As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

http://users.encs.concordia.ca/~mojtaba/elec6271/silver%20nanoparticles.pdf

Silver nanoparticles: green synthesis and their antimicrobial activities.

Here, we present a review of the antibacterial effects of silver nanomaterials, including proposed antibacterial mechanisms and possible toxicity to higher organisms. For purpose of this review, silver nanomaterials include silver nanoparticles, stabilized silver salts, silver–dendrimer, polymer and metal oxide composites, and silver-impregnated zeolite and activated carbon materials. While there is some evidence that silver nanoparticles can directly damage bacteria cell membranes, silver nanomaterials appear to exert bacteriocidal activity predominantly through release of silver ions followed (individually or in combination) by increased membrane permeability, loss of the proton motive force, inducing de-energization of the cells and efflux of phosphate, leakage of cellular content, and disruption DNA replication. Eukaryotic cells could be similarly impacted by most of these mechanisms and, indeed, a small but growing body of literature supports this concern. Most antimicrobial studies are performed in simple aquatic media or cell culture media without proper characterization of silver nanomaterial stability (aggregation, dissolution, and re-precipitation). Silver nanoparticle stability is governed by particle size, shape, and capping agents as well as solution pH, ionic strength, specific ions and ligands, and organic macromolecules—all of which influence silver nanoparticle stability and bioavailability. Although none of the studies reviewed definitively proved any immediate impacts to human health or the environment by a silver nanomaterial containing product, the entirety of the science reviewed suggests some caution and further research are warranted given the already widespread and rapidly growing use of silver nanomaterials.

https://link.springer.com/content/pdf/10.1007%2Fs11051-010-9900-y.pdf

A review of the antibacterial effects of silver nanomaterials and potential implications for human health and the environment

Green synthesis of metal nanoparticles using plants

Synthesis of metallic nanoparticles using plant extracts.

https://www.rsc.org/suppdata/gc/b6/b615357g/b615357g.pdf

Green synthesis of silver nanoparticles using Capsicum annuum L. extract

In this paper, we report a novel matchlike zinc oxide (ZnO)/gold (Au) heterostructure with plasmonic-enhanced photoelectrochemical (PEC) activity for solar hydrogen production. The matchlike heterostructure with Au nanoparticles coated on the tip of ZnO nanorods is in situ grown on a zinc (Zn) substrate by using a facile hydrothermal and photoreduction combined approach. This unique heterostructure exhibits plasmonic-enhanced light absorption, efficient charge separation and transportation properties with tunable Au contents. The photocurrent density of the matchlike ZnO/Au heterostructure reaches 9.11 mA/cm(2) at an applied potential of 1.0 V (vs Ag/AgCl) with an Au/Zn atomic ratio of 0.039, which is much higher than that of the pristine ZnO nanorod array (0.33 mA/cm(2)). Moreover, the solar-to-hydrogen conversion efficiency of this special heterostructure can reach 0.48%, 16 times higher than that of the pristine ZnO nanorod array (0.03%). What is more, the efficiency could be further improved by optimizing the Au content of the heterostructure. The formation mechanism of such a unique heterostructure is proposed to explain the plasmonic-enhanced PEC performance. This study might contribute to the rational design of the visible-light-responsive plasmonic semiconductor/metal heterostructure photoanode to harvest the solar spectrum.

In situ growth of matchlike ZnO/Au plasmonic heterostructure for enhanced photoelectrochemical water splitting.

We describe the formation of amorphous selenium (α-Se)/protein composites using Capsicum annuum L extract to reduce selenium ions (SeO32−) at room temperature. The reaction occurs rapidly and the process is simple and easy to handle. A protein with a molecular weight of 30 kDa extracted from Capsicum annuum L not only reduces the SeO32− ions to Se0, but also controls the nucleation and growth of Se0, and even participates in the formation of α-Se/protein composites. The size and shell thickness of the α-Se/protein composites increases with high Capsicum annuum L extract concentration, and decreases with low reaction solution pH. The results suggest that this eco-friendly, biogenic synthesis strategy could be widely used for preparing inorganic/organic biocomposites. In addition, we also discuss the possible mechanism of the reduction of SeO32− ions by Capsicum annuum L extract.

http://iopscience.iop.org/article/10.1088/0957-4484/18/40/405101/pdf

Rapid, room-temperature synthesis of amorphous selenium/protein composites using Capsicum annuum L extract

Three-dimensional (3D) flowerlike hierarchical Fe3O4@Bi2O3 core–shell architectures were synthesized by a simple and direct solvothermal route without any linker shell. The results indicated that the size of the 3D flowerlike hierarchical microspheres was about 420 nm and the shell was composed of several nanosheets with a thickness of 4–10 nm and a width of 100–140 nm. The saturation magnetization of the superparamagnetic composite microspheres was about 41 emu g−1 at room temperature. Moreover, the Fe3O4@Bi2O3 composite microspheres showed much higher (7–10 times) photocatalytic activity than commercial Bi2O3 particles under visible-light irradiation. The possible formation mechanism was proposed for Ostwald ripening and the self-assembled process. This novel composite material may have potential applications in water treatment, degradation of dye pollutants, and environmental cleaning, for example.

Self-assembled 3D flowerlike hierarchical Fe3O4@Bi2O3 core-shell architectures and their enhanced photocatalytic activity under visible light.

Magnetic Fe3O4@C@Cu2O composites with a bean-like core/shell nanostructure have been successfully synthesized by a self-assembly approach. The synthetic route is feasible, low-cost and green. The size of the as-prepared magnetic composites is about 420 nm and the shells are composed of several nanoparticles in the range of 5∼10 nm. Interestingly, the carbonaceous layer with bound hydrophilic groups inherited from the starting materials acted as both the linker and the stabilizer between Fe3O4 and Cu2O. The Fe3O4@C@Cu2O composites exhibit ferromagnetic behaviour, and good dispersibility in aqueous solution. Importantly, the bean-like core/shell composites show universal and powerful visible-light-photocatalytic activity for the degradation of Rhodamine-B (RhB), methyl orange (MO), and alizarin red (AR) relative to commercial Cu2O and Degussa P-25 powders. These novel magnetic composites may find applications in dye water treatment, degradation of organic pollutants and environmental cleaning etc.

Magnetic Fe3O4@C@Cu2O composites with bean-like core/shell nanostructures: Synthesis, properties and application in recyclable photocatalytic degradation of dye pollutants

Shikuo Li

Papers

Green synthesis of silver nanoparticles using Capsicum annuum L. extract

In situ growth of matchlike ZnO/Au plasmonic heterostructure for enhanced photoelectrochemical water splitting.

Rapid, room-temperature synthesis of amorphous selenium/protein composites using Capsicum annuum L extract

Self-assembled 3D flowerlike hierarchical Fe3O4@Bi2O3 core-shell architectures and their enhanced photocatalytic activity under visible light.

Magnetic Fe3O4@C@Cu2O composites with bean-like core/shell nanostructures: Synthesis, properties and application in recyclable photocatalytic degradation of dye pollutants