Cyanobacterial chlorophyll as a sensitizer for colloidal TiO2

UV responsive quercetin derived and functionalized CuO/ZnO nanocomposite in ameliorating photocatalytic degradation of rhodamine B dye and enhanced biocidal activity against selected pathogenic strains

Quercetin was investigated for its role as a reducing agent in biosynthesizing CuO/ZnO nanocomposite, its subsequent surface functionalization and influence in Rhodamine B dye degradation and biocidal activity. The as synthesized quercetin functionalized CuO/ZnO nanocomposite (CuO/ZnO@Q) was analyzed using X-ray diffraction (XRD), Fourier transform infra red spectroscopy (FTIR), Transmission electron microscopy (TEM), Energy dispersive spectroscopy (EDS) and Ultraviolet-visible spectroscopy (UV-Vis). XRD showed the formation of crystalline CuO, ZnO phases and FTIR analysis revealed the incorporation of quercetin functional groups in the synthesized nanocomposite. TEM image displayed the formation of quercetin deposited spherical CuO/ZnO nanostructure with the EDAX results confirming the presence of organic carbon composition from quercetin. The UV absorption spectra ascertained the presence and role of quercetin in the enhanced absorption of radiation in the UV range. CuO/ZnO@Q showed improved photocatalysis with complete Rhodamine B dye degradation after 75 min of UV irradiation, as against pure CuO/ZnO, which exhibited incomplete dye degradation even after 90 min of irradiation. Moreover, quercetin surface functionalization effectively ameliorated its antimicrobial activity against E. coli, S. aureus, Shigella, B. subtilis, A. niger and C. albicans, proving its potential in significantly enhancing biocidal activity along with photocatalytic dye degradation in a natural and eco-friendly route.

In vitro and in vivo impact assessment of eco-designed CuO nanoparticles on non-target aquatic photoautotrophic organisms

This work has assessed the impact of copper oxide nanoparticles (CuONPs), designed via green route, toward photosynthetic apparatus on aquatic photoautotrophic organisms. In order to filling knowledge gaps, in vitro and in vivo assays were performed, using cyanobacterial phycocyanin (C-PC) from Arthrospira platensis and Lemna valdiviana plants (duckweed), respectively. Impairment in light energy transfer became evident in C-PC exposed to CuONPs, giving rise to an increase of light absorption and a suppression of fluorescence emission. Fourier transform infrared spectroscopy (FTIR) results showed that C-PC structures might be altered by the nanoparticles, also revealed that CuONPs preferably interacts with -NH functional groups. The data also revealed that CuONPs affected the chlorophyll a content in duckweed leaves. In addition, photosystem II (PSII) performance was significantly affected by CuONPs, negatively impacting the PSII photochemical network. In summary, the results point out that, even eco-friendly designed, CuONPs may negatively affect the photosynthetic process when accumulated by aquatic photoautotrophs.

Ceramic-based photocatalytic membrane reactors for water treatment – where to next?

Ceramic-based photocatalytic membrane reactors (cPMRs) are becoming increasingly popular among researchers and will soon be seen on the water/wastewater-treatment market. This review provides a thorough analysis of the available data on cPMRs fabricated to date based on coating method, support and coating materials, membrane design, pore size and model compounds used to evaluate process efficiency and light source. While all of the studies describe cPMR preparation in great detail, over half do not provide any information about their performance. The rest used various dyes that can be conveniently detected by spectrophotometry/fluorimetry, or micropollutants that require analytical equipment available only in specialized laboratories. In addition, cPMRs are viewed as a convenient way of incorporating a photocatalyst on an inert surface assuming that the surface itself, i.e. the membrane, does not participate in the treatment process. A unified test for cPMR performance should be developed and implemented for all cPMRs that have the potential for commercialization. There is a need for standardization in cPMR testing; only then can the true performance of cPMRs be evaluated and compared. Such testing will also answer the question of whether the cPMR membrane is indeed an inert support or an active part of the treatment process.

Understanding the fate and biological effects of Ag- and TiO₂-nanoparticles in the environment: The quest for advanced analytics and interdisciplinary concepts

