Mean Size Distribution Research Articles

Laser-Induced Shockwave Crystallization in Supersaturated Solutions and Conceivable Clustering in Undersaturated Aqueous Potassium Nitrate Solutions.

In this study, a newly developed setup based on laser-induced shockwave crystallization coupled with electric conductivity monitoring was employed to study the growth of crystals in supersaturated solutions and to investigate possible clustering in undersaturated solutions of potassium nitrate (KNO3). A comparison was drawn between crystals induced by laser irradiation, by shockwaves, and spontaneously in terms of crystals' mean size, shape, and size distribution. The size distribution of produced crystals by shockwaves was also characterized in terms of laser irradiation time. The results show that produced crystals by shockwaves propagation have the sharpest size distribution and the smallest mean dimensions compared to crystals grown spontaneously or by direct laser induction. Real-time monitoring of nucleation was also performed in supersaturated solutions, while decrease in conductivity was observed in undersaturated solutions as a function of laser irradiation time.

Dual pulsed laser deposition of Ag nanoparticles on calcium phosphate coatings for biomedical applications

Pulsed laser deposition (PLD) represents a promising bottom-up methodology for the synthesis and transference of nanoparticles to the surface of a biomedical device. Silver (Ag) nanoparticles directly incorporated on the metallic implant emerge as an alternative strategy for local action against prosthetic joint-associated infections. In the present research, a dual sequential PLD process is proposed to obtain a bilayer coating with (1) a bio-derived calcium phosphate (CaP) layer, to provide osteointegrative properties and (2) the controlled growth of the Ag nanoparticles over it, ranging the number of laser pulses from 100 to 500. The characterization by SEM, EDS, TEM, XPS and AFM revealed the uniform deposit of Ag rounded nanoparticles, with a narrow mean size distribution, in the original non-oxidized metallic state. Moreover, given the evidences from XPS and AFM techniques, the occurrence of a coalescence phenomenon from 400 pulses onwards was proposed together with the expected positive linear relation between the number of pulses and Ag contribution with a deposition rate of 0.05 at. % of Ag per pulse. Conversely, the decrease in roughness as the Ag content increased was also verified. Finally, the expected bacteriostatic activity for these PLD deposited metallic state Ag nanoparticles against the bacterial strain Staphylococcus aureus was confirmed. Moreover, the evaluation of the osteoblast-like MG-63 cells viability on the Ag(100–500)-CaP coatings revealed a significant increased proliferation (p > 0.05) on the Ag100-CaP coating compared to the control (Ag0-CaP). When same coating was evaluated against S. aureus the effect was not significant. The possibility of modulating the amount of nanoparticles in the bilayer coating to obtain a greater or lesser effect in combination with CaP was revealed.

Key Health Benefits of Korean Ueong Dry Root Extract Combined Silver Nanoparticles.

IntroductionNowadays, in nanotechnology and material science, biosynthesis of the metal nanoparticle is a promising approach.MethodsIn the current research, the extract of the Korean Ueong dry root (BdkR), which belongs to the Asteraceae family, was used as a reducing and capping agent, for the green synthesis of the BdkR-Ag nanoparticles in a cost-effective and highly efficient manner. In this study for the reaction measures, UV-Vis spectroscopy was applied. SEM, EDX, FTIR, XRD, mean size distribution, and zeta potential were used for the characterization of the green synthesized BdkR-AgNPs. In the beginning, the primary phytochemical screening of BdkR extract was estimated and the cytotoxicity, antidiabetic, antioxidant, and antibacterial activities of the green synthesized BdkR-AgNPs were evaluated.ResultsAccording to the results, the BdkR extract is rich in various phytochemicals and the generated AgNPs were crystalline in nature. The surface plasmon resonance value of the BdkR-AgNPs was 444 nm confirming the synthesis of AgNPs. The BdkR-AgNPs displayed four clear diffraction peaks at 2 theta angles (38.22); (46.15); (64.88); (76.83), respectively, which are equivalent to (111), (200), (220) and (311). The obtained nanoparticles have a zeta potential of −17.0 mV. Furthermore, the generated BdkR-AgNPs exhibited considerable antidiabetic effect in terms of the inhibition of α-glucosidase with a maximum inhibition value of 95.41% at 5.0 µg/mL and more than 86% inhibition at 2.5 µg/mL and the estimated IC50 value was found to be 0.653 µg/mL. Further, it also displayed a significant cytotoxicity activity against the HepG2 cancer cell lines at 10 µg/mL and 100 µg/mL concentrations with 86% and 88% of inhibition, respectively. Besides this, the synthesized AgNPs also displayed promising antioxidant activities in terms of the DPPH (IC50 value - 56.26 µg/mL), ABTS (IC50 value - 171.43 µg/mL) and reducing power (IC0.5 value - 227.42 µg/mL).DiscussionThe multipotential effects of the synthesized BdkR-AgNPs might be attributed to the presence of the bioactive compounds in the BdkR extract that acted as the capping and reducing agent in the synthesis process. The green synthesized BdkR-AgNPs exhibited promising bioactive potential for their future applications in the food and biomedical field.

