Colloidal Solution Of Nanoparticles Research Articles

Characterization of Silver Nanoparticles Obtained by a Green Route and Their Evaluation in the Bacterium of Pseudomonas aeruginosa

Metal nanoparticles are widely used in different areas such as biotechnology and biomedicine, for example in drug delivery, imaging and control of bacterial growth. The antimicrobial effect of silver has been identified as an alternative approach to the increasing bacterial resistance to antibiotics. Silver nanoparticles were synthesized by the green route using the Geranium extract as a reducing agent. The characterization was carried out by the techniques of UV-Vis spectrophotometry, transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray emitted photoelectron spectroscopy (XPS) and X-ray diffraction. Nanoparticle diameters between 15 and 50 nm were obtained and the interplanar spaces calculated from the electron diffraction pattern corresponding to a mixture of silver with 4H and FCC structures. To determine the minimum inhibitory concentration of silver nanoparticles (AgNPs) on the Pseudomonas aeruginosa bacteria (ATCC-27853), different concentrations of colloidal solution 0.36, 0.18, 0.09 and 0.05 μg/mL were evaluated as a function of the incubation time, measuring the inhibition halo and colony forming unit (CFU) during 0, 2 and 4 h of incubation. The minimum inhibitory AgNPs concentration (MIC) is 0.36 μg/mL at 0 h while the concentration of 0.18 μg/mL presents a total inhibition of the bacterium after 2 h. For the rest of the dilutions, gradual inhibitions as a function of time were observed. We evaluate the antibacterial effect of silver nanoparticles obtained by a green methodology in Pseudomonas aeruginosa bacteria. Finally, the colloidal nanoparticle solution can be an antibacterial alternative for different biomedical approaches.

Improvement of the carbon monoxide gas sensing properties of polyaniline in the presence of gold nanoparticles at room temperature

In the present work, the influence of gold (Au) nanoparticles on carbon monoxide gas sensing performance of polyaniline (PAni) at room temperature was comprehensively studied. The Au/PAni nanocomposites were synthesized by the ultrasound mixing of emeraldine salt polyaniline and different amounts of Au nanoparticles colloidal solution. The analyses of field emission scanning electron microscope in conjunction with energy-dispersive X-ray spectroscopy indicated that the surface of PAni fibers was well decorated with Au nanoparticles due to the electrostatic interaction and hydrogen bonding. Then, the gas sensing performance of all sensors was investigated toward various concentrations of carbon monoxide gas ranging from 200 to 6000 ppm at room temperature. The results indicated that the 2.5 %Au/PAni sensor possesses high response(14 %–1000 ppm), low detection limit(33 ppm), the acceptable response time(180 s), wide dynamic range(200−6000 ppm) and good selectivity owing to catalytic properties of Au nanoparticles. Thus, the one-dimensional nanostructure might give a promise for high-performance sensing applications.

Antimicrobial effect of ZnO nanoparticles synthesized by different methods against food borne pathogens and phytopathogens

Phytopathogens and food-borne pathogens are a major threat to human health, so there is an urgent need to find some alternatives to overcome these issues. Nanomaterials have shown great potential as antimicrobials therefore, in this study, ZnO nanoparticles were synthesized using Azadirachta indica leaf extract and studied for their antimicrobial activity. Their antimicrobial efficacy was studied against phyto and food borne pathogens and compared with the commercially available chemically synthesized ZnO nanoparticles (Chem-ZnO-NPs). The Azadirachta indica synthesized ZnO-NPs were characterized using UV–VIS spectroscopy, DLS, and FTIR. DLS data depicts that the size of nanoparticles in colloidal solution is approximately 96 nm, with polydispersity index (PDI) of 0.37. The antimicrobial activity was studied using pour plate method. The MIC data for food borne pathogens (E. coli and S. aureus) shows that Azadirachta indica mediated ZnO-NP are more efficient as compared to Chem-ZnO-NPs. For phytopathogens (Alternaria alternata, Sclerotium rolfsii and Stemphylium solani) also the result shows that Azadirachta indica mediated ZnO-NP exhibit more efficient antifungal properties. Therefore, the synthesized ZnO-NP can be efficiently used in place of commercially available fungal pesticides.

SiO2 NPs-PQ/PMMA Photopolymer Material Doped with a High-Concentration Photosensitizer for Holographic Storage.

