Concentration Of Capping Agent Research Articles

Fast synthesis of gold nanoparticles by cold atmospheric pressure plasma jet in the presence of Au+ ions and a capping agent

Homogeneous gold nanoparticles were synthesized under atmospheric pressure using a non-thermal helium plasma jet in a single-step process. A current power supply was used to generate the plasma discharge rich in diverse reactive species. These species induce rapid chemical reactions responsible for the reduction of the gold salts upon contact with the liquid solution. In this study, spherical and monodispersed gold nanoparticles were obtained within 5 min of plasma exposure using a solution containing gold (III) chloride hydrate (HAuCl4) as a precursor and polyvinylpyrrolidone (PVP) as a capping agent to inhibit agglomerations. The formation of these metal nanoparticles was initially perceptible through a visible change in the sample’s color, transitioning from light yellow to a red/pink color. This was subsequently corroborated by UV-vis spectroscopy, which revealed an optical absorption in the 520‒550 nm range for Au NPs, corresponding to the surface plasmon resonance (SPR) band. An investigation into the impact of various parameters, including plasma discharge duration, precursor and capping agent concentrations, was carried out to optimize conditions for the formation of well-separated, spherical gold nanoparticles. Dynamic light scattering (DLS) was used to measure the size of these nanoparticles, transmission electron microscopy (TEM) was used to observe their morphology and X-ray diffraction (XRD) was also employed to determine their crystallographic structure. The results confirm that homogeneous spherical gold nanoparticles with an average diameter of 13 nm can be easily synthesized through a rapid, straightforward, and environmentally friendly approach utilizing a helium atmospheric pressure plasma.

Regulating the multifactor during wet chemical synthesis to obtain calcium phosphate powders with controllable phase purity for bone repair

Calcium phosphate ceramics are widely used as bone repair materials owing to their excellent biocompatibility, bone conductivity, bone induction, and degradability. Although there are many methods for synthesizing calcium phosphate and controlling its phase composition, it is necessary to explore effective preparation methods by understanding the formation of calcium phosphate and its influencing factors. In this study, calcium phosphate powders with controllable phase compositions were synthesized using a wet chemical precipitation method by adjusting the process parameters (aging time, bipolar solution, initial Ca-P molar ratio, capping agent concentration, and system concentration). Subsequently, a certain biphasic proportion of (biphasic calcium phosphate, BCP) products was prepared, and pure (β-tricalcium phosphate, β-TCP) can be obtained according to the customer's requirements. BCP ceramics with desired phase compositions were obtained by pressing and sintering different calcium-deficient powders. Specifically, β-TCP powder with a purity of 99.83 wt% was obtained when the aging time, bipolar solution, initial Ca-P molar ratio, capping agent concentration, and system concentration were 0 h, 50% ethanol, 1, 0.27 M, and 0.0135 M, respectively. The BCP synthesized in this study shows great application potential in the field of bone tissue repair materials.

Fabrication of conifer-like TiSnO2 nanorods for sensing H2S gas at room temperature.

Conifer-like TiSnO2 nanorods mixed metal oxide was synthesized via the one-pot polyol method utilizing ethylene glycol (EG), poly(diallyldimethylammonium chloride) (PDDA), tin(II) chloride dihydrate (SnCl2·2H2O), and titanium(IV)-ethylhexanoate (TE) as precursor materials, aimed at room temperature H2S gas sensing. The effects of polyol duration time and capping agent concentration (PDDA) were examined to explore the morphological, structural, and gas-sensing characteristics, as well as to propose potential growth mechanisms of conifer-like TiSnO2 nanorods mixed metal oxide. The morphology and composition of the synthesized TiSnO2 mixed metal oxide were carried out employing scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffractometry (XRD). The experimental findings demonstrated a significant influence of polyol duration time and PDDA concentration on the morphological evolution of the synthesized TiSnO2 mixed metal oxide structures. Comparative gas-sensing analysis indicated that the conifer-like TiSnO2 nanorods mixed metal oxide exhibited the highest response (2.45%) towards H2S gas at a concentration of 1 ppm, along with a low detection limit (0.20 ppm) and good linearity (R2 = 0.9865) within the range of 1-15 ppm of H2S gas at room temperature.

