Quantum Yield Research Papers - Academia.edu (original) (raw)

The present study is focused on developing a nanoparticle carrier for the photosensitizer protoporphyrin IX for use in photodynamic therapy. The entrapment of protoporphyrin IX (Pp IX) in silica spheres was achieved by modification of Pp IX molecules with an organosilane reagent. The immobilized drug preserved its optical properties and the capacity to generate singlet oxygen, which was detected by a direct method from its characteristic phosphorescence decay curve at near-infrared and by a chemical method using 1,3-diphenylisobenzofuran to trap singlet oxygen. The lifetime of singlet oxygen when a suspension of Pp IX-loaded particles in acetonitrile was excited at 532 nm was determined as 52 µs, which is in good agreement with the value determined for methylene blue in acetonitrile solution under the same conditions. The Pp IX-loaded silica particles have an efficiency of singlet oxygen generation (η ∆) higher than the quantum yield of free porphyrins. This high efficiency of singlet oxygen generation was attributed to changes on the monomer-dimer equilibrium after photosentisizer immobilization.

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- Chemistry, Photochemistry, Nanoparticle, Nanoparticles

The present study investigated the dynamics of nutrient utilization and various growth and physiological parameters during in vitro proliferation of apple root stock 'M9 EMLA' in two different bioreactor systems, i.e. temporary and continuous immersions. Individual shoots obtained from temporary immersion system had higher dry mass and were of better quality than those obtained from continuous immersion. In continuous immersion bioreactor, apple shoots appeared to utilize more nutrients from liquid culture medium than that from temporary immersion. The shoot growth was limited by the availability of phosphate and nitrogen in continuous immersion system. The shoots produced in temporary immersion bioreactor showed higher photosynthetic rate, maximum quantum yield of photosystem-II and slow but steady rate of nutrient absorption, indicating the occurrence of higher photomixotrophic metabolism. The study also showed that high level of antioxidant scavenging enzymes in shoots grown in continuous immersion system induced physiological changes to foster adaptation to stresses.

- by Kee Paek
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- Plant Biology, Plant growth, Nitrogen, Plant Growth Regulation

The photochemical behavior of oxyfluorfen [2-chloro-1-(3-etoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene] on two Greek soils was investigated. Soils were sampled from Nea Malgara and Preveza regions, characterized by a different organic matter content. Soils were spiked with the diphenyl-ether herbicide and irradiation experiments were performed either in the laboratory with a solar simulator (xenon lamp) or outside, under natural sunlight irradiation; other soil samples were kept in the dark to control the retention reaction. Kinetic parameters of both retention and photochemical reactions were calculated using zero-, first- and second- (Langmuir-Hinshelwood) order equations, and best fit was checked through statistical analysis. The soil behaviors were qualitatively similar but quantitatively different, with the soil sampled from the Nea Malgara region much more sorbent as compared with Preveza soil. All studied reactions followed second-order kinetics and photochemical reaction...

- by Laura Scrano
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- Earth Sciences, Kinetics, Photochemistry, Statistical Analysis

Within the sheltered creeks of Ca Â diz bay, Ulva thalli form extended mat-like canopies. The effect of solar ultraviolet radiation on photosynthetic activity, the composition of photosynthetic and xanthophyll cycle pigments, and the amount of RubisCO, chaperonin 60 (CPN 60), and the induction of DNA damage in Ulva aff. rotundata Bliding from southern Spain was assessed in the ®eld. Samples collected from the natural community were covered by screening ®lters, generating different radiation conditions. During daily cycles, individual thalli showed photoinhibitory effects of the natural solar radiation. This inhibition was even more pronounced in samples only exposed to photosynthetically active radiation (PAR). Strongly increased heat dissipation in these samples indicated the activity of regulatory mechanisms involved in dynamic photoinhibition. Adverse effects of UV-B radiation on photosynthesis were only observed in combination with high levels of PAR, indicating the synergistic effects of the two wavelength ranges. In samples exposed either to PAR+UV-A or to UV-B+UV-A without PAR, no inhibition of photosynthetic quantum yield was found in the course of the day. At the natural site, the top layer of the mat-like canopies is generally completely bleached. Arti®cially designed Ulva canopies exhibited fast bleaching of the top layer under the natural solar radiation conditions, while this was not observed in canopies either shielded from UV or from PAR. The bleached ®rst layer of the canopies acts as a selective UV-B ®lter, and thus prevents subcanopy thalli from exposure to harmful radiation. This was con®rmed by the differences in photosynthetic activity, pigment composition, and the concentration of RubisCO in thalli with different positions within the canopy. In addition, the induction of the stress protein CPN 60 under UV exposure and the low accumulation of DNA damage indicate the presence of physiological protection mechanisms against harmful UV-B. A mechanism of UV-B-induced inhibition of photosynthesis under ®eld conditions is proposed.

- by Jose Lucas Perez-Llorens
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- Plant Biology, DNA damage, Spain, Experimental Botany

A detailed spectroscopic and photophysical study has been carried out on a series of heterocyclic compounds-known to display nonlinear optical properties-consisting on a electron donating thienylpyrrolyl p-conjugated system functionalized with an electron acceptor benzothiazole moiety. The absorption, emission and triplet-triplet absorption together with all relevant quantum yields (fluorescence, intersystem crossing and internal conversion), excited state lifetimes and the overall set of deactivation rate constants (k F , k IC and k ISC) were obtained in solution at room (293 K) and low (77 K) temperature. The optimized ground-state molecular geometries for the compounds together with the prediction of the lowest vertical one-electron excitation energy and the relevant molecular orbital contours for the compounds were also determined using density functional theory (DFT) at the B3LYP/3-21G* level. The experimental results showed that the photophysical properties are influenced by the relative position of the pyrrole and thiophene relative to the benzothiazole group.

- by Rosa Batista
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- Fluorescence, Prediction, Geometry, Conversion

A complete set of platinum(II) solketal substituted phthalocyanines has been synthesized and characterized. To evaluate their potential as Type II photosensitizers for photodynamic therapy, comparative studies of their photophysical and photochemical properties with analogous zinc(II) series have been achieved: electronic absorption, fluorescence quantum yields, lifetimes, and fluorescence quenching by benzoquinone, as well as singlet oxygen generation and photodegradation. It appears that platinum(II) phthalocyanines are worth being used as Type II photosensitizers, as they exhibit good singlet oxygen generation and appropriate photodegradation.

