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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.

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.