Nano Arrays Research Articles

MOF-reinforced Co9S8 self-supported nanowire arrays for highly durable and flexible supercapacitor

The structural stability of the electrode material is very important to achieve a long cycle life of a supercapacitor. In this work, we demonstrate a multi-step preparation of metal organic framework (MOF)-reinforced Co9S8 self-supported nanowire arrays for high-performance supercapacitor with very high durability. Co-based nanowires with a composition of Co2(OH)2(CO3)2 are first synthesized on the nickel foam substrate by a facile hydrothermal method. After converting them into Co3O4 nanowires by calcination, leaf-like Co-based MOF (Co-MOF) has been deposited on the surface of the oxide nanoarrays (NAs), forming Co3O4 NAs@Co-MOF core-shell structure. Co9S8 nanoarrays are finally obtained by an in-situ hydrothermal sulfurization, and this process not only realizes the chemical transformation, but also changes the morphology of the Co-MOF from leaf-like microplatelets into nanosheets wrapping around the one-dimensional (1D) nanowires. When this sample has been applied for supercapacitor, it exhibits a 4.48 F cm−2 at a current density of 2 mA cm−2. The long-term cycling test is conducted at 25 mA cm−2, and the sample can maintain a high and stable capacitance of 1.6 F cm−2 after 100k cycles. This gives rise to a capacitance loss of only 5.1 × 10−4% per cycle, demonstrating an exceptional cycling stability. Furthermore, an asymmetric supercapacitor is assembled by pairing the Co9S8 nanoarrays with activated carbon, and the device delivers excellent cycle stability with a reversible capacitance of 416 mF cm−2 after 100k cycles, leading to a capacitance loss of 2.8 × 10−4% per cycle. Furthermore, a quasi-solid-state asymmetric supercapacitor is able to light up 16 red LEDs, demonstrating great potential for practical application with excellent cycle stability and mechanical flexibility.

The mechanism and kinetics of the transformation from marcasite to pyrite: in situ and ex situ experiments and geological implications

Despite the natural abundance of pyrite and marcasite and their intergrowth, and a wealth of information they can provide on the physical–chemical conditions of mineral deposits, a complete mechanistic and kinetic study on the phase transformation from the thermodynamically metastable polymorph marcasite to the stable polymorph pyrite is yet to be made. This limits the application of marcasite as an indicator mineral for low-temperature geological environments. Here, we report results from in situ synchrotron powder X-ray diffraction and ex situ anneal/quench experiments at 400–540 °C, demonstrating that the mechanism and kinetics of this transformation depend not only on temperature, but also on particle size, the presence of water vapor, and the presence of pyrite inclusions in marcasite. Under dry conditions, the transformation is limited by surface nucleation and occurs via epitaxial nucleation of pyrite on marcasite, with {100}pyrite//{101}marcasite and {001}pyrite//{010}marcasite. In contrast, in the presence of water vapor, there is little crystallographic orientation relationship between the two phases; the transformation is still limited by surface nucleation, but modification of the surface properties by water vapor results in a different nucleation mechanism, and consequently different kinetics. Kinetic analysis estimates a half-life of 1.5 Ma at 300 °C for the transformation under dry conditions with small and pyrite-free marcasite grains, but this estimation should be used with extreme caution due to the complexity of the transformation. From synchrotron X-ray fluorescence elemental mapping, trace elements (As and Pb) play an insignificant role in the transformation. However, the presence of a fluid phase changes the behavior of Pb. Under dry conditions randomly oriented particles of galena formed in pyrite, while under water vapor conditions arrays of nano- to microparticles of galena precipitated in pores. This study highlights that although the natural occurrence of marcasite can indicate low-temperature environments, precise estimation of temperature should not be made without considering the influences from various reaction parameters.

The transparent device of CdS quantum dots modified Cu2O/ZnO orderly nano array p-n junction towards the enhanced photovoltaic conversion

The transparent device of CdS QDs modified Cu2O/ZnO nano array p-n junction is prepared via simple continuous magnetron sputtering method and chemical deposition. The p-n junction device with good stability exhibits decent transparency of about ∼80% in visible light, and evident photovoltaic response enhancement of about ∼100 times than the unmodified sample, that can be mainly attributed to the CdS QDs with high QY can improve the visible light response, the p-n junction with self-photovoltage and the ZnO order arrays can improve the transport of the photon-generated carriers.

A Tunable Triple-Band Near-Infrared Metamaterial Absorber Based on Au Nano-Cuboids Array.

