Weitang Yao

Ordered array of Ag semishells on different diameter monolayer polystyrene colloidal crystals: An ultrasensitive and reproducible SERS substrate

Ag semishells (AgSS) ordered arrays for surface-enhanced Raman scattering (SERS) spectroscopy have been prepared by depositing Ag film onto polystyrene colloidal particle (PSCP) monolayer templates array. The diversified activity for SERS activity with the ordered AgSS arrays mainly depends on the PSCP diameter and Ag film thickness. The high SERS sensitivity and reproducibility are proved by the detection of rhodamine 6G (R6G) and 4-aminothiophenol (4-ATP) molecules. The prominent enhancements of SERS are mainly from the “V”-shaped or “U”-shaped nanogaps on AgSS, which are experimentally and theoretically investigated. The higher SERS activity, stability and reproducibility make the ordered AgSS a promising choice for practical SERS low concentration detection applications.

One-step hydrothermal synthesis of iron and nitrogen co-doped TiO2 nanotubes with enhanced visible-light photocatalytic activity

TiO2 nanotubes co-doped with iron and nitrogen were successfully synthesized with commercial TiO2 powders (CTPs) using a one-step hydrothermal method. The morphology, structure and composition of the as-prepared nanotubes were characterized using transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (UV-vis), photoluminescence (PL) spectroscopy and Raman spectroscopy. The photocatalytic activities of the samples are evaluated for the degradation of tannic acid (TA, 25 mg L−1) in aqueous solutions under visible light (λ > 420 nm). The results of TEM suggest that all the samples present a diameter of approximately 9 nm and a length of approximately 200–600 nm. The results of XRD suggest that the predominant phase of all the as-prepared samples was the anatase crystal. The XPS results indicate that Fe and N were successfully introduced into the TiO2 nanotubes (TNTs). Compared with the CTPs and pure TNTs, the Fe and N co-doped TiO2 nanotubes (Fe/N-TNTs) exhibit a stronger visible-light absorption capability, and an enhanced photocatalytic activity toward the photodegradation of TA aqueous solution under visible-light irradiation. Notably, the xFe/N-TNT catalysts can be easily recycled due to their one-dimensional nanostructural properties.

Mesoporous gold sponges: electric charge-assisted seed mediated synthesis and application as surface-enhanced Raman scattering substrates

Mesoporous gold sponges were prepared using 4-dimethylaminopyridine (DMAP)-stabilized Au seeds. This is a general process, which involves a simple template-free method, room temperature reduction of HAuCl4·4H2O with hydroxylamine. The formation process of mesoporous gold sponges could be accounted for the electrostatic interaction (the small Au nanoparticles (~3 nm) and the positively charged DMAP-stabilized Au seeds) and Ostwald ripening process. The mesoporous gold sponges had appeared to undergo electrostatic adsorption initially, sequentially linear aggregation, welding and Ostwald ripening, then, they randomly cross link into self-supporting, three-dimensional networks with time. The mesoporous gold sponges exhibit higher surface area than the literature. In addition, application of the spongelike networks as an active material for surface-enhanced Raman scattering has been investigated by employing 4-aminothiophenol (4-ATP) molecules as a probe.

High Performances of Artificial Nacre-Like Graphene Oxide-Carrageenan Bio-Nanocomposite Films

This study was inspired by the unique multi-scale and multi-level ‘brick-and-mortar’ (B&M) structure of nacre layers. We prepared the B&M, environmentally-friendly graphene oxide-carrageenan (GO-Car) nanocomposite films using the following steps. A natural polyhydroxy polymer, carrageenan, was absorbed on the surface of monolayer GO nanosheets through hydrogen-bond interactions. Following this, a GO-Car hybridized film was produced through a natural drying process. We conducted structural characterization in addition to analyzing mechanical properties and cytotoxicity of the films. Scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses showed that the nanocomposite films had a similar morphology and structure to nacre. Furthermore, the results from Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Thermogravimetric (TG/DTG) were used to explain the GO-Car interaction. Analysis from static mechanical testers showed that GO-Car had enhanced Young’s modulus, maximum tensile strength and breaking elongation compared to pure GO. The GO-Car nanocomposite films, containing 5% wt. of Car, was able to reach a tensile strength of 117 MPa. The biocompatibility was demonstrated using a RAW264.7 cell test, with no significant alteration found in cellular morphology and cytotoxicity. The preparation process for GO-Car films is simple and requires little time, with GO-Car films also having favorable biocompatibility and mechanical properties. These advantages make GO-Car nanocomposite films promising materials in replacing traditional petroleum-based plastics and tissue engineering-oriented support materials.

