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To prepare g-C3N4 for photocatalytic tetracycline (TC) removal, KCl was employed to mix with or cover the top of the precursors, namely, melamine and urea. The mixing of KCl with the precursor will result in the incorporation of KCl within the layer structure of g-C3N4, whereas KCl covering the top might not have such an effect. Different precursor ratios contributed to the formation of heptazine-rich or triazine-rich units in the g-C3N4 structure. Melamine applied alone as a precursor will undergo a phase transformation into melam and triazine-rich g-C3N4, whereas with the addition of urea, the mixture will polymerize to form melem and heptazine-rich g-C3N4. The KCl-incorporated, heptazine-rich g-C3N4 (KCN80m) exhibited an improved photocatalytic activity for TC removal (greater than 80% during a 120-min period for 50 mL of a 20-ppm TC solution). The enhanced activity can be attributed to the improved charge separation through an electron and hole transfer through the K+ and Cl- sites, respectively; the formation of a nanojunction between the triazine and heptazine units of g-C3N4; an increased number of photoexcited electrons, indicated by the electron paramagnetic resonance spectroscopy results. We varied the mixing conditions of KCl and precursor ratio to synthesize different KCl-incorporated heptazine-rich g-C3N4 samples for effective removal of TC from water through photocatalysis.

Stimuli-responsive structural color in nature has fascinated scientists, directing them to develop artificial coloration materials that adjust colors in response to external stimuli. Many stimuli-responsive structural color materials have been realized. However, only a few have reported on all-liquid-type materials, which have a particularly desirable feature because they impart their function to the device of any shape. We have previously reported the development of a consistent structural color within a narrow temperature range for all-liquid-type emulsions comprising a long-chain amidoamine derivative (C18AA) and tetraoctylammonium bromide (TOAB). In the present study, we demonstrate that introducing NaCl as an electrolyte affords a highly thermo-sensitive color-changing ability to the emulsions. The structural color of the emulsions can be controlled from red to blue by tuning the temperature. Furthermore, the C18AA and TOAB concentrations can independently regulate the color and coloring-temperature, respectively, realizing that the desired color can develop at a given temperature.

Background Self-assembly monolayers (SAMs) had been used widely to tailor the surface properties; and alkanthiols were the most common molecules which have been intensively studied. However, the assembly behavior of amine molecules and the characteristics of the SAMs are not well understood. Method In this study, dodecylamine (DDA) is used as a model molecule to study the self-assembly behavior of amine molecules from HClO4 solution onto an Au(111) surface. The adsorption process and the SAM characteristics are studied via cyclic voltammetry (CV), in-situ surface-enhanced infrared absorption spectroscopy (SEIRAS) and scanning tunneling microscopy (STM). Significant findings The CV spectra show that the current densities of Fe+2/Fe+3 redox reaction decrease slightly after the treatment of DDA, implying the formation of a DDA adlayer. The in-situ SEIRAS spectra demonstrate that the adsorption of DDA performed slowly. These results imply a weak interaction of DDA with the gold surface. The STM observation in the HClO4 solution demonstrates that the adsorbed molecules arranged in an orderly manner, forming a flat-lying orientation. The lift-off orientation commonly found for thiol molecules doesn't occur for the DDA adlayer. On the basis of this study, the self-assembly ability of DDA on a gold surface is confirmed, and a weak DDA-Au interaction is verified.

Metal nanowires (NWs) with a diameter of a few nanometers have attracted considerable attention as a promising one-dimensional nanomaterial due to their inherent flexibility and conductive properties and their weak plasmon absorption in the visible region. In a previous paper, we reported the synthesis of ultrathin 1.8 nm-diameter Au NWs using toluene-solubilized aqueous solutions of a long-chain amidoamine derivative (C18AA). This study investigates the effect of different organic solvents solubilized in C18AA aqueous solutions on the morphology of the Au products and demonstrates that solubilizing methylcyclohexane yields thick 2.7 nm-diameter Au NWs and 3.3 nm-diameter Au-Ag alloy NWs. Further, the surface-enhanced Raman scattering sensitivity of ultrathin Au NWs, thick Au NWs, and thick Au-Ag alloy NWs were assessed using 4-mercaptopyridine and found that their enhancement factors are 10

We previously showed that the hybridization of water-insoluble 12-hydroxystearic acid (HSA) with water-soluble long-chain amidoamine derivatives yields hydrogels composed of self-assembled helical ...

