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(a) Absorption spectra and the corresponding photograph (inset) of the adsorptive RhB aqueous solutions without adsorbent as well as in the presence of the SnO 2 QDs, P25 TiO 2 , GA and SGA (SGA3) adsorbent. (b) Dye adsorption isotherms of RhB on the SGA3 (the mass ratio of SnO 2 to graphene is 1:1, concentration of the SGA is 0.5 mg/mL (100 mg/200 mL), initial concentration of RhB is from 4.79 × 10 −3 g/L to 2 g/L, respectively, operating temperature is 298 K).
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The visible-light-driven photocatalytic activities of graphene-semiconductor catalysts have recently been demonstrated, however, the transfer pathway of photogenerated carriers especially where the role of graphene still remains controversial. Here we report graphene-SnO2 aerosol nanocomposites that exhibit more superior dye adsorption capacity and...
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Context 1
... Adsorptivity of The SGA. Pollutants adsorptivity is allimportant for catalytic efficiency of the photocatalyst. Hence, the adsorption processes of different samples to RhB dye were recorded and shown in Figure S4 (see the Supporting Information). All suspensions of catalyst and dye achieve the adsorption−desorption equilibration after a 60-min dark adsorption process. ...
Context 2
... with SnO 2 QDs, P25 TiO 2 , and GA, the stronger dye adsorption capacity of the SGA may be due to the special π-conjugation structure of graphene and larger specific surface area of the 3D porous layered structure, 28,31 as surpported by the BET areas of SnO 2 QDs, P25 TiO 2 (around 50 m 2 /g), 56 GA, and SGA3 in Figure S6 (see the Supporting Information). The excellent adsorptivity of the SGA can be also intuitively reflected by the absorption spectra and corresponding photos of the RhB aqueous solutions adsorbed by different samples, as displayed in Figure 4a. ...
Context 3
... hypothesis can be demonstrated by the results of SEM and TEM images (Figure 1 and Figure S10, see the Supporting Information) and BET areas ( Figure S6, Supporting Information). Furthermore, to ascertain the maximum adsorptivity (Q max ) of the SGA, the adsorption isotherm of RhB dye as a function of its concentration over the SGA was depicted in Figure 4b. The Q max of the SGA is approximately 126 mg/g, outperforming many currently available adsorbents. ...
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Citations
... At present, the research on the interaction between graphene (its derivatives) and organic dyes is still a hotspot, but there are few studies on the ultra-fast energy/electron transfer of organic dyes induced by graphene and its derivatives, which is an important basis for dye-sensitized solar cells, photocatalysis, and pollutant treatment. [31][32][33] In our work, we synthesized and used GO to study the FL quenching effect of GO on Rhodamine B (RdB) through steadystate spectroscopy and nanosecond time-resolved FL (TRFL) spectroscopy. The electron transfer process between GO and RdB has been studied using femtosecond fluorescence up-conversion and This research provides support for the application of GO/RGOorganic dye composites in dye-sensitized solar cells and photocatalysis, etc., and confirms that RGO may have a broader application prospect than GO does. ...
Graphene and its derivatives, due to its two-dimensional carbon nanostructures, have provided new opportunities to fortify organic dyes based photovoltaic and photocatalytic assemblies. In this article, we employed organic dyes Rhodamine B (RdB) and graphene oxide (GO) (or reduced graphene oxide (RGO)) to assemble the composite materials RdB-GO & RdB-RGO. It is found that both GO and RGO could strongly quench the fluorescence (FL) intensity of RdB. The mechanisms of FL quenching in both RdB-GO and RdB-RGO have been investigated by using femtosecond fluorescence up-conversion and transient absorption spectroscopy. When RdB was anchored on GO (or RGO) surface, the solvent relaxation component 3.1ps of pure RdB disappeared, instead the ultrafast excited state electron transfer process (1-2ps) in RdB-GO and RdB-RGO was found and originated from the LUMO of RdB to the conduction band of GO (or RGO). We further reveal that the energy level change caused by GO reduction makes the energy levels of RGO closer to that of RdB, resulting in the electron transfer being more effective in RdB-RGO. Therefore, the RdB-RGO composite materials may have higher application values for dye-sensitized solar cells.
... The mixed metal oxide nanocomposite materials with having two different energy-level systems can play an important role in increasing charge separation. Now-a-days, SnO 2 has been exploited as promising photocatalytic material for environmental cleanup (Zhuang et al. 2014). However, the CdO or CdO-based semiconductor heterostructure is to be investigated as photocatalyst, since they have the potential for the visible light photocatalytic application (Kumar et al. 2014;Navarro et al. 2008;Saravanan et al. 2015). ...
