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Chemically functional core/shell microtubes made of biodegradable polymers are fabricated using coaxial electrospinning. The luminal walls are chemically functionalized, allowing for regioselective chemical binding or adsorption inside the microtube. Attaching catalytic nanoparticles or enzymes to the luminal walls converts the microtubes into bubble-propelled microrockets. Upon exposure to ultrasound, the microtubes undergo shape shifting, transforming them into picoliter-scale containers.

Herein we report the hydrothermal synthesis of yellow emitting carbon dots, CDs, in high salinity water and compare them with those prepared in distilled water. The saline environment significantly affects the surface chemistry and charge of the CDs. We also present data on their long-term colloidal and photochemical stability in distilled and saline water at ambient and high temperatures. The facile preparation and shelf life stability coupled with their improved photochemical and thermal properties make them potential applicants as tracers for biomedical, subsurface and other technologies that require stability under harsh conditions.

We report a simple methodology for synthesizing a hybrid of cuprous oxide (Cu2O) nanoparticles with a size less than 6 nm embedded into a porous graphitic nitrogen-rich carbon matrix. The mesoporous composite, Cu2O@C3N, with a surface area of 112 m2 g−1 was prepared by mild pyrolysis (450 °C) of a copper based metal organic framework, Cu3(BTC)2 loaded with urea, (H2N)2CO. The Cu2O@C3N shows a band gap energy of 1.97 eV and acts as an efficient photocatalyst for hydrogen evolution from water under visible light. The amount of evolved H2 is more than 2 times higher than that evolved over pristine carbon nitride and cuprous oxide under the same conditions. Importantly, the composite maintains its catalytic activity even after three catalytic cycles maintaining similar yields. Therefore, the nitrogen-rich porous carbon support serves as a functional scaffold preventing the agglomeration of Cu2O nanoparticles. The key factors responsible for enhanced hydrogen evolution from water are improved visible light absorption, suppressed charge carrier recombination, increased charge separation and high surface area of the composite. We investigated the effect of different pyrolysis temperatures set at 550 and 700 °C on the photocatalytic hydrogen evolution rates. The pyrolysis conditions affect not only the phase transition of copper (copper oxide at 550 °C and pure copper metal at 700 °C) in the resultant composites, but also nitrogen amount incorporation. We believe that this work provides a new insight into the design and fabrication of various efficient and cost-effective nitrogen-rich carbon composites (alternative for noble metals) with superior photocatalytic hydrogen evolution activity.

Maghemite-supported ultra-fine Pd (1–3 nm) nanoparticles, prepared by a simple co-precipitation method, find application in the catalytic continuous flow hydrogenation of nitroarenes, azides, and alkenes wherein they play an important role in the reduction of various functional groups on the surface of maghemite with catalyst loading (~6 wt% Pd). The salient features of the protocol include expeditious formation of reduced products in high yields under near ambient conditions with recycling of the catalyst (up to 12 cycles) without any decrease in selectivity and yield.

A nanocatalyst comprising ultra-small Pd/PdO nanoparticles (

A template-free solid-state synthesis of a morphologically controlled and highly organized iron(III)oxide micro–mesoporous Fenton catalyst has been engineered through a simple two-step synthetic procedure. The 3D nanoassembly of hematite nanoparticles (5–7 nm) organized into a rod/flower-like morphology shows the highest rate constant reported to date for the decomposition of H2O2 (1.43 × 10−1 min−1) with superior efficiency for the degradation of aromatic (phenol, benzene, ethylbenzene) and chlorinated (trichloroethylene) pollutants in contaminated water. The morphological arrangement of nanoparticles is therefore considered one of the key variables that drive catalysis.

The use of magnetic nanoparticles as a solid support material for the development of magnetically retrievable catalytic systems has led to a dramatic expansion of their potential applications as they enable environmentally-friendly and sustainable catalytic processes. These quasi-homogeneous catalysts possess numerous benefits such as ease of isolation and separation from the desired reaction mixtures using an external magnet and excellent recyclability. Consequently, much effort has been directed towards the synthesis of magnetically isolable nano-sized particles by developing methods such as co-precipitation, thermal decomposition, microemulsion, hydrothermal techniques etc. Further, in order to render them suitable for catalytic applications, several protection strategies such as surfactant/polymer, silica and carbon coating of magnetic nanoparticles or embedding them in a matrix/support have been reported in the literature. This review focuses on the substantial progress made in the fabrication of nanostructured catalysts with special emphasis on the protection and functionalization of the magnetite nanoparticles (Fe3O4). Finally, considering the importance of coupling chemistry in the field of organic synthesis, a broad overview of the applications of these magnetite nanoparticle-based catalysts in several types of coupling reactions has been presented. The future of catalysis lies in the rational design and development of novel, highly active and recyclable nanocomposite catalysts which would eventually pave the pathway for the establishment of green and sustainable technologies.

Poly(vinylpyrrolidone) supported Cu nanoclusters were synthesized by reduction of Cu(ii) ions with ascorbic acid in water, and initially showed blue photoluminescence with a quantum yield of 8%. An enhancement of the emission quantum yield has been achieved by treatment of Cu clusters with different electron-rich ligands, with the most pronounced effect (photoluminescence quantum yield of 27%) achieved with glutathione. The bright blue emission of glutathione treated Cu NCs is fully preserved in the solid state powder, which has been combined with commercial green and red phosphors to fabricate down-conversion white light emitting diodes with a high colour rendering index of 92.

