Graphene materials: Armor against nosocomial infections and biofilm formation - A review

One-pot synthesis of g-C3N4/N-doped CeO2 nanocomposites and their potential visible light-driven photocatalytic degradation of methylene blue dye

In the pursuit of efficient photocatalytic materials for environmental applications, a new series of g-C3N4/N-doped CeO2 nanocomposites (g-C3N4/N-CeO2 NCs) was synthesized using a straightforward dispersion method. These nanocomposites were systematically characterized to understand their structural, optical, and chemical properties. The photocatalytic performance of g-C3N4/N-CeO2 NCs was evaluated by investigating their ability to degrade methylene blue (MB) dye, a model organic pollutant. The results demonstrate that the integration of g-C3N4 with N-doped CeO2 NCs reduces the optical energy gap compared to pristine N-doped CeO2, leading to enhanced photocatalytic efficiency. It is benefited from the existence of g-C3N4/N-CeO2 NCs not only in promoting the charge separation and inhibits the fast charge recombination but also in improving photocatalytic oxidation performance. Hence, this study highlights the potential of g-C3N4/N-CeO2 NCs as promising candidates for various photocatalytic applications, contributing to the advancement of sustainable environmental remediation technologies.

Central Countries' and Brazil's Contributions to Nanotechnology

Abstract:

Nanotechnology is a cornerstone of the scientific advances witnessed over the past few years. Nanotechnology applications are extensively broad, and an overview of the main trends worldwide can give an insight into the most researched areas and gaps to be covered. This document presents an overview of the trend topics of the three leading countries studying in this area, as well as Brazil for comparison. The data mining was made from the Scopus database and analyzed using the VOSviewer and Voyant Tools software. More than 44.000 indexed articles published from 2010 to 2020 revealed that the countries responsible for the highest number of published articles are The United States, China, and India, while Brazil is in the fifteenth position. Thematic global networks revealed that the standing-out research topics are health science, energy, wastewater treatment, and electronics. In a temporal observation, the primary topics of research are: India (2020), which was devoted to facing SARS-COV 2; Brazil (2019), which is developing promising strategies to combat cancer; China (2018), whit research on nanomedicine and triboelectric nanogenerators; the United States (2017) and the Global tendencies (2018) are also related to the development of triboelectric nanogenerators. The collected data are available on GitHub. This study demonstrates the innovative use of data-mining technologies to gain a comprehensive understanding of nanotechnology's contributions and trends and highlights the diverse priorities of nations in this cutting-edge field.

Aluminum oxide, cobalt aluminum oxide, and aluminum-doped zinc oxide nanoparticles as an effective antimicrobial agent against pathogens

Since the clock of antimicrobial resistance was set, modern medicine has shed light on a new cornerstone in technology to overcome the worldwide dread of the post-antimicrobial era. Research organizations are exploring the use of nanotechnology to modify metallic crystals from macro to nanoscale size, demonstrating significant interest in the field of antimicrobials. Herein, the antimicrobial activities of aluminum oxide (Al2O3), cobalt aluminum oxide (CoAl2O4), and aluminum doped zinc oxide (Zn0.9Al0.1O) nanoparticles were examined against some nosocomial pathogens. The study confirmed the formation and characterization of Al2O3, CoAl2O4, and Zn0.9Al0.1O nanoparticles using various techniques, revealing the generation of pure nanoscale nanoparticles. With inhibition zones ranging from 9 to 14 mm and minimum inhibitory concentrations varying from 4 mg/mL to 16 mg/mL, the produced nanoparticles showed strong antibacterial activity against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus. Meanwhile, the bactericidal concentrations ranged from 8 mg/mL to 40 mg/mL. In culture, Zn0.9Al0.1O NPs demonstrated a unique ability to inhibit the development of nosocomial infections with high bactericidal activity (8 mg/mL). Transmission electron microscope images revealed changes in cell shape, bacterial cell wall morphology, cytoplasmic membrane, and protoplasm due to the introduction of tested nanoparticles. These results pave the way for the use of these easily bacterial wall-piercing nanoparticles in combination with potent antibiotics to overcome the majority of bacterial strains' resistance.

Solar-activated and hydrothermally synthesized effective rGO/Ag2S composites for the destruction of naphthol green B dye and antibacterial applications

Graphene-based nanocomposites are developing as a new class of materials with several uses. The varied weight percentages of rGO on Ag2S catalysts were synthesized using a simple hydrothermal process and employed for the decomposition of anionic dye naphthol green B (NGB) under solar light. The reduced graphene oxide-based silver sulfide (rGO/Ag2S) nanoparticles were then examined using XRD, SEM, EDS, HR-TEM, XPS, UV-DRS, and PL analysis. Using solar light, the photocatalytic activity of the produced catalyst was examined for the degradation of naphthol green B (NGB) in an aqueous solution. At pH 9, rGO/Ag2S is discovered to be more effective than the other catalysts for the NGB dye mineralization. Analyses have been conducted on the influence of operational parameters on the photo-mineralization of NGB, including the initial pH, initial dye concentration, and catalyst dosage. The dye concentration increased; the efficiency of photocatalytic degradation tended to decrease. Chemical oxygen demand (COD) studies have verified the NGB dye mineralization. Active species trapping revealed that holes, hydroxyl radicals, and superoxide radicals all played major roles in the photocatalytic deterioration of NGB processes. Additionally, a potential mechanism of NGB dye degradation by rGO/Ag2S catalyst is presented. The synthesized compound was further evaluated for antibacterial activity, and the results indicated that rGO/Ag2S were potentially effective antibacterial agents.

