Syzygium cumini leaf and seed extract mediated biosynthesis of silver nanoparticles and their characterization

BACKGROUND: Plant mediated synthesis of metallic nanoparticles has been studied and reported, however, to date, the biomolecules involved in the synthesis of metallic nanoparticles have not been characterized. This study was therefore undertaken to characterize the biomolecules of Syzygium cumini involved in the synthesis of silver nanoparticles. RESULTS: Synthesis kinetics and morphological characterization of silver nanoparticles (SNP) synthesized using leaf extract (LE) and seed extract (SE) as well as their polar (water) fractions from Syzygium cumini were compared. The polyphenols content and high performance liquid chromatography (HPLC) profile of different fractions revealed good correlation between size and synthesis rate of SNP. SE contains more polyphenols and biochemical constituents than LE and therefore, showed higher synthesis rate and bigger sized SNP. To analyse the nature of biomolecules involved in the synthesis of SNP, LE and SE were fractionated on a polarity basis by solvent–solvent partitioning. Only the water fractions of LE and SE showed potential for SNP synthesis. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis of SNP indicated that all fractions catalyze the synthesis of spherical nanoparticles. The average size of SNP synthesized by LE, leaf water fraction, SE and seed water fraction were 30, 29, 92, and 73 nm respectively. CONCLUSION: Results suggest that only highly polar soluble constituents are responsible for SNP synthesis. The size of SNP was found to be directly correlated with the amount of polyphenols as well as surfactants present in the reaction solution. Thus, the amount of polyphenols could be one of the crucial parameters determining the size and distribution of SNP. Copyright © 2010 Society of Chemical Industry     

Monodisperse magnetic nanoparticles for biomedical applications

Magnetic nanoparticles that are superparamagnetic with high saturation moment have great potential for biomedical applications. Solution‐phase syntheses have recently been applied to make various kinds of monodisperse magnetic nanoparticles with standard deviation in diameter of less than 10%. However, the surface of these nanoparticles is coated with a layer of hydrocarbon molecules due to the use of lipid‐like carboxylic acid and amine in the syntheses. Surface functionalization leads to the formation of water‐soluble nanoparticles that can be further modified with various biomolecules. Such functionalization has brought about several series of monodisperse magnetic nanoparticle systems that have shown promising applications in protein or DNA separation, detection and magnetic resonance imaging contrast enhancement. The goal of this mini review is to summarize the recent progress in the synthesis and surface modification of monodisperse magnetic nanoparticles and their applications in biomedicine. Copyright © 2007 Society of Chemical Industry     

Plant mediated green synthesis and antibacterial activity of silver nanoparticles using Crataegus douglasii fruit extract

In this study, silver nanoparticles were synthesized using the Crataegus douglasii fruit extract as a reducing agent. The reaction process was monitored by UV–vis spectroscopy. Further characterization was carried out using scanning electron microscopy (SEM). To optimize the biosynthesis of silver nanoparticles, the effect of process variables such as extract concentrations, mixing ratio of the reactants, time and pH were also investigated. The SEM images showed silver nanoparticles with 29.28 nm size and nearly spherical shape at 24 h interaction time. The antibacterial activity of the synthesized silver nanoparticles was confirmed against Staphylococcus aureus and Escherichia coli.     

One-step synthesis and characterization of polyelectrolyte-protected gold nanoparticles through a thermal process

Polyelectrolyte-protected gold nanoparticles have been facilely obtained by heating an amine-containing polyelectrolyte/HAuCl₄ aqueous solution without the additional step of introducing other reducing agents. All experimental data indicate that different initial molar ratio of polyelectrolyte to gold can lead to the formation of dispersed nanoparticles, quasi one-dimensional aggregates of nanoparticles or bulk metal deposits. More importantly, the growth kinetics of gold particles thus formed can be tuned by changing the initial molar ratio of polyelectrolyte to gold.     

