جستجوی مقالات مرتبط با کلیدواژه « Atomic Force Microscopy » در نشریات گروه « علوم پایه »

The recent decade has seen a huge impact of nanotechnology in different sciences. In analytical chemistry, nanomaterials have been utilized for various purposes from sample preparation to detection. The impact of nanotechnology in analytical science is not limited to the improvement of analytical methodologies. Nanomaterials have been utilized for nanomaterials analysis as nanotools. Nanotools are used to investigate and work with materials at the nanoscale. Nanotechnology has also enabled new applications such as nanoscale tips used for topological microscopy in atomic force microscopy, scanning tunneling microscopy, and magnetic force microscopy. These techniques utilize nanotechnology to improve their efficiency. Furthermore, nanotechnology has enabled the construction of tweezers and robots in the nanoscale. These nano-enabled tools (nanotools) have been successfully utilized for nanoanalysis and nanomanipulation. atomic force microscopy, scanning tunneling microscope, and magnetic force microscopy are not only meant to image nanostructured surfaces but also they are utilized for the manipulation of materials at the atomic and nanoscale. Nanotweezers, nanorobots, and laser tweezers using nanoapertures are also able to manipulate nano and microscale materials. This paper reviews the principles and application of the mentioned nano-enabled techniques as nanotools in analytical chemistry with a focus on nanomaterials nanoanalysis and nanomanipulation as nanoanalytes.

The inhibiting effect of Lavendula stoechas extract on the corrosion of Monel alloy 400 in 0.5 M sulfuric acid at different temperatures (298–328 K) was evaluated by mass loss measurements and electrochemical techniques, including Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization. The corroded surfaces of metal samples were examined using an atomic force microscope (AFM). Experimental results revealed that the inhibition efficiency increases with increasing inhibitor content and decreases with increasing temperature. The maximum inhibition efficiency was approximately 90.81%, and was reached in the presence of 0.25 g/L inhibitor at 298 K. The inhibitory action of Lavendula extract was realized via the adsorption of phytochemical constituents on the metal surface. The adsorption follows the Langmuir adsorption mechanism. Thermodynamic parameters suggested that the adsorption was spontaneous at different temperatures, supporting a mixed physisorption and chemisorption mechanism. Electrochemical impedance spectroscopy indicated that the inhibitor ameliorates the film formed at the metal/solution interface. Potentiodynamic polarization studies reveal that the inhibitor behaves as a mixed-type inhibitor,  with a predominantly anodic tendency. AFM studies confirmed the adsorption of Lavendula extract on the Monel alloy surface.

Cellulose nanocrystals (CNCs) are charged nanoparticles with a high aspect ratio derived from the most common biological polymer, cellulose. Acid hydrolysis is one of the most common methods for CNC production. Whatman #1 filter paper was hydrolyzed by sulfuric acid and characterized by AFM in this research to examine the morphology and size distribution of CNCs. One drop of CNC suspension was air-dried on microscope cover glass to be analyzed by AFM with non-contact mode. The CNC dimensions were determined by measuring individual and isolated particles (n=88) via Nanosurf Easyscan2 software. The measurement data was analyzed by Excel statistically. Synthesized CNCs were ellipsoidal with the length, height, and aspect ratio of 219.87 ± 42.12, 6.25 ± 2.27, and 41.17 ± 21.70 nm, respectively. Although the length and height of the produced CNCs were in acceptable range, but the width of CNCs was an overestimation and it was not reliable, mostly due to AFM tip broadening effect. Particle size measurement of CNCs is a challenging process because of their rapid aggregation and rod shape. Although hydrolysis parameters are influential on the final shape and size of CNCs, but it is necessary to optimize and maximize the quality of sample preparation and AFM adjustment to obtain the size of CNCs with the most accuracy and reliability. The CNC dimensions were determined by AFM are slightly different in the literature but height (thickness) is the most reliable one based on this experiment. Further studies are required to standardize CNC size measurement by AFM.

The purpose of this study is to combine FIA and AFM to explain surface morphology utilizing a newly developed instrument, the NAG-4SX3-3D analyzer. The study is dedicated on a new approach for determining fluconazole drug via reaction with phosphomolybdic acid as a precipitating agent to obtain a sufficient amount of weight (pale yellow precipitate) for the AFM sample and determine through the roughness parameters. The main advantage of the proposed approach lies in its ability in determining number of nanoparticles that can occupy the empty surface area starting from the 1st ground monolayer calculates the unoccupied surface area and determines the nanoparticles concentration which participated on the surface. Thus, a microfluidic flow system is proposed for continuous synthesis of nanoparticles by chemical reaction of precipitation reagent with the pharmaceutical active ingredients. The flow system allows the nanoparticles synthesis in a smooth manner without clogging. All of the flow injections conditions (physical and chemical) were examined and fixed. The average diameters of drug is 62.02 nm, Grain No. 306, Roughness Average 2.76, peak to peak = 14 nm, ten point height = 13.9 nm, and surface kurtosis = 2.2 for surface area of scanned section with a dimension of 2362369 nm2.

