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Herein, we present the discovery and development of the first photoredox-catalyzed alkoxy diazomethylation of alkenes with hypervalent iodine reagents and alcohols. This multicomponent process represents a new disconnection approach to diazo compounds and is featured by a broad scope, mild reaction conditions, and excellent selectivity. Key to the process was the generation of diazomethyl radicals, which engaged alkenes and alcohols in an inter- and intramolecular fashion by a photoredox-catalyzed oxidative radical–polar crossover leading to unexplored ß-alkoxydiazo compounds. The synthetic utility of such diazo compounds was demonstrated with a series of transformations involving C–H, N–H, and O–H insertions as well as in the construction of complex sp3-rich heterocycles.

Crystal phase is a key factor determining the properties, and hence functions, of two-dimensional transition-metal dichalcogenides (TMDs)1,2. The TMD materials, explored for diverse applications3–8, commonly serve as templates for constructing nanomaterials3,9and supported metal catalysts4,6–8. However, how the TMD crystal phase affects the growth of the secondary material is poorly understood, although relevant, particularly for catalyst development. In the case of Pt nanoparticles on two-dimensional MoS2nanosheets used as electrocatalysts for the hydrogen evolution reaction7, only about two thirds of Pt nanoparticles were epitaxially grown on the MoS2template composed of the metallic/semimetallic 1T/1T′ phase but with thermodynamically stable and poorly conducting 2H phase mixed in. Here we report the production of MoS2nanosheets with high phase purity and show that the 2H-phase templates facilitate the epitaxial growth of Pt nanoparticles, whereas the 1T′ phase supports single-atomically dispersed Pt (s-Pt) atoms with Pt loading up to 10 wt%. We find that the Pt atoms in this s-Pt/1T′-MoS2system occupy three distinct sites, with density functional theory calculations indicating for Pt atoms located atop of Mo atoms a hydrogen adsorption free energy of close to zero. This probably contributes to efficient electrocatalytic H2evolution in acidic media, where we measure for s-Pt/1T′-MoS2a mass activity of 85 ± 23 A mgPt−1at the overpotential of −50 mV and a mass-normalized exchange current density of 127 A mgPt−1and we see stable performance in an H-type cell and prototype proton exchange membrane electrolyser operated at room temperature. Although phase stability limitations prevent operation at high temperatures, we anticipate that 1T′-TMDs will also be effective supports for other catalysts targeting other important reactions.

Phase transition with band gap modulation of materials has gained intensive research attention due to its various applications, including memories, neuromorphic computing, and transistors. As a powerful strategy to tune the crystal phase of transition-metal dichalcogenides (TMDs), the phase transition of TMDs provides opportunities to prepare new phases of TMDs for exploring their phase-dependent property, function, and application. However, the previously reported phase transition of TMDs is mainly irreversible. Here, we report a reversible phase transition in the semimetallic 1T′-WS2driven by proton intercalation and deintercalation, resulting in a newly discovered semiconducting WS2with a novel unconventional phase, denoted as the 1T′dphase. Impressively, an on/off ratio of >106has been achieved during the phase transition of WS2from the semimetallic 1T′ phase to the semiconducting 1T′dphase. Our work not only provides a unique insight into the phase transition of TMDs via proton intercalation but also opens up possibilities to tune their physicochemical properties for various applications.

On-chip electrocatalytic microdevices (OCEMs) are an emerging electrochemical platform specialized for investigating nanocatalysts at the microscopic level. The OCEM platform allows high-precision electrochemical measurements at the individual nanomaterial level and, more importantly, offers unique perspectives inaccessible with conventional electrochemical methods. This protocol describes the critical concepts, experimental standardization, operational principles and data analysis of OCEMs. Specifically, standard protocols for the measurement of the electrocatalytic hydrogen evolution reaction of individual 2D nanosheets are introduced with data validation, interpretation and benchmarking. A series of factors (e.g., the exposed area of material, the choice of passivation layer and current leakage) that could have effects on the accuracy and reliability of measurement are discussed. In addition, as an example of the high adaptability of OCEMs, the protocol for in situ electrical transport measurement is detailed. We believe that this protocol will promote the general adoption of the OCEM platform and inspire further development in the near future. This protocol requires essential knowledge in chemical synthesis, device fabrication and electrochemistry.