Size-controlled green synthesis of silver nanoparticles assisted by L-cysteine

A green and size-controlled synthesis of silver nanoparticles (Ag NPs) in aqueous solution with the assistance of L-cysteine is presented. The size of Ag NPs decreases with the increase of L-cysteine concentration, and thus can be controlled by adjusting L-cysteine concentration. TEM analysis shows that Ag NPs with an average size of 3 nm can be produced in the presence of 1.0 mmol/L L-cysteine, about one sixth of the size of Ag NPs obtained in the absence of L-cysteine (17 nm). The as-synthesized silver colloidal solution is stable and can be stored at room temperature for at least two months without any precipitation. This L-cysteine assisted method is simple, feasible and efficient, and would facilitate the production and application of Ag NPs.     

生物源材料绿色制备金纳米粒子的研究进展

传统合成金纳米粒子(AuNPs)的方法主要分为物理法和化学法.物理法合成效率低且合成的AuNPs的分散性差,使其在生物医学领域的应用大大受限;而化学法能耗大、运行成本高,使用会对人体健康和生态系统造成危害的化学试剂.为克服以上缺点,实现AuNPs合成的可持续路线,绿色化学合成法已成为该领域的研究热点.简要总结了AuNPs绿色合成技术的优点,重点介绍了近年来以植物源材料、藻类、真菌及其产物、细菌及其产物等天然试剂为原材料的AuNPs绿色合成的研究进展,剖析了AuNPs绿色制备方法未来将面临的挑战,并对该方法的应用前景进行了展望.     

Effect of accelerator in green synthesis of silver nanoparticles

Silver nanoparticles (Ag-NPs) were successfully synthesized in the natural polymeric matrix. Silver nitrate, gelatin, glucose, and sodium hydroxide have been used as silver precursor, stabilizer, reducing agent, and accelerator reagent, respectively. This study investigated the role of NaOH as the accelerator. The resultant products have been confirmed to be Ag-NPs using powder X-ray diffraction (PXRD), UV-vis spectroscopy, and transmission electron microscopy (TEM). The colloidal sols of Ag-NPs obtained at different volumes of NaOH show strong and different surface plasmon resonance (SPR) peaks, which can be explained from the TEM images of Ag-NPs and their particle size distribution. Compared with other synthetic methods, this work is green, rapid, and simple to use. The newly prepared Ag-NPs may have many potential applications in chemical and biological industries.     

绿色合成桑叶银纳米粒及其抗菌抗癌活性

为了更好地开发出具有良好物理化学及生物活性的银纳米粒,利用桑叶水提取物,通过绿色方法制得桑叶银纳米粒.以AgNO3浓度、反应温度、桑叶水提物与AgNO3溶液体积比、pH以及反应时间为影响因素,优化桑叶银纳米粒最佳合成条件;通过UV-Vis、SEM及FTIR等对产物进行结构表征;通过测定抑菌圈、最小抑菌浓度和细胞毒实验评价其抗菌及抗癌活性.结果显示,最佳制备条件为:AgNO3浓度5 mmol/L、反应温度35℃、桑叶水提液与AgNO3溶液体积比1:5、反应体系pH 11.0及反应时间6 h.在此条件下制备的桑叶银纳米粒为大小均一的球形,平均粒径(48.78±0.39)nm,电位(–27.8±2.00)mV;相比于桑叶水提物,桑叶银纳米粒对大肠杆菌、铜绿假单胞杆菌、金黄色葡萄球菌、枯草芽孢杆菌及白色念球菌均表现出较好的抑菌效果,其抑菌圈分别为(11.39±1.02)、(10.50±0.92)、(10.50±0.61)、(7.90±0.79)和(8.31±0.52)mm;桑叶银纳米粒对人宫颈癌细胞〔半数抑制浓度(IC50)为60.63 mg/L〕、人肝癌细胞(IC50为26.98 mg/L)和人乳腺癌细胞(IC50为18.65 mg/L)有很好的抑制作用.     

