Control Of Surface Morphology Research Articles

A new technique for the synthesis of lanthanum substituted nickel cobaltite nanocomposites for the photo catalytic degradation of organic dyes in wastewater

Developing cost-effective and more efficient nanocatalysts for the treatment of organic pollutants from process industry is always challenging for the researchers working in the field of chemistry, chemical, energy and environment engineering. In this work, a cost-effective and more efficient nanocatalysts, i.e., Nickel Cobaltite nanocomposites and its Lanthanum (La) doped derivatives with controlled surface morphology has been synthesized at 393.15 K through single step sol–gel method. The surface morphology, chemical composition, and crystal structure of the synthesized nanocomposites were analysed by scanning electron microscopy (SEM), Fourier transformed infrared spectroscopy (FTIR), and X-rays diffraction (XRD), respectively. The rough surface and well-crystallized metallic nanocomposites confirm the successful synthesis of nanocatalysts. The molar ratio of Lanthanum to Cobalt (Lax:Coy) showed a significant influence on the surface morphology and catalytic activity (Kapp = 0.15–0.47 min−1) of the products. Synthesized nanocomposites showed high catalytic activity for the reduction of methylene blue under solar irradiation. Photocatalytic results for the reduction of methylene blue show that the catalytic activity of synthesized nanocatalysts increases with the increase in the doping concentration of Lanthanum.

Gold-Nanoparticles/Boron-Doped-Diamond Composites as Surface-Enhanced Raman Scattering Substrates**Supported by the National Natural Science Foundation of China (Grant Nos. 51672102 and 51972135).

By vacuum sputtering and annealing processes of gold (Au) films on boron-doped diamond (BDD) surfaces, Au-nanoparticles/BDD (AuNP/BDD) composite substrates were prepared as surface-enhanced Raman scattering (SERS) substrates. The SERS performances of the substrate were investigated using methylene blue molecule as a probe. With the AuNPs having an average diameter of 20 nm, high performance of SERS was achieved at an enhancement factor of 9 × 105, arising from the synergistic effect of electromagnetic enhancement from AuNPs and chemical enhancement from diamond. The AuNP/BDD substrate is demonstrated to be highly sensitive, reproducible, stable, and reusable for the SERS examination. Due to the facile preparation process and controllable surface morphology, the AuNP/BDD substrates are favorable as a high performance SERS platform performed in practical applications.

One-step in situ preparation of flexible CuS/TiO2/polyvinylidene fluoride fibers with controlled surface morphology for visible light-driven photocatalysis

In this study, flexible CuS/TiO2/polyvinylidene fluoride (PVDF) fibers with controlled surface morphologies were successfully prepared in situ via one-step hydrothermal growth. The morphology was controlled based on the amounts of the Cu source and functional surfactant cetyltrimethylammonium bromide (CTAB) used in the preparation process. When the amount of CTAB was kept constant, the Cu source significantly affected the amount of CuS nanoflowers loaded on the TiO2/PVDF fibers as well as the morphology of the CuS. When the amount of Cu source was kept constant, the addition of CTAB had a key effect on the morphology of the CuS. By decreasing the amount of CTAB, the morphology of the CuS loaded on the TiO2/PVDF fibers gradually changed from dense nanoflowers into small flake particles. Under irradiation with visible light, experiments based on the photodegradation of levofloxacin hydrochloride (LFXH) showed that Cu1C0.01 (CuS/TiO2/PVDF fibers prepared with 1 mmol Cu(NO3)2·3H2O and 0.01 mmol CTAB) obtained the highest degradation efficiency. Due to the morphology of Cu1C0.01 comprising small flake particles, CuS could fully contact with the internal TiO2 and pollutants, thereby allowing photogenerated carriers to fully participate in the photodegradation reaction. Further analysis demonstrated that photogenerated holes (h+) played a key role in the photodegradation of LFXH.

