Size-controlled Synthesis Of Silver Nanoparticles Research Articles

Eco-friendly synthesis of size-controlled silver nanoparticles by using Areca catechu nut aqueous extract and investigation of their potent antioxidant and anti-bacterial activities

Silver nanoparticles (AgNPs) have attracted considerable attention owing to their unique biological applications. AgNPs synthesized by plant extract is considered as a convenient, efficient and eco-friendly material. In this work, the aqueous extract of Areca catechu L. nut (ACN) was used as the reducing and capping agents for one-pot synthesis of AgNPs, and their antioxidant and antibacterial activities were investigated. UV (Ultra Violet)-visible spectrum and dynamic light scattering (DLS) analysis revealed that the size of AgNPs was sensitive to the synthesis conditions. The synthesized AgNPs were composed of well-dispersed particles with an small size of about 10 nm under the optimal conditions (pH value of extract was 12.0; AgNO 3 concentration was 1.0 mM; reaction time was 90 min). In addition, scanning electron microscope with energy dispersive X-ray (SEM-EDX), transmission electron microscopy (TEM) and X-ray diffraction (XRD) results further verified that the synthesized AgNPs had a stable and well-dispersed form (Zeta potential value of −30.50 mV and polydispersity index of 0.328) and a regular spherical shape (average size of 15–20 nm). In addition, Fourier transform infrared spectrometry (FTIR) results revealed that phytochemical constituents in ACN aqueous extract accounted for Ag + ion reduction, capping and stabilization of AgNPs. The possible reductants in the aqueous extract of Areca catechu L. nut were identified by high-performance liquid chromatography-electrospray ionization-quadrupole-time of flight-mass spectrometry (HPLC-ESI-qTOF/MS) method. More importantly, the synthesized AgNPs indicated excellent free radical scavenging activity of 1,1-diphenyl-2-picrylhydrazyl (DPPH , IC 50 = 11.75 ± 0.29 μg/mL) and 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS + , IC 50 = 44.85 ± 0.37 μg/mL), which were significant higher than that of ascorbic acid. Moreover, AgNPs exhibited an enhanced antibacterial activity against six selected common pathogens (especially Escherichia coli and Staphylococcus aureus ) compared with AgNO 3 solution. In a short, this study showed that the Areca catechu L. nut aqueous extract could be applied for eco-friendly synthesis of AgNPs.

Pulse-Modulated Radio-Frequency Alternating-Current-Driven Atmospheric-Pressure Glow Discharge for Continuous-Flow Synthesis of Silver Nanoparticles and Evaluation of Their Cytotoxicity toward Human Melanoma Cells.

An innovative and environmentally friendly method for the synthesis of size-controlled silver nanoparticles (AgNPs) is presented. Pectin-stabilized AgNPs were synthesized in a plasma-reaction system in which pulse-modulated radio-frequency atmospheric-pressure glow discharge (pm-rf-APGD) was operated in contact with a flowing liquid electrode. The use of pm-rf-APGD allows for better control of the size of AgNPs and their stability and monodispersity. AgNPs synthesized under defined operating conditions exhibited average sizes of 41.62 ± 12.08 nm and 10.38 ± 4.56 nm, as determined by dynamic light scattering and transmission electron microscopy (TEM), respectively. Energy-dispersive X-ray spectroscopy (EDS) confirmed that the nanoparticles were composed of metallic Ag. Furthermore, the ξ-potential of the AgNPs was shown to be −43.11 ± 0.96 mV, which will facilitate their application in biological systems. Between 70% and 90% of the cancerous cells of the human melanoma Hs 294T cell line underwent necrosis following treatment with the synthesized AgNPs. Furthermore, optical emission spectrometry (OES) identified reactive species, such as NO, NH, N2, O, and H, as pm-rf-APGD produced compounds that may be involved in the reduction of the Ag(I) ions.

Shape- and Size-Controlled Synthesis of Silver Nanoparticles Using Aloe vera Plant Extract and Their Antimicrobial Activity.

Biogenic synthesis of silver nanoparticles (AgNP) was performed at room temperature using Aloe vera plant extract in the presence of ammoniacal silver nitrate as a metal salt precursor. The formation of AgNP was monitored by UV-visible spectroscopy at different time intervals. The shape and size of the synthesized particle were visualized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. These results were confirmed by X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses and further supported by surface-enhanced Raman spectroscopy/Raman scattering (SERS) study. UV-visible spectrum has shown a sharp peak at 420 nm and further evidenced by FTIR peak profile (at 1587.6, 1386.4, and 1076 cm−1 with corresponding compounds). The main band position with SERS was noticed at 1594 cm−1 (C–C stretching vibration). When samples were heated under microwave radiation, AgNP with octahedron shapes with 5–50 nm were found and this method can be one of the easier ways to synthesis anisotropic AgNP, in which the plant extract plays a vital role to regulate the size and shape of the nanoparticles. Enhanced antibacterial effects (two- to fourfold) were observed in the case of Aloe vera plant protected AgNP than the routinely synthesized antibiotic drugs.Graphical Shape and size-controlled synthesis of silver nanoparticles using Aloe vera plant extract Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-016-1725-x) contains supplementary material, which is available to authorized users.

