Ultrasmall Plasmonic Nanoparticles Decorated Hierarchical Mesoporous TiO2 as an Efficient Photocatalyst for Photocatalytic Degradation of Textile Dyes.
ABSTRACT: Hierarchical mesoporous TiO2 was synthesized via a solvothermal technique. The sonochemical method was adopted to decorate plasmonic nanoparticles (NPs) (Ag, Au) on the pores of mesoporous TiO2. The crystallinity, structure, and morphology were determined to understand the physicochemical nature of the nanocomposites. The catalytic efficiency of the plasmonic nanocatalysts was tested for the azo dyes (congo red, methyl orange, acid orange 10, and remazol red) under solar and visible light irradiations. The generation of hydroxyl radicals was also studied using terephthalic acid as a probe molecule. An attempt was made to understand the influence of size, work function and Fermi level of the metal NPs toward the efficiency of the photocatalyst. The efficiency of the nanocomposites was found to be in the order of P25 < mesoporous TiO2 < mesoporous Ag-TiO2 < mesoporous Au-TiO2 nanospheres under both direct solar light and visible light irradiation. The results indicated that the adsorption of dye, anatase phase, and surface plasmon resonance of NPs favored the effective degradation of dyes in aqueous solution. Further, the efficiency of the catalyst was also tested for xanthene (rose bengal), rhodamine (rhodamine B, rhodamine 6G), and thiazine (methylene blue) dyes. Both TiO2 and NPs (Ag & Au) possess a huge potential as an eco-friendly photocatalyst for wastewater treatment.
Project description:Membrane technology is an advanced approach to making a healthier and cleaner environment. Using such catalytic membrane technology to get clean, usable water by removal of dye impurities as well as pathogenic microbes is the main goal behind the research work. Here, we present the synthesis and efficacy study of polymethyl methacrylate (PMMA)-based Ag/ZnO/TiO<sub>2</sub> trimetallic bifunctional nanofibers with antibacterial and photocatalytic activity. The nanofibers have been proven to be effective for the degradation of methylene blue (MB 93.4%), rhodamine B (Rh 34.6%), auramine-<i>O</i> (Au 65.0%) and fuchsin basic (FB 69.8%) dyes individually within 90 min in daylight. The study is further extended in abating a mixture of these dyes from contaminated water using composite nanofibers. Also, in the case of a mixture of these dyes (3 ppm each), nanofibers show dye degradation efficiency (DDE) of 90.9% (MB), 62.4% (Au) and 90.3% (FB and Rh) in 60 min. The role of Ag nanoparticles with a synergic photocatalytic effect on ZnO and TiO<sub>2</sub> is also demonstrated. Also, PMMA/ZnO/TiO<sub>2</sub> composite fiber membrane in synergy with silver particles shows better antibacterial activity against Gram-negative bacteria <i>E. coli</i>, making PMMA/Ag/ZnO/TiO<sub>2</sub> fibers a promising candidate in water purification.
Project description:The use of the surface plasmon resonance (SPR) effect of plasmonic metal nanocomposites to promote photocarrier generation is a strongly emerging field for improving the catalytic performance under visible-light irradiation. In this study, a novel plasmonic photocatalyst, AuPt/N⁻TiO₂, was prepared via a photo-deposition⁻calcination technique. The Au nanoparticles (NPs) were used herein to harvest visible-light energy via the SPR effect, and Pt NPs were employed as a cocatalyst for trapping the energetic electrons from the semiconductor, leading to a high solar-energy conversion efficiency. The Au₂Pt₂/N⁻TiO₂ catalyst, herein with the irradiation wavelength in the range 460⁻800 nm, exhibited a reaction rate ~24 times greater than that of TiO₂, and the apparent quantum yield at 500 nm reached 5.86%, indicative of the successful functionalization of N⁻TiO₂ by the integration of Au plasmonic NPs and the Pt cocatalyst. Also, we investigated the effects of two parameters, light source intensity and wavelength, in photocatalytic reactions. It is indicated that the as-prepared AuPt/N⁻TiO₂ photocatalyst can cause selective oxidation of benzyl alcohol under visible-light irradiation with a markedly enhanced selectivity and yield.
Project description:The photocatalytic activity of TiO<sub>2</sub> based photocatalysts can be improved by structural modification and elemental doping. In this study, through rational design, one type of carbon and nitrogen co-doped TiO<sub>2</sub> (C, N-TiO<sub>2</sub>) photocatalyst with mesoporous structure was synthesized with improved photocatalytic activity in degrading 4-nitrophenol under simulated sunlight irradiation. The photocatalytic degradation efficiency of the C, N-TiO<sub>2</sub> was much higher than the anatase TiO<sub>2</sub> (A-TiO<sub>2</sub>) based on absorbance and HPLC analyses. Moreover, using zebrafish embryos, we showed that the intermediate degradation compounds generated by photocatalytic degradation of 4-nitrophenol had higher toxicity than the parent compound. A repeated degradation process was necessary to render complete degradation and non-toxicity to the zebrafish embryos. Our results demonstrated the importance of evaluating the photocatalytic degradation efficiency in conjunction with the toxicity assessment of the degradation compounds.
