Experimental and theoretical studies of linear and non-linear optical properties of novel fused-triazine derivatives for advanced technological applications.

Controlling photophysical properties is critical for the continued development of electroluminescent devices and luminescent materials. The preparation and study of novel molecules suitable as luminescent for the development of optoelectrical devices have recently received a lot of attention. Even though the as-triazine unit is a good building block for organic active substances, it is rarely used in this context. We created here novel bis-triazine derivative dyes in the far UV-Vis range by alkylation of triazine-thione derivatives with appropriate dibromo compounds. At the B3LYP/6-311**G(d,p) basis set, their optimal molecular structures were obtained. DFT technique confirmed that the new triazine derivatives are in noncoplanar with one of the two phenyl rings and the triazine plane rotating out by 102.09. Also, depending on the energy gap difference between HOMO and LUMO, some important parameters including chemical potential (π), electronegativity (χ), and chemical hardness (η) were calculated. The compounds may be readily polarized and have significant NLO characteristics, as seen by the tiny HOMO-LUMO energy gap. The calculated values for the polarizability (α) of the two new triazine derivatives have the range 6.09-10.75 × 10-24 (esu). The emission peaks seemed to move to the long-wavelength (redshift), with a rise in the fluorescence band, suggesting that the singlet excited state is more polar than the ground state. The influence of solvent polarity and the intermolecular charge transfer (ICT) processes are reflected in the photophysical properties of new fused triazine derivatives. These properties such as extinction coefficient, absorption and emission cross-sections, fluorescence quantum yield, fluorescence lifetime, oscillator strength, the dipole moment, radiative decay rate constant, the energy yield of fluorescence, and the attenuation length were assessed and discussed.

Performance of chitosan polymer as platform during sensors fabrication and sensing applications.

Chitosan is an important polymer produced from deacetylation of several sea and insects crusts. Due to its environmental fate and biological biocompatibility, it can be used in several biological and environmental applications. Sensing of biological compounds in human bodies and also in serum, blood, and different body fluids has found an important application instead of direct determination of the body fluids using complicated tools. Sensing process of biological compounds during bio-analysis of the biological systems, especially human fluids lack of several parameters including: high sensitivity, repeatability, speed of analysis and biocompatibility of the used analytical methods, especially in-vivo analysis. That was due to the time between sample handling and sample determination can change various components and concentrations of the bio-compounds. The need for in-situ analysis was directed the researchers for biosensors to overcome the upgrading problems of bio-analysis. Biosensors were the future of this issue. Chitosan can reserve as great platform for fabrication of different sensors to determine the elements, compounds and body bioactive compounds. The presence of different terminal amino and hydroxyl groups within chitosan framework facilitates the immobilization of different biomarkers to be used as sensing elements for the determined compounds. The use of chitosan as sensors platform was enhanced by using chitosan in its nanoforms.

Spectroscopic and Photo-Physical Properties of Near-IR Laser Dye in Novel Benign Green Solvents.

IR-792 as near IR (NIR) laser dye was dissolved with different concentrations in two types of ionic liquids (ILs) of different anion and cation, 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (EMIM TFSI) & 1-Butyl-3-methylimidazolium tetrafluoroborate (BMIM BF4), as the benign green solvent and in methanol (MeOH) as a standard solvent. The behavior of fluorescence of IR-792 dye was studied. The fluorescence of IR-792 dissolved in the ILs was heavily compared to organic solvent. Some photo-physical parameters of IR-792 were calculated. Mainly, IR-792 had a very low quantum yield of fluorescence with high intersystem crossing rate & fluorescence lifetime in picosecond range. Optical absorption and behavior of fluorescence for the rigorously the purified imidazolium ILs in the neat condition and effect of IR-792 on their fluorescence have been examined. The emission behavior of IR-792 in green solvents was independent upon the wavelength of excitation, while the emission behavior of green solvents dependent upon the wavelength of excitation whether in pure state or with NIR laser dye. At most, the intensity of fluorescence of ILs is dependent upon dye concentration.