Electrochemical molecular intercalation of layered semiconducting crystals with organic cations followed by ultrasonic exfoliation has proven to be an effective approach to producing a rich family of organic/inorganic hybrid superlattices and high-quality, solution-processable 2D semiconductors. A traditional method for exfoliating 2D crystals relies on the intercalation of inorganic alkali metal cations. The organic cations (e.g., alkyl chain–substituted quaternary ammonium cations) are much larger than their inorganic counterparts, and the bulky molecular structure endows distinct intercalation and exfoliation chemistry, as well as molecular tunability. By using this protocol, many layered 2D crystals (including graphene, black phosphorus and versatile metal chalcogenides) can be electrochemically intercalated with organic quaternary alkylammonium cations. Subsequent solution-phase exfoliation of the intercalated compounds is realized by regular bath sonication for a short period (5–30 min) to produce free-standing, thin 2D nanosheets. It is also possible to graft additional ligands on the nanosheet surface. The thickness of the exfoliated nanosheets can be measured by using atomic force microscopy and Raman spectroscopy. Modifying the chemical structure and geometrical configuration of alkylammonium cations results in different exfoliation behavior and a family of versatile organic/inorganic hybrid superlattices with tunable physical/chemical properties. The whole protocol takes ~6 h for the successful production of stable, ultrathin 2D nanosheet dispersion in solution and another 11 h for depositing thin films and transferring them onto an arbitrary surface. This protocol does not require expertise beyond basic electrochemistry knowledge and conventional colloidal nanocrystal synthesis and processing.

Purpose: The study aims to examine the effect of inclusions and inherent microstructure on fatigue behavior of 34Cr2Ni2Mo steel. Design/methodology/approach: Fatigue behavior of 34Cr2Ni2Mo steel was investigated for up to 1E10 cycles. Findings: Results showed that both inclusion and inherent microstructure have an influence on the crack initiation mechanism. Fatigue cracks mostly initiated from inclusions, whereas substrate-induced crack initiations were also observed. Fatigue life of inclusion-induced failures is mostly determined by the location of inclusions rather than the loading stress. The inherent microstructure seems to tolerate inclusions at a lower stress level in very high-cycle regime owing to the absence of internal inclusion-induced failure. For the substrate-induced crack initiations, high-density dislocations are found to be accumulated around the carbide particle-matrix interface, which may be the cause of crack initiation in the inherent structure due to strain localization. Originality/value: The effect of inclusions and inherent microstructure on fatigue behavior of 34Cr2Ni2Mo steel up to 1E10 cycles.

Purpose: In this paper, the combined rotor system of turbo-generator is taken as the research object, and the variation law of interface contact stress, contact stiffness and torsional natural frequency of the combined rotor system during operation is deeply analyzed. Method: A three-dimensional cross-scale dynamic model of the rotor is proposed based on the detailed research of the contact stress distribution characteristics and the contact stiffness between the combined rotor interfaces. By comparing the 3D simulation results with the experimental results, the essential reason why the natural frequency of the combined rotor varies with working conditions is explained. On this basis, by studying the influence of key structural parameters on the torsional vibration natural frequency of the combined rotor, a design method of torsional vibration natural frequency of the combined rotor based on the adjustment of structural parameters was proposed. Results and conclusions: This paper provides an important reference and theoretical basis for the dynamic characteristic design of turbo generator combined rotor system. The simulation analysis accurately revealed the phenomenon of static and dynamic frequency drift in the turbo generator rotor system. Through the comparison with the measured results of the generator rotor, the simulation results of the three-dimensional cross-scale model are closer to the reality than other models, with higher accuracy. Through cross-scale dynamic simulation, it can be found that the interface contact stress and torsion natural frequency in the combined rotor have obvious coupling characteristics. Through the analysis of the key factors influencing the dynamic characteristics of the turbo generator rotor system, improving the interface stiffness of the rotor structure can effectively improve the torsional natural frequency of the system. The design of the long slot wedge, the high elastic modulus slot wedge, the improvement of the fit between the slot wedge and the rotating shaft, and the enhancement of the interface contact stress all effectively increase the stiffness of the system, thus increasing the natural frequency of the turbo generator rotor system.

