Multilayer self-assembly of TiO₂ nanoparticles and polyaniline-grafted-chitosan copolymer (CPANI) for photocatalysis

Design of Biocompatible Chitosan/Polyaniline/Laponite Hydrogel with Photothermal Conversion Capability

In recent years, multifunctional hydrogels have received a great deal of attention because they are biocompatible and can mimic the extracellular matrix. Herein, we prepared hydrogels of biocompatible cross-linked networks with photothermal properties. In this study, a chitosan/polyaniline/laponite (COL) hydrogel with photothermal conversion capability was designed. Polyaniline was firstly grafted onto chitosan and its solution was mixed with oxidized dextran, which was then cross-linked into a hydrogel via a Schiff base reaction. Furthermore, an aluminosilicate clay material, laponite (LAP), was incorporated into the hydrogel. The swelling ratio of the COL hydrogel in various solutions was greater than 580%, and it showed good degradation ability (the mass-loss ratio was over 45% after 28 days). This composite hydrogel was demonstrated to have good photothermal conversion properties and biocompatibility at both the cell (cell viability was over 97%) and animal levels. The COL hydrogel showed a photothermal conversion efficiency of 23.7% under the irradiation of a near-infrared laser. Coupled with the osteogenic differentiation-inducing potential of LAP, the COL hydrogel has the potential to kill tumors via hyperthermia or serve as scaffolds for bone tissue regeneration.

Self-assembly in biobased nanocomposites for multifunctionality and improved performance

Concerns of petroleum dependence and environmental pollution prompt an urgent need for new sustainable approaches in developing polymeric products. Biobased polymers provide a potential solution, and biobased nanocomposites further enhance the performance and functionality of biobased polymers. Here we summarize the unique challenges and review recent progress in this field with an emphasis on self-assembly of inorganic nanoparticles. The conventional wisdom is to fully disperse nanoparticles in the polymer matrix to optimize the performance. However, self-assembly of the nanoparticles into clusters, networks, and layered structures provides an opportunity to address performance challenges and create new functionality in biobased polymers. We introduce basic assembly principles through both blending and in situ synthesis, and identify key technologies that benefit from the nanoparticle assembly in the polymer matrix. The fundamental forces and biobased polymer conformations are discussed in detail to correlate the nanoscale interactions and morphology with the macroscale properties. Different types of nanoparticles, their assembly structures and corresponding applications are surveyed. Through this review we hope to inspire the community to consider utilizing self-assembly to elevate functionality and performance of biobased materials. Development in this area sets the foundation for a new era of designing sustainable polymers in many applications including packaging, construction chemicals, adhesives, foams, coatings, personal care products, and advanced manufacturing.

Study of the effect of band gap and photoluminescence on biological properties of polyaniline/CdS QD nanocomposites based on natural polymer

In this work, band gap, photoluminescence and biological properties of new bionanocomposites based on polyaniline (PANi)/hydrolyzed pectin (HPEc)/cadmium sulfide (CdS) QD nanoparticles (NPs) were studied. In order to improve the morphology and properties, CdS NPs were modified with epichlorohydrin to obtain the modified CdS (mCdS). The CdS@HPEc-g-PANi and mCdS@HPEc-g-PANi samples were synthesized via heterogeneous chemical polymerization and characterized by FTIR, ¹HNMR, SEM/XRD, EDX/TEM/EDX-mapping and TGA analyses. The objective of this work is the study of physical, optical and cytotoxicity properties of the nanocomposites and comparison between them. The SEM, XRD and TGA images showed that the modification of NPs resulted in homogeneous morphology, increase of crystalline structure and high thermal stability which influenced on physical and biological property. According to UV-DRS analysis, the mCdS@HPEc-g-PANi indicated lower energy gap compared to the CdS@HPEc-g-PANi nancomposite. The presence of conductive polymer and synergy effect between the PANi and CdS caused higher PL intensity in the CdS@HPEc-g-PANi nanocomposite compared to pure CdS. The emission intensity in the mCdS@HPEc-g-PANi nanocomposite was reduced since the organic modifying agent cause reducing emission intensity. The mCdS@HPEc-g-PANi nanocomposite, due to more compatibility of organic agent with cellular walls of biological cells that help to the diffusion of metal CdS NPs into cell tissue indicated more toxicity effect on cell growth.

