Publications by authors named "Flemming Besenbacher"

Hydrogen peroxide (HO) is an important chemical in synthetic chemistry with huge demands. Photocatalytic synthesis of HO via oxygen reduction and water oxidation reactions (ORR and WOR) is considered as a promising and desirable solution for on-site applications. However, the efficiency of such a process is low due to the poor solubility of molecular oxygen and the rapid reverse reaction of hydroxyl radicals (OH) with hydrogen atoms (H).

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The role of tumor-resident intracellular microbiota (TRIM) in carcinogenesis has sparked enormous interest. Nevertheless, the impact of TRIM-targeted antibacteria on tumor inhibition and immune regulation in the tumor microenvironment (TME) remains unexplored. Herein, we report long-term relapse-free survival by coordinating antibacteria with antitumor treatment, addressing the aggravated immunosuppression and tumor overgrowth induced by TRIM using breast and prostate cancer models.

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Heterogeneous catalytic ammoxidation provides an eco-friendly route for the cyanide-free synthesis of nitrile compounds, which are important precursors for synthetic chemistry and pharmaceutical applications. However, in general such a process requires high pressures of molecular oxygen at elevated temperatures to accelerate the oxygen reduction and imine dehydrogenation steps, which is highly risky in practical applications. Here, we report an electric field enhanced ammoxidation system using a supported Fe clusters catalyst (Fe/NC), which enables efficient synthesis of nitriles from the corresponding aldehydes under ambient air pressure at room temperature (RT).

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As an efficient molecular engineering approach, on-surface synthesis (OSS) defines a special opportunity to investigate intermolecular coupling at the sub-molecular level and has delivered many appealing polymers. So far, all OSS is based on the lateral covalent bonding of molecular precursors within a single molecular layer; extending OSS from two to three dimensions is yet to be realized. Herein, we address this challenge by cycloaddition between C and an aromatic compound.

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Environmental-friendly halogenation of C-H bonds using abundant, non-toxic halogen salts is in high demand in various chemical industries, yet the efficiency and selectivity of laboratory available protocols are far behind the conventional photolytic halogenation process which uses hazardous halogen sources. Here we report an FeX (X=Br, Cl) coupled semiconductor system for efficient, selective, and continuous photocatalytic halogenation using NaX as halogen source under mild conditions. Herein, FeX catalyzes the reduction of molecular oxygen and the consumption of generated oxygen radicals, thus boosting the generation of halogen radicals and elemental halogen for direct halogenation and indirect halogenation via the formation of FeX .

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Heterogeneous photocatalysis is effective for the selective synthesis of value-added chemicals at lab-scale, yet falls short of requirements for mass production (low cost and user friendliness). Here we report the design and fabrication of a modular tubular flow system embedded with replaceable photocatalyst membranes for scalable photocatalytic C-C, C-N homocoupling and hydrogenation reactions, which can be operated in either circular and continuous flow mode with high performance. The photocatalyst membranes almost fully occupy the volume of the reactor, thus enabling optimal absorption of the incident light.

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Halide perovskite materials, especially lead-based perovskites, have been widely used for optoelectronic and catalytic applications. However, the high toxicity of the lead element is a major concern that directs the research work toward lead-free halide perovskites, which could utilize bismuth as a promising candidate. Until now, the replacement of lead by bismuth in perovskites has been well studied by designing bismuth-based halide perovskite (BHP) nanomaterials with versatile physical-chemical properties, which are emerging in various application fields, especially heterogeneous photocatalysis.

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Photocatalysis provides an eco-friendly route for the hydrogenation of aromatic carbonyls to O-free aromatics, which is an important refining process in the chemical industry that is generally carried out under high pressure of hydrogen at elevated temperatures. However, aromatic carbonyls are often only partially hydrogenated to alcohols, which readily desorbs and are hardly further deoxygenated under ambient conditions. Here, we show that by constructing an oxide surface over the Pd cocatalyst supported on graphitic carbon nitride, an alternative hydrogenation path of aromatic carbonyls becomes available via a step-wise acetalization and hydrogenation, thus allowing efficient and selective production of O-free aromatics.

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As a typical tumor microenvironment-responsive therapy, chemodynamic therapy (CDT), producing hydroxyl radicals ( OH) to eliminate tumor cells, has demonstrated great promise. Nevertheless, there are still major challenges: OH generated from endogenous H O is usually insufficient; the CDT effect is strongly dependent on the pre-reaction with glutathione. Addressing the challenges, Au@MnSe core-shell nanoagent for synergetic chemodynamic-photothermo-photocatalytic therapy combined with tetramodal imaging, including magnetic resonance imaging, computed tomography, photoacoustic, and infrared thermal imaging is reported.

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Employing pure water, the ultimate green source of hydrogen donor to initiate chemical reactions that involve a hydrogen atom transfer (HAT) step is fascinating but challenging due to its large H-O bond dissociation energy (BDE =5.1 eV). Many approaches have been explored to stimulate water for hydrogenative reactions, but the efficiency and productivity still require significant enhancement.

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A widely accepted theory is that life originated from the hydrothermal environment in the primordial ocean. Nevertheless, the low desorption temperature from inorganic substrates and the fragileness of hydrogen-bonded nucleobases do not support the required thermal stability in such an environment. Herein, we report the super-robust complexes of xanthine, one of the precursors for the primitive nucleic acids, with Na.