Characterization and optical studies of PVP-capped silver nanoparticles

In this study, the size-controlled synthesis of silver nanoparticles (Ag NPs) via chemical reduction method by NaBH4 as a reducing agent and poly(vinyl pyrrolidone) or PVP as a stabilizing agent is reported. Changing of ratios between reducing agent and stabilizing agent relative to AgNO3-optimized conditions for synthesis of stable Ag NPs was studied. The formation of Ag NPs was tracked by UV–Vis spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy. Particle size distribution was studied by particle size analyzer, and the morphology was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The optical properties of the synthesized Ag NPs were also investigated. The optimized Ag NPs were very stable even after 1 month that was due to effective stabilization by PVP molecules. The mechanism of Ag NPs formation and stabilization is discussed in detail.

Size-controlled synthesis of silver nanoparticles using Zizyphus mauritiana fruit extract

We demonstrated size-controlled synthesis of silver nanoparticles (AgNPs) using Zizyphus mauritiana fruit extract from an aqueous solution of silver nitrate. The size distribution of the resulting AgNPs were found to be dependent on the con- centration of fruit extract and reaction time, at the same concentration of silver nitrate. The AgNPs were characterised by UV-Visible spectroscopy (UV-Vis), particle size analysis (DLS), atomic force microscopy (AFM), transmission electron microscopy (TEM) and X- ray diffraction (XRD). The sizes of the AgNPs were found to decrease with the increase of concen- tration of fruit extract from 300 nm to 70 nm. The increase in reaction time from 5 min to 20 min significantly decreases the size of the AgNPs from 350 nm to 100 nm.

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 assynthesized 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.

Single-step, size-controlled synthesis of colloidal silver nanoparticles stabilized by octadecylamine

A single step process for the synthesis of size-controlled silver nanoparticles has been developed using a bifunctional molecule, octadecylamine (ODA). Octadecylamine complexes to Ag+ ions electrostatically, reduce them, and subsequently stabilizes the nanoparticles thus formed. Hence, octadecylamine simultaneously functions as both a reducing and a stabilizing agent. The amine-capped nanoparticles can be obtained in the form of dry powder, which is readily redispersible in aqueous and organic solvents. The particle size, and the nucleation and growth kinetics of silver nanoparticles could be tuned by varying the molar ratio of ODA to AgNO3. The UV–vis spectra of nanoparticles prepared with different concentrations of ODA displayed the well-defined plasmon band with maximum absorption around 425nm. The formation of silver metallic nanoparticles was confirmed by their XRD pattern. The binding of ODA molecule on the surface of silver has been studied by FT-IR and NMR spectroscopy. The formation of well-dispersed spherical Ag nanoparticles has been confirmed by TEM analysis. The particle size and distribution are found to be dependent on the molar concentration of the amine molecule. Open aperture z-scans have been performed to measure the nonlinearity of Ag nanoparticles.

Microwave-assisted synthesis of size-controlled silver nanoparticles using polyvinyl pyrrolidone as a reducing agent

In this work, stable concentrated aqueous dispersions of size-controlled silver nanoparticles were prepared by microwave irradiation of silver nitrate (AgNO3)/polyvinyl pyrrolidone (PVP) solution using polyvinyl pyrrolidone (PVP) as a reducing and stabilising agent. Crystal structure, size, optical properties of the silver nanoparticles were characterised by means of X-ray diffraction (XRD), scanning electron microscope (SEM), ultraviolet visible spectroscopy (UV-vis), Fourier transform infrared (FT-IR). Quasi-spherical nanoparticles, nanocube and flake-like nanoparticles were synthesised by controlling the experimental parameters such as the ratio of PVP to AgNO3, and the particle size can be conveniently adjusted to 50 nm.

New insight into the size-controlled synthesis of silver nanoparticles and its superiority in room temperature sintering

Silver nanoparticles with a controlled size present a high conductivity after room temperature sintering achieved by a chemical process.

Green, Rapid and Facile HPMo-Assisted Synthesis of Silver Nanoparticles

In the present paper, we have described the interesting behavior of molybdophosphoric acid (H3[PMo12O40], HPMo) in the size-controlled synthesis of silver nanoparticles under UV-irradiation. In this process which is based on the reduction of Ag+ (AgNO3), HPMo plays the role of photocatalyst, reducing agent as well as stabilizer, and propan-2-ol acts as a sacrificial agent. The method allows the rapid synthesis of uniform spherical nanoparticles with an average size that varies between 2.2 and 35.2 nm by altering the silver ion concentration, molar ratio of silver ion to HPMo (or dose of HPMo) and Propan-2-ol amount. It is found that there is a critical ratio for [Ag+]/[HPMo] (i.e. 3.8 in the present case), in which two opposing trends in the size of silver nanoparticles take place.

