Facile synthesis of carbon quantum dot/silver nanocomposite and its antimicrobial, catalytic and sensing applications.

Environmentally benign synthesis of nanocomposite, a pivotal facet of nanotechnology, and gaining prominence due to the increasing demand for facile, sustainable, and safe synthesis methods. The present research reports an facile/cost-effective method for the preparation of carbon dots (CDs) and carbon dot silver nanocomposites ( CD@AgNCs) via a hydrothermal treatment of peanut shells. The well-dispersed and spherical CDs with an average diameter of 5-6 nm were obtained and further employed for the preparation of CD@AgNCs. The formation of CD@AgNCs. was confirmed by optical and microscopic studies and ared shift in the λmax from 277 nm (CDs) to 450 nm (CD@AgNCs) with a size range of 30-40 nm was observed. The synthesized CD@AgNCs exhibit excellent catalytic potency for the reduction of 4-nitrophenol to 4-aminophenol, and also displaying a unique interaction and sensing ability towards heavy metal ions (Hg2+), causing a pronounced change in color from reddish-brown to transparent with limit of detection (LOD) of 23.47 ppm. Also, the prepared composite exhibit efficient antimicrobial potential against gram-negative (Escherichia coli) bacteria. Consequently, this study delves into a unified effective remediation platform with the integration of catalysis, sensing, and antimicrobial potentials.

Green Synthesis of CS-TiO2 NPs for Efficient Photocatalytic Degradation of Methylene Blue Dye.

The development of a non-malignant and sustainable treatment approach for eradicating mephitic organic dyes from freshwater resources is a daunting task. In a similar vein, the current work investigates the mitigation of methylene blue (MB) dye utilizing titanium dioxide nanoparticles (CS-TiO2 NPs) synthesized using cannabis sativa (bhang) leaf extract via a greener approach. The CS-TiO2 NPs are well characterized through XRD, FE-SEM, HR-TEM, UV-Vis spectroscopy, FTIR spectroscopy, and EDS spectroscopy. Microscopic studies confirm that the average particle size distribution of the individual particles was found to be in the range of 12.5 ± 1.5 nm, whereas the average size of the CS-TiO2 NPs aggregates is 24.5 ± 11.5 nm. Additionally, the synthesized CS-TiO2 NPs manifested remarkable photocatalytic degradation potential against methylene blue dye with a degradation efficiency of 98.2% and an apparent rate constant of 0.0398 min-1. As a result, this research offers a green/sustainable alternative for water purification.

Silver nanostructures prepared via novel green approach as an effective platform for biological and environmental applications.

Silver nanoparticles play a significant role in biomedical sciences due to their unique properties allowing for their use as an effective sensing and remediation platform Herein, the green synthesis of silver nanostructures (Ag NSs), prepared via aqueous extract of waste Brassica oleracea leaves in the presence of silver nitrate solution (10-4 M), is reported. The Ag NSs are fully characterized and their efficacy with respect to 4-nitrophenol reduction, glucose sensing, and microbes is determined. Visually, the color of silver nitrate containing solution altered from colorless to yellowish, then reddish grey, confirming the formation of Ag NSs. HRTEM and SEAD studies revealed the Ag NSs to have different morphologies (triangular, rod-shaped, hexagonal, etc., within a size range of 20-40 nm) with face-centered cubic (fcc) crystal structure. The Ag NSs possess high efficacy for nitrophenol reduction (<11 min and degradation efficiency of 98.2%), glucose sensing (LOD: 5.83 µM), and antimicrobial activity (E. coli and B. subtilis with clearance zones of 18.3 and 14 mm, respectively). Thus, the current study alludes towards the development of a cost-effective, sustainable, and efficient three-in-one platform for biomedical and environmental applications.

A Review on Green Synthesis of TiO2 NPs: Photocatalysis and Antimicrobial Applications.

Nanotechnology is a fast-expanding area with a wide range of applications in science, engineering, health, pharmacy, and other fields. Nanoparticles (NPs) are frequently prepared via a variety of physical and chemical processes. Simpler, sustainable, and cost-effective green synthesis technologies have recently been developed. The synthesis of titanium dioxide nanoparticles (TiO2 NPs) in a green/sustainable manner has gotten a lot of interest in the previous quarter. Bioactive components present in organisms such as plants and bacteria facilitate the bio-reduction and capping processes. The biogenic synthesis of TiO2 NPs, as well as the different synthesis methods and mechanistic perspectives, are discussed in this review. A range of natural reducing agents including proteins, enzymes, phytochemicals, and others, are involved in the synthesis of TiO2 NPs. The physics of antibacterial and photocatalysis applications were also thoroughly discussed. Finally, we provide an overview of current research and future concerns in biologically mediated TiO2 nanostructures-based feasible platforms for industrial applications.

Highly stable AgNPs prepared via a novel green approach for catalytic and photocatalytic removal of biological and non-biological pollutants.

Increases in biological and non-biological pollutants pose a significant threat to environmental systems. In an effort to develop an effective means to treat such pollutants, the use of Phaseolus vulgaris (kidney beans) as reducing and capping agents is proposed for the green synthesis of highly stable silver nanoparticles (AgNPs) with a face-centered cubic (fcc) crystalline structure (size range: 10-20 nm). The potent role of the resulting AgNPs was found as triple platforms (photocatalyst, catalyst, and antimicrobial disinfectant). AgNPs were able to photocatalytically degrade approximately 97% of reactive red-141 (RR-141) dye within 150 min of exposure (quantum efficiency of 3.68 × 10-6 molecule.photon-1 and a removal reaction kinetic rate of 1.13 × 10-2 mmol g-1 h-1). The role of specific reactive oxygen species (ROS) in the photocatalytic process and complete mineralization of dye was also explored through scavenger and chemical oxygen demand (COD) experiments, respectively. As an catalyst, AgNPs were also capable of reducing 4-nitrophenol to 4-aminophenol within 15 min. Overall, AgNPs showed excellent stability as catalyst and photocatalyst even after five test cycles. As an antimicrobial agent, the AgNPs are effective against both gram-positive (Bacillus subtilis) and -negative bacteria (Escherichia coli), with the zones of clearance as 15 and 18 mm, respectively. Thus, the results of this study validate the triple role of AgNPs derived via green synthesis as a photocatalyst, catalyst, and antimicrobial agent for effective environmental remediation.