We report on the effect of the degree of oxidation on the broadband non-linear optical response and magnetic behavior of graphene oxide, as well as on a route for obtaining reduced graphene oxide with enhanced optical properties without sacrificing the high dispersibility of the parent graphene oxide. As more sp(3) states evolved with the rise in oxidation degree, it turned out that the sp(2)/sp(3) fraction and sp(2) clustering are crucial parameters for tuning the broadband non-linear optical absorption over a wide range from ps to ns laser pulses for both visible and infrared laser irradiation. This was clearly confirmed by two different approaches, namely by a synthetic route through the gradual oxidation of graphene oxide from 1 to 3 oxidizing cycles, and reversely by in situ reduction of graphene oxide by UV laser irradiation. Furthermore, as the sp(3) states carry localized magnetic moments, ferromagnetic ordering is observed at low temperatures. The magnetization and temperature at which ferromagnetic ordering evolves are found to increase on increasing the oxidation degree. The tuning of non-linear optical and magnetic properties of graphene oxide by oxidation/reduction thus provides an easy way to endow graphene oxide with tunable physical features highly required in both optoelectronics and spintronics applications.

Iron is the most common metal by mass on earth and represents the basic element of industrial society. The usage of iron to synthesize consumer products and to remediate environment is an attractive approach. This perspective presents applications of the high-valent iron oxo compound FeVIO42– (ferrate) in sustainable organic synthesis and treatment technology. In synthesizing organic molecules, C–H bond activation and selectivity are two basic ingredients of efficiency, which are attainable by ferrate. Examples of hydroxylation of hydrocarbons and conversion of alcohols to aldehyde/ketone are presented. In addition, many other organic molecules of amines, aniline, phenolic, and thiol functionalities can be oxidized by ferrate. This oxidation chemistry of ferrate is expedient in transforming pharmaceuticals, micropollutants in bodies of water with implications for human and ecological health. A wide range of micropollutants, which are commonly found in drinking water resources and wastewater effluents, can...

Die Synthese von superhydrophoben/superoleophilen HFGO@ZIF-8-Kompositen aus hoch fluoriertem Graphenoxid (HFGO) und dem nanokristallinen zeolithischen Imidazolatgerust ZIF-8 wird vorgestellt. Die strukturdirigierenden und koordinativen Eigenschaften des HFGO erlauben eine selektive Nukleation der ZIF-8-Nanopartikel entlang der Sauerstoff-funktionalisierten Oberflache des Graphenoxids. Dies fuhrt zu einer lokalisierten Keimbildung und Grosenkontrolle der ZIF-8-Nanokristalle innerhalb der HFGO-Schichten. Die Mikrostruktur des Verbundmaterials ist durch die Anwesenheit von Fluorgruppen entlang der Graphenoberflache charakterisiert. Durch Selbstorganisation resultiert eine einzigartige mikro-mesoporose Struktur, deren Mikroporositat durch die enthaltenen ZIF-8-Nanokristalle begrundet ist. Das Hybridmaterial weist einen grosen Wasserkontaktwinkel von 162° und einen sehr niedrigen Olkontaktwinkel von 0° auf, wodurch eine hohe Sorptionsselektivitat sowie ein gutes Aufnahmevermogen fur nichtpolare/polare Losungsmittel und Ol-Wasser-Gemische gegeben ist. Demzufolge konnen die Sponge@HFGO@ZIF-8-Kompositmaterialien fur die Ol-Wasser-Trennung eingesetzt werden.

A facile synthesis based on the addition of ascorbic acid to a mixture of Na2 PdCl4, K2 PtCl6, and Pluronic P123 results in highly branched core-shell nanoparticles (NPs) with a micro-mesoporous dandelion-like morphology comprising Pd core and Pt shell. The slow reduction kinetics associated with the use of ascorbic acid as a weak reductant and suitable Pd/Pt atomic ratio (1:1) play a principal role in the formation mechanism of such branched Pd@Pt core-shell NPs, which differs from the traditional seed-mediated growth. The catalyst efficiently achieves the reduction of a variety of olefins in good to excellent yields. Importantly, higher catalytic efficiency of dandelion-like Pd@Pt core-shell NPs was observed for the olefin reduction than commercially available Pt black, Pd NPs, and physically admixed Pt black and Pd NPs. This superior catalytic behavior is not only due to larger surface area and synergistic effects but also to the unique micro-mesoporous structure with significant contribution of mesopores with sizes of several tens of nanometers.

In this critical review, we outline various covalent and non-covalent approaches for the functionalization of iron oxide nanoparticles (IONPs). Tuning the surface chemistry and design of magnetic nanoparticles are described in relation to their applicability in advanced medical technologies and biotechnologies including magnetic resonance imaging (MRI) contrast agents, targeted drug delivery, magnetic separations and immobilizations of proteins, enzymes, antibodies, targeting agents and other biosubstances. We review synthetic strategies for the controlled preparation of IONPs modified with frequently used functional groups including amine, carboxyl and hydroxyl groups as well as the preparation of IONPs functionalized with other species, e.g., epoxy, thiol, alkane, azide, and alkyne groups. Three main coupling strategies for linking IONPs with active agents are presented: (i) chemical modification of amine groups on the surface of IONPs, (ii) chemical modification of bioactive substances (e.g. with fluorescent dyes), and (iii) the activation of carboxyl groups mainly for enzyme immobilization. Applications for drug delivery using click chemistry linking or biodegradable bonds are compared to non-covalent methods based on polymer modified condensed magnetic nanoclusters. Among many challenges, we highlight the specific surface engineering allowing both therapeutic and diagnostic applications (theranostics) of IONPs and magnetic/metallic hybrid nanostructures possessing a huge potential in biocatalysis, green chemistry, magnetic bioseparations and bioimaging.