In this work, the electronic, optical and dielectric properties of pure CdO, mixed SnO2/CdO and PVP coated SnO2/CdO nanocomposites were calculated using the finite element method (FEM) and density functional theory. In this approach, the three studied nanostructures are modeled by the following geometric shapes: cubic-CdO, orthorhombic core/shell-SnO2/CdO and nanorod SnO2/CdO/PVP. The electronic structure shows that CdO and SnO2/CdO have semiconductor character. The complex dielectric function, absorption spectra, refractive index, and reflectivity are discussed based on the electronic structure calculations. The obtained results using FEM confirm that the complex permittivity, absorption cross section, reflectivity and complex optical conductivity of CdO nanoparticle depend on their concentration in the surrounding medium and on the nature of the latter. The optical parameters spectra of CdO, SnO2/CdO and CdO/SnO2/PVP have the same evolution in the VU–Vis–NIR band. The effect of PVP coating on the optical properties of CdO/SnO2/PVP nanocomposites is also studied.
... Studies on SnO 2 /reduced graphene oxide (rGO) photocatalysts have shown that the photocatalytic activity is significantly increased by fast charge transfer, which promotes electron-hole pair separation and limits fast recombination [6,12,15,22]. In addition, SnO 2 /rGO exhibits good photocatalytic activity under visible light [1,25]. Further, SnO 2 nanoparticles are more dispersible and rGO sheets are better separated in SnO 2 /rGO [1,2]. ...
... Figure 7(a) shows the UV-vis absorption spectra of the SnO 2 /rGO nanocomposites annealed at various temperatures. The absorption spectra of all samples include an absorption band for SnO 2 measuring 280-400 nm with a maximum of approximately 295 nm [6,23,25,36]. However, neither the absorption peaks of rGO at 265 nm [37][38][39] nor those of GO at 231 nm [37][38][39][40] were observed in the spectra of these samples, possibly owing to the low concentration of rGO. ...
... This research is funded by the Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 103.02-2018. 25 ...
Water pollution abatement is problem in today's society that requires urgent attention. Moreover, photocatalysts are an effective method to treat environmental pollution, and SnO2/reduced graphene oxide composite photocatalysts have been extensively studied in recent years. The synthesis parameters for these photocatalysts significantly affect their morphologies, structures, and properties. In this study, we investigate the effects of annealing temperatures on the properties of SnO2/reduced graphene oxide nanocomposites, which were hydrothermally fabricated at 180 ℃ for 24 h and annealed at 200-800 ℃. The structural characteristics of the fabricated nanocomposites were studied via X-ray diffraction, field emission scanning electron microscopy, and Raman scattering analyses. The observed results indicated that increasing the annealing temperature from 200 ℃ to 800 ℃ increased the average SnO2 nanoparticle size from 4.60 nm to 9.27 nm; in addition, the Raman scattering peaks of the SnO2 increased, and those of the reduced graphene oxide significantly decreased as the annealing temperature was increased. Furthermore, the specific surface area of the samples decreased due to the increase in calcination temperature. The amount of reduced graphene oxide content in all the samples was measured using thermo-gravimetric analysis. The optical properties of the samples were studied using the UV-visible (UV-vis) absorption spectra, and their photocatalytic activity was evaluated by decomposing the methylene blue under visible light using the samples as catalysts. In particular, the photocatalytic properties of nanocomposites decreased significantly with the increasing annealing temperature. Among the samples, the photocatalytic activity of that annealed at 200 ℃ is most satisfactory as it has the smallest particle size and the largest specific surface area. The results of our research could facilitate the production of efficient catalysts with suitable properties.
... Some other photo-generated holes can adsorb water and OH − , and the hydroxyl radicals ( ⋅OH ) can be formed (Eq. 7) [44,45]. ⋅OH is one of the oxidants with extremely strong oxidizability, which can degrade the RhB dye molecules into degradation products (Eq. ...
MoS2 nanomaterial with the micro-pompon structure was synthesized by a surfactant-assisted hydrothermal method. The morphologies and structures of as-prepared MoS2 micro-pompon were investigated by adding different types of surfactants such as cetyltrimethyl ammonium bromide (CTAB), sodium dodecylbenzene sulphonate (SDBS), and polyvinyl pyrrolidone (PVP). The results indicated that the morphology of MoS2 could be controlled and changed effectively by the cationic surfactant of CTAB. A reasonable growth mechanism for hollow structured MoS2 micro-pompon by hydrothermal processes was proposed. Further, photocatalytic degradation properties of MoS2 micro-pompon under visible light were evaluated by degradation of common organic dyes, which include rhodamine B (RhB), congo red, methyl orange, and methylene blue. The results indicated that MoS2 micro-pompon owned the highly selective catalytic ability to RhB with degradation efficiency of 95% in 60 min and 68% in 30 min. With the additive of the surfactant, the MoS2-CTAB sample exhibited an enhanced ability of photocatalytic activity where degradation efficiency was improved to 92% in 30 min. The method employed in this work could be expanded to fabricate other sulfides with the controllable morphology and structure to further regulate the photocatalytic performance.
