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Biomaterial-associated infections caused by pathogenic bacteria have important implications on human health. This study presents the design and preparation of a smart surface with pH-responsive wettability. The smart surface exhibited synergistic antibacterial function, with high liquid repellency against bacterial adhesion and highly effective bactericidal activity. The wettability of the surface can switch reversibly between superhydrophobicity and hydrophobicity in response to pH; this controls bacterial adhesion and release. Besides, the deposited silver nanoparticles of the surface were also responsible for bacterial inhibition. Benefiting from the excellent liquid repellency, the surface could highly resist bacterial adhesion after immersing in a bacterial suspension for 10 s (85%) and 1 h (71%). Adhered bacteria can be easily eliminated using deposited silver nanoparticles during the subsequent treatment of alkaline bacterial suspension, and the ratio of deactivated bacteria was above 75%. After the pH returned to neutral, the deactivated bacteria can be easily released from the surface. This antibacterial surface showed an improved bacterial removal efficiency of about 99%. The results shed light on future antibacterial applications of the smart surface combining both bactericidal and adhesion-resistant functionalities.

The ZnO-ZrO2 nanocompsite materials in the molar ratio (1:0; 1:1; 1:2; 2:1; 3:4; 4:3; 0:1) were prepared by a two-stage precipitation method with ultrasonic vibrations. The obtained ZnO-ZrO2 materials were characterized by XRD, SEM, UV-vis. XRD data identified phase of the ZnO and phase of ZrO2 in all obtained samples. The average crystallite size of the samples was between 18 to 30 nm. As UV-Vis spectra, the band gap of ZnO-ZrO2 composite (ZZ34R) is 3,06eV. The photocatalytic reactions confirmed that the nanocomposite sample showed higher photocatalytic activity than the pure oxides samples for the degradation phenol under 100W incandescent lamp. Among the prepared samples, the best sample for photocatalytic degration of phenol is the ZZ34R which the molar ratio ZnO:ZrO2 = 3:4 with 23% remaining phenol content after 300 minutes. The photodegradation phenol of sample with ultrasonic vibrations is higher than the sample without ultrasonic vibrations. This indicates that the materials are capable of treating phenol in wastewater.

CsPbBr3 perovskite nanocrystals with two different dimensionalities were synthesized at different temperatures and then integrated as optoelectronic transducers into transistor-type photoconversion devices. Postsynthesis transformation was observed for two-dimensional (2D) nanoplatelets, while the transformation was rarely found in 3D nanocubes. At ambient temperature and pressure, neighboring nanoplatelets made facet-to-facet contact and then fused into larger 2D nanoplatelets (2-5 times) without defects. The coalescence of 2D nanoplatelets at the ambient condition lowered the density of defects at the surface of the nanocrystals and thus could facilitate effective and stable photoconversion behavior in the nanocrystal film integrated into the device. Consequently, the ambient-condition aging of 2D nanoplatelets on device substrate led to 3 times higher retention in photoconversion performance. Importantly, these results provide a new concept of how perovskite nanocrystals can be integrated into a device for enhanced stability in device performance.

A combination of biomass-derived activated carbon and nano-carbonaceous materials has been considered as a sustainable approach to developing the highly electro-adsorptive electrode for desalination by capacitive deionization (CDI) technology. These composites can propose many enormous advantages such as non-toxicity, eco-friendly, high conductivity, and scalability. This work aimed to fabricate the composite coconut-shell-derived activated carbon/carbon nanotubes electrode with low CNTs content (1 wt%) for desalination. The nitrogen adsorption/desorption demonstrates the decrease of surface area of AC/CNTs-1% composite as compared to AC-pristine due to the blocking of micropores of AC. The SEM images evidenced good connection between CNTs and AC particles, where the fibrils of CNTs were featured as the electrical bridges to improve the electron transfer between the AC particles in the electrode structure. Comparison of the CDI performance of AC/CNTs-1% composite electrode in two regimes (batch mode and single-pass mode) in Ragone plot showed that the single-pass mode provided the essential factors of salt absorption capacity and average salt adsorption rate which shifted toward much upper and right regions, indicating the superior desalination performance. At the operation of 1.2 V, the batch mode and single-pass mode can deliver the salt absorption capacity of 10.93 mg g−1 and 11.97 mg g−1, respectively. The durability test of our CDI system in single-pass mode showed a stable performance on 100 cycles with the energy consumption of 0.284 kWh m−3 which is suitable for large-scale CDI applications using the renewable energy sources.

As a result of frequent food waste and environmental pollution, there has been an increasing demand for the development of packaging materials that intrinsically inhibit and reduce likelihood of non-Newtonian liquids adherence. In this work, inspired from ciliary structures on the leg of water strider, the hierarchical conical array was formed by magnetic field control and laser etching without any mask. Due to the tapered geometry of the cones and the multiscale surface roughness of the array, the droplets would bounce many times after impacting with the superhydrophobic surface (SHS) and roll off. By changing the spaces and apex angles of conical microcolumns the SHS has controlled adhesion, superior self-cleaning property and droplets bounce performance for a variety of non-Newtonian viscous liquids. After suffering from various types of damage including repeated tape tearing, finger touch and folding test, the SHS still maintained excellent superhydrophobic property, which may have potential application as all kinds of packaging interface materials. We demonstrate that the excellent droplets bounce behavior of the hierarchical array enables the efficient and robust prevention of food liquids adhesion.

In this work, MgAl2O4 transparent ceramics was fabricated from combustion-synthesized nanopowders by pulsed electric current sintering (PECS) combined with two-step sintering. Ceramic powder was densitified using two-step heating, namely the first-step temperature was 1100 oC with holding time of 60 min and the second-step temperatures in range from 1300 oC to 1450 oC with 20 min duration. The results showed that the transparent ceramic samples sintered at 1100 oC/60 min – 1400 oC/20 min had grain size of 177 ± 8 nm, relative density about 99 %, transmittance up to 80 %, and Vickers hardness of 18 GPa. These values were higher than that of samples obtained by one-step sintering at 1400 oC.