Ultrasonic-Assisted Synthesis and Characterization of Chitosan-Graft-Substituted Polyanilines: Promise Bio-Based Nanoparticles for Dye Removal and Bacterial Disinfection

The sonication-mediated oxidative-radical copolymerization using ammonium persulfate in acidic medium provides a new successful avenue to graft Chitosan with three methylaniline derivatives. The synthesized Chitosan-graft-polymethylanilines (CGPMA) were characterized using FTIR, UV-vis diffuse reflectance spectroscopy, XRD, thermogravimetric analysis (TGA), elemental analysis, and transmission electron microscopy (TEM). XRD spectra revealed that CGPMA have a higher crystallinity degree compared to the pristine Chitosan. In addition, a methyl position-dependent crystallinity is noticeable for the grafted copolymers. This could be confirmed from TEM images that reflect structure-affected morphologies of different ordering for the graft spherical nanoparticles. Interestingly, the copolymers prepared under ultrasonic irradiation show a high potency in dye uptake compared to nonsonicated ones. Moreover, an antibacterial preliminary test on the as-prepared materials was accomplished. We have achieved promising results, which encourages us to conduct more studies to process these materials in developing biomedical active composites.

Deposition of an ultra-thin polyaniline coating on a TiO2 surface by vapor phase polymerization for electrochemical glucose sensing and photocatalytic degradation

Here, we have synthesized an ultra-thin coating of polyaniline on a TiO₂ nanoparticle surface (PANI–TiO₂) using a simple vapor phase polymerization method.

Preparation of TiO2-Poly(3-Chloro-2-Hydroxypropyl Methacrylate) Nanocomposite for Selective Adsorption and Degradation of Dyes

We report a new nanocomposite TiO2-poly(3-chloro-2-hydroxypropyl methacrylate) (TiO2-PCHPMA) for selective adsorption/degradation of cationic dyes and degradation of anionic dyes. TiO2-PCHPMA was prepared by free radical polymerization of CHPMA in the presence of TiO2 modified with 3-(trimethoxysilyl)propyl methacrylate. TiO2-PCHPMA adsorbed cationic methylene blue (MB), but did not adsorb anionic methyl orange (MO) in their aqueous solutions. The adsorption efficiency for MB reached 99% within 5 min at 28 °C, and adsorbed MB could be recycled in 96% efficiency. The adsorption accelerated degradation of MB under UV irradiation. The degradation of anionic MO proceeded completely with TiO2-PCHPMA under UV irradiation, and the efficiency was not affected by the PCHPMA layer. TiO2-PCHPMA is potentially applicable as a material capable of selective removal and recovery of cationic dyes, and degradation of other dyes from industrial effluents.

Fluoride Removal from Aqueous Solutions Using Poly(Styrene Sulfonate)/Nanoalumina Multilayer Thin Films

In the present study, fluoride removal from drinking water is investigated using layer-by-layer (LbL) fabricated poly(sodium 4-styrene-sulfonate) (PSS)/Al2O3 thin films. The surface morphology of the fabricated thin films is characterized using atomic force microscopy and field emission-scanning electron microscopy. Optical profilometry is used to determine the self-assembly of the multilayer thin films. The effect of various parameters such as adsorbent dosage, contact time, initial fluoride content, number of bilayers, surface area, and pH is thoroughly studied. Fluoride removal increases with the number of bilayers and number of slides (total surface area). The amount of fluoride adsorbed increases from 11.32 to 26 mg L-1 when the number of substrates increases from 1 to 5. A 68% removal of fluoride is observed when 20 bilayers of PSS/Al2O3 thin films with three slides at an initial fluoride concentration of 5 mg L-1 are used, thereby bringing down the fluoride concentration level below the World Health Organization permissible limit. Slide reusability studies reveal that the fabricated thin films can be used for ten cycles without affecting the fluoride removal properties of the film. This study demonstrates the potential application of immobilized PSS/Al2O3 thin films as an effective adsorbent for drinking water purification.

