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1.	Aftab, Umair, et al. (author) Nickel-cobalt bimetallic sulfide NiCo(2)S(4)nanostructures for a robust hydrogen evolution reaction in acidic media 2020 In: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 10:37, s. 22196-22203 Journal article (peer-reviewed)abstract There are many challenges associated with the fabrication of efficient, inexpensive, durable and very stable nonprecious metal catalysts for the hydrogen evolution reaction (HER). In this study, we have designed a facile strategy by tailoring the concentration of precursors to successfully obtain nickel-cobalt bimetallic sulfide (NiCo2S4) using a simple hydrothermal method. The morphology of the newly prepared NiCo(2)S(4)comprised a mixture of microparticles and nanorods, which were few microns in dimension. The crystallinity of the composite sample was found to be excellent with a cubic phase. The sample that contained a higher amount of cobalt compared to nickel and produced single-phase NiCo(2)S(4)exhibited considerably improved HER performance. The variation in the salt precursor concentration during the synthesis of a material is a simple methodology to produce a scalable platinum-free catalyst for HER. The advantageous features of the multiple active sites of cobalt in the CN-21 sample as compared to that for pristine CoS and NiS laid the foundation for the provision of abundant active edges for HER. The composite sample produced a current density of 10 mA cm(-2)at an overpotential of 345 mV. Also, it exhibited a Tafel value of 60 mV dec(-1), which predominantly ensured rapid charge transfer kinetics during HER. CN-21 was highly durable and stable for 30 hours. Electrochemical impedance spectroscopy showed that the charge transfer resistance was 21.88 ohms, which further validated the HER polarization curves and Tafel results. CN-21 exhibited a double layer capacitance of 4.69 mu F cm(-2)and a significant electrochemically active surface area of 134.0 cm(2), which again supported the robust efficiency for HER. The obtained results reveal that our developed NiCo(2)S(4)catalyst has a high density of active edges, and it is a non-noble metal catalyst for the hydrogen evolution reaction. The present findings provide an alternative strategy and an active nonprecious material for the development of energy-related applications.
2.	Aftab, Umair, et al. (author) Two step synthesis of TiO2–Co3O4 composite for efficient oxygen evolution reaction 2021 In: International journal of hydrogen energy. - : Elsevier. - 0360-3199 .- 1879-3487. ; 46:13, s. 9110-9122 Journal article (peer-reviewed)abstract For an active hydrogen gas generation through water dissociation, the sluggish oxygen evolution reaction (OER) kinetics due to large overpotential is a main hindrance. Herein, a simple approach is used to produce composite material based on TiO2/Co3O4 for efficient OER and overpotential is linearly reduced with increasing amount of TiO2. The scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) investigations reveal the wire like morphology of composite materials, formed by the self-assembly of nanoparticles. The titania nanoparticles were homogenously distributed on the larger Co3O4 nanoparticles. The powder x-ray diffraction revealed a tetragonal phase of TiO2 and the cubic phase of Co3O4 in the composite materials. Composite samples with increasing TiO2 content were obtained (18%, 33%, 41% and 65% wt.). Among the composites, cobalt oxide-titanium oxide with the highest TiO2 content (CT-20) possesses the lowest overpotential for OER with a Tafel slope of 60 mV dec−1 and an exchange current density of 2.98 × 10−3A/cm2. The CT-20 is highly durable for 45 h at different current densities of 10, 20 and 30 mA/cm2. Electrochemical impedance spectroscopy (EIS) confirmed the fast charge transport for the CT-20 sample, which potentially accelerated the OER kinetics. These results based on a two-step methodology for the synthesis of TiO2/Co3O4 material can be useful and interesting for various energy storage and energy conversion systems.
3.	Backes, Claudia, et al. (author) Production and processing of graphene and related materials 2020 In: 2D Materials. - : IOP Publishing. - 2053-1583. ; 7:2 Journal article (peer-reviewed)abstract We present an overview of the main techniques for production and processing of graphene and related materials (GRMs), as well as the key characterization procedures. We adopt a 'hands-on' approach, providing practical details and procedures as derived from literature as well as from the authors' experience, in order to enable the reader to reproduce the results. Section I is devoted to 'bottom up' approaches, whereby individual constituents are pieced together into more complex structures. We consider graphene nanoribbons (GNRs) produced either by solution processing or by on-surface synthesis in ultra high vacuum (UHV), as well carbon nanomembranes (CNM). Production of a variety of GNRs with tailored band gaps and edge shapes is now possible. CNMs can be tuned in terms of porosity, crystallinity and electronic behaviour. Section II covers 'top down' techniques. These rely on breaking down of a layered precursor, in the graphene case usually natural crystals like graphite or artificially synthesized materials, such as highly oriented pyrolythic graphite, monolayers or few layers (FL) flakes. The main focus of this section is on various exfoliation techniques in a liquid media, either intercalation or liquid phase exfoliation (LPE). The choice of precursor, exfoliation method, medium as well as the control of parameters such as time or temperature are crucial. A definite choice of parameters and conditions yields a particular material with specific properties that makes it more suitable for a targeted application. We cover protocols for the graphitic precursors to graphene oxide (GO). This is an important material for a range of applications in biomedicine, energy storage, nanocomposites, etc. Hummers' and modified Hummers' methods are used to make GO that subsequently can be reduced to obtain reduced graphene oxide (RGO) with a variety of strategies. GO flakes are also employed to prepare three-dimensional (3d) low density structures, such as sponges, foams, hydro- or aerogels. The assembly of flakes into 3d structures can provide improved mechanical properties. Aerogels with a highly open structure, with interconnected hierarchical pores, can enhance the accessibility to the whole surface area, as relevant for a number of applications, such as energy storage. The main recipes to yield graphite intercalation compounds (GICs) are also discussed. GICs are suitable precursors for covalent functionalization of graphene, but can also be used for the synthesis of uncharged graphene in solution. Degradation of the molecules intercalated in GICs can be triggered by high temperature treatment or microwave irradiation, creating a gas pressure surge in graphite and exfoliation. Electrochemical exfoliation by applying a voltage in an electrolyte to a graphite electrode can be tuned by varying precursors, electrolytes and potential. Graphite electrodes can be either negatively or positively intercalated to obtain GICs that are subsequently exfoliated. We also discuss the materials that can be amenable to exfoliation, by employing a theoretical data-mining approach. The exfoliation of LMs usually results in a heterogeneous dispersion of flakes with different lateral size and thickness. This is a critical bottleneck for applications, and hinders the full exploitation of GRMs produced by solution processing. The establishment of procedures to control the morphological properties of exfoliated GRMs, which also need to be industrially scalable, is one of the key needs. Section III deals with the processing of flakes. (Ultra)centrifugation techniques have thus far been the most investigated to sort GRMs following ultrasonication, shear mixing, ball milling, microfluidization, and wet-jet milling. It allows sorting by size and thickness. Inks formulated from GRM dispersions can be printed using a number of processes, from inkjet to screen printing. Each