共查询到20条相似文献,搜索用时 156 毫秒
1.
The authors describe the synthesis of a multifunctional nanocomposite with an architecture of type Fe3O4@SiO2@graphene quantum dots with an average diameter of about 22 nm. The graphene quantum dots (GQDs) were covalently immobilized on the surface of silica-coated magnetite nanospheres via covalent linkage to surface amino groups. The nanocomposite displays a strong fluorescence (with excitation/emission peaks at 330/420 nm) that is fairly selectively quenched by Hg2+ ions, presumably due to nonradiative electron/hole recombination annihilation. Under the optimized experimental conditions, the linear response to Hg2+ covers the 0.1 to 70 μM concentration range, with a 30 nM lower detection limit. The high specific surface area and abundant binding sites of the GQDs result in a good adsorption capacity for Hg2+ (68 mg?g?1). The material, due to its superparamagnetism, can be separated by using a magnet and also is recyclable with EDTA so that it can be repeatedly used for simultaneous detection and removal of Hg2+ from contaminated water. 相似文献
2.
The authors describe a 3-component nanoparticle system composed of a silica-coated magnetite (Fe3O4) core and a layered double (Cu-Cr) hydroxide nanoplatelet shell. The sorbent has a high anion exchange capacity for extraction anionic species. A simple online system, referred to as "on-line packed magnetic-in-tube solid phase microextraction" was designed. The nanoparticles were placed in a stainless steel cartridge via dry packing. The cartridge was then applied to the preconcentration acidic drugs including naproxen and indomethacin from urine and plasma. Extraction and desorption times, pH values of the sample solution and flow rates of sample solution and eluent were optimized. Analytes were then quantified by HPLC with UV detection. Under optimal conditions, the limits of detection range from 70 to 800 ng L?1, with linear responses from 0.1–500 μg L?1 (water samples), 0.6–500 μg L?1 (spiked urine), and 0.9–500 μg L?1 (spiked plasma). The inter- and intra-assay precisions (RSDs, for n?=?5) are in the range of 2.2–5.4%, 2.8–4.9%, and 2.0–5.2% at concentration levels of 5, 25 and 50 μg L?1, respectively. The method was applied to the analysis of the drugs in spiked human urine and plasma, and good results were achieved. 相似文献
3.
An electrochemical microsensor for chloramphenicol (CAP) was fabricated by introducing magnetic Fe3O4 nanoparticles (NPs) onto the surface of activated carbon fibers. This microsensor exhibited increased electrochemical response toward CAP because of the synergetic effect of the Fe3O4 NPs and the carbon fibers. Cyclic voltammograms were acquired and displayed three stable and irreversible redox peaks in pH 7.0 solution. Under optimized conditions, the cathodic current peaks at ?0.67 V (vs. Ag/AgCl). The calibration plot is linear in the 40 pM to 1 μM CAP concentration range, with a 17 pM detection limit (at a signal-to-noise ratio of 3). The sensor was applied to the determination of CAP in spiked sediment samples. In our perception, this electrocatalytic platform provided a useful tool for fast, portable, and sensitive analysis of chloramphenicol. 相似文献
4.
Xiaoyu?Chen Qingquan?Liu Minghuan?Liu Xiaoyan?Zhang Suying?Lin Yisong?Chen Junyang?Zhuang Da-Peng?Yang
The authors describe an amperometric sensor for dopamine (DA) by employing olive-like Fe2O3 microspheres (OFMs) as the electrocatalyst for DA oxidization. The OFMs were prepared by using a protein templated method. The structure and properties of the OFMs were characterized by scanning electron microscopy, X-ray powder diffraction, energy dispersive x-ray spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The OFMs possess excellent catalytic activity towards DA oxidization due to their unique morphology. The sensor responds to DA within less than 5 s. The sensor, best operated at a voltage of +0.2 V (vs. SCE) responds linearly in the 0.2 to 115 μM DA concentration range and has a 30 nM detection limit. The selectivity, reproducibility and long-term stability of the sensor are acceptable. It performs well when applied to spiked human urine samples. 相似文献
5.