Investigation of Factors Influencing Formation of Nanoemulsion by Spontaneous Emulsification: Impact on Droplet Size, Polydispersity Index, and Stability.

Interest in nanoemulsion technology has increased steadily in recent years for its widespread applications in the delivery of pharmaceuticals, nutraceuticals, and cosmeceuticals. Rational selection of the composition and the preparation method is crucial for developing a stable nanoemulsion system with desired physicochemical characteristics. In the present study, we investigate the influence of intricate factors including composition and preparation conditions that affect characteristic parameters and the stability of the nanoemulsion formation prepared by the spontaneous emulsification method. Octanoic acid, capryol 90, and ethyl oleate were selected to represent oil phases of different carbon–chain lengths. We explored the impact of the addition mode of the oil–Smix phase and aqueous phase, vortexing time, Km (surfactant/cosurfactant) ratio, and the replacement of water by buffers of different pH as an aqueous system. The phase behavior study showed that the Smix phase had a significant impact on the nanoemulsifying ability of the nanoemulsions composed of oil phases of varying carbon-chain lengths. The mode of mixing of the oil–Smix phase to the aqueous phase markedly influenced the mean droplet size and size distribution of the nanoemulsions composed of oil phases as capryol 90. Vortexing time also impacted the mean droplet size and the stability of the generated nanoemulsion system depending on the varying carbon-chain length of the oil phase. The replacement of the water phase by aqueous buffers of pH 1.2, 5.5, 6.8, and 7.4 has altered the mean droplet size and size distribution of the nanoemulsion system. Further, the Km ratio also had a significant influence on the formation of the nanoemulsion system. The findings of this investigation are useful in understanding how the formulation composition and process parameters of the spontaneous emulsification technique are responsible for affecting the physicochemical characteristics and stability of the nanoemulsion system composed of oil of varying carbon-chain (C8-C18) length.

Noteworthy differences between vertical and horizontal sintering of ceramic samples

Sintering of ceramics is known to suffer from homogeneity issues (of phase, microstructure, etc.). The present work aims to provide a simple solution for the same via positioning the sample vertically during conventional sintering. Via vertical sintering, we present two different case studies (with doped-ZrO2 and La2Ce2O7 systems) and illustrate two distinct benefits; e.g., restricting the formation of an otherwise deleterious monoclinic phase in zirconia bodies, and ensuring uniform in-plane texture development on both sides of the ceramic. In each case, the issues observed in the horizontally placed ceramic have been explained in connection to the heat transfer in the ceramic body. Discrepancies in heat transfer resulted in variations in grain orientation and size (mean, median, and cumulative size distribution), eventually leading to different phase developments and texture. This small adjustment (of the positioning of ceramic bodies) may be beneficial at an industrial scale; especially with samples having a large length/diameter ratio.