Project description:In this contribution, the efficiencies of perovskite solar cells have been further enhanced, based on optical optimization studies. The photovoltaic devices with textured perovskite film can be obtained and a power conversion efficiency (PCE) of the textured fluorine-doped tin oxide (FTO)/Ag nanoparticles (NPs) embedded in c-TiO?/m-TiO?/CH?NH?PbI?/Spiro-OMeTAD/Au showed 33.7% enhancement, and a maximum of up to 14.01% was achieved. The efficiency enhancement can be attributed to the light trapping effect caused by the textured FTO and the incorporated Ag NPs, which can enhance scattering to extend the optical pathway in the photoactive layer of the solar cell. Interestingly, aside from enhanced light absorption, the charge transport characteristics of the devices can be improved by optimizing Ag NPs loading levels, which is due to the localized surface plasmon resonance (LSPR) from the incorporated Ag NPs. This light trapping strategy helps to provide an appropriated management for optical optimization of perovskite solar cells.
Project description:Plasmon-assisted energy conversion is investigated in a comparative study of dye-sensitized solar cells (DSCs) equipped with photo-anodes, which are fabricated by forming gold (Au) and silver (Ag) nanoparticles (NPs) on an fluorine-doped tin oxide (FTO) glass surface by means of dry plasma reduction (DPR) and coating TiO? paste onto the modified FTO glass through a screen printing method. As a result, the FTO/Ag-NPs/TiO? photo-anode showed an enhancement of its photocurrent, whereas the FTO/Au-NPs/TiO? photo-anode showed less photocurrent than even a standard photo-anode fabricated by simply coating TiO? paste onto the modified FTO glass through screen printing. This result stems from the small size and high areal number density of Au-NPs on FTO glass, which prevent the incident light from reaching the TiO? layer.
Project description:Nanoparticle (NP) catalysts are widely used for removal of dyes for single use, but there is an acute need for developing catalysts with high efficiency and reusability for mixed dyes. Here we first optimized the process (reactant proportion, temperature, time, and pH) for biosynthesis of monometallic Ag, Au and bimetallic Au-Ag alloy NP catalysts using Polyalthia longifolia leaf extract. The biosynthesized NP catalysts were characterized by UV-vis, DLS, Zeta potential, TEM and EDX study while the probable biomolecules responsible for biosynthesis were identified by FTIR and GC-MS/MS analysis. The NPs are found to be mostly spherical in shape (size 5-20?nm) with prolonged stability. We evaluated their chemo-catalytic performance through degradation of dyes (methyl orange, methyl violet, methylene blue) in individual and ternary mixture in presence of NaBH<sub>4</sub>. The degradation percentage (80.06-96.59% within 5?min), degradation kinetics (k?=?0.361-1.518?min<sup>-1</sup>), half-life (T<sub>50</sub>?=?0.457-1.920?min) and 80% degradation (T<sub>80</sub>?=?1.060-4.458?min) of dyes indicated highest catalytic activity of alloy in ternary mixture. Here we report a unique vacuum filtration system using alloy coated beads with excellent catalytic activity which could be reused thrice for removal of hazardous ternary mixed dyes with great promise for environmental remediation.
Project description:We investigated a novel approach by synthesizing an integrated material, which could act as both adsorbent and photocatalytic material, for bioaerosol purification under visible light conditions. Ag was used as a dopant agent to enhance photocatalytic activity of TiO<sub>2</sub>, leading to high photocatalytic activity of the doped TiO<sub>2</sub> even under visible light. Under visible light, the doped TiO<sub>2</sub> photocatalyst could produce oxy radicals, oxidative agents, that participate in oxidation reactions to decompose important organic components of bacteria, leading to death or removal of bacteria from an aerosol. Adsorption property was integrated into the enhanced TiO<sub>2</sub> photocatalyst by using polyurethane (PU), a honeycomb structure material, as a substrate for coating process of the doped TiO<sub>2</sub>. Three materials including pristine PU, TiO<sub>2</sub> coating on PU (TiO<sub>2</sub>/PU), and Ag-doped TiO<sub>2</sub> coating on PU (Ag-TiO<sub>2</sub>/PU) were used to remove <i>Escherichia coli</i> in an aerosol under visible light. Under dark conditions, the removal capacities of <i>E. coli</i> in the aerosol by PU, TiO<sub>2</sub>/PU, and Ag-TiO<sub>2</sub>/PU were 1.2 × 10<sup>5</sup>, 2.7 × 10<sup>5</sup>, and 6.2 × 10<sup>5</sup> (CFU/cm<sup>3</sup>), respectively. Under visible light irradiation, the removal capacities of <i>E. coli</i> in an aerosol by PU, TiO<sub>2</sub>/PU, and Ag-TiO<sub>2</sub>/PU were 1.2 × 10<sup>5</sup>, 2.7 × 10<sup>5</sup>, and 1.8 × 10<sup>6</sup> (CFU/cm<sup>3</sup>), respectively. The improvement of the removal capacity by TiO<sub>2</sub>/PU and Ag-TiO<sub>2</sub>/PU, versus PU, is due to adsorption alone and the combination of adsorption plus photocatalytic activity, respectively.
