High Effective Surface Area Research Articles

Resonance Energy Transfer in Hybrid Plasmonic-Polymetallophthalocyanine Nanoantennas Fabricated By Electropolymerization

Metal nanoparticles have exceptionally high photon absorption cross-sections at energies that excite a localized surface plasmon resonance compared to non-metallic particles. The light energy absorbed by these metal “nanoantennas” can be transferred non-radiatively to a coupled semiconductor material. The energy is stored in the semiconductor as electron-hole pairs through the dephasing of localized surface plasmon dipoles. The electrons and holes can then be extracted for charge transfer applications, such as catalysis. Here, we show that individual gold nanorods can be selectively coated via electropolymerization with metallophthalocyanines, a well-established class of oxygen and carbon dioxide reduction catalysts, to produce hybrid plasmonic-polymeric nanoantennas. The semiconducting polymer coatings have a high density of π-π* dipole transitions with energies matching the dipole resonance energy of the gold nanorods, enabling efficient dipole-dipole coupling. Using in situ hyperspectral dark-field imaging, we observed large plasmon resonance linewidth increases in the scattering spectra of single gold nanorods with the anodic deposition of the polymer coating, and attribute this to a greatly decreased plasmon dephasing time due to resonance energy transfer. In situ single particle spectroscopy was required to reveal that the increase in resonance linewidth was dependent on the polymer thickness and the energy of the uncoated gold nanorod longitudinal plasmon resonance. Permeable metallophthalocyanine polymer coatings are spectroscopically and chemically tunable, and have a high effective surface area opening up new opportunities for plasmonic antenna-reactor electrodes in energy sustainability applications.

Efficient double electrochemiluminescence quenching based label-free highly sensitive detection of haptoglobin on a novel nanocomposite modified carbon nanofibers interface

ECL behaviour is highly dependent on electrode surface, materials and dimensions. Therefore, in this work ECL intensity of [Ru(bpy)3]2+/TPrA system was studied with the bare carbon nanofiber screen-printed electrode (CNFs-SPE) and the novel AuNPs/CdTe-QDs/SWCNTs/Chitosan nanocomposite modified CNFs-SPE (CdTe/AuNPs/SWCNTs/Chitosan/CNFs-SPE). ECL intensity was enhanced about 1.0 time with the AuNPs/CdTe-QDs/SWCNTs/Chitosan/CNFs-SPE interface in comparison to the bare CNFs-SPE. Additionally, AuNPs/CdTe-QDs/SWCNTs/Chitosan/CNFs-SPE interface produced ~ 200% increase both in electronic conductivity and in effective surface area in comparison to the bare CNFs-SPE. AuNPs/CdTe-QDs/SWCNTs/Chitosan/CNFs-SPE interface with a combined advantage of high effective surface area, electronic conductivity and ECL intensity was for the first time used to develop an efficient double ECL quenching based immunosensor for the highly sensitive and selective label-free detection of haptoglobin (Hp). Under optimum conditions, the constructed Hp-immunosensor displayed a wide: 100 fg mL−1 to 10 ng mL−1 linear detection range, with a low limit of detection 100 fg mL−1. The calibration plot provides a negative linear relationship between log[c] of Hp and ECL intensity with a coefficient of correlation 0.99. Moreover, this novel biocompatible nanocomposite interface could be used for the ECL based detection of other biomarkers and biomolecules.

