Recent Developments about Conductive Polymer Based Composite Photocatalysts

Investigation of Doehlert matrix conception in novel intrinsically conducting polymers based on selenium nanoparticles for wastewater treatment: Synthesis, characterization, kinetic and chemometric study

The synthesis of robust intrinsically conducting polymers (ICPs) based on nanoparticles is becoming increasingly attractive to the research community due to the unique properties of these nanocomposites. Indeed, as organic semiconductors, ICPs combine both polymer and metal properties in a single structure. This study presents an innovative approach in which the Doehlert Matrix (DM) is applied to a novel ICP nanocomposite based on polyaniline (Pani) coupled with selenium (Se) loaded mesoporous titania (TiO2) for wastewater treatment by photocatalysis. It includes both the elaboration routes of ICP nanocomposites, characterization of materials by X-ray diffraction (XRD), BET analysis, thermogravimetric analysis (TGA), RAMAN spectroscopy and Fourier transform infrared spectroscopy (FTIR) and photodegradation of methylene blue (MB) as a representative of dye pollutant. In addition, the photocatalytic process has been optimized by a novel DM conception. The effect of the pH of the solution, the catalyst dosage and the initial pollutant concentration was investigated. The optimum conditions were found to be: initial MB concentration of 15 mg/L, the catalyst dosage of 69 mg and pH of 9.6 with an operating time of 75 min, with a coefficient of determination R2 equal to 0.9985. The removal efficiency of BM was close to 97 %. The study shows that the new ICP nanocomposites improve the photocatalytic efficiency compared to pure titania and/or pure Pani. In addition, as the ternary Pani-Se-TiO2 nanocomposite could be obtained from a low-cost synthesis, it is a very promising material for use in wastewater treatment.

Extremely-fast electrostatically-assisted direct ink writing of 2D, 2.5D and 3D functional traces of conducting polymer Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate- polyethylene oxide (PEDOT:PSS-PEO)

HYPOTHESIS

Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is an attractive conducting polymer, albeit its rheological properties are inappropriate for direct ink writing (DIW). Here it is hypothesized that a suspension of PEDOT:PSS with a non-conducting highly spinnable viscoelastic polymer, e.g., polyethylene oxide (PEO), will significantly facilitate printability and enhance the electrical conductivity (EC) of PEDOT:PSS-PEO. It is also hypothesized that high-humidity post-treatment will enhance the EC even further, and the application of the electric field can facilitate the DIW speed beyond the capabilities of current commercial 3D printers.

EXPERIMENTS

The rheological behavior of PEDOT:PSS suspensions with several non-conducting polymers was explored in the experiments. The EC of the suspensions was measured, including the effect of high-humidity post-treatment. High-speed DIW of the optimal suspension was experimentally demonstrated with the applied electric field.

FINDINGS

The findings revealed that PEO serves as a secondary dopant, and the suspension of 4.33 wt% PEDOT:PSS-52 wt% PEO possesses the EC > 15 times higher than that of PEDOT:PSS. Many 2D, 2.5D and 3D functional traces were printed at high resolution at the DIW speed up to 8.64 m/s (>10 times faster than current commercial printers), facilitated by the applied electric field. Post-treatment at 80-90% relative humidity enhanced the EC more than twice.

Insights on enhancing piezocatalytic performance of Bi2WO6@PDA homojunction from phase coexistence and electron transfer mediators

Piezocatalytic technology with controllable generation of reactive oxygen species (ROS) is emerging in wastewater treatment. This study employed the synergetic regulation of functional surface and phase interface modification to effectively accelerate redox reaction in piezocatalytic process. We anchored the conductive polydopamine (PDA) onto Bi2WO6 (BWO) using template method, in which a small amount of Bi precipitation to induce partial phase transition of BWO from tetragonal to orthorhombic (t/o) in virtue of simple calcination. ROS traceability studies have identified the synergistic relationship between charge separation and transfer. Polarization in two-phase coexistence is intimately modulated by the orthorhombic relative central cation displacement. The orthorhombic phase with large electric dipole moment significantly promotes the generation of piezoresistive effect of intrinsic tetragonal BWO and optimizes the charge distribution. PDA further overcomes the obstruction of carrier migration at the phases interface to accelerate the generation rate of free radicals. Consequently, the superior rhodamine B (RhB) piezocatalytic degradation rate of 0.10 and 0.32 min-1 were delivered by t/o-BWO and t/o-BWO@PDA, respectively. This work reveals a feasible polarization enhancement strategy for the phase coexistence, and flexibly introduces the in-situ synthesized economical polymer conductive unit into the piezocatalysts.

