The need to satisfy the growing global population’s enormous energy demands is a major challenge for modern societies. Photoelectrochemical (PEC) water splitting (WS) is seen as a leading strategy ...for producing an extremely promising renewable store of energy – hydrogen (H2). However, PEC-WS is a complex process involving several sequential physicochemical reaction steps including light absorption, separation of photoexcited charges, and surface redox reactions. At present, FeO-based semiconductors represent a unique class of materials known to exhibit very high performance in all these processes. This review summarizes and critically discusses the major components of PEC-WS systems incorporating FeO-based light-harvesting systems, and outlines the progress that has been made, particularly over the last decade. Emphasis is placed on materials used as photoanodes (including hematite and nonhematite iron oxides, spinel iron ferrites, and pseudobrookite iron titanates) as well as materials used as cocatalysts and passivation layers – notably iron hydroxyoxides and their composites. We discuss strategies for overcoming the main limitations of the aforementioned materials via nanostructuring, elemental doping, surface decoration, and the formation of advanced hybrid nanoarchitectures. Finally, we use this knowledge to present a critical overview of the field and the future prospects of Fe-O semiconductors in PEC-WS applications.
In the present study, the coupling of adsorption capacity and photocatalytic efficiency of two different industrially produced titania catalysts was investigated and compared. The azo dye Reactive ...Red 195 was selected as a model compound. The tested catalysts, PK-10 and PK-180, exhibited different adsorption capacities due to their significant difference in their specific surface, but both have proven to be effective photocatalysts for photodegradation of the studied dye. PK-10 exhibited strong adsorption of the studied dye due to its high specific surface area, while the second studied catalyst, PK-180, demonstrated negligible adsorption of Reactive Red 195. The effect of the pH, the concentration of the catalyst and the initial concentration of the dye appear to affect the photocatalytic rate. The effect of the presence of humic acids and inorganic ions was also examined, while the contribution of various reactive species was indirectly evaluated through the addition of various scavengers. To evaluate the extent of mineralisation of the studied dye, total organic carbon (TOC) measurements during the experiment were also conducted. Besides total colour removal, evident reduction of TOC was also achieved using both catalysts.
Graphene-based materials enable the sensing of diverse biomolecules using experimental approaches based on electrochemistry, spectroscopy, or other methods. Although basic sensing was achieved, it ...had until now not been possible to understand and control biomolecules' structural and morphological organization on graphene surfaces (i.e. their stacking, folding/unfolding, self-assembly, and nano-patterning). Here we present the insight into structural and morphological organization of biomolecules on graphene in water, using an RNA hairpin as a model system. We show that the key parameters governing the RNA's behavior on the graphene surface are the number of graphene layers, RNA concentration, and temperature. At high concentrations, the RNA forms a film on the graphene surface with entrapped nanobubbles. The density and the size of the bubbles depend on the number of graphene layers. At lower concentrations, unfolded RNA stacks on the graphene and forms molecular clusters on the surface. Such a control over the conformational behavior of interacting biomolecules at graphene/water interfaces would facilitate new applications of graphene derivatives in biotechnology and biomedicine.
In this work, the covalent attachment of an amine functionalized metal‐organic framework (UiO‐66‐NH2 = Zr6O4(OH)4(bdc‐NH2)6; bdc‐NH2 = 2‐amino‐1,4‐benzenedicarboxylate) (UiO‐Universitetet i Oslo) to ...the basal‐plane of carboxylate functionalized graphene (graphene acid = GA) via amide bonds is reported. The resultant GA@UiO‐66‐NH2 hybrid displayed a large specific surface area, hierarchical pores and an interconnected conductive network. The electrochemical characterizations demonstrated that the hybrid GA@UiO‐66‐NH2 acts as an effective charge storing material with a capacitance of up to 651 F g−1, significantly higher than traditional graphene‐based materials. The results suggest that the amide linkage plays a key role in the formation of a π‐conjugated structure, which facilitates charge transfer and consequently offers good capacitance and cycling stability. Furthermore, to realize the practical feasibility, an asymmetric supercapacitor using a GA@UiO‐66‐NH2 positive electrode with Ti3C2TX MXene as the opposing electrode has been constructed. The cell is able to deliver a power density of up to 16 kW kg−1 and an energy density of up to 73 Wh kg−1, which are comparable to several commercial devices such as Pb‐acid and Ni/MH batteries. Under an intermediate level of loading, the device retained 88% of its initial capacitance after 10 000 cycles.
A facile method for the preparation of graphene/metal–organic framework (MOF) hybrids with an amine‐functionalized MOF and carboxylate‐functionalized graphene via amide bonds for capacitance applications is demonstrated.
Cationic quaternized carbon dots (QCDs) and anionic graphene oxide sheets (GO) are combined via non-covalent interactions following a self-assembly pathway to form highly biocompatible and ...fluorescent hybrid materials. These hybrids act as selective probes with controlled labelling of the cell nucleus or cytoplasm depending on the QCD loading.
