Search

A photoassisted approach has been developed to synthesize a zinc indium oxide (Zn5In2O8)/oxysulfide composite through in situ sulfuration of vacancy-rich Zn5In2O8. It was found that vacancies have a considerable impact on the formation of the composite. The composite exhibited an increased photocatalytic H2 evolution activity under visible-light irradiation, which probably resulted from the enhanced ability to separate photoinduced electrons and holes. The H2 evolution rate over the composite was about 17 times higher when using vacancy-rich rather than conventional Zn5In2O8. This study provides a new method of improving the activity of photocatalysts.

Aw et chemical approach is used successfully to produce nanostructured Au material by the reduction of sulfonated polyaniline (SPANI) nanotubes. The Au nanostructures obtained are composed of single crystal Au nanoplates, which are aggregated layer-by-layer into stacks or edge-on-face into clusters at various conditions. The Au nanoplate diameter and thickness can be conveniently controlled in the range of 100 nm to 2 µ ma nd10 to 30 nm, respectively, with no accompanying single Au nanoparticles being observed. The formation of the Au nanostructures was controlled by the degradation of SPANI. The gradually and slowly released segments of SPANI served as the reductant during the growth of the 2D Au nanostructures. (Some figures in this article are in colour only in the electronic version)

We report a new synthetic route for preparation of nanoporous carbon nitride fibers with graphitic carbon nitride polymers, by calcination of Al-based porous coordination polymers (Al-PCPs) with dicyandiamide (DCDA) under a nitrogen atmosphere.

International audience; Nitrogen-doped carbons were produced using hydrothermal carbonization of nitrogen-containing carbohydrates under mild temperature (180 °C). The resulting materials contain significant amounts of nitrogen and display a high degree of aromatization. The nitrogen contents are also retained after further calcination at higher temperatures. All the resulting materials have been thoroughly characterized using X-ray photoelectron spectroscopy, solid state 15N and 13C-nuclear magnetic resonance, elemental chemical analysis, nitrogen adsorption, scanning and transmission electron microscopy. The nitrogen-doped materials proved to have superior performance with respect to their nitrogen-free counterparts in terms of electrical conductivity.

Carbon materials have attracted much attention because they are attractive for a wide range of applications, and also because of the scientific interest in the challenges posed by their synthesis, processing, and characterization. Recently, carbon materials with various morphologies and contain heteroatoms such as nitrogen and boron have been actively pursued and considered as the most promising candidates to complement carbon in materials applications. For example, graphitic carbon nitride (g-C3N4) is a potentially useful substitute for amorphous and graphitic carbon in a variety of applications, such as catalytic supports and gas storage. Because there are many ways to substitute carbon by nitrogen in graphite in a regular fashion, here the term carbon nitrides is understood to comprise a large family of related compounds (e.g. , C3N4, C3N2, C3N, C5N, C10N3, and others). Accordingly, various strategies have been adopted to prepare the nitrogen-enriched carbon materials. Many groups have succeeded in synthesizing graphitic carbon nitrides via condensation of C-, N-, and H-containing precursors. For example, Kawaguchi synthesized a graphitic hexagonal polymer, (C3N3)2(NH)3, which was found to be stable up to 500 8C. Through a solid-state reaction of 2,4,6-triamino1,3,5-triazine with 2,4,6-trichloro-1,3,5-triazine in a high pressure-high temperature condition, Wolf et al. obtained a wellcharacterized and highly crystalline graphitic carbon nitride derivative. The generated HCl played the role of a template by filling the nitridic in-plane pores of a triazine-based condensation pattern. Gao et al. were able to prepare carbon nitride at atmospheric pressure from polymerized (CH2NH2)2 and CCl4. [7]