- by yunus zorlu
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- Organic Chemistry, Fluorescence, Comparative Study, Photodynamic Therapy

We report first results of laboratory tests of Si:As blocked-impurity-band (BIB) mid-infrared (4 to 28 µm) detectors developed by IMEC. These prototypes feature 88 pixels hybridized on an integrated cryogenic readout electronics (CRE). They were developed as part of a technology demonstration program for the future Darwin mission. In order to be able to separate detector and readout effects, a custom build TIA circuitry was used to characterize additional single pixel detectors. We used a newly designed test setup at the MPIA to determine the relative spectral response, the quantum efficiency, and the dark current. All these properties were measured as a function of operating temperature and detector bias. In addition the effects of ionizing radiation on the detector were studied. For determining the relative spectral response we used a dualgrating monochromator and a bolometer with known response that was operated in parallel to the Si:As detectors. The quantum efficiency was measured by using a custom-build high-precision vacuum black body together with cold (T ∼ 4 K) filters of known (measured) transmission.

- by Patrick Merken
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- Performance, Astronomy, Radiation Detectors, Quantum Efficiency

The lifetimes and relative quantum yields of the three fluorescence components of the PI (red-absorbing) form of 124-kDa oat phytochrome in H 2 0 and D 2 0 solutions have been determined by single-photon-timing techniques. Lifetime and quantum yield of the main component, which is the shortest lived (about 40 ps a t low concentration) and reflects the photochromic properties of P,, are not affected by D20. The medium-lifetime component (about 180 ps at low concentration), which is attributable to a photochromic source behaving comparable to that responsible for the main component, is not affected

- by Silvia Braslavsky
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- Biochemistry, Chemistry, Radiation Chemistry, Global Analysis

Enhanced cyan fluorescent protein (ECFP) and its variant Cerulean are genetically encoded fluorophores widely used as donors in FRET-based cell imaging experiments. First, we have confirmed through denaturation experiments that the double-peak spectroscopic signature of these fluorescent proteins originates from the indole ring of the chromophore. Then, to explain the improvement in the fluorescence properties of Cerulean compared to those of ECFP, we have determined the high-resolution crystal structures of these two proteins at physiological pH and performed molecular dynamics simulations. In both proteins, the N-terminal half of the seventh strand exhibits two conformations. These conformations both have a complex set of van der Waals interactions with the chromophore and, as our simulations suggest, they interconvert on a nanosecond time scale. The Y145A and H148D mutations in Cerulean stabilize these interactions and allow the chromophore to be more planar, better packed, and less prone to collisional quenching, albeit only intermittently. As a consequence, the probability of nonradiative decay is significantly decreased. Our results highlight the considerable dynamical flexibility that exists in the vicinity of the tryptophan-based chromophore of these engineered fluorescent proteins and provide insights that should allow the design of mutants with enhanced optical properties.

Photosynthetic capacity, leaf nitrogen content, and stomatal conductance decreased with increasing leaf age in the chaparral shrub, Lepechinia calycina, growing in its natural habitat. Efficiency of resource use for three resources that potentially limit photosynthesis did not, however, decrease with increasing leaf age. Light-use efficiency, given by the quantum yield of photosynthesis at low light intensities, was unaffected by leaf aging but decreased slightly through the winter and spring growing season. Water-use efficiency, the ratio of photosynthesis to transpiration at light saturation and with a constant water vapor concentration gradient, was not affected by leaf aging or seasonal change. Nitrogen-use efficiency, the ratio of photosynthesis at light saturation to leaf nitrogen content did not change with leaf age but was lower in the leaves with the highest specific weights. This ensemble of leaf-age effects is consistent with the hypothesis that aging represents resource redistribution and not uncontrolled deterioration.

- by Harold Mooney
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- Ecology, Resource use, Water use efficiency, Oecologia

The results indicate that, in order to assess the environmental impact of musk tibetene on the aquatic ecosystem, great attention should be focused on the major photoproduct which is proved to be more persistent than the parent compound under light irradiation. The predicted halflife times of direct photolysis for both substances ranged from 1-1.5 hours at 20°N during the summer season to about 6-10 hours for highest latitudes in winter, indicating that, from a photochemical point of view, the environmental persistence of these substances increases by increasing the latitudes and during the cold seasons, making more realistic an intake of these xenobiotic molecules into the food chain of aquatic living organisms. Tanabe reports in his Editorial (Tanabe 2005) that "It is necessary to have knowledge of the global picture of synthetic musk pathways. So, it is conceivable that now is the time to study the transport, persistency, distribution, bioaccumulation and toxic potential of this new environmental menace on a global scale, especially in developing countries". Therefore, the future environmental analysis and investigations on the eco-toxicity of nitro musk compounds should take into account not only the presence of the parent compounds but also their photochemical intermediates or end-by-products.

- by Fabio Temussi and +1
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- Environmental Science, Kinetics, Numerical Modelling, Biological Sciences

We investigated, by a photoacoustic method, the changes in light energy distribution to the reaction centres upon state transitions in vivo in Chlamydomonas reinhardtii. We present spectra of the quantum yield of charge separation in the wild type and in several photosynthesis mutants lacking either cytochrome b6f complexes, the PS II cores or the PS I cores. Our results show unambiguously that in the wild-type LHCII becomes connected to PS I in state 2, in a cyt b6f-controlled process. We show that mutants lacking the PS II cores, but not those lacking PS I cores, display a behaviour very similar to that of the wild type upon state transition. Lateral displacement of LHCII, but not of minor antenna complexes (CP26), from the stacked to the unstacked membrane domains results in transfer to PS I of about 80% of the excitation energy absorbed by LHCII. Consequently, in state 2, more than 90% of the chlorophylls transfer energy to PS I in mutants lacking PS II cores. In contrast, a sig...

- by rené delosme
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- LHC, Room Temperature, Energy Distribution, Quantum Yield

Excimer laser radiation at 193 nm (ArF) and 308 nm (XeCl) is being used for medical applications. Because ultraviolet radiation is absorbed by DNA and causes cell killing, mutagenesis, and carcinogenesis, the effects of 193-and 308-nm excimer laser radiation on biological material have been studied. Radiation ut 193 nm causes less cell killing than conventional 254 nm germicidal light per incident photon. Radiation at 193 nm showed very low potential for causing mutation because proteins absorb strongly at 193 nm thereby reducing the photon flwc reaching the nuclear DNA. In addition, the quantum yield of a cytotoxic and mutagenic photoproduct of DNA is lower for I93 nm than for 254 nm. Radiation at 308 nm is cytotoxic and mutagenic. Results of in vitro assays indicate that the relative abilig of excimer laser radiation to cause DNA damage decreases in the order 248 nm > 308 nm > 193 nm.

