Green synthesis of plant supported Cu Ag and Cu Ni bimetallic nanoparticles in the reduction of nitrophenols and organic dyes for water treatment

Advanced oxidation processes (AOPs) introduce a hopeful technology for the removal of water polluted with hard degradable organic compounds. Today, one of the main effective AOP technologies to degrade these hazardous organics is via the photocatalytic process. The present review focuses on the recent progress in the fixed-bed and immobilized nanophotocatalysts and also their applications for resolving the environmental concerns. Various organics elimination using a variety of photocatalysts and innovative reactors are discussed. This critical review summarizes the recent progress in the synthesis and modification (physical and chemical) of semiconductors. Furthermore, different ways of photocatalysts immobilization are explained in details. By considering different dangerous chemicals present in wastewater and different industries, catalytic methods used by researchers to degrade these organic compounds are reviewed. In addition, the degradation pathway of some organics through the catalytic operation is described.

Application of Heterogeneous Nano-Semiconductors for Photocatalytic Advanced Oxidation of Organic Compounds: A Review

Covalent layer-by-layer (LbL) assembly is a powerful method used to construct functional ultrathin films that enables nanoscopic structural precision, componential diversity, and flexible design. Compared with conventional LbL films built using multiple noncovalent interactions, LbL films prepared using covalent crosslinking offer the following distinctive characteristics: (i) enhanced film endurance or rigidity; (ii) improved componential diversity when uncharged species or small molecules are stably built into the films by forming covalent bonds; and (iii) increased structural diversity when covalent crosslinking is employed in componential, spacial, or temporal (labile bonds) selective manners. In this review, we document the chemical methods used to build covalent LbL films as well as the film properties and applications achievable using various film design strategies. We expect to translate the achievement in the discipline of chemistry (film-building methods) into readily available techniques for materials engineers and thus provide diverse functional material design protocols to address the energy, biomedical, and environmental challenges faced by the entire scientific community.

Covalent layer-by-layer films: chemistry, design, and multidisciplinary applications

Enzymes are known to catalyze reactions at high efficiency, operate at milder conditions and are biodegradable. Due to enzyme limitations such as sensitivity to environmental conditions, enzyme immobilization is often used. The commonly employed immobilization methods include adsorption, entrapment, covalent attachment and cross-linking. Many research works have now focused on the immobilization of enzymes on nanoscale support due to the higher surface area to volume ratio, effective enzyme loading, significantly enhanced mass transfer efficiency and minimization of diffusional problems. The application of enzyme incorporated nanotechnology in the treatment of dye wastewater is thus, of high interest. Therefore, this paper has critically reviewed (1) the current technologies available for dye wastewater treatment; (2) different methods utilized for enzyme immobilization; and (3) the application and performance of enzyme incorporated nanotechnology for dye wastewater treatment. We identified that there is high potential for enzyme incorporated nanotechnology to be implemented in dye wastewater treatment due to the high decolorization performance (e.g. laccase immobilized on Fe3O4/SiO2 nanoparticles achieved 99% decolorization of Procion Red MX-5B in 20 min). We have also identified the key challenges faced by enzyme incorporated nanotechnology in dye wastewater treatment that includes: (i) realization of lab scale experiments to industrial applications; (ii) lack of understanding of enzymes incorporated nanotechnology; (iii) recovery of immobilized enzyme; (iv) synthesis of hybrid nanoflowers; and (v) sustainability of the nanomaterials used.

Potential and challenges of enzyme incorporated nanotechnology in dye wastewater treatment: A review

Paper and paper products are widely used without any antimicrobial efficacy in our everyday lives and thus can act as potential transporters of many diseases. Herein, we introduce antimicrobial activity to cellulose paper by presenting a tailored mussel-inspired strategy for the sustainable immobilization of silver nanoparticles (AgNPs), which are well-known for the effectiveness in preventing annexation and proliferation of microbes on materials surfaces. First, we functionalized the cellulose paper with succinic acid that eventually reacted with dopamine to give dopamine-modified paper. The dopamine molecules possess excellent adhesion and strong coordination with metal substrates through catechol groups offering a potentially robust interface between AgNPs and the organic structure of the paper. Next, AgNPs were deposited onto the paper by simply immersing dopamine-modified paper in a silver salt solution to accomplish the antimicrobial properties. Field emission scanning electron microscopic study of ...

Mussel-Inspired Immobilization of Silver Nanoparticles toward Antimicrobial Cellulose Paper

Complete photocatalytic degradation of methyl orange, methylene blue and rhodamine chloride was accomplished using immobilized silver nanoparticles as catalysts and tethered calix[7]hydroquinone molecules as nano-reactors. The nanoparticles were immobilized on quartz beads that were assembled in a packed bed configuration. The large interfacial area afforded by the packed bed geometry, presentation of the nanoparticles as a single, tethered layer, and the optically transparent packing material facilitated intimate interaction between the catalyst, dye solution and radiation. The degradation was accomplished using either UV or visible radiation and the nanoparticles displayed self-cleaning and anti-poisoning properties thereby demonstrating excellent durability and catalytic efficiency. The single-layer coverage of Ag nanoparticles facilitates use of very small amounts of the photocatalyst for degradation of relatively large amounts of dye. The method addresses multiple issues that constrain scale-up of photocatalytic systems that deploy nanoparticles as catalysts.

Photocatalysis in a packed bed: Degradation of organic dyes by immobilized silver nanoparticles

In situ formation of silver nanoparticle layer by supramolecule-directed assembly

A covalently immobilized calix[7]hydroquinone monolayer was used as the host matrix to synthesize metallic NPs using an in situ redox process. The characteristics of different metallic ions that affect the synthesis process were studied. Metallic ions with less charges, lower oxidation state in the reaction, and higher standard redox potential provided better yield. Bimetallic NPs with a core-shell structure were synthesized by a sequential deposition of different metals on the same monolayer. The process was applied to form a layer of immobilized NPs on flat and curved surfaces. The ability to synthesize and immobilize well-controlled NPs on different surfaces has promising applications in decoration of irregular surfaces of miniaturized, three-dimensional objects.

Ruitao Zhou

Papers

Photocatalysis in a packed bed: Degradation of organic dyes by immobilized silver nanoparticles

In situ formation of silver nanoparticle layer by supramolecule-directed assembly

In situ synthesis and immobilization of metallic nanoparticles on a calixarene monolayer.

Fabrication of anti-poisoning core-shell TiO2 photocatalytic system through a 4-methoxycalix[7]arene film

Covalent molecular assembly: construction of ultrathin multilayer films by a two-dimensional fabrication method.