Bio‐Inspired Nanospiky Metal Particles Enable Thin, Flexible, and Thermo‐Responsive Polymer Nanocomposites for Thermal Regulation

AbstractSafety issues remain a major obstacle toward large‐scale applications of high‐energy lithium‐ion batteries. Embedding thermo‐responsive polymer switching materials (TRPS) into batteries is a potential strategy to prevent thermal runaway, which is a major cause of battery failures. Here, thin, flexible, highly responsive polymer nanocomposites enabled by bio‐inspired nanospiky metal (Ni) particles are reported. These unique Ni particles are synthesized by a simple aqueous reaction at gram‐scale with controlled surface morphology and composition to optimize electrical properties of the nanocomposites. The Ni particles provide TRPS films with a high room‐temperature conductivity of up to 300 S cm−1. Such TRPS composite films also have a high rate (<1 s) of resistance switching within a narrow temperature range, good reversibility upon on/off switching, and a tunable switching temperature (Ts; 75 to 170 °C) that can be achieved by tailing their compositions. The small size (≈500 nm) of Ni particles enables ready fabrication of thin and flexible TPRS films with thickness approaching 5 µm or less. These features suggest the great potential of using this new type of responsive polymer composite for more effective battery thermal regulation without sacrificing cell performance.

Lattice bow in thick, homoepitaxial GaN layers for vertical power devices

Lattice bow generated by 40 µm thick HVPE homoepitaxial layers on commercial free-standing, ammonothermal and HVPE GaN wafers was studied. While a change in lattice bow was measured for all wafers, the additional bow on the ammonothermal GaN wafers was minimal. The main driving force for the observed increase in the lattice bow for HVPE wafers was related to stress in the films generated by the elongation of dislocations via climb and generation of new dislocations at the homoepitaxial interface. Lattice bow is a crucial wafer parameter as it determines the variation of the offcut across the surface. If an offcut variation of 0.1° is allowed for desired control surface morphology, composition of alloys, and uniformity of doping on this surface, the measured bow on the two HVPE GaN wafers and one ammonothermal GaN wafer limits their uniformity-diameter to ~0.5″, 1″ and >4″, respectively.

Intercalation-type electrodes of copper–cobalt oxides for high-energy-density supercapacitors

A series of CuxCo3-xO4 nanostructures (CCO) with a controllable surface morphology and oxygen vacancy density are directly grown on charge-collecting substrates via an electrochemical deposition process and subsequently used as intercalation-type electrodes for high-energy-density supercapacitors (SCs). The capacitive performance of the CCOs is strongly dependent on the rate of oxygen diffusion via intercalation in oxygen-deficient CCOs. The nanopetal electrode of Cu0.95Co2.05O4 calcined at 200 °C (CCO-200) exhibits a capacitance of ~1890 F g−1 at a scan rate of 10 mV s−1, whereas it decreases gradually with increasing sintering temperature. A symmetric CCO-200@stainless steel SCs exhibits a capacitance and an energy density as high as ~865.50 F g−1 and 108.18 W h kg−1, respectively, at a current density of 1.25 A g−1 with high durability for 10,000 cycles. The enhanced capacitive performance is attributed to the high electrical conductivity and high oxygen diffusion rate in CCO-200.

The enhanced performance of capacitive-type humidity sensors based on ZnO nanorods/WS2 nanosheets heterostructure

Zinc oxide (ZnO) is a promising candidate for humidity-sensing materials due to its low-cost preparation, superior chemical and thermal stability, controllable surface morphology, and low water solubility. However, pristine ZnO-based humidity sensors suffer from poor response and large hysteresis that limit their application. In this study, n-type semiconducting tungsten disulfide (WS2) was utilized to form ZnO nanorods/WS2 nanosheets heterostructure grown on indium tin oxide coplanar electrode-coated glass substrate. The capacitive-type humidity sensing characteristics were investigated at room temperature. The results show that for humidity ranges of 18–85 % RH, three deposition cycles of WS2 nanosheets onto ZnO nanorods produced significant improvements in the response, sensitivity, and hysteresis with an unchanged response and recovery times compared to pristine ZnO sensors. This improved sensor performance might be due to the ability of WS2 to provide more water molecule adsorption sites. The formation of an n-n junction between ZnO and WS2 created interfaces with high local charge density and built an internal electric field that increase the water dissociation rate. The improved hysteresis might be due to water molecule adsorption on WS2 nanosheets is physical adsorption that facilitates the desorption process.

