Upcycling discarded cellulosic surgical masks into catalytically active freestanding materials.

ABSTRACT: The COVID-19 pandemic outbreak has resulted in the massive fabrication of disposable surgical masks. As the accumulation of discarded face masks represents a booming threat to the environment, here we propose a solution to reuse and upcycle surgical masks according to one of the cornerstones of the circular economy. Specifically, the non-woven cellulosic layer of the masks is used as an environmentally sustainable and highly porous solid support for the controlled deposition of catalytically active metal-oxide nanoparticles. The native cellulosic fibers from the surgical masks are decorated by titanium dioxide (TiO2), iron oxide (FexOy), and cobalt oxide (CoOx) nanoparticles following a simple and scalable approach. The abundant surface -OH groups of cellulose enable the controlled deposition of metal-oxide nanoparticles that are photocatalytically active or shown enzyme-mimetic activities. Importantly, the hydrophilic highly porous character of the cellulosic non-woven offers higher accessibility of the pollutant to the catalytically active surfaces and high retention in its interior. As a result, good catalytic activities with long-term stability and reusability are achieved. Additionally, developed free-standing hybrids avoid undesired media contamination effects originating from the release of nanoscale particles. The upcycling of discarded cellulosic materials, such as the ones of masks, into high-added-value catalytic materials, results an efficient approach to lessen the waste´s hazards of plastics while enhancing their functionality. Interestingly, this procedure can be extended to the upcycling of other systems (cellulosic or not), opening the path to greener manufacturing approaches of catalytic materials. GRAPHICAL ABSTRACT: A novel approach to upcycle discarded cellulosic surgical masks is proposed, providing a solution to reduce the undesired accumulation of discarded face masks originating from the COVID-19 pandemic. The non-woven cellulosic layer formed by fibers is used as solid support for the controlled deposition of catalytically active titanium dioxide (TiO2), iron oxide (FexOy), and cobalt oxide (CoOx) nanoparticles. Cellulosic porous materials are proven useful for the photocatalytic decomposition of organic dyes, while their peroxidase-like activity opens the door to advanced applications such as electrochemical sensors. The upcycling of cellulose nonwoven fabrics into value-added catalytic materials lessens the waste´s hazards of discarded materials while enhancing their functionality. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10570-022-04441-9.

Magnetic Copper Ferrite Nanoparticles Functionalized by Aromatic Polyamide Chains for Hyperthermia Applications.

A new magnetic nanocomposite with a statistical star polymer structure was designed and synthesized. Nanocomposite fabrication is based on the polymerization of aromatic polyamide chains on the surface of functionalized magnetic copper ferrite nanoparticles (CuFe2O4 MNPs). This magnetic nanostructure was characterized by several analysis methods. All the analytical methods used, for instance, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, thermogravimetric, vibrating-sample magnetometer, and scanning electron microscopy (SEM), confirmed the formation of polyamide chains. The obtained images from SEM imaging showed a unique nanoflower morphology which was the proper orientation results of synthesized nanoplates. Finally, the magnetic nanostructure showed a good potential for hyperthermia applications, with a maximum specific absorption rate of 7 W/g for 1 mg/mL of the sample under a magnetic field in different frequencies (100, 200, 300, and 400 MHz) and 5 to 20 min time intervals.

Retraction notice to "Biogenic synthesis and cytotoxic effects of silver nanoparticles mediated by white rot fungi" [Heliyon 7 (2021) e06470].

[This retracts the article DOI: 10.1016/j.heliyon.2021.e06470.].

Expression of concern: Highly porous copper-supported magnetic nanocatalysts: made of volcanic pumice textured by cellulose and applied for the reduction of nitrobenzene derivatives.

Expression of concern for 'Highly porous copper-supported magnetic nanocatalysts: made of volcanic pumice textured by cellulose and applied for the reduction of nitrobenzene derivatives' by Reza Taheri-Ledari et al., RSC Adv., 2021, 11, 25284-25295, https://doi.org/10.1039/D1RA03538J.

Expression of concern: Facile route to synthesize Fe3O4@acacia-SO3H nanocomposite as a heterogeneous magnetic system for catalytic applications.

Expression of concern for 'Facile route to synthesize Fe3O4@acacia-SO3H nanocomposite as a heterogeneous magnetic system for catalytic applications' by Reza Taheri-Ledari et al., RSC Adv., 2020, 10, 40055-40067, https://doi.org/10.1039/D0RA07986C.

Expression of concern: Investigation of the biological activity, mechanical properties and wound healing application of a novel scaffold based on lignin-agarose hydrogel and silk fibroin embedded zinc chromite nanoparticles.

Expression of concern for 'Investigation of the biological activity, mechanical properties and wound healing application of a novel scaffold based on lignin-agarose hydrogel and silk fibroin embedded zinc chromite nanoparticles' by Reza Eivazzadeh-Keihan et al., RSC Adv., 2021, 11, 17914-17923, https://doi.org/10.1039/D1RA01300A.

