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Doping and compositional tuning of Cs(2)AInCl(6) (A = Ag, Na) double perovskite nanocrystals (PNCs) is considered a promising strategy toward the development of light-emitting sources for applications in solution-processed optoelectronic devices. Oleic acid and oleylamine are by far the most often used surface capping ligands for PNCs. However, the undesirable desorption of these ligands due to proton-exchange reaction during isolation and purification processing results in colloidal and structural instabilities. Thus, the improvement of colloidal and optical stability of PNCs represents one of the greatest challenges in the field. Here, we report a trioctylphosphine-mediated synthesis and purification method toward Sb-alloyed Cs2NaInCl6 PNCs with excellent stability and optical features. Nuclear magnetic resonance spectroscopy enabled one to explain the role of trioctylphosphine and to reveal the reaction mechanism during crystal nucleation and growth. Under the optimized reaction conditions, in situ-generated trioctylphosphonium chloride and benzoyl trioctylphosphonium chloride serve as highly reactive halide sources, while benzoyl trioctylphosphonium and oleylammonium cations together with the oleate anion serve as surface capping ligands, which are bound strongly to the PNC surface. The tightly bound ionic pair of oleylammonium oleate and benzoyl trioctylphosphonium chloride/oleate ligands allows one to obtain monodispersed bright-blue-emitting PNCs with high photoluminescence quantum yields exceeding 50% at an optimum Sb content (0.5%), which also exhibit long-term colloidal stability. The approach based on dual cationic ligand passivation of double PNCs opens the doors for applications in other systems with a potential to achieve higher stability along with superior optical properties. Web of Science 13 40 47859 47845

Magnetic iron oxide nanocrystals (MIONs) are established as potent theranostic nanoplatforms due to their biocompatibility and the multifunctionality of their spin-active atomic framework. Recent insights have also unveiled their attractive near-infrared photothermal properties, which are, however, limited by their low near-infrared absorbance, resulting in noncompetitive photothermal conversion efficiencies (PCEs). Herein, we report on the dramatically improved photothermal conversion of condensed clustered MIONs, reaching an ultrahigh PCE of 71% at 808 nm, surpassing the so-far MION-based photothermal agents and even benchmark near-infrared photothermal nanomaterials. Moreover, their surface passivation is achieved through a simple self-assembly process, securing high colloidal stability and structural integrity in complex biological media. The bifunctional polymeric canopy simultaneously provided binding sites for anchoring additional cargo, such as a strong near-infrared-absorbing and fluorescent dye, enabling in vivo optical and photoacoustic imaging in deep tissues, while the iron oxide core ensures detection by magnetic resonance imaging. In vitro studies also highlighted a synergy-amplified photothermal effect that significantly reduces the viability of A549 cancer cells upon 808 nm laser irradiation. Integration of such-previously elusive-photophysical properties with simple and cost-effective nanoengineering through self-assembly represents a significant step toward sophisticated nanotheranostics, with great potential in the field of nanomedicine.

Fully fluorinated graphene (fluorographene) exhibits a weak nonlinear optical response, in contrast to its unfunctionalized counterpart, graphene. However, diethyl-amino-functionalized fluorographene is shown to exhibit a dramatic enhancement of its nonlinear optical response. Diethyl-amino-fluorographene is obtained by the reaction of fluorographene with lithium diethylamide. Partial nucleophilic substitution/reduction of the substrate results in sp3 carbons bonded to diethylamine or fluorine groups and in distinct sp2 domains. The diethylamine groups act as strong electron donors, the C–F groups as strong electron acceptors, and the sp2 domains as π-conjugated bridges, thus forming a donor−π bridge–acceptor nonlinear optical chromophore scheme. As such, the diethyl-amino-fluorographene displays a large enhancement of its nonlinear optical response compared to fluorographene and other fluorographene derivatives under ps, both visible and infrared laser excitation.

In the present work we introduce a simple approach to produce porous PtPdAg alloy nanoparticles on TiO2 nanotubes by a simple combined sputtering-dewetting-dealloying process. In a first step, three individual metals (Pt, Pd and Ag) were sequentially sputter-deposited on spaced TiO2 nanotubes, followed by a thermal dewetting treatment in Ar to convert these metal layers into ternary PtPdAg alloyed particles. Dealloying was carried out by a selective chemical dissolution of Ag in piranha solution that finally generated porous alloyed nanoparticles located on the TiO2 nanotube walls. The porous PtPdAg-decorated TiO2 nanotubes show enhanced photocatalytic H2 generation in comparison with porous Pt (67% increase) or any monometallic decoration (>120% increase). The photocatalytic enhancement is not only due to the increased number of active sites (larger surface area) of the porous particles but also due to the synergistic effects of the different alloying elements.

Ni, Cu and Cu–Ni nanostructures have been fabricated and homogeneously embedded on ultrathin two-dimensional (2D) carbon nitride (g-C3N4), and the surface morphology and composition of the resulting hybrid nanostructures were studied by XRD, TEM, HRTEM-elemental mapping, Raman spectroscopy and XPS. The new hierarchical hetero-structures dropcasted on GC anodes have been visualised by SEM and their catalytic performance have been examined in methanol electrooxidation reaction (MOR) under alkaline conditions. Nanosized Ni particles dispersed finely over g-C3N4 are very active electrocatalysts with MOR onset at potential 0.35 V and charge transfer resistance 0.12 kΩ. The stability of modyfied GC electrodes, examined under chronoamperometric conditions showed that for electrode loading with 4% (wt. %) of NiO the stable current density ca. 36 A g−1 (12 A cm2) was obtained during whole experiment (up to 160 min). For all catalyst studied the curent density obtained during MOR reaction was enhanced when electrode was iluminated by UV light λ∼400 nm, and the highest value were obtained for 4% Ni/CN catalyst ca. 127 A g−1 (22 A cm2). The Cu incorporation in the hybrid material evoke loss of activity mostly due to Cu+ irreversible reduction/oxidation to Cu° and Cu2+, CuO segregation and influencing electron transfer process which results in the increasing in the redox potential. These results represent an important step towards light-enhanced electro-reactive systems and sensors in which heterojunction formation can facilitate electron-hole separation and enable more efficient energy transfer.

