Nm In Ethanol Research Articles

Characterization and Conversion of Microbial Pigments into Water Soluble Pigments for Application in Food Products

Microbial colours with different shades like pink (Rhodotorula), red (Chromobacterium), yellow (Sarcina) and light yellow (Micrococcus) using apple pomace (a waste from apple juice) were produced by solid state fermentation, characterized and modified into water soluble pigments. Biocolour from Rhodotorula had maximum absorption in ethanol, hexane and acetone at 200–550 nm with λ-max between 480 and 490 nm. In case of Chromobacterium sp., ethanol, petroleum ether and hexane gave the highest absorption between 520 and 540 nm (narrow range). Pigment of Micrococcus sp., had maximum absorption between 200 and 400 nm with λ-max in narrow range (400–600 nm) scanning between 480 and 490 nm in ethanol. Dark yellow colour pigment of Sarcina gave the maximum absorption between 200 and 500 nm in ethanol. All the biocolours examined were carotenoids, insoluble in water and thus, have limited applications in food. Aminoacid, benzoic acid and gelatin were employed to make these pigments water soluble by reflexing at different pH values viz., 3, 7 and 9.2 for each pigment. Maximum conversion (51 %) of pigment of Rhodotorula occurred using gelatin at pH 9.2. In case of Chromobacterium using amino acetic acid at pH 9.2 it was 60 %. It was 55 and 56 % at pH 7 and 3, respectively. In Sarcina, at pH 9.2 maximum conversion (48 %) took place using amino acetic acid, whereas in pigment of Micrococcus sp. 40 % conversion took place using amino acetic acid at pH 9.2 and the minimum conversion occurred using amino benzoic acid at pH 3. It is concluded that the pigments produced by Rhodotorula, Micrococcus and Chromobacterium can be modified chemically to make them water soluble thus, making possible their use in various food products.

Preparation of highly luminescent and biocompatible carbon dots using a new extraction method

C dots (CDs) are among the most promising emerging fluorescent labels for biological imaging and sensing. A facile new synthesis method was developed using common organic solvents for fabricating CDs from candle soot. The common organic solvents were used as extractants and the obtained CDs have a narrow size distribution with average diameters of about 3.4 nm for ethylene glycol, 3.5 nm for ethanol, and 3.4 nm for n-butanol. This approach is simpler, easier, and more effective than other methods currently used for CD fabrication. The obtained CDs had a high quantum yield (38 %), tunable emission and are water-soluble. The mechanism for the luminescence of the CDs was investigated and the results indicate that the ability of the solvent to disperse the CDs plays a very important role in the photoluminescence of these CDs. The type of organic solvent and the surface groups on the CDs also influenced the optical properties of the CDs. Different emissive traps are shown to play the major role in the luminescence of the carbon materials. An in vitro hemolysis assay was performed and showed that the CDs are biocompatible.

Hydrophilic annulated dinuclear zinc(II) phthalocyanine as Type II photosensitizers for PDT: a combined experimental and (TD)-DFT investigation

The design, synthesis and theoretical calculations of a mononuclear and its corresponding annulated dinuclear hydrophilic zinc(II) phthalocyanines (ZnPcs) are reported here, the hydrophilic substituent being 1,3-bis((2,2-dimethyl-1,3-dioxolan-4-yl)methoxy)propan-2-ol. These novel compounds have been characterized by UV-vis spectroscopy in ethanol and ethanol:water (50:50) solutions. The electronic spectra of the mononuclear derivatives retain the main spectral features of ZnPc with a strong Q-band absorbance at 678 nm in ethanol and a less intense B-band at 370 nm. The annulated dinuclear derivatives show a broad Q-band absorbance with main wavelength maxima between 600 and 720 nm. From time-dependent density functional (TDDFT) UV-vis spectra simulation performed on selected isomers, Q-band absorption maxima of the non-peripherally substituted forms are more red-shifted compared to those of peripheral forms.

