Aqueous starch as a stabilizer in zinc oxide nanoparticle synthesis via laser ablation.

Zinc oxide is a semiconductor with exceptional thermal, luminescent and electrical properties, even compared with other semiconducting nanoparticles. Its potential for advanced applications in lasers and light emitting diodes, as bio-imaging agent, in biosensors and as drug delivery vehicles, in ointments, coatings and pigments has pulled zinc oxide into the focus of various scientific and engineering research fields. Recently we started investigating if nanoparticle synthesis via laser ablation in the presence of natural stabilizers allows control over size and shape and constitutes a useful, uncomplicated alternative over conventional synthesis methods. In the current paper, we determined the ability of natural starch to act as a size controller and stabilizer in the preparation of zinc oxide nanoparticles via ablation of a ZnO plate in a starch solution with a nanosecond Q-Switched Nd:YAG pulsed laser at its original wavelength (λ = 1064 nm). Our results show that the particle diameter decreases with increasing laser irradiation time to a mean nanoparticle size of approximately 15 nm with a narrow size distribution. Furthermore, the obtained particle size in starch solution is considerably smaller compared with analogous ZnO nanoparticle synthesis in distilled water. The synthesized and capped nanoparticles retained their photoluminescent properties, but showed blue emission rather than the often reported green luminescence. Evaluation of old preparations compared with freshly made samples showed no agglomeration or flocculation, which was reflected in no significant change in the ZnO nanoparticle size and size distribution. Overall, our experimental results demonstrate that starch can indeed be effectively used to both control particle size and stabilize ZnO nanoparticles in solution

The effect of laser repetition rate on the LASiS synthesis of biocompatible silver nanoparticles in aqueous starch solution.

Laser ablation-based nanoparticle synthesis in solution is rapidly becoming popular, particularly for potential biomedical and life science applications. This method promises one pot synthesis and concomitant bio-functionalization, is devoid of toxic chemicals, does not require complicated apparatus, can be combined with natural stabilizers, is directly biocompatible, and has high particle size uniformity. Size control and reduction is generally determined by the laser settings; that the size and size distribution scales with laser fluence is well described. Conversely, the effect of the laser repetition rate on the final nanoparticle product in laser ablation is less well-documented, especially in the presence of stabilizers. Here, the influence of the laser repetition rate during laser ablation synthesis of silver nanoparticles in the presence of starch as a stabilizer was investigated. The increment of the repetition rate does not negatively influence the ablation efficiency, but rather shows increased productivity, causes a red-shift in the plasmon resonance peak of the silver-starch nanoparticles, an increase in mean particle size and size distribution, and a distinct lack of agglomerate formation. Optimal results were achieved at 10 Hz repetition rate, with a mean particle size of ~10 nm and a bandwidth of ~6 nm 'full width at half maximum' (FWHM). Stability measurements showed no significant changes in mean particle size or agglomeration or even flocculation. However, zeta potential measurements showed that optimal double layer charge is achieved at 30 Hz. Consequently, Ag-NP synthesis via the laser ablation synthesis in solution (LASiS) method in starch solution seems to be a trade-off between small size and narrow size distributions and inherent and long-term stability

Simple synthesis and characterization of cobalt ferrite nanoparticles by a thermal treatment method

Crystalline, magnetic, cobalt ferrite nanoparticles were synthesized from an aqueous solution containing metal nitrates and polyvinyl pyrrolidone (PVP) as a capping agent by a thermal treatment followed by calcination at various temperatures from 673 to 923?K. The structural characteristics of the calcined samples were determined by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM). A completed crystallization occurred at 823 and 923?K, as shown by the absence of organic absorption bands in the FT-IR spectrum. Magnetization measurements were obtained at room temperature by using a vibrating sample magnetometer (VSM), which showed that the calcined samples exhibited typical magnetic behaviors

Electrohydrodynamic (EHD) –assisted extraction of protein from mung bean (Vigna radiate L.) sprout: Effect of solid to solvent ratio on the functional properties

Background & Aim: Mung bean knwn as a traditional food which has been used both as nutritional food and herbal medicine over 2000 years. Mung bean sprouts are one of the most commonly used bean sprouts and considered an as appropriate source for the extraction of highly valuable proteins. Experimental: In this study, the effect of different solid to solvent ratios (1:5, 1:10, 1:15 and 1:20 g/mL in electrohydrodynamic (EHD)-assisted extraction on the extraction yield and functional characteristics of sprouted mung bean protein isolate (SMPI) was evaluated. In addition, the structural and thermal properties of SMPI were investigated using Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC), respectively. Results: The highest protein extraction yield, protein solubility (PS), oil absorption capacity (OAC), foaming capacity (FC) and foaming stability (FS) were obtained in the solid to solvent ratio of 1:20 g/mL. The results of FTIR showed that in the solid to solvent ratio of 1:20, the α-helix structure in SMPI decreased and transformed to random coil structure, leading to increased protein solubility. According to the DSC analysis, the highest denaturation temperature and protein stability were attributed to the solid-to-solvent ratio of 1:20 due to higher water content. Recommended applications/industries: The present results indicated that EHD pretreatment with the solid to solvent ratio of 1:20 could improve the functional properties of SMPI and EHD-assisted extracted SMPI could be considered as a potential nutraceutical or ingredient of functional and health-promoting foods