Influence of annealing temperature on the physical and photoelectric properties of Gd/Fe1.727Sn0.205O3 nanoparticles for solid oxides fuel cell application

Gadolinium doped tin oxide–iron oxide nanoparticles (Gd/Fe1.727Sn0.205O3) were synthesized via sol–gel method followed by hydrothermal method. Ethylene glycol played the role of directing agent to control surface morphology. Physical and optical properties of Gd/Fe1.727Sn0.205O3 nanoparticles were studied as a function of calcination temperature. Characterization techniques like thermogravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), particle size analyzer (PSA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Visible spectroscopy (UV–VIS), and four-point probe technique have been used to study the thermal degradation, kinetics, thermodynamic properties, structural analysis, surface morphology, optical and electrical properties of nanoparticles. Prominent peaks in FTIR spectra at 563, 418, and 542 cm−1 were observed for Fe–O, Sn–O, and Gd–O, respectively. The uncalcined nanoparticles follow first order kinetics and Freeman–Carrol method was applied for calculating the activation energy. It was observed that nanoparticles calcined at 700 °C have 8.9 nm particle size calculated with particle size analyzer, which is smallest among all and having band gap energy of 2.3 eV. SEM micrographs show hexagonal geometry. The dependence of electrical resistance on temperature shows that these nanoparticles possess semiconducting behavior. These nanoparticles can be used as cathode material for solid oxides fuel cells (SOFCs) application. The nanoparticles calcined at 700 °C showed highest power density of 83.27 W cm−2 at 650 °C with open current voltage of 0.793 V.

Controlling surface morphology by nanocrystalline/amorphous competitive self-phase separation in thin films: Thickness-modulated reflectance and interference phenomena

Controlling surface morphology is a key issue for obtaining functional materials with surface-based properties. In this paper, we explore the possibility of using the self-separation of phases as a way of controlling the surface morphology features. We demonstrate using X-ray diffraction and transmission electron microscopy that a competitive self-separation of a nanocrystalline and an amorphous phases occurs in co-sputtered Zr-Mo thin films with a Mo content of 60 at%, corresponding to a composition intermediate to those necessary to form single-phased amorphous and nanocrystalline films. The dependence of the residual stress with the thickness at the biphased composition is discussed in terms of the morphology evolution and a possible mechanism for the self-separation of phases is presented. We show that the self-separation of phases as presented here is not limited to Zr-Mo alloys and can be extended to other systems. By changing the film thickness, it is possible to change the surface morphology of the films at the biphasic composition, due to the competitive growth of the nanocrystalline phase in the amorphous phase. In this way, it was possible to control the surface roughness and, because of this, tuning the film reflectance at a determined wavelength. The occurrence of an interference pattern in the reflectance spectra was discussed and associated to the presence of two different height levels at the film surface.

Development of alginate hydrogel modified multifunctional filtration membrane with robust anti-fouling property for efficient water purification

Anti-fouling behavior of separation membranes has attracted continuous interest. In particular, crude oil is easy to adhere to many surfaces owing to its high adhesive characteristic, and the issue of treatment of crude oil-in-water emulsion is a challenge. Hydrogel modified composite has the robust potential to deal with crude oil-in-water waste, and the critical issue is the development of a hydrogel layer with controllable thickness and micro- and nanosized membrane pores. Thus, novel separation composite membrane derived from porous Ca2+/alginate hydrogel thin film on commercial filter paper supporting substrate (alginate@FP) was fabricated via freeze drying and subsequent in-situ gelation. Furthermore, SEM, FT-IR, EDS and contact angle tests were used to characterize the physical and chemical properties of the composite membranes, and the permeance and rejection ability of the as-prepared filtration membranes were determined. As a result, the alginate@FP behaves an excellent superhydrophilicity, underwater superoleophobicity, anti-crude oil-fouling performance and self-cleaning effect. Besides, with controllable thickness and surface morphology, both the high flux and efficient emulsion separation were well-obtained. At the same time, it exhibits good reusability, and is stable in kinds of chemical environments. On the other hand, due to the negatively charged membrane surface, soluble dyes and some metal ions can also be removed with a high efficiency through filtration, simultaneously.