Although colorless ionic liquids (ILs) are most desirable, as synthesized they frequently bear color, despite appearing pure by most analytical techniques. It leads to some uncertainties and limits for the fundamental research and applications of ILs, such as spectroscopy. Using 1-butyl-3-methylimidazolium bromide (BMIMBr), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF(4)) and 1-hexyl-3-methylimidazolium bromide (HMIMBr) as models, we demonstrated that following classic preparing method except that the water was added as solvent, colorless ILs could be facilely prepared. Neither critical pre-treatment of starting materials and pre-cautions during the reaction nor time-consuming and costly post-decolor-purification was needed. The effects of "on water" reaction conditions on preparing colorless IL and the reason why using water as solvent could produce colorless ILs were also preliminary investigated. It was found that the reactant solubility played an important role in the preparation of colorless ILs. Not only as a method to evaluate the quality of as-synthesized ILs, but also as a spectroscopic analytical applications, UV-vis spectra showed that the ILs by this "on water" method was spectral pure and sufficient for future fundamental spectroscopic research and applications.

In underdetermined blind separation, the 'two-step approach' is often adopted, which depends on source signals' sparse representation. The first step is to estimate the mixture matrix by K-mean clustering algorithm using the sensor signals; and in the second step, the shortest-path algorithm is used to recover source signals. Generally, people suppose that the number of source signals is known when they estimate the mixture matrix by the K-mean clustering algorithm. In fact, the number of source signals is unknown or blind, so it is very important to estimate the number of source signals. In this paper, it gives a novel underdetermined blind separation algorithm based on fuzzy clustering, which can accurately estimate the number of sources and the mixture matrix respectively, by which source signals can be reconstructed. The last simulations show the good performance of the paper's algorithm.

Based on the fact that the temporal predictability of signals is often different, new algorithm using second order statistics for blind source separation (BSS) is proposed in this work. The novel measure of signal temporal predictability is developed. Based on which, the proposed method is less time-consuming and requires minimal assumptions regarding the probability density functions of the source signals. Also, the online mode is provided. Simulations show that the proposed algorithm is robust with the best precision for batch mode, and its convergence is quite well for online mode.

For their biocompatibility and potential bionanoelectronic applications, integration of carbon nanotubes (CNTs) with biomolecules such as redox enzyme is highly anticipated. Therein, CNTs are expected to act not only as an electron transfer promoter, but also as immobilizing substrate for biomolecules. In this report, a novel method for immobilization of biomolecules on CNTs was proposed based on ionic interaction, which is of universality and widespread use in biological system. As illustrated, glucose oxidase (GOD) and single-walled carbon nanotubes (SWNTs) were integrated into a unitary bionanocomposite by means of ionic liquid-like unit on functionalized SWNTs. The resulted bionanocomposite illustrated better redox response of immobilized GOD in comparison of that prepared by weak physical absorption without ionic interaction. As a potential application of concept, the electrochemical detection of glucose was exemplified based on this novel bionanocomposite.

An all-purpose approach to immobilize ionic liquids onto solid supports is proposed by chemical grafting on a polyelectrolyte carrier.

Electrochemical functionalization of single-walled carbon nanotubes (SWNTs) was one of selective, clean, and nondestructive chemical methods. But in previous studies it met difficulties in homogeneous electrografting of SWNTs in large quantities because the reaction was often localized on a very thin film (ca. 2 microm). In this report, a room-temperature ionic liquid (RTIL) supported three-dimensional network SWNT electrode was first utilized to break through this barrier. In this work, large quantities of SWNTs were considerably untangled in RTILs so as to greatly increase the effective area of the electrode. N-succinimidyl acrylate (NSA), as a model monomer, was dissolved in the supporting RTILs and was electrografted onto SWNTs (SWNTs-poly-NSA). As an application example, glucose oxidase was directly covalently anchored on the SWNTs-poly-NSA assembly, and the electrocatalytic oxidation of glucose in this assembly was investigated. RTILs opened a new path in electrochemical functionalization of SWNTs.

The interaction of the conjugated system between functionalized polydiacetylene-glycolipid vesicles and Escherichia coliwas investigated under the bactericidal effect of TiO2 colloid. With various pre-incubation and irradiation time, controllable bacteria quantity in the presence of TiO2 colloid was obtained in real time. UV–visible and Raman spectra were utilized to monitor and evaluate the structural transition of bacteria-polydiacetylene-glycolipid vesicles conjugated system under the different conditions, which supplied the detailed information of the transform of the polydiacetylene backbone in real time. Thus controllable conjugated bio-interaction between two bio-interfaces was obtained through the introduction of the third factor and monitored in real time. This would be great aid in fundamental understanding more complex interfaces in the biological environment and would be applicable to the biomedical and biophysical fields. © 2004 Elsevier B.V. All rights reserved.