Starch-capped silver oxide (Ag2O) nanoparticles: synthesis, characterization and antibacterial activity

Silver oxide nanoparticles were synthesized at room temperature using a green synthetic method and water as a solvent. Starch was used as a capping and reducing agent because it is cheap, non-toxic and environmentally friendly. The effect of precursor and capping agent concentrations were investigated. The nanoparticles have been characterized using spectroscopic and morphological techniques. The spectrum of Ag2O nanoparticles showed the maximum absorbance range at 350-366 nm. TEM analysis showed a size particle range of 2-14 nm. The increase in precursor concentration showed an increase in particle size while increasing the capping agent concentration resulting in reduced particle size. Increased capping concentration also resulted in the change to nanofibers. The nanoparticles showed antibacterial activities against both Staphylococcus aureus and Escherichia coli strains. The 2:1 Ag2O ratio showed the best activity towards both strains, 15 ± 0.19 and 14 ± 0.11 mm diameter, respectively.

On the electrodeposition of conically nano-structured nickel layers assisted by a capping agent

• Systematic study of capping agent concentration during electrodeposition of Ni nanostructures. • Optimum deposition conditions for conical growth are derived. • New modeling approach to simulate and quantify local growth of cones. Capping agents are frequently used in electrodeposition to support spatially inhomogeneous mass transfer at small scales. As such, chloride ions are known to support the deposition of conically nanostructured nickel layers. This work presents a systematic experimental study of the impact of a capping agent on the electrochemical growth of conically-shaped nickel deposits. Furthermore, a modeling approach on the scale of cones for numerical simulations of electrodeposition with capping agents is provided for the first time to give deeper insight on how the capping agent influences the local growth of the deposit. The growth rates of the nano-cones obtained numerically are compared with experimental data, and a good agreement is found. The impact of the capping agent concentration, the deposition time, the electrolyte temperature and the current density are investigated systematically, and optimum conditions for conical growth are derived.

Dual-effect core–shell polyphenol coated silver nanoparticles for tissue engineering

The development of silver nanoparticles has attracted great attention due to their potential applications in biomedicine, tissue engineering and materials science. In this study, polyphenol coated silver nanoparticles (PAgNp) were synthesized using yerba mate (Ilex paraguariensis) aqueous extract as green reducing and stabilizing agent. This one-pot and economic process lead to a potent antimicrobial and antioxidant nanomaterial, both activities strongly essential for tissue engineering and wound healing. Yerba mate dried leaves are highly available and inexpensive industrial product in South America and other countries. Yerba mate plant aqueous extract was used as a reducing reactant and stabilizer agent, due its great content of phenolic compounds. Different parameters (i.e.: silver salt and reducing agent concentration, pH, temperature and capping agent concentration) were evaluated to establish the optimal synthesis condition. The reaction was evaluated by UV–vis spectrophotometry. Reaction efficiency (98%) and stability were measured by atomic absorption spectroscopy. The green synthesized nanomaterial was characterized by transmission electron microscopy (TEM), Dynamic Light Scattering (DLS), Energy-dispersive X-ray spectroscopy (EDS) and ATR-FTIR. Moreover, antimicrobial, antioxidant and cytocompatibility test were performed. The present study revealed that the low-cost, simple and environmentally friendly synthesis of a nanomaterial that can be widely used in biomedicine and nanobiotechnology as an antimicrobial and antioxidant agent.

On the Electrodeposition of Conically Nano-Structured Nickel Layers Assisted by a Capping Agent

Capping agents are frequently used in electrodeposition to support spatially inhomogeneous mass transfer at small scales. As such, chloride ions are known to support the deposition of conically nanostructured nickel layers. This work presents a systematic experimental study of the impact of a capping agent on the electrochemical growth of conically-shaped nickel deposits. Furthermore, a modeling approach on the scale of cones for numerical simulations of electrodeposition with capping agents is provided for the first time to give deeper insight on how the capping agent influences the local growth of the deposit. The growth rates of the nano-cones obtained numerically are compared with experimental data, and a good agreement is found. The impact of the capping agent concentration, the deposition time, the electrolyte temperature and the current density are investigated systematically, and optimum conditions for conical growth are derived.