Project description:Both phototherapy via photocatalysts and physical puncture by artificial nanostructures are promising substitutes for antibiotics when treating drug-resistant bacterial infectious diseases. However, the photodynamic therapeutic efficacy of photocatalysts is seriously restricted by the rapid recombination of photogenerated electron-hole pairs. Meanwhile, the nanostructures of physical puncture are limited to two-dimensional (2D) platforms, and they cannot be fully used yet. Thus, this research developed a synergistic system of Ag<sub>3</sub>PO<sub>4</sub> nanoparticles (NPs), decorated with black urchin-like defective TiO<sub>2</sub> (BU-TiO<sub>2-X</sub>/Ag<sub>3</sub>PO<sub>4</sub>). These NPs had a decreased bandgap compared to BU-TiO<sub>2-X</sub>, and BU-TiO<sub>2-X</sub>/Ag<sub>3</sub>PO<sub>4</sub> (3:1) exhibited the lowest bandgap and the highest separation efficiency for photogenerated electron-hole pairs. After combination with BU-TiO<sub>2-X</sub>, the photostability of Ag<sub>3</sub>PO<sub>4</sub> improved because the oxygen vacancy of BU-TiO<sub>2-X</sub> retards the reduction of Ag<sup>+</sup> in Ag<sub>3</sub>PO<sub>4</sub> into Ag<sup>0</sup>, thus reducing its toxicity. In addition, the nanospikes on the surface of BU-TiO<sub>2-X</sub> can, from all directions, physically puncture bacterial cells, thus assisting the hybrid's photodynamic therapeutic effects, alongside the small amount of Ag<sup>+</sup> released from Ag<sub>3</sub>PO<sub>4</sub>. This achieves synergy, endowing the hybrid with high antibacterial efficacy of 99.76 ± 0.15% and 99.85 ± 0.09% against <i>Escherichia coli</i> and <i>Staphylococcus aureus</i>, respectively, after light irradiation for 20 min followed by darkness for 12 h. It is anticipated that these findings may bring new insight for developing synergistic treatment strategies against bacterial infectious diseases or pathogenic bacterial polluted environments.
Project description:Three component hybrid (MoS<sub>2</sub>-TiO<sub>2</sub>)/Au substrate is fabricated by loading plasmonic Au nanorods on the MoS<sub>2</sub> nanosheets coated TiO<sub>2</sub> nanorod arrays. It is used for photoelectrochemical (PEC) cell and photocatalyst for hydrogen generation. Owing to the charge transfer between the MoS<sub>2</sub>-TiO<sub>2</sub> hetero-structure, the PEC current density and hydrogen generation of TiO<sub>2</sub> nanoarrays are enhanced 2.8 and 2.6 times. The broadband photochemical properties are further enhanced after Au nanorods loading. The plasmon resonance of Au nanorods provides more effective light-harvesting, induces hot-electron injection, and accelerates photo-excited charges separation. The results have suggested a route to construct nanohybrid by combining one-dimensional arrays and two-dimensional nanosheets, meanwhile have successfully utilized plasmonic nanorods as a sensitizer to improve the photochemical properties of the semiconductor nanocomposite.
Project description:The development of high efficiency dye-sensitized solar cells (DSSCs) has received tremendous attention. Many researchers have introduced new materials for use in DSSCs to achieve high efficiency. In this study, the change in power conversion efficiency (PCE) of DSSCs was investigated by introducing two types of materials-Au nanoparticles (Au NPs) and a scattering layer. A DSSC fabricated without neither Au NPs nor a scattering layer achieved a PCE of 5.85%. The PCE of a DSSC based on freestanding TiO<sub>2</sub> nanotube arrays (f-TNTAs) with Au NPs was 6.50% due to better electron generation because the plasmonic absorption band of Au NPs is 530 nm, which matches the dye absorbance. Thus, more electrons were generated at 530 nm, which affected the PCE of the DSSC. The PCE of DSSCs based on f-TNTAs with a scattering layer was 6.61% due to better light harvesting by scattering. The scattering layer reflects all wavelengths of light that improve the light harvesting in the active layer in DSSCs. Finally, the PCE of DSSCs based on the f-TNTAs with Au NPs and a scattering layer was 7.12% due to the synergy of better electron generation and light harvesting by plasmonics and scattering. The application of Au NPs and a scattering layer is a promising research area for DSSCs as they can increase the electron generation and light harvesting ability.