Novel synthesis of ZnO/PMMA nanocomposites for photocatalytic applications

Advanced photocatalysis as a viable and sustainable wastewater treatment process: A comprehensive review

In our era, water pollution not only poses a serious threat to human, animal, and biotic life but also causes serious damage to infrastructure and the ecosystem. A set of physical, chemical, and biological technologies have been exploited to decontaminate and/or disinfect water pollutants, toxins, microbes, and contaminants, but none of these could be ranked as sustainable and scalable wastewater technology. The photocatalytic process can harmonize the sunlight to degrade certain toxins, chemicals, microbes, and antibiotics, present in water. For example, transition metal oxides (ZnO, SnO2, TiO2, etc.), when integrated into an organic framework of graphene or nitrides, can bring about more than 90% removal of dyes, microbial load, pesticides, and antibiotics. Similarly, a modified network of graphitic carbon nitride can completely decontaminate petrochemicals. The present review will primarily highlight the mechanistic aspects for the removal and/or degradation of highly concerned contaminants, factors affecting photocatalysis, engineering designs of photoreactors, and pros and cons of various wastewater treatment technologies already in practice. The photocatalytic reactor can be a more viable and sustainable wastewater treatment opportunity. We hope the researcher will find a handful of information regarding the advanced oxidation process accomplished via photocatalysis and the benefits associated with the photocatalytic-type degradation of water pollutants and contaminants.

Green synthesis of silver doped zinc oxide/magnesium oxide nanocomposite for waste water treatment and examination of their cytotoxicity properties

This research attempted to prepare silver-doped zinc oxide/magnesium oxide nanocomposite (Ag-doped ZnO/MgO-NCP) using Mentha pulegium plant extract. The synthesized NCP was investigated by X-ray diffraction analysis (XRD), Fourier Transform Infrared (FT-IR), Field Emission Scanning Electron Microscope (FESEM), Energy dispersive X-ray spectroscopy (EDX), Mapping, and UV-Visible analyses. The XRD data displayed cubic crystal structures for silver & magnesium oxide and a hexagonal framework for zinc oxide. Also, FESEM and PSA images of NCP pointed out, that the average size of the spherical morphology is about 10-16 nm, while the analysis of EDX confirmed the attendance of Zn, Mg, Ag, and O elements. Under UVA light, we tested the photocatalytic activity of NCP to the degradation of Methylene blue (MB) and Rhodamine B (RhB) dyes in various temperatures (400, 500, and 600 °C). The results of the photocatalytic test displayed that the degradation percentage of MB dye in pH = 9, nanocomposite amount ∼30 mg, and dye concentration ∼1 × 10 -5 M was about 98 %. We also evaluated the cytotoxicity of nanocomposite on cancer CT-26 cell line through the MTT method and obtained an IC50 value of 250 μg/mL.

Synthesis of double-shelled periodic mesoporous organosilica nanospheres/MIL-88A-Fe composite and its elevated performance for Pb2+ removal in water

Herein, we report the synthesis of double-shelled periodic mesoporous organosilica nanospheres/MIL-88A-Fe (DSS/MIL-88A-Fe) composite through a hydrothermal method. To survey the structural and compositional features of the synthesized composite, a variety of spectroscopic and microscopic techniques, including FT-IR, XRD, BET, TEM, FE-SEM, EDX, and EDX-mapping, have been employed. A noteworthy point in this synthesis procedure is the integration of MOF with PMO to increase the adsorbent performance, such as higher specific surface area and more active sites. This combination leads to achieving a structure with an average size of 280 nm and 1.1 μm long attributed to DSS and MOF, respectively, microporous structure and relatively large specific surface area (312.87 m²/g). The as-prepared composite could be used as an effective adsorbent with a high adsorption capacity (250 mg/g) and quick adsorption time (30 min) for the removal of Pb²⁺ from water. Importantly, DSS/MIL-88A-Fe composite revealed acceptable recycling and stability, since the performance in Pb²⁺ removal from water remained above 70% even after 4 consecutive cycles.

Renewable and eco-friendly ZnO immobilized onto dead sea sponge floating materials with dual practical aspects for enhanced photocatalysis and disinfection applications

In this study, we have investigated the role of natural dead sea sponge (DSS, Porifera) as a three-dimensional (3D) porous host substrate for the immobilization of nanostructured ZnO material towards the development of ZnO based floating photocatalysts for efficient removal of methylene blue (MB) dye under the illumination of sunlight. After photodegradation, the treated water after dye degradation contains several pathogens, different disinfectants or chemical reagents that are essentially used. This is not the case for DSS as it can naturally kill any pathogens during the wastewater treatment process. To explore these functions, ZnO nanosheets were incorporated onto DSS via hydrothermal protocol and the as prepared ZnO/DSS hybrid material exhibited approximately ∼100% degradation efficiency for the removal of MB. Importantly, the degradation kinetics associated with the fabricated ZnO/DSS was remarkably accelerated as evidenced by the high values of degradation reaction rate constants (3.35 × 10^-2min^-1). The outperformance of ZnO/DSS could be attributed to the adsorption caused by its 3D porous structure together with the high rapid oxidation of MB. Furthermore, the high charge separation of electron-hole pairs, natural porosity, and abundant catalytic sites offered by the hybrid ZnO/DSS floating photocatalyst have enabled quantitative (∼100%) degradation efficiency for MB. Finally, the excellent reusability results confirm the feasibility of using natural ZnO/DSS-based photocatalyst for practical solution of wastewater treatment and other environmental problems.