Boron-doped Ni/SBA-15 catalysts with enhanced coke resistance and catalytic performance for dry reforming of methane

Nickel-based heterogeneous catalysts have shown promising results in many industrial-scale catalytic reforming processes and hydrocarbon reforming reactions such as dry reforming of methane (DRM). However, it is also reported that Ni-based catalysts generally show less resistance to the carbonaceous deposition, which ultimately causes their rapid deactivation during the reaction. One possible solution to improve the coke resistance is the addition of a promoter to the catalyst, which has shown successful results to reduce the coke formation. Therefore, this study also aimed to prepare boron-promoted Ni-based catalysts and investigate their efficiency for DRM reactions. A series of different catalysts with 10% nickel and x% boron (x: 1%, 2%, 3%, and 5%) were prepared by using an ordered mesoporous silica as a support and tested in DRM. The results demonstrated that boron-promoted Ni/SBA-15 catalysts obtained significant catalytic activity for CH4 and CO2 conversions. Meanwhile, it was noticed that a lower concentration of boron (1 and 2%) was more favourable to achieve higher catalytic activity, whereas the higher concentration (3% and 5%) resulted in a comparatively lower conversion for CH4 and CO2. Evidently, the higher activity of 2% B-promoted catalyst was ascribed to the synergistic effect of high surface area and lower crystallite size that greatly improved the active sites accessibility. Moreover, the results confirmed 14% carbon deposition on unpromoted (NS) catalyst and it was reduced to 1.3% for 2% boron-promoted catalyst owing to the presence of B-OH species on catalyst surface.

Effects of the support on the characteristics and permselectivity of thin film composite membranes

How the membrane support affects the performance of thin-film composite (TFC) membranes has long been under debate. Our present study experimentally establishes that the support pore number density (number per unit area) as well as its surface porosity play pivotal roles in affecting the characteristics and permselectivity of TFC membranes. The structure of hollow fiber supports was finely tuned and characterized via a series of techniques, which provided a link to the physicochemical properties of the interfacially polymerized polyamide films. During the spinning process, decreasing the content of N-methyl-2-pyrrolidone in the bore fluid drastically reduced the pore size and surface porosity of the support. The resultant TFC membranes showed a lower water permeability (tested under 1 bar using 500 ppm NaCl). Adding lithium chloride to the polymer dope also led to a support with smaller pores and lower porosity, but increased surface pore number density. The resulting TFC membranes had a substantially higher water permeability and slightly higher salt rejection. In both arrays of membranes, all membranes shared similar thickness of polyamide leaf but a more crumpled film was found on a less porous support, suggesting that the surface porosity of the support affected the effective surface area of films. However, the TFC membrane with a higher effective surface area did not necessarily possess a higher permeability. Rather, a TFC membrane having a support with a higher surface porosity or a higher pore number density exhibited a higher water permeability, demonstrating that the lateral transport path of water through films had a significant impact on the water permeability of TFC membranes. Interestingly, in both cases, the selectivity of the TFC membranes was maintained when the water permeability increased. This study clarifies longstanding misunderstandings concerning the effects of the support on TFC membrane performance and provides insight into fabricating highly permeable and selective TFC membranes.

Enhancement of visible and UV light photocatalytic activity of rGO-TiO2 nanocomposites: The effect of TiO2/Graphene oxide weight ratio

Abstract In this study, rGO − TiO 2 nanocomposites were prepared by means of a simple hydrothermal approach using TiO 2 powder and GO nanosheets as starting materials. The TiO 2 / GO weight ratio varied from 0.25 to 2 wt%. The prepared samples were characterized using AFM, SEM and TEM microscopy as well as XRD, EDX, Raman, FTIR and UV–Vis spectroscopies. BET and BJH measurements were also performed to obtain the specific surface area and pore diameter size of the synthesized samples. It was found that the samples with TiO 2 / GO weight ratio below one have high effective surface area about 124 g/m2 and pore size of 6 nm. Photocatalyst evaluation revealed that only 0.06 mg/ml of prepared composite degraded 90% of 20 ppm Methylene blue (MB) in 15 min under 50 mW / cm 2 UV light intensity. The linear kinetic rate constant (k) of the samples promoted from 22 × 10 − 3 min−1 for TiO 2 under UV exposure up to 153 × 10 − 3 min − 1 and 65 × 10 − 3 min − 1 for composites under UV and visible irradiation, respectively. More detailed analyses showed that the photocatalytic activity of samples obtained figure of merit below unity. To the best of our knowledge this seems to be an impressive result. Impedance spectroscopy analysis revealed that the enhancement of charge transfer in composites as well as high effective surface area and their mesoporous structure are mainly responsible for the significant enhancement of MB photodegradation. The reactive species trapping experiments were performed by a series of radical scavengers. On the basis of the experimental results, the electrons and superoxide ions species play the main role in degradation of MB.