- by Irene Kochevar
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- Biomedical Engineering, Photochemistry, DNA damage, DNA

We report results from high-resolution studies of D 5 + cluster ion collisions with low-energy electrons performed in a heavy ion storage ring. Absolute dissociative recombination (DR) and dissociative excitation (DE) cross sections were determined for the energy range from 0.0005 to 20 eV. The DR cross sections were exceedingly large at low energies, and DR resulted in efficient internal energy redistribution and pronounced fragmentation with two main product channels: D 2 + 3D (0.62 ± 0.03) and 2D 2 + D (0.35 ± 0.01). The DR and DE cross sections were comparable in the energy range from 0.2 to 20 eV, which suggest that the two processes follow similar dynamics and are competing outcomes of the ion-electron interaction. A simple picture of the recombination process of D 5 + which captures the essential physics is suggested.

- by Achilleas Mavrellis
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- Engineering, Molecular Physics, Organic Chemistry, Chemical Physics

The photosensitizing properties of six anthraquinones (AQs): soranjidiol (1), soranjidiol-1-methyl ether (2), rubiadin (3), rubiadin-1-methyl ether (4), damnacanthal (5) and damnacanthol (6), isolated from leaves and stems of Heterophyllaea pustulata Hook. f. (Rubiaceae) were studied. By means of photobiological and photophysical methods in vitro, the type of photosensitization that these metabolites are capable of producing was determined. Whereas the photosensitized generation of superoxide anion radical ðO ÅÀ 2 Þ (Type I) was evaluated in leukocyte suspensions, singlet molecular oxygen ( 1 O 2 ) production (Type II) was examined in organic solution. In addition, the quantum yield of 1 O 2 (U) in chloroform was measured for those AQs that generate it. It was established that 4 behaves exclusively as a Type I photosensitizer. By contrast, the others AQs act by both types of mechanisms, among which 5 showed the largest U of 1 O 2 .

- by laura comini
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- Anions, Anthraquinones, Monocytes, Spectrum analysis

Marine aerosols produced by bursting bubbles at the ocean surface are highly enriched in organic matter (OM) relative to seawater. The importance of this OM in the photochemical evolution of marine aerosols and particularly as a source of reactive oxidants are unknown but likely significant. To investigate oxidant production, nascent aerosols were generated by bubbling zero air through flowing Sargasso seawater and photochemical production of OH radical and hydroperoxide were quantified in aqueous extracts exposed to solar radiation. Extrapolation to ambient conditions indicates that OM photolysis was the primary in situ source for OH (1.1 x10 -8 M s -1 ) and hydroperoxides (1.7 x 10 -8 M s -1 ) in nascent aerosols; NO 3 photolysis was the primary source in aged, acidified aerosols (1.4×10 -7 and 4.1×10 -8 M s -1 , respectively). In situ OH photoproduction was comparable to gas-phase uptake whereas H 2 O 2 photoproduction was slower.

- by Maben Net
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- Engineering, Geochemistry, Oceanography, Organic Chemistry

For the first time, the photosynthetic performance of field-grown macroalgae from the Magellan Strait was evaluated with respect to their photoadaptation in the field and acclimation potential to ultraviolet radiation. Five macroalgal species were collected in the eulittoral and the upper sublittoral: Ulva intestinalis, Porphyra columbina, Adenocystis utricularis, Desmarestia confervoides and D. ligulata. Photosynthesis vs. irradiance (P-I) curves of macroalgae

- by Christian Wiencke
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- Biological Sciences, Uv Radiation, Functional Group, White Light

We report on a systematic investigation of temperature dependent current-voltage (I-V) characteristics of Pd/ZnO Schottky barrier diodes in the 30-300 K temperature range. The ideality factor was observed to decrease with increase in temperature, whilst the barrier height increases with increase in temperature. The observed trend has been attributed to barrier inhomogeneities, which results in a distribution of barrier heights at the interface. Using the dependence of saturation current values on temperature, we have calculated the Richardson constant (A *) which was investigated in the two distinct temperature regions: 140-200 K and 210-300 K and values of and A cm-2 K-2 were obtained, respectively. A mean barrier height of 0.97 eV was obtained in the 140-300 K temperature range. Applying the barrier height inhomogeneities correction, the value of A * was obtained from the modified Richardson plots as 39.43 and 39.03 A cm-2 K-2 in the 140-200 K and 210-300 K temperature range. The modified Richardson constant (A **) has proved to be strongly affected by barrier inhomogeneities and dependent on contact quality.

- by Wilbert Mtangi
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- Engineering, Materials Science, Advanced Materials, Optoelectronics

Titania, TiO2, irradiated by ultraviolet/visible light was used to mediate the photocatalyzed degradation of ortho-cresol, meta-cresol, and para-cresol. The total photomineralization of these phenols to carbon dioxide and water occurs in air-equilibrated aqueous media. Two major hydroxylated aromatic intermediate species have been identified by liquid chromatographic methods: 4methylcatechol and methylhydroquinone. Photochemical efficiencies (lower limits of quantum yields, 365 nm) of compound disappearance are, respectively, 0.0096, 0.0076, and 0.010 for o-, m-, and p-cresol. The effect of such parameters as pH, initial cresol concentration, and radiant power levels on the degradation of m-cresol was examined in detail. Although the photodegradation process kinetics show similarities with Langmuir-Hinshelwood-type behavior, namely saturation, it is shown that the resulting kinetic expression for the rate of degradation is a complicated function of various parameters and is silent as to the details of the initial photooxidative steps. It is implicitly argued, however, that the reaction takes place on the semiconductor particle surface.

