Rapid, simple, and simultaneous electrochemical determination of cadmium, copper, and lead in Baijiu using a novel covalent organic framework based nanocomposite.

It is of great significance to develop a simple and rapid electrochemical sensor for simultaneous determination of heavy metal ions (HMIs) in Baijiu by using new nanomaterials. Here, graphene (GR) was utilized to combine with covalent organic frameworks (COFs) that was synthesized via the aldehyde-amine condensation between 2, 5-dimethoxyterephthalaldehyde (DMTP) and 1, 3, 5-tris(4-aminophenyl) benzene (TAPB) to prepare a new GR/COFDPTB/GCE sensor for electrochemical sensing multiple HMIs. Compared with the glass carbon electrode (GCE), GR/GCE and COFDPTB/GCE, the developed sensor exhibited excellent electrochemical analysis ability for the simultaneous detection of Cd2+, Pb2+, and Cu2+ owing to the synergistically increased the specific surface area, the periodic porous network and plenty of effective binding sites, as well as the enhanced conductivity. Under the optimized experimental parameters, the proposed sensor showed good linearity range of 0.1-25 µM for Cd2+, and both 0.1-11 µM for Pb2+ and Cu2+ with the detection limits of Cd2+, Pb2+, and Cu2+ being 0.011 µM, 8.747 nM, and 6.373 nM, respectively. Besides, the designed sensor was successfully applied to the simultaneous detection of the three HMIs in Baijiu samples, suggesting its good practical application performance and a new method for the rapid detection of HMIs being expended.

Molecularly imprinted ultrasensitive cholesterol photoelectrochemical sensor based on perfluorinated organics functionalization and hollow carbon spheres anchored organic-inorganic perovskite.

In spite of organic-inorganic perovskite emerging as a novel efficient light-harvesting material owing to their superior optical properties, excitonic properties, and electrical conductivity, the related applications are severely limited for their poor stability and selectivity. Herein, we introduced hollow carbon spheres (HCSs) and 2-(perfluorohexyl) ethyl methacrylate (PFEM) based molecularly imprinted polymers (MIPs) to dual-functionalize CH3NH3PbI3. HCSs can provide perovskite load conditions, passivate perovskite defects, increase carrier transport and effectively improve its hydrophobicity. The perfluorinated organic compound based MIPs film can not only enhance the water and oxygen stability of perovskite, but also endow it specific selectivity. Moreover, it can reduce the photoexcited electron-hole pair recombination and prolong the electron lifetime. Benefiting from the synergistic sensitization of HCSs and MIPs, an ultrasensitive photoelectrochemical platform (MIPs@CH3NH3PbI3@HCSs/ITO) for cholesterol sensing was acquired with a very wide linear range of 5.0 × 10-14-5.0 × 10-8 mol/L and an extremely low detection limit of 2.39 × 10-15 mol/L. The designed PEC sensor exhibited good selectivity and stability, as well as practicality for real sample analysis. The present work extended the development of the high-performance perovskite and showed its broad application prospect for advanced PEC construction.

Highly efficient determination of Mn2+ in Chinese liquor by using a novel electrochemical sensor based on TiO2-NH2@covalent organic framework nanocomposites.

This study developed an electrochemical sensor for the determination of Mn2+ in Chinese liquor by modifying a glass carbon electrode with TiO2-NH2@COFDPTB, which was synthesized via the controllable growth of COFDPTB onto the surface of TiO2-NH2 using the Schiff-base condensation reaction between 2,5-dimethoxyterephthalaldehyde and 1,3,5-tris(4-aminophenyl)benzene. The morphological and structural characterization studies of the proposed TiO2-NH2@COFDPTB were carried out by SEM, TEM, HRTEM, EDX, BET, XRD and FTIR techniques. Owing to the excellent properties and the synergism between TiO2 and COFDPTB, the introduction of TiO2-NH2@COFDPTB improved the electrochemical response significantly. By optimizing the experimental parameters, the sensor exhibited good linearity in the range of 0.1-1.0 nM and 0.08-10 µM with a detection limit of 2.83 × 10-11 M and 9.50 × 10-9 M, respectively, showing competitive performance for Mn2+ determination. Besides, the proposed sensor was successfully applied to Mn2+ detection in liquor samples, suggesting its practical application performance.

Nanomaterials-Based Ion-Imprinted Electrochemical Sensors for Heavy Metal Ions Detection: A Review.

Heavy metal ions (HMIs) pose a serious threat to the environment and human body because they are toxic and non-biodegradable and widely exist in environmental ecosystems. It is necessary to develop a rapid, sensitive and convenient method for HMIs detection to provide a strong guarantee for ecology and human health. Ion-imprinted electrochemical sensors (IIECSs) based on nanomaterials have been regarded as an excellent technology because of the good selectivity, the advantages of fast detection speed, low cost, and portability. Electrode surfaces modified with nanomaterials can obtain excellent nano-effects, such as size effect, macroscopic quantum tunneling effect and surface effect, which greatly improve its surface area and conductivity, so as to improve the detection sensitivity and reduce the detection limit of the sensor. Hence, the present review focused on the fundamentals and the synthetic strategies of ion-imprinted polymers (IIPs) and IIECSs for HMIs detection, as well as the applications of various nanomaterials as modifiers and sensitizers in the construction of HMIIECSs and the influence on the sensing performance of the fabricated sensors. Finally, the potential challenges and outlook on the future development of the HMIIECSs technology were also highlighted. By means of the points presented in this review, we hope to provide some help in further developing the preparation methods of high-performance HMIIECSs and expanding their potential applications.