technique has specific rheological requirements, as well as geometrical constraints. The solvent choice is critical, not only for the GRM stability, but also in terms of optimizing printing on different substrates, such as glass, Si, plastic, paper, etc, all with different surface energies. Chemical modifications of such substrates is also a key step. Sections IV-VII are devoted to the growth of GRMs on various substrates and their processing after growth to place them on the surface of choice for specific applications. The substrate for graphene growth is a key determinant of the nature and quality of the resultant film. The lattice mismatch between graphene and substrate influences the resulting crystallinity. Growth on insulators, such as SiO2, typically results in films with small crystallites, whereas growth on the close-packed surfaces of metals yields highly crystalline films. Section IV outlines the growth of graphene on SiC substrates. This satisfies the requirements for electronic applications, with well-defined graphene-substrate interface, low trapped impurities and no need for transfer. It also allows graphene structures and devices to be measured directly on the growth substrate. The flatness of the substrate results in graphene with minimal strain and ripples on large areas, allowing spectroscopies and surface science to be performed. We also discuss the surface engineering by intercalation of the resulting graphene, its integration with Si-wafers and the production of nanostructures with the desired shape, with no need for patterning. Section V deals with chemical vapour deposition (CVD) onto various transition metals and on insulators. Growth on Ni results in graphitized polycrystalline films. While the thickness of these films can be optimized by controlling the deposition parameters, such as the type of hydrocarbon precursor and temperature, it is difficult to attain single layer graphene (SLG) across large areas, owing to the simultaneous nucleation/growth and solution/precipitation mechanisms. The differing characteristics of polycrystalline Ni films facilitate the growth of graphitic layers at different rates, resulting in regions with differing numbers of graphitic layers. High-quality films can be grown on Cu. Cu is available in a variety of shapes and forms, such as foils, bulks, foams, thin films on other materials and powders, making it attractive for industrial production of large area graphene films. The push to use CVD graphene in applications has also triggered a research line for the direct growth on insulators. The quality of the resulting films is lower than possible to date on metals, but enough, in terms of transmittance and resistivity, for many applications as described in section V. Transfer technologies are the focus of section VI. CVD synthesis of graphene on metals and bottom up molecular approaches require SLG to be transferred to the final target substrates. To have technological impact, the advances in production of high-quality large-area CVD graphene must be commensurate with those on transfer and placement on the final substrates. This is a prerequisite for most applications, such as touch panels, anticorrosion coatings, transparent electrodes and gas sensors etc. New strategies have improved the transferred graphene quality, making CVD graphene a feasible option for CMOS foundries. Methods based on complete etching of the metal substrate in suitable etchants, typically iron chloride, ammonium persulfate, or hydrogen chloride although reliable, are time- and resource-consuming, with damage to graphene and production of metal and etchant residues. Electrochemical delamination in a low-concentration aqueous solution is an alternative. In this case metallic substrates can be reused. Dry transfer is less detrimental for the SLG quality, enabling a deterministic transfer. There is a large range of layered materials (LMs) beyond graphite. Only few of them have been already exfoliated and fully characterized. Section VII deals with the growth of some of these materials. Amongst them, h-BN, transition metal tri- and di-chalcogenides are of paramount importance. The growth of h-BN is at present considered essential for the development of graphene in (opto) electronic applications, as h-BN is ideal as capping layer or substrate. The interesting optical and electronic properties of TMDs also require the development of scalable methods for their production. Large scale growth using chemical/physical vapour deposition or thermal assisted conversion has been thus far limited to a small set, such as h-BN or some TMDs. Heterostructures could also be directly grown. Section VIII discusses advances in GRM functionalization. A broad range of organic molecules can be anchored to the sp(2) basal plane by reductive functionalization. Negatively charged graphene can be prepared in liquid phase (e.g. via intercalation chemistry or electrochemically) and can react with electrophiles. This can be achieved both in dispersion or on substrate. The functional groups of GO can be further derivatized. Graphene can also be noncovalently functionalized, in particular with polycyclic aromatic hydrocarbons that assemble on the sp(2) carbon network by pi-pi stacking. In the liquid phase, this can enhance the colloidal stability of SLG/FLG. Approaches to achieve noncovalent on-substrate functionalization are also discussed, which can chemically dope graphene. Research efforts to derivatize CNMs are also summarized, as well as novel routes to selectively address defect sites. In dispersion, edges are the most dominant defects and can be covalently modified. This enhances colloidal stability without modifying the graphene basal plane. Basal plane point defects can also be modified, passivated and healed in ultra-high vacuum. The decoration of graphene with metal nanoparticles (NPs) has also received considerable attention, as it allows to exploit synergistic effects between NPs and graphene. Decoration can be either achieved chemically or in the gas phase. All LMs,
4.	Bhatti, Adeel Liaquat, et al. (author) Nanostructured Co3O4 electrocatalyst for OER : The role of organic polyelectrolytes as soft templates 2021 In: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 398 Journal article (peer-reviewed)abstract Designing an efficient electrocatalyst for the oxygen evolution reaction (OER) in alkaline media is highly needed but very challenging task. Herein, we used organic polyelectrolytes such as (carboxymethyl cellulose) CMC and polyacrylamide polymers for the growth of Co3O4 nanostructures by aqueous chemical growth method. The morphology and composition studies were performed on scanning electron microscopy (SEM), energy dispersive X-ray (EDX), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM) techniques. The structural properties and the surface chemistry of the Co3O4 electrocatalysts were correlated to the OER performance, and the enhancement mechanism with respect to pristine Co3O4 was observed to be specifically related to the polyelectrolyte templating role.Co3O4@CMC composites displayed reduced crystallite size, producing OER overpotential as low as 290 mV at 10 mAcm−2 in 1.0 KOH and Tafel slope of 71 mVdec−1, suggesting fast transfer of intermediates and electrons during water electrolysis. On the other hand, the use of polyacrylamide and its different templating mechanism resulted in similar crystallite size, but preferential exposed faces and larger surface vacancies content, as demonstrated by HR-TEM and XPS, respectively. Consistently, this material displays cutting-edge OER performance, such as overpotential of 260 mV at 10 mAcm−2 and a low Tafel slope of 63 mVdec−1. The proposed strategy for the preparation of Co3O4 nanostructures in the presence of CMC and polyacrylamide is facile, mass production, thus it could equally contributed towards the realization of hydrogen energy. Therefore, these nanostructures of Co3O4 can be regarded as an alternative and promising materials for the different electrochemical applications including fuel cells, metal air batteries, overall water electrolysis and other energy storage devices.
