Promoting nickel oxidation state transitions in single-layer NiFeB hydroxide nanosheets for efficient oxygen evolution.

Promoting the formation of high-oxidation-state transition metal species in a hydroxide catalyst may improve its catalytic activity in the oxygen evolution reaction, which remains difficult to achieve with current synthetic strategies. Herein, we present a synthesis of single-layer NiFeB hydroxide nanosheets and demonstrate the efficacy of electron-deficient boron in promoting the formation of high-oxidation-state Ni for improved oxygen evolution activity. Raman spectroscopy, X-ray absorption spectroscopy, and electrochemical analyses show that incorporation of B into a NiFe hydroxide causes a cathodic shift of the Ni2+(OH)2 → Ni3+δOOH transition potential. Density functional theory calculations suggest an elevated oxidation state for Ni and decreased energy barriers for the reaction with the NiFeB hydroxide catalyst. Consequently, a current density of 100 mA cm-2 was achieved in 1 M KOH at an overpotential of 252 mV, placing it among the best Ni-based catalysts for this reaction. This work opens new opportunities in electronic engineering of metal hydroxides (or oxides) for efficient oxygen evolution in water-splitting applications.

Renal-Clearable Ultrasmall Coordination Polymer Nanodots for Chelator-Free 64Cu-Labeling and Imaging-Guided Enhanced Radiotherapy of Cancer.

Developing tumor-homing nanoparticles with integrated diagnostic and therapeutic functions, and meanwhile could be rapidly excreted from the body, would be of great interest to realize imaging-guided precision treatment of cancer. In this study, an ultrasmall coordination polymer nanodot (CPN) based on the coordination between tungsten ions (WVI) and gallic acid (W-GA) was developed via a simple method. After polyethylene glycol (PEG) modification, PEGylated W-GA (W-GA-PEG) CPNs with an ultrasmall hydrodynamic diameter of 5 nm were rather stable in various physiological solutions. Without the need of chelator molecules, W-GA-PEG CPNs could be efficiently labeled with radioisotope 64Cu2+, enabling positron emission tomography (PET) imaging, which reveals efficient tumor accumulation and rapid renal clearance of W-GA-PEG CPNs upon intravenous injection. Utilizing the radio-sensitizing function of tungsten with strong X-ray absorption, such W-GA-PEG CPNs were able to greatly enhance the efficacy of cancer radiotherapy in inhibiting the tumor growth. With fast clearance and little long-term body retention, those W-GA-PEG CPNs exhibited no appreciable in vivo toxicity. This study presents a type of CPNs with excellent imaging and therapeutic abilities as well as rapid renal clearance behavior, promising for further clinic translation.

Spectroscopic Investigation of Plasma-Fluorinated Monolayer Graphene and Application for Gas Sensing.

Large-area monolayer fluorinated graphene (FG) is synthesized by a controllable SF6 plasma treatment. The functional groups of FG are elucidated by various spectroscopies, including Raman spectroscopy, X-ray photoemission spectroscopy (XPS), and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Raman results suggest that the defects are introduced into the monolayer graphene during the fluorination process. The fluorine content can be varied by the plasma treatment and can reach the maximum (∼24.6 atom % F) under 20 s of plasma treatment as examined by XPS measurement. The angle-dependent NEXAFS results reveal that the fluorine atoms interact with the graphene matrix to form covalent C-F bonds, which are perpendicular to the basal plane of FG. FG is applied as a gas-sensing material and owns much better performance for ammonia detection compared to pristine graphene. On the basis of our density functional theory simulation results, the fast response/recovery behavior and high sensitivity of the FG gas sensor are attributed to enhanced physical absorption due to the C-F covalent bonds on the surface of FG.