Study on controllable surface morphology of the micro-pattern fabricated on metallic foil by laser shock imprinting

Laser shock imprinting was an advanced micro/nanostructure forming method, and had great potential application in Micro Electro Mechanical Systems (MEMS) and optoelectronic devices. However, the residual rough structure and micro defects on imprinted micro-pattern limited the industrial application of laser shock imprinting. In the study, the laser pre-shocked aluminum foil was introduced for fabricating ultrasmooth micro-pattern with high mechanical properties. The effect of laser pulse energy and overlap ratio on the micro-pattern imprinting was characterized by 3D morphology and deformation depth. The local morphology and nanoindentation of micro-pattern on different locations were also investigated to reveal robustness of roughness and mechanical properties. The experimental results indicated that the morphology and mechanical properties of micro-pattern on laser pre-shocked aluminum foil were greatly improved than that of on original aluminum foil. The laser pulse energy and overlap ratio had great influence on forming depth, and the morphology and mechanical properties of micro-pattern groove were better than that of the micro-pattern center. The hardness and roughness on micro-pattern groove were changed obviously (the hardness increased about 10% and the average roughness decreased to 4 nm). The laser pre-shock imprinting physics mechanism was evaluated by finite element modeling. The presented study demonstrated that appropriate laser shock imprinting parameter can realize to fabricate ultrasmooth, precise, controllable, and high mechanical properties micro-pattern on laser pre-shocked aluminum foil.

Nickel-iron selenide polyhedral nanocrystal with optimized surface morphology as a high-performance bifunctional electrocatalyst for overall water splitting

Abstract Constructing earth-abundant and efficient electrocatalysts for overall water splitting are still in the research and exploration stage. In this work, the Fe-doped NiSe2 polyhedron nanocrystals grown on Ni foam (Ni0.75Fe0.25Se2@NF) with controllable surface morphology are developed as high-performance bifunctional electrocatalysts. The surfaces of the optimized polyhedron nanocrystals provide high density of catalytic active sites. NiSe2 is originally a catalytic active substance, and the Fe doping in NiSe2 can greatly enhance the conductivity. The optimized Ni0.75Fe0.25Se2@NF (6 h) electrode are performed in an alkaline solution, exhibiting outstanding OER and HER activity with small overpotentials of 210 mV and −117 mV to reach current density of 10 mA cm−2 and −10 mA cm−2, respectively. Remarkably, the Ni0.75Fe0.25Se2@NF (6 h) electrode serve as cathode and anode in water splitting electrolyzer also demonstrates highly efficient overall water electrolysis performance, with a relatively low cell voltage of 1.61 V at 10 mA cm−2 (1.57 V for RuO2(+)//Pt/C(−) couple) and excellent long-term stability of 50 h for overall water electrolysis.

Controlled Surface Wettability by Plasma Polymer Surface Modification

Inspired by nature, tunable wettability has attracted a lot of attention in both academia and industry. Various methods of polymer surface tailoring have been studied to control the changes in wetting behavior. Polymers with a precisely controlled wetting behavior in a specific environment are blessed with a wealth of opportunities and potential applications exploitable in biomaterial engineering. Controlled wetting behavior can be obtained by combining surface chemistry and morphology. Plasma assisted polymer surface modification technique has played a significant part to control surface chemistry and morphology, thus improving the surface wetting properties of polymers in many applications. This review focuses on plasma polymerization and investigations regarding surface chemistry, surface wettability and coating kinetics, as well as coating stability. We begin with a brief overview of plasma polymerization; this includes growth mechanisms of plasma polymerization and influence of plasma parameters. Next, surface wettability and theoretical background structures and chemistry of superhydrophobic and superhydrophilic surfaces are discussed. In this review, a summary is made of recent work on tunable wettability by tailoring surface chemistry with physical appearance (i.e. substrate texture). The formation of smart polymer coatings, which adjust their surface wettability according to outside environment, including, pH, light, electric field and temperature, is also discussed. Finally, the applications of tunable wettability and pH responsiveness of polymer coatings in real life are addressed. This review should be of interest to plasma surface science communality particularly focused controlled wettability of smart polymer surfaces.