Expression of concern: Acceleration of ammonium phosphate hydrolysis using TiO2 microspheres as a catalyst for hydrogen production.

Expression of concern for 'Acceleration of ammonium phosphate hydrolysis using TiO2 microspheres as a catalyst for hydrogen production' by Ayman H. Zaki et al., Nanoscale Adv., 2020, 2, 2080-2086, https://doi.org/10.1039/D0NA00204F.

Expression of concern: Cobalt metal-organic framework-based ZIF-67 for the trace determination of herbicide molinate by ion mobility spectrometry: investigation of different morphologies.

Expression of concern for 'Cobalt metal-organic framework-based ZIF-67 for the trace determination of herbicide molinate by ion mobility spectrometry: investigation of different morphologies' by Mehdi Davoodi et al., RSC Adv., 2021, 11, 2643-2655, DOI: https://doi.org/10.1039/D0RA09298C.

Retraction to "Silver-Doped Cadmium Selenide/Graphene Oxide-Filled Cellulose Acetate Nanocomposites for Photocatalytic Degradation of Malachite Green toward Wastewater Treatment".

[This retracts the article DOI: 10.1021/acsomega.1c02667.].

Expression of concern: Synthesis and characterization of a new ZIF-67@MgAl2O4 nanocomposite and its adsorption behaviour.

Expression of concern for 'Synthesis and characterization of a new ZIF-67@MgAl2O4 nanocomposite and its adsorption behaviour' by Mehdi Davoodi et al., RSC Adv., 2021, 11, 13245-13255, https://doi.org/10.1039/D1RA01056E.

Expression of Concern: Statistical optimization of photo-induced biofabrication of silver nanoparticles using the cell extract of Oscillatoria limnetica: insight on characterization and antioxidant potentiality.

Expression of Concern for 'Statistical optimization of photo-induced biofabrication of silver nanoparticles using the cell extract of Oscillatoria limnetica: insight on characterization and antioxidant potentiality' by Rasha A. Abo-Elmagd et al., RSC Adv., 2020, 10, 44232-44246, DOI: https://doi.org/10.1039/D0RA08206F.

Expression of Concern: The controlled synthesis and DFT investigation of novel (0D)-(3D) ZnS/SiO2 heterostructures for photocatalytic applications.

Expression of Concern for 'The controlled synthesis and DFT investigation of novel (0D)-(3D) ZnS/SiO2 heterostructures for photocatalytic applications' by Mohamed F. Sanad et al., RSC Adv., 2021, 11, 22352-22364, https://doi.org/10.1039/D1RA02284A.

Expression of concern: Versatile plasmonic-effects at the interface of inverted perovskite solar cells.

Expression of concern for 'Versatile plasmonic-effects at the interface of inverted perovskite solar cells' by Ahmed Esmail Shalan, et al., Nanoscale, 2017, 9, 1229-1236, https://doi.org/10.1039/C6NR06741G.

Expression of Concern: Concordantly fabricated heterojunction ZnO-TiO2 nanocomposite electrodes via a co-precipitation method for efficient stable quasi-solid-state dye-sensitized solar cells.

Expression of concern for 'Concordantly fabricated heterojunction ZnO-TiO2 nanocomposite electrodes via a co-precipitation method for efficient stable quasi-solid-state dye-sensitized solar cells' by Ahmed Esmail Shalan et al., RSC Adv., 2015, 5, 103095-103104, DOI: 10.1039/C5RA21822E.

Expression of Concern: Solid-state dye-sensitized solar cells based on Zn1-xSnxO nanocomposite photoanodes.

Expression of Concern for 'Solid-state dye-sensitized solar cells based on Zn1-xSnxO nanocomposite photoanodes' by Ayat Nasr El-Shazly et al., RSC Adv., 2018,8, 24059-24067, DOI: https://doi.org/10.1039/c8ra02852d.

Correction to "Silver-Doped Cadmium Selenide/Graphene Oxide-Filled Cellulose Acetate Nanocomposites for Photocatalytic Degradation of Malachite Green toward Wastewater Treatment".

[This corrects the article DOI: 10.1021/acsomega.1c02667.].

Recent Progress in Graphene- and Related Carbon-Nanomaterial-based Electrochemical Biosensors for Early Disease Detection.