Cost-effective, rapid, and accurate virus detection technologies play key roles in reducing viral transmission. Prompt and accurate virus detection enables timely treatment and effective quarantine of virus carrier, and therefore effectively reduces the possibility of large-scale spread. However, conventional virus detection techniques often suffer from slow response, high cost or sophisticated procedures. Recently, two-dimensional (2D) materials have been used as promising sensing platforms for the high-performance detection of a variety of chemical and biological substances. The unique properties of 2D materials, such as large specific area, active surface interaction with biomolecules and facile surface functionalization, provide advantages in developing novel virus detection technologies with fast response and high sensitivity. Furthermore, 2D materials possess versatile and tunable electronic, electrochemical and optical properties, making them ideal platforms to demonstrate conceptual sensing techniques and explore complex sensing mechanisms in next-generation biosensors. In this review, we first briefly summarize the virus detection techniques with an emphasis on the current efforts in fighting again COVID-19. Then, we introduce the preparation methods and properties of 2D materials utilized in biosensors, including graphene, transition metal dichalcogenides (TMDs) and other 2D materials. Furthermore, we discuss the working principles of various virus detection technologies based on emerging 2D materials, such as field-effect transistor-based virus detection, electrochemical virus detection, optical virus detection and other virus detection techniques. Then, we elaborate on the essential works in 2D material-based high-performance virus detection. Finally, our perspective on the challenges and future research direction in this field is discussed.

The rhodium(I)-catalyzed reaction of N-8-aminoquinolinyl aromatic amides with maleimides results in C–H alkylation at the ortho position of the amide. The reaction path and formation of the alkylation product with density functional theory (DFT) calculations were done. The detailed computational study showed that the reaction proceeds in the following steps: (I) deprotonation of the NH amide proton, (II) oxidative addition of the ortho C–H bond, (III) migratory insertion of the maleimide, (IV) reductive elimination with the C–C bond formation, and (V) protonation. The energetic span model showed that the turnover frequency (TOF)-determining transition state (TDTS) is the oxidative addition, while the TOF-determining intermediate (TDI) is the formation of an Rh(I)-complex after N–H deprotonation. It was also found that the change in the oxidation number of the Rh catalyst is a key determinant of the reaction path.

The palladium-catalyzed intramolecular C-H oxidative cyclization of 2-methylbenzamides that contain an N,S-chelation system in air, leading to the production of phthalimides is reported. A C-H bond of a methyl group at the ortho-position is selectively activated. The air serves as an oxidant.The palladium-catalyzed intramolecular C-H oxidative cyclization of 2-methylbenzamides that contain an N,S-chelation system in air, leading to the production of phthalimides is reported. A methyl C-H bond at the ortho-position is selectively activated. The air serves as an oxidant.

Metastable 1T′-phase transition metal dichalcogenides (1T′-TMDs) with semi-metallic natures have attracted increasing interest owing to their uniquely distorted structures and fascinating phase-dependent physicochemical properties. However, the synthesis of high-quality metastable 1T′-TMD crystals, especially for the group VIB TMDs, remains a challenge. Here, we report a general synthetic method for the large-scale preparation of metastable 1T′-phase group VIB TMDs, including WS2, WSe2, MoS2, MoSe2, WS2xSe2(1−x)and MoS2xSe2(1−x). We solve the crystal structures of 1T′-WS2, -WSe2, -MoS2and -MoSe2with single-crystal X-ray diffraction. The as-prepared 1T′-WS2exhibits thickness-dependent intrinsic superconductivity, showing critical transition temperatures of 8.6 K for the thickness of 90.1 nm and 5.7 K for the single layer, which we attribute to the high intrinsic carrier concentration and the semi-metallic nature of 1T′-WS2. This synthesis method will allow a more systematic investigation of the intrinsic properties of metastable TMDs.

The rapid diffusion kinetics and smallest ion radius make protons the ideal cations toward the ultimate energy storage technology combining the ultrafast charging capabilities of supercapacitors and the high energy densities of batteries. Despite the concept existing for centuries, the lack of satisfactory electrode materials hinders its practical development. Recently, the rapid advancement of the emerging two-dimensional (2D) materials, characterized by their ultrathin morphology, interlayer van der Waals gaps, and distinctive electrochemical properties, injects promises into future proton-based energy storage systems. In this perspective, we comprehensively summarize the current advances in proton-based energy storage based on 2D materials. We begin by providing an overview of proton-based energy storage systems, including proton batteries, pseudocapacitors and electrical double layer capacitors. We then elucidate the fundamental knowledge about proton transport characteristics, including in electrolytes, at electrolyte/electrode interfaces, and within electrode materials, particularly in 2D material systems. We comprehensively summarize specific cases of 2D materials as proton electrodes, detailing their design concepts, proton transport mechanism and electrochemical performance. Finally, we provide insights into the prospects of proton-based energy storage systems, emphasizing the importance of rational design of 2D electrode materials and matching electrolyte systems.

