Plasma parameters of magnetically confined Cobalt (Co) plasma have been evaluated by using laser-induced breakdown spectroscopy at various laser irradiances, under different ambient pressures of two ...environments such as Ar and Ne and at different time delays. The effect of laser irradiance on Co plasma is exposed in the presence and absence of a Transverse Magnetic field (TMF) while keeping environmental gas pressure constant, i.e., 10 Torr. For this purpose, Co pellets were exposed to Nd: YAG laser (1064 nm, 10 ns) at various laser irradiances ranging from 1 to 2.9 GW cm−2. To investigate the impact of background gas pressures, Co pellets were exposed to various pressure varying from 5 to 760 Torr of Ar and Ne. In the case of time delay variation, the Co plasma parameters Texc and ne decrease exponentially. A significantly pronounced effect of the presence of an external TMF of strength 0.9 T on time-integrated Co plasma parameters has been revealed. Plasma parameters Texc and ne are considerably increased in the presence of TMF in both ambient environments because of being constrained to a very small region due to which collisions will be enhanced. Implementation of the 0.9 T TMF on a laser-induced plasma of Co is responsible for the confinement of plasma. The surface morphology of laser-irradiated Co samples was also discussed to confirm the effect of TMF. Fine and uniform structures are observed in samples treated in the presence of TMF by using the SEM technique.
In this work, effects of laser irradiation on several characteristics of vanadium (99.999%) are examined. The square-shaped vanadium samples were irradiated using pulsed Nd:YAG laser (532 nm, 6 ns) ...at a high fluence (7.46 J/cm
2
) with 100, 200, 300, and 400 laser shots under vacuum. X-ray diffraction results revealed the preferred orientation of the unirradiated vanadium along (200) plane that remained un-changed upon laser irradiation. The crystallite size varied in the range 30–62 nm and the average diameter of laser-ablated region was decreased with the increase of laser shots. On the contrary, the heat-affected area around the ablated region and the surface roughness progressively increased on increasing the number of laser shots. The morphological features of the laser-irradiated vanadium comprised of cavities, microcones, cracks, grooves dips, bubbles, droplets, ripples, micro-pillars, and wave-like structures. The hardness of the samples (166–184 HV) was decreased with increase of the crystallite size (30–62 nm) and vice versa. The samples irradiated with the laser for 100 and 200 shots exhibited a higher corrosion rate as compared to the un-irradiated sample. However, the corrosion rate was reduced as the number of laser shots were increased to 300 and then 400, demonstrating an improvement in the vanadium corrosion resistance.
Abstract
The encapsulation of plant extract in nanomatrices has limitations due to its adhesion to walls, size control, high cost and long durations that results in low yield. Macroscale and ...microscale level techniques for development of micro/nanoparticles may impact the encapsulation of plant extract. This study aimed to evaluate the relative efficiency of microscale and macroscale techniques for encapsulation of plant extract, which is not compared yet. Keeping this in view, encapsulation of
Calotropis gigantea
leaves extract (CaG) was attained in silver-conjugated poliglusam nanomatrices (POL/Ag) to induce apoptosis in invasive ductal carcinoma (IDC) cells. The ethanolic CaG extract was prepared using percolation method and characterized by chemical tests for its active phytochemical compounds. The droplet-based microfluidic system was utilized as microscale encapsulation technique for CaG in nanomatrices at two different aqueous to oil flow rate ratios 1.0:1.5, and 1.0:3.0. Moreover, conventional batch system was utilized as macroscale encapsulation technique consisted of hot plate magnetic stirrer. The prepared nanomatrices were analysed for antioxidant activity using DPPH test and for cytotoxicity analysis using MCF-7 cells. The characteristic peaks of UV–Vis, FTIR and XRD spectrum confirmed the synthesis of CaG(POL/Ag) by both the encapsulation methods. However, microfluidic system was found to be more expedient because of attaining small and uniform sized silver nanoparticles (92 ± 19 nm) at high flow rate and achieving high encapsulation efficiency (80.25%) as compared to the conventional batch method (52.5%). CaG(POL/Ag) nanomatrices found to have significant antioxidant activity (
p
= 0.0014) against DPPH radical scavenging activity. The CaG(POL/Ag) of the smallest sized formulated by the microfluidic system has also shown the highest cytotoxicity (90%) as compared to batch method (70%) at 80 µg/mL. Our results indicate that the microscale technique using microfluidic system is a more efficient method to formulate size-controlled CaG(POL/Ag) nanomatrices and achieve high encapsulation of plant extract. Additionally, CaG(Pol/Ag) was found to be an efficient new combination for inducing potent (
p
< 0.0001) apoptosis in IDC cells. Therefore, CaG(Pol/Ag) can be further tested as an anti-cancer agent for in-vivo experiments.
