Jianwei Fu

Selective adsorption and separation of organic dyes from aqueous solution on polydopamine microspheres.

Polydopamine (PDA) microspheres, synthesized by a facile oxidation polymerization route, were evaluated as a potential adsorbent for selective adsorption and separation of organic dyes. The adsorption processes towards nine water-soluble dyes (anionic dyes: methyl orange (MO), eosin-Y (EY), eosin-B (EB), acid chrome blue K (ACBK), neutral dye: neutral red (NR), and cationic dyes: rhodamine B (RhB), malachite green (MG), methylene blue (MB), safranine T (ST)) were thoroughly investigated. The adsorption selectivity of organic dyes onto PDA microspheres was successfully applied for the separation of dyes mixtures. Various influential factors such as solution pH, temperature, and contact time were employed to ascertain the optimal condition for adsorption of representative organic dyes including MB, MG and NR. The pseudo-first-order and pseudo-second-order kinetics models were used to fit the adsorption kinetics process. Five isothermal adsorption models (Langmuir, Dubnin-Radushkevich, Temkin, Freundlich and Harkins-Jura) were used to investigate the adsorption thermodynamics properties. The results showed that the PDA microspheres owned good selective adsorption ability towards cationic dyes. The adsorption kinetics process conformed to the pseudo-second-order kinetics model and the Langmuir isotherm model was more appropriate for tracing the adsorption behavior than other isotherm models. Thus, we can conclude PDA microspheres may be a high-efficiency selective adsorbent towards some cationic dyes.

High‐Efficiency Encapsulation of Pt Nanoparticles into the Channel of Carbon Nanotubes as an Enhanced Electrocatalyst for Methanol Oxidation

Pt-based nanostructures serving as anode catalysts for the methanol oxidation reaction (MOR) have been widely studied for many years. Nevertheless, challenging issues such as poor reaction kinetics and the short-term stability of the MOR are the main drawbacks of such catalysts and limit their applications. Herein, we have developed a facile approach to encapsulate Pt nanoparticles (NPs) inside the nanochannels of porous carbon nanotubes (CNTs; Pt-in-CNTs) as a new enhanced electrocatalytic material. The as-prepared CNTs offer simultaneously ordered diffusion channels for ions and a confinement effect for the NPs, which both facilitate the promotion of catalytic kinetics and avoid the Ostwald ripening of Pt NPs, thus leading to high activity and durable cycle life as an anode catalyst for MOR. This work provides a new approach for enhancing the stability and activity by optimizing the structure of the catalyst, and the Pt-in-CNTs represent the most durable catalysts ever reported for MOR.

Modification of Graphene Oxide with Amphiphilic Double-Crystalline Block Copolymer Polyethylene-b-poly(ethylene oxide) with Assistance of Supercritical CO2 and Its Further Functionalization

Graphene oxide (GO) sheets were noncovalently modified with an amphiphilic double-crystalline block copolymer, polyethylene-b-poly(ethylene oxide) (PE-b-PEO) with assistance of supercritical CO(2) (SC CO(2)) in this work. The resulting PE-b-PEO/GO nanohybrids were characterized by transmission electron microscopy (TEM), wide-angle X-ray diffraction (WAXD), Fourier transform infrared spectroscopy (FTIR), and Raman spectra. Distinct morphologies of PE-b-PEO decorating on the surface of GO were obtained in different solvent systems and at different SC CO(2) pressures. We found that the solvent system and the SC CO(2) have significant influence on the crystallization, aggregation, or assembly behaviors of PE-b-PEO molecular chains on the GO sheets. The formation mechanism of the distinct nanohybrid structures is attributed to a relevant easy heteronucleation and the limited crystal growth of the block polymer on the surface of GO. The resulting modified GO sheets could find a broad spectrum of applications not only in producing graphene-based nanocomposites but also being used as a template to fabricate multifunctional structures due to the unique properties of PE-b-PEO. As a proof-of-concept, we further decorated the GO sheets with the as-prepared Au nanoparticles (Au NPs) and CdTe nanoparticles (CdTe NPs) with PE-b-PEO as the interlinker. Using the thiol-terminated PE-b-PEO as an interlinker, Au NPs can be densely assembled on the surface of GO via robust Au-S bonds. Furthermore, the photoluminescence quenching of CdTe NPs was more notable for PE-b-PEO/GO-CdTe hybrid compared to the GO-CdTe hybrid, suggesting that the electron transfer from the CdTe NPs to the GO sheets was enhanced with the PE-b-PEO interlinker. The availability of these affordable graphene-based multifunctional structures and their fundamental properties will open up new opportunities for nanoscience and nanotechnology and accelerate their applications.

In vivo characterization of hair and skin derived carbon quantum dots with high quantum yield as long-term bioprobes in zebrafish

Carbon quantum dots (CDs) were widely investigated because of their tunable fluorescence properties and low toxicity. However, so far there have been no reports on in vivo functional studies of hair and skin derived CDs. Here, hair derived CDs (HCDs) and skin derived CDs (SCDs) were produced by using human hair and pig skin as precursors. The quantum yields (QYs) of HCDs and SCDs were quite high, compared to citric acid derived CDs (CCDs). HCDs and SCDs possess optimal photostability, hypotoxicity and biocompatibility in zebrafish, indicating that HCDs and SCDs possess the capacity of being used as fluorescence probes for in vivo biological imaging. The long-time observation for fluorescence alternation of CDs in zebrafish and the quenching assay of CDs by ATP, NADH and Fe3+ ions demonstrated that the decaying process of CDs in vivo might be induced by the synergistic effect of the metabolism process. All results indicated that large batches and high QYs of CDs can be acquired by employing natural and nontoxic hair and skin as precursors. To our knowledge, this is the first time to report SCDs, in vivo comparative studies of HCDs, SCDs and CCDs as bioprobes, and explore their mechanism of photostability in zebrafish.