Hybrid composite TiO2/reduced graphene oxide (TiO2/rGO) is considered as a potential photoanode for dye-sensitized solar cells (DSSC) due to their excellent charge transport. This work aimed to prepare the composite TiO2/rGO from TiO2 and GO via a facile reduction step by ascorbic acid and annealing step at 450 °C. Incorporation 1%wt rGO into TiO2 photoanode can boost the overall performance of DSSC with the photocurrent of 13.5 mA/cm2 and the efficiency of 6.1% which is 37% enhanced than the bare TiO2 photoanode. The XPS, Raman spectroscopy and FT–IR results revealed the formation of the chemical bonding titania–carbon in composites TiO2/rGO-1% by ex-situ preparation. The interfacial charge transfer through chemical bonds significantly improves the photoelectrons transport and suppresses the recombination of electron holes in TiO2 structure.

TiO2-Eu2O3 catalyst nanocomposite materials were synthesized from tetra-n-butyl orthotitanate, rare earth oxide Eu2O3 by a sol gel method, with a polyvinyl alcohol gel agent. Characteristic structures and properties were determined by infrared (IR) spectrometry, X-ray diffraction, a scanning electron microscope (SEM), and a transmission electron microscope (TEM). The composition and ingredients of TiO2-Eu2O3 and the Ti/Eu ratio were shown in the XRD diagram and Energy Dispersive X-ray (EDX) fluorescence spectroscopy. The results of testing the photocatalytic properties of the material to treat phenol with a concentration of 10 ppm in water for processing efficiency reached over 90 %. The obtained materials, namely photochemical catalyst materials, can be applied in the field of enviromental treatment, especially photochemical catalytic decomposition catalysts in visible light to treat textile wastewater and organic pollutants in water, as well as bactericidal effects.

We numerically and experimentally investigate single-band and dual-band isotropic metamaterial absorbers (IMAs) based on metallic disks. By optimizing the diameter of the metallic disks and the thickness of the dielectric substrate, the single-band IMA is observed at 16.2 GHz with absorptivity of 97%. When adding one disk-pair to the structure, the dual-band IMA is obtained at 12.8 and 15.5 GHz due to the symmetry breaking. The physical mechanics is explained by near-field coupling effect and equivalent LC circuit model. The measurement results performed in the range 12–18 GHz show a good agreement with simulation and theoretical analysis. Our findings demonstrate a new approach to achieve dual-band and multi-band IMAs.

A platinum-reduced graphene oxide thin film composite (Pt@rGO, 100 nm) was prepared on a fluorine-doped tin oxide- (FTO-) coated glass substrate by a screen printing method using a Pt@rGO screen printing paste (0.12% Pt; Pt/rGO=1.5 w/w). The as-prepared electrode (denoted as Pt@rGO/FTO) was used as the cathode for the assembly of dye-sensitized solar cells (DSSCs). It showed a well-dispersed and high loading of Pt on rGO surface with a particle size distributed around 10 nm. The redox behavior of ferrocene was performed at Pt/FTO, Pt@rGO/FTO, and rGO/FTO electrodes by a cyclic voltammetry (CV) method. The kinetic parameters, in particular, the standard reduction potential (E0, V), the transfer coefficient (α), the heterogeneous rate constant (k0, cm·s-1), and the diffusion coefficient (D, cm2 s-1), were determined by CV data treatment using convolution-deconvolution and fitting methods. The values of E0, α, k0, and D at Pt@rGO/FTO electrode were, respectively, 326 mV, 0.471, 3.33 cm·s-1, and 4.19 cm2·s-1, equivalent to those of Pt/FTO electrode (340 mV, 0.474, 3.18 cm·s-1, and 4.19 cm2·s-1). The Pt@rGO/FTO electrode exhibited excellent electrocatalytic activity compared to that of Pt thin film (Pt/FTO electrode) prepared from Pt commercial paste. The heterogeneous electron transfer rate constant k0 (cm·s-1) for I3-/I- at Pt@rGO/FTO is 1.3 times faster than that at Pt/FTO. The energy conversion efficiency of the DSSCs assembled from Pt@rGO-DSSC cathode reached 7.0%, an increase of 20.7% over the commercial Pt-based cathode (Pt-DSSC, 5.8%). The rGO component in the Pt@rGO composite plays two important roles: (i) facilitating the electron transfer between Pt NPs catalyst and the FTO substrate via the bandgap effect and (ii) the enlargement catalytic surface area of Pt NPs via the loading effect. The rGO material has, therefore, potential to replace the Pt content and improve the performance of the DSSC device.

Understanding the effect of Al doping on CO adsorption at ZnO(100) is crucial for designing a high-performance CO gas sensor. In this work, we investigated the adsorption properties of CO on pristine and Al-doped ZnO(100) by performing DFT+U calculations. It is found that the doping of Al on ZnO(100) induces the semiconductor-to-metal transition and thus enhances the conductance of the substrate. Compared to the pristine ZnO(100), the adsorption energy of CO on the Al-doped surfaces is significantly enhanced since Al doping has the effect of strengthening the adsorption bond. The bonding analysis reveals that CO adsorbs on pristine ZnO(100) via the sole σ-dative donation between the CO HOMO 5σ and the empty states of the Zn cation while π-back donation from filled states of Zn or Al cations to the CO 2π* LUMO is facilitated on the Al-doped surfaces. The π-back donation also results in the red-shift of the CO stretching frequency on the Al-doped surfaces, contrasting to the blue-shift on the pristine surface. The simulated results demonstrate that the doping of Al to a three-fold coordinated site on ZnO(100) is highly beneficial for boosting the performance of the CO gas sensor. Our theoretical investigation provides fundamental insights into the effect of Al doping on the sensing mechanism for CO at the ZnO(100) surface.