- by Claudio Minero
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- Chemical Engineering, Analytical Chemistry, Carbon Dioxide, Catalysis
- by Daniel Smith
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- Water, Kinetics, Water Purification, Pesticide Residues

Vetiver grass (Vetiveria zizanioides) has been widely confirmed to have very strong tolerance to flooding and even complete submergence and, therefore, is a considerably excellent species for stabilization and revegetation of "wet" barren slopes and for wastewater treatment. However, it is poorly documented why vetiver is so tolerant to submergence. To understand the mechanisms of vetiver's tolerance to submergence, an

1,2-naphtho)(1,8-naphtho)thioindigo (PNT) has been synthesized following a simple Friedel-Crafts route and its photochemical properties in toluene and polymethylmethacrylate (PMMA) have been characterized. PNT is a photochromic molecule capable of reversible photoisomerization between a yellow form (cis-PNT, k max = 484 nm) and a purple form (trans-PNT, k max = 595 nm). The stable purple form converts to the yellow form with a trans-PNT to cis-PNT conversion quantum yield of 0.027 in toluene and 0.062 in PMMA. The unstable yellow form exhibits a cis-PNT to trans-PNT quantum efficiency of conversion of 0.27-0.85 in toluene and 0.17-0.68 PMMA, with highest conversion efficiency occurring in the vicinity of its k max of 484 nm. trans-PNT has a strong fluorescence quantum yield, 0.14 (toluene) and 0.16 (PMMA). For samples prepared photochemically in the cis-PNT form, slow thermal relaxation to the trans form occurs in the dark, with a half life of about 17 h in toluene (25°C) and even slower, 168 h, in PMMA. The property of photoswitching between fluorescent and non-fluorescent forms makes this material a candidate for many applications in imaging and data storage.

- by Nerine Cherepy
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- Materials Engineering, Sample Preparation, Data storage, Quantum Efficiency

In order to investigate the mechanisms of maize adaptation to temperate climate, we studied photosynthetic efficiency, as evaluated by means of F PSII and chloroplast ultrastructure, as well as growth and development of two inbred lines (the chillingtolerant KW 1074 and the chilling-sensitive CM 109) under laboratory conditions. Plants were grown from seed to the 3rd leaf stage at a suboptimal temperature (14 1C/ 12 1C) and then the temperature was increased to 24 1C/22 1C. To verify the results obtained with the two model lines, twelve inbred lines were tested under both laboratory and field conditions. .pl (P. Sowiński).

- by Józef Adamczyk
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- Photosynthesis, Plant Biology, Plant Physiology, Maize

Young plants of two Brazilian Green Dwarf coconut ecotypes from contrasting regions in relation to climate (UGD, from a hot and humid climate and JGD, from a hot and dry climate) were submitted to three consecutive drying/recovery cycles, under greenhouse conditions to determine the photosynthetic limitations encountered during the recovery phase of water deficiency. Three hypotheses were tested: (1) non-stomatal factors contribute to the incomplete recovery of net photosynthesis rate (A), (2) photochemical impairment is an important component of the non-stomatal limitations to A and (3) the two coconut ecotypes respond differently to the drought recovery. In each drying/recovery cycle, irrigation was suppressed until A reached zero. Then the plants were rewatered and the recovery was accompanied for 8 days. After 4 days of rewatering, CO 2 and light response curve parameters were used to discriminate the stomatal and non-stomatal factors contributing to the incomplete recovery of A. Upon rewatering for 4 days, the pre-dawn leaf water potential of the stressed plants increased from −1.20 to −0.15 MPa on average. Only small differences were detected in the intercellular to atmospheric CO 2 concentration ratio but A did not recover completely to the control values. In both ecotypes, light and CO 2-saturated A, carboxylation efficiency, maximum quantum yield of PSII and maximum electron transport rate were significantly lower in stressed plants in comparison with the well-watered ones. Relative stomatal limitation (L S) ranged from 16 to 20% without significant differences between treatments and between ecotypes. The relative mesophyll limitation (L m) was significantly higher in JGD in cycle 1 but this changed after repeated drought stress, decreasing to values significantly lower than those in UGD in the other two cycles. The results showed that after 4 days of rewatering stressed plant stomatal limitations were comparable to that of well-watered control plants (∼20%). However A did not recover completely after drought stress due to non-stomatal factors. Important differences between the ecotypes were identified. The ecotype JGD presented smaller L m , faster recovery of the apparent quantum efficiency of CO 2 assimilation, adjustment of some carbon balance components and signs of photosynthetic capacity acclimation after repeated drying/recovery cycles.

- by Fábio Gomes
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- Photosynthesis, Stress, Drought Stress, Biological Sciences

CdSe, CdTe and InP nanocrystals were prepared by an organometallic synthesis using mixtures of highly boiling primary amines and trioctylphosphine (TOP) as the coordinating solvent, and were characterized by powder XRD, SAXS, HRTEM, absorption and luminescence spectroscopy. The use of amines allowed us to obtain small crystalline nanoparticles for all materials investigated. In all cases, as-prepared colloids show rather narrow particle size distributions which can be further improved by standard size selective precipitation. Amino-capped II -VI nanocrystals show strong size-dependent band edge photoluminescence (PL). CdSe nanocrystals with the mean particle size in the range of 1.2-3.0 nm exhibit emission from blue to green with room temperature quantum yields of 15 -20%. CdTe nanocrystals (2.5-5.0 nm size range) show a PL tunable from green to red with quantum yields up to 65% at room temperature. InP nanocrystals (1.5-4.0 nm size range) possess a weak emission ( B 1% quantum efficiency (QE)). A simple method is proposed to transfer nanocrystals from organic solvents to water which allows to retain sufficiently strong luminescence of CdTe nanoparticles. CdSe nanocrystals synthesized in trioctylphosphine-trioctylphosphine oxide mixture (TOP-TOPO) show an increased QE of about 70% after subsequent treatment with primary amines.

- by Dmitri Talapin
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- Engineering, Surface modification, Semiconductor, Surface

The photoisomerization kinetics of trifloxystrobin (TFS) in acetone under artificial sunlight is reported. HPLC analysis showed the TFS, a strobilurine fungicide of EE conformation, was converted into an equilibrium mixture of four isomers after illumination for 7 h. The isomers were identified as EZ, EE, ZZ, and ZE and were separated in the crystalline form by preparative HPLC and characterized by use of a variety of spectroscopic techniques. The quantum yield and reaction constants for the isomerization reactions were determined. The detailed spectral features of the individual isomers measured by UV, IR, Raman, NMR and mass spectroscopy are presented and compared. The spectra of the isomers were found to be very characteristic, with good analytical significance.

