Penglei Chen

Graphene Oxide Enwrapped Ag/AgX (X = Br, Cl) Nanocomposite as a Highly Efficient Visible-Light Plasmonic Photocatalyst

In this paper, we have reported that well-defined graphene oxide (GO) enwrapped Ag/AgX (X = Br, Cl) nanocomposites, which are composed of Ag/AgX nanoparticles and gauze-like GO nanosheets, could be facilely fabricated via a water/oil system. We have shown that thus-synthesized GO-based hybrid nanocomposites could be used as a stable plasmonic photocatalyst for the photodegradation of methyl orange (MO) pollutant under visible-light irradiation. Compared with the corresponding bare Ag/AgX nanospecies, the GO-involved nanocomposites (Ag/AgX/GO) display distinctly enhanced photocatalytic activities. The hybridization of Ag/AgX with GO nanosheets causes the nice adsorptive capacity of Ag/AgX/GO to MO molecules, the smaller size of the Ag/AgX nanoparticles in Ag/AgX/GO, the facilitated charge transfer, and the suppressed recombination of electron-hole pairs in Ag/AgX/GO. It is suggested that these multifactors, resulting from the hybridization of GO, contribute to the enhanced photocatalytic performance observed from Ag/AgX/GO. The investigation likely opens up new possibilities for the development of original yet highly efficient and stable GO-based plasmonic photocatalysts that utilize visible light as an energy source.

Ag/AgBr/Graphene Oxide Nanocomposite Synthesized via Oil/Water and Water/Oil Microemulsions: A Comparison of Sunlight Energized Plasmonic Photocatalytic Activity

In this article, we report that Ag/AgBr nanostructures and the corresponding graphene oxide (GO) hybridized nanocomposite, Ag/AgBr/GO, could be facilely synthesized by means of a surfactant-assisted assembly protocol, where an oil/water microemulsion is used as the synthesis medium. We show that thus-produced nanomaterials could be used as highly efficient and stable plasmonic photocatalysts for the photodegradation of methyl orange (MO) pollutant under sunlight irradiation. Compared with the bare Ag/AgBr nanospecies, Ag/AgBr/GO displays distinctly enhanced photocatalytic activity. More importantly, the as-prepared nanostructures exhibit higher photocatalytic activity than that of the corresponding Ag/AgBr-based nanomaterials synthesized viaa water/oil microemulsion and than that of the corresponding Ag/AgCl-based nanospecies synthesized by an oil/water microemulsion. An explanation has been proposed for these interesting findings. Our results suggest that thus-manufactured Ag/AgBr/GO plasmonic photocatalysts are promising alternatives to the traditional UV light or visible-light driven photocatalysts.

Evolution of Various Porphyrin Nanostructures via an Oil/Aqueous Medium: Controlled Self-Assembly, Further Organization, and Supramolecular Chirality

We have shown that various porphyrin-containing nanostructures can be easily synthesized by a surfactant-assisted self-assembly (SAS) method, where an oil/aqueous medium is employed. When a chloroform solution of zinc 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (ZnTPyP) was added dropwise into cetyltrimethylammonium bromide (CTAB) aqueous solution, diverse ZnTPyP-based nanostructures, including hollow nanospheres, solid nanospheres, nanotubes, nanorods, and nanofibers, were successfully assembled. Depending on the aging time, when a low-concentration CTAB aqueous solution was employed, hollow nanospheres or nanotubes were produced. In contrast, either solid nanospheres or nanorods were obtained by using a CTAB aqueous solution in moderate concentration. Moreover, solid nanospheres or nanofibers were produced, when a high-concentration CTAB aqueous solution was used. We have further shown that the nanorods can be hierarchically organized into a regular nanoarray on silicon substrates over a large area, while the other nanostructures cannot. Interestingly, the nanorods displayed distinct supramolecular chirality although the employed ZnTPyP is achiral. On the basis of the information obtained from scanning electron microscopy, high-resolution transmission electron microscopy, fast Fourier transformation, energy-dispersive X-ray spectroscopy, X-ray diffraction, and UV-vis and circular dichroism spectra, a tentative explanation has been proposed. Our investigation suggests that the SAS method via an oil/aqueous medium is an efficient way to synthesize organic nanostructures in a controlled manner, and that such nanostructures can show different chiroptical and assembly properties.

