Neurotransmitters are endogenous chemical messengers which play an important role in many of the brain functions, abnormal levels being correlated with physical, psychotic and neurodegenerative diseases such as Alzheimer’s, Parkinson’s, and Huntington’s disease. Therefore, their sensitive and robust detection is of great clinical significance. Electrochemical methods have been intensively used in the last decades for neurotransmitter detection, outclassing more complicated analytical techniques such as conventional spectrophotometry, chromatography, fluorescence, flow injection, and capillary electrophoresis. In this manuscript, the most successful and promising electrochemical enzyme-free and enzymatic sensors for neurotransmitter detection are reviewed. Focusing on the activity of worldwide researchers mainly during the last ten years (2010–2019), without pretending to be exhaustive, we present an overview of the progress made in sensing strategies during this time. Particular emphasis is placed on nanostructured-based sensors, which show a substantial improvement of the analytical performances. This review also examines the progress made in biosensors for neurotransmitter measurements in vitro, in vivo and ex vivo.

https://www.mdpi.com/1424-8220/19/9/2037/pdf

Latest Trends in Electrochemical Sensors for Neurotransmitters: A Review.

In recent years, heteroatoms-doped graphene, with its exceptional properties, has generated significant advances in many fields of modern nanoscience and nanotechnology. With the rapid progress in ...

Heteroatom doping of 2D graphene materials for electromagnetic interference shielding: a review of recent progress

Sulfide-modified nanoscale zero-valent iron (S-nZVI) is a promising material for removal of organic pollutants from water, but S-nZVI nanoparticles (NPs) easily agglomerate and have poor contact with organic contaminants. Herein, we propose a new S-nZVI/graphene aerogel (S-nZVI/GA) composite which exhibits superior removal capability for trichloroethylene (TCE) from water. Three-dimensional porous graphene aerogel (GA) can improve the efficiency of electron transport, enhance the adsorption of organic pollutants and restrain the agglomeration of the core-shell S-nZVI NPs. The TCE removal rates of FeS, nZVI, GA and S-nZVI were 27.8%, 42%, 63% and 75% in 2 hr, respectively. Furthermore, TCE was completely removed within 50 min by S-nZVI/GA. The TCE removal rate increased with increasing pH and temperature, and TCE removal followed the pseudo-first-order kinetic model. The results demonstrate the great potential of S-nZVI/GA composite as a low-cost, easily separated and superior monolithic adsorbent for removal of organic pollutants.

Superior trichloroethylene removal from water by sulfide-modified nanoscale zero-valent iron/graphene aerogel composite.

The alginate/reduced graphene oxide composite hydrogels with hierarchical network structures were synthesized through the hydrothermal treatment of graphene oxide and alginate in an aqueous solution followed by ionically cross-linking of metal ions. The network of reduced graphene oxide was prepared via self-assembly of graphene nanosheets in the presence of alginate during the hydrothermal process; then, the polymer network of alginate was obtained by ionically cross-linking, forming the composite hydrogel. The effect of metal ions on the physical properties of the composite hydrogels was investigated. The prepared alginate/reduced graphene oxide composite hydrogel cross-linked by Fe3+ ions showed higher compression strength and lower swelling ratio. Moreover, due to the synergetic interaction between graphene and alginate, the composite hydrogels exhibited the improved dye adsorption performance, especially for cationic dyes. Even after ten adsorption/desorption cycles, the composite hydrogels can retain more than 90% dye adsorption capacity. The results indicated that the composite hydrogel with good stability, adsorption and regeneration ability could be a promising candidate for dye removal from waste aqueous solutions.

Strong alginate/reduced graphene oxide composite hydrogels with enhanced dye adsorption performance

In this work, a novel molecularly imprinted electrochemical sensor of dopamine (DA) has been fabricated with multi-walled carbon nanotubes spaced graphene aerogels (MWCNT/GAs) as the sensing substrate and polypyrrole (PPy) as the molecularly imprinted polymer (MIP). Morphological characterization showed that the MWCNTs were well dispersed on the graphene walls of the aerogels and the spaced GAs exhibited an outstanding loose structure and large effective surface area. Moreover, the introduction of conductive MWCNTs greatly increased the electrical conductivity and electrochemical performance of the composite aerogel. Benefiting from these features, the MWCNT/GAs showed significantly enhanced electrocatalytic activity for DA. Additionally, the MIPs as recognition elements were used for the selective detection of DA. The effects of various experimental parameters, including the volume ratio of the amount of functional monomer to that of template molecules, number of electropolymerization cycles, incubation time and pH of supporting electrolyte were tested and optimized. Under the best conditions, the MIP/MWCNT/GAs electrode could detect DA at concentrations down to 1.67 nM (S/N = 3) with a wide linear range from 5 nM to 20.0 μM. Moreover, the sensor exhibited specific selectivity and good stability. The developed sensor was successfully used for detecting DA in serum, suggesting that the as-prepared sensor could be used for determining the concentration of DA in complex real samples.

Novel electrochemical sensing platform based on a molecularly imprinted polymer-decorated 3D-multi-walled carbon nanotube intercalated graphene aerogel for selective and sensitive detection of dopamine

Shun Ai

Papers

Facile synthesis of nitrogen-doped graphene aerogels for electrochemical detection of dopamine