Deep Ultraviolet to Near-Infrared Emission and Photoresponse in Layered N-Doped Graphene Quantum Dots

Abstract

Material that can emit broad spectral wavelengths covering deep ultraviolet, visible, and near-infrared is highly desirable. It can lead to important applications such as broadband modulators, photodetectors, solar cells, bioimaging, and fiber communications. However, there is currently no material that meets such desirable requirement. Here, we report the layered structure of nitrogen-doped graphene quantum dots (N-GQDs) which possess broadband emission ranging from 300 to >1000 nm. The broadband emission is attributed to the layered structure of the N-GQDs that contains a large conjugated system and provides extensive delocalized π electrons. In addition, a broadband photodetector with responsivity as high as 325 V/W is demonstrated by coating N-GQDs onto interdigital gold electrodes. The unusual negative photocurrent is observed which is attributed to the trapping sites induced by the self-passivated surface states in the N-GQDs.

Ultrafast ammonia-driven, microwave-assisted synthesis of nitrogen-doped graphene quantum dots and their optical properties

“…The monodispersed NGQDs emitted blue under a UV light at 365 nm, as shown in Figure S3. The fluorescence (FL) quantum yield (QY) of NGQDs was determined to be 6.42%, as measured by the absolute QY measurement method, which is comparable to that of NGQDs prepared by other methods [12,14].…”

“…As shown in Figure 3, one can find that NGQDs exhibit high crystalline quality as revealed by the presence of the lattice fringes. The distances between the lattice fringes are 0.346 nm ( Figure 3A [14]. It is worth noting that the basal plane distance (0.346 nm) is slightly larger than that of bulk graphite (0.334 nm) due to the presence of the functional groups and nitrogen doping atoms that enlarge the basal plane spacing of NGQDs.…”

“…These enable GQDs to be used in photovoltaic devices [4], bioimaging [5], biosensing [6], and environmental monitoring [7]. The doping of nitrogen into GQDs (NGQDs) gives rise to much more attractive properties, such as electrocatalytic activity [8,9], photocatalytic activity [10,11], biocompatibility [12], selective detection [13], and broad tunable luminescence [14].…”

“…For example, NGQDs have been synthesized using glycine [21], glucose [14], or citric acid [22][23][24][25][26][27] as carbon source or using ammonia [14,22,23], dicyandiamide [24,25], tris(hydroxymethyl) aminomethane [26], 3,4-dihydroxy-L-phenylalanine [27], or glycine [21] as nitrogen source through hydrothermal reaction [14,[21][22][23][24][25] or high-temperature treatment [26,27]. Such one-step methods usually require high temperature and/ or high pressure.…”

Properties and Synthesis Strategies of Graphene Quantum Dots

“…[52][53][54][55][56][57] Compared with the top-down methods, the bottom-up strategy has advantages in modulating the chemical composition and PL features because organic precursors and reaction conditions can be adjusted and controlled conveniently. Self-passivated GQDs can be prepared by microwave treatment of glucose aqueous solutions (Figure 4(A)).…”