We demonstrate a controlled, systematic method to tune the charge transport in graphene field-effect transistors based on alternating layer-by-layer assembly of positively and negatively charged graphene oxide followed by thermal reduction. Surprisingly, tuning the number of bilayers of thermally reduced graphene oxide multilayer films allowed achieving either ambipolar or unipolar (both n- and p-type) transport in graphene transistors. On the basis of X-ray photoemission spectroscopy, Raman spectroscopy, time-of-flight secondary ion mass spectrometry, and temperature-dependent charge transport measurements, we found that nitrogen atoms from the functional groups of positively charged graphene oxide are incorporated into the reduced graphene oxide films and substitute carbon atoms during the thermal reduction. This nitrogen-doping process occurs in different degrees for graphene multilayers with varying numbers of bilayers and thereby results in the interesting transition in the electrical behavior in graphene multilayer transistors. We believe that such a versatile method to control the charge transport in graphene multilayers will further promote their applications in solution-processable electronic devices based on graphene.

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Purpose -The authors aimed to develop environmentally stable NIR-absorbing windows by blending a near-infrared (NIR)-absorbing dye and a photocrosslinkable polymer. Design/methodology/approach -To prepare an environmentally stable NIR-absorbing window, a NIR-absorbing dye was mixed with crosslinkable poly(vinyl cinnamate) (PVCn). The crosslinking of PVCn was carried out by photo-dimerisation reaction of cinnamate with UV-exposure at a wavelength of 254 nm for 4 min. Findings -The resistance of the photo-crosslinked hybrid films against humidity, heat, and ultraviolet radiation damage was improved dramatically relative to the pristine NIR-absorbing dye. These improvements result from the protection of NIR-absorbing dye to moisture exposure in the presence of the polymer network. Originality/value -The simple and practical method resulted in a dramatic improvement in the environmental stability of NIR-absorbing window.

Purpose -The purpose of this paper is to develop environmentally stable near-infrared (NIR)-absorbing windows by blending an NIR-absorbing dye and a thermally-crosslinkable polymer. Design/methodology/approach -To enhance the environmental stability of the NIR-absorbing window, a poly(vinyl phenol-co-methyl methacrylate) (poly(VP-co-MMA)) prepolymer and a poly(melamine-co-formaldehyde) (PMF) cross-linking agent were mixed, and thermal crosslinking was performed under mild conditions (1008C). Findings -The resistance of the crosslinked hybrid films to heat, humidity, and ultraviolet radiation damage improved dramatically relative to the pristine NIR-absorbing dye. The improved environmental stability of the crosslinked NIR hybrid film resulted from the reduced free volume and restrictions in the molecular thermal dynamic motions of the polymer due to the presence of the crosslinked network surrounding the NIR-absorbing dye molecules. Originality/value -The methods provided a novel, simple, and practical solution to improving environmentally stability of NIR-absorbing window.