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This review aimed to discuss the emergence of tetracyanobutadiene (TCBD) and dicyanoquinodimethane (DCNQ)-functionalized push–pull chromophores as key active layer materials in organic solar cells (OSCs). Although TCBD/DCNQ-based π-materials have been extensively applied in functional organic devices, their scope in OSCs is largely limited by their non-planar molecular geometry. This inherent structural feature is a barrier for effective charge carrier mobility, which considerably diminishes the overall photovoltaic efficiency. Alternatively, other appealing properties associated with TCBD/DCNQ-based chromophores have widened the space for the further screening of their OSC potential. To date, TCBD and DCNQ have been proven to be promising functional entities for the construction of tailor-made π-semiconductors for OSC devices. Through rational molecular design, many structural cores have been appended to TCBD and DCNQ units to satisfy the requirements of OSC application. These strategies also allow for the modulation of π-orbital properties, which not only determine their role as either a donor (p-type) or acceptor (n-type) but also affect their photovoltaic performance. Therefore, this review comprehensively discusses the various TCBD/DCNQ-based π-semiconductors investigated for OSCs with deeper insights into the fundamental understanding of their opto-electrochemical properties contributing to the device performance. Additionally, we have highlighted the impact of processing methods on power conversion efficiencies. [ABSTRACT FROM AUTHOR]

Fullerene chemistry has come a long way since 1990, when the first bulk production of C60 was reported. In the past decade, progress in supramolecular chemistry has opened some remarkable and previously unexpected opportunities regarding the selective (multiple) functionalization of fullerenes and their (self)assembly into larger structures and frameworks. The purpose of this review article is to provide a comprehensive overview of these recent developments. We describe how macrocycles and cages that bind strongly to C60 can be used to block undesired addition patterns and thus allow the selective preparation of single-isomer addition products. We also discuss how the emergence of highly shape-persistent macrocycles has opened opportunities for the study of photoactive fullerene dyads and triads as well as the preparation of mechanically interlocked compounds. The preparation of two- or three-dimensional fullerene materials is another research area that has seen remarkable progress over the past few years. Due to the rapidly decreasing price of C60 and C70, we believe that these achievements will translate into all fields where fullerenes have traditionally (third-generation solar cells) and more recently been applied (catalysis, spintronics). [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cells require reduced construction costs to improve commercial viability, which can be fueled by elimination of platinum as the O2 reduction electrocatalyst. The past 10 years has seen significant developments in synthesis, characterisation, and electrocatalytic performance of the most promising alternative electrocatalyst; single metal atoms coordinated to nitrogen-doped carbon (M-N-C). In this Perspective we recap some of the important achievements of M-N-Cs in the last decade, as well as discussing current knowledge gaps and future research directions for the community. We provide a new outlook on M-N-C stability and atomistic understanding with a set of original density functional theory simulations. [ABSTRACT FROM AUTHOR]

Scalable and low-cost synthesis of high-quality ferroic films is critical for the development of advanced electronic devices and sensors. Here, we employ solution-based spray pyrolysis to fabricate bismuth ferrite thin films on glass substrates and explore the impact of annealing conditions to attain functional thin films of superior quality and switchable polarization. Optimised thin films display polycrystalline nanostructured grains with the highest X-ray diffraction intensity along the (110) orientation and a mixed Fe2+/3+ valence suggesting the presence of oxygen vacancies. The optimized films show a complex ferroelectric domain microstructure and exhibit robust nanoscale polarization switching in the range of several volts. Domains are found to scale with the sizes of nanocrystalline grains, which points to the role of surface-energy-related mechanisms affecting the domain patterns. Our results demonstrate the potential of spray pyrolysis for the fabrication of high-quality ferroelectric thin films and provide new opportunities for the development of low-cost scalable advanced electronic devices. [ABSTRACT FROM AUTHOR]

