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Nanoscale self-assembly, as a technique to transform two-dimensional (2D) planar patterns into three-dimensional (3D) nanoscale architectures, has achieved tremendous success in the past decade. However, an assembly process at nanoscale is easily affected by small unavoidable variations in sample conditions and reaction environment, resulting in a low yield. Recently, in-situ monitored self-assembly based on ion and electron irradiation has stood out as a promising candidate to overcome this limitation. The usage of ion and electron beam allows stress generation and real-time observation simultaneously, which significantly enhances the controllability of self-assembly. This enables the realization of various complex 3D nanostructures with a high yield. The additional dimension of the self-assembled 3D nanostructures opens the possibility to explore novel properties that cannot be demonstrated in 2D planar patterns. Here, we present a rapid review on the recent achievements and challenges in nanoscale self-assembly using electron and ion beam techniques, followed by a discussion of the novel optical properties achieved in the self-assembled 3D nanostructures.

Plasmonic sensors are commonly defined on two-dimensional (2D) surfaces with an enhanced electromagnetic field only near the surface, which requires precise positioning of the targeted molecules within hotspots. To address this challenge, we realize segmented nanocylinders that incorporate plasmonic (1-50 nm) gaps within three-dimensional (3D) nanostructures (nanocylinders) using electron irradiation triggered self-assembly. The 3D structures allow desired plasmonic patterns on their inner cylindrical walls forming the nanofluidic channels. The nanocylinders bridge nanoplasmonics and nanofluidics by achieving electromagnetic field enhancement and fluid confinement simultaneously. This hybrid system enables rapid diffusion of targeted species to the larger spatial hotspots in the 3D plasmonic structures, leading to enhanced interactions that contribute to a higher sensitivity. This concept has been demonstrated by characterizing an optical response of the 3D plasmonic nanostructures using surface-enhanced Raman spectroscopy (SERS), which shows enhancement over a 22 times higher intensity for hemoglobin fingerprints with nanocylinders compared to 2D nanostructures.

Conjugated polymers have recently been under active investigation as promising alternatives to traditional inorganic semiconductors for photocatalysis. This is due to their unique advantages of low cost, high chemical stability, and molecularly tunable optoelectronic properties. This critical review summarizes the recent advancements in π-conjugated polymers for visible-light-driven photocatalytic applications including water splitting, CO2 reduction, organic transformation and degradation of organic dyes. Special emphasis is placed on how the changes in the polymer structure could influence their physicochemical properties and photocatalytic activities. This structure–activity relationship analysis should guide rational molecular design of conjugated polymers for improved photocatalytic activity.

A gradient cobalt-doped MgIn2S4 (MgIn2S4-Co) homojunction photocatalyst was reported, creating an oriented built-in electric field for efficient extraction of photogenerated carriers from the inside to the surface of the photocatalyst. The MgIn2S4-Co photocatalysts showed remarkably enhanced photocatalytic CO2 reduction activity compared with pristine MgIn2S4.

Reversible self-assembly that allows materials to switch between structural configurations has triggered innovation in various applications, especially for reconfigurable devices and robotics. However, reversible motion with nanoscale controllability remains challenging. This paper introduces a reversible self-assembly using stress generated by electron irradiation triggered degradation (shrinkage) of a single polymer layer. The peak position of the absorbed energy along the depth of a polymer layer can be modified by tuning the electron energy; the peak absorption location controls the position of the shrinkage generating stress along the depth of the polymer layer. The stress gradient can shift between the top and bottom surface of the polymer by repeatedly tuning the irradiation location at the nanoscale and the electron beam voltage, resulting in reversible motion. This reversible self-assembly process paves the path for the innovation of small-scale machines and reconfigurable functional devices.

Current graphene-based plasmonic devices are restricted to 2D patterns defined on planar substrates; thus, they suffer from spatially limited 2D plasmon fields. Here, 3D graphene forming freestanding nanocylinders realized by a plasma-triggered self-assembly process are introduced. The graphene-based nanocylinders induce hybridized edge (in-plane) and radial (out-of-plane) coupled 3D plasmon modes stemming from their curvature, resulting in a four orders of magnitude stronger field at the openings of the cylinders than in rectangular 2D graphene ribbons. For the characterization of the 3D plasmon modes, synchrotron nanospectroscopy measurements are performed, which provides the evidence of preservation of the hybridized 3D graphene plasmons in the high precision curved nanocylinders. The distinct 3D modes introduced in this paper, provide an insight into geometry-dependent 3D coupled plasmon modes and their ability to achieve non-surface-limited (volumetric) field enhancements.

