Showing papers in "Journal of Photochemistry and Photobiology A-chemistry in 2011"
TL;DR: The photo-to-electric conversion efficiency of the DSC sensitized by the ethanol extract of mangosteen pericarp without purification reached 1.17%.
Abstract: Twenty natural dyes, extracted from natural materials such as flowers, leaves, fruits, traditional Chinese medicines, and beverages, were used as sensitizers to fabricate dye-sensitized solar cells (DSCs). The photoelectrochemical performance of the DSCs based on these dyes showed that the open circuit voltages (Voc) varied from 0.337 to 0.689 V, and the short circuit photocurrent densities (Jsc) ranged from 0.14 to 2.69 mA cm −2 . Specifically, a high Voc of 0.686 V was obtained from the dye extracted from mangosteen pericarp sensitizer. The photo-to-electric conversion efficiency of the DSC sensitized by the ethanol extract of mangosteen pericarp without purification reached 1.17%. Moreover, various components of the ethanol extract were extracted using different organic solvents. The photoelectrochemical performance of these extracts demonstrated that rutin was the most effectual component of the sensitizer for DSC. © 2011 Elsevier B.V. All rights reserved.
503 citations
TL;DR: In this paper, the quantum yields for two actinometers have been determined using a tunable laser light source at the National Institute of Standards and Technology (NIST) in Gaithersburg, MD.
Abstract: The quantum yields for two actinometers have been determined using a tunable laser light source at the National Institute of Standards and Technology (NIST) in Gaithersburg, MD. The power of this light source has been calibrated against an absolute cryogenic radiometer, considered accurate with an uncertainty better than 0.1% at a coverage factor k = 2. The quantum yield at 253.7 nm for the ferrioxalate actinometer was found to be 1.38 ± 0.03, which compares favorably with the value 1.40 ± 0.03 determined by Goldstein and Rabani. The quantum yield at 253.7 nm for the KI/KIO3 actinometer was found to be 0.69 ± 0.02 at 23.5 °C. Again this compares favorably with 0.72 ± 0.03 determined by Goldstein and Rabani and 0.73 ± 0.02 determined by Rahn et al. Based on the determinations to date, including the present investigation, the recommended values for the quantum yields at 253.7 nm are 1.39 ± 0.02 (temperature independent) for the ferrioxalate actinometer and [(0.71 ± 0.02) + (0.0099 ± 0.0004)(t − 24)] for the KI/KIO3 actinometer, where t is the temperature (°C) of the actinometer solution. Finally, a protocol is recommended for the use of the KI/KIO3 actinometer to calibrate radiometer detectors at 253.7 nm.
224 citations
TL;DR: In this article, a comparative study of the photodeposition of Pt, Au and Pd under the same experimental conditions on pre-sulphated and non sulfated TiO2 was performed.
Abstract: A comparative study of the photodeposition of Pt, Au and Pd under the same experimental conditions onto pre-sulphated and non-sulphated TiO2 was performed. Morphological and surface characterisation of the samples as well as photocatalytic activity for phenol photooxidation was studied. The influence of sulphate pre-treatment on the deposits size and dispersion onto the TiO2 surface, and photodeposition yields with the different metals were also analysed. The photocatalytic activity of the doped materials was then investigated, observing that catalytic behaviour can be correlated to physical characteristics of the samples determined by (XRD) X-ray diffraction, (XPS) X-ray photoelectron spectroscopy, (XRF) X-ray fluorescence spectrometry and (TEM) transmission electron microscopy. Sulphate pre-treatment was found to influence both the level of dispersion and the size of metal clusters on the TiO2 surface. Sulphation and metallisation of samples was found to produce a synergistic enhancement in photoactivity for the degradation of phenol. The photoactivity of the catalysts with respect to the doped metal species was ordered Pt > Pd > Au.
163 citations
TL;DR: In this article, mesostructrured CeO 2 -TiO 2 nanoparticles with different contents have been successfully synthesized using ionic liquid (1hexadecane-3methylimidazolium bromide, C 16 MIM + Br − ) as a template by a hydrothermal method.
Abstract: Mesostructrured CeO 2 –TiO 2 nanoparticles with different CeO 2 contents have been successfully synthesized using ionic liquid (1-hexadecane-3-methylimidazolium bromide, C 16 MIM + Br − ) as a template by a hydrothermal method. The prepared materials were characterized by means of X-ray diffraction (XRD), nitrogen adsorption–desorption, transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectra analysis. The obtained CeO 2 –TiO 2 materials exhibit large specific surface area and uniform pore sizes. Introduction of CeO 2 species can effectively extend the spectral response from UV to visible area and enhance the surface hydroxyl groups of the mesoporous TiO 2 . The CeO 2 –TiO 2 nanocomposites show high photocatalytic activity in the degradation of the p -chlorophenol aqueous solution under the UV or visible irradiation.