Metallic aerogels with the hierarchical porous structure are promising materials for various electrocatalytic reactions; however, the regulation of their morphology and components remains a great challenge. Herein, three-dimensional porous PtNi aerogels composed of PtNi alloyed nanotubes with the tunable diameter and wall thickness were designed through a nanoengineering strategy of gelation and post treatment. The factors affecting the morphology and the mechanism for the growth of the multi-metallic aerogels were systematically investigated during their synthesis. Benefitting from the original interconnected networks and PtNi alloyed hollow blocks, the PtNi nanotubular aerogels displayed remarkable mass activity compared to the commercial Pt/C towards the oxygen reduction and methanol oxidation reactions for methanol fuel cells. Furthermore, different multi-component nanotubular aerogels of RuNi, Au-PtNi, and Ru-PtNi were also successfully fabricated using this nanoengineering strategy as active electrocatalysts. Therefore, the controllable nanoengineering strategy is considered a general pathway to obtain multi-metallic nanotubular aerogels, further providing a new idea for the design of hollow metallic aerogels as efficient electrocatalysts for fuel cell applications. [ABSTRACT FROM AUTHOR]

The prepared heparin-coated iron oxide nanoparticles (Hep-IONPs) contrasted cholangioma tumors in the liver in T2 MRI. The NPs were not toxic to rats and rabbits after 14 days of consecutive IV injections as observed from the monitoring of the body weight and biochemical and hematological parameters. No embryotoxic or immunotoxic side effects of the material were detected. However, we observed mutagenicity of iron oxide NPs in the Ames test and micronucleus assay. The pharmacokinetic studies showed that Hep-IONPs circulated in the blood for 14 days after IV injection. The liver iron level reached its maximum after 6 hours and slowly decreased within 30 days. Altogether, these results suggest that the synthesized Hep-IONPs are promising for use as the MRI contrast agent to identify liver malignancies. [ABSTRACT FROM AUTHOR]

Developing active, stable and phosphate anion resistant catalysts is critical for high-temperature proton exchange membrane fuel cells based on phosphoric acid-doped polybenzimidazole (PA-PBI) membranes. Herein, an iron catalyst with a five-coordinated Fe active center is elaborately designed. The experimental and theoretical studies show that the planar Fe–N4 moiety with an axial O ligand, benefiting from the optimized charge redistribution, weakens phosphate anion adsorption on Fe active centers and simultaneously promotes oxygen molecule dissociation, resulting in excellent phosphate anion tolerance and ORR activity with the half-wave potential remaining at 0.81 V. The axial-ligand promoted Fe–N–C catalyst is assembled for the first time in a PA-PBI fuel cell, delivering a decent performance. This study sheds light on the intrinsic cause for the phosphate anion tolerance of Fe–N–C catalysts at a molecular level, which provides guidance for designing highly active and stable electrocatalysts for PA-PBI fuel cells. [ABSTRACT FROM AUTHOR]

Metallic nanowire networks (MNNs) have attracted increasing attention due to their high surface area and tunable compositions. Although enormous efforts have been devoted to preparing noble metal MNNs with different compositions, the composition optimization and the formation mechanism of Ir-based MNNs have not been thoroughly investigated. This work presents a facile method for synthesizing robust Ir-based bimetallic MNNs by chemical reduction. As unveiled by our characterization, the network structure is constructed by ultrafine nanowires evolved from aggregated nanoparticles. The element analysis confirms the even distribution of Pb and Ir elements. The introduction of Pb is found to be beneficial to the stable formation of IrxPb MNNs in the sol–gel process. By tuning the precursor ratio of Ir and Pb, the optimized IrxPb catalyst delivers an enhanced oxygen evolution reaction (OER) performance in acid media (307 mV at 10 mA cm−2), which is superior to that of the commercial IrO2 catalyst. Besides, due to the robust structure of the IrxPb MNNs, excellent OER durability is observed in the accelerated durability test (ADT) (2000 cycles). [ABSTRACT FROM AUTHOR]