Engineered inorganic nanoparticles (EINP) from consumers' products and industrial applications, especially silver and titanium dioxide nanoparticles (NP), are emitted into the aquatic and terrestrial environments in increasing amounts. However, the current knowledge on their environmental fate and biological effects is diverse and renders reliable predictions complicated. This review critically evaluates existing knowledge on colloidal aging mechanisms, biological functioning and transport of Ag NP and TiO2 NP in water and soil and it discusses challenges for concepts, experimental approaches and analytical methods in order to obtain a comprehensive understanding of the processes linking NP fate and effects. Ag NP undergo dissolution and oxidation with Ag2S as a thermodynamically determined endpoint. Nonetheless, Ag NP also undergo colloidal transformations in the nanoparticulate state and may act as carriers for other substances. Ag NP and TiO2 NP can have adverse biological effects on organisms. Whereas Ag NP reveal higher colloidal stability and mobility, the efficiency of NOM as a stabilizing agent is greater towards TiO2 NP than towards Ag NP, and multivalent cations can dominate the colloidal behavior over NOM. Many of the past analytical obstacles have been overcome just recently. Single particle ICP-MS based methods in combination with field flow fractionation techniques and hydrodynamic chromatography have the potential to fill the gaps currently hampering a comprehensive understanding of fate and effects also at a low field relevant concentrations. These analytical developments will allow for mechanistically orientated research and transfer to a larger set of EINP. This includes separating processes driven by NP specific properties and bulk chemical properties, categorization of effect-triggering pathways directing the EINP effects towards specific recipients, and identification of dominant environmental parameters triggering fate and effect of EINP in specific ecosystems (e.g. soil, lake, or riverine systems).

Instantaneous physico-chemical analysis of suspension-based nanomaterials

High-throughput manufacturing of nanomaterial-based products demands robust online characterization and quality control tools capable of continuously probing the in-suspension state. But existing analytical techniques are challenging to deploy in production settings because they are primarily geared toward small-batch ex-situ operation in research laboratory environments. Here we introduce an approach that overcomes these limitations by exploiting surface complexation interactions that emerge when a micron-scale chemical discontinuity is established between suspended nanoparticles and a molecular tracer. The resulting fluorescence signature is easily detectable and embeds surprisingly rich information about composition, quantity, size, and morphology of nanoparticles in suspension independent of their agglomeration state. We show how this method can be straightforwardly applied to enable continuous sizing of commercial ZnO nanoparticles, and to instantaneously quantify the anatase and rutile composition of multicomponent TiO₂ nanoparticle mixtures pertinent to photocatalysis and solar energy conversion.

Spectroscopic investigations on the simulated solar light induced photodegradation of 4-nitrophenol by using three novel copper(II) porphyrin-TiO2 photocatalysts

Three porphyrins containing different functional groups (-OH, C-O2C2H5, -COOH), 5-(4-hydroxy) phenyl-10,15,20-triphenyl porphyrin (1a), 5-(4-ethylacetatatomethoxy) phenyl-10,15,20-triphenyl porphyrin (1b), 5-(4-carboxylatomethoxy) phenyl-10,15,20-triphenyl porphyrin (1c), were synthesized and characterized spectroscopically. The CuPp(2a, 2b, 2c)-TiO2 photocatalysts were then prepared and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (UV-vis-DRS), Fourier-transform infrared spectroscopy (FT-IR). The photocatalytic activities of the photocatalysts were investigated by carrying out the photodegradation of 4-nitrophenol in aqueous solution under simulated solar irradiation. It was found that the CuPp(2a, 2b, 2c)-TiO2 enhanced the photocatalytic efficiency of bare TiO2 in photodegrading the 4-NP due to the interaction between CuPp(2a, 2b, 2c) and TiO2, resulted in the enhancement of the photogenerated electron-hole separation. The reasons of this enhanced photocatalytic activity were also discussed. Based on the present study, it could be considered as a promising photocatalyst for the further industrial application.

Spectrophotometric studies of visible light induced photocatalytic degradation of methyl orange using phthalocyanine-modified Fe-doped TiO2 nanocrystals

In this paper, preparation and visible light induced photocatalytic activity of phthalocyanine-modified Fe-doped TiO(2) nanocrystals (Pc/Fe-TiO(2)) with different Fe doping content (0, 0.05, 0.5 and 3.0 mol% Fe) as photocatalysts for the degradation of methyl orange have been reported. The study carried out using XRD, FT-IR, EDX, BET, DRS, UV-Vis, SEM and TEM techniques. Results revealed that modified TiO(2) nanocrystals possessed only the anatase phase with crystal sizes of about 10-23 nm and high surface areas of 2.8-37.3 m(2)/g. It can be seen phthalocyanine and Fe(3+) ion exist in photocatalysts based on analysis of FT-IR and EDX. The doping amount of Fe remarkably affects the activity of modified TiO(2) nanocrystals as catalysts. The 0.5 mol% Fe doping exhibited enhanced photocatalytic activity in this work. It was found that phthalocyanine and Fe induced a shift in the energy band gap to lower energies, which changes from 3.26 to 2.26 eV for pure TiO(2) and Pc/3% Fe-TiO(2) nanocrystals, respectively. Results of the degradation of methyl orange revealed that modified TiO(2) nanocrystals showed much more photocatalytic activity than pure TiO(2) under visible light which makes the applicability of TiO(2) photocatalysts even more versatile.