Novel heterostructured InN/TiO2 submicron fibers designed for high performance visible-light-driven photocatalysis

InN phase was successfully integrated into TiO₂ fiber, which greatly improved its visible-light photocatalytic property.

Synthesis of chitosan/polyvinyl alcohol/zeolite composite for removal of methyl orange, Congo red and chromium(VI) by flocculation/adsorption

A chitosan/polyvinyl alcohol (PVA)/zeolite composite was fabricated in this study. The composite was analyzed through field emission scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis, and weight loss test. FTIR and XRD results revealed a strong interaction among chitosan, PVA, and zeolite. Weight loss test results indicated that the composite was stable in acidic and basic media. Congo red was removed through flocculation, and the removal rate was 94% at an initial concentration of 100mg/L for a dose of 1g/L. The removal rate of methyl orange was controlled by adsorption at an initial concentration of less than 100mg/L. Flocculation occurred at high concentrations. The removal rate was also 94% at an initial concentration of 500mg/L for a dose of 5g/L. The adsorption behavior of the composite for the removal of methyl orange and Cr(VI) was described by using a pseudo-second-order kinetic model. The adsorption capacity of the composite for Cr(VI) was 450mg/g. Therefore, the synthesized composite exhibited versatility during the removal of dyes and heavy metals.

Characteristics of two-dimensional millimetric microarrays of TiO2 nanowires and their photocatalytic properties

Two-dimensional millimetric microarrays of TiO₂ nanowires were fabricated in this work.

Synthesis of polyaniline/TiO2 composite with excellent adsorption performance on acid red G

Polyaniline-modified TiO₂ (PANI/TiO₂) composite was designed and synthesized as a novel adsorbent for the removal of ARG; and the probable adsorption mechanism was proposed.

Layer-by-layer assembled thin films and microcapsules of nanocrystalline cellulose for hydrophobic drug delivery

A layer-by-layer (LbL) approach has been employed for the fabrication of multilayer thin films and microcapsules having nanofibrous morphology using nanocrystalline cellulose (NCC) as one of the components of the assembly. The applicability of these nanoassemblies as drug delivery carriers has been explored by the loading of an anticancer drug, doxorubicin hydrochloride, and a water-insoluble drug, curcumin. Doxorubicin hydrochloride, having a good water solubility, is postloaded in the assembly. In the case of curcumin, which is very hydrophobic and has limited solubility in water, a stable dispersion is prepared via noncovalent interaction with NCC prior to incorporation in the LbL assembly. The interaction of various other lipophilic drugs with NCC was analyzed theoretically by molecular docking in consideration of NCC as a general carrier for hydrophobic drugs.

Conjugated polymer/nanocrystal nanocomposites for renewable energy applications in photovoltaics and photocatalysis

Conjugated polymer/nanocrystal composites have attracted much attention for use in renewable energy applications because of their versatile and synergistic optical and electronic properties. Upon absorbing photons, charge separation occurs in the nanocrystals, generating electrons and holes for photocurrent flow or reduction/oxidation (redox) reactions under proper conditions. Incorporating these nanocrystals into conjugated polymers can complement the visible light absorption range of the polymers for photovoltaics applications or allow the polymers to sensitize or immobilize the nanocrystals for photocatalysis. Here, the current developments of conjugated polymer/nanocrystal nanocomposites for bulk heterojunction-type photovoltaics incorporating Cd- and Pb-based nanocrystals or quantum dots are reviewed. The effects of manipulating the organic ligands and the concentration of the nanocrystal precursor, critical factors that affect the shape and aggregation of the nanocrystals, are also discussed. In the conclusion, the mechanisms through which conjugated polymers can sensitize semiconductor nanocrystals (TiO2 , ZnO) to ensure efficient charge separation, as well as how they can support immobilized nanocrystals for use in photocatalysis, are addressed.