The functionalization of nanocarbon materials such as graphene has attracted considerable attention over the past decades. In this work, we designed and synthesized a unique N-heterocyclic carbene compound with a pyrene tail group (NHCp) to investigate how carbene species can be used for the functionalization of graphene. Although the carbene moiety of NHCp has the ability to covalently bond to graphene, the pyrene tail can noncovalently interact with graphene and allows monitoring its surrounding microenvironment. The major characteristics of the resulting nanohybrids were highly dependent on the type of graphene and the NHCp-to-graphene weight ratio. Importantly, despite the covalent functionalization of graphene, an anomalous decrease in the intensity of the Raman D peak and improved conductivity were observed for the nanohybrids. It was found that the covalent bond of NHCp to the graphene edge may allow the hybridization of their orbitals, which affects electronic energy levels and alters the double resonance process that originates the D peak at the edge defect. Importantly, the NHCp compound can act as a π acceptor (not just as a σ donor) via the NHCp-graphene covalent bridge. This is the first report showing that the concept of π-backdonation can be realized in two-dimensional materials, such as graphene, and rationally designed carbene molecules can functionalize graphene without losing their beneficial sp2 hybridization characteristics.

We report on the fabrication and modification of a top-down nanofabrication platform for enormous parallel silicon nanowire-based devices. We explain the nanowire formation in detail, using an additive hybrid lithography step, optimising a reactive ion etching recipe for obtaining smooth and vertical nanowires under a hybrid mask, and embedding the nanowire in a dielectric membrane. The nanowires are used as a sacrificial template, removal of the nanowires forms arrays of well-defined nano-pores with a high surface density. This platform is expected to find applications in many different physical domains, including nanofluidics, (3D) nanoelectronics, as well as nanophotonics. We demonstrate the employment of the platform as field emitter arrays, as well as a state-of-the-art electro-osmotic pump.

Rutting is a key distress taking place in the lifecycle of the asphalt pavement, in particular at high-temperature zone. The dynamic modulus |E*| of an asphalt mixture is extensively utilized as an important index in mechanistic–empirical pavement design and analysis. The objective of this study is to find the correlation with the rutting by Hamburg wheel-tracking test and dynamic modulus test in laboratory. Four types of asphalt mixtures were employed, including (i) SMA mixture produced in Warm Mix Asphalt technology; (ii) Dense-graded HMA mixture produced in Warm Mix Asphalt technology; (iii) SMA mixture produced in Hot Mix Asphalt technology; (iv) Dense-graded HMA mixture produced in Hot Mix Asphalt technology. The results showed that the high correlation coefficient was obtained between the rutting depth (40,000 passes, at 50 °C) and dynamic modulus |E*| at 45 °C, 10 Hz; Thus dynamic modulus test might be a more reliable test in evaluating the rut resistance of asphalt concrete mixture.

This paper describes a rapid bottom-up approach to selectively functionalize gold nanoparticles (AuNPs) on an indium tin oxide (ITO) substrate using the plasmon confinement effect. The plasmonic substrates based on a AuNP-free surfactant were fabricated by electrochemical deposition. Using this bottom-up technique, many sub-30 nm spatial gaps between the deposited AuNPs were randomly generated on the ITO substrate, which is difficult to obtain with a top-down approach (i.e., E-beam lithography) due to its fabrication limits. The 4-Aminodiphenyl (ADP) molecules were grafted directly onto the AuNPs through a plasmon-induced reduction of the 4-Aminodiphenyl diazonium salts (ADPD). The ADP organic layer preferentially grew in the narrow gaps between the many adjacent AuNPs to create interconnected AuNPs. This novel strategy opens up an efficient technique for the localized surface modification at the nanoscale over a macroscopic area, which is anticipated to be an advanced nanofabrication technique.

Nano-silver-titanium dioxide (Ag-TiO2) composites were prepared from commercial TiO2 (P25, Degussa) and silver nitrate (AgNO3) by gamma Co-60 irradiation method with various initial concentrations of AgNO3. The nano-AgTiO2 composites are utilized as the photoanode for dye-sensitized solar cells (DSCs). Under full sunlight illumination (1000 W/m2, AM 1.5), the efficiency of DSCs has improved significantly despite the Ag content of below 1%. The DSC—assembled with 0.75 Ag-TiO2 (0.75% Ag) photoanode—showed that the photocurrent was significantly enhanced from 8.1 mA.cm−2 to 9.5 mA.cm−2 compared to the DSCs using bared TiO2 photoanode. The unchanged open-circuit voltage resulted in the overall energy conversion efficiency to be increased by 25% from 3.75% to 4.86%. Electrochemical impedance spectroscopy (EIS) analysis showed that the charge transfer resistance is reduced when increasing Ag content, demonstrating that the charge transfer at TiO2/dye interface was enhanced in the presence of silver nanoparticles.

The microstructure-mechanical property relationships of a non-equiatomic FeMnCoCr high entropy alloy (HEA), which shows a single face-centered cubic (fcc) structure in the undeformed state, have been systematically investigated at room and cryogenic temperatures. Both strength and ductility increase significantly when reducing the probing temperature from 293 K to 77 K. During tensile deformation at 293 K, dislocation slip and mechanical twinning prevail. At 173 K deformation-driven athermal transformation from the fcc phase to the hexagonal close-packed (hcp) martensite is the dominant mechanism while mechanical twinning occurs in grains with high Schmid factors. At 77 K athermal martensitic transformation continues to prevail in addition to dislocation slip and twinning. The reduction in the mean free path for dislocation slip through the fine martensite bundles and deformation twins leads to the further increased strength. The joint activation of transformation and twinning under cryogenic conditions is attributed to the decreased stacking fault energy and the enhanced flow stress of the fcc matrix with decreasing temperature. These mechanisms lead to an elevated strain hardening capacity and an enhanced strength-ductility combination. The temperature-dependent synergy effects of martensite formation, twinning and dislocation plasticity originate from the metastability alloy design concept. This is realized by relaxing the equiatomic HEA constraints towards reduced Ni and increased Mn contents, enabling a non-equiatomic material with low stacking fault energy. These insights are important for designing strong and ductile Ni-saving alloys for cryogenic applications.

