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1.
Environ Res ; 214(Pt 3): 114007, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-35934146

RESUMO

A novel electrochemical sensor was prepared using N-doped carbon mesoporous materials supported with nickel nanoparticles (Ni-NCs) for environmental p-nitrophenol (p-NP) detection in a specific geographical area. These as-prepared Ni-NCs were dispersed in polyethyleneimine (PEI) solution and modified onto a glassy carbon electrode (GCE) for electrocatalytic reduction of p-NP. The Ni-NCs-PEI/GCE showed a high Faraday current at -0.302 V during p-NP reduction, because of the synergistic effect between Ni-NCs and PEI. Under ideal conditions, the Ni-NCs-PEI/GCE was used in the voltametric determination of p-NP, with high sensitivity. The linear ranges for p-NP are 0.06-10 µM and 10-100 µM with low detection limit (4.0 nM) and high sensitivity (1.465 µA µM-1 cm-2). In the presence of other phenolic compounds, this sensor showed good selectivity for p-NP detection. The Ni-NCs-PEI/GCE was also used to determine p-NP in environmental water samples of a specific geographical area, with recoveries ranging from 95.9% to 109.4%, and an RSD of less than 3.6%. Therefore, this novel Ni-NCs-PEI/GCE provides a good example for the design of other carbon-based nanocomposite materials, for electrochemical detection of trace p-NP in a specific geographical area.


Assuntos
Carbono , Nanocompostos , Carbono/química , Nanocompostos/química , Níquel , Nitrogênio , Nitrofenóis
2.
Int J Mol Sci ; 23(20)2022 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-36293039

RESUMO

Sensing trace amounts of 4-nitrophenol (4-NP) as a harmful substance to organisms even in small quantities is of great importance. The present study includes a sensitive and selective electrochemical sensor for detecting 4-NP in natural water samples using formamide-converted nitrogen-carbon materials (shortened to f-NC) as a new material for electrode modification. The structure and morphology of the f-NC were set apart by SEM, TEM, XRD, XPS, FTIR, Raman, and the electrochemical performance of the f-NC were set apart by CV, EIS and CC. We studied the electrochemical behaviour of 4-NP on the glassy carbon electrode modified with f-NC before and after pyrolysis treatment (denoted as f-NC1/GCE and f-NC2/GCE). In 0.2 M of H2SO4 solution, the f-NC2/GCE has an apparent electrocatalytic activity to reduce 4-NP. Under the optimal conditions, the reduction peak current of 4-NP varies linearly, with its concentration in the range of 0.2 to 100 mM, and the detection limit obtained as 0.02 mM (S/N = 3). In addition, the electrochemical sensor has high selectivity, and the stability is quite good. The preparation and application of the sensor to detect 4-NP in water samples produced satisfactory results, which provides a new method for the simple, sensitive and quantitative detection of 4-NP.


Assuntos
Carbono , Nitrogênio , Carbono/química , Eletrodos , Formamidas , Água , Técnicas Eletroquímicas/métodos
3.
Molecules ; 27(18)2022 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-36144756

RESUMO

Adefovir (ADV) is an anti-retroviral drug, which can be used to treat acquired immune deficiency syndrome (AIDS) and chronic hepatitis B (CHB), so its quantitative analysis is of great significance. In this work, zirconium molybdate (ZrMo2O8) was synthesized by a wet chemical method, and a composite with multi-walled carbon nanotubes (MWCNTs) was made. ZrMo2O8-MWCNTs composite was dropped onto the surface of a glassy carbon electrode (GCE) to prepare ZrMo2O8-MWCNTs/GCE, and ZrMo2O8-MWCNTs/GCE was used in the electrochemical detection of ADV for the first time. The preparation method is fast and simple. The materials were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and cyclic voltammetry (CV). It was electrochemically analysed by differential pulse voltammetry (DPV). Compared with single-material modified electrodes, ZrMo2O8-MWCNTs/GCE showed a vastly improved electrochemical response to ADV. Moreover, the sensor complements the study of the electrochemical detection of ADV. Under optimal conditions, the proposed electrochemical method showed a wide linear range (from 1 to 100 µM) and a low detection limit (0.253 µM). It was successfully tested in serum and urine. In addition, the sensor has the advantages of a simple preparation, fast response, good reproducibility and repeatability. It may be helpful in the potential applications of other substances with similar structures.