Organic π-conjugated polymers (CPs) have been intensively explored for a variety of critical photocatalytic applications in the past few years. Nevertheless, CPs for efficient CO2 photoreduction have been rarely reported, which is mainly due to the lack of suitable polymers with sufficient solar light harvesting ability, appropriate energy level alignment and good activity and selectivity in multi-electron-transfer photoreduction of CO2 reaction. We report here the rational design and synthesis of two novel triphenylamine (TPA) based conjugated microporous polymers (CMPs), which can efficiently catalyze the reduction of CO2 to CO using water vapor as an electron donor under ambient conditions without adding any co-catalyst. Nearly 100% selectivity and a high CO production rate of 37.15 μmol h−1 g−1 are obtained for OXD-TPA, which is significantly better than that for BP-TPA (0.9 μmol h−1 g−1) as a result of co-monomer change from biphenyl to 2,5-diphenyl-1,3,4-oxadiazole. This difference could be mainly ascribed to the synergistic effect of a decreased optical band gap, improved interface charge transfer and increased CO2 uptake for OXD-TPA. This contribution is expected to spur further interest in the rational design of porous conjugated polymers for CO2 photoreduction. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version

Three new boron ketoiminate-based conjugated polymers P1, P2, and P3 were designed and synthesized through the Sonogashira coupling reaction of 4,6-bis(4-bromophenyl)-2,2-difluoro-3-phenyl-2H-1,3,2-oxazaborinin-3-ium-2-uide (M1) with 1,4-diethynyl-2,5-bis(octyloxy)benzene (M2), 3,6-diethynyl-9-octyl-9H-carbazole (M3) and 3,7-diethynyl-10-octyl-10H-phenothiazine-S,S-dioxide (M4), respectively. All the resulting polymers showed obvious aggregation-induced emission (AIE) behaviours. Interestingly, it was found that a great difference in the electron-donating abilities of the D–A type polymer linkers can lead to the unique AIE behaviour of the alternating polymers in the aggregate state, which provides us with a practical strategy to design tunable AIE-active conjugated polymers. Most importantly, studies on MCF-7 breast cancer cell imaging revealed that the nanoparticles fabricated from the conjugated polymers could serve as promising fluorescent probes with low cytotoxicity and high photostability.

The ability to transform two-dimensional (2D) materials into a three-dimensional (3D) structure while preserving their unique inherent properties might offer great enticing opportunities in the development of diverse applications for next generation micro/nanodevices. Here, a self-assembly process is introduced for building free-standing 3D, micro/nanoscale, hollow, polyhedral structures configured with a few layers of graphene-based materials: graphene and graphene oxide. The 3D structures have been further modified with surface patterning, realized through the inclusion of metal patterns on their 3D surfaces. The 3D geometry leads to a nontrivial spatial distribution of strong electric fields (volumetric light confinement) induced by 3D plasmon hybridization on the surface of the graphene forming the 3D structures. Due to coupling in all directions, resulting in 3D plasmon hybridization, the 3D closed box graphene generates a highly confined electric field within as well as outside of the cubes. Moreover, since the uniform coupling reduces the decay of the field enhancement away from the surface, the confined electric field inside of the 3D structure shows two orders of magnitude higher than that of 2D graphene before transformation into the 3D structure. Therefore, these structures might be used for detection of target substances (not limited to only the graphene surfaces, but using the entire volume formed by the 3D graphene-based structure) in sensor applications.

A series of Sn2+ doped MgIn2S4 photocatalysts were prepared via a facial hydrothermal method. The Sn dopants substitute the sites of Mg atom in MgIn2S4 unit cell, but not alter the crystal structure, demonstrated by the results of XRD and XPS. Compared to pristine MgIn2S4, Sn-doped MgIn2S4 samples exhibit significantly enhanced photocatalytic CO2 reduction activity. With increasing the Sn dopant content, the CO2 conversion rate first ascends, achieving the maximum rate at Sn-MgIn2S4-2 sample, and then decreases. After illumination for 4 h, the highest yield of CO and CH4 for Sn-MgIn2S4-2 sample reaches about 3.35 and 3.33 times higher than that of pristine MgIn2S4. The theoretical results based on density functional theory calculations reveal that Sn doping in MgIn2S4 tunes the band structure from the direct-transition of MgIn2S4 to indirect-transition, diminishes band gap and extends the light absorption range, reduces the effective masses of holes and promotes the migration of photoinduced carriers. The experimental results also demonstrate the positive role of Sn dopant in accelerating the separation and transportation of charges, and improving CO2 adsorption ability. This work systematically investigates and discusses the Sn2+ doping effect in MgIn2S4 on crystal structure, lattice variations, electronic band structures, CO2 adsorption ability, and photocatalytic CO2 reduction activity, which can provide a new hint for the fabrication of efficient photocatalyst by metal ion doping.

The numerical simulation analysis of the fluid-solid coupling of the ship’s boring water-lubricated bearing is carried out to study the influence law of the inclination and eccentricity of the rotating shaft on the pressure distribution and fluid flow state in the bearing. The results show that the tilt of the rotating shaft changes the shape of the inner flow passage of the water-lubricated bearing, resulting in unstable flow in the bearing. When rotating shaft is in normal, the pressure value in the water-lubricated bearing decreases first and then increases in the axial direction. However, after the rotation of the shaft is tilted, the change of the pressure value is the opposite; the stress of the rubber layer generally shows an increasing trend with the increase of the inclination angle.

