Black pepper (Piper nigrum) fruit-based gold nanoparticles (BP-AuNPs): Synthesis, characterization, biological activities, and catalytic applications – A green approach

As compared to conventional techniques, currently nanotechnology has gained significant attention of scientists for the development of plant-based natural nanoparticles (NPs) due to their safety, effectiveness, and environment friendly nature. The current study was aimed for development, characterization (energy-dispersive X-ray, ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, and scanning electron microscopy), and evaluation of the biological efficiency of black pepper (BP; Piper nigrum) fruit-based gold NPs (BP-AuNPs) through different in vitro and in vivo assays. BP extract revealed maximum antibacterial and antifungal potential against Escherichia coli (24 mm) and Aspergillus flavus (47 mm), respectively. However, BP-AuNPs (200 µg·mL−1) inhibited the urease, xanthine oxidase, and carbonic acid-II activities with a percent inhibition of 83.11%, 91.28%, and 86.87%, respectively. Further, the anti-inflammatory effect of BP extract at the dose of 100 mg·kg−1 was 72.66%, whereas for BP-AuNPs it was noticed to be 91.93% at the dose of 10 mg·kg−1. Similarly, the extract of BP and prepared AuNPs demonstrated significant (p < 0.01) sedative effect at all tested doses. The BP-AuNPs catalytically reduced methyl orange dye. Results suggest that BP-AuNPs possess significant biological activities, and further studies must be conducted to identify the probable mechanism of action associated with these activities.

A comprehensive review on green synthesis of titanium dioxide nanoparticles and their diverse biomedical applications

Metal oxide nanoparticles (NPs) have found a variety of applications in numerous industrial, medical, and environmental fields s, attributable to recent advances in the nanotechnology field. Titanium dioxide nanoparticles (TiO2-NPs) have gained importance as metal oxide NPs due to their potential in various fields, particularly nanomedicine and other biomedicine fields. Several studies have confirmed that NPs produced via the biosynthesis route using natural resources have significant advantages such as fewer toxic contaminants, less subsequent complex chemical synthesis, environmental friendliness, cost-effectiveness, and stability when compared to NPs produced by conventional methods, and its production with controlled shapes and sizes. Therefore, considerable effort is being expended to implement biological synthesis methods with these proven advantages. TiO2-NPs can be made using a variety of biological, chemical, and physical methods. Physicochemical methods are costly, emit high levels of toxic chemicals into the atmosphere, and consume a lot of energy. On the other hand, the biological approach is an environmentally safe, cost-effective, dependable, convenient, and easy way to synthesize TiO2-NPs. In this review, the bio-mediated synthesis, as well as various biomedical applications of TiO2-NPs, were discussed.

Protective role of foliar application of green-synthesized silver nanoparticles against wheat stripe rust disease caused by Puccinia striiformis

Green-synthesized nanoparticles have a tremendous antimicrobial potential to be used as an alternative to hazardous fungicides. In this study, the green synthesis of silver nanoparticles (AgNPs) was performed by using Moringa oleifera leaf extract as a reducing and stabilizing agent. The synthesized AgNPs were subjected to different characterization techniques. UV-visible spectroscopy confirmed the surface plasmon resonance band in the range of 400–450 nm, and zeta analysis revealed that the synthesized AgNPs ranged 4–30 nm in size. Scanning electron microscopy depicted tiny fused rectangular segments and the crystalline nature of the synthesized AgNPs was confirmed using X-ray diffraction. Energy dispersive X-ray (EDX) detector confirmed the presence of metallic silver ions. Fourier-transform infrared analysis revealed the presence of phenols as main reducing agents in the plant extract. Foliar application of different concentrations (25, 50, 75, and 100 ppm) of AgNPs was applied on wheat plants inoculated with Puccinia striiformis to assess the disease incidence against stripe rust disease. AgNPs at a conc. of 75 ppm were found to be more effective against wheat stripe rust disease. Furthermore, the application of AgNPs enhanced morpho-physiological attributes and reduced nonenzymatic compounds and antioxidant enzymes in wheat. The present study highlights the potential role of the green-synthesized AgNPs as a biological control of yellow rust disease.

Efficient degradation of methyl orange and methylene blue in aqueous solution using a novel Fenton-like catalyst of CuCo-ZIFs

In this study, the synthesized CuCo-zeolitic imidazolate framework (ZIF) catalyst was used to degrade methyl orange (MO) and methylene blue (MB) in water via a novel Fenton-like catalytic reaction. Effects of catalyst dosage, H2O2 concentration, initial concentration of the contaminants, and reaction time were evaluated. The results showed that MO and MB decomposition efficiencies were highly influenced by CuCo-ZIF concentration. The presence of H2O2 accelerated the degradation reaction of both MO and MB. Although it took 100 min to complete the removal of MB, it was 60 min for MO. At concentrations of MO and MB lower than 40 mg·L−1, the catalyst showed an almost complete degradation. The CuCo-ZIF catalyst presented a good recyclability with more than 90% removal of MO and MB after four times and five times reuse, respectively. These results demonstrated that MO and MB were efficiently degraded by a Fenton-like catalyst of CuCo-ZIFs and its potential in industrial wastewater treatment.

