Showing papers in "Journal of Photochemistry and Photobiology A-chemistry in 2016"

Photocatalytic degradation of highly toxic dyes using chitosan-g-poly(acrylamide)/ZnS in presence of solar irradiation

Abstract: The photocatalytic degradation of methyl orange (MO) and congo red (CR) dyes from aqueous solution have been attempted using chitosan-g-poly(acrylamide)/ZnS (ChPA/ZS) nanocomposite materials. Nanocomposites were successfully prepared in the aqueous solution through microwave radiations. Band gap property of composite was studied using UV–vis spectrophotometer. The ChPA/ZS nanocomposite was characterized by various techniques. The photocatalytic activity of ChPA/ZS was evaluated for methyl orange and congo red dyes degradation in aqueous solution under simulated solar irradiation. The degradation of dyes was recorded higher for ChPA/ZS nanocomposite. After 2 h of irradiation, 75% of congo red dye was degraded and 69% of methyl orange was degraded after 4 h of simulated solar irradiation. ChPA/ZS composite showed a higher rate of dye degradation owing to outstanding adsorbing properties of cross linked polyacrylamide.

Effective photocatalytic degradation of Congo red dye using alginate/carboxymethyl cellulose/TiO2 nanocomposite hydrogel under direct sunlight irradiation

Abstract: Nanocomposite hydrogels of barium ion crosslinked alginate/carboxymethyl cellulose (CMC) with encapulation of TiO 2 -NPs were synthesized sucessfully using dissipative convective method followed by freeze-drying procedure. As-prepared composite hydrogels were charecterized by different techniques such as Fourier Transform Infrared spectroscopy (FT-IR), Powder X-ray diffraction (PXRD), UV- Diffuse reflectance spectroscopy (UV-DRS), BET-Surface area study, Scanning Electron Microscopy with Energy Dispersive X-ray analysis (SEM-EDAX), Transmission Electron Microscopy (TEM) and mechanical strength study. Ba/Alg/CMC/TiO2 composite hydrogels exhibited excellent photocatalytic activity towards CR under direct solar light irradiation with pseudo-first order kinetics. The recycling ability of Ba/Alg/CMC/TiO2 composite hydrogels confirms that photocatalyst is highly photostable.

Photocatalytic degradation of methyl green dye in aqueous solution over natural clay-supported ZnO–TiO2 catalysts

Abstract: A ZnO–TiO2/clay photcatalyst was prepared using a natural Tunisian clay as support. Its activity was assayed in the photocatalytic degradation of methyl green in aqueous solutions, in the presence of UVA irradiation. The photocatalyst was synthesized using a metal organic chemical vapor deposition (MOCVD) with Ti (OPri)4 deposed on the natural Na+–clay, followed by a modified sol–gel synthesis method for introduction. The sample was then characterized by scanning electronic microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), N2 adsorption, X-ray diffraction (XRD) and titration for the determination of the zero point charge (pHZPC). The activity tests showed that the photodegradation efficiency for ZnO–TiO2/clay is higher than for the TiO2/clay catalyst, clearly pointing to a promoting effect of ZnO. The influence of operational parameters such as pH, catalyst dosage, initial dye concentration, UV irradiation intensity, as well as the influence of the presence of different oxidants was evaluated. Almost complete mineralization was obtained upon 30 min of light irradiation in the presence of the ZnO–TiO2/clay catalyst.

Application of Fe3O4@C catalyzing heterogeneous UV-Fenton system for tetracycline removal with a focus on optimization by a response surface method

Abstract: Herein, we synthesized a heterogeneous catalyst incorporating magnetite nanoparticles (Fe 3 O 4 , with an average size of 80 nm) supported on powder activated carbon (Fe 3 O 4 @C) as a highly active, easily separable and recyclable catalyst for the degradation of tetracycline (TC) antibiotic in aqueous solution in UV-Fenton conditions The influences of reaction time, TC, catalyst and H 2 O 2 concentration at pH 3 ± 02 on TC degradation efficiency were all evaluated in detail using a response surface method (RSM) The degradation kinetics and mineralization as well as durability and reactivity of the catalyst were also investigated Recycling tests were performed in order to evaluate the stability of the catalyst during successive UV-Fenton reactions and the possibility of its use in a batch system Analysis of variance (ANOVA) showed that the quadratic model fitted best to the experimental data with the correlation coefficients of 09669, 09933 and 0984 for R 2 , adjusted- R 2 , predicted- R 2 , respectively Results from the studies relating to the characteristics and performance of Fe 3 O 4 @C showed that high adsorption capacity led to a sharp enhancement in the catalytic activity Under the optimized conditions, the removal efficiency of TC was determined to be 79% within 44 min reaction The degradation process followed the pseudo-first-order kinetic model with a good correlation coefficient The removal efficiency of total organic carbon (TOC) reached 437% within 120 min It was observed that Fe 3 O 4 @C retained its stability and activity even after several cycles, which could significantly reduce the operation cost in practical applications

