Multifunctional carbon dots originated from waste garlic peel for rapid sensing of heavy metals and fluorescent imaging of 2D and 3D spheroids cultured fibroblast cells

Here, we prepared sulfur and nitrogen self-doped carbon dots derived from garlic peel extract (GPSNCDs) using a hydrothermal method. The as-synthesized GPSNCDs were confirmed using Fourier-transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The analytical techniques indicate that the resulting GPSNCDs exhibit distinct emissive carbon-core with functionalities (owing to various ligands in the GPSNCDs). These functionalities are responsible for excellent hydrophilic and optical properties, including excitation-dependent emission and anti-photobleaching. Fluorescence intensities of GPSNCDs were quenched in the existence of Mn2+ and Fe3+ ions. This indicates that the GPSNCDs were sensitive to Fe3+ and Mn2+ ions with a limited range from 5 to 50 µM and showed lower recognition at ∼0.75 and 0.95 µM, respectively. In addition, the sensing results were generated in a short time (20 s). The cytotoxicity of GPSNCDs was tested to demonstrate that they are sufficiently safe to use for cellular imaging. The novel fluorescent GPSNCDs-based sensor can be used as a high-performance sensor for environmental monitoring. Further, GPSNCDs showed greater biocompatibility with normal fibroblast cells, and In Vitro fluorescent imaging of GPSNCDs revealed strong fluorescence signals in the two-dimensional (2D) and three-dimensional (3D) spheroids cultured fibroblast cells. The properties mentioned above demonstrate that the GPSNCDs can be applied to imaging normal cells without further modifications.

Mesoporous bimetallic S-doped nanoparticles prepared via hydrothermal method for enhanced photodegradation of 4-chlorophenol

Magnesium oxides (MgO) have gained shown significant promise for a variety of applications, which can be modified by ions doping. In this study, bimetallic Ag-doped S-MgO nanoparticles were prepared by hydrothermal method and used for photocatalytic degradation of 4-chlorophenl (4-CP). EDX suggested the presence of no impurities, which mainly contained Mg, Ag, and S elements, suggesting that S and Ag were incorporated into the lattice of MgO as a result of successful doping. Estimated bandgap of Ag-doped S-MgO nanoparticles was 3.7 eV, lower than MgO (7.8 eV), but useful to improve optical characteristics and photocatalytic efficiency to degrade 4-CP up to a maximum of 99.60 ± 0.50%. The synergetic parameter during photocatalysis of 4-CP was 6.91, confirming the degradation of 4-CP. Quenching experiments proved the presence of hydroxyl radicals (•OH) and singlet dioxygen (1O2) that were critical in 4-CP degradation. The kinetics rate constant was increased by 24.8% from 0.086 ± 0.004 to 0.108 ± 0.005 min-1 by the addition of sulfate in the reaction medium. The work proposes a new synthetic method for preparing catalysts that are capable of producing in-situ •OH radicals and 1O2 to decompose the organic contaminants.

Experimental and computational study of metal oxide nanoparticles for the photocatalytic degradation of organic pollutants: a review

Photocatalysis is a more proficient technique that involves the breakdown or decomposition of different organic contaminants, various dyes, and harmful viruses and fungi using UV or visible light solar spectrum. Metal oxides are considered promising candidate photocatalysts owing to their low cost, efficiency, simple fabricating method, sufficient availability, and environment-friendliness for photocatalytic applications. Among metal oxides, TiO2 is the most studied photocatalyst and is highly applied in wastewater treatment and hydrogen production. However, TiO2 is relatively active only under ultraviolet light due to its wide bandgap, which limits its applicability because the production of ultraviolet is expensive. At present, the discovery of a photocatalyst of suitable bandgap with visible light or modification of the existing photocatalyst is becoming very attractive for photocatalysis technology. However, the major drawbacks of photocatalysts are the high recombination rate of photogenerated electron-hole pairs, the ultraviolet light activity limitations, and low surface coverage. In this review, the most commonly used synthesis method for metal oxide nanoparticles, photocatalytic applications of metal oxides, and applications and toxicity of different dyes are comprehensively highlighted. In addition, the challenges in the photocatalytic applications of metal oxides, strategies to suppress these challenges, and metal oxide studied by density functional theory for photocatalytic applications are described in detail.

Anchoring ZnO on spinel cobalt ferrite for highly synergic sono-photo-catalytic, surfactant-assisted PAH degradation from soil washing solutions

