RESUMO
Photodynamic therapy (PDT) by near-infrared (NIR) irradiation is a promising technique for treating various cancers. Here, we reported the development of free-standing wafer-scale Au nanosheets (NSs) that exhibited an impressive PDT effect. The Au NSs were synthesized by ionic layer epitaxy at the air-water interface with a uniform thickness in the range from 2 to 8.5 nm. These Au NSs were found very effective in generating singlet oxygen under NIR irradiation. In vitro cellular study showed that the Au NSs had very low cytotoxicity and high PDT efficiency due to their uniform 2D morphology. Au NSs could kill cancer cells after 5 min NIR irradiation with little heat generation. This performance is comparable to using 10 times mass loading of Au nanoparticles (NPs). This work suggests that two-dimensional (2D) Au NSs could be a new type of biocompatible nanomaterial for PDT of cancer with an extraordinary photon conversion and cancer cell killing efficiency.
RESUMO
Room-temperature ferromagnetism in two-dimensional (2D) oxide materials is an intriguing phenomenon for spintronic applications. Here, we report significantly enhanced room-temperature ferromagnetism observed from ultrathin cerium oxide nanosheets hybridized with organic surfactant molecules. The hybrid nanosheets were synthesized by ionic layer epitaxy over a large area at the water-air interface. The nanosheets exhibited a saturation magnetization of 0.149 emu/g as their thickness reduced to 0.67 nm. This value was 5 times higher than that for CeO2 thin films and more than 20 times higher than that for CeO2 nanoparticles. The magnetization was attributed to the high concentration (15.5%) of oxygen vacancies stabilized by surfactant hybridization as well as electron transfer between organic and oxide layers. This work brings an effective strategy of introducing strong ferromagnetism to functional oxide materials, which leads to a promising route toward exploring new physical properties in 2D hybrid nanomaterials.
RESUMO
Efficient charge separation and transportation are key factors that determine the photoelectrochemical (PEC) water-splitting efficiency. Here, a simultaneous enhancement of charge separation and hole transportation on the basis of ferroelectric polarization in TiO2 -SrTiO3 core-shell nanowires (NWs) is reported. The SrTiO3 shell with controllable thicknesses generates a considerable spontaneous polarization, which effectively tunes the electrical band bending of TiO2 . Combined with its intrinsically high charge mobility, the ferroelectric SrTiO3 thin shell significantly improves the charge-separation efficiency (ηseparation ) with minimized influence on the hole-migration property of TiO2 photoelectrodes, leading to a drastically increased photocurrent density ( Jph ). Specifically, the 10 nm-thick SrTiO3 shell yields the highest Jph and ηseparation of 1.43 mA cm-2 and 87.7% at 1.23 V versus reversible hydrogen electrode, respectively, corresponding to 83% and 79% improvements compared with those of pristine TiO2 NWs. The PEC performance can be further manipulated by thermal treatment, and the control of SrTiO3 film thicknesses and electric poling directions. This work suggests a material with combined ferroelectric and semiconducting features could be a promising solution for advancing PEC systems by concurrently promoting the charge-separation and hole-transportation properties.
