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61.
New mercapto-grafted graphene oxide–magnetic chitosan (GO–MC) has been developed as a novel biosorbent for the preconcentration and extraction of mercury ion from water samples. A facile and ecofriendly synthesis procedure was also developed for modification of GO–MC with 3-mercaptopropyltrimethoxysilane. The prepared nanocomposite material (mercapto/GO–MC) was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and energy-dispersive X-ray spectroscopy (EDX). The mercury analysis was performed by continuous-flow cold vapor atomic absorption spectrometry. The parameters affecting the extraction and preconcentration processes were carried out. The optimum conditions were found to be 60 mg of sorbent, pH of 6.5, 10 min for adsorption time, 3 mL of HCl (0.1 mol L−1)/thiourea (2% w/v) as the eluent and 250 mL for breakthrough volume. An excellent linearity was achieved in the range of 0.12–80 ng mL−1 (R2 = 0.999) at a preconcentration factor of 80. The limit of detection and quantification were achieved as 0.06 ng mL−1 and 0.12 ng mL−1, respectively. A good repeatability was obtained with the relative standard deviation (RSD) of 4.7%. Furthermore, real water samples were analyzed and good recoveries were obtained from 95 to 100%. 相似文献
62.
This work is a first study on extraction efficiency and thermal stability of nano-structured self-doped polyaniline (SPAN) as a coating of solid-phase microextraction (SPME) fibers. SPAN-based fibers were prepared using electrochemical deposition on platinum wires. The particle sizes of prepared nano-structure were in the range of 50–100 nm. Extraction properties of the fiber to 1,4-dioxane were examined using headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography-flame ionization detection (GC-FID). The results have proved higher thermal stability of the proposed fiber compared to common PANI fiber. The SPAN coating was proved to be very stable at relatively high temperatures (up to 350 °C) with high extraction capacity and long lifespan (more than 50 times). Therefore, it can be a good substitute of polyaniline (PANI) as a SPME coating. The extraction procedure was optimized by selecting the appropriate extraction parameters including extraction time, extraction temperature, salt concentration, stirring rate and headspace volume. Calibration graph was linear in the concentration range of 1–100 ng mL−1 (R2 > 0.993) with detection limit of 0.1 ng mL−1. Single fiber and fiber-to-fiber repeatability were lower than 6.0% and 10.4%, respectively. Different water samples were analyzed as real samples and good recoveries (98–120%) were obtained. 相似文献
63.
The protonation constants of three different flavonoids (naringenin, chrysin, and daidzein) were determined in water–DMSO
mixed solvents using a potentiometric method at 25.0 (±0.1) °C and 1.00 mol⋅dm−3 tetra-n-butylammonium chloride as supporting electrolyte. The protonation constants were characterized and were analyzed in various
solvent media in terms of the Kamlet, Abboud and Taft (KAT) parameters. Single-parameter correlations of the protonation constants
versus α (hydrogen-bond donor acidity), β (hydrogen-bond acceptor basicity) or π
∗ (dipolarity/polarizability) are poor for all compounds, but the dual-parameter α and π
∗ correlation presents significant improvement with regard to the single- and multi-parameter models. A linear correlation
is observed when the logarithm of the experimental protonation constants is plotted versus the calculated ones when the KAT
parameters are considered. The protonation constants of the flavonoids in water were also calculated by the Yasuda-Shedlovsky
extrapolation method at zero percent organic solvent. Finally, the results are discussed in terms of the effect of solvent
composition on the protonation constants. 相似文献
64.
Journal of Fluorescence - Development of an efficient, portable and simple nanosensor-based systems with reliable analytical performance for on-site monitoring of vitamin B12 (VB12) are still major... 相似文献
65.
66.
Jabbari F. Rajabpour A. Saedodin S. 《Journal of Thermal Analysis and Calorimetry》2019,135(3):1787-1796
Journal of Thermal Analysis and Calorimetry - Special features of nanofluids as heat transfer media have made them very important. The first step for investigating nanofluids was to know the... 相似文献
67.