Convert inert CO2 into chemical fuel via photocatalytic reduction is very intriguing. However, high charge recombination rate and inadequate CO2 absorption severely impede photocatalytic CO2 reduction activity. To address these drawbacks, we developed a strategy of MgIn2S4 modification by carbon. Two types of photocatalysts with carbon modifications, carbon-coated MgIn2S4 (MgIn2S4-SC); carbon coating and doping MgIn2S4 (MgIn2S4-Cx), were obtained and exhibited significantly enhanced catalytic activity. The CO evolution rate of MgIn2S4-C2 and MgIn2S4-SC reached 19.5 and 7.03 times higher than that of unmodified MgIn2S4, respectively. Our experimental and theoretical results disclosed that doped carbon for MgIn2S4 could prevent charge recombination in the bulk, facilitate CO2 adsorption, and decrease photocatalytic reaction energy barrier, while coated carbon could accelerate surface carrier migration, but had smaller and greater effect on fascinating CO2 adsorption and decreasing reaction energy barrier. The synergistic effect of surface coated and bulk doped carbon could maximize the photocatalysis efficiency.

Photoelectrochemical water splitting over semiconductors offers a sustainable solar light conversion technique capable of alleviating worldwide energy crisis. Conjugated polymers have recently received increasing attention as a class of promising photoelectrode materials due to their advantages of earth-abundance, non-toxicity, light weight, and molecularly tunable functionalities, etc. However, the development of highly efficient organic photoelectrodes remains a big challenge. In this study, two covalent organic frameworks (COFs) incorporated 2,4,6-triphenyl-1,3,5-triazine are demonstrated as excellent photocathodes for H production. By introducing 2,4,6-triphenylbenene to properly create donor/acceptor pairs within COF, a significantly enhanced visible-light photocurrent of TAPB-TTB COF (110 µA cm ) compared to TTA-TTB COF (35 µA cm ) at 0 V versus reversible hydrogen electrode (RHE) is obtained without adding organic sacrificial agent and metal cocatalysts (>420 nm). The enhanced photocurrent density is attributed to the narrowed bandgap and improved charge transfer by intramolecular donor–acceptor combination. This work highlights the great promising applications of crystalline donor–acceptor COFs as high-efficiency organic photoelectrode for water splitting. Ministry of Education (MOE) National Research Foundation (NRF) Accepted version Financial work was provided by the Singapore National Research Foundation (grant no. R279-000-444-281), the National 11 University of Singapore (grant no. R279-000-482-133), Research Foundation for Advanced Talents of East China University of Technology (No. DHBK201927), National Science Foundation for Young Scientists of China (grant no. 21905122), National Science Foundation of Jiangxi province of China (No. 20202BAB203007). D. J. acknowledges supports by MOE tier 1 grant (R-143-000-A71-114) and NUS start-up grant (R-143-000-A28-133). C. X. thanks the support from the Ministry of Education, Singapore, under AcRF-Tier2 (MOE2018-T2-1- 017) and AcRF-Tier1 (MOE2019-T1-002-012, RG102/19).

Binary metal oxides have been considered as promising anode materials, which exhibit much better performances than single metal oxides in view of their variable oxidation state and fairly high electrical conductivity. In this research, NiCo2O4 nanocrystals are prepared from a facile procedure including microemulsion-solvothermal reaction and subsequent calcination at 400 °C for 4 hours. The as-prepared NiCo2O4 nanocrystals are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). When applied as an anode for a lithium ion battery, it demonstrates excellent cycling and rate stability. The initial charge/discharge efficiency is as high as 75.41% at a current density of 100 mA g−1. After 45 cycles, the discharge capacity still retains up to 1175.9 mA h g−1, which is even much higher than that of the initial discharge capacity. Meanwhile, the reversible capacity remains over 644.9 mA h g−1 at a large current density of 1600 mA g−1, ascribed to the dispersed nanoparticles, which will help to improve the conductivity of the electrode material during the lithium-ion insertion/deintercalation process, shorten the ion diffusion path and reduce the charge transfer resistance (Rct).

This paper presents a double-tube once-through steam generator (DOTSG), whose tube unit includes an outer straight tube and an inner helical tube, in an integral pressurized water reactor (IPWR). To obtain the optimum structure of the inner helical tube and the arrangement of DOTSGs in the reactor pressure vessel, a two-level optimization method is used, aiming at the lower pumping power needed, and a smaller reactor pressure vessel volume is used. The pitch of inner helical tubes and the central distance of outer tubes are considered design parameters when minimizing the pumping power with the genetic algorithm in the bottom level, while the number of tube units in a single DOTSG and the number of DOTSGs in the reactor pressure vessel (RPV) are optimized to obtain the minimum volume of the IPWR, which is conducted in the top level. The optimum pitch of the helical tube varies in the sub-cooled region, boiling region and superheated region. The results show that the smaller pitch brings a shorter tube length and a higher pressure drop, and the effects are strong in the sub-cooled region and the superheated region but weak in the boiling region. In this way, the optimal structure of the inner helical tube is a small pitch in the single-phase region and a large pitch in the boiling region. According to the bottom level results, the optimum arrangement of DOTSGs in the pressure vessel is determined.