The electrochemical stability of self-assembled monolayers was greatly enhanced by using room-temperature ionic liquids as media.

By incorporating bio-specific receptors, such as p-10,12-pentacosadiyne-1-N-(3,6,9-trioxaundecylamide)-α- d -mannopyranoside (MPDA), into 10,12-pentacosadiyonic acid (PDA) monolayer, the MPDA/PDA monolayer underwent affinochromatic transition in response to the bacteria binding to the receptor. Here, we described a new method to study the membrane/macromolececular interaction between Escherichia coli (E. coli) and mannose and its relative affinochromism by modifying MPDA/PDA with CdS nano-crystallites (MPDA/PDA-CdS). CdS not only triggered the strong tropism of the bacteria but also reduced the rigidity of the MPDA/PDA backbone, resulting in the enhanced affinochromism. This discovery might be of significance in basic biophysical studies of membrane/macromolececular and designing novel biosensor.

Supramolecular assemblies of liposomes (vesicles) made of diacetylenic lipids and synthetic mannoside derivative glycolipid receptors were successfully used to mimic the molecular recognition occurring between mannose and Escherichia coli. This specific molecular recognition was translated into visible blue-to-red color transition (biochromism) of the polymerized liposomes, readily quantified by UV-visible spectroscopy. Some transition metal cations (Cd(2+), Ag(+), Cu(2+), Fe(3+), Zn(2+) and Ni(2+)) and alkali earth metal cations (Ca(2+), Mg(2+) and Ba(2+)) were introduced into the system to analyze their effects on specific biochromism. Results showed that the presence of Cd(2+), Ag(+), Ca(2+), Mg(2+) and Ba(2+) enhanced biochromism. A possible enhancement mechanism was proposed in the process of bacterial adhesion to host cells. However, Cu(2+), Fe(3+), Zn(2+) and Ni(2+) exhibited inhibitory effects that cooperated with diacetylene lipid with a carboxylic group and increased the rigidity of the liposomal outer leaflet, blocking changes in the side chain conformation and electrical structure of polydiacetylene polymer during biochromism.

Numerous reports have focused on ferrocene-terminated electroactive self-assembled monolayers (SAMs) on a flat Au surface but only a few on ferrocene SAMs on Au colloid. In this paper, we employ 4-ferrocene thiophenol as a novel capping agent to produce electroactive gold nanoparticles in consideration of the peculiar pi-conjugated structure. Transmission electron microscopy shows the narrow-dispersed gold core with an average core diameter of ca. 2.5 nm. UV/vis spectra examine the pi-conjugated structure of 4-ferrocene thiophenol and surface plasmon absorbance of the indicated gold nanoparticles. X-ray photoelectron spectroscopy reveals electronic properties of the Au core and thiol ligands. Electrochemical measurement shows that the oxidation peak current is proportional to the scan rate, indicating the electrode process is controlled by adsorbed layer reaction. The formal potential of the Fc-MPCs is compared with that of free ferrocene in MeCN solution and the Fc-SAMs. The shifts are attributed to the phenyl moiety in the 4-ferrocene thiophenol and dielectric constant of the solvation environment.

Covalently bonded carbon nitride materials (e.g., g-C(3)N(4)) have numerous potential applications ranging from semiconductors to fuel cells. But their solubility is poor, which makes characterization and processing difficult. Moreover, the chemistry of the as-synthesized carbon nitrides has been widely neglected. Here we report that some of these handicaps might be overcome by a controllable and reversible protonation. It was found that protonation not only provides better dispersion and exposes a high surface area for g-C(3)N(4) but also enables an adjustment of electronic band gaps and higher ionic conductivity. Recovery or deprotonation toward the original g-C(3)N(4) could be obtained by simple heating, which enables improved sintering but also a potential preservation of the higher surface area of the protonated material. This proton-enhanced sintering process allowed for the first time direct measurement of the photoconductivity of the material. By aid of protonation, other promising g-C(3)N(4) based hybrid composites could also be facilely obtained by simple counteranion exchange.

