Surface Area Of Substrate Research Articles

Conformal coating of amorphous silicon and germanium by high pressure chemical vapor deposition for photovoltaic fabrics

Conformally coating textured, high surface area substrates with high quality semiconductors is challenging. Here, we show that a high pressure chemical vapor deposition process can be employed to conformally coat the individual fibers of several types of flexible fabrics (cotton, carbon, steel) with electronically or optoelectronically active materials. The high pressure (∼30 MPa) significantly increases the deposition rate at low temperatures. As a result, it becomes possible to deposit technologically important hydrogenated amorphous silicon (a-Si:H) from silane by a simple and very practical pyrolysis process without the use of plasma, photochemical, hot-wire, or other forms of activation. By confining gas phase reactions in microscale reactors, we show that the formation of undesired particles is inhibited within the microscale spaces between the individual wires in the fabric structures. Such a conformal coating approach enables the direct fabrication of hydrogenated amorphous silicon-based Schottky ...

Diatomite-Templated Synthesis of Freestanding 3D Graphdiyne for Energy Storage and Catalysis Application.

Graphdiyne (GDY), a new kind of two-dimensional (2D) carbon allotropes, has extraordinary electrical, mechanical, and optical properties, leading to advanced applications in the fields of energy storage, photocatalysis, electrochemical catalysis, and sensors. However, almost all reported methods require metallic copper as a substrate, which severely limits their large-scale application because of the high cost and low specific surface area (SSA) of copper substrate. Here, freestanding three-dimensional GDY (3DGDY) is successfully prepared using naturally abundant and inexpensive diatomite as template. In addition to the intrinsic properties of GDY, the fabricated 3DGDY exhibits a porous structure and high SSA that enable it to be directly used as a lithium-ion battery anode material and a 3D scaffold to create Rh@3DGDY composites, which would hold great potential applications in energy storage and catalysts, respectively.

Laminated Hybrid Junction of Sulfur-Doped TiO2 and a Carbon Substrate Derived from Ti3C2 MXenes: Toward Highly Visible Light-Driven Photocatalytic Hydrogen Evolution.

TiO2 is an ideal photocatalyst candidate except for its large bandgap and fast charge recombination. A novel laminated junction composed of defect‐controlled and sulfur‐doped TiO2 with carbon substrate (LDC‐S‐TiO2/C) is synthesized using the 2D transition metal carbides (MXenes) as a template to enhance light absorption and improve charge separation. The prepared LDC‐S‐TiO2/C catalyst delivers a high photocatalytic H2 evolution rate of 333 µmol g−1 h−1 with a high apparent quantum yield of 7.36% at 400 nm and it is also active even at 600 nm, resulting into a 48 time activity compared with L‐TiO2/C under visible light irradiation. Further theoretical modeling calculation indicates that such novel approach also reduces activation energy of hydrogen production apart from broadening the absorption wavelength, facilitating charge separation, and creating a large surface area substrate. This synergic effect can also be applied to other photocatalysts' modification. The study provides a novel approach for synthesis defective metal oxides based hybrids and broaden the applications of MXene family.

Highly transparent, flexible and hydrophilic ZnS thin films prepared by a facile and environmentally friendly chemical bath deposition method

Growth of highly transparent and hydrophilic ZnS thin films on flexible polymeric and glass substrates has been performed using an environmentally friendly chemical bath deposition method with an ammonia and thioacetamide free reaction solution. Deposition time effect on surface morphology, structure and optical properties of the ZnS thin films has been investigated by field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffractometer (XRD), ultraviolet-visible light (UV–vis) spectroscopy, and photoluminescence (PL) spectroscopy. Also, the chemical composition of the prepared films has been studied in detail by energy-dispersive X-ray spectrometer (EDX), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. TEM images show that the ZnS films consisted of small nanocrystals with diameters ≤5 nm. Moreover, the water contact angles, 38.5° and 25.4° for ZnS films deposited on PS and on glass substrates, respectively, indicate a highly hydrophilic nature. Undoubtedly, the chemical analysis shows the formation of the films with a chemical composition of ZnS0.89, lacking impurities such as ZnO and/or Zn (OH)2. Additionally, FE-SEM images show a homogenous deposition over a very large surface area substrates. Ultimately, the obtained photoluminescence spectrum indicates a strong and broad emission peak ranging from 400 to 600 nm, which are due to deep levels or trap state defects in the crystalline structure of the ZnS films.