Palladium is a late transition metal element in the 4d row of the periodic table. Palladium nanoparticles show efficient catalytic activity and selectivity in a number of chemical reactions. In this paper, we review the structural and electronic properties of palladium nanoclusters, both isolated and deposited on the surface of different substrates. Careful experiments and extensive calculations have been performed for small Pd clusters which provide ample information on their properties. Work on large Pd clusters is less abundant and more difficult to perform and interpret. Cluster deposition is a method to modify material surfaces for different applications, and we report the known results for the deposition of Pd clusters on the surfaces of a number of interesting substrates: carbonaceous substrates like graphene and some layered novel materials related to graphene, metal oxide substrates, silicon and silicon-related substrates and metallic alloy substrates. Emphasis is placed on revealing how the structural, electronic and magnetic properties change when the clusters are deposited on the substrate surfaces. Some examples of chemical reactions catalyzed by supported Pd clusters and nanoparticles are reported. An issue discussed in detail is the influence of Pd on the storage of hydrogen in porous materials. Experimental work shows that the amount of stored hydrogen increases when the absorbing material is doped with Pd atoms, clusters and nanoparticles, and a spillover mechanism from the metal particle to the substrate is usually accepted as the explanation. To shed light on this issue, a critical analysis based on density functional simulations of the mechanisms of hydrogen spillover in perfect and defective graphene doped with palladium clusters is presented. [ABSTRACT FROM AUTHOR]

Copper subgroup metal ions in the +1 oxidation state are classical candidates for aggregation via non-covalent metal–metal interactions, which are supported by a number of bridging ligands. The bridging phosphines, soft donors with a relatively labile coordination to coinage metals, serve as convenient and essential components of the ligand environment that allow for efficient self-assembly of discrete polynuclear aggregates. Simultaneously, accessible and rich modification of the organic spacer of such P-donors has been used to generate many fascinating structures with attractive photoluminescent behavior. In this work we consider the development of di- and polynuclear complexes of M(I) (M = Cu, Ag, Au) and their photophysical properties, focusing on the effect of phosphine bridging ligands, their flexibility and denticity. [ABSTRACT FROM AUTHOR]

In the present work, we performed a theoretical study at the density functional theory (DFT) level of both optical and charge transport properties in a series of molecular junctions consisting of an expanded porphyrin such as hexaphyrin (1.0.0.1.0.0) named amethyrin (free base FB) and its Zn(II)- and Cu(II)-bimetallic derivatives with four different anchoring groups (ethyl, phenyl, ethynyl, direct). After a calibration procedure with five density functionals, the electronic absorption spectra were computed (TPSSh/def2-TZVP) with time-dependent DFT (TD-DFT). The bimetalation produces a decrease in both Q and Soret bands' intensity and a red-shift in the absorption. Still, the effect is more significant for the singlet Cu(II) systems where the Q bands are shifted to near-infrared (∼900 nm). It means that they could be attractive for solar cells by the absorption at the longest wavelength. DFT and wavefunction-based calculations for the coupling constant (J) demonstrated a ferromagnetic behavior for Cu(II) systems, which is coherent with the higher stability of the Cu(II) triplet compared to the singlet. The differential conductance and the I–V profiles of each system are calculated using DFT and nonequilibrium Green's function (NEGF) formalism to rationalize the charge transport mechanisms. It was found that the conductance does not drastically change with both Zn(II) and Cu(II) metalation, being larger for the latter, but it is strongly dependent on the anchoring group (ethyl < phenyl < ethynyl < direct). In Cu(II) bridge junctions, in both high and low spin configurations, the antiferromagnetically coupled systems exhibit an increase in conductance compared to the ferromagnetic ones. The important difference (around 100–200%) in the total current calculated between the triplet and the singlet configurations with ethynyl, for the voltage range of 0.1–0.5 V, suggests that Cu(II)-amethyrins could have applications as a molecular switch operated by the application of an external magnetic field. [ABSTRACT FROM AUTHOR]

Heparin has a variety of pharmacological uses, including applications for anti-tumor metastasis, anti-inflammatory and anti-viral activities and is widely used as a clinical anticoagulant. Due to its widespread applications in the clinical procedures, monitoring heparin levels is critically important to ensure the safe use of heparin and to prevent overdose and complications, such as hemorrhage and thrombocytopenia. However, traditional heparin detection relies on the measurements of the activated clotting time or activated partial thromboplastin time, which are not sufficiently reliable or accurate measurements for certain clinical settings. In this work, we describe a dumbbell probe-aided strategy for ultrasensitive and isothermal detection of heparin based on a uniquely strong protamine–heparin interaction and rolling circle amplification driven signal amplification. The detection limit for heparin is 12.5 ng mL−1 (0.83 nM), which is much lower than the therapeutic level of heparin in cardiovascular surgery (17–67 μM) and in postoperative and long-term treatment (1.7–10 μM). Additionally, the proposed sensing platform works well for heparin monitoring in human plasma samples. This simple and ultrasensitive heparin biosensor has potential application in diagnostics, therapeutics, and in biological research. [ABSTRACT FROM AUTHOR]

