  Graphene as a single-atomic-layer material is fully exposed to environment
and has therefore a great potential for creating of sensitive gas sensors.
However, in order to realize this potential for different polluting gases,
graphene has to be functionalized - adsorption centers of different type and
with high affinity to target gases have to be created at its surface. In this
present work, modification of graphene by small amounts of laser ablated
materials is introduced for this purpose as a versatile and precise tool. The
approach was demonstrated with two very different materials chosen for pulsed
laser deposition (PLD), a metal (Ag) and a dielectric oxide (ZrO2). It was
shown that the gas response and its recovery rate can be significantly enhanced
by choosing the PLD target material and deposition conditions. The response to
NO2 gas in air was amplified up to 40 times in case of PLD-modified graphene in
comparison with pristine graphene and reached 7-8% at 40 ppb of NO2 and 20-30%
at 1 ppm of N2. These results were obtained after PLD in gas environment (5 x
10-2 mbar oxygen or nitrogen) and atomic areal densities of deposited materials
of were about 10 15 cm-2. The ultimate level of NO2 detection in air, as
extrapolated from the experimental data obtained at room temperature under mild
UV-excitation, was below 1 ppb.