A promising voltammetric biosensor based on glutamate dehydrogenase/Fe3O4/graphene/chitosan nanobiocomposite for sensitive ammonium determination in PM2.5.

A novel NH4+ voltammetric electrochemical biosensor was constructed by immobilizing glutamate dehydrogenase (GLDH)/Fe3O4/graphene (GR)/chitosan (CS) nanobiocomposite onto a glassy carbon electrode (GCE). On the GLDH/Fe3O4/GR/CS/GCE, GLDH catalyzed the reversible reaction, i.e., the reductive amination of α-ketoglutaric acid and the oxidative deamination of L-glutamate. The electrons produced in the enzymatic reactions were transferred to the surface of the electrode via the [Fe(CN)6]3-/4- couple, which helped for the amplification of the electrochemical signal. The electrochemical detection of NH4+ was based on the fact that the enhanced response current was proportional to the NH4+ concentration. Owing to the combination of the advantages of the synergistic effects of Fe3O4 nanospheres, GR and CS, a promising platform for NH4+ sensing was provided. Under optimum conditions, the introduced biosensor had a linear range of 0.4-2.0 µM for NH4+ with the detection and quantification limits of 0.08 and 0.27 µM, respectively. Moreover, the biosensor exhibited good sensitivity and excellent reproducibility. It could retain 91.8% of its original response after two weeks of storage at 4 °C, suggesting satisfactory stability. Additionally, the proposed biosensor was successfully applied to detect NH4+ levels in PM2.5 samples, indicating its feasibility for application in NH4+monitoring in the environmental fields.

A novel sensor for the detection of acetamiprid in vegetables based on its photocatalytic degradation compound.

An electrochemical method for the indirect determination of acetamiprid was studied, using titanium dioxide photocatalysts coupled with a carbon paste electrode. The cyclic voltammetric results indicated that the photocatalytic degradation compound of acetamiprid had electroactivity in neutral solutions. The amount of acetamiprid was further indirectly determined by differential pulse anodic stripping voltammetric analysis as a sensitive detection technique. The experimental parameters were optimized with regard to the photocatalytic degradation time, pH of buffer solution, accumulation potential and accumulation time. Under optimal conditions, the proposed electrochemical method could detect acetamiprid concentrations ranging from 0.01 to 2.0µM, with a detection limit (3S/N) of 0.2nM. Moreover, the proposed method displays excellent selectivity, good reproducibility, and acceptable operational stability and can be successfully applied to acetamiprid determination in vegetable samples with satisfying results.

Fabrication of electrochemical sensor for paracetamol based on multi-walled carbon nanotubes and chitosan-copper complex by self-assembly technique.

An electrochemical sensor for paracetamol based on multi-walled carbon nanotubes and chitosan-copper complex (MWCNTs/CTS-Cu) was fabricated by self-assembly technique. The MWCNTs/CTS-Cu modified GCE showed an excellent electrocatalytic activity for the oxidation of paracetamol, and accelerated electron transfer between the electrode and paracetamol. Under optimal experimental conditions, the differential pulse peak current was linear with the concentration of paracetamol in the range of 0.1-200 µmol L(-1) with a detection limit of 0.024 µmol L(-1). The sensitivity was found to be 0.603 A/mol L(-1). The proposed sensor also showed a high selectivity for paracetamol in the presence of ascorbic acid and dopamine. Moreover, the proposed electrode revealed good reproducibility and stability. The proposed method was successfully applied for the determination of paracetamol in tablet and human serum samples.

Electrochemical detection of nitrate in PM2.5 with a copper-modified carbon fiber micro-disk electrode.

The accurate measurement of nitrate in PM2.5 is essential for a complete understanding of the effects of aerosols on human health, the impact of aerosols on the radiative balance of the earth and the role of aerosols in visibility problems. In this paper, we present a novel, quick, easy, cheap and eco-friendly electroanalytical procedure for the determination of nitrate in PM2.5 samples using a carbon-fiber micro-disk electrode (CFMDE) coupled with square-wave voltammetry (SWV). Under optimal experimental conditions the nitrate SWV response increases linearly with nitrate concentration over a range of 0.003-2.0 mmol L(-1), and the detection limit is 1.10 µmol L(-1) (S/N=3). Nitrate contents in daily PM2.5 of Yangzhou in China were detected successfully by employing this novel method, and the results were compared well with those obtained by using ion chromatography. Then, we detected nitrate in two-hour PM2.5 filter samples via the standard addition method, and the concentrations were applied in an analysis of the daily change of nitrate contained in PM2.5 of Yangzhou. The research in this work indicates that the electrochemical method opens a new opportunity for fast, portable, and sensitive analysis of components in PM2.5.