Dispersing nanoparticles and increasing the photosensitizer concentration have been regarded as effective approaches for improving the performance of a holographic storage material. In this paper, SiO2 nanoparticle (NP)-dispersed PQ/PMMA nanocomposite material (SiO2 NP-PQ/PMMA) with a high PQ doping concentration was prepared. By introducing the co-monomer methyl isobutyl ketone (MIBK) that comes from an SiO2 NP colloidal solution, the concentration of PQ in the system increased to 1.2 wt %. We investigated the performance of polarization holographic recordings in both traditional PQ/PMMA and nanocomposite material SiO2 NP-PQ/PMMA with the orthogonally polarized signal and reference waves. With the dispersion of the SiO2 NPs colloidal solution and the increase in the PQ concentration, diffraction efficiency and photoinduced birefringence were multiplied. In addition, high-quality holographic image reconstruction was achieved by our homemade material.

Quantification of Free Radical Scavenging Properties and SOD-Like Activity of Cerium Dioxide Nanoparticles in Biochemical Models

The enhanced chemiluminescence method in combination with mathematical modeling has been used to quantify the antioxidant properties and to study the superoxide dismutase-like (SOD-like) activity of a citrate-stabilized colloid solution of ultrasmall CeO2 nanoparticles (3 nm) in biochemical models. The trolox (a water-soluble analogue of vitamin E) equivalent antioxidant capacity of a 1 µmol/L CeO2 sol was 0.049 ± 0.004 µmol/L; thus, the ability of CeO2 to act as a free radical scavenger is about 20 times lower than that of trolox. The antioxidant activity was estimated by the mathematical modeling method. The free radical scavenging rate constants were 2000 nM–1 min–1 for trolox and k1 = 300 nM–1 min–1 and k2 = 4 nM–1 min–1 for cerium dioxide. The SOD-like activity of 1 mmol/L СеО2 in SOD activity units was 2.00 ± 0.03 nmol/L. Thus, the activity of CeO2 as a SOD mimetic is about six orders of magnitude lower than the activity of the native enzyme.

Synthesis and characterization of silver nanoparticles as a potential sensor for volatile organosulfides for visual detection of postharvest storage in garlic

Garlic, one of the most popular spices used in manufacturing many food products, is subjected to fungal and bacterial diseases resulting to substantial losses in quantity and quality. Specific detection tools for garlic spoilage will be an asset in relieving these losses during postharvest storage. In this study, stable yellow-colored silver nanoparticle colloidal solution was studied as a potential sensor for volatile organosulfides in garlic. The silver nanoparticles (AgNPs) were synthesized by chemical reduction method where silver nitrate was taken as metal precursor, sodium borohydride as reducing agent, and polyethylene glycol as stabilizing agent. The silver nanoparticles were characterized by UV-Vis Spectroscopy and Dynamic Light Scattering (DLS). The spectral analysis revealed the formation of silver nanoparticles by exhibiting the typical surface plasmon absorption peak at around 395 nm. The DLS results show two populations of AgNPs with particle sizes of 3 nm and 50 nm. The volume ratio of sodium sulfite to be added in the silver nanoparticle and the reaction time was also determined. Synthesized AgNPs could detect sodium sulfite at 0.52 to 50 µM concentration range. This simple method indicated the potential of silver nanoparticles as a powerful detection tool for volatile organosulfides in garlic.

Effect of laser energy and wavelength on average size of gold nanoparticles synthesized by pulsed laser ablation in deionized water

In this paper, the effect of Nd:YAG laser wavelength and energy on the synthesis of gold nanoparticles is reported. Gold nanoparticles colloidal solutions were prepared by pulsed laser ablation of gold target in deionized water. The Nd:YAG laser with repetition rate of 1 Hz was assigned to supply energy at fundamental and second harmonic wavelengths i.e., 1064 nm and 532 nm, respectively. Synthesized nanoparticles were characterized using particle size analyzer (PSA). Four different laser energies were used to ablate the samples and synthesize gold nanoparticles. The average size of gold nanoparticles was found to decrease with increasing laser energy. The gold nanoparticles of smaller size were obtained when the target was ablated with 532nm wavelength of Nd:YAG laser. Higher laser energies and efficient absorption of 532 nm wavelength resulted in size reduction by fragmentation of colloidal nanoparticles.