Hybrids containing nanodiamonds with controllable content of gold nanoparticles (ND/Au) were prepared and characterized by XRD, TGA, and TEM/HRTEM techniques including STEM–EDS chemical mapping. For the first time, the nonlinear optical response of the prepared ND/Au dispersions in DMF was investigated by means of the Z-scan technique using 35 ps (532 and 1064 nm) and 40 fs (800 nm) laser excitations and is compared with that of neat nanodiamonds. The nanohybrids exhibited important nonlinear optical response, significantly larger than that of neat nanodiamonds under visible 35 ps laser excitation, while they were found to exhibit negligible nonlinear optical response when excited by 1064 nm, 35 ps, or 800 nm, 40 fs laser pulses. Gold loading was found to affect significantly their nonlinear optical properties, therefore providing an easy mean of modulation of their nonlinear optical response in view of different photonic and optoelectronic applications, such as optical limiters, optical switches, saturab...

Three new two-dimensional (2D) Hofmann-type coordination polymers with general formula [Fe(3-NH2py)2M(CN)4] (3-NH2py = 3-aminopyridine, M = Ni (1), Pd (2), Pt (3)) have been synthesized. Magnetic susceptibility measurements show that they exhibited cooperative spin crossover (SCO) with remarkable hysteretic behaviors. Their hysteresis widths are 25, 37, and 30 K for 1-3, respectively. The single-crystal structure of 1 suggest that the pseudo-octahedral Fe sites are equatorially bridged by [M(CN)4](2-) to form 2D grids and axially coordinated by 3-NH2py ligands. The intermolecular interactions between layers (the offset face-to-face π···π interactions, hydrogen bonds, and weak N(amino)···Ni(II) contacts) together with the covalent bonds bridged by [M(CN)4](2-) units are responsible to the significant cooperativity.

Hematite, α-Fe2O3, is considered as one of the most promising materials for sustainable hydrogen production via photoelectrochemical water splitting with a theoretical solar-to-hydrogen efficiency of 17%. However, the poor electrical conductivity of hematite is a substantial limitation reducing its efficiency in real experimental conditions. Despite of computing models suggesting that the electrical conductivity is extremely anisotropic, revealing up to 4 orders of magnitude higher electron transport with conduction along the (110) hematite crystal plane, synthetic approaches allowing the sole growth in that direction have not been reported yet. Here, we present a strategy for controlling the crystal orientation of very thin hematite films by adjusting energy of ion flux during advanced pulsed reactive magnetron sputtering technique. The texture and effect of the deposition mode on the film properties were monitored by XRD, conversion electron Mössbauer spectroscopy, XPS, SEM, AFM, PEC water splitting, IPCE, transient photocurrent measurements, and Mott-Schottky analysis. The precise control of the synthetic conditions allowed to fabricate hematite photoanodes exhibiting fully textured structures along (110) and (104) crystal planes with huge differences in photocurrents of 0.65 and 0.02 mA cm(-2) (both at 1.55 V versus RHE), respectively. The photocurrent registered for fully textured (110) film is among record values reported for thin planar films. Moreover, the developed fine-tuning of crystal orientation having a huge impact on the photoefficiency would induce further improvement of thin hematite films mainly if cation doping will be combined with the controllable texture.

The development of sustainable methods directed towards the synthesis of molecules is due to the heightened awareness and recognition of alternative eco-friendly and economical protocols that have minimum impact on environment. Among others, microwave (MW)-assisted methodology has matured and can be used safely to substitute for conventional laboratory heating techniques; a number of chemical transformations have been achieved thereby improving many existing protocols with superior results when compared to reactions performed under conventional heating conditions. The focus of this review is to summarize recent MW-assisted catalytic reactions performed in aqueous media for the development of environmentally benign protocols. We review the catalytic MW-assisted methods employed for the synthesis of a variety of heterocycles, cross-coupling reactions, C H activation reactions, synthesis of peptides, ureas, and carboxyl-containing coordination polymers and a host of miscellaneous reactions. In addition, some recent newer developments such as continuous flow capillary MW microreactors and other related flow applications are included. This sustainable approach represents the fusion of friendly reaction medium (water) and microwave activation in conjunction with a variety of catalysts.

Stringent demands from society to address environmental issues and achieve an economically sustainable environment have placed tremendous pressure on industries to replace homogeneous catalyst with recoverable heterogeneous alternatives. Owing to recent advances in science and catalysis technology, these transformations have been revisited for the purpose of developing new nanocatalysts. In this review, we first discuss the background behind the huge interest in the important class of silica-coated magnetic nanoparticles (SMNPs) as nanocatalysts. Next, we discuss the importance of the unique arrangement of silica over magnetic nanoparticles (MNPs). Particular attention is given to recent developments and advances in spatial organization, functionalization and protection of these silica supported nanocatalysts. Synthetic protocols and applications of these nanomaterials for different organic transformations, such as carbon–carbon coupling reactions, acetylation, oxidation, hydrogenation, olefin-metathesis, asymmetric synthesis, photo-catalytic and other green reactions, are briefly discussed, providing a basic outline of the work performed to date. Exploration of the potential contribution of these nanoparticles (NPs) as recoverable, efficient and selective catalysts in various industrially significant organic transformations is the primary objective of these methodologies.

