Substrates In Aqueous Solution Research Articles

Properties and corrosion protection of polypyrrole prepared by electrochemical polymerization on aluminum

AbstractIn a one‐step procedure that did not require any surface preparation, polypyrrole (PPy) films doped with 3‐nitrosalicylic acid (3Nisa) became effectively electropolymerized on the aluminum substrate in aqueous solutions. Fourier transform infrared, scanning electron microscopy, and thermal gravimetric analysis were used to analyze the properties of PPy‐based films. Open circuit potential (OCP), electrochemical impedance spectroscopy, Tafel polarization, and salt spray tests were used to study the corrosion‐resistant efficiency of the coatings. The as‐prepared PPy films performed corrosion resistance on aluminum in the 3% NaCl solution. However, the PPy films prepared in the 0.01 m solution of 3Nisa showed the best protection ability on aluminum. The self‐healing characteristic of the PPy films was recorded by varying the potential in the OCP measurement. The findings indicate the potential of using 3‐nitrosalicylic acid‐doped PPy films for applications as anti‐corrosion coatings for aluminum.

Tribological Properties and Corrosion Resistance of Multilayer a-C:H:Ti Films at Different Target Currents

To meet the requirements of friction and corrosion resistance performance of helicopter transmission bearings under harsh environments, Ti/TiN/Ti-DLC multilayer composite films were prepared on a 40Cr15Mo2VN substrate by a non-equilibrium magnetron sputtering technique. The effects of different titanium currents on the structure, mechanical properties, and friction properties of the films were investigated by SEM, Raman spectroscopy, and nanoindentation. Moreover, the tribological and corrosion resistance of developed films under acidic conditions were investigated. The results show that the sp3-C/sp2-C ratio in the films gradually decreases with increasing Ti current from 0 A to 2 A, leading to decreased hardness and elastic modulus. The bonding force of the DLC films also gradually increases with increasing Ti current and reaches the maximum value of 41.69 N at 2 A; the friction coefficient of the films gradually decreases under a load of 20 N. In summary, the best performance of thin film at Ti-2 A was compared with the corrosion and wear performance of thin film and substrate in acetic acid solution and aqueous solution at Ti-2 A. The wear amount of thin film and substrate in aqueous solution is significantly lower than in acetic acid solution, and the corrosion potential of thin film is higher than that of substrate in both solutions, which can play a protective role against the substrate.

Photo-reforming and degradation of waste plastics under UV and visible light for H2 production using nanocomposite photocatalysts

Plastics are recalcitrant and difficult to be removed from a natural environment. As a result, plastics have accumulated in the environment and food chain, causing adverse effects on living organisms and human health. Photo-reforming, a process of generating H2 from an organic substrate in aqueous solutions using catalysts, is promising to address the challenge of treating plastics and recovering energy from these large-volume waste products. TiO2 nanoparticles doped with Au and Pt and ZnO doped with Pt were studied to enhance the light utilization efficiency and catalytic activity. The preliminary photodegradation screening experiments revealed that 5 % Au-doped TiO2 (Au/TiO2) was the most photoactive catalyst among the developed catalysts. However, Pt/TiO2, Au/TiO2, and Pt/ZnO performed differently in H2 evolution experiments. The change of the Au/TiO2 properties was characterized using a transmission electron microscope (TEM), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy. Computational simulation using Quantum ESPRESSO was performed to predict the narrowed bandgap of TiO2 when the surface of nano-TiO2 particles was modified with nano-Au particles.Polyethylene terephthalate (PET) was selected as representative plastic for photo-reforming, which was demonstrated effective for degrading and converting common plastic wastes to H2. The effectiveness of pre-treatment using different KOH concentrations and temperatures was studied to achieve efficient PET hydrolysis. H2 production under the different pretreatment conditions showed that higher temperature and KOH concentration increased hydrogen yield. Further, Pt/TiO2 performed better than Au/TiO2 in H2 production while Pt/ZnO was the lowest hydrogen producer. Microscopic examination and FTIR analysis were conducted to identify the morphology and functionality change during the photo-reforming of PET. The variation of carbonyl index, vinyl index, and band area ratios respective to the C-H band area confirmed the plastic degradability. This study demonstrates that photo-reforming is an attractive, low-cost, easy-to-use clean H2 technology, which improves environmental sustainability by reducing greenhouse gas emissions and removing plastic waste using solar energy.

