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Free-standing nanocrystalline graphite (NCG) membranes directly grew on SiNx substrates with the aid of the catalyst-free chemical vapor deposition method. A new type of NCG nanopore was formed in the NCG membrane via controlled dielectric breakdown in KCl electrolyte. The electrical properties, especially the ionic conductance of the NCG nanoporewere examined under different physical parameters (pore size, ion strength, and pH condition). Due to their impressive transport properties, we first realized DNA sensing using the NCG nanopores.

A helium ion beam (HIB) is ideal for milling monolayer graphene in nanopore applications, but the optimizing irradiation parameter requires a comprehensive microscopic understanding of the interact...

Due to the good photocatalytic performance, which ensures the decomposition of pollutants under light, g-C3N4 is considered as an ideal photocatalytic material. Montmorillonite has a high adsorption capacity and layered structure, which has positive effects on increasing the specific surface area of g-C3N4 and avoid its polymerization agglomeration. In this paper, montmorillonite was used as carrier for g-C3N4 to obtain a new photocatalytic composite g-C3N4/Mt. Then the morphological and (micro)structural properties were characterized. The well-characterized materials were evaluated for the photocatalytic activity in degradation of methylene blue and Bisphenol A. The effects of the mass fraction of g-C3N4, light irradiation time, and pollutant concentration on the photocatalytic performance of g-C3N4/Mt composites were studied. Under the optimal experimental plan, the rate of photocatalytic degradation can reach to 99.3% within 120 min. Through the MS spectrum, it can be found that methylene blue molecule were catalysed and degraded into many harmless substances with low-molecular weight. Finally, based on the obtained reaction products, the mechanism by which the pollutants are removed was proposed. This study provides a new strategy to improve the photocatalysis ability of g-C3N4, which is of great significance for a sustainable pollution treatment.

Gallium Nitride High Electron Mobility Transistors (GaN HEMTs) enable higher efficiency, higher power density, and smaller passive components resulting in lighter, smaller and more efficient electrical systems as opposed to conventional Silicon (Si) based devices. This paper investigates the detailed benefits of using GaN devices in transportation electrification applications. The material properties of GaN including the applications of GaN HEMTs at different switch ratings are presented. The challenges currently facing the transportation industry are introduced and possible solutions are presented. A detailed review of the use of GaN in the Electric Vehicle (EV) powertrain is discussed. The implementation of GaN devices in aircraft, ships, rail vehicles and heavy-duty vehicles is briefly covered. Future trends of GaN devices in terms of cost, voltage level, gate driver design, thermal management and packaging are investigated.

In order to improve the biological activity and antibacterial properties of polyetheretherketone (PK) as bone implants, nano zinc-magnesium silicate (nZMS)/PK bioactive composites (nZPC) were fabricated. The results revealed that the mechanical properties, surface roughness and hydrophilicity of the nZPC gradually increased with nZMS content, in which nZPC with 50 w% of nZMS (50nZPC) exhibited the best properties. In addition, incorporation of nZMS into PK significantly improved the apatite mineralization ability of nZPC, which depended on nZMS content. Moreover, the attachment, proliferation and differentiation of MC3T3-E1 cells on nZPC were significantly enhanced with increasing nZMS content. Furthermore, after incorporation of nZMS into PK, the nZPC could inhibit the growth of Escherichia coli (E. coli), in which 50nZPC revealed the best antibacterial activity. The results suggested that 50nZMPC with good bioactivity, cytocompatibility and antibacterial activity might be a promising candidate as an implant for bone repair and anti-infection.

Herein, we develop a fluorescent sensor for simple detection of miRNA-10b, which combines the fluorescence quenching ability of graphene oxide (GO) and the duplex-specific nuclease (DSN) mediated target recycling amplification. Our sensor exhibits desirable sensitivity for miRNA-10b with a 530 fM detection limit that could be achieved within 75 min. Furthermore, our sensor showed good selectivity for discriminating target miRNA and other microRNAs.

Reproducible surface enhanced Raman scattering (SERS) enhanced performance, affected by molecular orientations in plasmonic nanostructures, attracts more attention than SERS detection sensitivity for satisfying requirements of practical applications. In this work, by coating silver films on the inverted cone-shaped nanopore array anodic aluminum oxide membranes, we provide a way to study the effect of molecular orientations on SERS enhancement with mapping technology. SERS enhanced performance of the fabricated substrates is assessed with trace Rhodamine 6G detection, enhancement factor calculation and 3D finite-difference time-domain simulation respectively. It is found that inverted cone-shaped nanopore and silver films both contribute to the highly SERS enhancement. And special inverted cone-shaped nanopore plasmonic structures limit molecular vibrations so as to affect Raman scattering enhancement. These findings can help us to understand the electromagnetic mechanism of molecular orientations on SERS enhancement, so as to design highly reproducible SERS substrates for various applications.

Electrochemical water splitting, which is economical and sustainable, has been considered as one of the most potential methods to produce large amounts of hydrogen with high purity. However, the de...