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Transition-metal carbides have sparked unprecedented enthusiasm as high-performance catalysts in recent years. Still, the catalytic properties of copper carbide remain unexplored. By introducing subsurface carbon to Cu(111), a displacement reaction of a proton in a carboxyl acid group with a single Cu atom is demonstrated at the atomic scale and room temperature.

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As a new member in two-dimensional materials family, transition metal carbides (TMCs) have many excellent properties, such as chemical stability, in-plane anisotropy, high conductivity and flexibility, and remarkable energy conversation efficiency, which predispose them for promising applications as transparent electrode, flexible electronics, broadband photodetectors and battery electrodes. However, up to now, their device applications are in the early stage, especially because their controllable synthesis is still a great challenge. This review systematically summarized the state-of-the-art research in this rapidly developing field with particular focus on structure, property, synthesis and applicability of TMCs.

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Thanks to the low cost, free dendritic hazards, and high volumetric capacity, magnesium (Mg)-ion batteries have attracted increasing attention as alternative energy storage devices to lithium-ion batteries. Despite the successful development of electrode materials, the real-life application potential of Mg-ion full battery systems (MIFBSs) is largely hindered by the lack of suitable electrode couples and hence low diffusion kinetics, which induce low specific capacity, poor rate performance, and low working voltage. Herein, we report an aqueous rechargeable MIFBS by employing copper hexacyanoferrate (CuHCF) as the cathode and 3,4,9,10-perylene-tetracarboxylic acid diimide (PTCDI) as the anode in 1 moL L MgCl electrolyte.

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Chemical reactions that convert sp to sp hybridization have been demonstrated to be a fascinating yet challenging route to functionalize graphene. So far it has not been possible to precisely control the reaction sites nor their lateral order at the atomic/molecular scale. The application prospects have been limited for reactions that require long soaking, heating, electric pulses or probe-tip press.

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In vivo chemical reactions activated by the tumor microenvironment (TME) are particularly promising for antitumor treatments. Herein, employing CuSe-Au Janus nanoparticles (NPs), photothermal conversion-coordinated Fenton-like and photocatalytic reactions are demonstrated in vitro/vivo. The amorphous form of CuSe and the catalytic effect of Au benefit the OH generation, and the photo-induced electron‒hole separation of the Janus NPs produces additional OH.

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Developing graphene-like two-dimensional materials naturally possessing a band gap has sparked enormous interest. Thanks to the inherent wide band gap and high mobility in the 2D plane, covalent organic frameworks containing triazine rings (t-COFs) hold great promise in this regard, whilst the synthesis of single-layer t-COFs remains highly challenging. Herein, we present the fabrication of a well-defined graphene-like t-COF on Au(111).

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Bioelectricity generation, by Shewanella oneidensis (S. oneidensis) MR-1, has become particularly alluring, thanks to its extraordinary prospects for energy production, pollution treatment, and biosynthesis. Attempts to improve its technological output by modification of S.

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An improved understanding of the origin of the electrocatalytic activity is of importance to the rational design of highly efficient electrocatalysts for the hydrogen evolution reaction. Here, an ambipolar single-crystal tungsten diselenide (WSe) semiconductor is employed as a model system where the conductance and carrier of WSe can be individually tuned by external electric fields. The field-tuned electrochemical microcell is fabricated based on the single-crystal WSe and the catalytic activity of the WSe microcell is measured versus the external electric field.

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Transition metal selenides (TMSs) with excellent electrochemical activity and high intrinsic electrical conductivity have attracted considerable attention owing to their potential use in energy storage devices. However, the low energy densities of the reported TMSs, which originate from the small active surface area and poor electrolyte ion mobility, substantially restrict their application potential. In this work, porous ultrathin nickel selenide nanosheet networks (NiSe NNs) on nickel foam are fabricated by using a novel, facile method, that is, selenylation/pickling of the pre-formed manganese-doped α-Ni(OH) .

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Charge transfer at interfaces plays a critical role in the performance of graphene based electronic devices. However, separate control of the charge transfer process in the graphene/SiO system is still challenging. Herein, we investigate the effects of the trapped interfacial icelike water layer on the charge transfer between graphene and the SiO/Si substrate through recording the surface potential changes induced by partial removal of the interfacial icelike water layer upon in situ heating.

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Development of fluorescence enhancement (FE) platforms based on ZnO nanorods (NRs) has sparked considerable interest, thanks to their well-demonstrated potential in chemical and biological detection. Among the multiple factors determining the FE performance, high-order waveguide modes are specifically promising in boosting the sensitivity and realizing selective detection. However, quantitative experimental studies on the influence of the NR diameter, substrate, and surrounding medium, on the waveguide-based FE properties remain lacking.

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Research and development of lithium-ion batteries (LIBs) require powerful characterization approaches. Atomic force microscopy (AFM) is a multifunctional method that allows investigation of the topography, the electrochemical reactions, the ion transport phenomena, and the surface potential of samples at high resolution. Thus, this technique plays an increasingly important role in the study of LIBs.

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The selective oxidation of primary alcohols to aldehydes by O instead of stoichiometric oxidants (for example, Mn , Cr , and Os ) is an important but challenging process. Most heterogeneous catalytic systems (thermal and photocatalysis) require noble metals or harsh reaction conditions. Here we show that the Bi O Br (OH) photocatalyst is very efficient in the selective oxidation of a series of aliphatic (carbon chain from C to C ) and aromatic alcohols to their corresponding aldehydes/ketones under visible-light irradiation in air at room temperature, which would be challenging for conventional thermal and light-driven processes.

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