Photocatalytic effect-assisted antimicrobial activities of acrylic resin incorporating zinc oxide nanoflakes

To overcome the deficiency of the antimicrobial effect of polymer, zinc oxide nanoparticles have been widely utilized as advanced nanofillers due to their antimicrobial and photocatalytic activity. However, the underlying antimicrobial mechanism has not been fully understood apart from topological and physical characteristics. In this study, we prepared zinc oxide nanoparticles-based acrylic resin to explore its antimicrobial mechanism under controlled mechanophysical conditions by using silane-treated zinc oxide nanoflakes (S-ZnNFs). S-ZnNFs incorporated acrylic resin (poly(methyl methacrylate), PMMA) composites up to 2 wt% were selected based on comparable mechanophysical properties (e.g., roughness, wettability, strength and hardness), possibly affecting antimicrobial properties beyond the zinc oxide nanoparticle effect, to bare PMMA. Antimicrobial adhesion results were still observed in 2 wt% S-ZnNFs incorporated PMMA using Candida albicans (C. albicans), one of the fungal infection species. In order to confirm the antimicrobial effects by photocatalysis, we pre-exposed the UV light on 2 wt% S-ZnNF composites before cell seeding, revealing synergetic antimicrobial effect via additional reactive oxygen species (ROS) generation to C. albicans over zinc oxide nanoparticle-induced one. RNA-seq analysis revealed distinguished cellular responses between zinc oxide nanoparticles and UV-mediated photocatalytic effect, but both linked to generation of intracellular ROS. Thus, the above data suggest that induction of high intracellular ROS of C. albicans was the main antimicrobial mechanism under controlled mechanophysical parameters and synergetic ROS accumulation can be induced by photocatalysis, recapitulating a promising use of a S-ZnNFs or possibly zinc oxide nanoparticles as intracellular-ROS-generating antimicrobial nanofillers in acrylic composite for biomedical applications.

Improved Characteristics of CdSe/CdS/ZnS Core-Shell Quantum Dots Using an Oleylamine-Modified Process

CdSe/CdS with ZnS/ZnO shell quantum dots (QDs) are synthesized by a one-pot method with various oleylamine (OLA) contents. The crystal structures of the QDs were analyzed by X-ray diffractometry, which showed ZnS diffraction peaks. It was represented that the ZnS shell was formed on the surface of the CdSe/CdS core. Interestingly, QDs with a high OLA concentration exhibit diffraction peaks of ZnS/ZnO. As a result, the thermal stability of QDs with ZnS/ZnO shells exhibits better performance than those with ZnS shells. In addition, the photoluminescence intensity of QDs with ZnS/ZnO shells shows a relatively slow decay of 7.1% compared with ZnS shells at 85 °C/85% relative humidity aging test for 500 h. These indicate that QDs with different OLA modifications can form ZnS/ZnO shells and have good stability in a harsh environment. The emission wavelength of QDs can be tuned from 505 to 610 nm, suitable for micro-LED display applications.

Polymethylmethacrylate nanoplastics can cause developmental malformations in early life stages of Xenopus laevis

Polymethylmethacrylate (PMMA) production has increased almost 20% over the last years. With its release into the aquatic environment, its breakdown or degradation to nano dimensions (nanoplastics-NPLs) due to biological and physical/mechanical action is, theoretically, anticipated. The occurrence of PMMA-NPLs in aquatic ecosystems may thus cause adverse effects particularly to early life stages of amphibians, which may be in contact with PMMA-NPLs suspended in the water column or deposited in upper layers of the sediments. Accordingly, this work aimed at assessing the effects of PMMA-NPLs to aquatic early life stages of the model anuran species Xenopus laevis. To attain this objective, two types of toxicity assays were carried out by exposing embryos [Nieuwkoop and Faber (NF) stage 8-11] or tadpoles (NF 45) to three concentrations of PMMA-NPLs (1, 100 and 1000 μg/L): i) 96-h embryo teratogenicity assay, where survival, malformation, and total body length (BL) of embryos were assessed; and ii) 48-h feeding rate assay, where survival, feeding (FR), malformations and growth rates (body weight-BW and BL) of tadpoles were evaluated. PMMA-NPLs exposure had no significant effects on mortality, malformations of X. laevis embryos but BL was lower at 1000 μg PMMA-NPLs/L. In tadpoles, no effects on survival or FR were observed after exposure to PMMA-NPLs, but significant changes occured in BW and BL. Moreover, anatomical changes in the abdominal region (externalization of the gut) were observed in 62.5% of the tadpoles exposed to 1000 μg PMMA-NPLs/L. Despite the lack of knowledge regarding the environmental levels of NPLs, it is expected that sediments constitute a sink for these contaminants, where they can become available for organisms that, like tadpoles, feed on the organic matter at the surface of sediments. Considering the continuous release and subsequent accumulation of PMMA, the malformations obtained in the feeding assays suggest that, in the future, these nano-polymers may constitute a risk for aquatic life stages of amphibians.