The Effect of Polyvinyl Alcohol Concentration on the Growth Kinetics of KTiOPO4 Nanoparticles Synthesized by the Co-precipitation Method

KTiOPO4 nanoparticles are known as the best candidate to utilize for second-harmonic generation in multiphoton microscopes and bio labels. Size and shape are important and effective parameters to control the properties of nanoparticles. In this paper, we will investigate the role of capping agent concentration on the size and shape control of KTP nanoparticles. We synthesized KTP nanoparticles by the co-precipitation method. Polyvinyl alcohol with different mole ratios to titanium ion (1:3, 1:2, 1:1) was used as a capping agent. Products were examined by X-ray diffraction patterns and scanning electron microscopy analyses. X-ray diffraction patterns confirmed the formation of the KTP structure. The biggest (56.36nm) and smallest (39.42nm) grain size were obtained by 1:3 and 1:1 mole ratios of capping agent, respectively. Dumbly, spherical and polyhedral forms of KTP nanoparticles were observed by the change in capping agent mole ratio. The narrowest size distribution of KTiOPO4 nanoparticles was obtained at 1:1 mole ratio of capping agent. Doi: 10.28991/HIJ-2020-01-04-06 Full Text: PDF

Influence of Temperature, Time, pH, Capping Agent Concentration and Zn/Se Molar Ratio on Morphology and Phase Evolution of Zinc Selenide Nanoparticles Synthesized by Hydrothermal Method

Influence of Temperature, Time, pH, Capping Agent Concentration and Zn/Se Molar Ratio on Morphology and Phase Evolution of Zinc Selenide Nanoparticles Synthesized by Hydrothermal Method

Exploring the potential of laser desorption ionisation time-of-flight mass spectrometry to analyse organic capping agents on inorganic nanoparticle surfaces

Analytical techniques are in high demand for the determination of organic capping agents on surfaces of metallic nanoparticles (NPs) such as gold (Au) and silver (Ag). In this study, the potential of laser desorption ionisation time-of-flight mass spectrometry (LDI-ToF-MS) as a technique fit for this purpose is demonstrated. First, a collection of reference spectra of most commonly used organic capping agents, including small molecules and polymers was established. Second, the robustness of the method was tested towards parameters like NP core material and NP size. In a third step, the quantitative capabilities of LDI-ToF-MS were determined. Finally, the potential to detect chemical alterations of the organic capping agent was evaluated. LDI-ToF-MS is able to detect capping agents ranging from small molecules (citric acid, tannic acid, lipoic acid) to large polymers (polyvinylpyrrolidone, branched polyethylenimine and methoxy polyethylene glycol sulfhydryl) on Au and Ag NPs based on characteristic signals for each capping agent. Small molecules showed characteristic fragment ions with low intensities, whereas polymers showed intense signals of the monomeric subunit. The NP concentration range comprises about two orders of magnitude with lowest detection limits of 5 mg/L or a capping agent concentration in the lower nM range. Changes in capping agent composition are detectable at NP concentrations in the g/L range. Thus, LDI-ToF-MS is particularly suitable for characterisation of polymer-capped NPs with high NP concentrations. This may be the case for quality control as part of the material synthesis and testing.Graphical abstract

Capping Ligand Size-Dependent LSPR Property Based on DNA Nanostructure-Mediated Morphological Evolution of Gold Nanorods for Ultrasensitive Visualization of Target DNA.

