Pingyu Wan

Photocatalytic, antimicrobial activities of biogenic silver nanoparticles and electrochemical degradation of water soluble dyes at glassy carbon/silver modified past electrode using buffer solution

In the present research work a novel, nontoxic and ecofriendly procedure was developed for the green synthesis of silver nano particle (AgNPs) using Caruluma edulis (C. edulis) extract act as reductant as well as stabilizer agents. The formation of AgNPs was confirmed by UV/Vis spectroscopy. The small and spherical sizes of AgNPs were conformed from high resolution transmission electron microscopy (HRTEM) analysis and were found in the range of 2-10nm, which were highly dispersion without any aggregation. The crystalline structure of AgNPs was conformed from X-ray diffraction (XRD) analysis. For the elemental composition EDX was used and FTIR helped to determine the type of organic compounds in the extract. The potential electrochemical property of modified silver electrode was also studied. The AgNPs showed prominent antibacterial motion with MIC values of 125 μg/mL against Bacillus subtilis and Staphylococcus aureus while 250 μg/mL against Escherichia coli. High cell constituents release was exhibited by B. subtilis with 2 × MIC value of silver nanoparticles. Silver nanoparticles also showed significant DPPH free radical scavenging activity. This research would have an important implication for the synthesis of more efficient antimicrobial and antioxidant agent. The AgNP modified electrode (GC/AgNPs) exhibited an excellent electro-catalytic activity toward the redox reaction of phenolic compounds. The AgNPs were evaluated for electrochemical degradation of bromothymol blue (BTB) dyes which showed a significant activity. From the strong reductive properties it is obvious that AgNPs can be used in water sanitization and converting some organic perilous in to non-hazardous materials. The AgNPs showed potential applications in the field of electro chemistry, sensor, catalyst, nano-devices and medical.

Antioxidant and catalytic applications of silver nanoparticles using Dimocarpus longan seed extract as a reducing and stabilizing agent

In this study, a simple and environmental friendly method was developed for the synthesis of silver nanoparticles (Ag-NPs) using Dimocarpus longan seed extract as a source of reducing and stabilizing agent. The appearance of a surface plasmon resonance peak at 432nm confirmed the synthesis of silver nanoparticles (UV-visible spectroscopy). The biosynthesized Ag-NPs were face centered cubic structures (XRD) with an approximate particle size of 40nm (TEM). Optimization study revealed that 10mL of plant extract (2mM AgNO3) at 180min of incubation resulted the optimum product synthesis. Poly-phenolic compounds were majorly involved in the reduction of silver ions into Ag-NPs (FT-IR). The catalytic activities of Ag-NPs were assessed against the photo-catalytic degradation of methylene blue and chemo catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The results indicated that the prepared Ag-NPs have strong chemo catalytic activity with a complete reduction of 4-NP to 4-AP within 10min. Similarly, Ag-NPs displayed higher photo-catalytic activity (K=0.12) as compared to commercial Ag-NPs (K=0.003). In addition, the silver nanoparticles exhibited a promising antioxidant activity in scavenging DPPH radicals. The findings of this study conclude that the biosynthesized Ag-NPs are promising agent possessing strong catalytic and reducing properties.

Biomedical applications of green synthesized Nobel metal nanoparticles

Synthesis of Nobel metal nanoparticles, play a key role in the field of medicine. Plants contain a substantial number of organic constituents, like phenolic compounds and various types of glycosides that help in synthesis of metal nanoparticles. Synthesis of metal nanoparticles by green method is one of the best and environment friendly methods. The major significance of the green synthesis is lack of toxic by-products produced during metal nanoparticle synthesis. The nanoparticles, synthesized by green method show various significant biological activities. Most of the research articles report the synthesized nanoparticles to be active against gram positive and gram negative bacteria. Some of these bacteria include Escherichia coli, Bacillus subtilis, Klebsiella pneumonia and Pseudomonas fluorescens. The synthesized nanoparticles also show significant antifungal activity against Trichophyton simii, Trichophyton mentagrophytes and Trichophyton rubrum as well as different types of cancer cells such as breast cancer cell line. They also exhibit significant antioxidant activity. The activities of these Nobel metal nano-particles mainly depend on the size and shape. The particles of small size with large surface area show good activity in the field of medicine. The synthesized nanoparticles are also active against leishmanial diseases. This research article explores in detail the green synthesis of the nanoparticles and their uses thereof.

Visible light inactivation of E. coli, Cytotoxicity and ROS determination of biochemically capped gold nanoparticles

The formation of metal nanoparticles is one of the most vast and intensifying research areas in favor of prospective applications for the advancement of new technologies. It is a well-founded, significant feature of green chemistry that making marvelous interconnection between nano-biotechnology and microbial biotechnology. In the present research, the aqueous extract of medicinally important plant Coptis Chinensis (in Chinese called gold thread) was applied for the synthesis of gold nanoparticles (Au-NPs). The crystalline structure, size, shape and dispersion of Au-NPs were confirmed by using various characterization techniques i.e. X-ray Diffraction (XRD), High Resolution Transmission Electron Microscope (HRTEM) and Energy Dispersive X-ray (EDX). Well dispersed face centered cubic crystalline structures were obtained in the this contribution. The possible phyto-chemicals involved in the reduction and stabilization of Au-NPs were confirmed by Fourier Transform Infrared Spectroscopy (FT-IR). The prepared NPs were tested against highly drug resistance bacterium Escherichia coli both in light and dark. The results illustrated that the antibacterial efficiency of photo irradiated Au-NPs was several times higher than in dark Au-NPs. The zone of inhibition for irradiated Au-NPs was19xa0±xa00.5xa0mm, which was higher than in dark 14xa0±xa00.4xa0mm. This high antibacterial activity of photo irradiated Au-NPs are due to the production of reactive oxygen species which is responsible for the inhibition of bacteria.

