News Excerpt
Scientists from the Institute of Nano Science and Technology (INST), an autonomous institute of the Department of Science and Technology, Government of India, have developed an equipment, ‘free fluoride ion detection and quantification in drinking water with the naked-eye’.

What is Fluorosis?
1.    Fluorosis is a crippling disease resulting from deposition of fluorides in the hard and soft tissues of body due to excess intake of fluoride through drinking water/food products/industrial pollutants over a long period.
2.    It results in dental fluorosis, skeletal fluorosis, and non-skeletal fluorosis. Easy detection of fluorides in water can help preventing the public health hazards.

Highlights
    The equipment can be operated by laymen to evade Fluorosis-based disorders.
    The technology involves a push-pull chromophore based on 2,3-disubstituted 1,1,4,4-tetracyano-1,3-butadienes (TCBDs) that changes colour upon exposure to fluoride ion.
    The researchers designed urea as an unusual donating moiety instead of traditional donor moieties, such as amines, to obtain better optoelectronic properties.
    The charge-transfer (CT) property that arises through-bond in aniline donor is usually quenched due to photoinduced electron transfer (PET) mechanism.
    Whereas upon introducing urea as an electron donor, the CT exhibited both spaces as well as through bond due to “Field-effect”. Thus, partial overcoming of PET process, which led to white light emission.
    Later, they extended its applicability in sensing of biologically relevant fluoride, as it is well known that fluoride can bind with urea via H-bonding interaction.
    Furthermore, the design and synthesis can be slightly modulated to increase the sensitivity from 3 ppm to less than 1 ppm. Currently, the INST team is working in this direction.
    The major cost involves only the synthesis of the chromophore, making it affordable and accessible.
    Currently available, commercial kits for F– detection need analytical methods, mainly spectrometers (mobile or static).
    Some colorimetric detection kits are available, but they have some handling issues like work only with pH<1 (use of HCl), etc. The kit developed by the INST scientists’ scores above these in its ease of usage.
    The non-planar push-pull chromophores sense fluoride ion with the naked eye in both solutions- as well as solid-phases.