As several photovoltaic materials experimentally approach the Shockley–Queisser limit, there has been a growing interest in unconventional materials and approaches with the potential to cross this ...efficiency barrier. One such candidate is dark state protection induced by the dipole–dipole interaction between molecular excited states. This phenomenon has been shown to significantly reduce carrier recombination rate and enhance photon‐to‐current conversion, in elementary models consisting of few interacting chromophore centers. Atomically thin 2D transition metal di‐chalcogenides (TMDCs) have shown great potential for use as ultra‐thin photovoltaic materials in solar cells due to their favorable photon absorption and electronic transport properties. TMDC alloys exhibit tunable direct bandgaps and significant dipole moments. In this work, the dark state protection mechanism has been introduced to a TMDC based photovoltaic system with pure tungsten diselenide (WSe2) as the acceptor material and the TMDC alloy tungsten sulfo‐selenide (WSeS) as the donor material. Our numerical model demonstrates the first application of the dark state protection mechanism to a photovoltaic material with a photon current enhancement of up to 35% and an ideal photon‐to‐current efficiency exceeding the Shockley–Queisser limit.
A transition metal di‐chalcogenide (TMDC) based donor–acceptor photovoltaic model with dark state protection is demonstrated, where the dark state protection mechanism reduces carrier recombination and enhances photon‐to‐electron conversion due to dipole–dipole interactions. This model has a significantly higher output current compared to standard heterojunction solar cells, with a potential to exhibit efficiencies above conventional limits.
Monolayer transition metal dichalcogenides (TMDs) have emerged as widely accepted 2D gain materials in the field of light sources owing to their direct bandgap and high photoluminescence quantum ...yield. However, the monolayer medium suffers from weak emission because only a single layer of molecules can absorb the pump energy. Moreover, the material degradation when transferring these fragile materials hinders their cooperation with the optical cavity further. In this study, for the first time, a high‐quality monolithic structure is developed by directly growing single‐domain tungsten diselenide (WSe2) bilayers on single silica microsphere (MS) cavities. Such a completely wrapped structure guides the indirect‐to‐direct bandgap transition of WSe2 bilayers, leading to a significantly improved photoluminescence intensity by about 60‐fold. Moreover, the high‐quality monolithic structure enhances the confinement factor of the cavity by more than 20‐fold. Based on the above advantages, a bilayer WSe2/MS microlaser is realized with an ultralow threshold of 0.72 W cm−2, nearly an order of magnitude lower than the existing records. The results demonstrate the possibility of using multilayer TMD materials as 2D gain media and provide insights into a new ultracompact monolithic platform of TMD material/cavity for lasing devices.
A transition metal dichalcogenide (TMD)/cavity monolithic cavity is achieved by directly growing single‐domain tungsten diselenide (WSe2) bilayers on single silica microsphere (MS) surfaces. The thermal strain induces bilayer bandgap from indirect to direct, and the cavity confinement factor is also improved, which directly realizes room‐temperature whispering‐gallery‐mode lasing, with a threshold nearly an order of magnitude lower than the existing records.
Tungsten diselenide (WSe2) is the material with the lowest thermal conductivity in the world. Most physical methods are used for the synthesis of tungsten diselenide. Here, a simple colloidal method ...is reported for the synthesis of WSe2 nanosheets. The composition, valence, size, morphology and properties of the samples were characterized and measured. Results showed that the obtained WSe2 nanosheets with a thickness of 0.7 nm had strong blue fluorescence. Significantly, the synthesized WSe2 nanosheets exhibited excellent catalytic activity for the aerobic coupling of amines to imines, with 100% yield under visible light irradiation and air atmosphere. As a photocatalyst, it exhibited excellent recyclability, and maintained a high yield after 5 cycles. It was found that this reaction could also happen in the presence of natural light by slightly extending the reaction time. Moreover, H2O was used as a solvent in the catalytic process, avoiding expensive and toxic organic solvents. This work provides an efficient, economical and sustainable process for the synthesis of imines and shows the great potential of WSe2 nanosheets as photocatalysts for organic synthesis.
