Graphene hybrids: synthesis strategies and applications in sensors and sensitized solar cells

Abstract

Graphene exhibits unique 2-D structural, chemical, and electronic properties that lead to its many potential applications. In order to expand the scope of its usage, graphene hybrids which combine the synergetic properties of graphene along with metals/metal oxides and other nanostructured materials have been synthesized and are a widely emerging field of research. This review presents an overview of the recent progress made in the field of graphene hybrid architectures with a focus on the synthesis of graphene-carbon nanotube (G-CNT), graphene-semiconductor nanomaterial (G-SNM), and graphene-metal nanomaterial (G-MNM) hybrids. It attempts to identify the bottlenecks involved and outlines future directions for development and comprehensively summarizes their applications in the field of sensing and sensitized solar cells.

Keywords: energy conversion; graphene hybrids; graphene-CNTs; graphene-QDs; sensors.

Figure 1

Preparation of rGO-CNT hybrid by dispersion and reduction of GO-CNT mixture in anhydrous hydrazine. (A) SEM image of GO-CNT, (B) Stable dispersion of GO-CNT in anhdrous hydrazine (left) compared to organic solvent (right) after 12 h. [Reprinted with permission from Tung et al. (2009). Copyright (2009) American Chemical Society].

Figure 2

Core shell G-CNT hybrid structure. (A) SEM image of SWCNTs, (B) SEM image of SWCNT/GO, (C) TEM image of SWCNT/GO, (D) High-resolution TEM image of SWCNT/GO (Dong et al., 2011b). [Reprinted with permission from Dong et al. (2011b). Copyright (2011) Elsevier].

Figure 3

Schematics of Layer by Layer assembly of rGO-CNT. [Reprinted with permission from Hong et al. (2010a). Copyright (2010) American Chemical Society].

Figure 4

Schematic representation of functionalized QDs stacked on exfoliated graphene and nanographene stacked with pyrene and functionalized with QDs, and their TEM images, on the left and on the right, respectively. [Reprinted with permission from Katsukis et al. (2012). Copyright (2012) American Chemical Society].

Figure 5

AFM image of TiO₂-GO hybrid synthesized by photochemical reduction. [Adapted with permission from Williams et al. (2008). Copyright (2008) American Chemical Society].

Figure 6

Self-assembly of already synthesized AuNP on (A) RGO/chitosan (B) on polyelectrolyte poly(diallyldimethyl ammonium chloride) (PDDA) functionalized graphene nanosheets (GNs). [Reprinted with permission from Chang et al. (2011); The Royal Society of Chemistry and Fang et al. (2010). Copyright (2010) American Chemical Society].

Figure 7

Few layer graphene leafy structure grown on CNT (CNT-FLG) (A) SEM image CNT-FLG hybrid of (B) TEM image CNT-FLG hybrid (C) closer view of tip of CNT-FLG hybrid. [Reprinted with permission from Yu et al. (2011). Copyright (2011) American Chemical Society].

Figure 8

SEM image Cu₂S/rGO composite grown in situ through solution chemistry. [Reprinted with permission from Radich et al. (2011). Copyright (2011) American Chemical Society].

Figure 9

In situ grown graphene-AuNP hybrid. Schematics of synthesis of graphene-AuNP hybrid (A) using chemical and (B) biocatalytic reduction method. [Reprinted with permission from Chen et al. (2011b) and Zheng et al. (2011); The Royal Society of Chemistry].

Figure 10

Schematic representation of electron transfer from redox center of immobilized GOx molecule on G-CNT and enzyme catalyzed oxidation of glucose in biosensing (Not to the scale).

Figure 11

Biosensing mechanism using GO-induced fluorescence quenching of QDs functionalized with molecular beacons. In the absence of the target, the fluorescence of the QD is quenched through resonance transfer to the GO. In the presence of the target, resonance transfer is suppressed and the fluorescence signal is high (Dong et al., 2010a). [Reprinted with permission from Dong et al. (2010a). Copyright (2010) American Chemical Society].

Figure 12

Energy diagram illustrating the energetically favorable transfer routes for photogenerated charges in hybrid materials at the photoanode (solid arrows) and the undesired recombination processes (dashed arrows) (Chih-Hung et al., 2014).