The work deals with fabrication of iron oxide (α-Fe 2 O 3 ) hematite films by a novel high-power impulse magnetron sputtering method (HiPIMS). Hematite is regarded as a highly promising material for sustainable production of hydrogen via photoelectrochemical (PEC) water splitting. Some of the crucial issues of hematite are a large overpotential needed to develop the water oxidation photocurrent onset, high extent of surface defects acting as traps, and a short diffusion length (2–4 nm) of photogenerated holes. We report on minimizing these limits by deposition of highly photoactive nanocrystalline very thin (∼30 nm) absorbing hematite films by HiPIMS and their passivation by ultra-thin (∼2 nm) atomic layer deposited (ALD) isocrystalline alumina oxide (α-Al 2 O 3 ) films. A new approach of one-step annealing of this bilayer system is introduced. The films were judged on the basis of physical properties such as crystalline structure, optical absorption, surface topography, and electronic properties. The functional properties were investigated under simulated photoelectrochemical (PEC) water-splitting conditions. The shift by 1 V vs. RHE and the maximal photocurrent value of 0.48 mA cm −2 at 1.23 V vs. RHE were achieved.

Graphene and carbon quantum (QDs) dots exhibit interesting and well-defined properties owing to their quantum confinement. In this work, graphene QDs (G-QDs) and carbon QDs of size ~6 nm and ~2 nm, respectively, were prepared and their potential uses in electrochemistry and electrochemical sensing were subsequently investigated. It was discovered that the C-QDs surface displayed a faster electron transfer rate compared to the G-QDs following analyses with the ferro/ferricyanide redox probe. Studies were also carried out with redox biomarkers such as uric acid (UA) and ascorbic acid (AA), and it was found that while the C-QDs displayed electrocatalytic properties toward the oxidation of both UA and AA, the G-QDs seemed to only have an impact on AA, from the decrease in the oxidation peak potential. This work provides direct electrochemical comparison of the two latest frontiers of carbon nanomaterials and opens the way for their electrochemical sensing applications. Keywords: Quantum dots, Graphene, Carbon, Electron transfer

Microwave heating of an aqueous solution of citric acid, boric acid and urea affords boron-doped carbon dots (C-dots) with ultrafine size (2–6 nm) and quasi-spherical shape. The new dots are freely dispersible in water providing stable, optically transparent dispersions with olive-green color. The optical properties of the dots were studied in respect to their photoluminescence and nonlinear optical response. Boron-doped C-dots exhibit absorption–emission features that strongly resemble the optical properties of conventional quantum dots with a strong blue fluorescence under UV excitation. Importantly, we demonstrate for the first time that boron doping in C-dots causes a significant enhancement of the nonlinear optical response compared to un-doped carbon dots. This result is in line with previous studies reporting a similar effect on the non-linear optical properties of boron-doped silicon nanocrystals.

Transfer of semiconductor thin films on transparent and or flexible substrates is a highly desirable process to enable photonic, catalytic, and sensing technologies. A promising approach to fabricate nanostructured TiO2 films on transparent substrates is self-ordering by anodizing of thin metal films on fluorine-doped tin oxide (FTO). Here, we report pulsed direct current (DC) magnetron sputtering for the deposition of titanium thin films on conductive glass substrates at temperatures ranging from room temperature to 450 °C. We describe in detail the influence that deposition temperature has on mechanical, adhesion and microstructural properties of titanium film, as well as on the corresponding TiO2 nanotube array obtained after anodization and annealing. Finally, we measure the photoelectrochemical water splitting activity of different TiO2 nanotube samples showing that the film deposited at 150 °C has much higher activity correlating well with the lower crystallite size and the higher degree of self-organization observed in comparison with the nanotubes obtained at different temperatures. Importantly, the film showing higher water splitting activity does not have the best adhesion on glass substrate, highlighting an important trade-off for future optimization.

The design of advanced high‐energy‐density supercapacitors requires the design of unique materials that combine hierarchical nanoporous structures with high surface area to facilitate ion transport and excellent electrolyte permeability. Here, shape‐controlled 2D nanoporous carbon sheets (NPSs) with graphitic wall structure through the pyrolysis of metal–organic frameworks (MOFs) are developed. As a proof‐of‐concept application, the obtained NPSs are used as the electrode material for a supercapacitor. The carbon‐sheet‐based symmetric cell shows an ultrahigh Brunauer–Emmett–Teller (BET)‐area‐normalized capacitance of 21.4 µF cm−2 (233 F g−1), exceeding other carbon‐based supercapacitors. The addition of potassium iodide as redox‐active species in a sulfuric acid (supporting electrolyte) leads to the ground‐breaking enhancement in the energy density up to 90 Wh kg−1, which is higher than commercial aqueous rechargeable batteries, maintaining its superior power density. Thus, the new material provides a double profits strategy such as battery‐level energy and capacitor‐level power density., K.J. is grateful to the Alexander von Humboldt (AvH) foundation for a postdoctoral fellowship. D.P.D. acknowledges the support of University of Adelaide, Australia for grant of Research Fellowship (VC Fellow). D.P.D. and P.G.R. acknowledge funding from MINECO‐FEDER (MAT2015‐68394‐R) and AGAUR (NESTOR 2014_SGR_1505) ICN2 acknowledges support from the Severo Ochoa Program (MINECO, Grant SEV‐2013‐0295) and funding from the CERCA Programme/Generalitat de Catalunya. The authors also gratefully acknowledge support by the Catalysis Research Centre (CRC) at TU Munich, the support from the Ministry of Education, Youth and Sports of the Czech Republic (LO1305), and the assistance provided by the Research Infrastructure NanoEnviCz, supported by the Ministry of Education, Youth and Sports of the Czech Republic under Project No. LM2015073. The work was further supported by the Operational Programme Research, Development and Education—European Regional Development Fund, Project No. CZ.02.1.01/0.0/0.0/15_003/0000416 of the Ministry of Education, Youth and Sports of the Czech Republic.