The aim of the present work was to prepare high loading capacity carriers for immobilizing glucoamylase. Different sizes of chitosan based particles were successfully prepared by different methods to evaluate the performance in immobilization. Chitosan particles on millimeter size were prepared by dripping granulation method, chitosan covered magnetic nanoparticles and chitosan mixted graphene oxide nanosheets covered magnetic nanoparticles were synthesized by one-step method, chitosan-glucoamylase nanoparticles were synthesized by ionic cross linking method with Sodium tripolyphosphate. These particles were characterized by SEM, TEM, FTIR and DLS analysis. The performance of the immobilized enzyme was also investigated. The results showed that the loading capacity was greatly increased on chitosan based nanoparticles. The reaction conditions of immobilized enzyme were optimized, the reusability and storage stability was also investigated. The results showed the pH durance and storage stability of the immobilized enzyme on nanosize particles were enhanced.

In order to improve the OER performance, Ni3S2-based catalysts were directly grown on Ni substrate by simultaneously doping of Fe and compositing with reduced graphene oxide (rGO). Synthesis and loading of Ni3S2/rGO were completed during a one-step hydrothermal process, in which Ni foam acted as support and Ni source of Ni3S2, as well as the subsequent current collector. It is found that either GO or Fe salt tuned Ni3S2 nanosheets into thinner and smaller interconnected nanosheets anchored on rGO, which enhanced the charge transfer resistance and improved the active sites. Hence, as-synthesized Fe-doped Ni3S2/rGO composite at 120 °C (Fe-2-Ni3S2/rGO@NF-120) exhibited an enhancement on OER performances: An overpotential of 247 mV at 20 mA cm−2, and a small Tafel slope of 63 mV dec−1, as well as an excellent stability of: 20 h maintaining at 20 mA cm−2 or 50 mA cm−2.

As society progresses, the task of developing new green energy brooks no delay. Li-O2 batteries have high theoretical capacity, but are difficult to put into practical use due to problems such as high overvoltage, low charge-discharge efficiency, poor rate, and cycle performance. The development of high-efficiency catalysts to effectively solve the shortcomings of Li-O2 batteries is of great significance to finding a solution for energy problems. Herein, we design CoFe2O4/g-C3N4 composites, and combine the advantages of the g-C3N4 material with the spinel-type metal oxide material. The flaky structure of g-C3N4 accelerates the transportation of oxygen and lithium ions and inhibits the accumulation of CoFe2O4 particles. The CoFe2O4 materials accelerate the decomposition of Li2O2 and reduce electrode polarization in the charge–discharge reaction. When CoFe2O4/g-C3N4 composites are used as catalysts in Li-O2 batteries, the battery has a better discharge specific capacity of 9550 mA h g−1 (catalyst mass), and the cycle stability of the battery has been improved, which is stable for 85 cycles.

The low noise and the high transconductance of graphene field-effect transistor uplift it as an auspicious candidate for different standard biological applications. Recently, a reliable determination of DNA hybridization's binding kinetics plays an essential role in biological systems, personalization and precision medicine. Here, we demonstrate a field-effect transistor based on a single CVD-grown graphene layer for label-free DNA hybridization detection. The developed biosensor displays a 7 mV/dec sensitivity in a wide dynamic range spanning 7 orders of magnitude with a detection limit of 15 fM, and exhibited a good selectivity against the non-complementary target. Bio-recognition events result in a negative gate voltage shift of the graphene Dirac point.

The fluid-solid interaction force has a decisive influence on the flow characteristics of micro-nano scale. Based on the dissipative particle dynamics (DPD) method, static and flow simulations of fluid in typical shale slits were carried out. The Lennard-Jones (LJ) potential function of 96X was applied to characterize the fluid-solid interaction force. The slit width ranged 3–10nm, the wall material was quartz, the fluid was n-hexane, and the driving force of the flow simulation ranged 1–20kcal/(mol·A). The results show that due to the attraction of solid wall, the aggregation of fluid molecules near the wall was enhanced, fluid density there increased, and the diffusion coefficient there was significantly lower than that in the middle of the slit. The fluidity of the fluid near the wall is significantly reduced. In the flow model, when the fluid-solid interaction force was ignored, the flow profile was piston-like, and the velocity gradient at the edge of the slit was extremely large, showing the characteristics of slip flow. When the fluid-solid interaction force was taken into account, the velocity was reduced significantly, and the profile was parabolic. When the LJ96X was replaced by LJ126X potential function to characterize the fluid-solid interaction force, the attractive force from the wall on the fluid near the wall decreased, the fluidity was enhanced, and the velocity profile increased. When the conservative force parameter of fluid was changed, enhancing the wettability of oil phase, the affinity between fluid and solid was increased, and the velocity profile was reduced.

Nanopores have a unique advantage for detecting biomolecules in a label-free fashion, such as DNA that can be synthesized into specific structures to perform computations. This method has been considered for the detection of diseased molecules. Here, we propose a novel marker molecule detection method based on DNA logic gate by deciphering a variable DNA tetrahedron structure using a nanopore. We designed two types of probes containing a tetrahedron and a single-strand DNA tail which paired with different parts of the target molecule. In the presence of the target, the two probes formed a double tetrahedron structure. As translocation of the single and the double tetrahedron structures under bias voltage produced different blockage signals, the events could be assigned into four different operations, i.e., (0, 0), (0, 1), (1, 0), (1, 1), according to the predefined structure by logic gate. The pattern signal produced by the AND operation is obviously different from the signal of the other three operations. This pattern recognition method has been differentiated from simple detection methods based on DNA self-assembly and nanopore technologies.