Assuntos
Nanocompostos , Nanotubos de Carbono , Adenina/análogos & derivados , Técnicas Eletroquímicas/métodos , Eletrodos , Limite de Detecção , Molibdênio , Nanocompostos/química , Nanotubos de Carbono/química , Organofosfonatos , Reprodutibilidade dos Testes , Zircônio
4.
Molecules ; 26(21)2021 Oct 29.
Artigo em Inglês | MEDLINE | ID: mdl-34770975

RESUMO

Acyclovir (ACV) is an effective and selective antiviral drug, and the study of its toxicology and the use of appropriate detection techniques to control its toxicity at safe levels are extremely important for medicine efforts and human health. This review discusses the mechanism driving ACV's ability to inhibit viral coding, starting from its development and pharmacology. A comprehensive summary of the existing preparation methods and synthetic materials, such as 5-aminoimidazole-4-carboxamide, guanine and its derivatives, and other purine derivatives, is presented to elucidate the preparation of ACV in detail. In addition, it presents valuable analytical procedures for the toxicological studies of ACV, which are essential for human use and dosing. Analytical methods, including spectrophotometry, high performance liquid chromatography (HPLC), liquid chromatography/tandem mass spectrometry (LC-MS/MS), electrochemical sensors, molecularly imprinted polymers (MIPs), and flow injection-chemiluminescence (FI-CL) are also highlighted. A brief description of the characteristics of each of these methods is also presented. Finally, insight is provided for the development of ACV to drive further innovation of ACV in pharmaceutical applications. This review provides a comprehensive summary of the past life and future challenges of ACV.


Assuntos
Aciclovir/efeitos adversos , Aciclovir/análise , Antivirais/efeitos adversos , Antivirais/análise , Aciclovir/síntese química , Antivirais/síntese química , Humanos , Estrutura Molecular
5.
J Nanobiotechnology ; 18(1): 112, 2020 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-32778119

RESUMO

A method with high sensitivity, good accuracy and fast response is of ever increasing importance for the simultaneous detection of AA, DA and UA. In this paper, a simple and sensitive electrochemical sensor, which based on the polyvinylpyrrolidone (PVP)-graphene composite film modified glassy carbon electrode (PVP-GR/GCE), was presented for detecting ascorbic acid (AA), dopamine (DA) and uric acid (UA) simultaneously. The PVP-GR/GCE has excellent electrocatalytic activity for the oxidation of AA, DA and UA. The second-order derivative linear sweep voltammetry was used for the electrochemical measurements. The peak potential differences of DA-AA, DA-UA, and UA-AA (measured on the PVP-GR/GCE) were 212, 130 and 342 mV respectively. Besides, the over potential of AA, DA and UA reduced obviously, so did the peak current increase. Under the optimum conditions, the linear ranges of AA, DA and UA were 4.0 µM-1.0 mM, 0.02-100 µM, and 0.04-100 µM, respectively. The detection limits were 0.8 µM, 0.002 µM and 0.02 µM for AA, DA, and UA. The electrochemical sensor presented the advantages of high sensitivity and selectivity, excellent reproducibility and long-term stability. Furthermore, the sensor was successfully applied to the analysis of real samples.