Importance of Microstructure on Precipitation in Tempering of Martensitic Steels

Precipitation hardening is one of most effective strengthening mechanisms in steels, and much research has been performed in the past. To evaluate the contribution of precipitates, the quantitative features of precipitates including mean size and particle size distribution etc., are vital and needed. However, the predictive modeling of precipitation is still a challenge so far, especially on a quantitative level. Thus, in the present work, precipitation of carbides after tempering of martensitic Fe-Cr-C alloys, consisting of hierarchically arranged substructures within the prior-austenite grains, namely packets and blocks of individual laths, up to 1000h has been investigated. Experimental measurements using electron microscopy and modeling using a Langer-Schwartz theory with the Kampmann-Wagner -Numerical (KWN) method have been conducted. The importance of a proper definition of the initial microstructure for predictive modeling is discussed, in terms of the comparison of calculated and experimental results.

Characterization of extracellular vesicles isolated from different liquid biopsies of uveal melanoma patients.

Purpose: Uveal melanoma (UM) is the most common intraocular malignant tumor in adults. Extracellular vesicles (EVs) have been extensively studied as a biomarker to monitor disease in patients. The study of new biomarkers in melanoma patients could prevent metastasis by earlier diagnosis. In this study, we determined the proteomic profile of EVs isolated from aqueous humor (AH), vitreous humor (VH), and plasma from UM patients in comparison with cancer-free control patients. Methods: AH, VH and plasma were collected from seven patients with UM after enucleation; AH and plasma were collected from seven cancer-free patients with cataract (CAT; control group). EVs were isolated using the membrane-based affinity binding column method. Nanoparticle tracking analysis (NTA) was performed to determine the size and concentration of EVs. EV markers, CD63 and TSG101, were assessed by immunoblotting, and the EV proteome was characterized by mass spectrometry. Results: Mean EV concentration was higher in all analytes of UM patients compared to those in the CAT group. In the UM cohort, the mean concentration of EVs was significantly lower in AH and plasma than in VH. In contrast, the mean size and size distribution of EVs was invariably identical in all analyzed analytes and in both studied groups (UM vs. CAT). Mass spectrometry analyses from the different analytes from UM patients showed the presence of EV markers. Conclusion: EVs isolated from AH, VH, and plasma from patients with UM showed consistent profiles and support the use of blood to monitor UM patients as a noninvasive liquid biopsy.

Gas Bubble Dynamics During Methane Hydrate Formation and its Influence on Geophysical Properties of Sediment Using High-Resolution Synchrotron Imaging and Rock Physics Modeling

Gas bubble in aquatic sediments has a significant effect on its geophysical and geomechanical properties. Recent studies have shown that methane gas and hydrate can coexist in gas hydrate–bearing sediments. Accurate calibration and understanding of the fundamental processes regarding such coexisting gas bubble dynamics is essential for geophysical characterization and hazard mitigation. We conducted high-resolution synchrotron imaging of methane hydrate formation from methane gas in water-saturated sand. While previous hydrate synchrotron imaging has focused on hydrate evolution, here we focus on the gas bubble dynamics. We used a novel semantic segmentation technique based on convolutional neural networks to observe bubble dynamics before and during hydrate formation. Our results show that bubbles change shape and size even before hydrate formation. Hydrate forms on the outer surface of the bubbles, leading to reduction in bubble size, connectivity of bubbles, and the development of nano-to micro-sized bubbles. Interestingly, methane gas bubble size does not monotonously decrease with hydrate formation; rather, we observe some bubbles being completely used up during hydrate formation, while bubbles originate from hydrates in other parts. This indicates the dynamic nature of gas and hydrate formation. We also used an effective medium model including gas bubble resonance effects to study how these bubble sizes affect the geophysical properties. Gas bubble resonance modeling for field or experimental data generally considers an average or equivalent bubble size. We use synchrotron imaging data to extract individual gas bubble volumes and equivalent spherical radii from the segmented images and implement this into the rock physics model. Our modeling results show that using actual bubble size distribution has a different effect on the geophysical properties compared to the using mean and median bubble size distributions. Our imaging and modeling studies show that the existence of these small gas bubbles of a specific size range, compared to a bigger bubble of equivalent volume, may give rise to significant uncertainties in the geophysical inversion of gas quantification.