High surface area TiO2 nanotubes (TNTs) were used as a catalyst support for well dispersed, stable and ultra-small (3–5 nm) Pt nanoparticles (Pt@TNTs) for the reduction of olefins. Pt@TNT catalyst was synthesized by a simple soaking of anodized TNTs in the chloroplatinic (H2PtCl6) acid solution. Various techniques such as XRD, SEM, TEM, and XPS were used to characterize the materials and its catalytic property for the olefin reduction has been described along with a proposed mechanism. The Pt@TNT catalyst showed moderate to high catalytic conversions of styrene and its derivative to ethyl benzene-based products using hydrazine hydrate as a reducing agent. An excellent catalytic activity along with high product selectivity was achieved using low amount (10 mg) of Pt@TNT catalyst containing ∼2.2 wt.% Pt and short reaction time (45 min).

In article number https://doi.org/10.1002/advs.201801029, Kolleboyina Jayaramulu, Justus Masa, Wolfgang Schuhmann, Roland A. Fischer, and co‐workers report simple and facile synthesis of cobalt‐based 2D zeolite imidazole framework nanosheets [Co‐ZIF‐9(III)] by mechano‐chemical grinding with subsequent liquid‐phase exfoliation. The resultant 2D material exhibits highly efficient oxygen evolution reaction (OER) activity under alkaline conditions, attributed to increased accessibility of redox‐active cobalt oxyhydroxide active sites with a nitrogen coordination environment N4CoOOH, and efficiently mimics Co‐Porphyrin electrocatalysts.

A new category of iron oxide nanoparticles (surface active maghemite nanoparticles (SAMNs, γ-Fe2O3)) allows the intimate chemical and electrical contact with DNA by direct covalent binding. On these basis, different DNA-nanoparticle architectures are developed and used as platform for studying electrical properties of DNA. The macroscopic 3D nanobioconjugate, constituted of 5% SAMNs, 70% water, and 25% DNA, shows high stability, electrochemical reversibility and, moreover, electrical conductivity (70–80 Ω cm−1). Reversible electron transfer at the interface between nanoparticles and DNA is unequivocally demonstrated by Mossbauer spectroscopy, which shows the appearance of Fe(II) atoms on nanoparticles following nanobioconjugate formation. This represents the first example of permanent electron exchange by DNA, as well as, of DNA conductivity at a macroscopic scale. Finally, the most probable configuration of the binding is tentatively modeled by density functional theory (DFT/UBP86/6-31+G*), showing the occurrence of electron transfer from the organic orbitals of DNA to surface exposed Fe(III) on nanoparticles, as well as the generation of defects (holes) on the DNA bases. The unequivocal demonstration of DNA conduction provides a new perspective in the five decades long debate about electrical properties of this biopolymer, further suggesting novel approaches for DNA exploitation in nanoelectronics.

This paper critically reviews the current understanding of the analysis of selenium in the natural environment. Several inorganic species of Se (−2, 0, +4, and +6) and organic species (monomethylated and dimethylated) have been reported in aquatic systems. Inorganic speciation of Se varies with pH and Eh. Many different analytical methods including UV–visible spectrophotometry, spectrofluorimetry, atomic fluorescence spectroscopy (AFS), chromatography, flameless atomic absorption spectroscopy (FAAS), electrochemistry, and inductively coupled plasma with atomic emission (ICP-AES) or mass spectrometry (ICP-MS) are available for quantification of selenium levels in different matrices. In recent years, analytical speciation techniques made a great leap in separating and detecting low levels of Se, but analyzing reduced species such as Se(0), polyselenides, and sulfur–selenium mixed species in the environment need further development. A number of selenium compounds has been identified in biota, but positive identification of such compounds in environmental samples is needed to understand the speciation of selenium in natural waters, sediments, and soils.

Nanoscale zerovalent iron (nZVI) particles with a narrow size distribution (40–80 nm) were modified with an environmentally acceptable non-ionic surfactant, Tween 80, with the aim to produce a highly concentrated aqueous dispersion (20% (w/w)) exhibiting temporal stability against aggregation and therefore retaining its mobility and extreme reactivity with pollutants. Powdered nZVI particles, prepared via a large-scale thermally induced process, were directly transferred into the 5% (w/w) aqueous solution of the Tween 80, which has not been performed before. Due to the nature of the surfactant molecules, they adsorb immediately at the new phase interface, which results in the formation of a thin, compact but pollutant permeable surface layer on nZVI particles (confirmed by TEM analysis). The temporal stability against aggregation and oxidation of the Tween 80 modified nZVI particles was monitored by XRD, Mossbauer spectroscopy, and DLS during its two-month storage. These analyses revealed an extraordinarily low degree of oxidation of the nZVI surface (estimated to represent less than 15%) and a high stability against aggregation even after two-month storage. The batch experiments with solutions contaminated by a mixture of chlorinated ethenes confirmed excellent reactivity of the Tween 80 stabilized nZVI particles with all studied pollutants (i.e., PCE, TCE, cis-DCE, trans-DCE). The decomposition rates achieved with Tween 80 modified nZVI particles were significantly higher compared to the non-stabilized nZVI particles prepared via the borohydride reduction method.