Effects of nitrogen and phosphorus on Microcystis aeruginosa growth and microcystin production

In the present study, the effects of nitrogen (N) and phosphorus (P) on the growth of Microcystis aeruginosa and the production of microcystins (MCs) were investigated. The results showed that the growth of M. aeruginosa was not merely determined by N or P, but both nutrients were limiting for the species. Moreover, an excess of N and constant P in the culture medium could stimulate the growth of M. aeruginosa, whereas the growth of the species was inhibited in the culture medium containing excess of P and constant N. The optimal growth of M. aeruginosa was at an N:P ratio of 0.1 with the maximal optical density of 1.197 at 680 nm (OD680), whereas the maximal microcystin-LR (MC-LR) content of 228.2 μg·L−1 observed in the culture medium with an N:P ratio of 5. Interestingly, MC-LR production occurred under conditions of N starvation, thereby suggesting that the growth rate of M. aeruginosa was not related to MC-LR production under conditions of nutrient stress.

Kinetic study on the reaction between Incoloy 825 alloy and low-fluoride slag for electroslag remelting

A kinetic model for the reactions between the low-fluoride slag CaF2–CaO–Al2O3–MgO–Li2O–TiO2 and Incoloy 825 alloy was proposed based on the two-film theory. The applicability of the model was verified to predict the variation of components in the slag–metal reaction process. The results show that the controlling step of the reaction 4[Al] + 3(TiO2) = 3[Ti] + 2(Al2O3) is the mass transfer of Al and Ti in the liquid alloy and the controlling step of the reactions 4[Al] + 3(SiO2) = 3[Si] + 2(Al2O3) and [Si] + (TiO2) = [Ti] + (SiO2) is the mass transfer of SiO2 in the molten slag. With increasing TiO2 content in the slag from 3.57% to 11.27%, the Al content in the alloy decreased whereas the Ti content increased gradually. The Si content continued to decrease during the slag–metal reaction. Soluble oxygen in the alloy reacts with Al, Ti, and Si, resulting in a decrease of the oxygen content in the alloy. The variations of TiO2 content were in good agreement with the calculated results by the kinetic model whereas the measured results of Al2O3 and SiO2 in the slag were lower than the calculated results, which is mainly due to the volatilization of fluoride.

Stille, Heck, and Sonogashira coupling and hydrogenation catalyzed by porous-silica-gel-supported palladium in batch and flow

Owing to their recyclability, heterogeneous transition metal catalysts represent a means of conserving depletable resources for the synthesis of pharmaceutical, agricultural, and functional chemicals. We recently developed a novel heterogeneous palladium catalyst and demonstrated its synthetic availability for Suzuki–Miyaura cross-coupling. Herein, we report the further application of the present catalyst to cross-coupling reactions in batch and flow, as well as a hydrogenative reduction reaction in flow. We demonstrate the flow synthesis for useful material, a liquid crystal, and a 1 h sequential operation of the coupling reaction and hydrogenation reaction.

In-flow enantioselective homogeneous organic synthesis

The use of enabling technologies, such as flow reactors, three-dimensional-printed devices, and electrochemistry, in the stereoselective synthesis of enantioenriched compounds is presented, with a special focus on the most significant contributions to the field reported in the last few years.

Green synthesis of silver nanoparticles using aqueous extract of Citrus sinensis peels and evaluation of their antibacterial efficacy

The resistance of microorganisms towards antibiotics remains a big challenge in medicine. Silver nanoparticles (AgNPs) received attention recently for their characteristic nanosized features and their ability to display antimicrobial activities. This work reports the synthesis of AgNPs using the Citrus sinensis peels extract in their aqueous, mild, and less hazardous conditions. The effect of concentration variation (1%, 2%, and 3%) of the plant extracts on the size and shape of the AgNPs was investigated. The antimicrobial activities were tested against gram-positive Staphylococcus aureus and gram-negative Klebsiella pneumoniae. Absorption spectra confirmed the synthesis by the surface Plasmon resonance peaks in the range 400–450 nm for all the AgNPs. FTIR spectra confirmed that Citrus sinensis peels extract acted as both reducing and surface passivating agent for the synthesized AgNPs. TEM revealed spherical AgNPs with average size of 12 nm for 3% concentration as compared to the agglomeration at 1% and 2%. All the AgNPs synthesized using Citrus sinensis peels extracts (1%, 2%, and 3%) exhibited antimicrobial activity against both gram-positive and negative bacteria. These results indicated a simple, fast, and inexpensive synthesis of silver nanoparticles using the Citrus sinensis peels extract that has promising antibacterial activity.

Study on titanium dioxide nanoparticles as MALDI MS matrix for the determination of lipids in the brain

The structures of lipids are diverse, and thus, lipids show various biological functions. Systematic determination of lipids in organisms has always been a concern. In this paper, a methodology on the matrix-assisted laser desorption ionization mass spectrometry (MALDI MS), with titanium dioxide nanoparticles (TiO2 NPs) as the matrix, was studied for lipid determination. The results showed that the following conditions were preferable in the determination of small-molecule lipids (such as hypoxanthine, guanosine, uridine, and cytidine), lipid standards (such as GC, GM, TG, phosphatidylethanolamine, phosphatidylcholine, and ceramide), and mixed lipids (extracted from brain homogenate with methanol alone and with the B&D method): TiO2 NPs as the matrix, absolute ethanol as the solvent, 1 mg of TiO2 NPs dispersed in 1 mL of absolute ethanol as the matrix solution, NaCl as the ionization reagent, and positive mass spectrometry (MS) as the mode. Modified TiO2 NP as a new matrix for MALDI MS will be a future research direction; in addition, the characteristics of TiO2 NPs make it a potential matrix for imaging MS.