The effects of antiaromaticity and destructive quantum interference (DQI) are investigated on the charge transport through dibenzo-[a,e]pentalene (DBP). 5,10-Connectivity gives high single-molecule conductance whereas 2,7 gives low conductance due to DQI. Comparison of the 5,10-DBP with phenyl and anthracene analogues yields the trend GDBP ≈ GAnth > GPh, despite the aromatic anthracene having a larger HOMO–LUMO gap than 5,10-DBP. This is explained by unfavourable level alignment for 5,10-DBP. [ABSTRACT FROM AUTHOR]

Neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases, are a class of heterogeneous pathologies of the central nervous system (CNS) affecting millions of people worldwide. CNS-related pathologies represent a global health burden in developed and developing countries with no curative treatments currently available. Thus, the development of novel multitarget neuroprotective drugs is a health priority. In this work, a bioinspired methodology in solution-phase for the assembly and regioselective conjugation of Glypromate® neuropeptide with active pharmaceutical ingredients (APIs) is described. The main purpose is to design new hybrid molecules which may offer increased systemic resistance of Glypromate® towards proteases and/or allow the controlled release of both APIs and the neuroprotective peptide within CNS. For the synthesis of such peptide-hybrid compounds (R)-1-aminoindane, amantadine, and memantine were selected as APIs for conjugation with Glypromate®. Furthermore, capping strategies are explored to prepare Glypromate® conjugates with more favorable pharmacodynamic profiles by masking polar exposed groups. Overall, this synthetic approach led to the development of a small library of 12 conjugates with improved drug-like properties in comparison with Glypromate®, paving the way for the discovery of novel CNS multitarget drugs. Additionally, by exploring the bis-functionalization of glutamate, the formation of chiral glutarimides is disclosed for the first time employing TBTU as the coupling reagent. This unusual reactivity of TBTU with glutamate offers a new synthetic approach for the preparation of chiral glutarimide alkaloids. [ABSTRACT FROM AUTHOR]

This work describes an improved and greener methodology of solution-phase synthesis for the preparation of Glypromate® (glycyl- L -prolyl- L -glutamic acid, GPE), a potent neuropeptide for applications in neurodegenerative conditions such as Huntington's, Parkinson's and Alzheimer's diseases. This protocol comprises the assembly of the perbenzylated form of Glypromate® [Cbz-Gly-Pro-Glu(OBn)-OBn (5)] from L -proline. Following a tandem sequential peptide coupling strategy, two chemoselective peptide bonds are formed without the need for purifying the intermediates ensuing a one-pot fashion synthesis. EcoScale score and E-factor were selected as the green metrics to assess the environmental impact of the preparation of tripeptide 5 using this protocol. After optimization and application of greener conditions, intermediate 5 was obtained with 95% global yield and 99% purity (NMR, HRMS, and rp-HPLC), with excellent final EcoScale score of 75 out of 100 and global E-factor of 1.8. Glypromate® is achieved by removing N- and C-protecting groups by hydrogenolysis using Pd/C as the catalyst in 98% yield, avoiding chromatographic techniques. Moreover, the protocol ensures stereochemical integrity (determined by VT-NMR and rp-HPLC) and was also successfully applied for the preparation of structurally-related Glypromate® analogues with higher degree of molecular complexity compatible with functionalized amino acids with different side chains. For the first time a one-pot protocol for the assembly of tripeptides with the removal of protecting groups in the same reaction vessel is reported. [ABSTRACT FROM AUTHOR]

We have joined two fundamental concepts of organic chemistry to provide a deep, yet intuitive, understanding of how side groups influence destructive quantum interference (DQI) in the transport through conjugated molecules. Using density functional theory combined with Green's function techniques, and employing tight-binding models in which all the π-systems are considered, we elucidate the separate roles of bond-resonance and induction in tuning DQI. We show that the position of the anti-resonances produced by DQI is sensitive to the number of side groups, but not in a simple additive way. Instead, addition of multiple groups results in a weaker overall contribution per group, and this can be understood using a straight forward graphical analysis. Furthermore, we show that additional fine tuning of DQI is possible via attachment of a chain of atoms to a second site around the ring. DQI is controlled by modifying the length of the chain, thus providing exquisite control over the anti-resonance position. This insight provides chemists with a large number of options to tune DQI for unprecedented device optimization. [ABSTRACT FROM AUTHOR]

