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1.
J Fluoresc ; 2023 Oct 14.
Artículo en Inglés | MEDLINE | ID: mdl-37837509

RESUMEN

A benzene ring and a lactone ring combine to form the chemical coumarin. Dye lasers have made significant advances in laser technology. The coumarin molecule itself is a non-fluorescent but it displays high fluorescence when electron-denoting substituents such as sulfonamide, benzopyrone, amine, benzothiazole, hydroxyl, methoxy are substituted at various positions. Substituted coumarin possesses the highest energy properties, photostability, and alteration in electron mobility, and therefore could be effectively used as dye lasers. These are considered some of the best fluorophores due to their outstanding photophysical and photochemical properties, which include high fluorescence quantum yields, great photostability, good functionality, and a wide spectrum range. Various inorganic materials are used in classic laser technology to generate the necessary emission. Inorganic lasers come in various types and can emit light in the electromagnetic spectrum's ultraviolet, visible, or infrared parts. Inorganic lasers have certain limitations, which is why coumarin lasers are becoming increasingly popular due to their many advantages. Compared to inorganic lasers, dye lasers offer far better tunability and cover the entire visible and near-infrared range. They only emit at very few specific wavelengths and in extremely narrow bands. The property is therefore presented in this review.

2.
Chirality ; 35(3): 172-177, 2023 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-36625726

RESUMEN

Chiral information transmission in helical polymers bearing multi-chiral pendant groups is usually determined by the absolute configuration of the first chiral center. The second chiral residue usually has low-to-null influence in the macromolecular handedness of the polymer, due to its remote position respect to the polyene main chain. Here, we demonstrate how the stimuli responsive properties of diastereomeric polymers, obtained by changing the absolute configuration of the second chiral center, are different due to the unlike properties of diastereoisomers.

3.
Int J Mol Sci ; 24(11)2023 May 30.
Artículo en Inglés | MEDLINE | ID: mdl-37298430

RESUMEN

Glyphosate is an herbicide widely used in agriculture but can present chronic toxicity in low concentrations. Artemia salina is a common bio-indicator of ecotoxicity; it was used herein as a model to evaluate the effect of highly diluted-succussed glyphosate (potentized glyphosate) in glyphosate-based herbicide (GBH) exposed living systems. Artemia salina cysts were kept in artificial seawater with 0.02% glyphosate (corresponding to 10% lethal concentration or LC10) under constant oxygenation, luminosity, and controlled temperature, to promote hatching in 48 h. Cysts were treated with 1% (v/v) potentized glyphosate in different dilution levels (Gly 6 cH, 30 cH, 200 cH) prepared the day before according to homeopathic techniques, using GBH from the same batch. Controls were unchallenged cysts, and cysts treated with succussed water or potentized vehicle. After 48 h, the number of born nauplii per 100 µL, nauplii vitality, and morphology were evaluated. The remaining seawater was used for physicochemical analyses using solvatochromic dyes. In a second set of experiments, Gly 6 cH treated cysts were observed under different degrees of salinity (50 to 100% seawater) and GBH concentrations (zero to LC 50); hatching and nauplii activity were recorded and analyzed using the ImageJ 1.52, plug-in Trackmate. The treatments were performed blind, and the codes were revealed after statistical analysis. Gly 6 cH increased nauplii vitality (p = 0.01) and improved the healthy/defective nauplii ratio (p = 0.005) but delayed hatching (p = 0.02). Overall, these results suggest Gly 6cH treatment promotes the emergence of the more GBH-resistant phenotype in the nauplii population. Also, Gly 6cH delays hatching, another useful survival mechanism in the presence of stress. Hatching arrest was most marked in 80% seawater when exposed to glyphosate at LC10. Water samples treated with Gly 6 cH showed specific interactions with solvatochromic dyes, mainly Coumarin 7, such that it appears to be a potential physicochemical marker for Gly 6 cH. In short, Gly 6 cH treatment appears to protect the Artemia salina population exposed to GBH at low concentrations.