Ammonium Glycyrrhizinate and Bergamot Essential Oil Co-Loaded Ultradeformable Nanocarriers: An Effective Natural Nanomedicine for In Vivo Anti-Inflammatory Topical Therapies.

Bergamot essential oil (BEO) and Ammonium glycyrrhizinate (AG), naturally derived compounds, have remarkable anti-inflammatory properties, thus making them suitable candidates for the treatment of skin disorders. Despite this, their inadequate physicochemical properties strongly compromise their topical application. Ultradeformable nanocarriers containing both BEO and AG were used to allow their passage through the skin, thus maximizing their therapeutic activity. Physicochemical characterization studies were performed using Zetasizer Nano ZS and Turbiscan Lab®. The dialysis method was used to investigate the release profile of the active compounds. In vivo studies were performed on human healthy volunteers through the X-Rite spectrophotometer. The nanosystems showed suitable features for topical cutaneous administration in terms of mean size, surface charge, size distribution, and long-term stability/storability. The co-delivery of BEO and AG in the deformable systems improved both the release profile kinetic of ammonium glycyrrhizinate and deformability properties of the resulting nanosystems. The topical cutaneous administration on human volunteers confirmed the efficacy of the nanosystems. In detail, BEO and AG-co-loaded ultradeformable vesicles showed a superior activity compared to that recorded from the ones containing AG as a single agent. These results are promising and strongly encourage a potential topical application of AG/BEO co-loaded nanocarriers for anti-inflammatory therapies.

Optimization of large-scale manufacturing of biopolymeric and lipid nanoparticles using microfluidic swirl mixers

Nanoparticles (NPs) have great potential as efficient drug delivery systems (DDSs) that have been widely used in cancer therapy and vaccines especially in the past decade. The rise in demand from the pharmaceutical industry drives the growth of the global NPs market. However, complex production processes have hindered the market growth. Therefore, the development of advanced preparation techniques such as microfluidics is required to improve productivity and controllability. In this study, we present a novel microfluidic design (swirl mixer) that helps accelerating the translation of many DDSs from laboratory to clinical application. The new swirl mixer provides high production rate, reproducibility, and precise control of particle size with low polydispersity index (PDI). To assess the performance of the swirl mixer, two different types of nanoformulations were used: silk nanoparticles (SNPs) and lipid nanoparticles (LNPs). The microfluidic device produced NPs efficiently with high productivity and allowed for tuning the mean size and size distribution by changing multiple processing parameters.

A coupled MMC-LES and sectional kinetic scheme for soot formation in a turbulent flame

A soot kinetic sectional scheme is coupled with the sparse multiple mapping conditioning / large eddy simulation (MMC-LES) method to model soot formation in a turbulent, non-premixed, piloted methane flame (Delft Flame III). The kinetic sectional scheme used here discretises the population balance equation according to soot particle size. The sections (or bins) are treated as lumped species, and the physico-chemical soot formation is modelled through elementary-like reaction pathways with Arrhenius rate expressions. This allows the soot kinetics to be naturally coupled with the gas phase molecular kinetics. Interactions of soot formation and molecular chemistry with turbulence is achieved through the MMC-LES model. This is a Monte Carlo filtered density function approach in which the micromixing is local in an independent reference space permitting use of a computationally efficient sparse distribution of stochastic notional particles. The model results are compared to experimental data for the gas-phase velocity and molecular species in the upstream low-soot region and with soot statistics in the downstream region. The gaseous quantities have very good agreement with the experimental data. Overall the soot predictions are in good qualitative agreement with the data, particularly with respect to the peak value of the mean soot volume fraction, the shape and range of the joint probability density function of soot volume fraction and spatial location, and the rate of soot oxidation and burnout. However, in common with other published attempts at the Delft Flame III using a range of different models, the predicted soot formation begins and peaks well upstream of the experimental measurements. The minimum soot intermittency is underpredicted relative to the data but shows a significant improvement on previous attempts to model it. The analysis also explores the evolution of the mean and instantaneous particle size distributions and some aspects of soot-chemistry-turbulence interactions.