Detailed experimental and numerical studies have been conducted on the heat transfer, pressure loss, and turbulent flow structure of a three-short-pass serpentine cooling channel with miniature W-shaped ribs on the wall under the Reynolds numbers from 8500 to 60,000. Steady-state heat transfer experiments were done to obtain the globally averaged and total heat transfer performance of each ribbed pass of the serpentine channel, and the streamwise pressure loss characteristics of the serpentine-channel flow were also obtained by multipoint pressure measurements. Additionally, the transient liquid crystal thermography technique was also used to obtain the local heat transfer distributions on the miniature W-ribbed surface of each pass. Furthermore, numerical simulations were done by using the AKN k–ε turbulence model to reveal the detailed turbulent flow and heat transfer characteristics in the serpentine channel. The experiments indicate that the miniature W-ribbed short pass has significantly enhanced total heat transfer by a factor of up to 4.0. The total heat transfer enhancement shows appreciably different values in different passes of the serpentine channel, and the second pass shows about 15% higher heat transfer enhancement than the first pass, and the third pass shows the highest heat transfer enhancement, which is about 15% higher than the second pass. The pressure loss measurements indicate that the two flow turnings contribute more than 90% of the total pressure loss in the serpentine channel with one ribbed pass with the miniature W ribs. The numerical simulations indicate that the flow turnings significantly increase the turbulent mixing in the flow of the downstream pass, and the miniature W-ribs on the wall appreciably improve the near-wall vortex mixing, which contributes the heat transfer enhancement.

As an important technology in improving oil recovery, CO2 miscible flooding has achieved great success in many oil fields. However, studies on CO2 transport in porous media are mostly based on equilibrium adsorption in one-dimensional displacement where rate-controlled adsorption is not taken into consideration. In this work, we develop a radial convection–dispersion model, which simultaneously combines rate-controlled adsorption, convection, and dispersion. Based on this model, four dimensionless groups representing CO2 dispersion, adsorption capacity, flow rate, and kinetic rate groups are proposed for the first time. Subsequently, the Barakat–Clark forward and backward difference methods are combined to solve the mathematical model. CO2 concentration and adsorption at different positions in the porous media (including the effluent concentration and adsorption histories) are then calculated. Furthermore, the effects of the parameters on CO2 transport behavior are studied in detail. The results reveal that CO2 gradually moves forward with the increase in the CO2 injection volume. Once CO2 reaches a certain position, its concentration there increases and an S-shaped curve is formed. Moreover, the adsorption capacity at this position also increases significantly, and the changing rate is much higher than CO2 concentration. CO2 effluent concentration grows more uniform, and the breakthrough occurs earlier with increased dispersion velocity and CO2 injection rate and decreased adsorption capacity and adsorption rate. The mathematical model developed in this study is of great importance in predicting CO2 transport behavior in radial miscible flooding.

Fe3O4/Au binary nanocrystals have been widely utilized in catalysis, biology, medicine and other fields due to their unique magnetic and optical properties. In the present work, diversely structured Fe3O4/Au core-satellite nanocubes and Fe3O4@Au core-shell nanocrystals are fabricated by a seed deposition and a seed-mediated growth process, respectively. The developed binary nanocrystals equipped with highly efficient and recyclable catalytic reduction characteristics for 4-nitrophenol (4-NP). Extensive x-ray diffraction and transmission electron microscopy studies demonstrate that the amount of Au seeds deposited onto the surfaces of Fe3O4 nanocubes increases with increasing the additive amount of Au seeds. Aiming at structure tailored engineering, Fe3O4@Au core-shell nanocrystals are formed when Fe3O4/Au-50 mL core-satellite nanocubes are chosen as a template for further coating with gold shell by seed-mediated growth. Moreover, the magnetic saturation is gradually weakened with increasing addition quantity of Au seeds. Importantly, 4-NP is employed as a model molecule to investigate the effect of developed Fe3O4/Au binary nanocrystals on the catalytic performance. The rate constant of Fe3O4/Au core-satellite nanocubes is higher than that of Fe3O4@Au core-shell nanocrystals because of distinctly different surface area-to-volume ratio of Au nanocrystals. Fe3O4/Au core-satellite nanocubes show good separation ability and reusability, which could be repeatedly applied for nearly complete reduction of 4-NP for at least six successive cycles. Such cost effective and recyclable catalyst provides a new material paradigm for environmental protection applications.

Hybrid Fe3O4-Ag nanocrystals, a new type of highly efficient and reusable catalyst for methylene blue (MB) reduction, are fabricated by a novel seed deposition process. X-ray diffraction and Mossbauer spectroscopy results show that the developed iron oxides are in a pure magnetite Fe3O4 phase. Upon manipulating the amount of Ag seeds capsuled on the modified surfaces of Fe3O4 nanocrystals, the catalytic capacities on the reduction of MB can be precisely adjusted with a tunable fabrication cost control. The linear correlation of the reduced MB concentration versus reaction time catalyzed by our developed hybrid Fe3O4-Ag nanocrystals is coherent with pseudo first order kinetics. Importantly, with remarkable recyclability features, the hybrid Fe3O4-Ag nanocrystals can be easily separated by applying an external magnetic field. The tailored catalytic performances of the hybrid Fe3O4-Ag nanocrystals during MB reduction are attributed to the optimized dynamic electron transfer process, which dominates the electrochemical mechanism wherein the nucleophilic BH4− ions donate electrons to electrophilic organic MB through Ag seeds in a regulated amount. Such developed hybrid Fe3O4-Ag nanocrystals pave the way towards the mass production of highly efficient and low cost catalysts for methylene blue reduction.