Development of novel TiO2-Cu2(OH)PO4 heterojunction as nanophotocatalyst for improved Cr (VI) reduction

TiO2-Cu2(OH)PO4 heterojunction nanomaterials with 2–10% of Cu2(OH)PO4 were synthesized by hydrothermal method. The physiochemical properties of synthesized nanomaterials were studied using XRD, FESEM, HRTEM, N2 physisorption, UV–vis (DRS) and XPS. XRD indicates the formation of anatase phase. HRTEM conforms the proper heterojunction formation of diamond shaped crystalline nanoparticles with average size 20–30 nm. Addition of 10% Cu2(OH)PO4 with titania extend the light absorption to visible-NIR region and decrease the overall band gap to 2.6 eV thus enhancing the visible light absorption. The in-situ generated Ti3+ and oxygen vacancies in the TiO2 lattice along with the metallic copper at the interface results in extended visible light absorption up to NIR range and improved charge separation. Photocatalytic reduction of Cr (VI) under visible light was studied to evaluate the effect of Cu2(OH)PO4 addition. TiO2 heterojunction with 10% of Cu2(OH)PO4 can completely reduce Cr (VI) into Cr (III) within 90 min of visible light irradiation whereas in same interval TiO2 and Cu2(OH)PO4 shows negligible and 10% reduction, respectively. Improved photocatalytic activity of TiO2-Cu2(OH)PO4 nanophotocatalyst under visible radiation is attributed to the synergistic effect of high surface area, improved visible-NIR light absorption and formation of proper heterojunction.

Selective voltammetric determination of α-lipoic acid on the electrode modified with SnO2 nanoparticles and cetyltriphenylphosphonium bromide

Sensitive voltammetric method for α-lipoic acid determination based on glassy carbon electrode (GCE) modified with SnO2 nanoparticles (SnO2 NP) dispersion in cetyltriphenylphosphonium bromide (CTPPB) (SnO2 NP-CTPPB/GCE) has been developed. The comparison to other surface active compounds as dispersive agents has been performed. The electrodes surface has been characterized by scanning electron microscopy, electrochemical impedance spectroscopy, cyclic voltammetry, and chronoamperometry. Statistically significant decrease of charge transfer resistance (10.8 ± 0.4 kΩ vs. 181 ± 7 kΩ for GCE and 71 ± 3 kΩ for SnO2 NP-H2O/GCE) and higher effective surface area (13.7 ± 0.2 mm2 vs. 8.2 ± 0.3 mm2 for GCE and 12.1 ± 0.2 mm2 for SnO2 NP-H2O/GCE) has been obtained for SnO2 NP-CTPPB/GCE. α-Lipoic acid oxidation on SnO2 NP-CTPPB/GCE is a two-electron diffusion-controlled pH independent process leading to β-lipoic acid formation. Under conditions of differential pulse voltammetry in Britton–Robinson buffer pH 4.5, the linear dynamic ranges are 0.50–50 and 50–400 μmol dm−3 of α-lipoic acid with the limits of detection and quantification of 0.13 and 0.43 μmol dm−3, respectively. The method developed has been successfully applied for the pharmaceutical dosage form analysis.

Rich N/O/S co-doped porous carbon with a high surface area from silkworm cocoons for superior supercapacitors

The synergistic effects of high surface area and abundant heteroatoms make porous carbons superior electrode materials.