One of the biggest challenges for materials science is to design facile routes to structurally complex materials, which is particularly important for global applications such as fuel cells. Doped nanostructured carbons are targeted as noble metal-free electrocatalysts for this purpose. Their intended widespread use, however, necessitates simple and robust preparation methods that do not compromise on material performance. Here, we demonstrate a versatile one-pot synthesis of nitrogen-doped carbons that exploits the templating ability of biological polymers. Starting with just metal nitrates and gelatin, multiphase C/Fe3C/MgO nanomaterials are formed, which are then etched to produce active carbon electrocatalysts with accessible trimodal porosity. These show remarkable performance in the oxygen reduction reaction – a key process in proton exchange membrane fuel cells. The activity is comparable to commercial platinum catalysts and shows improved stability with reduced crossover effects. This simple method offers a new route to widely applicable porous multicomponent nanocomposites.

Nitrogen-doped carbon hollow spheres (NCHSs) have been fabricated by carbonization of poly(o-phenylenediamine) hollow spheres. The NCHSs exhibited superior performances to glassy carbon and carbon nanotubes for the simultaneous determination of uric acid and dopamine in the presence of high concentration ascorbic acid.

We report a facile one-step chemical method to synthesize partially reduced TiO2 nanotube arrays (NTAs). The NaBH4 treatment introduces oxygen vacancies on the surface and interior of TiO2. Oxygen vacancy extends the photocatalytic activity of TiO2 NTAs from the UV to visible light region, and enhances the electrical conductivity as well as charge transportation. Surface oxygen vacancies serve as charge carrier traps as well as adsorption sites where the charge transfer to adsorbed species inhibits the surface charge recombination, whereas bulk oxygen vacancies tend to act as charge carrier traps where e–h recombination occurs. The optimally reduced TiO2 NTAs yield a photocurrent density of 0.73 mA cm−2 at 1.23 VRHE and a highest photoconversion efficiency of 1.31% at a rather low bias of 0.40 VRHE under a standard AM 1.5G solar illumination. Not only does the incident photon to current conversion efficiency (IPCE) spectrum increase in the UV region, but photoactivity in visible light also emerged. Surface oxygen vacancies, serving as electron donors, cause a noticeable negative flatband shift and increase the donor density of TiO2 NTAs 2-fold. Electron paramagnetic resonance (EPR) spectra confirm the presence of oxygen vacancies on the surface and interior of TiO2. Benefitting from the oxygen vacancy, a narrowed band gap of 2.46 eV and suitable localized states for hydrogen production are observed.

Ultrafine Zn1−xCuxS nanocrystallites were fabricated in a controlled manner by a wet chemical method using thiourea as the complexing reagent. Zn0.951Cu0.049S exhibited high photocatalytic activity for H2 evolution without a cocatalyst under visible light irradiation, which is about 11 times higher than that of CdS prepared by the same procedure.

SrTiO3 is a promising photocatalyst for the production of hydrogen from water splitting under solar light. Cr doping is an effective treatment for adjusting its absorption edge to the visible-light range, although the performance of Cr-doped SrTiO3 is strongly affected by the oxidation number of the Cr ions. In this study, we theoretically predict that elevating the Fermi level, i.e., n-type carrier doping in SrTiO3, can stabilize the desirable oxidation number of chromium (Cr3+), contributing to a higher activity for H2 evolution. Our computational results, based on hybrid density-functional calculations, reveal that such an n-type condition is realized by substituting group-V metals (Ta, Sb, and Nb), group-III metals (La and Y), and fluorine atoms for the Ti, Sr, and O sites in SrTiO3, respectively. From our systematic study of the capability of each dopant, we conclude that La is the most effective donor for stabilizing Cr3+. This prediction is successfully evidenced by experiments showing that the La and Cr codoped SrTiO3 dramatically increases the amount of H2 gas evolved from water under visible-light irradiation, which demonstrates that our guiding principle based on Fermi level tuning by the codoping scheme is valid for the design of advanced photocatalysts.

