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Although tris(8-hydroxyquinoline)aluminum (Alq 3 ), a fluorescent optical organometallic material, is known for its applications in optoelectronics, it has only few and limited applications in the biological field. In this study, the antibacterial activity of Alq 3 micro and nanostructures was investigated. We prepared Alq 3 nanostructures. We prepared nanosized Alq 3 as rice-like structures that assembled into flower shapes with an α-crystal phase. Then, Alq 3 micro and nanostructure antibacterial activities were estimated against seven human pathogenic bacterial strains. Besides, we compared their antibacterial activities with those of standard antibiotics. The minimal inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and IC50 were evaluated. Alq 3 micro and nanostructure antibacterial activity showed considerable values compared to standard antibiotics. Besides, the obtained data revealed that the antibacterial activity of Alq 3 in nanostructures with a new morphology is more than that in microstructures. The antibacterial activity of Alq 3 nanostructures was attributed to their more surface interactions with the bacterial cell wall. The molecules of 8-hydroxyquinoline in the Alq 3 structure could play crucial roles in its antibacterial activity. To apply the achieved results, Alq 3 was incorporated with polystyrene (PS) in a ratio of 2% to fabricate a PS/Alq 3 composite and used to coat glass beakers, which showed inhibition in the bacterial growth reduced to 65% compared with non-coated beakers. The finding of this study showed that Alq 3 could be used as a promising antimicrobial coating., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

Novel heterocyclic azomethine dyes were prepared by the reaction of anthracene-9-carbaldehyde with different heterocyclic amines under microwave irradiation. Structures of the azomethine dyes were confirmed by the elemental analysis, mass spectrometry and several spectroscopic techniques. We studied absorbance and fluorescence spectra of the azomethine dyes in various solvents. They are found to be good absorbers and emitters. We also report photophysical properties like, extinction coefficient, oscillator strength, stokes shift and transition dipole moment. This reflects physicochemical behaviors of synthesized dyes. In addition, their intramolecular charge transfer and nonlinear optical properties, supported by natural bond orbital technique, were also studied computationally by density functional theory. The negative nonlinear refractive index and nonlinear absorption coefficient were measured for these dyes using the closed and open aperture Z-scan technique with a continuous wave helium-neon laser. These are found to vary linearly with solution concentration., Competing Interests: The authors have declared that no competing interests exist.

Objectives: Various agents are currently available for treatment of hypersensitive dentine, however, their resistance to erosion intraorally by various erosive drinks is still questionable. The aim of this study is to test the efficacy of a hydroxyapatite paste to decrease dentine permeability and resist an erosion challenge., Methods: Hydroxyapatite powder was mixed with 25% phosphoric acid to form a paste which was applied on dentine having patent dentinal tubules orifices (treated with EDTA, 2 min) and the resulting layer formed on top of dentine was irradiated by Nd:YAG laser. The treated dentin surfaces were exposed to erosion challenge (6% citric acid, 1 min). Dentine permeability was measured before/after the application of the hydroxyapatite paste before/after the erosion challenge before/after the application of Nd:YAG laser using a split chamber device. The top and the fractured dentine surfaces were examined with scanning electron microscope (SEM). Moreover, the chemical nature of the compounds formed on top of dentine surface was examined using the SEM equipped with energy- dispersive X-ray spectroscope (EDS) and FTIR/ATR (Attenuated Total Reflectance Fourier Transform Infrared) techniques. The Mann-Whitney test (p < 0.05) was used to compare the effects of using the hydroxyapatite paste on dentine permeability and calcium/phosphate ratio of the treated dentine surfaces., Results: The application of the hydroxyapatite paste to dentine significantly decreased dentine permeability (p < 0.05). Hydroxyapatite paste was able to occlude patent dentinal tubule orifices with a layer of calcium-phosphate compounds and the application of Nd:YAG laser on the aforementioned layer improved its erosion resistance., Conclusion: Hydroxyapatite paste applied with the technique adopted in the current study has a high potential to be a useful aid in the treatment of dentine hypersensitivity. However, cost and knowledge for using Nd:YAG laser are important factors should be taken into consideration before using the aforementioned technique.