Size-Controlled Green Synthesis of Silver Nanoparticles using Dual Functional Plant Leaf Extract at Room Temperature

ABSTRACT A simple synthesis of size-controlled silver nanoparticles using plant leaf extract at room temperature is described in this report. The reaction of AgNO3 with the leaf extract of Azadirachta indica in different concentrations and different reaction pH yields silver nanoparticles with control over size and distribution. The sizes of the as-synthesized silver nanoparticles were in the range between 10 to 63 nm and the size of nanoparticles were attributed to the concentration of leaf extract and pH of the reaction solution. The as-synthesized silver nanoparticles showed an excellent level of stability in water, and the nanoparticles formed in solution between pH 7 and pH 10.5 were not only stable in water, but also in NaCl solution and in different pH. The nanoparticles were characterized using various techniques.

Micellar assemblies from amphiphilic polyurethanes for size-controlled synthesis of silver nanoparticles dispersible both in polar and nonpolar media

A size-controlled synthesis of silver nanoparticles (AgNPs) dispersible in polar and nonpolar media was carried out in micellar assemblies from amphiphilic invertible polyurethanes (AIPUs) based on poly(ethylene glycol) as a hydrophilic constituent and polytetrahydrofuran as a hydrophobic constituent. At a low concentration, AIPUs form micelles with a hydrophilic interior and a hydrophobic exterior. As concentration increases, individual micelles self-assemble into micellar assemblies with hydrophilic interior and hydrophobic exterior domains. It was shown that these domains can be applied simultaneously as nanoreactors and colloidal stabilizers to synthesize size-controlled batches of AgNPs in a nonpolar solvent. Size control and narrow particle size distribution can be facilitated by changes in the AIPU composition, macromolecular configuration, and polymer solution concentration. Depending on the length of polymer hydrophilic and hydrophobic fragments, and fragment distribution along the macromolecule, the size of fabricated AgNPs has been changed from 6 to 14 nm. Owing to the invertible properties of polyurethanes, the synthesized silver nanoparticles can be successfully dispersed in either polar or nonpolar media, where they form stable colloidal solutions.

Facile Synthesis of Size-Controlled Silver Nanoparticles Using Plant Tannin Grafted Collagen Fiber As Reductant and Stabilizer for Microwave Absorption Application in the Whole Ku Band

Size-controlled silver nanoparticles (AgNPs) were facilely synthesized on collagen fiber (CF), in which bayberry tannin (BT), a natural plant polyphenol, was grafted on CF to act as a reductant and stabilizer without any additional reagent (surfactant, template, and capping agent) or treatment (heat and photoirradiation) needed. The as-synthetic AgNPs-BT@CF was well characterized via combined techniques including SEM, HTEM, XRD, XPS, and FT-IR. The particle diameter and size distribution of AgNPs in BT@CF matrix are feasible to adjust by varying the grafting degree of BT on the CF surface. When the grafting degree of BT was 0.4, the particle size of AgNPs is as small as 5.2 ± 1.9 nm. Furthermore, the complex permittivity, and complex permeability of the AgNPs-BT@CF were also investigated in detail. It was found that with the increase of grafting degree of BT on CF the imaginary part (ε″) of complex permittivity was dramatically increased, whereas the real part (μ′) and imaginary part (μ″) of complex permittivity were not obviously changed. The reflection loss (RL) of AgNPs-BT@CF exceeding −10 dB was achieved in the whole Ku band (12.5–18 GHz).

Size-controlled synthesis of silver nanoparticles on Ti-containing mesoporous silica thin film and photoluminescence enhancement of rhodamine 6G dyes by surface plasmon resonance

Silver nanoparticles having a narrow size distribution were synthesized on Ti-containing mesoporous silica thin film (Ti-MSTF) using a simple photo-assisted deposition (PAD) method. Their particle sizes were successfully controlled by changing the photo-irradiation time during the deposition and average particle sizes at irradiation times of 1, 5 and 24 h were determined to be 2.7, 4.7 and 7.6 nm, respectively. The XPS depth profile analysis indicated that silver nanoparticles mainly exist not on the surface but in the thin film. UV–vis absorption spectra of these films showed an absorption band in the visible-wavelength region attributed to the surface plasmon resonance of silver nanoparticles. Rhodamine 6G (R6G) dye molecules were further embedded on Ti-MSTF after silver nanoparticle deposition. Photoluminescence properties of R6G dyes on these thin films were enhanced due to surface plasmon excitation from silver nanoparticles and the photoluminescence intensity reached up to 3 times as high as that achieved without silver nanoparticles. It was proven that the silver nanoparticle size had a strong influence on these enhancement effects.