Scanning tunneling microscopy research of Bi(110) thin films grown on NbSe2

Due to the novel physical properties induced by the strong spin orbit coupling and band inversions in the energy band structure, two-dimensional topological insulator has become a hot research point in the field of condensed matter physics and material science in recent years. Particularly, two-dimensional topological insulator may host exotic Majorana fermionic excitations in its edge state if superconductivity is introduced. Bi thin film with (111) orientation proves to be a two-dimensional topological insulator both in theory and in experiment. However, the topological nature of Bi thin film with (110) orientation has not yet been confirmed. In this study, high quality Bi(110) thin films are successfully prepared on superconductor NbSe2 surfaces, by the molecular beam epitaxial technology at ambient temperature and a low deposition rate (~24℃,~3 min/bilayer). The morphologies and electronic properties of the samples are studied by using scanning tunneling microscopy and spectroscopy. The experimental results reveal that the growth mode changes from bilayer (BL) in BL mode to monolayer (ML) in ML mode. Such transition takes place at a critical height of about 4 BLs. The mechanism of the growth mode transition is believed to be induced by the drastic variation of the surface energies of the thin films with different thickness values. Due to the large coverage of Bi(110) film on the NbSe2 substrate, it is almost impossible to find the exposed areas of NbSe2 substrate surface in practice. Especially on the sample with a large number of layers of Bi thin film, it is hard to directly determine the number of layers for each film. Hence, the critical thickness could be only estimated by controlling the deposition time and growth rate combining with the measurements of stage height of the film. The nearly identical local density of states wherever measured in the interior of a terrace or at the step edges can be discerned from the dI/dV spectra, which is thus hard to corroborate with non-trivial topology in either BL or ML thick Bi(110) film. The superconductivity induced by proximity effect from the superconducting substrate NbSe2 is also observed on the thin films. Through Bardeen-Cooper-Schrieffer type data fitting, the superconducting gap on the Bi thin film is estimated at about 0.5 meV. In addition, the quantum well state, which is often observed in thin films, is also revealed from the Bi(110) thin films, whose characteristic is equal energy spacing between peaks in dI/dV spectra. Noticeably, the spectral shapes of BL and ML are similar, and the local density of states from adjacent film layers displays an approximate πup phase shift.

3D intermetallic anodes for Lithium-ion batteries

Recently various three-dimensional (3D) battery architectures have emerged as a new direction for powering microelectromechanical systems and other small autonomous devices. The ultimate goal of such unique battery architecture is to obtain a high surface area substrate coated with thin layers of anode, electrolyte and cathode materials to enhance the energy density per foot print area, while maintaining a large power density. In view of this, attempts on formulating 3D structured anode utilizing widely available three dimensional mesoporous nickel foam and tin alloy matrix are reported

Periodic silver nanocluster arrays over large-area silica nanosphere template as highly sensitive SERS substrate

Periodic Ag nanocluster arrays for surface enhanced Raman spectroscopy (SERS) were fabricated through magnetron sputtering Ag over a large-area monolayer template which is based on silica (SiO2) nanospheres. High-density nanogaps between the adjacent Ag nanoclusters acted as “hot-spots”, making a dominant contribution to the high-performance SERS detection. Moreover, the nanospheres and Ag nanoclusters effectively increased the surface roughness and also enlarged the surface area of as-obtained SERS substrate, which resulted in a further enhancement in Raman signals. As-prepared SERS substrates showed very high sensitivity with the enhancement factor (EF) value of 4.1 × 1012 for Rhodamine 6G (R6G), allowing the corresponding detection limit as low as 10–16 M. Additionally, SERS signal of melamine was still strong even though its concentration was lowered to 10–7 M. Our results show that preparing highly sensitive SERS substrate with periodic Ag nanoclusters over SiO2 nanosphere template is a convenient and promising pathway for chemical and biologic sensing.