5.	Comini, Elisabetta, et al. (author) Effects of Ta/Nb-doping on titania-based thin films for gas-sensing 2005 In: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 108:1-2 SPEC. ISS., s. 21-28 Journal article (peer-reviewed)abstract Thin films of titania with the addition of niobium and tantalum have been achieved by reactive sputtering process. Structural and morphological studies have been carried out by means of XRD, RBS, TEM and AFM in order to correlate the microstructural features to the sensing performance of the layers. The films proved sensitive to ethanol and carbon monoxide and ammonia. In the case of niobium addition, it was shown that annealing temperature and niobium content strongly influence the gas response of the films converting a n-type response, which is typical of pure TiO2 and of most of metal-oxide sensors, to a p-type response; this peculiarity is crucial for the discrimination of different gases. In the case of tantalum addition, the annealing treatment at 800 °C led only to a phase transformation that reduced the sensing performance of the layer. High sensitivity to CO is achieved with anatase or mixed anatase and rutile phases, while the rutile phase only exhibit a low gas sensitivity. © 2005 Elsevier B.V. All rights reserved.
6.	Di Maria, Francesca, et al. (author) Controlling the Functional Properties of Oligothiophene Crystalline Nano/Microfibers via Tailoring of the Self-Assembling Molecular Precursors 2018 In: Advanced Functional Materials. - : John Wiley & Sons. - 1616-301X .- 1616-3028. ; 28:32 Journal article (peer-reviewed)abstract Oligothiophenes are π-conjugated semiconducting and fluorescent molecules whose self-assembly properties are widely investigated for application in organic electronics, optoelectronics, biophotonics, and sensing. Here an approach to the preparation of crystalline oligothiophene nano/microfibers is reported based on the use of a “sulfur overrich” quaterthiophene building block, T4S4 , containing in its covalent network all the information needed to promote the directional, π–π stacking-driven, self-assembly of Y-T4S4-Y oligomers into fibers with hierarchical supramolecular arrangement from nano- to microscale. It is shown that when Y varies from unsubstituted thiophene to thiophene substituted with electron-withdrawing groups, a wide redistribution of the molecular electronic charge takes place without substantially affecting the aggregation modalities of the oligomer. In this way, a structurally comparable series of fibers is obtained having progressively varying optical properties, redox potentials, photoconductivity, and type of prevailing charge carriers (from p- to n-type). With the aid of density functional theory (DFT) calculations, combined with powder X-ray diffraction data, a model accounting for the growth of the fibers from molecular to nano- and microscale is proposed
7.	Fedorenko, Svetlana V., et al. (author) Silica Nanospheres Coated by Ultrasmall Ag0 Nanoparticles for Oxidative Catalytic Application 2017 In: Colloid and Interface Science Communications. - : Elsevier. - 2215-0382. ; 21, s. 1-5 Journal article (peer-reviewed)abstract The present work introduces optimal modifiсation of core-shell composite nanomaterial, where small (2–8 nm) Ag0 nanoparticles are deposited onto large (about 140 nm) silica spheres for application in oxidative catalysis. The size of Ag0 and density of its deposition onto silica spheres was modified by the post treatment of initially deposited Ag0 (about 30 nm) by hydrogen peroxide in specific conditions. The comparison of catalytic effect of the post-treated and initial SN-Ag0 in electrochemical phosphonation of benzo(thia)oxazoles by diethyl phosphite in oxidative conditions revealed the difference between the composite nanoparticles. In particular, the post-treated SNs-Ag0 nanoparticles exhibit efficient catalytic effect in oxidative conditions resulting in facile and green method for synthesis of phosphonated benzooxa(thia)zoles, while no catalytic effect is observed under the use of larger Ag0 nanoparticles deposited onto silica spheres. The use of Ag0-based nanomaterial in oxidative catalysis had been never demonstrated before
8.	Ghamgosar, Pedram, 1979-, et al. (author) Self-Powered Photodetectors Based on Core-Shell ZnO-Co3O4 Nanowire Heterojunctions 2019 In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 11:26, s. 23454-23462 Journal article (peer-reviewed)abstract Self-powered photodetectors operating in the UV–visible–NIR window made of environmentally friendly, earth abundant, and cheap materials are appealing systems to exploit natural solar radiation without external power sources. In this study, we propose a new p–n junction nanostructure, based on a ZnO–Co3O4 core–shell nanowire (NW) system, with a suitable electronic band structure and improved light absorption, charge transport, and charge collection, to build an efficient UV–visible–NIR p–n heterojunction photodetector. Ultrathin Co3O4 films (in the range 1–15 nm) were sputter-deposited on hydrothermally grown ZnO NW arrays. The effect of a thin layer of the Al2O3 buffer layer between ZnO and Co3O4 was investigated, which may inhibit charge recombination, boosting device performance. The photoresponse of the ZnO–Al2O3–Co3O4 system at zero bias is 6 times higher compared to that of ZnO–Co3O4. The responsivity (R) and specific detectivity (D*) of the best device were 21.80 mA W–1and 4.12 × 1012 Jones, respectively. These results suggest a novel p–n junction structure to develop all-oxide UV–vis photodetectors based on stable, nontoxic, low-cost materials.
9.	Gilzad Kohan, Mojtaba, et al. (author) Plasma assisted vapor solid deposition of Co3O4 tapered nanorods for energy applications 2019 In: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 7:46, s. 26302-26310 Journal article (peer-reviewed)abstract Self-standing, 1-dimensional (1D) structures of p-type metal oxide (MOx) have been the focus of considerable attention, due to their unique properties in energy storage and solar light conversion. However, the practical performance of p-type MOx is intrinsically limited by their interfacial defects and strong charge recombination losses. Single crystalline assembly can significantly reduce recombination at interface and grain boundaries. Here, we present a one-step route based on plasma assisted physical vapor deposition (PVD), for the rational and scalable synthesis of single crystalline 1D vertically aligned Co3O4 tapered nanorods (NRs). The effect of PVD parameters (deposition pressure, temperature and duration) in tuning the morphology, composition and crystalline structure of resultant NRs is investigated. Crystallographic data obtained from X-ray diffraction and high-resolution transmission electron microscopy (TEM) indicated the single crystalline nature of NRs with [111] facet preferred orientation. The NRs present two optical band gaps at about 1.48 eV and 2.1 eV. Current–voltage (I–V) characteristic of the Co3O4 NRs electrodes, 400 nm long, present two times higher current density at −1 V forward bias, compared to the benchmarking thin film counterpart. These array structures exhibit good electrochemical performance in lithium-ion adsorption–desorption processes. Among all, the longest Co3O4 NRs electrodes delivers a 1438.4 F g−1 at current density of 0.5 mA cm−2 and presents 98% capacitance retention after 200 charge–discharge cycles. The very low values of charge transfer resistance (Rct = 5.2 Ω for 400 nm long NRs) of the NRs testifies their high conductivity. Plasma assisted PVD is demonstrated as a facile technique for synthesizing high quality 1D structures of Co3O4, which can be of interest for further development of different desirable 1D systems based on transition MOx.