A glycoluril-based molecular clip incorporating two tetrathiafulvalene (TTF) sidewalls has been synthesized using a straightforward Diels–Alder synthetic route and its ability to self-assemble with fullerene C60 in a 2 : 1 stoichiometry has been demonstrated in solution. [ABSTRACT FROM AUTHOR]

The development of metal complexes for optoelectronic applications is a fertile area of research. In contrast to the rigorous development of mononuclear metal complexes, dinuclear species have been less well studied and their fundamental chemistry and applications are under-explored. However, dinuclear species present special properties and functions compared with mononuclear species as a consequence of tuning the bridging ligands, the cyclometalated ligands or the two metal centers. More recently, dinuclear species have enabled important breakthroughs in the fields of OLEDs, photocatalytic water splitting and CO2 reduction, DSPEC, chemosensors, biosensors, PDT, smart materials and so on. Here we present an overview of recent developments of dinuclear metal complexes, their multifunctional properties and their various applications. The relationship between structure and property of dinuclear species and important factors which influence device performance are discussed. Finally, we illustrate some challenges and opportunities for future research into dinuclear metal complexes. This review aims to provide an up-to-date summary and outlook of functional dinuclear metal complexes and to stimulate more researchers to contribute to this exciting interdisciplinary field. [ABSTRACT FROM AUTHOR]

High-level nitrogen-doped (＞10 at%), high-surface-area (＞1600 m2 g−1) micro/mesoporous carbon derived from coconut mesocarp was prepared by a solvent-free ball-milling process using melamine as a solid-state nitrogen dopant and potassium bicarbonate as a safe and green activating agent. Synergistic nitrogen doping and pore formation maximize the nitrogen doping concentration/specific surface area/pore volume and minimize the pore blockage. This nitrogen-doped porous carbon exhibits comparable catalytic activity for the oxygen reduction reaction (ORR) to the commercial Pt/C catalyst in terms of the onset potential and the current density and exhibits superior stability and methanol tolerance to the benchmark catalyst, thanks to its optimized reaction surface area. [ABSTRACT FROM AUTHOR]

A new series of fullerene receptors based on exTTF macrocycles with alkyl ether chains of increasing length is reported. The novel macrocyclic receptors are able to favourably interact with fullerene C60 through a synergistic combination of π–π, CH…π and n…π noncovalent interactions. We identify that the highest affinity towards C60 recognition is achieved for the host with the tightest fit; that is, the smallest receptor with a cavity large enough to host the buckyball inside (log Ka = 5.2 in chlorobenzene at 298 K). However, besides this expected observation, theoretical calculations evidence that the most stable self-assembling configuration corresponds for all the receptors to an outside-ring binding mode, in which the C60 guest is out of the cavity of the receptor. The higher stability of this configuration results from the smaller deformation energy it implies for the receptor, and allows to explain the experimental trends in the association constants. [ABSTRACT FROM AUTHOR]

Redox-active organic molecules have found interest in various areas of materials chemistry, from organic conductors, electrochromic materials, sensors, to constituents of molecular machines. Tetrathiafulvalene (TTF) has been one of the most exploited molecules for advanced materials owing to its two reversible one-electron oxidations. Polycyclic aromatic hydrocarbons (PAHs) are another class of organic molecules that has played a unique role in materials chemistry on account of their electronic properties. By combining TTFs and PAHs new electronic properties emerge. Indeed, an extension of the TTF by a large π-conjugated spacer between the two dithiole rings has significant implications for the redox properties, the optical properties of the various redox states, and the ability to form mixed valence and π-dimer associates upon oxidation; i.e., neutral·radical cation (nc) and radical cation·radical cation (cc) complexes. Here we review the properties of such extended and “super-extended” TTFs, divided into two classes based on the nature of the spacer: (i) one- and two-dimensional PAH spacers comprised of fused benzene rings, (ii) indacene- and benzo- or thieno-fused indacene spacers where the dithiafulvene units are placed at five-membered rings in the spacer. The two classes will be limited to structures where the exocyclic fulvene carbon atom of each dithiafulvene unit is part of a five- or six-membered all-carbon ring (while heterocyclic rings may be fused to this ring). Digital simulation of the experimental cyclic voltammograms is key to understanding the complex associations occurring upon oxidation, and the last part of the review gives a small tutorial on this method. [ABSTRACT FROM AUTHOR]