Synthesis and UV–vis spectroscopic study of silver nanoparticles in aqueous SDS solution

A method for the size-controlled synthesis of silver nanoparticles is proposed and described. Synthesis is based on the reduction of AgNO 3 in aqueous SDS solution by hydrogen. These nanoparticles are poly-disperse in size and shape and their dimensions can be easily controlled in the range of 20 to 60 nm by varying the concentration of AgNO 3. Silver nanoparticles are analyzed using transmission electron microscope (TEM) and UV–vis spectroscopic technique. A comparison between the experimentally observed UV–vis spectra and the simulated one obtained from the modified Mie's theory, are made to understand the nature of shift of the SPR band.

Size Controlled Miniscale Synthesis of Silver Nanoparticles Using TEM Electron Beam

A method for one-pot size-controlled synthesis of silver nanoparticles is proposed and described. The synthesis is based on the reduction of silver-alkanethiolates complexes having highly ordered supramolecular structures through electron beam irradiation in transmission electron microscope (TEM). The method allows synthesis of silver nanoparticles of diameters between 1.9 nm and 5.9 nm. Different diameters within this range can be selected for by varying the acceleration voltage in TEM, alkyl chain length, and structure of the silver-alkanethiolates complexes.

Morphology and size-controlled synthesis of silver nanoparticles in aqueous surfactant polymer solutions

We have employed a number of reducing and capping agents to obtain Ag(0) metallic nanoparticles of various sizes and morphologies. The size and morphology were tuned by selecting reducing and capping agents. Spherical particles of 15 and 43 nm diameter were obtained when 1 wt% aqueous starch solution of AgNO3 precursor salt was reduced by d(+)-glucose and NaOH, respectively, on heating at 70 °C for 30 min. Smaller size particles obtained in the case of d(+)-glucose reduction has been attributed to the slow reduction rate by mild reducing agent d(+)-glucose compared to strong NaOH. Conducting the reduction at ambient temperature of silver salt in liquid crystalline pluronic P123 and L64 also gave spherical particles of 8 and 24 nm, respectively, without the addition of any separate reducing agent. NaOH reduction of salt in ethylene glycol (11 g)/polyvinyl pyrolidone (PVP; 0.053 g) mixture produced large self-assembled cubes of 520 nm when smaller (26–53 nm) star-shaped sharp-edged structures formed initially aggregated on heating the preparation at 190 °C for 1 h. Increasing the amount of PVP (0.5 g) in ethylene glycol (11 g) and heating at 70 °C for 30 min yielded a mixture of spherical and non-spherical (cubes, hexagons, pentagons, and triangle) particles without the addition of an extra reducing agent. Addition of 5 wt% PVP to 1 wt% aqueous starched solution resulted in the formation of a mixture of spherical and anisotropic structures when solution heated at 70 °C for 1 h. Homogeneous smaller sized (29 nm) cubes were synthesized by NaOH reduction of AgNO3 in 12.5 wt% of water-soluble polymer poly(methyl vinyl ether) at ambient temperature in 30 min reaction time.

Facile Size-Controlled Synthesis of Silver Nanoparticles in UV-Irradiated Tungstosilicate Acid Solution

A method for size-controlled synthesis of silver nanocomplex is proposed and described. The synthesis is based on the reduction of silver nitrate (AgNO3) by a UV-irradiated arginine (Arg)−tungstosilicate acid (TSA, H4SiW12O40) solution. The method allows synthesis of spherical particles of diameter between several nanometers and several hundreds of nanometers by varying the molar ratio of silver nitrate to TSA, the pH of the reaction solution, and the reaction temperature. The formation of the Arg complexed with TSA ions is demonstrated. The experimental results show that Arg−TSA colloidal particles are a new kind of organic−inorganic template for the synthesis of organized assemblies of silver nanocomplex, wherein the Arg−TSA complex acts as a UV-switchable reducing agent for silver ion. The conductance of the Arg−TSA solution was measured as a function of reaction time. The nanoparticles were characterized by ultraviolet−visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy, electron diffraction, and transmission electron microscopy and by use of a Zetasizer instrument.

Large-scale and size-controlled synthesis of silver nanoparticles under microwave irradiation

Large-scale and size-controlled silver nanoparticles can be rapidly prepared under microwave irradiation from an aqueous solution of silver nitrate and trisodium citrate in the presence of formaldehyde as a reductant. The size and size distribution of the resulting silver nanoparticles prepared under microwave irradiation are strongly dependent on the states of silver cations in the initial reaction solution. The formation of silver citrate in the initial reaction solution allows for yielding silver nanoparticles with a small size.