Preparation and Perfomance of an Aging-Resistant Nanocomposite Film of Binary Natural Polymer–Graphene Oxide

As one of the materials having a bionic structure, nacrelike layered composites, inspired by their natural hybrid structures, have been studied via a variety of approaches. Graphene oxide (GO), which differed from inert graphene, was used as a new building block because it could be readily chemically functionalized. Rather than natural polymers, synthetic polymers were most commonly used to fabricate nacrelike GO–polymer materials. However, naturally occurring polymers complied more easily with the requirements of biocompatibility, biodegradability, and nontoxicity. Here, a simple solution-casting method was used to mimic natural nacre and fabricate a self-assembled and aging-resistant binary natural polymer, (κ-carrageenan (κ-CAR)–Konjac glucomannan (KGM))–GO nanocomposites, with varying GO concentrations. The investigation results revealed that κ-CAR–KGM and GO mostly self-assemble via the formation of intermolecular hydrogen bonds to form a well-defined layered structure. The mechanical properties of the natural polymer–GO films were improved significantly compared to those of pure natural polymer films. With the addition of 7.5 wt % GO, the tensile strength (TS) and Young’s modulus were found to increase by 129.5 and 491.5%, respectively. In addition, the composite films demonstrated high reliability and aging resistance as well as a definite TS after cold and hot shock and ozone aging tests, especially showing a superior ozone resistance. The composite films can potentially be used as biomaterials or packing materials.

A biomass carbon mass coated with modified TiO2 nanotube/graphene for photocatalysis

Powdered modified TiO2 materials are commonly used for photocatalysis. They are easily dispersed in solution but difficult to recycle. In addition, the low light transmission and lack of oxygen in solution also cause a decrease of the photocatalytic efficiency for practical applications. Here we prepare a low-density circular slice which can be suspended on the surface of an aqueous solution and can be used to enrich methylene blue easily. The body of the circular slice is a kind of biomass carbon derived from fungus while the surface of the circular slice is coated with Fe/N co-doped TiO2 nanotubes and a N-doped graphene composite. The advantages are that the circular slice cannot only be convenient to recycle, but also be easy to receive light and oxygen. According to the photocatalytic activity test, the floatable material consisting of Fe/N-TNTs/NG and fungus shows superb performance on the degradation of methylene blue under simulated solar irradiation, which makes it a promising photocatalytic material.

Fabricating a graphene oxide—bayberry tannin sponge for effective radionuclide removal

Bayberry tannin (BT)–reduced graphene oxide (rGO) sponges have been prepared by self–assembly, with bayberry tannin serving as both reductant and surface functionalization agent. The synthetic method is based on the self-assembly of graphene oxide (GO) sheets into porous hydrogel structures. By varying the weight ratio of GO to BT, a series of sorbents with different densities of organic molecules have been obtained and applied to remove Sr2+ from aqueous solutions. Adsorption isotherms (Langmuir and Freundlich) and kinetics (pseudo-first order and pseudo-second order) have been investigated to discuss the sorption performance of rGO/BT sponges. The rGO/BT (w/w 1:1) sponge shows excellent adsorption properties for Sr2+, with maximum capacities of 67.98 mg g−1. The adsorption capacity is much higher than those in classic Sr2+ adsorbents, such as hydrous manganese dioxide, Egyptian soils, Hydroxyapatite nanoparticles, sodium hexa-titanate nanofibers, Graphene oxide, artificially altered phlogopite(Ca–Phl), and PB/Fe3O4/GO. Adsorption mechanisms have been examined using the x-ray photoelectron spectra of sorbents before and after Sr2+ adsorption, and the results indicate that the sorption of Sr2+ on GO and GO/BT 1.0 is largely depended on oxygen functional groups. The results show that the GO/BT sponge is a promising candidate for adsorbing Sr2+ ion.

In situ preparation of mycelium/bayberry tannin for the removal of strontium from aqueous solution

A new sustainable filamentous fungi-based process is reported to synthesize mycelium/bayberry tannin (BT) hybrid materials. The hybrid materials are produced with fungi growing in solution, where the cell wall interacted with BT by hydrogen-bond from the phenolic hydroxyl and amino in protein. In the adsorption experiment, This hybrid biologic material show excellent performances for strontium ions adsorption and experimental data obey a pseudo second-order model of the chemical adsorption process. This study reported a new method for the producing of bio-based materials, which had the potential applications in waste water treatment.

Bioconcentration of organic dyes via fungal hyphae and their derived carbon fibers for supercapacitors

Heteroatom doping can change the electrochemical properties of carbon materials, but the simple, cheap and environmentally friendly preparation of these materials still remains a challenge. Herein, we have reported a new general strategy to fabricate heteroatom-doped carbon fiber materials based on the bioconcentration of different toxic organic dyes via fungal hyphae. The doped carbon fibers had a high content of heteroatoms and a three-dimensional network structure, exhibiting great potential as electrode materials for supercapacitors. Among these products, the N–S doped carbon fiber prepared by bioconcentration of methylene blue had the highest specific capacitance of 235 F g−1 at 1 A g−1 and good rate capability (72.8% retention from 1 A g−1 to 20 A g−1). This strategy can turn toxic waste into valuable materials, converting trash to treasure in the most literal sense; this bioconcentration method is green, general, low-cost and suitable for the preparation of fungal hyphae heteroatom-doped carbon fiber materials from different heteroatom precursors.