Modulating the Lipase‐Mediated Bioactivity of Particle‐Lipid Conjugates Through Changes in Nanostructure and Surface Chemistry

The lipase‐mediated hydrolysis of triglycerides can be controlled by confining lipid droplets within highly porous nanostructured particle matrices. Novel hybrid materials with varying bioactivities toward lipase have been developed by spray drying particle‐stabilized emulsions to form highly organized three‐dimensional architectures. In this study, the particle size, nanostructure, and surface chemistry of hybrid particles are tailored to systematically investigate the influence of material characteristics on lipase activity. This is achieved by varying (i) the spray drying process and (ii) the structure and composition of particulate colloids employed to stabilize the precursor emulsions. In all cases, the colloidal self‐assembly of particles and droplets into nanostructured conjugates during the water removal process facilitated enhanced lipase activity compared to submicron triglyceride emulsions, with lipolysis kinetics increasing in the following order: polymer‐lipid hybrid (PLH) < silica‐lipid hybrid (SLH) ≤ clay‐lipid hybrid (CLH). Lipase activity increased as a function of increasing interfacial surface area of the lipid substrate and increasing hydrophilicity of the solid matrix support. The novel insights into the role of hybrid particle nanostructure and surface chemistry on the mechanism of lipase action can be harnessed for the intelligent design of new and improved lipid‐based drug delivery vehicles and functional foods.Practical Applications: Understanding and controlling the interaction between triglyceride molecules and pancreatic lipase is of fundamental importance for the rational design of new functional foods and drug formulations. Lipid digestion in the body facilitates the delivery of fat and encapsulated bioactive compounds from the gastrointestinal tract (GIT) to the blood and surrounding tissues. Hence, the bioavailability of poorly soluble compounds can be controlled by engineering lipid‐based systems that regulate lipase activity. In this study, three novel solid‐state systems have been designed that finely control the catalytic activity of lipase, and therefore, demonstrate high commercial potential within the pharmaceutical and biotechnology industries.The lipase‐mediated hydrolysis of triglycerides is controlled by designing novel solid‐state particle‐lipid conjugates with unique nanostructures and surface chemistries. The hybrid materials are prepared by spray‐drying particle‐stabilized lipid droplets, which induced the forced agglomeration of particles and droplets into micron‐sized particles with distinctive three‐dimensional architectures. The ability to modulate lipase activity through material design presented novel insights into the mechanism of digestive enzyme action, which is of fundamental importance for the rational design of new functional foods and drug formulations.

Investigating the Electrode-Electrolyte Behaviour of Carbon Materials in Various Non-Aqueous Electrolytes

Charge storage in electrochemical capacitors has been shown to be via charge separation at the electrode-electrolyte interface (so called electrical double layer charge storage) and via pseudo-capacitance, which is often described as fast redox reactions through the same interface. Charge storage via both of these mechanisms depends heavily on the interaction between the electrode morphology (electrochemically active surface area, pore size distribution, etc.) and the solvated ion in the electrolyte. In this work the interaction between a series of carbon-based substrates and various electrolyte species has been investigated. Electrolytes examined include tetraethylammonium bis(trifluoromethane)sulfonimide (Et4NTFSI), 1-butyl-1-methylpyrrolidinium tetrafluoroborate (PYR14BF4), 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI), and tetraethylammonium tetrafluoroborate (Et4NBF4) in acetonitrile. The interaction between these electrolytes and various carbon-based substrates was examined using a combination of cyclic voltammetry (CV) and step potential electrochemical spectroscopy (SPECS). These techniques have enabled differentiation of the charge storage mechanisms based on ion size, solvated ion size and charge density, as well as substrate surface area and porosity.

