Abstract
Single molecule detection using graphene can be brought by tuning the interactions via specific dopants. Electrostatic interaction between the most electronegative element fluorine (F) and hydrogen (H) is one of the strong interactions in hydrogen bonding, and here we report the selective binding of ammonia/ammonium with F in fluorographene (FG) resulting to a change in the impedance of the system. Very low limit of detection value of ~0.44 pM with linearity over wide range of concentrations (1 pM–0.1 μM) is achieved using the FG based impedance sensor, andthisscreen printed FG sensor works in both ionized (ammonium) and un-ionized ammonia sensing platforms. The interaction energies of FG and NH3/NH4+ are evaluated using density functional theory calculations and the interactions are mapped. Here FGs with two different amounts of fluorinecontents −~5 atomic% (C39H16F2) and ~24 atomic% (C39H16F12) - are theoretically and experimentally studied for selective, high sensitive and ultra-low level detection of ammonia. Fast responding, high sensitive, large area patternable FG based sensor platform demonstrated here can open new avenues for the development of point-of-care devices and clinical sensors.
Highlights
Single molecule detection using graphene can be brought by tuning the interactions via specific dopants
Low level detection of ammonia (< 2 ppb for environmental monitoring and < 50 ppb for breath analysis) is still lacking a state of the art detection method, and its development is highly desirable for the development of clinical ammonia sensors[1]
Various sensing platforms are existing for ammonia: metal oxide based sensors[6,7,8], catalytic ammonia sensors[9,10], conducting polymer based ammonia sensors[11,12], optical and spectrometric ammonia detection[13], gas permeable membranes based selective detection techniques etc. are the most frequently used techniques[14,15]
Summary
Single molecule detection using graphene can be brought by tuning the interactions via specific dopants. Various sensing platforms are existing for ammonia: metal oxide based sensors[6,7,8] (by conductance change due to the chemisorption of gas molecule), catalytic ammonia sensors (by catalytic activity of certain metals towards ammonia gas and the ammonia concentration dependency in the charge carriers)[9,10], conducting polymer based ammonia sensors (by a two-fold oxidation-reduction mechanism)[11,12], optical and spectrometric ammonia detection (cause in the coloration up on ammonia exposure as a measure)[13], gas permeable membranes based selective detection techniques etc. Electrostatic interaction can bring specificity in the binding of molecules to graphene and graphene based sensors are capable of detecting individual gas molecules[19]. It is important to study the interaction between adsorbed molecules and graphene to understand the charge transfer mechanism, and tailoring the response by defects/dopants[20]
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