... It is clearly observed that the visible light absorption of the SQD/Au nanocomposites increases with increasing Au content. This can be attributed to the increase of surface charges on the SQD nanocomposite [42]. Thus, the formation of an interface between SQD and Au NPs can significantly shift the light response from the UV to the visible region, which enhances the potential for applications of SQD/Au nanocomposites in photocatalysis. ...
Discovery and development of novel photocatalysts with superior performance in visible light is a fundamental step toward tackling several environment and energy related issues. In this study, a simple one-pot solvothermal approach was adopted to fabricate a series of novel SnO2 quantum dot/gold (SQD/Au) nanocomposites. The structure, morphology, chemical composition, and the optical and photocatalytic performance of the as-prepared SQD/Au nanocomposites were described. The dispersion of Au nanoparticles (NPs) over SQDs can significantly improve the synergistic charge transfer mechanism, which retards the reunion of photoinduced electron-hole pairs and results in decreased emission intensity. In particular, the SQD/Au nanocomposites with 1.00 mL in 100 mM gold chloride loading achieve a methylene blue (MB) degradation of 99% under visible light illumination within 150 min. This can be ascribed to the plasmonic effect of Au NPs in the visible region and the SQDs acting as an electron tank to receive the photoinduced electrons. Furthermore, the formation of a Schottky barrier between SQDs and Au NPs improved the charge separation efficiency, and enhanced the photocatalytic activity. A possible photocatalytic mechanism for the improved degradation efficiency of MB by SQD/Au nanocomposites is also proposed.
... The XRD patterns of rGO/SnO 2 appear the similar diffraction peaks with pure SnO 2 owing to the crystal phase of tetragonal rutile SnO 2 , proving the presence of SnO 2 crystals again. It is also found that obvious peaks originating from rGO are not observed in the XRD patterns of rGO/SnO 2 sample, which may be attributed to the relatively low content of rGO in composites or insertion of rGO into SnO 2 lattice [37,38]. Furthermore, the diffraction peak intensities of rGO/SnO 2 composites are weakened compared with those of pure SnO 2 owing to the destroyed orderliness during stacking of rGO/SnO 2 composite networks [33]. ...
... In addition, the fast recombination of photoinduced electron-hole pairs hinders the commercialization of this technology for water treatment (Dong et al., 2015b;Jiang et al., 2012;Ratna, 2012). Therefore, various coupled semiconductor metal oxide photocatalysts including CdO-SnO 2 , ZnO-Cu 2 O, Cu 2 O/ TiO 2 , SnO 2 -TiO 2 , SnO 2 -Graphene, SnS 2 -SnO 2 , TiO 2 /CuS, NaNbO 3 / CdS etc., have been developed, which can extend the absorption range to the visible region and suppress the recombination of photo-induced electron-hole pairs to improve the photocatalytic efficiency of the photocatalyst (Khan and Kim, 2009;Khanchandani et al., 2016;Kumar et al., 2016;Liu et al., 2014;Luo et al., 2013;Nedjalkov et al., 2016;Pan et al., 2011;Rakibuddin and Ananthakrishnan, 2017;Shao et al., 2015;Shi et al., 2017;Wu et al., 2011;Zhang et al., 2012;Zhuang et al., 2014). Among these catalysts, SnO 2 -based coupled photocatalysts have attracted more attention because of the versatile multifunctional applications of SnO 2 in Li-batteries, gas sensing etc. ...
Appropriate recycling of waste to reusable materials is much sought after in the scientific community to control the incessant rising pollution in environment due to insufficient management of waste materials. To address this issue, efforts were directed to obtain SnO 2 -Fe 3 O 4 nanocomposites from scrap tin plated steel and the use of these composites for the degradation of organic pollutant. We have demonstrated a novel, efficient and facile hydrometallurgy approach for the extraction of iron from waste tin plated steel containers found in plenty in the common waste generated in society. The extracted iron has further been utilized for the preparation of SnO 2 :Fe 3 O 4 nanocomposites with different compositions (SnO 2 :Fe 3 O 4 ratio of 93.2:6.8, 85:15, 58:42 and 40:60) using hydrothermal route. The photocatalytic activities of nanocomposite were determined spectroscopically using Rhodamine-B (RhB) as a model dye. Our results indicate that among all the composites with SnO 2 (85%):Fe 3 O 4 (15%) exhibits the best photocatalytic efficiency under UV light whereas the composition of SnO 2 (93.2%):Fe 3 O 4 (6.28%) is the most efficient in visible light. The above visible light efficiency was supported by density functional theory (DFT) studies which suggest a small amount of pure Fe is present at the Sn sites in the nanocomposite, leading to the reduction in the band gap of the nanocomposite and resulting in absorption in the visible range. Thus, in the present study, we have shown a process of conversion of waste to nanomaterials and its utilization for treatment of organic pollutants.
