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.     

One step green synthesis of hexagonal silver nanoparticles and their biological activity

Hexagonal and spherical silver nanoparticles were prepared by in situ and green synthesis using sun light as reducing agent with assistance newly prepared cationic surfactant which act also as capping agents. The silver nanoparticles formation was investigated using UV–vis spectrophotometer, transmission electron microscope (TEM), dynamic light scattering (DLS), energy dispersive X-ray (EDX) and FTIR. The results showed formation uniform, well arrangement hexagonal and spherical shapes. Increasing hydrophobic chain length increase the stability and amount of AgNPS. Both prepared surfactants and surfactants capping silver nanoparticles showed high antimicrobial activity against Gram-positive and Gram-negative bacteria.     

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.     

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.     

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.     

Synthesis of silver nanoparticles and antibacterial property of silk fabrics treated by silver nanoparticles

A silver nanoparticle solution was prepared in one step by mixing AgNO₃ and a multi-amino compound (RSD-NH₂) solution under ambient condition. RSD-NH₂ was in-house synthesized by methacrylate and polyethylene polyamine in methanol, which has abundant amino and imino groups. However, the characterization of silver nanoparticles indicated that these nanoparticles are easy to agglomerate in solution. Therefore, an in situ synthesis method of silver nanoparticles on the silk fabrics was developed. The examined results confirmed that the in situ synthesized silver nanoparticles were evenly distributed on the surface of fibers. The inhibition zone test and the antibacterial rate demonstrated that the finished fabrics have an excellent antibacterial property against Staphylococcus aureus and Escherichia coli. Moreover, the nanosilver-treated silk fabrics were laundered 0, 5, 10, 20, and 50 times and still retained the exceptional antibacterial property. When the treated fabrics were washed 50 times, the antibacterial rate is more than 97.43% for S. aureus and 99.86% for E. coli. The excellent laundering durability may be attributed to the tight binding between silver nanoparticles and silk fibers through the in situ synthesis. This method provides an economic method to enhance the antibacterial capability of silk fabrics with good resistance to washings.     

Rapid biological synthesis of silver nanoparticles using Kalopanax pictus plant extract and their antimicrobial activity

Silver nanoparticles (AgNPs) have promising potential in biomedicine, energy science, optics, and health care applications. We synthesized AgNPs using plant, Kalopanax pictus leaf extract. UV-visible spectrophotometric study showed the characteristic peak for AgNPs at wavelength 430 nm. The optical density at 430 nm increased after addition of plant leaf extract, indicating increase in formation of nanoparticles. Comparative time course analyses for AgNP synthesis carried out at different reaction temperatures (20, 60, and 90 °C) revealed higher reaction rate for K. pictus than Magnolia kobus plant leaf extract, which showed highest AgNP synthesis rate in the previous report. Electron microscopy analyses confirmed the presence of well dispersed AgNPs, predominantly with spherical shapes. In transmission electron microscopy, the particle size decreased with increase in temperature. Electron dispersive X-ray spectroscopy analyses indicated that Ag content increased with increase in reaction temperature. Fourier transform-infrared spectroscopy studies revealed capping of bioorganics from plant to the synthesized AgNPs. The antimicrobial activity of the synthesized AgNPs against Escherichia coli increased with increase in reaction temperature. The observations in this study will prove beneficial in approaching rapid synthesis of AgNPs and their antimicrobial application.     

纳米银材料绿色制备及其在水处理中的应用进展

针对纳米银粒子最常用的制备方法化学还原法中化学试剂的大量使用及其对环境的污染,结合近几年国内外的研究成果,介绍了纳米银的绿色制备方法,包括二糖法、多糖法、微生物合成法、植物提取物法等。同时介绍了纳米银离子在净水处理和废水处理方面的应用进展。分析认为,糖类作为还原剂可生成具有良好催化及杀菌性能的纳米银粒子。纳米银的形貌可控制备以及生物合成法中微生物及植物的选择技术等是今后纳米银绿色制备的发展方向。     

Coating of modified poly(ethylene terephthalate) fibers with sericin-capped silver nanoparticles for antimicrobial application

Polymer Bulletin - In this work, a kind of amine-type PET fibers was synthesized by reacting hexamethylenediamine (HMDA) with methacrylic acid-g-poly(ethylene terephthalate) (PET-g-MAA) fibers for...     

