Highly Sensitive Surface-Enhanced Raman spectroscopy for the Surface Corrosion Analysis of Bronze Relics Using the Polyacrylonitrile/Polyvinylpyrrolidone Silver Nanoparticle Flexible Substrate

Surface-enhanced Raman spectroscopy (SERS) is widely used in biological and chemical analyses and in other fields because of its advantages such as high sensitivity and nondestructive nature. Ancient bronze cultural relics of China are exquisitely shaped and highly ornamental. Harmful rust components on the surface of bronze cultural relics have been extensively analyzed. SERS is beneficial to the surface composition analysis of ancient Chinese bronze relics and can be used for accurate characterization with almost zero damage to the surface. In this study, we designed a solution with polyacrylonitrile (PAN) and polyvinylpyrrolidone (PVP) macromolecules as precursors, which were electrospun and used as the nanofiber substrate. After tannic acid modification, the substrate was loaded with silver nanoparticles by using Tollens' reagent as the silver source and glutaraldehyde as the reducing agent in a water bath. The morphology and size of silver nanoparticles were adjusted by changing the reaction times. The effects of tannic acid and PVP as stabilizers were investigated. R6G and basic copper chloride were used as probe molecules for substrate SERS, and the Raman enhancement factor was calculated. The SERS performance of the substrate with high sensitivity was verified through characterization.

Astaxanthin–garlic oil nanoemulsions preparation using spontaneous microemulsification technique: optimization and their physico–chemical properties

Garlic oil in water nanoemulsion was resulted through subcritical water method (temperature of 120 °C and pressure of 1.5 bar, for 2 h), using aponin, as emulsifier. Based on the prepared garlic oil nanoemulsion, astaxanthin–garlic oil nanoemulsions were prepared using spontaneous microemulsification technique. Response surface methodology was employed to evaluate the effects of independent variables namely, amount of garlic oil nanoemulsion (1–9 mL) and amount of provided astaxanthin powder (1–9 g) on particle size and polydispersity index (PDI) of the resulted nanoemulsions. Results of optimization indicated that well dispersed and spherical nanodroplets were formed in the nanoemulsions with minimum particle size (76 nm) and polydispersity index (PDI, 0.358) and maximum zeta potential value (−8.01 mV), using garlic oil nanoemulsion amount of 8.27 mL and 4.15 g of astaxanthin powder. Strong antioxidant activity (>100%) of the prepared astaxanthin–garlic oil nanoemulsion, using obtained optimum amounts of the components, could be related to the highest antioxidant activity of the colloidal astaxanthin (>100%) as compared to that of the garlic oil nanoemulsion (16.4%). However, higher bactericidal activity of the resulted nanoemulsion against Escherichia coli and Staphylococcus aureus, were related to the main sulfur bioactive components of the garlic oil in which their main functional groups were detected by Fourier transform-infrared spectroscopy.

Preparation of Ginger Oil in Water Nanoemulsion Using Phase Inversion Composition Technique: Effects of Stirring and Water Addition Rates on their Physico-Chemical Properties and Stability

Ginger oil in water (O/W) nanoemulsions, were produced using phase inversion composition method and Tween 80, as emulsifier. Effects of processing parameters namely, stirring rate (100 to1000 rpm) and water addition rate (1–10 mL/min) were evaluated on the physico-chemical, morphological, antioxidant and antimicrobial properties of the prepared O/W nanoemulsions using response surface methodology (RSM). Results indicated that well dispersed and spherical ginger nanodroplets were formed in the nanoemulsions with minimum particle size (8.80 nm) and polydispersity index (PDI, 0.285) and maximum zeta potential value (−9.15 mV), using stirring rate and water addition rate of 736 rpm and 8.18 mL/min, respectively. Insignificant differences between predicted and experimental values of the response variables, indicated suitability of fitted models using RSM. Mean particle size of the prepared nanoemulsion using optimum conditions were changed from 8.81 ± 1 to 9.80 ± 1 nm, during 4 weeks of storage, which revealed high stability of the resulted ginger O/W nanoemulsion. High antioxidant activity (55.4%), bactericidal (against Streptococcus mutans) and fungicidal (against Aspergillus niger) activities of the prepared nanoemulsion could be related to the presence of gingerols and shogaols, a group of phenolic alkanones, in the ginger oil, which those were detected by gas chromatography method.

Adsorption of 2,4-Dichlorophenoxyacetic Acid from Aqueous Solution Using Carbonized Chest Nut as Low Cost Adsorbent: Kinetic and Thermodynamic

The activated carbon was made of carbonized chest nut shell (CCS) and used as low cost adsorbent for 2,4-D (2,4-dichlorophenoxyacetic acid) removal. The experiments were conducted at different temperatures such as 35, 45 and 55 °C and this system represents as L type adsorption behavior. The experimental data were modelled using several isotherm models such as Langmuir, Freundlich, Temkin and Dubinin Radushkevich. The adsorption dynamics were searched by applying pseudo first, pseudo second and intra particle diffusion models. The thermodynamic approach was conducted for determining the thermodynamic values of ΔH°, ΔS° and ΔG°.