Asunto(s)
Quistes , Herbicidas , Animales , Artemia , Herbicidas/toxicidad , Agua/farmacología , Glifosato
4.
J Fluoresc ; 32(1): 95-108, 2022 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-34562204

RESUMEN

In this study, we investigated the solvent effects on the photophysical properties of α,ω-di(4-pyridyl)polyenes 1-5 having 1-5 double bonds. The solution photoproperties depend strongly on conjugation chain length. The absorption maximum (λa) of dipyridylethylene 1 is observed at around 290 nm and only slightly redshifts as the solvent polarity increases, whereas its fluorescence maximum (λf) redshifts from 368 nm in hexane to 403 nm in acetonitrile. Although 1 is a centrosymmetric molecule, its fluorescence energy linearly correlates with the Onsager solvent polarity function f(ε) - f(n2) = (ε - 1)/(2ε + 1)-(n2 - 1)/(2n2 + 1), indicating that the emission originates from an intramolecular charge transfer (CT) excited state. Exceptionally, λf in methanol is largely blue-shifted to 341 nm from those in other aprotic solvents. The fluorescence solvatochromism of longer polyenes 2-5 is much less significant than that of 1. Upon protonation and N-alkylation, both the absorption and fluorescence spectra of all five compounds are red-shifted in methanol. The largest shifts in λa and λf on protonation are observed for pentaene 5 (73 nm) and diene 2 (57 nm), respectively.

5.
Molecules ; 27(21)2022 Oct 22.
Artículo en Inglés | MEDLINE | ID: mdl-36363973

RESUMEN

Photophysical properties of two Re(I) complexes [ReCl(CO)3(R-C6H4-terpy-κ2N)] with remote amine groups, N-methyl-piperazinyl (1) and (2-cyanoethyl)methylamine (2), were investigated. The complexes show strong absorption in the visible region corresponding to metal-to-ligand charge transfer (1MLCT) and intraligand-charge-transfer (1ILCT) transitions. The energy levels of 3MLCT and 3ILCT excited-states, and thus photoluminescence properties of 1 and 2, were found to be strongly affected by the solvent polarity. Compared to the parent chromophore [ReCl(CO)3(C6H5-terpy-κ2N)] (3), both designed complexes show significantly prolonged (by 1-2 orders of magnitude) phosphorescence lifetimes in acetonitrile and dimethylformamide, contrary to their lifetimes in less polar chloroform and tetrahydrofuran, which are comparable to those for 3. The femtosecond transient absorption (fsTA) measurements confirmed the interconversion between the 3MLCT and 3ILCT excited-states in polar solvents. In contrast, the emissive state of 1 and 2 in less polar environments is of predominant 3MLCT nature.


Asunto(s)
Renio , Renio/química , Ligandos , Metales , Análisis Espectral , Aminas
6.
Photochem Photobiol Sci ; 20(9): 1183-1194, 2021 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-34463933

RESUMEN

Density functional theory (DFT) and time-dependent density functional theory (TDDFT) are used to study the solvatochromic effect and the excited-state intramolecular double proton transfer (ESIDPT) of 1,3-Bis(2-pyridylimino)-4,7-dihydroxyisoindole (BPI-OH) in different kinds of solvents. The hydrogen bonding parameters and IR spectra reveal that in the excited state, the strength of excited hydrogen bond increase with the decrease of solvent polarity. Furthermore, the reduction density gradient (RDG) analysis confirms the corresponding conclusion. Frontier molecular orbitals (FMOs) are analyzed, illuminating that the smaller the polarity of solvent, the smaller the energy gap between the HOMO and LUMO. The structures of BPI-OH (N) (normal), BPI-OH (T1) (single), and BPI-OH (T2) (double) were optimized. Previous reports found the double protons in BPI-OH molecule are transferred step-by-step process BPI-OH(N)→BPI-OH(T1)→BPI-OH(T2) in the ground state (S0) and the first excited singlet state (S1). Here, the potential energy curves of O1-H2 and O4-H5 in the S0 and S1 states were scanned in four kinds of solvents, respectively. It was found that in S1 state, BPI-OH(N)→BPI-OH(T1) was more prone to proton transfer than BPI-OH(T1)→BPI-OH(T2). In addition, by comparing the reaction energy barriers of the four kinds of solvents, it can be found that ESIPT is difficult to occur with the increase of solvent polarity. Meanwhile, it was also studied that MeOH as an explicit solvent was more likely to promote the ESIPT process than other implicit solvents.