Shanmughasundaram Duraisamy Tirupathi Rao Penki Brij Kishore Prabeer Barpanda Prasant Kumar Nayak Doron Aurbach Nookala Munichandraiah 《Journal of Solid State Electrochemistry》2017,21(2):437-445
A porous, hollow, microspherical composite of Li2MnO3 and LiMn1/3Co1/3Ni1/3O2 (composition: Li1.2Mn0.53Ni0.13Co0.13O2) was prepared using hollow MnO2 as the sacrificial template. The resulting composite was found to be mesoporous; its pores were about 20 nm in diameter. It also delivered a reversible discharge capacity value of 220 mAh g?1 at a specific current of 25 mA g?1 with excellent cycling stability and a high rate capability. A discharge capacity of 100 mAh g?1 was obtained for this composite at a specific current of 1000 mA g?1. The high rate capability of this hollow microspherical composite can be attributed to its porous nature. 相似文献
6.
Thin films of La2O3 were deposited onto glass substrates by ultrasonic spray pyrolysis. Their structural and morphological properties were characterized by X-ray diffraction, Fourier transform Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photo-electron spectroscopy, Brunauer-Emmett-Teller and optical absorption techniques. The sensor displays superior CO2 gas sensing performance at a low operating temperature of 498 K. The signal change on exposure to 300 ppm of CO2 is about 75%, and the signal only drops to 91% after 30 days of operation. 相似文献
7.
Abolfazl Bezaatpour Sahar Khatami Kamellia Nejati 《Journal of the Iranian Chemical Society》2017,14(10):2105-2115
In this work, paramagnetic Fe3O4/SiO2 nanoparticles were synthesized, characterized and functionalized with dioxo-Mo(VI) tetradentate Schiff base complex and characterized using IR spectroscopy, X-ray powder diffraction spectroscopy, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, diffuse reflectance spectroscopy and atomic absorption spectroscopy. Catalyst was used for the selective epoxidation of cyclooctene, cyclohexene, styrene, indene, α-pinene, 1-hepten, 1-octene, 1-dodecen and trans-stilbene using tert-butyl hydroperoxide as oxidant in 1,2-dichloroethane. This catalyst is efficient for oxidation of cyclooctene with a 100% selectivity for epoxidation with 100% conversion in 1 h. After the reaction, the magnetic nanocatalyst was easily separated by simply applying an external magnetic field and was used at least five successive times without significant decrease in conversion.
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8.
The synthesis of rattle-type nanostructured Fe3O4@SnO2 is described along with their application to dispersive solid-phase extraction of trace amounts of mercury(II) ions prior to their determination by continuous-flow cold vapor atomic absorption spectrometry. The voids present in rattle-type structures make the material an effective substrate for adsorption of Hg(II), and also warrant high loading capacity. The unique morphology, large specific surface, magnetism property and the synergistic effect of magnetic cores and SnO2 shells render these magnetic nanorattles an attractive candidate for solid-phase extraction of heavy metal ions.The sorbent was characterized by transmission electron microscopy, scanning electron microscopy, FTIR, energy-dispersive X-ray spectroscopy and by the Brunnauer-Emmett-Teller technique. The effects of pH value, adsorption time, amount of sorbent, volume of sample solutions, concentration and volume of eluent on extraction efficiencies were evaluated. The calibration plot is linear in the 0.1 to 40 μg·L?1 concentration range, and the preconcentration factor is 49. The detection limit is 28 ng·L?1. The sorbent was applied to the analysis of (spiked) river and sea water samples. Recoveries ranged from 97.2 to 100.5%. 相似文献
9.