Greener synthesis and medical applications of metal oxide nanoparticles

Over the past decade, the subject of “greener chemistry" and chemical processes has been emphasized. The “greener chemistry” improves environmental efficiency in reducing the consumption of resources and energy and achieving a stable economic development of the environment. Nanotechnology is investigating nanoscale materials that have applications in the area of biotechnology and nanomedicine alongside several other significant applications such as cosmetics, drug delivery, and biosensors. The different shapes and sizes of nanoparticles can be synthesized with physical, chemical, or biological methods. The tendency to produce nanomaterials, especially metal oxides, and use them, is increasing because of their exciting properties in the nanoscale. However, metal oxide nanoparticles produced by chemical methods have significant concerns due to hazardous and toxic chemicals and their environmental damage. The production of metal oxide nanoparticles using the principles of greener chemistry has found a special place in research. Increased awareness of greener chemistry and biological processes has necessitated using environmentally friendly methods for the production of non-toxic nanomaterials. Plants and polymeric materials as renewable and inexpensive sources have received particular attention to prepare nano biomaterials. The use of plants to synthesize metal oxide nanoparticles because of the non-use toxic pollutants is one of the environmentally friendly methods, and that's why this type of synthesis is called greener synthesis. In this review, we exhibit a total sight of greener synthesis methods for producing metal oxide nanoparticles and their medical applications.     

Plant mediated green biosynthesis of silver nanoparticles using Vitex negundo L. extract

In the present study silver nanoparticles (Ag-NPs) were synthesized from aqueous silver nitrate through a biosynthetic route using water extract of Vitex negundo L. extract which acted as a reductant and stabilizer agents, simultaneously. Formations of Ag/V. negundo were determined by UV–vis spectroscopy where surface plasmon absorption maxima can be observed at 423–432 nm. The XRD analysis shows that the Ag-NPs are of face centered cubic structure. TEM images show the well dispersed of Ag-NPs with average particle size less than 20 nm. The FT-IR spectrum indicates the presence of V. negundo in capping with silver nanoparticles.     

Green synthesis of silk sericin-capped silver nanoparticles and their potent anti-bacterial activity

In this study, a ‘green chemistry’ approach was introduced to synthesize silk sericin (SS)-capped silver nanoparticles (AgNPs) under an alkaline condition (pH 11) using SS as a reducing and stabilizing agent instead of toxic chemicals. The SS-capped AgNPs were successfully synthesized at various concentrations of SS and AgNO₃, but the yields were different. A higher yield of SS-capped AgNPs was obtained when the concentrations of SS and AgNO₃ were increased. The SS-capped AgNPs showed a round shape and uniform size with diameter at around 48 to 117 nm. The Fourier transform infrared (FT-IR) spectroscopy result proved that the carboxylate groups obtained from alkaline degradation of SS would be a reducing agent for the generation of AgNPs while COO⁻ and NH₂ ⁺ groups stabilized the AgNPs and prevented their precipitation or aggregation. Furthermore, the SS-capped AgNPs showed potent anti-bacterial activity against various gram-positive bacteria (minimal inhibitory concentration (MIC) 0.008 mM) and gram-negative bacteria (MIC ranging from 0.001 to 0.004 mM). Therefore, the SS-capped AgNPs would be a safe candidate for anti-bacterial applications.     