10.	Infantes-Molina, Antonia, et al. (author) Au-Decorated Ce–Ti Mixed Oxides for Efficient CO Preferential Photooxidation 2020 In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 12:34, s. 38019-38030 Journal article (peer-reviewed)abstract We investigated the photocatalytic behavior of gold nanoparticles supported on CeO2–TiO2 nanostructured matrixes in the CO preferential oxidation in H2-rich stream (photo-CO-PROX), by modifying the electronic band structure of ceria through addition of titania and making it more suitable for interacting with free electrons excited in gold nanoparticles through surface plasmon resonance. CeO2 samples with different TiO2 concentrations (0–20 wt %) were prepared through a slow coprecipitation method in alkaline conditions. The synthetic route is surfactant-free and environmentally friendly. Au nanoparticles (<1.0 wt % loading) were deposited on the surface of the CeO2–TiO2 oxides by deposition–precipitation. A benchmarking sample was also considered, prepared by standard fast coprecipitation, to assess how a peculiar morphology can affect the photocatalytic behavior. The samples appeared organized in a hierarchical needle-like structure, with different morphologies depending on the Ti content and preparation method, with homogeneously distributed Au nanoparticles decorating the Ce–Ti mixed oxides. The morphology influences the preferential photooxidation of CO to CO2 in excess of H2 under simulated solar light irradiation at room temperature and atmospheric pressure. The Au/CeO2–TiO2 systems exhibit much higher activity compared to a benchmark sample with a non-organized structure. The most efficient sample exhibited CO conversions of 52.9 and 80.2%, and CO2 selectivities equal to 95.3 and 59.4%, in the dark and under simulated sunlight, respectively. A clear morphology–functionality correlation was found in our systematic analysis, with CO conversion maximized for a TiO2 content equal to 15 wt %. The outcomes of this study are significant advancements toward the development of an effective strategy for exploitation of hydrogen as a viable clean fuel in stationary, automotive, and portable power generators.
11.	Jin, Lei, et al. (author) Engineering Interfacial Structure in “Giant” PbS/CdS Quantum Dots for Photoelectrochemical Solar Energy Conversion 2016 In: Nano Energy. - : Elsevier BV. - 2211-2855. ; 30, s. 531-541 Journal article (peer-reviewed)abstract The interfacial structure in “giant” PbS/CdS quantum dots (QDs) was engineered by modulating the Cd:S molar ratio during in situ growth. The control of the gradient interfacial layer could facilitate hole transfer, regulate the transition from double- to single-color emission, as a consequence. These QDs are optically active close-to-the near-infrared (NIR) spectral region and are candidates as absorber materials in solar energy conversion. Photoinduced charge transfer from “giant” QDs to electron scavenger can still take place despite the ultra-thick (~5 nm) shell. The hybrid architecture based on a TiO2 mesoporous framework sensitized by the “giant” QDs with alloyed interface can produce a saturated photocurrent density as high as ~5.3 mA/cm2 in a photoelectrochemical (PEC) cell under 1 Sun illumination, which is around 2 times higher than that of bare PbS and core/thin-shell PbS/CdS QDs sensitizer. The as-prepared PEC device presented very good stability thanks to the “giant” core/shell QDs architecture with tailored interfacial layer and a further coating of the ZnS shell. 78% of the initial current density is kept after 2-hour irradiation at 1 Sun. Engineering of electronic band structure plays a key role in boosting the functional properties of these composite systems, which hold great potential for H2 production in PEC devices.
12.	Khrizanforov, Mikhail N, et al. (author) Silica-supported silver nanoparticles as an efficient catalyst for aromatic C-H alkylation and fluoroalkylation 2018 In: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 47:29, s. 9608-9616 Journal article (peer-reviewed)abstract The efficient catalysis of oxidative alkylation and fluoroalkylation of aromatic C-H bonds is of paramount importance in the pharmaceutical and agrochemical industries, and requires the development of convenient Ag0-based nano-architectures with high catalytic activity and recyclability. We prepared Ag-doped silica nanoparticles (Ag0/+@SiO2) with a specific nano-architecture, where ultra-small sized silver cores are immersed in silica spheres, 40 nm in size. The nano-architecture provides an efficient electrochemical oxidation of Ag+@SiO2 without any external oxidant. In turn, Ag+@SiO2 5 mol% results in 100% conversion of arenes into their alkylated and fluoroalkylated derivatives in a single step at room temperature under nanoheterogeneous electrochemical conditions. Negligible oxidative leaching of silver from Ag0/+@SiO2 is recorded during the catalytic coupling of arenes with acetic, difluoroacetic and trifluoroacetic acids, which enables the good recyclability of the catalytic function of the Ag0/+@SiO2 nanostructure. The catalyst can be easily separated from the reaction mixture and reused a minimum of five times upon electrochemical regeneration. The use of the developed Ag0@SiO2 nano-architecture as a heterogeneous catalyst facilitates aromatic C-H bond substitution by alkyl and fluoroalkyl groups, which are privileged structural motifs in pharmaceuticals and agrochemicals.
13.	Landström, Anton, et al. (author) Reduced graphene oxide-ZnO hybrid composites as photocatalysts : The role of nature of the molecular target in catalytic performance 2021 In: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 47:14, s. 19346-19355 Journal article (peer-reviewed)abstract Spurred by controversial literature findings, we enwrapped reduced graphene oxide (rGO) in ZnO hierarchical microstructures (rGO loadings spanning from 0.01 to 2 wt%) using an in situ synthetic procedure. The obtained hybrid composites were carefully characterized, aiming at shining light on the possible role of rGO on the claimed increased performance as photocatalysts. Several characterization tools were exploited to unveil the effect exerted by rGO, including steady state and time resolved photoluminescence, electron microscopies and electrochemical techniques, in order to evaluate the physical, optical and electrical features involved in determining the catalytic degradation of rhodamine B and phenol in water.Several properties of native ZnO structures were found changed upon the rGO enwrapping (including optical absorbance, concentration of native defects in the ZnO matrix and double-layer capacitance), which are all involved in determining the photocatalytic performance of the hybrid composites. The findings discussed in the present work highlight the high complexity of the field of application of graphene-derivatives as supporters of semiconducting metal oxides functionality, which has to be analyzed through a multi-parametric approach.
14.	Marin, Riccardo, et al. (author) Mercaptosilane-Passivated CuInS2 Quantum Dots for Luminescence Thermometry and Luminescent Labels 2019 In: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 2:4, s. 2426-2436 Journal article (peer-reviewed)abstract Bright and nontoxic quantum dots (QDs) are highly desirable in a variety of applications, from solid-state devices to luminescent probes in assays. However, the processability of these species is often curbed by their surface chemistry, which limits their dispersibility in selected solvents. This renders a surface modification step often mandatory to make the QDs compatible with the solvent of interest. Here, we present a new synthetic approach to produce CuInS2 QDs compatible with organic polar solvents and readily usable for the preparation of composite materials. 3-Mercaptopropyl trimethoxysilane (MPTS) was used simultaneously as solvent, sulfur source, and capping agent for the QD synthesis. The synthesized QDs possessed a maximum photoluminescence quantum yield around 6%, reaching approximately 55% after growing a ZnS shell. The partial condensation of MPTS molecules on the surface of QDs was probed by solid-state nuclear magnetic resonance, whose results were used to interpret the interaction of the QDs with different solvents. To prove the versatility of the developed QDs, imparted by the thiolated silane molecules, we prepared via straightforward procedures two nanocomposites of practical interest: (i) silica nanoparticles decorated with QDs and (ii) an inexpensive polymeric film with embedded QDs. We further demonstrate the potential of this composite film as a luminescence thermometer operational over a broad temperature interval, with relative thermal sensitivity above 1% K–1 in the range of biological interest.