7.
J Fluoresc ; 31(6): 1719-1729, 2021 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-34427839

RESUMEN

A computational study based on the DFT/TD-DFT approach was performed to explore various properties of 6-aminoquinoline (6AQ). The geometrical parameters, molecular orbitals (MOs), electronic spectra, electrostatic potential, molecular surface, reactivity parameters and thermodynamic properties of 6AQ were explored. The absorption and emission spectra of 6AQ in solvents have been estimated by TD-DFT coupled with the PCM model and correlated with the available experimental results. Depending on the solvents, the computed absorption maxima of 6AQ were noticed between 327 nm - 340 nm and ascribed to [Formula: see text] transition. The simulated emission maxima were obtained between 389 to 407 nm and ascribed to [Formula: see text] transition. On increasing the solvent polarity, both the emission and absorption maxima showed a bathochromic shift. The LUMO and HOMO were localized on the entire molecule. It was observed that the lowest excited state is possibly the [Formula: see text] charge-transfer (CT) state. The natural bonding orbital (NBO) study points out that ICT plays a significant role in stabilizing the molecular system. Moreover, the NLO (nonlinear optical) properties (polarizability, first-order hyperpolarizability and dipole moment) were computed using different hybrid functionals. The estimated values indicate that 6AQ can be considered a desirable molecule for further studies of the NLO applications.

8.
Angew Chem Int Ed Engl ; 60(45): 24299-24305, 2021 Nov 02.
Artículo en Inglés | MEDLINE | ID: mdl-34498361

RESUMEN

Triazine-based materials with porous structure have recently received numerous attentions as a fascinating new class because of their superior potential for various applications. However, it is still a formidable challenge to obtain triazine-based materials with precise adjustable meso-scaled pore sizes and controllable pore structures by reported synthesis approaches. Herein, we develop a solvent polarity induced interface self-assembly strategy to construct mesoporous triazine-based carbon materials. In this method, we employ a mixed solvent system within a suitable range of polarity (0.223≤Lippert-Mataga parameter (Δf) ≤0.295) to induce valid self-assembly of skeleton precursor and surfactant. The as-prepared mesoporous triazine-based carbon materials possess uniform tunable pore sizes (8.2-14.0 nm), high surface areas and ultrahigh nitrogen content (up to 18 %). Owing to these intriguing advantages, the fabricated mesoporous triazine-based carbon materials as functionalized porous solid absorbents exhibit predominant CO2 adsorption performance and exceptional selectivity for the capture of CO2 over N2 .

9.
Molecules ; 24(17)2019 Aug 29.
Artículo en Inglés | MEDLINE | ID: mdl-31470596

RESUMEN

Sequential extraction and purification stages are required to obtain extracts rich in specific polyphenols. However, both separation processes are often optimized independently and the effect of the integrated process on the global recovery of polyphenols has not been fully elucidated yet. We assessed the impact of hot-pressurized liquid extraction (HPLE) conditions (temperature: 90-150 °C; ethanol concentration: 15%-50%) on the global recovery of specific phenolic acids, flavanols, flavonols and stilbenes from Carménère grape pomace in an integrated HPLE/resin purification (RP) process. HPLE of phenolic acids, flavanols and stilbenes were favored when temperature and ethanol concentration increased, except for chlorogenic acid which showed an increment of its Gibbs free energy of solvation at higher ethanol contents. Ethanol concentration significantly impacted the global yield of the integrated HPLE/RP process. The lower the ethanol content of the HPLE extracts, the higher the recovery of phenolic acids, flavanols and stilbenes after RP, except for flavonols which present more polar functional groups. The best specific recovery conditions were 150 °C and ethanol concentrations of 15%, 32.5% and 50% for phenolic acids, flavanols and stilbenes, and flavonols, respectively. At 150 °C and 32.5% of ethanol, the extracts presented the highest total polyphenol content and antioxidant capacity. The integrated HPLE/RP process allows a selective separation of specific polyphenols and eliminates the interfering compounds, ensuring the safety of the extracts at all evaluated conditions.