Nanoparticles are regarded as attractive candidates for heterogeneous catalysis in various imperative catalytic processes as they are now easy to prepare with a desired size, structure, morphology and composition. Advanced integrated nanocatalysts (INCs) are considered to be a new class of heterogeneous catalysts distinctly different from the conventional ones. INCs are multicomponent materials with a nanoarchitecture typically designed by incorporating nanoparticles into a defined matrix. Thus, INCs can exhibit various morphologies depending on the targeted catalytic process and the type of the immobilized catalyst. In this highlight, we would like to demonstrate the sophisticated nanoarchitecture, synthetic approaches and unique catalytic properties of specifically selected INCs.

The static and dynamic magnetic response of the newly synthesized CoFe2O4–Ag hetero nano-system showed significant enhancement in the effective energy barrier and reduction of the magnetic hardness of CoFe2O4 upon interaction with non-magnetic Ag as compared to neat CoFe2O4. The observed magnetic properties of CoFe2O4–Ag have been dissected in detail using the superparamagnetic Stoner–Wohlfarth and Neel–Arrhenius/Vogel–Fulcher models with the aid of micromagnetic simulations. Fil: Sharma, Surender K.. Universidade Estadual de Campinas; Brasil. Université Paris Diderot - Paris 7; Francia. Palacký University Olomouc; República Checa Fil: Vargas, Jose Marcelo. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Vargas, Nicolás Manuel. Universidad de Santiago de Chile; Chile Fil: Castillo Sepúlveda, Sebastián. Universidad de Santiago de Chile; Chile Fil: Altbir Drullinsky, Dora Rosa. Universidad de Santiago de Chile; Chile Fil: Kleber, Roberto Pirota. Universidade Estadual de Campinas; Brasil Fil: Zboril, Radek. Universidade Estadual de Campinas; Brasil Fil: Zoppellaro, Giorgio. Palacký University Olomouc; República Checa Fil: Knobel, Marcelo. Universidade Estadual de Campinas; Brasil

Core-shell nanoparticles (CSNs) are a class of nanostructured materials that have recently received increased attention owing to their interesting properties and broad range of applications in catalysis, biology, materials chemistry and sensors. By rationally tuning the cores as well as the shells of such materials, a range of core-shell nanoparticles can be produced with tailorable properties that can play important roles in various catalytic processes and offer sustainable solutions to current energy problems. Various synthetic methods for preparing different classes of CSNs, including the Stöber method, solvothermal method, one-pot synthetic method involving surfactants, etc., are briefly mentioned here. The roles of various classes of CSNs are exemplified for both catalytic and electrocatalytic applications, including oxidation, reduction, coupling reactions, etc.

The self-assembly process in a solution of a mononuclear iron(II) complex based on the bispyrazolylpyridine scaffold with graphene oxide (GO) micrometer-sheets allows not only the devising of a new hybrid-architecture for GO-based materials suitable for nanomedicine, but also the unveiling of the reactive nature of GO as a drug-carrier. The neat iron complex is found to be highly active in disrupting the cell cycle through DNA binding, with behaviour and efficiency similar to that expressed by ruthenium-complexes as well as antibiotic-drugs such as doxorubicin. On the contrary, in the hybrid material the proclivity of neat GO to produce reactive oxygen species (ROS) became down-regulated by the electron-buffering properties of the loaded iron complex, evidencing the presence of an active electron transfer from the drug to GO. These findings question the use of the neat GO platform as a suitable carrier for metal-based anticancer drugs and highlight the importance of addressing the chemical/physical integrity of the drug being loaded into GO before drawing conclusions on the potential effectiveness of the hybrid material for medical applications.

The synthesis, stability, and toxicity of engineered metal nanoparticles (ENPs) have been extensively studied during the past two decades. In contrast, research on the formation, fate, and ecological effects of naturally-occurring nanoparticles (NNPs) has become a focus of attention only recently. The natural existence of metal nanoparticles and their oxides/sulfides in waters, wastewaters, ore deposits, mining regions, and hydrothermal vents, as exemplified by the formation of nanoparticles containing silver and gold (AgNPs and AuNPs), Fe, Mn, pyrite (FeS2), Ag2S, CuS, CdS, and ZnS, is dictated largely by environmental conditions (temperature, pH, oxic/anoxic, light, and concentration and characteristics of natural organic matter (NOM)). Examples include the formation of nanoparticles containing pyrite, Cu and Zn-containing pyrite, and iron in hydrothermal vent black smoker emissions. Metal sulfide nanoparticles can be formed directly from their precursor ions or indirectly by sulfide ion-assisted transformation of the corresponding metal oxides under anaerobic conditions. This tutorial focuses on the formation mechanisms, fate, and toxicity of natural metal nanoparticles. Natural waters containing Ag(I) and Au(III) ions in the presence of NOM generate AgNPs and AuNPs under thermal, non-thermal, and photochemical conditions. These processes are significantly accelerated by existing redox species of iron (Fe(II)/Fe(III)). NOM, metal-NOM complexes, and reactive oxygen species (ROS) such as O2˙(-), ˙OH, and H2O2 are largely responsible for the natural occurrence of nanoparticles. AgNPs and AuNPs emanating from Ag(I)/Au(III)-NOM reactions are stable for several months, thus indicating their potential to be transported over long distances from their point of origin. However, endogenous cations present in natural waters can destabilize the nanoparticles, with divalent cations (e.g., Ca(2+), Mg(2+)) being more influential than their monovalent equivalents (e.g., Na(+), K(+)). The toxicity of NNPs may differ from that of ENPs because of differences in the coatings on the nanoparticle surfaces. An example of this phenomenon is presented and is briefly discussed.