Synthesis of metallic copper nanoparticles in aqueous solution by surfactant-free reduction and silica coating

A safe, simple, and low environmental impact method for controlling the oxidation and aggregation of metallic copper (Cu) nanoparticles has yet to be developed. This paper describes the synthesis of metallic Cu nanoparticles dispersed in water fabricated by a surfactant-free method and silica coating of metallic Cu nanoparticles. A colloid solution of metallic Cu nanoparticles was prepared from Cu(CH3COO)2 (Cu source), hydrazine (reducing reagent), and citric acid (stabilizer) in water in air. Silica coating of the metallic Cu nanoparticles was performed by adding sodium silicate to the metallic Cu nanoparticles in water. The silica-coated nanoparticles had a particle size of 99.2 ± 34.8 nm, a silica shell thickness of 5.8 nm, and a crystal size of metallic Cu of 28.5 nm. The metallic Cu nanoparticles in the silica-coated particles were not so oxidized even with annealing in air at 200 °C: the silica shells functioned as a physical barrier to control oxidation of the metallic Cu nanoparticles.

Impact of the matrix on optical properties of nanocomposites with CdS QDs

In the present work the silica-based matrix effect on the luminescence properties of the nanocomposites which contain cadmium sulfide quantum dots (CdS QDs) was studied. Water alkaline solution of sodium silicates Na2O(SiO2)n, or liquid glass, or tetraethyl orthosilicate (TEOS) were used as simple models of a dielectric matrix. The synthesis of nanocomposites by sol-gel method using liquid glass and TEOS was carried out in two ways: mixing the prepared colloidal solution of nanoparticles with silica precursor or synthesis of nanoparticles directly in the matrix. The composite based on CdS QDs in a more complex matrix of silicate glass was also studied. The optical absorption and luminescence were studied in detail depending on the synthesis method. It was shown that various atomic defects contribute predominantly to the luminescence of QDs formed in different matrices, the matrix affects on the formation of the defects, therefore the luminescence range. In addition it was shown that method of synthesis affected the intensity of luminescence.

Zeta Potential Determination from Molecular Simulations

Zeta potential (ZP) is among key physical properties characterizing the behavior of nanoparticles in colloidal solutions. Despite many attempts to calculate and neatly interpret the ZP, full understanding of various factors influencing its values has not been reached yet even for standard metal-oxides, particularly when considering high ionic concentrations and the effect of temperature. This contribution extends our recent work [Langmuir 2016, 32, 10189−10198], where we suggested a direct approach to calculate the ZP from nonequilibrium molecular dynamics (NEMD) simulations. Here we investigate NaCl, RbCl, CaCl2, SrCl2, and Na2C2O4 aqueous solutions interacting with TiO2 and SiO2 surfaces, and show contrasting ZP behavior for these metal-oxides, elucidated by theoretical insights gained by molecular simulations. We show that both surface-specific and ion-specific properties play a key role in the observed electrokinetics. Additionally, we explore concentration and temperature influence on the ZP of selec...

A Green, Rapid and Efficient Dual-Sensors for Highly Selective and Sensitive Detection of Cation (Hg2+) and Anion (S2-) Ions Based on CMS/AgNPs Composites.

Detection of mercury (Hg2+) and sulfide (S2−), universal and well-known toxic ions, is crucial in monitoring several diseases. How to design and fabricate the high-performance sensor for simultaneously and accurately detecting the Hg2+ and S2− is critical. Herein, we proposed a novel and convenient strategy for optical detection of Hg2+ and S2− by employing a carboxymethyl cellulose sodium/silver nanoparticle (CMS/AgNPs) colloidal solution, in which AgNPs were used as monitor for Hg2+ and S2−, and the CMS was utilized as both the stabilizer and the hydrophilic substrate for AgNPs. Well-identifiable peaks for Hg2+ and S2– were obtained in water based on UV–VIS absorption spectra, the absorbance intensity and/or position of nano-silver vary with the addition of Hg2+ cation and S2– anion, accompanying with color change. Impressively, the optimal AgNPs anchored CMS exhibited a high sensitivity and selectivity toward Hg2+ and S2−, the change in absorbance was linear with the concentration of Hg2+ (0–50 μM) and S2− (15–70 μM), and the lowest limits of detection (LOD) were 1.8 × 10−8 M and 2.4 × 10−7 M, respectively. More importantly, owing to the superior properties in testing Hg2+ and S2−, the fabricated sensor was successfully applied for detection of target ions in lake and tap water samples. All these good results implied that the designed strategy and as-designed samples is promising in detecting cation (Hg2+) and anion (S2−) ions and open up new opportunities for selecting other kinds of ions.