In this study, the photocatalytic activity of ZnO was effectively improved via its combination with spinel cobalt ferrite (SCF) nanoparticles. The catalytic performance of ZnO@SCF (ZSCF) was investigated in coupling with UV irradiation and ultrasound (US), as a heterogeneous sono-photocatalytic process, for the decontamination of phenanthrene (PHE) from contaminated soil. Soil washing tests were conducted in a batch environment, after extraction assisted by using Tween 80. Several characterization techniques such as XRD, FESEM-EDS, BET, TEM, UV-vis DRS, PL and VSM were utilized to determine the features of the as-prepared catalysts. ZSCF showed an excellent catalytic activity toward degradation of PHE in the presence of US and UV with a significant synergic effect. It was found that more than 93% of PHE (35 mg/L) and 87.5% of TOC could be eliminated by the integrated ZSCF/US/UV system under optimum operational conditions (pH: 8.0, ZSCF: 1.5 g/L, UV power: 6.0 W and US power: 70 W) within 90 min of reaction. After five times of use, ZSCF illustrated good reusability in the decontamination of PHE (87%) and TOC (79%). Quenching tests revealed the contribution of h⁺, HO^• and e^- species during PHE degradation over ZSCF/UV/US and an S-scheme photocatalytic mechanisms was proposed for the possible charge transfer routes under the ZSCF system. This study provides the important role of SCF in enhancing the ZnO photocatalytic activity due to its high performance, easy recovery and excellent durability, which it make an efficient and promising catalyst in environmental clean-up applications.

Mechanical Response of Glass-Epoxy Composites with Graphene Oxide Nanoparticles

Graphene-based fillers possess exceptional properties that encourage researchers toward their incorporation in glass-epoxy (GE) polymer composites. Regarding the mechanical and wear properties of glass-epoxy composites, the effect of graphene oxide (GO) reinforced in glass-epoxy was examined. A decrease in tensile modulus and increase in tensile strength was reported for 1 wt. % of GO. A shift in glass transition temperature T_g was observed with the addition of GO. The cross-link density and storage modulus of the composite decreased with the addition of GO. The decrease in dissipation energy and wear rate was reported with the increase in GO concentration. A simple one-dimensional damage model of nonlinear nature was developed to capture the stress-strain behavior of the unfilled and filled glass-epoxy composite. Tensile modulus E, Weibull scale parameter σ_o, and Weibull shape parameter β were considered to develop the model. Finally, to understand the failure mechanisms in GO-filled composites, a scanning electron microscopic (SEM) examination was carried out for tensile fractured composites.

Inhibition of Staphylococcus aureus α-Hemolysin Production Using Nanocurcumin Capped Au@ZnO Nanocomposite

Nanoparticles of gold with zinc oxide (Au@ZnO NPs) were prepared by laser ablation and then capped with curcumin nanoparticles (Cur-Au@ZnO NPs). The synthesized NPs were characterized using different techniques, including transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), UV-visible spectroscopy, and X-ray diffraction. In addition, the ability of NPs as a promising antibacterial agent was tested against Staphylococcus aureus through the agar well diffusion method and AO/EtBr staining assay. The results showed that the prepared nanoparticles (Cur-Au@ZnO) served as an antibacterial agent and can destroy the bacterial cells by losing the cell wall integrity and penetrating the cytoplasmic membrane. Moreover, the findings confirmed the role of the formed NPs in attenuation of the adherence and invasion of S. aureus to rat embryonic fibroblast (REF) cells. Furthermore, the activity of Cur-Au@ZnO NPs against the S. aureus α-hemolysin toxin was evaluated using the western blot technique, using human alveolar epithelial cells (A549), and through histopathology examination in a mouse model. In conclusion, the built Cur-Au@ZnO NPs can be used as a potential antibacterial agent and an inhibitor of α-hemolysin toxin secreted by S. aureus. These NPs may offer a new strategy in combating pathogen infections and in the future for biomedical and pharmaceutical applications.

A Critical Study of Cu2O: Synthesis and Its Application in CO2 Reduction by Photochemical and Electrochemical Approaches

Copper oxide (Cu2O) is a potential material as a catalyst for CO2 reduction. Cu2O nanostructures have many advantages, including interfacial charge separation and transportation, enhanced surface area, quantum efficiency, and feasibility of modification via composite development or integration of the favorable surface functional groups. We cover the current advancements in the synthesis of Cu2O nanomaterials in various morphological dimensions and their photochemical and electrochemical applications, which complies with the physical enrichment of their enhanced activity in every application they are employed in. The scope of fresh designs, namely composites or the hierarchy of copper oxide nanostructures, and various ways to improve CO2 reduction performance are also discussed in this review. Photochemical and electrochemical CO2 transformations have received tremendous attention in the last few years, thanks to the growing interest in renewable sources of energy and green facile chemistry. The current review provides an idea of current photochemical and electrochemical carbon dioxide fixing techniques by using Cu2O-based materials. Carboxylation and carboxylative cyclization, yield valuable chemicals such as carboxylic acids and heterocyclic compounds. Radical ions, which are induced by photo- and electrochemical reactions, as well as other high-energy organic molecules, are regarded as essential mid-products in photochemical and electrochemical reactions with CO2. It has also been claimed that CO2 can be activated to form radical anions.

Boosting the photocatalytic performance of Cu2O for hydrogen generation by Au nanostructures and rGO nanosheets

Au@Cu2O/rGO exhibited boosting photocatalytic performance due to the yolk–shelled structure, abundant hot charges on Au, and quick charge transfer by rGO.

