DJL

Homogeneous blue luminescent MoS₂ quantum dots are fabricated by using a lithium intercalation method from MoS₂ nanoparticles, and the unique blue photoluminescence property is utilized in the Alexa Fluor 430-dsDNA-MoS₂ FRET system, demonstrating the dual function of MoS₂ quantum dots as a donor and an acceptor.

2D MoS₂ nanosheets have been utilized to fabricate 2D MoS₂/CdS p–n nanohybrids through a one-pot solvothermal process. Due to the unique p–n junction heterostructure, large specific surface area, and decreased band gap, MoS₂/CdS nanohybrids manifested a superior H₂-production rate of ∼137 μmol h⁻¹ under visible-light irradiation and an apparent quantum yield of 10.5 % at 450 nm.

Photocatalysis: 2D MoS₂/CdS p–n nanohybrids are constructed by a one-pot solvothermal method. Due to the unique p–n junction heterostructure, large specific surface area, and decreased band gap, MoS₂/CdS p–n nanohybrids provide an excellent H₂-evolution rate of 137 μmol h⁻¹ under visible-light irradiation and an apparent quantum yield of 10.5 % at 450 nm (see figure).

Hierarchical ZnO nanorods composed of interconnected nanoparticles, which were synthesized by controlling precursor concentrations in a solvothermally assisted process, were exploited as photoanodes in dye-sensitized solar cells (DSCs). The as-prepared hierarchical nanorods showed greatly enhanced light scattering compared to ZnO nanoparticles for boosting light harvesting while maintaining sufficient dye-adsorption capability. The charge-transfer characteristics were studied by electrochemical impedance measurements, and reduced electron recombination and longer electron lifetime were observed for the ZnO nanorods. Photovoltaic characterization demonstrated that DSCs utilizing the hierarchical nanorods significantly improved the overall conversion efficiency by 34 % compared to nanoparticle-based DSCs.

Multifunctional photoanode: Hierarchical ZnO nanorods composed of interconnected nanoparticles exhibit effective light harvesting, dye loading, and electron transport. When applied as photoanodes in dye-sensitized solar cells, such ZnO nanorods achieved a 34 % improvement in efficiency compared to ZnO nanoparticles (see figure).

Studies involving transition-metal dichalcogenides (TMDs) have been around for many decades and in recent years, many were focused on using TMDs to synthesize inorganic analogues of carbon nanotubes, fullerene, as well as graphene and its derivatives with the ultimate aim of employing these materials into consumer products. In view of this rising trend, we investigated the cytotoxicity of three common exfoliated TMDs (exTMDs), namely MoS₂, WS₂, and WSe₂, and compared their toxicological effects with graphene oxides and halogenated graphenes to find out whether these inorganic analogues of graphenes and derivatives would show improved biocompatibility. Based on the cell viability assessments using methylthiazolyldiphenyl-tetrazolium bromide (MTT) and water-soluble tetrazolium salt (WST-8) assays on human lung carcinoma epithelial cells (A549) following a 24 h exposure to varying concentrations of the three exTMDs, it was concluded that MoS₂ and WS₂ nanosheets induced very low cytotoxicity to A549 cells, even at high concentrations. On the other hand, WSe₂ exhibited dose-dependent toxicological effects on A549 cells, reducing cell viability to 31.8 % at the maximum concentration of 400 μg mL⁻¹; the higher cytotoxicity displayed by WSe₂ might be linked to the identity of the chalcogen. In comparison with graphene oxides and halogenated graphenes, MoS₂ and WS₂ were much less hazardous, whereas WSe₂ showed similar degree of cytotoxicity. Future in-depth studies should be built upon this first work on the in vitro cytotoxicity of MoS₂ and WS₂ to ensure that they do not pose acute toxicity. Lastly, nanomaterial-induced interference control experiments revealed that exTMDs were capable of reacting with MTT assay viability markers in the absence of cells, but not with WST-8 assay. This suggests that the MTT assay is not suitable for measuring the cytotoxicity of exTMDs because inflated results will be obtained, giving false impressions that the materials are less toxic.

A matter of safety: An assessment on the in vitro cytotoxicity of three different exfoliated transition-metal dichalcogenides (exTMDs), namely, MoS₂, WS₂, and WSe₂, has been conducted to determine if the exposure to this class of nanomaterials may have an adverse impact on our wellbeing should they be commercialized in the future.

A series of highly efficient semiconductor nanocrystal (NC) photocatalysts have been synthesized by growing wurtzite-ZnO tetrahedrons around pre-formed CdS, CdSe, and CdTe quantum dots (QDs). The resulting contact between two small but high-quality crystals creates novel CdX/ZnO heterostructured semiconductor nanocrystals (HSNCs) with extensive type-II nanojunctions that exhibit more efficient photocatalytic decomposition of aqueous organic molecules under UV irradiation. Catalytic testing and characterization indicate that catalytic activity increases as a result of a combination of both the intrinsic chemistry of the chalcogenide anions and the heterojunction structure. Atomic probe tomography (APT) is employed for the first time to probe the spatial characteristics of the nanojunction between cadmium chalcogenide and ZnO crystalline phases, which reveals various degrees of ion exchange between the two crystals to relax large lattice mismatches. In the most extreme case, total encapsulation of CdTe by ZnO as a result of interfacial alloying is observed, with the expected advantage of facilitating hole transport for enhanced exciton separation during catalysis.