A recent update on development, synthesis methods, properties and application of natural products derived carbon dots

Natural resources are practically infinitely abundant in nature, which stimulates scientists to create new materials with inventive uses and minimal environmental impact. Due to the various benefits of natural carbon dots (NCDs) from them has received a lot of attention recently. Natural products-derived carbon dots have recently emerged as a highly promising class of nanomaterials, showcasing exceptional properties and eco-friendly nature, which make them appealing for diverse applications in various fields such as biomedical, environmental sensing and monitoring, energy storage and conversion, optoelectronics and photonics, agriculture, quantum computing, nanomedicine and cancer therapy. Characterization techniques such as Photoinduced electron transfer, Aggregation-Induced-Emission (AIE), Absorbance, Fluorescence in UV-Vis and NIR Regions play crucial roles in understanding the structural and optical properties of Carbon dots (CDs). The exceptional photoluminescence properties exhibited by CDs derived from natural products have paved the way for applications in tissue engineering, cancer treatment, bioimaging, sensing, drug delivery, photocatalysis, and promising remarkable advancements in these fields. In this review, we summarized the various synthesis methods, physical and optical properties, applications, challenges, future prospects of natural products-derived carbon dots etc. In this expanding sector, the difficulties and prospects for NCD-based materials research will also be explored.

Wearable Liquid Metal Composite with Skin-Adhesive Chitosan-Alginate-Chitosan Hydrogel for Stable Electromyogram Signal Monitoring

In wearable bioelectronics, various studies have focused on enhancing prosthetic control accuracy by improving the quality of physiological signals. The fabrication of conductive composites through the addition of metal fillers is one way to achieve stretchability, conductivity, and biocompatibility. However, it is difficult to measure stable biological signals using these soft electronics during physical activities because of the slipping issues of the devices, which results in the inaccurate placement of the device at the target part of the body. To address these limitations, it is necessary to reduce the stiffness of the conductive materials and enhance the adhesion between the device and the skin. In this study, we measured the electromyography (EMG) signals by applying a three-layered hydrogel structure composed of chitosan-alginate-chitosan (CAC) to a stretchable electrode fabricated using a composite of styrene-ethylene-butylene-styrene and eutectic gallium-indium. We observed stable adhesion of the CAC hydrogel to the skin, which aided in keeping the electrode attached to the skin during the subject movement. Finally, we fabricated a multichannel array of CAC-coated composite electrodes (CACCE) to demonstrate the accurate classification of the EMG signals based on hand movements and channel placement, which was followed by the movement of the robot arm.

Flexible PTh/GQDs/TiO2 composite with superior visible-light photocatalytic properties for rapid degradation pollutants

Flexible fiber membranes for pollutant removal have received increasing attention due to their high adsorption performance and easy recycling characteristics. However, due to the lack of environmentally friendly regeneration, some adsorption membranes have low regeneration efficiency, especially in terms of chemical adsorption, so they lack reusability. This study prepares a series of conducting polymer [PAn (polyaniline) or PPy (polypyrrole) or PTh (polythiophene)] graphene quantum dots (GQDs, the size of GQDs is about 20 nm)/TiO₂ ternary fiber membranes via a facile electrospinning method with chemical deposition. Remarkably, this creates an anatase TiO₂ and π-conjugated system. The combination is beneficial to the photocatalytic degradation of organic pollutants, showing synergistic promotion in both the degradation rate and the degree of decomposition. The UV-vis test shows that the combination of GQDs broadens the optical response threshold of TiO₂, from near ultraviolet region excitation to visible region excitation. At the same time, the conductive polymer load further reduces the energy required for photogenerated electron transfer, which theoretically improves the degradation effect. Photocatalytic degradation tests showed that the PTh/GQDs/TiO₂ fiber membrane exhibited significant high photocatalytic activity of visible-light in the methylene blue (MB) and TC degradation. The degradation rate level is 92.90% and 80.58%, respectively and the MB removal is more than 4 times that of bare TiO₂ membrane. After photocatalytic regeneration four times, the regeneration efficiency can be maintained above 95%. Notably, various experimental results show that the interface charge transfer mechanism between GQDs/TiO₂ and PTh follows the Z-scheme heterojunction, which maximizes the retention of strong reducing electrons and oxidation holes. In the degradation, the active species of ·O₂ ^- and ·OH, make different contributions in the photocatalysts, which oxidize and break down the pollutant molecules into small molecules and then to harmless substances. According to the electronegativity difference of the material itself, PTh acts as electron acceptor in the degradation system, and TiO₂ fiber membrane doped with GQDs acts as electron donor. The present research, not only offers feasibility of the PTh/GQDs/TiO₂ flexible fiber membrane as an environment-friendly catalyst, but also motivates researchers to develop flexible fiber materials for future photocatalytic technology.