Plant‐mediated synthesis of silver and gold nanoparticles and their applications

Nanobiotechnology deals with the synthesis of nanostructures using living organisms. Among the use of living organisms for nanoparticle synthesis, plants have found application particularly in metal nanoparticle synthesis. Use of plants for synthesis of nanoparticles could be advantageous over other environmentally benign biological processes as this eliminates the elaborate process of maintaining cell cultures. Biosynthetic processes for nanoparticles would be more useful if nanoparticles were produced extracellularly using plants or their extracts and in a controlled manner according to their size, dispersity and shape. Plant use can also be suitably scaled up for large‐scale synthesis of nanoparticles. In view of this, we have reviewed here the use of plants or their extracts in the synthesis of silver and gold nanoparticles for various human applications. Copyright © 2008 Society of Chemical Industry     

Microwave-assisted green synthesis of silver nanostructures

Over the past 25 years, microwave (MW) chemistry has moved from a laboratory curiosity to a well-established synthetic technique used in many academic and industrial laboratories around the world. Although the overwhelming number of MW-assisted applications today are still performed on a laboratory (mL) scale, we expect that this enabling technology may be used on a larger, perhaps even production, scale in conjunction with radio frequency or conventional heating. Microwave chemistry is based on two main principles, the dipolar mechanism and the electrical conductor mechanism. The dipolar mechanism occurs when, under a very high frequency electric field, a polar molecule attempts to follow the field in the same alignment. When this happens, the molecules release enough heat to drive the reaction forward. In the second mechanism, the irradiated sample is an electrical conductor and the charge carriers, ions and electrons, move through the material under the influence of the electric field and lead to polarization within the sample. These induced currents and any electrical resistance will heat the sample. This Account summarizes a microwave (MW)-assisted synthetic approach for producing silver nanostructures. MW heating has received considerable attention as a promising new method for the one-pot synthesis of metallic nanostructures in solutions. Researchers have successfully demonstrated the application of this method in the preparation of silver (Ag), gold (Au), platinum (Pt), and gold-palladium (Au-Pd) nanostructures. MW heating conditions allow not only for the preparation of spherical nanoparticles within a few minutes but also for the formation of single crystalline polygonal plates, sheets, rods, wires, tubes, and dendrites. The morphologies and sizes of the nanostructures can be controlled by changing various experimental parameters, such as the concentration of metallic salt precursors, the surfactant polymers, the chain length of the surfactant polymers, the solvents, and the operation reaction temperature. In general, nanostructures with smaller sizes, narrower size distributions, and a higher degree of crystallization have been obtained more consistently via MW heating than by heating with a conventional oil-bath. The use of microwaves to heat samples is a viable avenue for the greener synthesis of nanomaterials and provides several desirable features such as shorter reaction times, reduced energy consumption, and better product yields.     

Biofilm-inactivating activity of silver nanoparticles: A comparison with silver ions

The antimicrobial activity of silver nanoparticles (AgNPs) against Pseudomonas aeruginosa PA01 planktonic and biofilm bacteria was examined; their activity was compared with that of silver ions. The inactivation of biofilms by AgNPs was greatly influenced by stirring, which caused an increased AgNP biosorption. Although the activity of AgNPs against planktonic cells was ca. 10% that of silver ions, their activity against biofilm cells was comparable to the silver ions’ activity at the same concentration after 90 min under stirring (ca. 3.5 log inactivation). AgNPs inactivated biofilms in a biosorption-dependent manner, whereas this was not the case for silver ions.     

Designed synthesis of silver nanoparticles in responsive polymeric system for their thermally tailored catalytic activity towards hydrogenation reaction

Poly(N-isopropylacrylamide-acrylamide-methacrylic acid) [p(NIPa-AAm-Ma)] polymer microgels were prepared by free radical precipitation polymerization method. AgNPs were fabricated in the sieves of polymer network by chemical reduction using AgNO₃ salt as a precursor of silver ions. Various techniques like dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier transform infrared microscopy (FTIR), and UV-Visible spectroscopy were used for characterization of pure and composite microgels. The diameter of AgNPs fabricated in polymeric network was found to be in the range of 10-15 nm. Stimuli responsive behavior of hybrid microgels was same as that of pure microgels. Catalytic efficiency of the hybrid microgels was investigated by reducing 4-Nitroaniline (4-NA) into 4-Aminoaniline (4-AA) using NaBH₄ as reducing agent under different conditions of temperature of the medium, concentration of reducing agent, 4-Nitroaniline and hybrid microgels to explore the catalysis process. Kinetic and thermodynamic aspects of reduction of 4-Nitroaniline in the presence of catalyst were also discussed on the basis of values of Arrhenius and Eyring parameters like pre-exponential factor, activation energy, enthalpy of activation and entropy of activation. Catalytic activity of the hybrid microgels was found to be thermally tunable in the temperature range of 25-70 oC. The value of rate constant (k _app ) for reduction of 4-NA was minimum at 55 °C, which can be attributed to volume phase transition of the hybrid microgels.     