Ordered porous structure of nitrogen-self-doped carbon supporting Co3O4nanoparticles as anode for improving cycle stability in lithium-ion batteries

Abstract

Electrocatalytic hydrogen evolution reaction activity comparable to platinum exhibited by the Ni/Ni(OH)2/graphite electrode

Electrochemical dual-pulse plating with sequential galvanostatic and potentiostatic pulses has been used to fabricate an electrocatalytically active Ni/Ni(OH)2/graphite electrode. This electrode design strategy to generate the Ni/Ni(OH)2 interface on graphite from Ni deposits is promising for electrochemical applications and has been used by us for hydrogen generation. The synergetic effect of nickel, colloidal nickel hydroxide islands, and the enhanced surface area of the graphite substrate facilitating HO-H cleavage followed by H(ad) recombination, results in the high current density [200 mA/cm2 at an overpotential of 0.3 V comparable to platinum (0.44 V)]. The easy method of fabrication of the electrode, which is also inexpensive, prompts us to explore its use in fabrication of solar-driven electrolysis.

Microhabitat use in the amblypygid Paraphrynus laevifrons

Amblypygids (Order: Amblypygi) can be found across different habitat types, each with very different microhabitat structure, including rainforests, deserts, and caves in the tropics and subtropics. Most prior studies on amblypygid microhabitat use have focused on characteristics of trees and their relationship with amblypygid abundance, though many species regularly occupy refuges away from trees. Here we explore microhabitat use in the amblypygid Paraphrynus laevifrons Pocock, 1894 through mark-recapture surveys conducted along creeks and trails in a secondary forest in southeastern Costa Rica. We identified (1) microhabitat characteristics associated with abundance of P. laevifrons and (2) resighting ratio—the likelihood of finding individual P. laevifrons over multiple nights, potentially in association with a particular area (a putative territory). We measured four microhabitat characteristics: (i) number of visible refuges, (ii) surface area of vertical substrate, (iii) estimated plant cover of substrate, and (iv) presence/absence of an overhang. We found that the number of P. laevifrons sighted did not differ across wet and dry seasons, but P. laevifrons were sighted in greater numbers in creeks than trails. The abundance of P. laevifrons was positively affected by the presence of overhangs, there was no effect of plant cover, and the positive effect of number of refuges was stronger in trails, where overhangs were less common, than in creeks. Our results support earlier studies showing that amblypygids can be found more abundantly in areas with greater available refuges and potential shelter, suggesting that predation may be a strong source of selection on amblypygid microhabitat use.

Development of Composite Adsorbent Coating Based Acrylic Polymer/Bentonite for Methylene Blue Removal

The development of composite adsorbent coating based acrylic polymer solution (APS) mixed with bentonite (ben) was investigated. The composite adsorbent coating was prepared and coated to a high surface area substrate, cotton cellulosic fiber (CCF). The APS/ben-CCF was used for a single cationic methylene blue (MB) dye adsorption system. Characterization of composition and structure of materials and coating was carried out by X-ray fluorescence (XRF), scanning electron microscopy (SEM), and UV-spectroscopy (UV-VIS). The adsorption properties of the APS/ben-CCF were investigated as a function of solution pH, initial dye concentration and contact time as well as solution temperature of MB dye. The result revealed that the APS/ben-CCF functioned well in solutions of various pH (acidic to alkaline), achieving 100% removal of MB within 2 hours of adsorption for 50 ppm. Kinetic studies showed that APS/ben-CCF is endothermic in nature since the adsorption capacity increased with increasing solution temperature. These results demonstrate that APS/ben-CCF composite adsorbent coating is an advanced adsorbent with advantages such as easy phase separation and capability to remove cationic dyes in a short time period.