Antimicrobial Antioxidant Polymer Films with Green Silver Nanoparticles from Symphyti radix

Antimicrobial natural polymer film with silver nanoparticles (AgNPs) biosynthesized using aqueous plant root extracts as reducing capping agents and for film formatting show extensive applicability for pathogenic microorganism problems. The formation of AgNPs was confirmed by transmission electron microscopy (TEM) and scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS) techniques. The antimicrobial activity of biofilm with green AgNPs was analysed by inhibiting the growth of Gram-negative and Gram-positive bacteria culture using the Kirby-Bauer disk diffusion susceptibility test. Total phenolic content and antioxidant activity were slightly higher in aqueous extracts of Sym. Radix than in Sym. Radix/AgNPs. The antimicrobial effect of polymer film/AgNPs against selected test bacteria cultures was substantially more robust than with pure film. Pictures of AgNPs obtained by TEM revealed the presence of spherical-shaped nano-objects with an average size 27.45 nm. SEM-EDS studies confirmed the uniform distribution of metal nanoparticles throughout the biopolymeric matrix. Morphological studies of the surface showed that the obtained surface of the films was even, without holes or other relief irregularities. These apparent Symphyti radix polymer film/AgNPs' biological functions could provide a platform for fighting pathogenic bacteria in the era of multi-drug resistance.

Fractional Factorial Design to Evaluate the Synthesis and Electrochemical Transfer Parameters of h-BN Coatings

In this study, we present a fractional factorial design approach for exploring the effects and interactions of key synthesis and electrochemical transfer parameters on the roughness and wettability of hexagonal boron nitride (h-BN) coatings, due to their essential role in biofilm formation. The studied parameters for the synthesis process include precursor mass, growth time, and substrate conditioning, whereas for the transfer process, applied voltage and aqueous medium concentration were studied. Through this polynomial model, we confirmed the strong influence of precursor mass and medium concentration parameters on h-BN surface roughness and its resulting antibiofilm properties.

Biodegradable composites from poly(butylene adipate-co-terephthalate) with carbon nanoparticles: Preparation, characterization and performances

The development of composites for food packaging that have good mechanical and antimicrobial characteristics is still a major challenge. In applications like food packaging, the usage of poly (butylene adipate-co-terephthalate) (PBAT), which has an adversative effect on the environment and reduces petroleum resources, has grown widespread. The present work reveals PBAT composites reinforced with CNPs at a few percentages up to 5.0 wt %. The PBAT/CNPs composites were produced using the solvent casting method. The results of TGA studies, CNPs significantly enhanced the thermal stability of composites using PBAT. The mechanical strength of the PBAT composites was improved by increasing CNPs concentration. Tensile strength increased from 7.38 to 10.22 MPa, respectively. The oxygen transmission rate (OTR) decreased with increasing the CNPs concentrations. The barrier properties (H2O and O2) of PBAT were improved by the presence of CNPs. WVTR was calculated to be 108.6 ± 1.8 g/m2/day for PBAT. WVTR reduced when CNPs concentration in PBAT increased. The PCN-5.0 film sample had the lowest WVTR value, 34.1 ± 3.1 g/m2/day. For PCN-3.0, WVTR dropped by 45.39%, indicating and even with a 3.0 wt% loading of CNPs in PBAT, the rise is noticeable. Contact angle measurements indicate that PBAT/CNPs composites becomes hydrophobic after reinforcing. Gram-positive (S. aureus) and Gram-negative (E. coli) food-borne pathogenic microorganisms showed enhanced antimicrobial activity against the developed PBAT composites. The carrot pieces preserved their freshness for an extended period of 12 days while packaged in the PBAT/CNPs composite film, indicating that the film is an effective and excellent packaging for food materials.

Development of luminescence carbon quantum dots for metal ions detection and photocatalytic degradation of organic dyes from aqueous media

In the present study, fish scale waste was used for the organic synthesis of luminescence CQDs by the hydrothermal method. The impact of CQDs on improved photocatalytic degradation of organic dyes and metal ions detection is examined in this study. The synthesized CQDs had a variety of characteristics that were detected, such as crystallinity, morphology, functional groups, and binding energies. The luminescence CQDs showed outstanding photocatalytic effectiveness for the destruction of methylene blue (96.5%) and reactive red 120 dye (97.8%), respectively after 120 min exposure to visible light (420 nm). The high electron transport properties of the CQDs edges, which make it possible to efficiently separate electron-hole pairs, are attributed to the enhanced photocatalytic activity of the CQDs. These degradation results prove that the CQDs are the outcome of a synergistic interaction between visible light (adsorption); a potential mechanism is also suggested, and the kinetics is analyzed to use a pseudo-first-order model. Additionally, the metal ions detection of CQDs was studied by various metal ions (Hg²⁺, Fe²⁺, Cu²⁺, Ni²⁺, and Cd²⁺) in an aqueous solution and results revealed that the PL intensity of CQDs in presence of cadmium ions decreased. Studies show that the organic fabrication of CQDs are effective photocatalyst and may one day serve as the ideal material to reduce water pollution.