Efficient extraction of carrageenans from Chondrus crispus for the green synthesis of gold nanoparticles and formulation of printable hydrogels

The integral utilization of sustainable resources with versatile, efficient and cleaner processes is encouraged. Hydrothermal treatment with subcritical water is a chemical free, tunable and rapid technology providing enhanced yield compared to conventional extraction and was explored for the benign by design extraction and depolymerization of carrageenan from Chondrus crispus. Up to 90% of the seaweed was solubilized operating under nonisothermal regime during heating up to 200 °C and 75.5% crude carrageenan yield was attained at 140 °C. Crude carrageenan could not be precipitated by ethanol from the extracts produced at 180 °C and higher temperatures, but ultrafiltration (100 kDa) of the extract obtained at 160 °C provided comparable recovery yields and similar rheological features to those of the ethanol precipitated product. Operation at 140 °C was preferred based on the higher recovery yield of the biopolymer and the whole extract was suitable for the green synthesis of polycrystalline decahedral quasi-spherical gold nanoparticles with a mean size distribution of 8.4 nm and Z potential value of −40.2 mV. Alternatively, the crude carrageen fraction was used for the formulation of printable biopolymer based gels with suitable mechanical properties, including a relevant gel strength enhancement (about 10-fold) when compared with conventional procedures.

Photo-oxidative degradation of polyacids derived ceria nanoparticle modulation for chemical mechanical polishing

The effects of photo-oxidative degradation of polyacids at various concentrations and with different durations of ultraviolet (UV) irradiation on the photo-reduction of ceria nanoparticles were investigated. The effect of UV-treated ceria on the performance of chemical mechanical polishing (CMP) for the dielectric layer was also evaluated. When the polyacids were exposed to UV light, they underwent photo-oxidation with consumption of the dissolved oxygen in slurry. UV-treated ceria particles formed oxygen vacancies by absorbing photon energy, resulting in increased Ce3+ ions concentration on the surface, and when the oxygen level of the solution was lowered by the photo-oxidation of polymers, the formation of Ce3+ ions was promoted from 14.2 to 36.5%. Furthermore, chain scissions of polymers occurred during the oxidation process, and polyacids with lower molecular weights were found to be effective in ceria particle dispersion in terms of the decrease in the mean diameter and size distribution maintaining under 0.1 of polydispersity index. With increasing polyacid concentration and UV irradiation time, the Ce3+ concentration and the dispersity of ceria both increased due to the photo-oxidative degradation of the polymer; this enhanced the CMP performance in terms of 87% improved material removal rate and 48% lowered wafer surface roughness.

Drug Delivery from Stimuli-Responsive Poly(N-isopropylacrylamide-co-N-isopropylmethacrylamide)/Chitosan Core/Shell Nanohydrogels

The synthesis of stimulus-responsive poly(N-isopropylacrylamide-co-N-isopropylmethacrylamide)/chitosan core/shell nanohydrogels made by batch emulsion polymerization in the presence of chitosan (CS) micelles is reported. The ratio of monomers required to obtain copolymers with a volume phase transition temperature (TVPT) in the range of the temperatures observed in the human body in response to an infection (38 to 40 °C) was estimated with the Fox equation. The conversion was determined by gravimetry; mean particle size, size distribution, and thermal response were measured by quasi-elastic light scattering (QLS). The core/shell structure was confirmed by TEM, and FTIR showed the presence of N-isopropyl acrilamide (NIPA), N-isopropyl methacrylamide (NIPMA), and CS in the nanohydrogels. The nanohydrogels were loaded with the drug doxycycline hyclate, and their release kinetic profile was determined at pH = 2.0 and 7.4 at their volume phase transition temperatures (TVPT). A higher amount of drug was released at acidic pH. Some mathematical models described in the literature were used to fit the experimental drug release data.