This paper presents a study on ZnO-based n-type thin films doped with Al, Ga, and Sn deposited on the glass substrates, using the solution derived by sol–gel reactions. The basic material properties associated with using the alternative chemical substances in synthesis process and different dopants to generate n-type conductivity in ZnO-based thin films which are transparent oxides, are investigated and discussed. Namely, the crystal structure and surface morphology of the obtained films were examined by means of XRD analysis and field-effect scanning electron microscope (FESEM). The electric properties of those films were characterized by Hall-effect measurements and temperature dependence of electrical conductivity, as well as Seebeck coefficients. The remarkable advantages corresponding to the certain characterization of each material composition were compared together. The aim is to fully understand the performance limitation of known materials and to set the scene for a suitable synthesis condition to get optimized materials for thermoelectric applications.

Construction of textured bioinspired surfaces with refined structures that exhibit superior wetting properties is of great importance for many applications ranging from self-cleaning, antibiofouling, anti-icing, oil/water separation, smart membrane, and microfluidic devices. Previously, the preparation of artificial surfaces generally relies on the combination of different approaches together, which is a lack of flexibility to control over the individual architecture unit, the surface topology, as well as the complex procedure needed. In this work, we report a method for rapid fabrication of three-tier hierarchical microunits (structures consisting of multiple levels) using a facile droplet microfluidics approach. These units include the first-tier microspheres consisting of the second-tier close-packed polystyrene (PS) nanoparticles decorated with the third-tier elegant polymer nanowrinkles. These nanowrinkles on the PS nanoparticles are formed according to the interfacial instability induced by gradient photopolymerization of N-isopropylacrylamide (NIPAM) monomers. The formation process and topologies of nanowrinkles can be regulated by the photopolymerization process and the fraction of carboxylic groups on the PS nanoparticle surface. Such a hierarchical microsphere mimics individual units of bioinspired surfaces. Therefore, the surfaces from self-assembly of these fabricated two-tier and three-tier hierarchical microunits collectively exhibit "gecko" and "rose petal" wetting states, with the micro- and nanoscale structures amplifying the initial hydrophobicity but still being highly adhesive to water. This approach offers promising advantages of high-yield fabrication, precise control over the size and component of the microspheres, and integration of microfluidic droplet generation, colloidal nanoparticle self-assembly, and interfacial polymerization-induced nanowrinkles in a straightforward manner.

Sn-doped n-type and Cu-doped p-type ZnO films were fabricated by depositing solutions derrived by sol–gel route on glass substrates through dip-coating cycles. The X-ray diffractometry demonstrates the typical crystalline structure of hexagonal wurzite of ZnO. The surface morphology was made through scanning electronmicroscopy showing the density and shape of films’ grains of which size was determined between 40 and 55 µm. The results of Hall measurement indicate clearly the material nature of fabricated films at room temperature. The best electrical property of Sn-doped n-type ZnO films is corresponding to Sn content of 2 at.% with carrier concentration of 3.0 × 1018 cm−3. The formation of p-type ZnO thin films was elucidated by the manner of solution synthesis that glucose was added into the solube mixer of zinc acetate and copper(II) nitrate trihydrate and the way of thermal treatment for films in vacuum with pretty good hole concentration of about 1015 cm−3. The electrical transport properties characterizing thermoelectric (TE) behavior of all films were investigated between room temperature to 400 °C (or from 300 to 673 K). The obtained results of electrical conductivity, Seebeck coefficient and power factor revealed that Sn-doped n-type ZnO films have the quality and properties similar to Al-doped ones and Cu-doped ZnO films can be promising p-type materials for TE applications.

We report a robust and high-yield fabrication method for wafer-scale patterning of high-quality arrays of dense gold nanogaps, combining displacement Talbot lithography based shrink-etching with dry etching, wet etching, and thin film deposition techniques. By using the self-sharpening of < 111 >-oriented silicon crystal planes during the wet etching process, silicon structures with extremely smooth nanogaps are obtained. Subsequent conformal deposition of a silicon nitride layer and a gold layer results in dense arrays of narrow gold nanogaps. Using this method, we successfully fabricate high-quality Au nanogaps down to 10 nm over full wafer areas. Moreover, the gap spacing can be tuned by changing the thickness of deposited Au layers. Since the roughness of the template is minimized by the crystallographic etching of silicon, the roughness of the gold nanogaps depends almost exclusively on the roughness of the sputtered gold layers. Additionally, our fabricated Au nanogaps show a significant enhancement of surface-enhanced Raman scattering (SERS) signals of benzenethiol molecules chemisorbed on the structure surface, at an average enhancement factor up to 1.5 x 10(6).

Nature presents delicate and complex materials systems beyond those fathomable by humans, and therefore, extensive effort has been made to utilize or mimic bio-materials and bio-systems in various fields. Biomass, an inexhaustible natural materials source, can also present good opportunities for the development of unprecedented, advanced materials and processing systems. Herein, we demonstrate the use of pine cones as a biomass mold for creating new and useful metal/carbon nanohybrids (MCNHs). The inherent water-induced folding actuation of the cone scales allows the casting of an aqueous solution of a single metal precursor or a binary metal mixture into the cone mold by simply immersing the cone in the solution. The cone actively absorbs aqueous-phase metal precursors through the bract scales and the precursor ions introduced into the cone are anchored to the functional groups of the interior tissues of the cone. Subsequent heat treatment successfully led to the formation of unique MCNHs. Iron, manganese, and cobalt were employed as model metals, binary mixtures of which were also cast into the cone mold to create further versatile MCNHs. Nanoparticulate metals were formed on the carbon supports, where the size, size distribution, and crystallinity of the nanoparticles were highly dependent on the identity of the single-component precursor and the combination of precursors. Consequently, the electrochemical activity of the MCNHs also depended on which metal precursors were cast into the cone mold. The MCNH prepared from the mixture of iron and manganese precursors (MFeMnCNH) showed the best electrochemical activity. As model applications, MFeMnCNH was applied to electrode materials for electrochemical charge storage and the oxygen evolution reaction. An electrochemical capacitor cell based on the MFeMnCNH electrodes showed excellent performance with energy densities of 38.7–54.2 W h kg−1 at power densities of 16 000–160 kW kg−1. In addition, MFeMnCNH demonstrated a low overpotential of 464 mV and fast kinetics with a Tafel slope of 64.6 mV dec−1 as an electrocatalyst for the oxygen evolution reaction in 1.0 M KOH. These results substantiate that pine cones as a biomass mold show great promise for creating versatile MCNHs through further combination of various precursors.