Facile method to activate substrate for oxygen evolution by a galvanic-cell reaction.

NiFe layered double hydroxide (NiFe LDH) is a promising material with multiple functions. In this communication, a novel method is used to prepare NiFe LDH. This synthesis method is achieved via galvanic-cell corrosion between nickel and iron substrates in aqueous solutions containing a halogen group anion (e.g., Cl) at ambient temperature. The as-prepared NiFe LDH electrodes are developed as electrocatalysts for the oxygen evolution reaction (OER) and exhibit excellent catalytic activities and durability. This work provides an energy-efficient, cost-effective, and scaled-up corrosion engineering approach for manufacturing NiFe LDH materials.

Wafer-Scale Full-Coverage Self-Limiting Assembly of Particles on Flexible Substrates.

Self-limiting assembly of particles represents the state-of-the-art controllability in nanomanufacturing processes where the assembly stops at a designated stage, providing a desirable platform for applications requiring delicate thickness control such as optics, electronics, and catalytic systems. Most successes in self-limiting assembly are limited to self-assembled monolayers (SAMs) of small molecules on inorganic, chemically homogeneous rigid substrates (e.g., Au and SiO2) through surface-interaction mechanisms. Similar mechanisms, however, cannot achieve a uniform assembly of particles on flexible polymer substrates. The complex configurations and conformations of polymer chains create a surface with nonuniform distributions of chemical groups and phases. In addition, most assembly mechanisms require good solvent wettability, where many desirable but hard-to-wet particles and polymer substrates are excluded. Here, we demonstrate a collision-based self-limiting assembly (CSA) to achieve wafer-scale, full-coverage, close-packed monolayers of hydrophobic particles on hydrophobic polymer substrates in aqueous solutions. The kinetic assembly and self-limiting processes are facilitated and controlled by the combined acoustic and shear fields. We envision many applications in functional coatings and showcase their feasibility in structural coloration. Importantly, such functional coatings can be repaired using CSA, and both particles and polymer substrate can be recycled.

Plasmonic photocatalysis in aqueous solution: assessing the contribution of thermal effects and evaluating the role of photogenerated ROS.

Plasmon-induced photocatalysis can drive photochemical processes with an unprecedented control of reactivity, using light as sole energy source. Nevertheless, disentangling the relative importance of thermal and non-thermal features upon plasmonic excitation remains a difficult task. In this work we intend to separate the role played by the photogenerated charge carriers from thermal mechanisms in the plasmonic photo-oxidation of a model organic substrate in aqueous solution and using a metal-semiconductor hybrid as model photocatalyst. Accordingly, we present a simple set of experimental procedures and simulations that allow us to discard the thermal dissipation upon plasmonic excitation as the main driving force behind these chemical reactions. Moreover, we also study the photogeneration of reactive oxygen species (ROS), discussing their fundamental role in photo-oxidation reactions and the information they provide regarding the reactivity of the photogenerated electrons and holes.

Substrate Protection in Controlled Enzymatic Transformation of Peptides and Proteins.

Proteins are involved in practically every single biological process. The many enzymes involved in their synthesis, cleavage, and posttranslational modification (PTM) carry out highly specific tasks with no usage of protecting groups. Yet, the chemists’ strategy of protection/deprotection potentially can be highly useful, for example, when a specific biochemical reaction catalyzed by a broad‐specificity enzyme needs to be inhibited, during infection of cells by enveloped viruses, in the invasion and spread of cancer cells, and upon mechanistic investigation of signal‐transduction pathways. Doing so requires highly specific binding of peptide substrates in aqueous solution with biologically competitive affinities. Recent development of peptide‐imprinted cross‐linked micelles allows such protection and affords previously impossible ways of manipulating peptides and proteins in enzymatic transformations.