Efficient and Sustainable Production of Alumina by Electrolysis of Sodium Carbonate

Aluminium is a leading material for the expanding global economy and its precursor alumina has been produced by extraction of bauxite ores using Bayer and sinter processes for over 100 years. The Bayer process involves digesting and leaching the ores using a hot alkali solution and precipitating aluminum hydroxide from the supersaturated aluminate leachate (green liquor) using aluminum hydroxide seed particles. The caustic liquor remaining after precipitation (spent green liquor) is concentrated by evaporation and recycled back to the extraction step (Figure 1A). The sinter process consists of sintering the ores with sodium carbonate and calcium oxide at above 1000 8C, leaching the sinter mass with water (or dilute NaOH solution) and precipitating Al(OH)3 with carbon dioxide, concentrating the spent green liquor by evaporation, and circulating the concentrate to the next sinter step (Figure 1B). The sinter process is more effective for poor-grade diaspore ores than the Bayer process, but its high energy consumption makes it uneconomical compared to the Bayer process and its environmental impact has been a critical issue. The Bayer process is relatively simple because of the ease of automation and delivers 90% of the world-wide production of alumina. However, the seed precipitation of the Bayer process is typically very slow (generally it takes 48–70 h) and requires a large quantity of aluminum hydroxide seeds (seed ratios of 1–2) while only up to 50% of sodium aluminate in the green liquor is decomposed into aluminum hydroxide precipitates. Consequently, large tonnages of sodium aluminate remain in the circuit of the process. The presence of a large amount of aluminate in the Bayer liquor has significant adverse effects on the leaching efficiency of ore digestion. These problems are the major factors for the loss of productivity of the Bayer-based plants. In addition, the Bayer process becomes uneconomical for processing diaspore ores of alumina-to-silica (A/ S) mass ratios < 9. Since the 1970s, the world-wide production of minerals and metals from degrading natural resources has increased. The global production of alumina increased at an average rate of 3.3% per year while the Chinese production of alumina grew at an average rate of 25% between 2001 and 2007. The aluminum industry is one of the major high-pollution and energy-intensive industries. With increasing environmental constraints, continuously increasing demand for aluminum and at the same time the depletion of high-grade bauxite ores, the development of efficient and sustainable production processes for alumina is of great significance. The key to improving the efficiency of the Bayer process is to increase the efficiency of aluminate decomposition and the precipitation rate of aluminum hydroxide. The strategies include addition of surfactants, glucose or methanol, to the green liquor. However, the improvement is limited because of the inherent equilibrium between Al(OH)4 , Al(OH)3, and OH of the seeded precipitation [Eq. (1)],

Energy-saving synthesis of potassium iodatevia electrolysis of potassium iodine and O2 in a membraneless cell

An electrochemical process for producing potassium iodate based on oxidation of KI coupled with oxygen reduction reaction in a newly designed cell is reported. By using an Ag-modified oxygen reduction cathode, the proposed cell needed no ion exchange membrane, and the current efficiency for KIO3 was confirmed to be over 96%, the corresponding cell voltage was only 0.7–0.8 V.

In vitro pharmacological screening of three newly synthesised pyrimidine derivatives

The antibacterial and antifungal activities of three new pyrimidine derivatives, namely, 2,6-bis(4,6-dimethylpyrimidin-2-ylthio)benzene-1,4-diol (1),3,5-bis(4,6-dimethylpyrimidin-2-ylthio)-2-methylbenzene-1,4-diol (2) and 3,5-bis(4,6-dimethylpyrimidin-2-ylthio)-2-methoxybenzene-1,4-diol (3), synthesised by electrochemical method are presented here. The compounds were screened for their activities against Gram-positive and Gram-negative bacteria, Bacillus subtilis, Staphylococcusaureus, Escherichia coli and a pathogenic fungus Aspergillus niger. The results show that these compounds have significant activity against these bacteria and fungus. The minimum inhibitory concentration of compound 1 was determined as 62.5 μg/mL against B. subtilis, 125 μg/mL against E. coli and 250 μg/mL against S. aureus establishing its promising activities higher than susceptible ranges.

Enhanced antimicrobial, anti-oxidant applications of green synthesized AgNPs- an acute chronic toxicity study of phenolic azo dyes & study of materials surface using X-ray photoelectron spectroscopy

The drug resistant bacteria and textile contaminations of water cause different sever health problem throughout the world. To overcome this issue, new environmental benign materials and methods are needed. Plant metabolites directed synthesis of nanoparticles is considered eco-friendly and easy in synthesis. Therefore, it was explicit for the synthesis of AgNPs. The prepared AgNPs were evaluated for antibacterial, antioxidant, photo-catalytic and electrochemical degradation properties as well as toxicity of degradation products on aquatic life. X-Ray Photoelectron Spectroscopy (XPS) has been used for analyzing the surface chemistry of prepared AgNPs. The particle size determines the interaction of nanoparticles with pathogens. Both Gram positive and negative bacteria (Escherichia coli and Staphylococcus areous) are used to determine the anti-microbial potency of the green synthesized AgNPs. The synthesized silver nanoparticles showed significant anti-bacterial applications against B. subtilus and S. aureus. The anti-oxidant applications of AgNPs also studied on comparison with vitamin C. The toxicity of the phenolic Azo dyes (PDA) has been studied against Fish, Daphnia and Green Algae. The electrode potential was studied in the electrochemical redox reaction of hydroxy phenol in aqueous media. Simple electrolyte was used to determine the current efficiency. For the stability of electrode multi cyclic voltammetry was also studied during redox reaction, which showed stability under the potential 0.4 to 0.2u202fV.