TiN Thin Film Electrodes on Textured Silicon Substrates for Supercapacitors

TiN thin film electrodes for supercapacitors were deposited successfully on textured silicon substrates by reactive magnetron sputtering and silicon surface texturization. The areal specific capacitance of the rough TiN electrodes was nearly two-fold higher than that of the smooth electrodes. Meanwhile, the textured TiN electrodes exhibit rough surfaces comprising a large number of random pyramids and good cycling stability with about 28% decay in capacitance value after 3500 cycles. In addition, the rough electrodes also exhibit relatively favorable charge transfer and ion diffusion due to their higher effective surface area. These results demonstrate that TiN electrodes on textured silicon substrates will have promising prospects for high-performance supercapacitors.

Sub-ppm level NO2 sensing properties of polyethyleneimine-mediated WO3 nanoparticles synthesized by a one-pot hydrothermal method

A novel sensing material of polyethyleneimine-mediated WO3 nanoparticles was prepared by a simple and efficient one-pot hydrothermal method. The structure and morphology characteristics of the as-prepared WO3 nanoparticles were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The results showed that the as-prepared WO3 nanomaterials were composed of highly dispersible WO3 nanoparticles, and these nanoparticles with the particle size in the range of 10–50 nm showed a monoclinic structure. NO2 sensing measurements demonstrated that WO3 nanoparticles-based gas sensor exhibited superior response, outstanding selectivity, excellent reversibility, and good long-term stability. The sensor response increased as NO2 concentration increased. The highest response value of 251.7 was achieved to 5 ppm NO2 at the optimal operating temperature of 100 °C. Especially, the sensor response could reach 3.2–50 ppb NO2. It also exhibited fast response and recovery times with a high sensor response even in a high-humidity environment. The excellent gas sensing properties of WO3 nanoparticles could be ascribed to their high effective surface areas as well as numerous oxygen vacancies, which foresee the great potential application for fast and effective detection of sub-ppm level NO2 under different humidity environments.

Synthesis of Al-MCM-41@Ag/TiO2 Nanocomposite and Its Photocatalytic Activity for Degradation of Dibenzothiophene

Mesoporous Al-MCM-41@Ag/TiO2 nanocomposites were synthesized successfully by combining the sol-gel method and hydrothermal treatment, using titanium isopropoxide (TTIP), AgNO3, and Vietnamese bentonite as precursors of Ti, Ag, and Si, respectively. The synthesized materials were well characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption isotherm measurements, energy dispersive X-ray spectroscopy (EDX), UV-visible diffuse reflectance spectroscopy (UV-Vis/DRS), and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity was evaluated by the photodegradation of dibenzothiophene (DBT) under both UV and visible light irradiation. MCM-41@Ag/TiO2 catalyst exhibited high catalytic activity for the oxidative desulfurization (ODS) of DBT reaching almost 100% conversions at 50°C after 2 h under UV and visible light irradiations. The significant enhanced degradation of DBT over Al-MCM-41@Ag/TiO2 might be due to the synergy effects of high surface area of MCM-41, well-distributed TiO2 anatase, and reduced electron-hole recombination rates due to the dispersion of Ag nanoparticles.

Effective Surface Area Tuning of Noble Metal-Free CuBO2/rGO Nanohybrid for Efficient Hydrogen Production with “On–Off” Switching

Noble metal-free CuBO2/rGO nanohybrid is synthesized and examined as a catalyst for NaBH4 hydrolysis. Detailed characterization reveals that the hybridization generates a charge imbalance between CuBO2 and rGO and creates an electron transport channel which facilitates H2 generation during NaBH4 hydrolysis. High surface roughness, consequently with high effective surface area, is obtained by varying the synthesis conditions. The high activity (specific rate activity, 2500 mL min–1 g–1) and low activation energy (49.8 kJ mol–1) establish this noble metal-free catalyst as a potential candidate in the field of fuel cell based hydrogen economy. The mechanistic investigation confirms that protonation and deprotonation can control the H2 generation kinetics and the same is validated by changing the pH of the reaction medium for an on-site and on-demand H2 production with easy “on–off” switching.