Performance of the polymeric g-C3N4 photocatalyst through the degradation of pharmaceutical pollutants under UV–vis irradiation

Abstract: The graphite-like C3N4 was prepared by means the polycondensation of melamine at 500 °C for 4 h. The polymeric photocatalyst was characterized by several techniques such as X-ray powder diffraction (XRD), UV–vis diffuse reflectance spectroscopy (DRS) and scanning electron microscopy (SEM). Also, nitrogen adsorption-desorption measurements were performed in order to estimate the surface area (BET) and pore size distribution (BJH) of the photocatalyst. The g-C3N4 material was used in the degradation of four different pharmaceutical compounds in aqueous solution under UV–vis irradiation. In this way, the photocatalyst showed the capacity to degrade the pharmaceutical compounds in the following sequence: tetracycline > ciprofloxacin > salicylic acid > ibuprofen. However, the degree of mineralization was different with the sequence: tetracycline > salicylic acid > ciprofloxacin > ibuprofen. Also, several scavengers agents were used in order to elucidate the importance of the different reactive oxidizing species during the photocatalytic process.

N-doped carbon quantum dots/TiO2 hybrid composites with enhanced visible light driven photocatalytic activity toward dye wastewater degradation and mechanism insight

Abstract: N-doped carbon quantum dots/TiO2 (NCQDs/TiO2) hybrid composites were prepared via a simple and efficient low-temperature process. The resulted composites were characterized by various techniques, such as X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscope, transmission electron microscopy and high-resolution TEM, and UV–vis diffuse reflectance spectra. The results indicated that the NCQDs were successfully introduced onto the TiO2 surface. The photocatalytic activity of the NCQDs/TiO2 hybrid composites were investigated by using Methylene blue (MB) as the target pollutant. The photodegradation efficiency of MB over 1NCQDs/TiO2 was 86.9% within 420 min, which was much higher than those of pristine TiO2 (53.8%) and the hybrid composites with other NCQDs contents (lower than 80.1%). This suggested that the NCQDs played important roles for MB degradation under visible light irradiation. The functions of NCQDs were discussed and a new synergistic mechanism was proposed for the degradation of MB on the surface of NCQDs/TiO2 hybrid composites. The enhanced activities were attributed to the interfacial transfer of photogenerated charges from the conductive band (CB) of TiO2 to NCQDs, leading to effective charge separation of TiO2.

Fabrication of g-C3N4/TiO2 composite photocatalyst with extended absorption wavelength range and enhanced photocatalytic performance

Abstract: Not only for utilizing both ultraviolet (UV) and visible light but also for enhancing photoinduced carriers separation capability, a composite photocatalyst composed of graphite-like carbon nitride (g-C 3 N 4 ) and TiO 2 has been successfully prepared by an acetic acid assisted sol–gel method combined with calcination process. The as-prepared g-C 3 N 4 /TiO 2 composite photocatalyst was characterized by using XRD, SEM, TEM, XPS, FT-IR spectra, UV-DRS and TGA. Combined XRD results with SEM images, it indicated that the obtained anatase TiO 2 nanoparticles dispersed well on the surface of g-C 3 N 4 sheets and the aggregation degree of TiO 2 nanoparticles could be effectively alleviated due to the introduction of g-C 3 N 4 . The results of UV-DRS further displayed that the optical absorption edge of g-C 3 N 4 /TiO 2 composites had an obvious red shift to the longer wavelength in comparison with pure TiO 2 . Profiting from the above-mentioned advantages, g-C 3 N 4 /TiO 2 composite showed excellent photocatalytic performance. Under visible light irradiation, all g-C 3 N 4 /TiO 2 composite samples had more excellent photodegradation performance than pure g-C 3 N 4 or TiO 2 , and the pseudo-first-order kinetic constant of methyl orange (MO) degradation on optimal g-C 3 N 4 /TiO 2 composite was 2.80 times as great as that on pure g-C 3 N 4 . The photodegradation performance of optimal g-C 3 N 4 /TiO 2 composite was also investigated under UV–vis light irradiation. Compared with the pure phase (TiO 2 or g-C 3 N 4 ), the composite photocatalytic capability was remarkably enhanced by coupling TiO 2 with g-C 3 N 4 , which mainly benefited from the effective separation of photoinduced electron–hole pairs and the extended optical absorption range, both owing to the heterojunction built-in between g-C 3 N 4 and TiO 2 .