High-yield synthesis of ZnO nanoparticles homogeneously coated on exfoliated graphite and simplified method to determine the surface coverage

Highly dispersed ZnO nanoparticles (NPs) with an average diameter of 4.7nm were attached to exfoliated graphite (EG) by a facile, free of hazardous chemicals, scalable synthesis route providing a high yield. The adsorption of ZnO NPs on EG results in a monolayer of NPs with a maximum coverage of 40% according to the random sequential adsorption (RSA) model. Furthermore, we introduce a novel simplified method to determine the surface coverage, by taking only four parameters into account – namely the specific surface area of the initial substrate and the concentration, size, and density of the adsorbed particles. Up to now, the determination of the surface coverage has required to count the single particles within the investigated surface area. Besides, this method reached its limit for inhomogeneously coated surfaces due to the imprecise results. The main idea here is to calculate the surface coverage for the complete sample in contrast to the abovementioned method that is limited by the investigated area. Moreover, according to our method, counting single particles per unit area is not necessary anymore, leading not only to substantial time savings but also to an improved calculation precision due to the consideration of the whole sample. Due to the application of tailored parameters, the here-derived equation can be applied for various composites including adsorbed spherical particles on the substrate.

Single-Step Electrodeposited Molybdenum Incorporated Nickel Sulfide Thin Films from Low-Cost Precursors as Highly Efficient Hydrogen Evolution Electrocatalysts in Acid Medium

Large-scale production of hydrogen—the energy carrier of the future—remains challenging on economy grounds. Low-cost synthetic designs are necessary to produce electrocatalysts for hydrogen evolution reaction (HER). Ternary nickel molybdenum sulfides Ni1–xMoxS (x = 0, 0.04, 0.08, 0.16) have been electrochemically grown on fluorine-doped tin oxide substrate as highly active and stable HER electrocatalysts. The merits of this method are (1) the electrochemical method is energy efficient at ambient conditions and can be easily scaled up on large surface area substrates; (2) Ni, Mo, and S precursors used for the deposition are readily available and relatively cheaper compared to similar methods; and (3) the synthesis procedure is simple, one step, and requires no further heat treatments. The deposited thin films have been examined using regular physical characterization techniques, and their HER activity has been evaluated through electrochemical methods. Ni0.96Mo0.04S, especially, has exhibited a promising H...

Large Wood and Instream Habitat for Juvenile Coho Salmon and Larval Lampreys in a Pacific Northwest Stream

AbstractThe influences of large wood on Pacific salmon are well‐studied, but such studies on nonsalmonid species such as lampreys are uncommon. To address this need, we evaluated the potential effects of large wood on larval lampreys (Pacific Lamprey Entosphenus tridentatus and potentially Western Brook Lamprey Lampetra richardsoni) as well as on juvenile Coho Salmon Oncorhynchus kisutch in a small, coastal, Oregon stream. Our objectives were to (1) identify instream habitat characteristics associated with the presence of larval lampreys and abundance of juvenile Coho Salmon and (2) evaluate how these characteristics were associated with instream wood. To address habitat use, we quantified presence of larval lampreys in 92 pools and abundance of juvenile Coho Salmon in 44 pools during summer low flows. We focused on a study reach where large wood was introduced into the stream between 2008 and 2009. Results indicated that presence of larval lampreys was significantly associated with the availability of fine sediment and deeper substrate. The abundance of juvenile Coho Salmon (fish per pool) was strongly associated with pool surface area and to a weaker extent with the proportion of cobble and boulder substrates in pools. Pools with wood, regardless of whether they were formed by wood, had significantly greater coverage of fine sediment, deeper substrate, and greater pool surface area. Taken together, these results suggest that instream wood can provide habitat associated with the presence of larval lampreys and greater abundance of juvenile Coho Salmon.Received September 11, 2016; accepted March 25, 2017 Published online May 31, 2017

Bipolar Electrodeposition: A Pathway for Direct-Write Patterning of Metals without Electrical Connections to the Substrate