Optical, photo physical parameters and photo stability of 6-Substituted-1, 2, 4-Triazine mono glucosyl derivative to act as a laser dye in various solvents.

The optical properties of a visible absorption range6-Substituted-1, 2, 4-Triazine mono glucosyl fluorescent derivative dye, such as absorption spectra, emission spectra in different solvents, were experimentally investigated. As well, some important photo physical parameters such as extinction coefficient (ε), cross-sections of the absorption (σa) and the emission (σe), quantum yield (фf), fluorescence lifetime, oscillator strength (f), the dipole moment (µ), decay rate radiative constant (kr), energy yield of fluorescence (Ef) and the length of attenuation Λ (λ) were assessed. The ground-state (µg) and excited-state (µe) dipole moments by solvatochromic correlations method were reported. The dye amplified spontaneous emission (ASE) of 2 × 10-4M with different input pumping energies of a continuous wave blue diode laser (λ = 450 nm) was studied. Photostability of dye was observed that was decreased to 53% of its initial energy by pumping with 100 mW of diode laser after exposure to 120 min.

Advancement on modification of chitosan biopolymer and its potential applications.

Chitosan is the second abundant biopolymer present on earth after cellulose. Chitosan is extracted from the shells of shrimp and other crustaceans. Several methods were reported for its extraction, but the most commercial is the deacetylation of chitin. Chitosan as a biopolymer has numerous applications and uses. But, its mechanical, chemical and biological characteristics can be enhanced by modification of its chemical structures. Several modification methods and derivatives were reviewed in the literatures, and several were collected in this review. The reviewed modified chitosan derivatives herein were five types of derivatives. The first is substituted chitosan derivatives including thiolated, phosphorylated, and N-phthaloylated derivatives. The second is crosslinked chitosan derivatives including chitosan-glutaraldehyde, chitosan-ethylene diamine tetraacetic acid, and chitosan-epichlorohydrin derivatives. The third is carboxylic acid derivatives of chitosan obtained from carboxyalkylation, acrylation, methacrylation, and benzoylation of chitosan. The fourth is ionic chitosan derivatives including highly cationic and sulfated derivatives. The last is bounded chitosan to specific molecules including cyclodextrin, thiosemicarbazone, dioxime, and crown ether precursors. The review also highlights the reported advantages and applications of the modified chitosan and the synthetic routes of the biopolymer modification.

Spectroscopic Study of Solvent Polarity on the Optical and Photo-Physical Properties of Novel 9,10-bis(coumarinyl)anthracene.

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.

Laser Performance of Some Oxazole Laser Dyes in Restricted Matrices.

This article reports the optical properties such as absorption profile, molar absorptivity, fluorescence profile and photo-physical parameters such as dipole moment, oscillator strength, fluorescence quantum yields, fluorescence lifetimes, laser performance and finally photostability of 2,5-Bis(5-tert-butyl-benzoxazol-2-yl)thiophene (BBOT),1,4-Bis(5-phenyl-2-oxazolyl)benzene (POPOB), 5-diphenyel-oxazole (PPO) laser dyes in different restricted hosts. (BBOT), (POPOB) and (PPO) are embedded in transparent silica-based nanoporous sol-gel glass and copolymer matrix of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA). The absorption and fluorescence properties of these laser dyes in sol-gel glass matrices are compared with their respective properties in copolymer host. In case of sol-gel matrix, all dyes had higher quantum yields as well as lasing wavelength maxima. The laser performances as well as the photostability of these laser dyes in sol-gel glass displayed senior behavior compared with (MMA/ HEMA) copolymer samples upon using nitrogen laser (337.1 nm) as pumping energy.

Fluorescein dye derivatives and their nanohybrids: Synthesis, characterization and antimicrobial activity.