Colloidal photolithography is a versatile advanced technique for fabricating periodic nanopatterned arrays, with patterns carved exclusively on photoresist films deposited on solid substrates in a typical photolithographic process. In this study, we apply colloidal photolithography to polystyrene (PS) films half-covered with poly(methyl methacrylate) (PMMA) colloids at the air-water interface and demonstrate that periodic hole structures can be carved in PS films by two processes: photodecomposing PS films with ultraviolet (UV) light and removing PMMA colloids with a fluorinated solvent. Nonspherical holes, such as C-shaped and chiral comma-shaped holes, are also fabricated by regulating the UV illumination conditions. Furthermore, in addition to holes, convex patterns on PS films are realized by combining weak UV illumination with solvent treatment. We also demonstrate that actively using the water surface as the UV illumination field enables periodic silver nanoparticle spots to be deposited on PS films simply by dissolving silver ions in the water phase.

This work reports the first demonstration of the chemical reactions on the C–F groups of perfluorosulfonic acid polymers. The Nafion chains show chemical reactivity for atom transfer radical addition onto multiwalled carbon nanotubes and ability to serve as a macroinitiator for atom transfer radical polymerization. The C–F groups and mainchain −CF2 groups have been demonstrated, under a study with 19F NMR, as the active sites responsible for the reactions. The results could certainly extend both the scopes of chemistry and application of perfluorosulfonic acid polymers as well as the windows of atom transfer radical addition/polymerization to fluorinated compounds.

The electrolysis of water using renewable energy is a promising approach to developing a sustainable hydrogen-based economy. To improve the efficiency of this process, it will be necessary to develop highly active electrocatalysts that promote the oxygen evolution reaction (OER). In the present study, the OER activity of a nickel oxide electrocatalyst was dramatically improved following the addition of a diamine to the electrolyte solution during electrodeposition. Operando UV/vis absorption spectroscopy was used to assess a number of nickel catalysts containing various diamines and other organic compounds. The data indicate that Ni(II) complexes were formed with the diamines during electrodeposition. Consequently, the catalytic activity of these materials was enhanced based on increased concentrations of active reaction sites for the OER process. Ni K-edge X-ray absorption spectra showed that these catalysts were composed of γ-NiOOH with a Ni3.6+ valence state. The coordination of the diamine molecules to the γ-NiOOH produced structural distortion that contributed to improved OER activity. This structural distortion is likely the most important factor in enhancing the OER activity of inorganic–organic composite catalysts.

A lanthanum-modified zeolitic imidazolate framework (La/ZIF-8) was developed to produce glycerol carbonate using CO2 and glycerol as raw materials. La/ZIF-8 provides a high catalytic glycerol conversion efficiency owing to its surface-attached nanoclusters of La2O3, which can be viewed as La3+–O2− pairs that strengthen the Lewis basicity and acidity, and the large specific surface area of ZIF-8. The catalytic glycerol conversion and the yield of glycerol carbonate were 46.5% and 35.3%, respectively, using CH3CN as a dehydrating agent. With increase in the amount of CH3CN, the water molecules could react with CH3CN to reduce the selectivity. When an inorganic dehydrating agent, MgCO3, was used to physically adsorb and remove water molecules in the reaction, the selectivity of the reaction could be increased to over 95%, which is the highest ever reported. Reaction kinetics analysis also revealed that the activation energy of using MgCO3 (5.4 kJ mol−1) as a dehydrating agent is lower than that using CH3CN (7.8 kJ mol−1). Moreover, the La/ZIF-8 could be recycled and reused at least three times with high catalytic performance. This study provides an effective material with dual Lewis basicity and acidity for CO2/glycerol conversion and significantly improves the catalytic performance using an inorganic dehydrating agent.