Generation of phthalocyanine nanoparticles by laser fragmentation

The optical properties and morphology of laser generated aluminum and copper phthalocyanine nanoparticles (nAlPc and nCuPc) in water are experimentally studied. A near-infrared laser source of nanosecond pulse duration was used for the fragmentation of a Pc micro-powder suspended in H2O. The extinction spectra in the visible and near-IR range of nanoparticle colloidal solutions in milli-Q water were acquired by means of optical spectroscopy. The optical density of both nCuPc and nAlPc increases with the laser fragmentation time. Transmission electron microscopy shows that nCuPcs are made of short (100 nm) rectangular bars interconnected at various angles with other bars. A similar morphology is observed for nAlPc.

Single-Stage Formation of Film Polymer Composites in Supercritical Colloid Solutions of Nanoparticles Obtained by Laser Ablation

Abstract—A review of earlier studies is presented together with new results on the creation of highly concentrated colloid solutions with nanoparticles of noble metals (gold and silver) in a supercritical carbon dioxide (SC–CO2) medium and the development of a single-stage method for the production of polymer nanocomposites. The effect of the SC–CO2 density on the dynamics of the formation and decomposition of supercritical fluids (SCFs) of silver and gold nanocolloids in the process of pulsed laser ablation and after its termination is studied. The possibility of the formation of colloids from bimetallic nanoparticles was considered. The effective dielectric permittivity of a colloid solution of silver nanoparticles in SC–CO2 is calculated by the numerical modeling of extinction spectra in the dipole approximation at various densities, with consideration for the size of nanoparticles and the degree of their asphericity. The formation of various film nanocomposites based on a porous copolymer polytetrafluoroethylene—vinylidenefluoride with ruby nanoparticles and two modifications of pure porous polytetrafluoroethylene with silver nanoparticles in the same SCF reactor and with a single technological process is considered.

Особенности свойств наночастиц Cu, полученных методом лазерной абляции в различных жидкостях

The results of the experimental investigations of water properties impact (distilled thorough treated water washed with helium), ethyl alcohol and acetone upon a process of Cu nano-particle obtaining by a laser ablation method are shown. Differences are defined in the spectra of the absorption of Cu nano-particle colloidal solutions, and also in the forms and dimensions of nano-particles obtained in different liquids.

Aunps and Agμps-functionalized zirconia surfaces by hybrid laser technology for dental implants

This work presents innovative zirconia surfaces functionalized with gold nanoparticles (Aunps) and silver microparticles (Agμps) through versatile laser technology where laser parameters and subtractive/additive strategies were combined to apply in dental implant surfaces regarding antibacterial potentialities. Aunps-functionalized zirconia surfaces were produced by a hybrid process starting with nanoparticles production by Nd:YAG laser ablation, followed by its deposition through spray system and its adhesion to the zirconia surface by the laser CO2 action, varying laser power and scan speed parameters. Agμps-functionalized zirconia surfaces were obtained through a hybrid laser process starting by laser texturing of the compacted zirconia surface, followed by allocation of Ag powder into the texture and its subsequent laser sintering, varying laser power. The functionalized zirconia surfaces were analyzed through SEM/EDS. In order to mimic the implant screwing effect, the samples were subjected to reciprocating friction tests against bone. It allows to evaluate the adhesion of the zirconia surface to the bone and the resistance to surface detachment. A purple colloidal solution of spherical gold nanoparticles with an average size of 5 ± 3 nm was successfully produced by laser. The friction tests revealed a good behavior of both functionalized zirconia surfaces indicating that their integrity is not affected during implant screwing insertion. A good dispersion of nanoparticles on the zirconia surface was observed indicating that the spray system is an effective way to deposit nanoparticles on the surface. A high amount of agglomerates was found for samples where low laser power (P = 11W) and scan speed (v = 1000 mm/s) were applied, probably due to the high density of energy (E). A decrease of defects on the sintered Ag layer with increasing laser power from 3 to 6 W was found, mainly related with the amount of laser energy density. The ion release showed to be strongly dependent on particle size.