3D CNTs-threaded N-doped hierarchical porous carbon hybrid with embedded Co/CoOx nanoparticles as efficient bifunctional catalysts for oxygen electrode reactions

Developing an efficient non-precious metal catalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in regenerative energy conversion and storage devices is very imperative but still challenging. Herein, a three-dimensional (3D) hierarchical porous Co/CoOx nanoparticles embedded N-doped carbon hybrid threaded with carbon nanotubes (Co/CoOx@NC-CNTs) was prepared via in situ threading CNTs through ZIF-67 polyhedron and a succedent carbonation process. Compared to those of commercial electrocatalysts (Pt/C and RuO2), the as-prepared hybrid showed comparable electrocatalytic activity with positive ORR half-wave potential (E1/2) of 0.836 V, low OER potential (Ej=10 = 1.62 V), good methanol tolerance and excellent electrocatalytic stability. Moreover, the small overpotential difference value (ΔE = Ej=10-E1/2) of 0.784 V is competitive to those of recent reported outstanding bifunctional oxygen electrocatalysts. The high electrocatalytic properties of the Co/CoOx@NC-CNTs hybrid are attributed to the synergistic effect of high surface area, desirable pore structure and reasonable chemical composition.

Ultrahigh volumetric capacitance and cycle stability via structure design and synergistic action between CoMoO4 nanosheets and 3D porous Ni-Co film

The rational design of the composites constituted by active materials and self-supported conductive current collectors has been turned out to be an effective way to achieve excellent electrochemical performance of supercapacitors. In this work, the 3D network-like continuous porous Ni-Co film (3DNC) with high conductivity and controllable porous structure was obtained through simple de-alloying and annealing processes, and then ultrathin CoMoO4 nanosheets were homogeneously grown onto skeleton of 3DNC film by hydrothermal and low-temperature annealing processes. The 3DNC film exhibits considerable electrochemical performance, whose controllable pore structure insures optimized mass loading of CoMoO4 and maximized space utilization of integrated electrode. The highly interconnected porous channels among the ultrathin CoMoO4 nanosheets provide high ion-accessible effective surface area and fast ion diffusion path, which significantly increases the reaction kinetics of the CoMoO4 nanosheets. Such outstanding structural advantages and the synergistic effect between CoMoO4 nanosheets and 3DNC film result in desired electrochemical performance with an extremely high volumetric capacitance of 2601.3 F cm−3 (325.2 mAh cm−3), excellent rate performance and superior cycle stability up to 20,000 cycles. The impressive results open an avenue toward the rational design of free-standing composites with high-performance electrochemical performance through both structure design and the synergistic action between active materials and conductive current collectors.

Selective fabrication of porous iron oxides hollow spheres and nanofibers by electrospinning for photocatalytic water purification

Porous hematite (α-Fe2O3) hollow spheres and nanofibers could be obtained via electrospinning and subsequent thermal decomposition in air. The precursor could be fabricated by electrospinning using Fe(NO3)3 as the iron source and Polyvinylpyrrolidone (PVP) as a complexing reagent. Upon calcination, pure porous α-Fe2O3 hollow spheres and nanofibers could be obtained at 650 °C for 3 h. The novel hollow spheres have an abundantly porous structure as well as large surface areas. Benefitting from the special porous structure, narrow bandgap, and higher surface area, porous α-Fe2O3 hollow materials are used as visible-light-responsive photocatalysts. So we have investigated the visible light photodegradation behavior of porous hematite (α-Fe2O3) hollow spheres and nanofibers towards organic dyes, as Rhodamine B (RhB). The synergetic effects of higher surface area, pore structures promoted the photocatalytic efficiency for RhB degradation under visible light and contributed to achieving the enhanced and stable photocatalytic activity.