Self-assembly processes commonly occur in various biological contexts to form functional biological structures. However, the self-assembly of nanofibers within cells by heterologous molecules showing a biological function is rare. In this work, we reported the intracellular formation of fluorescent nanofibers by a natural small molecule, lycobetaine (LBT), which facilitated the direct physical connection between mitochondria and synchronized their membrane potential oscillations. The luminescent properties of LBT enabled the real-time observation of nanofiber formation, while the semiconductive nature of the LBT nanofiber facilitated electrical signal transduction among the connected mitochondria. This study introduces an approach to modulate mitochondrial connectivity within cells using “nano-cables” which facilitate studies on synchronized mitochondrial operations and the underlying mechanisms of drug action.

Recently, crystal-phase engineering has been emerging as a promising strategy to tune the physicochemical properties of noble metal catalysts and further improve their catalytic performance. However, the synthesis of noble metal catalysts with an unconventional crystal phase as well as desired composition and morphology still remains a great challenge. Herein, a series of PdM (M = Zn, Cd, ZnCd) nanosheets (NSs) with thickness less than 5 nm have been synthesized viaa facile one-pot wet-chemical method. In particular, different from the conventional face-centered cubic (fcc) phase, PdM NSs possess an unconventional face-centered tetragonal (fct) phase. As a proof-of-concept application, the fctPdZn NSs exhibit significantly enhanced mass activity and stability in ethanol oxidation reaction, compared to the pure Pd NSs and commercial Pd black catalyst.

Two-dimensional (2D) semiconductors have demonstrated great potential in modern nanotechnologies across a variety of research fields, including (opto-)electronics, spintronics, and electro-/photocatalysis. Interestingly, the vast majority of 2D semiconductors, such as the widely explored transition-metal dichalcogenides, are n-type or ambipolar. The search for p-type 2D semiconductors in the past decade has succeeded in identifying only a few promising candidate materials. In this Perspective, we discuss various strategies to obtain p-type conduction in normally n-type or ambipolar 2D semiconductors and, more importantly, the direct synthesis of p-type 2D semiconductors such as black phosphorus, 2D tellurium, and, most recently, α-MnS.

The electrochemical molecular intercalation of two-dimensional layered materials (2DLMs) produces stable and highly tunable superlattices between monolayer 2DLMs and self-assembled molecular layers. This process allows unprecedented flexibility in integrating highly distinct materials with atomic/molecular precision to produce a new generation of organic/inorganic superlattices with tunable chemical, electronic, and optical properties. To better understand the intercalation process, we developed an on-chip platform based on MoS2model devices and used optical, electrochemical, and in situ electronic characterizations to resolve the intermediate stages during the intercalation process and monitor the evolution of the molecular superlattices. With sufficient charge injection, the organic cetyltrimethylammonium bromide (CTAB) intercalation induces the phase transition of MoS2from semiconducting 2H phase to semimetallic 1T phase, resulting in a dramatic increase of electrical conductivity. Therefore, in situ monitoring the evolution of the device conductance reveals the electrochemical intercalation dynamics with an abrupt conductivity change, signifying the onset of the molecule intercalation. In contrast, the intercalation of tetraheptylammonium bromide (THAB), a branched molecule in a larger size, resulting in a much smaller number of charges injected to avoid the 2H to 1T phase transition. Our study demonstrates a powerful platform for in situ monitoring the molecular intercalation of many 2DLMs (MoS2, WSe2, ReS2, PdSe2, TiS2, and graphene) and systematically probing electronic, optical, and optoelectronic properties at the single-nanosheet level.