123 citations
TL;DR: In this paper, the photovoltaic performances of four ruthenium trisbipyridine complexes in NiO-based dye-sensitized solar cells (DSSC) were investigated.
Abstract: In this contribution, we investigate the photovoltaic performances of four ruthenium trisbipyridine complexes in NiO based dye-sensitized solar cells (DSSC). The four complexes differ by the nature of the anchoring groups, which are either carboxylic acids, biscarbodithioic acids catechol or methyl phosphonic acids. The properties of the dyes were studied by electrochemistry, absorption and emission spectroscopies, surface binding measurements, time-dependent density functional theory (TDDFT) as well as by determining their photoconversion efficiencies in DSSCs under AM 1.5. We show that these simple dyes are relatively efficient sensitizers in NiO-based DSSCs, since some of them give photoconversion efficiencies comparable to that of a standard benchmark dye coumarin C343. We also demonstrate that both catechol and methyl phosphonic acid are promising binding groups for NiO sensitizers to replace classical carboxylic acids in NiO sensitizers and finally we report molecular design rules to elaborate a new generation of better performing ruthenium polypyridine sensitizers.
123 citations
TL;DR: In this article, the performance and selectivity of terephthalic acid (TA) as a trapping molecule for the laboratory quantification of photogenerated 2-hydroxyterephthalric acid in synthetic water (where the organic and inorganic concentration is perfectly controlled) was investigated.
Abstract: In the present study, we investigated the performance and selectivity of terephthalic acid (TA) as a trapping molecule for the laboratory quantification of photogenerated OH in synthetic water (where the organic and inorganic concentration is perfectly controlled), adopted as a proxy of natural atmospheric water (i.e. cloud droplets). TA reacts with OH to yield 2-hydroxyterephthalic acid (TAOH). First, we focused our investigation on the reactivity of TA as a function of pH and temperature of laboratory-made solutions, by using nitrate and hydrogen peroxide as photochemical OH sources. For the pH dependence of the TAOH formation yield ( Y TAOH ), by fitting data using linear regression we obtained the relationship Y TAOH = (0.0248 ± 0.0059)pH + (0.046 ± 0.035) at T = 288 K, in the pH range 3.9–7.5. For the temperature dependence we got Y TAOH = (0.0059 ± 0.0011) T − (1.50 ± 0.31), between 278 and 303 K at pH 5.4. Furthermore, the performance and selectivity of TA were assessed in the presence of different photochemical OH sources (nitrate and H 2 O 2 ) and scavengers (alcohols and carboxylic acids) at variable concentrations. These species are naturally present in the atmospheric aqueous phase. From these experiments we obtained the second-order reaction rate constant between TA and OH, k TA, OH = (4.0 ± 0.1) × 10 9 M −1 s −1 in aerated solution, at pH 6.0 and 293 ± 2 K.
121 citations
TL;DR: In this article, the photoinitiated polymerization of a commercial polyether acrylate oligomer with 2,2-dimethoxy-1, 2-phenyl acetophenone (DMPA) as radical photo-initiator was studied by using real-time infrared spectroscopy (RTIR).
Abstract: The photoinitiated polymerization of a commercial polyether acrylate oligomer with 2,2-dimethoxy-1,2-phenyl acetophenone (DMPA) as radical photoinitiator was studied by using real time infrared spectroscopy (RTIR). First, the effect of light intensity, photoinitiator concentration and reactive diluent (1,6-hexanediol diacrylate, HDDA) on reaction was investigated in homogeneous phase. The maximum conversion was obtained for 0.5 wt% of DMPA and 10–15 vol% of HDDA. Then, ceramic fillers (SiO 2 , Al 2 O 3 , ZrO 2 and SiC) were added to the acrylate oligomer in order to be used later as reactive suspensions for stereolithography. The influence of the nature, size and concentration of these fillers on the kinetics and the final conversion was characterized. The index ratio between filler and organic matrix as well as the intergranular phase viscosity were found to be the main parameters governing the reaction in heterogeneous phase.
114 citations
TL;DR: In this article, photodegradation of 17β-estradiol (E2), an endocrine disrupting hormone which is commonly released into aquatic environments, was investigated under simulated sunlight (290-700nm) using a solar simulator in the presence of several natural water constituents including NO3−, Fe3+, HCO3+, humic acid and turbidity.