Asunto(s)
Flavonoles/aislamiento & purificación , Hidroxibenzoatos/aislamiento & purificación , Extracción Líquido-Líquido/métodos , Polifenoles/aislamiento & purificación , Estilbenos/aislamiento & purificación , Vitis/química , Ácido Clorogénico/aislamiento & purificación , Etanol/química , Calor , Extractos Vegetales/química , Presión , Solventes/química , Termodinámica
10.
J Fluoresc ; 28(6): 1421-1430, 2018 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-30343361

RESUMEN

Novel 7,7'-((anthracene-9,10-diylbis(methylene))bis(oxy))bis(4-methyl-2H-chromen-2-one) (BisCA) was prepared as fluorescent probe. The chemical structure of the novel BisCA was confirmed by spectroscopic data as well as elemental analyses. The solvatochromic characteristics of the new proble and its precursors were investigated in different solvents including, ethanol, DMF and toluene as protic polar, aprotic polar and non-polar solvents, respectively. Photo-physical parameters of probes, such as fluorescence quantum yields, fluorescence lifetime of excited state, radiative and non-radiative decay, were assessed in different media. The intermolecular H-bond effect on absorption and excitation spectra of the novel probe was reported in different solvents. Also, Onsager cavity radius and dipole moment of ground state and excited state of the probe were calculated as described by Bakhshiev and Reichardt methods.

11.
Molecules ; 23(4)2018 Mar 22.
Artículo en Inglés | MEDLINE | ID: mdl-29565816

RESUMEN

The effect of solvent polarity on the quality of self-assembled n-octadecanethiol (C18SH) on Cu surfaces was systematically analyzed using first-principles calculations. The results indicate that the adsorption energy for C18SH on a Cu surface is -3.37 eV, which is higher than the adsorption energies of the solvent molecules. The higher adsorption energy of dissociated C18SH makes the monolayer self-assembly easier on a Cu (111) surface through competitive adsorption. Furthermore, the adsorption energy per unit area for C18SH decreases from -3.24 eV·Å-2 to -3.37 eV·Å-2 in solvents with an increased dielectric constant of 1 to 78.54. Detailed energy analysis reveals that the electrostatic energy gradually increases, while the kinetic energy decreases with increasing dielectric constant. The increased electrostatic energies are mainly attributable to the disappearance of electrostatic interactions on the sulfur end of C18SH. The decreased kinetic energy is mainly due to the generated push force in the polar solvent, which limits the mobility of C18SH. A molecular dynamics simulation also confirms that the -CH3 site has a great interaction with CH3(CH2)4CH3 molecules and a weak interaction with CH3CH2OH molecules. The different types of interactions help to explain why the surface coverage of C18SH on Cu in a high-polarity ethanol solution is significantly larger than that in a low-polarity n-hexane solution at the stabilized stage.