Galvanostatically deposited Co3O4–NiO nanocomposite thin films onto FTO glass substrates: An investigation of their microstructural and supercapacitive properties

Co3O4-NiO based nanocomposite films were electrochemically deposited onto FTO glass substrates in aqueous solutions containing different mole ratio of cobalt (II) and nickel (II). The structural characteristics of the films examined by X-ray diffraction reveal that the Co3O4 cubic phase dominates over the NiO cubic phase in the composite films. Field emission scanning electron micrographs show that the composite films 1C1NO (Co/Ni mole ratio 1:1) and 2C1NO (Co/Ni mole ratio 2:1) have the porous nanofibers-like structure and the porous nanorods-like structure, respectively. The nanocomposite films exhibit the synergistic effect of both metal oxides, resulting in a significantly higher specific capacitance. The cyclic voltammetry measurements show that the 2C1NO film has the optimum specific capacitance values of 256 and 233.3 Fg−1 at the scan rates of 10 and 20 mVs−1, respectively. However, at higher scan rates of 50 and 100 mVs−1, the 1C1NO composite film exhibits the optimum specific capacitance. The galvanostatic charge-discharge measurements show that the 2C1NO composite film has the highest specific capacitance (267.2 Fg−1) and energy density (6.48 Whkg−1) at the current density of 1 mAcm−2, whereas it exhibits the highest power density (6885.36 Wkg−1) at 3 mAcm−2 current density.

Morphology Controlled Synthesis of γ-Al2O3 Nano-Crystallites in Al@Al2O3 Core-Shell Micro-Architectures by Interfacial Hydrothermal Reactions of Al Metal Substrates.

Fine control of morphology and exposed crystal facets of porous γ-Al2O3 is of significant importance in many application areas such as functional nanomaterials and heterogeneous catalysts. Herein, a morphology controlled in situ synthesis of Al@Al2O3 core–shell architecture consisting of an Al metal core and a porous γ-Al2O3 shell is explored based on interfacial hydrothermal reactions of an Al metal substrate in aqueous solutions of inorganic anions. It was found that the morphology and structure of boehmite (γ-AlOOH) nano-crystallites grown at the Al-metal/solution interface exhibit significant dependence on temperature, type of inorganic anions (Cl−, NO3−, and SO42−), and acid–base environment of the synthesis solution. Different extents of the electrostatic interactions between the protonated hydroxyl groups on (010) and (001) facets of γ-AlOOH and the inorganic anions (Cl−, NO3−, SO42−) appear to result in the preferential growth of γ-AlOOH toward specific crystallographic directions due to the selective capping of the facets by adsorption of the anions. It is hypothesized that the unique Al@Al2O3 core–shell architecture with controlled morphology and exposed crystal-facets of the γ-Al2O3 shell can provide significant intrinsic catalytic properties with enhanced heat and mass transport to heterogeneous catalysts for applications in many thermochemical reaction processes. The direct fabrication of γ-Al2O3 nano-crystallites from Al metal substrate with in-situ modulation of their morphologies and structures into 1D, 2D, and 3D nano-architectures explored in this work is unique and can offer significant opportunities over the conventional methods.

Facile synthesis and coating of aqueous antifouling polymers for inhibiting pathogenic bacterial adhesion on medical devices

Bacterial colonization in the form of biofilms on surfaces causes persistent infections and is an issue of considerable concern to healthcare providers. Thus, there is an urgent need for novel modification of antibiofilm surfaces on polymeric medical devices to inhibit pathogenic bacterial adhesion. Herein, we describe the development of water-soluble, antifouling polymers (APs) containing benzene moieties capable of anchoring to hydrophobic surfaces and hydrophilic poly (ethylene) glycol and carboxyl groups to inhibit pathogenic bacterial adhesion on polymeric medical devices. We found that the optimized APs could be facilely and controllably synthesized on and modify the surfaces of commercial hydrophobic substrates in aqueous solution, with the resulting polymer-coated surfaces capable of efficiently preventing pathogenic bacterial adhesion and subsequent bacterial colonization as precursors to biofilm formation. These results suggest the potential efficacy of the developed and optimized polymers for use as an antibiofilm platform to inhibit healthcare-associated infections on various polymer-based medical devices.

