Fabrication of Stable MIL-53(Al) for Excellent Removal of Rhodamine B.

Adsorptive purification of organic dyes in wastewater is significant to protect the water environment. Herein, MIL-53(Al) was successfully fabricated through a facile and versatile solvothermal strategy. The stability of MIL-53(Al) under high temperature, acid, base, and peroxide conditions was investigated. The porous MIL-53(Al) had high chemical stability, and the thermal stability reached up to 500 °C, which provided a good foundation for dye removal. MIL-53(Al) showed excellent adsorption performance. The maximum adsorption capacity of MIL-53(Al) for rhodamine B (RhB) can reach 1547 mg g-1 under 303 K, and the corresponding removal efficiency exceeded 90% at the equilibrium time (120 min). The Langmuir model and pseudo-second-order model can well fit RhB adsorption on MIL-53(Al). Thermodynamic study and activation energy values over the range of 298-323 K revealed that the adsorption of RhB was a spontaneous and endothermic physical process in nature. The batch experimental results, X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared (FTIR) spectroscopy analyses suggested that the hydrogen bonding and electrostatic interactions between the hydroxyl/carboxyl groups of MIL-53(Al) and RhB were the primary adsorption mechanisms. Besides, MIL-53(Al) had a higher selectivity to RhB than the coexisting ions in aqueous solution and a superior adsorption performance after five cycles.

Construction of uric acid biosensor based on biomimetic titanate nanotubes.

A uric acid biosensor has been fabricated through the immobilization of uricase on glassy carbon electrode modified by biomimetic titanate nanotubes of high specific surface area synthesized by hydrothermal decomposition. The so-constructed biosensor presents a high affinity to uric acid with a small apparent Michaelis-Menten constant of only 0.66 mM. The biosensor exhibits fairly good electrochemical properties such as the high sensitivity of 184.3 microAcm(-2)mM(-1), the fast response of less than 2 s, as well as the wide linear range from 1 microM to 5 mM. These performances indicate that titanate nanotubes could provide a favorable microenvironment for uricase immobilization, stabilize its biological activity, and function as an efficient electron conducting tunnel to facilitate the electron transfer. This suggests an important potential of titanate nanotubes in uric acid biosensors.

Highly dispersed Pt-Ni nanoparticles on nitrogen-doped carbon nanotubes for application in direct methanol fuel cells.

Binary Pt-Ni alloyed nanoparticles supported on nitrogen-doped carbon nanotubes (NCNTs) have been facilely constructed without pre-modification by making use of the active sites in NCNTs due to the N-participation. So-obtained binary Pt-Ni alloyed nanoparticles have been highly dispersed on the outer surface of the support with the size of about 3-4 nm. The electrochemical properties of the catalysts for methanol oxidation have been systematically evaluated. Binary Pt-Ni alloyed composites with molar ratio (Pt:Ni) of 3:2 and 3:1 present enhanced electrocatalytic activities and improved tolerance to CO poisoning as well as the similar stability, in comparison with the commercial Pt/C catalyst and the monometallic Pt/NCNTs catalysts. These results imply that so-constructed nanocomposite catalysts have the potential for applications in direct methanol fuel cells.

An ion release controlled Cr(VI) treatment agent: Nano zero-valent iron/carbon/alginate composite gel.

A simple iron/carbon composite was prepared by ion exchange and carbothermal reduction, and the characterization results showed that this material contained a large amount of nanoscale zero-valent iron. Then above material was coated with alginate to form a stable gel, which combined adsorption and reduction to remove Cr(VI) efficiently and controllably. The experiment showed that the optimal conditions for Cr(VI) removal were pH value, dosage and Cr(VI) concentration of 2, 2 g L-1 and 20 mg L-1, respectively. For 150 mL of 20 mg L-1 Cr(VI) solution, the removal efficiency could reach 100% in 6 h (dosage: 2 g L-1). Compared with activated carbon-alginate complex and pure alginate, the introduction of nanoscale zero-valent iron greatly accelerated the rate of Cr(VI) removal. In addition, adsorption isotherm and kinetics conformed to Freundlich and Elovich model, respectively. Under pH 2, the release of iron ion increased linearly with time and reached 51.87 mg L-1 in 8 h. The mechanism of Cr(VI) removal of iron/carbon composite coated with alginate might be controlled by two steps: the initial adsorption and fixation, and subsequent reduction. In general, the material is efficient, recyclable and controllable, which provides a new idea for the treatment of chromium-containing wastewater.

Adsorption of divalent cadmium by calcified iron-embedded carbon beads.

A novel iron-embedded carbon bead was prepared by the calcination of a calcium alginate gel bead mixed with iron nanoparticles coated by polydopamine. The prepared iron-embedded carbon bead was characterized by infrared spectrum analysis, X-ray diffraction, Raman spectroscopy, vibrating sample magnetometry, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. It was discovered that the novel structure efficaciously prevented the agglomeration of iron nanoparticles. Additionally, the effects of dose, pH, exposure time, temperature and initial concentration on the adsorption of Cd(ii) were studied, and the reusability of the material was analyzed. Fe/SA-C showed high Cd(ii) removal capability (220.3, 225.7, 240.8 mg g-1 at 288, 298, 308 K), easy recoverability and high stability. In addition, some slightly different interpretations of the adsorption mechanism are given. This study clearly revealed that Fe/SA-C has potential application in the removal of Cd(ii).

