Nanographene oxide–TiO₂ photonic films as plasmon-free substrates for surface-enhanced Raman scattering

Abstract

Nanographene oxide–TiO2 photonic crystal films are demonstrated as sensitive, recyclable SERS substrates that integrate slow-photon amplification effects with the high adsorption capacity of GO nanosheets.

Graphene Quantum Dot-TiO2 Photonic Crystal Films for Photocatalytic Applications

“…The increase of pH resulted in the continuous decrease of r UV−Vis (inset of Figure 9b), in agreement with previous reports [55,57]. This variation supports the major role of acidic pH in the formation of SA-TiO 2 surface complexes via bidentate binding of salicylate to single undercoordinated Ti(IV) ions on titania [16,61] and subsequent oxidation by valence band holes [62]. The latter effect was further explored by photodegradation tests in the presence of MeOH as • OH scavenger under identical conditions at Ph = 3.…”

“…8 nm anatase nanoparticles can be accordingly predicted from the frequency vs. width correlation curves of the E g mode [54], in agreement with recent results on the formation of sub-10 nm anatase nanocrystals in co-assembled TiO 2 inverse opals using the TiBALDH precursor [13,15]. Furthermore, no Raman mode such as the G band arising from the stretching of sp 2 carbon atoms and the highly dispersive D-band activated by defects [15,16,40], could be traced for the GQD-PC films in the frequency range of 1000-2000 cm −1 . However, GQD's deposition on the titania PC films resulted systematically in the upsurge of an intense PL background, most pronounced for the GQD-PC films after 48 h impregnation, correlating with the variation of the GQDs loading amount.…”

“…The derived 1 − f were smaller than the theoretical value of 0.26 for complete filling of the inverse fcc lattice and increased systematically with the decrease of macropore size. It should be noted that although the obtained 1 − f values provide only a rough estimate based on modified Bragg's law, they agree with those obtained by rigorous theoretical simulations of R% spectra for TiO 2 PCs [16]. Moreover, the observed increase of the filling fraction for the smaller macropores complies favorably with recent results on co-assembled TiO 2 PC films [13].…”

“…This diameter-dependent variation can be related to the slow photon amplification for PC211, whose stop band is expected at about 367 nm in water (Table 1). According to the FWHM of the Bragg R% peak ( Figure 2) and rigorous theoretical simulations of the R% spectra for anatase PC films [16], the stop band's spectral width without the contribution of unresolved Fabry-Pérot fringes, can be estimated to be of ca. 40 nm.…”

“…Significant efforts have been accordingly devoted to combine these distinctive structural features with competent compositional modifications of the materials properties such as heterostructuring with noble metal nanoparticles [7][8][9][10], metal oxide nanoclusters [11][12][13], and graphene oxide nanosheets [14][15][16] in order to amplify photocatalytic performance for environmental remediation and solar energy conversion applications. Among the diverse TiO 2 heterojunction photocatalysts, interfacial coupling of titania with graphene and its derivatives has been an effective method to enhance charge separation and visible light harvesting based on graphene materials' electron acceptor action and charge transport along with its broadband light absorption [17][18][19].…”