A non-covalent approach to prepare nanotube-containing gels was developed based on the physical gelation of two polymers, polyvinyl alcohol (PVA) and polyacrylonitrile (PAN), with different microphase behaviors in water/dimethyl sulfoxide (DMSO) mixture. Single-walled carbon nanotubes (SWNTs) were incorporated into the binary-polymer/binary-solvent system to alter the physical gelation behavior and, in turn, to achieve unique physicochemical characteristics of the resulting gels. SWNTs were wrapped with PVA, which extended the binary polymer system to a ternary polymer system consisting of PVA bound to SWNTs, free PVA, and PAN. It was observed that the SWNT/PVA/PAN ensembles gelled with appropriate amounts of water in DMSO and the gelation behavior was reversible. The amounts of water and SWNT were determined to be key parameters affecting the formation of the gels. The SWNT/PVA/PAN gels were successfully converted to carbonaceous gels via heat treatment in an inert atmosphere, which can be extended to several applications such as electrode materials. The macroporous carbonaceous gels were further functionalized via manganese deposition followed by potassium hydroxide activation, which yielded excellent cell performance in a neutral electrolyte with the energy density of 9.6–24.8 Wh kg−1 and power density of 8.0–0.1 kW kg−1.

We report a robust fabrication method for patterning free-standing Pt nanowires for the use as thermal anemometry probes for small-scale turbulence measurements. Using e-beam lithography, high aspect ratio Pt nanowires (~300 nm width, ~70 $\mu$m length, ~100 nm thickness) were patterned on the surface of oxidized silicon (Si) wafers. Combining precise wet etching processes with dry etching processes, these Pt nanowires have been successfully released free-standing between two silicon dioxide (SiO2) beams supported on Si cantilevers. Moreover, the unique design of the bridge holding the device allowed to release the device gently without damaging the Pt nanowires. The total fabrication time was minimized by restricting the use of e-beam lithography to the patterning of the Pt nanowires while standard photolithography was employed for other parts of the devices. We demonstrate that the fabricated sensors are suitable for turbulence measurements when operated in a constant-current mode. A robust calibration between output voltage and fluid velocity was established over the velocity range from 0.5 m s-1 to 5 m s-1 in an SF6 atmosphere at a pressure of 2 bar and a temperature of 21{\deg}C. The sensing signal from the nanowires showed negligible drift over a period of several hours. Moreover, we confirmed that the nanowires are able to withstand high dynamic pressures by testing them in air at room temperature velocities up to 55 m/s., Comment: 25 pages, 8 figures, Revised Version

A simple, scalable, surfactant-in-polymer templating approach is demonstrated to create controlled long-range secondary substructures in a primary structure. A metal bis(2-ethylhexyl) sulfosuccinate (MAOT) as the surfactant is shown to be capable of serving as a sacrificial template and metal precursor in carbon nanofibers. The low interfacial tension and controllable dimensions of the MAOT are maintained in the solid-phase polymer, even during electrospinning and heat-treatment processes, allowing for the long-range uniform formation of substructures in the nanofibers. The MAOT content is found to be a critical parameter for tailoring the diameter of the nanofibers and their textural properties, such as size and volume of interior pores. The metal counterion species in the MAOT determine the introduction of metallic phases in the nanofiber interior. The incorporation of MAOT with Na as the counterion into the polymer phase leads to the formation of a built-in pore structure in the nanofibers. In contrast, MAOT with Fe as a counterion generates unique iron-in-pore substructures in the nanofibers (FeCNFs). The FeCNFs exhibit outstanding charge storage and water splitting performances. As a result, the MAOT-in-polymer templating approach can be extended to combinations of various metal precursors and thus create desirable functionalities for different target applications.

The removal of microbubbles from substrates is crucial for the efficiency of many catalytic and electrochemical gas evolution reactions in liquids. The current work investigates the coalescence and detachment of bubbles generated from catalytic decomposition of hydrogen peroxide. Self-propelled detachment, induced by the coalescence of two bubbles, is observed at sizes much smaller than those determined by buoyancy. Upon coalescence, the released surface energy is partly dissipated by the bubble oscillations, working against viscous drag. The remaining energy is converted to the kinetic energy of the out-of-plane jumping motion of the merged bubble. The critical ratio of the parent bubble sizes for the jumping to occur is theoretically derived from an energy balance argument and found to be in agreement with the experimental results. The present results provide both physical insight for the bubble interactions and practical strategies for applications in chemical engineering and renewable energy technologies like electrolysis.

The synthesis of poly(L-glutamic acid) (PG) was investigated. Reduction of poly(benzyl-L-glutamate) by the palladium/charcoal catalyst proved to be an effective method for obtaining polyglutamic acid pure and particularly exhibiting in the α-helix secondary structure. The structure of this synthetic polypeptide was assessed by infrared spectroscopy, gel permeation chromatography, proton nuclear magnetic resonance spectroscopy, temperature-modulated differential scanning calorimetry and wide-angle powder X-ray diffraction methods. The α-helical PG was, for the first time, combined with multi-walled carbon nanotubes (MWCNTs). The obtained PG was demonstrated to be a promising matrix to disperse MWCNTs, forming MWCNT/PG biocomposites.