Single‐atom catalysts (SACs) are highly enviable to exploit the utmost utilization of metallic catalysts; their efficiency by utilizing nearly all atoms to often exhibit high catalytic performances. To architect the isolated single atom on an ideal solid support with strong coordination has remained a crucial trial. Herein, graphene functionalized with nitrile groups (cyanographene) as an ideal support to immobilize isolated copper atoms G(CN)‐Cu with strong coordination is reported. The precisely designed mixed‐valence single atom copper (G(CN)‐Cu) catalysts deliver exceptional conversions for electrochemical methanol oxidation (MOR) and CO2reduction (CO2RR) targeting a “closed carbon cycle.” An onset of MOR and CO2RR are obtained to be ≈0.4V and ≈−0.7 versus Ag/AgCl, respectively, with single active sites located in an unsaturated coordination environment, it being the most active Cu sites for both studied reactions. Moreover, G(CN)‐Cu exhibited significantly lower resistivity and higher current density toward MOR and CO2RR than observed for reference catalysts.

A hybrid of GA@UiO-66-NH2 was synthesized based on the covalent assembly of graphene acid (GA) and the amine functionalized UiO-66 metal-organic framework through amide bonds. This strategy endows the material with unique properties, such as hierarchical pores, a porous conductive network decorated with functional groups, a high specific surface area, and a good chemical and thermal stability. The resultant hybrid has an electrical resistance of similar to 10(4) omega, whereas the pristine GA and UiO-66-NH2 possess an electrical resistance of similar to 10(2) omega and similar to 10(9) omega, respectively. The hybrid GA@UiO-66-NH2 was demonstrated for CO2 chemiresistive sensing and displayed a very fast response and quick recovery time of similar to 18 s for 100% CO2, at 200 degrees C. While the pristine GA exhibits negligible response under the same conditions, GA@UiO-66-NH2 exhibited a response of 10 +/- 0.6%. Further, in situ temperature dependent Raman studies during CO2 exposure confirm the presence of strong hydrogen bonding interaction between CO2 and the amide functionality present on GA@UiO-66-NH2. The resulting gas sensing characteristics of GA@UiO-66-NH2 are majorly attributed to the better interaction of CO2 at the amide/amine functional groups and the readily accessible hierarchical pores. This design strategy opens new horizons in the development of covalently linked hybrids with hierarchical porous conductive networks which can help to improve the gas sensing properties of MOF-based materials. Web of Science 9 32 17441 17434

Highly ordered multi-leg TiO2 nanotubes (MLTNTs) functionalized with platinized cyanographene are proposed as a hybrid photoelectrode for enhanced photoelectrochemical water splitting. The platinized cyanographene and cyanographene/MLTNTs composite yielded photocurrent densities 1.66 and 1.25 times higher than those of the pristine MLTNTs nanotubes, respectively. Open circuit VOC decay (VOCD), electrochemical impedance spectroscopy (EIS), and intensity-modulated photocurrent spectroscopy (IMPS) analyses were performed to study the recombination rate, charge transfer characteristics, and transfer time of photogenerated electrons, respectively. According to the VOCD and IMPS results, the addition of (platinized) cynographene decreased the recombination rate and the transfer time of photogenerated electrons by one order of magnitude. Furthermore, EIS results showed that the (platinized) cyanographene MLTNTs composite has the lowest charge transfer resistance and therefore the highest photoelectrochemical performance.

Hematite is a low band gap, earth abundant semiconductor and it is considered to be a promising choice for photoelectrochemical water splitting. However, as a bulk material its efficiency is low because of excessive bulk, surface, and interface recombination. In the present work, we propose a strategy to prepare a hematite (&alpha, Fe2O3) photoanode consisting of hematite nanorods grown onto an iron oxide blocking layer. This blocking layer is formed from a sputter deposited thin metallic iron film on fluorine doped tin oxide (FTO) by using cyclic voltammetry to fully convert the film into an anodic oxide. In a second step, hematite nanorods (NR) are grown onto the layer using a hydrothermal approach. In this geometry, the hematite sub-layer works as a barrier for electron back diffusion (a blocking layer). This suppresses recombination, and the maximum of the incident photon to current efficiency is increased from 12% to 17%. Under AM 1.5 conditions, the photocurrent density reaches approximately 1.2 mA/cm2 at 1.5 V vs. RHE and the onset potential changes to 0.8 V vs. RHE (using a Zn-Co co-catalyst).

In this work, we grow intrinsically Cu-doped TiO2 nanotubes (TiNTs) by self-organizing anodization of Ti–Cu binary alloys. We demonstrate that up to a copper concentration of 1.5 at.% in the alloy, self-ordered Cu2+-doped nanotubes can be grown. Under UV illumination the Cu2+ ion-doped oxide structures can be converted to nanotubes that carry metallic nanoparticles (NPs) uniformly decorated on top of the TiNTs. We investigate the formation of these metallic nanoparticles under UV illumination by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). The resulting intrinsic copper-doped and decorated TiNTs have a strongly enhanced photocatalytic activity for H2 evolution in comparison to pristine TiNTs. Key is the light-induced conversion of the intrinsic Cu dopant to metallic copper nanoparticles that act as a stable co-catalyst for H2 generation. Keywords: TiO2, Cu doped TiO2, Photocatalytic activity, Intrinsic copper decoration