We present the preparation of disk-like graphene nanoflakes, highly dispersible in dimethylformamide (DMF), with uniform size and thickness. The preparation procedure includes an overnight mild sonication of natural graphite in DMF, followed by a purification step using ultra-centrifugation. The mean diameter of the as produced well defined round shaped graphene nanoflakes is about 100 nm and they consisted of less than twenty graphenic layers.

The design and development of organic–inorganic hybrid nanomaterials and their applications in catalysis – an important area in sustainable chemistry – have captivated the attention of several researchers worldwide, as they enable environmentally friendly and benign catalytic processes. In recent years, novel approaches have been adopted to design highly selective nanostructured catalysts by controlling the interaction between the active catalytic species and the support material. There are extensive reports wherein silica nanoparticles (NPs) have been employed as solid supports for the fabrication of organic–inorganic hybrid nanocatalysts, possessing several outstanding features such as high activity and selectivity, excellent stability, efficient recovery and recyclability. Moreover, such quasi-homogeneous catalytic systems are free from diffusion problems that are generally associated with bulk catalytic systems, as these NPs can be dispersed in a wide range of organic solvents, eventually facilitating the accessibility of the substrates to the metal centres. This review attempts to summarise recent progress in the development of hybrid materials based on silica NPs, with special emphasis on the various fabrication strategies employed in previously published reports. Furthermore, a broad overview of the applications of these heterogeneous nanocatalysts in numerous organic transformations, including oxidation, reduction, condensation, amination, coupling, polymerization, addition and many more, is presented. It is believed that the successful applications of such versatile nanocatalytic systems would play a key role in establishing sustainable technologies.

Regularly spaced TiO2 nanotubes were prepared by anodizing a titanium substrate in triethylene glycol electrolyte at elevated temperature. In comparison to conventional TiO2 nanotubes, spaced nanotubes possess an adjustable spacing between the individual nanotubes; this allows for controlled buildup of a hierarchical nanoparticle‐on‐nanotube structure. Here, we use this principle for layer‐by‐layer decoration of the tubes with TiO2 nanoparticles. The hierarchical structure after N doping and NH3 treatment at 450 °C shows a significant enhancement of visible‐light absorption, although it only carries a low doping concentration of nitrogen. For optimized N‐doped and particle‐decorated spaced TiO2 nanotubes, a considerable improvement in photocatalytic activity is obtained in comparison with conventional N‐doped TiO2 nanotubes or comparable N‐doped nanoparticle films. This is attributed to an enhanced visible‐light absorption through the N‐doped nanoparticle shell and a fast charge separation between the shell and the one‐dimensional nanotubular core.

A facile approach for the synthesis of magnetite microspheres with flower-like morphology is reported that proceeds via the reduction of iron(III) oxide under a hydrogen atmosphere. The ensuing magnetic catalyst is well characterized by XRD, FE-SEM, TEM, N2 adsorption-desorption isotherm, and Mössbauer spectroscopy and explored for a simple yet efficient transfer hydrogenation reduction of a variety of nitroarenes to respective anilines in good to excellent yields (up to 98%) employing hydrazine hydrate. The catalyst could be easily separated at the end of a reaction using an external magnet and can be recycled up to 10 times without any loss in catalytic activity.

An unprecedented two-step spin-crossover behavior with the sequence of γ

Solar driven photoelectrochemical water splitting (PEC-WS) using semiconductor photoelectrodes represents a promising approach for a sustainable and environmentally friendly production of renewable energy vectors and fuel sources, such as dihydrogen (H

Background Conversely to common coated iron oxide nanoparticles, novel naked surface active maghemite nanoparticles (SAMNs) can covalently bind DNA. Plasmid (pDNA) harboring the coding gene for GFP was directly chemisorbed onto SAMNs, leading to a novel DNA nanovector (SAMN@pDNA). The spontaneous internalization of SAMN@pDNA into cells was compared with an extensively studied fluorescent SAMN derivative (SAMN@RITC). Moreover, the transfection efficiency of SAMN@pDNA was evaluated and explained by computational model. Methods SAMN@pDNA was prepared and characterized by spectroscopic and computational methods, and molecular dynamic simulation. The size and hydrodynamic properties of SAMN@pDNA and SAMN@RITC were studied by electron transmission microscopy, light scattering and zeta-potential. The two nanomaterials were tested by confocal scanning microscopy on equine peripheral blood-derived mesenchymal stem cells (ePB-MSCs) and GFP expression by SAMN@pDNA was determined. Results Nanomaterials characterized by similar hydrodynamic properties were successfully internalized and stored into mesenchymal stem cells. Transfection by SAMN@pDNA occurred and GFP expression was higher than lipofectamine procedure, even in the absence of an external magnetic field. A computational model clarified that transfection efficiency can be ascribed to DNA availability inside cells. Conclusions Direct covalent binding of DNA on naked magnetic nanoparticles led to an extremely robust gene delivery tool. Hydrodynamic and chemical-physical properties of SAMN@pDNA were responsible of the successful uptake by cells and of the efficiency of GFP gene transfection. General significance SAMNs are characterized by colloidal stability, excellent cell uptake, persistence in the host cells, low toxicity and are proposed as novel intelligent DNA nanovectors for efficient cell transfection.