Scavenging of Black Carbon Aerosols by Radiation Fog in Urban Central China

Radiation fog episodes are characterized by aerosol radiative properties measured at Hefei in urban central China, which hopefully benefits numerical weather prediction and air quality improvement for local governments. In this study, a high mean aerosol optical depth (AOD) is seen over Hefei during the sampling period, whereas an AOD of ~3.0 at 550 nm is observed during the fog episodes. We redefine the fog scavenging coefficient based on its starting and ending points in time, and a black carbon (BC) scavenging coefficient of 30% is observed. Meanwhile, the fog process cannot reduce aerosol number concentrations at size bins between 0.5 and 0.6 μm, whereas a mean particle scavenging coefficient of 21% at sizes within 0.6–1 μm is seen. Significantly large median aerosol scattering coefficient (2690 Mm−1) and absorption coefficient (446 Mm−1) at 550 nm, and low scattering Angstrom exponent in fog are observed, while distinctive particle size distributions between fog and haze are shown. Particle mean size distribution in fog is lower than that in haze at size bins between 0.7 and 2.1 μm, whereas the reverse is true for sizes within 0.5–0.7 μm and larger than 2.1 μm. Aerosol scattering during fog episodes undergoes a bigger increase than particle absorption, and this increase of scattering in fog is even higher than in haze. Median single scattering albedos of 0.86, 0.82, and 0.76 at 550 nm and aerosol radiative forcing efficiencies of −15.0, −14.0, and −10.0 W/m2 are seen for fog, haze and clear periods, respectively, and more negative radiative forcing efficiency emphasizes the significance of fog episodes on climate forcing. Our study clearly reveals the changes of aerosol radiative properties during radiation fog, particularly a synchronous variation of fog aerosol backscattering ratio with the visibility, indicating that more large particles are formed with fog becoming thicker and are scavenged with the dissipation of fog.

A novel method for the microencapsulation of curcumin by high-pressure processing for enhancing the stability and preservation

Curcumin is used for the development of new pharmaceutical and food products, but its application is generally hindered by the poor solubility of curcumin and thermal instability during storage and processing. In this study, the liposomes of curcumin (cur-liposomes) were prepared by a novel combination of ethanol injection and high-pressure processing (HPP) to enhance the stability and preservation of curcumin. The pasteurization, mean particle size, size distribution, and encapsulation efficiency of cur-liposomes and the kinetics of their thermal degradation were also investigated in this research. From the results, the kinetic rate constants of curcumin in samples of free curcumin and cur-liposome at 25 °C were found to be 1.6 × 10−3 and 0.8 × 10−3 min−1, respectively. The phospholipid bilayer structure could protect curcumin. The results propose that the HPP method for liposome preparation is superior to the probe-sonication method in terms of stability, encapsulation efficiency, and homogeneity. Furthermore, the preparation of cur-liposomes by HPP with a hydrostatic pressure of 200 MPa could maintain the optimal particle size (206.4 nm) and polydispersity index (0.19). Conclusively, the combination of ethanol injection and HPP can not only successfully inactivate the microorganisms during liposome preparation for microencapsulation of bioactive compounds but also effectively preventthe thermal degradation of heat-sensitive substances in non-thermal processing for practical applications.

Control of electrostatic self-assembly seeding of diamond nanoparticles on carbon nanowalls

Seeding of diamond nanoparticles on vertically-aligned multi-layer graphene, the so-called carbon nanowalls (CNWs), is studied by using deionized water, ethylene glycol, ethanol, and formamide as dispersion mediums. Detonation nanodiamond particles show the smallest mean size and size distribution with a high positive zeta potential when dispersed in ethanol. The contact angle of ethanol on CNWs is almost zero degree, confirming highly wetting behaviour. The diamond nanoparticles dispersed in ethanol are distributed the most uniformly with minimal aggregation on CNWs as opposed to those dispersed in other liquids. The resulting diamond nanoparticle-seeded CNWs, followed by short-term growth in microwave plasma chemical vapor deposition, show a marked decrease in field emission turn-on field down to 1.3 V μm−1 together with a large increase in current density, compared to bare CNWs without diamond seeding. The results provide a way to control the density, size, and uniformity (spacing) of diamond nanoparticles on CNWs and should be applied to fabricate hybrid materials and devices using nanodiamond and nanocarbons.

