Solid Silver Nanoparticles Research Articles

Solid and liquid green Ag nanoparticles based on banana peel extract as an eco‐friendly remedy for ringworm in pets

Green chemistry‐based biowaste has been taken attention toward new components for many applications especially in dermatophytes of animals and humans. The main goal of this study is to assist the synthetic pathways; clean and large‐scale synthesis of silver nanoparticles is achieved as a promising alternative green technique with high efficiency, simplicity and less hazardous waste based on agro‐waste of banana peels extract powder. The preparation of silver nanoparticles is directly via solid‐state reaction and the liquid one based on the natural agro‐waste of banana peels under specific conditions for treating ringworm in pets. Ultraviolet (UV)‐visible spectroscopy, Fourier transform infrared spectroscopy (FT‐IR), and transmission electron microscope (TEM) were used to prove the prepared nanoparticles. A total of 30 samples from pets (dogs and cats) were subjected to mycological examination. Ten (33.3%) were culture positive, and 100% of the positive samples were Microsporum canis. In vitro antifungal activity against M. canis isolates using both the disc diffusion and the broth microdilution methods was evaluated. The significant results for solid silver nanoparticles (Ags1 and Ags2) than liquid Ag NPs (AgL) with p < 0.05 compared with itraconazole were observed. This biomaterial from waste could be used as a fast, simple, eco‐friendly, and efficient method to prepare Ag NPs on solid that can be applied in the veterinary sector against ringworm.

Production of silver nanoparticles via green method using banana raja peel extract as a reducing agent

In this study, biosynthesis of silver nanoparticles using the extract of a local banana peel (variant name: Raja) as bio-reductor was carried out. This study aimed to determine the effect of two different ratios of Banana Peel Extract (BPE)/distilled water on the synthesis of silver nanoparticles. The two of BPE/water ratios were 1% (v/v) and 5%(v/v), named as Sample A and Sample B, respectively. Whereas, the concentrations of AgNO3 solution as the precursor were varied as follows: 0.125; 0.1; 0.075; and 0.05 M. The synthesized colloidal silver nanoparticles were characterized using a UV-Vis spectrometer, while the BPE solution was analyzed using Fourier Transform Infra-Red (FT-IR) to study its functional groups. While, the solid silver nanoparticles was characterized using a Scanning Electron Microscopy (SEM) with an Energy-dispersive X-ray spectroscopy (EDX) analysis. The UV-Vis spectrometer results qualitatively showed that sample A produced better silver nanoparticles than that of sample B. All samples showed absorbance peaks at wavelength of 450 nm. It was found that the highest absorbance value (i.e. 1.59) occurred at sample A with a concentration of AgNO3 solution 0.1 M. Additionally, FT-IR analysis result showed the presence of a hydroxyl group specifically for alcohols as phenols, which indicated the possibility of polyphenol compounds. The SEM micrograph showed that some of the silver nanoparticles were in the shape of tetrahedron or triangular like particle and spherical The SEM image analysis results using ImageJ software showed that most of the silver nanoparticles produced had the size of 100-300 nm. Furthermore, the EDX analysis result showed a peak count at 3 keV, which confirmed the formation of silver nanoparticles.

Femtosecond-Laser-Induced Saturable Absorption and Optical Limiting of Hollow Silver Nanocubes: Implications for Optical Switching and Bioimaging

The effects of shape, size, and surface plasmon resonance (SPR) peak position (λSPR) on nonlinear absorption (NLA) were investigated at 808 nm, using a femtosecond laser. We found that NLA behavior is the result of competition between saturable absorption (SA) and reverse saturable absorption (RSA). SA behavior, i.e., optical transparency in silver nanocrystals, is introduced by the change in shape and structure from solid nanospheres to hollow nanocubes. For the latter, SA behavior dominates at low input irradiance, while RSA dominates at higher laser powers. A series of hollow silver nanocubes (HAgNCs) was synthesized that exhibit SPR peaks at 510, 550, 590, and 630 nm, hence named as HAgNC-510, HAgNC-550, HAgNC-590, and HAgNC-630, respectively. The edge lengths (l) of HAgNC-510, HAgNC-550, HAgNC-590, and HAgNC-630 were determined to be 33 ± 4, 45 ± 8, 70 ± 10, and 100 ± 15 nm. The switching of SA to RSA occurred at lower laser power for larger HAgNCs as compared to the smaller ones. The saturation intensity (Isat) was found to vary linearly with the size of HAgNCs. Moreover, for a four-times rise in input pulse intensity (63 → 252 GW/cm2), a huge increase of 3650% in the NLA coefficient, βeff, was observed for HAgNC-590, whereas merely 19% increase was found for the solid silver nanoparticles (SAgNP-400). The extraordinary enhancement in βeff is attributed to the enhanced electric field at the sharp edges and corners of the nanocubes. The red-tailing of SPR peaks also had a significant effect on the values of βeff. The outcomes, i.e., optical transparency and SA–RSA switching, will open vistas for a variety of diverse applications such as optical switching, limiting, and bioimaging.