Reduced titanium dioxide has recently attracted large attention, particularly for its unique co-catalyst-free H$_2$ heterogeneous photocatalytic application. The enhanced photocatalytic activity of the reduced TiO$_2$ was previously ascribed to the introduction of point crystal defects (mainly Ti$_3^+$ centers), which result in the formation of intrinsic co-catalytic centers and enhanced visible light absorption. In this work, we systematically investigate the effect of different defects in the TiO$_{2-x}$ lattice on photocatalytic H$_2$ evolution. To introduce different types of defects, thermal annealing in air (oxidative), Ar (inert), Ar/H$_2$ (reducing), and H$_2$ (reducing) atmospheres were performed on commercially available anatase nanopowder. Then, the powders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) to clarify the effect of treatment on material properties. Furthermore, the defect types were characterized by electron paramagnetic resonance (EPR) spectroscopy. We show that thermal annealing in different atmospheres can form different amounts of different defect types in the TiO$_2$ structure. The highest photocatalytic activation is achieved by annealing the anatase powder in a reducing atmosphere for an appropriate temperature/annealing time. By combining the results from H$_2$ generation and EPR analysis we show that the simultaneous presence of two types of defects, i.e. surface exposed Ti$_3^+$ and lattice embedded Ti$_3^+$ centers, in an optimum low concentration, is the determining factor for an optimized photocatalytic H$_2$ evolution rate. In fact, annealing anatase powder under the so-reported optimized conditions in reducing atmosphere leads to the generation of a considerable amount of H$_2$, with rates as high as 338 $\mu$molh-1g-1.

We report calcium phosphate (CaP) nanocapsule crowned multiwalled carbon nanotubes (CNT–GSH–G4–CaP) as a novel platform for intracellular delivery of an anticancer drug. As a proof-of-concept, CNT–GSH–G4–CaP demonstrates release of anticancer drug doxorubicin hydrochloride (DOX) within intracellular lysosomes from the interior cavity of CNT upon pH triggered CaP dissolution. Importantly, we found that the CNT with a CaP nanolid can efficiently prevent untimely drug release at physiological pH but promotes DOX release at increased acidic milieu as observed in subcellular compartments such as lysosomes (∼5.0). This “zero premature release” characteristic is of clinical significance in delivering cytotoxic drugs, by reducing systemic toxicity and thus beneficial for the effective anticancer treatment. We envision that this pH triggered CaP crowned CNT nanosystem would lead to a new generation of self-regulated platforms for intracellular delivery of a variety of anticancer drugs.

Microporous organic polymers (MOPs) encapsulated with palladium nanoparticles (NPs) and immobilized on magnetic Co/C nanobeads show excellent activity in hydrogenation reactions of alkenes, alkynes, and nitro arenes with turnover frequencies (TOFs) up to 3000 h–1. The magnetic core of the nanobeads ensures an easy and fast recyclability for at least six consecutive runs by applying an external magnet to recapture the catalyst. The catalytic system reported here uses cross-linked toluene as a polymer structure and is readily prepared via a cost-efficient and versatile synthesis based on commercially available starting materials. The novel catalysts combine the advantages of a heterogeneous magnetic support with MOPs that prevent NPs from agglomeration or deactivation. In addition, the advantages of palladium NPs as exceedingly active catalyst due to their high surface-area-to-volume ratio are exploited. Furthermore, the polymeric structure can easily be varied by the change of the aromatic monomer. Introdu...

The pyrite iron disulfide thin films are regarded as suitable candidates for construction of low-cost photoelectrochemical (PEC) solar cells. Iron oxide hematite has attracted much attention as possibly convenient material for hydrogen production via PEC water splitting. We refer on preparation of pyrite thin films via thermal sulfidation of hematite films synthetized by a physical methodology of high power impulse magnetron sputtering (HiPIMS) and purely chemical approach of sol-gel. We studied for the first time the correlation between PEC functionality of hematite films and after their sulfidation into pyrite. The highest PEC activity of hematite films of 560 μA cm−2 at 700 mV vs. Ag/AgCl was achieved with the HiPIMS photoelectrodes. The photoefficiency dropped dramatically to 4 μA cm−2 at 600 mV vs. Ag/AgCl after the sulfidation. A significant increase of grains‘ size, residual unreacted hematite, surface defects were the main reasons for the poor photoactivity. The sol-gel produced hematite yielded photocurrent of 30 μA cm−2 and a slight increase to 40 μA cm−2 (recorded at 500 mV vs. Ag/AgCl) of the corresponding pyrite version. Both these electrodes showed also similar morphological characteristics. The structural, electronic and optical properties of the deposited films were determined using various methods e.g. Raman spectroscopy, SEM, and PDS.

Emerging sodium-selenium batteries suffer from volume expansion of the selenium cathode and shuttling effects of soluble intermediates. Confining selenium within the carbon matrix is the most adopted strategy to address these two issues, which is generally realized via a melt-infusion method. Herein, we developed a vapor-infiltration method to fabricate selenium/carbon composites that are advantageous over the melt-infusion route in terms of several aspects: it relieves the requirement of intensive mechanical mixing and simplifies the ratio optimization between selenium and carbon; it avoids selenium aggregation and makes it possible to utilize all of the surface and pores of the carbon host. Utilizing this method, we fabricated a selenium/graphene composite from thermally reduced graphene oxide with a selenium loading equal to 71 wt %, thus approaching the record value. The obtained composite achieved the highest reported to date initial Coulombic efficiency of 88% among various selenium cathodes, with superior rate and cycle performance (410 and 367 mA h g

Au and Pt do not form homogeneous bulk alloys as they are thermodynamically not miscible. However, we show that anodic TiO2 nanotubes (NTs) can in situ be uniformly decorated with homogeneous AuPt alloy nanoparticles (NPs) during their anodic growth. For this, a metallic Ti substrate containing low amounts of dissolved Au (0.1 atom %) and Pt (0.1 atom %) is used for anodizing. The matrix metal (Ti) is converted to oxide, whereas at the oxide/metal interface direct noble metal particle formation and alloying of Au and Pt takes place; continuously these particles are then picked up by the growing nanotube wall. In our experiments, the AuPt alloy NPs have an average size of 4.2 nm, and at the end of the anodic process, these are regularly dispersed over the TiO2 nanotubes. These alloyed AuPt particles act as excellent co-catalyst in photocatalytic H2 generation, with a H2 production rate of 12.04 μL h–1 under solar light. This represents a strongly enhanced activity as compared to TiO2 NTs decorated with mon...