Recent advances in additive manufacturing technologies have been primarily driven by the availability of simple, integrated software/hardware platforms capable of rendering computer aided design files into fabricated objects. These easy-to-use systems facilitate a wider range of users, allowing highly technological hardware (such as 3D-printing) to be used both by hobbyists and trained technicians [1]. Despite these advances in 3D-printing, a similar shift to fully software-reconfigurable electrodeposition-based prototyping has yet to emerge. The commercial electrodeposition patterning standard, through-mask plating, requires a mask and several deposition and etch steps to fully develop the pattern. More sophisticated electrochemical fabrication technology, such as EFAB or MICA, also need a series of deposition, planarization, and chemical etch steps to build 3D objects layer-by-layer. The reliance on masks and chemical etching limits the reconfigurability of these technologies. However, direct-write electrodeposition methods can bridge the advantages of electrodeposition-based fabrication to user friendly software reconfigurable additive manufacturing techniques. Microelectrodes and microjet nozzles have demonstrated local electrodeposition dictated by the geometry of the electrode or nozzle for direct-write patterning of materials [2-3]. Impinging jet electroplating was further expanded by our research group by implementing full software control of electrodeposition and mass transport conditions with a system called Electrochemical Printing (EcP) [4]. More recently, our lab modified the EcP system to operate in a bipolar manner, enabling direct-write electrodeposition and patterning without direct electrical connections to the substrate [5]. This configuration, which we call a scanning bipolar cell (SBC), is potentially advantageous for direct electrodeposition on surfaces that are difficult to connect to and allows for further automation of the software/hardware. Bipolar electrochemistry involves spatially segregated, equal and opposite oxidation and reduction reactions on a single substrate. In the SBC (shown schematically in Figure 1), reduction of metal ions to metal occurs beneath the microjet nozzle and oxidation of an electron-donating species in solution takes place across the far-field area of the conductive substrate. The constraint of connecting to the substrate in standard electroplating techniques is eliminated through more intricate electrolyte design. In this presentation, we outline the design guidelines for bipolar electrodeposition of metals across a wide range of nobilities (Ni, Cu, Ag, and Au), and discuss how the kinetic reversibility affects the spatiotemporal stability of the electrodeposited patterns. Selecting a suitable electron-donating oxidation chemistry for a given reduction chemistry depends on the reversibility and thermodynamics of the reduction redox couple. Nickel deposition is mostly irreversible, and therefore an electron-donator such as ascorbic acid oxidation to dehydroascorbic acid with an equilibrium potential more positive than that of nickel is used. This bipolar pair is thermodynamically uphill and the reactions are driven by additional current supplied by the SBC. For reversible deposition chemistries, such as silver reduction, previously patterned material can be electrochemically erased during subsequent patterning, since silver etching can act as the equal and opposite oxidation chemistry. This challenge is overcome by designing pseudo-stable baths, similar to electroless formulations, which protect the metal from oxidation. For silver reduction, Fe2+ oxidation to Fe3+ is used as the far-field oxidation chemistry. The electrolyte is designed so the equilibrium potential for Fe2+/Fe3+ is marginally less than that of Ag+/Ag(s) (about 20mV), creating a system where Fe2+ oxidation is preferential to silver etching. Electrodeposition manufacturing processes are unique for their ability to control vertical material resolution at the nanometer scale. Incorporating micropipettes and nanopipettes through direct-write electroplating with EcP or the SBC adds control of lateral resolution ideal for additive manufacturing and patterning. The highest value commercial application for metal patterning in this domain is in integrated circuit and printed circuit board manufacturing. Bipolar electrodeposition with the SBC offers a solution for automated direct-write patterning by eliminating the need to electrically connect to the multifaceted substrates in these industries. Further research in this area will explore scale-down of the SBC nozzles to sub-micron dimensions as well as the impact of substrate surface area on the spatiotemporal behavior of bipolar electrodeposition.