... Some metal oxides such as TiO 2 , zinc oxide (ZnO), and stannic oxide (SnO 2 ) have been used as photoanode in DSSCs. Among these metal oxide, TiO 2 nanocrystals gives the best PCE as compared to ZnO and SnO 2 due to the higher photocatalysis activity, abundance, and high quantum yield [39][40][41][42][43][44][45][46]. However, TiO 2 has limited solar light harvesting ability due to its wide band gap (3.0-3.2 eV) [47]. ...
Renewable solar cell energy is a key target for sustainable energies development, which are inexhaustible and non-polluting for our energy system. To bring more solar related technologies to the point of commercial readiness and viability in terms of performance and cost, substantial research on the development of high efficient renewable dye-sensitized solar cell (DSSCs) device is necessary. Recent studies have indicated that graphene is a relatively novel material with unique properties that could apply in photoanode/counter electrode component as efficient electrode. In fact, the atom-thick 2D structure of graphene (rGO) provides an extraordinarily high conductivity, repeatability, productivity, and prolong lifetime to the related solar cell applications. Continuous efforts have been exerted to further improve the graphene textural and electronic properties by loading an optimum content of titanium dioxide (TiO 2) as an efficient photocatalyst in DSSCs. In this chapter, different synthesis strategies and characterization analyses for TiO 2-rGO nanocomposites (NC) as well as its prospects in DSSCs will be reviewed in detail.
... The degradation rates of methylene blue in the presence of ZnO nanostructures are depicted in Fig. 6(b). The chemisorbed oxygen on the surface of ZnO nanostructure has a significant role in the regenera- tion mechanism of hydroxyl and superoxide species for the degradation of dye and the same can be represented as follows [51]. ...
An interesting architecture of robust, highly reproducible, template-free synthesis of phase pure carbon-incorporated short ZnO nanotubes through polymer assisted sol–gel method is presented here. These nanotubes exhibit enormous surface oxygen vacancies and mid bandgap levels confirmed by X-ray photoelectron spectroscopy. These carbon-modified nanotubes exhibit encouraging results in photocatalytic studies, as there is a 16% greater degradation of contaminant dye than in the pristine ZnO nanotube. The reactive oxygen species generated from the photocatalysts were experimentally confirmed and quantified. Super hydrophilic nature renders these nanotubes suitable for antifogging application as observed from contact angle measurements. Characterisation and mechanism of a competent material with improved photoresponse, promising greater energy efficiency and anti-fog have been described in this investigation.
... Graphene material having unique characteristics can be used as a photosensitizer [242][243][244]. Graphene and GO under light irradiation show photoactivity [245] either through photoexcitation or via stimulation of electron transmission from substrate e.g. dye [246]. ...
Graphene, the mother of all carbon materials has unlocked a new era of biomedical nanomaterials due to its exceptional biocompatibility, physicochemical and mechanical properties. It is a single atom thick, nanosized, 2-dimensional structure and provides high surface area with adjustable surface chemistry to form hybrids. The present article provides a comprehensive review of ever-expanding application of graphene nanomaterials with different inorganic and organic materials in drug delivery and theranostics. Methods of preparation of nanomaterials are elaborated and biological and physicochemical characteristics of biomedical relevance are also discussed. Graphene form nanomaterials with metallic nanoparticles with multiscale application. First, graphene act as a platform to attach nanoparticles and provide excellent mechanical strength. Second, graphene improves efficacy of metallic nanoparticles in diagnostic, biosensing, therapeutic and drug delivery application. Graphene based polymeric nanocomposites find wider application in drug delivery with flexibility to incorporate hydrophilic, hydrophobic, sensitive and macromolecules. In addition, grapheme quantum dots and graphene hybrids with inorganic nanocrystal and carbon nanotubes hybrids have shown interesting properties for diagnosis and therapy. Finally, we have pointed out research trends that may be more common in future for graphene based nanomaterials.
Keywords: Graphene, Graphene oxide, Nanomaterials, Biosensors, Theranostics