That's a (quantum dot) wrap! A series of highly active semiconductor photocatalysts have been synthesized by growing wurtzite-ZnO tetrahedrons around pre-formed CdS, CdSe, and CdTe quantum dots. The resulting heterostructured CdX/ZnO nanocrystals with extensive type-II nanojunctions exhibit rapid photocatalytic decomposition of organic molecules in aqueous media.

The chemical production of graphene as well as its controlled wet chemical modification is a challenge for synthetic chemists. Furthermore, the characterization of reaction products requires sophisticated analytical methods. In this Review we first describe the structure of graphene and graphene oxide and then outline the most important synthetic methods that are used for the production of these carbon-based nanomaterials. We summarize the state-of-the-art for their chemical functionalization by noncovalent and covalent approaches. We put special emphasis on the differentiation of the terms graphite, graphene, graphite oxide, and graphene oxide. An improved fundamental knowledge of the structure and the chemical properties of graphene and graphene oxide is an important prerequisite for the development of practical applications.

The well-controlled synthesis of new graphene and graphene oxide derivatives as well as determination of the atomic structure are key challenges for synthetic chemists. Structure–property relationships must be exploited to use the full potential of graphene derivatives in upcoming applications. This Review focuses on concepts in the chemistry of graphene and graphene oxide with the aim of encouraging chemists to enhance the field of research.

The creation of organic dyes with excellent high power conversion efficiency (PCE) is important for the further improvement of dye-sensitized solar cells. We wish to describe the rapid synthesis of a 112-membered donor-π-acceptor dye library by a one-pot procedure, evaluation of PCEs, and elucidation of structure–property relationships. No obvious correlations between ε, and the η were observed, whereas the HOMO and LUMO levels of the dyes were critical for η. The dyes with a more positive E_HOMO, and with an E_LUMO<−0.80 V, exerted higher PCEs. The proper driving forces were crucial for a high J_sc, and it was the most important parameter for a high η. The above criteria of E_HOMO and E_LUMO should be useful for creating high PCE dyes; nevertheless, that was not sufficient for identifying the best combination of donor, π, and acceptor blocks. Combinatorial synthesis and evaluation was important for identifying the best dye.

Combinatorial chemistry: A 112-membered donor–π-acceptor dye library was rapidly constructed by a one-pot, three-component coupling procedure (see scheme, SM=Suzuki–Miyaura). The evaluation of absorption spectroscopic and electrochemical measurements of all synthesized dyes, and cell performances of the selected 54 dyes were performed. The dyes with a more positive E_HOMO, and with an E_LUMO<−0.80 V, exerted higher power conversion efficiencies.

In “old man flower”, a Japanese story, the kind old man sprinkled ashes and made dead trees blossom all over. Incorporation of a methoxy group to an amide group opens the door to new reactivities and allows beautiful chemical transformations to blossom in organic synthesis. For more details, see the Full paper by T. Sato, N. Chida et al. on page 8210 ff. We thank Miwako Yoritate and Takamasa Wada for their assistance with artwork.

Thin-film solar cells are made by vapor deposition of Earth-abundant materials: tin, zinc, oxygen and sulfur. These solar cells had previously achieved an efficiency of about 2%, less than 1/10 of their theoretical potential. Loss mechanisms are systematically investigated and mitigated in solar cells based on p-type tin monosulfide, SnS, absorber layers combined with n-type zinc oxysulfide, Zn(O,S) layers that selectively transmit electrons, but block holes. Recombination at grain boundaries is reduced by annealing the SnS films in H₂S to form larger grains with fewer grain boundaries. Recombination near the p-SnS/n-Zn(O,S) junction is reduced by inserting a few monolayers of SnO₂ between these layers. Recombination at the junction is also reduced by adjusting the conduction band offset by tuning the composition of the Zn(O,S), and by reducing its free electron concentration with nitrogen doping. The resulting cells have an efficiency over 4.4%, which is more than twice as large as the highest efficiency obtained previously by solar cells using SnS absorber layers.

Solar cells are made by vapor deposition of Earth-abundant materials, i.e., p-type tin monosulfide (SnS) absorber layers with surfaces passivated by tin dioxide (SnO₂) covered by n-type nitrogen-doped zinc oxysulfide (Zn(O,S):N) buffer layers. The cells show energy conversion efficiencies over 4.4%, which is more than twice as large as the highest efficiency obtained previously by solar cells using SnS absorber layers.

A new epoxy-based ink is reported, which enables 3D printing of lightweight cellular composites with controlled alignment of multiscale, high-aspectratio fiber reinforcement to create hierarchical structures inspired by balsa wood. Young's modulus values up to 10 times higher than existing commercially available 3D-printed polymers are attainable, while comparable strength values are maintained.