A novel graphitic carbon nitride (GCN) material has been synthesized through a low-temperature solvolysis of sodium cyanide in formamide. The structure and morphology of the so-obtained GCN solid were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman/Infrared (IR) spectroscopy and thermal gravimetric analysis (TGA). GCN is characterized by a compacted layered structure bearing a high content of pendant amine groups (1.4 mmol g −1 ). Electron Paramagnetic Resonance spectroscopy reveals that the pendant amine groups are readily accessible by extrinsic metal cations. Moreover, GCN has a considerable electron-donating capacity to adsorbed electron accepting ions such as Cu 2+ . GCN shows an appreciable As(III) uptake capacity of 39.7 mg g −1 . Based on theoretical Surface Complexation Model we provide a consistent interfacial/structural picture that describes quantitatively observed phenomena.

There is renewed interest in the tetra-oxy compound of +6 oxidation states of iron, ferrate(VI) (Fe(VI)O4(2-)), commonly called ferrate. Ferrate has the potential in cleaner ("greener") technologies for water treatment and remediation processes, as it produces potentially less toxic byproducts than other treatment chemicals (e.g., chlorine). Ferrate has strong potential to oxidize a number of contaminants, including sulfur- and nitrogen-containing compounds, estrogens, and antibiotics. This oxidation capability of ferrate combines with its efficient disinfection and coagulation properties as a multi-purpose treatment chemical in a single dose. This review focuses on the engineering aspects of ferrate use at the pilot scale to remove contaminants in and enhance physical treatment of water and wastewater. In most of the pilot-scale studies, in-line and on-line electrochemical ferrate syntheses have been applied. In this ferrate synthesis, ferrate was directly prepared in solution from an iron anode, followed by direct addition to the contaminant stream. Some older studies applied ferrate as a solid. This review presents examples of removing a range of contaminants by adding ferrate solution to the stream. Results showed that ferrate alone and in combination with additional coagulants can reduce total suspended solids (TSS), chemical oxygen demand (COD), biological oxygen demand (BOD), and organic matter. Ferrate also oxidizes cyanide, sulfide, arsenic, phenols, anilines, and dyes and disinfects a variety of viruses and bacteria. Limitations and drawbacks of the application of ferrate in treating contaminated water on the pilot scale are also presented.

The presence of the potent cyanotoxin, microcystin-LR (MC-LR), in drinking water sources poses a serious risk to public health. The kinetics of the reactivity of ferrate(VI) (Fe(VI)O4(2-), Fe(VI)) with MC-LR and model compounds (sorbic acid, sorbic alcohol, and glycine anhydride) are reported over a range of solution pH. The degradation of MC-LR followed second-order kinetics with the bimolecular rate constant (kMCLR+Fe(VI)) decreasing from 1.3 ± 0.1 × 10(2) M(-1) s(-1) at pH 7.5 to 8.1 ± 0.08 M(-1) s(-1) at pH 10.0. The specific rate constants for the individual ferrate species were determined and compared with a number of common chemical oxidants employed for water treatment. Detailed product studies using liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) indicated the oxidized products (OPs) were primarily the result of hydroxylation of the aromatic ring, double bond of the methyldehydroalanine (Mdha) amino acid residue, and diene functionality. Products studies also indicate fragmentation of the cyclic MC-LR structure occurs under the reaction conditions. The analysis of protein phosphatase (PP1) activity suggested that the degradation byproducts of MC-LR did not possess significant biological toxicity. Fe(VI) was effective for the degradation MC-LR in water containing carbonate ions and fulvic acid (FA) and in lake water samples, but higher Fe(VI) dosages would be needed to completely remove MC-LR in lake water compared to deionized water.

Carbon dots represent an emerging class of fluorescent materials and provide a broad application potential in various fields of biomedicine and optoelectronics. In this review, we introduce various synthetic strategies and basic photoluminescence properties of carbon dots, and then address their advanced in vitro and in vivo bioapplications including cell imaging, photoacoustic imaging, photodynamic therapy and targeted drug delivery. We further consider the applicability of carbon dots as components of light emitting diodes, which include carbon dot based electroluminescence, optical down-conversion, and hybrid plasmonic devices. The review concludes with an outlook towards future developments of these emerging light-emitting materials.

The synthesis of tin-titanate nanotubes (Sn-titanate) by reacting hydrogen titanate (H-titanate) with a tin salt through ion adsorption-incorporation is reported. The interactions between tin(II) ions and H-titanate are thoroughly investigated. Tin ions can be easily adsorbed by H-titanate, owing to its large surface area and lattice spacing, and the negatively charged layered structures. With Sn-titanate nanotubes as precursors, Sn-doped TiO2 nanoparticles are prepared by annealing and are investigated as anode materials in lithium-ion batteries, which show much enhanced capacity and rate capability. Such improved electrochemical properties of Sn-doped TiO2 benefit from structural characteristics such as the small size of the constituent nanoparticles, high crystallinity, and uniform tin doping. This synthetic strategy towards Sn-doped TiO2 anode materials, thus offers the synergistic effect of combining the advantages of TiO2 (cycle life and rate) and SnO2 (high capacity).

An efficient and benign protocol is reported for the synthesis of medicinally important pyrazole derivatives, 4-methoxyaniline, and Ullmann-type condensation reaction using magnetically separable and reusable magnetite-supported copper (nanocat-Fe-CuO) nanoparticles under mild conditions. Nanoparticles with average size of 20–30 nm have been synthesized using simple impregnation techniques in aqueous medium from readily available inexpensive starting materials and were recycled six times without loss in catalytic activity.