Dielectrophoretic analysis of the impact of isopropyl alcohol on the electric polarisability of Escherichia coli whole-cells

Whole-cell biocatalysts are versatile tools in (industrial) production processes; though, the effects that impact the efficiency are not fully understood yet. One main factor that affects whole-cell biocatalysts is the surrounding medium, which often consists of organic solvents due to low solubility of substrates in aqueous solutions. It is expected that organic solvents change the biophysical and biochemical properties of the whole-cell biocatalysts, e.g. by permeabilising the cell membrane, and thus analysis of these effects is of high importance. In this work, we present an analysis method to study the impact of organic solvents on whole-cell biocatalysts by means of dielectrophoresis. For instance, we evaluate the changes of the characteristic dielectrophoretic trapping ratio induced by incubation of Escherichia coli, serving as a model system, in an aqueous medium containing isopropyl alcohol. Therefore, we could evaluate the impact on the electric polarisability of the cells. For this purpose, a special microchannel device was designed and Escherichia coli cells were genetically modified to reliably synthesise a green fluorescent protein. We could demonstrate that our method was capable of revealing different responses to small changes in isopropyl alcohol concentration and incubation duration. Complementary spectrophotometric UV-Vis (ultraviolet-visible light) absorbance analysis of released NAD(P)+/NAD(P)H cofactor and proteins confirmed our results. Based on our results, we discuss the biophysical effects taking place during incubation.Graphical abstract

Highly Loaded Mildly Edge‐Oxidized Graphene Nanosheet Dispersions for Large‐Scale Inkjet Printing of Electrochemical Sensors

AbstractInkjet printing of electrochemical sensors using a highly loaded mildly edge‐oxidized graphene nanosheet (EOGN) ink is presented. An ink with 30 mg/mL EOGNs is formulated in a mixture of N‐methyl pyrrolidone and propylene glycol with only 30 min of sonication. The absence of additives, such as polymeric stabilizers or surfactants, circumvents reduced electrochemical activity of coated particles and avoids harsh post‐printing conditions for additive removal. A single light pulse from a xenon flash lamp dries the printed EGON film within a fraction of a second and creates a compact electrode surface. An accurate coverage with only 30.4 μg of EOGNs per printed layer and cm2 is achieved. The EOGN films adhere well to flexible polyimide substrates in aqueous solution. Electrochemical measurements were performed using cyclic voltammetry and differential pulse voltammetry. An all inkjet‐printed three‐electrode living bacterial cell detector is prepared with EOGN working and counter electrodes and silver‐based quasi‐reference electrode. The presence of E. coli in liquid samples is recorded with four electroactive metabolic activity indicators.

Electrochromic properties of ITO/WO3/LiClO4-PC-PMMA-ACN/NiO/ITO framework

The development of the preparation of tungsten oxide (WO 3 ) nanorods (NRs) using hydrothermal method is still underway. This study demonstrated the growth of WO 3 NRs on indium tin oxide (ITO) coated glass substrates in aqueous solution using single synthesis step hydrothermal synthesis. The surface area and size of the NRs which should be tunable for electrochromic(EC) applications were controlled by adjusting the concentration of surfactants such as propylene glycol (PG). The synthesized WO 3 NRs exhibited fast switching speed and high contrast ratio implying superior EC properties for smart window application. Furthermore, an EC device with the dimensions of 2×4 cm 2 was assembled using the synthesizedWO 3 NRswith the ITO/WO 3 /Lithium perchlorate-propylene carbonate-poly(methyl methacrylate)-acetonitrile/nickel oxide/ITO configuration. The device had an average optical modulation in the visible region, a fast EC response time (1.2s for coloration and 1.5s for decoloration), excellent coloration efficiency (243 cm 2 C ­1 ) anda superior EC stability (over 20000 color/decolor cycles)

Dibutyl phthalate adsorption characteristics using three common substrates in aqueous solutions

In recent years, the presence and adverse impacts of phthalic acid esters in aquatic environments have gained increasing attention. This work investigated the adsorption behavior of a typical phthalic acid ester, dibutyl phthalate (DBP), onto steel slag, gravel, and shell sand (substrates commonly used in constructed wetlands). The influence of dissolved organic matter (DOM) on DBP adsorption was investigated using humic acid as a proxy for DOM. The results demonstrated that the adsorption of DBP to three substrates reached equilibrium within 96 h, and the adsorption kinetics were well fitted by a pseudo-second-order model. The DBP adsorption isotherms were best fitted by the Langmuir adsorption model. The DBP adsorption capacity decreased in the order of steel slag>gravel>shell sand, with values of 656 mg/kg, 598 mg/kg, and 6.62 mg/kg at 25°C, respectively. DBP adsorbed to the surface of all substrates in a monolayer via an endothermic process. The DBP adsorption capacities of steel slag and gravel decreased as the DOM content increased. The DBP adsorption mechanisms to steel slag and gravel mainly involved the surface coordination of DBP with −OH or −COOH groups and electrostatic interactions. The results of this work suggest that steel slag and gravel may be ideal substrates for use in constructed wetlands to treat wastewater polluted with DBP.

