  Molecular recognition and discrimination of carbohydrates are important
because carbohydrates perform essential roles in most living organisms for
energy metabolism and cell-to-cell communication. Nevertheless, it is difficult
to identify or distinguish various carbohydrate molecules owing to the lack of
a significant distinction in the physical or chemical characteristics. Although
there has been considerable effort to develop a sensing platform for individual
carbohydrates selectively using chemical receptors or an ensemble array, their
detection and discrimination limits have been as high in the millimolar
concentration range. Here we show a highly sensitive and selective detection
method for the discrimination of carbohydrate molecules using nano-slot-antenna
array-based sensing chips which operate in the terahertz frequency range. This
THz metamaterial sensing tool recognizes various types of carbohydrate
molecules over a wide range of molecular concentrations. Strongly localized and
enhanced terahertz transmission by nano-antennas can effectively increase the
molecular absorption cross sections, thereby enabling the detection of these
molecules even at low concentrations. We verified the performance of
nano-antenna sensing chip by both THz spectra and images of transmittance.
Screening and identification of various carbohydrates can be applied to test
even real market beverages with a high sensitivity and selectivity.
