Honeybee pollen assisted biosynthesis of nanogold and its application as catalyst in reduction of 4-nitrophenol

Advances in 4-Nitrophenol Detection and Reduction Methods and Mechanisms: An Updated Review

This review emphasizes the progress in identifying and eliminating para-nitrophenol (4-NP), a toxic organic compound. It covers various strategical methods and materials, including organic and inorganic nanomaterials, for detecting and reducing 4-NP. Detection techniques such as electrochemical methods. Optical fiber-based surface plasmon resonance and photoluminescence, as well as the mechanisms of Förster Resonance Energy Transfer (FRET) and Inner Filter Effect (IFE) in fluorescence detection, are presented. Removal techniques for this contaminant include homogeneous catalysis, electrocatalysis, photocatalysis, and thermocatalysis, and their reaction mechanisms are also discussed. Further, the theoretical perspectives of 4-NP detection and reduction, parameters influencing the activities, and future perspectives are also reviewed in detail.

Identification of Marker Molecules in Aqueous Plant Extracts Affecting the Gold Nanostructures' Morphology and Size

This work was performed as a comparative study using nine different aqueous pollen grain extracts from eight different genera (Juniperus, Biota, Cupressus, Abies, Pinus, Cedrus, Populus and Corylus) to synthesize gold nanostructures (AuNSs) to understand if there is any possible marker that helps to predict the final morphology and size of the AuNSs. Principal component analysis (PCA) revealed that Apigenin and Pinoresinol compounds are the marker molecules in determination of the AuNSs physical characteristics while total protein, reducing carbohydrate, flavonoid and phenol contents did not show any statistically meaningful outcome. The "dominancy hypothesis" was tested by paying attention to the most concentrated phenolic acids and flavonoids in the control of AuNSs morphology and size, for which correlation analysis were performed. The statistical findings were tested using two new more pollen extracts to validate the models. Three main findings of the study were (i) determination of Apigenin and Pinoresinol levels in pollen extract can give an insight into the AuNSs physical characters, (ii) the most concentrated phenolic acids and flavonoids don't need to be same to pose same dictative effect on AuNSs morphology and size, rather relatively abundant ones in the extract play the key role and (iii) differences in the polymeric structures (e. g. lignin, cellulosic compounds etc.) have minor effect on the final morphology and size of the AuNSs.

Chitosan hydrogel anchored phthalocyanine supported metal nanoparticles: Bifunctional catalysts for pollutants reduction and hydrogen production

Metal nanoparticles possess high catalytic activity in various organic transformation reactions. A catalyst must be recovered and re-used effectively and economically to lower the overall reaction cost. The recovery of a catalyst remains a challenge due to their extreme small size. In this research work, catalytic metal nanoparticles were synthesized on Zn-phthalocyanine (ZnPc) and chitosan hydrogel (CH) composite which acts as catalyst support. The ZnPc-CH support facilitate the easy recovery of the loaded metal nanoparticles. Metal nanoparticles (M⁰) based on Cu⁰, Ag⁰, Ni⁰, Co⁰ and Fe⁰ were decorated inside and on ZnPc-CH hydrogel surface. The developed M⁰@ZnPc-CH were utilized for the enhanced selective reduction of toxins and hydrogen production by methanolysis and hydrolysis of NaBH₄. Effective catalytic reduction and hydrogen generation was successfully achieved with Co⁰@ZnPc-CH and ZnPc-CH. Under optimized conditions, Co⁰@ZnPc-CH showed complete reduction of 4-nitrophenol (4-NP) in 8.0 min with the fast 4-NP reduction kinetics (K = 0.611 min^-1). Among the developed catalysts, ZnPc-CH showed fast H₂ generation with high H₂ generation rate (HGR = 4100 mLg^-1min^-1) under optimized conditions. Metal leaching from Co⁰@ZnPc-CH was negligible during recycling of the catalyst, suggesting that it could be implemented to 4-NP treatment from real water samples. Similarly, ZnPc-CH could produce same quantity of H₂ throughout 4 continuous cycles of durability testing without any deactivation and leaching and ZnPc-CH showed high stability, indicating the effectiveness of the catalyst to be applied for H₂ production on large scale.