A series of homo- and hetero-nuclear, bi- and trimetallic compounds are accessible using polyfunctional linkers with carboxylic acid and alkynyl or pyridyl donor combinations. This versatile approach affords reaction at a specific donor site in each case, to accommodate both ruthenium(ii) or osmium(ii) units and also rhenium and gold centres. Due to the orientation of the nitrogen donors of the bipyridyl moiety in 2,2′-bipyridine-4,4′-dicarboxylic acid, the metal addition must be performed in a certain sequence due to steric considerations. One example was investigated crystallographically to add to the spectroscopic and analytical characterisation performed for all complexes. Photophysical investigations reveal the effect of incorporating second or third row transition metal centres. This approach was expanded through the use of a linker bearing both carboxylic acid and alkynyl functionalities, 1,1′-ethynylferrocene carboxylic acid. This allows initial coordination of the carboxylate donors to be followed by the formation of either an acetylide or a vinyl bridge to another metal, providing access to heterotrimetallic (FeRuOs and FeRuAu) compounds as well as a heteroheptametallic Fe3Ru2Au2 example. Preliminary electrochemical studies were performed on the latter compound. [ABSTRACT FROM AUTHOR]

We report a novel biomimetic drug discovery platform using high expression epidermal growth factor receptor (EGFR) HEK 293 cell membrane camouflaged magnetic nanoparticles. The EGFR/magnetic cell membrane nanoparticles (MCMNs) integrated desirable magnetic features and special binding bioaffinity. Application of this drug-targeting concept is expected to pave ways to a new drug discovery strategy. [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis of a non-precious metal dual-doped catalyst. Melamine and lipoic acid were used as precursors for the nitrogen and sulfur dopant atoms, respectively, which were mixed with iron precursors and carbon black and pyrolyzed at 700 °C to yield the catalyst Fe-M-LA/C. Fe-M-LA/C shows high oxygen reduction reaction (ORR) capability, with an almost-ideal electron transfer number of 3.99. It shows almost no degradation after potential cycling for 30 000 cycles, and the structural analysis indicates that a graphene-like structure of Fe-M-LA/C can improve its ORR activity, electrical conductivity, and corrosion resistance. X-ray photoelectron spectroscopy (XPS) results show that the catalyst has high contents of pyridinic- and quaternary N atoms and thiophene S atoms that can significantly enhance the ORR performance of Fe-M-LA/C. X-ray absorption spectroscopy (XAS) data show that the oxidation state of iron and the interatomic distance of the heteroatoms in Fe-M-LA/C play an important role in determining the ORR ability. These data confirm that the presence of a nitrogen and sulfur dual-doped –Fe–N–S– structure can enhance the ORR kinetics. [ABSTRACT FROM AUTHOR]

This work introduces a luminescent dinuclear Au(i) complex with a cyclic PNNP ligand ((AuCl)2L) as a “host” molecule with two binding sites, “upper” and “lower”. The “upper” binding site is nucleophilic due to two preorganized Au–Cl moieties, while the “lower” one is electrophilic due to positive partial charges of hydrogen atoms of P–CH2–N moieties. The “host–guest” binding is a reason for both solvent- and substrate-induced tuning of the complex luminescence. Organic cations, namely N-methylpyridinium and trimethylammonium, are revealed as substrates able to bind via the “upper” site of the complex. Acetone, diphenylketone, DMSO, DMF and acetonitrile exemplify substrates able to bind with both the binding sites of the complex. The binding via“lower” sites leads to changes in mutual arrangement of pyridyl moieties and P–Au bonds of the complex, which results in a more pronounced effect on the excited state energy relative to the binding via the “upper” site. Substrate-induced tuning of the luminescence is affected by the nature of the solvent due to competitive “host–guest” binding of (AuCl)2L with solvent molecules. [ABSTRACT FROM AUTHOR]

