Construction of Co-Se-W at Interfaces of Phase-Mixed Cobalt Selenide via Spontaneous Phase Transition for Platinum-Like Hydrogen Evolution Activity and Long-Term Durability in Alkaline and Acidic Media.

Cost-effective transition metal chalcogenides are highly promising electrocatalysts for both alkaline and acidic hydrogen evolution reactions (HER). However, unsatisfactory HER kinetics and stability have severely hindered their applications in industrial water electrolysis. Herein, a nanoflowers-shaped W-doped cubic/orthorhombic phase-mixed CoSe2 catalyst ((c/o)-CoSe2-W) is reported. The W doping induces spontaneous phase transition from stable phase cubic CoSe2 (c-CoSe2) to metastable phase orthorhombic CoSe2, which not only enables precise regulation of the ratio of two phases but also realizes W doping at the interfaces of two phases. The (c/o)-CoSe2-W catalyst exhibits a Pt-like HER activity in both alkaline and acidic media, with record-low HER overpotentials of 29.8 mV (alkaline) and 35.9 mV (acidic) at 10 mA cm-2, respectively, surpassing the vast majority of previously reported non-precious metal electrocatalysts for both alkaline and acidic HER. The Pt-like HER activities originate from the formation of Co-Se-W active species on the c-CoSe2 side at the phase interface, which effectively modulates electron structures of active sites, not only enhancing H2O adsorption and dissociation at Co sites but also optimizing H* adsorption to ΔGH* ≈ 0 at W sites. Benefiting from the abundant phase interfaces, the catalyst also displays outstanding long-term durability in both acidic and alkaline media.

Amorphous/Crystalline Phases Mixed Nanosheets Array Rich in Oxygen Vacancies Boost Oxygen Evolution Reaction of Spinel Oxides in Alkaline Media.

As promising oxygen evolution reaction (OER) catalysts, spinel-type oxides face the bottleneck of weak adsorption for oxygen-containing intermediates, so it is challenging to make a further breakthrough in remarkably lowering the OER overpotential. In this study, a novel strategy is proposed to substantially enhance the OER activity of spinel oxides based on amorphous/crystalline phases mixed spinel FeNi2O4 nanosheets array, enriched with oxygen vacancies, in situ grown on a nickel foam (NF). This unique architecture is achieved through a one-step millisecond laser direct writing method. The presence of amorphous phases with abundant oxygen vacancies significantly enhances the adsorption of oxygen-containing intermediates and changes the rate-determining step from OH*→O* to O*→OOH*, which greatly reduces the thermodynamic energy barrier. Moreover, the crystalline phase interweaving with amorphous domains serves as a conductive shortcut to facilitate rapid electron transfer from active sites in the amorphous domain to NF, guaranteeing fast OER kinetics. Such an anodic electrode exhibits a nearly ten fold enhancement in OER intrinsic activity compared to the pristine counterpart. Remarkably, it demonstrates record-low overpotentials of 246 and 315 mV at 50 and 500 mA cm-2 in 1 m KOH with superior long-term stability, outperforming other NiFe-based spinel oxides catalysts.

A Strongly Coupled Ag(S)@NiO/Nickel Foam Electrode Induced by Laser Direct Writing for Hydrogen Evolution at Ultrahigh Current Densities with Long-Term Durability.

Highly active, durable, and cost-effective electrodes for hydrogen evolution reaction (HER) at ultrahigh current densities (≥1 A cm-2 ) are extremely demanded for industrial high-rate hydrogen production, but challenging. Here, a robust strongly coupled Ag(S)@NiO/nickel foam (NF) electrode is reported. Taking advantage of millisecond laser direct writing in liquid nitrogen technique, lattice-matched and coherent interfaces are formed between Ag nanoparticles with stacking faults (denoted by Ag(S)) and NiO nanosheets, leading to strong interfacial electronic coupling, not only promoting H2 O adsorption and dissociation on Ni2+ but also enhancing H* adsorption on intrinsically inactive but most electrically conductive Ag. Strong chemical bonding is established at NiO/NF interface, guaranteeing rapid electron transfer and excellent mechanical durability under high-rate hydrogen evolution. The physicochemically stable electrode achieves record-low alkaline HER overpotential of 167 and 180 mV at 1 and 1.5 A cm-2 , respectively, along with negligible activity decay after 120 h test at ≈1.5 A cm-2 , surpassing reported non-platinum group metal electrocatalysts.

Searching for the Optimized Luminescent Lanthanide Phosphor Using Heuristic Algorithms.

In this research, four heuristic algorithms (HAs), including simulated annealing (SA), improved annealing with a harmony search algorithm (HSA), particle swarm optimization (PSO), and genetic algorithm (GA), were used to optimize the luminescent intensity of phosphor. Among the four HAs, the improved algorithm HSA got better phosphors than SA (without using the known coded concentration). The PSO algorithm got gradually better results with increased generation, and the GA could find the best local phosphors with shorter time. After further analysis of the 340 phosphors, we found that the final brightness has an optimized activator concentration (Tb: 0.21-0.26), and the results were further proved by another uniform host of NaGdF4:Ce,Tb nanoparticles. The HA was proper to find the optimal concentration of the activator of Tb. Furthermore, the optimal phosphor could be used as a bioimaging agent and improved QR code.