Engineered Nanoporous Anodic Alumina Structures for the Development of Advanced Sensing and Drug Delivery Systems

Nanoporous anodic alumina (NAA) is a semiconductor material with interesting physical, mechanical, chemical and optical properties [1]. NAA is formed by the electrochemical etching of aluminum and presents a self-ordered hexagonal pore distribution with tunable pore diameters, pore lengths and interpore distances (figure 1) [2]. The high effective surface area of NAA (hundreds of m2/cm3) makes it a versatile and interesting platform for loading active agents like drugs or molecules as pores are used as reservoirs [3]. Based on this principle, we present here the use of NAA to develop advanced drug delivery systems and gated materials for biosensing applications. The development of a new generation of local and selective drug delivery platforms with sustained release profiles is necessary to overcome the disadvantages of conventional treatments (generally oral or intravenous administrations) with considerable adverse effects [4]. The high effective surface area of NAA makes it an ideal material for drug delivery applications: the pores are nanocontainers with regular and controlled structural characteristics where active agents like drugs or molecules can be loaded [5]. Besides, the surface of NAA can be easily functionalized to be selective for specific molecules and covered with biodegradable, chemical, or pH responsive agents to trigger and regulate the release [6]. The pore geometry is one of the most important factors for the drug loading and for the release profile. Three-dimensional pore structures, with complex pore geometries and increasing surface area are promising morphologies for sustained drug release. However, their fabrication can be expensive and difficult. NAA, readily and cost-effectively fabricated by electrochemical anodization, permits obtaining elaborate and reproducible three dimensional pore geometries for sustained drug release platforms (figure 1) [7]. The biosensors we propose also follow the same concept of nanocontainer-pores introduced for the drug delivery systems. They consist of a NAA platform where the pores are loaded with a fluorophore and blocked by selected molecules that are able to recognize selectively a certain target analyte. The presence of the analyte unblocks the pores resulting in the selected release of the entrapped reporter. These gated biosensors based on NAA have high potential for the selective and sensitive detection of molecules that currently require complex and/or long processing. These nanostructured biosensors are very simple to prepare, easy to handle, reusable, and do not require trained personnel. We report here the use of these NAA biosensors for the selective detection of drugs and bacteria Figure 1

A new sensing platform based on magnetic Fe3O4@NiO core/shell nanoparticles modified carbon paste electrode for simultaneous voltammetric determination of Quercetin and Tryptophan

In current study, electrochemical sensing electrode based on uniform three–dimensional (3D) flowerlike Fe3O4@NiO magnetic nanoparticles (MNPs) modified carbon paste electrode (Fe3O4@NiO/CPE) is introduced for simultaneous determination of Quercetin (Q) and Tryptophan (Trp).The Fe3O4@NiO nano-flowers were synthesized by solvothermal/decomposition method in a hierarchical architecture with microspheres of 70–80nm, and the outer shells consisted of several nano flakes with 10–20nm in thickness via a facile, cost effective technique. Various techniques were employed to thoroughly characterize of the sensor as well as the synthesizes magnetic nanoparticles, namely field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and voltammetry. Electrochemical studies revealed that the proposed sensor exhibited some major advantages, including high effective surface area, numerous reactive sites and excellent electrochemical catalytic activity toward oxidation of Q and Trp. Under the optimal conditions, the electrode showed linear responses for Q and Trp in wide ranges of concentrations, e.g. 0.08–60 and 0.1–120μM for Q and Trp, respectively. The estimated detection limits were 2.18 and 14.23nM for Q and Trp, respectively. This sensor displayed an excellent stability, selectivity, sensitivity and good reproducibility for the modified electrode, suggesting that the sensor was a promising one for the simultaneous determination of Q and Trp in human breast milk, cow milk and honey with an excellent recovery and without the interferences of coexisting substances.