Asunto(s)
Cobre/química , Solventes/química , Compuestos de Sulfhidrilo/química , Simulación de Dinámica Molecular , Propiedades de Superficie
12.
Chemphyschem ; 18(7): 763-771, 2017 Apr 05.
Artículo en Inglés | MEDLINE | ID: mdl-28087990

RESUMEN

Solvent polarity is an important solvent property. The Onsager's theory of reaction field was the most classic model to describe solvent effects and was widely used in relating dielectric constant and other solvent polarity parameters. In this study, a modified semi-empirical reaction field was presented to relate electron transition energies or hyperfine coupling constants with the dielectric constants of solvents. In previous work, this relationship was well established by traditional Onsager reaction field for nonhydrogen-bonding systems but failed for hydrogen-bonding systems. In this modified reaction field model, the radius of the field was replaced by that of the primary solvation shell or the molecular fragment rather than that of the probe. In this way, the molecular volume of the solvent which contains information of the molecular size and overall interactions is involved in the reaction field. The 154 sets of electron transition energies and 44 sets of nitrogen isotropic hyperfine coupling constants were used to verify the modified model, indicating it works far better than the traditional model for hydrogen-bonding systems.

13.
Biochim Biophys Acta Gen Subj ; 1861(9): 2206-2217, 2017 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-28652076

RESUMEN

BACKGROUND: Melatonin is well known for its antioxidant capacity, which has been attributed to the combined protective effects of the parent molecule and its metabolites. However, the potential role of 2-hydroxymelatonin (2OHM) and 4-hydroxymelatonin (4OHM) in such protection has not been previously investigated. METHODS: The calculations were performed using the Density Functional Theory, with the M05-2X and M05 functionals, the 6-311+G(d,p) basis set and the solvation model based on density (SMD). RESULTS: 4OHM shows excellent antioxidant activity via radical-trapping, reacting with peroxyl radicals faster than Trolox and melatonin. 4OHM can be moderately efficient as a preventing antioxidant by inhibiting Cu(II). This effect would lower the Cu(I) availability, which is the redox state required for the OH to be formed, via Fenton-like reactions. 4OHM turns off the oxidant effects of copper-ascorbate mixtures. The presence of a phenolic group was identified as the key structural feature in the antioxidant activity of 4OHM. On the other hand, 2OHM does not present a phenolic group, despite its formal name. Its keto tautomer was identified as the most abundant one (~100%). This may explain the relative low antioxidant protection of 2OHM. CONCLUSIONS: 4OHM significantly contributes to the overall antioxidant activity exhibited by melatonin, while the effects of 2OHM in this context are predicted to be only minor. This low reactivity might justify the relatively large abundance of 2OHM in biological systems. GENERAL SIGNIFICANCE: Hydroxylated melatonin metabolites, such as 4OHM, may play an important role in the protective effects of melatonin against oxidative stress.


Asunto(s)
Antioxidantes/farmacología , Depuradores de Radicales Libres/farmacología , Melatonina/análogos & derivados , Melatonina/farmacología , Estrés Oxidativo , Melatonina/metabolismo
14.
J Fluoresc ; 27(4): 1531-1540, 2017 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-28434062

RESUMEN

Synthesis of novel 3,6-di(substituted quinoxalin) carbazole fluorophores by the condensation of 1,1'-(9-ethyl-9H-carbazole-3,6-diyl)bis(2-bromoethanone) with methyl, chloro and unsubstituted o-phenylenediamine is presented. Synthesized derivatives are well characterized by 1H NMR, 13C NMR, FTIR and Mass spectroscopy. Photophysical studies are carried out using solvents of varying polarities revealed positive solvatochromism and intramolecular charge transfer from carbazole (Donor) to quinoxalin (Acceptor). Intramolecular charge transfer properties are correlated by dipole moment changes and different polarity functions like Lippert-Mataga, Bilot-Kawski, Bakhshiev and Liptay plots with very good regression factors. Mulliken hush-analysis further support charge transfer characteristic. Linear and Nonlinear optical properties are explained by solvatochromic data using two-level quantum mechanical model and are correlated with computational calculations using density functional theory at B3LYP/6-31G(d) level. First hyperpolarizability value of all the synthesized compounds is found to be greater than urea by >333 times. Moreover, increase of hyperpolarizability values from non-polar to polar solvents are in good correlation with the significant charge transfer characteristic in polar solvents.