Assuntos
Ácido Ascórbico/urina , Dopamina/urina , Técnicas Eletroquímicas/métodos , Ácido Úrico/urina , Grafite/química , Humanos , Limite de Detecção , Modelos Lineares , Povidona/química , Reprodutibilidade dos Testes
6.
Molecules ; 24(6)2019 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-30934654

RESUMO

The nanohybrid of electrochemically-reduced graphene oxide (ERGO) nanosheets decorated with MnO2 nanorods (MnO2 NRs) was modified on the surface of a glassy carbon electrode (GCE). Controlled potential reduction was applied for the reduction of graphene oxide (GO). The characterization was performed by scanning electron microscopy, X-ray diffraction and cyclic voltammetry. Compared with the poor electrochemical response at bare GCE, a well-defined oxidation peak of sunset yellow (SY) was observed at the MnO2 NRs-ERGO/GCE, which was attributed to the high accumulation efficiency as well as considerable electrocatalytic activity of ERGO and MnO2 NRs on the electrode surface. The experimental parameters for SY detection were optimized in detail. Under the optimized experiment conditions, the MnO2 NRs-ERGO/GCE showed good linear response to SY in concentration range of 0.01⁻2.0 µM, 2.0⁻10.0 µM and 10.0⁻100.0 µM with a detection limit of 2.0 nM. This developed method was applied for SY detection in soft drinks with satisfied detected results.


Assuntos
Técnicas Eletroquímicas , Eletrodos , Corantes de Alimentos/análise , Grafite/química , Compostos de Manganês/química , Nanotubos/química , Óxidos/química , Concentração de Íons de Hidrogênio , Nanotubos/ultraestrutura , Reprodutibilidade dos Testes , Análise Espectral
7.
Sensors (Basel) ; 18(1)2018 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-29329206

RESUMO

Cu2O-reduced graphene oxide nanocomposite (Cu2O-RGO) was used to modify glassy carbon electrodes (GCE), and applied for the determination of dopamine (DA). The microstructure of Cu2O-RGO nanocomposite material was characterized by scanning electron microscope. Then the electrochemical reduction condition for preparing Cu2O-RGO/GCE and experimental conditions for determining DA were further optimized. The electrochemical behaviors of DA on the bare electrode, RGO- and Cu2O-RGO-modified electrodes were also investigated using cyclic voltammetry in phosphate-buffered saline solution (PBS, pH 3.5). The results show that the oxidation peaks of ascorbic acid (AA), dopamine (DA), and uric acid (UA) could be well separated and the peak-to-peak separations are 204 mV (AA-DA) and 144 mV (DA-UA), respectively. Moreover, the linear response ranges for the determination of 1 × 10-8 mol/L~1 × 10-6 mol/L and 1 × 10-6 mol/L~8 × 10-5 mol/L with the detection limit 6.0 × 10-9 mol/L (S/N = 3). The proposed Cu2O-RGO/GCE was further applied to the determination of DA in dopamine hydrochloride injections with satisfactory results.


Assuntos
Nanocompostos , Ácido Ascórbico , Cobre , Dopamina , Técnicas Eletroquímicas , Eletrodos , Grafite , Oxirredução , Ácido Úrico
8.
Sensors (Basel) ; 18(6)2018 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-29895779

RESUMO

TiO2-reduced graphene oxide composite-modified glassy carbon electrodes (TiO2⁻ErGO⁻GCE) for the sensitive detection of tartrazine were prepared by drop casting followed by electrochemical reduction. The as-prepared material was characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Cyclic voltammetry and second-order derivative linear scan voltammetry were performed to analyze the electrochemical sensing of tartrazine on different electrodes. The determination conditions (including pH, accumulation potential, and accumulation time) were optimized systematically. The results showed that the TiO2⁻ErGO composites increased the electrochemical active area of the electrode and enhanced the electrochemical responses to tartrazine significantly. Under the optimum detection conditions, the peak current was found to be linear for tartrazine concentrations in the range of 2.0 × 10−8⁻2.0 × 10−5 mol/L, with a lower detection limit of 8.0 × 10−9 mol/L (S/N = 3). Finally, the proposed TiO2⁻ErGO⁻GCEs were successfully applied for the detection of trace tartrazine in carbonated beverage samples.