Review on Methylene Blue: Its Properties, Uses, Toxicity and Photodegradation

The unavailability of clean drinking water is one of the significant health issues in modern times. Industrial dyes are one of the dominant chemicals that make water unfit for drinking. Among these dyes, methylene blue (MB) is toxic, carcinogenic, and non-biodegradable and can cause a severe threat to human health and environmental safety. It is usually released in natural water sources, which becomes a health threat to human beings and living organisms. Hence, there is a need to develop an environmentally friendly, efficient technology for removing MB from wastewater. Photodegradation is an advanced oxidation process widely used for MB removal. It has the advantages of complete mineralization of dye into simple and nontoxic species with the potential to decrease the processing cost. This review provides a tutorial basis for the readers working in the dye degradation research area. We not only covered the basic principles of the process but also provided a wide range of previously published work on advanced photocatalytic systems (single-component and multi-component photocatalysts). Our study has focused on critical parameters that can affect the photodegradation rate of MB, such as photocatalyst type and loading, irradiation reaction time, pH of reaction media, initial concentration of dye, radical scavengers and oxidising agents. The photodegradation mechanism, reaction pathways, intermediate products, and final products of MB are also summarized. An overview of the future perspectives to utilize MB at an industrial scale is also provided. This paper identifies strategies for the development of effective MB photodegradation systems.

Thermal and optical properties of PMMA films reinforced with Nb2O5 nanoparticles

The article presents the thermal and physical properties of PMMA composite films with the addition of Nb2O5 nanoparticles. The addition of nanoparticles to PMMA mainly influenced the optical transmission and glass transition temperature of composite films compared to pure PMMA. It is clearly visible in the results of the conducted ellipsometric and differential scanning calorimetry tests. X-ray studies showed that the heat treatment of the samples resulted in the ordering of the polymer structure (flattening of the polymer chains). Examining the surface of the samples with scanning electron microscopy, it can be seen that Nb2O5 nanoparticles formed unusual, branched formations resembling "snowflakes".

Photocatalytic Degradation of Methylene Blue Using Polymeric Membranes Based on Cellulose Acetate Impregnated with ZnO Nanostructures

This paper studied the photocatalytic degradation of methylene blue (MB) using polymeric membrane impregnated with ZnO nanostructures under UV-light and sunlight irradiation. ZnO nanoparticles and ZnO nanowires were prepared using the hydrothermal technique. Cellulose acetate polymeric membranes were fabricated by the phase inversion method using dimethylformamide (DMF) as a solvent and ZnO nanostructures. The structural properties of the nanostructures and the membranes were investigated using XRD, SEM, FTIR, and TGA measurements. The membranes were tested for photocatalytic degradation of MB using a UV lamp and a sunlight simulator. The photocatalytic results under sunlight irradiation in the presence of cellulose acetate impregnated with ZnO nanoparticles (CA-ZnO-NP) showed a more rapid degradation of MB (about 75%) compared to the results obtained under UV-light irradiation degradation (about 30%). The results show that CA-ZnO-NP possesses the photocatalytic ability to degrade MB efficiently at different levels under UV-light and sunlight irradiation. Modified membranes with ZnO nanoparticles and ZnO nanowires were found to be chemically stable, recyclable, and reproducible. The addition of ZnO nanostructure to the cellulose membranes generally enhanced their photocatalytic activity toward MB, making these potential membranes candidates for removing organic pollutants from aqueous solutions.

Visible light-conducting polymer nanocomposites as efficient photocatalysts for the treatment of organic pollutants in wastewater

This review compiles recent advances and challenges on photocatalytic treatment of wastewater using nanoparticles, nanocomposites, and polymer nanocomposites as photocatalyst. The review provides an overview of the fundamental principles of photocatalytic treatment along the recent advances on photocatalytic treatment, especially on the modification strategies and operational conditions to enhance treatment efficiency and removal of recalcitrant organic contaminants. The different types of photocatalysts along the key factors influencing their performance are also critically discussed and recommendations for future research are provided.

Characterizing and Optimizing Piezoelectric Response of ZnO Nanowire/PMMA Composite-Based Sensor

Due to the outstanding coupling between piezoelectric and semiconducting properties of zinc oxide nanowires, ZnO NW-based structures have been demonstrating promising potential with respect to their applicability in piezoelectric, piezotronic and piezo-phototronic devices. Particularly considering their biocompatibility and biosafety for applications regarding implantable medical detection, this paper proposed a new concept of piezoelectric composite, i.e., one consisting of vertically aligned ZnO NW arrays and an insulating polymer matrix. First, the finite element method (FEM) was employed to drive optimization strategies through adjustment of the key parameters such as Young’s modules and the dielectric constant of the dielectric constituents, together with the density and dimension of nanowire (NW) itself. Second, to investigate the functionality of each individual layer of composite, different designed structures were fabricated and characterized in terms of electrical and piezoelectric properties. Next, experimental and simulation tests were performed, indicating that the decreasing thickness of the top poly(methyl methacrylate) layer (PMMA) can substantially enhance the piezoelectric sensitivity of the ZnO NW composite. Besides the further benefit of no polarization being needed, our material has a comparable charge coefficient (d₃₃) with respect to other lead-free alternatives (e.g., BaTiO₃), confirming the high sensing abilities of the developed structure based on vertically aligned ZnO NW arrays. Finally, a time-varying model combining piezoelectricity and electric circuit modules was investigated in detail, giving rise to an estimation of the d₃₃ coefficient for ZnO NWs. Based on this study, the developed material is revealed to be highly promising in medical applications, particularly regarding the FFR technique, where coronary pressure can be measured through a piezoelectric sensor.

