Graphene as a Quencher of Electronic Excited States of Photochemical Probes

Abstract

Graphene sheets quench the singlet and triplet excited states of a series of six photochemical probes including pyrene, acridine orange, tris(2,2́-bipyridyl)ruthenium(II) dichloride, methylene blue, meso-tetrakis(phenylsulphonate)porphyrin, and 5,10,15,20-tetraphenyl-21H,28H-porphine zinc. It was found that Stern-Volmer fluorescence quenching can fit to one or two different quenching regimes depending on the probe. In addition, the quenching can be either static or dynamic depending on the fluorophore. The occurrence of several quenching regimes has been interpreted considering that quenching arises from the crowding of the fluorophore on both graphene faces, or site isolation on the graphene sheets. Laser flash photolysis has shown that the triplet lifetime of the probes generally decreases due to graphene quenching and that no new transients appear except in the case of methylene blue, where a new absorption spectrum characterized by a continuous absorption band is observed and attributed to graphene radical ion. This spectroscopic evidence suggests that the most general quenching mechanism is energy transfer from the singlet or triplet excited state of the dye to graphene. This raises the issue of determining the energy of the electronic excited states of graphene.

Influence of Dopant Loading on the Photo‐ and Electrochemical Properties of (N, O)‐Co‐doped Graphene.

“…All the signals recorded at different wavelengths from 300 to 800 nm have coincident temporal profiles (see Figure 3), which indicates that the continuousa bsorptionh as ah omogeneous distribution of transients pecies. On the basis of the precedents reported in the literature,t his continuoust ransient absorption [23,24] can be attributed to the charge-separation state with the contributiono ft he absorption resulting from delocalizede lectrons and positive holes in the valence band. Figure 4s hows the temporal profile of the signal monitored at 420 nm for the series of (N, O)graphene suspensions matched to the same absorbance at 355 nm.…”

Direct Observation of Quantum‐Confined Graphene‐Like States and Novel Hybrid States in Graphene Oxide by Transient Spectroscopy

“…[1][2][3][4][5][6][7] It not only contains local sp 2 domains, which are analogues of graphitic crystalline graphene with high carrier transport mobility, [8][9][10] but also possesses sp 3 -hybridized carbon atoms that are bound to plentiful oxygen-containing functional groups on the basal plane and sheet edge, which can interact with strong light absorbers or emitters (that is, dyes, polymers, and nanoparticles). [11][12][13][14][15][16][17][18] Originally, it was thought that through removal of oxygen atoms on GO via chemical or thermal reduction, large-scale production of graphene sheets could be readily fabricated. [ 19,20 ] Unfortunately, remaining defects still exist widely in reduced GO (rGO).…”

Fluorescence imaging of hybrid nanostructures composed of natural photosynthetic complexes and reduced graphene oxide

“…The scale of this effect, both in terms of the number of these localized spots as well as their intensity, depends on the rGO concentration. Emission quenching by rGO, which is a signature of efficient energy transfer, was previously reported for several different emitters [5,7,10,11,[17][18][19][20][21][22][23]. More interesting is the appearance of the localized highintensity spots across the sample surface, as evidenced by fluorescence imaging of PCP/rGO composites.…”

“…Such a scenario appears in hybrid nanostructures that involve metallic nanoparticles [3] or carbon-based materials [4][5][6][7]. Following the first reports on obtaining graphene [8,9], a two-dimensional honeycomb carbon lattice known for its unique optoelectronic, thermal, and mechanical properties, several groups have applied this material as an acceptor in studying fluorescence of emitters placed in its vicinity [10][11][12][13]. The results indicate that incorporating graphene in such structures provides unexplored opportunities in devising novel architectures possibly applicable in photonics, optoelectronics, and biosensing [12][13][14][15].…”