Steric hindrance colloidal microsphere approach to fabricate ordered and interconnected Pt or Pt/Ag hollow hemispheres

A steric hindrance colloidal microspheres approach (SHCMA) has been developed for the fabrication of ordered Pt or Pt/Ag nanoparticles composite interconnected hollow hemispheres via colloidal lithography and physical vapor deposition. Monolayer ordered silica or silica/Ag nanoparticles composite microspheres partly embedded into the polydimethylsiloxane (PDMS) were used as template, and Pt was sputtered on it. Due to the PDMS stamp functionalized as a steric hindrance substrate, which guaranteed that the ordered silica or silica/Ag nanoparticles composite microspheres were only coated with Pt film on the sides that exposed in air. After removing the template particles, large area ordered interconnected Pt or Pt/Ag nanoparticles composite hollow hemispheres were generated. The fabricated Pt hollow hemispheres have flat bottoms and are flexible and robust enough to be easily folded. In addition to successfully solving the challenge about ordered structure construction of the hollow Pt or Pt/Ag nanoparticles composite hemispheres here, we also could finely control the wall thickness of these hemispheres easily by changing the sputtering time or current.

Fabrication of poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) nanotubes decorated with Ag–Au bimetallic nanoparticles with enhanced catalytic activity for the reduction of 4-nitrophenol

Ag–Au bimetallic nanoparticles (NPs) are deposited on poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) nanotubes by a facile and effective co-reduction method, wherein the PZS nanotubes with abundant hydroxyl groups have been prepared via an in situ template approach. Upon varying the feeding amounts of the Ag and Au precursors, the bimetallic compositions of the PZS nanotubes can be readily tuned resulting in a series of bimetallic catalysts with different Ag to Au molar ratios, thus leading to the tunable catalytic properties. Characterization results show that the Ag–Au bimetallic nanoparticles with smaller size and good dispersibility are well anchored onto the surface of the PZS nanotubes. Furthermore, the reduction of 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) by NaBH4 is applied as a model reaction to study the effect of different Ag-to-Au molar ratios on the catalytic capabilities of the resulting composites. It is found that the catalytic capability is remarkably enhanced when the Au content is increased. The maximum activity parameter value reaches 92.2 s−1 g−1, which is far higher than that of PZS nanotubes decorated with either Ag or Au nanoparticles alone.

Removal of Rhodamine B, a Cationic Dye From Aqueous Solution Using Poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) Nanotubes

Poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) nanotubes were evaluated as an efficient adsorbent for the removal of Rhodamine B (RhB), a cationic dye from aqueous solution. The as-synthesized adsorbent (PZS nanotubes) were characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR) and N2 adsorption/desorption isotherms. The factors influencing the adsorption efficiency and capacity had been systematically studied. Results showed that the adsorption was highly dependent on temperature, initial RhB concentration and adsorbent dose. Effects of initial solution pH indicate that the adsorption can proceed in both basic and acidic environment. The equilibrium absorption capacity at 25°C can reach up to 35.58 mg/g within 60 min implying the adsorption procedure was highly rapid. The kinetic data was better described by the pseudo-second-order model with the correlation coefficient (R2 = 0.9981), and the adsorption process followed Webers intraparticle model, indicating the adsorption process could be divided into two stages. Results also showed that the adsorption equilibrium obeyed the Langmuir isotherm, and the value of equilibrium parameter RL suggested that the PZS nanotubes were an efficient adsorbent for the removal of RhB from aqueous solution.

A novel method to fabricate discrete porous carbon hemispheres and their electrochemical properties as supercapacitors

A simple and efficient method to produce discrete, hierarchical porous carbon hemispheres (CHs) with high uniformity has been successfully developed by constructing nanoreactors and using low crosslinked poly(styrene-co-divinylbenzene) (P(St-co-DVB)) capsules as precursors. The samples are characterized by scanning and transmission electron microscopy, Fourier transform infrared and Raman spectroscopy, X-ray diffraction, and N2 adsorption and desorption. Considering their application, the cyclic voltammetry and electrochemical impedance spectroscopy characterization are tested. The experimental results show that the achievement of discrete and perfect carbon hemispheres is dependent on the proper amount of DVB in the P(St-co-DVB) capsules, which can contribute to the ideal thickness or mechanical strength of the shells. When the amount of DVB is 35 wt% in the precursors, a high Brunauer-Emmett-Teller surface area of 676 m(2) g(-1) can be obtained for the carbon hemispheres, and the extremely large pore volume of 2.63 cm(3) g(-1) can also be achieved at the same time. The electrochemical test shows the carbon hemispheres have a higher specific capacitance of ca. 83 F g(-1) at 10 mV s(-1), compared to other carbon materials. So this method supplies a platform to extend the fabrication field of carbon materials and supplies more chances for the application of carbon materials including carbon hemispheres that are important components and substrates for supercapacitors.

The controlled preparation of cross-linked polyphosphazene nanotubes of high stability via a sacrificial template route

We report on the controlled preparation of cross-linked poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) nanotubes using Ag nanowires as sacrificial templates. The as-prepared PZS nanotubes have a good chemical stability in concentrated nitric acid and an initial 475 °C thermal decomposition temperature in air.

Novel N-doped porous carbon microspheres containing oxygen and phosphorus for CO2 absorbent and metal-free electrocatalysts

Novel N-doped porous carbon microspheres were synthesized facilely from polyphosphazene. These carbons exhibit a considerable performance for CO2 capture with high uptake, excellent selectivity, and good recyclability, and also show good electrocatalytic activity for oxygen reduction reaction.