Systematically tuning the structures and properties of noble-metal nanoparticles through biomolecule-mediated overgrowth is of significant importance for their applications in biosensing and imaging. Herein thiolated biomolecules with different concentrations and sizes (molecular weight and spatial structure) were used as a class of capping ligands to control the longitudinal surface plasmon resonance (LSPR) property of gold nanorods (GNRs). The LSPR peaks were red-shifted by increasing the capping agent concentration. The size effect could be divided to two aspects: (1) When the ligands are small molecules, the LSPR peak is blue-shifted as the size of the capping ligand increases. (2) When the ligands are macromolecular proteins, the LSPR property is similar to that of the overgrown nanoparticle (Au@gap@GNR) without thiolated biomolecules as capping agents. Interestingly, thiol-free and nonhomooligomeric DNA strands as capping agents present a similar influence in shaping the overgrowth of GNRs by varying their concentrations and sizes. In addition, the size effect of a DNA nanostructure was used to construct a ΔλLSPR-based catalytic nucleic acid biosensor using a DNA dendritic nanostructure as a capping agent combined with LSPR signals generated from the Au@gap@GNRs with morphological evolution. More importantly, the ΔλLSPR-based biosensor possesses three advantages in nucleic acid biosensing: (1) It is completely label- and wash-free, (2) it has an ultrahigh sensitivity and signal-to-noise ratio, and (3) it can be visualized without any instrumental aid, indicating a significant potential for ultrasensitive biosensing.

Opto-electronics properties of starch capped CdSe nanoparticles

The nanoparticles of a prominent luminescent material, cadmium selenide (CdSe) have been prepared by simple wet chemical route using starch as capping agent. The X-ray diffraction of the synthesized CdSe nanocrystals exhibits hexagonal phase with average crystallite size decreasing with capping agent concentration. Surface morphology of CdSe nanoparticles has been studied using scanning electron microscopy. The UV–Vis absorption shows blue shift in absorption edge indicating increased band gap with decreasing the particle size due to quantum confinement. The photoluminescence and electroluminescence (EL) measurement show single peak at about 650 nm with increasing intensity for smaller nanocrystals, however emission peak is quite broad in case of EL indicating involvement of impurity states. The luminescence intensity increases because of increased oscillator strength and the better passivation of the surface defects responsible for non-radiative relaxation process. The light emission starts at lower threshold voltage when the concentration of capping agent is increased.

Green synthesis of silver nanoparticles using aqueous extract of <i>Combretum molle</i> leaves, their antibacterial, antifungal and antioxidant activity

There are several reports on the use of the plant extracts from Combretum molle species but very limited to the extracts used effectively in the synthesis of metal nanoparticles. The present study reports on the green synthetic method in the preparation of silver nanoparticles. Combretum molle leave's extracts were used as capping as well as reducing agent. Phytochemical studies carried out on the plant leaves showed the presence of tannins, proteins, flavonoids and phenols. The effect of capping agent concentration on the size and shape of silver nanoparticles followed by the antimicrobial activity of the synthesised particles were studied. Silver nanoparticles were characterised by a combination of spectroscopic (UV-VIS, FTIR, PL), X-ray diffraction and microscopic techniques to confirm capping of the nanoparticles by the extracts. TEM results showed that the obtained particles were spherical in shape with the size ranging from 1 nm to 30 nm and they had face-centred cubic phase in their XRD patterns. The synthesised silver nanoparticle also showed slightly increased antifungal and antibacterial activity against Candida albicans, Cryptococcus neoformans, Staphylococcus aureus, Enterococcus faecalis, Klebsiella pneumonia and Pseudomonas aeruginosa as compared to the control. The MIC values obtained were between 0.20 mg/ml and 6.25 mg/ml.

Green synthesis of silver nanoparticles using aqueous extract of <i>Combretum molle</i> leaves, their antibacterial, antifungal and antioxidant activity

There are several reports on the use of the plant extracts from Combretum molle species but very limited to the extracts used effectively in the synthesis of metal nanoparticles. The present study reports on the green synthetic method in the preparation of silver nanoparticles. Combretum molle leave's extracts were used as capping as well as reducing agent. Phytochemical studies carried out on the plant leaves showed the presence of tannins, proteins, flavonoids and phenols. The effect of capping agent concentration on the size and shape of silver nanoparticles followed by the antimicrobial activity of the synthesised particles were studied. Silver nanoparticles were characterised by a combination of spectroscopic (UV-VIS, FTIR, PL), X-ray diffraction and microscopic techniques to confirm capping of the nanoparticles by the extracts. TEM results showed that the obtained particles were spherical in shape with the size ranging from 1 nm to 30 nm and they had face-centred cubic phase in their XRD patterns. The synthesised silver nanoparticle also showed slightly increased antifungal and antibacterial activity against Candida albicans, Cryptococcus neoformans, Staphylococcus aureus, Enterococcus faecalis, Klebsiella pneumonia and Pseudomonas aeruginosa as compared to the control. The MIC values obtained were between 0.20 mg/ml and 6.25 mg/ml.