The limited spatial coverage of the plasmon enhanced near-field in 2D graphene ribbons presents a major hurdle in practical applications. In this study, diverse self-assembled 3D graphene architectures are explored that induce hybridized plasmon modes by simultaneous in-plane and out-of-plane coupling to overcome the limited coverage in 2D ribbons. While 2D graphene can only demonstrate in-plane, bidirectional coupling through the edges, 3D architectures benefit from fully symmetric 360° coupling at the apex of pyramidal graphene, orthogonal four-directional coupling in cubic graphene, and uniform cross-sectional radial coupling in tubular graphene. The 3D coupled vertices, edges, surfaces, and volume induce corresponding enhancement modes that are highly dependent on the shape and dimensions comprising the 3D geometries. The hybridized modes introduced through the 3D coupling amplify the limited plasmon response in 2D ribbons to deliver nondiffusion limited sensors, high efficiency fuel cells, and extreme propagation length optical interconnects.

Pre-treatment of graphitic carbon nitride (GCN) with H2O2 introduces active C–OH groups that can react with HAuCl4 to immobilize single atom Au(I) in the GCN matrix through creating robust Au(I)–O coordination bonds. This strong bonding can effectively restrict the diffusion of intermediate Au(0) towards the formation of Au particles during the photocatalytic hydrogen evolution process. As such, the single atom Au(I) incorporated GCN maintained superior activities with excellent stabilities for photocatalytic hydrogen generation. Accepted version

Conjugated polymer-based photocatalysts have shown great potential in H2 production via water splitting, but an intrinsic drawback of conventional hydrophobic polymer photocatalysts is their poor wettability and relatively large particle size in aqueous media, which is favorable for charge recombination with limited interfacial reaction efficiency. Herein, a well-dispersed organic water reduction system using cationic conjugated polyelectrolyte as the photocatalyst has been reported for the first time. In comparison to a model polymer (PFBT) bearing the same conjugated backbone, the polyelectrolyte exhibits significantly enhanced photocatalytic efficiency due to the extended light absorption and improved charge separation of the polymer aggregates. Ministry of Education (MOE) National Research Foundation (NRF) Accepted version This work was financially supported by the Singapore National Research Foundation (R279-000-444-281 and R279-000-483-281), National Univer- sity of Singapore (R279-000-482-133), Singapore MOE AcRF-Tier1 (RG 12/15), Singapore MOE AcRF-Tier1 (2016-T1-002-087, RG 120/16), and AcRF-Tier2 (MOE2016-T2-2-056).

The assembly of two-dimensional (2D) graphene into three-dimensional (3D) polyhedral structures while preserving the graphene's excellent inherent properties has been of great interest for the development of novel device applications. Here, fabrication of 3D, microscale, hollow polyhedrons (cubes) consisting of a few layers of 2D graphene or graphene oxide sheets via an origami-like self-folding process is described. This method involves the use of polymer frames and hinges, and aluminum oxide/chromium protection layers that reduce tensile, spatial, and surface tension stresses on the graphene-based membranes when the 2D nets are transformed into 3D cubes. The process offers control of the size and shape of the structures as well as parallel production. In addition, this approach allows the creation of surface modifications by metal patterning on each face of the 3D cubes. Raman spectroscopy studies show the method allows the preservation of the intrinsic properties of the graphene-based membranes, demonstrating the robustness of our method.

Thermal reflow of polymers is a well-established phenomenon that has been used in various microfabrication processes. However, present techniques have critical limitations in controlling the various attributes of polymer reflow, such as the position and extent of reflow, especially at the nanoscale. These challenges primarily result from the reflow heat source supplying heat energy to the entire substrate rather than a specific area. In this work, a focused ion beam (FIB) microscope is used to achieve controllable localized heat generation, leading to precise control over the nanoscale polymer reflow. Through the use of the patterning capability of FIB microscopy, dramatically different reflow performances within nanoscale distances of each other are demonstrated in both discrete periodic and continuous polymer structures. Further, we utilize a self-assembly process induced by nanoscale polymer reflow to realize 3D optical devices, specifically, vertically aligned nanoresonators and graphene-based nanocubes. HFSS and Comsol simulations have been carried out to analyze the advantages of the polymer-based 3D metamaterials as opposed to those fabricated with a metallic hinge. The simulation results clearly demonstrate that the polymer hinges have a dual advantage; first, the removal of any interference from the transmission spectrum leading to strong and distinct resonance peaks and, second, the elimination of parasitic leeching of the enhanced field by the metallic hinge resulting in stronger volumetric enhancement. Thus, the 2-fold advantages existing in 3D polymer-hinge optical metamaterials can open pathways for applications in 3D optoelectronic devices and sensors, vibrational molecular spectroscopy, and other nanoscale 3D plasmonic devices.

