Journal of Nano Research Vol. 75

Abstract: Drug resistant microbial strains are becoming continuous dilemma for researchers; hence, some alternates are required to combat this issue. In this way, nanotechnology is fascinating researchers to put forward a step in order to synthesize metals nanoparticles via adopting an ecofriendly, facile, and quick approach using medicinal plants. By means of aqueous extract of Polyalthia longifolia (AEPl), gold nanoparticles (AuPl) were synthesized for the mechanism study of synthesis and antibacterial bahavior. The reddish colored solution was an indicative clue of synthesis showing surface plasmon band at 540nm using UV/Visble spectroscopy. Various functional groups in the extract were identified which participated in the reduction of metal ions to metallic form as indicated from the Fourier Transform Infrared (FTIR) spectra of AuPl. Moving ahead, the synthesized AuPl were characterized through Transmission Electron Microscopy (TEM) showed spherical shape with more or less 50nm size. Besides, Scanning Electron Microscopy (SEM) study revealed some aggregates formation. Further, structural characterization via X-Rays Diffractometry (XRD) displayed crystallline nature of these nanoparticles. Finally, Energy Dispersive X-rays (EDX) analysis described their metallic form. The antibacterial activity at increased concentration when measured; AuPl showed 15 and 18mm bacterial growth inhibition zones against Escherichia coli and Bacillus subtilis at 100μg/mL concentration respectively. In addition, significant least minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of AuPl against these microbes were also observed. In the light of the above knowledge, it is inferred that the biogenic AuPl exhibit strong antibacterial potential enabling them to be a good substitute of antibiotics.

Abstract: Nanotechnology is arising as a fast-developing research discipline with many usages areas. The silver nanoparticles synthesis (sm-AgNPs) is accomplished by reduction of silver ions in treatment with aqueous extract of Sideritis montana L. leaves. The colour change from yellow to dark brown confirmed the structures. The spectroscopic studies revealed the desired structure. In the UV-Vis spectrum, the maximum absorption was observed at 480 nm. The diffraction peaks (2θ) at the degrees of 38.14°, 44.29°, 64.48°, and 77.38° can correspond to 111, 200, 220, and 311 facets that indicates the nanostructure to be a face-centered cubic unit structure. The scanning electron microscope (SEM) and dynamic light scattering (DLS) analyses indicated that the synthesized nanoparticles were spherical with an average particle size of 36.42 nm. The zeta potential of sm-AgNPs was found as -35.2 mV which indicated the repulsion among nanoparticles and their stability. The peaks from Fourier transform infrared spectrometer (FTIR) were associated with the phenols, flavonoids, terpenoids, and alkaloids, indicating that the corresponding compounds might act as reducing agents. The photocatalytic effect of sm-AgNPs was examined by degradation of methylene blue and sm-AgNPs were able to degrade the dye by about 67% at 96 h.

Abstract: AbstractTitanium dioxide nanoparticles are great boosters for better sunlight absorption by plants. However, their band gap is so wide that they can only absorb UV light, which is a small portion of the sunlight. To improve the absorption of visible light, in this work, titanium nanoparticles were sensitized by saffron dye and the effect of foliar application of the dyed nanoparticles on growth parameters and enzymatic properties of sorghum was investigated and the results were compared with those of conventional titanium dioxide nanoparticles. The experiment was conducted in Zabol region, Iran. Saffron, a natural organic dye, was used as a sensitizer because of its availability and high extinction coefficient in the visible regions. To perform sensitization, titanium dioxide nanoparticles were immersed in saffron dye solution to absorb the dye on their surface. Then different concentrations of the sensitized nanoparticles were applied on plants by foliar spraying. The most improved growth parameters including root and shoot lengths, shoot fresh and dry weights, root fresh and dry weights were obtained after application of dye-sensitized TiO₂ nanoparticles. Zinc and iron are the elements highly affected by the application of new nanoparticles. Enzyme activities of catalase, ascorbate peroxidase and guaiacol peroxidase were also increased significantly. Chlorophyll a and Chlorophyll a/b ratio showed the highest values in 500 ppm dye-sensitized TiO₂ nanoparticles. The obtained results confirm the improvement in growth parameters and enzymatic properties of Sorghum after application of the new TiO₂ nanoparticles.