Hierarchical Assembly of Peptoid‐Based Cylindrical Micelles Exhibiting Efficient Resonance Energy Transfer in Aqueous Solution

AbstractHerein we show that by appending bulky β‐cyclodextrin (CD) groups onto sheet‐forming peptoids, we obtain cylindrical micelles that further assembly into membranes and intertwined ribbons on substrates in aqueous solution, depending on the choice of solution and substrate conditions. In situ atomic force microscopy (AFM) shows that micelle assembly occurs in two steps, starting with “precursor” particles that transform into worm‐like micelles, which extend and coalesce to form the higher order structures with a rate and a degree of cooperativity dependent on pH and Ca2+ concentration. After co‐assembly with hydrophobic 4‐(2‐hydroxyethylamino)‐7‐nitro‐2,1,3‐benzoxadiazole (NBD) donors that occupy the hydrophobic core, followed by exposure to hydrophilic Rhodamine B as acceptors that insert into cyclodextrin, the micelles exhibit highly efficient Förster resonance energy transfer efficiency in aqueous solution, thereby mimicking natural light harvesting systems.

Hierarchical Assembly of Peptoid-Based Cylindrical Micelles Exhibiting Efficient Resonance Energy Transfer in Aqueous Solution.

Herein we show that by appending bulky β-cyclodextrin (CD) groups onto sheet-forming peptoids, we obtain cylindrical micelles that further assembly into membranes and intertwined ribbons on substrates in aqueous solution, depending on the choice of solution and substrate conditions. In situ atomic force microscopy (AFM) shows that micelle assembly occurs in two steps, starting with "precursor" particles that transform into worm-like micelles, which extend and coalesce to form the higher order structures with a rate and a degree of cooperativity dependent on pH and Ca2+ concentration. After co-assembly with hydrophobic 4-(2-hydroxyethylamino)-7-nitro-2,1,3-benzoxadiazole (NBD) donors that occupy the hydrophobic core, followed by exposure to hydrophilic Rhodamine B as acceptors that insert into cyclodextrin, the micelles exhibit highly efficient Förster resonance energy transfer efficiency in aqueous solution, thereby mimicking natural light harvesting systems.

Features of inorganic nanocrystals formation in conditions of successive ionic layers deposition in water solutions and the Co(II)Co(III) 2D layered double hydroxide synthesis

The article provides a brief overview of the results concerning synthesis of inorganic nanocrystals including such compounds as Ag, Au, NiO1+x∙nH2O, CoAl and ZnCo layered double hydroxides (LDH) by Successive Ionic Layer Deposition (SILD) method in aqueous solutions. It is shown that by specifying the synthesis conditions, for example, the number of SILD cycles, it is possible to change the size of nanocrystals, and for 2D crystals - their orientation with respect to the substrate. Along with this, in the article for the first time a novel SILD route of Co(II)Co(III) LDH synthesis is presented. It was stated that the nanolayers of this compound consist of randomly oriented 2D nanocrystals aggregates with hexagonal hydrotalcite-like crystal structure, each of which has a thickness of less than 3 nm. The method is based on the sequential processing of the substrate in aqueous solutions of CoCl2 and NaBH4 salts of certain concentrations and intermediate washing excess of these reagents with distilled water. The obtained nanolayers were characterized via SEM, TEM, XRD, FT-IR and XPS methods. Models of chemical processes occurring on the surface during the synthesis were suggested on the basis of the obtained experimental results. The samples were acquired on the nickel foam (NF) surface and were studied as electrodes for pseudocapacitors and as electrocatalysts for oxygen evolution reaction (OER) in alkaline medium. The electrodes of the pseudocapacitor showed high specific capacitance (2260 F/g at the current density of 1 A/g), as well as good cyclic stability (after 500 charge-discharge cycles, the capacitance drop do not exceed 2%). In addition, the obtained material showed a high electrocatalytic activity for OER in alkaline medium, characterized at a current density of 10 mA/cm2 by a relatively low overpotential of 285 mV and Tafel slope of 95 mV/dec.