A conjugated polymer of poly(fluorene-co-benzothiadiazole) (PFBT) was modified by a soft segment of poly(dimethylsiloxane) (PDMS) to yield a copolymer via dynamic imine bonds. The copolymer was casted as a free-standing film, which was intrinsically flexible, stretchable, and showed tunable shape memory, healable and degradable effects.

The Brayton cycle with supercritical carbon (S-CO2) as working medium is one of the most promising new nuclear power systems. Turbine is the key device during the working process in the Brayton power cycle. The turbine structural presents small size and extremely high rotational speed for the special physical properties of S-CO2, which increase the difficulty for the structural design and strength safety significantly. According to the aerodynamic design and optimization results of 200 kW S-CO2 radial inflow turbine, this paper proposes a detail structural design and analysis method for turbine impeller. Based on the three-dimensional blade profile data and meridional planes data, key structural design parameters are chosen and the parametric geometry model is established by CAD tools. On this basis, numerical simulation models of turbine are established to analyze the structural strength in detail. Then the influence of parameters on the turbine impeller strength is studied by a series of finite element numerical procedures. The influence mechanisms of key structural design parameters on impeller strength are discussed. Moreover, the final model of turbine impeller is obtained by parameter comparison and selection. The results show that for the initial model, the maximum von-Mises equivalent stress is 400.10 MPa, the maximum radial deformation is 0.0333 mm and the maximum axial deformation is 0.0770 mm. For the final model, the maximum von-Mises equivalent stress is 294.26 MPa, the maximum radial deformation is 0.0279 mm and the maximum axial deformation is 0.0769 mm. The maximum von-Mises equivalent stress and maximum radial deformation of structural decreases 26.45 % and 16.22 % respectively compared with the initial model. As a result, the impeller structural strength safety margin is obviously improved by the parameter analysis.

Steam submerged jetting is an important process in depressurization tank and condenser deaerator tank of nuclear power plant. As the steam contact the liquid water directly, some complicated behaviors such as strong turbulence and phase transition would happens. Especially when the sub-cooling degree is low, the condensation may cause vigorous pressure pulsation and radiation noise, which not only causes noise damage to workers but also affect the safety of the heat exchanger tubes bundle because of vibration transmission. An experiment is proposed to study the complex evolutionary behavior and vibration and noise characteristics of gas-water two-phase flow. The experimental results show that in the case of low subcooling, the mass flow rate of steam has a great influence on gas plume, and, as the mass flow rate increases, the main contribution frequency of noise is gradually increasing from low frequency to high frequency. The researches in this paper can provide the technical basis for the design of the deoxygenation system of condenser in onshore and ship nuclear power plant.

Three dibenzothiophene-S,S-dioxide-based alternating copolymers were synthesized by facile Suzuki polymerization for visible light-responsive hydrogen production from water (> 420 nm). Without addition of any cocatalyst, FluPh2-SO showed a photocatalytic efficiency of 3.48 mmol h-1 g-1 , while a larger hydrogen evolution rate (HER) of 4.74 mmol h-1 g-1 was achieved for Py-SO, which was ascribed to the improved coplanarity of the polymer that facilitated both intermolecular packing and charge transport. To minimize the possible steric hindrance of FluPh2-SO by replacing 9,9'-diphenylfluorene with fluorene, Flu-SO exhibited a more red-shifted absorption than FluPh2-SO and yielded the highest HER of 5.04 mmol h-1 g-1 . This work highlights the potential of dibenzothiophene-S,S-dioxide as a versatile building block and the rational design strategy for achieving high photocatalytic efficiency. NRF (Natl Research Foundation, S’pore) ASTAR (Agency for Sci., Tech. and Research, S’pore) MOE (Min. of Education, S’pore)

Three conjugated polymers (CPs) bearing a common fluorene-dibenzothiophene-S,S-dioxide backbone were designed and synthesized for photoelectrochemical (PEC) water oxidation upon visible-light irradiation (>420 nm). Without the assistance of additional sacrificial agents or co-catalysts, a good photocurrent response of 4.1 μA cm−2 at +0.6 V (vs. Ag/AgCl) was achieved through facile molecular modulation of the polymer, which improved the uniformity and crystallinity of the film and facilitated charge transport among polymer chains. Moreover, C12 was used for preparation of a composite film with TiO2 nanorod arrays via spin-coating to yield an approximately 11-fold higher anodic PEC activity than that of pure TiO2. Our results demonstrated the great potential of solution-processable conjugated polymers for facile construction of highly efficient PEC devices for water splitting. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore)