Efficient removal of aqueous hexavalent chromium by activated carbon derived from Bermuda grass.

In this study, a novel raw material, Bermuda grass had been devised for the synthesis of activated carbon (BGAC) and enhanced the pore volume by potassium hydroxide. The effects of different factors on activated carbon products by orthogonal experiment was optimized. The synthesized BGAC was characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) analysis, energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS) and then, Cr(VI) removal batch experiments were conducted to investigate the Cr(VI) removal performance. Kinetic model and Weber-Morris diffusion model were fitted to the Cr(VI) removal process indicated that the chemisorption was the predominant removal mechanism and intraparticle diffusion was the sole rate-controlling mechanism. Langmuir isotherms could fit the experimental date well, which revealed that the adsorption of Cr(VI) ions was monolayer adsorption and the maximum adsorption capacity could be reached at 403.23 mg g-1. The results also promulgated that BGAC had an excellent potential on Cr(VI) removal. The removal processes were considered to comprise adsorption, reduction, precipitation and other ways through the study of the removal mechanism.

Facile Construction of Pt-Co/CNx Nanotube Electrocatalysts and Their Application to the Oxygen Reduction Reaction.

A straight forward method for immobilizing Pt-Co alloyed nanoparticles onto nitrogen-doped CNx nanotubes is presented. The as-prepared electrocatalysts exhibit good performance for oxygen reduction reaction in acidic medium arising from the high-dispersion and alloying effect of the Pt-Co nanoparticles and the intrinsic catalytic capacity of the CNx nanotubes.

Electrocatalysts: Facile Construction of Pt-Co/CNx Nanotube Electrocatalysts and Their Application to the Oxygen Reduction Reaction (Adv. Mater. 48/2009).

Pt-Co alloyed nanoparticles can be facilely immobilized onto CNx nanotubes due to the incorporated nitrogen, report Yanwen Ma, Zheng Hu, and co-workers on p. 4953. The as-prepared electrocatalysts exhibit good performance for oxygen reduction reactions in acidic media arising from the high dispersion and alloying effect of Pt-Co nanoparticles, as well as the intrinsic catalytic capacity of CNx nanotubes, which is significant for the development of fuel cells.

Electrocatalytical oxidation of hydroquinone with ferrocene covalently bound to L-cysteine self-assembled monolayers on a gold electrode.

The preparation of a gold electrode modified by ferrocenecarboxylic acid (FcA) covalently bound to L-cysteine self-assembled monolayer (FcA-SAM) is described. The modified electrode shows an excellent electrocatalytic activity for the oxidation of hydroquinone (QH2) and accelerates the electron transfer rate. The anodic overpotential is reduced by ca. 290 mV compared to those obtained at bare gold electrodes. The charge transfer coefficient and the apparent surface electron transfer rate constant for the redox couple of Q/QH2 at the modified electrode are found to be 0.425 and 0.96 s(-1), respectively. The catalytic current response of DPV increases linearly with the QH2 concentration from 5.7 x 10(-7) to 3.2 x 10(-4) M. The estimation of QH2 in a simulative sample is satisfactory. The method is simple, quick, and sensitive.

Carbon nanocages as supercapacitor electrode materials.

Supercapacitor electrode materials: Carbon nanocages are conveniently produced by an in situ MgO template method and demonstrate high specific capacitance over a wide range of charging-discharging rates with high stability, superior to the most carbonaceous supercapacitor electrode materials to date. The large specific surface area, good mesoporosity, and regular structure are responsible for the excellent performance.

Patterned growth and field-emission properties of AlN nanocones.

Patterned growth of AlN nanocones on a Ni-coated Si substrate is demonstrated through the reaction between AlCl(3) and NH(3) at 700 degrees C with Mo grid as a mask. The AlN nanocones are selectively deposited in the hollow region of the mask with diameters of approximately 10 nm at the tips and 50-60 nm at the roots. The field-emission (FE) performance is effectively enhanced by the patterned growth mainly because of the decreased screening effect, and both turn-on and threshold fields are dramatically decreased, less than half of the corresponding ones for the unpatterned product with similar sizes. The results indicate that patterned growth is an efficient and reproducible way to enhance the FE performance of AlN nanocones, which could be applied to optimize the FE properties of other nanoscale field emitters.

Simultaneous determination of uric acid and ascorbic acid at a ferrocenium-thioglycollate modified electrode.

Self-assembled monolayers (SAMS) of chemisorbed thioglycollate on a gold electrode surface have been used as a base interface for the electrostatic adsorption of ferrocenium ion. Electrochemical impedance spectra (EIS) and cyclic voltammetry (CV) were used to evaluate the electrochemical properties of the supramolecular film. The bare gold electrode failed to distinguish the oxidation peaks of ascorbic acid (AA) and uric acid (UA) in phosphate buffer solution (PBS, pH 7.0), while the ferrocenium-thioglycollate modified electrode could separate them efficiently. In differential pulse voltammetric measurements, the prepared gold electrode could separate AA and UA signals, allowing the simultaneous determination of AA and UA. Under optimal conditions and within the linear range of 1.0 x 10(-6) to 5.0 x 10(-4) M, the detection limits of AA and UA achieved were 2.0 x 10(-7) and 1.0 x 10(-7) M, respectively. The applicability of the prepared electrode was demonstrated by measuring AA and UA in human urine without any pretreatment.