15.	Mazzaro, Raffaello, et al. (author) Hematite nanostructures : An old material for a new story. Simultaneous photoelectrochemical oxidation of benzylamine and hydrogen production through Ti doping 2019 In: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 61, s. 36-46 Journal article (peer-reviewed)abstract Overall water splitting represents one of the most promising approaches toward solar energy conversion and storage, which is, however, severely challenged by the four-electron/four-proton nature of the oxygen evolution reaction (OER). One option to overcome this issue is to replace OER with a more useful reaction, for simultaneous production of both hydrogen and chemicals of interest. For the purpose, in this paper a cheap, hydrothermally prepared Ti-doped nanostructured hematite photoanode was employed for the first time as highly stable, heterogeneous catalyst for the low bias, efficient and highly selective photoinduced oxidation of benzylamine to N-benzylidenebenzylamine, and for the simultaneous production of hydrogen in a double solvent/environment cell. A preliminary estimate indicates the possibility to obtain a ∼150 μmol h−1 H2 production, with the contemporary production of stoichiometric benzylidene N-benzylamine in a 5 × 5 cm2 area electrode. This study contributes to overcome the 40-year lasting issues limiting the use of hematite in industrial photoelectrochemical sunlight conversion and storage, due to poor performance of hematite and lack of economic value of oxygen production, providing solid evidence for the simultaneous use of hematite in hydrogen production and alternative oxidation reactions of industrial importance.
16.	Sanchez Sanchez, Jaime, 1990, et al. (author) All-Electrochemical Nanofabrication of Stacked Ternary Metal Sulfide/Graphene Electrodes for High-Performance Alkaline Batteries 2022 In: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 18 Journal article (peer-reviewed)abstract Energy-storage materials can be assembled directly on the electrodes of a battery using electrochemical methods, this allowing sequential deposition, high structural control, and low cost. Here, a two-step approach combining electrophoretic deposition (EPD) and cathodic electrodeposition (CED) is demonstrated to fabricate multilayer hierarchical electrodes of reduced graphene oxide (rGO) and mixed transition metal sulfides (NiCoMnSx). The process is performed directly on conductive electrodes applying a small electric bias to electro-deposit rGO and NiCoMnSx in alternated cycles, yielding an ideal porous network and a continuous path for transport of ions and electrons. A fully rechargeable alkaline battery (RAB) assembled with such electrodes gives maximum energy density of 97.2 Wh kg−1 and maximum power density of 3.1 kW kg−1, calculated on the total mass of active materials, and outstanding cycling stability (retention 72% after 7000 charge/discharge cycles at 10 A g−1). When the total electrode mass of the cell is considered, the authors achieve an unprecedented gravimetric energy density of 68.5 Wh kg−1, sevenfold higher than that of typical commercial supercapacitors, higher than that of Ni/Cd or lead–acid Batteries and similar to Ni–MH Batteries. The approach can be used to assemble multilayer composite structures on arbitrary electrode shapes.
17.	Selopal, Gurpreet Singh, et al. (author) Graphene as transparent front contact for dye sensitized solar cells 2015 In: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 135, s. 99-105 Journal article (peer-reviewed)abstract A transparent conductive graphene film is investigated as front contact in dye-sensitized solar cells (DSSCs), as an alternative to traditional transparent conducting oxides (TCO). The film is composed of poly-crystalline few-layers graphene, covering homogeneously an area of 1 cm2, deposited by chemical vapour deposition (CVD) technique on larger area Cu catalyst substrate and transferred on glass. DSSC photoanode is then fabricated, according to consolidated procedure, by sequential casting of TiO2 films through tape casting technique, followed by annealing at 500 °C, and sensitization with N719 dye. An outstanding value of photoconversion efficiency as high as 2% is recorded for the best cell, under one sun irradiation (AM 1.5 G, 100 mW cm−2), which is the highest ever reported for this kind of devices using graphene as front conducting film. Compared to previous results in the literature, the application of a large area continuous graphene film, guaranteed by the CVD deposition, definitely outperforms graphene layers composed by smaller graphene platelets (at micrometer scale). Morphological and electrical characterizations of graphene are reported and the functional performances of the best cell are compared with those obtained from classical DSSC exploiting fluorine-doped tin oxide. Obtained results encourage further investigation of graphene homogeneous thin film as viable alternative to standard TCOs for application in advanced devices, requiring high temperature processing or flexible substrates, incompatible with standard TCO films.
18.	Shifa, Tofik Ahmed, et al. (author) Controllable Synthesis of 2D Nonlayered Cr2S3 Nanosheets and Their Electrocatalytic Activity Toward Oxygen Evolution Reaction 2021 In: Frontiers in Chemical Engineering. - : Frontiers Media Sa. - 2673-2718. ; 3 Journal article (peer-reviewed)abstract The design of oxygen evolution reaction (OER) electrocatalysts based on Earth-abundant materials holds great promise for realizing practically viable water-splitting systems. In this regard, two-dimensional (2D) nonlayered materials have received considerable attention in recent years owing to their intrinsic dangling bonds which give rise to the exposure of unsaturated active sites. In this work, we solved the synthesis challenge in the development of a 2D nonlayered Cr2S3 catalyst for OER application via introducing a controllable chemical vapor deposition scheme. The as-obtained catalyst exhibits a very good OER activity requiring overpotentials of only 230 mV and 300 mV to deliver current densities of 10 mA cm(-2) and 30 mA cm(-2), respectively, with robust stability. This study provides a general approach to optimize the controllable growth of 2D nonlayered material and opens up a fertile ground for studying the various strategies to enhance the water splitting reactions.
19.	Shifa, Tofik Ahmed, et al. (author) Interfacing CrOx and CuS for synergistically enhanced water oxidation catalysis 2023 In: Chemical Engineering Journal. - : Elsevier B.V.. - 1385-8947 .- 1873-3212. ; 453:Part 1 Journal article (peer-reviewed)abstract The sluggish kinetics associated with the oxygen evolution reaction (OER) limits the sustainability of fuel production and chemical synthesis. Developing catalysts based on Earth abundant elements with a reasonable strategy could solve the challenge. Here, we present a heterostructure built from CrOx and CuS whose interface gives rise to the advent of new functionalities in catalytic activity. Using X-ray photoelectron and absorption spectroscopies, we identified the multiple oxidation states and low coordination number of Cr metal in CrOx-CuS heterostructure. Benefitting from these features, CrOx-CuS generates oxygen gas through water splitting with a low over potential of 190 mV vs RHE at a current density of 10 mA cm−2. The catalyst shows no evident deactivation after a 36-hours operation in alkaline medium. The high catalytic activity, inspired by first principles calculations, and long-time durability make it one of the most effective OER electrocatalysts.