Is Poly(methyl methacrylate) (PMMA) a Suitable Substrate for ALD?: A Review

Poly (methyl methacrylate) (PMMA) is a thermoplastic synthetic polymer, which displays superior characteristics such as transparency, good tensile strength, and processability. Its performance can be improved by surface engineering via the use of functionalized thin film coatings, resulting in its versatility across a host of applications including, energy harvesting, dielectric layers and water purification. Modification of the PMMA surface can be achieved by atomic layer deposition (ALD), a vapor-phase, chemical deposition technique, which permits atomic-level control. However, PMMA presents a challenge for ALD due to its lack of active surface sites, necessary for gas precursor reaction, nucleation, and subsequent growth. The purpose of this review is to discuss the research related to the employment of PMMA as either a substrate, support, or masking layer over a range of ALD thin film growth techniques, namely, thermal, plasma-enhanced, and area-selective atomic layer deposition. It also highlights applications in the selected fields of flexible electronics, biomaterials, sensing, and photocatalysis, and underscores relevant characterization techniques. Further, it concludes with a prospective view of the role of ALD in PMMA processing.

Green Synthesis of Luminescent Gold-Zinc Oxide Nanocomposites: Cell Imaging and Visible Light-Induced Dye Degradation

Green synthesis of gold-zinc oxide (Au-ZnO) nanocomposite was successfully attempted under organic solvent–free conditions at room temperature. Prolonged stirring of the reaction mixture introduced crystallinity in the ZnO phase of Au-ZnO nanocomposites. Luminescence properties were observed in these crystalline Au-ZnO nanocomposites due to in situ embedding of gold nanoparticles (AuNP) of 5–6 nm diameter on the surface. This efficient strategy involved the reduction of Au(III) by Zn(0) powder in aqueous medium, where sodium citrate (NaCt) was the stabilizing agent. Reaction time and variation of reagent concentrations were investigated to control the Au:Zn ratio within the nanocomposites. The reaction with the least amount of NaCt for a long duration resulted in Au-ZnO/Zn(OH)₂ nanocomposite. X-ray photoelectron spectroscopy (XPS) confirmed the formation of Zn(OH)₂ and ZnO in the same nanocomposite. These nanocomposites were reconnoitered as bioimaging materials in human cells and applied for visible light–induced photodegradation of rhodamine-B dye.

Innovative Polymeric Hybrid Nanocomposites for Application in Photocatalysis

The immobilization of inorganic nanomaterials on polymeric substrates has been drawing a lot of attention in recent years owing to the extraordinary properties of the as-obtained materials. The hybrid materials, indeed, combine the benefits of the plastic matter such as flexibility, low-cost, mechanical stability and high durability, with them deriving from their inorganic counterparts. In particular, if the inorganic fillers are nanostructured photocatalysts, the originated hybrid systems will be able to utilize the energy delivered by light, catalysing chemical reactions in a sustainable pathway. Most importantly, since the nanofillers can be ad-hoc anchored to the macromolecular structure, their release in the environment will be prevented, thus overcoming one of the main restrictions that impedes their applications on a large scale. In this review, several typologies of hybrid photocatalytic nanomaterials, obtained by using both organic and inorganic semiconductors and realized with different synthetic protocols, were reported and discussed. In the first part of the manuscript, nanocomposites realized by simply blending the TiO2 or ZnO nanomaterials in thermoplastic polymeric matrices are illustrated. Subsequently, the atomic layer deposition (ALD) technique is presented as an excellent method to formulate polymeric nanocomposites. Successively, some examples of polyporphyrins hybrid systems containing graphene, acting as photocatalysts under visible light irradiation, are discussed. Lastly, photocatalytic polymeric nanosponges, with extraordinary adsorption properties, are shown. All the described materials were deeply characterized and their photocatalytic abilities were evaluated by the degradation of several organic water pollutants such as dyes, phenol, pesticides, drugs, and personal care products. The antibacterial performance was also evaluated for selected systems. The relevance of the obtained results is widely overviewed, opening the route for the application of such multifunctional photocatalytic hybrid materials in wastewater remediation.

CuO/PMMA Polymer Nanocomposites as Novel Resist Materials for E-Beam Lithography

Polymer nanocomposites have emerged as a new powerful class of materials because of their versatility, adaptability and wide applicability to a variety of fields. In this work, a facile and cost-effective method to develop poly(methyl methacrylate) (PMMA)-based polymer nanocomposites with copper oxide (CuO) nanofillers is presented. The study concentrates on finding an appropriate methodology to realize CuO/PMMA nanocomposites that could be used as resist materials for e-beam lithography (EBL) with the intention of being integrated into nanodevices. The CuO nanofillers were synthesized via a low-cost chemical synthesis, while several loadings, spin coating conditions and two solvents (acetone and methyl ethyl ketone) were explored and assessed with regards to their effect on producing CuO/PMMA nanocomposites. The nanocomposite films were patterned with EBL and contrast curve data and resolution analysis were used to evaluate their performance and suitability as a resist material. Micro-X-ray fluorescence spectroscopy (μ-XRF) complemented with XRF measurements via a handheld instrument (hh-XRF) was additionally employed as an alternative rapid and non-destructive technique in order to investigate the uniform dispersion of the nanofillers within the polymer matrix and to assist in the selection of the optimum preparation conditions. This study revealed that it is possible to produce low-cost CuO/PMMA nanocomposites as a novel resist material without resorting to complicated preparation techniques.