Fabrication of an electrochromic device by using WO3 thin films synthesized using facile single-step hydrothermal process

The development of an uncomplicated process for the preparation of tungsten oxide (WO3) nanorods (NRs) using hydrothermal method is still underway. Thus, this study demonstrated the growth of WO3 NRs on indium tin oxide (ITO) coated glass substrates in aqueous solution using single synthesis step hydrothermally. The surface area and size of the NRs which should be tunable for electrochromic (EC) applications were controlled by adjusting the concentration of surfactants such as propylene glycol (PG). The synthesized NRs were illustrated using crystal structure study, surface morphology, chemical analysis, and the measure of the luminance of a color. The results manifested that increasing the PG content increased the size of the crystallite with a nanoparticle-like morphology on the ITO substrate, indicating the direct deposition of a stable WO3 thin film. In addition, the synthesized WO3 NRs exhibited fast switching speed and high contrast ratio implying superior EC properties for smart window application. Furthermore, an EC device with the dimensions of 2 × 4 cm2 was assembled using the synthesized WO3 NRs with the ITO/WO3/Lithium perchlorate-propylene carbonate-poly(methyl methacrylate)-acetonitrile/nickel oxide/ITO configuration. The device had an average optical modulation in the visible region, a fast EC response time (1.2 s for coloration and 1.5 s for decoloration), excellent coloration efficiency (243 cm2 C−1) and a superior EC stability (over 20,000 color/decolor cycles).

Structure and Catalytic Mechanism of a Bacterial Friedel-Crafts Acylase.

C−C bond‐forming reactions are key transformations for setting up the carbon frameworks of organic compounds. In this context, Friedel–Crafts acylation is commonly used for the synthesis of aryl ketones, which are common motifs in many fine chemicals and natural products. A bacterial multicomponent acyltransferase from Pseudomonas protegens (PpATase) catalyzes such Friedel–Crafts C‐acylation of phenolic substrates in aqueous solution, reaching up to >99 % conversion without the need for CoA‐activated reagents. We determined X‐ray crystal structures of the native and ligand‐bound complexes. This multimeric enzyme consists of three subunits: PhlA, PhlB, and PhlC, arranged in a Phl(A2C2)2B4 composition. The structure of a reaction intermediate obtained from crystals soaked with the natural substrate 1‐(2,4,6‐trihydroxyphenyl)ethanone together with site‐directed mutagenesis studies revealed that only residues from the PhlC subunits are involved in the acyl transfer reaction, with Cys88 very likely playing a significant role during catalysis. These structural and mechanistic insights form the basis of further enzyme engineering efforts directed towards enhancing the substrate scope of this enzyme.

Effect of coexisting ions on Cr(VI) adsorption onto surfactant modified Auricularia auricula spent substrate in aqueous solution

In this paper, the effect of coexisting cations and anions on Cr(VI)(in the form of Cr2O72-) adsorption onto Auricularia auricula spent substrate (AASS) modified by cetyl trimethyl ammonium bromide (CTAB) was investigated in batch adsorption experiment. The Cr(VI) adsorption capacity of 9.327 mg/g, obtained at pH 3.0, 303 K, adsorbent dosage of 2 g/L, initial Cr(VI) concentration of 20 mg/L, rotational speed of 150 r/min for 120 min, was decreased in the presence of coexisting cations and anions, among which Pb2+ and PO43- affected most by 21.79% and 12.43%, respectively. XRD, XPS and FTIR detection found that coexisting Pb2+ and PO43- would not only interfere Cr(VI) to form crystals and reduce to Cr(III), but also compete with Cr(VI) for oxygen-containing and amino groups to form Pb-O and P-NH2, respectively. In addition, the single Cr(VI) adsorption fitted with Langmuir isotherm model, while the competitive adsorption was well described by Freundlich isotherm model. Both single adsorption and competitive adsorption were in line with the pseudo-second-order kinetic model.