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A simple wet ball‐milling method for exfoliating pristine graphite to graphene nanosheets is proposed. The surfactant of cetyltrimethyl ammonium bromide is utilized to greatly improve the exfoliation efficiency of graphene nanosheets. Variation of the ball‐milling time is an efficient way to control the size and thickness of graphene nanosheets, as well as the level of edge defects. With an increase of ball‐milling time, superior electrochemical reactivity is imparted owing to enlarged active area and increased catalytic ability. The obtained graphene nanosheets are sensitive for electrochemical oxidation of phenols (e.g., hydroquinone, p‐chlorophenol, and p‐nitrophenol), and thus qualified for the simultaneous sensing of trace level of phenols. The detection limits of simultaneous monitoring of hydroquinone, p‐chlorophenol, and p‐nitrophenol are as low as 0.017, 0.024, and 0.42 mg L−1, respectively. The proposed strategy thus opens up a new way to tune electrochemistry of graphene materials as well as to design their new applications.

A thorough understanding about the crystallographic and topographical evolution of wet-etched patterned sapphire substrates (PSS) is essential for revealing the etching mechanism and critical for fabricating optimized PSS for enhanced performance of GaN-based LED devices. As the first one of a series of three papers, using complementary scanning electron microscope (SEM) and atomic force microscope (AFM), we carried out a systematic study on the crystallographic and topographical evolution of cone-shaped PSS etched with an ordinary etchant (H 2 SO 4 :H 3 PO 4 = 3:1 at volume ratio, 230 • C) which enables crystallographic specific etching. The topography of patterns was found to evolve from normal cones to truncated cones, to triangular pyramids with multiple families of exposed crystallographic planes, then to hexagonal and triangular pyramids with a single family of planes. The Miller indexes of three major exposed crystallographic planes, with decreasing slant angles, were determined to be {11 0 5}, {45 1 38} and {11 0 12} with the last two being reported for the first time to our best knowledge. It was clearly demonstrated that AFM, thanks to its 3D topography imaging capability compared to SEM and focused ion beam, can be an indispensable tool for fast and reliable characterization of routine PSS samples.

A comparison is made between the electronic structures determined in ultrahigh vacuum of three surfaces using scanning tunneling spectroscopy ͑STS͒ and Kelvin probe force microscopy ͑KPFM͒. STS and KPFM illustrates Fermi level pinning of clean InAs͑001͒-͑4 ϫ 2͒ and InGaAs͑001͒-͑4 ϫ 2͒ surfaces and near flat band conditions for InAs͑110͒ cleaved surfaces. However, for InAs͑001͒-͑4 ϫ 2͒ and InGaAs͑001͒-͑4 ϫ 2͒, STS and KPFM data show very different positions for the surface Fermi level on identical samples; it is hypothesized that the difference is due to the Fermi level measured by KPFM being shifted by a static charge dipole to which STS is much less sensitive.

Chiral nanophotonic devices are promising candidates for chiral molecules sensing, polarization diverse nanophotonics and display technologies. Active chiral nanophotonic devices, where the optical chirality can be controlled by an external stimulus has triggered great research interest.However, efficient modulation of the optical chirality has been challenging. Here, we demonstrate switching of the extrinsic chirality by applied magnetic fields in a magneto-plasmonic metasurface device based on a magneto-optical oxide material, Ce1Y2Fe5O12 (Ce:YIG). Thanks to the low optical loss and strong magneto-optical effect of Ce:YIG, we experimentally demonstrated a giant and continuous far-field circular dichroism (CD) modulation by applied magnetic fields from -0.65° to +1.9° at 950 nm wavelength under glancing incident conditions. The far field CD modulation is due to both magneto-optical circular dichroism and near-field modulation of the superchiral fields by applied magnetic fields. Finally, we demonstrate magnetic field tunable chiral imaging in millimeter-scale magneto-plasmonic metasurfaces fabricated using self-assembly. Our results 2 provide a new way for achieving planar integrated, large-scale and active chiral metasurfaces for polarization diverse nanophotonics. KEYWORDS: Magnetoplasmonic, Metasurface, Optical Chirality, Magneto-optical effectChirality describes the symmetry property of a structure, that its mirror image cannot be superimposed with itself through translation and rotation operations, like our two hands. The chirality of biomolecules is universal in our living body, such as amino acid and proteins, which has significance in biomolecules recognition. 1,2 However, the chiroptical signal of chiral biomolecules is very weak. Recently, chiral plasmonic 3,4 and all dielectric structures 5,6 with large chiroptical response have attracted great research interest. Benefitted from advanced nano-fabrication technologies, 3D or planar chiroptical nanostructures, such as helices, 7,8 shurikens, 9 gammadions, 6,10 and twisted split-rings 11 have been fabricated. On the other hand, extrinsic chirality can also be observed in achiral photonic nanostructures under obliquely incidence conditions. The extrinsic chirality is originated from asymmetric distributions of electromagnetic fields, i.e. the electromagnetic near field distribution is chiral. 12 Nanophotonic structures such as nanoholes, 12 squares 13 and split ring resonators 14,15 showed large extrinsic chirality. For instance, Ben et al.demonstrated a ~4 times stronger optical chirality in achiral periodic nanoholes compared to the gammadion structure. 12 Recently, Abraham et. al. experimentally demonstrated that the achiral nanohole structures can also show superchiral near-fields even at perpendicular incidence conditions. 16 In that case, the far-field circular dichroism (CD) background signals from the plasmonic structures is eliminated, improving the sensitivity for chiral molecule sensing applications. These reports demonstrate a promising potent...