15.
J Fluoresc ; 27(1): 167-180, 2017 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-27757692

RESUMEN

Three new Y-shaped styryl dyes were designed and synthesized from thiazole carbaldehyde with different active methylene compounds as acceptor moieties. All the dyes were characterized by IR, 1HNMR, MS/LCMS/HRMS. Spectroscopic properties and non-linear optical properties styryl derivatives were analyzed and the effect of change in solvent polarity on their absorption and emissive properties has been investigated. The dye with (1-phenylethylidene) propanedinitrile unit shows red shift absorption/emission profile among all the dyes. Density Functional Theory and Time Dependent-Density Functional Theory computations have been used for comparative study with the experimental data and also to understand the structural, molecular, electronic and photophysical parameters of the styryl dyes. The computational method was also employed to investigate the nonlinear optical properties of the styryl dyes in different organic solvent. The unsubstituted benzimidazolyl thiazole styryl dyes possess good non-linear optical properties.

16.
Luminescence ; 32(7): 1328-1338, 2017 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-28581184

RESUMEN

The UV/Vis absorption and fluorescence characteristics of 3-cyano-7-hydroxycoumarin [CHC] and 7-amino-4-methyl-3-coumarinylacetic acid [AMCA-H] were studied at room temperature in several neat solvents and binary solvent mixtures of 1,4-dioxane/acetonitrile. The effects of solvent on the spectral properties are analyzed using single and multi-parameter solvent polarity scales. Both general solute/solvent interactions and hydrogen bond interactions are operative in these systems. The solvation of CHC and AMCA-H dyes in 1,4-dioxane/acetonitrile solvent mixtures has been studied. The solutes CHC and AMCA-H are preferentially solvated by acetonitrile and a synergistic effect is observed for both molecules in dioxane/acetonitrile solvent mixtures. In addition, using the solvatochromic method the ground- and the excited-state dipole moments of both the dyes were calculated. The ground- and excited-state dipole moments, absorption and emission maxima and HOMO-LUMO gap were also estimated theoretically using B3LYP/6-311+ G (d,p) level of theory in the gaseous phase, dioxane and acetonitrile solvents. Furthermore, changes in dipole moment values were also calculated using the variation of Stokes shift with the molecular-microscopic empirical solvent polarity parameter ( ETN). The observed excited-state dipole moments are larger than their ground-state counterparts, indicating a substantial redistribution of the electron densities in a more dipolar excited state for both coumarins investigated.


Asunto(s)
Acetatos/química , Colorantes/química , Cumarinas/química , Nitrilos/química , Enlace de Hidrógeno , Modelos Químicos , Soluciones , Solventes/química , Espectrometría de Fluorescencia , Espectrofotometría Ultravioleta
17.
Phytochem Anal ; 28(6): 584-592, 2017 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-28741753

RESUMEN

INTRODUCTION: The phytochemical composition and biological activity of non-volatile components of Centaurea ragusina L. has not been studied previously. OBJECTIVES: Our aim was to evaluate the phytochemical and bioactive potential (including interactions with polynucleotides) of C. ragusina L. depending on the origin of plant material (in vivo - leaves from natural habitats, ex vitro - leaves from plants acclimated from culture media, in vitro - leaves and calli from plants grown in culture media) and polarity of solvents used in extract preparation (80 and 96% ethanol and water combinations or single solvents). METHODOLOGY: The polyphenol composition was determined by spectrophotometric and HPLC analysis. Biological activity of extracts was evaluated by following methods: 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) methods for antioxidative activity, 2,3,5-triphenyl tetrazolium chloride (TTC) microdilution method for antibacterial activity, crystal-violet test for cytotoxic activity and thermal denaturation (TD) and circular dichroism (CD) for DNA/RNA interactions. RESULTS: Conditions for the most efficient polyphenol extraction were determined: the 80% ethanol/water solvent system was the most suitable for callus and leaf ex vitro samples and 80 or 96% ethanol for leaf in vivo samples. Significantly higher levels of chlorogenic acid and naringenin were detected in callus tissue than in vivo plant. Ethanolic extracts exhibited the significant antibacterial activity against Staphylococcus aureus ATCC 25923. DNA/RNA active compounds in plant extracts were detected by TD and CD methods. CONCLUSIONS: Callus tissue and ex vitro leaves represent a valuable source of polyphenols as in vivo leaves. TD and CD can be applied for detection of DNA/RNA active compounds in extracts from natural resources. Copyright © 2017 John Wiley & Sons, Ltd.