20.	Sirigu, Gianluca, et al. (author) Ultrafast exciton dynamics in doubly emitting asymmetric giant PbS/CdS/CdS Nanocrystals 2015 Conference paper (peer-reviewed)abstract Semiconductor nanocrystals (NCs) are interesting optical materials that have been explored for a range of applications such as light emitting diodes (LEDs), photovoltaic cells, lasers and biologic markers. For practical optical uses heterostructured NCs with thick shells (“giant NCs”) offer the advantage of supressed photoluminescence intermittency and reduced rates of Auger recombination. Giant NCs with proper structures can present simultaneous two-colour emission, due to core and shell states [1-2]. These NCs can be convenient for example in very accurate and self-calibrating nanosystems.
21.	Solangi, Muhammad Yameen, et al. (author) In-situ growth of nonstoichiometric CrO0.87 and Co3O4 hybrid system for the enhanced electrocatalytic water splitting in alkaline media 2023 In: International journal of hydrogen energy. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0360-3199 .- 1879-3487. ; 48:93, s. 36439-36451 Journal article (peer-reviewed)abstract The development of electrocatalysts for electrochemical water splitting has received considerable attention in response to the growing demand for renewable energy sources and environmental concerns. In this study, a simple hydrothermal growth approach was developed for the in-situ growth of non-stoichiometric CrO0.87 and Co3O4 hybrid materials. It is apparent that the morphology of the prepared material shows a heterogeneous aggregate of irregularly shaped nanoparticles. Both CrO0.87 and Co3O4 have cubic crystal structures. Its chemical composition was governed by the presence of Co, Cr, and O as its main constituents. For understanding the role CrO0.87 plays in the half-cell oxygen evolu-tion reaction (OER) in alkaline conditions, CrO0.87 was optimized into Co3O4 nanostructures. The hybrid material with the highest concentration of CrO0.87 was found to be highly efficient at driving OER reactions at 255 mV and 20 mA cm(-2). The optimized material demonstrated excellent durability for 45 h and a Tafel slope of 56 mV dec(-1). Several factors may explain the outstanding performance of CrO0.87 and Co3O4 hybrid materials, including multiple metallic oxidation states, tailored surface properties, fast charge transport, and surface defects. An alternative method is proposed for the preparation of new generations of electrocatalysts for the conversion and storage of energy. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
22.	Solomon, Getachew, et al. (author) Ag2S/MoS2 Nanocomposites Anchored on Reduced Graphene Oxide : Fast Interfacial Charge Transfer for Hydrogen Evolution Reaction 2019 In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 11:25, s. 22380-22389 Journal article (peer-reviewed)abstract Hydrogen evolution reaction through electrolysis holds great potential as a clean, renewable, and sustainable energy source. Platinum-based catalysts are the most efficient to catalyze and convert water into molecular hydrogen; however, their large-scale application is prevented by scarcity and cost of Pt. In this work, we propose a new ternary composite of Ag2S, MoS2, and reduced graphene oxide (RGO) flakes via a one-pot synthesis. The RGO support assists the growth of two-dimensional MoS2 nanosheets partially covered by silver sulfides as revealed by high-resolution transmission electron microscopy. Compared with the bare MoS2 and MoS2/RGO, the Ag2S/MoS2 anchored on the RGO surface (the ternary system Ag2S/MoS2/RGO) demonstrated a high catalytic activity toward hydrogen evolution reaction (HER). Its superior electrochemical activity toward HER is evidenced by the positively shifted (−190 mV vs reversible hydrogen electrode (RHE)) overpotential at a current density of −10 mA/cm2 and a small Tafel slope (56 mV/dec) compared with a bare and binary system. The Ag2S/MoS2/RGO ternary catalyst at an overpotential of −200 mV demonstrated a turnover frequency equal to 0.38 s–1. Electrochemical impedance spectroscopy was applied to understand the charge-transfer resistance; the ternary sample shows a very small charge-transfer resistance (98 Ω) at −155 mV vs RHE. Such a large improvement can be attributed to the synergistic effect resulting from the enhanced active site density of both sulfides and to the improved electrical conductivity at the interfaces between MoS2 and Ag2S. This ternary catalyst opens up further optimization strategies to design a stable and cheap catalyst for hydrogen evolution reaction, which holds great promise for the development of a clean energy landscape.
23.	Solomon, Getachew, et al. (author) Decorating vertically aligned MoS2 nanoflakes with silver nanoparticles for inducing a bifunctional electrocatalyst towards oxygen evolution and oxygen reduction reaction 2021 In: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 81 Journal article (peer-reviewed)abstract Catalysts capable of improving the performance of oxygen evolution reaction (OER) and oxygen reduction reactions (ORR) are essential for the advancement of renewable energy technologies. Herein, Ag-decorated vertically aligned MoS2 nanoflakes are developed via magnetron co-sputtering and investigated as electrocatalyst towards OER and ORR. Due to the presence of silver, the catalyst shows more than 1.5 times an increase in the roughness-normalized rate of OER, featuring a very low Tafel slope (58.6 mv dec−1), thus suggesting that the catalyst surface favors the thermodynamics of hydroxyl radical (OH•) adsorption with the deprotonation steps being the rate-determining steps. The improved performance is attributed to the strong interactions between OOH intermediates and the Ag surface which reduces the activation energy. Rotating ring disk electrode (RRDE) analysis shows that the net disk currents on the Ag-MoS2 sample are two times higher at 0.65 V compared to MoS2, demonstrating the co-catalysis effect of silver doping. Based on the rate constant values, Ag-MoS2 proceeds through a mixed 4 electron and a 2 + 2 serial route reduction mechanism, in which the ionized hydrogen peroxide is formed as a mobile intermediate. The presence of silver decreases the electron transfer number and increases the peroxide yield due to the interplay of a 2 + 2 electron reduction pathway. A 2.5–6 times faster conversion rate of peroxide to OH- observed due to the presence of silver, indicating its effective cocatalyst nature. This strategy can help in designing a highly active bifunctional catalyst that has great potential as a viable alternative to precious-metal-based catalysts.Graphica
24.	Solomon, Getachew, et al. (author) Microwave-Assisted vs. Conventional Hydrothermal Synthesis of MoS2 Nanosheets : Application towards Hydrogen Evolution Reaction 2020 In: Crystals. - : MDPI. - 2073-4352. ; 10:11 Journal article (peer-reviewed)abstract Molybdenum sulfide (MoS2) has emerged as a promising catalyst for hydrogen evolution applications. The synthesis method mainly employed is a conventional hydrothermal method. This method requires a longer time compared to other methods such as microwave synthesis methods. There is a lack of comparison of the two synthesis methods in terms of crystal morphology and its electrochemical activities. In this work, MoS2 nanosheets are synthesized using both hydrothermal (HT-MoS2) and advanced microwave methods (MW-MoS2), their crystal morphology, and catalytical efficiency towards hydrogen evolution reaction (HER) were compared. MoS2 nanosheet is obtained using microwave-assisted synthesis in a very short time (30 min) compared to the 24 h hydrothermal synthesis method. Both methods produce thin and aggregated nanosheets. However, the nanosheets synthesized by the microwave method have a less crumpled structure and smoother edges compared to the hydrothermal method. The as-prepared nanosheets are tested and used as a catalyst for hydrogen evolution results in nearly similar electrocatalytic performance. Experimental results showed that: HT-MoS2 displays a current density of 10 mA/cm2 at overpotential (−280 mV) compared to MW-MoS2 which requires −320 mV to produce a similar current density, suggesting that the HT-MoS2 more active towards hydrogen evolutions reaction.