Transport and Kinetic Effects on the Morphology of Silver Nanoparticles in a Millifluidic System

This work investigates the synthesis of silver nanoparticles of different shapes using silver nitrate as a precursor and ascorbic acid as a reducing agent in different reactors. The main focus of this work is to study the effect of capping agent concentrations and ratios of reducing agent to precursor concentrations (reactant ratios) on the shape and size of the nanoparticles synthesized. Three reactor configurations, namely, batch, straight millichannel, and spiral millichannel, are considered to study the transport effect on the morphology of silver nanoparticles synthesized. The kinetic effect on the particle morphology is studied by changing the capping agent concentrations and reactant ratios. It is shown that these variables play an important role in determining the nanoparticle shape and size. In this work, spherical nanoparticles (30–60 nm), triangular plates (80–200 nm), nanorods (130–150 nm), and bent wires (130–150 nm) morphologies are synthesized by controlling thermodynamic and kinetic parame...

Continuous preparation of nimesulide nanoparticles by liquid antisolvent precipitation using spinning disc reactor

AbstractBACKGROUNDNimesulide (NIM), a nonsteroidal anti‐inflammatory drug (NSAID) acts as an antipyretic, analgesic and anti‐inflammatory agent, and it is widely used in treating acute pain due to various diseases such as headache, migraine, back pain and postoperative pain. Nimesulide is reported to have poor solubility in water (0.01 mg mL−1). In this work, the solvent–antisolvent (S:AS) precipitation of NIM using spinning disc reactor (SDR) was investigated.RESULTSComparative studies were investigated between stirred tank reactor and SDR. The effects of different functional parameters of spinning disc process such as S:AS ratio and flow rate, nimesulide concentration, disc surface texture, capping agent concentration, different capping agents and speed of rotating disc were studied on the particle size of nimesulide. The average particle size of 192 nm for nimesulide was successfully achieved with a considerable particle size distribution at a 300 mL min−1 total flow rate, with the following parameters: concentration of nimesulide in ethanol 0.5 mg mL−1; concentration of polyvinylpyrrolidone (PVP) in deionized water 1 mg mL−1; S:AS ratio 1:6 and at 3000 rpm rotating disc speed. This result should be compared with 9.5 µm particle size with mechanical agitated contactor at S:AS ratio 1:6 and speed of agitation 600 rpm.CONCLUSIONThe NIM nanoparticles can be continuously prepared in a SDR with a control and uniform particle size. This leads to increased dissolution rate and bioavailability of poorly water soluble drugs. © 2018 Society of Chemical Industry

Preparation of Cadmium Sulfide Nanostructures in Presence of Polyvinyl Alcohol and Polyvinylpyrrolidone as a Capping Agent and Investigation of Their Structural and Optical Properties

In this research, cadmium sulfide nanostructures have been prepared by an ultrasound-assisted method in presence of polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) as capping agents. The effects of two different capping agents on the structural and optical properties of cadmium sulfide nanostructures have been investigated by X-ray diffraction (XRD), UV-Vis spectroscopy, scanning electron microscopy (SEM) and Fourier transform Infrared (FT-IR) spectroscopy. The XRD patterns show the high purity of samples. The mean crystal's sizes have been estimated by Debye-Sherrer equation and results show the mean crystallite size is decreasing with increase capping agent concentrations. UV-Vis spectroscopy results show a shift in the peaks and broadening with the PVA and PVP increasing. The broadening of the absorbance spectrum with increasing in capping agent concentrations is due to the quantum confinement of nanostructures. The band gap of prepared samples has been estimated by Tauc equation and graph and results show that the band gaps of samples are increasing with increase in the capping agent's concentration. The SEM images show the distribution of the uncapped sample is different from capped samples. FT-IR spectroscopy results show by increasing of capping agent concentration the energy between the functional group is changed and some peaks show a slight shift.