In this article, we present a design for a triple-band tunable metamaterial absorber with an Au nano-cuboids array, and undertake numerical research about its optical properties and local electromagnetic field enhancement. The proposed structure is investigated by the finite-difference time domain (FDTD) method, and we find that it has triple-band tunable perfect absorption peaks in the near infrared band (1000–2500 nm). We investigate some of structure parameters that influence the fields of surface plasmons (SP) resonances of the nano array structure. By adjusting the relevant structural parameters, we can accomplish the regulation of the surface plasmons resonance (SPR) peaks. In addition, the triple-band resonant wavelength of the absorber has good operational angle-polarization-tolerance. We believe that the excellent properties of our designed absorber have promising applications in plasma-enhanced photovoltaic, optical absorption switching and infrared modulator optical communication.

Fabrication and ultraviolet-visible-near infrared absorption properties of silver nano arrays based on aluminum

In this paper, the highly ordered periodic silver nanosphere arrays are fabricated by vacuum evaporation based on anodic aluminum oxide (AAO) template. The diameter and spacing of silver nanosphere in the arrays are adjusted just by controlling the thickness of evaporation. Furthermore, this can effectively modulate the absorption peaks and bandwidths in ultraviolet-visible-near-infrared regions. The measurement results of absorption spectra show that the nano-arrays have obvious electromagnetic wave absorption characteristics in the ultraviolet, visible and near-infrared bands. The finite-difference time-domain theoretical simulation combined with experiments is used to analyze the physical mechanism of light absorption characteristics in different wavebands. The ultraviolet strong absorption is due to the Fano resonance induced by asymmetric dielectric environment of silver and aluminum; the visible absorption originates from local surface plasmon resonance of silver nanoparticles; the near-infrared strong absorption is attributed to the surface lattice resonance of silver nanosphere arrays.

Zinc Titanate Nanoarrays with Superior Optoelectrochemical Properties for Chemical Sensing.

In this report, the gas sensing performance of zinc titanate (ZnTiO3) nanoarrays (NAs) synthesized by coating hydrothermally formed zinc oxide (ZnO) NAs with TiO2 using low-temperature chemical vapor deposition is presented. By controlling the annealing temperature, diffusion of ZnO into TiO2 forms a mixed oxide of ZnTiO3 NAs. The uniformity and the electrical properties of ZnTiO3 NAs made them ideal for light-activated acetone gas sensing applications for which such materials are not well studied. The acetone sensing performance of the ZnTiO3 NAs is tested by biasing the sensor with voltages from 0.1 to 9 V dc in an amperometric mode. An increase in the applied bias was found to increase the sensitivity of the device toward acetone under photoinduced and nonphotoinduced (dark) conditions. When illuminated with 365 nm UV light, the sensitivity was observed to increase by 3.4 times toward 12.5 ppm acetone at 350 °C with an applied bias of 9 V, as compared to dark conditions. The sensor was also observed to have significantly reduced the adsorption time, desorption time, and limit of detection (LoD) when excited by the light source. For example, LoD of the sensor in the dark and under UV light at 350 °C with a 9 V bias is found to be 80 and 10 ppb, respectively. The described approach also enabled acetone sensing at an operating temperature down to 45 °C with a repeatability of >99% and a LoD of 90 ppb when operated under light, thus indicating that the ZnTiO3 NAs are a promising material for low concentration acetone gas sensing applications.

Cholesteric-type cellulosic structures: from plants to applications

ABSTRACTThe structural support of plant cells is provided by the cell wall, which major load-bearing component is an array of hierarchical orientedhierarchical-oriented cellulose nano-, micro- and meso-structures of cellulose microfibrils. Cellulosic structures can respond to humidity changes by expanding or shrinking and this allows, for example, the dispersion of seeds. Previous studies have shown that nanorods, extracted from cell walls, can generate lyotropic liquid crystals that are at the origin of solid cholesteric-like arrangements. Not only photonic films, but also right and left helical filaments, anisotropic films with the ability to bend back and forth under the action of a moisture gradient at room temperature, are some of the materials that were produced from cellulose liquid crystal systems. This work is a review that focus on liquid crystalline-based structures obtained from cellulosic materials and how small perturbations on their structures affect significantly the response to external stimulus and interactions with the environment. Special emphasis is given to cholesteric-like organization of cellulose structures existing in plants, which are an inspiration for the production of the next generation of soft interactive materials.

Oxygen vacancy-engineered Fe2O3 nanoarrays as free-standing electrodes for flexible asymmetric supercapacitors.