The semiconductor–electrolyte interface dominates the behaviours of semiconductor electrocatalysis, which has been modelled as a Schottky-analogue junction according to classical electron transfer theories. However, this model cannot be used to explain the extremely high carrier accumulations in ultrathin semiconductor catalysis observed in our work. Inspired by the recently developed ion-controlled electronics, we revisit the semiconductor–electrolyte interface and unravel a universal self-gating phenomenon through microcell-based in situ electronic/electrochemical measurements to clarify the electronic-conduction modulation of semiconductors during the electrocatalytic reaction. We then demonstrate that the type of semiconductor catalyst strongly correlates with their electrocatalysis; that is, n-type semiconductor catalysts favour cathodic reactions such as the hydrogen evolution reaction, p-type ones prefer anodic reactions such as the oxygen evolution reaction and bipolar ones tend to perform both anodic and cathodic reactions. Our study provides new insight into the electronic origin of the semiconductor–electrolyte interface during electrocatalysis, paving the way for designing high-performance semiconductor catalysts.

The alkylation of C–H bonds with N-vinylphthalimide by a rhodium-catalyzed reaction of aromatic amides containing an 8-aminoquinoline moiety as the directing group is reported. N-Vinylphthalimide functions as a 2-aminoethylating reagent. The resulting alkylated products can be converted into 3,4-dihydroisoquinolin-1(2H)-one derivatives in a one-pot transformation. Deuterium-labeling experiments suggest that the reaction proceeds through a carbene mechanism.

Phase control plays an important role in the precise synthesis of inorganic materials, as the phase structure has a profound influence on properties such as conductivity and chemical stability. Phase-controlled preparation has been challenging for the metallic-phase group-VI transition metal dichalcogenides (the transition metals are Mo and W, and the chalcogens are S, Se and Te), which show better performance in electrocatalysis than their semiconducting counterparts. Here, we report the large-scale preparation of micrometre-sized metallic-phase 1T′-MoX2(X = S, Se)-layered bulk crystals in high purity. We reveal that 1T′-MoS2crystals feature a distorted octahedral coordination structure and are convertible to 2H-MoS2following thermal annealing or laser irradiation. Electrochemical measurements show that the basal plane of 1T′-MoS2is much more active than that of 2H-MoS2for the electrocatalytic hydrogen evolution reaction in an acidic medium.

One-dimensional (1D) nanoscrolls derived from two-dimensional (2D) nanosheets own unusual physical and chemical properties that arise from the spiraled 1D morphology and the atomic thin 2D building blocks. Unfortunately, preparation of large-sized nanoscrolls of transition-metal dichalcogenides (TMDCs) remains a big challenge, which greatly restricts the fabrication of single-scroll devices for their fundamental studies and further applications. In this work, we report a universal and facile method, by making use of the evaporation process of volatile organic solvent, to prepare TMDC (e.g., MoS2and WS2) nanoscrolls with lengths of several tens to one hundred micrometers from their 2D precursors presynthesized by chemical vapor deposition on Si/SiO2. Both atomic force microscopy and electron microscopy characterizations confirmed the spirally rolledup structure in the resulting nanoscrolls. An interlayer spacing of as small as ∼0.65 nm was observed, suggesting the strong coupling between adjacent layers, which was further evidenced by the emergence of new breathing mode peaks in the ultralow frequency Raman spectrum. Importantly, compared with the photodetector fabricated from a monolayer MoS2or WS2nanosheet, the device based on an MoS2or WS2nanoscroll showed the much enhanced performance, respectively, with the photosensitivity greatly increased up to 2 orders of magnitude. Our work suggests that turning 2D TMDCs into 1D scrolls is promising in achieving high performances in various electronic/optoelectronic applications, and our general method can be extended to the preparation of large-sized nanoscrolls of other kinds of 2D materials that may bring about new properties and phenomena.

Artificial superlattices, based on van der Waals heterostructures of two-dimensional atomic crystals such as graphene or molybdenum disulfide, offer technological opportunities beyond the reach of existing materials. Typical strategies for creating such artificial superlattices rely on arduous layer-by-layer exfoliation and restacking, with limited yield and reproducibility. The bottom-up approach of using chemical-vapour deposition produces high-quality heterostructures but becomes increasingly difficult for high-order superlattices. The intercalation of selected two-dimensional atomic crystals with alkali metal ions offers an alternative way to superlattice structures, but these usually have poor stability and seriously altered electronic properties. Here we report an electrochemical molecular intercalation approach to a new class of stable superlattices in which monolayer atomic crystals alternate with molecular layers. Using black phosphorus as a model system, we show that intercalation with cetyl-trimethylammonium bromide produces monolayer phosphorene molecular superlattices in which the interlayer distance is more than double that in black phosphorus, effectively isolating the phosphorene monolayers. Electrical transport studies of transistors fabricated from the monolayer phosphorene molecular superlattice show an on/off current ratio exceeding 107, along with excellent mobility and superior stability. We further show that several different two-dimensional atomic crystals, such as molybdenum disulfide and tungsten diselenide, can be intercalated with quaternary ammonium molecules of varying sizes and symmetries to produce a broad class of superlattices with tailored molecular structures, interlayer distances, phase compositions, electronic and optical properties. These studies define a versatile material platform for fundamental studies and potential technological applications.

