Oxygen evolution reaction (OER) involves multiple electron transfer processes, resulting in high activation barrier. Developing catalysts with low overpotential and high intrinsic activity towards OER is critical but challenging. Here we demonstrate a facile hydrothermal method of functionalizing Ni foam with Fe-doped β-Ni(OH) 2 nanosheets, which exhibit an overpotential of 219 mV at the geometric current density of 10 mA cm -2 . To our knowledge, it is the best value reported for Ni-/Fe hydroxide based OER catalyst. In addition, the catalyst achieves a current density of 6.25 mA cm -2 at the overpotential of 300 mV when it is normalized to the electrochemical surface area of catalyst. This value is better than most of the state-of-the-art OER catalysts. The enhanced catalytic activity is believed to be due to the unique combination of structural and chemical properties of the catalyst.
The surprising discovery of salutary
effects of low doses of carbon
monoxide (CO) in mammalian physiology has raised intense research
interest in CO delivery to biological targets under controlled conditions.
In recent attempts, photoactive metal carbonyl complexes (photoCORMs)
have been employed to trigger CO release at the target sites. In this
work, a designed photoCORM namely, fac-[Re(CO)3(pbt) (PPh3)](CF3SO3) (1, pbt =2-(2-pyridyl)benzothiazole) has been synthesized and
characterized by spectroscopic methods and crystallography. This photoCORM
not only releases CO upon illumination with low-power UV light (305
nm, 5 mW cm–2) but also exhibits a “turn-off”
of its orange luminescence (λem = 605 nm) upon release
of one CO ligand. The latter property provides a convenient way to
track the CO release event. The photoCORM 1 has been
entrapped within the pores of the narrow channels of 100 nm mesoporous
Al-MCM-41 nanoparticles and the loaded {Re-CO}@Al-MCM-41 MSNs have
been characterized by powder X-ray diffraction (PXRD), FTIR spectroscopy
and chemical analysis. Results of scanning electron microscopy (SEM),
transmission electron microscopy (TEM), and the SEM-EDX elemental
maps of C, Si, O, Re, and P confirm that the carbonyl complex is retained
within the pores of the MSNs. Strong electrostatic binding of the
cationic photoCORM to the negatively charged walls of the Al-MCM-41
nanoparticles results in very little leaching of the CO donor from
the host matrix. The hydrodynamic parameters (155 nm diameter in PBS,
ζ-potential = −28.53 ± 1.00 mV) of the biocompatible
{Re-CO}@Al-MCM-41 MSNs fall in the right range of the drug-carriers
and the particles are readily endocytosed by MDA-MB-231 (human breast
cancer) cells. The entry of the {Re-CO}@Al-MCM-41 MSNs into the cellular
matrix is easily visualized by the intense orange luminescence (λex = 400 nm) of the loaded cells. Short exposure of the cells
to low-power UV light brings about a rapid diminution of the orange
luminescence due to CO release from the photoCORM locked within the
MSNs and causes CO-induced death of the cancer cells. Recently, CO
has been shown to induce apoptotic death in different types of cancer
cells as well as enhance the efficacy of cancer chemotherapy. The
simple design of the {Re-CO}@Al-MCM-41 MSNs and their response to
light allows for the first time to deliver the drug (CO) from a pro-drug
locked within a biocompatible MSNs that can readily accumulate within
malignant sites due to the “enhance permeability and retention”
(EPR) effect. In addition, the CO delivery process can be conveniently
tracked through the loss of luminescence of the MSNs.
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