α- MnO 2 electrode materials with sphere-, rod- and flower-like nanostructures were for the first time fabricated by a redox reaction between KMnO4 and NaHSO3 in chemical bath. Crystal structure and morphology of the as-crystallized samples were characterized by X-ray diffraction and scanning electron microscopy. The influence of reaction temperature and H+ concentration on both morphology and crystalline nature was investigated. Their electrochemical behaviors were investigated by cycling voltammetry and galvanostatic charge/discharge measurements in a three-electrode glass cell. Depending upon different synthesis conditions of α- MnO 2 electrodes, their specific capacitance values varied in the range of 43 to 197 F g-1 at the current density of 1 A g-1. Moreover, their specific capacitance values decrease with increasing crystallinity and particle size. In this work, we conclude that the energy storage mechanism is closely related to the particle aggregation state of electrode materials.

Nanostructured manganese oxides with different crystallization behaviors were fabricated by a simple redox reaction between KMnO4 and NaNO2 aqueous solution. MnO2 nanostructures with sphere-, rod-, wire-, plate- and flower-like morphologies were crystallized, and the relationship between crystallization characteristics and their electrochemical performances were studied. The electrochemical energy storage behaviors of these samples were investigated by cyclic voltammetry and galvanostatic charge–discharge measurements processed using noncorrosive Na2SO4 as the electrolyte. A maximum specific capacitance 200 F g−1 was obtained for poorly crystallized α-MnO2 at a current density of 1 A g−1. For different crystallographic MnO2 phases, their specific capacitance values increase in the order: β < γ < δ < α, meanwhile, for any particular MnO2 phase, their electrochemical energy storage performances decrease with increasing crystalline nature and particle size.

Selective local N-doped TiO(2) electrodes were fabricated using a pulsed laser deposition method. Different from the uniform nitrogen-doping in TiO(2) electrodes showing the diminution of IPCE in the UV light region, the inner nitrogen-doped TiO(2) electrode uniquely enhanced IPCE in the UV light region significantly (up to 95% at 320 nm, 1.23 V vs. SHE).

The oxygen reduction reaction (ORR) is one of the important reactions not only in life processes but also in artificial energy conversion systems, such as fuel cells and metal/air batteries. As one of the non-precious ORR catalysts, N-doped carbon materials show an exciting activity, but most of them were universally synthesized by high-temperature pyrolysis or annealing up to 1100 °C in the past few decades, which makes the structural manipulation of the catalysts extremely difficult. Here, we propose that ORR active N-doped carbon catalysts could, in principle, be prepared via a sophisticated wet chemical reaction between a reactive graphitic carbon template (e.g. graphene oxide) and N-containing molecules (e.g. dicyandiamide) at temperatures as low as 180 °C. Without any high-temperature treatments, for example, the as-prepared N-doped reduced graphene oxide with additional Fe-containing nanoparticles showed an impressive ORR catalytic activity that was comparable to many previous N-doped carbon from high-temperature pyrolysis. Rational utilization of the graphitic carbon template, the N-containing molecules, and the wet chemical reactions may offer a low-temperature route to create interesting ORR electrocatalysts with easier surface properties manipulation.

not Available.

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich. This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively. Mesoporous composite materials of nitrogen-doped carbon and silica were synthesised in a one-step-process applying a soft templating procedure. The template used in the sol–gel synthesis of the silica is a cationic surfactant with distinct reactivity to form nitrogen-doped graphitic carbon upon heating. This reactivity is derived from the combination of the dicyanamide anion with a nitrogen-containing pyridinium cation, as it is known from ionic liquids used as nitrogen-doped carbon precursors. Thus applying this surfactant in a conventional sol–gel synthesis yields a silica gel doped with a precursor for N-doped carbon. By subsequent annealing mesoporous composite materials of silica and nitrogen-doped carbon are obtained.

Micro/mesoporous Zn(2)GeO(4) with crystalline pore-walls was successfully synthesized via a simple ion exchange method at room temperature. This structure showed enhanced activity in photoreduction of CO(2) in comparison with Zn(2)GeO(4) prepared by a solid state reaction.