Ultrathin Au nanowires (NWs) with a diameter below 2 nm have attracted considerable attention as a promising one-dimensional nanomaterial. However, they are practically synthesized in organic solve...

A layered manganese oxide catalyst containing K+ cations [K/MnOx catalyst] was developed, and its ability to efficiently decompose water was demonstrated. Operando hard/tender/soft X-ray absorption...

In a previous work, we demonstrated that an amidoamine amphiphile with a stearyl group as the alkyl chain (C18AA) and 12-hydroxystearic acid (HSA) can produce hydrogels consisting of self-assembled...

The use of coordination complexes as metal precursors in electrodeposition of transition-metal oxides has been shown to be important for film formation at the nanoscale. Here, we present a systemat...

The electrolyte pH has been determined to be an important factor that has a direct influence on the formation of film morphologies. Herein, we investigate the effect of electrolyte pH on the formation of nickel oxide (NiOx) films in borate solutions and examine their corresponding electrochromic characteristics. The result shows that the formation of hexa-aquo Ni complexes due to an appropriate electrolyte pH can aid the electrodeposition of NiOx films and produce a film of small grains. Raman and in situ X-ray absorption fine structure (XAFS) measurements indicate that the structure of the NiOx films in their oxidized state is similar to γ-NiOOH, regardless of the electrolyte pH, although the grain size of the films is dependent on the electrolyte pH. The different grain size results in significant differences in electrochromic performance. The film made of small grain size exhibits the best electrochromic performance. The optical contrast of the NiOx film achieved 87%. The coloration efficiency increased by about 50% to 51 cm2/C and the switching time reduced to 5.4 s for bleaching. These results demonstrate the imperative for an appropriate electrolyte pH to enable sustained electrochemical activity, reactive site formation, and functional stability.

Metal-free, visible light-responsive, carbon-based graphitic carbon nitride (g-C3N4) is a well-known photocatalyst. It is necessary to develop a g-C3N4 for use as a photocatalyst in a green, economically viable, and effective manner. In this study, a waste-derived g-C3N4 was successfully prepared from the mixture of dicyandiamide (DICY) and mushroom waste (MW). The waste-derived g-C3N4 (1MDCN) exhibited enhanced photocatalytic activity compared to the conventional dicyandiamide-derived g-C3N4 for the degradation of an azo dye, methyl blue (MB), which is a most commonly used dye in the pharmaceutical industry. Under visible light irradiation, the improved activity could be attributed to its greater graphitic degree and fewer pyrrolic-N forming repeated tri-s-triazine units oriented along the [100] plane, which was evidenced by high-resolution X-ray photoelectron spectroscopy. In addition, the waste-derived g-C3N4 in this study is less harmful and exhibited good cell viability for Chinese hamster ovary cells, with over 50% of the cells surviving, whereas more than 85% of the cells were killed using melamine-derived g-C3N4 at a concentration of 1000 μg mL−1. The present study shows that g-C3N4 derived from the mixture of DICY and MW can be a harmless, economically viable, and effective photocatalyst for environmental remediation.

Electrochemical water splitting using renewable energy shows promise for the development of sustainable hydrogen production methods. The process requires a highly active electrocatalyst for oxygen evolution to improve the overall water splitting efficiency. The present study showed that oxygen evolution improved dramatically upon the addition of glycine to cobalt phosphate, when the glycine was added to the electrolyte solution during electrodeposition. The functionality of the organic molecules was investigated using in situ UV-vis absorption, in situ X-ray absorption fine structure, and in situ infrared (IR) absorption spectroscopy in the attenuated total reflection mode. The results demonstrated that the glycine molecules assembled cobalt oxide clusters composed of CoO6 (CoOOH) octahedrons a few nanometers in diameter upon the electrodeposition of cobalt catalysts. This suggests that the cobalt-glycine catalyst can decompose water to oxygen gas efficiently, because the number of cobalt oxide clusters increased as active reaction sites upon the addition of glycine molecules.