Asunto(s)
Centaurea/química , ADN/química , Fitoquímicos/química , Extractos Vegetales/química , Polifenoles/química , ARN/química , Cromatografía Líquida de Alta Presión , Dicroismo Circular , Fitoquímicos/metabolismo , Espectrofotometría
18.
Nano Lett ; 16(7): 4630-4, 2016 07 13.
Artículo en Inglés | MEDLINE | ID: mdl-27351104

RESUMEN

Colloidal quantum dot (CQD) solar cells are solution-processed photovoltaics with broad spectral absorption tunability. Major advances in their efficiency have been made via improved CQD surface passivation and device architectures with enhanced charge carrier collection. Herein, we demonstrate a new strategy to improve further the passivation of CQDs starting from the solution phase. A cosolvent system is employed to tune the solvent polarity in order to achieve the solvation of methylammonium iodide (MAI) and the dispersion of hydrophobic PbS CQDs simultaneously in a homogeneous phase, otherwise not achieved in a single solvent. This process enables MAI to access the CQDs to confer improved passivation. This, in turn, allows for efficient charge extraction from a thicker photoactive layer device, leading to a certified solar cell power conversion efficiency of 10.6%, a new certified record in CQD photovoltaics.

19.
J Fluoresc ; 26(4): 1391-400, 2016 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-27220623

RESUMEN

We report the effect of solvents on absorption and fluorescence spectra of biologically active 3(2H)-pyridazinone namely 5-(2-hydroxy-naphthalen-1-yl)-2-phenyl-2H-pyridazin-3-one (HNP) in different solvents at room temperature. The ground and the excited state dipole moments of HNP molecule was estimated from Lippert's, Bakshiev's and Kawski-Chamma-Viallet's equations using the solvatochromic shift method. The ground state dipole moment (µ g ) was also estimated by Guggenheim and Higasi method using the dielectric constant and refractive index of solute at different concentrations, the µ g value obtained from these two methods are comparable to the µ g value obtained by the solvatochromic shift method. The excited state dipole moment (µ e ) is greater than the ground state dipole moment (µ g ), which indicates that the excited state is more polar than the ground state. Further, we have evaluated the change in dipole moment (Δµ) from the solvatochromic shift method and on the basis of molecular-microscopic solvent polarity parameter[Formula: see text], later on the values were compared.

20.
Beilstein J Org Chem ; 12: 245-52, 2016.
Artículo en Inglés | MEDLINE | ID: mdl-26977183

RESUMEN

We describe the synthesis of bromo-tert-butyloxycarbonyl (Br-t-BOC)-amino-protected monomers 2-((1-bromo-2-methylpropan-2-yl)oxycarbonylamino)ethyl (meth)acrylate 3a,b. For this purpose, 2-isocyanatoethyl (meth)acrylate 1a,b was reacted with 1-bromo-2-methylpropan-2-ol (2a). The free radical polymerization of (Br-t-BOC)-aminoethyl (meth)acrylates 3a,b yielded poly((Br-t-BOC)-aminoethyl (meth)acrylate) 6a,b bearing protected amino side groups. The subsequent solvolysis of the Br-t-BOC function led to the new polymers poly(2-aminoethyl (meth)acrylate) 8a,b with protonated free amino groups. The monomers and the resulting polymers were thoroughly characterized by (1)H NMR, IR, GPC and DSC methods. The kinetics of the deprotection step was followed by (1)H NMR spectroscopy. The solvent polarity and neighboring group effects on the kinetics of deprotection are discussed.

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