With the advantages of simple equipment and in-situ preparation of nanopores, the CBD method has been widely concerned by researchers. In this work, a fluorescence platform was set up to directly observe the λ-DNA motions near the CBD prepared different kinds of SiNx nanopores. At first, for the one nanopore film, the λ-DNA post-translocation motion was observed. Then, for the multiple nanopores film, the current modulation phenomena of each nanopore after the DNA clogged the pores was observed. When the distance of asymmetric pores is less than the length of λ-DNA, the larger nanopores are easy to be blocked preferentially by considering the tug-of-war on λ-DNA; when the asymmetric porous distance is larger than the DNA two polymer length, due to the forming a folded structure, the smaller nanopores are preferentially blocked. These results reveal that the clogging phenomena during the DNA translocation analysis for the nanopores are varied, and it should be considered for CBD-prepared nanopores.

Ever since the more than decade-old discovery of the mechanical exfoliation method for graphene isolation, this miraculous 2-dimensional material is still widely used in various applications because of its exceptional electron mobility and thermal conductivity. Graphene, commonly grown on a metallic substrate using chemical vapor deposition (CVD), needs to be transferred onto dielectric substrates compatible with complementary metal oxide–semiconductor (CMOS) technology for various electronic and optical applications. However, the ultra-clean transfer of graphene with defect-free is still crucial for large-area graphene devices' efficiency. This review introduces a comprehensive and up-to-date account of the transfer of the most attention kinds of CVD-grown graphene on copper substrates. The advances and main challenges of both wet and dry transfer methods are also carefully described. Particular emphasis is also given on graphene-based BioFET devices, revising their sensing mechanism and the optimum operational conditions toward high specificity and sensitivity. The authors have been convinced that upgrading the transfer process to accomplish the cleanest graphene surface and exploiting the optimum operating conditions will undoubtedly be of considerable significance to fabricate graphene-based devices.

The effective sensing area is the key point of solid-state nanopore single-molecule detection, which is determined by the diameter of the hole and the thickness of the membrane. High spatial resolution can be achieved by using single-atom thickness two-dimensional materials, such as single-layer graphene and molybdenum disulfide. Helium ion beam microscopy provides an effective technique for manufacturing small-sized nanopores. Here, we show that the precise fabrication of sub-2 nanometer nanopores has been successfully achieved on a single-layer graphene film, which provides the best spatial resolution in room-temperature ionic liquid-assisted single-molecule detection. Many graphene nanopores of different sizes have been fabricated, with a minimum pore diameter of 1.4 nm. The application of these graphene nanopores manufactured by HIM shows that single-layer graphene nanopores can distinguish different homopolymer single-stranded DNA lengths and types, and can even identify four single nucleotides.

Engineered nanomaterials have been increasingly utilized in industry for various consumer products, environmental treatments, energy storage, and biomedical applications. Meanwhile, it has been established that certain nanomaterials can be toxic to biological cells from extensive experimental and theoretical studies. Despite that the exact molecular mechanisms of this nanomaterial toxicity are still not well understood, it is ubiquitous that their interactions with cell membranes, through either endocytosis or penetration (and thus potential lysis), act as the first step toward the inflammation or even the death of a cell. To facilitate the study of nanomaterial-membrane interactions, here we demonstrate a nanopore-based single-molecule approach that can be applied to monitor a specific nanomaterial-membrane interaction in real time. Combined with molecular dynamics and experimental approaches, we show how an ionic current can be used to detect membrane damage by a graphene nanosheet and illustrate the underlying molecular mechanism. More generally, we expect that measured transmembrane ionic currents (both DC and AC) can signify many particle-induced membrane modifications, such as hole formation, particle adsorption, and protein insertion.

Ultra-long and laterally aligned Zinc Oxide (ZnO) nanorod arrays were directly synthesized around the edges of SiNx micro pores by using a facile and effective chemical vapour deposition process without any catalysts or additives. ZnO nanorods can grow controllably with a preferential orientation as a bridge beyond the edges and gradually seal into a planar free-standing mesh layer. The optimized growth parameters have been thoroughly investigated and identified. A vapour solid synthesis mechanism with source vapour flow rate control has been tentatively proposed on the basis of the experimental data to explain the synthesis: ZnO nanodots first form around the edges of pores due to the local large binding energy and high Zinc (Zn) vapour concentration, and subsequently nanorods grow epitaxially from the nanodots. This precisely-controlled micro pore sealing approach is an important step toward a coherent mechanism for applications in DNA extraction, separation and the next generation DNA sequencing.