- by Kaushik Banerjee
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- Engineering, Chemistry, Kinetics, Mass Spectrometry

The effects of water deficit on photochemical parameters and activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), as well as, cellular damages were investigated in two clones of Coffea canephora differing in drought tolerance. After 6 days without irrigation, predawn leaf water potential fell to −3.0 MPa that was accompanied by the suppression of net photosynthesis in both clones. The variable to maximum chlorophyll fluorescence ratio remained unchanged regardless of the imposed treatments. Both clones showed a similar decline (about 25%) in the photochemical quenching coefficient, but only the drought-sensitive clone exhibited an enhancement (31%) of thermal deactivation under water deficit conditions. The quantum yield of electron transport decreased similarly in both genotypes. Under drought conditions, activities of SOD, CAT and APX increased to a greater extent in the drought-tolerant clone than in the drought-sensitive one. This seemed to be matched with higher protection against oxidative stress, as judged from the lower levels of lipid peroxidation and electrolyte leakage in the drought-tolerant clone. Thus, the ability to increase the antioxidant system activity in order to limit cellular damages might be an important attribute linked to the drought tolerance in C. canephora.

- by Ana Silva
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- Photochemistry, Photosynthesis, Biological Sciences, Environmental Sciences

Some photo-physical parameters of 1 Â 10 À4 and 5X9 Â 10 À4 M samples of rhodamine 6G in a 2-hydroxyethylmethacrylate methyl-methacrylate copolymer (volume mixture 1:1) are determined and compared with rhodamine 6G in methanol. They include the absorption cross-section and stimulated emission cross-section spectra, the¯uorescence quantum distributions, quantum yields and lifetimes. The photo-degradation under steady-state and pulsed excitation is investigated. The saturable absorption behaviour under picosecond laser excitation is studied. Ó

- by A. Penzkofer
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- Engineering, Chemical Physics, Physical sciences, Steady state

Pulse amplitude modulation (PAM) fluorometry is ideally suited to measure the sub-lethal impacts of photosystem II (PSII)-inhibiting herbicides on microalgae, but key relationships between effective quantum yield [Y(II)] and the traditional endpoints growth rate (l) and biomass increase are unknown. The effects of three PSII-inhibiting herbicides; diuron, hexazinone and atrazine, were examined on two tropical benthic microalgae; Navicula sp. (Heterokontophyta) and Nephroselmis pyriformis (Chlorophyta). The relationships between Y(II), l and biomass increase were consistent (r 2 P 0.90) and linear (1:1), validating the utility of PAM fluorometry as a rapid and reliable technique to measure sub-lethal toxicity thresholds of PSII-inhibiting herbicides in these microalgae. The order of toxicity (EC 50 range) was: diuron (16-33 nM) > hexazinone (25-110 nM) > atrazine (130-620 nm) for both algal species. Growth rate and photosynthesis were affected at diuron concentrations that have been detected in coastal areas of the Great Barrier Reef.

- by Kirsten Heimann
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- Photosynthesis, Biomass, Multidisciplinary, Herbicides
- by Hironori Arakawa
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- Pharmacology, Biochemistry, Bioinformatics, Evolutionary Biology
- by Cees Ronda
- •
- Materials Engineering, Condensed Matter Physics, Materials Science, Chemistry

A synthesis of a novel zinc phthalocyanine with four 3-[(2-diethylamino) ethyl]-7-oxo-4-methylcoumarin dye groups at the non-peripheral positions was performed and characterized. The photophysical and photochemical properties of the... more

- by Mustafa Bulut
- •
- Engineering, Photochemistry, Biological Sciences, Fluorescence Lifetime

A study was carried out on the dependence of the optical properties such as the maxima in the absorption and luminescence spectra, Stokes shift, and quantum yield on the composition of the three-component Cd2+—L-Cys—S2− reaction system under synthesis conditions at 298 ± 2 K and pH 7. Equations describing the dependence of the position of the maximum in the luminescence and absorption spectra of solutions on their composition were obtained by mathematical planning using the Scheffe simplex-lattice design and treatment of the data. The region of compositions for unstable colloidal solutions was determined.

- by Khalavka Yuriy
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- Optical Properties, Quantum Yield, Absorption Spectra

The synthesis and characterization of 2,9,16,23-chloro-3,10,17,24-triethyleneoxysulphanylphthalocyaninato zinc(II) (CTESZnPc) is described. The photophysics and photochemistry of CTESZnPc and those of tetrakis(triethyleneoxysulphanyl)zinc phthalocyanine (TTESZnPc) and octakis-(triethyleneoxysulphanyl)zinc phthalocyanine (OTESZnPc), are presented and compared with those of unsubstituted zinc phthalocyanine (ZnPc). The presence of triethyleneoxysulphanyl substituents on the ZnPc ring gave rise to higher values of singlet oxygen (˚ ) and photodegradation (˚P d ) quantum yields in DMF. However, TTESZnPc, OTESZnPc and CTESZnPc are less fluorescent than ZnPc, judging from their fluorescence quantum yield (˚F) values. Fluorescence was lower in toluene than in DMF due to aggregation in the former solvent. Triplet quantum yield (˚T) values were found to increase with the presence of substituents on the ZnPc ring, while triplet lifetimes ( T ) were found to vary linearly with the logarithms of solvent viscosities. The fluorescences of the substituted ZnPc complexes were effectively quenched by benzoquinone (BQ), and the quenching data analyzed by the Stern-Volmer equation. The Stern-Volmer constants and the diffusion-controlled bimolecular rate constants were calculated.

The electronic absorption, emission and excitation spectra of POHC were measured in different solvents and are affected by solvent polarity. The fluorescence quantum yield of POHC decreases with increasing Richardt and Dimorth solvent parameter (E T ) value of the solvent. In dilute solutions POHC is almost totally present in its protonated nitrogen tautomer form. The deprotonation is a reversible process. A shoulder in the absorption spectra at :473 nm indicates the presence of a portion of the tautomer (s) that disappears on lowering the temperature. Molecular oxygen acts as a quencher with quenching rate constant of 1.8 × 10 10 M − 1 s − 1 in DMF. Energy transfer from POHC to rhodamine 6G in ethanol was also studied. POHC is relatively photostable in ethanol ( c : 1.7× 10 − 4 ). Quantum chemical calculations were carried out and correlated to experimental observations.