Highly fluorescent carbon dots derived from Mangifera indica leaves for selective detection of metal ions.

In this study, we report an inexpensive, green, and one-pot synthesis method for highly fluorescent carbon quantum dots (CQDs) using mango (Mangifera indica: M. indica) leaves to develop an efficient sensing platform for metal ions. The CQDs synthesized from M. indica leaves via pyrolysis treatment at 300 °C for 3 h were characterized by various spectroscopic and electron microscopy techniques for their structural, morphological, and optical properties. Accordingly, the synthesized CQDs showed an absorption peak at 213 nm to confirm the p-p* transition of the carbon core state, while the CQD particles were spherical with a size less than 10 nm. The prepared CQDs showed excellent fluorescent properties with blue emission spectra (around 525 nm) upon excitation at 435 nm. The synthesized CQDs had the prodigious sensing potential to detect Fe2+ ions in water with a limit of detection of 0.62 ppm. Additionally, their sensing capability was tested using a real sample (e.g., Livogen tablet). Moreover, the synthesized CQDs showed substantial stability over a long period (three months). Thus, this study provides an inexpensive and facile method for CQD-based sensing of Fe2+ ions with a photoluminescence quenching mechanism.

Biogenic synthesis of copper oxide nanoparticles using plant extract and its prodigious potential for photocatalytic degradation of dyes.

The development of benign and efficient approaches for treating industrial grade toxic organic dyes is an ongoing challenge. To this end, copper oxide nanoparticles (CuO NPs) were prepared by a simple, environment friendly, and economical green synthesis procedure by using Psidium guajava leaf extract as reducing agent (i.e., for the reduction of metal salt) as well as capping agent and copper acetate monohydrate as metal salt. The formation of mono-dispersed and spherical (average size 2-6 nm with BET surface area 52.6 m2/g) CuO NPs was confirmed by various spectroscopic and microscopic techniques. The CuO NPs exhibited excellent degradation efficiency for the industrial dyes, i.e., Nile blue (NB) (93% removal in 120 min) and reactive yellow 160 (RY160) (81% removal in 120 min) with apparent rate constants of 0.023 and 0.014 min-1, respectively. The CuO catalyst was found to be reusable for photocatalytic dye degradation even after five consecutive cycles. The limit of detection (LOD) values for NB and RY160 were 4 and 9 mg/L, respectively. In light of their high reusability and photocatalytic efficiency along with adaptability to green synthesis, the use of biogenic CuO NPs is a promising option for the purification of water resources contaminated with industrial dye.

Amphiphilic carbon dots derived by cationic surfactant for selective and sensitive detection of metal ions.

Carbon Dots (CDs) the kind of recently exposed fluorescent nanomaterials have become increasingly popular in the precedent decade due to their distinctive physical and optical properties. Relating to above recognition for the first time we present the synthesis of CDs by cationic surfactant, Cetylpyridinium Bromide (CPB). Due to good carbon content amphiphilicity, and existence of heteroaromatic π system, CPB reveals three advantageous properties including a good carbon source, stabilizing agent, and contributing fluorophore in the CDs system. The as prepared CDs synthesized by hydrothermal technique reveals excellent fluorescent properties having strong green emission at 525 nm when excited over 470 nm. The FTIR results showed the presence of CC, CO, NH, CH and OH bonds. The presence of hydrophilic groups such as carboxyl and hydroxyl groups present on the surface confer them water solubility. The HRTEM results revealed the size of prepared CDs to be in the range of 7-10 nm. The XPS spectrum confirms the presence of Carbon, Oxygen and Nitrogen, suggesting that the CDs have good purity and very little impurities. Latterly CDs were used for the selective and sensitive detection towards Fe2+ ions. Also the as prepared CDs were utilized for real sample analysis.

'Green' synthesis of metals and their oxide nanoparticles: applications for environmental remediation.

In materials science, "green" synthesis has gained extensive attention as a reliable, sustainable, and eco-friendly protocol for synthesizing a wide range of materials/nanomaterials including metal/metal oxides nanomaterials, hybrid materials, and bioinspired materials. As such, green synthesis is regarded as an important tool to reduce the destructive effects associated with the traditional methods of synthesis for nanoparticles commonly utilized in laboratory and industry. In this review, we summarized the fundamental processes and mechanisms of "green" synthesis approaches, especially for metal and metal oxide [e.g., gold (Au), silver (Ag), copper oxide (CuO), and zinc oxide (ZnO)] nanoparticles using natural extracts. Importantly, we explored the role of biological components, essential phytochemicals (e.g., flavonoids, alkaloids, terpenoids, amides, and aldehydes) as reducing agents and solvent systems. The stability/toxicity of nanoparticles and the associated surface engineering techniques for achieving biocompatibility are also discussed. Finally, we covered applications of such synthesized products to environmental remediation in terms of antimicrobial activity, catalytic activity, removal of pollutants dyes, and heavy metal ion sensing.