Abstract: Photodegradation of the natural steroid 17β-estradiol (E2), an endocrine disrupting hormone which is commonly released into aquatic environments, was investigated under simulated sunlight (290–700 nm) using a solar simulator in the presence of several natural water constituents including NO3−, Fe3+, HCO3−, humic acid and turbidity. The E2 degradation followed pseudo-first-order kinetics, with the rate constant decreasing slightly with increasing initial constituent concentration while increasing with the square root of solar intensity in the region of 25–100 mW cm−2. The rate of mineralization based on the total organic carbon (TOC) reduction was always lower than E2 degradation, although the TOC of the solution decreased steadily with irradiation time. In the presence of NO3−, Fe3+, and humic acid, the photodegradation rate increased significantly, attributed to photosensitization by the reactive species, while HCO3− slowed down the degradation rate because of OH scavenging. Turbidity also reduced the photodegradation of E2 by decreasing light transmittance due to attenuation. The solution pH also had a considerable effect on the rate with maximum degradation occurring around a neutral pH of 7.
110 citations
TL;DR: In this paper, the photocatalytic mechanism was proposed on the basis of the fact that the Ag NPs are photoexcited due to plasmon resonance, and then charge separation was accomplished by the transfer of photo-excited electrons from the Ag nPs to the TiO2 conduction band and the simultaneous formation of OH radical and Cl0, which cause the degradation of organic pollutants.
Abstract: The Ag/AgCl/TiO2 nanocomposite thin films are prepared on the pre-coated SiO2 soda-lime glass substrates by a sol–gel method for depositing TiO2 films, and then loaded with Ag/AgCl nanoparticles (NPs) by an impregnating precipitation photoreduction method. The as-prepared composite thin film exhibits a highly visible-light photocatalytic activity for degradation of 4-chlorophenol (4-CP) in water. The photocatalytic mechanism is proposed on the basis of the fact that the Ag NPs are photoexcited due to plasmon resonance, and then charge separation is accomplished by the transfer of photoexcited electrons from the Ag NPs to the TiO2 conduction band and the simultaneous formation of OH radical and Cl0, which cause the photocatalytic degradation of organic pollutants. The proposed mechanism is further confirmed by the detection of hydroxyl radicals. On the other hand, 4-CP can also be oxidized directly by plasmon-induced h+ (or Ag+) on Ag NPs, thereby accelerating the photooxidized Ag NPs back to their initial state. Therefore, the Ag NPs can be rapidly regenerated and the Ag/AgCl/TiO2 system remains self-stability.
109 citations
TL;DR: An improved separation technique employing medium pressure liquid chromatography is used to purify betanin from beet root for use as a sensitizer in a TiO2-based dye-sensitized solar cell.
Abstract: An improved separation technique employing medium pressure liquid chromatography is used to purify betanin from beet root for use as a sensitizer in a TiO2-based dye-sensitized solar cell. The use of a blocking layer and treatment by TiCl4 were explored in order to optimize the performance of the solar cell, resulting in energy conversion efficiencies as high as 2.7%, the highest yet recorded for a DSSC containing a single unmodified natural dye sensitizer. The fluorescence spectrum of betanin in aqueous solution is reported as a function of added colloidal TiO2, demonstrating efficient electron injection. Quenching of betanin fluorescence by TiO2 permits the observation of its resonance Raman spectrum, reported here for the first time and discussed in light of recent theoretical work on the electronic structure of betanin. We report the results of stability tests under continuous illumination and suggest ways to extend the lifetime of these solar cells.
108 citations
TL;DR: In this paper, the authors used gold nanoparticles (GNPs) as probes to evaluate the pH and temperature-induced conformational changes of Bovine Serum Albumin (BSA) adsorbed on their surface.
Abstract: In this work we used gold nanoparticles (GNPs) as probes to evaluate the pH- and temperature-induced conformational changes of Bovine Serum Albumin (BSA) adsorbed on their surface. UV–vis and fluorescence spectroscopy were employed to monitor the adsorption and binding modes of BSA on GNPs. The results suggest that GNPs quenched the fluorescence emission of tryptophan residues of BSA mainly through a static mechanism, the binding constant (Kb) being sensitive to the pH values. The Stern–Volmer quenching constant (KSV) and the corresponding thermodynamic parameters (ΔH, ΔS and ΔG) were also determined. In addition, the results concerning the thermally induced conformation changes of BSA, before and after interfacing with GNPs, demonstrate the dependence of the protein conformational transition temperature on pH. Moreover, the linking between BSA and GNPs was monitored by surface-enhanced Raman scattering (SERS), assessing the influence of pH on this specific nano–bio interface.
TL;DR: In this paper, the photophysical properties of low symmetry carboxy phthalocyanines with glutathione capped gold nanoparticles (GSH-AuNPs) were investigated.