A novel hybrid composite material, PMo10V2@MIL-101 was prepared by the encapsulation of the tetra-butylammonium (TBA) salt of the vanadium-substituted phosphomolybdate PMo10V2O405– (PMo10V2) into the ...porous metal-organic framework (MOF) MIL-101(Cr). The materials characterization by powder X-ray diffraction, Fourier transform infrared spectra and scanning electron microscopy confirmed the preparation of the composite material without disruption of the MOF porous structure. Pyrolytic graphite electrodes modified with the original components (MIL-101(Cr), PMo10V2), and the composite material PMo10V2@MIL-101 were prepared and their electrochemical responses were studied by cyclic voltammetry. Surface confined redox processes were observed for all the immobilized materials. MIL-101(Cr) showed one-electron reduction process due to chromium centers (CrIII→CrII), while PMo10V2 presented five reduction processes: the peak at more positive potentials is attributed to two superimposed 1-electron vanadium reduction processes (VV→VIV) and the other four peaks to Mo-centred two-electron reduction processes (MoVI→MoV). The electrochemical behavior of the composite material PMo10V2@MIL-101 showed both MIL-101(Cr) and PMo10V2 redox features, although with the splitting of the two vanadium processes and the shift of the Mo- and Cr- centered processes to more negative potentials. Finally, PMo10V2@MIL-101 modified electrode showed outstanding enhanced vanadium-based electrocatalytic properties towards ascorbic acid oxidation, in comparison with the free PMo10V2, as a result of its immobilization into the porous structure of the MOF. Furthermore, PMo10V2@MIL-101 modified electrode showed successful simultaneous detection of ascorbic acid and dopamine.
Antimicrobial action of nanomaterials is typically assigned to the nanomaterial composition, size and/or shape, whereas influence of complex corona stabilizing the nanoparticle surface is often ...neglected. We demonstrate sequential surface functionalization of tyrosine-reduced gold nanoparticles (AuNPs(Tyr)) with polyoxometalates (POMs) and lysine to explore controlled chemical functionality-driven antimicrobial activity. Our investigations reveal that highly biocompatible gold nanoparticles can be tuned to be a strong antibacterial agent by fine-tuning their surface properties in a controllable manner. The observation from the antimicrobial studies on a gram negative bacterium Escherichia coli were further validated by investigating the anticancer properties of these step-wise surface-controlled materials against A549 human lung carcinoma cells, which showed a similar toxicity pattern. These studies highlight that the nanomaterial toxicity and biological applicability are strongly governed by their surface corona.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Hen‐egg‐white lysozyme (HEWL) is specifically cleaved at the Trp28–Val29 and Asn44–Arg45 peptide bonds in the presence of a Keggin‐type Ce(α‐PW11O39)210− polyoxometalate (POM; 1) at pH 7.4 and 37 °C. ...The reactivity of 1 towards a range of dipeptides was also examined and the calculated reaction rates were comparable to those observed for the hydrolysis of HEWL. Experiments with α‐lactalbumin (α‐LA), a protein that is structurally highly homologous to HEWL but has a different surface potential, showed no evidence of hydrolysis, which indicates the importance of electrostatic interactions between 1 and the protein surface for the hydrolytic reaction to occur. A combination of spectroscopic techniques was used to reveal the molecular interactions between HEWL and 1 that lead to hydrolysis. NMR spectroscopy titration experiments showed that on protein addition the intensity of the 31P NMR signal of 1 gradually decreased due to the formation of a large protein/polyoxometalate complex and completely disappeared when the HEWL/1 ratio reached 1:2. Circular dichroism (CD) measurements of HEWL indicate that addition of 1 results in a clear decrease in the signal at λ=208 nm, which is attributed to changes in the α‐helical content of the protein. 15N–1H heteronuclear single quantum coherence (HSQC) NMR measurements of HEWL in the presence of 1 reveal that the interaction is mainly observed for residues that are located in close proximity to the first site in the α‐helical part of the structure (Trp28–Val29). The less pronounced NMR spectroscopic shifts around the second cleavage site (Asn44–Arg45), which is found in the β‐strand region of the protein, might be caused by weaker metal‐directed binding, compared with strong POM‐directed binding at the first site.
It's a snip! Hen‐egg‐white lysozyme (HEWL) is specifically hydrolyzed at the Trp28–Val29 and Asn44–Arg45 peptide bonds in the presence of a Keggin‐type Ce(α‐PW11O39)210− polyoxometalate (1) at pH 7.4 and 37 °C (see figure). The reactivity of 1 towards a range of dipeptides was also examined and the calculated reaction rates were comparable to those observed for the hydrolysis of HEWL.