Single-walled carbon nanotubes (SWCNTs) have attracted great attention on account of their superior and tunable electrical properties for promising applications in low-cost and high-performance nano-electronics and thin-film devices. However, SWCNTs are usually produced as a mixture of m-/s-nanotubes with small diameters and long aspect ratios and tend to form bundles or entangled ropes owing to their high van der Waals attraction and π–π interactions among their inter-tubes. Therefore, the dispersion and sorting of SWCNTs with both a high yield and desirable electronic structures has been a great challenge but a long-term motivation to achieve greater practical utility of SWCNTs. This review provides a comprehensive summary of the strategies for the surface modification and dispersion of SWCNTs, and surveys progress on the up-to-date development of SWCNTs enrichment via mainly non-covalent interactions with molecular species. The effect of the molecular architecture on the selective dispersion and sorting of SWCNTs by surfactants, bio-macromolecules, and conjugated polymers is discussed with respect to the structure–property relationship and interaction mechanism.

Silicon nitride (SN) with good osteoconductivity has been introduced as an implantable biomaterial for joint replacement and interbody fusion devices. In this study, SN was coated on a polyetheretherketone (PEEK) surface by inductively coupled plasma-enhanced chemical vapor deposition (ICPECVD). The results showed that a dense coating (thickness of about 500 nm) of amorphous SN was closely combined with a PEEK substrate (PKSN) with a binding strength of 6.88 N. In addition, the coating surface showed hierarchical nanostructures containing many spherical bulges (sizes about 150 nm), which were composed of many small humps (sizes about 10 nm). Moreover, the roughness, hydrophilicity, surface energy, surface charge and adsorption of bovine serum albumin (BSA) of PKSN were obviously higher than those of PEEK. After immersion into simulated body fluid (SBF), the Si ions were gradually released from PKSN into SBF and a weak alkaline environment was created. Antibacterial experiments showed that PKSN exhibited a greater antibacterial activity than that of PEEK. Moreover, compared with PEEK, PKSN significantly promoted adhesion, proliferation, differentiation and expression of osteogenic related genes of the rat bone marrow stromal cells (rBMSCs). In conclusion, the SN coating of PKSN with hierarchical nanostructures exhibited excellent antibacterial activity and cytocompatibility, which would make it a great candidate for orthopedic applications.

Monolayer WS2 (Tungsten Disulfide) with a direct-energy gap and excellent photoluminescence quantum yield at room temperature shows potential applications in optoelectronics. However, controllable synthesis of large-area monolayer WS2 is still challenging because of the difficulty in controlling the interrelated growth parameters. Herein, we report a facile and controllable method for synthesis of large-area monolayer WS2 flakes by direct sulfurization of powdered WO3 (Tungsten Trioxide) drop-casted on SiO2/Si substrates in a one-end sealed quartz tube. The samples were thoroughly characterized by an optical microscope, atomic force microscope, transmission electron microscope, fluorescence microscope, photoluminescence spectrometer, and Raman spectrometer. The obtained results indicate that large triangular monolayer WS2 flakes with an edge length up to 250 to 370 &mu, m and homogeneous crystallinity were readily synthesized within 5 min of growth. We demonstrate that the as-grown monolayer WS2 flakes show distinctly size-dependent fluorescence emission, which is mainly attributed to the heterogeneous release of intrinsic tensile strain after growth.

Terahertz signature detection of biological samples in aqueous solution remains a great challenge due to the strong terahertz absorption of water. Here we propose a new preparation process for fabricating a microfluidic chip and use it as an effective sensor to probe the terahertz absorption signatures of microcystin aptamer (a linear single-stranded DNA with 60 nucleotides) dissolved in TE buffer with different concentrations. The microfluidic chip made of silicon includes thousands of 2.4 &mu, m &times, 2.4 &mu, m square-cross-section channels. One repeatable terahertz absorption signature is detected and recognized around 830 GHz, fitted to a Lorentz oscillator. This signature is theorized to originate from the bending of hydrogen bonds formed between adjacent hydrated DNA bases surrounded by water molecules. Furthermore, the low-lying vibrational modes are also investigated by molecular dynamics simulations which suggest that strong resonant oscillations are highly probable in the 815&ndash, 830 GHz frequency band.

Helium ion beam (HIB) technology plays an important role in the extreme fields of nanofabrication. This paper reviews the latest developments in HIB technology as well as its extreme processing capabilities and widespread applications in nanofabrication. HIB-based nanofabrication includes direct-write milling, ion beam-induced deposition, and direct-write lithography without resist assistance. HIB nanoscale applications have also been evaluated in the areas of integrated circuits, materials sciences, nano-optics, and biological sciences. This review covers four thematic applications of HIB: (1) helium ion microscopy imaging for biological samples and semiconductors; (2) HIB milling and swelling for 2D/3D nanopore fabrication; (3) HIB-induced deposition for nanopillars, nanowires, and 3D nanostructures; (4) additional HIB direct writing for resist, graphene, and plasmonic nanostructures. This paper concludes with a summary of potential future applications and areas of improvement for HIB extreme nanofabrication technology.

Non-through and through nanopores were introduced to study the Raman band shift of suspended graphene by the substrate edge and the helium ion beam irradiation during the fabrication of nanopore in graphene. Before the ion beam irradiation, there is a blue-shift in the G band and G’ band of suspended graphene on the micro-scale non-through and through holes edge because of the n-type mixing for suspended graphene from the translocation. After different doses of the helium ion irradiation, G’ band Raman of suspended graphene on through are blue-shift, and the G band positions are red-shift. Helium ion irradiation introduces n-type doping during the graphene nanopore fabrication. The observed Raman shifts help us to gain more intrinsic properties of the graphene nanopore. Thus, Raman spectroscopy can be used as a quantitative diagnostic tool to character graphene-based nanopore.