Abstract: This work reports on conjugation of low symmetry Ge (GeMCPc), Ti (TiMCPc) and Sn (SnMCPc) carboxy phthalocyanines with glutathione capped gold nanoparticles (GSH-AuNPs). The photophysical behaviour of the novel phthalocyanines–GSH-AuNPs conjugate was investigated and compared to the monocarboxy Pcs and to the mixture of Pc with GSH-AuNPs without a chemical bond. Blue shifting of Q band of the phthalocyanines was observed on linking to GSH-AuNPs. An improvement in triplet lifetimes was obtained for all the MPcs–GSH-AuNPs-linked conjugates compared to the MPcs alone. The highest triplet quantum yield of 0.75 and the longest triplet lifetime of 130 μs were obtained for the GeMCPc–GSH-AuNPs-linked conjugate. Fluorescence quantum yields and lifetimes were low for the conjugates due to quenching by the nanoparticles.
TL;DR: In this paper, the amine linked type II photoinitiator (BPDEA) was used for photopolymerization of mono and multi-acrylate monomers in the absence of a coinitiator.
Abstract: Synthesis of amine linked type II photoinitiator (BPDEA) was achieved in high yields and photopolymerization of mono and multiacrylate monomers was performed with this photoinitiator in the absence of a coinitiator. BPDEA is more effective than benzophenone (BP) with the coinitiator (MDEA) system under inert atmosphere in photoinduced free radical polymerization of acrylates.
TL;DR: In this article, photoactive TiO2 was directly obtained by sol-gel method or from titanium dioxide/activated carbon composite (TiO2/AC), then calcinated under air at 700°C.
Abstract: Photoactive TiO2 was directly obtained by sol–gel method or from titanium dioxide/activated carbon composite (TiO2/AC), then calcinated under air at 700 °C. The obtained materials were characterized by N2 adsorption (77 K), X-ray diffraction (XRD), diffuse reflectance UV-vis spectroscopy (UV/DRS) and transmission electron microscopy (TEM). The solid prepared from (TiO2/AC) composite was found to be mainly pure anatase phase with SiO2 and Fe2O3 traces, whereas, pure TiO2 was predominantly rutile. Adding activated carbon increases the surface area of photocatalyst, reduces the grain size of titania particles and causes a blue shift of the light absorption spectrum due to the quantization of band structure. Photocatalytic activity was tested and compared with that of TiO2 Degussa P25 on the degradation of methylene blue (MB) in an aqueous solution under visible irradiation. TiO2(AC-700) catalyst was found to be two times more active than TiO2-P25.
TL;DR: In this paper, the role of surface hydration in the conversion of nitric oxide, NO, under irradiation of UVA light is highlighted and a model based on a rapid initial NO reactive photoadsorption is used to interpret the high initial removal of NO which develops in a lower NO conversion transient regime.
Abstract: The paper highlights the role of TiO2 surface hydration in the conversion of nitric oxide, NO, under irradiation of UVA light. H2O desorption thermokinetics of TiO2 surface is studied to characterise the state of water on TiO2 and identify criteria for potential thermal dehydration. Hydrated and dehydrated surfaces are then studied for their ability to oxidise gaseous NO and emphasise the overall role of H2Oads and OHads groups and the differences between initial and transient regimes before reaching steady state. A model based on a rapid initial NO reactive photoadsorption is used to interpret the high initial removal of NO which develops in a lower NO conversion transient regime. The development of NO and NO2 profiles as a function of time coupled with the total NOx balance in the gas phase, also offer ways to understand deactivation phenomena at the catalyst surface.
TL;DR: In this article, the authors reported facile fabrication of polypyrrole (Ppy)/functionalized multiwalled carbon nanotube ( f -MWCNT) nanocomposite films on rigid fluorine-doped tin oxide (FTO) and flexible ITO-coated polyethylene naphthalate (PEN) substrates by a drop casting method, and their application as counter electrodes in dye-sensitized solar cells.
Abstract: This paper reports facile fabrication of polypyrrole (Ppy)/functionalized multiwalled carbon nanotube ( f -MWCNT) nanocomposite films on rigid fluorine-doped tin oxide (FTO) and flexible ITO-coated polyethylene naphthalate (PEN) substrates by a drop casting method, and their application as counter electrodes in dye-sensitized solar cells (DSSCs). The electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measurements of this solution processed Ppy/ f -MWCNT nanocomposite film display good catalytic performance for I 3 − /I − solution. The photoelectric conversion efficiency of the DSSCs with the Ppy/ f -MWCNT counter electrodes on FTO and PEN substrates reaches 7.02% and 4.04%, respectively, under AM1.5 illumination of 100 mW cm −2 , comparable to that of the DSSCs based on sputtered Pt electrodes. The fabrication method of such counter electrodes is simple under room temperature and can be applicable in large-scale production.