Silver-nanoparticle based bactericidal coating for poly(glycolide-co-lactide) suture threads obtained by the method of laser ablation of bulk targets in alcohol solutions

A laser ablation method is suggested to synthesize a dispersion of silver nanoparticles to create a bactericidal coating of biodegradable suture material from poly(glycolide-co-lactide) using a bulk target immersed in a liquid. The laser ablation method with nanosecond excitation by a Nd:YAG laser (1064 nm, 7 ns) is used to obtain silver nanoparticles with mean diameter of 27 nm in ethanol. Nanoparticle concentrations up to 12 mass% were obtained on the polymer surfaces by multiple impregnation.

Photocatalytic hydrodenitrogenation of aromatic cyanides on TiO2 loaded with Pd nanoparticles

Photocatalytic hydrodenitrogenation of aromatic cyanides has been carried out on TiO2 loaded with Pd nanoparticles (Pd–TiO2) in the presence of ethanol as a hydrogen source. Photoirradiation of Pd–TiO2 at λ > 300 nm in ethanol containing aromatic cyanides successfully produces the corresponding toluene derivatives and triethylamine with almost quantitative yields. Photoexcited Pd–TiO2 catalysts promote oxidation of ethanol and reduction of protons, producing acetaldehyde and hydrogen atoms on the surface of Pd particles (H–Pd species). Aromatic cyanides undergo hydrodenitrogenation via consecutive reactions involving hydrogenation by the H–Pd species and condensation with aldehydes. The catalytic activity strongly depends on the amount of Pd loaded. The catalyst containing 2 wt% Pd, with a relatively low Schottky barrier height at the Pd–TiO2 heterojunction and a large number of surface Pd atoms, exhibits the highest denitrogenation activity.

Synthesis of Fluorescent Dichromophoric Benzothiazole-Based Polyenes

Syntheses of some novel dichromophoric cyanine dyes based on 2-aminobenzothiazoles have been reported. Their highly extended conjugated systems are in symmetrical and unsymmetrical structures, both of which are divided into two electron-rich and electron-poor series. The sixteen synthesized compounds absorb visible light in the region of 462-523 nm in ethanol in deep orange, red and purple color with high molar absorption coefficients ( : 2.1 – 4.4 104 M1.cm1). Besides the study of their electronic spectroscopic properties, broad solvatochromic effects have been observed 70-200 nm shifts in nine different solvents. In fluorescence spectroscopic studies, their emissions have been observed to be 400–500 nm at excitation wavelengths 347-375 nm in DMF. Keywords: Aminobenzothiazole, antibacterial effect, bis-azo, polyene dyes, solvatochromic effect

A time-resolved luminescence study on singlet oxygen quenching by hydroxycinnamic acids under acidic, neutral and basic conditions

A kinetic study on singlet oxygen (1O2) quenching by 4-hydroxycinnamic acid derivatives (ferulic acid (FA) and caffeic acid (CA)) has been performed by measuring time-evolutions of 1O2 phosphorescence at 1274 nm in ethanol, in an ethanol/acetone mixed solvent and in an ethanol/H2O mixed solvent under acidic, neutral and basic conditions. In organic solvents, the estimated second-order rate constants of 1O2 quenching (kQ) were distributed between 105 and 106 M−1 s−1; for example, in ethanol, 2.2 × 105 M−1 s−1 for FA and 5.2 × 105 M−1 s−1 for CA. On the other hand, the kQ values in ethanol/H2O solutions were enlarged from those in organic solvents, and varied largely with pH from 106 to over 108 M−1 s−1. In the case of FA, the 1O2 quenching activity decreased in the order of FA2− (at pH > 10) ≫ FA− (pH 5–9) > FA (pH < 4). The result suggests that deprotonation due to the acid–base equilibrium affects the 1O2 quenching activity. For both of FA and CA, the phenolate anion under basic conditions (pH 10–12) showed the largest activity probably because of occurrence of the favored chemical quenching through the electron transfer from the phenolate anion to 1O2. These behaviors would affect several antioxidant assays in vivo and in vitro targeting 1O2.