Cunliang Zhang Nie Ping Laifa Shen Hongshen Li Gang Pang Xiaogang Zhang 《Journal of Solid State Electrochemistry》2016,20(7):1983-1990
The three-dimensional porous Li3V2(PO4)3/nitrogen-doped reduced graphene oxide (LVP/N-RGO) composite was prepared by a facile one-pot hydrothermal method and evaluated as cathode material for lithium-ion batteries. It is clearly seen that the novel porous structure of the as-prepared LVP/N-RGO significantly facilitates electron transfer and lithium-ion diffusion, as well as markedly restrains the agglomeration of Li3V2(PO4)3 (LVP) nanoparticles. The introduction of N atom also has positive influence on the conductivity of RGO, which improves the kinetics of electrochemical reaction during the charge and discharge cycles. It can be found that the resultant LVP/N-RGO composite exhibits superior rate properties (92 mA h g?1 at 30 C) and outstanding cycle performance (122 mA h g?1 after 300 cycles at 5 C), indicating that nitrogen-doped RGO could be used to improve the electrochemical properties of LVP cathodes for high-power lithium-ion battery application. 相似文献
10.
Mohamed A. Habila Zeid A. ALOthman Ahmed Mohamed El-Toni Joselito Puzon Labis Xiaomin Li Fan Zhang Mustafa Soylak 《Mikrochimica acta》2016,183(8):2377-2384
The authors describe double-shell magnetic nanoparticles functionalized with 2-mercaptobenzothiazole (MBT) to give nanospheres of the type MBT-Fe3O4@SiO2@C). These are shown to be viable and acid-resistant adsorbents for magnetic separation of the heavy metal ions Ni(II), Cu(II) and Pb(II). MBT act as a binding reagent, and the carbon shell and the silica shell protect the magnetic core. Following 12 min incubation, the loaded nanospheres are magnetically separated, the ions are eluted with 2 M nitric acid and then determined by inductively coupled plasma-mass spectroscopy. The limits of detection of this method are 2, 82 and 103 ng L ̄1 for Ni(II), Cu(II), and Pb(II) ions, respectively, and the relative standard deviations (for n = 7) are 6, 7.8, and 7.4 %. The protocol is successfully applied to the quantitation of these ions in tap water and food samples (mint, cabbage, potato, peas). Recoveries from spiked water samples ranged from 97 to 100 %. 相似文献
11.
A nanocomposite consisting of cetyltrimethylammonium bromide (CTAB), Fe3O4 nanoparticles and reduced graphene oxide (CTAB-Fe3O4-rGO) was prepared, characterized, and used to modify the surface of a glassy carbon electrode (GCE). The voltammetric response of the modified GCE to 4-nonylphenol (NPh) was investigated by cyclic voltammetry and revealed a strong peak at around 0.57 V (vs. SCE). Under optimum conditions, the calibration plot is linear in the ranges from 0.03 to 7.0 μM and from 7.0 to 15.0 μM, with a 8 nM detection limit which is lower that that of many other methods. The modified electrode has excellent fabrication reproducibility and was applied to the determination of NPh in spiked real water samples to give recoveries (at a spiking level of 1 μM) between 102.1 and 99.1%. 相似文献
12.
Dan Zhu Weiwei Wang Junwu Zhu Shenming Chen Xiaoheng Liu 《Journal of Solid State Electrochemistry》2017,21(2):403-408
In this work, Bi3.64Mo0.36O6.55 nanoparticles (NPs) were successfully prepared by a facile hydrothermal method and utilized in pseudocapacitor for the first time. Within a redox potential range from ?1.0 to 0 V vs. Hg/HgO in a 1 M aqueous KOH solution by cyclic voltammetry (CV), chronopotentiometry (CP) and AC impendence, the specific capacitance could reach 998 F g?1 at 1 A g?1, which is possibly ascribed to the higher Bi content of Bi3.64Mo0.36O6.55 NPs. Furthermore, the Bi3.64Mo0.36O6.55 NP electrode exhibited good cycle stability maintaining over 85 % after 5000 cycles. These results demonstrated Bi3.64Mo0.36O6.55 NPs might be a promising electrode material for pseudocapacitor. 相似文献
13.