Raphanus sativus Mediated Synthesis, Characterization and Biological Evaluation of Zinc Oxide Nanoparticles

Biological synthesis of nanoparticles employing plants and their extracts is cheap and eco-friendly technique as compared to physical and chemical procedures that are expensive and hazardous to the environment. In this study, Zinc oxide (ZnO) nanoparticles were synthesized using leaf extract of Raphanus sativus. Energy Dispersive X-ray, Scanning Electron Microscopy and X-ray Diffraction were used for characterization. In-vitro, antibacterial activity against, Listeria monocytogenes, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus, and antifungal activity against, Candida albicans and Aspergillus flavus were investigated. Furthermore, the influence of precursor salt and capping agent concentrations on the size, morphology and subsequently on the antimicrobial activity of nanoparticles was examined by synthesizing six samples of ZnO nanoparticles at varying concentrations of zinc sulphate heptahydrate (ZnSO4·7H2O) and R. sativus leaf extract. Synthesized nanoparticles were spherical shaped and their size and agglomeration inclined with increasing zinc sulphate concentration, while declined with increasing R. sativus leaf extract. The antimicrobial results varied with the size and concentration of ZnO nanoparticles proving that these are two significant factors affecting their antimicrobial activity. The work reported in this paper demonstrates that R. sativus leaf extract can be successfully employed for the synthesis of ZnO nanoparticles for their antimicrobial applications.

Control of copper nanowire network properties and application to transparent conducting layer in LED

We report the control of structural, optical, and electrical properties of solution processed copper (Cu) nanowires (NWs) by varying the capping agent concentration and demonstrating the enhanced light extraction of GaN-based light-emitting diodes (LEDs) using Cu NWs. Cu NWs were prepared by a simple solvothermal method, and the capping agent concentration effects on the growth of Cu NWs were systematically investigated. The different diameters of Cu NWs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible absorption, and conductivity measurements. All characterization results showed high aspect ratio nanowires with efficient transmittance and conductivity properties. When the synthesized Cu NWs were adopted as a transparent conducting layer, the electroluminescence intensity was improved by its spreading effects. This work will elucidate the influence of capping agents on the physical properties, optical properties, and electrical conductivity of Cu NWs for use as a transparent conductor in optoelectronic devices.

Synthesis, characterisation and antimicrobial effect of starch capped silver sulphide nanoparticles against Escherichia coli and Staphylococcus aureus

Silver sulphide nanoparticles were synthesised at room temperature using a green synthetic method. Silver nitrate and thiourea have been used as the sources of silver and sulphide ions, respectively. Starch was used as the capping agent while water was used as the solvent. The effect of precursor and capping agent concentrations was investigated for their influence on the size and shape of the synthesised nanoparticles. The concentrations were varied in the ranges 0.1-;0.6 g and 0.25-1 g for the precursor and capping molecule, respectively. The nanoparticles obtained were spherical and cubic shaped with size distribution of 7-31 nm. Absorption spectra gave blue shifted band edges with Stokes shift of 2 nm. XRD patterns were confirmed to have monoclinic crystallinity with α-phase. FTIR results showed that the nanoparticles were successfully capped with starch capping agent. Increasing both the precursor and capping agent concentrations resulted in a decrease in the nanoparticle sizes. The antibacterial activity of Ag2S nanoparticles against Escherichia coli and Staphylococcus aureus showed susceptibility towards the Gram negative and positive bacteria, respectively. The lower precursor ratio had the lowest minimum inhibitory concentration (MIC) of less than 0.023 mg/ml, while the higher precursor ratios had MIC value of 0.046 mg/ml. The growth curve studies of bacteria treated with nanoparticles showed an increase in growth and then a decrease as the exposure time was increased. This indicated that the growth inhibition is dependent on time exposure of the bacteria to the nanoparticles.