9.
Sensors (Basel) ; 18(9)2018 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-30135387

RESUMO

A facile cuprous oxide nanoparticles functionalized electro-reduced graphene oxide modified glassy carbon electrode (denoted as Cu2O NPs-ERGO/GCE) was fabricated via a simple physical adsorption and electrochemical reduction approach. Cyclic voltammetry and second-order derivative linear scan voltammetry were used to investigate the electrocatalysis oxidation of vanillin on the Cu2O NPs-ERGO/GCE. The compound yielded a well-defined voltammetric response in 0.1 M H2SO4 at 0.916 V (vs. saturated calomel electrode (SCE)). A linear calibration graph was obtained in the concentration range of 0.1 µM to 10 µM and 10 µM to 100 µM, while the detection limit (S/N = 3) is 10 nM. In addition, the Cu2O NPs-ERGO/GCE presented well anti-interference ability, stability, and reproducibility. It was used to detect vanillin sensitively and rapidly in different commercial food products, and the results were in agreement with the values obtained by high performance liquid chromatography.

10.
Molecules ; 23(9)2018 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-30149513

RESUMO

Control and detection of sunset yellow is an utmost demanding issue, due to the presence of potential risks for human health if excessively consumed or added. Herein, cuprous oxide-electrochemically reduced graphene nanocomposite modified glassy carbon electrode (Cu2O-ErGO/GCE) was developed for the determination of sunset yellow. The Cu2O-ErGO/GCE was fabricated by drop-casting Cu2O-GO dispersion on the GCE surface following a potentiostatic reduction of graphene oxide (GO). Scanning electron microscope and X-ray powder diffractometer was used to characterize the morphology and microstructure of the modification materials, such as Cu2O nanoparticles and Cu2O-ErGO nanocomposites. The electrochemical behavior of sunset yellow on the bare GCE, ErGO/GCE, and Cu2O-ErGO/GCE were investigated by cyclic voltammetry and second-derivative linear sweep voltammetry, respectively. The analytical parameters (including pH value, sweep rate, and accumulation parameters) were explored systematically. The results show that the anodic peak currents of Cu2O-ErGO /GCE are 25-fold higher than that of the bare GCE, due to the synergistic enhancement effect between Cu2O nanoparticles and ErGO sheets. Under the optimum detection conditions, the anodic peak currents are well linear to the concentrations of sunset yellow, ranging from 2.0 × 10-8 mol/L to 2.0 × 10-5 mol/L and from 2.0 × 10-5 mol/L to 1.0 × 10-4 mol/L with a low limit of detection (S/N = 3, 6.0 × 10-9 mol/L). Moreover, Cu2O-ErGO/GCE was successfully used for the determination of sunset yellow in beverages and food with good recovery. This proposed Cu2O-ErGO/GCE has an attractive prospect applications on the determination of sunset yellow in diverse real samples.


Assuntos
Compostos Azo/análise , Cobre/química , Técnicas Eletroquímicas , Eletrodos , Grafite/química , Nanocompostos/química , Óxidos/química , Concentração de Íons de Hidrogênio , Nanocompostos/ultraestrutura , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
11.
Materials (Basel) ; 16(13)2023 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-37445035

RESUMO

In order to avoid slackening of differential housing and gear joined by bolts, the laser-welding process is proposed in this paper, and the strength of a connecting joint was estimated by numerical analysis with consideration of welding residual stress. The process parameters of laser welding for dissimilar materials QT600 cast iron and 20MnCr5 structural alloy steel were introduced, and chemical composition analysis and microstructure analysis were conducted on the welded joints. The finite element model of laser-welded differential housing and gear was established to obtain the welding residual stress by applying a moving heat source. To verify the accuracy of the simulated result, static pressing tests were employed. The maximum tensile residual stress was 319.4 MPa, located at the same point as the maximum temperature. The simulated stress agreed well with the experimental data. Finally, the dynamic strength of laser-welded differential housing and gear under forward, reverse, and start-up conditions was assessed by regarding welding residual stress as the initial stress field, which showed that all safety factors were greater than 1.4.