•Novel WSe2/rGO firstly synthesized for energy storage applications.•WSe2/rGO shows large surface area and superior conductivity.•WSe2/rGO composite exhibits high specific capacitance and outstanding ...cycling stability.
Nanosheet-like tungsten diselenide (WSe2)/reduced graphene oxide (rGO) hybrid has been developed for the first time by facile one-step hydrothermal route for supercapacitor applications. Electrochemical measurements show that the WSe2/rGO-based supercapacitor electrode exhibits a maximum specific capacitance of 389 F g−1 at 1 A g−1 with capacitance retention of 98.7% after 3000 charge/discharge cycles at a high current density of 7 A g−1, and delivered a energy density of 34.5 W h kg−1 at 400 W kg−1 and 22.4 W h kg−1 at a high power density of 4000 W kg−1.
2D materials with atomic thickness display strong gate controllability and emerge as promising materials to build area‐efficient electronic circuits. However, achieving the effective and ...nondestructive modulation of carrier density/type in 2D materials is still challenging because the introduction of dopants will greatly degrade the carrier transport via Coulomb scattering. Here, a strategy to control the polarity of tungsten diselenide (WSe2) field‐effect transistors (FETs) via introducing hexagonal boron nitride (h‐BN) as the interfacial dielectric layer is devised. By modulating the h‐BN thickness, the carrier type of WSe2 FETs has been switched from hole to electron. The ultrathin body of WSe2, combined with the effective polarity control, together contribute to the versatile single‐transistor logic gates, including NOR, AND, and XNOR gates, and the operation of only two transistors as a half adder in logic circuits. Compared with the use of 12 transistors based on static Si CMOS technology, the transistor number of the half adder is reduced by 83.3%. The unique carrier modulation approach has general applicability toward 2D logic gates and circuits for the improvement of area efficiency in logic computation.
A carrier modulation method for WSe2 transistors has been demonstrated by tuning the thickness of the interfacial hexagonal boron nitride dielectric layer. The carrier type of the WSe2 channel can be tuned from holes to electrons, contributing to the construction of versatile two‐surface‐channel WSe2 transistors and high area‐efficiency logic gates and circuits.
Two-dimensional (2D) materials such as graphene, molybdenum disulfide (MoS2), tungsten diselenide (WSe2), and black phosphorous are being developed for sensing applications with excellent selectivity ...and high sensitivity. In such applications, 2D materials extensively interact with various analytes including biological molecules. Understanding the interfacial molecular interactions of 2D materials with various targets becomes increasingly important for the progression of better-performing 2D-material based sensors. In this research, molecular interactions between several de novo designed alpha-helical peptides and monolayer MoS2 have been studied. Molecular dynamics simulations were used to validate experimental data. The results suggest that, in contrast to peptide–graphene interactions, peptide aromatic residues do not interact strongly with the MoS2 surface. It is also found that charged amino acids are important for ensuring a standing-up pose for peptides interacting with MoS2. By performing site-specific mutations on the peptide, we could mediate the peptide–MoS2 interactions to control the peptide orientation on MoS2.
•Low temperature electrical transport properties in thermally evaporated WSe2 thin films.•Temperature dependent carrier transport by Mott, Seto and thermal conduction mechanism.•Light-on/off current ...cycles show stable and reversible properties.
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This work reports the electrical-transport and temperature-dependent photoconductivity in tungsten diselenide (WSe2) thin films. Temperature-dependent electrical conductivity has been demonstrated using different models. At lower temperatures (< 190 K), carriers become localized to small regions in the film due to Mott’s hopping mechanism. The middle-temperature region (190–273 K) follows Seto’s parameters and obtained low barrier height (0.0873 eV) may be responsible for the improved carrier mobility. At higher temperature (> 273 K) region, thermally activated conduction is dominated with two activation energies of ~138 meV and 98 meV. The peaks obtained in photoluminescent analysis attributes to the presence of mid-bandgap states or defect states which play an important role in the photoconductivity of WSe2. The transient photoconductivity measurements show consistent temperature-dependent behaviour. The effect of light intensity and wavelength variation on the photoconductivity of WSe2 thin films is also discussed. The photo-current is 1.19 * 10−5 A at 125 K, while at 350 K was observed to be 3.12 * 10−4 A. The light-on/off current cycles show that the current can recover to its initial state after various cycles, which points to the WSe2 thin-film device's stable and reversible properties that can be used in optoelectronic applications.
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