In a previous study, we demonstrated that conductive Au nanosheets can be prepared by UV irradiation of an Au nanoparticle monolayer spreading on water. In this study, we applied this UV irradiation technique to inexpensive Ag nanoparticles (NPs) to expand their versatility. UV irradiation of Ag NPs on water resulted in the formation of large Ag NPs and was ineffective for preparing conductive Ag films. The solubilization of additives in the water phase, however, resulted in the conversion of the large Ag NPs into a nanosheet, and the solubilization method was highly effective for preparing transparent conductive Ag films with an optical transmittance of above 70%.

In the present study, carbon-dots (CDs) were derived from the thermal oxidation of an agricultural waste, bitter tea residue, to obtain different sp2/sp3 ratios and electronic structures for metal sensing. The CDs obtained from calcination at 700 °C exhibited the highest photoluminescence (PL) quantum yield (QY) of 11.8% among all the samples treated at different temperatures. These CDs had a high degree of graphitization, which resulted in a strong π-π* electron transition, and hence in a high QY. The strong photoluminescence of the CDs could be used to sense the metal ions Ag+, Sr2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+, and Sn2+ by monitoring their PL intensity at an excitation wavelength of 320 nm. The metals inhibited the PL intensity in the order Ag+ > Fe2+, Fe3+, Ni2+ > Sr2+, Co2+, Cu2+, Sn2+, which demonstrated that the CDs exhibited high metal ion detection capability and selectivity. The detection of Fe3+ using CDs was performed in the range of 10–100 ppm with a LOD (limit of detection) value of 0.380 ppm. Theoretical calculations demonstrated that Ag+, Sr2+, and Sn2+ induced charge transfer excitation and that Fe2+ and Ni2+ induced d-d transitions via complexation with the sp2 clusters. The charge transfer excitation and d-d transitions hindered the π-π* transition of the sp2 clusters, leading to a quenching effect. On the other hand, Li+, Na+, and K+ ions did not alter the π-π* transition of the sp2 clusters, resulting in a negligible quenching effect. In summary, the oxidation level and electronic structure of CDs derived from bitter tea residue could be tailored, and the CDs were shown to be a facile, sustainable, and eco-friendly material for metal sensing.

Metallic nanorings have attracted much attention of researchers owing to their unique optical, electrical, and magnetic properties, and now, simple and large-scale synthesis methods must be developed for their practical application in various fields. Here, we report the one-pot synthesis of ultrathin Pd nanorings through a simple and novel soft-template approach based on wet-chemical synthesis. A spindle-shaped assembly of a long-chain amidoamine derivative (C18AA) served as the soft template of Pd nanorings that were prepared in an aqueous solution containing the Pd precursor and a suitable amount of C18AA and toluene, and the chemical reduction of the Pd precursor in the aqueous solution produced an array of almost circular Pd nanorings covering the assembly. Pd nanorings that were parallel to the amine group, which is the head group of C18AA, appeared on the assembly surface. The amount of toluene strongly affected the formation of the spindle-shaped assembly and Pd nanorings. Furthermore, transmission...

Electrochromic (EC) windows enhance the energy efficiency of climate control systems in the building sector. Here, we evaluate a strategy for electrodeposition of a high-performance EC nickel oxide by controlled release of Ni(II) ions from amino acid ligands. We compare the structural properties and EC characteristics of the samples deposited from Ni(II)-L-alanine or Ni(II)-phenylalanine complexes. During the deposition process, a film containing closely packed nanodeposits was formed by rapid release of Ni(II) ions from L-alanine ligands. This structure led to a high coloration efficiency of 76.4 cm2/C and nearly 100% retention of the initial optical modulation value even after 60 cycles of coloration. In contrast, the slow release of Ni(II) ions from phenylalanine ligands resulted in the formation of conglomerated island structures, which caused a low coloration efficiency and poor cycling stability. However, the bulky aromatic side chains on phenylalanine could passivate the sample surface, thereby lowering the transmittance loss to 1.38% under 24 h voltage-off. The aromatic side chains also contributed to the charge transfer between the solid–liquid interface of the sample. Furthermore, the sample deposited from the mixed L-alanine and phenylalanine complexes show greatly improved EC performance without compromising its superior optical memory and fast charge transfer characteristics.