Properties and Characterization Techniques of Graphene Modified Asphalt Binders

Graphene is a carbon-based nanomaterial used in various industries to improve the performance of hundreds of materials. For instance, graphene-like materials have been employed as asphalt binder modifying agents in pavement engineering. In the literature, it has been reported that (in comparison to an unmodified binder) the Graphene Modified Asphalt Binders (GMABs) exhibit an enhanced performance grade, a lower thermal susceptibility, a higher fatigue life, and a decreased accumulation of permanent deformations. Nonetheless, although GMABs stand out significantly from traditional alternatives, there is still no consensus on their behavior regarding chemical, rheological, microstructural, morphological, thermogravimetric, and surface topography properties. Therefore, this research conducted a literature review on the properties and advanced characterization techniques of GMABs. Thus, the laboratory protocols covered by this manuscript are atomic force microscopy, differential scanning calorimetry, dynamic shear rheometer, elemental analysis, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. Consequently, the main contribution of this investigation to the state-of-the-art is the identification of the prominent trends and gaps in the current state of knowledge.

Recent Nanotechnologies to Overcome the Bacterial Biofilm Matrix Barriers

Bacterial biofilm-related infectious diseases severely influence human health. Under typical situations, pathogens can colonize inert or biological surfaces and form biofilms. Biofilms are functional aggregates that coat bacteria with extracellular polymeric substances (EPS). The main reason for the failure of biofilm infection treatment is the low permeability and enrichment of therapeutic agents within the biofilm, which results from the particular features of biofilm matrix barriers such as negatively charged biofilm components and highly viscous compact EPS structures. Hence, developing novel therapeutic strategies with enhanced biofilm penetrability is crucial. Herein, the current progress of nanotechnology methods to improve therapeutic agents' penetrability against biofilm matrix, such as regulating material morphology and surface properties, utilizing the physical penetration of nano/micromotors or microneedle patches, and equipping nanoparticles with EPS degradation enzymes or signal molecules, is first summarized. Finally, the challenges, perspectives, and future implementations of engineered delivery systems to manage biofilm infections are presented in detail.

Visible light active hybrid silver decorated g-C3N4-CeO2 nanocomposite for ultrafast photocatalytic activity and toxicity evaluation

Development of hybrid graphitic carbon nitride (GCN) nanocomposite is an emerging research area in wastewater treatment. Herein, hybrid visible light active photocatalyst of silver decorated polymeric graphitic carbon nitride and (Ag-GCN) with cerium oxide (CeO₂) nanocomposite was prepared and characterized in detail. The Ag-GCN/CeO₂ photocatalyst has successfully prepared by an electrostatic self-assembly approach. The synthesized Ag-GCN/CeO₂ NCs photocatalysts are characterized by various physio-chemical techniques. Using the Ag-GCN/CeO₂ catalyst, the excellent photodegradation efficiency of Acid yellow-36 (AY-36) and Direct yellow-12 (DY-12) dye solution were achieved 100% within 150 min sun light irradiation. The Ag-GCN/CeO₂ rate constant values of 0.048 and 0.046/min has been determined for AY-36 and DR-12 dyes, respectively. The extraordinary photocatalytic activity is due to incorporation of CeO₂ with Ag-GCN which play a significant role in visible light absorption, superior reactive oxygen generation (ROS) and excellent pollutant catalyst interaction. The toxicity of the photocatalytically degraded AY-36 and DR-12 dyes were measured using the soil nematode Caenorhabditis elegans, a well-established in vivo model in biology, by analyzing survival, physiological functions, intracellular ROS levels, and stress-protective gene expressions.

Influence of Graphene Sheets Accumulation on Optical Band Gap Enhanced Graphite Exfoliation

Recently, graphene has been adopted to replace other expansive materials in various devices that perform numerous functionalities in many industrial fields. Meanwhile, researchers are still investigating the amazing properties of graphene. Herein, reduced graphene oxide (rGO) has been successfully exfoliated directly using a graphite rod in a modified electrolyte including a table salt as a co-electrolyte. The structure of graphene obtained by using exfoliation methods shows a low ratio of O/C and confirms the high crystallinity of rGO. The thickness of rGO was adjusted during the drying of the drops of rGO solution and obtained about an 8-80 nm rGO thick. The increased O/C ratio and crystallinity enhancement could be attributed to the quantum confinement effect. Further investigations to estimate the decay constant of the optical band gap during the thinning of the rGO layers show that the optical band gap was associated with thicknesses of the rGO at a decay constant of 0.3367±0.00205. These results would be crucial in several optical applications that depend on the thicknesses and the band gap.