Photocatalytic oxidation and simultaneous removal of arsenite with CuO/ZnO photocatalyst

Abstract: We investigated the photocatalytic oxidation and simultaneous removal of arsenite in synthetic aqueous As solution with high concentration. The process was performed by using CuO/ZnO nanoparticles under UV irradiation at around neutral pH. The effects of CuO addition, initial arsenite concentration and photocatalyst loading on the treatment efficiency were investigated. Adsorption of arsenic onto catalytic surface was evaluated with fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Batch results showed it that CuO has a significant effect on the photocatalytic performance of ZnO. The rate constant of photocatalytic oxidation with CuO(20%)/ZnO was 4 times better than those obtained with pristine ZnO. The removal amount (mg g −1 ) of arsenic increased with an increase in initial arsenic concentration. As(III) solution of 30 mg L −1 could be completely removed with photocatalyst of 0.67 g L −1 during 10 h of irradiation time. The maximum As(III) removal amount by photocatalytic oxidation and simultaneous removal was 6.5 times larger relative to that observed in the adsorption in dark. The excellent photocatalytic oxidation and high uptake performances make CuO/ZnO a potentially attractive candidate for the removal of As(III) from highly arsenic contaminated water.

Photocatalytic activity of TiO2, ZnO and Nb2O5 applied to degradation of textile wastewater

Abstract: In this work, photocatalysis was employed in the treatment of textile effluent from industrial laundry jeans using the catalysts TiO2 P25 (commercial), TiO2, ZnO and Nb2O5, under artificial UV irradiation. The parameters investigated were: pH of the solution and catalyst concentration. The photocatalytic activity was evaluated by means of kinetic efficiency (rate constant and half life time), thermodynamic (absorbance reduction at 228, 254, 284, 310, 350, 500 and 660 nm), COD reduction, mineralization in terms of the formation of inorganic ions (NH4+, NO3−, NO2−, SO42− and Cl−) and toxicity reduction (bioassays using Artemia salina). The photocatalytic degradation of textile effluent at pH 3.0 and catalyst concentration of 0.250 g L−1 showed the best results, being found 95.91%; 87.35%; 86.95% and 59.18% of absorbance reduction at 660 nm (λmax) after 300 min of artificial irradiation with TiO2 P25, Nb2O5, TiO2 and ZnO, respectively. TiO2 and Nb2O5 were responsible for the reduction of approximately 70 and 66% of COD and the photocatalytic activity of TiO2 was very close to TiO2 P25. In this sense, Nb2O5 becomes a promising alternative to replace the commercial TiO2 P25. Bioassays with Artemia salina confirmed the efficacy of the treatment, indicating that after photodegradation there was an expressive decrease in effluent toxicity for up to 3 times.

Efficient degradation of lindane in aqueous solution by iron (II) and/or UV activated peroxymonosulfate

Abstract: Degradation of lindane, a highly persistent and potentially carcinogenic pesticide, by iron (II) activated peroxymonosulfate (Fe 2+ /HSO 5 − ) was investigated. The efficiency of this process was found to increase with UV light irradiation, probably due to an improved regeneration of Fe 2+ for a fast generation of highly reactive OH and SO 4 − . A greater mineralization and dechlorination efficiency was also observed by UV/Fe 2+ /HSO 5 − , with a 92.2% total organic carbon removal and 96.4% chloride ion release after 180 min UV illumination. Removal of lindane by such a photochemical process was further promoted with increasing the initial concentration of either Fe 2+ (10–1000 μM) or HSO 5 − (50–1000 μM). The initial degradation rate of lindane increased while the observed pseudo first - order rate constant ( k obs ) decreased with increasing the initial concentration of lindane. Higher pH (>4) resulted in a lower efficiency of UV/Fe 2+ /HSO 5 − , attributable to the complexation or precipitation of Fe 2+ /Fe 3+ . A Fe 2+ level of 50 and 500 μM showed a comparable effect on lindane mineralization, probably due to the scavenging of SO 4 − and OH or the faster decomposition of the oxidant by excess Fe 2+ . Additionally, potential activation of Fe 2+ /HSO 5 − by fluorescence light was evaluated. Despite an enhanced degradation of lindane, no significant mineralization of lindane was observed. The results indicate that UV/Fe 2+ /HSO 5 − is effective and has a strong application potential for the degradation of lindane and other chlorinated pesticides.