Scalability is the major challenge for scanning probe lithography (SPL). Recently developed cantilever-free scanning probe technologies provide a solution to the issue of scalability by incorporating massive arrays of polymer pens, which fundamentally overcome the low-throughput nature of SPL. The further development of cantilever-free SPL brings up a variety of applications in electronics, biology, and chemical synthesis. In this Perspective, we highlight the space-confined synthesis of complex nanostructures enabled by different types of cantilever-free SPL technologies.

Van der Waals heterostructures (vdWHs) are showing considerable potential in both fundamental exploration and practical applications. Built upon the synthetic successes of (two-dimensional) 2D materials, several synthetic strategies of vdWHs have been developed, allowing the convenient fabrication of diverse vdWHs with decent controllability, quality, and scalability. This review first summarizes the current state of the art in synthetic strategies of vdWHs, including physical combination, deposition, solvothermal synthesis, and synchronous evolution. Then three major applications and their representative vdWH devices have been reviewed, including electronics (tunneling field effect transistors and 2D contact), optoelectronics (photodetector), and energy conversion (electrocatalysts and metal ion batteries), to unveil the potentials of vdWHs in practical applications and provide the general design principles of functional vdWHs for different applications. Besides, moiré superlattices based on vdWHs are discussed to showcase the importance of vdWHs as a platform for novel condensed matter physics. Finally, the crucial challenges towards ideal vdWHs with high performance are discussed, and the outlook for future development is presented. By the systematical integration of synthetic strategies and applications, we hope this review can further light up the rational designs of vdWHs for emerging applications.

Composition modulation and edge enrichment are established protocols to steer the electronic structures and catalytic activities of two-dimensional (2D) materials. It is believed that a heteroatom enhances the catalytic performance by activating the chemically inert basal plane of 2D crystals. However, the edge and basal plane have inherently different electronic states, and how the dopants affect the edge activity remains ambiguous. Here we provide mechanistic insights into this issue by monitoring the hydrogen evolution reaction (HER) performance of phosphorus-doped MoS2(P-MoS2) nanosheets via on-chip electrocatalytic microdevices. Upon phosphorus doping, MoS2nanosheet gets catalytically activated and, more importantly, shows higher HER activity in the edge than the basal plane. In situ transport measurement demonstrates that the improved HER performance of P-MoS2is derived from intrinsic catalytic activity rather than charge transfer. Density functional theory calculations manifest that the edge sites of P-MoS2are energetically more favorable for HER. The finding guides the rational design of edge-dominant P-MoS2, reaching a minuscule onset potential of ∼30 mV and Tafel slope of 48 mV/dec that are benchmarked against other activation methods. Our results disclose the hitherto overlooked edge activity of 2D materials induced by heteroatom doping that will provide perspectives for preparing next-generation 2D catalysts.

In this study, the unsteady flow of an ultra-high-head model pump turbine in pump mode is numerically investigated, revealing the evolution mechanism of unsteady flow diffusion and propagation. Under high-flow-rate and high-efficiency conditions, stable flow separation occurs in the channel of the stay vanes. As the flow rate decreases, the flow separation gradually spreads in the radial direction and expands from the stay vanes to the guide vanes. This causes a partial blockage in the channel of the guide vanes. Meanwhile, the flow separation gradually switches from stable to unstable with a low-frequency rotation (about 4.8 % of the impeller rotational frequency) in the circumferential direction. In addition, the correlation between the hump characteristics and unsteady flow is discussed. For an ultra-high-head pump turbine, the unstable flow initiates at static operating conditions from the pump performance curve with negative slope, which is significantly different from medium and low-head pump turbines.