- by SAMY EL-DALY
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- Analytical Chemistry, Nitrogen, Energy Transfer, Spectral Properties

Chemicals and solvents of commercial grade were used without further purification. 1 H, and 13 C NMR spectra were recorded in CDCl 3 and DMSO-d 6 at room temperature on Bruker Avance300 and Avance400 spectrometer (δ in ppm, J in Hz) at 1 H operating frequencies of 300.13 MHz and 400.13 MHz (75 MHz and 100 MHz for 13 C); spectra were referenced using the solvent signal as internal standard. The mass spectra (MALDI+) were recorded from CHCl 3 solutions on a MALDI-TOF Microflex (Bruker) spectrometer (DCTB as matrix); APCI mass spectra were Abstract:

- by Romina Crăsneanu and +2
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- Central European history, Fluorescence, CHEMICAL SCIENCES, Quantum Yield

A series of fluorescent compounds derived from carbazole were synthesized via the Wittig-Horner reaction. The compounds had high glass transition temperatures (T g ), in the region of 172-232°C, and high decomposition temperatures (T d ), ranging from 456 to 491°C. The derivatives showed very high fluorescence efficiency in solution, with fluorescence quantum yields in the range of 0.88-1.00. The substituent effects on fluorescence emission differed between solution and solid state. In dichloromethane solutions, the substituents had only a minimal effect on the maximum emission wavelength of the compounds with the same bridge.

- by Siwei Liu
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- Materials Engineering, Optical physics, Glass Transition Temperature, Optical Materials

The weakly bound HOONO product of the OHϩNO 2 ϩM reaction is studied using the vibrational predissociation that follows excitation of the first OH overtone (2 1 ). We observe formation of both cis-cis and trans-perp conformers of HOONO. The trans-perp HOONO 2 1 band is observed under thermal ͑223-238 K͒ conditions at 6971 cm Ϫ1 . We assign the previously published ͑warmer temperature͒ HOONO spectrum to the 2 1 band at 6365 cm Ϫ1 and 2 1 -containing combination bands of the cis-cis conformer of HOONO. The band shape of the trans-perp HOONO spectrum is in excellent agreement with the predicted rotational contour based on previous experimental and theoretical results, but the apparent origin of the cis-cis HOONO spectrum at 6365 cm Ϫ1 is featureless and significantly broader, suggesting more rapid intramolecular vibrational redistribution or predissociation in the latter isomer. The thermally less stable trans-perp HOONO isomerizes rapidly to cis-cis HOONO with an experimentally determined lifetime of 39 ms at 233 K at 13 hPa ͑in a buffer gas of predominantly Ar͒. The temperature dependence of the trans-perp HOONO lifetime in the range 223-238 K yields an isomerization barrier of 33Ϯ12 kJ/mol. New ab initio calculations of the structure and vibrational mode frequencies of the transition state perp-perp HOONO are performed using the coupled cluster singles and doubles with perturbative triples ͓CCSD͑T͔͒ model, using a correlation consistent polarized triple basis set ͑cc-pVTZ͒. The energetics of cis-cis, trans-perp, and perp-perp HOONO are also calculated at this level ͓CCSD͑T͒/ cc-pVTZ͔ and with a quadruple basis set using the structure determined at the triple basis set ͓CCSD͑T͒/cc-pVQZ//CCSD͑T͒/cc-pVTZ͔. These calculations predict that the anti form of perp-perp HOONO has an energy of ⌬E 0 ϭ42.4 kJ/mol above trans-perp HOONO, corresponding to an activation enthalpy of ⌬H 298 ‡0 ϭ41.1 kJ/mol. These results are in good agreement with statistical simulations based on a model developed by Golden, Barker, and Lohr. The simulated isomerization rates match the observed decay rates when modeled with a trans-perp to cis-cis HOONO isomerization barrier of 40.8 kJ/mol and a strong collision model. The quantum yield of cis-cis HOONO dissociation to OH and NO 2 is also calculated as a function of photon excitation energy in the range 3500-7500 cm Ϫ1 , assuming D 0 ϭ83 kJ/mol. The quantum yield is predicted to vary from 0.15 to 1 over the observed spectrum at 298 K, leading to band intensities in the action spectrum that are highly temperature dependent; however, the observed relative band strengths in the cis-cis HOONO spectrum do not change substantially with temperature over the range 193-273 K. Semiempirical calculations of the oscillator strengths for 2 1 (cis-cis HOONO) and 2 1 (trans-perp HOONO) are performed using ͑1͒ a one-dimensional anharmonic model and ͑2͒ a͒

- by Sergey Nizkorodov
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- Engineering, Kinetics, Density-functional theory, Chemical Physics

The early effects of heat stress on the photosynthesis of symbiotic dinoflagellates (zooxanthellae) within the tissues of a reef-building coral were examined using pulseamplitude-modulated (PAM) chlorophyll fluorescence and photorespirometry. Exposure of Stylophora pistillata to 33 and 34°C for 4 h resulted in (1) the development of strong non-photochemical quenching (qN) of the chlorophyll fluorescence signal, (2) marked decreases in photosynthetic oxygen evolution, and (3) decreases in optimal quantum yield (F v /F m ) of photosystem II (PSII). Quantum yield decreased to a greater extent on the illuminated surfaces of coral branches than on lower (shaded) surfaces, and also when high irradiance intensities were combined with elevated temperature (33°C as opposed to 28°C). qN collapsed in heat-stressed samples when quenching analysis was conducted in the absence of oxygen. Collectively, these observations are interpreted as the initiation of photoprotective dissipation of excess absorbed energy as heat (qN) and O 2 -dependent electron flow through the Mehler-Ascorbate-Peroxidase cycle (MAP-cycle) following the point at which the rate of light-driven electron transport exceeds the capacity of the Calvin cycle. A model for coral bleaching is proposed whereby the primary site of heat damage in S. pistillata is carboxylation within the Calvin cycle, as has been observed during heat damage in higher plants. Damage to PSII and a reduction in F v /F m (i.e. photoinhibition) are secondary effects following the overwhelming of photoprotective mechanisms by light. This secondary factor increases the effect of the primary variable, temperature. Potential restrictions of electron flow in heat-stressed zooxanthellae are discussed with respect to Calvin cycle enzymes and the unusual status of the dinoflagellate Rubisco. Significant features of our model are that (1) damage to PSII is not the initial step in the sequence of heat stress in zooxanthellae, and (2) light plays a key secondary role in the initiation of the bleaching phenomena.