Fluorescein (resorcinolphthalein) is a synthetic organic photoactive dye compound soluble in water, alcohol and polar solvents. It is widely used as a fluorescent tracer in medicinal and biological applications and tumor infected tissues tracer. In this study, fluorescein (F) was condensed by five coupling agents namely: p,p-phenylene diamine, p-hydroxy aniline, o-hydroxy aniline, p-methoxy aniline and p-methyl aniline in a molar ratio of 2(F):1 (coupling agent). The chemical structures of the synthesized fluorescein derivatives were confirmed using: microelemental analysis, FTIR spectroscopy, 1H-NMR spectroscopy, and mass spectroscopy. The synthesized compounds were loaded on chemically prepared silver nanoparticles via reduction reaction of silver nitrate. The structures and properties of the formed fluorescein derivatives silver nanohybrids were determined using: UV/Vis spectroscopy, TEM images and dynamic light scattering (DLS). The synthesized compounds and their nanohybrids were evaluated for their antimicrobial activities against different bacterial strains and fungi. The results showed that the formed fluorescein derivatives silver nanohybrids are in moderate diameter range, and the loading of the synthesized compounds protect the silver nanoparticles against coagulation. The antimicrobial activity against the studied microorganisms was comparable to the standard used. Moreover, the antimicrobial activity was increased considerably in case of using fluorescein derivatives silver nanohybrids. The antimicrobial activities were correlated to the chemical structures of the compounds, diameter of the formed nanohybrids and to the nature of the tested bacterial strains. The mechanism of the antimicrobial action of the synthesized compounds and their nanohybrids was proposed.

Synthesis and implementation of nano-chitosan and its acetophenone derivative for enhanced removal of metals.

In the present study, nano-chitosan (Nano-Ch) was synthesized by ionic gelation of chitosan/tripolyphosphate system and successfully modified with acetophenone via Schiff's base condensation to produce nano-chitosan-modified-actophenone (Nano-Ch-Ac). The produced nano-materials were characterized by FT-IR, SEM, HR-TEM and TGA techniques. The average particle sizes were found in the range of 5.20-14.54nm based on the HR-TEM analysis. The metal interaction properties of Nano-Ch and Nano-Ch-Ac with Cu(II), Cd(II), Hg(II) and Pb(II) were compared in presence of various experimental parameters. Nano-Ch-Ac sorbent was found more superior in the extraction processes of all examined metal ions under the evaluated experimental parameters. This trend was confirmed from the highest determined metal sorption capacity values of metal ions as 1298-1608 and 810-1236µmolg(-1) in pH 7.0 by Nano-Ch-Ac and Nano-Ch sorbents, respectively. The adsorption equilibrium was established at 30.0min of contact time by the two nano-chitosan sorbents. The superiority of Nano-Ch-Ac was also confirmed from the dynamic applications of this nano-sorbent for removal of divalent metal ions from tap water, sea water and industrial wastewater (91.3-100.0±1.0-3.0).

Fluorescence enhancement monitoring of pyrromethene laser dyes by metallic Ag nanoparticles.

Fluorescence enhancement monitoring of pyrromethene laser dyes using their complexation with Ag nanoparticles (Ag NPs) was studied. The size of the prepared Ag NPs was determined by transmission electron spectroscopy and UV/Vis absorption spectroscopy. Mie theory was also used to confirm the size of NPs theoretically. The effect of different nanoparticle concentrations on the optical properties of 1 × 10(-4) M PM dyes shows that 40%of Ag NPs concentration (40%C Ag NPs) in complex is the optimum concentration. Also, the effects of different concentrations of PM dyes in a complex was measured. Emission enhancement factors were calculated for all samples. Fluorescence enhancement efficiencies depended on the input pumping energy of a Nd-YAG laser (wavelength 532 nm and 8 ns pulse duration) were reported and showed the lowest energy (28 and 32 mJ) in the case of PM567 and PM597, respectively.