Corrosion Resistance of Stainless Steel Coated with Hydrogen Silsesquioxane Based Spin-on-Glass Coatings Cured in Oxygen Deprived Atmosphere

Thin coatings are applied as a promising surface finish to stainless steel engineering components in highly corrosive environments, where only minor deviations from the component geometry due to coating thickness can be tolerated. In particular silica-based coating systems have gained academic as well as industrial interest due to their outstanding performance in terms of mechanical and electrochemical performance. The aim of this study is to investigate the protective behavior of SiOx coatings from hydrogen silsesquioxane, (HSiO3/2)n, spin-on-glass precursor on AISI 316L 2B substrates in saline environment. The precursor has been deposited on the substrate and thermally cured in oxygen deprived atmosphere at temperatures ranging from 400-800 ˚C. The results showed the formation of highly polymerized SiOx coatings containing various amounts of residual Si-H and silanol moieties. Moreover, the degree of coating polymerization was assessed based on the amount of residual Si-H and an increase in polymerization was found with increasing curing temperature up to 800 ºC. Further, the electrochemical behavior of the coating systems was characterized by linear cyclic polarization and electrochemical impedance spectroscopy. The results showed that the coatings decreased the electrolyte-exposed substrate surface area significantly and possessed enhanced barrier properties with respect to films cured in oxidizing ambient, yielding a minimal corrosion rate in electrochemical tests. Furthermore, the excellent performance of the coating systems in short term electrochemical studies were critically evaluated in comparison to prolonged exposure in accelerated corrosion tests and substrate sensitization due to the deposition process.

Ultra-high open-circuit voltage of perovskite solar cells induced by nucleation thermodynamics on rough substrates

To obtain high performance CH3NH3PbI3 perovskite solar cells, it is highly important to realise a high open-circuit voltage. Calculation results based on a modified diode model have indicated that a low bare ratio ϕ of the perovskite film is the most important factor determining the open-circuit voltage, where ϕ is defined as the ratio of the projection of the uncovered area of the perovskite film to the apparent area of the total substrate surface. To realise a low ϕ, we investigate the nucleation behaviour of crystals on rough substrates. The analysis results predict that, when CH3NH3PbI3 is deposited on conventional transparent conductive oxide substrates such as fluorine-doped tin oxide, preferential heterogeneous nucleation will occur on the concave regions of the substrate; then, depending on the subsequent growth step, full coverage of the perovskite film at both the macroscopic and microscopic scales is realised. As a result, an ultra-high open-circuit voltage, i.e., 1.20 V, can be achieved in devices using the full coverage CH3NH3PbI3 film. The thermodynamics theory of precipitation nucleation should shed light on solution engineering of thin films.

Three-Dimensional Copper Foam Supported CuO Nanowire Arrays: An Efficient Non-enzymatic Glucose Sensor

Metal and metal oxides with various nanostructures have been widely studied in non-enzymatic glucose sensing. In this work, we report an efficient catalyst platform, which is made of three-dimensional copper foam (CF) skeleton and copper oxide nanowire arrays (CuONWA), is used to construct glucose sensor. The three-dimensional CuONWA/CF was synthesized via a facile wet-chemical method and subsequent annealing. The CuONWA is evenly covered by CuO nanoflowers. The morphology and composition of the platform were characterized. The nanowire arrays and nanoflowers both enhanced the electrocatalytic performance of the integrated electrode via greatly increasing the surface area of the CF substrate. The electrocatalytic properties of the non-enzymatic glucose sensor were characterized by a series of electrochemical measurements. The sensor exhibits excellent performance, with a linear range of 0.10μM–0.50mM, a sensitivity of 32330μAmM−1cm−2, a low limit of detection of 20nM (S/N=3), excellent selectivity, reproducibility, and stability. The sensor was also used for glucose sensing in human serum and Wahaha ice black tea, with relative standard deviations (for n=6) of 3.15% and 2.43%, respectively.