Photocatalytic reduction of nitrate in seawater using C/TiO2 nanoparticles

Abstract: This study investigates the photocatalytic reduction of nitrate in seawater using carbon-modified titanium oxide (C/TiO2) nanoparticles under different reaction conditions. Formic acid was used as a sacrificial electron donor for inhibiting the mechanism of electron/hole recombination on the photocatalyst. Unmodified titanium oxide (TiO2) and reference TiO2 P25 photocatalysts were used for comparison. The elemental composition determined through energy dispersive spectroscopy (EDS) analysis evidenced the carbon modification for C/TiO2 nanoparticles. The optical bandgap energy for C/TiO2 has been remarkably reduced to 1.78 eV which in turn enhanced its performance towards the photocatalytic removal of nitrate under ultraviolet as well as natural sunlight irradiation. Factors including C/TiO2 loading, initial nitrate concentration, solution pH and hole scavenger concentration were studied to attain the optimal reaction conditions. The highest nitrate photocatalytic removal rate was obtained at catalyst loading of 0.5 g L−1, pH 3 and 0.04 M of formic acid. The kinetic study showed that the photocatalytic nitrate removal from seawater using carbon-modified titanium oxide was successfully expressed by the pseudo first-order reaction kinetics.

Structure related aggregation behavior of carotenoids and carotenoid esters

Abstract: Carotenoids are lipophilic natural pigments inherently aggregating in hydrophilic environments. Such molecular self-assembly is crucial for the proper functioning of biological systems. Although several carotenoid aggregates have been investigated in recent years, our study provided further insights into the influence of specific structural modifications. For this purpose, the aggregation of 12 structurally-related carotenoids was studied in hydrated polar solvents, thin films, and precipitates from saturated solutions by UV/vis and circular dichroism spectroscopy, light microscopy, point-dipole approximation and computational modeling. Regarding the acyclic ψ,ψ-carotene (lycopene), the monocyclic β,ψ-carotene (γ-carotene), and the bicyclic β,β-carotene (β-carotene), the replacement of acyclic ψ-end groups by β-rings was demonstrated to consecutively modulate spectroscopic properties and the intermolecular distance within the aggregate. The presence of at least one open chain ψ-end, as found in γ-carotene and lycopene, fostered the formation of strongly coupled H-aggregates, whereas β,β-carotene prevailed as J-aggregate. While the insertion of one hydroxyl function to the β,β-carotenoid molecule (β-cryptoxanthin) similarly yielded J-aggregates, the presence of two hydroxyl functions (zeaxanthin) led to tightly-packed H-aggregates due to the formation of intermolecular hydrogen bonds. When blocking at least one of these hydrogen bonding sites, as studied with short-, middle-, and long-chain acyl zeaxanthins, H-type switched to J-type aggregation, irrespective of the chain length of the acyl moiety. Moreover, ( Z )-isomerization was shown to prevent an ordered aggregation of carotenoid molecules. In brief, the optical properties and the aggregate structure of several most frequently occurring carotenoids are highly influenced by typical biosynthetic reactions, such as cyclization, isomerization, hydroxylation and esterification.

Immobilization of nanomaterials in PMMA composites for photocatalytic removal of dyes, phenols and bacteria from water

Abstract: Nanomaterials represent a possible solution to solve many of the current issues involving water quality, but several limitations exist for efficient applications, primarily concerning the dispersion of such nanomaterials in water, their recovery after water treatment and the resulting impact on human health and ecosystems. We present an approach based on the incorporation of several nanomaterials into polymeric composites as a valid solution to overcome these problems. We embedded active TiO 2 nanostructures in poly (methyl methacrylate) (PMMA), with the advantage of no need of recovery of the nanoparticles after water treatment. Furthermore, we combined titanium dioxide nanoparticles with single walled carbon nanotubes, as acceptor of electrons, and obtained a significantly higher photocatalytic efficiency under UV irradiation, compared to the systems with TiO 2 only. Photoactive materials even under visible light were synthesized thanks to the functionalization of the TiO 2 nanoparticle surface with meso- tetraphenylporphyrin-4,4′,4′′,4′′′-tetracarboxylic acid (TCPP) as dye sensitizer. We realized these polymeric nanocomposites by low-cost solution casting and evaluated their photocatalytic activity by degradation of some dyes and phenol in an aqueous medium. A significant antibacterial activity, measured through CFU (colony forming units) count using Escherichia coli as a model organism, is also reported.

Photocatalytic degradation of methyl orange and real wastewater by silver doped mesoporous TiO2 catalysts

Abstract: The photocatalytic activity of silver doped mesoporous TiO 2 catalysts was evaluated for water treatment. Doped catalysts were prepared by impregnation-reduction with citrate using various Ag loadings (0.5 wt%, 1.5 wt% and 3 wt%) and characterized by X-Ray powder diffraction (XRD), BET and diffuse reflectance UV–vis spectroscopy (DR/UV–vis). Silver doped TiO 2 catalysts retain the physical properties of mesoporous TiO 2 and its hexagonal order. The degradation of methyl orange (MO) as a model organic pollutant and of a real wastewater effluent was carried out under UVC, UVB, UVA and simulated solar light irradiation. Mesoporous TiO 2 showed a better activity than P25 TiO 2 and photocatalytic performance of silver doped mesoporous TiO 2 was enhanced compare to undoped. The mineralization of the organic pollutant was investigated by total organic carbon (TOC) measurements. The 0.5 wt%Ag/TiO 2 exhibited the highest TOC abatement both for the mineralization of MO and of real wastewater under UV and simulated solar light. Moreover, the catalyst was stable and could be used repeatedly. Therefore, this catalyst is promising for photocatalytic wastewater treatment under solar irradiation, leading to a cheap technology for developing countries.

