International Journal of Nano Dimension
Year:2019 | Volume:10 | Issue:2|Papers Count:10

This paper gives a comprehensive review about the most recent progress in graphene and graphene oxide based electrochemical sensors and biosensors. Graphene, emerging as a true 2-dimensional material, has received increasing attention due to its unique physicochemical properties (high surface area, excellent conductivity, high mechanical strength, and ease of functionalization and mass production). The application of graphene and graphene oxide in the modification processes leads to improved sensitivity, electrocatalytic behavior, and reduced fouling. The development of graphene and graphene oxide based sensors in biosensing and detection of chemicals have been resulted in great achievements towards more sensitive health care instruments and preventing the environmental problems. To facilitate further research and development, the technical challenges are discussed, and several future research directions are also suggested in this paper.

Buckling analysis of a functionally graded (FG) nanobeam resting on two-parameter elastic foundation is presented based on third-order shear deformation beam theory (TOSDBT). The in-plane displacement of TOSDBT has parabolic variation through the beam thickness. Also, TOSDBT accounts for shear deformation effect and verifies stress-free boundary conditions on upper and lower faces of FG nanobeam. The twoparameter elastic foundation model including linear Winkler's springs along with Pasternak's shear layer is in contact with the beam in deformation. Material properties of FG nanobeam are supposed to vary gradually along the thickness according to both power-law and Mori– Tanaka laws. Small-scale effect of Eringen's nonlocal elasticity theory has been considered. Nonlocal equilibrium equations are obtained based on the minimum potential energy principle and solved analytically. The accuracy of current method is examined by comparing current results with the available ones in literature. Effects of foundation parameters, gradient index, nonlocal parameter and slenderness ratio on buckling behavior of FG nanobeams are examined.

In this study, the La3+/Co3O4 nanoflowers were synthesized by co-precipitation method. The morphology of the La3+/Co3O4NFs were characterized using scanning electron microscopy (SEM), and were further used to modify the graphite screen printed electrode (GSPE). The electrochemical behavior of acetaminophen at La3+/Co3O4NFs/GSPE has been studied in aqueous solutions. Experimental results showed that the La3+/ Co3O4NFs modified GSPE possess excellent electrocatalytic activity toward the detection of acetaminophen. Under optimum conditions, the La3+/Co3O4NFs modified electrode exhibited high sensitivity and stability to acetaminophen over a wide linear range of concentrations from 0. 5μ M to 250. 0μ M, with a detection limit of 0. 09μ M. Finally, the proposed sensor was successfully applied to the detection of acetaminophen in real samples.

The use of less hazardous chemicals or natural material in place of toxic chemical for the formation of metal nanoparticle is known as green synthesis. The present paper deals with greener approach for the synthesis of silver (Ag) nanoparticles. The Saraca asoca plant leaves extract solution was used for the silver nanoparticles. Confirmation of Ag nanoparticles has been done using various characterization techniques viz. structure by X-Ray Diffraction (XRD), morphological analysis by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and elemental analysis by Energy Dispersive X-ray Spectroscopy (EDX). The particle size of silver nanoparticle is found to be 24. 85 nm. The particle exhibits good antibacterial properties against Staphylococci aures, Streptococci pyogens, Salmonella typhi.

In recent years, nanocomposite scaffolds made of bioactive polymers have found multiple applications in bone tissue engineering. In this study composite nanofibrous structure of gelatin (Gel)/chitosan (Cs)-polycaprolactone (PCL) containing hydroxyapatite (HA) were fabricated using co-electrospinning process. To assay the biocompatibility and bioactivity of electrospun nanocomposite scaffolds, the behavior of human osteosarcoma cells (MG63) on fabricated nanofibers was evaluated using scanning electron microscopy (SEM), fluorescence microscopy analysis, measuring calcium deposits and MTT assay. The SEM micrographs at days 3 and 7 showed high cell attachment and spreading on the nanofibrous scaffolds. The MTT results demonstrated the proliferation of MG-63 cells during 10 days and the positive effect of nanofibers in comparison of cell culture plate. Considering the proliferation rate and calcification extent, the Gel-Cs-HA nanofibers reveal highest biocompatibility for osteoblast cells which could be attributed to the smaller diameter fibers and more mechanical strength in the Gel-Cs-HA scaffold.