Polypyrrole-based nanomaterials: A novel strategy for reducing toxic chemicals and others related to environmental sustainability applications

Aqueous contaminants such as pharmaceuticals, dyes, personal care products, etc., are the common water contaminants that show adverse health effects. Photocatalysis is one of the well-known techniques to treat these water contaminants. Currently, most inorganic photocatalysts show a poor balance between adsorption and photocatalytic activity. In addition, heavy metal pollution and low biosafety are significant concerns in photocatalysis. Thus, environmentally friendly photocatalysts are required to avoid the secondary pollution caused by some inorganic semiconductor-photocatalysts. Organic polymer-based photocatalysts are low-cost, stable, non-toxic, and can utilize visible and NIR light for photocatalysis. In this review, we have discussed polypyrrole as a photocatalyst. Polypyrrole is a conducting organic polymer photocatalyst that is highly stable with high charge mobility and strong binding sites for photocatalytic reactions. Besides these advantages, polypyrrole has limitations, such as high charge recombination due to a small bandgap and poor dispersity. So we have explored the modifications to polypyrrole photocatalysts, such as doping and heterojunctions. Further, we have explained the applications of polypyrrole in photocatalysis as an adsorbent, sensitizer, degradation of pollutants, and energy production. Finally, the future aspects of polypyrrole photocatalysis are also explored to improve the path of future research.

Synthesis of Polyaniline Supported CdS/CdS-ZnS/CdS-TiO2 Nanocomposite for Efficient Photocatalytic Applications

Photocatalytic degradation can be increased by improving photo-generated electrons and broadening the region of light absorption through conductive polymers. In that view, we have synthesized Polyaniline (PANI) with CdS, CdS-ZnS, and CdS-TiO₂ nanocomposites using the chemical precipitation method, characterized and verified for the photo-degradation of Acid blue-29 dye. This paper provides a methodical conception about in what way conductive polymers “PANI” enhances the performance rate of composite photocatalysts (CdS, CdS-ZnS and CdS-TiO₂). The nanocomposites charge transfer, molar ratio, surface morphology, particle size, diffraction pattern, thermal stability, optical and recombination of photo-generated charge carrier properties were determined. The production of nanocomposites and their efficient photocatalytic capabilities were observed. The mechanism of photocatalysis involved with PC, CZP and CTP nanocomposites are well presented by suitable diagrams representing the exchange of electrons and protons among themselves with supported equations. We discovered that increasing the number of nanocomposites in the membranes boosted both photocatalytic activity and degradation rate. CdS-Zinc-PANI (CZP) and CdS-TiO₂-PANI(CTP) nanocomposites show entrapment at the surface defects of Zinc and TiO₂ nanoparticles due to the demolition of unfavorable electron kinetics, and by reducing the charge recombination, greater photocatalytic activity than CdS-PANI (CP) with the same nanoparticle loading was achieved. With repeated use, the photocatalysts’ efficiency dropped very little, hinting that they may be used to remove organic pollutants from water. The photocatalytic activity of CZP and CTP photocatalytic membranes was greater when compared to CdS-PANI, which may be due to the good compatibility between CdS and Zinc and TiO₂, as well efficient charge carrier separation. PANI can also increase the split-up of photo-excited charge carriers and extend the absorption zone when combined with these nanoparticles. As a result, the development of outrageous performance photocatalysts and their potential uses in ecological purification and solar power conversion has been facilitated. The novelty of this article is to present the degradation of AB-29 Dye using nanocomposites with polymers and study the enhanced degradation rate. Few studies have been carried out on polymer nanocomposites and their application in the degradation of AB-29 dyes and remediation of water purposes. Nanoparticle CdS is a very effective photocatalyst, commonly used for water purification along with nanoparticle ZnS and TiO₂; but cadmium ion-leaching makes it ineffective for practical and commercial use. In the present work, we have reduced the leaching of hazardous cadmium ions by trapping them in a polyaniline matrix, hence making it suitable for commercial use. We have embedded ZnS and TiO₂ along with CdS in a polyaniline matrix and compared their photocatalytic activity, stability, and reusability, proving our nano-composites suitable for commercial purposes with enhanced activities and stabilities, which is a novelty. All synthesized nanocomposites are active within the near-ultraviolet to deep infrared (i.e., 340–850 nm). This gives us full efficiency of the photocatalysts in the sunlight and further proves the commercial utility of our nanocomposites.

