Two-dimensional nanosheets have attracted tremendous attention because of their promising practical application and theoretical values. The atomic-thick nanosheets are able to not only enhance the intrinsic properties of their bulk counterparts but also give birth to new promising properties. Herein, we highlight an available pathway to prepare the ultrathin graphitic-phase C(3)N(4) (g-C(3)N(4)) nanosheets by a "green" liquid exfoliation route from bulk g-C(3)N(4) in water for the first time. The as-obtained ultrathin g-C(3)N(4) nanosheet solution is very stable in both the acidic and alkaline environment and shows pH-dependent photoluminenscence (PL). Compared to the bulk g-C(3)N(4), ultrathin g-C(3)N(4) nanosheets show enhanced intrinsic photoabsorption and photoresponse, which induce their extremely high PL quantum yield up to 19.6%. Thus, benefiting from the inherent blue light PL with high quantum yields and high stability, good biocompatibility, and nontoxicity, the water-soluble ultrathin g-C(3)N(4) nanosheet is a brand-new but promising candidate for bioimaging application.

Articles you may be interested inThe effect of ionization on the global minima of small and medium sized silicon and magnesium clusters Energies and spatial features for the rotationless bound states of He 3 + 4 ( Σ g + 2 ) : A cationic core from helium cluster ionization One-photon mass-analyzed threshold ionization spectroscopy of 1,3,5-trifluorobenzene: The Jahn-Teller effect and vibrational analysis for the molecular cation in the ground electronic state Vacuum ultraviolet mass-analyzed threshold ionization spectroscopy of hexafluorobenzene: The Jahn-Teller effect and vibrational analysis Vacuum ultraviolet mass-analyzed threshold ionization spectroscopy of p -, m -, and o -difluorobenzenes. Ionization energies and vibrational frequencies and structures of the cationsWe have performed a systematic ground state geometry search for the singly charged Si n cations in the medium-size range (nр20) using density functional theory in the local density approximation ͑LDA͒ and generalized gradient approximation ͑GGA͒. The structures resulting for nр18 generally follow the prolate ''stacked Si 9 tricapped trigonal prism'' pattern recently established for the lowest energy geometries of neutral silicon clusters in this size range. However, the global minima of Si n and Si n ϩ for nϭ6, 8, 11, 12, and 13 differ significantly in their details. For Si 19 and Si 20 neutrals and cations, GGA renders the prolate stacks practically isoenergetic with the near-spherical structures that are global minima in LDA. The mobilities in He gas evaluated for all lowest energy Si n ϩ geometries using the trajectory method agree with the experiment, except for nϭ18 where the second lowest isomer fits the measurements. The effect of gradient corrections for either the neutral or cationic clusters is subtle, but their inclusion proves to be critical for obtaining agreement with the mobility measurements in the nϭ15-20 range. We have also determined ionization potentials for our Si n neutral geometries and found that all experimental size-dependent trends are reproduced for nр19. This particularly supports our structural assignments for Si 9 , Si 11 , Si 12 , and Si 17 neutrals. The good overall agreement between the measured and calculated properties supports the elucidation of the ''prolate'' family of silicon clusters as stacks of trigonal prisms.

Controlling the synthesis of atomic-thick nanosheets of nonlayered materials is extremely challenging because of the lack of an intrinsic driving force for anisotropic growth of two-dimensional (2D) structures. In that case, control of the anisotropy such as oriented attachment of small building blocks during the reaction process will be an effective way to achieve 2D nanosheets. Those atomic-thick nanosheets possess novel electronic structures and physical properties compared with the corresponding bulk samples. Here we report Co(9)Se(8) single-crystalline nanosheets with atomic thickness and unique lamellar stacking formed by 2D oriented attachment. The atomic-thick Co(9)Se(8) nanosheets were found to exhibit intrinsic half-metallic ferromagnetism, as supported by both our experimental measurements and theoretical calculations. This work will not only open a new door in the search for new half-metallic ferromagnetic systems but also pave a practical way to design ultrathin, transparent, and flexible paperlike spintronic devices.