Aqueous solution synthesis of reduced graphene oxide-germanium nanoparticles and their electrical property testing

Aqueous solution synthesis of reduced graphene oxide-germanium nanoparticles (RGO-GeNPs) was developed using graphene oxide (GO) as stabilizer, which could be conducive to obtain better excellent electrical properties. The information about morphology and chemical composition of the nanomaterials were obtained by TEM, FTIR, EDS, and XRD measurements. Stable aqueous dispersibility of RGO-GeNPs was further improved by poly(sodium 4-styrenesulfonate) (PSS) to obtain amphiphilic polymer-coated RGO-GeNPs (PSS-RGO-GeNPs). A possible mechanism to interpret the formation of RGO-GeNPs was proposed. The as-synthesized RGO-GeNPs showed excellent battery performance when used as an anode material for Li ion batteries. The resulting nanocomposites exhibited high specific capacity and good cycling stability after 80 cycles. This study showed a facile strategy to synthetize graphene and Ge nanocomposites which can be a hopeful anode material with excellent electrical properties for lithium ion batteries.     

Spontaneous synthesis of gold nanoparticles on gum arabic-modified iron oxide nanoparticles as a magnetically recoverable nanocatalyst

A novel magnetically recoverable Au nanocatalyst was fabricated by spontaneous green synthesis of Au nanoparticles on the surface of gum arabic-modified Fe₃O₄ nanoparticles. A layer of Au nanoparticles with thickness of about 2 nm was deposited on the surface of gum arabic-modified Fe₃O₄ nanoparticles, because gum arabic acted as a reducing agent and a stabilizing agent simultaneously. The resultant magnetically recoverable Au nanocatalyst exhibited good catalytic activity for the reduction of 4-nitrophenol with sodium borohydride. The rate constants evaluated in terms of pseudo-first-order kinetic model increased with increase in the amount of Au nanocatalyst or decrease in the initial concentration of 4-nitrophenol. The kinetic data suggested that this catalytic reaction was diffusion-controlled, owing to the presence of gum arabic layer. In addition, this nanocatalyst exhibited good stability. Its activity had no significant decrease after five recycles. This work is useful for the development and application of magnetically recoverable Au nanocatalyst on the basis of green chemistry principles.     

Hydrothermal synthesis of well-stable silver nanoparticles and their application for enzymeless hydrogen peroxide detection

We reported on a facile hydrothermal synthesis of well-stable silver nanopartiles (AgNPs) from an aqueous solution of AgNO₃ and poly[(2-ethyldimethylammonioethyl methacrylate ethyl sulfate)-co-(1-vinylpyrrolidone)] (PQ11), a kind of cationic polyelectrolyte, at 100 °C without the extra introduction of other reducing agents and protective agents. Transmission electron microscopy (TEM) observation reveals that the AgNPs thus formed mainly consist of small nanoparticles about 5 nm in diameter. It is found that such dispersion can form stable AgNPs-embedded films on bare electrode surfaces and these nanoparticles exhibit remarkable catalytic performance for hydrogen peroxide (H₂O₂) detection. The sensor has a fast amperometric response time of less than 2 s. The linear range is estimated to be from 1 × 10⁻⁴ M to 0.18 M (r = 0.998) and the detection limit is estimated to be 3.39 × 10⁻⁵ M at a signal-to-noise ratio of 3, respectively.     

Synthesis of CdS nanoparticles dispersed within amphiphilic poly(urethane acrylate‐co‐styrene) films

CdS nanoparticles were prepared using amphiphilic urethane acrylate nonionomer (UAN) precursor chains having a poly(propylene oxide)‐based hydrophobic segment and a hydrophilic poly(ethylene oxide) segment. Cadmium salts were first dissolved in UAN/styrene solutions, and then the solutions were copolymerized to obtain poly(urethane acrylate‐co‐styrene) films containing dissolved cadmium salts. After reduction with H₂S gas, freestanding films containing CdS nanoparticles were obtained. Transmission electron microscopy images of the films showed that 9.67‐nm CdS nanoparticles were dispersed within the poly(urethane acrylate‐co‐styrene) matrix. The formation of CdS nanoparticles was also confirmed with UV absorption spectra and photoluminescence emission spectra of the films. Transmission electron microscopy and dynamic mechanical analysis measurements confirmed that hydrophilic/hydrophobic microphase separation in UAN/styrene solutions occurred during the dissociation of the cadmium salts, and the microphase‐separated structures were locked in by crosslinking copolymerization. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2357–2363, 2005     

