title: Phenomenal Ultraviolet Photoresponsivity and Detectivity of Graphene Dots Immobilized on Zinc Oxide Nanorods.
abstract: A combination of dimensionally reduced graphene quantum dots (GQDs) having edge effects and the vertically aligned ZnO nanorods shows highly selective visible-blind ultraviolet (UV) sensing. The GQD immobilized ZnO nanorod heterostructure shows remarkable responsivity of ∼6.62 × 104A/W and detectivity of ∼1.78 × 1015Jones under 365 nm (10 μW) incident light and 2 V bias potential with high stability of at least 5 cycles, fast response time of 2.14 s, and recovery time of 0.91 s. The grain boundary assisted electron transport across GQDs was calculated from the normalized absorption below bandgap. The highest UV responsivity and detectivity were found to be proportional to the lowest trap state density at the grain boundaries (Qt) and minimum grain boundary potential (Eb). For the best GQD, Qtand Ebwere found to be ∼4 × 1013cm-2and 0.4 meV, respectively. The phenomenal performance of ZnO-GQD heterostructure is attributed to the efficient immobilization of GQDs on ZnO nanorods and the idea of employing GQDs as photosensitizers than solely as electron transporting medium. The efficiency of GQDs is superior to carbon quantum dots (CQDs) containing minimal graphitic domains, and graphene oxide (GO) or reduced graphene oxide (rGO) having larger dimensions preventing their immobilization on ZnO nanorods.
authors.affiliation: Department of Chemical Sciences and Centre for Advanced Functional Materials, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur - 741246, India.
authors.forename: Dibyendu
authors.initials: D
authors.lastname: Ghosh
authors.affiliation: Department of Chemical Sciences and Centre for Advanced Functional Materials, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur - 741246, India.
authors.forename: Sutanu
authors.initials: S
authors.lastname: Kapri
authors.affiliation: Department of Chemical Sciences and Centre for Advanced Functional Materials, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur - 741246, India.
authors.forename: Sayan
authors.identifier: http://orcid.org/0000-0001-8074-965X
authors.initials: S
authors.lastname: Bhattacharyya
keywords: UV detection; ZnO nanorod; grain boundary; graphene dots; photoresponsivity