12.
J Neural Eng ; 20(2)2023 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-36863014

RESUMO

Objective.Reliable and user-friendly electrodes can continuously and real-time capture the electroencephalography (EEG) signals, which is essential for real-life brain-computer interfaces (BCIs). This study develops a flexible, durable, and low-contact-impedance polyvinyl alcohol/polyacrylamide double-network hydrogel (PVA/PAM DNH)-based semi-dry electrode for robust EEG recording at hairy scalp.Approach.The PVA/PAM DNHs are developed using a cyclic freeze-thaw strategy and used as a saline reservoir for semi-dry electrodes. The PVA/PAM DNHs steadily deliver trace amounts of saline onto the scalp, enabling low and stable electrode-scalp impedance. The hydrogel also conforms well to the wet scalp, stabilizing the electrode-scalp interface. The feasibility of the real-life BCIs is validated by conducting four classic BCI paradigms on 16 participants.Main results.The results show that the PVA/PAM DNHs with 7.5 wt% PVA achieve a satisfactory trade-off between the saline load-unloading capacity and the compressive strength. The proposed semi-dry electrode exhibits a low contact impedance (18 ± 8.9 kΩ at 10 Hz), a small offset potential (0.46 mV), and negligible potential drift (1.5 ± 0.4µV min-1). The temporal cross-correlation between the semi-dry and wet electrodes is 0.91, and the spectral coherence is higher than 0.90 at frequencies below 45 Hz. Furthermore, no significant differences are present in BCI classification accuracy between these two typical electrodes.Significance.Based on the durability, rapid setup, wear-comfort, and robust signals of the developed hydrogel, PVA/PAM DNH-based semi-dry electrodes are a promising alternative to wet electrodes in real-life BCIs.


Assuntos
Interfaces Cérebro-Computador , Couro Cabeludo , Humanos , Álcool de Polivinil , Eletroencefalografia/métodos , Hidrogéis , Eletrodos
13.
J Nanosci Nanotechnol ; 12(4): 2943-54, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22849051

RESUMO

Magnetic hollow particles (MHP) are widely used in biomedicine field due to their biocompatibility, low-toxicity, low-density and the large fraction void space in the MHP, which have been successfully used to encapsulate and control drugs release, and magnetic resonance imaging (MRI). This review focuses on all kinds of MHP preparation method, compares the advantages and disadvantages in the process of synthesis, and introduces especially the special formation mechanisms such as the Kirkendall effect and Ostwald ripening. Both the compatible interior space and good magnetism of magnetic hollow structures enable them promising and unique candidates as biomedicine vehicles. Particularly, the progress of MHP widely used in the biomedical engineering applications containing drug delivery and magnetic resonance imaging are described. The main problems and the directions in the future researches are pointed out.


Assuntos
Magnetismo , Nanopartículas , Engenharia Biomédica , Imageamento por Ressonância Magnética , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão
14.
Polymers (Basel) ; 14(4)2022 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-35215579

RESUMO

Pultrusion of thermoplastic composites has been the hotspot of manufacturing high-performance thermoplastic composites in recent years. The optimization of process parameters in the pultrusion usually needed repeated attempts, which wasted lots of manpower and material resources. A numerical simulation method can accelerate the optimization of process parameters. In this work, the impregnation process of reactive injection pultrusion for glass fiber reinforced nylon 6 (GF/PA6) composites was modeled and numerically simulated by a finite element/controlled volume (Fe/CV) method. Based on Darcy's law, the impregnation process can be regarded as the two-phase flow (liquid resin and air) in porous media (undirectional glass fibers). The distribution of resin flow during the impregnation was explored. The effects of pulling rate and injection pressure on the impregnation time and resin reflux distance were analyzed, and the appropriate range of relevant process parameters was determined. The results showed that increasing the pulling rate can significantly control the reflux distance of resin in the impregnation mold and shorten the impregnation time, but too high a pulling rate would increase the impregnation time. Increasing the injection pressure can greatly shorten the resin impregnation time, but it would significantly increase the resin reflux distance. This work can effectively guide the subsequent optimization of process parameters of reactive injection pultrusion for GF/PA6 composites.