Numerical investigation of mixed convection heat transfer behavior of nanofluid in a cavity with different heat transfer areas

The main purpose of this research is the numerical modeling of laminar mixed convection heat transfer inside an open square cavity with different heat transfer areas. In the considered geometry, cold fluid enters the cavity. At the middle of the cavity, there is a hot isothermal circular heat source. For increasing the heat transfer, solid silver nanoparticles with volume fractions (φ) of 0, 2 and 4% are added to water. Studied Re numbers are 10, 50, 120 and 200. The location of the hot zone changes the temperature distribution in the fluid layers. If the heat transfer area is located in an appropriate location, temperature distribution becomes more uniform. Increasing Re leads to smaller temperature gradients in regions near the hot surface and higher temperature at fluid layers close to the surface. By increasing fluid velocity, backflows do not improve heat transfer but it is able to change the heat transfer mechanism. By decreasing the fluid velocity, the effects of velocity gradients and extension of the velocity boundary layer increase and friction coefficient attains the maximum value.

Interaction of coumarin 6 with carbon nanotubes: Disintegration of the microcrystalline state by surfactant aggregation on the nanotube surface

The laser dye coumarin 6 (C6) readily forms microcrystals in water through π-π stacking and hence the compound loses its inherent fluorescence yield. However, the C6 molecules can be extracted from the aggregates by creating vicinal hydrophobic environment. Herein, we have used carboxylic acid derivatives of SWCNTs that could internalize the C6 microcrystals due to less microchannel polarity. Molecular C6 could be extracted from the microcrystals trapped inside the SWCNTs by inducing hydrophobicity developed by aggregating surfactants on the outer wall of the nanotube. Spectroscopic results prove the interaction and internalization of the C6 microcrystals in the SWCNT channel and disintegration by the externally adsorbed surfactants. Internalization of the C6 microcrystals has also been proved by a control experiment using solid silver nanoparticles coated with surfactant double layer.

Placement of Single Proteins within the SERS Hot Spots of Self-Assembled Silver Nanolenses.

This study demonstrates the bottom-up synthesis of silver nanolenses. A robust coating protocol enabled the functionalization of differently sized silver nanoparticles with DNA single strands of orthogonal sequence. Coated particles 10 nm, 20 nm, and 60 nm in diameter were self-assembled by DNA origami scaffolds to form silver nanolenses. Single molecules of the protein streptavidin were selectively placed in the gap of highest electric field enhancement. Streptavidin labelled with alkyne groups served as model analyte in surface-enhanced Raman scattering (SERS) experiments. By correlated Raman mapping and atomic force microscopy, SERS signals of the alkyne labels of a single streptavidin molecule, from a single silver nanolens, were detected. The discrete, self-similar aggregates of solid silver nanoparticles are promising for plasmonic applications.

Food Quality Monitor: Paper-Based Plasmonic Sensors Prepared Through Reversal Nanoimprinting for Rapid Detection of Biogenic Amine Odorants.

This paper describes the fabrication of paper-based plasmonic refractometric sensors through the embedding of metal nanoparticles (NPs) onto flexible papers using reversal nanoimprint lithography. The NP-embedded papers can serve as gas sensors for the detection of volatile biogenic amines (BAs) released from spoiled food. Commercial inkjet papers were employed as sensor substrates-their high reflectance (>80%) and smooth surfaces (roughness: ca. 4.9 nm) providing significant optical signals for reflection-mode plasmonic refractometric sensing and high particle transfer efficiency, respectively; in addition, because inkjet papers have lightweight and are burnable and flexible, they are especially suitable for developing portable, disposable, cost-effective, eco-friendly sensing platforms. Solid silver NPs (SNPs), solid gold NPs (GNPs), and hollow Au-Ag alloyed NPs (HGNs) were immobilized on a solid mold and then transferred directly onto the softened paper surfaces. The particle number density and exposure height of the embedded NPs were dependent on two imprinting parameters: applied pressure and temperature. The optimal samples exhibited high particle transfer efficiency (ca. 85%), a sufficient exposure surface area (ca. 50% of particle surface area) presented to the target molecules, and a strong resonance reflectance dip for detection. Moreover, the HGN-embedded paper displayed a significant wavelength dip shift upon the spontaneous adsorption of BA vapors (e.g., Δλ = 33 nm for putrescine; Δλ = 24 nm for spermidine), indicating high refractometric sensitivity; in contrast, no visible spectroscopic responses were observed with respect to other possibly coexisting gases (e.g., air, N2, CO2, water vapor) during the food storage process, indicating high selectivity. Finally, the plasmonic sensing papers were used to monitor the freshness of a food product (salmon).