Role of pH and pigment concentration for natural dye-sensitized solar cells treated with anthocyanin extracts of common fruits

Abstract: Natural dyes, extracted from cherry, blackberry, blueberry, raspberry and strawberry fruits, were used as sensitizers to fabricate dye-sensitized solar cells (DSSCs). The conversion efficiency (η%) ranged from 0.14 to 0.69. Specifically, the highest η% was obtained from the dye extracted with ethanol 70% from blueberry fruit and epicarp (1.13 and 0.75, respectively), without other chemicals, pH adjustments and thermal or purification processes. The absorbance spectra of the dyes and their photoelectrochemical performances demonstrated that anthocyanins (ANCs) were the most effectual component of the sensitizer for DSSC. To check the affinity of the dyes for the TiO2 a new adsorption/desorption procedure was established. The comparison of the percentage distribution of each anthocyanin class in blueberry epicarp dye, before its adsorption and after its recovery from TiO2 powder, showed a better sensitizing performance of delphinidine derivatives compared to the other ANCs.

Photodegradation of methyl violet 6B and methylene blue using tin-oxide nanoparticles (synthesized via a green route)

Abstract: Green synthesis of tin dioxide nanoparticles were developed by microwave heating method using 1:1, 1:2 and 1:3 volumetric ratio of water and glycerol, wherein glycerol acts as a good complexing as well as capping agent. This method resulted in the formation of spherical SnO 2 nanoparticles with an average diameter ∼8–30 nm. The synthesized SnO 2 NPs were characterized by transmission electron microscopy (TEM), selected area electron diffraction (SAED) and Fourier transformed infrared spectroscopy (FT-IR). The optical properties were investigated using UV–vis spectroscopy. The photocatalytic activity of synthesized SnO 2 NPs was evaluated for the degradation of two different toxic dyes namely, Methyl Violet 6B and Methylene blue dye under direct sunlight.

Nitrous acid (HONO): An emerging indoor pollutant

Abstract: Nitrous acid (HONO) is an emergent household pollutant exhibiting adverse health effects. It can be easily photodissociated by the solar light penetrating through the windows leading to an important production of hydroxyl radical (OH) which in turn controls the oxidative capacity of indoor atmospheres. Indeed, recent campaign performed in a school classroom in Marseille, France revealed high levels of OH radicals in order of 10 6 cm −3 which were directly associated with the photolysis of HONO. Chamber experiments confirmed that photolysis of HONO is the main source of OH radicals indoors. Very recent laboratory measurements have demonstrated that the photo-enhanced reaction of NO 2 on various surfaces commonly found indoors is a powerful source of HONO indicating that indoor surfaces are not only physical but also photochemical substrates that play an active role in the enhancement of the production of HONO indoors. These results provided a significant contribution towards a comprehensive understanding of HONO chemistry indoors, a knowledge that should be implemented in photochemical models in order to properly describe the indoor air chemistry.

Visible light photo-induced antibacterial activity of TiO2-MWCNTs nanocomposites with varying the contents of MWCNTs

Abstract: Nanocrystalline TiO 2 and MWCNTs are important functional materials that have received considerable research interest in the last few decade. In this work, the composites of TiO 2 nanoparticles with varying amount of functionalized MWCNTs were prepared by using a solution-based method. The physico-chemical properties of these composites were studied in connection with their antibacterial activity. TiO 2 particles have non-spherical shape with size in the range of 8–15 nm; which were confirmed through TEM analysis and these particles were well hosted on the surface of MWCNTs. The tuning of optical band gap of nanocomposites was studied by using DR UV-visible spectroscopy. The photocatalytic inactivation of Escherichia coli and Staphylococcus aureus using TiO 2 -MWCNTs nanocomposites in the presence of visible light (λ > 420 nm) has been carried out. These nanocomposites show efficient antibacterial activity under visible light illumination, whereas bare TiO 2 nanoparticles did not show any inhibitory effect on bacteria under visible light exposure. These results suggest that UV light or TiO 2 alone is not effective for photocatalytic disinfection applications. Also, cytotoxicity study reveals that the nanocomposites show better cell viability than bare TiO 2 nanoparticles. Overall, the experimental results suggest that TiO 2 -MWCNTs nanocomposites have been developed as efficient antibacterial agents against a wide range of microorganisms to prevent and control the persistence and spreading of bacterial infections.