25.	Solomon, Getachew, et al. (author) MoS2 Nanosheets Uniformly Anchored on NiMoO4 Nanorods, a Highly Active Hierarchical Nanostructure Catalyst for Oxygen Evolution Reaction and Pseudo-Capacitors 2023 In: Advanced sustainable systems. - : John Wiley & Sons. - 2366-7486. ; 7:2 Journal article (peer-reviewed)abstract Hierarchical nanostructures have attracted considerable research attention due to their applications in the catalysis field. Herein, we design a versatile hierarchical nanostructure composed of NiMoO4 nanorods surrounded by active MoS2 nanosheets on an interconnected nickel foam substrate. The as-prepared nanostructure exhibits excellent oxygen evolution reaction performance, producing a current density of 10 mA cm−2 at an overpotential of 90 mV, in comparison with 220 mV necessary to reach a similar current density for NiMoO4. This behavior originates from the structural/morphological properties of the MoS2 nanosheets, which present numerous surface-active sites and allow good contact with the electrolyte. Besides, the structures can effectively store charges, due to their unique branched network providing accessible active surface area, which facilitates intermediates adsorptions. Particularly, NiMoO4/MoS2 shows a charge capacity of 358 mAhg−1 at a current of 0.5 A g−1 (230 mAhg−1 for NiMoO4), thus suggesting promising applications for charge-storing devices.
26.	Solomon, Getachew, et al. (author) NiMoO4@Co3O4 Core–Shell Nanorods : In Situ Catalyst Reconstruction toward High Efficiency Oxygen Evolution Reaction 2021 In: Advanced Energy Materials. - : Wiley-VCH Verlagsgesellschaft. - 1614-6832 .- 1614-6840. ; 11:32 Journal article (peer-reviewed)abstract The sluggish kinetics of the oxygen evolution reaction (OER) is the bottleneck for the practical exploitation of water splitting. Here, the potential of a core–shell structure of hydrous NiMoO4 microrods conformally covered by Co3O4 nanoparticles via atomic layer depositions is demonstrated. In situ Raman and synchrotron-based photoemission spectroscopy analysis confirms the leaching out of Mo facilitates the catalyst reconstruction, and it is one of the centers of active sites responsible for higher catalytic activity. Post OER characterization indicates that the leaching of Mo from the crystal structure, induces the surface of the catalyst to become porous and rougher, hence facilitating the penetration of the electrolyte. The presence of Co3O4 improves the onset potential of the hydrated catalyst due to its higher conductivity, confirmed by the shift in the Fermi level of the heterostructure. In particular NiMoO4@Co3O4 shows a record low overpotential of 120 mV at a current density of 10 mA cm−2, sustaining a remarkable performance operating at a constant current density of 10, 50, and 100 mA cm−2 with negligible decay. Presented outcomes can significantly contribute to the practical use of the water-splitting process, by offering a clear and in-depth understanding of the preparation of a robust and efficient catalyst for water-splitting.
27.	Tahira, Aneela, et al. (author) Advanced Electrocatalysts for Hydrogen Evolution Reaction Based on Core–Shell MoS2/TiO2 Nanostructures in Acidic and Alkaline Media 2019 In: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 2:3, s. 2053-2062 Journal article (peer-reviewed)abstract Hydrogen production as alternative energy source is still a challenge due to the lack of efficient and inexpensive catalysts, alternative to platinum. Thus, stable, earth abundant, and inexpensive catalysts are of prime need for hydrogen production via hydrogen evolution reaction (HER). Herein, we present an efficient and stable electrocatalyst composed of earth abundant TiO2 nanorods decorated with molybdenum disulfide thin nanosheets, a few nanometers thick. We grew rutile TiO2 nanorods via the hydrothermal method on conducting glass substrate, and then we nucleated the molybdenum disulfide nanosheets as the top layer. This composite possesses excellent hydrogen evolution activity in both acidic and alkaline media at considerably low overpotentials (350 mV and 700 mV in acidic and alkaline media, respectively) and small Tafel slopes (48 and 60 mV/dec in acidic and alkaline conditions, respectively), which are better than several transition metal dichalcogenides, such as pure molybdenum disulfide and cobalt diselenide. A good stability in acidic and alkaline media is reported here for the new MoS2/TiO2 electrocatalyst. These results demonstrate the potential of composite electrocatalysts for HER based on earth abundant, cost-effective, and environmentally friendly materials, which can also be of interest for a broader range of scalable applications in renewable energies, such as lithium sulfur batteries, solar cells, and fuel cells.
28.	Tahira, Aneela, et al. (author) Role of cobalt precursors in the synthesis of Co 3 O 4 hierarchical nanostructures toward the development of cobalt‐based functional electrocatalysts for bifunctional water splitting in alkaline and acidic media 2022 In: Journal of the Chinese Chemical Society (Taipei). - : John Wiley & Sons. - 0009-4536 .- 2192-6549. ; 69:4, s. 681-691 Journal article (peer-reviewed)abstract The precursors have significant influence on the catalytic activity of nonprecious electrocatalysts for effective water splitting. Herein, we report active electrocatalysts based on cobalt oxide (Co3O4) hierarchical nanostructures derived from four different precursors of cobalt (acetate, nitrate, chloride, and sulfate salts) using the low-temperature aqueous chemical growth method. It has been found that the effect of precursor on the morphology of nanostructured material depends on the synthetic method. The Co3O4 nanostructures exhibited cubic phase derived from these four precursors. The Co3O4 nanostructures obtained from chloride precursor have demonstrated improved oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) compared to other precursors due relatively higher content of Co3O4 nanostructures at the surface of material. An overpotential of 400 mV versus reversible hydrogen electrode (RHE) at 10 mA cm−2 was observed for HER. The Co3O4 nanostructures derived from the chloride precursor have shown favorable reaction kinetics via 34 mV dec−1 value of the Tafel slope for HER reaction. The Co3O4 nanostructures derived from chloride precursor have also shown an excellent HER durability for 15 hr in alkaline media. Furthermore, the OER functional characterization was carried out onto Co3O4 nanostructures derived from chloride precursor exhibited 220 mV overpotential at 10 mA cm−2 and Tafel slope of 56 mV dec−1. Importantly, the reason behind the favorable catalytic activity of Co3O4 nanostructures derived from chloride precursor was linked to one order of magnitude smaller charge transfer resistance and higher amount of Co3O4 content at the surface of nanostructures than the Co3O4 nanostructures derived from other precursors. The performance of Co3O4 nanostructures derived from chloride precursor via the wet chemical method suggests that cobalt chloride precursor could be of great interest for the development of efficient, stable, nonprecious, and environmentally friendly electrocatalysts for the chemical energy conversion and storage devices.