Organ-on-chip devices are intensively studied in academia and industry due to their high potential in pharmaceutical and biomedical applications. However, most of the existing organ-on-chip models focus on proof of concept of individual functional units without the possibility of testing multiple experimental stimuli in parallel. Here we developed a polydimethylsiloxane (PDMS) multiplexed chip with eight parallel channels branching from a common access port through which all eight channels can be addressed simultaneously without the need for extra pipetting steps thus increasing the reproducibility of the experimental results. At the same time, eight outlets provide individual entry to each channel with the opportunity to create eight different experimental conditions. A multiplexed chip can be assembled as a one-layer device for studying monocultures or as a two-layer device for studying barrier tissue functions. For a two-layer device, a similar to 2 mu m thick transparent PDMS membrane with 5 mu m through-hole pores was fabricated in-house using a soft lithography technique, thereby allowing visual inspection of the cell-culture in real-time. The functionality of the chip was studied by recapitulating the blood-brain barrier. For this, human cerebral microvascular endothelial cells (hCMEC/D3) were cultured in mono- or coculture with human astrocytes. Immunostaining revealed a cellular monolayer with the expression of tight junction ZO-1 and adherence junction VE-cadherin proteins in endothelial cells as well as glial fibrillary acidic protein (GFAP) expression in astrocytes. Furthermore, multiplexed permeability studies of molecule passage through the cellular barrier exhibited expected high permeability coefficients for smaller molecules (4 kDa FITC-dextran) whereas larger molecules (20 kDa) crossed the barrier at a lower rate. With these results, we show that our device can be used as an organ-on-chip model for future multiplexed drug testing.

Hierarchical plasmonic–photonic microspheres (PPMs) with high controllability in their structures and optical properties have been explored toward surface-enhanced Raman spectroscopy. The PPMs consist of gold nanocrystal (AuNC) arrays (3rd-tier) anchored on a hexagonal nanopattern (2nd-tier) assembled from silica nanoparticles (SiO2NPs) where the uniform microsphere backbone is termed the 1st-tier. The PPMs sustain both photonic stop band (PSB) properties, resulting from periodic SiO2NP arrangements of the 2nd-tier, and a surface plasmon resonance (SPR), resulting from AuNC arrays of the 3rd-tier. Thanks to the synergistic effects of the photonic crystal (PC) structure and the AuNC array, the electromagnetic (EM) field in such a multiscale composite structure can tremendously be enhanced at certain wavelengths. These effects are demonstrated by experimentally evaluating the Raman enhancement of benzenethiol (BT) as a probe molecule and are confirmed via numerical simulations. We achieve a maximum SERS enhancement factor of up to ∼108 when the resonances are tailored to coincide with the excitation wavelength by suitable structural modifications.

CO2 microbubbles have recently been used in enhanced oil recovery for blocking the high permeability zone in heterogeneous reservoirs. Microbubbles are colloidal gas aphrons stabilized by thick shells of polymer and surfactant. The stability of CO2 microbubbles plays an important role in improving the performance of enhanced oil recovery. In this study, a new class of design of experiment (DOE)&mdash, definitive screening design (DSD) was employed to investigate the effect of five quantitative parameters: xanthan gum polymer concentration, sodium dodecyl sulfate surfactant concentration, salinity, stirring time, and stirring rate. This is a three-level design that required only 11 experimental runs. The results suggest that DSD successfully evaluated how various parameters contribute to CO2 microbubble stability. The definitive screening design revealed a polynomial regression model has ability to estimate the main effect factor, two-factor interactions and pure-quadratic effect of factors with high determination coefficients for its smaller number of experiments compared to traditional design of experiment approach. The experimental results showed that the stability depend primarily on xanthan gum polymer concentration. It was also found that the stability of CO2 microbubbles increases at a higher sodium dodecyl sulfate surfactant concentration and stirring rate, but decreases with increasing salinity. In addition, several interactions are presented to be significant including the polymer&ndash, salinity interaction, surfactant&ndash, salinity interaction and stirring rate&ndash, salinity interaction.

Spherical photonic crystals (SPCs) with tailorable multiscale structure, versatile surface morphology, and controllable optical properties of both photonic stop band (PSB) and surface plasmon resonance (SPR), have been fabricated using a robust and facile method. The fabricated SPCs consist of well-spaced gold nanocrystals (AuNCs) (3rd-tier) anchored on silica nanopatterns (2nd-tier) confined in microspherical templates (1st-tier). Droplet microfluidics is used to produce microdroplets containing silica nanoparticles (SiO2NPs) which assemble to form two-tier SPCs. Subsequently, three-tier SPCs are obtained by thermal dewetting and evaporation of metal films deposited on the two-tier SPCs, with the 3rd-tier morphology being controlled by the deposited film morphology and programmed thermal annealing. Optical PSB and SPR properties of the prepared SPCs can be on-demand tailored by the 2nd and 3rd-tier morphology and their corresponding constituent materials. It is found that the scattering from AuNC arrays on the SPCs can be amplified by tailoring the PSB properties. The hierarchical SPCs manufactured by this method take advantages of low-cost, high controllability, and further processability. The manufacturing of flexible film encapsulated well-assembled SPCs as anticounterfeiting stamps, which are easy to be identified using the mobile phone with a flash, is demonstrated.

System miniaturization: Shaping with multistep plasma etching and corner lithography A novel 3-D silicon shaping technology has been developed that combines a multistep etching process with corner lithography. Currently, system miniaturization relies extensively on 3-D machining techniques. A team headed by Shu Ni and Niels R. Tas at the University of Twente, Netherlands developed a versatile fabrication technique for wafer-scale micro- and nano-machining using a combination of multistep etching and corner lithography (layer deposition and subsequent timed etching of the layer, resulting in a well-defined residue in concave corners and layer removal on flat surfaces and convex corners). The multistep etching creates high-aspect-ratio structures with stacked semicircles etched deeply into the sidewall; corners are introduced with proper geometry for the subsequent corner lithography. The authors believe their technique has excellent potential for constructing high-density 3-D structures with good dimensional control in most silicon wafers.