Sunlight-driven plasmonic photocatalysts based on Ag/AgCl nanostructures synthesized via an oil-in-water medium: enhanced catalytic performance by morphology selection

Herein, we have demonstrated that spherical and quasi-cubic Ag/AgCl-based plasmonic photocatalysts could be controllably synthesized by means of a one-pot surfactant-assisted method, wherein an oil-in-water system is employed as synthesis medium. We have found that thus-produced nanostructures can display stable photocatalytic performance for the photodegradation of Methyl Orange (MO) pollutant when energized with sunlight or visible light, where morphology dependent and enhanced photocatalytic activity could be realized. Compared with the Ag/AgCl nanospheres, their quasi-cubic counterparts exhibit much higher photocatalytic activity, which could be further enhanced upon hybridization with graphene oxide (GO). Moreover, in contrast to the spherical Ag/AgCl nanospecies formulated via a water-in-oil medium, those synthesized through the oil-in-water system display higher photocatalytic activity. On the basis of our experimental facts, a plausible explanation has been proposed for these significant findings. The investigation has not only one-pot controllably produced sunlight energized Ag/AgCl-based plasmonic photocatalysts with morphology dependent catalytic performance, but also essentially increased their catalytic activity.

Template-Free Synthesis of Cube-like Ag/AgCl Nanostructures via a Direct-Precipitation Protocol: Highly Efficient Sunlight-Driven Plasmonic Photocatalysts

In this paper, we report that cube-like Ag/AgCl nanostructures could be facilely fabricated in a one-pot manner through a direct-precipitation protocol under ambient conditions, wherein no additional issues such as external energy (e.g., high temperature or high pressure), surfactants, or reducing agents are required. In terms of using sodium chloride (NaCl) as chlorine source and silver acetate (CH₃COOAg) as silver source, it is disclosed that simply by adding an aqueous solution of NaCl into an aqueous solution of CH₃COOAg, Ag/AgCl nanostructures with a cube-like geometry, could be successfully formulated. We show that thus-formulated cube-like Ag/AgCl nanospecies could be used as high-performance yet durable visible-light-driven or sunlight-driven plasmonic photocatalysts for the photodegradation of methyl orange (MO) and 4-chlorophenol (4-CP) pollutants. Compared with the commercially available P25-TiO₂, and the Ag/AgCl nanospheres previously fabricated via a surfactant-assisted method, our current cube-like Ag/AgCl nanostructures could exhibit much higher photocatalytic performance. Our template free protocol might open up new and varied opportunities for an easy synthesis of cube-like Ag/AgCl-based high-performance sunlight-driven plasmonic photocatalysts for organic pollutant elimination.

High-Performance Visible-Light-Driven Plasmonic Photocatalysts Ag/AgCl with Controlled Size and Shape Using Graphene Oxide as Capping Agent and Catalyst Promoter

We report herein that Ag/AgCl-based plasmonic photocatalysts with controlled size and shape could be easily formulated by a one-pot approach via a precipitation reaction between AgNO3 or Ag(NH3)2NO3 and NaCl. It is found that near-spherical and cube-like Ag/AgCl nanoarchitectures of 500 nm could be fabricated at lower and higher temperature, respectively. Fascinatingly, when graphene oxide (GO) nanosheets are introduced into the synthesis medium, the size of the formulated near-spherical and cube-like nanostructures, Ag/AgCl/GO, could be 2.5 and 5 times reduced to ca. 200 and 100 nm, respectively, when AgNO3 and Ag(NH3)2NO3 are employed as the silver source. The series of our Ag/AgCl-based nanostructures could be used as visible-light-driven plasmonic photocatalysts for the photodegradation of methyl orange pollutants, wherein the cube-like Ag/AgCl/GO nanoarchitectures of 100 nm display the highest catalytic activity. It is disclosed that the synergistic effect of size, shape, and GO nanosheets plays an important role for their boosted photocatalytic performances. The investigation reveals that GO nanosheets work not only as a capping agent for a controllable fabrication of Ag/AgCl nanostructures, but also as catalyst promoter during the photocatalytic performances, leading to an enhanced catalytic activity. Our unique GO-assisted method likely paves a facile avenue and initiates new opportunities for the exploration of GO-hybridized high-performance catalysts.