TL;DR: In this paper, the first in vivo observation of chlorophyll a fluorescence quenching induced by gold nanoparticles was reported, using a portable optical fiber-based spectrofluorimeter.
Abstract: To our knowledge, the present work reports the first in vivo observation of chlorophyll a fluorescence quenching induced by gold nanoparticles. Laser-induced fluorescence spectroscopy was used to collect in vivo chlorophyll a fluorescence, using a portable optical fiber-based spectrofluorimeter. Fluorescence quenching was observed for all plants submitted to the gold nanoparticle treatment, and both excitation wavelengths, 405 nm and 532 nm, were capable of detecting interactions between gold nanoparticles and plants. Our results also suggest that gold nanoparticles were able to translocate and accumulate in the soybean plants after seed inoculation.
TL;DR: In this paper, Ag oxide-titania films were shown to be active photocatalysts under visible light conditions as well as displaying white light induced superhydrophilicity.
Abstract: Antimicrobial films containing silver nanoparticles on a titania substrate were prepared and shown to have marked visible light photocatalytic properties. The films could be transformed from purple (silver oxide) to orange (silver) by 254 nm, 365 nm or white light radiation and the process reversed when the films were stored in air and in the dark. The films were characterized by XRD, Raman, AFM, SEM, EDX, UV–Vis spectroscopy and XPS as well as tested for functionality using a range of techniques including water contact angle measurement, the photo-destruction of stearic acid to a range of light sources and antimicrobial activity against MRSA and Escherichia coli bacteria under hospital lighting conditions. XRD and Raman indicated that the films were anatase, X-ray photoelectron measurements confirmed the presence of silver loading on the titania surface and EDX showed silver doping in the TiO2 layer. There appears to be an interaction between the phonon resonance of the silver nanoparticles and the band onset of the titania leading to significant visible light photo-oxidation of stearic acid as well as visible light induced superhydrophilicity. Samples were tested for photo-degradation of stearic acid under three different lighting conditions: UVA – 365 nm, white light (commonly found in UK hospitals) and UVA filtered white light. The Ag oxide-titania films were seen to be active photocatalysts under visible light conditions as well as displaying white light induced superhydrophilicity. These surfaces demonstrated a 99.996% reduction in the number of viable E. coli bacteria due to the silver ion presence and a 99.99% reduction in the number of MRSA bacteria due to the enhanced photocatalysis in a double pronged approach to antimicrobial mechanisms consisting of a synergistic relationship between the photocatalyst (TiO2) and the surface bound silver nanoparticles.
TL;DR: In this paper, the photocatalytic activity of Cu x S/TiO 2 nanocomposites depends on the ratio of the CuSO 4 :Na 2 S 2 O 3 molar ratio while keeping other conditions unchanged (solutions pH, solutions volume, irradiation time and intensity).
Abstract: Copper sulphide powder was obtained by the photochemical synthesis and thin films were developed by doctor blade deposition of Cu x S and Cu x S/TiO 2 composites with photocatalytic properties. The photochemical process could be adjusted to prepare Cu x S with different photocatalytic activities by changing the CuSO 4 :Na 2 S 2 O 3 molar ratio while keeping other conditions unchanged (solutions pH, solutions volume, irradiation time and intensity). The powder and thin film properties were characterized in terms of: the Fourier transform infra-red (FTIR), the X-ray diffraction (XRD), UV–vis spectroscopy, atomic force microscopy (AFM). The photocatalytic process using Cu x S and coupled Cu x S/TiO 2 thin film semiconductors in the dyes photodegradation (methyl orange and methylene blue) was investigated. The photocatalytic activity of Cu x S/TiO 2 nanocomposites depends on the Cu x S:TiO 2 ratio; the best results correspond to the Cu x S/TiO 2 (Cu x S:TiO 2 = 3:7) photocatalysts, with high efficiency (almost 99%) after 300 min for methyl orange, respectively after 180 min for methylene blue degradation, under UV irradiation, when H 2 O 2 is added in photocatalytic process. The semiconductors association and the films homogeneity limit the electron–hole recombination, resulting in good efficiency in dyes photodegradation even under visible light irradiation.
TL;DR: In this paper, the photocatalytic activity of titania/silica mixed materials was investigated using X-ray diffraction, transmission electron microscopy (TEM) and UV-visible spectroscopy.