Graphene sheets grafted three-dimensional BiOBr0.2I0.8 microspheres with excellent photocatalytic activity under visible light

A series of graphene sheets grafted three-dimensional BiOBr0.2I0.8 microspheres with different graphene contents have been synthesized by a simple one-step solvothermal method. The BiOBr0.2I0.8 microspheres were composed of numerous nanoplates with a thickness of about 10nm and dispersed uniformly on the surface of graphene. The assembled BiOBr0.2I0.8/graphene composites exhibited excellent photocatalytic activity in the degradation of rhodamine B (RhB) and phenol under visible light irradiation (λ>420 nm). The optimal graphene content was found to be 10.0 wt.%, and the corresponding photocatalytic activity in degradation of RhB and phenol was 3.19 and 3.27 times that of pure BiOBr0.2I0.8, respectively. The enhanced photocatalytic activity could be attributed to more effective charge transportations and separations, larger specific surface areas and the increased light absorption. A possible photocatalytic mechanism of the BiOBr0.2I0.8/graphene composites was also proposed.

Visible-light-responsive photocatalysts toward water oxidation based on NiTi-layered double hydroxide/reduced graphene oxide composite materials

A visible-light responsive photocatalyst was fabricated by anchoring NiTi-layered double hydroxide (NiTi-LDH) nanosheets to the surface of reduced graphene oxide sheets (RGO) via an in situ growth method; the resulting NiTi-LDH/RGO composite displays excellent photocatalytic activity toward water splitting into oxygen with a rate of 1.968 mmol g(-1) h(-1) and a quantum efficiency as high as 61.2% at 500 nm, which is among the most effective visible-light photocatalysts. XRD patterns and SEM images indicate that the NiTi-LDH nanosheets (diameter: 100-200 nm) are highly dispersed on the surface of RGO. UV-vis absorption spectroscopy exhibits that the introduction of RGO enhances the visible-light absorption range of photocatalysts, which is further verified by the largely decreased band gap (∼1.78 eV) studied by cyclic voltammetry measurements. Moreover, photoluminescence (PL) measurements indicate a more efficient separation of electron-hole pairs; electron spin resonance (ESR) and Raman scattering spectroscopy confirm the electrons transfer from NiTi-LDH nanosheets to RGO, accounting for the largely enhanced carrier mobility and the resulting photocatalytic activity in comparison with pristine NiTi-LDH material. Therefore, this work demonstrates a facile approach for the fabrication of visible-light responsive NiTi-LDH/RGO composite photocatalysts, which can be used as a promising candidate in solar energy conversion and environmental science.

High-performance visible-light-driven SnS₂/SnO₂ nanocomposite photocatalyst prepared via in situ hydrothermal oxidation of SnS₂ nanoparticles

SnS₂/SnO₂ nanocomposites with tunable SnO₂ contents were prepared via in situ hydrothermal oxidation of SnS₂ nanoparticles in 0.375-4.5 mass% H₂O₂ aqueous solutions at 180 °C for 0-12 h. The structure, composition and optical properties of the as-prepared SnS₂/SnO₂ nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, Brunauer-Emmett-Teller (BET) surface area analysis, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and UV-vis diffuse reflectance spectra. Furthermore, their photocatalytic properties were tested for the degradation of methyl orange in water under visible light (λ > 420 nm) irradiation. It was found that the as-prepared SnS₂/SnO₂ nanocomposites with suitable SnO₂ content not only demonstrated superior photocatalytic activity to both SnS₂ nanoparticles and physically mixed SnS₂/SnO₂ composite nanoparticles, but also had remarkable photocatalytic stability. The tight attachment of SnO₂ nanoparticles to SnS₂ nanoparticles, which can facilitate interfacial electron transfer and reduce the self-agglomeration of two components, was considered to play an important role in achieving the high photocatalytic performances exhibited by the as-prepared SnS₂/SnO₂ nanocomposites.