Enhanced photocatalytic activities of silicon nanowires/graphene oxide nanocomposite: Effect of etching parameters

Homogeneous and vertically aligned silicon nanowires (SiNWs) were successfully fabricated using silver assisted chemical etching technique. The prepared samples were characterized using scanning electron microscopy, transmission electron microscopy and atomic force microscopy. Photocatalytic degradation properties of graphene oxide (GO) modified SiNWs have been investigated. We found that the SiNWs morphology depends on etching time and etchant composition. The SiNWs length could be tuned from 1 to 42 µm, respectively when varying the etching time from 5 to 30 min. The etchant concentration was found to accelerate the etching process; doubling the concentrations increases the length of the SiNWs by a factor of two for fixed etching time. Changes in bundle morphology were also studied as function of etching parameters. The SiNWs diameter was found to be independent of etching time or etchant composition while the size of the SiNWs bundle increases with increasing etching time and etchant concentration. The addition of GO was found to improve significantly the photocatalytic activity of SiNWs. A strong correlation between etching parameters and photocatalysis efficiency has been observed, mainly for SiNWs prepared at optimum etching time and etchant concentrations of 10 min and 4:1:8. A degradation of 92% was obtained which further improved to 96% by addition of hydrogen peroxide. Only degradation efficiency of 16% and 31% has been observed for bare Si and GO/bare Si samples respectively. The obtained results demonstrate that the developed SiNWs/GO composite exhibits excellent photocatalytic performance and could be used as potential platform for the degradation of organic pollutants.

Thin Films of Plasma-Polymerized n-Hexane and ZnO Nanoparticles Co-Deposited via Atmospheric Pressure Plasma Jet

This study explores the co-deposition of thin polymeric films loaded with nanoparticles for its possible future application as radiation detectors. Thin films containing zinc oxide (ZnO) nanoparticles in plasma polymerized n-hexane (PPH) were deposited on silicon substrates using an atmospheric pressure plasma jet (APPJ). Crystalline ZnO nanoparticles were produced by wet chemistry, characterized, and injected through the plasma with an aerosol buffer. The precursor hydrocarbon was polymerized in atmosphere at room temperature by the plasma, resulting in a highly crosslinked structure chemically stable against common solvents. The polymer structure was characterized by FT-IR, NMR, and thermal analyses. Photoluminescence analysis revealed that ZnO UV excitonic emission is recovered owing to the passivation through polymeric encapsulation, with a remarkable increase in luminescence yield.

Aquatic environment remediation by atomic layer deposition-based multi-functional materials: A review

Water pollution still poses significant threats to the ecosystem and human health today. The adsorption, advanced oxidation and membranes filtration have been extensively investigated and utilized for aquatic contaminants remediation, and their efficiency is closely correlated with the advanced materials design and fabrication (e.g. adsorbents, catalysts and membranes). Thanks to uniform deposition, three-dimensional conformity and process controllability, the atomic layer deposition (ALD) has emerged as a promising strategy for fabrication of these multifunctional materials, arising their successful application in aquatic contaminants remediation. Therefore, a timely review on ALD-based water treatment materials is highly important to summarize the current opportunity and elucidate unaddressed problems in this field. Herein, in this review, the advantages of ALD process, the superiority of ALD-based materials and the corresponding decontamination performance were analyzed comprehensively, highlighting key advantages offered by this technology.

Crosslinked chitosan embedded TiO2 NPs and carbon dots-based nanocomposite: An excellent photocatalyst under sunlight irradiation

Herein, a new hybrid nanocomposite, comprising of titania nanoparticles (TiO₂ NPs) and carbon dots (CDs) deposited polyvinyl imidazole crosslinked chitosan [cl-Ch-p(VI)/TiO₂NPs-CDs] has been developed. The nanocomposite has been synthesised by in-situ deposition of TiO₂ NPs and CDs onto the surface of the copolymer under microwave irradiation. To the best of our knowledge, this in-situ approach has effectively been applied for the first time to fabricate green fluorescent CDs from sugar cane juice at moderate temperature (75 °C) under microwave irradiation. The developed nanocomposite has been characterized using UV-Vis spectroscopy, ¹³C NMR, XRD, HR-TEM, STEM and XPS analyses. The results suggest that the successful deposition of TiO₂ NPs and CDs onto the surface of crosslinked chitosan is achieved. The experimental studies indicate that the NPs/CDs-impregnated nanocomposite allows efficient photocatalytic degradation of toxic organic compounds (~98.6% degradation of 2,4-dicholorophenol, ~95.8% degradation of Reactive Blue 4, ~98.2% degradation of Reactive Red 15) in the presence of sunlight. Finally, LC-MS analysis of the resultant degraded materials reveals the formation of organic molecules with lower molecular mass.

Trimetallic composite nanofibers for antibacterial and photocatalytic dye degradation of mixed dye water

Membrane technology is an advanced approach to making a healthier and cleaner environment. Using such catalytic membrane technology to get clean, usable water by removal of dye impurities as well as pathogenic microbes is the main goal behind the research work. Here, we present the synthesis and efficacy study of polymethyl methacrylate (PMMA)-based Ag/ZnO/TiO₂ trimetallic bifunctional nanofibers with antibacterial and photocatalytic activity. The nanofibers have been proven to be effective for the degradation of methylene blue (MB 93.4%), rhodamine B (Rh 34.6%), auramine-O (Au 65.0%) and fuchsin basic (FB 69.8%) dyes individually within 90 min in daylight. The study is further extended in abating a mixture of these dyes from contaminated water using composite nanofibers. Also, in the case of a mixture of these dyes (3 ppm each), nanofibers show dye degradation efficiency (DDE) of 90.9% (MB), 62.4% (Au) and 90.3% (FB and Rh) in 60 min. The role of Ag nanoparticles with a synergic photocatalytic effect on ZnO and TiO₂ is also demonstrated. Also, PMMA/ZnO/TiO₂ composite fiber membrane in synergy with silver particles shows better antibacterial activity against Gram-negative bacteria E. coli, making PMMA/Ag/ZnO/TiO₂ fibers a promising candidate in water purification.