29.	Taranova, Anastasiia, et al. (author) Nickel and Cobalt Selenite Hydrates as Broad Solar Absorbers for Enhanced Solar Water Evaporation 2024 In: Solar RRL. - : John Wiley and Sons Inc. - 2367-198X. Journal article (peer-reviewed)abstract Inorganic black materials possessing hydrophilicity are scarce but can be of great importance in areas such as solar water evaporation and solar steam generation. Herein, for the first time, transition-metal selenite hydrates (specifically, Earth-abundant metals Ni and Co) not only possess high solar absorbance (>96 %) in the solar spectral range (UV–vis–NIR) but also excellent hydrophilicity, which plays a key role in water transport in the solar steam generation. The hydrophilic behavior in selenite hydrates originates from trapped “water of hydration” inside its crystal lattice, which can easily form hydrogen bonds with other water molecules, facilitating water transport. Owing to the abovementioned properties, the studied selenite hydrates are tested for solar water evaporation, showing excellent water evaporation rates of 1.83 and 2.34 kg m−2 h−1 for nickel selenite hydrate and cobalt selenite hydrate, exceeding the theoretical limit of 1.47 kg m−2 h−1.
30.	Taranova, Anastasiia, et al. (author) Unraveling the optoelectronic properties of CoSbx intrinsic selective solar absorber towards high-temperature surfaces 2023 In: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1 Journal article (peer-reviewed)abstract The combination of the ability to absorb most of the solar radiation and simultaneously suppress infrared re-radiation allows selective solar absorbers (SSAs) to maximize solar energy to heat conversion, which is critical to several advanced applications. The intrinsic spectral selective materials are rare in nature and only a few demonstrated complete solar absorption. Typically, intrinsic materials exhibit high performances when integrated into complex multilayered solar absorber systems due to their limited spectral selectivity and solar absorption. In this study, we propose CoSbx (2 < x < 3) as a new exceptionally efficient SSA. Here we demonstrate that the low bandgap nature of CoSbx endows broadband solar absorption (0.96) over the solar spectral range and simultaneous low emissivity (0.18) in the mid-infrared region, resulting in a remarkable intrinsic spectral solar selectivity of 5.3. Under 1 sun illumination, the heat concentrates on the surface of the CoSbx thin film, and an impressive temperature of 101.7 °C is reached, demonstrating the highest value among reported intrinsic SSAs. Furthermore, the CoSbx was tested for solar water evaporation achieving an evaporation rate of 1.4 kg m−2 h−1. This study could expand the use of narrow bandgap semiconductors as efficient intrinsic SSAs with high surface temperatures in solar applications.
31.	Xia, Zhenyuan, 1983, et al. (author) Dispersion Stability and Surface Morphology Study of Electrochemically Exfoliated Bilayer Graphene Oxide 2019 In: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 123:24, s. 15122-15130 Journal article (peer-reviewed)abstract During the last decade, electrochemical exfoliation of graphite has aroused great interest from both academia and industry for mass production of graphene sheets. Electrochemically exfoliated graphene oxide (EGO) features a much better tunability than chemically EGO, or even than graphene obtained with ultrasonic exfoliation. Chemical and electrical properties of EGO can be modified extensively, thanks to its step-controllable oxidation process, varying the electrolytes and/or the applied potential. It is thus possible, using tunable electrochemical oxidation, to produce low-defect EGO sheets, featuring both good electric conductivity and good dispersibility in common solvents (e.g., acetonitrile or isopropanol). This greatly facilitates its application in several fields, for example, in flexible electronics. In this work, we correlate the dispersion behavior of EGO with its chemical properties using the relative Hansen solubility parameter, zeta potential values, X-ray photoemission spectroscopy, and Raman analysis. A surface morphology study by atomic force microscopy and transmission electron microscopy analyses also reveals that EGO sheets are multiple structures of (partially oxidized) graphene bilayers. Conductive EGO films could be easily prepared by vacuum filtration on different substrates, obtaining electrical conductivity values of up to ∼104 S/m with no need for further reduction procedures.
32.	Yazdani-Asrami, Mohammad, et al. (author) Roadmap on artificial intelligence and big data techniques for superconductivity 2023 In: Superconductors Science and Technology. - : IOP Publishing. - 0953-2048 .- 1361-6668. ; 36:4, s. 043501-043501 Journal article (peer-reviewed)abstract This paper presents a roadmap to the application of AI techniques and big data (BD) for different modelling, design, monitoring, manufacturing and operation purposes of different superconducting applications. To help superconductivity researchers, engineers, and manufacturers understand the viability of using AI and BD techniques as future solutions for challenges in superconductivity, a series of short articles are presented to outline some of the potential applications and solutions. These potential futuristic routes and their materials/technologies are considered for a 10–20 yr time-frame.
33.	Zhao, Haiguang, et al. (author) Dual emission in Asymmetric “Giant” PbS/CdS/CdS Core/Shell/Shell Quantum Dots 2016 In: Nanoscale. - 2040-3364 .- 2040-3372. ; 8:7, s. 4217-4226 Journal article (peer-reviewed)abstract Semiconducting nanocrystals optically active in the infrared region of the electromagnetic spectrum enable exciting avenues in fundamental research and novel applications compatible with the infrared transparency windows of biosystems such as chemical and biological optical sensing, including nanoscale thermometry. In this context, quantum dots (QDs) with double color emission may represent ultra-accurate and self-calibrating nanosystems. We present the synthesis of giant core/shell/shell asymmetric QDs having a PbS/CdS Zincblende (Zb)/CdS Wurtzite (Wz) structure with double color emission close to the near-infrared (NIR)region. We show that the double emission depends on the excitation condition and analyze the electron-hole distribution responsible of the independent and simultaneous radiative exciton recombination in the PbS core and in the CdS Wz shell, respectively. These results highlight the importance of the driving force leading to preferential crystal growth in asymmetric QDs, and provide a pathway for a rational control of the synthesis of double color emitting giant QDs, leading to the effective exploitation of visible/NIR transparency windows.

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