Over the past years, α-Fe2 O3 (hematite) has re-emerged as a promising photoanode material in photoelectrochemical (PEC) water splitting. In spite of considerable success in obtaining relatively high solar conversion efficiency, the main drawbacks hindering practical application of hematite are its intrinsically hampered charge transport and sluggish oxygen evolution reaction (OER) kinetics on the photoelectrode surface. In the present work, we report a strategy that synergistically addresses both of these critical limitations. Our approach is based on three key features that are applied simultaneously: i) a careful nanostructuring of the hematite photoanode in the form of nanorods, ii) doping of hematite by Sn4+ ions using a controlled gradient, and iii) surface decoration of hematite by a new class of layered double hydroxide (LDH) OER co-catalysts based on Zn-Co LDH. All three interconnected forms of functionalization result in an extraordinary cathodic shift of the photocurrent onset potential by more than 300 mV and a PEC performance that reaches a photocurrent density of 2.00 mA cm-2 at 1.50 V vs. the reversible hydrogen electrode.

In this work, we describe a simple and general procedure for the purification of carbon dots. Following a hydrothermal heating procedure, the reaction mixture usually contains unreacted starting material and by-products alongside the carbon dots, which often appear among otherwise intense photoluminescence. The proposed purification method is based on a solid phase extraction technique, where the reaction mixture is absorbed on porous alumina and the carbon dots are isolated from the by-products and unreacted organics using proper solvents, and are finally recovered from the alumina using a simple extraction.

Energy storage is increasingly demanded in many new niches of applications from wearables to unmanned autonomous vehicles. However, current energy storage systems are unable to fulfill the power requirements (high energy at high power) needed for these novel applications. Recently, Li-ion capacitors (LICs) have been spotted as hybrid devices with the potential to display high energy and high power. Nevertheless, it is still a great challenge to achieve high performance LICs due to the unmatched kinetic properties and capacity between anode and cathode materials. Herein, we are presenting our first seminal report on the use of BiVO4 nanorods as a new anode material for LICs coupled with a partially reduced graphene oxide (PRGO) cathode. The BiVO4 nanorods show an excellent reversible capacity of 877 mA h g−1 (ultrahigh volumetric capacity of 4560 mA h cm−3) at 1.1 A g−1 with a great capacity retention (in half-cell design), which is the highest value reported so far for metal vanadates. Later on, a LIC was constructed with BiVO4 as the anode and PRGO as the cathode electrode, delivering a high energy density of 152 W h kg−1 and a maximum power density of 9.6 kW kg−1 compared to that for hard carbon and intercalation (such as Li4Ti5O12 and Li3VO4) based anode materials. Additionally, the BiVO4//PRGO LIC exhibits a good cyclability of 81% over 6000 cycles. Thus, this investigation opens up new opportunities to develop different LIC systems., DPD acknowledges the support of University of Adelaide, Australia for the grant of Research Fellowship (Research for Impact). Funding from MINECO (MAT2015-68394-R) is acknowledged. The ICN2 is supported by the Severo Ochoa programme of the Spanish Ministry of Economy, Industry and Competitiveness (MINECO, grant no. SEV-2013-0295) and funded by the CERCA programme/Generalitat de Catalunya. K. J. R. is grateful to the Alexander von Humboldt (AvH) foundation for a post-doctoral fellowship. The authors also gratefully acknowledge support by the Catalysis Research Centre at TU Munich and 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 authors gratefully acknowledge the support 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 and the project CZ.02.1.01/0.0/0.0/16_019/0000754.

In the present work the authors show that anodic TiO2 nanotubes (NT) show excellent harvesting properties for Pt single atoms (Pt SAs) from highly dilute Pt solutions. The tube walls of anodic nanotubes, after adequate annealing to anatase, provide ample of suitable trapping sites—that is, surface Ti3+‐Ov (Ov: oxygen vacancy) defects that are highly effective to extract and accumulate Pt in the form of SAs. A saturated (maximized) SA density can be achieved by an overnight immersion of a TiO2 NT layer to a H2PtCl6 solution with a concentration that is as low as 0.01 mm Pt. Such TiO2 NTs with surface trapped Pt SAs provide a maximized high activity for photocatalytic H2 generation (reaching a turnover frequency (TOF) of 1.24 × 106 h−1 at a density of 1.4 × 105 Pt atoms µm−2)—a higher loading with Pt nanoparticles does not further increase the photocatalytic activity. Overall, these findings show that anodic TiO2 nanotubes provide a remarkable substrate for Pt extraction and recovery from very dilute solutions that directly results in a highly efficient photocatalyst, fabricated by a simple immersion technique.