CONTROLLED MORPHOLOGICAL EVOLUTIONS OF SILVER FILMS ON COMPLIANT SUBSTRATES BY TUNING MECHANICAL STRAIN

Controlled surface morphologies of stiff films on compliant substrates possess a variety of applications, ranging from stretchable electronics, surface engineering to biomimics. Here, we report on the morphological evolutions of silver films deposited on prestretched compliant PDMS substrates by tuning the film strain in unloading, reloading and further stretching processes. It is found that the silver films generate transverse (perpendicular to the loading direction) wrinkles and longitudinal (parallel to the loading direction) cracks during the unloading process. On the contrary, longitudinal wrinkles and transverse cracks can be observed during the further stretching process. The morphological characteristics, evolution behaviors and mechanical mechanisms of the crack and wrinkle patterns are investigated in detail. The report in this work could promote a better understanding of the morphological evolutions of stiff films on compliant substrates by tuning the mechanical strain.

Role of Oxygen Vacancy in Copper-Cobalt Spinel Nanostructures for Electrochemical Energy-Storage

The incorporation of oxygen vacancies in metal oxides has been reported to remarkably increase their electrochemical performance in water splitting, photoluminescence, and electrochemical energy-storage. The oxygen vacancies are originated by removal of neutral oxygen atoms from the metal oxides, leaving excess electrons in the vacancies. The excess electrons offer high electrical conductivity, huge number of electroactive sites at or within the surface of metal oxides that could facilitate a adsorption/intercalation of anions (e.g., OH-) at or within the electrode surface and diffusion of ions and electrons within the electrode/electrolyte interface for efficient energy-storage. It has been reported that the spinels with the proper oxygen vacancies could exhibit higher capacitance values compared with that for perfect-crystal. The agglomerated nanostructures of the spinels, Cu2Co2O4 are often prepared by conventional solid-phase or solvothermal/hydrothermal methods, which require non-conductive binders (e.g., Nafion and polyvinylidene fluoride (PVDF)) to achieve strong and stable adhesion onto a substrate. In addition, the conventional synthetic method usually requires high-temperature sintering with complicated procedures, which creates morphological deformation and severe aggregation, decreasing the content of electroactive oxygen vacancies. Therefore, the development of a synthetic procedure is one of the most important tasks needed to get effective nanostructures of Cu2Co2O4 with controllable surface morphology, oxygen vacancies/electroactive sites, and electrical conductivity for the application in capacitors as effective electrode materials. In the present report, we directly grew a series of CuxCo3 - xO4 nanostructures with controllable surface morphology, oxygen vacancies/electroactive sites and electrical conductivity on a stainless steel substrate by a simple and straightforward electrochemical deposition process and applied them as electrodes for electrochemical charge-storage.

Improved performance of ferroelectric nanocomposite flexible film based triboelectric nanogenerator by controlling surface morphology, polarizability, and hydrophobicity

In recent years, triboelectric nanogenerator (TENG) has been attracting lots of attention for harvesting electrical energy from mechanical energy, because of its simplicity in designing, cost-effectiveness, and high output power. In the present trend, the performance of TENG is improved mainly by surface modification using complex techniques. In the present work, we have demonstrated enhanced triboelectrification between polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) by incorporating ZnO nanorods into PVDF polymer. The fabricated ZnO-PVDF/PTFE based TENG showed 21% enhanced output voltage and 60% enhanced short-circuit current in comparison to PVDF/PTFE based TENG with an instantaneous output power density of ∼10.6 μW/cm2. The increase in triboelectrification comes not only from the enhancement in β-phase content, which leads to increase polarizability, but also from the enhancement in surface roughness, hydrophobicity, and a decrease in the work function of PVDF after incorporating ZnO nanorods.