Ultrasonic-Assisted Synthesis of CdS/Microcrystalline Cellulose Nanocomposites With Enhanced Visible-Light-Driven Photocatalytic Degradation of MB and the Corresponding Mechanism Study

A simple and efficient ultrasonic-assisted approach was designed to synthesize CdS/microcrystalline cellulose (MCC) nanocomposite photocatalyst. The obtained products have been characterized by XRD, FE-SEM, TEM, UV-Vis DRS, and nitrogen adsorption isotherms. The results showed that the intimate contact of MCC and CdS is beneficial for enhancing the photocatalytic performance because heterojunction formation can efficiently promote the separation of photogenerated electrons and holes of the nanocomposite photocatalyst. By using 10% MCC coupled CdS, the decoloration rate of methylene blue (MB) in the solution under visible-light was increased nearly 50%. In addition, the reuse experiments confirmed that the CdS/MCC nanocomposite photocatalyst had outstanding cycle performance and durability. Mechanism study demonstrated that hydroxyl radicals, photogenerated holes and superoxide radicals were the active species in the photocatalytic oxidization degradation of MB.

Multifunctional cotton with PANI-Ag NPs heterojunction for solar-driven water evaporation

Water evaporation using photothermal materials is a cost-effective and sustainable technology for alleviating the world's freshwater crisis, but oil contaminants and organic pollutants exist in the original water sources, which severely degrade the evaporation performance and pose environmental hazards. In this paper, we demonstrate a photothermal material (multifunctional cotton) that simultaneously demonstrates oil-resistance, organic pollutant removal, and a high water evaporation rate. A Schottky heterostructure was formed between polyaniline (PANI) and Ag NPs, which improved the photothermal conversion and achieved a water evaporation rate of 1.37 kg m^-2 h^-1 and photothermal conversion efficiency of 84.7% under one-sun illumination (1 kW m^-2). Notably, various organic pollutants in the water source were thoroughly removed by visible-light catalytic degradation and adsorption, which displayed efficiencies of 99.3% and 97%, respectively. The multifunctional cotton also possessed excellent superoleophobicity, and repelled oil contaminants and organic pollutants in water. Considering these merits, the as-prepared multifunctional cotton is an outstanding candidate for water evaporation from various sources.

Multifunctional nanofibrous membranes with sunlight-driven self-cleaning performance for complex oily wastewater remediation

Developing multifunctional, efficient and durable membrane for long-term usage for treating complex oily wastewater is highly desirable but still a challenge due to the severe membrane fouling. Herein, a hierarchical structured superhydrophilic/underwater superoleophobic nanofibrous with antifouling and visible-light-induced self-cleaning performance was manufactured by a facile combination of electrospun silver/β-cyclodextrin/polyacrylonitrile (Ag/β-CD/PAN) nanofibers and then the in-situ growth of a zinc oxide (ZnO) layer. The formed micro/nano sized hierarchical structure greatly increased the roughness and improved the underwater superoleophobic ability of the membrane. Therefore, the resultant ZnO/Ag/β-CD/PAN membrane displays splendid separation performance for oil/dye/water complex emulsions and high flux recovery (>90%). Meanwhile, the permeation flux of a variety of oil/water emulsions was higher than 619 L m^-2h^-1 with a separation efficiency above 99.7% under the action of gravity. Furthermore, the as-fabricated membrane exhibits excellent stability towards different harsh conditions (e. g. corrosive solution, high temperature, UV irradiation and ultrasound washing). The robust mechanical and chemical stability, outstanding separation capabilities as well as excellent flux recovery capabilities makes the self-cleaning membrane a good candidate for the remediation of complex oily wastewater.