Particle size significantly affects the properties and therefore the potential applications of multiferroics. However, is there special particle size effect in BiFeO3, which has a spiral modulated spin structure? This is still under investigation for sub-5 nm BiFeO3. In this report, the structural, electronic and magnetic properties are investigated for chemically synthesized BiFeO3 nanoparticles with an average size of 3 nm. We observed nanotwinning features in the specific size regime of the nanoparticles (2–4 nm). A weak Bi–O–Fe coordination and weak covalent nature has been observed in the nanoparticles through high-resolution electron energy loss spectroscopy and theoretical analysis, confirming that BiFeO3 nanoparticles a retain rudimentary R3c phase even at sub-5 nm dimensions. The R3c phase of sub-5 nm BiFeO3 nanoparticles has also been confirmed using Raman spectroscopy and Raman mapping of the vibrational modes. The nanoparticles display cluster spin glass, room temperature ferromagnetism, and a metamictization-davidite phase. The observation of weak magnetic entropy features confirmed the presence of a weak correlation between the magnetic and ferroelectric components. To support our experimental observations, we have simulated a sub-5 nm BiFeO3 nanocluster. Using density functional theory, the ferromagnetic ground state and the presence of a weak covalent nature in the nanocluster is established considering the first Brillouin zone, thus confirming our experimental results. Finding of new physicochemical features in sub-5 nm BiFeO3 would be beneficial for the understanding of the fundamental physical and chemical science as well as potential device development. [ABSTRACT FROM AUTHOR]

The high cost of Pt-based membrane electrode assemblies (MEAs) is a critical hurdle for the commercialization of polymer electrolyte fuel cells (PEFCs). Recently, non-precious metal-based catalysts (NPMCs) have demonstrated much enhanced activity but their oxygen reduction reaction (ORR) activity is still inferior to that of Pt-based catalysts resulting in a much thicker electrode in the MEA. For the reduction of mass transport and ohmic overpotential we adopted a new concept of catalyst that combines an ultra-low amount of Pt nanoclusters with metal–nitrogen (M–Nx) doped ordered mesoporous porphyrinic carbon (FeCo–OMPC(L)). The 5 wt% Pt/FeCo–OMPC(L) showed a 2-fold enhancement in activities compared to a higher loading of Pt. Our experimental results supported by first-principles calculations indicate that a trace amount of Pt nanoclusters on FeCo–OMPC(L) significantly enhances the ORR activity due to their electronic effect as well as geometric effect from the reduced active sites. In terms of fuel cell commercialization, this class of catalysts is a promising candidate due to the limited use of Pt in the MEA. [ABSTRACT FROM AUTHOR]

A new class of platinum(ii) acetylide complexes with urea group, [Pt(tBu3tpy)(C≡CC6H4-4-NHC(O)NHC6H4-4-R)](OTf) (tBu3tpy = 4,4′,4′′-tri-tert-butyl-2,2′:6′,2′′-terpyridine; R = H (3a), Cl (3b), CF3 (3c), and NO2 (3d)), has been synthesized and characterized. The crystal structures of 3a, 3a·DMF·THF, 3b·CH3CN, and 3c·CH3CN have been determined by X-ray diffraction. Upon excitation at λ ＞ 380 nm, the solid samples of complexes 3a–3d show orange light at 298 K. The anion binding properties of complexes 3a–3d have been studied by UV-vis titration experiments in CH3CN and DMSO. In general, the log K values of 3a–3d with the same anion in CH3CN depend on the substituent R on the acetylide ligand of 3a–3d and follow this order: R = NO2 (3d) ＞ CF3 (3c) ＞ Cl (3b) ＞ H (3a). For the same complex with different anions, the log K values are in the following order: F− ＞ OAc− ＞ Cl− ＞ Br−≈ HSO4−≈ NO3− ＞ I−, which is in accordance with the decrease in the basicity of anions. Complex 3d with NO2 group shows a dramatic colour change towards F− in DMSO, allowing the naked eye detection of F−. [ABSTRACT FROM AUTHOR]