Low-temperature solution-processable electronic materials are of considerable interest for large-area, low-cost electronics, thermoelectrics, and photovoltaics. Using a soluble precursor and suitable solvent to formulate a semiconductor ink is essential for large-area fabrication of semiconductor thin films. To date, it has been shown that hydrazine can be used as a versatile solvent to process a wide range of inorganic semiconductors. However, hydrazine is highly toxic and not suitable for large-scale manufacturing. Here we report a binary mixed solvent of amine and thiol for effective dispersion and dissolution of a large number of inorganic semiconductors including Cu2S, Cu2Se, In2S3, In2Se3, CdS, SnSe, and others. The mixed solvent is significantly less toxic and safer than hydrazine, while at the same time offering the comparable capability of formulating diverse semiconductor ink with a concentration as high as >200 mg/mL. We further show that such ink material can be readily processed into high-performance semiconducting thin films (Cu2S and Cu2Se) with the highest room-temperature conductivity among solution-based materials. Furthermore, we show that complex semiconductor alloys with tunable band gaps, such as CuIn(SxSe1–x)2(0 ≤ x≤ 1), can also be readily prepared by simply mixing Cu2S, Cu2Se, In2S3, and In2Se3ink solutions in a proper ratio. Our study outlines a general strategy for the formulation of inorganic semiconductor ink for low-temperature processing of large-area electronic thin films on diverse substrates and can greatly impact diverse areas including flexible electronics, thermoelectrics, and photovoltaics.

Poly(l-lactic acid) (PLLA) is widely used in drug delivery and medical implants. Surface modification of PLLA with functional groups to immobilize gelatin or other extracellular matrix proteins is commonly used to improve its cellular affinity. In this work, we use the oxygen plasma to treat PLLA film followed by modification with organosilanes with different functional groups, such as amine, epoxy, and aldehyde groups. Gelatin is then immobilized on the modified PLLA film, which is confirmed by water contact angle measurement, atomic force microscopy (AFM), and laser scanning confocal microscopy (LSCM). Among the used organosilanes, aminosilane is the best one for modification of PLLA used for immobilization of gelatin with the highest efficiency. Moreover, the cellular affinity of gelatin-immobilized PLLA is studied through the evaluation of cell proliferation and focal adhesion using the human umbilical vein endothelial cells (HUVECs). Our experimental results show that the gelatin immobilized on aminosilane- and aldehyde-silane-modified PLLA improves the cellular affinity of HUVECs, whereas that immobilized on epoxy-silane-modified PLLA does not show significant improvement on the cell proliferation.

Properly piled up: Single‐layer 2D semiconducting nanomaterials of MoS2, WS2, TiS2, TaS2, ZrS2, and graphene were fabricated through an electrochemical lithiation process (see picture). The production of single‐layer MoS2was achieved in 92 % yield. A single‐layer MoS2‐based thin‐film transistor was fabricated, which was used for sensing NO at a detection limit of 190 ppt.

Ordentlich gestapelt: 2D‐halbleitende Nanomaterialien aus einzelnen MoS2‐, WS2‐, TiS2‐, TaS2‐, ZrS2‐ und Graphenschichten wurden durch elektrochemische Lithiierung hergestellt (siehe Bild). Eine Ausbeute von 92 % wurde bei der Produktion einzelner MoS2‐Schichten erreicht. Aus den MoS2‐Schichten wurde ein Dünnschichttransistor hergestellt, der zum Nachweis von NO bis zu einer Detektionsgrenze von 190 ppt verwendet wurde.

The nucleation mechanism of electrochemical deposition of Cu on reduced graphene oxide (rGO) electrodes has been systematically studied on the basis of the cyclic voltammetry, Tafel plot, and chronoamperometry. Our results show that the experimental parameters including electrolyte concentration, deposition potential, solution pH, and the presence of background electrolyte can determine the nucleation mechanism. Scanning electron microscopy is employed to study the nucleation and growth of Cu on rGO electrodes. This study is significant in development of the electrochemical method in practical applications based on the rGO electrodes.