Photocatalytic degradation of methylene blue using polyaniline-based silver-doped zinc sulfide (PANI-Ag/ZnS) composites

This study set out to determine the photocatalytic degradation potential of polyaniline-based silver-doped zinc sulfide composite (PANI-Ag/ZnS) for effective degradation of methylene blue. The heterogeneous photocatalytic experiments were carried out by irradiating aqueous dye solutions with ultraviolet light (UV-254 nm). The catalysts (ZnS, Ag/ZnS, PANI-ZnS, and PANI-Ag/ZnS) were prepared successfully and characterized by Fourier Transforms Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Energy-dispersive X-ray diffraction (EDX). Combined with density functional theory calculations, a set of calculations has been performed for optimization, computation, and accuracy of the structure. After the optimization, the equilibrium lattice were a=b= (0.54447 nm), in good agreement with experimental results (a=b=c=0.54093 nm). Fermi energy levels E_f, indicating Ag-doped in ZnS as the impurity acceptor and for better visible-light photo-catalysis, narrow bandgap, and acceptor states are beneficial. The optimization of effective parameters like pH, catalyst dose, oxidant dose, dye concentration, and reaction time was carried out. The best degradation efficiency (> 95%) of PANI-Ag/ZnS composite against methylene was achieved within 60 min of reaction time under optimized conditions. The optimized conditions were recoded as follows: pH = 7, catalysts dose = 30 mg/L, oxidant dose = 3 mM, and irradiation time = 60 min under UV-254 nm for all catalysts. The central composite design (CCD) under the Response Surface Methodology (RSM) was chosen as a statistical tool to obtain the correlation of influential parameters. Five successive reusability trials were carried out to check the stability of catalysts.

Use of PEDOT:PSS/Graphene/Nafion Composite in Biosensors Based on Acetic Acid Bacteria

Immobilization of the biocomponent is one of the most important stages in the development of microbial biosensors. In this study, we examined the electrochemical properties of a novel PEDOT:PSS/graphene/Nafion composite used to immobilize Gluconobacter oxydans bacterial cells on the surface of a graphite screen-printed electrode. Bioelectrode responses to glucose in the presence of a redox mediator 2,6-dichlorophenolindophenol were studied. The presence of graphene in the composite reduced the negative effect of PEDOT:PSS on cells and improved its conductivity. The use of Nafion enabled maintaining the activity of acetic acid bacteria at the original level for 120 days. The sensitivity of the bioelectrode based on G. oxydans/PEDOT:PSS/graphene/Nafion composite was shown to be 22 μA × mM⁻¹ × cm⁻² within the linear range of glucose concentrations. The developed composite can be used both in designing bioelectrochemical microbial devices and in biotechnology productions for long-term immobilization of microorganisms.

The removal of metformin and other selected PPCPs from water by poly(3,4-ethylenedioxythiophene) photocatalyst

The objective of this study was to investigate the photocatalytic removal of PPCPs using poly(3,4-ethylenedioxythiophene) (PEDOT) polymer. PEDOT is a conducting polymer that exhibits excellent photocatalytic activity and was used in this study without any additives or metal co-catalysts. The PEDOT was synthesized using chemical oxidative polymerization and characterized further for composition and morphology. PEDOT, in the presence of UV irradiation, showed >99% degradation of one of the most widely prescribed antidiabetic drugs, metformin, within 60 min. The effect of varying concentration of PEDOT, pH, and light irradiance was studied to achieve maximum photocatalytic efficiency. Two major degradation products of metformin of m/z 116 and 126 were detected using triple quadrupole LC-MS/MS, while the degradation kinetics was found to be of pseudo-first-order. Results revealed that photogenerated electrons, holes, and radical species played a role in the PPCPs' degradation. When a mixture of seven PPCPs in the ultra-pure water matrix was tested, more than 99% removal was observed for most of the PPCPs within 60 min. The removal efficiency decreased in a real wastewater effluent due to the presence of dissolved organic matter; however, still, more than 50% removal was observed for majority of the studied PPCPs. The results of PEDOT reusability revealed that the reuse contributed to the drop in the conductivity and subsequent drop in the photocatalytic activity; however, a simple acid treatment was found to be effective to recoup its conductivity. PEDOT was successfully immobilized on an electrospun fiber mat to enhance its applicability.

Potential Applications of Conducting Polymers to Reduce Secondary Bacterial Infections among COVID-19 Patients: a Review

The COVID-19 pandemic is a motivation for material scientists to search for functional materials with valuable properties to alleviate the risks associated with the coronavirus. The formulation of functional materials requires synergistic understanding on the properties of materials and mechanisms of virus transmission and disease progression, including secondary bacterial infections that are prevalent in COVID-19 patients. A viable candidate in the struggle against the pandemic is antimicrobial polymer, due to their favorable properties of flexibility, lightweight, and ease of synthesis. Polymers are the base material for personal protective equipment (PPE), such as gloves, face mask, face shield, and coverall suit for frontliners. Conducting polymers (CPs) are polymers with electrical properties due to the addition of dopant in the polymer structure. The conductivity of polymers augments their antiviral and antibacterial properties. This review discusses the types of CPs and how their properties could be exploited to ward off bacterial infections in hospital settings, specifically in cases involving COVID-19 patients. This review also covers common CPs fabrication techniques. The key components to produce CPs at several possibilities to fit the current needs in fighting secondary bacterial infections are also discussed.