Upconversion of near infrared (NIR) into ultraviolet (UV) radiation could lead to a number of applications in bio-imaging, diagnostics and drug delivery. However, for bare nanoparticles, the conversion efficiency is extremely low. In this work, we experimentally demonstrate strongly enhanced upconversion emission from an ensemble of β-NaYF 4 :Gd 3+ /Yb 3+ /Tm 3+ @NaLuF 4 core-shell nanoparticles trapped in judiciously designed plasmonic nanocavities. In doing so, different metal platforms and nanostructures are systematically investigated. Our results indicate that using a cross-shape silver nanocavity, a record high enhancement of 170-fold can be obtained in the UV band centered at a wavelength of 345 nm. The observed upconversion efficiency improvement may be attributed to the increased absorption at NIR, the tailored photonic local density of states, and the light out-coupling characteristics of the cavity.

Laser ablation of dental hard tissues is one of the most important laser applications in dentistry. Many works have reported the interaction of laser radiations with tooth material to optimize laser parameters such as wavelength, energy density, etc. This work has focused on determining the relationship between energy density and ablation thresholds using pulsed, 5 nanosecond, neodymium-doped yttrium aluminum garnet; Nd:Y3Al5O12 (Nd:YAG) laser at 1064 nanometer. For enamel and dentin tissues, the ablations have been performed using laser-induced breakdown spectroscopy (LIBS) technique. The ablation thresholds and relationship between energy densities and peak areas of calcium lines, which appeared in LIBS, were determined using data fitting. Furthermore, the morphological changes were studied using Scanning Electron Microscope (SEM). Moreover, the chemical stability of the tooth material after ablation has been studied using Energy-Dispersive X-Ray Spectroscopy (EDX). The differences between carbon atomic % of non-irradiated and irradiated samples were tested using statistical t-test. Results revealed that the best fitting between energy densities and peak areas of calcium lines were exponential and linear for enamel and dentin, respectively. In addition, the ablation threshold of Nd:YAG lasers in enamel was higher than that of dentin. The morphology of the surrounded ablated region of enamel showed thermal damages. For enamel, the EDX quantitative analysis showed that the atomic % of carbon increased significantly when laser energy density increased.

Blue emitting 2-amino-4-(3, 4, 5-tri methoxyphenyl)-9-methoxy-5,6 dihydrobenzo[f]isoquinoline-1-carbonitrile (AMQC) dye was synthesized by one-pot multicomponent reactions (MCRs) of 3,4,5-trimethoxybenzaldehyd, malononitrile, 6-methoxy-1,2,3,4-tetrahydro-naphthalin-1-one and ammonium acetate. Results obtained from spectroscopic and elemental analysis of synthesized AMQC was in good agreement with their chemical structures. Fluorescence polarity study demonstrated that AMQC was sensitive to the polarity of the microenvironment provided by different solvents. In addition, spectroscopic and physicochemical parameters, including electronic absorption, excitation coefficient, stokes shift, oscillator strength, transition dipole moment and fluorescence quantum yield were investigated in order to explore the analytical potential of AMQC. Dye undergoes solubilization in different micelles and may be used as a quencher and a probe to determine the critical micelle concentration (CMC) of SDS and CTAB. Nonlinear optical parameters of AMQC dye shows relatively lower nonlinear refractive index and nonlinear absorption coefficient at the power levels. Variation of n2 with concentration is linear in the concentration range used in the present study.

Bis chromophores were synthesized by the terephthalaldehyde with (4-nitrophenyl) acetonitrile/(4-flurophenyl) acetonitrile under microwave irradiation. Bis-chromophores were obtained in good to excellent yields. The structures of bis-chromophores were established by FT-IR, (1)H NMR, (13)C NMR, EI-MS and elemental analyses. Physical chemical properties such as singlet absorption, extinction coefficient, stokes shift, oscillator strength and dipole moment, were investigated by UV-Vis and fluorescence spectroscopy measurements. Further we also measured the nonlinear refractive index and nonlinear absorption coefficients of these compounds using the single beam z-scan technique with a cw argon ion laser at 514.5 nm at different concentrations in DMSO solvent. The third order nonlinear susceptibility was estimated from these measurements and it shows high nonlinearity. The high negative refractive index makes these compounds suitable for optical limiting application., (Copyright © 2014 Elsevier B.V. All rights reserved.)

This paper presents the application of a genetic algorithm (GA) to optimize the operating parameters, namely pulse voltage and extraction delay time, when using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOFMS). Simulations predict the presence of several combinations of these parameters that give a local maximum. The aim is to locate the optimal combination (a global maximum) of pulse voltage and extraction time delay in order to focus the ions of a particular m/z value to achieve the best resolution in a given instrumental geometry. The GA locates the global maximum quickly. The results indicate that it may be possible to achieve very high resolving power by using delayed extraction (DE)-MALDI-TOFMS with parameters obtained from the GA.