Synthesis of monolayer WS2 crystals on SiO2/Si substrate has attracted interests due to the advantage of fabrication of field effect transistor without WS2 transfer process. Although substantial efforts have been achieved in recent years, controllable synthesis of uniform and large-area monolayer WS2 crystals on SiO2/Si substrate is still challenging. Herein, we report an elegant method to synthesize monolayer WS2 crystals on SiO2/Si substrate by using NaCl as a growth promoter in one semi-sealed quartz tube. It is found that triangular monolayer WS2 with edge lengths ranged from 10 to 460 μm can be readily synthesized within 5 min of growth by adjusting the growth temperature and weight ratio of NaCl and WO3. The Raman mapping results indicate that the as-synthesized WS2 crystals exhibit homogeneous distributions of the crystallinity, electron doping and residual strain across the entire triangular domains regardless of their dimensions. However, the smaller WS2 crystals exhibit a higher electron doping and less residual strain compared to the larger one obtained under the same growth conditions. Importantly, the amount of WO3 used in this study is three orders lower than the commonly reported one and the semi-sealed quartz tube can be reused more than 50 times after mildly cleaning.

The dielectric breakdown used to fabricate solid-state nanopores has separated the device from capital-intensive industries and has been widely adopted by various research teams, but there are still problems with low production efficiency and uncertain location. In this work, based on the transient breakdown phenomenon of nanofilms, a new type of dielectric breakdown apparatus for nanopore fabrication is reported. It integrates both nano-manipulation technology and dielectric breakdown nanopore fabrication technology. The nanometer distance detection method and circuit are introduced in detail. The generation principle and procedures of the transient high electric field are explained step by step. The characterization of the nanopores shows that this apparatus can fabricate sub-2 nm nanopores at a pre-located position. Besides, the nanopore diameter can be easily adjusted by setting the transient high electric field value.

To improve the surface bio-performances of polyimide (PI), tantalum pentoxide (Ta2O5)/PI composites (TPC) were prepared, and concentrated sulfuric acid was utilized to modify TPC surface. The results revealed that sulfonated TPC (STPC) exhibited microporous surface with pores size of about 3 μm, and sulfonic acid (-SO3H) groups were introduced onto the microporous surface. In addition, many Ta2O5 submicro particles appeared on the microporous surface, which formed micro-submicro structures. Compared with PI, the surface roughness, hydrophilicity, surface energy and protein adsorption as well as apatite mineralization of STPC in simulated body fluid were obviously enhanced, which increased with Ta2O5 content increasing. In addition, STPC exhibited antibacterial performances due to the presence of -SO3H groups and Ta2O5. Furthermore, the responses (adhesion, proliferation and differentiation) of rat bone marrow mesenchymal stem cells to STPC were remarkably promoted with the increase of Ta2O5 content. In short, STPC with 50w% Ta2O5 content (STPC 50) with sulfonated microporous surface contained micro-submicro structures, which exhibited antibacterial performances and stimulated cell responses. STPC50 with improved surface properties and cytocompatibility might have large potentials for bone repair applications. Keywords: Tantalum pentoxide, Polyimide based composite, Sulfonation, Micro-submicro structures, Antibacterial performances

The CO2 injection in tight reservoir is different from the conventional reservoir. For the porous media, the pore throat in the matrix reaches the level of nanopore, and the heterogeneity leads to huge difference during CO2 injection. For the interaction of fluids, the reduction of interfacial tension caused by CO2 is benefit to enhance oil recovery. To reveal the mechanism, pore scale model from tight formation is built and the influences of interfacial tension and heterogeneity are investigated. First, the migration of two-phase interface is studied by coupled with level set (LS) equation and Navier-Stokes (NS) equation. And finite element method (FEM) with interfacial adaptive mesh refinement is employed to solve the equation system. The results reach highly agreement compared with analytical solution and phase field method. Then, the pore throat distribution characteristics of porous media model are built by the scanning electron micrograph (SEM). Finally, based on the real porous media model from the SEM image, the influences of interfacial tension and heterogeneity are investigated. The pore scale model considering fluid and medium mechanism during CO2 injection provides a better understanding of interfacial tension and heterogeneity effect in tight oil reservoirs.

