5 research outputs found

    Hydrophobic Carbon-Doped TiO<sub>2</sub>/MCF‑F Composite as a High Performance Photocatalyst

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    A novel hydrophobic photocatalyst carbon-doped TiO<sub>2</sub>/MCF-F was prepared by using silica mesoporous cellular foam (MCF) as host material, glucose as carbon source, and NH<sub>4</sub>F as hydrophobic modifying agent. It was confirmed that titania nanoparticles were loaded in pore of MCF by XRD, N<sub>2</sub> sorption isotherms, and TEM. The loaded titania nanoparticles exhibited higher photocatalytic performance. UV–vis absorption spectra and XPS suggested carbon atoms were doped in the lattice of titania by replacing titanium atoms and narrowed the band gap so that visible light absorption and photocatalytic activity of the photocatalyst were highly promoted. On the other hand, water contact angle measurement and XPS proved that the photocatalyst was endowed with hydrophobic property, which was caused by Si–F bonds. Carbon-doped TiO<sub>2</sub>/MCF-F photocatalyst showed good adsorptive ability and photocatalytic activity in the photodegradation test of methyl orange under visible light

    Improved SERS Sensitivity on Plasmon-Free TiO<sub>2</sub> Photonic Microarray by Enhancing Light-Matter Coupling

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    Highly sensitive surface-enhanced Raman scattering (SERS) detection was achieved on plasmon-free TiO<sub>2</sub> photonic artificial microarray, which can be quickly recovered under simulated solar light irradiation and repeatedly used. The sensitive detection performance is attributed to the enhanced matter-light interaction through repeated and multiple light scattering in photonic microarray. Moreover, the SERS sensitivity is unprecedentedly found to be dependent on the different light-coupling performance of microarray with various photonic band gaps, where microarray with band gap center near to laser wavelength shows a lower SERS signal due to depressed light propagation, while those with band gap edges near to laser wavelength show higher sensitivity due to slow light effect

    Fabry–Perot Cavity-Enhanced Optical Absorption in Ultrasensitive Tunable Photodiodes Based on Hybrid 2D Materials

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    Monolayer two-dimensional (2D) transition metal dichalcogenides (TMDs) show interesting optical and electrical properties because of their direct bandgap. However, the low absorption of atomically thin TMDs limits their applications. Here, we report enhanced absorption and optoelectronic properties of monolayer molybdenum disulfide (MoS<sub>2</sub>) by using an asymmetric Fabry–Perot cavity. The cavity is based on a hybrid structure of MoS<sub>2</sub>/ hexagonal boron nitride (BN)/Au/SiO<sub>2</sub> realized through layer-by-layer vertical stacking. Photoluminescence (PL) intensity of monolayer MoS<sub>2</sub> is enhanced over 2 orders of magnitude. Theoretical calculations show that the strong absorption of MoS<sub>2</sub> comes from photonic localization on the top of the microcavity at optimal BN spacer thickness. The n/n<sup>+</sup> MoS<sub>2</sub> homojunction photodiode incorporating this asymmetric Fabry–Perot cavity exhibits excellent current rectifying behavior with an ideality factor of 1 and an ultrasensitive and gate-tunable external photo gain and specific detectivity. Our work offers an effective method to achieve uniform enhanced light absorption by monolayer TMDs, which has promising applications for highly sensitive optoelectronic devices

    Molecular Alignment and Electronic Structure of <i>N</i>,<i>N</i>′‑Dibutyl-3,4,9,10-perylene-tetracarboxylic-diimide Molecules on MoS<sub>2</sub> Surfaces

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    The molecular orientation of organic semiconductors on a solid surface could be an indispensable factor to determine the electrical performance of organic-based devices. Despite its fundamental prominence, a clear description of the emergent two-dimensional layered material–organic interface is not fully understood yet. In this study, we reveal the molecular alignment and electronic structure of thermally deposited <i>N</i>,<i>N</i>′-dibutyl-3,4,9,10-perylene-dicarboximide (PTCDI-C4) molecules on natural molybdenum disulfide (MoS<sub>2</sub>) using near-edge X-ray absorption fine structure spectroscopy (NEXAFS). The average tilt angle determination reveals that the anisotropy in the π* symmetry transition of the carbon <i>K</i>-edge (284–288 eV range) is present at the sub-monolayer regime. Supported by ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), and resonant photoemission spectroscopy (RPES) measurements, we find that our spectroscopic measurements indicate a weak charge transfer established at the PTCDI-C4/MoS<sub>2</sub> interface. Sterical hindrance due to the C4 alkyl chain caused tilting of the molecular plane at the initial thin film deposition. Our result shows a tunable interfacial alignment of organic molecules on transition metal dichalcogenide surfaces effectively enhancing the electronic properties of hybrid organic–inorganic heterostructure devices

    Surface Functionalization of Black Phosphorus via Potassium toward High-Performance Complementary Devices

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    Two-dimensional black phosphorus configured field-effect transistor devices generally show a hole-dominated ambipolar transport characteristic, thereby limiting its applications in complementary electronics. Herein, we demonstrate an effective surface functionalization scheme on few-layer black phosphorus, through in situ surface modification with potassium, with a view toward high performance complementary device applications. Potassium induces a giant electron doping effect on black phosphorus along with a clear bandgap reduction, which is further corroborated by in situ photoelectron spectroscopy characterizations. The electron mobility of black phosphorus is significantly enhanced to 262 (377) cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> by over 1 order of magnitude after potassium modification for two-terminal (four-terminal) measurements. Using lithography technique, a spatially controlled potassium doping technique is developed to establish high-performance complementary devices on a single black phosphorus nanosheet, for example, the p–n homojunction-based diode achieves a near-unity ideality factor of 1.007 with an on/off ratio of ∼10<sup>4</sup>. Our findings coupled with the tunable nature of in situ modification scheme enable black phosphorus as a promising candidate for further complementary electronics
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