Hossein Yadegari Ali Jabbari Hossein Heli 《Journal of Solid State Electrochemistry》2012,16(1):227-234
Nanoparticles of lithium cobalt oxide (LiCoO2) and nanosheets of lithium vanadium oxide (LiV3O8) were synthesized by a citrate sol–gel combustion route. The physical characterizations of the electrodic materials were
carried out by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and also X-ray diffraction (XRD)
measurements. Near spherical nanoparticles of ≈100 nm and compact nanosheets with a few nanometers thick were observed by
SEM and TEM for LiCoO2 and LiV3O8, respectively. XRD data indicated that the as-prepared active materials presented pure phase of rhombohedral LiCoO2 with R-3m symmetry and monoclinic LiV3O8 with p21/m symmetry. The kinetics of electrochemical intercalation of lithium ion into the nanoparticles of LiCoO2 and nanosheets of LiV3O8 from 1.0 mol l−1 LiNO3 aqueous solution were investigated by cyclic voltammetry and chronoamperometry. An aqueous rechargeable lithium-ion battery
consisting of LiCoO2 nanoparticles as positive and LiV3O8 nanosheets as negative electrode was assembled. This battery represented a discharge voltage of about 1 V with good cycling
performance. 相似文献
68.
The universal minimal one parameter system will be characterized as the space $$\Gamma ^{\infty }$$, in which $$\Gamma$$ is the Bohr compactification of the additive group $${\mathbb {R}}$$ of real numbers. In this way, we need to show that $$\Gamma ^\infty$$ is isomorphic to the spectrum of $$W({\mathbb {R}})$$, the norm closure of the invariant algebra generated by the maps $$\exp q(t)$$, where q(t) is a real polynomial on $${\mathbb {R}}$$. 相似文献
69.
Sabrina Reuter Marek A. Smolarczyk André Istock Uh-Myong Ha Olga Schneider Natalie Worapattrakul Safoura Nazemroaya Hai Hoang Ludmilla Gomer Frank Pilger Markus Maniak Hartmut Hillmer 《Journal of nanoparticle research》2017,19(5):184
Nanoimprinting enables the implementation of nanoparticle shapes with complex 2D shapes involving different materials. In addition to these objects, this article presents 3D-shaped nanoparticles fabricated by substrate conformal imprint technique. The imprint polymer AMONIL is used either in pure form or in combination with fluorescent dyes for the preparation of particles. The substrate conformal imprint lithography process, including etching and particle release, is conducted for both materials in a similar fashion. In this work, cuboidal particles with a high aspect ratio (1:120) are compared to particles with a T-shaped cross section with respect to their abilities to enhance or reduce their stiffness. Additionally, particles with a high aspect ratio are compared to particles with a lower aspect ratio (1:20). The local stiffness is found to depend strongly on the particle thickness and the geometry of their cross section. Thicker and 3D T-shaped particles present higher local stiffness than thinner and 2D cuboidal-shaped particles. The local bending angle was determined to be 77° for 2D-shaped particles and 83° for 3D-shaped particles, of the same total height of 176 nm. Very thin particles (<50 nm) of high aspect ratio prefer to curl finally forming loops. 相似文献
70.
In this paper, novel adaptive neural network (NN) controllers with input saturation are presented for n-link robotic exoskeletons. The controllers consist of a state feedback controller and an output feedback controller. Through utilizing auxiliary dynamics, the controllers provide a new framework for input saturated control of these robotic systems which can feature the global stability for state feedback control. To compensate for the unknown dynamics of the system, adaptive schemes based on NNs are exploited. Furthermore, adaptive robust terms are utilized to deal with unknown external disturbances. Stability studies show that the closed-loop system is globally uniformly ultimately bounded (UUB) with the state feedback controller, where the global property of the NN-based controller is achieved exploiting a smooth switching function and a robust control term. Also, the system is semi-globally UUB with the output feedback controller. Effectiveness of the controllers is validated by simulations and experimental tests. 相似文献