Hybrid nanodevices for ion detection
Global water supply shortages have increased the demand for low-cost and rapid contaminant-detection technologies. In clinical diagnostics, innovative, low-cost electrolyte analysis technologies for emergency room use are needed for rapid detection of specific diseases. To address these issues, the 'Hybrid molecule-nanocrystal assemblies for photonic and electronic sensing applications' (HYSENS) project turned organic functional molecules and inorganic nanocrystals into novel smart materials capable of accurate sensing of ions in water and artificial serum matrices. The project was an overwhelming success, resulting in 3 patent applications, 38 peer-reviewed publications and 5 doctoral theses. More accurate, rapid and cost-effective detection of important ions is expected to have major impact on sectors from point-of-care and home diagnostics to laboratory and environmental applications. Organic ligands were engineered to have anchor groups to bind inorganic nanocrystals and functional groups to form selective complexes with ions. Formation of the complexes (sensing of the ions) produced an optical or electrical read-out transduced by the inorganic nanocrystals. Four different classes of hybrid inorganic–organic structures were produced and characterised. Partners achieved optical sensing in water and serum. Luminescent sensing showed high affinity for heavy metal ions such as lead (Pb2+) and for copper (Cu2+) with limits of detection (LOD) below 10 and 1 microgramme/litre, respectively. The team also detected sodium (Na+) with an LOD in the range of milligrammes/litre. Sensing based on changes in scattering intensity of inorganic nanoparticles showed high sensitivity for mercury (Hg2+) and Cu2+. The team fabricated an optical sensor with built-in optical reader for fluorescence and scattering read out. Electrical sensing was also successful. Electrochemical detection of potassium (K+) in the millimolar range was achieved with ion-selective organic electrochemical transistors. Silicon nanowire field effect transistors (FETs) were used to detect Na+ with an LOD of 100 microgrammes/litre. Silicon nanowire FETs integrated into microfluidic flow cells were capable of multiplex Na+ and fluoride (F–) detection in both water and serum. Research into organic–inorganic hybrid nanosystems is currently concentrated in the United States, and there is also growing competition from Asia. The HYSENS project will help to strengthen Europe's market position and, in the long term, provide important benefits in the areas of health and environmental safety.
Keywords
Hybrid nanodevices, ion detection, nanocrystal assemblies, photonic, electronic sensing
