Acridine Orange Base Research Articles

Visible-Light-Mediated Synthesis of Phenanthrenes through Successive Photosensitization and Photoredox by a Single Organocatalyst.

An efficient approach for the synthesis of phenanthrene scaffolds by utilizing the dual catalytic activity of an organo-photocatalyst is documented. The controlled cascade transformation proceeds via in situ diazotization followed by olefin isomerization and subsequent arene radical generation through photoreduction. The overall process demonstrates both the photosensitization and photoredox properties of a single organo-photocatalyst and facilitates the desired intramolecular annulation with high precision and efficacy. In this context, the underexplored organocatalyst acridine orange base is employed and the photophysical interactions between the catalyst and the substrates along with the detailed reaction kinetics are documented.

Fabricate organic thermoelectric modules use modified PCBM and PEDOT:PSS materials

In this paper, we fabricated an organic thermoelectric (TE) device with modified [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS); the device showed good stability in air condition. For n-leg, PCBM were doped with acridine orange base (3,6-bis (dimethylamino)acridine) (AOB) and 1,3-dimethyl-2,3-dihydro-1H-benzoimidazole (N-DMBI). Co-doped PCBM utilizes synergistic effects of AOB and N-DMBI, resulting in excellent electrical conductivity and Seebeck coefficient values reaching 2 S/cm and -500 mV/K, respectively, at room temperature with dopant molar ratio of 0.11. P-type leg used modified PEDOT:PSS. Based on modified PCBM and PEDOT:PSS materials, we fabricated a TE module device with 48 p-type and n-type thermocouple and tested their output voltage, short current, and power. Output voltage measured ~0.82 V, and generated power reached almost 945 mW with 75 K temperature gradient at 453 K hot-side temperature. These promising results showed potential of modified PEDOT and PCBM as TE materials for application in device optimization.

On the design of a versatile ionic liquid, AOBH-DEHP, which can be used as a new molecular probe to investigate supramolecular assemblies

The motivation of our work is to find an exciting new molecular probe, which has the advantages that contains the acridine orange moiety but also has an ample range of solubility in different media. The probe is obtained through the acid-base reaction between acridine orange base (AOB) and bis-(2-ethylhexyl) phosphoric acid (HDEHP) giving AOBH-DEHP. This synthesized dye results to be a protic ionic liquid, since it is a viscous liquid at room temperature and, it is only constituted by ions.The spectroscopic behavior of AOBH-DEHP in homogeneous medium, using water, benzene and n-heptane as solvents and, in benzene or n-heptane/sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT)/water reverse micelles (RMs) has been investigated. Absorption, emission and single photon counting techniques, were used to fully characterize the new molecule in different environments.It is shown that AOBH-DEHP has all the advantages of its chromophore, AOBH+ but, the presence of the hydrophobic anion, DEHP−, gives to the dye, unique solubility in solvents of very different polarities. As such and, in contrast to AOBH+ chloride salts, AOBH-DEHP can be used to determine different properties, such as micropolarity, restricted motion environment, critical micellar concentration in different RMs media.

Solvent-resistant ITO work function tuning by an acridine derivative enables high performance inverted polymer solar cells

In order to avoid an interpenetration of the buffer and the photoactive layers during preparation of polymer solar cells (PSCs), solvent-resistant buffer films were chemically modified on indium tin oxide (ITO) surface. The conjugated aromatics acridine orange base (AOB) was introduced into the films using 3-bromopropyltrimethoxysilane (BrTMS) as coupling agent. Upon ITO surface modification, the respective work functions show a significant decrease. The modified ITO substrates were implemented in inverted PSCs based on PBDTTT-C-T:PC71BM. With the modification, the power conversion efficiency (PCE) was improved significantly from 4.10% (for the inverted PSC without this buffer layer) to 7.56%. The PCE enhancement is mainly caused by the increase of the open-circuit voltage (43%). These results indicate that the solvent-resistant film is able to facilitate electron collection and transportation, thus providing a novel route to high efficient PSCs by surface engineering.

Electron-Donor Dye Molecule on ZnO(101̅0), (0001), and (0001̅) Studied by Photoelectron Spectroscopy and X-ray Absorption Spectroscopy

Interaction between an air-stable orange-colored dye molecule, acridine orange base (AOB), and single-crystal surfaces of ZnO(1010), (0001), and (0001) is examined by synchrotron-radiation-excited photoelectron spectroscopy and X-ray absorption spectroscopy. AOB adsorbs molecularly on the ZnO surfaces to form chemical bonds with the surface O atoms. AOB tends to lie flat on the surfaces, whereas a more stand-up orientation is preferred on the AOB-crowded surfaces. AOB adsorption induces downward bending of the ZnO band with the largest amount on ZnO(0001), followed by the ZnO(1010) and ZnO(0001) surfaces, indicating an electron donor property of AOB. The energy level alignment at the AOB/ZnO interface is determined and is found to be characterized by a type-II heterojunction, which favors the charge transfer of the excited electron from AOB to ZnO.

