Nanosecond laser-induced photomodification of gold nanostars of various sizes

Gold nanostars are one of the new types of nanoparticles with advantages such as plasmon resonance tunability and low toxicity. Therefore, gold nanostars are promising candidates for various biomedical applications including bioimaging, cell optoporation and plasmonic photothermal therapy (PTT) in NIR I, II, and III optical transparency windows of biotissues. However, the stability and possible transformation of gold nanostars under laser irradiation still remains unexplored. In this work, we studied the photomodification of gold nanostars under the 1064-nm nanosecond pulsed laser irradiation by the transmission electron microscopy and spectrophotometry. The photostability of nanostars depends on their morphology and the plasmonic properties. Specifically, for large nanostars with a plasmon resonance at 950 nm remarkable changes occur at a threshold pulse energy of 5 μJ. At this threshold, a significant part of nanostars spikes melts and most of the nanostars start to transform into gold spheres. For higher pulse energies of about 50 μJ, all stars transform into spheres. For smaller gold stars with a plasmon resonance at 680 nm, the changes are less pronounced. Up to pulse energy of 50 μJ, they retain the shape of stars and have spikes on their surface. Moreover, the complete transformation of these stars into spheres does not occur up to pulse energy of about 150 μJ. The obtained results can be important for optimization of PTT treatment with gold nanostars and nanosecond laser irradiation

Indocyanine green-laser thermolysis of acne vulgaris

ABSTRACT The near-infrared (NIR) laser radiation due to its high penetration depth is widely used in phototherapy and photothermolysis. In application to skin appendages a high selectivity of laser treatment is needed to prevent light action on surrounding tissues. Indocyanine Green (ICG) dye may provide a high selectivity of treatment due to effective ICG uploading by a target and its narrow band of considerable absorption just at the wavelength of the NIR diode laser. The goal of this study is to demonstrate the efficacy of the NIR diode laser photothermolysis in combination with topical application of ICG suggested for treatment of acne vulgaris. Two volunteers with back-located acne were enrolled. Skin sites of subjects were stained by ICG and irradiated by NIR laser-diode light (803 or 809 nm). The individual acne lesions were photothermally treated at 18 W/cm 2 (803 nm, 0.5 sec) without skin surface cooling or at 200 W/cm 2 (809 nm, 0.5 sec) with cooling. The results of the observations during a month after the treatment have shown that ICG stained acne inflammatory elements were destructed for light exposures of 0.5 sec

Application of universal computer modeling system for development of LCSs with high contrast and wide viewing angles

The effective applications of universal modeling systems MOUSE-LCD for the development of new LCDs with high contrast and wide viewing angles are presented. The software enables to combine LCDs both with uni and biaxial phase retardation plates as well as to use double cell configuration for the purpose of optimization. Any type of the director distribution inside LC cell with arbitrary (nonsymmetric) tilts and twist angles can be taken into account. The wideness of viewing angles can be estimated using equi-contrast ratio and equi-transmission curves for various angles of light incidence. Special examples demonstrate the effectiveness of application of MOUSE-LCD for the purpose of the design of new color displays with high brightness and wide viewing angles