Zinc oxide/Curcumin (Zn(CUR)O) nanocomposites were prepared via hydrothermal treatment of Zn(NO3)2 in the presence of hexamethylenetetramine as a stabilizing agent and CUR as a bioactive element. Three ZnO : CUR ratios were investigated, namely 57 : 43 (Zn(CUR)O-A), 60 : 40 (Zn(CUR)O-B) and 81 : 19 (Zn(CUR)O-C), as assessed by thermogravimetric analyses, with an average hydrodynamic diameter of nanoaggregates in the range of 223 to 361 nm. The interaction of CUR with ZnO via hydroxyl and ketoenol groups (as proved by X-ray photoelectron spectroscopy analyses) was found to significantly modify the key properties of ZnO nanoparticles with the obtainment of a bilobed shape (as shown by scanning electron microscopy), and influenced the growth process of the composite nanoparticles as indicated by the varying particle sizes determined by powder X-ray diffraction. The efficacy of Zn(CUR)O as anticancer agents was evaluated on MCF-7 and MDA-MB-231 cancer cells, obtaining a synergistic activity with a cell viability depending on the CUR amount within the nanocomposite. Finally, the determination of reactive oxygen species production in the presence of Zn(CUR)O was used as a preliminary evaluation of the mechanism of action of the nanocomposites.
Transition metal phosphide alloying is an effective approach for optimizing the electronic structure and improving the intrinsic performance of the hydrogen evolution reaction (HER). However, obtaining 3d transition metal phosphides alloyed with noble metals is still a challenge owing to their difference in electronegativity, and the influence of their electronic structure modulated by noble metals on the HER reaction also remains unclear. In this study, we successfully incorporated Ru into an Fe2P single crystal via the Bridgeman method and used it as a model catalyst, which effectively promoted HER. Hall transport measurements combined with first-principles calculations revealed that Ru acted as an electron dopant in the structure and increased the Fermi level, leading to a decreased water dissociation barrier and an improved electron-transfer Volmer step at low overpotentials. Additionally, the (21Ì 1) facet of Ru-Fe2P was found to be more active than its (001) facet, mainly due to the lower H desorption barrier at high overpotentials. The synergistic effect of Ru and Fe sites was also revealed to facilitate H* and OH* desorption compared with Fe2P. Therefore, this study elucidates the boosting effect of Ru-alloyed iron phosphides and offers new understanding about the relationship between their electronic structure and HER performance.
Solid solutions of 2D transition metal trihalides are rapidly growing in interest for the search for new 2D materials with novel properties at nanoscale dimensions. In this regard, we present a synthesis method for the Cr1-xRuxCl3 solid solution and describe the behaviour of the unit cell parameters over the whole composition range, which in general follows Vegard's law in the range of a = 5.958(6)CrCl3 5.9731(5)RuCl3 Å, b = 10.3328(20)CrCl3 10.34606(21)RuCl3 Å, c = 6.110(5)CrCl3 6.0385(5)RuCl3 Å and ß = 108.522(15)CrCl3 108.8314(14)RuCl3 °. The synthesized solid solution powder was subsequently used to deposit micro- and nanosheets directly on a substrate by applying chemical vapour transport in a temperature gradient of 575 °C â 525 °C for 2 h and 650 °C â 600 °C for 0.5 h as a bottom-up approach without the need for an external transport agent. The observed chromium chloride enrichment of the deposited crystals is predicted by thermodynamic simulation. The results allow for a nanostructure synthesis of this solid solution with a predictable composition down to about 30 nm in height and lateral size of several µm. When applying a quick consecutive delamination step, it is possible to obtain few- and monolayer structures, which could be used for further studies of downscaling effects for the CrCl3-RuCl3 solid solution. X-ray photoelectron spectroscopy, transmission electron microscopy and Raman spectroscopy were used to confirm the purity and quality of the synthesized crystals.
Molecular devices constructed by sub-10 nm thick molecular layers are promising candidates for a new generation of integratable nanoelectronic applications. Here, we report integrated molecular devices based on ultrathin copper phthalocyanine/fullerene hybrid layers with microtubular soft-contacts, which exhibit process-programmable functionality switching between photomultiplication and memristive behaviour. The local electric field at the interface between the polymer bottom electrode and the enclosed molecular channels modulates the ionic-electronic charge interaction and hence determines the transition of the device function. When ions are not driven into the molecular channels at a low interface electric field, photogenerated holes are trapped as electronic space charges, resulting in photomultiplication with a high external quantum efficiency. Once mobile ions are polarized and accumulated as ionic space charges in the molecular channels at a high interface electric field, the molecular devices show ferroelectric-like memristive switching with remarkable resistive ON/OFF and rectification ratios.
2D transition metal carbides and/or nitrides, so-called MXenes, are noted as ideal fast-charging cation-intercalation electrode materials, which nevertheless suffer from limited specific capacities. Herein, it is reported that constructing redox-active phosphorus-oxygen terminals can be an attractive strategy for Nb4 C3 MXenes to remarkably boost their specific capacities for ultrafast Na+ storage. As revealed, redox-active terminals with a stoichiometric formula of PO2 - display a metaphosphate-like configuration with each P atom sustaining three PO bonds and one PO dangling bond. Compared with conventional O-terminals, metaphosphate-like terminals empower Nb4 C3 (denoted PO2 -Nb4 C3 ) with considerably enriched carrier density (fourfold), improved conductivity (12.3-fold at 300 K), additional redox-active sites, boosted Nb redox depth, nondeclined Na+ -diffusion capability, and buffered internal stress during Na+ intercalation/de-intercalation. Consequently, compared with O-terminated Nb4 C3 , PO2 -Nb4 C3 exhibits a doubled Na+ -storage capacity (221.0 mAh g-1 ), well-retained fast-charging capability (4.9 min at 80% capacity retention), significantly promoted cycle life (nondegraded capacity over 2000 cycles), and justified feasibility for assembling energy-power-balanced Na-ion capacitors. This study unveils that the molecular-level design of MXene terminals provides opportunities for developing simultaneously high-capacity and fast-charging electrodes, alleviating the energy-power tradeoff typical for energy-storage devices.
