Search

We present that activation of CoMoO4-based microrod arrays in KOH (1.0 M, 2 h) allows us to significantly improve their electrochemical hydrogen evolution performance in phosphate buffer solution (1.0 M, pH = 7.1). The activation mechanism originates from the conversion of the surface layer of CoMoO4to Co(OH)2nanosheets, together with the release of Mo3O102–ions into the activation solution. Our experimental and calculated results suggest that the Co(OH)2nanosheets on the surface of the CoMoO4-based microrod arrays show the ability to improve water molecule disassociation and stabilize the catalytic activity of the two-component catalysts by decreasing their overpotentials in the hydrogen evolution reaction. When extending this strategy to activate P-doped CoMoO4with a low hydrogen absorption free energy, we report the synthesis of a new class of superior neutral electrochemical hydrogen evolution catalysts of P-doped CoMoO4–Co(OH)2microrod arrays. We show that a low overpotential of about 30 mV (obtained from bulk electrolysis) is required to deliver a current density of 10 mA cm–2in the neutral media. By making use of our catalyst and NiFe double hydroxide as cathodic and anodic electrodes, respectively, we fabricated a two-electrode electrolysis device for neutral overall water splitting. Our results showed a low cell voltage of 1.78 V (obtained from bulk electrolysis) that is needed for delivering a current density of about 10 mA cm–2in the neutral electrolyte, even outperforming the state-of-the-art catalyst combination of Pt/C∥RuO2in terms of catalytic activity and stability. These findings suggest that our strategy may be utilized as a facile but useful strategy toward the activation of molybdate catalysts to improve their HER performance in both basic and neutral media.

Cesium-based two-dimensional (2D) perovskites with attractive phase and environmental stability have broad application prospects in single-junction and tandem perovskite solar cells (PSCs). However, the severe nonradiative recombination and significant energy losses due to disordered phase orientations and phase distributions greatly hinder the carrier transport performance of cesium-based 2D PSCs and severely limit their photovoltaic performance. Here, we employ an asymmetric chiral spacer cation source, (R)-α-phenylethylamine acrylate (R-α-PEAAA), to prepare high-quality 2D cesium-based films with uniform phase distribution and high out-of-plane orientation by air processing, resulting in efficient carrier transport. More importantly, the asymmetric chiral spacer R-α-PEA has a stronger dipole moment than its isomer (PEA), which can regulate the dielectric properties of cesium-based 2D perovskites and promote charge dissociation. In addition, the chiral R-α-PEA can optimize the morphology and out-of-plane orientation of perovskite films, reduce trap density and nonradiative recombination loss, and optimize energy level alignment, thus enhancing carrier transport. As a result, cesium-based 2D PSCs (R-α-PEA2Cs4Pb5I16, n= 5) achieved a record power conversion efficiency of 19.71% and the unencapsulated device maintained over 90% efficiency after 1500 h of continuous light exposure and ambient storage (35 ± 5% relative humidity). This study provides an idea for the development of chiral 2D perovskite with efficient charge carrier transport toward efficient and stable cesium-based 2D PSCs.

Blue-emitting perovskite nanoplates (NPLs) have been widely investigated for display application. However, the traditional synthetic techniques for high-quality perovskite NPLs are still limited due to their rapid crystallization rate. Here, we developed an inorganic ligand (NOBF4) mediated transformation strategy to obtain blue-emitting CsPbBr3NPLs. The transformation process was based on the dissolution–recrystallization in a nonpolar environment, involving the dissociation of Cs4PbBr6NCs to Pb ions, which then reformed PbBr64–octahedrons and finally formed two monolayer NPLs with pure blue-emission (line width ∼12 nm). The whole transformation process was clearly detected, and during the process the reorganization of organic ligands tuned by NO+played a crucial role in the formation of NPLs. This work provides an effective strategy for obtaining pure blue-emitting NPLs and builds a platform for exploring the mechanism for the anisotropic growth of perovskite crystals.

Luminescent nanoparticles with dual-mode long-lived luminescence are of great importance for their attractive applications in biosensing, bioimaging, and data encoding. Herein, we report the realization of up- and downconversion emission of Mn2+dopants in multilayer nanoparticles of NaGdF4:Yb/Tm@NaGdF4:Ce/Mn@NaYF4upon excitation at 980 and 254 nm, respectively. The dual-mode emission of the Mn2+dopants at 531 nm have a long-lived lifetime up to ∼30 ms as a result of the spin-forbidden optical transition of Mn2+within the 3d5configuration. After ceasing steady excitation at the two wavelengths, the long-lived feature of Mn2+luminescence allows a longer persistent time than lanthanide emissions, thereby enabling the ease of data decoding by a cell phone camera under a burst mode. The long-lived green upconversion emission also permits the generation of a long green tail emission upon dynamic excitation at 980 nm. These attributes make the as-prepared Mn2+-doped multilayer nanoparticles particularly attractive for multilevel anticounterfeiting.

The ability to reversibly manipulate the surface nature of luminescent nanoparticles upon external stimulation enables the development of advanced optical probes for biological sensing and data encoding. Herein, we report the synthesis of a new class of smart carbon dots (CDs) via surface modification of amine-enriched CDs with CO2-responsive groups of amidine. We present that alternative CO2and N2bubbling can not only lead to a reversible phase transfer of the CDs between an organic phase and an aqueous phase but also give rise to a corresponding reversible luminescence change between blue and cyan-green. We attribute these observations to changes in both the surface chemistry and the emission states of the CDs triggered by the alternative CO2/N2introduction. We also find a similar luminescence change of the CDs upon alternative exposure to a humid vapor of CO2and a mixture of NH3and N2at room temperature, allowing them to be used as a new class of optical materials for optical encoding.