The charge storage performance of Fe2O3 nanoarrays (NAs) as negative electrodes are limited by their poor conductivity and rate capability. Herein, we have reported the delicate interfacial engineering on carbon cloth (CC) fibers and oxygen vacancy (VO) generation on Fe2O3 nanorod arrays to boost the capacitive performance. Polydopamine-derived nitrogen-doped carbon layers were fabricated on CC fibers to govern the growth of FeOOH NAs. Rich VOs were generated in Fe2O3 NAs to construct a unique heterostructure with a crystalline core and amorphous shell via successive N2 thermal treatment and chemical reduction. Optimized by 2 h chemical reduction, the VO-rich Fe2O3 NA electrode, featuring a charged voltage of -1.10 V, exhibited a high areal specific capacitance of 2.63 F cm-2 at 0.5 mA cm-2 and 0.12 F cm-2 even at 60 mA cm-2. Impressively, 86.7% specific capacitance was retained after 10 000 cycles at 10 mA cm-2. The flexible asymmetric supercapacitor by assembling free-standing CN-Fe2O3-2 h (negative electrode) and MnO2 (positive electrode) showed an energy density of 1.33 mW h cm-3 at 15.4 mW cm-3. To the best of our knowledge, these results are the record performance for Fe2O3-based electrodes. The two-step interfacial engineering reported in this study may open a new door in the design of high energy-density electrodes for advanced energy storage.

High responsivity ultraviolet detector based on novel SnO2 nanoarrays.

In this work, tin oxide (SnO2) nanoarrays (NAs) with a novel morphology were fabricated by a hydrothermal method. Each SnO2 nanorod (NR) consisted of a bunch of nearly ten primary NRs with a width of 4–7 nm. On this basis, gold (Au) nanoparticles (NPs) were used to induce the growth of smaller and more orderly SnO2 NAs. The prepared ultraviolet (UV) detectors based on SnO2 NAs have high responsivity and high external quantum efficiency (EQE) under 20 μW cm−2 UV light with only 1 V external bias voltage.

Effects of current density and time on the characteristics of P-type silicon nano array

In this study, experimental variables pertaining to the formation of nano-pillar arrays using p-type silicon were optimized by controlling current density and chamber temperature. Three factors affecting pillar formation were optimized to improve the efficiency of the pillar array formation process. First, the experiment chamber was designed to maintain a fixed temperature regardless of the external temperature. Second, the Pt counter electrode was changed from a rod type to a mesh type to obtain a uniform distribution of current density. Third, a Cr-Cu alloy electrode was used instead of Cu to increase the electrode current density. The etching area was expanded to form a fine pillar array. This study shows that it is possible to form a nano-pillar array of 600-nm thickness and 44-μm depth.

Enhanced photocathodic protection performance of Fe2O3/TiO2 heterojunction for carbon steel under simulated solar light

Titanium dioxide nano array (TNAs) was successfully modified with Fe2O3 (FTNAs) to enhance the photocathodic protection performance for carbon steel. Fe2O3 as a sensitizer captures large quantities of light photons, resulting in a strong light harvest capability of FTNAs. Meanwhile, the bandgap of FTNAs decreased to 2.26 eV, and the photo-generated current densities were 90 and 400 μA cm−2 for TNAs and FTNAs under simulated solar light illumination, respectively. The narrowed bandgap and the sensitive photoelectric response together contribute to a good photocathodic protection performance of FTNAs, which was confirmed by the electrochemical impedance spectroscopy and electrochemical noise.

Nanoantenna structures for the detection of phonons in nanocrystals.

We report a study of the infrared response by localized surface plasmon resonance (LSPR) modes in gold micro- and nanoantenna arrays with various morphologies and surface-enhanced infrared absorption (SEIRA) by optical phonons of semiconductor nanocrystals (NCs) deposited on the arrays. The arrays of nano- and microantennas fabricated with nano- and photolithography reveal infrared-active LSPR modes of energy ranging from the mid to far-infrared that allow the IR response from very low concentrations of organic and inorganic materials deposited onto the arrays to be analyzed. The Langmuir–Blodgett technology was used for homogeneous deposition of CdSe, CdS, and PbS NC monolayers on the antenna arrays. The structural parameters of the arrays were confirmed by scanning electron microscopy. 3D full-wave electromagnetic simulations of the electromagnetic field distribution around the micro- and nanoantennas were employed to realize the maximal SEIRA enhancement for structural parameters of the arrays whereby the LSPR and the NC optical phonon energies coincide. The SEIRA experiments quantitatively confirmed the computational results. The maximum SEIRA enhancement was observed for linear nanoantennas with optimized structural parameters determined from the electromagnetic simulations. The frequency position of the feature’s absorption seen in the SEIRA response evidences that the NC surface and transverse optical phonons are activated in the infrared spectra.