In this study, four boron ketoiminate-based conjugated polymers P1–P4 are designed and synthesized via Suzuki polymerization. The resulting polymers are weakly fluorescent in pure THF solutions, but become highly emissive when aggregated in THF/water mixtures or fabricated into conjugated polymer nanoparticles (CPNs), showing typical AIE (AIEE) behaviors. CPNs from P1–P4 could be prepared by reprecipitation with the particle size ranging from 85 to 95 nm. Interestingly, the tuning of the emission color of P1–P4 nanoparticles (NPs) could be conveniently accomplished by varying the substituent in the phenyl ring, which can be ascribed to the donor–acceptor interaction between the substituted phenyl ring and the boron chelating ring. The DFT theoretical calculation of the polymer repeating units indicates that the band gaps of P1–P4 can be tuned in the range 2.72–3.40 eV, suggesting that substituents in the polymer backbone have a great influence on their electronic structures and thus change AIE (AIEE) properties. Furthermore, all of the four CPNs with low cytotoxicity and high photostability could be further employed for HeLa cell imaging.

A novel chiral conjugated polymer is developed and used for the preparation of conjugated polymer nanoparticles (CPNs) with particle sizes ranging from 80 to 190 nm. The size-dependent optical properties of chiral CPNs are fully studied and it was found that the nanoparticles exhibited a prominent red shift both in UV-vis and fluorescence emission with increasing diameters. The circular dichroism (CD) spectra and anisotropy r values of the CPNs display size-tunable chirality features, which can be attributed to the nature of the aggregates as nanoparticles grow. Meanwhile, the obtained CPNs can serve as efficient far-red/near-infrared (FR/NIR) fluorescent probes with low cytotoxicity and high photostability for HeLa cell imaging.

The special fluid flow and heat transfer characteristics of supercritical CO2 in a horizontal double-pipe heat exchanger have been numerically investigated. The AKN k-epsilon model was selected to model the turbulent flow and heat transfer of supercritical fluid. In conjugate heat transfer process, there exists obvious heat transfer deterioration on the top wall for horizontal flow. The region of heat transfer deterioration expands with the increased GShell or TShell,0, and the influence of TShell,0 on conjugate heat transfer is greater than that of GShell. The high-temperature fluid will gather near the top region. The intensity and position of the secondary flow can represent the turbulence heat transfer. When the supercritical fluid temperature is much higher than Tpc, buoyancy force can be omitted, but it can not been neglected even under relatively high mass flux.

A novel conjugated polymer (PDBDBM) was developed by the polymerization of 1,4-dioctyloxy-2,5-diethynylbenzene with 1,3-bis(4-bromophenyl)propane-1,3-dione based on Pd-catalyzed Sonogashira-coupling reaction. The obtained polymer PDBDBM exhibited bright green photoluminescence under UV irradiation. According to the metal ion titration experiments, PDBDBM showed high sensitivity and selectivity for detection of Cu2+ and Fe3+ over other metal ions. The fluorescent detection limits of PDBDBM were calculated to be 5 nM for Cu2+ and 0.4 μM for Fe3+ and the Stern–Volmer quenching constant for Cu2+ and Fe3+ were found to be 1.28 × 108 M−1 and 2.40 × 104 M−1, respectively. These results indicated that the polymer can be used as a potential probe for Cu2+ and Fe3+ detection.

THIS ARTICLE FOCUSES ON a ?microsized microbial solar cell (MSC) that can produce sustainable energy through photosynthetic reactions of cyanobacteria Synechocystis PCC 6803 in the anode. The MSC has 57-?L anode/cathode chambers defined by laser-machined poly(methyl methacrylate) (PMMA) substrates. We obtained a maximum power density of 7.09 nW/cm2, which is 170 times more power than previously reported microelectromechanical system (MEMS) MSCs. The importance of the light intensity was demonstrated by the higher values of generated current during the day than at night, indicating light-dependent photosynthetic processes. Considering that sunlight offers an ?unlimited source of energy, the development of self-sustainable MSCs that rely on light as an energy source will become an increasingly important area of research in the future. In accordance with the MSC, we developed a photosynthetic cathode-based microbial fuel cell (MFC), showing that the use of cyanobacteria can be useful as well as efficient and sustainable catalysts for the cathode since they act as oxygenators.

We present a double-tube once-through steam generator (DOTSG) with an outer straight tube and an inner helical tube in this paper. For the purpose of the compact structure and lower pressure drop, the inner helical tube is optimized. The tube length and the combined pressure drop are considered as the two objective functions, and the pitch of the inner helical tube is considered as a design parameter. The multi-objective optimization model is established and translated into a single-objective function by objective product method (OPM). The single-objective function is optimized by fmincon routine in Matlab. The optimal pitches of the helical tube vary in sub-cooled region, boiling region and superheated region. The results show that the smaller pitch brings shorter tube length and higher pressure drop, and the effects are strong in sub-cooled region and superheated region, but weak in the boiling region.