Abstract: The Cu²⁺ in the drinking water has a very serious impact on human health and social ecology. Many countries have the policy on the Cu²⁺ concentration limitation in drinking water and the industrial Cu²⁺ emission standards for the treated wastewater. Scientists have developed many methods to remove Cu²⁺ from wastewater. Among all the adsorption method is widely used due to its high efficacy, feasibility and low cost. The adsorbent is critical to achieving superior Cu²⁺ removal result. In this paper, Fe₃O₄/carbon-graphene oxide nanocomposites (Fe₃O₄@C-GO) were prepared by a hydrothermal method. The Fe₃O₄@C-GO is the main absorbent to Cu²⁺ through chemisorption. The specific surface area of Fe₃O₄@C-GO dramatically increases from 16 m²/g of Fe₃O₄@C to 62 m²/g, which expands the Cu²⁺ absorption capacity up to 350 mg/g. Fe₃O₄ nanoparticles with about 12 nm in diameter are uniformly encapsulated in the C-GO matrix, and therefore the Fe₃O₄@C-GO can be easily separated from the solution via magnetics. This adsorbent is also very easily recovered by an external magnetic field from the treated wastewater and has high reusability.

Abstract: A well-controlled multistage hydrothermal technique was developed to synthesise hierarchical zinc oxide (ZnO) nanomaterials with a high surface-to-volume ratio. Hierarchical ZnO nanomaterials, hierarchical nanowires (HNWs) and hierarchical nanodiscs (HNDs), assembled from initial mono-morphological nanomaterials, ZnO nanowires, and ZnO nanodiscs respectively were prepared by sequential nucleation and growth following a hydrothermal course. The hierarchical nanomaterials composed of one-dimensional nanowire building blocks were obtained by introducing zinc nitrate as a source of zinc ions during the second growth phase. In comparison to their initial monomorphological counterparts, the prepared HNWs and HNDs showed superior photocatalytic performances. The improvement in the photocatalytic performance was ascribed to the reduction in dimensionality, the ultrahigh surface-to-volume ratio, the expanded proportion of the exposed polar area, and the creation of nanojunctions between the secondary nanowires and initial ZnO nanowires or nanodiscs. This work paves the way for the low-cost, large-scale, and low-temperature production of ZnO nanomaterials with superior photocatalytic properties.

Abstract: The anatase titanium dioxide nanotube array (TiO₂ NTA) with short and independent nanotube film structure is applied as stable metal oxide electrode substrate. The influence of different proton acid electrolytes is fully investigated on the electrical double-layer capacitance. The anatase TiO₂ NTA electrode substrate conducts reversible protonation-deprotonation process of dissociation hydrogen ion and electrostatic adsorption-desorption process of equilibrium anion in the cycling charge-discharge process. The reversible properties could be well proved by highly symmetric characteristic of positive-negative sweeping current and charge-discharge potential. The protonated TiO₂ NTA electrode substrate reveals cyclic voltammetry-based capacitances of 0.147 and 0.124 mF cm^-2, galvanostatic charge-discharge-based capacitances of 0.167 and 0.148 mF cm^-2 when similar dissociation proton concentration is maintained in 1.0 M H₂SO₄ and 1.0 M HCl. The TiO₂/H₂SO₄ exhibits similar capacitance enhancement ratio of 1.19 and 1.13 in comparison with of the TiO₂/HCl. The corresponding electrical double-layer capacitance at the same dissociation proton condition is mostly dependent on the electrostatic interaction between the protonated TiO₂ and equilibrium anions in different proton acid electrolytes rather than anion diffusion. The theoretical simulation calculation reveals that TiOOH⁺-HSO₄^- shows lower interaction interface energy and higher total densities of states than TiOOH⁺-Cl^-. Accordingly, TiO₂/H₂SO₄ conducts more feasible protonation and electrostatic adsorption process rather than TiO₂/HCl, contributing to its superior electrical double-layer capacitance.