Improved Surface Functional and Photocatalytic Properties of Hybrid ZnO-MoS2-Deposited Membrane for Photocatalysis-Assisted Dye Filtration

The synergistic mechanism of photocatalytic-assisted dye degradation has been demonstrated using a hybrid ZnO-MoS₂-deposited photocatalytic membrane (PCM). Few layers of MoS₂ sheets were produced using the facile and efficient surfactant-assisted liquid-phase exfoliation method. In this process, hydrophilic moieties of an anionic surfactant were adsorbed on the surface of MoS₂, which aided exfoliation and promoted a stable dispersion due to the higher negative zeta potential of the exfoliated MoS₂ sheets. Further, the decoration of ZnO on the exfoliated MoS₂ sheets offered a bandgap energy reduction to about 2.77 eV, thus achieving an 87.12% degradation of methylene blue (MB) dye within 15 min of near UV-A irradiation (365 nm), as compared with pristine ZnO achieving only 56.89%. The photocatalysis-enhanced membrane filtration studies on the ZnO-MoS₂ PCM showed a complete removal of MB dye (~99.95%). The UV-assisted dye degradation on the ZnO-MoS₂ PCM offered a reduced membrane resistance, with the permeate flux gradually improving with the increase in the UV-irradiation time. The regeneration of the active ZnO-MoS₂ layer also proved to be quite efficient with no compromise in the dye removal efficiency.

Resistive Switching in Nonperovskite-Phase CsPbI3 Film-Based Memory Devices

Because of their attractive photoelectrical properties, perovskite-phase, CsPbX₃ (X = I, Br, or Cl) materials have recently gained attention for their applications in resistive switching (RS) memories. However, phase transition of the CsPbI₃ from perovskite (cubic phase) to nonperovskite (orthorhombic phase) at room temperature is problematic; it remains a challenge to apply nonperovskite CsPbI₃ in RS memories. In the present work, a polymethylmethacrylate (PMMA)-assisted deposition method for nonperovskite CsPbI₃ is introduced to fabricate a composite film of CsPbI₃ with PMMA (PMMA@CsPbI₃) with a smooth surface morphology on fluorine-doped tin oxide (FTO) substrates. Devices with a Ag/PMMA@CsPbI₃/FTO architecture show nonvolatile RS characteristics with an ON/OFF ratio around 10², endurance over 500 cycles, and a retention time of 10³ s. Analyses suggested that a Schottky barrier at the Ag/PMMA@CsPbI₃ interface and a bias-induced migration of Ag ions within the composite films are responsible for the RS operation. This is the first record for RS devices based on nonperovskite CsPbI₃, and it may bring the future research on nonperovskite CsPbI₃ applied in RS memory devices some new inspiration..

Polypropylene/ZnO Nanocomposites: Mechanical Properties, Photocatalytic Dye Degradation, and Antibacterial Property

Nanocomposite materials were prepared by compounding polypropylene (PP) with zinc oxide (ZnO) nanoparticles, using a twin-screw extruder. The compound was molded by injection molding to form dumbbell-shaped specimens. The influence of ZnO nanoparticle content on the morphology, mechanical properties, chemical structure, photocatalytic activity, and antibacterial properties of the obtained nanocomposites was investigated. The morphological images showed that the ZnO nanoparticles were well distributed in the PP matrix. Characterizations of the mechanical properties and chemical structures before and after sunlight exposure found that at the shortest exposure time, crosslinks could occur in the nanocomposites, which resulted in improved mechanical properties. However, sunlight exposure with the time period longer than 18 weeks caused the reduction of the mechanical properties, due to degradation of the PP matrix. It was found that PP with 2% ZnO could achieve the photocatalytic degradation of methylene blue up to 59%. Moreover, the result of antibacterial tests indicated that the nanocomposites had better antibacterial properties than neat PP.

Role of Nanomaterials in the Treatment of Wastewater: A Review

Water is an essential part of life and its availability is important for all living creatures. On the other side, the world is suffering from a major problem of drinking water. There are several gases, microorganisms and other toxins (chemicals and heavy metals) added into water during rain, flowing water, etc. which is responsible for water pollution. This review article describes various applications of nanomaterial in removing different types of impurities from polluted water. There are various kinds of nanomaterials, which carried huge potential to treat polluted water (containing metal toxin substance, different organic and inorganic impurities) very effectively due to their unique properties like greater surface area, able to work at low concentration, etc. The nanostructured catalytic membranes, nanosorbents and nanophotocatalyst based approaches to remove pollutants from wastewater are eco-friendly and efficient, but they require more energy, more investment in order to purify the wastewater. There are many challenges and issues of wastewater treatment. Some precautions are also required to keep away from ecological and health issues. New modern equipment for wastewater treatment should be flexible, low cost and efficient for the commercialization purpose.