A new colorimetric and turn-on fluorescent chemosensor for Al3+ in aqueous medium and its application in live-cell imaging

Abstract: A new simple Schiff-base ligand 2-Hydroxy-1-naphthaldehyde-(2-pyridyl) hydrazone (HL) was synthesized and characterized as a fluorescent probe. In aqueous solution containing 10% ethanol (Hexamethylenetetramine-HCl buffer, pH5.3), HL selectively binds Al3+to form a 1:1 ligand/metal complex, resulting in a color change from colorless to yellow–green and a significant fluorescence enhancement at 454 nm. The addition of EDTA quenches fluorescence of the HL·Al3+ complex, indicating that HL serves as a reversible chemosensor for Al3+. Under the optimum conditions, the dynamic range of the system was found to be linear up to 4.0 × 10−6 M Al3+ ions with a limit of detection of 36.6 nM. The probe is very effective for detection of intracellular Al3+ through fluorescence microscopic imaging.

Facile synthesis of highly efficient graphitic-C3N4/ZnFe2O4 heterostructures enhanced visible-light photocatalysis for spiramycin degradation

Abstract: Highly efficient and easily recycled visible-light-driven g-C 3 N 4 /ZnFe 2 O 4 heterostructured photocatalysts were prepared by a simple hydrothermal synthesis method. The composition, structure, morphology, and optical absorption properties of the as-prepared g-C 3 N 4 /ZnFe 2 O 4 composites were characterized by X-ray diffraction, scanning electron and transmission microscopy, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectroscopy, Photoluminescence (PL) spectra, Brunauer–Emmett–Teller (BET) and FTIR spectra, respectively. The result shows that we have found a phenomenon of different proportions of the g-C 3 N 4 /ZnFe 2 O 4 composition, 1:2 fraction has the highest rate of the degradation of spiramycin under visible light irradiation. The composite catalyst has better photocatalytic activity, the compound has the characteristics of good stability and easy recycling.

Pluronic® mixed micelles as efficient nanocarriers for benzoporphyrin derivatives applied to photodynamic therapy in cancer cells

Abstract: In this study we attempted to develop Pluronic micelles delivering the photodynamic therapy photosensitizers benzoporphyrin derivatives (BPD). The BPD A-ring (BPDMA or Verteporfin ® , the active drug of FDA/USA approved Visudyne ® ), its regioisomer ring-B (BPDMB, not used in Visudyne ® formulation due its poor solubility) and a BPDMA/BPDMB mixture (BPD-Mixt) were formulated in Pluronic P123 or F127 as well as P123/F127 mixed micelles at two different mass ratios. P123/F127 presented the lowest critical micelle concentration showing high stability due synergistic aggregation of P123 and F127. Mixed micelles allowed the encapsulation of BPD as monomers enhancing their photophysical properties and stability during time even under diluted conditions. High loading was attributed to the strong hydrophobic affinity of BPD for micelle core especially in the binary system due synergistic aggregation of P123 and F127 demonstrating the high potential of these micelles to encapsulate hydrophobic drugs. The in vitro assays showed a photo-activity of BPD-Mixt comparable to that of BPDMA against HeLa and A549 cancer cells under red light. The use of BPD-mixed formulations avoids the complex separation steps of these regioisomers and implies in cost reduction. The proposed system allies costs reduction and photodynamic efficiency, which stimulates further development on this nanosystem and may be of clinical interest for cancer PDT.

Enhanced photocatalytic activity of Zn-doped dendritic-like CdS structures synthesized by hydrothermal synthesis

Abstract: In this work, a series of Zn-doped dendritic-like CdS structures have been synthesized by a simple hydrothermal method. The as-prepared samples have been characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy dispersive spectrometer (EDS), ultraviolet-visible (UV–vis) and room temperature photoluminescence (PL). Their photocatalytic activities have been evaluated by the photocatalytic degradation of methylene blue (MB) under simulated visible-light irradiation. XRD results indicate that the phase of Zn:CdS was hexagonal phase. XRD and EDS results indicate that Zn 2+ was successfully introduced into CdS. FESEM results indicate that low Zn 2+ doping concentration can keep the dendritic-like CdS structures, but the morphologies of Zn:CdS are flower-like structures at high Zn 2+ doping concentration. UV–vis results indicate that doping Zn 2+ can be used to improve the absorbing capability of dendritic-like CdS for visible light, and the content of Zn 2+ affects the band gap. PL results indicate that doping Zn 2+ can be used to improve the luminescence property of dendritic-like CdS. Photocatalytic results indicate that doping Zn 2+ is conducive to improve the photocatalytic efficiency of dendritic-like CdS to MB, and the highest degradation rate is 92.8%. And the photocatalytic mechanism of Zn-doped dendritic-like CdS to MB is also described.