A microbial biosensor is an analytical device that immobilizes microorganisms onto a transducer for the detection of target analytes. With the development of nanotechnology, nanomaterials have been used to achieve better immobilization for developing a more reliable and selective microbial biosensor. Also, significant progress has been made in the development of transducer technology leading to higher sensitivity. Microbial biosensors have become one of the most useful means of monitoring environmental, food and clinical samples. In this review, we focus on the newly developed technologies and applications of microbial biosensors in recent years.

Grain coalescence has been applied in many areas of nanofabrication technology, including modification of thin-film properties, nanowelding, and self-assembly of nanostructures. However, very few systematic studies of self-assembly using the grain coalescence, especially for three-dimensional (3D) nanostructures, exist at present. Here, we investigate the mechanism of plasma triggered grain coalescence to achieve the precise control of nanoscale phase and morphology of the grain coalescence induced by exothermic energy. Exothermic energy is generated through etching a silicon substrate via application of plasma. By tuning the plasma power and the flow rates of reactive gases, different etching rates and profiles can be achieved, resulting in various morphologies of grain coalescence. Balancing the isotropic/anisotropic substrate etching profile and the etching rate makes it possible to simultaneously release 2D nanostructures from the substrate and induce enough surface tension force, generated by grain coalescence, to form 3D nanostructures. Diverse morphologies of 3D nanostructures have been obtained by the grain coalescence, and a strategy to achieve self-assembly, resulting in desired 3D nanostructures, has been proposed and demonstrated.

The special fluid flow and heat transfer characteristics of supercritical CO2 in a vertical annular channel have been numerically investigated. The AKN k-ε model was selected to model the turbulent flow and heat transfer of supercritical fluid. The three heating types were individual outer-wall heating, simultaneous outer/inner walls heating and outer-wall heating (inner-wall cooling) separately. The local heat transfer coefficients were obtained to investigate the influence of inner-wall thermal boundary conditions, supercritical fluid mass flux, fluid temperature and flow direction on outer-wall heat transfer phenomenon. The mechanisms of abnormal heat transfer and primary influence factors were analyzed by the detailed information on the flow, turbulence and thermal fields. When the supercritical fluid is in the large-property-variation (LPV) region and flows upward, the inner-wall thermal boundary condition obviously affects the heat transfer characteristics of outer wall. When supercritical fluid flows downward, the inner-wall boundary condition hardly affects the heat transfer phenomena of outer wall. The increase of inner-wall heating heat flux will result in the larger deterioration region and heat transfer decline on outer wall when the other conditions remain unchanged. When the heat transfer deterioration also appears on the inner wall with the increase in the inner-wall heat flux, the outer-wall heat transfer no longer decreases, but the deterioration region abruptly increases. However, as inner-wall cooling heat flux increases, the heat transfer deterioration phenomenon on outer wall will weaken gradually.

The boiling vapor-liquid flow at the shell side of shell-and-tube heat exchangers was simulated by Euler-Euler transient 3D method in this paper. The mass and heat transfers between the two-phase fluid and heated wall for the subcooled boiling phenomenon were described by the Rensselaer Polytechnic Institute model (RPI model), while the steam condensation within the subcooled liquid was described by the Lee model. Firstly, different turbulence and interfacial force models were evaluated by comparing with the experimental data of Bartolomej (1982). It was found that the turbulence models have minor influence on the temperature and vapor volume fraction distributions. As the bubble size in the subcooled boiling process is small (usually

The self-assembly of 3D nanostructures is a promising technology for the fabrication of next generation nanodevices and the exploration of novel phenomena. However, the present techniques for assembly of 3D nanostructures are invisible and have to be done without physical contact, which bring great challenges in controlling the shapes with nanoscale precision. This situation leads to an extremely low yield of self-assembly, especially in 3D nanostructures built with metal and semiconductor materials. Here, an in situ self-assembly process using a focused ion beam (FIB) microscopy system has been demonstrated to realize 3D polyhedral nanostructures from 2D multiple pieces. An excited ion beam in the FIB microscopy system offers not only a visualization of the nanoscale self-assembly process but also the necessary energy for inducing the process. Because the beam energy that induces the self-assembly can be precisely adjusted while monitoring the status of the self-assembly, it is possible to control the self-assembly process with sub-10 nm scale precision, resulting in the realization of diverse 3D nanoarchitectures with a high yield. This approach will lead to state-of-the-art applications utilizing properties of 3D nanostructures in diverse fields.