Synergistic effect of zinc oxide nanorods on the photocatalytic performance and the biological activity of graphene nano sheets

In this work, decoration of the graphene surface with 5 wt. % ZnO nanorods (ZnO NRs), to ensure the potential photocatalytic performance of the formed nanocomposites, is demonstrated. Graphene oxide (GO) was synthesized with Hummer method followed by reduction to give reduced graphene oxide (RGO). The adjustable nano-compositing exhibited long-sought workability not only in in-situ incorporation of nanorods while reduction of graphene oxide (IZG) but also in ex-situ mixing of RGO or GO with the nanorods, (EZG) and (ZGO) respectively. The demineralization of synthetic wastewater has been evaluated by chemical oxygen demand and the obtained nanocomposites possess enhanced photocatalytic activities with 30 % and 35% over pure RGO and GO, respectively. This higher efficiency could be attributed to the synergistic effect between ZnO and the planner structure of graphene sheets which developed unprecedented polycrystalline structure. Also, the results proved that even the RGO or GO have played a dual function in photocatalysis, adsorption, and degradation. Also, the bactericidal effect of the prepared samples was studied against deleterious microorganisms. The findings of this work pave the way for the new generation of highly efficient photocatalysts based graphene with economic attraction and environmental impact.

High-Performing Au-Ag Bimetallic Catalysts Supported on Macro-Mesoporous CeO2 for Preferential Oxidation of CO in H2-Rich Gases

We report here an investigation on the preferential oxidation of carbon monoxide in an H2-rich stream (CO-PROX reaction) over mono and bimetallic Au-Ag samples supported on macro-mesoporous CeO2. The highly porous structure of ceria and the synergistic effect, which occurs between the bimetallic Au-Ag system and the support, led to promising catalytic performance at low temperature (CO2 yield of 88% and CO2 selectivity of 100% at 60 °C), which is suitable for a possible application in the polymer electrolyte membrane fuel cell (PEMFC). The morphological, structural, textural and surface features of the catalysts were determined by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), N2-adsoprtion-desorption measurements, Temperature Programmed Reduction in hydrogen (H2-TPR), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS). Furthermore, the catalytic stability of the best active catalyst, i.e., the AuAg/CeO2 sample, was evaluated also in the presence of water vapor and carbon dioxide in the gas stream. The excellent performances of the bimetallic sample, favored by the peculiar porosity of the macro-mesoporous CeO2, are promising for possible scale-up applications in the H2 purification for PEM fuel cells.

Evaluation of the Photocatalytic Activity of a Cordierite-Honeycomb-Supported TiO2 Film with a Liquid-Solid Photoreactor

Anatase nanoparticles in suspension have demonstrated high photoactivity that can be exploited for pollutant removal in water phases. The main drawback of this system is the difficulty of recovering (and eventually reusing) the nanoparticles after their use, and the possible interference of inorganic salts (e.g., sulfates) that can reduce the performance of the photocatalyst. The present work describes the development of a cordierite-honeycomb-supported TiO₂ film to eliminate the problems of catalyst recovery. The catalyst was then tested against phenol in the presence of increasing concentrations of sulfates in a specially developed recirculating modular photoreactor, able to accommodate the supported catalyst and scalable for application at industrial level. The effect of SO₄^2- was evaluated at different concentrations, showing a slight deactivation only at very high sulfate concentration (≥3 g L^-1). Lastly, in the framework of the EU project Project Ô, the catalyst was tested in the treatment of real wastewater from a textile company containing a relevant concentration of sulfates, highlighting the stability of the photocatalyst.

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.

Au/ZnO Hybrid Nanostructures on Electrospun Polymeric Mats for Improved Photocatalytic Degradation of Organic Pollutants

An innovative approach for the fabrication of hybrid photocatalysts on a solid porous polymeric system for the heterogeneous photocatalytic degradation of organic pollutants is herein presented. Specifically, gold/zinc oxide (Au/ZnO)-based porous nanocomposites are formed in situ by a two-step process. In the first step, branched ZnO nanostructures fixed on poly(methyl methacrylate) (PMMA) fibers are obtained upon the thermal conversion of zinc acetate-loaded PMMA electrospun mats. Subsequently, Au nanoparticles (NPs) are directly formed on the surface of the ZnO through an adsorption dipping process and thermal treatment. The effect of different concentrations of the Au ion solutions to the formation of Au/ZnO hybrids is investigated, proving that for 1 wt % of Au NPs with respect to the composite there is an effective metal–semiconductor interfacial interaction. As a result, a significant improvement of the photocatalytic performance of the ZnO/PMMA electrospun nanocomposite for the degradation of methylene blue (MB) and bisphenol A (BPA) under UV light is observed. Therefore, the proposed method can be used to prepare flexible fibrous composites characterized by a high surface area, flexibility, and light weight. These can be used for heterogeneous photocatalytic applications in water treatment, without the need of post treatment steps for their removal from the treated water which may restrict their wide applicability and cause secondary pollution.