Application of PANI/TiO2 Composite for Photocatalytic Degradation of Contaminants from Aqueous Solution

Polyaniline (PANI) is a promising conducting polymer for surface modification of TiO2 to achieve extended photoresponse to visible light and increased photocatalytic efficiency. In this study, we report the synthesis of a PANI/TiO2 composite with different weight ratios of PANI, which was subsequently employed for photocatalytic degradation of methylene blue (MB), bisphenol A (BPA), and bacteriophage MS2 under visible-light irradiation. The functional groups, morphology, and light response of the composite were characterized by Fourier-transform infrared spectroscopy, field-emission transmission electron microscopy, and diffuse reflectance UV–visible spectroscopy, respectively. The PANI/TiO2 composite containing 4% by weight ratio of PANI was most suitable for MB degradation, and this photocatalyst was very stable even after repeated use (four cycles). The degradation of BPA and bacteriophage MS2 by PANI/TiO2 composite reached 80% in 360 min and 96.2% in 120 min, respectively, under visible-light irradiation. Therefore, the PANI/TiO2 composite with enhanced visible-light photocatalytic efficiency and stability can be widely used for the degradation of water contaminants.

Polymer/BiOBr-Modified Gauze as a Dual-Functional Membrane for Heavy Metal Removal and Photocatalytic Dye Decolorization

It is crucial to remove heavy metals and dyes before discharging industrial effluents. Gauze substrate was surface-modified by coating with a polymeric adsorbent and a spray coating of BiOBr photocatalyst to develop a novel dual-functional membrane, polymer/BiOBr-modified gauze, for water remediation. The polymeric adsorbent was crosslinked to prevent the dissolving of the adsorbent during operation in contaminated water. The morphology and surface chemistry of the modified gauze were characterized before and after the adsorption of Ni²⁺. The surface wettability, isotherms, and kinetics of Ni²⁺ adsorption were studied. We also studied the effect of pH, initial Ni²⁺ concentration, monomer molar ratio, and monomer chemical structure on the Ni²⁺ adsorption capacity. To achieve a high Ni²⁺ adsorption capacity and good photocatalytic decolorization activity, the amount of decorated BiOBr was tuned by changing the spray-coating time to optimize the exposed BiOBr and polymer on the surface. The optimized dual-functional membrane PB20 possesses excellent adsorption capacity (650 mg g^-1) for Ni²⁺ ions and photocatalytic decolorization activity (100% degradation of RhB within 7 min). Decorating the optimized amount of BiOBr on the surface can introduce photocatalytic decolorization activity without sacrificing the adsorption capacity for Ni²⁺.

Preparation and Photocatalytic Properties of Heterostructured Ceria/Polyaniline Nanoparticles

Cerium dioxide (CeO2, ceria), a promising and abundant catalytic material with high-efficiency, nontoxicity, photochemical stability, and affordability, can be used as a photocatalyst to photocatalytically degrade organics and split water for hydrogen production under ultraviolet (UV) irradiation (about 5% of solar energy). However, the applications of the CeO2 photocatalyst are limited due to low photocatalytic efficiency under sunlight irradiation. In this study, a nanosized CeO2 powder was prepared by the precipitation method. Subsequently, various amounts of polyaniline (PANI) nanoparticles were deposited onto the surface of the CeO2 nanoparticles to form a heterostructure by the polymerization method. The crystal structure, morphology, surface and optical properties of the CeO2/PANI nanoparticles were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), ultraviolet-visible (UV-Vis) absorption spectroscopy, and photoluminescence (PL). Experimental results demonstrated that PANI deposition improved the light absorption of CeO2 nanoparticles in the visible light region. The heterostructured CeO2/PANI nanoparticle with 4 wt % PANI deposition exhibited optimal photocatalytic activities with a hydrogen production rate of 462 μmolg−1 within 6 h and a methyl orange (MO) degradation rate of 45% within 4 h under visible light irradiation. The photocatalytic mechanisms of the composite powder are also proposed in this report.

