The surface effect on the photodetection of metal oxide nanostructures acting as a double-edged sword achieves ultrahigh photogain but unavoidably prolongs the response time due to slow oxygen adsorption/desorption processes. In this study, we break the compromise to enhance the UV photogain by 3 orders of magnitude as well as increase the photoresponse speed by 5 times via incorporating opencircuit p−n nanoscale heterojunctions (NHJs) by forming single-crystalline p-NiO nanoparticles on n-ZnO nanowires. This is because the formation of NHJs enhances surface band bending of ZnO nanowires, improving the spatial separation efficiency of photogenerated electrons and holes, and passivates the ZnO surfaces by minimizing the interaction of photocarriers with chemisorbed oxygen molecules. The concept using NHJs explores a new pathway toward ultrafast and supersensitive photodetection.

Gadolinium oxide nanocrystal ͑Gd 2 O 3 -NC͒ memories treated by postdeposition rapid thermal annealing were investigated. Bandgap offset performed by a crystallized Gd 2 O 3 -NC dot surrounded by amorphous Gd 2 O 3 dielectrics is successfully demonstrated and proven by the transmission electron microscopy images and electron diffraction pattern. The Gd 2 O 3 -NC memory exhibits a hysteresis memory window of 4 V and NC dot density of more than 8.5 ϫ 10 11 cm −2 . In addition, the formation of Gd 2 O 3 -NC and charge loss characteristics on annealing temperature were analyzed and optimized at 850°C. The data endurance of 10 4 program and erase cycling for a sufficient memory window ͑Ͼ2 V͒ was also observed for the Gd 2 O 3 nanocrystal memory.In order to scale down floating gate ͑FG͒ nonvolatile memory ͑NVM͒, tunnel oxide limitation for sufficient charge retention has to be overcome. 1 One way is to implement high-dielectric-constant ͑high-k͒ materials such as Al 2 O 3 thin film as the tunnel oxide for the reduction of operation voltage while satisfying the data retention and endurance. 2 The other is using a discrete charge-storage concept for thinner tunnel oxide without sacrificing nonvolatility. Isolated Si and Ge semiconductor nanocrystal ͑NC͒ memories are NVMs that have been demonstrated to have a more simplified fabrication process, better punchthrough effect, and immunity to oxide defects as compared to conventional FG NVMs. 1,3,4 To achieve the fast write/ erase and long retention time simultaneously, metal NC memories are presented to engineer the depth of the potential well at storage nodes. Heavy metals, 4-7 silicide, 8,9 nitrided-metal, 10 and metal-oxide 11,12 are NC memories used as storage nodes. Compared with the semiconductor NC memories, metal counterparts exhibit a higher density of states around the Fermi level, stronger coupling with the conduction channel, a wider range of available work functions, and smaller energy perturbation due to carrier confinement. 13 Gadolinium oxide ͑Gd 2 O 3 ͒, the rare-earth sesquioxides ͑R 2 O 3 ͒, has been reported to be candidates as gate dielectrics for silicon and compound semiconductor device applications. 14,15 They are demonstrated to exhibit three different structures such as cubic, monoclinic, and hexagonal under different growth temperatures. 16 In addition, a different energy bandgap of amorphous ͑6.3-6.4 eV͒ and crystallized ͑5.0-5.4 eV͒ Gd 2 O 3 thin films has also been discovered. 17,18 Recently, magnetic nanocrystalline Gd 2 O 3 particles embedded in silica glass have been proposed for memory applications. 19 In this work, we demonstrate that a crystallized gadolinium oxide with low bandgap acts as a charge-storage node when it is surrounded by amorphous gadolinium oxide with higher bandgap to form Gd 2 O 3 nanocrystal memories ͑Gd 2 O 3 -NC͒. This separate charge-storage structure is different from the previous research regarding NC memory devices, 4-12 and the tunnel oxide thickness is effectively increased for better charge retention. The memory...

Covalent triazine frameworks are an emerging material class that have shown promising performance for a range of applications. In this work, we report on a metal-assisted and solvent-mediated reaction between calcium carbide and cyanuric chloride, as cheap and commercially available precursors, to synthesize two-dimensional triazine structures (2DTSs). The reaction between the solvent, dimethylformamide, and cyanuric chloride was promoted by calcium carbide and resulted in dimethylamino-s-triazine intermediates, which in turn undergo nucleophilic substitutions. This reaction was directed into two dimensions by calcium ions derived from calcium carbide and induced the formation of 2DTSs. The role of calcium ions to direct the two-dimensionality of the final structure was simulated using DFT and further proven by synthesizing molecular intermediates. The water content of the reaction medium was found to be a crucial factor that affected the structure of the products dramatically. While 2DTSs were obtained under anhydrous conditions, a mixture of graphitic material/2DTSs or only graphitic material (GM) was obtained in aqueous solutions. Due to the straightforward and gram-scale synthesis of 2DTSs, as well as their photothermal and photodynamic properties, they are promising materials for a wide range of future applications, including bacteria and virus incapacitation.

Improved multiphoton-excited imaging and microspectroscopy require nanoprobes that can give different nonlinear optical signals. Here, composite nanostructures with a barium titanate core and a plasmonic moiety at their surface are synthesized and characterized. It is found that the core provides a high second-order nonlinear susceptibility for sensitive second harmonic generation (SHG) imaging in living cells. As a second function in the twophoton regime, the plasmonic part yields high local fields for resonant and nonresonant surface enhanced hyper Raman scattering (SEHRS). SEHRS complements the one-photon surface enhanced Raman scattering (SERS) spectra that are also enhanced by the plasmonic shells. Barium titanate silver core-shell (Ag@BaTiO 3 ) composites are specifically suited for SEHRS and SHG excited at 1064 nm, while gold at barium titanate (Au@BaTiO 3 ) nanoparticles can be useful in a combination of SHG and SERS at lower wavelengths, here at 785 nm and 850 nm. The theoretical models show that the optical properties of the BaTiO 3 dielectric core depend on probing frequency, shape, size, and plasmonic properties of the surrounding gold nanoparticles so that they can be optimized for a particular type of experiment. These versatile, tunable probes give new opportunities for combined multiphoton probing of morphological structure and chemical properties of biosystems.very attractive in laser microspectroscopy and imaging. They include two-photonexcited fluorescence, [3] second harmonic generation (SHG), [4] stimulated Raman scattering [5] and coherent anti-Stokes Raman scattering [6] microscopies, and imaging based on spontaneous hyper Raman scattering (HRS). [7] Nonlinear processes are attractive in microscopy and spectroscopy since they can be excited with light in the near-infrared, which offers several advantages. The latter include deep tissue penetration capability, reduced photo damage due to the lower photon energy, and spatially more confined probed volume, which can result in an improved lateral resolution. [8] Nevertheless, when multiphoton-excited processes are complemented with their one-photon-excited counterparts, this can yield unprecedented structural information from a sample. As an example, the spontaneous twophoton-excited Raman process, termed HRS, is governed by different selection rules than the (conventional) spontaneous one-photon-excited RS. Both HRS and RS can be enhanced in the local fields of plasmonic nanostructures, resulting in surface enhanced hyper Raman scattering (SEHRS) [9] and surface enhanced Raman scattering (SERS) spectra, respectively. While imaging based on vibrational spectra gives detailed molecular structure, other nonlinear optical signals, such as SHG, are less specific but lead to information about the microscopic morphology of a sample. SHG is a two-photon process, where a

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