Highly Erbium-Doped Nanoplatform with Enhanced Red Emission for Dual-Modal Optical-Imaging-Guided Photodynamic Therapy.

Generally, luminescence quenching at high doping concentrations typically limits the concentration of doped ions in the lanthanide material to less than 0.05-20 mol %, and this is still a major hindrance in designing nanoplatforms with improved brightness. In this research, a nanoplatform capable of dual-modal imaging and synergetic antitumor cells therapy was designed. NaYF4: x%Er@NaXF4 ( x = 5, 25, 50, and 100; X = Lu and Y) core@shell nanoparticles with Er3+ ion concentration up to 100 mol % were synthesized, and the luminescence properties under near-infrared (NIR) excitation were detected. The results show the strong coupled of surface and concentration quenching effects in upconversion nanoparticles (UCNP). Upconversion luminescence (UCL) and NIR-II emission intensity increased with negligible concentration quenching effect under 980 and 800 nm NIR lasers because of the growth of epitaxial shells. Therefore, the enhanced red luminescence transfers energy to photosensitizer ZnPc as the photodynamic therapy (PDT) agent for tumor inhibition efficacy.

Optimization of Red Luminescent Intensity in Eu3+-Doped Lanthanide Phosphors Using Genetic Algorithm.

In this research, four steps including synthesis experiment, brightness evaluation, optimized calculation using brightness as fitness reference, and new calculated composition for the next preparation have been proceeded to find the brightest Eu3+ doped phosphors combined with chemical experiments and genetic algorithm (GA) calculation. The evolutionary operations, such as elitism, selection, crossover, and mutation, are applied to the compound combination. Feasible optimized combination would be obtained until the phosphor is found to be satisfactory. Through GA calculation and thd experimental process, the final luminescence enhancement factor of the optimal phosphor is up to 141% compared with the best one in the first generation. Thus, the GA calculation could be well applied to combinatorial chemistry to find the better phosphor. Additionally, the optimized phosphor is potentially applied as the fingerprint detection nanoparticle and dual-modal imaging agent of the CT/luminescent agent with high penetration and resolution.

Multilevel Nanoarchitecture Exhibiting Biosensing for Cancer Diagnostics by Dual-Modal Switching of Optical and Magnetic Resonance Signals.

In this research, the fabrication and application of a multifunctional core-shell nanoarchitecture are proposed. NaYF4:Yb,Er@NaYF4:Yb,Nd exhibits upconversion luminescence (UCL) of erbium ions but has quenched UCL emission when it is coated with MnO2 nanosheets. This hierarchical multilevel UCNP-MnO2 exhibits restoration of UCL and generation of a magnetic resonance imaging (MRI) signal when it is exposed to a microenvironment containing glutathione (GSH)/H2O2, which strips the MnO2 sheets by converting them to paramagnetic Mn2+ ions. This dual-modal switching feature of the optical emission and MRI signals provides a platform for stimuli-responsive biosensing of GSH/H2O2. Our new formulation as a dual-modal biosensor for detecting aberrant levels of intracellular GSH/H2O2 associated in cancer cells could be a potential diagnostic probe to distinguish tumor cells from normal cells.

Stable ICG-loaded upconversion nanoparticles: silica core/shell theranostic nanoplatform for dual-modal upconversion and photoacoustic imaging together with photothermal therapy.

We report here the design and multiple functions of a new hierarchical nanotheronostic platform consisting of an upconversion nanoparticle (UCNP) core: shell with an additional mesoporous silica (mSiO2) matrix load shell containing sealed, high concentration of ICG molecules. We demonstrate that this UCNP@mSiO2-ICG nanoplatform can perform the following multiple functions under NIR excitation at 800 nm: 1) Light harvesting by the UCNP shell containing Nd and subsequent energy transfer to Er in the Core to produce efficient green and red upconversion luminescence for optical imaging; 2) Efficient nonradiative relaxation and local heating produced by concentration quenching in aggregated ICG imbedded in the mesopourous silica shell to enable both photoacoustic imaging and photothermal therapy. Compared to pure ICG, sealing of mesoporous silica platforms prevents the leak-out and improves the stability of ICG by protecting from rapid hydrolysis. Under 800 nm laser excitation, we performed both optical and photoacoustic (PA) imaging in vitro and in vivo. Our results demonstrated that UCNP@mSiO2-ICG with sealed structures could be systemically delivered to brain vessels, with a long circulation time. In addition, these nanoplatforms were capable of producing strong hyperthermia efforts to kill cancer cells and hela cells under 800 nm laser irradiation.