Intermetallic phases are usually obtained by crystallization from the melt. However, phases containing elements with widely different melting and boiling points, as well as nanoparticles, which provide a high specific surface area, are hardly accessible via such a high-temperature process. The polyol process is one option to circumvent these obstacles by using a solution-based approach at moderate temperatures. In this study, the formation of Bi2Ir nanoparticles in a microwave-assisted polyol process was investigated. Solutions were analyzed using UV-Vis spectroscopy and the reaction was tracked with synchrotron-based in situ powder X-ray diffraction (PXRD). The products were characterized by PXRD and high-resolution transmission electron microscopy. Starting from Bi(NO3)3 and Ir(OAc)3, the new suboxide Bi4Ir2O forms as an intermediate phase at about 160 °C. Its structure was determined by a combination of PXRD and quantum-chemical calculations. Bi4Ir2O decomposes in vacuum at about 250 °C and is reduced to Bi2Ir by hydrogen at 150 °C. At about 240 °C, the polyol process leads to the immediate reduction of the two metal-containing precursors and crystallization of Bi2Ir nanoparticles.
Dielectric properties and spectral dependence of the photocatalytic constant of Co doped P25 Degussa powder were studied. Doping of TiO2 matrix with cobalt was achieved by precipitation method using of Tris(diethylditiocarbamate)Co(III) precursor (CoDtc-Co[(C2H5)2NCS2]3). Five different Co contents with nominal Co/Ti atomic ratios of 0.005, 0.01, 0.02, 0.05 and 0.10 were chosen. Along with TiO2:Co samples, a few samples of nanopowders prepared by Sol-Gel method were also studied. As it follows from XPS and NMR studies, there is a concentration limit (TiO2:0.1Co) where cobalt atoms can be uniformly distributed across the TiO2 matrix before metallic clusters start to form. It was also shown that CoTiO3 phases are formed during annealing at high temperatures. From the temperature dependence of the dielectric constant it can be concluded that the relaxation processes still take place even at temperatures below 400 °C and that oxygen defect Ti-O octahedron reorientation take place at higher temperatures. The spectral dependency of the photocatalytic constant reveals the presence of some electronic states inside the energy gap of TiO2 for all nanopowdered samples.
Developing resource-abundant and sustainable metal-free bifunctional oxygen electrocatalysts is essential for the practical application of zinc-air batteries (ZABs). 2D black phosphorus (BP) with fully exposed atoms and active lone pair electrons can be promising for oxygen electrocatalysts, which, however, suffers from low catalytic activity and poor electrochemical stability. Herein, guided by density functional theory (DFT) calculations, an efficient metal-free electrocatalyst is demonstrated via covalently bonding BP nanosheets with graphitic carbon nitride (denoted BP-CN-c). The polarized PN covalent bonds in BP-CN-c can efficiently regulate the electron transfer from BP to graphitic carbon nitride and significantly promote the OOH* adsorption on phosphorus atoms. Impressively, the oxygen evolution reaction performance of BP-CN-c (overpotential of 350 mV at 10 mA cm-2 , 90% retention after 10 h operation) represents the state-of-the-art among the reported BP-based metal-free catalysts. Additionally, BP-CN-c exhibits a small half-wave overpotential of 390 mV for oxygen reduction reaction, representing the first bifunctional BP-based metal-free oxygen catalyst. Moreover, ZABs are assembled incorporating BP-CN-c cathodes, delivering a substantially higher peak power density (168.3 mW cm-2 ) than the Pt/C+RuO2 -based ZABs (101.3 mW cm-2 ). The acquired insights into interfacial covalent bonds pave the way for the rational design of new and affordable metal-free catalysts.
Considerable efforts have been made to realize nanoscale diodes based on single molecules or molecular ensembles for implementing the concept of molecular electronics. However, so far, functional molecular diodes have only been demonstrated in the very low alternating current frequency regime, which is partially due to their extremely low conductance and the poor degree of device integration. Here, we report about fully integrated rectifiers with microtubular soft-contacts, which are based on a molecularly thin organic heterojunction and are able to convert alternating current with a frequency of up to 10 MHz. The unidirectional current behavior of our devices originates mainly from the intrinsically different surfaces of the bottom planar and top microtubular Au electrodes while the excellent high frequency response benefits from the charge accumulation in the phthalocyanine molecular heterojunction, which not only improves the charge injection but also increases the carrier density.
A novel ruthenium-acetylide complex was synthesised and characterised in solid state and solution. Thin films of the complex were evaporated on silver and gold foils in ultra high vacuum in order to probe the electronic properties with photoemission spectroscopy. The charge transfer characteristics of the complex with the strong acceptor F6TCNNQ were investigated by UV-vis absorption in solution as well as at an interface with photoemission spectroscopy. A new excitation in the former optical gap of the pristine materials was probed in solution. Moreover, it was possible to identify the oxidised complex as well as the reduced acceptor by X-ray photoemission spectroscopy. In particular, our data reveal that oxidation of the complex mainly occurs at the Ru centre. The charge transfer can be characterised as localised and mainly ionic although signs of a reaction of the acceptors aminogroups with the ruthenium-acetylide complex were found.