Q-Absorbance Ratio Spectrophotometric Method for the Simultaneous Estimation of Prednisolone and 5-Amino Salicylic Acid in Tablet Dosage form

The present work carries an analytical method development of prednisolone and 5amino salicylic acid in tablet dosage form. The method is based upon Q – absorption ratio method for the simultaneous determination of the prednisolone and 5-amino salicylic acid. Both the drugs are widely used for bacterial cure and are recommended for the patients with mild to moderate inflammation of the digestive tract. Ulcerative colitis and crohn’s disease are the target disorders which are treated by both drug candidates. Absorption ratio method is used for the ratio of the absorption at two selected wavelength one of which is the iso-absorptive point and other being the λmax of one of the two components. Prednisolone and 5-ASA shows their iso-absorptive point at 283 nm in ethanol and 0.1N HCl respectively. The second wavelength used is 302 nm which is the λmax of 5-ASA in 0.1N HCl. The linearity was obtained in the concentration range of 1-10 µg/ml for prednisolone and 5-ASA. This method was applied to all pharmaceutical dosage form because there is no excipients interference between them. The results have been validated by recovery studies.

Synthesis and Photophysical Properties of a Series of Cyclopenta[b]naphthalene Solvatochromic Fluorophores

The synthesis and photophysical properties of a series of naphthalene-containing solvatochromic fluorophores are described within. These novel fluorophores are prepared using a microwave-assisted dehydrogenative Diels-Alder reaction of styrene, followed by a palladium-catalyzed cross coupling reaction to install an electron donating amine group. The new fluorophores are structurally related to Prodan. Photophysical properties of the new fluorophores were studied and intriguing solvatochromic behavior was observed. For most of these fluorophores, high quantum yields (60-99%) were observed in methylene chloride in addition to large Stokes shifts (95-226 nm) in this same solvent. As the solvent polarity increased, so did the observed Stokes shift with one derivative displaying a Stokes shift of ~300 nm in ethanol. All fluorophore emission maxima, and nearly all absorption maxima were significantly red-shifted when compared to Prodan. Shifting the absorption and emission maxima of a fluorophore into the visible region increases its utility in biological applications. Moreover, the cyclopentane portion of the fluorophore structure provides an attachment point for biomolecules that will minimize disruptions of the photophysical properties.

FT-IR, FT-Raman, UV spectra and DFT calculations on monomeric and dimeric structure of 2-amino-5-bromobenzoic acid

In this work, the molecular conformation, vibrational and electronic transition analysis of 2-amino-5-bromobenzoic acid (2A5BrBA) were presented for the ground state using experimental techniques (FT-IR, FT-Raman and UV) and density functional theory (DFT) employing B3LYP exchange correlation with the 6-311++G(d,p) basis set. FT-IR and FT-Raman spectra were recorded in the regions of 400–4000 cm −1 and 50–4000 cm −1, respectively. There are four conformers, C1, C2, C3 and C4 for this molecule. The geometrical parameters, energies and wavenumbers have been obtained for all four conformers. The computational results diagnose the most stable conformer of 2A5BrBA as the C1 form. The complete assignments of fundamental vibrations were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. Raman activities calculated by DFT method have been converted to the corresponding Raman intensities using Raman scattering theory. The UV spectra of investigated compound were recorded in the region of 200–400 nm for ethanol and water solutions. The electronic properties were evaluated with help of time-dependent DFT (TD-DFT) theoretically and results were compared with experimental observations. The thermodynamic properties of the studied compound at different temperatures were calculated, revealing the correlations between standard heat capacity, standard entropy, standard enthalpy changes and temperatures. The observed and the calculated geometric parameters, vibrational wavenumbers and electronic transitions were compared with observed data and found to be in good agreement.