Simultaneous Enhancement of Photocatalytic Bactericidal Activity and Strength Properties of Acrylonitrile-Butadiene-Styrene Plastic Via a Facile Preparation with Silane/TiO2

This work aims to enhance the photocatalytic antibacterial performance of plastics according to the JIS Z 2801:2010 standard, and to determine their mechanical properties by studying: (i) the influence of calcination on titanium dioxide (TiO₂); (ii) modification with different TiO₂ concentrations, and; (iii) the effect of silane as a coupling agent. Acrylonitrile-butadiene-styrene plastics (ABS) and Escherichia coli (E. coli) were chosen as the model plastic and bacteria, respectively. The 500 °C calcined TiO₂ successfully provided the best photoantibacterial activity, with an approximately 62% decrease of E. coli colony counts following 30 min of exposure. Heat treatment improved the crystallinity of anatase TiO₂, resulting in low electron-hole recombination, while effectively adsorbing reactants on the surface. ABS with 500 °C-calcined TiO₂ at the concentration of 1 wt % gave rise to the highest performance due to the improved distribution of TiO₂. At this point, blending silane coupling agent could further improve the efficacy of photoantibacterial activity up to 75% due to greater interactions with the polymer matrix. Moreover, it could promote a 1.6-fold increase of yield strength via increased adherent bonding between TiO₂ and the ABS matrix. Excellent photocatalytic and material stability can be achieved, with constant photocatalytic efficiency remaining for up to five reuse cycles without loss in the yield strength.

The Impact of In Situ Polymerization Conditions on the Structures and Properties of PANI/ZnO-Based Multiphase Composite Photocatalysts

We have synthesized polyaniline/ZnO-based (PANI/ZnO) multiphase composite photocatalysts from acid media by a newly proposed two-step in situ polymerization. The first step of synthesis yielded PANI salt required for the PANI/ZnO synergistic effect. In the second step, the aniline oxidation continued, without ZnO dissolution, and it produced PANI base. Thus, both PANI salt and base phases in the composites were detected by FTIR and UV/Vis, while the presence of both ZnO and PANI polymer was confirmed by XRD. Additionally, XRD also showed Zn5(OH)8(NO3)2·2H2O and Zn(SO4)(H2O) phases in PANI/ZnO-based multiphase composites. Furthermore, the impact of the synthesis conditions on the morphology of the composites was investigated by FE-SEM. The images displayed that ZnO particles were encapsulated in PANI sheets that were formed by the aniline oligomers. Photocatalytic evaluation of PANI/ZnO-based catalysts (i.e., degradation of Acid Blue 25 dye) was conducted and the obtained results confirmed that all the studied composites experienced the PANI/ZnO synergistic effect. It was observed that the best photocatalytic properties were held by the PANI/ZnO_2 sample due to its optimal particle size.

Application Progress of Polyaniline, Polypyrrole and Polythiophene in Lithium-Sulfur Batteries

With the urgent requirement for high-performance rechargeable Li-S batteries, besides various carbon materials and metal compounds, lots of conducting polymers have been developed and used as components in Li-S batteries. In this review, the synthesis of polyaniline (PANI), polypyrrole (PPy) and polythiophene (PTh) is introduced briefly. Then, the application progress of the three conducting polymers is summarized according to the function in Li-S batteries, including coating layers, conductive hosts, sulfur-containing compounds, separator modifier/functional interlayer, binder and current collector. Finally, according to the current problems of conducting polymers, some practical strategies and potential research directions are put forward. We expect that this review will provide novel design ideas to develop conducting polymer-containing high-performance Li-S batteries.

Photosensitive Hybrid Nanostructured Materials: The Big Challenges for Sunlight Capture

Solar radiation is becoming increasingly appreciated because of its influence on living matter and the feasibility of its application for a variety of purposes. It is an available and everlasting natural source of energy, rapidly gaining ground as a supplement and alternative to the nonrenewable energy feedstock. Actually, an increasing interest is involved in the development of efficient materials as the core of photocatalytic and photothermal processes, allowing solar energy harvesting and conversion for many technological applications, including hydrogen production, CO2 reduction, pollutants degradation, as well as organic syntheses. Particularly, photosensitive nanostructured hybrid materials synthesized coupling inorganic semiconductors with organic compounds, and polymers or carbon-based materials are attracting ever-growing research attention since their peculiar properties overcome several limitations of photocatalytic semiconductors through different approaches, including dye or charge transfer complex sensitization and heterostructures formation. The aim of this review was to describe the most promising recent advances in the field of hybrid nanostructured materials for sunlight capture and solar energy exploitation by photocatalytic processes. Beside diverse materials based on metal oxide semiconductors, emerging photoactive systems, such as metal-organic frameworks (MOFs) and hybrid perovskites, were discussed. Finally, future research opportunities and challenges associated with the design and development of highly efficient and cost-effective photosensitive nanomaterials for technological claims were outlined.