- by Anthony Larkum
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- Fluorescence, Biological Sciences, Coral Bleaching, RuBisCO

Despite increasing popularity of 'electric' reefs as a means for reef restoration, there is a distinct lack of quantitative evidence supporting the alleged benefits of this method. This study investigated the effects of an electric field versus an electric field in combination with a cathode on coral growth (skeletal extension) rates, coral survival, zooxanthella densities, chlorophyll a (chl a) concentrations, and chlorophyll fluorescence of Acropora pulchra and A. yongei. Coral transplants were grown for 4 months under three treatment conditions: (1) on an iron cathode, (2) on bamboo inside an electric field, or (3) on bamboo in the absence of an electric field. Contrary to predictions, coral growth rates of both species were highest inside the electric field and not on the cathode. Except for chl a concentrations, the cathode had a significant adverse effect on all measured variables for A. yongei but not for A. pulchra. Treatment had no effect on the survival of A. pulchra, while mortality rates of A. yongei were significantly higher in the presence of mineral accretion compared to the electric field and control. A. yongei on the cathode featured low zooxanthella densities, depressed electron transport rates (rETR) and maximum quantum yield (F v /F m ), and reduced growth. By contrast, treatment had no effect on the fluorescence characteristics of A. pulchra, and zooxanthella densities were highest for corals on the cathode, coincident with high growth rates relative to the control. Overall, the data indicate that the proposed benefits of the mineral accretion technology to meet important objectives of reef rehabilitation with regard to colony growth and survival should be considered with caution.

- by Esther Borell
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- Earth Sciences, Coral Reefs, Biological Sciences, Environmental Sciences

Fluorescence-based observations provide useful, sensitive information concerning the nature and distribution of colored dissolved organic matter (CDOM) in coastal and freshwater environments. The excitation -emission matrix (EEM) technique has become widely used for evaluating sources and sinks of CDOM. Water scattering peaks, however, can create problems for quantitative analysis and display of the EEMs, especially for samples with low CDOM concentrations. Here we report a new method for eliminating Rayleigh and Raman scatter peaks from EEMs during post-processing of the data in MATLABR. An algorithm was developed to excise scatter peaks (i.e. peak emission F 10 -15 nm at each excitation wavelength) from the scan data and replace the excised values using three-dimensional interpolation of the remaining data (Delaunay triangulation method). The interpolated surface was constrained to pass through the non-excised values so that only data in excised portions were replaced. Tests of the algorithm in non-scatter regions indicate expected deviations of 0 -4% for interpolated regions of DOM fluorescence peaks (i.e. difference between measured and interpolated intensity after removal/interpolation), which is within machine error for the primary observations. This new scattering correction method is shown to provide much improved results in the quantitative analysis of EEMs compared to the conventional blanksubtraction procedure. The method is used to process EEMs and fluorescence quantum yields for water samples obtained along a salinity transect in a river located on the coast of the southeastern United States. Results of this analysis demonstrate observed shifts in EEM peak positions along most of the transect cannot be accounted for by a simple model that computes EEMs as a function of salinity assuming that the dominant driver of EEM spectral change is mixing between riverine and marine waters within the estuary. Other results show that fluorescence apparent quantum yields (AQYs) increased with increasing salinity and pH in the estuary and that the highest quantum yields are observed on excitation by 350 -380-nm light. Modeling results and the observed EEM spectral changes indicate that photoreactions had an important effect on the fluorescent dissolved organic matter (FDOM) optical properties in the estuary. The increase in fluorescence quantum yields with increasing salinity and pH in the estuary likely were caused by reactions involving magnesium or hydroxide ions that reduced fluorescence quenching by chelated iron and possibly other paramagnetic ions. The results of the study indicate that 0304-4203/$ -see front matter D Marine Chemistry 89 (2004) 15 -36 EEM analysis with careful scatter correction can provide a powerful tool for evaluating pathways for carbon cycling in estuaries. D

- by Wade Sheldon
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- Geochemistry, Oceanography, Carbon Cycle, Quantitative analysis

The photochemical behaviour in different solvents of the herbicide oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene (CAS RN 42874-03-3)] was studied. Photochemical reactions were carried out by using a high pressure mercury arc and a solar simulator. Kinetic parameters and quantum yields were determined. Identification of the photoproducts was performed by GC-MS and the main compounds were confirmed by [ 1 H] NMR. The photochemical reactions were also carried out in the presence of either a singlet or a triplet quencher, and in the presence of either a radical initiator or a radical inhibitor. Results indicate that the first excited singlet state can undergo both homolytic and heterolytic cleavage of the ethyl-oxygen bond in the side chain of oxyfluorfen. Moreover, the presence of reduction products in the reaction mixture is supposed to occur via a monoelectron transfer process with the formation of a transient exciplex during the reaction. (S.A. Bufo) 1010-6030/99/$ -see front matter ©1999 Published by Elsevier Science S.A. All rights reserved. PII: S 1 0 1 0 -6 0 3 0 ( 9 9 ) 0 0 1 7 3 -2

- by Laura Scrano
- •
- Engineering, High Pressure, Photochemistry, Biological Sciences

The fabrication and full characterization of luminescent solar concentrators (LSCs) comprising CdSe core/multishell quantum dots (QDs) is reported. TEM analysis shows that the QDs are well dispersed in the acrylic medium while maintaining a high quantum yield of 45%, resulting in highly transparent and luminescent polymer plates. A detailed optical analysis of the QD-LSCs including absorption, emission, and time-resolved fluorescence measurements is presented. Both silicon and GaAs solar cells attached to the side of the QD-LSCs are used to measure the external quantum efficiency and power conversion efficiency (2.8%) of the devices. Stability tests show only a minor decrease of 4% in photocurrent upon an equivalent of three months outdoor illumination. The optical data are used as input for a ray-trace model that is shown to describe the properties of the QD-LSCs well. The model was then used to extrapolate the properties of the small test devices to predict the power conversion efficiency of a 50 Â 50 cm 2 module with a variety of different solar cells. The work described here gives a detailed insight into the promise of QD-based LSCs.