Abstract: This study employed the template-free chemical oxidative polymerisation method to synthesise polyaniline (PANI) and polyaniline/tin-doped titania (PANI/Sn-doped TiO₂) nanocomposite as corrosion inhibitors. FTIR and XRD were employed to characterise the chemical composition of the prepared samples. TEM and FESEM microscopy validated the presence of the PANI and that the Sn-doped TiO₂ nanoparticle were successfully incorporated into PANI to form the nanocomposite. The synthesised materials were mixed in the polyvinyl butyral (PVB) binder, coated onto mild steel substrates, and exposed to 3.5 wt.% NaCl solution for 30 days. Altogether, three coating systems were tested, i.e., pure PVB, PVB + PANI, and PVB + PANI/Sn-doped TiO_2. The corrosion parameters were measured via EIS and Tafel polarisation techniques. Overall, the PANI/Sn-doped TiO₂ nanocomposite as a corrosion inhibitor effectively inhibited the corrosion of the mild steel, and its corrosion rate was 3.484 x 10^-7 mm/year.

Abstract: The electrochemical synthesis of poly (o-aminobenzyl alcohol) (PABA) coatings containing three different amounts of NiZnFe₄O₄ nanoparticle (NP) with and without 0.25 mM Schiff base (ORG) on stainless steel (SS) was carried out in 0.15 M LiClO₄ containing acetonitrile (ACN) solution. The synthesis curves of PABA-NP and PABA-ORG-NP films exhibited the different current and monomer oxidation potential values indicating the presence of NP and ORG compounds. Besides, the addition of ORG to the NP-containing synthesis solution resulted in an increase in the electropolymerization rate of the PABA film compared to the NP-containing medium alone. Indeed, SEM images of PABA-NP and PABA-ORG-NP also showed that their morphological structures were different. As a result of the evaluation of the impedance analysis, it was seen that PABA-NP and PABA-ORG-NP films provided significant physical barrier behavior to the SS electrode, in 3.5% NaCl solution. PABA-NP₂₅ and PABA-ORG-NP₂₅ coatings exhibited more protection behavior against to the move of corrosive substances to SS. The presence of both NP and ORG in the polymer coating further improved the superior protection property of the PABA film, in a longer time.

Abstract: In this study, carbon nanotube films, densifying with ethanol/water, acetone/water, acetic acid/water, sulfuric acid/water with volume rate of 4:1 and following rolling process, were manufactured. Afterwards, the electrothermal, mechanical properties and performance stability of these carbon nanotube films were investigated, along with mechanism analysis. Based on our investigations, the ability of rapid electrothermal response within 5 second, higher steady-state temperature of above 120~160°C at low input voltages of 5V, excellent cycling stability of electrical heating are reported by the aforementioned methods, revealing better outcome as compared with previous reports of congeneric carbon nanotube films. The electrothermal and mechanical properties of treated carbon nanotube films were superior to carbon nanotube film pressed from carbon nanotube aerosol, and the best outcomes could be synchronously achieved at an immersion of 0.5h in solvents and rolling. The consequences, which are attributable to treatments by the first three mixed solvents as well as rolling, were similar, however, the electrical and electrothermal properties of carbon nanotube film treated with sulfuric acid/water and rolling were significantly improved comparative to others due to p-type doping and purification, which could enhance the electrical conductivity of carbon nanotube film, while the mechanical property was not degraded compared to films treated by other ways. Particularly, electrical and mechanical properties of carbon nanotube films were unchanged through repeated electrical heating owing to the stability of their structure and morphology, which contributed to exceedingly stable electrothermal property and established foundation for application as heater with long-term stability. Lastly, we have also proposed the mechanism concerning performance stability of electrical heating film.

Abstract: The impact of nanoparticle shapes (i.e., blade, brick, cylindrical, platelet, and spherical) on the MHD flow of Ag-MgO/water hybrid nanofluid over a stretching/shrinking sheet is scrutinized in this study. Chemical reaction and activation energy are included in the governing partial differential equations of the flow problem. On the boundary, velocity slip and zero mass flux conditions are considered. The simplification of the governing equations and boundary conditions into non-linear ordinary differential equations is done through similarity transformation. Then, the bvp4c solver in Matlab is deployed for computation, with the results generated in the form of numerical solutions and graphs. It is found that the usage of spherical-shaped nanoparticles produces the lowest magnitude of skin friction coefficient, and the implementation of blade-shaped nanoparticles in the hybrid nanofluid provides the highest enhancement of heat transfer rate. The increment in activation energy slows down the chemical reaction that raises the concentration profile of the hybrid nanofluid. However, the concentration profile decreases as the reaction rate increases.