Chemosensor
Chemosensor is a sensory receptor that transduces a chemical signal into an action potential. In more general terms, a chemosensor detects certain chemical stimuli in the environment. Chemosensors are finding increased use in fields as diverse as biology, medical analysis, and environmental monitoring.
Gold nanoparticles
Nanoparticles are versatile materials and find applications in different areas going from industry, to bio-analysis, and catalysis. Gold nanoparticles exhibit excellent catalytic activity due to their relative high surface area-to-volume ratio, and their interface-dominated properties, which significantly differ from their bulk. They have been used extensively for the design and fabrication of electro catalysts and as an enhancing component of catalytic activity or selectivity.
For electro catalytic applications techniques like anchoring by electrostatic interaction, covalent linkage, electrochemical deposition, etc.  are used. Such modified interfaces behaving as nanoelectrodes have been widely used as enhancing catalytic interface for the development of electrochemical sensors.
Development
The electro analytical detection limit at a nanoelectrode ensemble can be much lower than that at an analogous macro sized electrode because the ratio between the faradic and capacitive currents is higher. Several researchers have developed novel 2-D or 3-D AuNPs
modified nanoelectrode ensembles for enhancing electrochemical responses.
Electrodes are used to enhancing detection of small biomolecules such as glucose. AuNPs could also be employed as enhancing materials for electrochemical investigation of cell and electro catalyzing some small biomolecules such as glucose. This can be done by using AuNPs self-assembled on a 3D silicate network obtained by using sol–gel processes, norepinephrine, dopamine, catechol, epinephrine and ascorbic acid, etc.
Glucose sensor
For sensing glucose electrodes have been self-assembled on the thiol tail groups of the silicate network and enlarged by hydroxylamine. The AuNPs can efficiently catalyze the oxidation of glucose at less-positive potential in phosphate buffer solution in the absence of any enzymes or redox mediators. This novel nonenzymatic glucose sensor shows excellent sensitivity with a detection limit of 50 nM.
AuNPs derivated electrodes
Electrodes can be used to detect some toxic substances also. AuNPs modified carbon screen-printed, glassy carbon and basal plane pyrolytic graphite electrodes can be used to detect Sb (III) and As (III) with high sensitivity. The electrolytic oxidation of nitric oxide and hydrazine was also developed by several groups. It is found that the AuNPs modified electrode exhibited high catalytic activity for NO and hydrazine. Ultra sensitive electrochemical detection of hydrazine can be made using AuNPs self-assembled on a sol–gel-derived 3D silicate network and also by seed-mediated growth of gold. This nanostructured platform is highly sensitive toward the electrochemical oxidation of hydrazine.