Innovative multiple nanoemulsion (W/O/W) based on Chilean honeybee pollen improves their permeability, antioxidant and antibacterial activity

Beehive derivatives, including honeybee pollen (HBP), have been extensively studied for their beneficial health properties and potential therapeutic use. Its high polyphenol content gives it excellent antioxidant and antibacterial properties. Today its use is limited due to poor organoleptic properties, low solubility, stability, and permeability under physiological conditions. A novel edible multiple W/O/W nanoemulsion (BP-MNE) to encapsulate the HBP extract was designed and optimized to overcome these limitations. The new BP-MNE has a small size (∼100 nm), a zeta potential greater than +30 mV, and efficiently encapsulated phenolic compounds (∼82%). BP-MNE stability was measured under simulated physiological conditions and storage conditions (4 months); in both cases, stability was promoted. The formulation's antioxidant and antibacterial (Streptococcus pyogenes) activity was analyzed, obtaining a higher effect than the non-encapsulated compounds in both cases. In vitro permeability was tested, observing a high permeability of the phenolic compounds when they are nanoencapsulated. With these results, we propose our BP-MNE as an innovative solution to encapsulate complex matrices, such as HBP extract, as a platform to develop functional foods.

Ag NPs decorated on the magnetic rod-like hydroxyapatite/MIL-101(Fe) nanocomposite as an efficient catalyst for the reduction of some nitroaromatic compounds and as an effective antimicrobial agent

A rod-like magnetic nanocomposite was successfully synthesized in this work by loading Ag and Fe₃O₄ nanoparticles onto the surface of the hydroxyapatite/MIL-101(Fe) metal-organic framework. Various techniques were used to investigate the crystalline nature, size, morphology, and magnetic and structural properties of the HAP/MIL-101(Fe)/Ag/Fe₃O₄ nanocomposite, including X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), BET surface area measurements, and zeta potential analysis. The results indicate that the nanocomposite sample is composed of Ag and Fe₃O₄ nanoparticles adhered to rod-like hydroxyapatite/MIL-101(Fe). The catalytic and antibacterial abilities of the as-prepared HAP/MIL-101(Fe)/Ag/Fe₃O₄ were studied. This nanocomposite was utilized as a heterogeneous catalyst for the catalytic reduction of toxic pollutants, including 4-nitrophenol (4-NP), 2-nitrophenol (2-NP), 2,4-dinitrophenol (2,4-NP), 4-nitroaniline (4-NA), and 2-nitroaniline (2-NA) by NaBH₄ in water and at room temperature. These compounds were converted to their amine derivatives within 8-18 min with rate constant values equal to 0.2, 0.3, 0.33, and 0.47 min^-1, respectively. This quaternary magnetic catalyst can be easily separated from the reaction medium using an external magnetic field and reused. The synthesized nanocomposite maintained its efficiency in reducing nitroaromatic compounds after 5 runs, showing the high stability of the catalyst. Besides, the antibacterial activity of the nanocomposite against Gram-negative and Gram-positive bacteria was evaluated using the disk diffusion method. The inhibition zone diameter of the nanocomposite against Staphylococcus aureus, Staphylococcus saprophyticus, and Escherichia coli was measured to be 17, 14, and 12 mm, respectively.

Progress in Laser Ablation and Biological Synthesis Processes: "Top-Down" and "Bottom-Up" Approaches for the Green Synthesis of Au/Ag Nanoparticles

Because of their small size and large specific surface area, nanoparticles (NPs) have special properties that are different from bulk materials. In particular, Au/Ag NPs have been intensively studied for a long time, especially for biomedical applications. Thereafter, they played a significant role in the fields of biology, medical testing, optical imaging, energy and catalysis, MRI contrast agents, tumor diagnosis and treatment, environmental protection, and so on. When synthesizing Au/Ag NPs, the laser ablation and biosynthesis methods are very promising green processes. Therefore, this review focuses on the progress in the laser ablation and biological synthesis processes for Au/Ag NP generation, especially in their fabrication fundamentals and potential applications. First, the fundamentals of the laser ablation method are critically reviewed, including the laser ablation mechanism for Au/Ag NPs and the controlling of their size and shape during fabrication using laser ablation. Second, the fundamentals of the biological method are comprehensively discussed, involving the synthesis principle and the process of controlling the size and shape and preparing Au/Ag NPs using biological methods. Third, the applications in biology, tumor diagnosis and treatment, and other fields are reviewed to demonstrate the potential value of Au/Ag NPs. Finally, a discussion surrounding three aspects (similarity, individuality, and complementarity) of the two green synthesis processes is presented, and the necessary outlook, including the current limitations and challenges, is suggested, which provides a reference for the low-cost and sustainable production of Au/Ag NPs in the future.