Fabrication of superhydrophobic surfaces with tunable water droplet adhesion force by a two-step method

Abstract In this paper, we present a convenient approach to prepare hierarchical structured superhydrophobic coatings with tunable adhesion force, composed of micro-size glass beads, nano-size SiO2 particles and epoxy resin. Surfaces of two types with different roughness were fabricated, one type is only with single-scale roughness demonstrating lotus effect with low sliding angle, the other type is hierarchically micro-nano-structured roughness exhibiting petal effect with high adhesion force. The surface roughness is pivotal for controlling the wetting behavior and regulating the contact angle including the contact angle hysteresis. Varying the density of micro-size glass beads could adjust the roughness of the surface, which means the adhesion force of the prepared surface could be easily controlled based on the proposed method. Through variation of glass beads’ amount, the surface could be designed to pin the water droplet with different adhesion force when the surface turned upside down. The surface wettability, surface morphology, adhesion force of the prepared samples are investigated and mechanism of the Cassie-to-Wenzel state transition are discussed in detail. Furthermore, the convenient method provides a possibility for controlling surface morphology, composition and corresponding surface adhesion which could be applied to various substrates such as tile, wood, steel and fabric.

Boosting Efficiency in Polycrystalline Metal Halide Perovskite Light-Emitting Diodes

Metal halide perovskites (MHPs) have outstanding photophysical properties and are therefore being evaluated as next-generation light emitters. Within just a few years, the efficiencies of polycrystalline perovskite light-emitting diodes (PeLEDs) have been drastically improved and are catching up with those of conventional organic LEDs. The electroluminescence efficiency of polycrystalline PeLEDs has been limited by shortcomings such as limited outcoupling efficiency, charge imbalance in MHP emitting layers, difficulty controlling surface morphology, small exciton binding energy at room temperature, and nonradiative recombination at defect sites. In this Perspective, we focus on promising strategies such as optical engineering, charge balance control, morphological and nanograin engineering, and chemical modification to overcome these shortcomings and suggest future directions for research to further improve the efficiencies of polycrystalline PeLEDs.

Synthesis of an Aqueous Self-Matting Acrylic Resin with Low Gloss and High Transparency via Controlling Surface Morphology.

This paper reports on a novel, film-forming acrylic polymer resin that exhibits low-gloss surface and high transparency via controlling film morphology at sub-micron roughness levels. Such microstructure is controlled by means of the copolymerization process increasing the allyl methacrylate (AMA) crosslinker content from 0 to 0.4 wt %. This acrylic resin makes it possible to avoid high loadings of matting agents, while also having good abrasion resistance and soft-touch feeling. Gloss levels of as low as 4 units at 60° incident angle and light transmittance of up to 85% have been achieved. The chemical structure of the aqueous acrylic resin was characterized by ATR-FTIR and NMR spectroscopy. The film morphology and surface roughness were measured by SEM and AFM analysis. The emulsion particle morphology and glass transition temperature were obtained by TEM and DSC, respectively. The effects of the crosslinker content on the light transmittance, glass transition temperature, and thermal degradation stability were also discussed in detail. The characterization results conclude that an acrylic polymer with interesting optical properties and high thermal stability can be obtained, which is desirable for leather applications.

Effect of Alkylamines on Morphology Control of Silver Nanoshells for Highly Enhanced Raman Scattering.

Morphology control of the surface of a nanostructure is a key issue in modulating its surface plasmon resonance and scattering properties. Here, we studied the effect of alkylamines on morphology control during the one-step fabrication of silver nanoshells (NSs) for highly enhanced Raman scattering. Various types of alkylamines were used to study the effects of chain length, existence of hydroxyl groups, and degree of alkyl chains on the surface morphology of silver NSs. The alkylamines influenced the silver ion reduction and the growth of silver domains, resulting in distinctive morphology changes. The optical properties of the silver NSs of different surface morphologies were characterized by surface-enhanced Raman spectra. Especially, when long alkylamines were used, intense and uniform surface-enhanced Raman scattering signals were obtained at the visible and near-infrared (NIR) region, and their enhancement factor was ∼107. To detect cancer biomarkers in vivo, as a feasibility test, silver NSs were modified to highly NIR-active nanoprobes and successfully applied to detect colon cancer without causing nonspecific interactions. Our one-step fabrication method of silver NSs is simple and can overcome various hurdles of morphology control and can be extended to other metal nanostructures of controlled surface morphologies or shape.