In this paper, a novel ternary nanocomposite namely reduced graphene oxide/hydroxyapatite/silver (rGO/ HAP/Ag) was prepared by a simple hydrothermal method using graphene oxide nanosheets, Ca(NO3)2, (NH4)2HPO4, and AgNO3 as starting materials. The as-prepared nanocomposite was characterized by using various photophysical techniques including Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), ultraviolet-visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX). Additionally, the antibacterial and catalytic activities of the nanocomposite were evaluated. The results showed that the rGO/HAP/Ag nanocomposite exhibited high performance in the reduction of toxic nitro compounds (4-nitrophenol, 2-nitrophenol, 4-nitroaniline, and 2-nitroaniline) into the less toxic corresponding amines using NaBH4 within 21-42 min with a rate constant equal to 0. 1646, 0. 0898, 0. 1071 and 0. 2 min-1, respectively. Moreover, the rGO/HAP/Ag nanocomposite could be separated from the reaction mixture due to its heterogeneous nature and reused without any change in structure. In addition, the antibacterial activity of the rGO/HAP/Ag nanocomposite by disk diffusion method was evaluated against Gram-positive bacteria (Bacillus cereus and Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Klebsiella pneumonia). The results showed that this novel ternary nanocomposite has good antibacterial activity against Gram-positive bacteria.

In this study, the use of TiO2/SiO2 nanocomposites investigated to remove nitrate and total iron from wastewater. The nanoparticles and nanocomposites were characterized by the Brunauer, Emmett, and Teller (BET), Field Emission Scanning electron microscopy (FESEM), Fourier transform infrared (FTIR), X-ray diffraction (XRD) and X-ray fluorescence (XRF). According to the BET results, the nanocomposite with 80%TiO2: 20%SiO2 considered an adsorbent for the treatment of water. In this work, the application of the Response Surface Methodology (RSM) was presented to optimize various parameters, including the D/C (mg adsorbent /(mg/L) initial) and the initial pH for removal of nitrate and total iron from wastewater with the nanocomposite. The maximum removal of nitrate and total iron obtained with 92. 84% and 94. 32%, respectively. In addition, the optimum conditions for the maximum removal of nitrate and total iron together were estimated at pH= 6. 81 and D/C= 40. 84. Langmuir and Freundlich isotherm models evaluated, and Freundlich isotherm described the equilibrium adsorption data well.

Polyethylene (PE) nanocomposites containing Cellulose Nano Crystal (CNC) were prepared via melt blending in a twin screw extruder. The evaluation of PE/CNC nanocomposites was studied for food packaging applications. The nanocomposites were investigated by thermal, mechanical analyses. Addition of CNC particle while having no effect on melting and crystallization temperature had intensive effect on the degree of crystallinity of the polyethylene. It is shown that due to the weak interfacial bonding between CNC and PE matrix, a decrease in yield stress and modulus of elasticity was observed for PE/CNC nanocomposites. According to the x-ray diffraction analyses, incorporation of the CNC into PE matrix induced a preferred crystalline orientation for PE crystallites.

The purpose of this study was to expand a trouble free biological method for the synthesis of silver nanoparticles (AgNPs) using the leaves extract of Rosa Chinensis L. to act as reducing and stabilizing agent. Water soluble phytochemicals played a vital role for the reduction silver ions into silver nanoparticles. The leaves extract was exposed to silver ions and the resultant biosynthesized AgNPs characterized by X-ray diffraction (XRD) spectrum showed crystalline structure while morphological shape, average size and the crystalline nature of the nanoparticles were determined by field emission scanning electron microscopy (FESEM), transmission electron microscopic with selected area electron diffraction (TEM-SAED). The elemental analysis displayed strong signal at 3 keV that agrees to silver ions and confirms the presence of metallic silver. FTIR analysis exhibits the possible reducing bio-molecules within the leaf extract. Moreover, AgNPs nanoparticles evinced excellent antibacterial activity against Staphylococcus aureus and Streptococcus pyogenus bacterial pathogens. The studies describing the synthesis of AgNPs nanoparticles by efficient and green method followed by the investigation of antibacterial activities may be opened new horizons to scientists and researchers for the medicinal purposes.

Selenium has many roles on the functioning of humans and animals. Chicks as animal model can play an important role to distinguish the role/function of selenium. The objective of the present study was to test the effect of variable doses of nano-selenium supplement on the chicken gastrointestinal tract. A total of 180 male Ross chicks were divided into six groups, with three replicates for each group and ten birds per replicate. Group 1 was the control group and was fed standard feeding for full experiment. Groups 2-6 were given variable doses of nano-selenium supplement from 1st-42nd days of age; Group 2 (0. 1 mg/kg), Group 3 (0. 2 mg/kg), Group 4 (0. 3 mg/kg), Group 5 (0. 4 mg/kg) and Group 6 (0. 5 mg/kg). The results showed a decrease in the weights of small and large bowels with simultaneous increase in their lengths. Optimum doses of supplementary nano-selenium for bowel development are suggested.