Abstract: Supported nanocrystalline titanium dioxide has been prepared by a sol–gel method through the use of mesoporous silica materials SBA-15. The synthesized titania/silica composites were characterized by X-ray diffraction, transmission electron microscopy (TEM) and UV–visible spectroscopy. The TiO2–SBA-15 composites presented in this study showed much higher photodegradation ability of methylene blue (MB) than commercial pure TiO2 nanoparticles Degussa P-25 using different light sources (UV, visible and solar light). Experimental results indicate that the photocatalytic activity of titania/silica mixed materials depends on the adsorption ability of composite and the photocatalytic activity of the titania, and the highest activity was observed on the sample with Ti/Si ratio is about 8.
TL;DR: In this article, a simple equation for the determination of the kinetic constants during the photocatalytic degradation is reported, which includes the hydrodynamic properties and a surface reaction model for the reaction (monomolecular Langmuir-Hinshelwood kinetics).
Abstract: The main objective of this article is to evaluate quantitatively the kinetic constants of a photocatalytic reaction in micro-channel reactors despite the presence of a radial concentration profile (mass-transfer limitation) and axial dispersion. Photocatalytic micro-channel reactors with immobilized titanium dioxide as photocatalyst have been fabricated using stereolithography process. The photocatalytic degradation of salicylic acid is investigated as a function of rectangular micro-channel size, contaminant concentration, flow rate and incident UV light intensity. All the micro-channel reactors exhibit the same tendency. Higher degradation is observed for high incident light intensities, low pollutant concentrations and flow rates. A simple equation for the determination of the kinetic constants during the photocatalytic degradation is reported. The equation includes the hydrodynamic properties and a surface reaction model for the photocatalytic reaction (monomolecular Langmuir–Hinshelwood kinetics). In the experimental system, we demonstrate that some external mass-transfer limitation and axial dispersion occur. They are included in the modeling with calculated values of the mass-transfer coefficient of salicylic acid from the solution to the catalyst surface and the axial dispersion coefficient. A single couple of values of the reaction rate constant k and the adsorption equilibrium constant K represent properly the experimental degradation ratios for all reactor dimensions, flow rates and pollutant concentrations. The major parameter that controls the values of the reaction rate constant is the incident light intensity. The dependence of the reaction rate on the incident light intensity is first order.
TL;DR: In this article, a Porous Photocatalytic Membrane Microreactor (P2M2) is proposed for multiphase photocatalytical reactions.
Abstract: In this study, a new membrane microreactor concept for multiphase photocatalytic reactions is demonstrated. Microfabrication, photocatalyst immobilization and surface modification steps were performed to develop a Porous Photocatalytic Membrane Microreactor (P2M2). This concept benefits from a stable gas–liquid–solid (G–L–S) interface allowing a continuous supply of gaseous reactants and a reduced light path. A surface modification technique was devised to alter the wetting conditions of the reactor wall. Through a complete hydrophobization and a selective hydrophilization step by use of UV-light, we obtained a hydrophobic porous membrane support with hydrophilic photocatalytic microchannels. The photocatalytic degradations of methylene blue and phenol were used as model reactions to test the device, demonstrating promising degradation performance. We further demonstrated the effect of additional oxygen supply to the performance of the reactor for both reaction systems
TL;DR: In this paper, the intrinsic photophysical properties of gaseous protonated rhodamine B (RBH+) were studied in the gas phase using electrospray ionization (ESI) and isolated in a quadrupole ion trap (QIT) mass spectrometer.
Abstract: Studying the photophysical properties of molecules in the gasphase can be advantageous, because it reduces the complexity of the system examined by eliminating effects due to theinteractions between the molecule of interest and other species present in the local environment, including those with the solvent itself. Here, we report on theintrinsic properties of gaseous protonated rhodamine B (RBH+), a well-known xanthene-based dye. Protonated rhodamine B was transferred into the gas phase using electrospray ionization (ESI) and isolated in a quadrupole ion trap (QIT) mass spectrometer, which has been modified to enable laser-induced fluorescence spectroscopy of trapped ions. The gas-phase fluorescence excitation and emission spectra of RBH+show maxima (λex (max) = 531 nm and λem (max) = 542 nm, respectively)that lie at higher energy than those of RBH+ in solution. The fluorescence lifetime of gaseous RBH+ is 5.97 ± 0.12 ns, which is significantly longer than that of solution-phase rhodamine B. Gaseous rhodamine B is signficiantly brighter than monoethylamino rhodamines such as gaseous rhodamine 6G. Knowledge of the intrinsic photophysical properties of chromophores, such as those presented here for rhodamine B, will enable a better understanding of how the local environment of the chromophore modulates its properties.
TL;DR: In this paper, a series of nitrogen-doped and undoped nanocrystals and nanoparticles were obtained from commercial TiO2 powders, and several dye-sensitized solar cells (DSCs) were fabricated based on Ndoped electrodes.