Inner Surface Coating of Non-Conductive Tubular Substrate Using Electrophoretic Deposition

Inner surface of microporous alumina tube was coated with nanoporous alumina layer using electrophoretic deposition (EPD) process. Polypyrrole (Ppy) film was formed on the inner wall of the porous tube to give electrical conductivity by chemical polymerization of pyrrole (Py). The nanoporous structure was controled using bimodal suspension of alumina powders with 0.6 μm and 30 nm in ethanol. The thickness of the coated layer was controlled by varying the processing parameters such as deposition time and DC applied voltage. After the deposition, the coated substrate was sintered at 1250°C for 2 h to bond the coated layer with the substrate.The microstructure of the substrate and the coated layer was observed by SEM. The results show the good interfacial joining between the substrate and the coated layer; they are not seperatated after the Ppy burnt-out. Crack-free and nanoporous layer on the microporous substrate was successfully fabricated.

Heck reactions catalyzed by Pd(0)-PVP nanoparticles under conventional and microwave heating

Pd(0) nanoparticles stabilized by polyvinylpyrrolidone (Pd-PVP) with a diameter of 3–6 nm in ethanol catalyzed Heck coupling of iodobenzene with different alkenes under microwave heating. Products were obtained in good yields (62–99%) and good selectivity to the E-isomers. Microwave heating proved to be superior to conventional heating, providing products in higher yields and selectivities in short times (12 min).

Fluorescence Ratiometry and Fluorescence Lifetime Imaging: Using a Single Molecular Sensor for Dual Mode Imaging of Cellular Viscosity

Intracellular viscosity strongly influences transportation of mass and signal, interactions between the biomacromolecules, and diffusion of reactive metabolites in live cells. Fluorescent molecular rotors are recently developed reagents used to determine the viscosity in solutions or biological fluid. Due to the complexity of live cells, it is important to carry out the viscosity determinations in multimode for high reliability and accuracy. The first molecular rotor (RY3) capable of dual mode fluorescence imaging (ratiometry imaging and fluorescence lifetime imaging) of intracellular viscosity is reported. RY3 is a pentamethine cyanine dye substituted at the central (meso-) position with an aldehyde group (CHO). In nonviscous media, rotation of the CHO group gives rise to internal conversion by a nonradiative process. The restraining of rotation in viscous or low-temperature media results in strong fluorescence (6-fold increase) and lengthens the fluorescence lifetime (from 200 to 1450 ps). The specially designed molecular sensor has two absorption maxima (λ(abs) 400 and 613 nm in ethanol) and two emission maxima (in blue, λ(em) 456 nm and red, 650 nm in ethanol). However it is only the red emission which is markedly sensitive to viscosity or temperature changes, providing a ratiometric response (12-fold) as well as a large pseudo-Stokes shift (250 nm). A mechanism is proposed, based on quantum chemical calculations and (1)H NMR spectra at low-temperature. Inside cells the viscosity changes, showing some regional differences, can be clearly observed by both ratiometry imaging and fluorescence lifetime imaging (FLIM). Although living cells are complex the correlation observed between the two imaging procedures offers the possibility of previously unavailable reliability and accuracy when determining intracellular viscosity.

The dynamical role of solvent on the ICN photodissociation reaction: connecting experimental observables directly with molecular dynamics simulations