A key requirement in developing oxygen evolution reaction (OER) electrocatalysts is increasing their surface area. Herein, we report the design of a hierarchical micro/nanostructured catalyst. Based on polystyrene colloidal template electrodeposition, an ordered microcup array surrounded by nanoflakes was fabricated. The effect of the deposition time on the formation of the catalyst and the corresponding OER performance of the catalyst were investigated using scanning electron microscopy, in situ X-ray absorption fine structure (XAFS) spectroscopy, and electrochemical analysis. The in situ XAFS measurements indicate that the structure of the hierarchical structured catalyst is similar to that of γ-FeOOH. The electrochemical analysis indicates that the hierarchical catalyst has a large surface area and a low charge transfer resistance, which lead to its excellent catalytic performance for the OER. Our study provides new insights in designing high-performance OER catalysts. Moreover, the synthesized hierarchical micro/nanostructured catalyst could be used as a platform for further studies on low-cost iron-based electrocatalysts.

The Langmuir-Blodgett (LB) deposition technique is employed to prepare nano-composite films consisting of glucose oxidase (GOx) and gold nanoparticles (AuNPs) for glucose sensing applications. The GOx and AuNPs are co-adsorbed from an aqueous solution onto an air/liquid interface in the presence of an octadecylamine (ODA) template monolayer, forming a mixed (GOx-AuNP) monolayer. Alternatively, a composite film with a cascade architecture (AuNP/GOx) is also prepared by sequentially depositing monolayers of AuNPs and GOx. The architecture effects of the composite LB films on the glucose sensing are studied. The results show that the presence of AuNPs in the co-adsorption system does not affect the adsorption amount and preferred conformation (α-helix) of GOx. Furthermore, the incorporation of AuNPs in both composite films can significantly improve the sensing performance. However, the enhancement effects of the AuNPs in the two architectures are distinct. The major effect of the AuNPs is on the facilitation of charge-transfer in the (GOx-AuNP) film, but on the increase of catalytic activity in the (AuNP/GOx) one. Therefore, the sensing performance can be greatly improved by utilizing a film combining both architectures (AuNP/GOx-AuNP).

In this study, a polymeric graphitic carbon nitride (g-C3N4) was prepared from melamine by adding mushroom waste. The waste-derived g-C3N4 sample exhibited improved adsorption efficiency for methyl blue (MB) with the increasing waste content. The enhanced adsorption efficiency could be attributed to the presence of the amorphous carbon domain in the waste-derived g-C3N4 structure and the reduced ratio of graphitic nitrogen in the tri-s-triazine unit of g-C3N4. MB adsorption using waste-derived g-C3N4 follows pseudo-second-order reaction kinetics, and can be represented by the Langmuir and Freundlich models, which suggested that the chemical states, graphitic degree, and surface properties of the waste-derived g-C3N4 greatly influenced the MB adsorption behavior. Compared to pristine g-C3N4, waste-derived g-C3N4 was relatively harmless and displayed high cell viability for Chinese hamster ovary cells (CHO-AS52), and showed intense luminescence under an excitation wavelength of 365 nm in the viewing cabinet. Our results demonstrated that the mushroom waste-derived g-C3N4 could be a green, facile, and effective material for many applications like dye removal, photocatalysis, bio-imaging, and as a raw material for the preparation of g-C3N4 dots.

