In this study, the interface effects of Cu 2 O and Au/Cu 2 O semiconductors were improved by addition of a magnesia (MgO) interface nanolayer (MIN) deposited via precipitation. The morphologies, crystal structures, chemical compositions, elemental states and optical properties of MgO/Cu 2 O and Au/MgO/Cu 2 O heterojunctions were characterized via SEM, XRD, XPS, UV–VIS–NIR and PL. It was found that the MIN has a surface passivation effect that inhibits the aggregation and oxidation of Cu 2 O. This enhances Cu 2 O semiconductors’ wettability and stability, improves crystallinity and reduces Au particle sizes. More importantly, the MIN promotes charge transfer via tunneling through the insulator, and enhances adsorption of molecular oxygen, facilitating superoxide radicals formation during photoreactivity. MgO/Cu 2 O and Au/MgO/Cu 2 O exhibited superior photodegradation of methyl orange, attributed to the boost of O 2 − and h + . This work confirmed the importance of MIN as a useful modification of semiconductor photocatalysts, and the MIN can significantly enhance the production of superoxide radicals in the photocatalytic activity with visible light.
As a green and sustainable corrosion protection technology, photoelectrochemical cathodic protection (PECCP) cannot be applied to protect metals having low corrosion potential ( E c ) due to the insufficient negative conduction band (CB) potential of the present semiconductor materials. Herein, for the first time, PECCP is reported to indirectly protect metals with low E c from corrosion by introduction of an interlayer with high E c between the substrate and semiconductor. As an example, a nickel interlayer was firstly deposited on magnesium alloy substrate by chemical deposition and electrodeposition to provide the high E c , followed by electrodeposition of Cu 2 O semiconductor layer on the nickel layer. A series of characterizations, including high-resolution transmission electron microscope and X-ray photoelectron spectroscopy, indicate that the resultant Cu 2 O semiconductor has an octahedral structure and an edge length of ca. 514 nm. The n-type property of the semiconductor is determined by the Mott-Schottky curve, and the photo-response behavior, such as obvious photo-induced potential drop and stable photocurrent density as high as 747 μA cm −2 under visible light illumination, is confirmed by electrochemical and photoelectrochemical measurements. The new proposed methodology described in this study is not limited to magnesium alloy but also can be possibly applied in other structural metals having low E c .
Reactive oxygen species generation efficiency of photosensitizers and hypoxia microenvironment in solid tumor hamper photodynamic therapy (PDT) efficacy. Here, we introduce an efficient inorganic photosensitizer by incorporating plasmonic gold metal nanostructures into Cu2O semiconductors for PDT. By utilizing the plasmon-induced resonance energy transfer (PIRET) process from Au to Cu2O, Au@SiO2@Cu2O (ASC) demonstrates a high singlet oxygen quantum yield of 0.71 under a 670 nm laser irradiation. The ASC is loaded into oxygen self-enriched perfluorohexane (PFH) droplets and coated with liposome (Lip) to form Lip(ASC/PFH) nanocomposites. The achieved Lip(ASC/PFH) shows considerable anticancer efficacy for in vitro cancer cells and in vivo tumor growth. The proposed oxygen self-enriched PIRET-PDT concept has significant implication in PDT design.
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