The ICN photodissociation reaction is the prototype system for understanding energy disposal and curve crossing in small molecule bond-breaking. The wide knowledge base on this reaction in the gas phase makes it an excellent test case to explore and understand the influence of a liquid solvent on the photo-induced reaction dynamics. Molecular dynamics simulations that include surface-hopping have addressed numerous aspects of how the solvent should influence non-adiabatic transitions and energy flow and ultimately determine product branching for this reaction system. In this paper, we report femtosecond transient absorption work directly combined with new molecular dynamics simulations that make direct connection with the spectroscopic observables. The full spectral evolution after initiating ICN photodissociation at 266 nm in water and ethanol is recorded with unprecedented time resolution, fast enough to see the nascent products emerge before interacting with the solvent cage. Use of a 266 nm pump maximizes the probability of subsequent caging on the upper diabat while launching large rotational energy release for trajectories emerging on the lower diabat. The 2D dataset yields a map of the different products and how they interconvert. In particular, information on the branching ratio and spectral evolution of the product bands is revealed as the products relax their electronic and rotational degrees of freedom. An evolution from rotationally hot gas-phase like CN (sharp band, at 390 nm) to equilibrated and solvated CN radicals (broad, at 326 nm in water and 415 nm in ethanol) is clearly observed in both solvents, and signals assignable to I* are also captured. The non-adiabatic molecular dynamics simulations focus on identifying when trajectories curve cross, filtering the trajectory ensemble into spectroscopically distinct sub-populations and analyzing the rotational energy for the CN product population. The experimental results, taken together with the MD simulations, establish the initial surface crossing probability and suggest multiple passes through the curve crossing region determine the final product yields and provide a source of freshly torqued CN radicals that continues to top up the population of rotationally hot photoproduct over the first few picoseconds.

Vitamin K analogue as a new fluorescence probe for quantitative antioxidant assay

A synthesized vitamin K model compound, NQ-6 (2-hexyloxy-1,4-naphthoquinone) showed weak fluorescence around 440 nm in ethanol. Addition of antioxidants such as vitamin E to a NQ-6 solution suppressed the NQ-6 emission quantitatively. A kinetic study on the quenching of the NQ-6 emission by hydrogen-donor type antioxidants (three tocopherol analogues, catechin, and 2,6-di- tert-butyl-4-methylphenol) in ethanol was performed. The quenching rate constant obtained from the Stern–Volmer plots for the steady-state fluorescence intensity was consistent with the second-order rate constant of each antioxidant for the free-radical scavenging. The NQ-6 emission is thought to be the delayed fluorescence caused by the thermal population to the excited singlet state from the triplet state. Thus, the fluorescence quenching occurred through a hydrogen atom transfer reaction from an antioxidant to NQ-6 in the excited triplet state ( 3NQ-6 *). The second-order rate constant for the reaction between 3NQ-6 * and α-tocopherol was estimated to be 1.2 × 10 10 M −1 s −1 from the quenching parameter and the 3NQ-6 * lifetime in ethanol (1.2 μs) measured with the transient absorption. From the high reactivity of 3NQ-6 * to the antioxidants and the amphiphilic property of NQ-6 as a vitamin K model, NQ-6 is applicable to the quantitative antioxidant assay as a new fluorescence probe.

Collapse of TA-Calmodulin (TACaM) upon Binding to Ca2+ Pump Peptide C28 Exposes the TA Moiety to Water and Quenches Its Fluorescence

CaM labeled with a fluorescent triazinylaniline (TA) derivative at Lys-75 shows 2 species upon binding to PMCA or to the CaM-binding peptide from PMCA (C28). The 1st, transient, species is slightly more fluorescent than the free CaM, while the 2nd, stable, species is much less fluorescent. The 1st species can also be emulated in a stable form by binding TA-CaM to a shorter peptide, C20. The fluorescence of TA derivatives is quenched and red-shifted by polarizable solvents such as water. TANMe2 has an emission maximum of 391 nm in a non-polar solvent (toluene), which is red-shifted to 419 nm in ethanol (permittivity = 24.5). The emission maxima of TACaM-C20 and TACaM-C28 are 409 nm and 421 nm respectively. Using the Lippert equation, we find that the effective permittivity that TA sees in TACaM-C20 is about 5 and in TACaM-C28 is about 30. Structures of TACaM-C20 (based on 1CFF) and TACaM-C28 (based on our new NMR data on CaM-C28) were made. The C20 complex has the TA residue surrounded by the extended CaM molecule, in an environment containing relatively little water. In the C28 complex the CaM molecule is collapsed. The surroundings of the TA residue are calculated from these molecular structures of hydrated TA-CaM, and the results are comparable with the experimental fluorescence data. (Supported by grants TW06837 and NS51769 from the NIH)