Microdroplet formation is an emerging area of research due to its wide-ranging applications within microfluidic based lab-on-a-chip devices. Our goal is to understand the dynamics of droplet ...formation in a microfluidic T-junction in order to optimize the operation of the microfluidic device. Understanding of this process forms the basis of many potential applications: synthesis of new materials, formulation of products in pharmaceutical, cosmetics and food industries. The two-phase level set method, which is ideally suited for tracking the interfaces between two immiscible fluids, has been used to perform numerical simulations of droplet formation in a T-junction. Numerical predictions compare well with experimental observations. The influence of parameters such as flow rate ratio, capillary number, viscosity ratio and the interfacial tension between the two immiscible fluids is known to affect the physical processes of droplet generation. In this study the effects of surface wettability, which can be controlled by altering the contact angle, are investigated systematically. As competitive wetting between liquids in a two-phase flow can give rise to erratic flow patterns, it is often desirable to minimize this phenomenon as it can lead to a disruption of the regular production of uniform droplets. The numerical simulations predicted that wettability effects on droplet length are more prominent when the viscosity ratio
λ
(the quotient of the viscosity of the dispersed phase with the viscosity of the continuous phase) is O(1), compared to the situation when
λ
is O(0.1). The droplet size becomes independent of contact angle in the superhydrophobic regime for all capillary numbers. At a given value of interfacial tension, the droplet length is greater when
λ
is O(1) compared to the case when
λ
is O(0.1). The increase in droplet length with interfacial tension,
σ
, is a function of
ln
σ
with the coefficients of the regression curves depending on the viscosity ratio.
► Two phase level set method suitable for simulating droplet formation. ► Wettability effects can be pronounced in droplet formation. ► Droplet size independent of contact angle in superhydrophobic regime. ► Droplet length is a function of the logarithm of the interfacial tension.
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•Tin sulfide films are grown by chemical bath deposition.•Role of complexing agent concentration on the physical properties is studied.•Control on structure is obtained over the ...triethanolamine (TEA) concentration range.•Films exhibit direct band gap which is found not affected significantly with TEA.
This paper reports the experimental results studying the structure, optical and dielectric properties of tin monosulfide thin films. Tin monosulfide (SnS) films were deposited on glass substrate by chemical bath deposition to study the role of triethanolamine (TEA: complexing agent) concentration on the film properties. X-ray diffraction spectra reveal that the films exhibit mainly cubic phase which remain stable over the range of TEA concentration (3.0 M − 5.0 M). FTIR spectra indicate the S-Sn bond stretching in all films. Raman spectroscopy analysis shows the presence of minor trace of secondary SnS2 phase (along with main cubic π-SnS phase) in all films. SEM micrographs show cauliflower-like surface morphology of all films. Optical results reveal that the films possess high value of absorption coefficient (≥105 cm−1) in the visible region. Direct optical transition behavior is observed in all films. From Tauc plots, the calculated optical band gap (Eg) varies from 1.79 eV to 1.91 eV with the variation in TEA concentration. The dielectric constant, refractive index and an extinction coefficient are also calculated and observed to decrease with increasing TEA concentration. Experimental results suggest that an appropriate concentration of a complexing agent (TEA) can be chosen to obtain crystalline films without deterioration of crystalline structure and phase, not effecting Eg significantly.
Intensive tilapia farming has contributed significantly to food security as well as to the emergence of novel pathogens. This includes Streptococcus agalactiae or Group B Streptococcus (GBS) sequence ...type (ST) 283, which caused the first known outbreak of foodborne GBS illness in humans. An oral, easy-to-administer fish vaccine is needed to reduce losses in fish production and the risk of zoonotic transmission associated with GBS. We conducted a proof-of-concept study to develop an oral vaccine formulation that would only release its vaccine cargo at the site of action, i.e., in the fish gastrointestinal tract, and to evaluate whether it provided protection from experimental challenge with GBS. Formalin-inactivated S. agalactiae ST283, was entrapped within microparticles of Eudragit® E100 polymer using a double-emulsification solvent evaporation method. Exposure to an acidic medium simulating the environment in tilapia stomach showed that the size of the vaccine-loaded microparticles decreased rapidly, reflecting microparticle erosion and release of the vaccine cargo. In vivo studies in tilapia showed that oral administration of vaccine-loaded microparticles to fish provided significant protection from subsequent homologous pathogen challenge with GBS ST283 by immersion compared to the control groups which received blank microparticles or buffer, reducing mortality from 70% to 20%. The high efficacy shows the promise of the vaccine platform developed herein, which might be adapted for other bacterial pathogens and other fish species.