A New Sensor for Methyl Paraben Using an Electrode Made of a Cellulose Nanocrystal-Reduced Graphene Oxide Nanocomposite

A new cellulose nanocrystal-reduced graphene oxide (CNC-rGO) nanocomposite was successfully used for mediatorless electrochemical sensing of methyl paraben (MP). Fourier-transform infrared spectroscopy (FTIR) and field-emission scanning electron microscopy (FESEM) studies confirmed the formation of the CNC-rGO nanocomposite. Cyclic voltammetry (CV) studies of the nanocomposite showed quasi-reversible redox behavior. Differential pulse voltammetry (DPV) was employed for the sensor optimization. Under optimized conditions, the sensor demonstrated a linear calibration curve in the range of 2 × 10^-4-9 × 10^-4 M with a limit of detection (LOD) of 1 × 10^-4 M. The MP sensor showed good reproducibility with a relative standard deviation (RSD) of about 8.20%. The sensor also exhibited good stability and repeatability toward MP determinations. Analysis of MP in cream samples showed recovery percentages between 83% and 106%. Advantages of this sensor are the possibility for the determination of higher concentrations of MP when compared with most other reported sensors for MP. The CNC-rGO nanocomposite-based sensor also depicted good reproducibility and reusability compared to the rGO-based sensor. Furthermore, the CNC-rGO nanocomposite sensor showed good selectivity toward MP with little interference from easily oxidizable species such as ascorbic acid.

Evaluation of the effects of silver nanoparticles on Danio rerio cornea: Morphological and ultrastructural analysis

Although in recent years there has been intensification in the use of nanoparticles (NPs) for the production of many commercial products, few studies have been carried out to assess the risks associated with its use. Among the most used NPs, silver nanoparticles (AgNPs) have a preponderant position as they have various applications. In this study, 40 adult zebrafish were exposed to increasing concentrations of AgNPs (8, 45, and 70 μg/L) for 30 days to evaluate the effects on eyes after chronic exposure to AgNPs with an average diameter of 50 nm. From the morphological and ultrastructural analysis performed, no alteration or lesions of the corneal epithelium were detected.

Eco-friendly nanocomposites derived from geranium oil and zinc oxide in one step approach

Nanocomposites offer attractive and cost-effective thin layers with superior properties for antimicrobial, drug delivery and microelectronic applications. This work reports single-step plasma-enabled synthesis of polymer/zinc nanocomposite thin films via co-deposition of renewable geranium essential oil-derived polymer and zinc nanoparticles produced by thermal decomposition of zinc acetylacetonate. The chemical composition, surfaces characteristics and antimicrobial performance of the designed nanocomposite were systematically investigated. XPS survey proved the presence of ZnO in the matrix of formed polymers at 10 W and 50 W. SEM images verified that the average size of a ZnO nanoparticle slightly increased with an increase in the power of deposition, from approximately 60 nm at 10 W to approximately 80 nm at 50 W. Confocal scanning laser microscopy images showed that viability of S. aureus and E.coli cells significantly reduced on surfaces of ZnO/polymer composites compared to pristine polymers. SEM observations further demonstrated that bacterial cells incubated on Zn/Ge 10 W and Zn/Ge 50 W had deteriorated cell walls, compared to pristine polymers and glass control. The release of ZnO nanoparticles from the composite thin films was confirmed using ICP measurements, and can be further controlled by coating the film with a thin polymeric layer. These eco-friendly nanocomposite films could be employed as encapsulation coatings to protect relevant surfaces of medical devices from microbial adhesion and colonization.

Mechanical milling: a sustainable route to induce structural transformations in MoS2 for applications in the treatment of contaminated water

Two-dimensional (2D) nanomaterials have received much attention in recent years, because of their unusual properties associated with their ultra-thin thickness and 2D morphology. Besides graphene, a new 2D material, molybdenum disulfide (MoS₂), has attracted immense interest in various applications. On the other hand, ball-milling process provides an original strategy to modify materials at the nanometer scale. This methodology represents a smart solution for the fabrication of MoS₂ nanopowders extremely-efficient in adsorbing water contaminants in aqueous solution. This work reports a comprehensive morphological, structural, and physicochemical investigation of MoS₂ nanopowders treated with dry ball-milling. The adsorption performances of the produced nanopowders were tested using methylene blue (MB) dye and phenol in aqueous solution. The adsorption capacity as a function of ball-milling time was deeply studied and explained. Importantly, the ball-milled MoS₂ nanopowders can be easily and efficiently regenerated without compromising their adsorption capacity, so to be reusable for dye adsorption. The eventual toxic effects of the prepared materials on microcrustacean Artemia salina were also studied. The present results demonstrate that ball-milling of MoS₂ offers a valid method for large-scale production of extremely efficient adsorbent for the decontamination of wastewaters from several pollutants.

Bridging the gap between laboratory and application in photocatalytic water purification

Despite a large number of publications in the field, photocatalytic water treatment is still somewhat disconnected from real world application and we highlight recent developments to address this.

An Experimental Study of Photocatalytic Degradation of Congo Red Using Polymer Nanocomposite Films

Eco-friendly polymer nanocomposite films were synthesized using biodegradable polymers of chitosan and polyvinyl alcohol as polymeric matrices and carbon black nanoparticles as the reinforcement. These films were applied to study their applicability to industrial wastewater purification as a photocatalyst for degradation of Congo red as a target pollutant and to study the effect of the polymeric matrix types of the films on their performance as a semiconductor photocatalyst. Fourier-transform infrared (FT-IR) spectra and X-ray diffraction (XRD) were used to characterize the films. Visible light photocatalytic degradation of Congo red as a pollutant under various operational conditions of pH, dye concentration, contact time, and light intensity was performed. Photocatalytic results revealed that the polymeric substrate type does not play a major role in the photodegradation of the dye, and the best operational conditions were at a pH of 6 and a dye solution concentration of 8 mg/L.