The effect of dimethylsulfoxide on absorption and fluorescence spectra of aqueous solutions of acridine orange base

The photophysical properties of aqueous solutions of acridine orange base (AOB) in wide concentration range of dimethylsulfoxide (DMSO) were studied by using absorption and steady-state fluorescence spectroscopy techniques at room temperature. The absorption spectrum of acridine orange in water shows two bands at 468 and 490nm which were attributed to the dimer ((AOBH)22+) and monomer (AOBH+) species respectively. In DMSO solution for the same AOB concentration only the basic form was detected with the band at 428nm. The addition of DMSO to AOB aqueous solution leads to the decrease of absorption band at 490nm and the new absorption band increases at 428nm due to deprotonated (basic) form of AO and the first isosbestic point occurs at 450nm. The evolution of isosbestic point reveals that an other equilibrium, due to the self-association of DMSO molecules takes place. From the steady-state fluorescence spectra Stokes shifts were calculated for AOB in aqueous and DMSO solutions. The addition of DMSO into the aqueous solution induced the enhancement in the fluorescence intensity of the dye compared to those in water.

Energy level alignment and interactive spin polarization at organic/ferromagnetic metal interfaces for organic spintronics

Energy level alignment and spin polarization at tetracyanoquinodimethane/Fe and acridine orange base/Fe interfaces are investigated by means of photoelectron spectroscopy and X-ray magnetic circular dichroism (XMCD), respectively, to explore their potential application in organic spintronics. Interface dipoles are observed at both hybrid interfaces, and the work function of Fe is increased by 0.7eV for the tetracyanoquinodimethane (TCNQ) case, while it is decreased by 1.2eV for the acridine orange base (AOB) case. According to XMCD results, TCNQ molecule has little influence on the spin polarization of Fe surface. In contrast, AOB molecule reduces the interfacial spin polarization of Fe significantly. Induced spin polarization of the two organic molecules at the interfaces is not observed. The results reveal the necessity of investigating the magnetic property changes of both the OSC and the FM during the process of energy level alignment engineering.

A facile method to immobilize cucurbituril on surfaces through photocrosslinking with azido groups

We develop a facile method to immobilize cucurbituril on silicon substrates through photochemical reaction with azido groups. Combining photolithography and the competitive molecular recognition between CB[7] and acridine orange base or 1-adamantanecarboxylic acid, a patterned surface with reversible fluorescence emission can be obtained.

Chemically modified polysulfones for molecular imprinting. Synthesis and complexation with a fluorescent model template

Polysulfone (PSU) was chemically modified to prepare new molecular imprinted membranes (MIMs). Several amounts of amine and sulfonyl groups were introduced into the PSU chemical structure in order to create interactions with acid or base templates, such as biomolecules or biomacromolecules. A fluorescent dye, Acridine Orange base (AO), was used as a model template and its complexation with the prepared PSUs was monitored by spectroscopic techniques. This study showed an absence of complexation with the native PSU and a strong complexation with the aminated and the sulfonated PSUs. Partially allylated PSU bearing amine or sulfonyl groups were also synthesized. These compounds are expected to be used as precursors for designing new crosslinked molecular imprinting membranes (MIMs), exhibiting high stability of the template memory.

Evaluation of delocalized lipophilic cationic dyes as delivery vehicles for photosensitizers to mitochondria

