Preparation of glucose sensors using gold nanoparticles modified diamond electrode

Modification of carbon foam with 4-mercaptobenzoic acid functionalised gold nanoparticles for an application in a yeast-based microbial fuel cell

Modification of carbon foam with gold nanoparticles (AuNPs) was successfully performed through a hydrothermal method. The modified AuNPs were functionalised with 4-mercaptobenzoic acid (MBA) to improve their affinity toward microorganisms. TEM and SEM characterization indicated that although polydisperse spherical nanoparticles of AuNPs with particle sizes around 17 nm were obtained, the attached nanoparticles were agglomerated to be around 0.4 to 1.5 μm in size on the carbon foam surface. The electrochemical studies using cyclic voltammetry technique affirmed that the modified carbon foam electrodes have electroactive properties against glucose. Evaluation of the electrode was performed for a microbial fuel cell using Candida fukuyamaensis yeast as the microorganisms. The polarization curves showed that functionalisation of AuNPs-modified carbon foam with MBA provides around three times higher current density (1226.93 mA m-2) and power density (330.61 mW m-2) compared to the unmodified one. This result indicated that the modification is suitable to improve yeast attachment on the electrode surface.

Electrochemical integrated paper-based immunosensor modified with multi-walled carbon nanotubes nanocomposites for point-of-care testing of 17β-estradiol

17β-estradiol (17β-E2) plays a critical role in regulating reproduction in human, there is therefore an urgent need to detect it sensitively and precisely in a cost-effective and easy method. In this paper, a label-free integrated microfluidic paper-based analytical device was developed for highly sensitive electrochemical detection of 17β-E2. The microfluidic channel of the paper-based sensor was fabricated with wax printing and the three electrodes, including working, counter and reference electrode were screen-printed. Multi-walled carbon nanotubes (MWCNTs)/ thionine (THI)/ gold nanoparticles (AuNPs) Nano composites were synthesized and coated on screen-printed working electrode (SPWE) for the immobilization of anti-E2. In this electro-chemical system of paper-based immunoassay, THI molecules serving as an electrochemical mediator while MWCNTs and AuNPs, due to their excellent electrical conductivities, could accelerate electron transfer for the signal amplification. Experimental results revealed that the immunoassay is able to detect 17β-E2 as low as 10 pg mL^-1, with a linear range from 0.01 to 100 ng mL^-1. This microfluidic paper-based immunosensor would provide a new platform for low cost, sensitive, specific, and point-of-care diagnosis of 17β-E2.