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Photocatalytic purification of polluted water is a very promising way to alleviate the increasingly serious water resources crisis. Despite tremendous efforts, developing visible-light-driven photocatalysts with high activity at low cost still remains a great challenge. Herein, we report for the first time the design and synthesis of ordered m-BiVO(4) quantum tubes-graphene nanocomposites that exhibit unprecedented visible-light-driven photocatalytic activities, over 20 times faster than that of commercial P25 or bulk BiVO(4) and roughly 1.5 times more active than that of bare m-BiVO(4) quantum tubes. Notably, the unusual photoreactivities arise from the synergistic effects between the microscopic crystal structure of m-BiVO(4) and macroscopic morphological features of ordered m-BiVO(4) quantum tubes and two-dimensional graphene sheets. These structural features help to provide increased photocatalytic reaction sites, extended photoresponding range, enhanced charge transportation and separation efficiency simultaneously. Briefly, this work not only provides a simple and straightforward strategy for fabricating highly efficient and stable graphene-based nanocomposites, but also proves that these unique structures are excellent platforms for significantly improving their visible-light-driven photoactivities, holding great promise for their applications in the field of purifying polluted water resources.

Recent measurements on cathodoluminescences spectra of natural and isotope-substituted boron nitride nanotubes (BNNTs) surprisingly suggest the existence of pronounced radiative transitions in BN tubes, which are possibly induced by the oxygen substitutional impurities of the samples. [Han, W. Q. et al. Nano Lett. 2008, 8, 491] However, the structural pattern of the O-doped BN tube is unknown, as a result, how does the substitutional impurity in BNNT contribute to the observed radiative transitions is still a puzzle. Using first-principle calculations, we predict a novel, stable O-doped BNNT configuration. Such a structure contains one B(3)O(6) group, which is similar to the structural unit of boron oxide. Our calculations demonstrate that this type of O substitutional impurity can result in some donor-like gap states in the electronic structure and lead to the significant changes on the optical properties of BNNTs. The vibrational properties of the O-doped BNNT and boron oxide are also investigated. Our work elucidates the origins for experimental findings and provides a strong theoretical evidence on the existence of O substitutional impurity-induced radiative transitions in BNNT systems.

Quantum tunneling of magnetization (QTMs), stemming from their importance for understanding materials with unconventional properties, has continued to attract widespread theoretical and experimental attention. However, the observation of QTMs in the most promising candidates of molecular magnets and few iron-based compounds is limited to very low temperature. Herein, we first highlight a simple system, ultrasmall half-metallic V3O4 quantum dots, as a promising candidate for the investigation of QTMs at high temperature. The quantum superparamagnetic state (QSP) as a high temperature signature of QTMs is observed at 16 K, which is beyond absolute zero temperature and much higher than that of conventional iron-based compounds due to the stronger spin-orbital coupling of V3+ ions bringing high anisotropy energy. It is undoubtedly that this ultrasmall quantum dots, V3O4, offers not only a promising candidate for theoretical understanding of QTMs but also a very exciting possibility for computers using mesoscopic magnets.

The extreme fast-charging capability of lithium-ion batteries (LIBs) is very essential for electric vehicles (EVs). However, currently used graphite anode materials cannot satisfy the requirements of fast charging. Herein, we demonstrate that intrinsic lattice defect engineering based on a thermal treatment of graphite in CO2 is an effective method to improve the fast-charging capability of the graphite anode. The activated graphite (AG) exhibits a superior rate capability of 209 mAh g–1 at 10 C (in comparison to 15 mAh g–1 for the pristine graphite), which is attributed to a pseudocapacitive lithium storage behavior. Furthermore, the full cell LiFePO4||AG can achieve SOCs of 82% and 96% within 6 and 15 min, respectively. The intrinsic carbon defect introduced by the CO2 treatment succeeds in improving the kinetics of lithium ion intercalation at the rate-determining step during lithiation, which is identified by the distribution of relaxation times (DRT) and density functional theory (DFT) calculations. Therefore, this study provides a novel strategy for fast-charging LIBs. Moreover, this facile method is also suitable for activating other carbon-based materials.