Preparation of silver nanoparticles in virgin coconut oil using laser ablation

Laser ablation of a silver plate immersed in virgin coconut oil was carried out for fabrication of silver nanoparticles. A Nd:YAG laser at wavelengths of 1064 nm was used for ablation of the plate at different times. The virgin coconut oil allowed formation of nanoparticles with well-dispersed, uniform particle diameters that were stable for a reasonable length of time. The particle sizes and volume fraction of nanoparticles inside the solutions obtained at 15, 30, 45 min ablation times were 4.84, 5.18, 6.33 nm and 1.0 × 10−8, 1.6 × 10−8, 2.4 × 10−8, respectively. The presented method for preparation of silver nanoparticles in virgin coconut oil is environmentally friendly and may be considered a green method

Conductometric determination of formation constants of tris(2-pyridyl)methylamine and titanium (III) in water-acetonitryl mixture.

A conductance study of the interaction between titanium (III) cation and tris(2-pyridyl) methylamine (tpm), in water-acetonitrile mixtures was carried out at various temperatures. The formation constants of the resulting 1:1 complexes were determined from the molar conductance-mole ratio data. The stability constants of 1:1 (M:L) complexes of tpm with titanium (III) cation, the Gibbs standard free energies (ΔGc o{script}), the standard enthalpy changes (ΔHc o{script}) and the standard entropy changes (ΔSc o{script}) for the formation of these complexes in acetonitrile-water (AN-H2O) binary mixtures have been determined conductometrically. The stability constants of the complexes were obtained from fitting of molar conductivity curves using a computer program, GENPLOT

Laser based fabrication of chitosan mediated silver nanoparticles

We report fabrication of silver nanoparticles (Ag NPs) by laser ablation technique in different concentrations of aqueous chitosan solution. The ablation process of silver plate was carried out by using a nanosecond Q-switched Nd:YAG pulsed laser and the characterization of Ag NPs was done by Transmission electron microscopy, UV-Vis spectroscopy, and X-ray diffraction. UV-visible plasmon absorption spectra revealed that the formation efficiency as well as the stability of nanoparticles was increased by addition of chitosan. On the other hand, the size decrement of nanoparticles was more remarkable in the higher chitosan concentration

Chemometric analysis of lipase-catalyzed synthesis of xylitol esters in a solvent-free system

Immobilized Candida antarctica lipase B-catalyzed esterification of xylitol and two fatty acids (capric and caproic acid) were studied in a solvent-free system. The Taguchi orthogonal array method based on three-level-four-variables with nine experiments was applied for the analysis and optimization of the reaction parameters including time, substrate molar ratio, amount of enzyme, and amount of molecular sieve. The obtained conversion was higher in the esterification of xylitol and capric acid with longer chain length. The optimum conditions derived via the Taguchi approach for the synthesis of xylitol caprate and xylitol caproate were reaction time, 29 and 18 h; substrate molar ratio, 0.3 and 1.0; enzyme amount, 0.20 and 0.05 g, and molecular sieve amount of 0.03 g, respectively. The good correlation between the predicted conversions (74.18% and 61.23%) and the actual values (74.05% and 60.5%) shows that the model derived from the Taguchi orthogonal array can be used for optimization and better understanding of the effect of reaction parameters on the enzymatic synthesis of xylitol esters in a solvent-free system

Preparation of silver nanoparticles in virgin coconut oil using laser ablation

Laser ablation of a silver plate immersed in virgin coconut oil was carried out for fabrication of silver nanoparticles. A Nd:YAG laser at wavelengths of 1064 nm was used for ablation of the plate at different times. The virgin coconut oil allowed formation of nanoparticles with well-dispersed, uniform particle diameters that were stable for a reasonable length of time. The particle sizes and volume fraction of nanoparticles inside the solutions obtained at 15, 30, 45 min ablation times were 4.84, 5.18, 6.33 nm and 1.0 × 10−8, 1.6 × 10−8, 2.4 × 10−8, respectively. The presented method for preparation of silver nanoparticles in virgin coconut oil is environmentally friendly and may be considered a green method

High performance enzyme-catalyzed synthesis and characterization of a nonionic surfactant

Sugar alcohol esters have a high potential for widespread application in various industries because of their surface active properties. In this work, fatty acid ester of a sugar alcohol was produced through Novozym 435-catalyzed esterification of xylitol and capric acid in nonaqueous media. Taguchi orthogonal array method based on three-level-six-variables (L27) and artificial neural network with Levenberg–Marquardt algorithm were applied to evaluate the effects of synthesis parameters and to optimize the reaction conditions. Both developed models have shown good quality predictions in terms of the conversion of xylitol caprate with a high R2 (>0.9) and a low mean square error (MSE). The maximum conversion of ester achieved was 88% requiring a small amount of enzyme and molecular sieve. Furthermore, the properties of the produced ester show that it is a suitable emulsifier for industrial application