Facile and Scalable Preparation of Solid Silver Nanoparticles (

Metal conductive ink for flexible electroncs has exhibited a promising future recently. Here, an innovative strategy was reported to synthesize silver nanocolloid (2.5±0.5 nm) and separate solid silver nanoparticles (<10 nm) effectively. Specifically, silver nitrate (AgNO3) was used as a silver precursor, sodium borohydride (NaBH4) as a reducing agent, fatty acid (CnH2n+1COOH) as a dispersant agent, and ammonia (NH3·H2O) and hydrochloride (HCl) as a pH regulator and complexing agent in aqueous solution. The main mechanism is the solubility changes of fatty acid salts (CnH2n+1COO-NH4+) and fatty acid (CnH2n+1COOH) coated on the synthesized silver nanoparticles (NPs) in aqueous solution. This change determines the suspension and precipitation of silver NPs directly. The results show that when n in dispersant is 12 and molar ratio (C12H24O2/AgNO3) is 1.0, the separation yield of silver NPs is up to 94.8%. After sintering at 125 °C for 20 min, the as-prepared conductive silver nanoink (20 wt %) presents a satisfactory resistivity (as low as 6.6 μΩ·cm on the polyester-PET substrate), about 4 times the bulk silver. In addition, the efficacy of the as-prepared conductive ink was verified with the construction of a radio frequency antenna by inkjet printing and conductive character pattern (Fudan-Fudan) by direct wiring, showing excellent electrical performance.

In situ functionalization of highly porous polymer microspheres with silver nanoparticles via bio-inspired chemistry

Organic–inorganic hybrid porous microparticles.

Preparation of solid silver nanoparticles for inkjet printed flexible electronics with high conductivity

Silver nanoparticles (NPs) which could be kept in solid form and were easily stored without degeneration or oxidation at room temperature for a long period of time were synthesized by a simple and environmentally friendly wet chemistry method in an aqueous phase. Highly stable dispersions of aqueous silver NP inks, sintered at room temperature, for printing highly conductive tracks (∼8.0 μΩ cm) were prepared simply by dispersing the synthesized silver NP powder in water. These inks are stable, fairly homogeneous and suitable for a wide range of patterning techniques. The inks were successfully printed on paper and polyethylene terephthalate (PET) substrates using a common color printer. Upon annealing at 180 °C, the resistivity of the printed silver patterns decreased to 3.7 μΩ cm, which is close to twice that of bulk silver. Various factors affecting the resistivity of the printed silver patterns, such as annealing temperature and the number of printing cycles, were investigated. The resulting high conductivity of the printed silver patterns reached over 20% of the bulk silver value under ambient conditions, which enabled the fabrication of flexible electronic devices, as demonstrated by the inkjet printing of conductive circuits of LED devices.

Synthesis of silver hollow nanoparticles and observation of photoluminescence emission properties

Preparation of hollow silver nanoparticles (HSNs) along-with solid silver nanoparticles are reported by Nd:YAG laser ablation of solid silver target immersed in water medium with a laser ablation time (LAT) duration of 50min and with the incident laser fluence of 151J/cm2. It is found that only solid silver nanoparticles are produced when the experiment is carried out with smaller values of LAT duration. The synthesized samples are characterized by using transmission electron microscopy and UV–Visible absorption spectroscopy. The UV–Visible absorption spectra of the samples show sharp absorptions in the ultraviolet and in visible regions due to interband transition and surface plasmon resonance oscillations in Ag nanoparticles, respectively. It is found that all samples exhibit photoluminescence (PL) emission, at room temperature, in the UV–Visible region peaked at ∼346nm, due to the recombination of electrons with holes from sp conduction band to d band of Ag. The sample containing HSNs exhibits strong PL emission and the value of peak PL emission intensity is enhanced by the factor of 2.4 in comparison to that obtained from the sample synthesized with LAT duration of 20min. The synthesized HSNs may find applications in catalysis and in chemical sensing.

Resonance light scattering characters of core–shell structure of Au–Ag nanoparticles

Nanoparticles containing gold cores and silver shells have been synthesized via electrochemical method. The resonance light scattering spectrum has been studied at room temperature. Scattering features show two peaks at 370 nm and 570 nm, which result from the scattering of solid silver nanoparticles and silver coated gold nanoparticles, respectively. The calculation results based on quasi-static theory indicate that with the increasing ratio of the core radius to the total radius of the compound nanoparticles, the peak of scattering cross section decreases first then increases and reaches the minimum when the ratio is about 0.5. And meanwhile the scattering peak red shifts nonlinearly. Furthermore, with the increasing dielectric constant of surrounding medium, the scattering peak increases monotonic and red shifts.