原位还原制备滤纸载纳米银粒子复合材料及其催化特性

基于绿色化学的角度,直接以滤纸(FP)为基底材料,在碱性条件下无需外加还原剂和稳定剂,原位还原得到负载纳米银(AgNPs)的AgNPs/FP复合材料。通过扫描电子显微镜(SEM)、X射线电子能谱仪(EDS)、热重分析仪(TGA)和紫外-可见(UV-vis)分光光度计等对复合材料的形貌、组成和催化性能进行表征。研究结果表明,Ag⁺被还原为AgNPs后致密又均匀地负载于滤纸表面上,所制得的AgNPs/FP复合材料中纳米银呈球形、尺寸均一且团聚较少。AgNPs/FP复合材料对对硝基苯酚(4-NP)的还原具有较好的催化活性,且易于回收再利用。     

Preparation and application of silver nanoparticles on silk for imparting antimicrobial properties

Silver nanoparticles were produced by a chemical reduction method that reduced silver nitrate with reducing agents such as hydrazine and glucose. The silver nanoparticles were characterized with transmission electron microscope, scanning electron microscope, and optical microscope. The effects of process parameters such as the stirring speed, temperature, type of reducing agent, and dispersing agent on the particle size were studied. The particle size decreased with an increase in the stirring speed and a decrease in the process temperature. Smaller particles were formed when the silver nitrate was reduced by glucose versus those that were formed by reduction with hydrazine. Silver nanoparticles with average sizes of 10 and 35 nm, produced by reduction with hydrazine at 5 and 40°C, were applied to silk by an exhaust method. Silk fabrics treated with 40 ppm silver hydrosol produced at 5°C and 60 ppm silver hydrosol produced at 40°C showed 100% antimicrobial activity against the gram‐positive bacterium Staphylococcus aureus. The durability of the antimicrobial property of the treated silk fabric to washing was also examined and is presented. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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.     

Garcinia xanthochymus mediated green synthesis of ZnO nanoparticles: Photoluminescence,photocatalytic and antioxidant activity studies

Green synthesis of multifunctional zinc oxide nanoparticles (ZnO Nps) was achieved employing water extract of Garcinia xanthochymus by solution combustion synthesis. The structure and morphology were determined by XRD, UV–visible and scanning electron microscopy studies. The ZnO Nps were evaluated for photoluminescence (PL), photocatalytic and antioxidant properties. The water extract was found to comprise significantly high amounts of polyphenols and flavonoids. Powder XRD studies indicate the formation of pure wurtzite structure with absorption maximum of 370 nm corresponding to band gap energy of 3.33 eV. SEM studies reveal the formation of spongy cave like structures. The PL spectra exhibited 4 emission edges at 397, 436, 556 and 651 nm upon excitation at 325 nm because of oxygen deficiencies and zinc interstitials. Nps exhibit remarkable photodegradation of methylene blue (MB) in presence of UV and sun light. They exhibit antioxidant activity by inhibiting the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals. Therefore, the study reveals an efficient, ecofriendly and simple method for the green synthesis of multifunctional ZnO Nps.     

Preparation of acacia‐stabilized silver nanoparticles: A green approach

We report a facile approach for the spontaneous formation of silver nanoparticles in the presence of gum acacia polymer (a natural polymer) without the addition of any typical reducing agent under mild conditions. Silver nanoparticles (～ 5 nm) have been obtained by the mixing of equal amounts of 0.5 wt % aqueous solutions of acacia and silver nitrate. The formation of silver nanoparticles has been confirmed with ultraviolet–visible, Fourier transform infrared, X‐ray diffraction, and X‐ray photoelectron spectroscopy analyses. Gum acacia polymeric chains promote the reduction process and act as good stabilizers over 5 months. To confirm the formation and stabilization of the nanoparticles, a transmission electron microscope has been employed. The advantage of this methodology is that it is possible to prepare silver nanoparticles without any organic solvents or reducing agents. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Catechin-capped gold nanoparticles: green synthesis,characterization, and catalytic activity toward 4-nitrophenol reduction

An eco-friendly approach is described for the green synthesis of gold nanoparticles using catechin as a reducing and capping agent. The reaction occurred at room temperature within 1 h without the use of any external energy and an excellent yield (99%) was obtained, as determined by inductively coupled plasma mass spectrometry. Various shapes of gold nanoparticles with an estimated diameter of 16.6 nm were green-synthesized. Notably, the capping of freshly synthesized gold nanoparticles by catechin was clearly visualized with the aid of microscopic techniques, including high-resolution transmission electron microscopy, atomic force microscopy, and field emission scanning electron microscopy. Strong peaks in the X-ray diffraction pattern of the as-prepared gold nanoparticles confirmed their crystalline nature. The catalytic activity of the as-prepared gold nanoparticles was observed in the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH₄. The results suggest that the newly prepared gold nanoparticles have potential uses in catalysis.     

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.