Functionalization of Synthesized NaP Zeolite with Silver Nanoparticles Capped with Alkyl Dimethyl Hydroxyethyl Ammonium for Sorption and Reduction of Chromate(VI) Oxoanions

NaP zeolite crystals were synthesized and used as templating support species for the purpose of hosting and the confinement of silver nanoparticles. This was being adapted primarily by introducing trace amounts of alkyl dimethyl hydroxyethyl ammonium chloride (ADHA) ranging from 50 to 200 ppm into the zeolite (Ag/ADH-NaP50–200). For comparison purposes, ADHA/NaP and Ag/NaP were also prepared under the same conditions. These solids have been examined by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), Raman spectroscopy (LRS), X-ray photoelectron spectroscopy (XPS), diffuse reflectance UV–Vis spectroscopy as well as surface texture measurements. By increasing the concentration of ADHA and under the effect of UV radiation, the XRD analysis of Ag/ADHA-NaP has shown increase in unit cell parameters of the zeolite along with new peaks attributed to silver nanoparticles (AgNPs) were observed at d values of 2.370 and 2.047 A. This was confirmed by XPS peaks corresponding to Ag 3d at 368.7 and 374.7 eV. Upon addition of aqueous Cr(VI) to the Ag/ADHA-NaP200 sample, adsorbed species on the silver surface such as CrO4 2− and Cr(OH)3 produced Raman scattering at 853 and 664 cm−1, respectively. The latter sample was able to adsorb the Cr(VI) completely, but unlike the other samples, at an initial concentration of 20 ppm. The high effective surface area of AgNPs shows enhanced adsorption and photreduction of Cr(VI) to Cr(III), in compatible with the evaluation of optical band gaps. The adsorption process of Cr(VI) was thought to result from a surface uptake and intra-particle diffusion which operate simultaneously through the interaction between Cr(VI)ions and Ag/ADHA-NaP200.

Dyeing behavior of polyacrylonitrile nanofibers: Physicochemical parameters of dyeing with basic dye in comparison with regular polyacrylonitrile fibers

Polyacrylonitrile nanofibers were produced using the electrospinning method and dyed with a basic dye alongside regular polyacrylonitrile fibers. In order to investigate the effect of high surface area to volume ratio of nanofibers on their adsorption behavior in comparison with regular fibers, the dyeing conditions for both types of fibers were kept just the same. Physiochemical parameters of dyeing such as adsorption isotherm, standard affinity, enthalpy change, rate of dyeing constant, diffusion coefficient, and activation energy of diffusion were investigated for both types of fibers. The results showed that the adsorption process can be well described with the Langmuir adsorption isotherm for both types of fibers whereas the standard affinity of dye to nanofibers was higher than regular fibers and the higher negative values of enthalpy changes were obtained for regular fibers. The nanofibers rate of dyeing was faster than regular fibers with higher amounts of diffusion coefficients and lower amounts of activation energy of diffusion. This study also revealed that in spite of the approximately same amount of dye exhaustion for both types of fibers, the color strength of regular fibers was noticeably higher than nanofibers.

Boron and oxygen-codoped porous carbon as efficient oxygen reduction catalysts

A low-cost boron- and oxygen-codoped porous carbon electrocatalyst towards oxygen reduction reaction (ORR) has been fabricated by a facile one-step pyrolysis approach, while a boron- and oxygen-rich polymer network was used as precursor. The boron- and oxygen-codoped carbon catalyst with high ORR electrocatalytic activity is comparable to that of Pt/C and is superior to that of catalysts doped solely with boron atoms or with oxygen atoms. Furthermore, the optimized boron- and oxygen-codoped carbon catalyst possesses excellent methanol tolerance and long-term durability in alkaline media. The high electrocatalytic activity of the dual-doped carbon catalysts can be attributed to the synergistic effects of high surface area, predominant mesostructure, abundant active oxygen-containing groups, and effective boron doping. The present results show that this boron- and oxygen-codoping strategy could be as a promising way for the preparation of highly efficient ORR catalysts.