Polyethylene Glycol Functionalized Graphene Oxide Nanoparticles Loaded with Nigella sativa Extract: A Smart Antibacterial Therapeutic Drug Delivery System

Flaky graphene oxide (GO) nanoparticles (NPs) were synthesized using Hummer’s method and then capped with polyethylene glycol (PEG) by an esterification reaction, then loaded with Nigella sativa (N. sativa) seed extract. Aiming to investigate their potential use as a smart drug delivery system against Staphylococcus aureus and Escherichia coli, the spectral and structural characteristics of GO-PEG NPs were comprehensively analyzed by XRD, AFM, TEM, FTIR, and UV- Vis. XRD patterns revealed that GO-PEG had different crystalline structures and defects, as well as a higher interlayer spacing. AFM results showed GONPs with the main grain size of 24.41 nm, while GONPs–PEG revealed graphene oxide aggregation with the main grain size of 287.04 nm after loading N. sativa seed extract, which was verified by TEM examination. A strong OH bond appeared in FTIR spectra. Furthermore, UV- Vis absorbance peaks at (275, 284, 324, and 327) nm seemed to be correlated with GONPs, GO–PEG, N. sativa seed extract, and GO –PEG- N. sativa extract. The drug delivery system was observed to destroy the bacteria by permeating the bacterial nucleic acid and cytoplasmic membrane, resulting in the loss of cell wall integrity, nucleic acid damage, and increased cell-wall permeability.

Review on the hazardous applications and photodegradation mechanisms of chlorophenols over different photocatalysts

Chlorophenols are very important environmental pollutants, which have created huge problems for both aquatic and terrestrial lives. Therefore, their removal needs urgent, effective, and advanced technologies to safeguard our environment for future generation. This review encompasses a comprehensive study of the applications of chlorophenols, their hazardous effects and photocatalytic degradation under light illumination. The effect of various factors such as pH and presence of different anions on the photocatalytic oxidation of chlorophenols have been elaborated comprehensively. The production of different oxidizing agents taking part in the photodegradation of chlorophenols are given a bird eye view. The photocatalytic degradation mechanism of different chlorophenols over various photocatalyts has been discussed in more detail and elaborated that how different photocatalysts degrade the same chlorophenols with the aid of different oxidizing agents produced during photocatalysis. Finally, a future perspective has been given to deal with the effective removal of these hazardous pollutants from the environment.

Photoinduced In Situ Spontaneous Formation of a Reduced Graphene Oxide-Enwrapped Cu-Cu2O Nanocomposite for Solar Hydrogen Evolution

The fast recombination of photogenerated charge carriers and poor stability have impeded the application of many narrow band gap semiconductors with otherwise excellent photocatalytic performance. A metal-semiconductor Schottky junction is a promising strategy to accelerate charge separation and enhance catalytic efficiency. However, the preparation of these structures often involves intricate processes and harsh conditions, which will inevitably destroy the electronic structures of the semiconductors and ruin their original properties in practical applications. In this study, a reduced graphene oxide (RGO)-enwrapped Cu-Cu₂O nanocomposite (Cu-Cu₂O@RGO) spontaneously evolved from an aqueous alcoholic solution containing cupric ions and graphene oxide (GO) under simulated sunlight irradiation. During this process, GO reduction and Cu-Cu₂O nanoparticles growth occurred simultaneously in conjunction with in situ RGO encapsulation. Benefiting from the superior intrinsic semiconductor characteristic retention under mild reaction conditions, strong component interactions, and efficient interfacial charge transfer, the distinctive Cu-Cu₂O@RGO nanocomposite supplied multiple channels for rapid electron transfer to substantially enhance the charge carrier separation efficiency and provide perfect chemical protection to effectively prevent Cu₂O photocorrosion. This product also greatly suppressed self-aggregation to decrease the size of nanoparticles. Based on these merits, the Cu-Cu₂O@RGO nanocomposite offered promising advances in photoelectrochemical and photocatalytic H₂ evolution. This work provides an innovative photoinduced strategy for constructing an RGO-enwrapped semiconductor nanocomposite with efficient charge transfer interfaces while providing novel insights for the efficient solar energy utilization.

Photocatalytic Applications of Metal Oxides for Sustainable Environmental Remediation

Along with industrialization and rapid urbanization, environmental remediation is globally a perpetual concept to deliver a sustainable environment. Various organic and inorganic wastes from industries and domestic homes are released into water systems. These wastes carry contaminants with detrimental effects on the environment. Consequently, there is an urgent need for an appropriate wastewater treatment technology for the effective decontamination of our water systems. One promising approach is employing nanoparticles of metal oxides as photocatalysts for the degradation of these water pollutants. Transition metal oxides and their composites exhibit excellent photocatalytic activities and along show favorable characteristics like non-toxicity and stability that also make them useful in a wide range of applications. This study discusses some characteristics of metal oxides and briefly outlined their various applications. It focuses on the metal oxides TiO2, ZnO, WO3, CuO, and Cu2O, which are the most common and recognized to be cost-effective, stable, efficient, and most of all, environmentally friendly for a sustainable approach for environmental remediation. Meanwhile, this study highlights the photocatalytic activities of these metal oxides, recent developments, challenges, and modifications made on these metal oxides to overcome their limitations and maximize their performance in the photodegradation of pollutants.