The method used to immobilize the polymer on the Disodium ethylenediamine tetraacetate (EDTA) modified carbon paste electrode (CPE/EDTA) has proved its effectiveness for the detection and chelation of heavy metals in aqueous solution. Its complex formation with Pb(II) was examined by square wave voltammetry and cyclic voltammetry. CPE/EDTA electrodes are predisposed to the phenomenon of dissolution due to several factors, such as pH, we thought to cover these electrodes with a selective polymer synthesized (9% of the polysulfone and 91% of the polyacrylonitrile) for remedy this problem. It was found that the CPE/EDTA/polymer electrode shows a better performance than the carbon paste electrode modified by EDTA molecular (CPE/EDTA). The polymer used protects the surface of the electrode while preserving its activity. These modified electrodes developed in this study allow simple, rapid and inexpensive identifi1cation of lead ions with 1.08×10-9mol/l of detection limit. The morphological study of polymer surface was examined by Atomic Force Microscopy (AFM).

Chromium oxide (α-Cr2O3) thin films were prepared using thermal annealing of chromium (Cr) films deposited on quartz substrates by direct current (DC) magnetron sputtering. The annealing process of the films was performed for different times of 60, 120,180 and 240 min. The influence of annealing time on structural, morphological and optical properties of the prepared films was investigated by different analysis including X-ray diffraction (XRD), atomic force microscopy (AFM) and spectrophotometry. The XRD patterns showed that upon thermal annealing the Cr films transformed to (α-Cr2O3) and the annealing time has a profound effect on crystalline structure of chromium oxide films. According to AFM results, the films surface morphologies were strongly dependent on annealing time and an increase in annealing time led to an increase in the grain size as well as in the surface roughness. The transmittance of the as deposited film was found very low and it improved after annealing.

The aim of this paper is to study the effect of substrate on the Cu3N thin films. At first Cu3N thin films are prepared using DC magnetron sputtering system. Then structural properties, surface roughness, and electrical resistance are studied using X-ray diffraction (XRD), the atomic force microscope (AFM) and four-point probe techniques respectively. Finally, the results are investigated and compared for glass and Si substrate. The results show a phase transition in orientation from (111) and (100) planes to (200) plane when the substrate of the sample is changed from glass to Si. Also, the grain size of deposited particles on films increased, changing substrate from glass to Si. Then, AFM results show that surface roughness on Si substrate is more than the glass substrate. Finally, four-point probe techniques show that surface electrical resistivity is increased sharply, changing substrate from silicon to glass.

Crystalline surface layer proteins (S-layer proteins) have considerable potential for the crystalline arrays in biotechnology, biomimetics and nonlife applications, including areas such as microelectronics and molecular nanotechnology. The extensive application potential of surface layers in nanobiotechnology is according to the particular inherent attributes of the single molecular arrays consisted of uniform protein or glycoprotein subunits. Most important, functional groups on the protein lattice are arrayed in well-specified positions and orientations. Many applications of S-layers are related to the ability of isolated subunits to recrystallize into single molecular arrays in suspension, suitable surfaces or interfaces. Utilization of the s-layers as template to pattern inorganic nanostructures, requires the separation and purification of these proteins and study of their structures on solid surfaces. The hexagonally packed intermediate (Hpi) protein of Deinococcus radiodurans belongs to the category of S-layer proteins which form crystalline two-dimensional arrays on bacterial cell surfaces. In this study, Deinococcus radiodurans R1 S-layer was purified and SDS-PAGE of purified HPI layer was analyzed by Core Laboratory Image Quantification Software. And also, secondary structure of Isolated HPI layer was evaluated by Circular Dichroism. and Zeta potential measurement was carried out to define surface charge of HPI surface layer sheets. In addition, hexagonally pattern of HPI sheets have been studied by atomic force microscopy and field emission scanning electron microscopy. According to our results, isolated HPI layer from Deinococcus radiodurans R1 can be used as template to array nanoparticles in future works.

The sensitivity analysis of atomic force microscope (AFM) based manipulation of gold spherical nanoparticles in air medium has been carried out in previous research works. In the AFM-based manipulations conducted in various biological liquid mediums, the new environmental parameters associated with these biological fluids also affect the dynamics of the manipulation process. Therefore in this research, the Sobol sensitivity analysis method has been employed to find out how these new parameters as well as the other effective parameters influence the manipulation process. The parameters have been classified into two groups of AFM parameters and environmental parameters. According to the obtained simulation results, in the group of AFM parameters, cantilever thickness (with a sensitivity index of 57%) is the most sensitive parameter in the manipulation of cylindrical biological micro/nanoparticles, followed by the parameters of cantilever length and cantilever width. By examining the sensitivity of environmental parameters for cylindrical biological micro/nanoparticles in biological mediums, it is observed that the highest sensitivity belongs to the dimensional parameters of target particles (the most sensitive environmental parameter is cross-sectional radius of target particle with a sensitivity index of 52%), followed by the sensitivity of adhesion work in the biological medium of manipulation. It is found that the critical force for the onset of movement increases substantially with the increase in the cross-sectional radius of target particle, ratio of particle length to its cross-sectional radius and also with the increase in the work of adhesion in the biological environment.