The development of visible-light-driven polymeric g-C3N4 is in response to an emerging demand for the photocatalytic dye degradation and reduction of hexavalent chromium ions. We report the synthesis of g-C3N4 from urea treated with various solvents such as methanol, ethanol, and ethylene glycol. The samples were characterized and the Williamson&ndash, Hall method was applied to investigate the lattice strain of the samples. The activity of the samples was evaluated by observing the degradation of methyl orange and K2Cr2O7 solution under light irradiation. Photocatalytic reaction kinetics were determined as pseudo-first-order and zero-order for the degradation of methyl orange and reduction of hexavalent chromium, respectively. Due to the inhibited charge separation resulting from the small lattice strain, reduced crystal imperfection, and sheet-like structure, g-C3N4 obtained from ethanol-treated urea exhibited the highest activity among the evaluated samples.

In our previous paper, we reported that thermo-responsive emulsions can be prepared based on a long-chain amidoamine derivative (C18AA) and tetraoctylammonium bromide (TOAB), and that the C18AA + TOAB emulsions developed a characteristic interference color in a narrow temperature range. However, the coloration of the original C18AA + TOAB at room temperature exhibited poor brightness. In the present study, we show that the addition of NaOH is effective in both lowering the coloration temperature and improving the brightness of C18AA + TOAB emulsion considerably. Furthermore, we demonstrate that photo-response function can be imparted to C18AA + TOAB iridescent emulsions by introducing a photochromic naphthopyran derivative (Pyran) that reversibly changes from white to yellow upon UV irradiation. The C18AA + TOAB emulsions containing Pyran shows a dual stimuli-responsive iridescent property, and the emulsion color is controllable and reversible through both UV irradiation and temperature.

Surface-modification of polybenzoimidazole (PBI) membrane with chitosan chains has been performed using 4-isocyanato-4′-(3,3′-dimethyl-2,4-dioxo-azetidino)diphenylmethane (IDD) as a coupling agent to build up chemical linkages between the PBI membrane surface and chitosan chains. Incorporation of chitosan chains to PBI membrane surface increases its surface hydrophilicity and enhances its performance of pervaporation dehydration on isopropanol aqueous solutions. The surface chemical structure of the chitosan-modified PBI membrane (PBI-CS) has been characterized with attenuated total reflectance Fourier transform infrared and X-ray photoelectron spectroscopies. The scanning electron micrographs of PBI-CS indicate the surface reaction between PBI and IDD might take place at the top surface of the PBI matrix in a thickness of about 2 μm as the PBI membrane is swollen with the used solvent. PBI-CS is effective for pervaporation dehydration on isopropanol aqueous solutions in a wide concentration range from 30 to 90 wt%. The chitosan layer increases the dissolution rate of water into the PBI-CS membrane so as to simultaneously increase the water permeability and selectivity of the membrane. PBI-CS shows high pervaporation separation indexes which are about 3.9-fold of the value measured with the neat PBI membrane.

The reactivity between the active species of atom transfer radical addition and the unsaturated groups of graphene oxides (GOs) has been demonstrated in this work. The reaction and the sequential surface-initiated atom transfer radical polymerization provide a convenient approach to anchor various polymer chains and to buildup various polymer architectures, such as linear polymer, V-shape block polymer, multibonded polymer layer, and hierarchical brush-on-layer polymer, on GO sheet surfaces. The chemical structures and morphology of the polymer-modified GOs have been characterized with Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. After organomodification, the GOs exhibit a good dispersion ability in organic solvent over 80 days, amphiphilic characteristics, and temperature-responsive properties. Reduction of the GOs has been performed to result in graphene-like materials showing certain extent of electron conductivities. An effective approach to synthesize GO/polymer hybrid materials possessing various polymer architectures and attractive properties has been developed. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1588–1596

