated into a sol–gel matrix and their behaviour in neutral salt spray test and during EIS measurements was investigated. The Ce–P–Pr inhibitor combination (Ce³⁺, PO₄ ³⁻, Pr³⁺) has shown the best long-term corrosion protection properties at low doping levels.     

A two-fold interpenetrating porous metal–organic framework with a large solvent-accessible volume and selective sensing of nitroaromatic explosives

A cadmium(II) 3-D porous metal–organic framework, (Me₂NH₂)₄[Cd₂(TTCA)₂Cl₂]·7DMF·2Diox·6H₂O (1) (TTCA = triphenylene-2,6,10-tricarboxylate, DMF = N,N-dimethylformamide, diox = 1,4-dioxane), has been synthesized through solvothermal conditions. Single-crystal X-ray analysis reveals that the structure of 1 has a two-fold interpenetrating framework with a large solvent-accessible volume of 52% per unit cell. The result of topological analysis shows that 1 is a (3,3)-connected 3-D network with {10³} topology. Luminescence tests illustrate that 1 can selectively sense nitroaromatic explosives via a luminescence quenching mechanism.     

Multivalent metal–sulfur batteries for green and cost-effective energy storage: Current status and challenges

Multivalent metal-sulfur(M-S,where M=Mg,Al,Ca,Zn,Fe,etc,) batteries offer unique opportunities to achieve high specific capacity,elemental abundancy and cost-effectiveness beyond lithium-ion batteries(LIBs).However,the slow diffusion of multivalent-metal ions and the shuttle of soluble polysulfide result in impoverished reversible capacity and limited cycle performance of M S(Mg-S,Al-S,Ca-S,Zn-S,Fe-S,etc.) batteries.It is a necessity to optimize the electrochemical performance,while deepening th...     

Construction and visible-light photocatalytic performance of carboxyethyltin/transition metal–functionalized wheel-like tungstophosphates

The wheel-like tungstophosphate ([P₈W₄₈O₁₈₄]⁴⁰⁻, abbreviated as P₈W₄₈) reacted with estertin trichloride (Cl₃SnRCH₃, R = CH₂CH₂COO) in aqueous solution, resulting in a new wheel-like polyoxometalate (POM) containing six SnR fragments, formulated as K₆Na₂₄[{(SnR(H₂O))₂(μ-OH)(μ-SnR(H₂O))}₂(P₈W₄₈O₁₈₄)]·59H₂O (abbreviated as Sn ₆ - P ₈ W ₄₈ ). Based on this, the transition metal (TM) was further introduced into the Sn ₆ - P ₈ W ₄₈ system, self-assembling three other wheel-like POMs with the general formula K_xNa_yH_{26 − x − y}[{TM(H₂O)₃(SnR(H₂O))₂(μ-OH)(μ-SnR(H₂O))}₂(P₈W₄₈O₁₈₄)]·nH₂O (abbreviated as TM ₂ - Sn ₆ - P ₈ W ₄₈ , TM = Mn, Co, Ni; x = 0, 1, 2; y = 19, 22, 15; n = 72, 85, 75, respectively). The structures of these new organometal and TM co-modified compounds were characterized using infrared, UV–Vis. spectroscopy, ¹¹⁹Sn NMR, and powder- and single-crystal X-ray diffraction analysis. The estertin precursor hydrolyzed into carboxyethyltin (SnR) fragment in these crystalline POM materials, which can improve their adhesion to titanium dioxide (TiO₂). The photocatalytic performance of Sn ₆ - P ₈ W ₄₈ , TM ₂ - Sn ₆ - P ₈ W ₄₈ , and their TiO₂ composites was examined by studying the degradation of a model dye pollutant Rhodamine B (RhB) under visible-light irradiation without adding hydrogen peroxide (H₂O₂), and the photocatalytic mechanism was also discussed. The experimental results show that the title compounds exhibit a quicker and better photocatalytic degradation effect on RhB compared with their parent compound, indicating that the introduced organotin groups play a significant role. Moreover, it was found that H₂O₂ was produced after illumination pretreatment for POM solution, promoting the photocatalytic reaction.