Phytochemical Synthesis of Silver Nanoparticles Using Anthemis Nobilis Extract and Its Antibacterial Activity

In this work, green synthesis of silver nanoparticles is described by phytochemical reducing silver nitrate aqueous solution using Anthemis nobilis. For this purpose, Anthemis nobilis extract was used for the synthesis of silver nanoparticles as both surfactant and reducing agent. Green synthesis method is a good alternative to physical and chemical methods, since it is fast, simple, environmentally-friendly and economic. The produced nanoparticles are identified using FE-SEM, EDX, and FT-IR and Uv/Vis techniques. Formation of silver nanoparticles is verified in 430–420 nm range. Reduction of silver ions by hydroxyl functional group is also confirmed by FT-IR device. EDX device confirms the presence of a peak for Ag element without any impurity peak. Silver nanoparticles are identified by FE-SEM device and found to have average size between 17 and 42 nm. Also, the antibacterial activity of the synthesized nanoparticles is compared with that of staphyloccusaureus and pseudomonasa aeruginosa and the maximum inhibitory activity against the bacteria is obtained using 1 mM nitrate solution.

Synthesis, Characterization and Electrical Conductivity of Silver Doped Polyvinyl Acetate/Graphene Nanocomposites: A Novel Humidity Sensor

In the present study, we have synthesized conducting polymer nanocomposites consist of silver nanoparticles (AgNPs), graphene, and polyvinyl acetate (PVAc) emulsion. The synthesized nanocomposite was characterized by UV/Vis, FT-IR, XRD, TGA, and SEM techniques. SEM images showed that AgNPs and graphene sheets are well dispersed in the PVAc matrix. The electrical conductivities of the nanocomposites were examined using the impedance analyzer instrument. It was ascertained that polymer composite containing silver nanoparticles and graphene exhibit higher conductivities. The PVAc-AgNPs/Graphene nanocomposite was also used as potential conducting materials for humidity measurement.

Preparation, Characterization and Evaluation of Curcumin Nanodispersions Using Three Different Methods – Novel Subcritical Water Conditions, Spontaneous Emulsification and Solvent Displacement

Curcumin as a lipophilic bioactive compound can be incorporated into water-based formulations when it turns into curcumin nanodispersions. In fact, nanodispersion systems, increase curcumin bioavailability, solubility and stability, and furthermore increase curcumin uses in aqueous food and pharmaceutical formulations. Present study focuses on the preparation of curcumin nanodispersions under subcritical water conditions (temperature of 120 °C and pressure of 1.5 bar for 2 h) and using selected another two different methods namely, spontaneous emulsification and solvent displacement. Lecithin as carrier oil, Tween 80 as emulsifier and polyethylene glycol as co-surfactant, with a ratio of 1:8:1, were used in all the preparation techniques. Obtained results indicated that curcumin nanodispersions with smallest mean particle size (70 nm), polydispersity index (0.57), curcumin loss (5.5%) and turbidity (0.04 Nephelometric Turbidity Unit), and maximum loading ability (0.189 g/L), loading efficiency (94.5%) and conductivity (0.157 mS/cm) were obtained under subcritical water conditions. The results also exhibited that the prepared spherical curcumin nanoparticles in the water by this technique had desirable physical stability as their mean zeta potential value was (−12.6 mV). It also observed that, as compared to spontaneous emulsification and solvent displacement methods, the prepared curcumin nanodispersions via subcritical water method had highest anti-oxidant and antibacterial activities.

Optimization of Processing Parameters for Hydrothermal Silver Nanoparticles Synthesis Using Aloe vera Leaf Extract and Estimation of their Physico-Chemical and Antifungal Properties

Aloe vera leaf extract has been obtained and utilized for silver nanoparticles (AgNPs) synthesis by autoclave at 121 °C and 1.5 bar (pressure) for 15 min. The results of GC-MS analysis of A. vera life extract indicated that there were several natural reducing agents such as acetic acid, hexanol and ethyl amine in the A. vera peel. Central composition design and response surface methodology have been used to design the experiment and to evaluate the effect of independent variables on dependent variables, respectively. After extraction of A. vera leaf extract with different concentrations (0.5–5.5% w/v), 0.1 mL of the prepared extract has been added into different amounts of 1 mM AgNO3 solution (9.5–20.5 mL) and placed into the autoclave. The obtained results indicated that the minimum particle size (53.9 nm) and maximum concentration (46.25 ppm) and color (0.851 IU) values for synthesized AgNPs were obtained using 4.69% w/v of A. vera leaf extract and 11.1 mL of AgNO3 solution (1 mM). The zeta potential value of the synthesized AgNPs at obtained optimum conditions was +15.5 mV which indicated the high stability of the synthesized AgNPs. The high antifungal activity of the synthesized AgNPs was evaluated against to Aspergillus flavus and Aspergillus terreus strains.