Thioxanthone-benzothiophenes as photoinitiator for free radical polymerization

Abstract: Photoinitiators for free radical polymerization based on the thioxanthone chromophore that contains benzothiophene were synthesized and characterized. Compared to thioxanthone, these compounds show a bathochromic shifted absorption up to ∼460 nm. High quantum yields for intersystem crossing generate sufficient amounts of triplet states. Initiator radicals are generated by reaction of the triplet states with tertiary amines, such as diethanolamine with high rate constants (2–6 × 10 9 M −1 s −1 ) as determined by laser flash photolysis. Photoinitiated polymerization experiments of MMA showed efficient polymerization with initiator concentrations as low as 0.1 mM.

Hollow cobalt ferrite–polyaniline nanofibers as magnetically separable visible-light photocatalyst for photodegradation of methyl orange

Abstract: Hollow cobalt ferrite–polyaniline nanofibers (CoFe 2 O 4 –PANI) functioning as a photocatalyst were prepared by using electrospinning technique, followed by calcination and in-situ chemical oxidative polymerization. The hollow CoFe 2 O 4 –PANI nanofibers with one dimensional (1D) structure provide well-developed mesoporous structure and enhanced electrical conductivity. The hollow CoFe 2 O 4 –PANI nanofibers consisted of hollow core-double shell nanostructure, which has CoFe 2 O 4 as inner shell and PANI as outer shell. The hollow CoFe 2 O 4 –PANI nanofibers coated with PANI nanograins facilitate the optical properties by easily capturing visible light. The intensive visible light absorption and effective charge separation lead to a remarkable improvement of visible light photocatalysis owing to the heterojunction built between CoFe 2 O 4 and PANI. The pseudo-first-order kinetic constant of photocatalytic degradation of the methyl orange (MO) dye under visible light irradiation with CoFe 2 O 4 –PANI was 80 times greater than CoFe 2 O 4 . This evidence shows the advantage of the unique core–shell mesoporous structure in the CoFe 2 O 4 –PANI for efficient photocatalysis. The recovery ratio is almost the same after three cycles under visible light irradiation, displaying the excellent characteristics of magnetic separation for CoFe 2 O 4 –PANI hollow nanofibers.

Fluorescence behavior of nanoconjugates of graphene quantum dots and zinc phthalocyanines

Abstract: Graphene quantum dots (GQDs) and zinc phthalocyanines interactions in different modes (covalent and non-covalent) are reported in this study. GQDs were covalently attached to the following complexes: zinc tetraamino phthalocyanine (ZnTAPc) via amide coupling, zinc tetracarboxyphenoxy Pc (ZnTCPPc) (π–π interaction) and cationic zinc tetrapyridiloxy Pc (ZnTmPyPc) (ionic interaction). GQDs fluorescence was quenched in the presence of the ZnPc derivatives. The nanoensembles of GQDs–ZnPcs showed stimulated emissions of the ZnPcs. The suggested quenching mechanism is through Forster resonance energy transfer (FRET). These novel nanoensembles hold promise for various optical and luminescence based applications.

Towards a large scale aqueous sol-gel synthesis of doped TiO2: Study of various metallic dopings for the photocatalytic degradation of p-nitrophenol

Abstract: In this paper, an easy aqueous sol-gel synthesis developed previously by Mahy et al. [1] is adapted to produce highly active TiO2 catalysts doped with Fe3+, Ag+, Cu2+, Zn2+, Cr3+, Al3+, Mn2+, and Co2+ ions and Pt metallic nanoparticles. Samples are characterized by inductively coupled plasma–atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), Mossbauer spectroscopy, transmission electron microscopy (TEM), nitrogen adsorption–desorption measurements and diffuse reflectance spectroscopy measurements. Results show that the samples are composed of anatase-brookite TiO2 nanoparticles with a spherical shape and mean diameter of around 5–8 nm and a surface area of between about 150 − 250 m2 g−1. In each doped sample, the dopant is present in the form added during the synthesis, given that the sample has not undergone any particular treatment. Photoactivity tests show improvement in catalyst activity for Fe3+, Ag+, Cu2+, Zn2+, and Al3+ ion and Pt metallic nanoparticle dopants, while a decrease of activity is obtained for Cr3+, Mn2+ and Co2+ ion dopants. For some dopants, the activity of TiO2 doped with metallic ions and synthesized from the aqueous sol-gel process is equal or superior to the activity of the commercial photocatalyst Degussa P25. Some mechanisms are proposed to explain these modifications of activity with doping. Furthermore, cost comparison at laboratory scale showed that Zn and Cu nitrate salt dopings are clearly less expensive for a halogen light (UV/visible) or low energy light enhanced catalyst and may be considered for industrial applications. Using this method, a large scale Zn-doped TiO2 photocatalyst is synthesized with properties homologous to the lab-scale product. Results show that the aqueous sol-gel synthesis developed previously can be easily adapted for doping in order to produce an up-scalable synthesis.