Effects of deposition of different contents of Ag nanoparticles on thickness and structural, morphological, compositional, optical, and photocatalytic properties of 1D TiO2 nanoarrays

One-dimensional (1D) TiO2 nanoarrays (NAs) were synthesized by a hydrothermal process, and Ag nanoparticles (NPs) were deposited on the arrays using a photodeposition technique. The content of Ag NPs was changed by altering the photodeposition time to 0, 5, 10, 15, and 20 min. The influence of the content of Ag NPs on the structural, morphological, compositional, optical, and photocatalytic properties of 1D TiO2 NAs was systematically investigated. The results demonstrated that 1D TiO2 NAs showed improved visible light absorption and enhanced photocatalytic properties after deposition of Ag NPs. Compared with bare TiO2 NAs, the TiO2 NAs after deposition of Ag NPs for 15 min showed the best optical and photoelectrochemical properties, and photodegradation efficiency (98.8 %).

Synthesis of High‐Quality Wurtzite Cu2ZnSn(S1−x,Sex)4 Nanocrystals With Non‐Toxic Selenium Precursor and the Photoelectrochemical Performance of ZnO NAs/CZTSSe Heterojunction

Fabrication of high performing CZTSSe absorber material from environmental benign nanocrystals ink is very important for large‐scale manufacturing production. Herein, the high‐quality metastable wurtzite Cu2ZnSnS4 (W‐CZTS) and wurtzite Cu2ZnSn(S1−x,Sex)4 (W‐CZTSSe) nanocrystals with small sizes have been synthesized successfully using dodecanethiol (DDT) and Se‐octadecylamine (Se‐ODA) as the sulfur and selenium sources, respectively. Compared to the thin film obtained from W‐CZTS nanocrystals ink, the thickness of small grain layer in the thin film obtained from W‐CZTSSe nanocrystals is reduced significantly. Further the ZnO nanoarrays (NAs)/CZTSSe heterojunction thin‐film grows on fluorine‐doped tin oxide (FTO) substrate and it exhibits superior photoelectrochemical (PEC) performance under light illumination. The ZnO NAs/CZTSSe heterojunction thin film shows the photocurrent density of 3.44 mA cm−2, which is nearly 2.7‐fold higher than the photocurrent density of ZnO NAs. The PEC efficiencies of ZnO NAs and ZnO NAs/CZTSSe are 0.4% and 1.89%, respectively. Our results demonstrate that the as‐synthesized W‐CZTSSe nanocrystals by using Se‐ODA are a promising precursor to fabricate high performing thin film, the Se‐ODA can be applied to prepare the precursors of chalcogenide thin film (including CISe, CIGSe, and CZTSSe).

Macroporous Ni foam-supported Co3O4 nanobrush and nanomace hybrid arrays for high-efficiency CO oxidation

Herein, we reported the synthesis of well-defined Co3O4 nanoarrays (NAs) supported on a monolithic three-dimensional macroporous nickel (Ni) foam substrate for use in high-efficiency CO oxidation. The monolithic Co3O4 NAs catalysts were obtained through a generic hydrothermal synthesis route with subsequent calcination. By controlling the reaction time, solvent polarity and deposition agent, these Co3O4 NAs catalysts exhibited various novel morphologies (single or hybrid arrays), whose physicochemical properties were further characterized by using several analytical techniques. Based on the catalytic and characterization analyses, it was found that the Co3O4 NAs-6 catalyst with nanobrush and nanomace arrays displayed enhanced catalytic activity for CO oxidation, achieving an efficient 100% CO oxidation conversion at a gas hourly space velocity (GHSV) 10,000hr−1 and 150°C with long-term stability. Compared with the other Co3O4 NAs catalysts, it had the highest abundance of surface-adsorbed oxygen species, excellent low-temperature reducibility and was rich in surface-active sites (Co3+/Co2+=1.26).

Metal-organic framework-templated synthesis of sulfur-doped core-sheath nanoarrays and nanoporous carbon for flexible all-solid-state asymmetric supercapacitors.

Metal-organic frameworks (MOFs) provide great opportunities for synthesizing advanced electrode materials with hierarchical hollow architectures for energy storage. Herein, we report the facile fabrication of core-sheath nanoarrays (NAs) on carbon cloth (CC@CoO@S-Co3O4) for binder-free electrode materials with MOFs as versatile scaffolds. The hollow S-doped Co3O4 sheath has been facilely prepared using a two-step synthetic protocol, which includes the surface etching of CoO nanowires for synchronous in situ growth of well-aligned ZIF-67 and its following hydrothermal process. The synergistic effect between CC nanofibers and hollow ordered NAs ensures efficient mass and electron transport. The pseudocapacitive NAs present a highest areal specific capacitance of 1013 mF cm-2 at 1 mA cm-2. By assembling the same MOF-derived nanoporous carbons and NAs as the corresponding binder-free anode and cathode, the flexible all-solid-state asymmetric supercapacitors deliver a highest energy density of 0.71 mW h cm-3 at 21.3 mW cm-3 power density, together with 87.9% capacitance retention over 5000 continuous cycles.