Selective impregnation of single-walled carbon nanotubes (SWNTs) into the interior of pine cones was achieved via inherent folding actuation of the cone by water absorption. Individually dispersed aqueous-phase SWNTs were incorporated into the cone along the pathway of water absorption, and consequently, a concentrated SWNT inclusion was formed on the scales of the cone. To fully exploit its properties as a carbon precursor, the cone was further treated with potassium hydroxide (KOH) solution. The KOH treatment altered the qualitative properties of the cone, which was used to generate activated carbons, and led to swelling of the cell wall of the cone to ultimately increase the size of the pores formed via carbonization. Inclusion of the SWNTs in the cone and the effect of KOH treatment were determined by the characteristics of the constituent tissues of the cone, which offered the opportunity of achieving tissue-dependent textural and electrochemical properties of the carbonized cones. Representatively, ...

A robust and simple method was developed for large-scale fabrication of free-standing and sub-μm PDMS through-hole membranes for biomedical applications., Free-standing polydimethylsiloxane (PDMS) through-hole membranes have been studied extensively in recent years for chemical and biomedical applications. However, robust fabrication of such membranes with sub-μm through-holes, and at a sub-μm thickness over large areas is challenging. In this paper, we report a robust and simple method for large-scale fabrication of free-standing and sub-μm PDMS through-hole membranes, combining soft-lithography with reactive plasma etching techniques. First, arrays of sub-μm photoresist (PR) columns were patterned on another spin-coated sacrificial PR layer, using conventional photolithography processes. Subsequently, a solution of PDMS : hexane at a 1 : 10 ratio was spin-coated over these fabricated arrays. The cured PDMS membrane was etched in a plasma mixture of sulfur hexafluoride (SF6) and oxygen (O2) to open the through-holes. This PDMS membrane can be smoothly released with a supporting ring by completely dissolving the sacrificial PR structures in acetone. Using this fabrication method, we demonstrated the fabrication of free-standing PDMS membranes at various sub-μm thicknesses down to 600 ± 20 nm, and nanometer-sized through-hole (810 ± 20 nm diameter) densities, over areas as large as 3 cm in diameter. Furthermore, we demonstrated the potential of the as-prepared membranes as cell-culture substrates for biomedical applications by culturing endothelial cells on these membranes in a Transwell-like set-up.

We numerically and experimentally investigated the metamaterial absorber (MMA) based on ring and dish structures in GHz region. It found that the combined structure of ring and dish (RD) exhibit dual-band absorption peaks at 8.6 and 15.6 GHz. By replacing the ring to the structure of split-ring and dish (SRD), the first magnetic resonance peak is shifted from 8.6 to 14.0 GHz. The physical mechanism of magnetic resonance frequencies was elucidated using simple LC circuit model. We achieved a broadband MMA with bandwidth of 3.7 GHz by arranging four SRD structures into a super unit-cell. The experimental results are good agreement with both the numerical simulation and calculation.

Hierarchical structuring of materials in the nanometer regime provides opportunities to achieve extraordinary characteristics of the resulting products. Here, we report unique one-dimensional hierarchical nanostructures consisting of single-walled carbon nanotubes (SWNTs), polyvinyl alcohol (PVA), and polyacrylonitrile (PAN). First, SWNT-in-binary-polymer nanofiber (SbPNF) structures were obtained through the incorporation of PVA-wrapped SWNTs into PAN, followed by the electrospinning of the SWNT/PVA/PAN solution. Importantly, the SbPNFs exhibited an aligned SWNT-in-nanofiber structure and enhanced ordering of the polymer chains. The SbPNFs were successfully converted to carbonized products [SWNT-in-carbon nanofibers (SbCNFs)] with enhanced crystallinity and tunable electrochemical properties. Compared to those of the control samples (no SWNT), the charge-transfer resistance and the surface area of the SbCNFs were two orders of magnitude lower and 11–20% higher, respectively, which resulted in better elec...

The phenolic compounds from natural plant extracts, which have strong antioxidant properties as inhibitors for browning retardants of fruits, have been extensively investigate in the last few decades. In this study, the polyphenols in Cleistocalyx operculatus (Roxb.), a distinct plant in tropical region, was successfully extracted and determined. The obtained Roxb. extract (CE) as an antioxidant additive was employed in Chitosan/Gum Arabic (CH/GA) edible coating for the fruit preservation. The resultant CE/CH/GA coating revealed the high effectiveness in improving the freshness of banana at ambient storage conditions. The properties of bananas before and after coated by CE/CH/GA were investigated and assessed. The surface structure of banana was examined by using scanning electron microscopy, showed wrinkle and crack structure for uncoated banana and smooth surface for banana coated with CE/CH/GA coating. The freshness of banana treated with CH/GA/CE edible coating could last for 21 days of storage at room conditions. Thus, it is promising for good potential practical application to preserve fruits.

Edible coatings or films are considered effective and sustainable in preventing the waste of millions of tons of fruits and vegetables resulting from decay and deterioration. In this study, we propose a new edible coating formulation to preserve avocado. The edible coating consisted of film-forming mixed polysaccharides (chitosan and gum arabic) supplemented with non-toxic zinc oxide (ZnO) nanoparticles using the mixing method. ZnO nanoparticles with diameters ranging from 10 to 40 nm were synthesized using hydrothermal method. The prepared ZnO and ZnO/chitosan/gum arabic edible coatings were characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The results showed that the edible film coated on the avocado's surface was smooth and uniform with an even distribution of ZnO nanoparticles in the film matrix. The physicochemical properties of avocados, such as appearance and brightness; weight; firmness; and reducing sugar content significantly improved after coating with the ZnO/chitosan/gum arabic edible film as compared to the uncoated samples. The best protective performance was achieved when the coating’s optimum ZnO concentration was 0.3 % w/w. While the uncoated avocados rotted after seven days of storage in room temperature, the coated avocados remained fresh under similar storage conditions.

