Simple synthesis of peanut shell-like MoCoFe-HO@CoMo-LDH for efficient alkaline oxygen evolution reaction.

Due to the depletion of fossil energy on earth, it is crucial to develop resource rich and efficient non-precious metal electrocatalysts for oxygen evolution reaction (OER). Herein, we synthesized an efficient and economical electrocatalyst using a simple self-assembly strategy. Firstly, rod-shaped MIL-88A was synthesized by hydrothermal method. Then, the surface of MIL-88A was functionalized and encapsulated in zeolitic imidazolate framework-67 (ZIF-67) by hydrothermal method. The combination of MIL-88A and ZIF-67 resulted in a slight ion-exchange reaction between Co2+ and the surface of MIL-88A to generate CoFe-LDH@ZIF-67 core-shell structure. Afterwards, in the presence of Mo6+, ZIF-67 was converted into CoMo-nanocages through ion-exchange reactions, forming a core-shell structure of MoCoFe hydr (oxy) oxide@CoMo-LDH (MoCoFe-HO@CoMo-LDH). Due to the advantages of core-shell structure and composition, this material exhibits excellent OER characteristics, with a small Tafel slope (45.11 mV dec-1) and low overpotential (324 mV) at 10 mA cm-2. It exhibits good stability in alkaline media. This research work provides a novel approach for the development of efficient and economical non-precious metal electrocatalysts.

Facile synthesis of Pt/polyoxometalate/hollow carbon sphere tri-component nanoparticles via a "double gain strategy" for high-performance electrochemical sensing of adrenaline.

In this study, we designed and successfully synthesized the Pt/polyoxometalate/hollow carbon sphere (Pt/POM/HCS) tri-component nanoparticles (NPs) by a pollution-free, efficient, and convenient method. HCSs with outstanding chemical stability and conductivity are self-generated by acid etching and calcination of silica spheres synthesized by a hard template method. HCSs have a hollow internal structure that provides specific three-dimensional storage space, and can increase the surface area. The mesoporous system is beneficial to providing numerous mass transfer passageways and immobilizing NPs. In addition, we introduced a "double gain strategy", by taking advantage of POMs as reducing and bridging agents, to achieve the loading of ultrafine Pt NPs on the surface of HCSs. Pt NPs have excellent stability and unique electrocatalytic activity. As a result of the synergistic effect of HCSs and ultrafine Pt NPs, the electrochemical sensing of adrenaline exhibits high-performance catalytic activity, sensitivity, suitable linearity range (0.16 µM-1.195 mM), and low limit of detection (57.5 nM, S/N = 3), excellent stability, and reproducibility. The developed platform is a sensitive and effective adrenaline electrical sensing platform with broad practical application prospects.

Facile synthesis of Co-Ni layered double hydroxides nanosheets wrapped on a prism-like metal-organic framework for efficient oxygen evolution reaction.

The construction of low-cost oxygen evolution reaction (OER) electrocatalysts with high activity and good durability is a considerable challenge for facilitating the efficient utilization of green energy. Herein, the prism-like materials of institute lavoisier frameworks-88 (MIL-88) was first synthesized by a hydrothermal method. Then, Co-Ni layered double hydroxides (CoNi-LDHs) nanosheets were directly wrapped on the MIL-88 surface by electrodeposition to form core-shell MIL-88@CoNi-LDHs composites. Due to the distinct structure and synergistic effect between the MIL-88 core and CoNi-LDHs shell, it was found that MIL-88@CoNi-LDHs had outstanding OER activity with a small Tafel slope (45.55 mV dec-1), low overpotential (314 mV) at 10 mA cm-2, and superior durability. This study provides a prospective pathway to exploit highly efficient low-cost electrocatalysts for OER.

Point-of-care testing of butyrylcholinesterase activity through modulating the photothermal effect of cuprous oxide nanoparticles.