15.
RSC Adv ; 12(43): 28196-28206, 2022 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-36320239

RESUMO

Magnesium alloys are attracting increasing attention for the fabrication of temporary implants because of their superior biodegradability and biocompatibility. However, their high degradation rate under physiological conditions limits their clinical applications. In this work, a Nb2O5/Nb2O5-Mg/Mg multilayer coating was prepared on the surface of AZ31 magnesium alloy by magnetron sputtering in order to improve its corrosion resistance. The microstructure and performance of the layers were studied by SEM, AFM, EDS, and XPS, and a scratch tester, nanoindenter, friction tester, and electrochemical workstation, using Nb2O5 monolayer coating as a control. The results show that these two coatings significantly improved the mechanical, tribological, and anticorrosion performance of AZ31 magnesium alloy. Compared with a Nb2O5 monolayer coating, the multilayer coating exhibits an increased adhesion by about 10.6 times, and a decreased wear rate and corrosion current density by one order of magnitude, meaning higher damage resistance. This study provides a feasible strategy for enhancing the properties of ceramic layers on magnesium alloys for medical applications.

16.
Biosensors (Basel) ; 12(12)2022 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-36551090

RESUMO

Tenofovir disoproxil fumarate (TDF) is an antiretroviral medication with significant curative effects, so its quantitative detection is important for human health. At present, there are few studies on the detection of TDF by electrochemical sensors. This work can be a supplement to the electrochemical detection of TDF. Moreover, bare electrodes are susceptible to pollution, and have high overvoltage and low sensitivity, so it is crucial to find a suitable electrode material. In this work, zirconium oxide (ZrO2) that has a certain selectivity to phosphoric acid groups was synthesized by a hydrothermal method with zirconyl chloride octahydrate as the precursor. A composite modified glassy carbon electrode for zirconium oxide-chitosan-multiwalled carbon nanotubes (ZrO2-CS-MWCNTs/GCE) was used for the first time to detect the TDF, and achieved rapid, sensitive detection of TDF with a detection limit of sub-micron content. The ZrO2-CS-MWCNTs composite was created using sonication of a mixture of ZrO2 and CS-MWCNTs solution. The composite was characterized using scanning electron microscopy (SEM) and cyclic voltammetry (CV). Electrochemical analysis was performed using differential pulse voltammetry (DPV). Compared with single-material electrodes, the ZrO2-CS-MWCNTs/GCE significantly improves the electrochemical sensing of TDF due to the synergistic effect of the composite. Under optimal conditions, the proposed method has achieved good results in linear range (0.3~30 µM; 30~100 µM) and detection limit (0.0625 µM). Moreover, the sensor has the merits of simple preparation, good reproducibility and good repeatability. The ZrO2-CS-MWCNTs/GCE has been applied to the determination of TDF in serum and urine, and it may be helpful for potential applications of other substances with similar structures.


Assuntos
Antivirais , Nanotubos de Carbono , Humanos , Tenofovir , Nanotubos de Carbono/química , Reprodutibilidade dos Testes , Técnicas Eletroquímicas/métodos , Eletrodos , Limite de Detecção
17.
Future Foods ; 6: 100198, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36276606

RESUMO

The global pandemic COVID-19 has led to an increase in the number of people purchasing food online, which has brought to a higher demand on the food supply chain. Such as the need to collect more information related to food safety and quality in real-time. Strengthening management of food logistics information flow can reduce food loss and waste and bring better quality and safety of food to consumers. In this review, the importance and applicability of RFID (Radio Frequency Identification) technology to smart food packaging are described. This study emphasizes the recent advancement of the RFID tags in humidity, temperature, gas, pH, integrity, and traceability sensor applications in connection with food packaging. RFID sensors are more suitable for smart packaging both in terms of sensing ability and data transmission. A simpler, low-cost, more robust and less power-demanding sensors network is the development direction of smart packaging in the future. Chipless RFID sensors have the potential to achieve these functions. But it still faces many challenges to be overcome. For example, biocompatible, cost, reading range, multi-tag collision, multi-parameter sensors, recycling issues, security and privacy of RFID system should be solved.