Green synthesis of silver nanoparticles using aganonerion polymorphum leaves extract and evaluation of their antibacterial and catalytic activity

This study provides a fast, eco-friendly and low-cost method to synthesize stable colloidal solution of silver nanoparticles (AgNPs) using the extract of Aganonerion polymorphum (AP) leaves as a reducing and capping agent. Major parameters affecting the formation of biosynthesized AgNPs including AP leaf/water ratio, reaction time, temperature and pH were optimized at 60 g/4 00 ml, 10 min, 70 °C and 8, respectively. The AgNPs synthesized at these optimum parameters were carefully characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), powder x-ray diffraction (XRD), dispersive x-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) techniques. TEM and DLS analysis revealed that the synthesized AgNPs were formed in multi-shapes with an average size of about 30 nm. Besides, XRD data showed a highly crystalline face-centered cubic structure of silver, while EDS spectra contained strong characteristic signals of silver element. Especially, the biosynthesized AgNPs demonstrated a good antibacterial ability toward E. coli and B. cereus after just one hour of exposure with high destroying efficiency up to 99.94% and 99.75%, respectively. It’s also been found that the biosynthesized AgNPs have a good catalytic activity for the reduction of 4-nitrophenol into 4-aminophenol by NaBH4 in accordance with a pseudo first-order rate constant of 0.31 min−1.

Liquid-Phase Synthesis of Silver Sulfide Nanoparticles in Supersaturated Aqueous Solutions

Silver sulfide powders and colloidal solutions were synthesized by chemical deposition from aqueous solutions of silver nitrate and sodium sulfide in the presence of sodium citrate as a stabilizing agent. X‑ray diffraction, electronic microscopy, the Brunauer–Emmett–Teller method, and dynamic light scattering were used to determine nanoparticle sizes in the deposited powders and colloidal solutions. The varying reagent concentrations in the reaction mixture provided nanopowders with average particle sizes ranging from ~1000 to ~40–50 nm. Silver sulfide nanoparticles in colloidal solutions have sizes of 15–20 nm. A qualitative correlation is found between the silver sulfide particle size and the supersaturation of the solutions used in the synthesis.

Using Coherent Spectroscopy to Determine the Presence of Nanoparticles in Colloidal Solutions

A review is presented of using nonlinear coherent spectroscopy to monitor the state of colloidal solutions of nanoparticles (Ti, Ni, and Ag) employed to improve the performance of supercapacitors, and to determine the effect nanosilver has on the hepatitis C virus. Examples of the spectra of a colloidal silver solution in two phase states (nanosilver and silver in the finely dispersed phase) are given.

Hydrogenation reactions catalyzed by colloidal palladium nanoparticles under flow regime

AbstractA glycerol colloidal solution of palladium nanoparticles stabilized by PVP (PdPVP, mean diameter of 2.2 ± 0.8 × 10−9 m) was employed under flow conditions for hydrogenation reactions. After optimization, we selected the tube‐in‐tube flow reactor as the more suitable system for this catalytic process due to its ability to regulate the addition of hydrogen. PdPVP nanoparticles were synthesized and fully characterized ((HR)‐TEM, PXRD, EA, and ICP) both in glycerol solution and at solid state. The reduction of different substrates, including nitrobenzene, 4‐phenylbut‐3‐en‐2‐one, and isophorone, was achieved under relatively smooth conditions (5–7 × 105 Pa of H2) in short times (<600 s). Unfortunately, the reduction of 1‐dodecene was not possible due to the faster isomerization reaction. The optimal effusion of hydrogen in the colloidal phase together with the catalytic efficiency of this system is noteworthy.

Preparation of high-concentration colloid solutions of metallic copper particles and their use in metal–metal bonding processes

A high-concentration colloid solution of metallic copper nanoparticles was prepared by the reduction of copper ions in aqueous solutions, and the nanoparticles were used to study metal–metal bonding. The colloid solution of metallic copper nanoparticles was prepared by mixing an aqueous solution of CuCl2 and an aqueous solution of hydrazine (reductant) in the presence of citric acid and n-hexadecyltrimethylammonium bromide (stabilizers) at a final copper concentration as high as 0.1 M. The copper-particle size was ca. submicrometer. Many tiny particles with sizes of ca. 10–20 nm were deposited on the submicron-sized particles at high hydrazine concentrations. The tiny particles were considered to be produced through the growth of particle nuclei generated at the final reaction stage by residual hydrazine derived from the high hydrazine concentration. Metallic-copper discs were successfully bonded by annealing at 400 °C and a pressure of 1.2 MPa for 5 min in hydrogen gas with the help of the metallic-copper particles. The shear strength of the bonded copper discs was then measured. The highest shear strength of 41.7 MPa was recorded for the tiny particles/immobilized particles, which could be explained by the low melting points of the tiny particles and the increase in bulk density provided by the dominant incorporation of the tiny particles into voids between the submicron-sized particles.