This paper reports the effect of Ti:Sapphire laser (800 nm, 30 fs) fluence on the surface morphology, ablated area, ablation rate and hardness of a femtosecond laser irradiated Zn in air and ethanol. ...Targets were exposed to 1000 succeeding pulses at various fluences ranging from 1.3 to 5 J cm
−2
. To characterize the growth of structures on the surface of irradiated Zn, Field Emission Scanning Electron Microscopy (FESEM) has been performed. The ablation depth has been measured using a confocal microscope. Nonuniform surface morphology with an appearance of both micro and nanoscale droplets, particulates and rims has been observed in case of air-assisted ablation, whereas, in ethanol, nanoscale colloids, droplets, pores and bowl-shaped cavities have been formed. The ablation of Zn in air is responsible for deep craters with pronounced melt expulsions and ripples. Whereas, shallow and clean craters are formed in ethanol. The ablation threshold fluence is evaluated analytically and experimentally by employing three methods, i.e., squared diameter, depth ablation rate, and volume ablation rates. The hardness of irradiated targets is higher as compared to untreated Zn and shows an increasing trend with increasing fluence for both environments. However, in the case of ethanol, the hardness values are higher than air.
Micro/nano structuring of KrF Excimer laser-irradiated Aluminum (Al) has been correlated with laser-produced structural and mechanical changes. The effect of non-reactive Argon (Ar) and reactive ...Oxygen (O2) environments on the surface, structural and mechanical characteristics of nano-second pulsed laser-ablated Aluminum (Al) has been revealed. KrF Excimer laser with pulse duration 20 ns, central wavelength of 248 nm and repetition rate of was utilized for this purpose. Exposure of targets has been carried out for 0.86, 1, 1.13 and 1.27 J·cm−2 laser fluences in non-reactive (Ar) and reactive (O2) ambient environments at a pressure of 100 torr. A variety of characteristics of the irradiated targets like the morphology of the surface, chemical composition, crystallinity and nano hardness were investigated by using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Energy Dispersive X-ray Spectroscopy (EDS), X-ray Diffractometer (XRD), Raman spectroscopy and Nanohardness tester techniques, respectively. The nature (reactive or non-reactive) and pressure of gas played an important role in modification of materials. In this study, a strong correlation is observed between the surface structuring, chemical composition, residual stress variation and the variation in hardness of Al surface after ablation in both ambient (Ar, O2). In the case of reactive environment (O2), the interplay among the deposition of laser energy and species of plasma of ambient gas enhances chemical reactivity, which causes the formation of oxides of aluminum (AlO, Al2O3) with high mechanical strength. That makes it useful in the field of process and aerospace industry as well as in surface engineering.
We report here the effect of the magnetic field on plasma parameters and the surface structuring of the Cu alloy after fs laser irradiation. A Ti:Sapphire (800 nm, 35 fs, 1 KHz) laser is employed at ...various irradiances (0.011–0.117 PW/cm2) to generate plasma. A Transvers Magnetic Field (TMF) of strength 1.1 T is employed for plasma confinement. All the measurements were performed with and without TMF. The Cu plasma parameters, i.e., excitation temperature (Texc) and electron number sensity (ne), determined by laser-induced breakdown spectroscopy analysis, are higher in the presence of TMF. This magnetic field confinement of Cu plasma was studied analytically by evaluating thermal beta (βt), directional beta (βd), confinement radius (Rb), and diffusion time (td). To correlate Cu-alloy plasma parameters with surface modifications, field emission scanning electron microscope analysis is performed. It reveals the formation of low-spatial-frequency laser-induced periodic surface structures (LIPSSs) and high-spatial-frequency LIPSSs, along with agglomers and nano-rims formation. Distinct and well-defined structures are observed in the presence of a magnetic field. It is concluded that controlled surface structuring can be achieved through magnetic confinement, which enhances key plasma parameters. The technique has the potential for enhancing the fabrication of nano-gratings and field emitters, where spatial uniformity is critically important.
The characteristic parameters as well as self-generated electric and magnetic fields of Nd:YAG laser (532 nm, 10 ns) ablated Al plasma have been measured by employing Langmuir, electric and magnetic ...probes, respectively. Plasma parameters such as electron temperature (
T
e
) and electron number density (
n
e
) as well as SGEMFs of Al plasma are measured as a function of laser irradiance ranging from 5.2 to 9.4 GW/cm
2
at fixed probes to target distance of 10 mm. Both
T
e
and
n
e
of Al plasma show an increasing trend with the increase of laser irradiance and vary from 8 to 11 eV and 3.9 × 10
14
to 7.07 × 10
14
/cm
3
, respectively. The SGEMFs show an overall increasing trend with the increase of laser irradiance and a decreasing trend with increasing probe to plume distances. The evaluated values of SGEMFs vary from 50 to 380 V/m and 89 to 165 G. The growth of SGEMFs has been explained on the basis of quadrupole distribution of charges at leading and trailing fronts of expanding plasma. By controlling plasma parameters such as electron temperature and electron density, laser generated plasmas can be efficiently used as sources of pulsed electric and magnetic fields in wake field accelerators.
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