18.
J Nanosci Nanotechnol ; 11(10): 8568-75, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-22400226

RESUMO

We present a facile solvothermal approach by employing ammonium bicarbonate (NH4HCO3) and ammonium acetate (NH4Ac) as dual gas-bubble-generating structure-directing agent to produce of magnetite (Fe3O4) particles with tunable size ranging from 90 nm to 400 nm and controllable structures including porous and hollow construction. The size, morphology and structure of the final products are achieved by simple adjustment of the molar ratio of NH4HCO3 and NH4Ac, ammonium ion concentration and the reaction time. The results reveal that the molar ratio of NH4HCO3 and NH4Ac strongly influenced the morphology and size of magnetite particles, even could decide the kind of architecture including solid, hollow and porous to form. Particularly, ammonium ion molar concentration plays a significant role in controlling size and magnetic property for magnetite particles. Simultaneously, prolonging the reaction time is beneficial to the magnetite particles growth and inner space escalation with altered reaction time at a certain concentration of ammonium and molar ratio of NH4HCO3 and NH4Ac. Such a design conception of dual gas-bubble-assistance used here is promisingly positive and significant for hollow magnetic particles fabrication and may be extended to other nano-scale hollow construction.

19.
Anal Chim Acta ; 1170: 338480, 2021 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-34090586

RESUMO

Since the discovery of liquid-phase-exfoliated black phosphorus (BP) as a field-effect transistor in 2014, BP, with its 2D layered structure, has attracted significant attention, owing to its anisotropic electroconductivity, tunable direct bandgap, extraordinary surface activity, moderate switching ratio, high hole mobility, good biocompatibility, and biodegradability. Several pioneering research efforts have explored the application of BP in different types of electrochemical sensors. This review summarizes the latest synthesis methods, protection strategies, and electrochemical sensing applications of BP and its derivatives. The typical synthesis methods for BP-based crystals, nanosheets, and quantum dots are discussed in detail; the degradation of BP under ambient conditions is introduced; and state-of-the-art protection methodologies for enhancing BP stability are explored. Various electrochemical sensing applications, including chemically modified electrodes, electrochemiluminescence sensors, enzyme electrodes, electrochemical aptasensors, electrochemical immunosensors, and ion-selective electrodes are discussed in detail, along with the mechanisms of BP functionalization, sensing strategies, and sensing properties. Finally, the major challenges in this field are outlined and future research avenues for BP-based electrochemical sensors are highlighted.

20.
Nanomaterials (Basel) ; 10(2)2020 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-32054018

RESUMO

Titania/electro-reduced graphene oxide nanohybrids (TiO2/ErGO) were synthesized by the hydrolysis of titanium sulfate in graphene oxide suspension and in situ electrochemical reduction. It provides a facile and efficient method to obtain nanohybrids with TiO2 nanoparticles (TiO2 NPs) uniformly coated by graphene nanoflakes. TiO2/ErGO nanohybrids were characterized by transmission electron microscopy, X-ray diffraction, cyclic voltammogram, and electrochemical impedance spectroscopy in detail. Compared with pure ErGO and TiO2 NPs, TiO2/ErGO nanohybrids greatly enhanced the electrocatalytic activity and voltammetric response of Allura Red. In the concentration range of 0.5-5.0 µM, the anodic peak currents of Allura Red were linearly correlated to their concentrations. However, the linear relationship was changed to the semi-logarithmic relationship at a higher concentration region (5.0-800 µM). The detection limit (LOD) was 0.05 µM at a signal-to-noise ratio of 3. The superior sensing performances of the proposed sensor can be ascribed to the synergistic effect between TiO2 NPs and ErGO, which provides a favorable microenvironment for the electrochemical oxidation of Allura Red. The proposed TiO2/ErGO/GCE showed good reproducibility and stability both in determination and in storage, and it can accurately detect the concentration of Allura Red in milk drinks, providing an efficient platform for the sensitive determination of Allura Red with high reliability, simplicity, and rapidness.

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