The covalent functionalization of graphene enabling to overcome its hydrophobicity and still keeping a high conductivity is a challenging task, particularly for advanced biosensing applications. We present a facile strategy towards water dispersible nanocarbon with excellent conductive and sensing properties. Graphene–fullerol (GFL) covalent hybrid is prepared by impregnation of chemically exfoliated graphene sheets with fullerol clusters followed by thermal treatment. The partial dehydroxylation of fullerol during heating is necessary for exposing the fullerene skeleton to graphene and promoting their covalent bonding. The remaining hydroxyl and ionic groups equip the final product with good dispersibility in water (0.04 mg mL−1). Simultaneously, the GFL hybrid retains a high electrical conductivity of 0.8 × 105 S m−1, which is comparable to that of unmodified graphene. The conductive and hydroxyl-bearing derivative was successfully applied for electrochemical sensing of dopamine, hydroquinone (HQ), and catechol (C) using cyclic voltammetry. GFL modified electrodes exhibited simultaneous HQ and C detection at lower potentials compared to other nanosensors.

Metal halide perovskite nanocrystals are promising materials for a diverse range of applications, such as light-emitting devices and photodetectors. We demonstrate the bandgap tunability of strongly emitting CH3NH3PbBr3 nanocrystals synthesized at both room and elevated (60 °C) temperature through the variation of the precursor and ligand concentrations. We discuss in detail the role of two ligands, oleylamine and oleic acid, in terms of the coordination of the lead precursors and the nanocrystal surface. The growth mechanism of nanocrystals is elucidated by combining the experimental results with the principles of nucleation/growth models. The proposed formation mechanism of perovskite nanocrystals will be helpful for further studies in this field and can be used as a guide to improve the synthetic methods in the future., The development of perovskite nanocrystals is limited by poor mechanistic understanding of their growth. Here, the authors systematically study the ligand-assisted reprecipitation synthesis of CH3NH3PbBr3 nanocrystals, revealing the effect of precursor and ligand concentrations on bandgap tunability.

We describe the benign wet chemical synthesis, characterization, and third-order nonlinear optical properties of hydrogenated fluorographene, namely, of a new 2D counterpart of hydrogenated graphene (graphane). The presence of hydrogen in hydrogenated fluorographene was confirmed using infrared spectroscopy, X-ray photoelectron spectroscopy, and thermal gravimetric analysis coupled with evolved gas analysis. The nonlinear optical properties of the derivative were investigated in the visible and infrared using picosecond laser excitation and were compared to those of graphene and fluorographene. All samples were found to exhibit important nonlinear optical response, with hydrogenated fluorographene exhibiting the largest response under visible excitation (ca. 1 order of magnitude higher compared to graphene and fluorographene). This is among the highest recorded effects ever observed for any graphene-based materials, including graphene oxide presented elsewhere. The results reveal the importance of the nat...

Titanium dioxide in the form of one-dimensional (1D) nanostructure arrays represent widely studied morphological arrangement for light harvesting and charge transfer applications such as photocatalysis and photoelectrochemistry (PEC). Here we report a comparative structural and PEC study of variously grown 1D TiO2 nanostructures including i) nanorod arrays prepared by a hydrothermal method (TNR), ii) nanotube arrays fabricated by a two-step hydrothermal method using a ZnO nanorod array film as a template (THNT) and finally iii) nanotubes grown by self-organized electrochemical anodization of Ti films deposited on the FTO substrate (TNT). These nanostructures are assumed to be utilized as photoanodes in PEC water splitting devices. Field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), TEM images and UV–vis absorption spectra were used to characterize TiO2 nanostructures. The SEM and TEM morphology images revealed that the main difference among the nanostructures grown on the FTO are the shape and diameter of the individual nanotubes/nanorods and also the array’s density in the range of TNR > THNT > TNT and the degree of organization in the range of TNT > TNR > THNT. The obtained photocurrents at 0 V vs. Ag/AgCl increased in the order of THNT (110 μA cm−2)

An efficient maghemite–ZnO nanocatalyst has been synthesized via a simple coprecipitation method, where ZnO nanoparticles are uniformly decorated on the maghemite core and characterized by XRD, SEM-EDS, ICP-AES, XPS, TEM, HRTEM, and Mossbauer spectroscopy; maghemite nanoparticles are in the typical size range 10–30 nm with ultrasmall (3–5 nm) ZnO nanoparticles. A competent and benign protocol is reported for various organic transformations, namely, transesterification, amidation, and O-acylation reaction in good to excellent yields (75–97%) using magnetically separable and reusable maghemite–ZnO nanocatalyst.

Hexagonal mesoporous silica (HMS)-supported copper oxides (CuO/HMS) have been prepared by a sol-gel method and characterized by X-ray diffraction, FTIR spectroscopy, transmission electron microscopy, N2 sorption, inductively coupled plasma (ICP), X-ray photoelectron spectroscopy (XPS), H2 temperature-programed reduction (TPR), NH3 temperature-programed desorption (TPD), and high-resolution (HR)-TEM techniques. An analysis of these results revealed a mesoporous material system with a high surface area (974 m2 g-1 ) and uniform pore-size distribution. The catalytic efficacy of CuO on the HMS support with varying Cu loadings (1, 3, 5, 10, and 15 wt %) was investigated for the transformation of aldehydes to primary amides; 3 wt % CuO/HMS exhibited good catalytic performance with good to excellent yields of amides (60-92 %) in benign aqueous medium. The intrinsically heterogeneous catalyst could be recovered after the reaction and reused without any noticeable loss in activity.

In the present work we show how to achieve different nanotube morphologies (namely, not only single- and double-walled tubes, but also a tube-in-tube configuration) by combining specific anodization parameters. We characterize as-grown tube layers in terms of morphology, chemical composition and properties. As-grown tubes exhibit a double-walled morphology, that is, they consist of an inner and an outer shell. The low quality inner shell can be removed by an optimized chemical treatment thus leading to nanotubes of a higher quality oxide and with a single-walled nature. Double-walled tubes grown at low electrolyte temperature provide a thick inner shell that after adequate annealing can form a unique tube-in-tube morphology.