Nanostructural hybrid organic-inorganic metal halide perovskites offer a wide range of potential applications including photovoltaics, solar cells, and light emitting diodes. Up to now the surface ...stabilizing ligands were used solely to obtain the optimal properties of nanoparticles in terms of dimensionality and stability, however their possible additional functionality was rarely considered. In the present work, hybrid lead bromide perovskite nanoparticles (PNP) were prepared using a unique approach where a peptide nucleic acid is used as a surface ligand. Methylammonium lead bromide perovskite colloidal nanoparticles stabilized by thymine-based peptide nucleic acid monomer (PNA-M) and relevant trimer (PNA-T) were prepared exhibiting the size below 10 nm. Perovskite structure and crystallinity were verified by X-ray powder diffraction spectroscopy and high resolution transmission electron microscopy. PNP-PNA-M and PNP-PNA-T colloidal dispersions in chloroform and toluene possessed green-blue fluorescence, while Fourier-transform infrared spectroscopy (FT-IR) and quantum chemical calculations showed that the PNA coordinates to the PNP surface through the primary amine group. Additionally, the sensing ability of the PNA ligand for adenine nucleic acid was demonstrated by photoluminescence quenching via charge transfer. Furthermore, PNP thin films were effectively produced by the centrifugal casting. We envision that combining the unique, tailored structure of peptide nucleic acids and the prospective optical features of lead halide perovskite nanoparticles could expand the field of applications of such hybrids exploiting analogous ligand chemistry.
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The impact of an external magnetic field upon changes in the crystallization kinetics of Fe90Zr7B3 metallic glass is studied by in situ nuclear forward scattering (NFS) of synchrotron ...radiation. Structural and magnetic information on the whole process of nanograin formation is monitored on fly in real time by means of time domain Mössbauer effect technique. Isothermal annealing performed at 753K under weak magnetic field (Bext=0.652T) exhibits more rapid crystallization in comparison with zero-field conditions. These surprising effects of an external magnetic field upon the process of phase transformation are attributed to energetic perturbations of magnetic interactions in comparison with the thermal energy. Consequently, the formation of nucleation centers is enhanced. Such accelerated crystallization was not reported so far for metallic glasses exposed to magnetic field during annealing. The influence of magnetic field on the resulting properties is usually assessed under static conditions after annealing. The use of NFS with rapid data acquisition has allowed in situ observation of the microstructure development throughout the fast annealing processes. In this way, not only the starting and the final stages of the structure can be characterized but also the intermediate transition period states of the transformation can be followed to fine details.
Ordered mesoporous carbons with innate carbonyl functionalities (MC-icf) have been synthesized via a nanocasting process using SBA-15 as a template and acetylenedicarboxylic acid as a carbon source, ...instead of the commonly used sugar. The structural, textural, and surface properties of as derived mesoporous carbon material were investigated by means of spectroscopic, microscopy, and surface physicochemical methods. The experimental results showed that the new mesoporous carbons exhibit basic structural and morphological features that resemble those of CMK-3 carbons, such as hexagonally ordered structure, high specific surface area (980 m2/g), and high mesoporosity. The pore surfaces are rich in functional moieties, such as carboxylate groups, carbonyl, and free radicals. The surface charge properties of MC-icf were studied using potentiometric acid–base titrations. A surface complexation model revealed two types of H-binding sites, each one with a different degree of accessibility by positively charged species. Heavy metal, e.g., Cd2+, Pb2+, and Cu2+, uptake was also studied in detail at different pH values by the combination of analytical and EPR spectroscopic techniques. The data indicate an improved and selective capability for Cd2+, Pb2+, and Cu2+ uptake by the MC-icf compared with the standard CMK-3.
In this work we report on the preparation of some aqueous graphene oxide (GO) dispersions and the investigation of their nonlinear optical response under visible (532 nm) and infrared (1064 nm), ...picosecond and nanosecond laser excitation. The GO colloids were prepared under specific and well-defined conditions resulting in finely dispersed heavily oxidized large GO sheets. In all cases, GO colloids were found to present large nonlinear absorption and negligible nonlinear refraction. The physical mechanisms responsible for their nonlinear optical response are discussed. In addition, the so-prepared GO dispersions were found to exhibit large broadband optical power limiting action for both pulse durations, comparable to that of C60 for visible laser pulses and much superior for infrared ones.
In this work, magnetosomes produced by microorganisms were chosen as a suitable magnetic carrier for covalent immobilization of thermostable trypsin conjugates with an expected applicability for ...efficient and rapid digestion of proteins at elevated temperatures. First, a biogenic magnetite was isolated from Magnetospirillum gryphiswaldense and its free surface was coated with the natural polysaccharide chitosan containing free amino and hydroxy groups. Prior to covalent immobilization, bovine trypsin was modified by conjugating with α-, β- and γ-cyclodextrin. Modified trypsin was bound to the magnetic carriers via amino groups using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysulfosuccinimide as coupling reagents. The magnetic biomaterial was characterized by magnetometric analysis and electron microscopy. With regard to their biochemical properties, the immobilized trypsin conjugates showed an increased resistance to elevated temperatures, eliminated autolysis, had an unchanged pH optimum and a significant storage stability and reusability. Considering these parameters, the presented enzymatic system exhibits properties that are superior to those of trypsin forms obtained by other frequently used approaches. The proteolytic performance was demonstrated during in-solution digestion of model proteins (horseradish peroxidase, bovine serum albumin and hen egg white lysozyme) followed by mass spectrometry. It is shown that both magnetic immobilization and chemical modification enhance the characteristics of trypsin making it a promising tool for protein digestion.
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