Mitochondria are attractive targets in photodynamic therapy. Two conjugates: TPP–Rh (a porphyrin–rhodamine B conjugate) and TPP–AO (a porphyrin–acridine orange conjugate), each possessing a single delocalized lipophilic cation, were designed and synthesized as photosensitizers. Their ability to target the mitochondria for photodynamic therapy was evaluated. The conjugates were synthesized by conjugating a monohydroxy porphyrin (TPP-OH) to rhodamine B (Rh B) and acridine orange base (AO), respectively, via a saturated hydrocarbon linker. To evaluate the efficiency of the conjugates as photosensitizers, their photophysical properties and in vitro photodynamic activities were studied in comparison to those of TPP-OH. Although fluorescence energy transfer (FRET) was observed in the conjugates, they were capable of generating singlet oxygen at rates comparable to TPP-OH. Biologically, exciting results were observed with TPP–Rh, which showed a much higher phototoxicity [IC 50, 3.95 μM: irradiation of 400–850 nm light (3 mW cm −2) for 1 h] than either TPP-OH or Rh B (both, IC 50, >20 μM) without significant dark toxicity at 20 μM. This improved photodynamic activity might be due to a greater cellular uptake and preferential localization in mitochondria. The cellular uptake of TPP–Rh was 8 and 14 times greater than TPP-OH and Rh B, respectively. In addition, fluorescence imaging studies suggest that TPP–Rh localized more in mitochondria than TPP-OH. On the other hand, TPP–AO showed some dark toxicity at 10 μM and stained both mitochondria and nucleus. Our study suggests that conjugation of photosensitizers to Rh might provide two benefits, higher cellular uptake and mitochondrial localization, which are two important subjects in photodynamic therapy.

Tuning Work Function of Noble Metals As Promising Cathodes in Organic Electronic Devices

Work function (WF) modification of metal electrodes by adsorbing electron-rich or electron-deficient molecules on metal surfaces has become a field of significant interest. The barrier for charge carrier injection in organic semiconductor devices can be reduced by molecular adsorption, leading to an interfacial dipole. Here, we demonstrate that the WF of noble metals such as Au can be decreased significantly by adsorbing air stable n-type dopant acridine orange base (AOB) thin film. When a (sub)monolayer AOB is deposited on sputter-cleaned Au, the WF of the substrate changes from 5.2 to 3.5 eV. At complete coverage of the Au surface, the WF is further reduced to 3.3 eV. When a (sub)monolayer of AOB is inserted between Au and C60 thin film, the barrier of electron injection is decreased by 0.4 ± 0.1 eV as compared to an Au−C60 interface without AOB. Polymer solar cells with AOB/Au as a cathode have a similar open circuit voltage and comparable power conversion efficiency with devices using LiF/Al as a cathode, demonstrating that the AOB-modified gold electrode is an efficient low-work-function contact. Given the low positive pinning energy of 3.3 eV for AOB, we expect that other conventional high-work-function materials (Ag, ITO, La0.7Sr0.3MnO3 and even PEDOT:PSS) can be modified by AOB as effectively as Au.

Acridinium Salt Based Fluorescent and Colorimetric Chemosensor for the Detection of Cyanide in Water

A new, selective chemosensor has been developed to detect cyanide in water at micromolar concentrations. The acridinium salt used in this sensor system is prepared in a single step from an acridine orange base. Detection is based on the irreversible, 1:1 stoichiometric, nucleophilic addition of cyanide to the 9-position of the acridinium ion. This process induces a large decrease in fluorescence intensity and a marked color change. The selectivity of the system in aqueous media for CN- over other anions is remarkably high. Also, the sensitivity of both the fluorescence- and colorimetric-based assay is below the 1.9 microM suggested by the World Health Organization (WHO) as the maximum allowable cyanide concentration in drinking water. Thus, the chemodosimeter should be applicable as a practical system for the monitoring of CN- concentrations in aqueous samples. [structure: see text]

Acridine orange base as a dopant for n doping of C60 thin films

We present a study on n doping of C60 thin films by acridine orange base [3,6-bis(dimethylamino)acridine(AOB)] combining conductivity, field effect, and Seebeck measurements. An increase of more than six orders of magnitude in conductivity is observed for a doping ratio of 6mol%, accompanied by a decrease in the activation energy from 0.64to0.15eV compared to the undoped C60. We observe a clear doping effect immediately after sample preparation, but also a further activation by annealing or illumination. The field effect and Seebeck measurements confirm n-type conduction of C60 thin films and show that deep donor states are formed in AOB-doped C60 thin films. A field effect mobility of 0.2cm2∕Vs is achieved for a doping level of 1.8mol%. Near Infrared (NIR) and Fourier transform infrared (FTIR) spectra demonstrate electron transfer from the dopant to the matrix: For C60 doped with AOB, C60− is present in NIR absorption and FTIR spectra. On the other hand, a peak corresponding to acridine orange [3,6-bis(dimethylamino)acridinium chloride (AOBH+)] is also observed in the FTIR spectrum of C60:AOB, where AOBH+ corresponds to AOB with one additional proton attached. Electrochemical data of AOB and AOBH+ in acetontrile suggest that the AOB radical cation is not stable, but is rapidly transformed into a compound with similar properties to AOBH+. Conductivities of C60 thin films doped with bis(ethylenedithio)-tetrathiafulvalene were also investigated to confirm that the doping effect of AOB in C60 does not result from a simple electron transfer from AOB to C60.