Excited state behavior of benzoxazole derivatives in a confined environment afforded by a water soluble octaacid capsule

Abstract: This feature article presents a brief description of the excited state intramolecular proton transfer mechanism (ESIPT), describes the solvent dependence of the ESIPT phenomenon and present the potential applications that can be envisaged for these fluorophores. Photophysics of three dye molecules exhibiting ESIPT were examined free in solution and within a water soluble supramolecular host, octaacid (OA) by steady-state and time resolved fluorescence emission techniques. Inclusion of the above dyes within OA was confirmed by 1H NMR spectra. The free and octaacid complexed dyes had electronic absorption in the UV region. Within the OA container the fluorophores showed fluorescence emission similar to that in benzene, dichloromethane and acetonitrile. Moreover, the observed large Stokes’ shift in the emission of the dyes when confined within OA capsule was unlike that in aqueous medium. The results suggest that a confined medium is a powerful tool to tailor the fluorescence emission of ESIPT compounds in aqueous media.

D-A-π-D Synthetic approach for thienyl chalcones – NLO – a structure activity study

Abstract: With the growing interest for organic molecules in Nonlinear Optical (NLO) applications, we have synthesized nine novel thienyl chalcones based on the D-A-π-D design. In order to establish the identity, these have been characterized in detail. Having followed the design based synthetic route, we have focused on two prime criteria for comparison; namely second harmonic generation (SHG) and non-linear absorption. In this work the role of the electron withdrawing groups, electron donating groups and extended conjugation, have been extensively studied vis-a-vis the NLO properties. The change in these properties by virtue of the molecular structure has been elucidated in this work as the structure activity relationship. Optical nonlinearity is studied using ultrafast (100 fs) laser pulses at 800 nm, employing the open aperture Z-scan technique. The compounds exhibit large effective three-photon absorption (3PA) coefficients, in the order of 10−28 m3/W2. These observations show that these compounds possess potential for application in all-optical limiting and switching devices.

Photoperoxi-coagulation using activated carbon fiber cathode as an efficient method for benzotriazole removal from aqueous solutions: Modeling, optimization and mechanism

Abstract: In this research, benzotriazole (BTA) was removed from aqueous solution using photoperoxi-coagulation (PPC) in which activated carbon fiber (ACF) was used as a cathode. Box-Behnken design was used to optimize and analyze four parameters i.e. time, applied current, initial BTA concentration and UV light power. According to the results, the R-squared and adjusted R-squared were 0.982 and 0.964, respectively, implying that the model was statistically suitable. It was shown that under the optimal condition for BTA removal i.e. 60 mg/L initial BTA concentration, 50 min time, 200 mA applied current and UV light power of 12W, the efficiency of the PPC process was maximum (97.8%). The removal mechanisms were determined and their results showed that the oxidation mechanism of photoperoxi-coagulation process had a more contribution in BTA removal in comparison with coagulation mechanism. The results of scavenging experiments also confirmed the determined removal mechanisms. Synergistic effect was observed in PPC while first order rate constant of PPC was 2.7 fold more than that of sum of each mechanism. The removals of TOC and COD were 64.5% and 76.3% respectively. Average oxidation state and carbon oxidation state of BTA solution were increased after PPC process indicating biodegradability improvement indirectly.

Coupling photocatalysis with ozonation for enhanced degradation of Atenolol by Ag-TiO2 micro-tube

Abstract: Ag-TiO 2 hollow micro-tube was successfully prepared using cotton fiber as template. It was used to photocatalytic ozonation of Atenolol (ATL) in present study (UV/Ag-TiO 2 /O 3 ). The results showed that 2% Ag-TiO 2 possessed the best catalytic performance for ATL mineralization and had a distinct advantage compared with bare TiO 2 . The variation of ozone concentration confirmed that Ag-TiO 2 hybrid not only increased the ozone amount in the solution, but also resulted in a fast decompose rate in the photocatalytic ozontion process. It meant that Ag act as a good photo-generated electron acceptor for photocatalysis and a beneficial decomposition center for ozone. Consequently, the synergistic effect of photocatalytic ozonation was enhanced and the mineralization of ATL was promoted. The recycle experiments proved that synthesized 2% Ag-TiO 2 micro-tube owned excellent stability in photocatalytic ozonation coupling system. In addition, the effect of pH value, doping amount of Ag on the ATL degradation was also investigated. It is indicated that 2% Ag-TiO 2 is an excellent catalyst for the photocatalytic ozonation of ATL.