Izabella Dascalu Cristian Hornoiu Jose Maria Calderon-Moreno Madalin Enache Daniela Culita Simona Somacescu 《Journal of Sol-Gel Science and Technology》2018,86(1):151-161
The aim of this work was an investigation of structural and electrical properties of ZnO/Zn2-xFexTiO4 (x?=?0.7, 1, 1.4) powders. The compounds obtained by sol-gel method are characterized by several techniques: X-ray diffraction (XRD), N2 adsorption–desorption isotherms, scanning and transmission electron microscopy (SEM and TEM), X-ray photoelectron spectroscopy (XPS), electrical and dielectrical measurements. The XRD, SEM and XPS analysis confirmed the formation of ZnFeTiO4 inverse spinel structure. The electrical and dielectrical properties of ZnO/Zn2-xFexTiO4 (x?=?0.7, 1, 1.4) were measured by impedance spectroscopy, revealing a decrease in the electrical conductivity and the dielectric constant with Fe content. 相似文献
14.
Yueyue?Song Guanhong?Xu Fangdi?Wei Yao?Cen Muhammad?Sohail Menglan?Shi Xiaoman?Xu Yunsu?Ma Yujie?Ma Qin?Hu
The authors describe an aptamer-based fluorescent assay for adenosine (Ade). It is based on the interaction between silver nanoparticles (AgNPs) and CdTe quantum dots (QDs). The beacon comprises a pair of aptamers, one conjugated to Fe3O4 magnetic nanoparticles, the other to AgNPs. In the presence of Ade, structural folding and sandwich association of the two attachments takes place. After magnetic separation, the associated sandwich structures are exposed to the QDs. The AgNPs in sandwich structures act as the signaling label of Ade by quenching the fluorescence of QDs (at excitation/emission wavelengths of 370/565 nm) via inner filter effect, electron transfer and trapping processes. As a result, the fluorescence of QDs drops with increasing Ade concentration. The assay has a linear response in the 0.1 nM to 30 nM Ade concentration range and a 60 pM limit of detection. The assay only takes 40 min which is the shortest among the aptamer-based methods ever reported. The method was successfully applied to the detection of Ade in spiked biological samples and satisfactory recoveries were obtained. 相似文献
15.
A SERS-based aptasensor for ochratoxin A (OTA) is described. It is making use of Fe3O4@Au magnetic nanoparticles (MGNPs) and of Au@Ag nanoprobes modified with the Raman reporter 5,5-dithiobis-(2-nitrobenzoic acid; DTNB). Au-DTNB@Ag NPs were modified with the OTA aptamer (aptamer-GSNPs) and used as Raman signal probes. The SERS peak of DTNB at 1331 cm?1 was used for quantitative analysis. MGNPs modified with cDNA (cDNA-MGNPs) were used as capture probes and reinforced substrates. When the Au-DTNB@Ag-Fe3O4@Au complexes are formed through oligonucleotide hybridization, the Raman signal intensity of the Raman probe is significantly enhanced. If the OTA concentration in samples increases, more Raman signal probes (aptamer-GSNPs) will dissociate from the cDNA-MGNPs because more OTA aptamer is bound by OTA. This leads to a lower Raman signal after magnetic separation. Under the optimal conditions, the detection limit for OTA is 0.48 pg·mL?1 based on 3σ criterion. This is attributed to the multiple Raman signal enhancement and the good performance of the OTA aptamer. The good recovery and accuracy of the assay was confirmed by evaluating spiked samples of wine and coffee. 相似文献
16.