Owing to their unique thickness-dependent electronic properties, together with perfect flexibility and transparency, graphene and its relatives make fantastic material for use in both active channel and electrodes in various electronic devices. On the other hand, the electronic sensors based on graphene show high potential in detection of both chemical and biological species with high sensitivity. In this contribution, we report the fabrication of all-reduced graphene oxide (rGO) thin film transistors by a combination of solution-processed rGO electrodes with a micropatterned rGO channel, and then study their applications in biosensing. Our all-rGO devices are cost-effective, highly reproducible, and reliable. The fabricated electronic sensor is perfectly flexible with high transparency, showing good sensitivity in detecting proteins in the physiological buffer. As a proof of concept, fibronectin as low as 0.5 nM was successfully detected, which is comparable with the previously reported protein sensors based on single-layer pristine graphene obtained from mechanical cleavage. The specific detection of avidin by using biotinylated all-rGO sensor is also successfully demonstrated.

The electrical property of graphene is highly sensitive to its local environment, which makes graphene an ideal channel material in electronic sensors. Reduced graphene oxide (rGO) has been used as the desirable alternative to the pristine graphene due to its low-cost, solution-processable, and scalable production. In this paper, we present a field-effect transistor sensor using micropatterned, protein-functionalized rGO film as the conducting or sensing channel. Such a nanoelectronic sensor is able to detect various metal ions in real-time with high sensitivity.

The chemically reduced graphene oxide (rGO) was transferred onto polyethylene terephthalate (PET) substrates and then used as transparent and conductive electrodes for flexible organic photovoltaic (OPV) devices. The performance of the OPV devices mainly depends on the charge transport efficiency through rGO electrodes when the optical transmittance of rGO is above 65%. However, if the transmittance of rGO is less than 65%, the performance of the OPV device is dominated by the light transmission efficiency, that is, the transparency of rGO films. After the tensile strain (∼2.9%) was applied on the fabricated OPV device, it can sustain a thousand cycles of bending. Our work demonstrates the highly flexible property of rGO films, which provide the potential applications in flexible optoelectronics.

Flexible, transparent, and conductive electrodes are prepared by reduction of the graphene oxide (GO) films which were spin-coated on the polyethylene terephthalate (PET) substrates. On the reduced graphene oxide (rGO) films, ZnO nanorods, as well as p-type and n-type Cu2O films with good crystallinity have been electrochemically deposited and then characterized. Meanwhile, the effect of pH value of the deposition bath on the morphology, structure, and semiconducting property of the electrochemical deposited Cu2O has been studied. Our results provide a possible way to replace the indium tin oxide (ITO) and fluorine tin oxide (FTO) electrodes with rGO films in the electrochemical synthesis, and make it promising to synthesize semiconductor oxides on rGO films for future flexible photovoltaic applications.

Recently, the field-effect transistors (FETs) with graphene as the conducting channels have been used as a promising chemical and biological sensors. However, the lack of low cost and reliable and large-scale preparation of graphene films limits their applications. In this contribution, we report the fabrication of centimeter-long, ultrathin (1−3 nm), and electrically continuous micropatterns of highly uniform parallel arrays of reduced graphene oxide (rGO) films on various substrates including the flexible polyethylene terephthalate (PET) films by using the micromolding in capillary method. Compared to other methods for the fabrication of graphene patterns, our method is fast, facile, and substrate independent. In addition, we demonstrate that the nanoelectronic FETs based on our rGO patterns are able to label-freely detect the hormonal catecholamine molecules and their dynamic secretion from living cells.

Herein, it is demonstrated that low temperature current injection and annealing (CIA) treatment can cause evident improvements in open circuit voltage, short‐circuit current, and fill factor of tunnel oxide‐passivated contact (TOPCon) silicon solar cells, leading to a notable conversion efficiency gain (over 0.4% absolute at the best condition). The effects of injected current and annealing temperatures toward the improvement of electrical performance of the TOPCon solar cells are compared. The more evident increase in the electrical performance after the CIA treatment may come from the higher fill factor improvements, which can be induced by the change of contact resistance after the CIA treatment, the potential involvement of hydrogen is discussed. The CIA treatment can be a reliable approach to further enhance the conversion efficiency of TOPCon solar cells, which is of great significance for the global PV industry. Herein, is been demonstrated that low temperature current injection and annealing can cause evident improvements in the conversion efficiency (over 0.4% absolute at the best condition) of tunnel oxide‐passivated contact silicon solar cells. Furthermore, the effects of injected current and annealing temperatures toward the electrical performance enhancement are compared and discussed.

Colloidal microparticles, with polymer composites encapsulated within two separate 2D material sheets, are fabricated by autoperforation, which can carry chemical and electronic information with long-term instability in complex environments.