Electrochromic materials can change their color under the application of an electrical voltage. The color change accordingly upon charge insertion/extraction, which induce in the material a process of redox reaction. Electrochromic materials are expected to serve an important role in efficient energy applications to control the brightness of light. High optical contrast, fast switching speed, and good cycling durability are required for an electrochromic material to function as a practical material in a device. These properties are influenced by the morphology of the electrochromic film and the associated changes in local ionic diffusion. In this work, we report a facile and cost-efficient preparation of electrochromic materials which are formed by assembly of nano-sized clusters of nickel oxides by electrodeposition integrating amino acids. Electrodeposited films were characterized using Raman spectroscopy, in situ X-ray absorption fine structure spectroscopy, and atomic force microscopy to determine the electronic and structural changes in the films during coloration. These results indicate that the structure of the nickel oxide films in their oxidized state is similar to γ-NiOOH, regardless of kinds of integrated amino acids, although the grain size of the films is dependent on kinds of integrated amino acids. The different grain size results in significant differences in electrochromic performance. The film made of small grain size exhibits the best electrochromic performance. This study demonstrates that a suitable integration of amino acid is essential to enable sustained electrochemical activity, reactive site formation, and functional stability. Figure 1

Poly(3-hexylthiophene) (P3HT) is utilized as a material to enhance the glucose sensing performance of glucose oxidase (GOx) Langmuir-Blodgett (LB) films. To enhance the extensibility and homogeneity of the P3HT in the LB films, octadecylamine (ODA) is introduced. The characteristics of the mixed P3HT/ODA Langmuir monolayers are investigated first and then, utilized as template layers to adsorb GOx from the subphase, preparing P3HT/ODA/GOx Langmuir-Blodgett films for glucose sensing. The results show that P3HT molecules tend to aggregate at the air/liquid interface and, furthermore, the P3HT monolayer has a weak ability to adsorb GOx from the subphase. By using mixed P3HT/ODA monolayer, the presence of ODA not only inhibits the aggregation of P3HT, but also increases the adsorption ability of the monolayer to GOx. The extensibility of P3HT and the homogeneity of the P3HT/ODA monolayers are closely related to the concentration of P3HT/ODA stock solutions. On the glucose sensing experiments, the performance of the P3HT/ODA/GOx LB film is greatly improved due to the presence of P3HT and, furthermore, the sensibility increases with increasing extensibility of P3HT molecules. The best sensitivity achieved for the P3HT/ODA/GOx film is 5.4 μA mM −1 cm −2 which is over two times the value obtained by the ODA/GOx film (2.3 μA mM −1 cm −2 ).

Glucose oxidase (GOx) molecules were adsorbed from aqueous solution onto template monolayer of octadecylamine (ODA) or stearic acid (SA) at the air/liquid interface. The effects of the template layers on the GOx adsorption and the characteristics of the mixed template/GOx monolayers are studied. The monolayers at the air/liquid interface were then transferred onto Pt substrates to prepare GOx Langmuir–Blodgett (LB) films for glucose sensing study. The results show that the SA/GOx monolayer has a pressure–area isotherm resembles that of a SA monolayer, indicating that only a small amount of GOx was incorporated in the mixed film. On the contrary, the ODA/GOx monolayers exhibit high expanded and high compressible characteristics, attributed to the high incorporation amount of GOx induced by the electrostatic interaction between ODA and GOx. The glucose sensing experiments demonstrate that the ODA/GOx LB films have much better performance than SA/GOx films in terms of current sensitivity and current responding rate. Furthermore, an ODA/GOx film prepared after approaching the second equilibrium stage of GOx adsorption (8 h adsorption) shows a better performance than that prepared at the first equilibrium stage. Good linear relationship between response current and glucose concentration was obtained for the GOx-LB films between 0.1 and 5 mM.

Gold nanoparticles were prepared by two different methods. The first method was chemically grafting the particles with different lengths of alkylthiol (C 6 SH, C 12 SH and C 18 SH). For the second method, the Au particles were surface modified first by mercaptosuccinic acid (MSA) to render a surface with carboxylic acid groups which play a role to physically adsorb cationic surfactant in chloroform. This method was termed physical/chemical method. In the first method, the effects of alkyl chain length and dispersion solvent on the monolayer behavior of surface modified gold nanoparticles was evaluated. The gold nanoparticles prepared by 1-hexanthiol demonstrated the narrowest size distribution. Most of them showed narrower particle size distributions in chloroform than in hexane. For the physical/chemical method, the particles can spread more uniformly on the water surface which is attributed to the amphiphilic character of the particles at the air/water interface. However, the particles cannot pack closely due to the relatively weak particle–particle interaction. The effect of alkyl chain length was also assessed for the second method.