PTFE emulsion treatment of polyimide/superfine glass fiber needle-punched complex filters

In order to improve the filtration properties of the filters, polytetrafluoroethylene (PTFE) emulsion was utilized to modify Polyimide (P84)/superfine glass fiber needle-punched complex filters. The orthogonal test was conducted to optimize treatment process based on quality factor of the filters. Under the optimal treatment conditions, the filtration performances, morphology, pore size, air permeability and tensile properties of complex filters without and with PTFE emulsion treatment were investigated and compared, respectively. The experimental results showed that quality factor was significantly improved compared to the untreated filters, meaning possessing better filtration properties. It benefited from the formation of echelon structure converted deep filtration to surface filtration due to the micro-porous effect. The decreased mean pore size, size distributions and air permeability verified this point. Additionally, tensile strength and elongation improved slightly due to compact entanglements appeared on the filters.

Comparative Analysis of Nanosilver Particles Synthesized by Different Approaches and Their Antimicrobial Efficacy

Silver nanoparticles (AgNPs) were extensively used in different fields worldwide. There is a continued increase in their productions to fulfill various uses. Biological and chemical AgNP syntheses were the most popular mechanisms in this field. Agrowastes are rich in proteins, phenolics, and flavonoids that could act as bioreductant agents in AgNP biological synthesis. The present study was aimed at synthesizing AgNPs via chemical and biological methods using trisodium citrate, pomegranate fruit peel, and coffee ground waste extracts. Moreover, silver nanoparticles were monitored by UV-vis spectroscopy and characterized using zeta potential, size distribution mean, scanning electron microscope (SEM), X-ray diffractometer (XRD), and Fourier transforms infrared spectroscopy (FTIR). Four pathogenic bacterial strains (Enterobacter aerogenes, Klebsiella pneumoniae, Pseudomonas aeruginosa, and MRSA) were used to assess the antimicrobial effect of the synthesized AgNPs (2, 4, and 8 mg/ml). Results report the successful formation of silver nanoparticles chemically (AgNPs_Chem) and biologically by using pomegranate peel extract (AgNPs_PPE) and coffee ground waste extract (AgNPs_CE) due to the change of color to dark brown that is confirmed by UV-vis sharp absorption spectra at specific wavelengths. Characterization using SEM and XRD revealed their crystalline shape with a mean size of AgNPs _ Chem = 62.75 , AgNPs _ CE = 273.7 nm , and AgNPs _ PPE = 591.9 nm . AgNPs_Chem show higher negativity of zeta potential (−46.7 mV) than AgNPs_CE (−12.6 mV), followed by AgNPs_PPE (−7.98 mV), which had the least stability. All the synthesized AgNPs show antimicrobial potential on all selected strains. However, 8 mg/ml shows the most effective concentration and has more efficiency on K. pneumoniae than others. Overall, the results highlight that the use of agrowastes could be an ecofriendly way to synthesize AgNPs biologically that have the same antimicrobial effect as the chemically synthesized AgNPs.

Fabrication of silver nanoparticle films by pulsed laser deposition in flowless open air and studying the effects of laser fluence and number of pulses

In the present work, pulsed laser deposition of silver in open air is used to fabricate Ag nanoparticle (NP) films on the substrate without using flowing gas. The target was ablated by trains of nanosecond pulsed Nd:YAG laser beam. The deposited NP films on the substrate were characterized using field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and UV/Vis absorption spectroscopy. Surface plasmon resonance (SPR) characteristics of NPs were extracted from the data of UV/Vis spectrum. Mean size and size distribution of NPs were achieved by analyzing the FESEM images and using image processing technique. In order to show an application of the fabricated NP film in sensors, surface enhanced Raman spectroscopy (SERS) of NP films were inspected. The results of SERS show that the fabricated NP films can significantly enhance Raman signals.