ACS catalysis 10, 8293 - 8302 (2020). doi:10.1021/acscatal.0c01373, Cu- or Ni-decorated semiconductors represent a potential low-cost alternative to noble-metal-modified photocatalysts. Even more effective are bimetallic NiCu nanoparticles, which can provide a remarkable photocatalytic H$_{2}$ evolution enhancement compared to single-element Cu or Ni systems. The main concern of such alloyed co-catalysts is their activity with respect to alteration of their elemental composition and oxidation state over reaction time. Ex situ characterization techniques provide controversial interpretations of the co-catalytic role of the individual elements. Hypotheses such as the in situ reduction of ���native��� Ni or Cu species during photocatalysis, the oxidation of metallic Cu or Ni into oxides or hydroxides, or the formation of p���n junctions or core/shell structures have been proposed. Herein, we present an operando X-ray absorption spectroscopy study of a NiCu���TiO$_{2}$ system under UV light illumination in ethanol���water solutions, i.e., under photocatalytic H$_{2}$ evolution conditions. The experimental approach allows for monitoring in real time chemical changes that take place in the co-catalyst under intermittent illumination, i.e., under light on���off cycles. We show that while Ni and Cu are partially oxidized in the as-formed NiCu co-catalyst (air-formed surface oxides or hydroxides) and undergo partial dissolution in the liquid phase under dark conditions, such Ni and Cu oxidized and dissolved species are reduced/redeposited as a bimetallic NiCu phase at the TiO$_{2}$ surface under illumination. The dissolution/redeposition mechanism is triggered by TiO$_{2}$ conduction band electrons. We not only prove a UV-light-induced healing of the NiCu co-catalyst but also unambiguously demonstrate that the species responsible for the strongly enhanced photocatalytic H$_{2}$ evolution of NiCu nanoparticles are the metallic states of Ni and Cu., Published by ACS, Washington, DC

Photocatalytic $H_2$ evolution reactions on pristine TiO$_2$ is characterized by low efficiencies due to trapping and recombination of charge carriers, and due to a sluggish kinetics of electron transfer. Noble metal (mainly Pt, Pd, Au) nanoparticles are typically decorated as cocatalyst on the TiO$_2$ surface to reach reasonable photocatalytic yields. However, owing to the high cost of noble metals, alternative metal cocatalysts are being developed. Here we introduce an approach to fabricate an efficient noble metal free photocatalytic platform for $H_2$ evolution based on alloyed NiCu cocatalytic nanoparticles at the surface of anodic TiO$_2$ nanotube arrays. NiCu bilayers are deposited onto the TiO$_2$ nanotubes by plasma sputtering. A subsequent thermal treatment is carried out that leads to dewetting, that is, owing to surface diffusion the Ni and Cu sputtered layers simultaneously mix with each other and split into NiCu nanoparticles at the nanotube surface. The approach allows for a full control over key features of the alloyed nanoparticles such as their composition, work function and cocatalytic ability towards $H_2$ generation. Dewetted-alloyed cocatalytic nanoparticles composed of equal Ni and Cu amounts not only are significantly more reactive than pure Ni or Cu nanoparticles, but also lead to $H_2$ generation rates that can be comparable to those obtained by conventional noble metal (Pt) decoration of TiO$_2$ nanotube arrays.

With a large-scale usage of portable electric appliances, a high demand for increasingly high density energy storage devices has emerged. MoO3 has, in principle, a large potential as negative electrode material in supercapacitive devices, due to high charge densities that can be obtained from its reversible redox reactions. Nevertheless, the extremely poor electrochemical stability of MoO3 in aqueous electrolytes prevents a practical use in high capacitance devices. In this work, we describe how to overcome this severe stability issue by forming amorphous molybdenum oxide/tantalum oxide nanotubes by anodic oxidation of a Mo-Ta alloy. The presence of a critical amount of Ta-oxide (> 20 at-%) prevents the electrochemical decay of the MoO3 phase and thus yields an extremely high stability. Due to the protection provided by tantalum oxide, no capacitance losses are measureable after 10000 charg-ing/discharging cycles.

The morphology-dependent catalytic performance of various supported metal nanocatalysts (Au, Pd, Pt, Co, Cu and Ru) deposited on oxide supports (cerium oxide and zinc oxide) with varying morphologies are discussed. The support morphology-dependent activity for important industrial reactions such as carbon monoxide oxidation, ammonia synthesis, the water–gas shift reaction, methanol steam reforming, and so forth is discerned. The nanoscale synthesis of metal nanoparticles and their deposition on nanosupports (CeO2 and ZnO) with diverse morphologies imparts unique properties to nanocatalysts owing to the distinctive metal-support interactions. Most of the nanocatalysts display diverse metal-support interactions because of the different planes exposed on their surface. Furthermore, the stability and uniform distribution of the metal nanoparticles is contingent on the morphology of the support. Consequently, it is imperative to tailor the morphology of the support, exposing active planes on the surface and exploiting the selective deposition of metal nanoparticles on these planes to enhance the catalytic activity of nanocatalysts. This chapter focuses on the fundamental understanding of the vital relationship between the support morphology and the ensuing catalyst reactivity, providing a new direction to the design and development of highly efficient heterogeneous catalysts.