Graphene- and carbon-based nanomaterials are key materials to develop advanced biosensors for the sensitive detection of many biomarkers owing to their unique properties. Biosensors have attracted increasing interest because they allow efficacious, sensitive, selective, rapid, and low-cost diagnosis. Biosensors are analytical devices based on receptors for the process of detection and transducers for response measuring. Biosensors can be based on electrochemical, piezoelectric, thermal, and optical transduction mechanisms. Early virus identification provides critical information about potentially effective and selective therapies, extends the therapeutic window, and thereby reduces morbidity. The sensitivity and selectivity of graphene can be amended via functionalizing it or conjoining it with further materials. Amendment of the optical and electrical features of the hybrid structure by introducing appropriate functional groups or counterparts is especially appealing for quick and easy-to-use virus detection. Various techniques for the electrochemical detection of viruses depending on antigen-antibody interactions or DNA hybridization are discussed in this work, and the reasons behind using graphene and related carbon nanomaterials for the fabrication are presented and discussed. We review the existing state-of-the-art directions of graphene-based classifications for detecting DNA, protein, and hormone biomarkers and summarize the use of the different biosensors to detect several diseases, like cancer, Alzheimer's disease, and diabetes, to sense numerous viruses, including SARS-CoV-2, human immunodeficiency virus, rotavirus, Zika virus, and hepatitis B virus, and to detect the recent pandemic virus COVID-19. The general concepts, mechanisms of action, benefits, and disadvantages of advanced virus biosensors are discussed to afford beneficial evidence of the creation and manufacture of innovative virus biosensors. We emphasize that graphene-based nanomaterials are ideal candidates for electrochemical biosensor engineering due to their special and tunable physicochemical properties.

Magnetic graphene oxide-lignin nanobiocomposite: a novel, eco-friendly and stable nanostructure suitable for hyperthermia in cancer therapy.

In this research, a novel magnetic nanobiocomposite was designed and synthesized in a mild condition, and its potential in an alternating magnetic field was evaluated for hyperthermia applications. For this purpose, in the first step, graphene oxide was functionalized with a natural lignin polymer using epichlorohydrin as the cross-linking agent. In the second step, the designed magnetic graphene oxide-lignin nanobiocomposite was fabricated by the in situ preparation of magnetic Fe3O4 nanoparticles in the presence of graphene oxide functionalized with lignin. The resultant magnetic nanobiocomposite possessed certain main properties, including stability and homogeneity in aqueous solutions, making it suitable for hyperthermia applications. The chemical and structural properties of the synthesized magnetic graphene oxide-lignin composite were characterized using FT-IR, EDX, FE-SEM, TEM, TG and VSM analyses. The saturation magnetization value of this magnetic nanocomposite was recorded as 17.2 emu g-1. Further, the maximum specific absorption rate was determined to be 121.22 W g-1. Given these results, this newly fabricated magnetic nanobiocomposite may achieve considerable performance under the alternating magnetic field in fluid hyperthermia therapy.

Synthesis, characterization and antimicrobial activity applications of grafted copolymer alginate-g-poly(N-vinyl imidazole).

N-Vinyl imidazole was grafted onto sodium alginate (PNVI-g-NaAlg) through a free radical polymerization technique in aqueous solution using potassium persulfate (K2S2O8, KPS) initiator material. The conditions of the grafting process onto sodium alginate were adjusted to obtain a grafted copolymer with a high percentage of poly(N-vinyl imidazole). The prepared grafted copolymer sodium alginate (NaAlg-g-PNVI), with high percentage yield, was investigated and characterized under certain conditions in order to detect its antibacterial effect. The prepared grafted copolymer was considered by means of several systems such as Fourier-Transform Infrared spectroscopy (FT-IR), 1H NMR spectroscopy and thermal analysis. The change in the morphology of the alginate distinguished after the grafting process was confirmed using a Scanning Electron Microscope (SEM). The biological activity of the grafted material was considered using Escherichia coli, Neisseria gonorrhoeae (Gram-negative), Bacillus subtilis (Gram-positive) and Candida albicans antifungal activities through the agar diffusion method. The obtained results show excellent improvement in antimicrobial activity of the alginate by grafting against Bacillus subtilis, Escherichia coli, Neisseria gonorrhoeae, and Candida albicans.

Graphene assisted crystallization and charge extraction for efficient and stable perovskite solar cells free of a hole-transport layer.

In recent times, perovskite solar cells (PSCs) have been of wide interest in solar energy research, which has ushered in a new era for photovoltaic power sources through the incredible enhancement in their power conversion efficiency (PCE). However, several serious challenges still face their high efficiency: upscaling and commercialization of the fabricated devices, including long-term stability as well as the humid environment conditions of the functional cells. To overcome these obstacles, stable graphene (G) materials with tunable electronic features have been used to assist the crystallization as well as the charge extraction inside the device configuration. Nonetheless, the hole transport layer (HTL)-free PSCs based on graphene materials exhibit unpredictable results, including a high efficiency and long-term stability even in the conditions of an ambient air atmosphere. Herein, we combine graphene materials into a mesoporous TiO2 electron transfer layer (ETL) to improve the coverage and crystallinity of the perovskite material and minimize charge recombination to augment both the stability and efficiency of the fabricated mixed cation PSCs in ambient air, even in the absence of a HTL. Our results demonstrate that an optimized PSC in the presence of different percentages of graphene materials displays a PCE of up to 17% in the case of a G:TiO2 ETL doped with 1.5% graphene. With this coverage and crystallinity amendment approach, we show hysteresis-free and stable PSCs, with less decomposition after ∼3000 h of storage under a moist ambient atmosphere. This work focuses on the originalities of the materials, expenses, and the assembling of stable and effective perovskite solar cells.