Poor cell adhesion and osteogenic activity impede the bone regeneration and osseointegration effects of polyetherketoneketone (PEKK) implants. Surface modification and incorporation of bioactive fillers are effective strategies to promote the cellular responses of PEKK implants and their integration with bone tissues. In this study, silicon nitride (SN) microparticles were blended with PEKK to develop bioactive composite implants (SPC). Femtosecond laser was then used to modify SPC surfaces inducing favorable micro/nano structural surface (FSPC). After the laser ablation, irregularly shaped SN microparticles were converted to “petal-like” clusters composed of “pin-like” SN nanoparticles, while the entire surface was covered by SN particles due to the removal of PEKK. The roughness, hydrophilicity, content of surface chemical groups (e.g., -NH2), and protein adsorption capability of FSPC were significantly enhanced compared to SPC and PEKK. Also, the release of biologically active Si ions was increased after the femtosecond laser treatment, inducing a positive microenvironment favorable for cellular activities. Moreover, FSPC exhibited a greater bacteriostatic activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) than SPC. The presence of micro/nano structure also remarkably promoted adhesion, proliferation, and osteogenic differentiation of rat bone mesenchymal stem cells (rBMSCs). In vivo evaluation of the composites in a rabbit femur defect model verified that FSPC could enhance osteogenesis and osseointegration to a greater extent than SPC, evidenced with greater bone-implant contacts and push-out force. These results indicate that the femtosecond laser induced micro/nano structural surface on SN/PEKK implants can significantly promote osseointegration and bone repair. The femtosecond laser exhibits great potential in surface modifying bioceramic/polymer composites. The fabricated FSPC have shown great potential as bone implants in orthopedic applications considering their excellent biocompatibility, bacteriostatic property, osteogenic activity, and osseointegration.

Solid-state nanopores are considered an attractive basis for single-molecule DNA sequencing. At present, one obstacle to be overcome is the improvement of their temporal resolution, with the DNA molecules remaining in the sensing volume of the nanopore for a long period of time. Here, we used a composite system of a concentration gradient of LiCl in solution and a nanofiber mesh to slow the DNA perforation speed. Compared to different alkali metal solutions with the same concentration, LiCl can extend the dwell time to 20 ms, five times longer than NaCl and KCl. Moreover, as the concentration gradient increases, the dwell time can be tuned from dozens of milliseconds to more than 100 ms. When we introduce a nanofiber mesh layer on top of the pore in the asymmetric solution, the DNA molecules get retarded by 162–185 $$\upmu $$ s/nt, which is three orders of magnitude slower than the bare nanopore. At the same time, because the molecule absorption region becomes larger at the pore vicinity, the higher molecule capture rate improves the detection efficiency.

Graphene-based nanopore devices have shown tantalizing potential in single molecule detection for their monoatomic membrane thickness which is roughly equal to the gap between nucleobases. However, high noise level hampers applications of graphene nanopore sensors, especially at low frequencies. In this article, we report on a study of the contribution of suspended graphene area to noise level in full frequency band. Monolayer graphene films are transferred onto SiNx substrates preset with holes in varied diameters and formed self-supported films. After that, the films are perforated with smaller, nanoscale holes. Experimental studies indicate a dependency of low-frequency 1/f noise on the underlying SiNx geometry. The contribution of the suspended graphene area to capacitance which affects the noise level in the high frequency range reveals that the graphene free-standing film area influences noise level over a wide frequency region. In addition, the low-frequency noise demonstrates a weak dependency on salt concentration, in deviation from Hooge&rsquo, s relation. These findings and attendant analysis provide a systematic understanding of the noise characteristics and can serve as a guide to designing free-standing monolayer graphene nanopore devices.

Polyetheretherketone (PEEK) biomaterial has become increasingly popular in orthopedic applications due to its favorable biocompatibility, biostability, mechanical strength and elastic modulus similar to natural bones. In this research, in order to improve the biological performances of PEEK, tantalum pentoxide (Ta2O5) was incorporated into PEEK to fabricate PEEK/Ta2O5 composites (PTC) using a method of cold press-sintering, and surface coarsening of PTC was prepared by sand blasting. The results showed that the Ta2O5 particles were uniformly disperse into PEEK, and thermal and mechanical properties of PTC were enhanced with the increase of Ta2O5 content. In addition, incorporating Ta2O5 into PEEK and surface coarsening could improve surface roughness, hydrophilicity, surface energy and protein absorption of PTC. Furthermore, the adhesion and proliferation as well as osteogenic differentiation of BMSCs on PTC were significantly promoted and regulated by Ta2O5 content and surface coarsening. The results indicated that surface coarsening of PTC (PTCS) with high surface roughness, hydrophilicity and surface energy could induce positive cellular responses, showing good cytocompatibility. PTCS might have a great potential as implants for bone repair.

An ideal artificial bone will likely be multifunctional, combining different technologies to simultaneously promote bone regeneration while inhibiting microbial infection. In this study, copper- (Cu-) doped nano laponite (cnLAP) was prepared by a cation-exchanged method, and the cnLAP coating on poly(butylene succinate) (PBSu) scaffold was fabricated by poly(dopamine) modification. The results showed that incorporation of Cu ions into nano laponite (nLAP) did not have obvious effects on the morphology and surface area of cnLAP (compared with nLAP), which could be coated easily on macroporous PBSu scaffolds. In addition, the cnLAP-coated PBSu scaffolds could inhibit the growth of both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), indicating good antibacterial activity. Moreover, the cnLAP-coated PBSu scaffolds significantly promoted proliferation and improved alkaline phosphatase (ALP) activity of bone mesenchymal stem cells (BMSCs) compared with PBSu scaffolds. Furthermore, no obvious differences in cell responses to cnLAP- and nLAP-coated PBSu scaffolds were found, indicating that incorporation of Cu into nLAP had no negative effects on its cytocompatibility. The results suggested that the cnLAP-coated PBSu scaffolds exhibited excellent cytocompatibility and antimicrobial activity, which might offer promising opportunities for promoting bone regeneration and prevention of infectious from bacteria and effective treatment of bone defects., National Natural Science Foundation of China [51772194, 81771990]; Key Medical Program of Science and Technology Development of Shanghai [17441900600, 15441902500]; Ministry of Education, Youth and Sports of the Czech Republic Program NPU I [LO1504]