Low-temperature CO oxidation over integrated penthorum chinense-like MnCo2O4 arrays anchored on three-dimensional Ni foam with enhanced moisture resistance

Advanced integrated nanoarray (NA) catalysts have been designed by growing metal-doped Co3O4 arrays on nickel foam with robust adhesion.

Parrotfish Teeth: Stiff Biominerals Whose Microstructure Makes Them Tough and Abrasion-Resistant To Bite Stony Corals.

Parrotfish (Scaridae) feed by biting stony corals. To investigate how their teeth endure the associated contact stresses, we examine the chemical composition, nano- and microscale structure, and the mechanical properties of the steephead parrotfish Chlorurus microrhinos tooth. Its enameloid is a fluorapatite (Ca5(PO4)3F) biomineral with outstanding mechanical characteristics: the mean elastic modulus is 124 GPa, and the mean hardness near the biting surface is 7.3 GPa, making this one of the stiffest and hardest biominerals measured; the mean indentation yield strength is above 6 GPa, and the mean fracture toughness is ∼2.5 MPa·m1/2, relatively high for a highly mineralized material. This combination of properties results in high abrasion resistance. Fluorapatite X-ray absorption spectroscopy exhibits linear dichroism at the Ca L-edge, an effect that makes peak intensities vary with crystal orientation, under linearly polarized X-ray illumination. This observation enables polarization-dependent imaging contrast mapping of apatite, a method to quantitatively measure and display nanocrystal orientations in large, pristine arrays of nano- and microcrystalline structures. Parrotfish enameloid consists of 100 nm-wide, microns long crystals co-oriented and assembled into bundles interwoven as the warp and the weave in fabric and therefore termed fibers here. These fibers gradually decrease in average diameter from 5 μm at the back to 2 μm at the tip of the tooth. Intriguingly, this size decrease is spatially correlated with an increase in hardness.

Gold nano disks arrays for localized surface plasmon resonance based detection of PSA cancer marker

Here in, we report prostate specific antigen (PSA) detection method using DNA aptamer functionalized gold nano disks array. The approach is based on DNA aptamer–PSA specific interaction and the localized surface plasmon resonance (LSPR) extinction λ max shifts of the transmitted light (UV–vis). The specific interaction results in a stable dynamic equilibrium. The concentration effect on equilibrium time has been described. We also describe the relationship between the aptamer concentration and the plasmon response. Using 2nM DNA aptamer on gold nano arrays, a detectable linear range from 1.7ng/mL to 20.4ng/mL was obtained with the R2 value>0.99. The limit of detection (LOD) value was found 1.49ng/mL. Finite difference time domain (FDTD) simulations were plotted for the gold substrate in air and water. Great agreement was found between the experimental and simulated shifts in both the cases. The refractive index sensitivities (S) of experimental spectra (113nm/RIU) and simulated spectra (116nm/RIU) were also found in good agreement. These results indicate that this NanoPlasmonic Sensing (NPS) detection platform is most suitable for the pre-biopsy test of prostate cancer patients. The DNA aptamers have been used as specific receptors for biomarkers for the first time; it provided the method with great potential for monitoring other biological interaction due to its great versatility and resistance to denaturation. Furthermore, substrate is recoverable which gives it clear advantage over most of the prevalent methods.

Design of two kinds of branched TiO2 nano array photoanodes and their comparison of photoelectrochemical performances

Two kinds of branched TiO2 nanorods arrays (TNRs), i.e. rutile nanorod covered with rutile branches (BTNRs) and rutile nanorod covered with anatase branches (ATNRs), were synthesized on FTO films as photoanodes. Photoelectrochemical (PEC) performances of the both photoanodes were comparably evaluated. The PEC hydrogen production rate of ATNRs photoanode is 4.2 and 2.7 times those of the TNRs and BTNRs photoanodes, respectively. The ATNRs showed a highly PEC response because of a lower intrinsic resistance and a heterophase structure between rutile nanorod and anatase branches. The study explicitly ascertains a kind of more effective structure for photoelectrical materials and gives new insight into intrinsic resistance based on PEC analyses.