Ultrahigh Vacuum Seebeck Effect and Conductivity Measurements on N-Doping of C60 Films

ABSTRACTWe constructed an ultrahigh vacuum (UHV) system with which in-situ conductivity and Seebeck coefficient measurements can be performed, including the detailed examination of the oxygen effect. It can also carry out the deposition of metal electrodes and organic films under UHV condition through measurements. The conductive characteristics of fullerene (C60) films were examined by the measurement at conductivity and Seebeck coefficient under UHV. We observed that the conductivity at room temperature was higher than 1×10−3 S cm−1. This value is two orders of magnitude in conductivity higher than the Hamed report. [A. Hamed et al., Phys. Rev. B 47, 10873 (1993).] Seebeck coefficient S was also measured. Its sign was negative, indicating electron conduction for C60 film. After the measurements under UHV, oxygen was introduced into the chamber by a variable leak valve. The conductivity decreased drastically by increasing the pressure of oxygen. It decreased more than five orders from under UHV to 1 atom oxygen. The temperature dependence of the conductivity was also examined. The conductivity was thermally activated. Activation energies of the conductivity increase by increase oxygen pressure. This means that the oxygen act as carrier traps. As an n-type dopant, acridine orange base (AOB) was co-deposited into C60 films. The magnitude in the conductivity increased but not drastic. The conductivity of doped film also decreased by increasing the pressure of oxygen. The conductivity even under 6.6×10−2 Pa, however, was high enough. Though AOB was not effective dopant against C60 film in UHV condition, AOB doped C60 film became resistant to oxygen.

The use of acridine orange base (AOB) as molecular probe to characterize nonaqueous AOT reverse micelles

The behavior of acridine orange base (AOB) in nonaqueous reverse micelles composed of n-heptane/AOT/polar solvent has been performed. Ethylene glycol (EG), propylene glycol (PG), glycerol (GY), formamide (FA), dimethylformamide (DMF), and dimethylacetamide (DMA) were employed as water substitutes. The studies were performed by static and time-resolved emission spectroscopy. Thus, the distribution of AOB between the two pseudophases of the aggregates was quantified by measuring the partition constants from emission spectra at different surfactant concentration. Similar values to those obtained by means of absorption spectroscopy were obtained. This match is indicating that AOB is not experiencing partition during the lifetime of the excited state. Partitioning to the micelles is strongly favored in micelles containing hydrogen-bond donor (HBD) solvents rather than non-HBD solvents. Variations of fluorescence lifetimes with AOT concentration confirm these results. By the solvatochromic behavior of AOB in the different systems it is shown that the microenvironment at the interface is distinct from that of the bulk polar solvent, indicating that the probe senses no “free” solvent. The steady state anisotropy ( 〈 r 〉 ) was measured for EG/AOT/ n-heptane and DMF/AOT/ n-heptane systems as representatives for HBD and non-HBD polar solvents, respectively. The value of 〈 r 〉 is higher in the micelles containing EG than that obtained with DMF, and increases with AOT concentration. This is explained as due to highly structured polar solvents in the inner core. EG is interacting with the polar heads of AOT through hydrogen-bond interaction, while DMF can only interact with the Na + counterions. This is confirmed by the time-resolved emission spectra (TRES) of the probe in the micellar systems, in comparison with the bulk solvents.

Exploratory Study of the Effect of Polar Solvents upon the Partitioning of Solutes in Nonaqueous Reverse Micellar Solutions

An exploratory study on the effect of polar solvents upon the partitioning of solutes in nonaqueous reverse micellar solutions composed by n-heptane/AOT/polar solvent has been performed. Ethylene glycol (EG), propylene glycol (PG), glycerol (GY), formamide (FA), dimethylformamide (DMF), and dimethylacetamide (DMA) were employed as water substitutes. The study has been carried out at a single value of the mole ratio between the polar solvent and AOT, Ws = [polar solvent]/[AOT] equal to 2. 9-Anthracenemethanol (9-AM) and acridine orange base (AOB) were the solutes considered. Partitioning of (9-AM) was determined following a fluorescence quenching method. AOB partition constants were evaluated by a method based on the dependence of the absorption spectra with AOT concentration. The results obtained show that, for both solutes, partitioning to the micelles is strongly favored in (EG), (PG), (GY), or (FA), rather than in (DMF) or (DMA) containing micelles. This trend is opposite to that observed for the parti...