Abstract: A series of nitrogen-doped and undoped TiO2 nanocrystals was prepared by several simple methods. Needle-like N-doped TiO2 nanocrystals and nanoparticles were obtained from commercial TiO2 powders. Several dye-sensitized solar cells (DSCs) were fabricated based on N-doped and undoped TiO2 electrodes. The N-doped DSCs achieved a high conversion efficiency of 10.1% and 4.8% using an organic electrolyte and an ionic liquid electrolyte, respectively. Systemic investigations were carried out on the properties of N-doped and undoped TiO2 powders, films, and DSCs. The electron transport time and electron lifetime were investigated by intensity-modulated photocurrent and photovoltage spectroscopy (IMPS/IMVS). Moreover, the electron injection of N-doped DSCs was studied by surface photovoltage spectroscopy (SPS). The synergetic effect of higher dye uptake, faster electron transport and higher photovoltage contributes to a higher conversion efficiency of N-doped DSCs. The stability test also demonstrated that the photodegradation of the DSCs was not accelerated and the DSC system was stabilized by the introduction of nitrogen into the TiO2 photoelectrode. These results indicate that the N-doped TiO2 nanocrystals prepared by our approach from commercial TiO2 are ideal semiconductor materials for DSCs.
TL;DR: In this paper, the interaction of photosensitizer methylene blue (MB) with single stranded oligonucleotides of composition AAA-AAA-AAA (A 9 ), CCC-CCC-CCC (C 9 ), GGG-GGG-GG (G 9 ), and TTT-TTT-TTT (T 9 ) has been studied using UV-vis and fluorescence spectroscopies.
Abstract: The interaction of photosensitizer methylene blue (MB) with single stranded oligonucleotides of composition AAA-AAA-AAA (A 9 ), CCC-CCC-CCC (C 9 ), GGG-GGG-GGG (G 9 ), and TTT-TTT-TTT (T 9 ) has been studied using UV–vis and fluorescence spectroscopies. The quenching effect of single stranded G 9 over MB is favored over the other sequences. The analysis of the fluorescence data by Benesi–Hildebrand plot shows that MB forms 1:1 complex with G 9 . Results from spectroscopic experiments, Stern-Volmer and van’t Hoff plots are consistent with a principal contribution of the static quenching on the overall quenching mechanism and with the electrostatic binding mode of MB-single stranded G 9 system. A quantum chemical modeling at DFT//B3LYP/6-31G(d,p) level confirms the experimental results. Asides from providing an insight into the underlying mechanism of the interaction between methylene blue and DNA, these results can be exploited for the design of novel DNA sensors using photoactive labels.
TL;DR: In this article, pure titania nanotubes (TNTs) were synthesized using hydrothermal method using a wet chemical procedure with dimethyl phosphite as a precursor, and they were tested using rhodamine B (RhB) as a model pollutant under a 9W fluorescent lamp and was significantly better than the benchmark Degussa P25 nanoparticles due to the band gap narrowing and increased surface area.
Abstract: Titania nanostructures have gained much attention lately due to their high specific surface area, ion-exchange ability, and better electrical properties. In this study, pure titania nanotubes (TNTs) were synthesized using hydrothermal method. Phosphorus-doped titania nanotubes (P-TNTs) were fabricated following a wet chemical procedure with dimethyl phosphite as a precursor. Characterization of the prepared pure/phosphorus-doped titania nanotubes was performed using transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), XRD analysis, UV–Vis absorption spectra, and BET specific surface area analysis. Phosphorus-doping slightly reduces the surface area but shifts the band gap towards the visible light region. When compared to pure TNTs, the optimal 0.75 wt.% P-TNTs have a similar surface area (272 m 2 /g vs. 274 m 2 /g) but with a band gap shift of 0.27 eV towards the visible light region. The photocatalytic activity of 0.75 wt.% P-TNTs was tested using rhodamine B (RhB) as a model pollutant under a 9 W fluorescent lamp and was significantly better than the benchmark Degussa P25 nanoparticles due to the band gap narrowing and an increased surface area. The decolorization follows first-order kinetics with the apparent rate constant k 1 of 0.13 min −1 for 0.75 wt.% P-TNT and 0.07 min −1 for Degussa P25.
TL;DR: A pyrazole-based fluorescent sensor, 5-amino-3-(5-phenyl-1H-pyrrol-2-yl)-1H pyrazoles-4-carboxamide (compound 1), was studied for fluoride anion (F−) detection in organic or water-containing solution as mentioned in this paper.
