Photoresponse of polyaniline-functionalized graphene quantum dots

Abstract

Polyaniline-functionalized graphene quantum dots (PANI-GQD) and pristine graphene quantum dots (GQDs) were utilized for optoelectronic devices. The PANI-GQD based photodetector exhibited higher responsivity which is about an order of magnitude at 405 nm and 7 folds at 532 nm as compared to GQD-based photodetectors. The improved photoresponse is attributed to the enhanced interconnection of GQD by island-like polymer matrices, which facilitate carrier transport within the polymer matrices. The optically tunable current-voltage (I-V) hysteresis of PANI-GQD was also demonstrated. The hysteresis magnifies progressively with light intensity at a scan range of ±1 V. Both GQD and PANI-GQD devices change from positive to negative photocurrent when the bias reaches 4 V. Photogenerated carriers are excited to the trapping states in GQDs with increased bias. The trapped charges interact with charges injected from the electrodes which results in a net decrease of free charge carriers and a negative photocurrent. The photocurrent switching phenomenon in GQD and PANI-GQD devices may open up novel applications in optoelectronics.

Potassium doping: Tuning the optical properties of graphene quantum dots

“…The good crystallinity of the K-GQDs can be clearly observed from the high resolution TEM (HR-TEM) image as shown in Figure 1(c) and 1(d). The d-spacing between the lattice planes is d = 0.246 nm which corresponds to the (100) planes of graphite 21 and illustrates that the K-GQDs retains the same hexagonal crystal structure as the un-doped GQDs, which would be further discussed below. Figure 1(f) provides evidence on the hexagonal crystal structure of the K-GQDs.…”

“…Two absorption peaks are found at 222 nm and 274 nm, which corresponds to the π → π * transition of C=C and n → π * transition of C=O respectively. 21 Comparing with the undoped GQDs, 20 the absorption peaks shows a blue shift (228 nm and 282 nm for un-doped GQDs) after K-doping. This is explained by the introduction of K-related energy band into the GQDs which shift the energy levels of the above two transitions.…”

Smart Utilization of Carbon Dots in Semiconductor Photocatalysis

“…This successful work combined the wide spectral response and the unique electrical properties of N‐GQDs together, offering a new path for the design of smarter photocatalysts systems. Lau and co‐workers synthesized polyaniline‐functionalized GQDs for use in optoelectronic devices . The responsivity increased by a factor of 7 at 532 nm, and by an order of magnitude at 405 nm compared with pristine GQD‐based photodetectors.…”

One-Step Synthesis of Diamine-Functionalized Graphene Quantum Dots from Graphene Oxide and Their Chelating and Antioxidant Activities

“…GQDs have recently attracted high interest as alternatives to metal-based semiconductor QDs for numerous applications, like bio-imaging [17,18] and drug delivery [19,20], light-emitting diodes [21][22][23], optoelectronic devices [24,25], electrocatalysis [26,27], or biosensors [28][29][30], due to these unique optical properties, high chemical and photo-stability, low toxicity, low cost, and easy functionalization.…”