Ionic liquid coated nanoparticles (IL-NPs) consisting of zero-valent iron are shown to display intrinsic peroxidase-like activity with enhanced potential to catalyze the oxidation of the chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide. This results in the formation of a blue green colored product that can be detected with bare eyes and quantified by photometry at 652 nm. The IL-NPs were further doped with bismuth to enhance its catalytic properties. The Bi-doped IL-NPs were characterized by FTIR, X-ray diffraction and scanning electron microscopy. A colorimetric assay was worked out for hydrogen peroxide that is simple, sensitive and selective. Response is linear in the 30–300 μM H2O2 concentration range, and the detection limit is 0.15 μM. 相似文献
17.
A nanocomposite composed of graphene oxide and magnetite (Fe3O4) was coated with the ionic liquid (IL) 1,3-didecyl-2-methylimidazolium chloride and used to capture and separate hemin from serum samples. The critical parameters affecting the extraction of analyte, such as pH, surfactant and adsorbent amounts, and desorption conditions were studied and optimized. Following magnetic separation and desorption with a 5:1 mixture of acetic acid and acetone, hemin (an iron porphyrin complex) was quantified by FAAS of iron. Under optimum conditions, the enrichment factor was 96. The calibration curve was linear in the 4.8 to 730 μg L?1 concentration range, the limit of detection was 3.0 μg L?1, and the relative standard deviations (RSDs) for single-sorbent repeatability and sorbent-to-sorbent reproducibility were less than 3.9 % and 10.2 % (n = 5), respectively. The adsorbent displayed adsorption capacity as high as 200 mg g?1, indicating IL-coated Fe3O4/GO to be a good sorbent for the adsorption of hemin. The method was validated by determining serum hemin in the presence of a large excess (480-fold) of Fe3+ without considerable interference. The results compare well to those obtained with a commercial hemin assay kit. The results show that this method can be successfully applied to the enrichment and determination of hemin in acid digested serum samples of breast cancer patients. 相似文献
18.
Hetero-dimeric magnetic nanoparticles of the type Au-Fe3O4 have been synthesised from separately prepared, differently shaped (spheres and cubes), monodisperse nanoparticles. This synthesis was achieved by the following steps: (a) Mono-functionalising each type of nanoparticles with aldehyde functional groups through a solid support approach, where nanoparticle decorated silica nanoparticles were fabricated as an intermediate step; (b) Derivatising the functional faces with complementary functionalities (e.g. amines and carboxylic acids); (c) Dimerising the two types of particles via amide bond formation. The resulting hetero-dimers were characterised by high-resolution TEM, Fourier transform IR spectroscopy and other appropriate methods. 相似文献
19.
MgF2 coating solutions were solvothermally treated at 160?°C for different time periods, this procedure induced crystallization and particle growth. Antireflection coatings prepared on glass from these solutions were compared to films derived from untreated precursor material. Ellipsometric porosimetry (EP) was employed to characterize structural features of coatings on glass as function of annealing temperature. Based on precursor solutions that had undergone solvothermal treatment antireflective coatings with a peak transparency exceeding 99% were prepared on PMMA substrates. 相似文献
20.
The authors report on the preparation of a hollow-structured cobalt ferrite (CoFe2O4) nanocomposite for use in a non-enzymatic sensor for hydrogen peroxide (H2O2). Silica (SiO2) nanoparticles were exploited as template for the deposition of Fe3O4/CoFe2O4 nanosheets, which was followed by the removal of SiO2 template under mild conditions. This leads to the formation of hollow-structured Fe3O4/CoFe2O4 interconnected nanosheets with cubic spinel structure of high crystallinity. The material was placed on a glassy carbon electrode where it acts as a viable sensor for non-enzymatic determination of H2O2. Operated at a potential of ?0.45 V vs. Ag/AgCl in 0.1 M NaOH solution, the modified GCE has a sensitivity of 17 nA μM?1 cm?2, a linear response in the range of 10 to 1200 μM H2O2 concentration range, and a 2.5 μM detection limit. The sensor is reproducible and stable and was applied to the analysis of spiked urine samples, where it provided excellent recoveries. 相似文献