The fuel height, rod diameter, pitch, and the loading pattern are all important parameters in the reactor core design process. Based on the analysis of the core performance, optimization calculation is performed on the three objective functions of ABV-6M reactor, i.e., power density, coolant temperature difference between the inlet and outlet, and flow-induced vibration are proposed for optimization calculation. Then a multi-objective problem (MOP) model is applied and computed optimally by non-dominated sorting genetic algorithm (NSGA-II) with the aim of maximizing power density and temperature difference as well as minimizing the flow-induced vibration. The results of optimal designs called ‘Pareto-optimal solutions’ are a set of multiple optimum solutions, from which the final optimization can be chosen after sensitivity analysis is performed. On the basis of lattice parameters optimization, the radial one-dimensional fuel loading pattern was optimized for achieving the optimum fuel utilization. The typical optimum design considered to be safe in a verification check showed that tight lattice effectively improved the reactor performances and saved the fuel consumption.

We report a nine-well MEMS-based parallel analyses platform for testing electricity generation capacity of eight microbial consortia, which provides high throughput characteristics for bacterial electrogenic screening. The presented device features independent fluidic access to each analysis unit allowing for long term analysis ability without contamination from chamber to chamber during operation. The device contains vertically stacked 57μL anode/cathode chambers separated by a proton exchange membrane (PEM) and each device component is thermally assembled without mechanical supporting frames/bolts/nuts. This device will create a compact screening system individually addressable for identification and characterization of electrochemically active microbes.

Integration of electrochemical analytical functionality into a micro-sized microbial fuel cell is demonstrated. Screen-printed carbon ink based working (anode) and counter (cathode) electrodes and Ag/AgCl ink based reference electrode were deployed for sensing. Using such three-electrode configuration, in-situ cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were successfully performed to study the behavior of microbial electron transfer at the anode and to evaluate electrochemical properties of the MFC. In this work, coupling of electrochemical studies to the MFC platform has provided valuable information leading to a quantitative understanding of bacterial redox potential mass transport and the electrode/bacteria electron transfer kinetics.

We report a microfabricated paper-based bacteria-powered battery generating 10 μW/cm 2 . Only four batteries connected in series provided desired values of current and potential to power an LED for more than 30 minutes without power management interface circuits. The battery features (i) a low-cost paper-based proton exchange membrane directly patterned on commercially available parchment paper with laser treatment and (ii) paper reservoirs for holding the anolyte and the catholyte for extended period of time. Since sewage or soiled water in a puddle can become an excellent source for extracting bioelectricity through bacterial metabolism, this paper-based bacteria-powered battery is expected to be a simple, low-cost, and easy-to-use power source for single-use paper-based diagnostic devices in resource-limited settings.

We report a micro-sized microbial solar cell (MSC) that can produce sustainable energy through photosynthetic reactions of cyanobacteria, Synechocystis PCC 6803 in the anode. The MSC has 57-μL anode/cathode chambers defined by laser-machined poly(methyl methacrylate) (PMMA) substrates. We obtained a maximum power density of 7.09 nW/cm 2 which is one hundred seventy times more power than previously reported MEMS MSCs. The importance of the light intensity was demonstrated by the higher values of generated current during daytimes than those through the nights, indicating light-dependent photosynthetic processes. Considering that sunlight offers an unlimited source of energy, development of self-sustainable MSCs that rely on light as an energy source will become an increasingly important area of research in the future. In accordance with the MSC, we developed a photosynthetic cathode-based microbial fuel cell (MFC) showing that the use of cyanobacteria can be useful as well as efficient and sustainable catalysts for the cathode since they act as oxygenators.

This paper presents a double-tube once-through steam generator (DOTSG) consisting of the outer straight tube and the inner helical tube. The tube length and pressure drop of are important parameters in optimal design of DOTSG. For optimal design of such a system, it was modeled to estimate its tube length and pressure drop. Pitch of inner helical tube, flow distribution ratio of the primary fluid, and tube assemblage are considered as design parameters. Then fast and elitist nondominated sorting genetic algorithm-II (NSGA-II) method was applied to find the optimum values of design parameters. In the presented optimal design approach, the tube length and the total pressure drop are two objective functions. The results of optimal designs were a set of multiple optimum solutions, called “Pareto optimal solutions.” The sensitivity analysis of change in optimum tube length and pressure drop with change in design parameters of the DOTSG is also performed and the results are reported.

The OTSG (Once-Through Steam Generator) is usually used in the integral nuclear power equipment which requires smaller size and better effect of heat transfer. The OTSG with double-side heat transfer component is presented in this paper. The heat transfer component is composed of straight tube outside and helix tube inside. In the both sides of the helix tube, the flow is spirally, therefore, the heat transfer is enhanced. The smaller the pitch, the stronger the spirally flow, the effect of heat transfer is better, but the flow resistance is raised. Especially the increased flow resistance in the secondary side brings a great influence to the pump. The heat transfer region of the secondary fluid are divided into three regions: sub-cooled region, boiling region, and superheated region, the effects of heat transfer induced by the spirally flow vary in different regions. Thus, there is an optimization problem which is to find an optimization pitch of the inner helix tube with the best effect of heat transfer and the minimum flow resistance. Based on analyzing the effects of the pitch on heat transfer enhancement and flow resistance, the pitch is optimized by the constrained nonlinear optimization method.Copyright © 2010 by ASME