Single atom (SA) catalysis, over the last 10 years, has become a forefront in heterogeneous catalysis, electrocatalysis, and most recently also in photocatalysis. Most crucial when engineering a SA catalyst/support system is the creation of defined anchoring points on the support surface to stabilize reactive SA sites. Here, a so far unexplored but evidently very effective approach to trap and stabilize SAs on a broadly used photocatalyst platform is introduced. In self-organized anodic TiO2 nanotubes, a high degree of stress is incorporated in the amorphous oxide during nanotube growth. During crystallization (by thermal annealing), this leads to a high density of Ti3+-O-v, surface defects that are hardly present in other common titania nanostructures (as nanoparticles). These defects are highly effective for SA iridium trapping. Thus a SA-Ir photocatalyst with a higher photocatalytic activity than for any classic co-catalyst arrangement on the semiconductive substrate is obtained. Hence, a tool for SA trapping on titania-based back-contacted platforms is provided for wide application in electrochemistry and photoelectrochemistry. Moreover, it is shown that stably trapped SAs provide virtually all photocatalytic reactivity, with turnover frequencies in the order of 4 x 10(6) h(-1) in spite of representing only a small fraction of the initially loaded SAs. Web of Science 31 30 art. no. 2102843

We report on the facile preparation of versatile MoS2–thiobarbituric acid conjugates, which, in addition to excellent electrochemical behavior, can serve as nanosheet platforms for further functionalization in a multitude of applications. We show that chemically exfoliated MoS2 was extensively modified with up to 50% surface coverage, while maintaining its metallic character, and that the strategy can be extended to MoSe2, WS2, and WSe2. The covalent functionalization endowed the materials not only with good aqueous dispersibility, but also with improved hydrogen evolution reaction (HER) activity, as well as promise in the oxidative detection of DNA nucleobases in solution.

Core-shell nanocatalysts are a distinctive class of nanomaterials with varied potential applications in view of their unique structure, composition-dependent physicochemical properties, and promising synergism among the individual components. A one-pot microwave (MW)-assisted approach is described to prepare the reduced graphene oxide (rGO)-supported Pd-Pt core-shell nanoparticles, (Pd@Pt/rGO); spherical core-shell nanomaterials (∼95 nm) with Pd core (∼80 nm) and 15 nm Pt shell were nicely distributed on the rGO matrix in view of the choice of reductant and reaction conditions. The well-characterized composite nanomaterials, endowed with synergism among its components and rGO support, served as catalysts in aromatic dehalogenation reactions and for the reduction of olefins with high yield (98%), excellent selectivity (98%) and recyclability (up to 5 times); both Pt/rGO and Pd/rGO and even their physical mixtures showed considerably lower conversions (20 and 57%) in dehalogenation of 3-bromoaniline. Similarly, in the reduction of styrene to ethylbenzene, Pd@Pt core-shell nanoparticles (without rGO support) possess considerably lower conversion (60%) compared to Pd@Pt/rGO. The mechanism of dehalogenation reactions with Pd@Pt/rGO catalyst is discussed with the explicit premise that rGO matrix facilitates the adsorption of the reducing agent, thus enhancing its local concentration and expediting the hydrazine decomposition rate. The versatility of the catalyst has been validated via diverse substrate scope for both reduction and dehalogenation reactions.

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 (H2). In this context, titanium dioxide (TiO$_2$) and iron oxide (hematite, $\alpha$-Fe$_2$O$_3$) are among the most investigated candidates as photoanode materials, mainly owing to their resistance to photocorrosion, non-toxicity, natural abundance, and low production cost. Major drawbacks are, however, an inherently low electrical conductivity and a limited hole diffusion length that significantly affect the performance of TiO$_2$ and $\alpha$-Fe$_2$O$_3$ in PEC devices. To this regard, one-dimensional (1D) nanostructuring is typically applied as it provides several superior features such as a significant enlargement of the material surface area, extended contact between the semiconductor and the electrolyte and, most remarkably, preferential electrical transport that overall suppress charge carrier recombination and improve TiO$_2$ and $\alpha$-Fe$_2$O$_3$ photo-electrocatalytic properties. The present review describes various synthetic methods, properties and PEC applications of 1D-photoanodes (nanotubes, nanorods, nanofibers, nanowires) based on titania, hematite, and on $\alpha$-Fe$_2$O$_3$/TiO$_2$ heterostructures. Various routes towards modification and enhancement of PEC activity of 1D photoanodes are also discussed including doping, decoration with co-catalysts and heterojunction engineering. Finally, the challenges related to the optimization of charge transfer kinetics in both oxides are highlighted.

Herein, the formation and selective organic derivatisation of graphene nanobud, an all carbon nanohybrid comprised by C 60 and graphene, are presented. C 60 cages are directly attached to the graphenic surface with stable covalent bonds. Importantly, prepared graphene nanobud shows remarkable dispersibility, decreased number of defects and highly aromatic character that are associated to improved electrical conductivity compared to pristine graphene. The high chemical reactivity of the curved sp 2 carbon atoms of C 60 led to a selective covalent attachment of organic groups onto C 60 avoiding damage of the graphene aromatic system.

Engineerings of facet exposure, nonstoichiometric defects and morphology are the key parameters affecting the SnO2 performance. Development of synthetic procedures enabling to control all these variables in one pot towards enhanced physicochemical performance is a big challenge. Herein we report such a facile microwave hydrothermal preparation of 3D hierarchical architecture assembled from single-crystalline nonstoichiometric SnO2 (denote as SnO2-δ) nanosheets with self-doped Sn2+ and controllably exposed {101} facets. Polyvinylpyrrolidone (PVP) is used as capping agent allowing to stabilize the ultrathin and ultra-large SnO2-δ nanosheets and avoid their dissolution in the highly alkaline environment due to the introduction of highly concentrated NaOH, which together with PVP contribute to the formation of nanosheet morphology with preferential growth plane (121) and dominant reactive {101} surfaces. The detailed structural characteristics are examined by XRD, SEM, TEM, FTIR, XPS and Mossbauer spectroscopy, revealing that SnO2-δ contains 17 at.% of Sn2+ dopant. These nonstoichiometric SnO2-δ hierarchical architectures capped with carbonized PVP manifest superior lithium storage properties compared with the stoichiometric SnO2, owing to the novel open hierarchical structure composed of flexible and ultrathin nanosheets with large surface area (82 m2/g) and carbon-coating, which avoid the aggregation and provide porous channels facilitating the diffusion of electrolyte and lithium ions.