Synthesis of fused heterocyclic systems via the Mallory photoreaction of arylthienylethenes

Photochemical oxidative cyclization of 2- and 3-thienylstilbenes (heterostilbenes) containing mono-, di- and trimethoxy groups in the benzene ring or heterocyclic fragment results in the formation of isomeric thieno-annelated polycyclic aromatic compounds demonstrating optical properties that differ from those of initial stilbene derivatives. The structures of cyclic products were evaluated via¹H and ¹³C NMR, HRMS, elemental analysis and X-ray crystallography. The research was aimed to study the effect of substituents in stilbene derivatives of thiophene as well as the position of the styryl fragment in the thiophene nucleus on the occurrence of photocyclization reactions.

Polymer Nanocomposites for Photocatalytic Applications

In the present comprehensive review we have specifically focused on polymer nanocomposites used as photocatalytic materials in fine organic reactions or in organic pollutants degradation. The selection of the polymer substrates for the immobilization of the active catalyst particles is motivated by several advantages displayed by them, such as: Environmental stability, chemical inertness and resistance to ultraviolet radiations, mechanical stability, low prices and ease availability. Additionally, the use of polymer nanocomposites as photocatalysts offers the possibility of a facile separation and reuse of the materials, eliminating thus the post-treatment separation processes and implicitly reducing the costs of the procedure. This review covers the polymer-based photocatalytic materials containing the most popular inorganic nanoparticles with good catalytic performance under UV or visible light, namely TiO2, ZnO, CeO2, or plasmonic (Ag, Au, Pt, Pd) NPs. The study is mainly targeted on the preparation, photocatalytic activity, strategies directed toward the increase of photocatalytic efficiency under visible light and reuse of the hybrid polymer catalysts.

Enhanced In-Vitro Hemozoin Polymerization by Optimized Process using Histidine-Rich Protein II (HRPII)

Conductive biopolymers, an important class of functional materials, have received attention in various fields because of their unique electrical, optical, and physical properties. In this study, the polymerization of heme into hemozoin was carried out in an in vitro system by the newly developed heme polymerase (histidine-rich protein 2 (HRP-II)). The HRP-II was produced by recombinant E. coli BL21 from the Plasmodium falciparum gene. To improve the hemozoin production, the reaction conditions on the polymerization were investigated and the maximum production was achieved after about 790 μM at 34 °C with 200 rpm for 24 h. As a result, the production was improved about two-fold according to the stepwise optimization in an in vitro system. The produced hemozoin was qualitatively analyzed using the Fourier transform infrared (FTIR) spectroscopy, energy dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM). Finally, it was confirmed that the enzymatically polymerized hemozoin had similar physical properties to chemically synthesized hemozoin. These results could represent a significant potential for nano-biotechnology applications, and also provide guidance in research related to hemozoin utilization.

Recent Progress on Metal Sulfide Composite Nanomaterials for Photocatalytic Hydrogen Production

Metal sulfide-based photocatalysts have gained much attention due to their outstanding photocatalytic properties. This review paper discusses recent developments on metal sulfide-based nanomaterials for H2 production, acting as either photocatalysts or cocatalysts, especially in the last decade. Recent progress on key experimental parameters, in-situ characterization methods, and the performance of the metal sulfide photocatalysts are systematically discussed, including the forms of heterogeneous composite photocatalysts, immobilized photocatalysts, and magnetically separable photocatalysts. Some methods have been studied to solve the problem of rapid recombination of photoinduced carriers. The electronic density of photocatalysts can be investigated by in-situ C K-edge near edge X-ray absorption fine structure (NEXAFS) spectra to study the mechanism of the photocatalytic process. The effects of crystal properties, nanostructure, cocatalyst, sacrificial agent, electrically conductive materials, doping, calcination, crystal size, and pH on the performance of composite photocatalysts are presented. Moreover, the facet effect and light trapping (or light harvesting) effect, which can improve the photocatalytic activity, are also discussed.

Efficient organic pollutant degradation under visible-light using functional polymers of intrinsic microporosity

Functional PIMs bearing D–π–A and zwitterionic structures were synthesized by a quaternization reaction, which exhibit efficient organic pollutant degradation under visible-light.