Highly efficient visible-light-driven plasmonic photocatalysts based on graphene oxide-hybridized one-dimensional Ag/AgCl heteroarchitectures

In this paper, we report that one-dimensional (1D) Ag/AgCl nanostructures could be facilely fabricated by means of an oxidation-chloridization process, wherein prefabricated 1D Ag nanowires are employed as a template. Graphene oxide (GO)-hybridized 1D Ag/AgCl nanocomposites, Ag/AgCl/GO, could also be easily formulated when GO nanosheets are involved during the oxidation-chloridization procedure. We find that compared with the parent plain 1D Ag nanowires, commercially available P25-TiO2, and spherical Ag/AgCl nanospecies, the as-produced 1D Ag/AgCl nanostructures could be used as high-performance visible-light-driven plasmonic photocatalysts for the photodegradation of organic pollutants. Moreover, the 1D Ag/AgCl/GO nanocomposites exhibit enhanced photocatalytic activity compared with the corresponding 1D Ag/AgCl nanostructures. Our experimental facts indicate that the cooperative or synergistic effects between the intrinsic morphological features of the 1D nanostructures, which facilitates an efficient directional electron transport and suppresses the scattering of the free electrons, and the advantages brought out by GO nanosheets, which favors a nice adsorption of methyl orange (MO) molecules and an efficient charge separation, conjointly contribute to the enhanced photocatalytic performance of the 1D Ag/AgCl/GO nanocomposites. This work might initiate new and more varied opportunities for the development of visible-light-driven high-performance plasmonic photocatalysts for the photodegradation of organic pollutants.

Electric Current Induced Reduction of Graphene Oxide and Its Application as Gap Electrodes in Organic Photoswitching Devices

This is owing to its exceptional physicochemical, electrical, mechanical, and biocompatible properties, which mean graphene-based materials have great prospects for applications in nanoscience and advanced materials. [ 1–3 ] Since the revival of the investigation of graphene in 2004, [ 4 ] various chemical and physical protocols have been developed to produce graphenebased materials. [ 1–8 ] Among these, chemical exfoliation of bulk graphite by intercalation using strong oxidizing acids has received much attention, since it can produce graphene-based materials on a large scale easily with low cost. [ 7 , 8 ]

Controllable fabrication of supramolecular nanocoils and nanoribbons and their morphology-dependent photoswitching.

Nanocoils and straight nanoribbons have been controllably fabricated through the interfacial organization of an anthracene derivative. A morphology-dependent photoswitching has been observed. While the nanocoils show no photocurrent response, the straight nanoribbons display a switchable photocurrent upon an on/off illumination.

One-Dimensional Porphyrin Nanoassemblies Assisted via Graphene Oxide: Sheetlike Functional Surfactant and Enhanced Photocatalytic Behaviors

Surfactant-assisted self-assembly (SAS) has received much attention for supramolecular nanoassemblies, due to its simplicity and easiness in realizing a controllable assembly. However, in most of the existing SAS protocols, the employed surfactants work only as a regulator for a controllable assembly but not as active species for function improvement. In this paper, we report that a porphyrin, zinc 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (ZnTPyP), could be assembled to form one-dimensional (1D) supramolecular nanostructures via a SAS method, wherein graphene oxide (GO) plays a fascinating role of sheetlike surfactant. We show that, when a chloroform or tetrahydrofuran solution of ZnTPyP is injected into an aqueous dispersion of GO, 1D supramolecular nanoassemblies of ZnTPyP with well-defined internal structures could be easily formulated in a controllable manner. Our experimental facts disclose that the complexation of ZnTPyP with the two-dimensional GO nanosheets plays an important role in this new type of SAS. More interestingly, compared with the 1D ZnTPyP nanoassemblies formulated via a conventional SAS, wherein cetyltrimethylammonium bromide is used as surfactant, those constructed via our GO-assisted SAS display distinctly enhanced photocatalytic activity for the photodegradation of rhodamine B under visible-light irradiation. Our new findings suggest that GO could work not only as an emergent sheetlike surfactant for SAS in terms of supramolecular nanoassembly but also as functional components during the performance of the assembled nanostructures.