Traditional Transwell inserts with track-etched 10 μm thick polymer membranes have been intensively used for studying cellular barriers. However, their thickness hampers direct cell-cell interaction between the adjacent cells which has been shown to critically influence the barrier formation. Therefore, here the effect of reduced distance between the cells by using fivefold thinner (2 μm) optically transparent polydimethylsiloxane (PDMS) membranes is studied and compared with polycarbonate (PC) membranes. The authors validate their applicability as an alternative substrate for the study of the blood–brain barrier by performing a monoculture of brain endothelial cells (hCMEC/D3) and co-culture with astrocytes in Transwells. The PDMS membranes supported the cellular protrusions through the well-defined pores and allowed control over cellular transmigration by varying the pore size. Cellular localization of tight and adherens junction proteins ZO-1, Claudin-5, and VE-cadherin is similar to PC membranes while their expression levels are affected as a function of membrane material and co-culture with astrocytes. Additionally, a permeability assay indicated tighter barrier formation on the PDMS membrane. These results suggest the potential use of 2 μm PDMS membranes for in vitro modeling of biological barriers with improved co-culture models and enhanced visibility of the cell culture.

We synthesized cubic-phase layered perovskite nanocrystals (PNCs) of different shapes, namely thin nanoplatelets, thick nanoplatelets, and nanocubes, to investigate their photoresponse characteristics in a phototransistor device. The PNCs were prepared using a one-pot hot-injection method, and their shape evolved from nanoplatelets to nanocubes (with zero-dimensional nanocrystals as a control) by controlling the reaction temperature and amount of cesium precursor. In addition, the PNCs were deposited into a film with a thickness of a few tens of nanometers by shear force using a solvent washing process combined with the spin-coating technique. The surface ligands and contaminating organic molecules were effectively removed from the deposited PNCs, and consequently, the drain current in the PNC-based phototransistors increased by 37–349% under illumination compared with the controls (purified or annealed). Of the four PNC shapes, the nanocubes showed the longest radiative lifetime and highest photosensitivity, with a photocurrent of up to 1.74 µA cm−2 under a 3.0 V bias. This work provides in-depth insight into the dependence of the intrinsic photophysical properties of PNCs on their morphology. Moreover, the morphology of the PNCs determined how they assembled into channels to bridge the transistor electrodes, which offers new opportunities for the development of high-performance, long-lifetime phototransistors and photovoltaics.

With increasing desalination demand worldwide, electrode materials for capacitive deionization (CDI) have attracted extensive attention recently. To compete with Reverse Osmosis, the performance of CDI electrode still needs to be further enhanced. In this work, graphene (Gr)/carbon nanotubes (CNTs) conducting hybrid was dispersed at as low as 1 wt% in coconut shell derived activated carbon (AC) to fabricate cost effective and high performance electrode for brackish water CDI desalination. The fabricated AC/Gr/CNTs electrodes show an excellent performance with the capacitance of 60 F/g (at 5 mV/s), the salt adsorption capacity of 9.58 mg/g and salt adsorption rate of 1.51 mg/g min at 1.0 V in 200 ppm NaCl solution. It should be highlighted that owing to the synergistic effect, the role of hybrid additive (1 wt%) was demonstrated to be more effective than that of single one, from a technical as well as from an economical viewpoint. To our best knowledge, this is the first study reporting the application of ultra-low content AC/CNTs hybrid in AC based CDI electrodes.

Insulating polymers have received little attention in electronic applications. Here, we synthesize a photoresponsive, amphiphilic block copolymer (PEO-b-PVBO) and further control the chain growth of the block segment (PVBO) to obtain different degrees of polymerization (DPs). The benzylidene oxazolone moiety in PEO-b-PVBO facilitated chain-conformational changes due to photoisomerization under visible/ultraviolet (UV) light illumination. Intercalation of the photoresponsive but electrically insulating PEO-b-PVBO into graphene sheets enabled electrical monitoring of the conformational change of the block copolymer at the molecular level. The current change at the microampere level was proportional to the DP of PVBO, demonstrating that the PEO-b-PVBO-intercalated graphene nanohybrid (PGNH) can be used in UV sensors. Additionally, discrete signals at the nanoampere level were separated from the first derivative of the time-dependent current using the fast Fourier transform (FFT). Analysis of the harmonic frequencies using the FFT revealed that the PGNH afforded sawtooth-type current flow mediated by Coulomb blockade oscillation., Block copolymers are electrically insulating and therefore characterization with electrical or electrochemical methods is not possible. Here, the authors demonstrate electrical monitoring of the photoisomerization transition in a benzylidene oxazolone block co-polymer intercalated into graphene sheets.

Designing a multifunctional metamaterial with programmable feature has become a new trend in mechanical, acoustic, and electromagnetic research fields due to the controllability of their structural behaviors and functionalities. The codable or reconfigurable structures have shown more remarkable characteristics than the traditional and conventional metamaterials to implement functional programmability. However, structural complexity and hi-tech requirement are the biggest constraints to their practical applications. This paper numerically and experimentally investigates a programmable metamaterial based on ternary foldable origami in the gigahertz-frequency regime. The proposed metamaterial provides four transformable modes corresponding to four different functions of electromagnetic reflector and frequency-selectable absorbers by programming unique ternary foldable origami coded as "0", "1", and "2" for different folding levels. Interestingly, the proposed foldable origami consists of a simple dielectric paper and a bottom conductor, while there is no conductive pattern on the top. Therefore, the proposed programmable metamaterial is extremely robust and can be extended to a multiresonance mode and origami computing.