Electrochromism is a phenomenon of reversible color change when an external voltage is applied, causing an electrochemical redox reaction. This interesting property leads to the development of several technological applications, such as electronic papers, rear-view mirrors and smart windows. A typical electrochromic device coating is a multi-layer device consisting of an active electrochromic electrode, a counter electrode, an electrolyte layer separating the two electrodes, and two transparent conducting layers serving as electrical leads. A key requirement in developing an electrochromic electrode is to increase the amount of reaction sites of the electrode. In this work, we report a facile and cost efficient preparation of electrochromic electrode which are formed by assembly of nano-sized clusters of nickel oxides by electrodeposition integrating amino acids. This nanostructured nickel-oxide film with interconnected clusters benefits electrolyte penetration and provide large surface area for charge-transfer reactions. Here, we show that the integration of amino acids resulted in increased nickel-oxide film thickness compared to the system without amino acids. Moreover, the nickel-oxide film also shows a remarkably enhanced electrochromic performance compared to the blank nickel sample. These results demonstrate that the thickness of electrodeposited nickel oxide film thickened with increased reaction site. A three-dimensional (3D) electrochromic material with many reaction sites is achieved. Further, the thickness of electrodeposited nickel oxide film can be tuned by altering kinds of amino acids. Figure 1

Stearic acid (SA) and octadecylamine (ODA) monolayers at the air/liquid interface were used as template layers to adsorb glucose oxidase (GOx) from aqueous solution. The effect of the template monolayers on the adsorption behavior of GOx was studied in terms of the variation of surface pressure, the evolution of surface morphology observed by BAM and AFM, and the conformation of adsorbed GOx. The results show that the presence of a template monolayer can enhance the adsorption rate of GOx; furthermore, ODA has a higher ability, compared to SA, to adsorb GOx, which is attributed to the electrostatic attractive interaction between ODA and GOx. For adsorption performed on a bare surface or on an SA monolayer, the surface pressure approaches an equilibrium value (ca. 8 mN/m) after 2 to 3 h of adsorption and remains nearly constant in the following adsorption process. For the adsorption on an ODA monolayer, the surface pressure will increase further 1 to 2 h after approaching the first equilibrium pressure, which is termed the second adsorption stage. The measurement of circular dichroism (CD) spectroscopy indicates that the Langmuir-Blodgett films of adsorbed GOx transferred at the first equilibrium state (π = 8 mN/m) have mainly a β-sheet conformation, which is independent of the type of template monolayers. However, the ODA/GOx LB film transferred at the second adsorption stage has mainly an α-helix conformation. It is concluded that the specific interaction between ODA and GOx not only leads to a higher adsorption rate and adsorbed amount of GOx but also induces a conformation change in adsorbed GOx from β-sheet to α-helix. The present results indicate that is possible to control the conformation of adsorbed protein by selecting the appropriate template monolayer.

An efficient method to monitor and control the secondary structures of globular proteins is developed by adsorption of proteins from a bulk solution onto an air–liquid interface. By controlling the concentration of a protein in the aqueous phase, as well as the attractive force exerted by the template layer, the adsorption of proteins can be classified into two stages according to the variation of surface pressure. In the first stage, the proteins adsorb as a single-molecular layer. The interface–molecule interactions induce a structural transition of the adsorbed proteins into a β-sheet conformation (α/β 10). The glucose sensing experiments demonstrate that GOx with α-helix conformation has a much higher sensitivity than β-sheet GOx, attributed to its lower charge transfer resistance at the GOx–electrolyte interface. The present study not only provides a new approach to monitor, control, and design protein conformations, but also raises the importance of adsorption states of proteins in performing bio-activities at bio-interfaces.