Abstract: A new pyrazole-based fluorescent sensor, 5-amino-3-(5-phenyl-1H-pyrrol-2-yl)-1H-pyrazole-4-carboxamide (compound 1), was studied for fluoride anion (F−) detection in organic or water-containing solution. This compound displayed both changes in UV–vis absorption and fluorescence emission spectra upon addition of F−. With increasing of F−, blue emission intensity increases drastically and reaches saturation with 607-fold enhancement at 424 nm. The results indicate that compound 1 has highly selectivity for fluoride detection over other anions, such as Cl−, Br−, I−, HSO4−, H2PO4− and AcO− in DMSO or aqueous DMSO solutions. 1H NMR titration and other experiments confirm that the sensing process is mainly from the deprotonation of the pyrazole–NH in compound 1.
TL;DR: In this paper, two novel TiO 2 sensitizers, based on the highly stable diketopyrrolopyrrole (DPP) skeleton, have been synthesized for application in the field of dye sensitized solar cells.
Abstract: Two novel TiO 2 sensitizers, based on the highly stable diketopyrrolopyrrole (DPP) skeleton, have been synthesized for application in the field of dye sensitized solar cells. The obtained dyes, DPP1 and DPP2 bear respectively a cyanoacrylic acid and a rhodanine acid anchoring groups, thus tuning the extent of the electronic communication with the semi-conducting oxide. The two chromophores were characterized by solution phase spectroscopy and electrochemistry. DFT calculations gave deeper insight into the electronic structure of both dyes, through the disclosure of their frontier orbitals. Photovoltaic performances unravelled the undisputable advantage of DPP1 over DPP2 , owing to the combination of a favourable dipolar moment interaction with TiO 2 , and more intimate orbital blending between the chemisorbed dye and the conduction band. Chenodeoxycholic acid proved to be useful in limiting the formation of dye aggregates, improving to a great extent the performances of DPP1 based DSSCs, reaching in our conditions a 4.47% yield and 57% IPCE at 500 nm.
TL;DR: In this article, the quaternized tetra-2]-2-(dimethylamino)ethoxy]ethoxy substituted zinc (II) phthalocyanine complexes (2 and 4) and their quaternised amphiphilic derivatives (2a and 4a) have been synthesized and characterized for the first time.
Abstract: The new peripherally and non-peripherally tetra-2-[2-(dimethylamino)ethoxy]ethoxy substituted zinc (II) phthalocyanine complexes (2 and 4) and their quaternized amphiphilic derivatives (2a and 4a) have been synthesized and characterized for the first time. The quaternized complexes show excellent solubility in both organic and aqueous solutions, which makes them potential photosensitizer for use in photodynamic therapy (PDT) of cancer. Photophysical (fluorescence quantum yields and lifetimes) and photochemical (singlet oxygen generation and photodegradation under light irradiation) properties of these novel phthalocyanines are investigated in dimethylsulfoxide (DMSO) for non-quaternized complexes and in DMSO, phosphate buffered solution (PBS) or PBS + triton X-100 (TX) for quaternized complexes. In this study, the effects of the aggregation of the molecules, quaternization and position (peripherally or non-peripherally) of the substituents and nature of the solvents (DMSO, PBS or PBS + triton X-100) on the photophysical and photochemical parameters of the zinc (II) phthalocyanines are also reported. A spectroscopic investigation of the binding of the quaternized cationic zinc (II) phthalocyanine complexes to bovine serum albumin (BSA) is also presented in this work.
TL;DR: In this paper, the interaction of a well characterized new complex 1 cis,fac-[RuCl(dmso-S)3(L)] LH = 1-(2-hydroxyphenyl)-3-(4-chlorophenyl) propenone with Calf-thymus DNA (CT-DNA) is monitored using UV-vis titration and ethidium bromide displacement studies.
Abstract: The interaction of a well characterized new complex 1 cis,fac-[RuCl(dmso-S)3(L)] LH = 1-(2-hydroxyphenyl)-3-(4-chlorophenyl) propenone with Calf-thymus DNA (CT-DNA) is monitored using UV–vis titration (Kb = 3.8 × 107) and ethidium bromide displacement studies (Ksv = 3.2). The molecular docking of the complex with DNA sequence d(ACCGACGTCGGT)2 reveals that complex is stabilized by additional electrostatic and hydrogen bonding interaction with DNA besides probable displacement of a labile DMSO by the N7 of guanine. The coordination of guanine is further supported by the isolation and characterization of its adduct with the complex 1.gua (gua = guanine). The nuclease property of complex 1 in the absence and presence of different activators and trappers demonstrates that complex efficiently cleaves supercoiled pBR322 plasmid DNA and binds through major groove of the DNA.