The development of earth-abundant catalysts for efficient hydrolysis of ammonia borane is of great importance in the conversion and utilization of hydrogen energy. Here, we report the synthesis of SiO2-encompassed Co@N-doped porous carbon assemblies as a new type of recyclable catalyst for the purpose by calcination of zeolitic imidazolate framework-67@SiO2microtubes at high temperatures under an N2atmosphere. We find that the surface layer of SiO2in the precursor microtubes is essential for the production of efficient catalysts by supplying an additional surface for Co nanoparticle dispersion in an effort to reduce their size. In addition, the SiO2layer renders a highly ordered arrangement of Co@N-doped porous carbon within the catalysts, possibly allowing the ease of mass transfer of ammonia borane within the catalysts. The optimized catalysts obtained via calcination at 800 °C show a set of remarkable catalytic benefits, including a high hydrogen generation rate of 8.4 mol min–1mol(Co)–1, a relatively low activation energy of 36.1 kJ mol–1, and a remarkable reusability (at least 10 times). Our results can provide new insight into the design and synthesis of highly ordered SiO2-supported catalysts for different reactions.

Dual-mode luminescent nanomaterials have outstanding performance in biosensing and multistage anticounterfeiting. Herein, we report the tuning of optical attributes of lanthanide-doped nanoparticles (NPs) via simultaneous binary cation exchange. We show that cation exchange of NaYF4:Yb/Er (18/2 mol %)@NaLnF4(Ln = Y and Gd) NPs with a combination of Ce3+and Tb3+enables the resultant nanoparticles to exhibit both upconversion and downshifting emissions upon excitation at 980 and 254 nm, respectively. We find that in addition to introducing downshifting emission attributes, the use of Tb3+ions allows conservation of the integrity of the parent core@shell NPs by decreasing the dissociation tendency caused by Ce3+ions during the cation exchange. The upconversion color output can be tuned from green to red and blue by changing lanthanide combinations in the core NPs. This work not only provides an effective strategy for the optical tuning of lanthanide-doped NPs but also builds a platform for probing the difference in the reactivity nature of lanthanides.

Three different nanostructures of CuO (wires, platelets, and spindles) have been synthesized by one precursor. First, Cu(OH) 2nanowires have been prepared by a two-step, template-free, wet chemical approach. And then the transformation from the 1D Cu(OH) 2nanostructures to a variety of novel CuO nanostructures has been realized by thermal dehydration of the as-prepared Cu(OH) 2in solution. The electrochemical characters of the three different nanostructures are studied by their investigation of electrochemical impendance spectrum and cyclic voltammetry. A comparison of the three nanostructures showed us an attractive phenomenon, that is, the electron transfer ability of CuO nanospindles was stronger than that of CuO nanowires or nanoplatelets. We suggest the possible reason is the assembly of the nanostructrue. The electrochemical response of the as-prepared samples on H 2O 2is also investigated, and good application in electrochemical detecting of glucose is exhibited.

This study presents a novel method for the preparation of Fe 3O 4/MS (M = Zn, Cd, Hg, Pb, Co, and Ni) nanocomposites via a sonochemical aqueous route. This method is mild, convenient, cheap, and efficient. A creditable synthetic mechanism for the formation of the nanocomposites has been proposed. It can be found that the concentration of TAA plays an important role in the controlling of the size and density of the nanoparticles immobilized on the surface of the magnetic microspheres. Fe 3O 4/ZnS and Fe 3O 4/CdS nanocomposites display fluorescence and exhibit ferromagnetic behavior at room temperature. Photocatalytic activity studies demonstrate that the former ones have highly photocatalytic activity toward the photodegradation of eosin Y in aqueous solution. The catalytic efficiency only decreased by 5% when cyclic time was up to 15 cycles, which means that as-prepared Fe 3O 4/ZnS nanocomposites have promising applications not only in biomedical fields but also in organic synthesis or wastewater treatment as recyclable photocatalysts. Furthermore, this method can be extended to the synthesis of other magnetic nanocomposites.

Ni0.85Se plate-like nanostructures (PNSs) had been prepared by a template method, and by a similar process, the Ni0.85Se nanoparticles were obtained by using NiCl2·6H2O as the nickel source. The Ni0.85Se nanostructures (NSs) with different shapes exhibited high catalytic activities for hydrogenation of 4-nitrophenol (4-NP) with excess NaBH4. To the best of our knowledge, this may be the first report on using Ni0.85Se NSs as catalysts for the reduction of 4-NP.

Morphologies à la carte: A kinetic control strategy has been utilized to fabricate bimetallic nanoparticles. Using cubic Pd nanocrystals as seeds and a syringe pump that enables precise control over precursor injection rate, it is possible to synthesize Pd–Ag bimetallic nanoparticles with tailored shapes (see picture: dimers, eccentric hybrid bars, and core–shell structures) and tunable localized surface plasmon resonances.

Morphologien à la carte: Eine Strategie der kinetischen Kontrolle wurde zur Herstellung dimetallischer Nanopartikel genutzt. Mithilfe kubischer Pd‐Nanokristalle als Keime und einer Spritzenpumpe, die eine präzise Kontrolle der Injektionsgeschwindigkeit der Vorstufe ermöglicht, gelang die Herstellung von Pd/Ag‐Nanopartikeln mit maßgeschneiderten Morphologien (siehe Bild: Dimere, exzentrische Hybridstäbe und Kern‐Schale‐Strukturen) und gezielt einstellbaren Plasmonenresonanzen.