Electronic absorption and emission spectra of Alq 3 in solution with special attention to a delayed fluorescence

Tris(8-quinolinolato)aluminum(III) (Alq 3) shows electronic absorption bands at 378, 360 (in a 1:1 mixed solvent of methanol and ethanol (ME) at 77 K), 334, 316, 300, 263, 255.8, and 233 nm in ethanol at room temperature. According to the polarized fluorescence excitation spectrum together with MO calculations, for instance, the 360 nm band is assigned to an LL CT transition (an intramolecular charge transfer transition between two ligands), and the 378 nm band to an LM/ML CT one (an intramolecular charge transfer transition between ligand and metal). Alq 3 shows a broad fluorescence band peaking at around 478 nm in the ME matrix at 77 K. The emission spectrum measured with a phosphoroscope has two emission bands at 567 and 478 nm. The 567 nm band accompanies vibronic bands at 578 and 605 nm, being safely assigned to a phosphorescence of Alq 3. The lifetimes of the 478 and 567 nm bands are both 5.4 ms. The lifetime of the 478 nm band together with the band position and its band shape indicate that this band can be assigned to a delayed fluorescence.

Ultrafast transient absorption spectroscopy of the photo-induced Z– E isomerization of a photochromic furylfulgide

The photo-induced Z– E isomerization of a photochromic furylfulgide following excitation at 387 nm was studied using time-resolved transient absorption spectroscopy with probing from 410 to 690 nm in ethanol as solvent. The excited-state absorption decayed dominantly on a time scale of 220 fs. An oscillatory behavior was interpreted as vibrational coherence involving a low-frequency torsional motion. A slow component with a decay time of 4.1 ps was assigned to hot ground state absorption. At 25 ps, the transient absorption resembled the stationary E- Z difference spectrum. The results indicate that the Z– E photoisomerization proceeds on a sub-ps time scale.

Excited‐state relaxation of some aminoquinolines

The absorption and fluorescence spectra, fluorescence quantum yields and lifetimes, and fluorescence rate constants (kf) of 2‐amino‐3‐(2′‐benzoxazolyl)quinoline (I), 2‐amino‐3‐(2′‐benzothiazolyl)quinoline (II), 2‐amino‐3‐(2′‐methoxybenzothiazolyl)‐quinoline (III), 2‐amino‐3‐(2′‐benzothiazolyl)benzoquinoline (IV) at different temperatures have been measured. The shortwavelength shift of fluorescence spectra of compounds studied (23–49 nm in ethanol) as the temperature decreases (the solvent viscosity increases) points out that the excited‐state relaxation process takes place. The rate of this process depends essentially on the solvent viscosity, but not the solvent polarity. The essential increasing of fluorescence rate constant kf (up to about 7 times) as the solvent viscosity increases proves the existence of excited‐state structural relaxation consisting in the mutual internal rotation of molecular fragments of aminoquinolines studied, followed by the solvent orientational relaxation.

Thickness of Solvation Layers on Nano‐scale Silica Dispersed in Water and Ethanol

In this work, the thickness of solvation layers on nano‐scale silica dispersed in water, ethanol, and water‐ethanol mixture (1∶1 by volume) have been determined with the viscosity method, which is based on the Einstein equation of viscosity of dispersion. This determination was carried out on a nano‐scale silica with the specific surface area of 189 m2/g through the measurements of relative viscosity of the silica dispersion as the function of volume fraction of the dry silica in the dispersion. The experimental results and the calculations showed that the thickness of the solvation layer on the nano‐scale silica was 12.8 nm in water, 11.9 nm in ethanol, and 13.2 nm in the water‐ethanol mixture. The results suggest that water‐ethanol mixture (1∶1 by volume) should be used as the liquid medium in order to prepare a high stability nano‐scale silica suspension.