A novel hybrid material (gC3N4-rFe) consisting of amine-rich graphitic carbon nitride (gC3N4), decorated with reduced iron nanoparticles (rFe) is presented. XRD and TEM show that gC3N4-rFe bears aggregation-free Fe-nanoparticles (10 nm) uniformly dispersed over the gC3N4 surface. In contrast, non-supported iron nanoparticles are strongly aggregated, with non-uniform size distribution (20–100 nm). 57Fe-Mossbauer spectroscopy, dual-mode electron paramagnetic resonance (EPR) and magnetization measurements, allow a detailed mapping of the evolution of the Fe-phases after exposure to ambient O2. The as-prepared gC3N4-rFe bears Fe2+ and Fe° phases, however only after long exposure to ambient O2, a Fe-oxide layer is formed around the Fe° core. In this [Fe°/Fe-oxide] core-shell configuration, the gC3N4-rFe hybrid shows enhanced AsIII uptake capacity of 76.5 mg g−1, i.e., ca 90% higher than the unmodified carbonaceous support, and 300% higher than the non-supported Fe-nanoparticles. gC3N4-rFe is a superior AsIII sorbent i.e., compared to its single counterparts or vs. graphite/graphite oxide or activated carbon analogues (11–36 mg g−1). The present results demonstrate that the gC3N4 matrix is not simply a net that holds the particles, but rather an active component that determines particle formation dynamics and ultimately their redox profile, size and surface dispersion homogeneity.

A variety of Titanium dioxide (TiO 2 ) phases and nanostructures have been explored for their applications in photoelectrochemical cells (PECs) for solar-driven water splitting. In this case, anatase phase and TiO 2 nanotubes offer significant advantages especially for PEC-based applications. Though, significant efforts have already been engaged to combine the advantages from both the fields, poor activation and the high electron-hole pair recombination rate of TiO 2 electrodes, originating from intrinsic physicochemical properties, limits its practical use. As an alternative, we report directly grown TiO 2 nanotubes (synthesized on Fluorine doped Tin Oxide (FTO) via facile electrospinning technique) on carbon nanofibers, using hydrothermal method. The hierarchical branch type configuration has an intimate contact between the TiO 2 nanotube and carbon nanofiber backbone and offers higher photocatalytic activity than their respective individual components (namely TiO 2 nanotubes and carbon nanostructures).

Carbon dots (CDs) are fluorescent nanoprobes offering a great potential in biological and medical applications due to their superior biocompatibility compared to metal chalcogenide quantum dots (e.g., CdSe). Key factors determining their cytotoxicity and cellular/intracellular tracking involve chemical nature and charge of surface functional groups. For the first time, we present a comprehensive cytotoxic study including cell cycle analysis of carbon dots differing in surface functionalization, namely pristine CDs (CDs-Pri) with negative charge due to carboxylic groups, polyethyleneglycol modified dots with neutral charge (CDs-PEG), and polyethylenimine coated dots with a positive charge (CDs-PEI). The CDs in vitro toxicity was studied on standard mouse fibroblasts (NIH/3T3). The results suggest that neutral CDs-PEG are the most promising for biological applications as they do not induce any abnormalities in cell morphology, intracellular trafficking, and cell cycle up to concentrations of 300 μg mL−1. Negatively charged CDs-Pri arrested the G2/M phase of the cell cycle, stimulated proliferation and led to higher oxidative stress, however they did not enter the cell nucleus. In contrast, positively charged CDs-PEI are the most cytotoxic, entering into the cell nucleus and inducing the largest changes in G0/G1 phase of cell cycle, even at concentrations of around 100 μg mL−1.

Cu-doping in titania is usually detrimental to the material’s photoconductivity which prevents the use of this combination in photoanodes. In this work, we produce TiO2 nanotube arrays intrinsically doped with copper and establish sufficient conductivity to use them as efficient photoanodes for methanol oxidation in a photoelectrochemical hydrogen generation setting. Firstly, Cu doped TiO2 nanotubes were produced by anodizing a Ti-Cu binary alloy. By subsequent thermal reduction of the structure in an Ar/H2 environment, conductive copper doped TiO2 nanotubes (TiCuTN-Ar/H2) can be achieved with an approximately 103 times higher conductivity than the non-reduced material. When these reduced Cu doped TiO2 nanotubes are used as photoanode, copper species embedded in the TiO2 wall catalyze the methanol oxidation reaction. As a result of the combined effect of conductivity and catalytic effect of Cu, such a reduced Cu:TiO2 nanotubes can generate a photocurrent of 0.76 mA.cm-2 at 1 V vs. RHE, under AM1.5 (100 mW/Cm2) irradiation – in a 50:50 MeOH/water solution – this is 33 times higher than for pristine Cu:TiO2 nanotubes.

The synthesis and characterization of two thiophenol-modified fluorographene derivatives, namely methoxythiophenol-and dimethylaminothiophenol-modified fluorographenes, are reported, while their third-order nonlinear optical response were thoroughly investigated under both visible (532 nm) and infrared (1064 nm) with 35 ps and 4 ns laser pulses. The graphene derivatives were obtained by partial nucleophilic substitution/ reduction of fluorographene by the corresponding organic thiophenols, and were fully characterized by techniques including infrared/Raman spectroscopy, X-ray photoelectron spectroscopy, atomic force spectroscopy, and high-resolution transmission microscopy. This type of modification resulted in graphenic structures where the attached thiol groups, sp2 domains, and the residual fluorine groups act as donors, π bridges, and acceptors, respectively. Both derivatives exhibited large nonlinear optical response compared to fluorographene, and have potential applications in optical limiting as an alternative to fullerenes.

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.

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.