Butyrylcholinesterase (BChE) is an important indicator for clinical diagnosis of liver dysfunction, organophosphate toxicity, and poststroke dementia. Point-of-care testing (POCT) of BChE activity is still a challenge, which is a critical requirement for the modern clinical diagnose. A portable photothermal BChE assay is proposed through modulating the photothermal effects of Cu2O nanoparticles. BChE can catalyze the decomposition of butyrylcholine, producing thiocholine, which further reduce and coordinate with CuO on surface of Cu2O nanoparticle. This leads to higher efficiency of formation of Cu9S8 nanoparticles, through the reaction between Cu2O nanoparticle and NaHS, together with the promotion of photothermal conversion efficiency from 3.1 to 59.0%, under the excitation of 1064 nm laser radiation. An excellent linear relationship between the temperature change and the logarithm of BChE concentration is obtained in the range 1.0 to 7.5 U/mL, with a limit of detection of 0.076 U/mL. In addition, the portable photothermal assay shows strong detection robustness, which endows the accurate detection of BChE in human serum, together with the screening and quantification of organophosphorus pesticides. Such a simple, sensitive, and robust assay shows great potential for the applications to clinical BChE detection and brings a new horizon for the development of temperature based POCT.

Synthesis of bifunctional fluorescent nanohybrids of carbon dots-copper nanoclusters via a facile method for Fe3+ and Tb3+ ratiometric detection.

In this work, a dual-emission ratiometric fluorescent probe of carbon dots-copper nanoclusters (CDs-Cu NCs) nanohybrids with bifunctional features was successfully assembled through mechanical mixing. The CDs were synthesized using ascorbic acid as a carbon source, and Cu NCs were prepared using d-penicillamine as the stabilizer and reducing agent. The as-prepared CDs-Cu NCs displayed two emission peaks (blue at 424 nm and red at 624 nm) when excited at 360 nm, and showed great stability. Interestingly, trace amount of Fe3+ could lead to the aggregation of Cu NCs, and induce a drastic static fluorescence quenching at 624 nm because of the electrostatic combination between them, while the fluorescence of the emission peak at 424 nm remained constant. Moreover, an attractive fluorescence enhancement phenomenon at 424 nm was observed when trace Tb3+ was added to the above system, which may due to the combination of fluorescence resonance energy transfer (FRET) and photo-induced electron transfer (PET) mechanisms. Thus, CDs-Cu NCs were applied for the ratiometric detection of Fe3+ and Tb3+ in aqueous solution, and the detection limit (3σ/slope) was 45 nM and 62 nM with the linear range from 0.01 to 40 µM and 0.1 to 50 µM, respectively. Furthermore, the developed sensor was successfully applied for the detection of Fe3+ and Tb3+ in real-water samples.

Evaluation of the fouling potential of sludge in a membrane bioreactor integrated with microbial fuel cell.

This study focused on the fouling characteristics evaluation of the sludge in a membrane bioreactor integrated with microbial fuel cell (MFC-MBR) to reveal the mechanisms of membrane fouling mitigation. The filtration of soluble microbial products (SMPs) in MFC-MBR showed lower flux decline rate than those in the control system (C-MBR). Based on the extended Derjaguin-Landau-Verwey-Overbeek analysis, decreases in free energies of adhesion between the SMPs and clean membrane or SMP-fouled membrane were observed in MFC-MBR. When approaching the clean membrane or SMP-fouled membrane, the SMPs in MFC-MBR had to overcome a higher energy barrier compared to those in C-MBR, indicating the inhibition of adsorption of SMPs on the membrane surface in MFC-MBR. Additionally, sludge flocs in MFC-MBR exhibited lower hydrophobicity and were less negative surface charged in comparison to those in the C-MBR. In MFC-MBR, the sludge flocs approaching the clean membrane, SMP-fouled membrane and cake layer all experienced higher energy barriers and lower secondary energy minimums compared to those in C-MBR, exhibiting the lower potential of cake layer formation. These results confirmed that decreases of the fouling potentials of SMPs and sludge flocs were essential for the membrane fouling mitigation in the MFC-MBR.