Self-doped SrTiO3−δ was prepared through a carbon-free one-step combustion method followed by a series of heat treatments in Ar at temperatures ranging from 1200 to 1400 °C. X-Ray Photoelectron Spectroscopy (XPS), Electron Paramagnetic Resonance (EPR) and High-Resolution TEM confirm the presence of Ti3+ in samples with oxygen vacancy accommodated in perovskite by forming Ruddlesden–Popper crystallographic shears. The UV-vis spectra and electronic structure calculations show that the oxygen vacancy and Ti3+ together induce an in-gap band to enhance the visible light absorption. Pulsed Adsorption of CO2 and Temperature Programmed Desorption (TPD) experiments show that the higher oxygen deficiency tends to improve the chemical adsorption of CO2 on the surface as well as in the bulk of SrTiO3−δ, especially the accommodation of CO2 molecule in the oxygen vacancy. It is the synergetic effect of visible light absorption and chemical adsorption of CO2 that improves the artificial photosynthesis to generate hydrocarbon fuels from CO2/H2O under visible light irradiation. We also demonstrated that the incorporation of oxygen from CO2/H2O into the oxygen vacancy of SrTiO3−δ leads to the absence of oxygen evolution which therefore results in the oxidation of SrTiO3−δ (Ti3+ → Ti4+).

By union of graphitic carbon nitride polymer with reduced graphene oxide (rGO, ≤1 wt%) via π–π stacking interaction, the band structure of carbon nitride could be well modulated. As a result, a significant increase of photocurrent was observed (e.g., when biased at 0.4 V vs.Ag/AgCl, the anodic photocurrent became 300% higher after doping). Not merely interesting in itself, graphene was also used as a general dopant for semiconductors in band-structure engineering.

not Available.

Both the behavior and the general key factors for assembling flexible SWNT films at the water/oil interface were investigated; the electron transfer, one of the most fundamental chemical processes, at the SWNT-sandwiched water/oil interface was also firstly illustrated using scanning electrochemical microscopy.

As a green process, electrochemistry in aqueous solution without a supporting electrolyte has been described based on a simple polyelectrolyte-functionalized ionic liquid (PFIL)-modified electrode. The studied PFIL material combines features of ionic liquids and traditional polyelectrolytes. The ionic liquid part provides a high ionic conductivity and affinity to many different compounds. The polyelectrolyte part has a good stability in aqueous solution and a capability of being immobilized on different substrates. The electrochemical properties of such a PFIL-modified electrode assembly in a supporting electrolyte-free solution have been investigated by using an electrically neutral electroactive species, hydroquinone (HQ) as the model compound. The partition coefficient and diffusion coefficient of HQ in the PFIL film were calculated to be 0.346 and 4.74 × 10−6 cm2 s−1, respectively. Electrochemistry in PFIL is similar to electrochemistry in a solution of traditional supporting electrolytes, except that the electrochemical reaction takes place in a thin film on the surface of the electrode. PFILs are easily immobilized on solid substrates, are inexpensive and electrochemically stable. A PFIL-modified electrode assembly is successfully used in the flow analysis of HQ by amperometric detection in solution without a supporting electrolyte. The results indicate a green electrochemical methodology in supporting electrolyte-free solution and a potential application in amperometric detection in a flow system without any supporting electrolyte in the solution, such as the high performance liquid chromatography electrochemical detection (HPLC-ECD) system.

Single-walled carbon nanotubes (SWCNTs) as reinforcing components were extended into silica monoliths and thin films via covalent functionalization for the first time. Silica materials have poor mechanical attributes, which limit their applications. Because of the extreme flexibility of SWCNTs and their large interfacial area, they may be very intriguing as reinforcing fillers for the silica matrix. To get more uniform dispersion and stronger interfacial interaction, SWCNTs were covalently functionalized with silane, and then integrated into silica via a sol–gel process, and their properties were also compared with those of pristine SWCNTs. Results show that the silane-functionalized nanotubes resulted in better mechanical properties (for example, 33% increase in stress, and 53% increase in toughness), as well as higher electron-transfer kinetics.