- by Toby Meyer
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- Engineering, Solar Cell, Nanocomposites, Solar Energy Materials

The photochemistry of five 11-hydroxy-1,5-cyclopregn-3-en-2-ones ('lumi' products from the corresponding pregna-1,4-dien-3ones) has been investigated. In all cases the photoproducts were 1,11-oxy derivatives, resulting from intramolecular attack of the hydroxyl group to the incipient positive charge at C-1. When a fluorine atom was present at C-6, HF elimination took place concurrently with the nucleophilic addition and led to linearly conjugated dienones, rather than the enones obtained in the other cases. Quantum yields were in the range 0.06 -0.2, the lower values applying when a fluorine atom was present in position 6 (not in position 9). The results add new evidence on the role of zwitterionic intermediates in the photochemistry of cross-conjugated dienones and the corresponding lumi photoproducts. q

- by Mariella Mella
- •
- Organic Chemistry, Tetrahedron, Quantum Yield

The extinction coefficient cT, of triplet benzophenone in benzene has been directly determined by absolute measurements of absorbed energy and triplet absorbance, AD:, under demonstrably linear conditions where incident excitation energy. Eo, and ground state absorbance, A,,. are both extrapolated to zero. The result, 7220 f 320 M-' cm-' at 530 nm, validates and slightly corrects many measurements relative to benzophenone of triplet extinction coefficients made by the energy transfer technique, and of triplet yields obtained by the comparative method. As Eo and A(, both decrease, AD; becomes proportional to their product. In this situation, the ratio R = (l/A,,)(dADt/dEo) = (E~-E G) Q~. Measurements of R, referred to benzophenone, give (E ,-eCI)QI for any substance. without necessity for absolute energy calibration. Both absolute and relative laser flash measurements on zinc tetraphenyl porphyrin (E~-cG at 470 nm = 7.3 x lo4 M-l cm-') give QT = 0.83 f 0.04.

- by John Hurley
- •
- Chemistry, Photochemistry, Biological Sciences, Electromagnetic Radiation

The Suzuki-Miyaura coupling between 3,6-dibromo-N-hexylcarbazole and aryl-boronic acids catalyzed by Pd(PPh 3 ) 4 afforded blue emitting molecules, 3,6-diaryl-N-hexylcarbazole: aryl = phenyl (1), p-methoxyphenyl (2), p-cyanophenyl (3), p-acetophenyl (4), pyrenyl (5), biphenyl (6), difluorophenyl (7) and p-nitrophenyl , in good yield. The HOMO level of the carbazole derivative varied between −5.67 and −6.02 eV due to the electron-withdrawing or donating substituent in the aryl group. This is confirmed by the linear correlation of the Hammett parameter of the substituent in the phenyl group with oxidation potential or energy levels. Density functional theory calculation (B3LYP/6-31G*) of carbazole derivatives confirmed the experimentally observed trend. Blue fluorescence quantum yield of these molecules is high (0.19-0.96), except for the nitrophenyl derivative (<0.1). Single layer organic light emitting devices (OLEDs) using spin-coated films of 2-5 showed blue electroluminescence (EL) with a turn-on voltage at ∼6-7 V. The performance of blue EL of molecules 3 and 4 improved dramatically (turn-on at ∼3 V, brightness at ∼1000 cd/m 2 , efficiency at ∼1 cd/A) in a multilayer OLED designed using standard molecules as electron and hole transport layers for efficient and balanced carrier injection.

- by Meghan Patankar
- •
- Materials Engineering, Condensed Matter Physics, Lancet, Transport Layer

Earlier steady-state fluorescence studies showed that 2-butylamino-6-methyl-4-nitropyridine N-oxide (2B6M) can undergo fast excited-state intramolecular proton transfer (ESIPT). In a nonpolar solvent such as n-octane, both normal and tautomeric fluorescence was observed. Strikingly, the relative ratio of those two emission bands and the fluorescence quantum yield of the normal emission were found to depend on the excitation wavelength in violation of the Kasha-Vavilov rule. In this work, the system was investigated further by means of transient absorption spectroscopy, followed by global and target analysis. Upon excitation at 420 nm, a normal excited singlet state S 1 (N) is reached, which decays in about 12 ps via fluorescence and ESIPT (minor pathways) and to a long-lived "dark" state (major pathway) that is most probably the triplet T 1 (N). Upon 330 nm excitation, however, a more complex pattern emerges and additional decay channels are opened. A set of four excited-state species is required to model the data, including a hot state S 1 (N)* that decays in about 3 ps to the tautomer, to the long-lived "dark" state and to the relaxed S 1 (N) state. A kinetic scheme is presented that can explain the observed transient absorption results as well as the earlier fluorescence data.

- by Freek Ariese
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- Steady state, Excited states, THEORETICAL AND COMPUTATIONAL CHEMISTRY, Quantum Yield

A field test of wych elm (Ulmus glabra Huds.) trees micropropagated in tissue culture was established to compare their photosynthetic characteristics with those from control grafted scions. Measurements were made at the sixth growing season after planting. The results showed similarities between the two stock types in terms of height, diameter at breast height, and leaf morphology. Grafted trees, which were markedly less rejuvenated than micropropagated trees, performed better in many of the light absorption and leaf gas exchange attributes including maximum CO 2 assimilation rate at saturating photosynthetic photon flux density (P max ), apparent quantum yield of photosynthesis (a), transpiration rate (E), and stomatal conductance (g s ). In the grafts, the direct effect of photosynthesis could be clearly identified by a significantly lower specific leaf area and a higher content of leaf dry mass. Chlorophyll a fluorescence parameters showed nonstressed growth patterns in both stock types. Rates of the maximal photochemical efficiency of photosystem II (F v /F m ), potential electron capacity ('area'), and variable-to-initial fluorescence ratio (F v /F 0 ) were higher in micropropagated elms. Findings from this study indicate that micropropagated elm stock is ready for testing on a larger scale.

- by Tibor Priwitzer
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- Plant Biology, Tissue culture, Chlorophyll Fluorescence, Leaf Morphology

A new simple method for synthesis of core/ shell CdSe/ZnS nanocrystals (NCs) is present. By adapting the use of cadmium stearate, oleylamine, and paraffin liquid to a non-injection synthesis and by applying a subsequent ZnS shelling procedure to CdSe NCs cores using Zinc acetate dihydrate and sulfur powder, luminescent CdSe/ZnS NCs with quantum yields of up to 36% (FWHM 42-43 nm) were obtained. A seeding-growth technique was first applied to the controlled synthesis of ZnS shell. This method has several attractive features, such as the usage of low-cost, green, and environmentally friendlier reagents and elimination of the need for air-sensitive, toxic, and expensive phosphines solvent. Furthermore, due to one-pot synthetic route for CdSe/ZnS NCs, the approach presented herein is accessible to a mass production of these NCs.

- by Xinyu Wang
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- Materials Engineering, Condensed Matter Physics, Nanotechnology, Zinc