Effective DNA translocation into nanochannels is critical for advancing genome mapping and future single-molecule DNA sequencing technologies. We present the design and hydrodynamic study of a diamond-shaped gradient pillar array connected to nanochannels for enhancing the success of DNA translocation events. Single-molecule fluorescence imaging is utilized to interrogate the hydrodynamic interactions of the DNA with this unique structure, evaluate key DNA translocation parameters, including speed, extension, and translocation time, and provide a detailed mapping of the translocation events in nanopillar arrays coupled with 10 and 50 μm long channels. Our analysis reveals the important roles of diamond-shaped nanopillars in guiding DNA into as small as 30 nm channels with minimized clogging, stretching DNA to nearly 100% of their dyed contour length, inducing location-specific straddling of DNA at nanopillar interfaces, and modulating DNA speeds by pillar geometries. Importantly, all critical features down to 30 nm wide nanochannels are defined using standard photolithography and fabrication processes, a feat aligned with the requirement of high-volume, low-cost production.

In order to confirm the relationship between the luminescence and the ratio of Ce3+/Ce4+ more clearly, a series of YAG:Ce3+ (Yttrium Aluminum Garnet, Y2.94Al5O12:0.06Ce3+) phosphors were pre- pared under different sintering atmosphere. A semi-quantitative analysis based on X-ray photoe-lectron spectroscopy (XPS) was introduced to study the mole ratio of Ce3+/Ce4+ in the as-synthesized YAG:Ce3+ phosphors. The results indicated that the percentage of Ce3+/(Ce3+ + Ce4+) reached 88.46% under the reduction atmosphere. The emission intensity of YAG:Ce3+ phosphors was in-creased significantly with the increasing of Ce3+ concentration.

Single crystal WS2 film has been paid much more attentions due to its special optical-electrical performance and potential application in the field of biosensor and photodetector in recent years. In this work, we focused on the growth of single crystal WS2 and explored the effect of the position of sulfur and carrier gas flow rate on the nucleation density systematically. The results indicated that the nucleation density of WS2 varies obviously correspond to sulfur position and gas flow, the reasons of the variety on the nucleation density was investigated. Meanwhile, granular and massive WS2 was characterized by an optical microscope, atomic force microscope and Raman spectra.

Gold nanoparticles hold unique optical and electronic properties and have been extensively applied as optical and electrochemical labels for DNA and protein detection. The nanopore based analysis of gold nanoparticles will provide us good insight for further study the conjugation of nanoparticles and DNA. In the present work, we demonstrated gold nanoparticles translocation through silicon nitride (SiN) nanopore via investigation of distribution of current blockage and dwell time of gold nanoparticles with different sizes, 10 nm and 15 nm respectively. 100 mM KCl solution with 0.075% Triton X-100 and 5 mM Tris was used to avoid the aggregation of negatively charged gold nanoparticles caused by van der Waals force. Nanopore based on SiN membrane was fabricated by current dielectric breakdown technology, and the diameter of the nanopore was calculated from an empirical equation, which is 18 nm. Experimental data was analyzed via Clampfit, version 10.6.0.13, and Origin 8 (OriginLab).

Solid-state nanopore is a promising alternative for current nucleic acid analysis in DNA sequencing. In this work, we employed current-stimulus dielectric breakdown to fabricate a 2 nm nanopore on SiNx membrane. The effect of this 2 nm SiNx nanopore was then examined by comparing the translocation behaviors of four types of ssDNA through this nanopore. Current signal collected from the nanopore can distinguish the four types of ssDNA with 30 nucleobases, providing information about the sequence and structure of the ssDNA molecule.

Polyimide (PI) may become a promising biomaterial for dental and orthopedic application due to its high mechanical strength, good biocompatibility and bio-stability as well as modulus of elasticity similar to the bone of human body. In this study, bioactive tantalum pentoxide (Ta2O5, TO)/polyimide (PI) composites (TPC) were fabricated by blending modification through a process of cold-pressing and sintering. The results revealed that the compressive strength, thermal stability, surface roughness, hydrophilicity and surface energy of TPC were significantly enhanced with the increase of TO content. Moreover, apatite mineralization of TPC in simulated body fluid (SBF) was obviously improved, in which TPC with TO of 50 wt% content (TPC50) displayed the best bioactivity. Furthermore, the cellular responses (adhesion, proliferation and differentiation) of rat bone mesenchymal stem cells (rBMSCs) to TPC were obviously upregulated with the increase of TO content. The results demonstrated that the TO content in the composites remarkably affected not only physical-chemical properties but also the cells behaviors. It can be suggested that TPC50 with improved surface properties and bioactivity as well as good cytocompatibility would have great potential and prospect for dental and orthopedic applications.

We present a method to fabricate diffractive optical elements (DOEs) with four phase levels by the Laser Direct Writing technology. One computation method is provided to optimize the step depth, which could improve efficiency of DOEs. The step depth and imaging results demonstrate the fabricated DOEs devices with good optical properties. The effective areas of the DOEs pattern are as large as 49 cm2, which could be replicated easily for mass production applications.