Acid Base Reactions Between Acridine Orange and Substituted Phenols in Benzonitrile Part I. Thermodynamics of Association and Ionic Equilibria

AbstractProton transfer reactions of the five substituted phenols 3‐Cl−4‐nitrophenol CNP, 4‐nitrophenol NP, 3‐methyl−4‐nitrophenol MNP, 4‐Cl−3,5‐dimethylphenol CMP, and 3,5‐dimethylphenol DMP with acridine orange, and the formation of hydrogen bonded complexes AHA− of the anions A− of CNP, NP, and MNP with the respective phenols AH in benzonitrile solution were investigated by means of absorption spectroscopy. Thermodynamic data for the formation of the complexes AHA− and of the ionic reactions (1) and (2) of CNP, NP, and MNP with the acridine orange base B magnified image and for the reactions (2) and (3) of CMP and DMP with B were determined. The reactions (1) ‐ (3) are exothermic. The absolute values of ΔH1 increase with the acidity of the phenols. The formation enthalpies of the hydrogen bonded anions AHA‐ are much larger than ΔH1, so that ΔH2 is mainly determined by this association. On the other hand there is no significant difference between ΔH2 and ΔH3; thus the hydrogen bond formed between a phenol and a complexed anion AHA‐ is very weak. Substituent effects on the acidity of phenols are about twice as large in benzonitrile as in aqueous solution.

Acid Base Reactions Between Acridine Orange and Substituted Phenols in Benzonitrile Part II. Kinetics: An Extended Eigen Mechanism of Proton Transfer

AbstractThe kinetics of proton transfer between five substituted phenols (AH) and the acridine orange base (B) are studied in benzonitrile solution using the temperature jump method. In the overall reactions (1)–(3) magnified image the formation and dissociation of an intermediate ion pair A‐.. HB+ is rate determining. The rate constants of the bimolecular recombination of the ions to the ion pair are kb1, kb2, and kb3. Their values are in the range (0.18‐ 1.7) · 109 M‐1 s‐1 (25 °C, I = 0.1 M). kb2 and kb3 do not depend on the pK of the phenol involved, although these rates are not diffusion controlled. The rate of proton transfer from the protonated acridine orange (BH+) to the free anions (A‐) does depend to some degree on the acidity of the corresponding phenol. In the case of the 3‐methyl‐ 4‐nitrophenolate ion this rate is diffusion controlled, as shown by the dependence of kb1 on the temperature and the ionic strength. Lower limits for the formation constants of the ion pairs are estimated from the rate data. The equilibria and the kinetics are discussed in terms of an extended Eigen scheme of proton transfer, and the separate steps of anion solvation by hydrogen bonding to phenol molecules shown to depend in different ways on the basicity of the anion.

Thermodynamics and kinetics of some acid base reactions in benzonitrile and acetonitrile

The proton transfer between an acid and a base involves a change of the total amount of charges in the reacting system: ▪ or a transfer of charge: ▪ Therefore the equilibria and the reaction mechanisms of acid basereactions depend strongly on the ability of the solvent to stabilize ions and to participate in the proton transfer process. We have studied the reactions between five-substituted phenols ( AH) and acridine orange ( B) in benzonitrile and between 4-nitrobenzoic acid and 4-nitrophenol and B in acetonitrile. In these systems, free cations are formed according to eqn. (1) and the anions are stabilized by hydrogen bonding to additional phenol in a second step (homoconjugation): ▪ Thermodynamic data were evaluated from spectrometric titrations of acridine orange base with the acids and of Bu 4N-salts of the phenols with phenol solutions at 10-50°C. Proton transfer rates were obtained by temperature jump relaxation measurements in solutions for the kinetic runs were prepared under nitrogen in an all glass apparatus and were filled into the measuring cell without opening the system to the atmosphere. The equilibrium (1) does not depend much on the solvent, if AH = 4-nitrophenol, whereas the formation constant of AHA − increases from k 2 = (4.6 ± 0.5· 10 3 in acetonitrile to K 2 = (2.5 ± 0.2)·10 4 in benzonitrile at 25°C. This has the remarkable consequence that in benzonitrile in spite of its lower polarity more ions are formed than in acetonitrile with the same concentrations of reactants. In acetonitrile acid and B are k 1 = 7.2·10 8 and k −1 = 1.8·10 8 ( M −1 s −1) at 25°C. The rates are significantly slower than those calculated for the diffusion controlled process. Similar observations had previously been made with other proton transfer reactions in acetonitrile [1]. In benzonitrile the proton transfer rates in reaction (1) are correlated with the equilibrium constants. The fastest observed rates are diffusion controlled. Consequences of the kinetic results for the interpretation of properties of the two solvents will be discussed.