Size‐controlled gold nanoparticles inside polyacrylamide microgels

Gold nanoparticles (AuNPs) of different sizes were synthesized into a crosslinked network of polyacrylamide (PAAm) microgels. PAAm was prepared by means of semicontinuous inverse heterophase polymerization under monomer‐starving conditions with a z‐average particle size of 384 ± 18 nm. AuNPs with controlled size were obtained by a reduction reaction of Au⁺³ to Au⁰ from a gold(III) chloride trihydrate (HAuCl₄) solution inside microgel the crosslinked network (AuNP‐PAAm). The reduction reaction was verified for 2 h by ultraviolet–visible spectroscopy (UV–vis). AuNP–PAAm exhibited a particle size between 288 ± 12 and 230 ± 15 nm at HAuCl₄ concentrations of 0.4 and 1.3 mM, respectively. The AuNP–PAAms were observed by transmission electron microscopy, and their sizes were determined to be 19 ± 2 nm (1.3 mM) and 17 ± 2 nm (1.1 mM). With UV–vis spectroscopy, we detected the formation of AuNPs at a wavelength of 552 nm, and with X‐ray diffraction analysis, we proved that the crystal arrangement was face‐centered cubic. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43560.     

金纳米颗粒的微反应连续合成

金纳米颗粒具有特征性紫外-可见吸收光谱,在分析检测领域被广泛应用。为了突破间歇搅拌反应制备金纳米颗粒的技术局限,提出了一种连续流微反应方法。该方法在酸性条件下借助螺纹管实施HAuCl₄和Na₃Ct水溶液的快速均匀混合,引入惰性溶剂避免颗粒在反应器内沉积,利用膜分相装置完成油水在线相分离,实现了金纳米颗粒的连续稳定制备。探索了反应物摩尔比、浓度、停留时间、水油体积比、pH等因素对于颗粒粒径分布和吸收光谱的影响规律,成功制备了平均粒径20~24 nm、分散因子小于10%的窄分布金纳米颗粒。     

Polymer electrets and their applications

Polymer electrets have revealed great potential application in electromechanical devices because of the low weight, large quasi-piezoelectric sensitivity, and excellent flexibility. For an electret, a permanent and macroscopic electric field exists on the surface, principally led by a macroscopic electrostatic charge on the surface or a net orientation of polar groups inside the object. Here, progress in the development of polymer electrets is reviewed. After a brief retrospect of the research courses and those typical polymer electrets that are classified into fluorine polymer and nonfluorine polymer, we present a survey on the charging methods, including corona, soft X-ray, contact, thermal and monoenergetic particle beams. The latest representative applications (i.e., power harvesting, sensors, field effect transistors, and biomedicine) based on polymer electrets are also summarized. Finally, we complete this review with a discussion on perspectives and challenges in this field.     

Morphological changes of gel-type functional polymers after intermatrix synthesis of polymer stabilized silver nanoparticles

This paper reports the results of intermatrix synthesis (IMS) of silver metal nanoparticles (Ag-MNPs) in Purolite C100E sulfonic ion exchange polymer of the gel-type structure. It has been shown that the surface morphology of the initial MNP-free polymer is absolutely smooth, but it dramatically changes after the kinetic loading of Ag on the polymer and then IMS of Ag-MNPs. These morphological changes can be explained by the interaction of Ag-NPs with the polymer chains, leading to a sort of additional cross-linking of the polymer. As a result, the modification of the gel-type matrix with Ag-MNPs leads to the increase of the matrix cross-linking, which results in the increase of its surface area and the appearance of nanoporosity in the polymer gel. Ag-MNPs are located near the polymer surface and do not form any visible agglomerations. All these features of the nanocomposites obtained are important for their practical applications in catalysis, sensor applications, and bactericide water treatment.